JPS597487B2 - Sansei Kitaijiyokiyonimochiil Senjiyouekinokairiyo Saiseihou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for regenerating CO2, H2S, HCN, COS, S
The present invention relates to an improved method for regenerating a regenerable cleaning aqueous solution used to remove a large amount of acidic gases such as O2 and mercaptans from a gas mixture by absorption.

The present invention further provides for the removal of large amounts of acid gases by absorption from a gas mixture containing acid gases in a cyclical process in which the aqueous cleaning liquid is regenerated by steam stripping before they are recycled to the absorption stage. The present invention relates to a method for regenerating a regenerable aqueous cleaning solution for use in a regeneration system, in which a portion of the cleaning solution is regenerated in a main regeneration section of a regeneration system and another portion is regenerated in a sub-regeneration section of the regeneration system.

The gas mixture to be purified may be a natural gas or a gas generated during the manufacturing process.

The most commonly used cleaning aqueous solution in the circulation method is a solution of alkali metal carbonates, especially potassium carbonate,
They also include additives such as arsenites, borates, amino acids, and known activating additives that increase the rate of absorption and dissipation of acidic gases in the cleaning solution, such as alkanolamines.

Besides alkali metal carbonate solutions, other regenerations such as aqueous solutions of ethanolamines and other alkanolamines, alkali metal amino acids, alkali metal phosphates, alkali metal phenoxides, alkali borates and other similar components Possible solutions can be used alone or in mixtures.

Alkali metal sulfites and bisulfites are often used for S02 absorption.

Corrosion inhibitors are usually included in these solutions.

Steam stripping and boiling regeneration of the used cleaning liquid (washing waste) is carried out with regeneration near atmospheric pressure, corresponding to a boiling point which is usually in the range from 70°C to 150°C.

Steam for IJ pulling can be generated by boiling the aqueous cleaning solution in an indirectly heated reboiler or obtained from an external live steam source.

The washing waste liquid leaving the absorption tower, where acid gas absorption is normally carried out under pressure, is first subjected to vacuum and flushing before being introduced into the steam stripping device of the regeneration section.

Commonly used regenerators include regenerators equipped with packings, bubble cap plates or sieve plates, or which bring the solution into intimate contact with the steam for stirring. including any other suitable means for.

A similar type of equipment is also used for the absorption stage.

Depending on the temperature at which the regenerated cleaning liquid is circulated to the absorber and the temperature at which the cleaning waste leaves the absorber, circulation methods are classified as "isothermal", "optimal" or "classical". .

In the conventional method (classical method) the absorption column is operated at a moderate temperature close to the ambient temperature.

Since regeneration by steam stripping occurs at higher temperatures, it requires several heat exchangers and/or solution heaters and solution coolers in addition to the usual absorption and regeneration equipment.

Such a conventional method is suitable for removing CO2, for example, when an aqueous monoethanolamine solution is used as the cleaning liquid.

If the gas mixture to be purified is obtained under pressure such that the partial pressure of the acid gas component to be removed is relatively high, it is possible to increase the temperature of the absorption stage.

In this case, isothermal type or optimal type circulation methods are suitable.

The difference between so-called isothermal circulation and optimal circulation is very easily demonstrated for the case of two-stage absorption regeneration processes.

In a typical two-stage absorption-regeneration cycle, the entire stream of washing waste is sent to the top of the regeneration column, from where the majority of the partially regenerated solution is withdrawn from the mid-height of the column, while the remaining small portion of the solution fully reproduce.

Only this small portion of "lean" solution is sent to the top of the absorption column, and the "semi-clean" main stream solution is recycled to the mid-height of the absorption column.

In so-called "isothermal" circulation, only a small stream of clean solution is cooled before being directed to the top of the absorber, while the majority of the semi-clean solution is recycled back to the absorber without intermediate cooling. .

In "optimal" circulation, a small portion of the clean solution stream is cooled to adjust the vapor pressure of the solution to a value corresponding to the required purity before being recycled to the top of the absorption column.

On the other hand, the temperature of the semi-clean solution recycled to the absorber mid-height is adjusted by cooling it to a value that provides an optimum temperature profile to achieve efficient absorption.

This optimal temperature profile is often important in order to prevent or suppress undesirable side reactions.

The "optimal" circulation is converted into a one-stage split flow (split.-fl
ow) When applied to a regeneration system, a small portion of the regeneration liquid that is recycled to the top of the absorber and a large portion of the stream that is recycled to the mid-height of the absorber are both cooled.

However, the degree of cooling is different. By comparison, in so-called isothermal single-stage split flow systems, only a small stream of regenerated solution is cooled, while the majority of the stream of regenerated solution is recirculated to the mid-level of the absorber without cooling. It is something that makes you

It is already well known that the total amount of heat required for these circulation processes can be reduced if a double pressure regeneration system is employed.

(eg DE 24 07 405) In this system, the majority of the washing waste is regenerated in the main regeneration column operated at higher pressure, while a small portion of this solution is regenerated in the secondary regeneration column operated at lower pressure. In the sub-regeneration column, regeneration is achieved by a stream of stripping steam generated solely by the flushing of the regeneration solution along with the decrease in pressure from a high pressure level to a low pressure level.

According to this system, substantially all of the heat required to generate the stripping steam used for regeneration in both the high pressure and low pressure regeneration columns is introduced into the high pressure column of the system.

The amount of heat required to obtain stripping steam for the low pressure regenerator is stored by increasing the temperature of the solution in the high pressure column.

The thermal efficiency of this dual pressure regeneration system increases as the difference between the two pressures increases.

Typically, the acidic gases liberated during the regeneration process must be collected for further processing, so low-pressure It is desirable that the pressure in the regeneration tower is slightly higher than atmospheric pressure.

This means, in practice, that the relative heat savings depend on the increase in pressure and therefore on the temperature of the column operating at higher pressure levels.

This temperature increase increases the risk of serious corrosion, as well as serious defects in various cleaning agents, especially the well-known undesirable side reactions such as thermal decomposition of alkanolamines and amino acids and the formation of formates. may result in

．． In a modified (improved) method of the double pressure regeneration process described above, a portion of the stripping steam required by the column operating at a lower regeneration pressure may be generated in a solution reboiler operated at the lower regeneration pressure. can.

Therefore, if milder operating conditions are desired, it is unnecessary to regenerate the main part of the solution at a higher pressure, nor to increase the pressure in the other high-pressure parts to the same extent.

However, relaxing operating conditions cannot be achieved without increasing overall heat requirements.

This increased heat requirement is at the high and low pressure levels2
The solution is introduced into the system through several reboilers.

Variants of Double Pressure Regeneration Systems 2 In reboiler sets, the problems associated with solution reboilers, ie the special problems of solution heating and reboiler corrosion, increase in conjunction with the increased role of the reboiler.

According to the invention, it is possible, quite unexpectedly, to reduce the severity of the operating conditions and the overall heat requirement at the same time as saving the load on the solution reboiler.

In the process of the present invention, a part of the aqueous washing waste liquid is regenerated in the main regeneration section (or column), and the σ part other than the washing waste liquid is regenerated in the auxiliary regeneration section (or column) of the regeneration system. Generally, the pressure in the sub-regeneration section can be selected independently of the pressure in the main regeneration section, and at least a portion of the stripping steam required by the sub-regeneration section is supplied to a vacuum connected to the suction side of the steam jet thermocompressor. It is characterized in that a mixture of the thermocompressor driving steam and the recompressed flushed steam is directly discharged into the sub-regeneration section.

In a particular embodiment of the invention, the pressure in the sub-regeneration section is lower than the pressure in the main regeneration section, and a portion of the steam required for the sub-regeneration section is used to transfer cleaning liquid from the high pressure main regeneration section to the low pressure sub-regeneration section. obtained by flushing directly to the area.

According to the invention, the surprising fact has been found that, contrary to hitherto known examples, the pressure in the auxiliary regeneration section can be equal to or higher than the pressure in the main regeneration section.

According to the invention, a small portion of the stripping steam required in the low pressure regeneration section is obtained by flushing based on the pressure reduction of the cleaning solution from the high pressure regeneration section to the low pressure regeneration section, while the remainder of the required stripping steam is obtained from the cleaning waste liquid. The fact that the mixed vapor obtained by (additional) flushing to a lower pressure is obtained by recompressing it by means of a steam jet thermocompressor process makes it possible to significantly improve the thermal efficiency of the regeneration process.

This technique completely avoids the risk of solution overheating in the added solution reboiler, and also eliminates the risk of solution overheating in the solution reboiler, which would otherwise be lost to the solution temperature condenser before being recycled to the absorption column. A certain amount of the stored heat is recovered in the form of useful stripping steam.

According to another feature of the invention, incompletely or fully regenerated cleaning liquid obtained from either the main regeneration section or the auxiliary regeneration section is flushed under reduced pressure created by operation of a thermocompressor.

According to yet another feature of the invention, a portion of the mixture of the steam that drove the thermocompressor and the steam recompressed after flashing is discharged to the main regeneration section.

