JP4580199B2 - Gas-liquid contact device - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a gas-liquid contact device, and more particularly, to a gas-liquid contact device that performs a distillation operation using a self-distribution-promoting regular packing, and in particular, a packed tower used for a distillation operation in an air liquefaction separation device. It is related with the gas-liquid contact apparatus suitable for.

Conventionally, it is known to use a packed tower for distillation operation in an air liquefaction separation apparatus. The packed tower mainly includes a packing, a liquid distributor disposed above the packing, and a liquid collector disposed below the packing, and the packed column includes: In general, self-distribution-promoting regular packing is used in which the distribution and mixing of liquid and gas is facilitated by a flow path in the packing. In addition, a liquid distributor having a liquid spraying density corresponding to the specific surface area of the packing is used. Usually, if the specific surface area of the packing is increased, the liquid spraying density of the liquid distributor is also increased. (For example, refer to Patent Document 1).
JP-A-9-250898

  In the air liquefaction separation apparatus, a distillation apparatus that can greatly increase or decrease the product production amount is desired. However, in the packed column using the self-distribution promoting regular packing, the amount of increase / decrease is within the range due to the upper limit of the liquid load due to the occurrence of flooding, the upper limit of the gas load, and the lower limit of the liquid load due to the deterioration of liquid distribution. There were major limitations. The distillation performance in a packed column can be enhanced by using a self-distribution-promoting ordered packing having a large specific surface area, but the operation range of the packed tower is narrowed by using a self-promoting ordered packing having a large specific surface area. As a result, there is a problem that the range of increase / decrease in the product production amount becomes small. On the other hand, if a self-distribution-promoting type regular packing with a small specific surface area is used in order to increase the increase / decrease range of the product production amount, the distillation performance is lowered, so that the height of the entire column is increased and the apparatus cost is increased There was a problem.

  In view of this, the present invention optimizes the combination of the liquid distributor and the self-distribution-promoting regular packing, and lowers the lower limit value of the liquid load amount to increase the range of increase or decrease of the descending liquid amount or the ascending gas amount. An object is to provide a liquid contact device.

In order to achieve the above object, the gas-liquid contact device of the present invention has a liquid distributor disposed above a packed bed filled with a self-distribution-promoting ordered packing, and is distributed by the liquid distributor in the packed bed. In the gas-liquid contact device for air liquefaction separation for contacting the liquid descending the gas and the gas rising in the packed bed from below, each packed bed is composed of a single self-distribution promoting regular packing. A lower main packing layer and an upper sub packing layer, and the sub packing layer has a specific surface area smaller than a specific surface area of the self-distribution promoting regular packing forming the main packing layer. The number of liquid spray holes per column cross-sectional area of the liquid distributor is equal to or greater than the number of liquid spray holes required to ensure the distillation performance of the sub-packed bed, Spraying the liquid necessary to ensure the distillation performance of the main packed bed It is characterized in that less than the number of.

Further, according to the present invention , the weight reduction operating width which is the operation lower limit value of the outflow volume flow rate per column cross-sectional area of the liquid disperser is the operation lower limit value of the volume flow rate of the descending liquid per column cross-sectional area of the main packed bed. The self-distribution promoting regular packing forming the main packed bed and the sub packed bed has a flow path having a channel inclined at 30 to 45 degrees with respect to the vertical line. It is made of sheet metal and has a specific surface area in the range of 250 to 750 m ² / m ³ , in particular, the self-distribution promoting regular packing has at least one of the shape of the upper end and the lower end of the flow path. It is characterized by being parallel to the vertical line .

  According to the gas-liquid contact device of the present invention, it is possible to increase the range of increase or decrease of the descending liquid amount or the ascending gas amount without reducing the distillation performance in the packed column and without increasing the overall height of the column. In particular, an air liquefaction separation apparatus equipped with a distillation tower using this gas-liquid contact apparatus can increase the range of increase or decrease in product production.

  FIG. 1 is a schematic configuration diagram showing an example of a packed tower using the gas-liquid contact device of the present invention. The packed column 11 is provided with a condenser 12 at the top of the column, and a first sub packed bed constituting a first liquid distributor 13 and a first packed bed 14 is arranged inside the column in order from the top of the column. 15, a first main packed bed 16, a liquid collector 17, a second liquid distributor 18, a second sub packed bed 20 and a second main packed bed 21 constituting the second packed bed 19 are arranged.