In the description that follows, reference is made to specific operations in an exemplary manner.

That is, a concentrated aqueous solution of potassium carbonate containing appropriate well-known additives is used as a cleaning liquid to remove a large amount of CO2 from the mixture.

The flow sheet shown in FIG.
By allowing adjustment of both wash solutions to a selected temperature, a predetermined temperature profile in the absorption column can be achieved with sufficient flexibility.

In this way, changes in the regeneration section result in a "semi-clean"
And it is possible to maintain the conditions at the outlet of the washing waste liquid in the absorption stage constant even when the temperature of the "clean" washing liquid is about to change.

The process gas to be purified is led to the bottom of the absorber 1 through line 30 and leaves the top of the absorption column after removing acid gases through line 31.

The hot wash waste leaving the bottom of the absorber 1 through line 21 passes partly to the main regenerator 2 through a pressure reducing valve 52 and line 22 and partly to the auxiliary regenerator 3 through a pressure reducing valve 53 and line 23. Sent.

In the flash zone 7 of the main regenerator 2, which is operated at higher pressure, a certain amount of steam and acid gases are released.

The remaining liquid, which has been cooled by flushing to the boiling point under ambient pressure, flows down towards the stripping area 15.

In this stripping zone, the cleaning solution flows countercurrently to the stripping steam and is heated by the stripping steam, so that the cleaning solution is maintained at its boiling temperature during the progress of regeneration.

A portion of the solution is discharged from the discharge tray 40 after being partially regenerated from the intermediate height of the column.

Meanwhile, the remaining solution flows down the stripping zone 16 to the bottom of the main column 2 and is heated in the solution reboiler 90.

The fully regenerated "clean" solution leaves the bottom of the regeneration column 2 and flows through line 25 and passes through the pressure reducing valve 57 before reaching the expansion vessel 4.

It is maintained at the same pressure as the bottom of the sub-regeneration tower 3.

The gas mixture produced by flashing in 4 flows to the lower part of column 3 where it is used as stripping steam.

Meanwhile, the "clean" solution cooled by flushing leaves container 4 and flows along line 26 to exchanger 99;
There, the regenerated condensate is preheated and then sent by a pump 81.
After being temperature-controlled by a cooler 91, it reaches the top of the absorption tower 1.

The partially regenerated "semi-clean" solution flows from discharge tray 40 through pressure reducing valve 56 and line 24 to flash 9 at the base of sub-regeneration column 30.

The gas mixture generated by the flushing is transferred to the expansion vessel 4.
It mixes with the incoming steam and flows upwards in the column 3 where it is used as stripping steam.

At the top of the sub-regeneration column 3, the solution provided through the pressure reducing valve 53 flows through the flash zone 8 towards the regeneration section 17 and is regenerated there by a stream of stripping steam rising from the bottom of the column.

After regeneration, the solution collected in the discharge tray 41 is discharged,
Pass line 271 and line 2 from flash area 9.
Mix with the solution flowing through 7.

These mixed vapor streams flow into expansion vessel 5 through pressure reducing valve 58 .

The expansion vessel 5 is connected to the suction side of a steam jet thermocompressor (hereinafter referred to as a steam jet ejector) 80.

The suction pressure in the sub-regeneration tower 3 is lower than the normal pressure in the expansion vessel 5.
The steam jet ejector 80 is operated by motive steam supplied by line 34 to maintain the temperature within the range.

Meanwhile, the discharge pressure of the ejector 80 is adjusted to recompress the flash vapor mixture discharged from the expansion vessel 5 to the normal pressure in the sub-regeneration column 3.

The recompressed mixture of flash steam and driving steam is led to the sub-regeneration tower 3 through line 35, where it is utilized as stripping steam.

The total amount of stripping steam used in the auxiliary regeneration tower 3 is thus divided between the portion where the steam generated by flushing of the solution provided by the main regeneration tower 2 passes through lines 24 and 33, and the portion where the steam generated by the flashing of the solution provided by the main regeneration tower 2 passes through lines 24 and 33, and the portion where the steam is removed by the steam jet ejector 80 into line 35. It consists of a portion of the mixture of flash steam and steam jet ejector driven steam provided through the steam jet ejector.

The relative pressure difference existing between columns 2 and 3 on the one hand and between column 3 and expansion vessel 50 on the other hand changes the significance of the relative quantities of these steam supplies. do.

1. Semi-clean after being flushed into the expansion vessel 5.
The solution is sent through line 28 and pump 82 to the intermediate height of the absorption tower through line 281 and cooler 92, where it is adjusted to a predetermined temperature.

The mixture of vented acid gases and residual stripping steam at the top of the secondary regenerator 3 flows through line 32 where it is mixed with the mixture of vented acid gases and steam discharged from the main regenerator 2 via the pressure reducing valve 54. Ru.

The combined flows are cooled by a cooler 93 and the steam dog portion is condensed.

The regenerated condensate is collected in reflux drum 6 and flows through line 29 to pump 83.

Also from the reflux drum, acid gas leaves the apparatus through line 37.

After being preheated in exchanger 99, the regenerated condensate is sent to boiling iron 95 to be vaporized and become the driving steam for the steam jet ejector, or returned to main regenerator 2 as process reflux through valve 62, or as required. The water is discharged out of the system through the valve 63 according to the amount of water.

In this case, preheating of the condensate takes place in exchanger 99, but it can be done in various other ways.

For this purpose, the heat can be recovered and utilized before the acid gas and vapor mixture in line 32 is cooled in exchanger 93, or the "semi-clean" solution in line 28 can be used as a heating medium. It is often preferred to do so.

These various variants have in common the preheating of the condensate by heat available within the regeneration system to reduce the overall external heat supply requirements.

If a separate cooler and condensate drum are installed for the vapors leaving the top of column 20, a pressure drop in the acid gas stream can be avoided, so that it is carried under the same high pressure as when it is dissipated. Become.

When the process gas to be purified in the absorption tower 1 can be obtained at a sufficiently high temperature, as is the case with certain industrial process gases, it is conveniently used as a heating medium in the iron 95 to generate driving steam. can be done.

Since the driving steam pressure is normally required to be 5 to 6 Kg/crrt, the temperature of the process gas leaving the boiler 95 through line 36 is still sufficiently high that the solution reboiler 90
It can also be used as a heating medium inside.

After passing through the heating coil 36 of the reboiler 90, the process gas must be further cooled to a lower temperature, which can be done, for example, in a boiler feedwater heater.

After such a series of cooling operations, the treated gas can now be introduced into the absorption column 1 through line 30.

When the process gas to be purified is obtained at relatively low temperatures, such as in some natural gas streams, it may be more convenient to use medium to low pressure steam as the heating medium in the solution reboiler 90 and steam oven 95. be.

The flow sheet of FIG. 1 clearly shows the difference between the process according to the invention and the known double pressure regeneration process.

In the conventional method, the sub-regeneration tower 3 is operated at a lower pressure.
flows directly through lines 27 and 271 to line 229 and pump 82 and from there to cooler 9
After the temperature is adjusted in step 2, it is returned to absorption tower 1.

One of the obvious differences between the two operating methods is that in the new method according to the invention part of the cooling of the solution is carried out by the container 5 and thus the solution that would otherwise be dumped into the cooler 92 is removed. Most of the required heat is recovered in an efficient manner by the steam jet ejector 80.

One of the advantages of the method according to the invention is that this heat saving can be used to reduce the total heat requirement of the system and also to relax the operating conditions without increasing heat consumption. That's true.

As a result of further research, we found that if a sufficient pressure difference can be created between the expansion vessel where the solution is flashed by the steam jet ejector and the regeneration tower where the recompressed flash mixture is discharged, the main regeneration tower 2 and the sub-regeneration tower 2 It has been shown that the same overall thermal efficiency is achieved even if the pressure difference with column 3 is reduced.

Therefore, the flow sheet of the regeneration process was rewritten as shown in Figure 2 to avoid direct flushing of the solution from the pressure level of the main regeneration tower 2 to the pressure level of the auxiliary regeneration tower 3.
It is possible to have all flushing take place under a pressure difference between the pressure level of each regeneration tower and the expansion vessel connected to the suction side of the steam jet ejector.

The transfer of stripping steam and heat from the main regeneration column 2, which is receiving the heat of the reboiler, to the auxiliary column 3, which does not have a reboiler, is now regulated by the operation of the steam jet ejectors 80 and 88, so that It is also possible to change the relative pressure levels of the main and auxiliary regenerators such that the main regenerator 2 with the solution reboiler 90 operates at a lower pressure level than the auxiliary regenerator 13, if desired.

It is possible to adjust the operating conditions so that the heat load on the solution reboiler 90 of the main regeneration tower 2 is reduced to the extent that the solution reboiler provides less than half of the total heat required to generate stripping steam in the regeneration system. I also learned that.

It is always possible to eliminate the reboiler completely by using live steam, but this would require removing an equivalent amount of product condensate from the system.

The reduction in the load on the boiler, which is the target here, corresponds to the water balance in the regeneration system being maintained in an equilibrium state, so there is no need to discharge the treated condensate out of the system.

As seen in FIGS. 1 and 2, the washing waste from absorption tower 1 is divided into two fractions and regenerated separately in two regeneration towers 2 and 3.

Since the pressure can be adjusted independently for each column, two fractions of emitted acid gas are obtained at two different pressure levels.

This suggests that for the fractions obtained at higher pressure levels, the cost of recompression for further processing is reduced.

As seen in FIG. 2, the two acid gas streams dissipated in columns 2 and 3 are separately cooled in coolers 93 and 96, respectively, and discharged via separate lines 37 and 39.

The process condensate collected in two different reflux drums 6 and 10, respectively, is conveniently mixed in line 29 for reuse.

If it is desired to obtain the entire amount of acid gas dissipated under the same pressure, the entire wash effluent from absorption column 1 can be introduced into a single flushing zone and one fraction of the flushed solution can then be transferred to main regeneration column 2. The second fraction is regenerated in the sub-regeneration tower 3.

In the sub-regeneration column 3, all or part of the flash steam is supplied by flushing of the solution caused by the vacuum provided by a steam jet ejector which recompresses the flash steam mixture to the required pressure level, and the supply of steam It would be more advantageous if the other portion of the regeneration pressure was obtained by flushing the solution caused by a pressure drop from a high regeneration pressure level to a low regeneration pressure level.

Further studies have also shown that after the initial flushing of one stream of waste solution in absorption column 1, if some regeneration takes place in the main regeneration column and the separation of the solution into two fractions is already partially The method of the present invention is also applicable to cases where the regenerated solution is taken out from the side as a flow stream, and the stripping vapor provided by the method of the present invention is received and completely regenerated in a sub-regeneration tower. I can do it.

In order to better understand this embodiment, it will be explained using FIG.

The washing waste liquid leaving the bottom of the absorption tower 1 passes through a pressure reducing valve 52 via a line 21 and reaches the main regeneration tower 2 .

After flushing in flash zone 7, the solution flows downwards to reach regeneration zone 18.

A first portion of the partially regenerated solution is also discharged from the discharge tray 42, while the remainder of the solution flows to the regeneration zone 15.

A second portion of the solution is discharged from the column at discharge tray 40.

The remainder of the solution then flows to the regeneration section 16 and from there to the solution reboiler 90 and then to the bottom of the regeneration tower 2.

According to an embodiment of the present invention, as shown in FIG. 3, the sub-regeneration tower 3 is located lower than the height of the discharge tray 42.

A first fraction of the solution discharged from discharge tray 42 also flows through line 23 to valve 53 and sub-regeneration column 3 .

The height difference between the discharge tray 42 and the auxiliary regenerator 3 should be such that the hydrostatic head created in the line 23 is sufficient to overcome the higher operating pressure maintained in the auxiliary column 3.

No flashing occurs in the flash zone 8 when the solution coming from the discharge tray 42 enters the column 3.

This is because the operating pressure is higher (in column 3).

In the sub-regeneration column 3, the solution flows to the regeneration zone 17 and is heated to the boiling point under pressure there.

It is then regenerated by a countercurrent of stripping steam rising from the bottom of the column 3.

Stripping steam and dissipated acidic gases are in line 3
21 and valve 55 to reach the main regeneration tower 2.

The regeneration solution collected at the bottom of column 3 passes through line 27 and pressure reducing valve 58 to expansion vessel 5 .

This expansion vessel is connected to the suction side of a steam jet ejector 80 which maintains the required low pressure in the vessel.

The vapor mixture discharged by flushing is recompressed by a steam jet ejector 80 and discharged to the bottom of the sub-regeneration tower 3 through a line 35 together with driving steam.

The flash solution collected at the bottom of the expansion vessel 5 is transferred to line 2.
8 by a pump 82, and after temperature adjustment by a cooler 92, it is supplied to the middle height of the absorption tower 1.

A second fraction of the incompletely regenerated liquid withdrawn from the main regenerator 2 at the discharge tray 40 is transferred to the pressure reducing valve 56 and the line 2.
4 to an expansion vessel 5 where the flash vapor mixture is discharged and recompressed by a steam jet ejector 80 and discharged through line 35 into column 3.

The "clean" solution that collects at the bottom of the main regeneration tower 2 passes through line 25 and pressure reducing valve 57 to steam jet ejector 8
The expansion container 4 is connected to the suction side of the 8.

The mixture of flash steam is produced by a steam jet ejector.
The driving steam and the recompressed flash steam are discharged by 88 and recompressed to the pressure of the column 3 and discharged into the sub-regeneration column 3 through the line 33 and valve 60.

The stripping steam supply to the auxiliary regenerator 3 thus consists of the discharge streams of the steam jet ejectors 80 and 88.

As shown in FIG. 3, if the total amount of stripping steam supplied exceeds the required amount of column 3, a portion or all of the output of steam jet ejector 88 is diverted to column 3 via valve 61.
It is possible to release it into the

The "clean" flush solution in expansion vessel 4 is in line 2
6 and is sent by a pump 81, resulting in a separated stream; a portion passes through a line 261 and enters the top of the absorption tower 10 after being cooled by a condenser 91, and a part passes through a line 262 and is temperature-controlled by a condenser 94. After that, enter the middle height of the absorption tower.

At the top of the main regeneration tower 2, the mixture of diffused acid gas and overhead vapor is cooled in an overhead cooling condenser 93.

Acid gas is discharged from the condensate reflux drum 6 through line 37.

The regenerated condensate passes through line 29 and pump 83 to boiling iron 95 .

The scope of application of the present invention is not limited only to the regeneration of one type of cleaning fluid.

It is also suitable for improving regeneration methods for acidic gas cleaning systems that use two different cleaning solutions to more completely remove acidic gases.

Referring to FIG. 4, this shows a flow sheet for a CO2 removal device.

The first cleaning solution is used to remove the main fraction of acidic gases, and the second aqueous solution is used to more completely remove the remaining acidic gases.

The first cleaning solution is, for example, potassium carbonate containing the usual active additives such as diethanolamine, and the second solution is another aqueous solution that can more effectively reduce the residual partial pressure of acidic gases in the process gas to be purified. can be used.

Most conveniently, the second wash solution is an aqueous solution of a potassium salt of an amino acid, such as diethanolamine or dimethylglycine.

A stream of process gas containing an acidic gas is introduced into the bottom of the absorption column 1 through line 30 and rises within the column to a first absorption zone 14 which is normally maintained at a temperature close to the boiling point of the solution at atmospheric pressure. , and passes successively through the second absorption zone 12, which is kept at a significantly lower temperature, for purification before leaving the top of the absorption column through line 31.

The thermal washing waste liquid from the first absorption zone 14 collects at the bottom of the absorption tower 1 and flows through a line 21 into the main regeneration tower 2 and partly into the auxiliary regeneration tower 3 .

A portion of the solution flowing to column 2 through pressure reducing valve 5-2 and line 22 is flushed in flash zone 7;
It flows towards regeneration zone 15 where it is regenerated by stripping steam rising from the bottom of the column.

Then, it collects at the discharge stage 40.

This regenerated liquid exits the column 2 and passes through the line 24 to the pressure reducing valve 56.
and reaches the expansion container 5.

The expansion vessel is maintained at low pressure by suction from a steam jet ejector 80.

A second portion of the cleaning liquid from line 21 passes through a pressure reducing valve 53 and line 23 to the sub-regenerator 3 where it passes through a flash zone 8 and then flows countercurrently to the upward flow of stripping steam to the lower regeneration zone 17. Go down to the target.

The regenerated solution collects at the base of the column 30, passes through the line 27 and the pressure reducing valve 58, and reaches the expansion vessel 5.

This expansion vessel is maintained at low pressure by a steam jet ejector 80.

The entire flow of the first wash liquid collects in the expansion vessel 5 and passes through the line 28 to the pump 82 and from there returns to the first absorption zone 14 of the absorption column 1 after being temperature-controlled in the cooler 92.

The second washing liquid from the second absorption zone 12 at a lower temperature is transferred to the absorption tower 1
is extracted by line 20 at discharge tray 43 and flows to heat exchanger 100, where it is reheated by the returning regeneration zone, and from there flows into the lower regeneration section of main regeneration tower 2 through pressure reduction valve 64.

After flushing in flash zone 9, it flows to regeneration zone 16 and reaches solution reboiler 90 where stripping steam is generated.

The regenerated liquid is withdrawn from the bottom of the column 2 through a line 25 and passes through a pressure reducing valve 57 to reach the expansion vessel 4.

This expansion vessel is kept at low pressure by the suction side of the steam jet ejector 88.

The flashed steam is sent to the steam jet ejector 8.
8 and the mixture thereof with motive steam is discharged through line 33.

Depending on the relative steam requirements of the two regeneration columns 2 and 3, the stripping vapor mixture generated in the thermocompressor 88 can be provided to either column or a portion thereof to each column. It is.

After flushing, the regeneration solution leaves expansion vessel 4 and is pumped through line 26 by pump 81 to heat exchanger 100 where it preheats the wash waste in line 20.