  The liquid condensed in the condenser 12 and introduced into the tower top through the path 22 is distributed by the first liquid distributor 13 and descends in the tower, and is introduced into the tower bottom from the path 23 (source gas). ) Rises in the tower through the second main packed bed 21. The liquid that descends in the tower (falling liquid) and the gas that rises in the tower (rising gas) are brought into gas-liquid contact with each other in the first packed bed 14 and the second packed bed 19 to perform a distillation operation. The liquid is concentrated at the bottom of the column, and the gas having a low boiling point is concentrated at the top of the column. The gas at the top of the column is withdrawn into the path 24 and introduced into the condenser 12 where it is cooled by the low-temperature fluid to be condensed and liquefied. A part of the liquid extracted from the condenser 12 to the path 25 is extracted out of the system through the path 26, and the remainder is introduced to the top of the tower through the path 22. Further, the liquid at the bottom of the column is extracted from the path 27.

The first filling layer 14 and the second filling layer 19 that contact the descending liquid and the ascending gas are made by bending a bent metal plate (corrugated sheet metal) such as aluminum, stainless steel, copper, etc. The self-distribution-promoting ordered packings are arranged in a slanted manner with respect to the liquid, and the liquid flows along a flow path formed by bending the surface of the metal plate by gravity. Thus, the fluid flowing on the surface of the self-distribution promoting ordered packing is moderately distributed by flowing through the inclined flow path. Furthermore, the distribution of the liquid can be promoted by providing irregularities or holes in the metal plate of the filling. The gas also rises while being distributed by the self-distribution promoting regular packing. In this way, highly efficient distillation is performed by bringing the sufficiently distributed liquid and gas into gas-liquid contact on the surface of the packing. The specific surface area of the self-distribution-promoting regular packing used in the packed column for distillation is generally in the range of 250 to 750 m ² / m ³ , typically 250 m ² / m ³ , 350 m ^2. / M ³ , 500 m ² / m ³ , and 750 m ² / m ³ are used.

  On the other hand, the first liquid distributor 13 and the second liquid distributor 18 are known to have various structures, but basically, the liquid descending from the top, for example, the liquid or liquid introduced from the path 22 The liquid collected by the collector 17 is distributed and distributed as evenly as possible to the lower first packed bed 14 and the second packed bed 19. Various shapes of the portion for spraying the liquid downward have been proposed, but normally, a plurality of spray holes having a hole diameter of several millimeters formed on the bottom surface of the spray box of the liquid distributor is used. In addition, in order to distribute liquid evenly with a liquid distributor having a large number of spray holes having a hole diameter of several mm, it is necessary to ensure a liquid depth of 50 mm or more on the bottom surface. Are known.

Here, the relationship between the flow rate of the liquid flowing out from one liquid spray hole of the liquid distributor and the liquid depth is expressed by the following equation.

Q: Outflow volume flow rate per spray hole [m ³ / s]
C: Outflow coefficient [-]
A: Area of spray hole [m ² ]
g: Gravity acceleration [m / s ² ]
H: Liquid depth in the spray box [m]

  Further, the hole diameter of the spray hole is suitably 3 mm or more, for example, about 4 mm in consideration of the production accuracy and the blockage by the solid suspended matter in the apparatus during operation. Furthermore, it is said that the number of spray holes per column cross-sectional area of the liquid distributor does not need to be increased or needs to be increased if the specific surface area of the self-distribution-promoting ordered packing exceeds a certain value. However, according to the results of the study by the present inventor, it was confirmed that the number of liquid spray holes per column cross-sectional area of the liquid distributor has an optimum number with respect to the specific surface area of the self-distribution promoting regular packing. Moreover, it was also confirmed that the optimum number should be determined in proportion to the specific surface area of the self-distribution promoting type regular packing.