This washing waste liquid flows toward the regeneration section.

After the final temperature adjustment in the cooler 91, it is the absorption tower 1.
It returns to the second absorption region of 1゛2゛.

The acidic gas diffused in the sub-regeneration tower 3 is cooled by a cooler 96 and discharged from the condensate reflux drum 10 through a line 39.

On the other hand, the acidic gas dissipated in the main column 2 passes through line 32 to heat exchanger 99 where it preheats the treated condensate before being sent to cooling concentrator 93, where it leaves condensate drum 6 via line 37.

The regenerated concentrate from the two condensate drums 10 and 6 flows to pump 83 where it is preheated in heat exchanger 99 and then sent to boiling furnace 95 or returned to the process as reflux through valve 62. Good too.

The steam generated by the chisel 95 is sent as driving steam for the steam jet ejectors 80 and 88 in the steam accumulator 34.

In column 2, the stripping steam required in second regeneration zone 16 is obtained primarily by reboiling the second stripping liquid in reboiler 90.

After passing through this lower regeneration zone 16, the mixture of the metering vapor and the acidic gas desorbed in this zone is transferred to the first regeneration zone 1.
5, where it is used to regenerate the first cleaning liquid.

In the absorption tower 1, only a portion of the acidic gas is absorbed by the second washing liquid, so that the amount of acidic gas in the stripping vapor exiting the second regeneration zone 16 is kept small.

The stripping vapor mixture can then be effectively used in the first regeneration zone 15.

The stripping steam required by the sub-regenerator 3 is supplied by the exhaust of thermocompressors 80 and 88.

As indicated above, the determining factor is the pressure difference between each regeneration tower and the expansion vessel, so the present invention allows each regeneration tower to select its optimum pressure level.

As already pointed out, various single-solution flowsheet variants have absorption columns that are always operating at the same end conditions (temperatures at the top and bottom of the absorption column), but at all "Optimum" with possibility of temperature regulation of circulating solution flow
It shows something as a cycle.

The reason for this in particular is merely to facilitate comparison of the various variant embodiments. However, it is clear to any person skilled in the art that the application of the invention is not limited to so-called "optimal" absorption cycles. .

Although the benefits of the present invention are specifically discussed herein with respect to wash liquid regeneration, the advantages of the present invention apply to any other operating conditions of the absorption column independent of whether or not the cycle liquid stream is tempered or cooled. This applies equally.

The present invention does indeed refer to regenerating the waste stream prior to recycling.

The following example illustrating the invention concerns the removal of CO2 from an industrial process gas resulting from catalytic steam reforming of natural gas that, once removed, can be used for ammonia synthesis.

It is well known that CO2 is an acidic gas with relatively low rates of absorption and dissipation, so that regeneration of cleaning waste is more difficult than with other acidic gases such as H2S.

It is therefore appropriate to describe the invention in terms of a method of CO2 removal.

Example 1 Referring again to FIG.

This figure shows a circulation process for removing acidic gases, and a potassium carbonate aqueous solution is used as the cleaning liquid.

CO to be removed.

The process gas stream containing 7.
5 Kl/rsl, flow rate 45, 700 Nm
'/hr (on a dry basis).

Is that 0.44 Nrr per I Nm3 of dry gas? contains water vapor.

Since the temperature at the inlet of the absorption tower is preferably 80°C, it is common practice to recover the heat contained in the treated gas, and by using one or more stages of heat exchangers, this acidic gas can be removed. It can meet some or all of the heat requirements of the removal system.

For example, the hot process gas is first passed through line 47 and into steam oven 95 6? It can be used to produce low pressure steam of f//cal.

The process gas leaving the chimney 95 through line 36 is then sent to a solution reboiler to generate stripping steam in the main regeneration tower 2.

It can then be further cooled to 80° C. in a boiler water heater (not shown).

The relative amounts of steam generated in steam furnace 95 and solution reboiler 90 depend on the intermediate temperature of the process gas in line 36.

For a temperature of 167°C, the amount of steam generated within the iron 95 is 5900 kg/hr.

Before the feed gas enters the absorption column 1, which is operated at a pressure of 27 Kg/cd, the condensate formed by the cooling of the gas is removed in a separation drum (not shown).

The process gas entering the absorption tower 1 from the line 30 has a volume of 17.
Contains 6% CO2.

CO absorbed in the cleaning solution.

reacts with potassium to form potassium bicarbonate.

That is, the K2CO3+CO2+H20-2KHCO3 wash solution thus contains a mixture of unreacted potassium carbonate and potassium bicarbonate.

The relative ratio of K2CO3 and KHC03 is expressed as percentage conversion.

As used herein, "potassium bicarbonate fraction" or "conversion percentage" is the percentage of K2CO3 converted to potassium bicarbonate by reaction with CO.

For example, a solution with a conversion percentage of 20 has potassium carbonate of 1
Of the 00 moles, only 20 moles are obtained by converting to potassium bicarbonate.

Therefore, the amount of potassium ion as K2CO3 is KH
80 for the amount of potassium ions present as Co3
/20.

Since 1 mole of K2C03 produces 2 moles of KHCOa, the molar ratio of K2CO3/KHCO3 is 8 074 0 at a conversion percentage of 20 parts.

Since the concentration of the solution is given here as a weight percent of potassium carbonate, the concentration is stated with respect to the original state without any bicarbonate.

In other words, it is expressed as a conversion percentage of 0.

The washing waste liquid collected at the bottom of the absorption tower 1 has a K2C03 concentration of 29 parts by weight, and also contains diethanolamine with a concentration of 3 parts by weight in addition to a common anticorrosive agent.

The supplied treatment gas passes through the absorption zones 14 and 1 in the absorption tower 1.
2, it is washed by a hot semi-clean solution introduced at the mid-height of the column, and a cooled cleaning solution introduced at the top of the absorption column at 80°C.

The amount of CO2 remaining in the process gas leaving the absorption tower at 80° C. through line 31 is less than 0.1 volume fraction.

A "clean solution" with a conversion of 22 parts is introduced into the absorption column at a flow rate corresponding to 18 parts of the total flow rate of the washing waste liquid.

A semi-clean solution introduced into the absorption column at a flow rate of 82 parts of the total wash waste flow rate at 101°C has a conversion of 42.8 parts.

The washing waste liquid leaving the bottom of the absorption column 1 via line 21 with a flow rate of 378,000 Kg/h has a conversion of 84.degree. C. and a temperature of 108.degree.

The loading factor of the solution is 0.45 per mole of K2C03
moles of CO.

, which is equal to the total conversion percentage change of 45 factors.

The wash waste stream is divided into two parts.

The main fraction of 1.60% flows via pressure reducing valve 52 and line 22 to the main regenerator and flash zone 7, where the operating pressure is 1.60%. It is set at 9Kg/cr/l.

The small fraction of 40% flows via pressure reducing valve 53 and line 23 to sub-regeneration tower 3 and flash zone 8, where the pressure is set at 1-3 Ky/cd.

In the main regeneration tower 2 the solution flows downwards after flushing into the regeneration zone 15 where it is washed by a countercurrent of stripping steam which dissipates acid gases.

From the discharge tray 40, 70 parts of the partially regenerated solution stream are withdrawn at 120° C. and with a conversion of 46.3%, while the remaining 30 parts are sent to the regeneration zone 16 and the solution reboiler 90. flowing towards.

The hot supply gas supplied by line 36 is 167°
The heat supplied in the reboiler 90 when cooled from

The CO2 emission rate in column 2 corresponds to 60 parts of the total acid gas removal of 8000 N7F18/hour of CO2.

The stripping steam requirement in column 2 is therefore CO21Nrr dissipated in the column. This corresponds to approximately 2.14 kg of steam per unit.

A portion of the vapor fed to the bottom of the column is condensed in the regeneration zone, thereby providing the endothermic dissipation heat requirement and thereby maintaining the solution at its boiling point.

The remainder reaches the top of the column as stripping vapor residue.

Since the amount of heat provided by the steam varies with system pressure and temperature, it is convenient to express the regeneration heat requirement in terms of kilocalories per N of CO2 dissipated, which in the present case is 1 16 5 Kcal/Nrr? CO2
corresponds to

The conversion rate of the clean solution collected at 125°C at the bottom of column 2 is 22
I am in charge.

A small fraction of 40% of the washing waste in the sub-regeneration column 3 must be regenerated to a conversion of 39 parts in order to achieve a given load factor, i.e. a total conversion change of 45 parts.

The amount of heat required for this regeneration load is the CO dissipated in the sub-regeneration tower 3.

Equivalent to 1090 Kcal per N, i.e. 320
This corresponds to about 6,400 kg of steam for a dissipation load of 0NrrlCO2, or 40 parts of the total acid gas removal load,
This should be carried out in the sub-regeneration tower.

The semi-clean solution from the discharge shelf 40 is 156,000 KI! /
42% of the total solution flow flows through the pressure reducing valve 56 and line 24 to the flash zone 9 at the bottom of the sub-regeneration column 3, where the operating pressure is slightly higher than that at the top of the column (1 .4V4/crl.

The solution is flushed to generate steam at a rate of 2,000~/hr and is cooled to 110°C.

In addition to steam, a small amount of C02 is liberated.

Due to the low rate of the dissipation process, the amount of COz generated in the flushing process is sufficiently small that it does not significantly interfere with the regeneration process of the auxiliary regenerator and therefore does not need to be taken into account for the understanding of this example.

The clean solution leaving the bottom of column 2 through line 25 and pressure reducing valve 57 flows into expansion vessel 4 .

The pressure in the expansion vessel 4 is essentially the same as the pressure in the bottom flash zone 9 of the column 3, from 1.4 to 1/d.

Steam is generated by flushing at a flow rate of 1000 Ky/hr, thereby reducing the solution temperature to 113°C.

The ratio of CO2 to vapor in the vapor mixture produced by flushing is in this case even smaller than in the case of flushing a semi-clean solution, and the small amount of CO2 thus liberated can be ignored for the purposes of this example. I can do it.

The total amount of flashed steam produced in both flash zone 9 and expansion vessel 40 is 3ooo Kt/hr or column 3.
CO2/Nrr desorbed inside? This corresponds to about 0.94 kg of steam per unit.

The heat thus supplied is 5 0 6 k c /
Nrr? In addition to this, an additional heat supply of 5 8 1 Kcal/Nm'CO2 is required to meet the regeneration heat requirement.

According to the invention, this additional heat supply is obtained through the use of a thermocompressor 80.

This compressor generates steam by vaporizing the treated condensate.
Line 3 generated at a pressure of 6 K5//crtt in 5
It is operated by driving steam from 4.

The smaller 40% fraction of the washing waste liquid is regenerated into the regeneration zone 17 of the sub-regeneration column 3 and collected on the discharge tray 41 at a temperature of 111° C. and a conversion rate of 39%.

It passes through line 271 and joins with the semi-clean solution leaving the bottom of column 3 via another line 27 and through pressure reducing valve 58 where it joins with the semi-clean solution leaving the bottom of column 3 and expands through pressure reducing valve 58. It flows into container 5.

This combined flow has a flow rate of ~305,000/hr and is maintained by the absorption side of the steam jet ejector 80 within the vessel 5. The combined solution stream was heated to 107° C. when flushed to a low pressure of 2 Kv/cd, producing 1400 Kg/h of steam and having a conversion of 42.8%.
Cool to

The flashed steam is transferred to the bottom of column 3 at 1.4Kg/c.
The amount of driving steam at a pressure of 6 Kp/ca used by the steam jet ejector 80 to recompress to a pressure of RL is 2000 Kg/hr.

3 4 of recompressed and flashed steam and driving steam
The combined flow is discharged through line 35 to the bottom of column 3.

As previously explained, the small amount of CO2 liberated by flushing can also be ignored for purposes of the present description; i.e. its relative importance is further reduced by the dilution effect of the motive steam. It will be understood.

With SteamZ Thermo Compressor 80, it takes 6K to recompress 0.7K9 of steam generated by flushing.
Driving steam I K9 at a pressure of g/cnt is consumed, resulting in a stripping steam of 1.7 K9.

Therefore, by using this steam jet thermo-compressor, the amount of externally supplied heat necessary for regeneration in the column 3 is reduced to the additional amount of heat 5 8 1 Kc
The ratio of 59 to a 1/Nm'CO2 will suffice.

In this way, the amount of heat input from the outside is reduced by the driving steam 3 4
1 Kc a l/N7? Z3C 02 and the remainder is obtained from the solution itself by flashing and recompression.

The total regeneration heat requirement of the circulation process is determined by the sum of the external heat supply to the main regenerator 2 via the solution reboiler 90 and the external heat supply to the auxiliary regenerator 3 in the form of driving steam.

The amount of heat supplied to the main column 2 solution reboiler includes 480
1165Kcal/for CO2 dissipation in 0N/hour
For the external regeneration heat supply to the solution reboiler of Nm3CO2, 3200 Ntrl/h of C dissipated in the sub-regeneration tower 3
3 4 1 Kc a l/Nw for O2? C
02 supplies must be added.

This is 8 3 6 Kcal/Nr calculated based on the total acid gas removal burden of CO2 of 8000 Ny &/hour.
r? of CO2.

The semi-clean solution leaving the expansion vessel 5 via line 28 is fed by pump 82 through line 281 to the mid-height of absorption column 1 after being cooled to 101° C. in cooler 92 .

The clean solution from expansion vessel 4 flows to heat exchanger 99, where it preheats the process condensate to 100°C.

It is passed through line 261 by pump 81 to cooler 9
1 and then cooled to 80° C. from where it is fed to the top of the absorption column 1.

The released CO2 and residual steam from the sub-regeneration tower 3 flows into the condensate separator 6 via the line 32 and the cooling condenser 93.

They are all kept at essentially the same pressure level of 1.3 Kg/crl.

The CO2 dissipated from the main column 2, which accounts for 60 parts of the total CO2 or 4800 N/hr, flows with the residual stripping steam through the pressure reducing valve 54 into the line 32 where it also mixes with the incoming stream from the secondary regenerator column 3.

The combined flow of 8000 Nnl/h of released CO2 is 6
The system is discharged at 0° C. via line 37, while the condensate leaves vessel 6 via line 29 at a flow rate of 7400° C./h.

This condensate is sent by a pump 83 to a heat exchanger 99 where it is heated from 60°C to 100°C, after which a portion of it is sent to a steamer 95 to provide driving steam for the operation of a steam jet ejector 80. and the remainder is returned to the main regenerator via valve 62 as process reflux.

4800 released at a pressure of 1.9Kg/cd
It is quite clear that the main stream of CO2 during Ndl could easily be discharged from the colored acid gas removal system in this pressurized state via suitable piping as shown in Figure 2, if necessary.

This example can be easily compared to the prior art of reproduction.

Is the required amount of stripping steam of sub-regeneration tower 3 IN? r? It has been shown that approximately 2 Kg of steam per hour, or a total amount of 6400 Kg/h, was reached, while the steam produced when flushed in the flash zone 9 and the expansion vessel 4 was only 3000 Kg/h.

The shortfall requirement of 3400 Kg/h was of course met by the solution reboiler.

Instead of sending the expanded solution streams to column 3, they are circulated through a solution reboiler in which the 5G IK
c a l /Nrr? It was also possible to generate the necessary stripping steam by adding C 0 2 heat.

However, compared to the method of the present invention, the use of a reboiler requires an increased amount of heat supply, including an increase in the temperature of the solution in the boiler.

This is contrary to the cooling of the solution in the expansion vessel 5.

According to other methods of the prior art, the cyclic process of FIG.
It can be operated by sending the combined semi-clean solution stream of all three columns directly to pump 82 via line 229.

The operating conditions must then be changed to balance the steam requirements and feed rates in column 3.

If 1. 9 Kq/ca and 1. If the same regeneration pressure Kalev of 3 Kt/cd is maintained, the main fraction of the solution regenerated in column 2 increases to 76.2%, and the solution flow to the sub-regeneration column increases to 23.8%. Must be reduced.

The total heat input to this system, which is limited to one solution reboiler 90, increases by increasing the solution flow ratio to the main column, which is 888 KC/Nrr? C.O.

corresponds to

However, in this method of operation it is possible to improve the thermal efficiency by increasing the pressure of the main regenerator in order to reduce as much as possible the heat losses due to flushing in the flash zone 7.

If the pressure is increased to a value equivalent to the vapor pressure of the wash waste, substantially no flushing will occur within the flash zone T.

In this example, 3K4/crl. pressure is required.

There is a corresponding increase in the heat requirement in column 2, which in this case is 1 4 3 5 K per Nrrl' of CO2 dissipated.
cal, but the overall heat requirement is 8 6 5 K
cal/N? r? The reason for this is that the cleaning waste liquid
This is because only 0.3 has to be regenerated in tower 2.

However, the temperature of the solution at the bottom of column 2 rose to 139°C.

Data for this example and a comparison with prior art implementations are summarized in Table ■.

Experiment n1 is for the prior art implementation shown in Figure 1, in which the combined stream of semi-clean solution leaving column 3 through lines 27 and 271 is pumped directly via line 229 to pump 8.
2 and recycled to absorption column 1 where it is not further processed.

Experiment n2 is the result of a prior art implementation in which one reboiler was added to the sub-regeneration tower 3 and used.

Experiment n3 is the result of Example 1 of the present invention.

Example 2 Let's talk about Figure 2.

The same process feed gases and cleaning solutions as in Example 1 are used.

The same amount of carbon dioxide is removed from the feed gas in absorber 1, in which the operating conditions are the same as in Example 1, with the following changes.

The flow rate of the cleaning solution is reduced to 15 times the total flow rate of the corresponding cleaning waste liquid.

The temperature and conversion rate are 80℃ and 220! ) is maintained.