The optimum number of liquid spray holes per section of the liquid distributor with respect to the specific surface area of the self-distribution-promoting ordered packing varies depending on the conditions such as the surface tension and viscosity of the liquid. An example of the optimum number of liquid spray holes per column cross section [pieces / m ² ] in the case of a liquid (liquid such as nitrogen, argon, oxygen, etc., or a mixed liquid thereof) composed of air components to be handled is a self-distribution promotion type rule Table 1 shows the specific surface area [m ² / m ³ ] of each packing. Furthermore, the lower limit flow rate of the liquid distributor (outflow volume flow rate per column cross-sectional area [m ³ / (m ² · S)]) when the hole diameter of the spray hole is set to 4 mm is determined according to each rule of the self-distribution promotion type. Table 2 corresponding to the specific surface area [m ² / m ³ ] of the packing, the optimum number of liquid spray holes per column cross-sectional area [pieces / m ² ], and the outflow volume flow rate [m ³ / s] per spray hole. Shown in

  Moreover, the cause of the deterioration of the liquid distribution at the lower limit of the liquid flow rate in the liquid distributor is considered to be the deterioration of the initial liquid distribution due to the deterioration of the performance of the liquid distributor and the lack of gas-liquid contact due to the liquid running out on the filling surface. However, the surface tension of the liquid composed of the air component as described above is very small, and the performance of the packing is not deteriorated in the operation range of a normal air liquefaction separation apparatus.

In FIG. 2, the horizontal axis represents the volumetric flow rate of the descending liquid per column cross-sectional area (liquid flow rate [m ³ / (m ² · S)]), and the vertical axis represents HETP (packing height of distillation performance equal to one theoretical plate [ m]). The self-distribution-promoting ordered packing used was Mellapak 500.Y (specific surface area 500 m ² / m ³ ) manufactured by Sulzer, the experimental conditions were an N ₂ -O ₂ distillation operation, and the experimental pressure was 150 kPa. Here, assuming that L / V = 1.0 when the density correction superficial velocity (F factor) is 1.6, the volumetric flow rate of the descending liquid per tower cross-sectional area is 2.8 × 10 ⁻³ m. ³ / (m ² · s), from which it can be seen that HETP hardly changes even when the volume flow rate is reduced. Similar results were obtained with other packings.

  From these results, the self-distribution-promoting ordered packing does not cause performance degradation in the normal operating range required for the air liquefaction separation device regardless of its specific surface area, and the column cross-sectional area of the liquid distributor. It can be seen that the number of permeate spray holes needs to increase or decrease in proportion to the specific surface area of the self-distribution promoting ordered packing. Therefore, in order to improve the distillation performance in the packed column, when using a self-distribution-promoting ordered packing having a large specific surface area, it is necessary to use a liquid distributor having a large number of liquid spray holes. If the number of the liquid distributor is less than the predetermined number, the distillation performance of the self-distribution-promoting ordered packing cannot be fully utilized.

  However, in the case of a liquid distributor having a large number of liquid spray holes, as is clear from Table 2, the operation lower limit value of the outflow volume flow rate per column cross-sectional area becomes large, so that the minimum amount of liquid drop in the packed tower is less The number of spray holes is larger than the minimum descending amount of the liquid distributor, and the reduction operation width of the packed tower is reduced, so that it is not possible to cope with the increase or decrease in the desired product production amount.

Therefore, a self-distribution promotion type regular packing having a large specific surface area, for example, a self-distribution promotion having a specific surface area smaller than this is formed on the upper part of the main packing layer composed of a self-distribution promotion type regular packing having a specific surface area of 500 m ² / m ^3. A sub-packing layer made of a self-distribution-promoting type regular packing having a specific surface area of 350 m ² / m ³ , for example, is placed on the sub-filling layer, and a self-distribution-promoting regular packing having a small specific surface area is placed on the sub-packing layer Liquid distributor, in this case, a liquid distributor having a number of liquid spray holes per column cross-sectional area of 140 / m ² corresponding to a self-distribution-promoting ordered packing having a specific surface area of 350 m ² / m ^3. The self-distribution-promoting regular packing having a specific surface area of 350 m ² / m ³ was used while maintaining the same distillation performance as the self-promoting regular packing having a specific surface area of 500 m ² / m ³ . Same as packed tower It becomes possible to widen the lower limit of operation.