The semi-clean solution flow rate here is 85q6 of the total flow rate of cleaning waste liquid.
be equivalent to.

The conversion is here 42 degrees and the temperature is 100°C.

The washing waste liquid collects at the bottom of the absorber at a temperature of 108 °C and a conversion rate of 84 degrees, and its flow rate is 378,000 per hour.
・Smell is the same as Example 1.

CO per mole of K2CO3. The loading factor of 0.45 molar remains unchanged.

The washing waste flowing through line 21 is divided into two equal fractions of 50 fractions each, which are regenerated separately in the main regeneration tower 2 and the auxiliary regeneration tower 3.

The operating pressure of the main regeneration tower is set to 1.3Kg/cd, and the operating pressure of the auxiliary regeneration tower is slightly higher than that, 1.5Kii/c.
rtt.

Solution flowing to main regenerator 2 through valve 52 and line 22 flushes to flash zone 7 and flows to regenerator zone 15.

Partially reproduced 46. ．． A 70% fraction of the semi-clean solution with a conversion of 3% is discharged from the discharge tray 40 at a temperature of 109°C, and the remaining 30% fraction (
15 parts of the total solution flow) is the regeneration zone "1" of the main regeneration tower 2.
6 and flows to the solution reboiler 90.

After passing through the reboiler, the cleaning solution with a conversion rate of 22 and a temperature of 115° C. collects at the bottom of column 2.

The second fraction, which is 50 parts of the washing waste liquid, is connected to the pressure reducing valve 53.
and flows through line 23 to sub-regeneration tower 3 and flash zone 8
and flows down toward the regeneration zone 17.

The semi-clean solution exiting column 3 must be regenerated to a conversion of 39 parts to achieve the desired total conversion change of 45 parts.

This is 111 per co20N released in tower 3.
Regenerative heat supply of 5Kcal is required, which is approximately 8200
This corresponds to Kg/h of stripping steam.

This stripping steam is supplied by a steam jet ejector 80 which discharges into column 3 through line 35.

The absorption side of the steam jet ejector 80 is the expansion container 5
The pressure in this container is maintained at 1.1 Kg/c4.

The 130,000 Kg/h semi-clean solution stream discharged from the discharge tray 40 flows via line 24 and pressure reducing valve 56 to the expansion vessel 5 where 900 Kg/h steam is generated by flushing, whereby the solution is Cooled to 103°C.

The semi-clean solution collected at the bottom of the sub-regeneration column 3 at a temperature of 115° C. and a conversion of 39° C. flows through the line 27 and the pressure reducing valve 58 to the expansion vessel 5 at a flow rate of 185,000 ~/h, and in the expansion vessel Flushing generates steam at 2200 kg/hr, which cools the solution to 105°C.

The motive steam at a pressure of 6 Kg/crA produced in the steam pit 95 is supplied by line 34 to a steam jet ejector 80 at a flow rate of 5100 Kf/hr, and the flashed steam and motive steam are recompressed. The mixture is transferred via line 35 to the bottom of JO column 3 at a pressure of 1.64 Kg/c by thermocompressor 80 at 8200 Kg/c.
released at a flow rate of

The required regeneration heat of column 3 is thus increased by the external supply of driving steam and by the heat extracted from the solution itself by the hot compression action of the steam jet ejector.
The person in charge is covered.

Therefore, the external heat supply to the sub-regeneration tower 3 is 1115K ca
l /Nm'' C 02 , that is, the 62nd factor of the regeneration heat requirement of 692 Kcal per 1 Nrr of CO2 dissipated in the column 3.

The heat requirement of the sub-regeneration tower 3 is determined by the steam jet ejector 8.
Another steam supply discharged by the steam jet ejector 88 can be used as stripping steam to the main regeneration column 2 since it is completely covered by the steam supplied by the steam jet ejector 88.

The clean wash solution at the bottom of column 2 is connected to line 25 and pressure reducing valve 57.
through the expansion vessel 4, which is connected to the absorption side of a steam jet ejector 88, which maintains the vessel at a low pressure of I Kti/c4.

Steam is generated by flashing at a rate of 600 cm/hr and the solution is cooled to 106°C.

The driving steam generated in the steam iron 95 at a pressure of 6 Kg/crA is 1000 KJ! /hour flow rate is fed to the steam jet ejector 88 via line 34 and the recompressed mixture of flashed steam and motive steam is passed through valve 61 at a pressure of 1. 5 Kg/ca is discharged to the bottom of column 2.

If a total output of 1600 Ky/hr of steam from steam jet ejector 88 is selected to be returned to column 2, valve 60 in line 33 is closed.

The required amount of regeneration heat in the main column 2 is the I of CO2 dissipated in the column.
It reaches 1044Kcal per N, which is 7700K
corresponds to a stripping steam supply of g/h.

Since the steam jet ejector 88 already supplies approximately 20 parts of the total demand for column 2, the solution reboiler 90
The heat supply by CO was reduced by the same proportion and dissipated in column 2.

It is 838 Kcal per INm'.

The total external regeneration heat supply to column 2 is thus
8 3 8 Kcal/Nm3CO2 from 0 and 6 2 Kcal/Ni as the form of driving steam? A total of 900 K per 1 fl of O2 or CO2 desorbed in column 2
It is established from cal.

The total regeneration load is divided equally between the main tower 2 and the auxiliary regeneration tower 3, each with an externally supplied heat requirement of 900 Kcal,
'Nrri'CO.

and 6 9 2 Kcal/Nrrl C 02, so the combined total external heat supply is 7 9 6 Kc per unit of CO2 removed from the spent cleaning solution.
reach al.

After being flushed in vessel 4, the cleaning solution passes through a heat exchanger 99 where the regenerated condensate is preheated to 100°C and
The pump 81 then passes the line 261 to the cooler 9.
Sent to 1.

In the cooler, the cleaning solution is heated to 80 ml before entering the top of the absorption tower 10.
cooled to ℃.

The semi-clean solution leaving the expansion vessel 5 at a conversion rate of 42 flows through line 28 to pump 82 from which it is cooled to 100 DEG C. in cooler 92 before being recycled to absorber 1.

The overhead mixture of steam and CO2 from main column 2 flows via line 32 to cooler 93 and reflux drum 6, in which the condensate is separated while the cooled CO2 has a temperature of about 60°C. 1.3 KI! 4 0 0 0 N through line 37 at a pressure of /crA? ? Z'
/hour flow rate.

The other fraction of the acidic gas dissipated in the auxiliary column 3 is cooled to 60° C. in the cooler 96 and then converted to 1. 5K
It is discharged via line 39 at a higher pressure of 9/cat.

The condensate from the reflux drum 10 flows through a pressure reducing valve 50 into line 29, through which it is combined with the condensate from the reflux drums 6 to a combined flow rate of 8700~/h and a temperature of 60°C. and flows to the pump 83.

From there it is pumped to a heat exchanger 99 where it is reheated to 100°C and after which it flows to an evaporator (steam iron) 95 at a flow rate of 6100 K9/h as a hot feed (process) gas. by 6Kti/c
Driving steam at a pressure of A is generated.

The hot gas is supplied to the chisel 95 by line 47 and leaves the chisel 95 through line 36 at 164°C.

The remainder of the regenerated condensate is returned to main column 2 through valve 62 as reflux.

According to this operating method, the solution reboiler is operated at low regeneration pressure, and the heat load on the reboiler is 4 19 Kc.
It is noteworthy that it is reduced to al/Nm'CO.

Example 3 Let's talk about Figure 3.

The composition and loading factors of the wash solution were the same as in Example 2, as were the conversions, flow rates and temperatures of the clean and semi-clean solution streams entering the absorption tower, and the temperature and flow rates of the wash waste stream leaving the absorption tower. be.

Recycle solution line 262 and cooler 94 are not used.

The same feed gas as in Example 2 is used.

The washing waste liquid with a conversion rate of 84 and a temperature of 108°C is in line 2.
1 and the flash zone 7 of the main regeneration tower 2 via the pressure reducing valve 52.
The pressure in the column is set at 1.5 Kg/ca.

Below the regeneration zone 18, the pressure is approximately 1. 6 Ky/cr
In the discharge tray 42, A, a 50 part fraction of the partially regenerated solution is withdrawn at a temperature of 110 DEG C. and a conversion of 55 parts.

The remaining 50 fractions are transferred to the regeneration area 15 and the discharge shelf 4.
70% of the remaining semi-clean solution in its tray.
A fraction, 35% of the total stream entering the top of the column, is withdrawn at a temperature of 113° C. and a conversion of 46.3%.

The remaining fraction of fraction 15 flows to regeneration zone 16 and, after passing through solution reboiler 90, collects at the bottom of the column at a temperature of 118° C. and 22% conversion and is withdrawn from discharge tray 42. The partially regenerated solution flows via line 23 to the sub-regeneration tower 3.

Column 3 is located at such a height that the hydrostatic head of the solution in line 23 is sufficient to exceed the pressure difference between columns 2 and 3.

In this example, the height difference between the discharge shelf 42 and the pressure reducing valve 53 is 2 m, which is approximately 0.0 m. 2 5K9/
Corresponding to the hydrostatic head of crA, the pressure inside the sub-regeneration tower 3 is 1. 7Ky/cd, that is, 0. I is larger by Kti/ca.

Due to the pressure increase in the flash zone 8, no flushing of the solution takes place there, and the solution collects at the bottom of the column after being regenerated in the regeneration zone 17.

In order to satisfy a constant loading factor of the solution with an overall conversion change of 45 parts, the solution stream in column 3 must be regenerated to a conversion of 39 parts.

However, because of this regeneration load, it is necessary to increase the stripping steam, resulting in line 3 from the top of regeneration zone 17.
The partial pressure of the acid gas in the vapor mixture returned to the main column 2 by 21 is kept sufficiently low to ensure that when said vapor mixture is transferred to the main column 2 it still has a stripping capacity.

? A conversion change of 6 parts is carried out for both parts of 50 parts of the total solution, which is] 4 2 0 Nrr? /hour CO2
This corresponds to the emission of

The stripping steam that must be fed to column 3 is CO2
//N? ? 5.7 Kf steam per Z2 or about 810
It corresponds to 0K9/hour.

In accordance with the present invention, this stripping steam requirement is met by the discharge stream of the steam jet injector 80.

The semi-clean solution regenerated in column 3 to a conversion rate of 39% and a temperature of 116°C passes through line 27 and pressure reducing valve 58 to expansion vessel 5.
In the container, the suction side of the steam jet injector 80 is maintained at a low pressure of 1.2 KIi/cst.

The flushing induced by this drop in pressure is 210
Generates 0K9/hr of steam thereby heating the solution to 105℃
It is cooling down.

The semi-clean solution which is also discharged from the main column 2 in the discharge tray 40 flows via the line 24 and the pressure reducing valve 56 to the expansion vessel 5 where 1200 kg/h of steam is generated by flushing, thereby increasing the temperature up to 105°C. The solution is cooled.

6K9/ supplied from steam iron 95 via line 34
The motive steam with a flow rate of 4800 Kf,/hr at a pressure of cyf
．． It is recompressed to a pressure of 8Kg/c4, and that pressure is transferred to column 3.
, where it discharges a mixture of motive steam and recompressed and flashed steam via line 35.

The regeneration heat requirement of the auxiliary regenerator 3 is thus supplied by the external heat supply of the driving regenerated vapor state, which is dissipated in the column by COINtr? per 1 8 5 1Kca
is equivalent to l.

The regeneration heat requirement in the main column 2 is met in part by stripping steam supplied by the auxiliary regenerator 3 via line 321, and the shortfall requirement is covered by the stripping steam supplied by the auxiliary regenerator 3 via line 321
This corresponds to a stripping steam supply of s o oKty/hour, a portion of which is supplied via line 33 and valve 61 by steam jet ejector 88 and a portion via solution reboiler 90 .

The cleaning solution at the bottom of the main column 2 flows via line 25 and pressure reducing valve 57 to expansion vessel 4, where the suction side of steam jet ejector 88 is maintained at a low pressure of 1.15 Kg/crA.

The resulting flushing generates 700 kg/h of steam, thereby cooling the solution to 108°C.

6KL via line 34 by steam iron 95! /cr
Driving steam at a flow rate of 1000 Kg/hr, supplied at a pressure of rt, brings the flashed steam to a temperature of 1.5 kg/h of the pressure at the bottom of column 2.
The mixture of driving steam and recompressed flash steam is recompressed to a pressure of 7 Kg/crA through line 33 and valve 6.
1 at a flow rate of 1700 Kg/hr.

During this operation, valve 60 is closed, thereby preventing the steam discharged from steam jet ejector 88 from entering sub-regeneration tower 3.

The remaining 6100 kc9/hr stripping steam feed is obtained from boiler 90, which is heated by hot synthetic feed gas.

Is the heat supply to the reboiler 8000N? ? If we talk about the total acid gas removal load in lCO2/hour, is it the total CO21N dissipated? ? This corresponds to 4 17 Kcal per fl.

The driving steam used in steam jet ejectors 80 and 88 has a total flow rate of 5800 Kp/hr, which is the total CO21 Ntr dissipated. This corresponds to a heat supply of 397 Kcal per hour, which is introduced into the regeneration system via the steam furnace 95.

In this way, the total amount of regeneration heat required for this regeneration method is determined by the amount of CO2N removed? ? It reaches 814 Kcal per Zl'.

The total CO2 dissipated in the regeneration system is collected at the top of the main regeneration tower 2 at a pressure of 1.5~/cd, from where it flows through line 32 to cooler 93 and discharge line 37, where it is Leave the unit at a temperature of °C.

The overhead regenerated condensate, which collects in the reflux drum 6 at a flow rate of 8000 Ky/hr, flows through line 29 and is sent by pump 83 to heat exchanger 99, where it is preheated to 100°C, after which part of it is converted into driving steam. is fed to the iron 95 to produce , and the remainder is returned to the main column 2 as treated reflux.

According to FIG. 3, this reflux is shown to be returned via valve 62 at the top of column 2.

However, it is widely known that it is equally satisfactory to return the reflux to the intermediate height of the column or to the bottom of the regeneration column or directly into a side stream flowing into the solution reboiler 90.

According to another widely known method of implementation, it is also possible to return the cold process condensate into the system directly into the line 26 without preheating it in the heat exchanger 99.

Are these various variations equivalent within the scope of the invention? Applicable.

After passing through the heat exchanger 99, the cleaning solution is cooled to 80° C. in the cooler 91 by the pump 81 and line 261 before being recycled to the top of the absorption column 1.

The semi-clean solution from container 5 with a conversion rate of 42 is pumped to pump 82.
It passes through a line 281 and is temperature-controlled to 100° C. by a cooler 92, and then recycled to the absorption tower 1.

Example 4 Let's talk about Figure 4.

It illustrates a dual solution removal system,
There, the potassium carbonate aqueous solution is absorbed into the first absorption zone 1 of the absorption tower 1.
CO within 4.

and a 20% aqueous solution of diethanolamine is used for the final scrubbing of the gas in the second absorption zone 12 of the absorption column 1.

The same process feed gas as in Example 1 is used.

The process feed gas (processing gas?) passes through the steam furnace 95, and at that time the gas temperature drops to 163K.
Driving steam of 7250~/hr at a pressure of flcrl is generated, and then passed through a solution reboiler 90 and another heat exchanger (not shown) to line 30. ?
It enters the absorption tower 1 at a flow rate of Z8/hr (dry basis).

The operating pressure of the absorption tower is 2.7~/cf! It is. When the gas passes through the first absorption zone 14, the CO content is reduced to 1.6 volume factors, is further washed in the second absorption zone, and then passes through line 31 at a temperature of 45° C. with a residual content of less than 0.01 volume factors. Leaves the absorption column with a CO2 content.

The regenerated potassium carbonate solution is passed through line 281 to
It is recycled to absorption column 1 at a temperature of 0.01° C. and a conversion of 41.5%.

The waste potassium carbonate solution that collects at the bottom of the absorption tower 1 has a potassium carbonate concentration of 29 parts by weight and further contains 3 parts by weight of diethanolamine along with a small amount of corrosion inhibitor.

It is 371,000 at a temperature of 110°C and a conversion rate of 84
It leaves via line 21 at a flow rate of Kf/h.

Clean diethanolamine (DEA) solution in line 26
0.08 per mole of DEA with a temperature of 45 °C through 1
It is recycled to the top of the absorption column 1 with an acid gas load of molar CO2.

The used DEA solution is transferred to the absorption towers 1 to 7 at the discharge tray 43.
It is extracted at a temperature of 7° C. and an acid gas loading of 0.38 mole per mole of DEA.

It flows through line 20 to heat exchanger 100 at a flow rate of 47 000 Kg/h, where it is preheated to 95° C. and after depressurization at valve 64 enters the lower regeneration section of main regeneration column 2.

Flash area 9 where the operating pressure is 1.45Kg/ca
After flushing within, the solution flows to regeneration zone 16, solution reboiler 90.

The heat supplied from line 36 by the hot process feed gas produces 4800 Kg/hr of steam.

A portion of this stripping steam is used in the regeneration zone 16 to provide heat for the endothermic dissipation process and to heat the liquid to its boiling point, and the remainder is used to dissipate the CO.

Along with this, the potassium carbonate solution flows (rises) towards the upper regeneration section for regeneration.

The waste potassium carbonate solution leaving the absorption column 1 is divided into two parts.

The fraction 30 is transferred to the main regeneration tower via the pressure reducing valve 52 and the line 22 at a pressure of 1.30. The data is sent to flash area 7, which is set to 3Ky/cd.

After flushing, the solution flows to the regenerant 15 and to the discharge tray 40, from where it is withdrawn at a temperature of 109 DEG C. and a conversion of 46 parts.

The regeneration steam requirement in zone 15 is 4600 Kg/hr, of which only 2550 Kg/hr rises from the lower regeneration section.