  That is, since the descending liquid can be precisely distributed by the sub-packing layer, the ratio of the specific surface area of the self-distribution promoting regular packing serving as the main packing layer to the ratio of the self-distribution promoting regular packing serving as the sub-packing layer By appropriately combining the surface area and appropriately setting the height of the sub-packing layer, even if a liquid distributor with a liquid spray hole corresponding to the self-distribution promoting regular packing of the sub-packing layer is used, The liquid can be supplied in a sufficiently distributed state from the lower part of the packed bed to the self-distribution promoting ordered packing of the main packed bed. Therefore, while obtaining the distillation performance of the self-distribution-promoting regular packing having a large specific surface area, it is possible to operate at the operation lower limit value of the liquid distributor with a small number of liquid spray holes, and the increase / decrease of the product production amount is greatly increased It becomes possible to take.

  In addition, the number of gas-liquid contact devices installed in the packed tower 11 is arbitrary, and three or more stages of gas-liquid contact devices including the above-described liquid distributor, sub-packed bed, and main packed bed are installed in the vertical direction. In addition, a liquid collector that collects the liquid flowing down from above or the liquid introduced from the outside and supplying the liquid distributor to the upper part of each gas-liquid contact device may be appropriately installed at a necessary place.

  In addition, a plurality of sub-packing layers can be installed above the main packing layer, and the plurality of sub-packing layers can be a combination of self-distribution promoting regular packing having different specific surface areas. The self-distribution-promoting ordered packing having a small size increases, the distillation efficiency decreases, and the height of the packed column must be increased.

  Furthermore, the self-distribution promoting type regular packing has a shape in which at least one of the upper end and the lower end of the flow path is deformed, for example, a flow path whose basic portion is inclined at 30 to 45 degrees with respect to the vertical line. By using an improved type in which the flow paths at the upper and lower ends of the packing are modified so as to be parallel to the vertical line, the operating range can be expanded and the distillation performance can be improved.

  FIG. 3 is a schematic system diagram of an essential part showing an example in which a packed tower using the gas-liquid contact apparatus of the present invention is applied to a distillation tower of an air liquefaction separation apparatus. This air liquefaction separation apparatus has three towers, a high-pressure tower 31, a low-pressure tower 32, and an argon tower 33, and the above-mentioned gas-liquid contact devices are arranged in each tower. In FIG. 3, each gas-liquid contact device shows only its position, and detailed illustration of the configuration is omitted. However, each gas-liquid contact device is similar to the liquid distributor and the gas-liquid contact device. The liquid collector is provided above the liquid distributor except for a part thereof.

  First, the operating state of the air liquefaction separation apparatus will be described. The compressed, refined, and cooled raw material air is introduced into the lower portion of the high-pressure tower 31 through the pipe 51 and becomes a gas (ascending gas) that rises in the high-pressure tower 31. In addition, a part of the liquefied nitrogen condensed by the main condenser 34 located at the upper part of the high-pressure column 31 is introduced into the upper part of the high-pressure column 31 from the pipe 52 and becomes a liquid that descends in the high-pressure column 31 (falling liquid). The descending liquid and the ascending gas are brought into gas-liquid contact by the first gas-liquid contact device 41, whereby a distillation operation is performed, and oxygen is enriched in the liquid descending to the bottom of the high-pressure column 31, thereby oxygen-enriched liquefaction. Nitrogen is concentrated in the gas that rises to the top and becomes high-pressure nitrogen gas.

  In the low-pressure column 32, a part of the oxygen-enriched liquefied air led out from the bottom of the high-pressure column 31 passes through the valve 53 through the pipe 54, and a part of the liquefied nitrogen condensed in the main condenser 34 passes through the valve 55. From the pipe 56, the bottom liquid of the argon tower 33 is introduced from the pipe 57 to become the descending liquid of the low-pressure tower 32. On the other hand, the oxygen gas evaporated in the main condenser 34 located at the bottom of the low-pressure column 32 and the oxygen-enriched air led out from the bottom of the high-pressure column 31 and introduced from the pipe 59 through the valve 58 and the argon condenser 35. Becomes the rising gas of the low-pressure column 32.