To meet the shortfall requirements, clean DEA solution is 11
Leaves the bottom of main column 2 via line 25 at 2°C and expands into expansion vessel 4.
guided by.

The expansion container is expanded by suction from the steam ejector 88.
It is maintained at a low pressure of 0.5 Kii/cd.

By flashing and reducing the pressure of this solution through valve 5T, 800 KIV/hour of steam is produced, which is recompressed by steam jet ejector 88.

This steam jet ejector is operated with 1250 edges/hour of drive steam supplied by steam iron 95 via line 34 at a pressure of 6 Kti/cnt.

Thermocompressor 88 discharges a mixture of recompressed flash steam and motive steam via line 33 and valve 611 to flash zone 9 at a flow rate of 2050 Ky/hr.

During this operation, valves 60 and 61 are closed.

A second fraction of 70 parts of the used potassium carbonate solution flows via the pressure reducing valve 53 and the line 23 to the flash zone 8 of the sub-regeneration column 3.

The pressure in the flash zone is set at 1-4 Kii/cd.

In order to achieve the desired total conversion change of 42.5%, regeneration in the side regenerator must be carried out to a conversion of 39 parts.

The corresponding regeneration steam requirement of 10,100 Kf/hr is supplied by the steam jet ejector 80.

The regenerated solution in the discharge tray 40 is connected to the line 24 and the pressure reducing valve 56.
to the expansion vessel 5, where the suction side of the steam jet ejector 80 is kept at a low pressure of IKy/cd.

During flushing, steam is generated at a rate of 1000 Kg/hr and the temperature of the solution is reduced to 101°C.

The solution regenerated in the sub-regeneration tower 3 is passed through line 27 to 1
flows into the expansion vessel 5 via the pressure reducing valve 58 at a temperature of 12°C;
A vapor flow of 3100 K9/h is then generated, at which time the solution temperature drops to 101°C.

The driving steam at a feed rate of 6000K97 hours is fed by line 34 to a steam jet ejector 80, which directs the flashed steam to a pressure of 1.54K at the bottom of column 3.
g/crA and further compressed to 10 g/crA via line 35.
A mixture of motive steam and recompressed steam is discharged to the bottom of column 3 at a flow rate of 100 Kg/h.

The combined stream of regenerated potassium carbonate solution at a conversion of 41.5% flows via line 28 to pump 82 at a temperature of 101°C and is recycled via line 281 to absorption column 1.

No cooling within cooler 92 is required.

The clean DEA solution leaving the expansion vessel 4 at a temperature of 102° C. flows via line 26 to pump 81 and is sent to heat exchanger 100 where it preheats the waste wash solution.

From there it flows to cooler 91 where its temperature is adjusted to 45°C.

3 sub-regeneration towers release CO.

The stream of 1. Leaves the regeneration unit at a pressure of 5 Ky/crA.

CO released within the main tower.

flows through line 32 to the heat exchanger where it preheats the process condensate and passes through cooler 93 before passing 1.
It leaves the unit via line 37 at a pressure of 3 Kg/crl.

The regenerated condensate that collects in condensate drums 10 and 6 is in line 2.
9 at a combined flow rate of 96 ooKy/hr to pump 83 from where it is sent to a heat exchanger.

This heat exchanger absorbs CO from the top of column 3. and steam.

After being preheated to 94° C., the condensate flows at a rate of 7250 Kg/hr to a steam pressure of 95, and the remainder returns to the lower part of the main regenerator via valve 62 as process reflux.

All external heat requirements of the regeneration system are 4 8'O OK
It is powered by a solution reboiler steam generation of 4/hr and a driving steam supply of 7250 Kg/hr to steam jet ejectors 80 and 88.

The total amount of CO2 at 8040N doors/hour is removed from the process gas, and the heat consumption rate is 82N/hour CO2 removed.
It becomes 5Kcal.

In this example, two separate absorption zones 12 and 14 were combined in the same absorption column.

It is clear that the regeneration method according to the invention can be applied equally well if the respective absorption zones are located in different columns.

It is noted that the flow diagrams of Figures 1 through 4 do not necessarily include all necessary equipment required for the operation of an industrial plant.

However, the additional equipment necessary for this purpose will be apparent to those skilled in the art.

The invention should not be limited to the four embodiments described above, and the flow diagrams can be varied within the scope of the invention.

The embodiments are listed below.

(1) The same method as shown in the claims.

(2) A method according to the claims, wherein all the stripping steam required in the sub-regeneration section is obtained by flushing in at least one reduced pressure region connected to the suction side of the steam jet ejector, and A method characterized in that a mixture of driving steam and recompressed steam generated in flushing is directly introduced into a sub-regeneration section.

(3) A method according to the claims, wherein the pressure in the sub-regeneration section is lower than the pressure in the main regeneration section, and a part of the stripping steam required by the sub-regeneration section is transferred from the high pressure of the main regeneration section to the sub-regeneration section. A method characterized in that the regeneration is obtained by direct flushing by lowering the pressure to a low cliff in the regeneration area.

(4) A method according to Claims or Embodiment 2, characterized in that the pressure in the auxiliary regeneration section is made equal to or higher than the pressure in the main regeneration section.

(5) A method according to any of the above claims and embodiments, wherein the flushing to the reduced pressure state generated by the operation of the steam jet ejector is performed using a partial regeneration unit obtained from the main regeneration unit or the sub-regeneration unit. Or a method characterized in that it is carried out using a completely regenerated cleaning solution.

(6) A method according to any of the preceding claims and embodiments, characterized in that steam jet ejector drive steam and recompressed flushing steam are introduced into the main regeneration tower.

(7) As claimed in the above claims, 《〉 is a method according to any of the embodiments, characterized in that the washing waste liquid is divided into two fractions and each is introduced into a main regeneration section and a sub-regeneration section. how to.

(8) A method according to any one of embodiments D to 6, wherein all of the washing waste liquid is introduced into the main regeneration section, and a part of the incompletely regenerated washing liquid is discharged from the main regeneration section and introduced into the sub-regeneration section. A method characterized by:

(9) A method according to any of the preceding embodiments, wherein two different cleaning liquids that have been used in separate gas absorption sections are regenerated in a single regeneration system comprising one main regeneration section and one sub-regeneration section. A method characterized in that the stripping steam used for regenerating one of the cleaning waste liquids is reused as stripping steam for regenerating at least a part of the other waste cleaning liquid.

00゛) A method according to embodiment 9, comprising flushing each of the one or different cleaning liquids in one or more corresponding vacuum zones connected to the suction side of one or more steam jet ejectors. There is also a method characterized in that stripping steam to be used in the sub-regeneration section is obtained by the above method, and a mixture of the steam for driving the steam jet ejector and the recompressed steam generated by flushing is directly discharged into the sub-regeneration section. 0υ A method according to embodiment 9, by flushing one or both of the different cleaning liquids in one or more corresponding vacuum zones connected to the suction side of one or more steam jet ejectors. Stripping steam to be used in the sub-regeneration section is obtained, and either the steam for driving the steam jet ejector 1 and the mixture of recompressed steam generated by flushing, or a part or all of each, is transferred into the sub-regeneration section and the other. A method characterized by discharging into a part of or into the main regeneration section.

(1) A method according to the claims and substantially as described by any of Examples 1 to 4.

[Brief explanation of drawings]

1-4 are flowcharts each illustrating an exemplary method of the present invention. Explanation of symbols of main parts, 1...absorption tower, 2...
...Main regeneration tower, 3...Sub-regeneration tower, 4...
... Expansion container, 5... Expansion container, 6...
... Condensate separator, 30 ... Mixed gas supply port, 80 ... Steam jet ejector, 90
...Reboiler, 95 ...Steam iron, 9
9... Heat exchanger, 91... Heat exchanger,
92... Heat exchanger, 56... Pressure reducing valve,
57...Reducing valve.

Claims (1)

[Scope of Claims] 1. When an aqueous cleaning liquid used to absorb and remove acidic gas from a gas mixture containing acidic gas is regenerated in a regeneration system using steam stripping and then recycled to the absorption stage, a part of the cleaning liquid is The main regeneration section may include a liquid reboiler, which is completely or completely and incompletely regenerated;
In an aqueous cleaning liquid regeneration/circulation method in which some of the other cleaning liquid is regenerated in a sub-regeneration section without a solution reboiler, and the pressures in both sections are set independently, a portion of the stripping steam required for the sub-regeneration section is used. (a) Flushing the recycled cleaning liquid from the sub-regeneration section or both the sub-regeneration section and the main regeneration section under a pressure lower than the respective pressures of the main regeneration section and the sub-regeneration section, and (b) By the flushing. The obtained water vapor is recompressed to the pressure of the sub-regeneration section using a steam jet thermocompressor, and a mixture of the vapor obtained by the recompression and the steam that drives the steam jet thermocompressor is directly introduced into the sub-regeneration tower. A method for regenerating an acidic gas aqueous cleaning liquid, which is characterized in that a part of the heat in the solution is recovered, and the heat efficiency in the regeneration process is significantly improved.