  These descending liquid and ascending gas are the second gas-liquid contact device 42, the third gas-liquid contact device 43, the fourth gas-liquid contact device 44, the fifth gas-liquid contact device 45, which are provided in the low-pressure tower 32, Distillation operation is performed by gas-liquid contact with the sixth gas-liquid contact device 46, oxygen is concentrated in the liquid flowing down to the bottom of the low pressure column 32 to become liquefied oxygen, and nitrogen is concentrated in the gas rising to the top. It becomes low-pressure nitrogen gas. The liquefied oxygen at the bottom is evaporated by the main condenser 34 to become oxygen gas, and a part thereof becomes the rising gas.

  Further, from the high-pressure tower 31, oxygen enriched liquefied air at the bottom is extracted into the pipes 54 and 59, and high-pressure nitrogen gas at the top is extracted into the pipe 60 and introduced into the main condenser 34. , Condensed into liquefied nitrogen. A part of the liquefied nitrogen is branched into the pipe 56 and the remaining part is extracted from the pipe 61. From the low pressure column 32, oxygen gas is extracted from the lower pipe 62, waste nitrogen gas is extracted from the upper pipe 63, low pressure nitrogen gas is extracted from the top pipe 64, and argon source gas is extracted from the intermediate pipe 65. It is.

  The argon source gas in the pipe 65 is introduced as a rising gas into the lower part of the argon tower 33, rises to the top of the tower through the seventh gas-liquid contact device 47, is extracted into the pipe 66, and is introduced into the argon condenser 35. Condensed into liquefied argon, a part of which is extracted from the pipe 67 and the remaining part passes through the pipe 68 and is returned to the upper part of the argon tower 33 as a descending liquid, descending the seventh gas-liquid contact device 47 Gas-liquid contact with the rising gas is performed.

  Here, as the argon tower 33 shown in FIG. 3, the two-stage packed tower (Example apparatus) shown in FIG. 1 is used, and liquefied argon from the upper part of the tower and argon source gas from the lower part of the tower are used. The result of conducting an experiment for confirming the operating range when the gas and liquid are brought into contact with each other will be described.

For the first main packed layer 16 and the second main packed layer 21, a self-distribution promoting ordered packing (Mellapak 750.Y made by Sulzer) having a specific surface area of 750 m ² / m ³ is used. The second subpacked layer 20 used was a self-distribution-promoting regular packing (MellapakPlus752.Y manufactured by Sulzer) having a specific surface area of 500 m ² / m ³ and deformed shapes of the upper and lower ends of the flow path. Further, in the first liquid distributor 13 and the second liquid distributor 18, the number of liquid spraying holes per column cross-sectional area corresponds to a self-distribution promoting regular packing having a specific surface area of 500 m ² / m ^3. Each / m ² liquid distributor was used.

In FIG. 1, the liquefied argon flowing into the first liquid distributor 13 at the top of the tower from the path 22 is suitable for the first subpacked layer 15 made of a self-distribution promoting ordered packing having a specific surface area of 500 m ² / m ³ . It is distributed to the state and descends in the first sub-filled layer 15. The liquefied argon descending in the first sub-filling layer 15 descends from the first sub-filling layer 15 to the first main filling layer 16 in a state of being more precisely distributed by the distribution promoting effect of the self-distribution promoting type regular packing. .

  The liquid that descends while making gas-liquid contact with the rising gas in the first main packed bed 16 drops and collects from the lower end of the first main packed bed 16 to the liquid collector 17, and then is collected by the second liquid distributor 18. It is distributed again and descends the second sub-packed layer 20, is precisely distributed by the second sub-packed layer 20 and descends to the second main packed layer 21, and makes gas-liquid contact in the second main packed layer 21. Go down to the bottom of the tower.

  The argon source gas flowing into the lower part of the tower from the path 23 is the second main packed bed 21, the second sub packed bed 20, the second liquid distributor 18, the liquid collector 17, the first main packed bed 16, the first sub packed. It passes through the layer 15 and the first liquid distributor 13 in order, and rises to the top of the tower while making gas-liquid contact with the falling liquid. By this gas-liquid contact distillation operation, the argon-concentrated gas rises at the top of the argon tower, and the liquid having a lower argon concentration flows down from the argon source gas at the bottom.

For comparison, the first filling layer 14 and the second filling layer 19 are not divided into main and sub, and the same specific surface area as that used for the first main filling layer 16 and the second main filling layer 21 is 750 m ² / m ³ . The first packed bed 14 and the second packed bed 19 are formed by filling the self-distribution promoting type regular packing, and the first liquid distributor 13 and the second liquid distributor 18 are sprayed with a liquid per column cross-sectional area. A packed tower (comparative example apparatus) was prepared in which 300 holes / m ² of liquid distributors corresponding to the self-distribution promoting ordered packing having a specific surface area of 750 m ² / m ³ were provided.

In the example apparatus and the comparative example apparatus, the lower limit [%] of the operation range when the upper limit of the operation range of the argon tower is 100%, the density corrected superficial velocity at that time [m / s (kg / m ³ ) ^0.5 ] and outflow volume flow rate [m ³ / (m ² · S)] per column cross-sectional area are summarized in Table 3.

  As is clear from Table 3, the lower limit of the comparative apparatus is 75%, whereas the lower limit of the embodiment apparatus can be expanded to 50%. Therefore, by using the packed tower using the gas-liquid contact device as the distillation column of the air liquefaction separation device, the product production amount in the air liquefaction separation device can be reduced to 100% to 75% of the conventional value while maintaining the product quality. Can be expanded to 100 to 50%.

It is a schematic block diagram which shows one example of a packed tower using the gas-liquid contact apparatus of this invention. It is a figure which shows the relationship between the volume flow volume of the falling liquid per tower cross-sectional area, and HETP. It is a general | schematic systematic diagram of the principal part which shows an example which applied the packed tower using the gas-liquid contact apparatus of this invention to the distillation tower of an air liquefaction separation apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Packing tower, 12 ... Condenser, 13 ... 1st liquid distributor, 14 ... 1st packed bed, 15 ... 1st subpacked bed, 16 ... 1st main packed bed, 17 ... Liquid collector, 18 ... 1st Two-liquid distributor, 19 ... second packed bed, 20 ... second subpacked bed, 21 ... second main packed bed, 31 ... high pressure column, 32 ... low pressure column, 33 ... argon column, 34 ... main condenser, 35 DESCRIPTION OF SYMBOLS ... Argon condenser, 41 ... 1st gas-liquid contact apparatus, 42 ... 2nd gas-liquid contact apparatus, 43 ... 3rd gas-liquid contact apparatus, 44 ... 4th gas-liquid contact apparatus, 45 ... 5th gas-liquid contact apparatus, 46 ... 6th gas-liquid contact apparatus, 47 ... 7th gas-liquid contact apparatus

Claims (4)

A liquid distributor is disposed above the packed bed filled with the self-distribution promoting regular packing, and a liquid that is distributed by the liquid distributor and descends in the packed bed, and a gas that rises in the packed bed from below. In the gas-liquid contact device for air liquefaction separation, the packed bed is formed by a lower main packed bed and an upper sub packed bed each composed of a single self-distribution promoting ordered packing. The sub-packing layer is formed of a self-distribution-promoting ordered packing having a specific surface area smaller than that of the self-distribution-promoting ordered packing forming the main packing layer, and the liquid distributor is cut off. The number of liquid spray holes per area is more than the number of liquid spray holes necessary to ensure the distillation performance of the secondary packed bed, and the liquid spray holes required to ensure the distillation performance of the main packed bed gas-liquid contact instrumentation, characterized in that it has less than the number of . The reduction operating width that is the operation lower limit value of the outflow volume flow rate per column cross-sectional area of the liquid disperser is smaller than the reduction operation width that is the operation lower limit value of the volume flow rate of the descending liquid per column cross-sectional area of the main packed bed The gas-liquid contact apparatus according to claim 1. The self-distribution-promoting regular packing forming the main packing layer and the sub-packing layer is made of corrugated sheet metal having a channel inclined at 30 to 45 degrees with respect to the vertical line, and has a specific surface area of 250 to 750 m. The gas-liquid contact device according to claim 1 or 2, wherein the gas-liquid contact device is in a range of ² / m ³ . The gas-liquid contact device according to claim 3, wherein the self-distribution promoting type regular packing has at least one of an upper end and a lower end of the flow path in parallel with a vertical line .

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