JPH0140764B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to the PSA method (pressure fluctuation adsorption separation method).
The present invention relates to a method for producing industrially useful gas by separating and concentrating or removing CO in a mixed gas containing CO.

[Technical background of the invention and its problems]

It is well known that the PSA method is one of the processes for separating, concentrating, or removing CO in a mixed gas containing CO.

In general, CO separation technology using the PSA method has the characteristics of the adsorbent used to adsorb a large amount of CO2 at around room temperature, so although it is operated at a temperature around room temperature, the amount of _CO2 adsorbed is small at temperatures around that temperature. is larger than that, so in order to separate CO from a mixed gas containing CO ₂ , CO ₂ is first removed in a pretreatment process, and then CO is separated using CO-PSA (hereinafter referred to as “ (referred to as "room temperature PSA").

For example, JP-A No. 59-22625 discloses a two-stage process in which PSA is used to remove moisture and CO ₂ in the pretreatment process, and JP-A No. 59-22625 discloses a two-stage process in which PSA is used to remove moisture and CO 2 in the pretreatment process, and JP-A No.
Publication No. 59-26121 proposes a two-stage treatment in which mordenite is used as an adsorbent and CO ₂ -PSA and CO-PSA are performed in separate steps.

On the other hand, the present inventors previously proposed a method for separating Ni, Mn, and
By using an adsorbent that can support one or a mixture of Rh, Cu(), and Ag, we break the common sense of the normal adsorption temperature (near room temperature) of 50°C to 150°C from a mixed gas containing CO. We proposed a method that can selectively separate, concentrate, or remove CO from a mixed gas containing CO ₂ in one step by performing PSA at high temperatures.

This is because, although the above-mentioned adsorbent has an equilibrium adsorption amount of CO ₂ several times that of CO at room temperature, by increasing the adsorption temperature, CO and CO ₂
This was based on the fact that the equilibrium adsorption amount of

Based on the previous proposal, the present inventors continued to
As a result of intensive research using a four-column PSA test equipment that can repeat the normal adsorption process → purge process → desorption process → pressurization process, mainly assuming normal converter gas in a steelworks, we found the method proposed above. In order to obtain a product CO purity of about 90-95%, CO
Although the recovery rate is approximately 70%, the product CO purity is 98%.
%, the CO recovery rate decreased to about 30%, and it was found that it was extremely difficult to obtain a purity of 99% or higher.

This is because in the CO-PSA method, purity and recovery rate are generally in an almost contradictory relationship, and if you try to increase the purity, the amount of product CO gas required for the purge process will increase, and the recovery rate will increase. If you are trying to lower the recovery rate and increase the recovery rate, the product required for the purge process will be
This is because the purity cannot be sufficiently improved because the required amount of CO gas has to be reduced.

However, in recent years, with the diversification of raw materials for the chemical industry, the demand for CO gas for _C1 chemicals is expected to increase, and the chemical industry that uses steelworks byproduct gas as raw material is attracting attention. When considered together, it is possible to obtain higher purity and higher recovery rate.
A CO separation process is desired.

[Purpose of the invention]

The present invention improves the previously proposed CO separation method and provides a CO-PSA process characterized by a one-stage treatment capable of obtaining CO with higher purity and higher recovery rate.

[Summary of the invention]

The adsorbents used in the method of the invention do not differ in any way from those described in previous proposals. That is, Ni,
An adsorbent supporting one or a mixture of two or more of Mn, Rh, Cu(), and Ag is used, but the supported metals are
It is preferable to use Cu() as the main component.

A feature of the present invention is that the adsorption operation is performed using the adsorbent by the PSA method in a temperature range of more than 150°C and less than 250°C.

The equilibrium adsorption characteristics of CO and CO ₂ in this temperature range show that, compared to the previously proposed temperature range of 50°C to 150°C, the equilibrium adsorption amount of CO shows a decreasing trend, albeit extremely slowly, and in this respect, This results in an increase in the amount of adsorbent required per amount of gas to be treated, which is not a desirable operating condition.

However, the equilibrium adsorption amounts of CO ₂ and N ₂ are
Because it decreases extremely rapidly compared to CO,
Increase the adsorbed CO/CO ₂ ratio and CO/N ₂ ratio, i.e.
The selective adsorption capacity of CO can be greatly improved.

Furthermore, in the method of the present invention, compared to the previous proposal,
Because it operates at a higher temperature, the purging process can be carried out more efficiently in a shorter time when purging impurity gas between adsorbent particles and co-adsorbed impurity gas with product CO gas. I can tighten it.

Therefore, for these reasons, it is possible to obtain CO with higher purity and higher recovery rate than with the previously proposed method.

However, if the temperature is increased beyond 250°C, (1) the amount of CO adsorbed will further decrease, and the amount of adsorbent required per unit amount of gas to be processed will increase.

(2) Increased energy for heating the adsorption tower and/or process gas.

(3) Materials for solenoid valves, etc. of PSA equipment will become more expensive due to heat resistance considerations.

(4) Side reactions such as H ₂ - CO and H ₂ O - CO occur.

etc., it is not wise.

〔Effect of the invention〕

As shown above, the method according to the present invention not only eliminates the need to treat CO and CO 2 in two stages in separate steps as in the conventional method, but also eliminates the need for two-stage treatment of CO and CO ₂ in separate steps, as compared to the method previously proposed by the present inventors. Therefore, using the same adsorbent, it is only necessary to increase the adsorption operation temperature to a higher temperature.
In exactly the same equipment, if high purity and high recovery rate are desired, use the method of the present invention, and if higher purity and/or recovery rate are not required than the method of the present invention, use the previous method. Just use the proposed method, and by easily changing the operating conditions,
Purity and recovery rate can be controlled.

Note that the CO separation method of the present invention can be applied to CO, CO ₂ ,
Natural gas containing _N2 , _H2 , etc., reformed gas such as naphtha, gasification gas such as coal, coke and heavy oil, steelworks byproduct gas, especially blast furnace gas, converter gas, and oil refineries, It can be applied to by-product gas from petrochemical plants.

[Embodiments of the invention]

Examples are shown below.

Example 1 Create a 0.5N solution of CuCl ₂ , add 10 g of NaY zeolite and 50 ml of 0.5NCuCl ₂ solution to a 100 ml round bottom flask, attach a condenser to the round bottom flask, and heat under reflux at 100°C with a mantle heater for 2 hours. Summer. After electrostatic discharge, the supernatant was collected by decantation, and 50 ml of 0.5NCuCl ₂ solution was added thereto and refluxed in the same manner. The reflux operation was performed three times in total, and the zeolite was thoroughly washed with pure water and dried at 110℃.
It was crushed and fired in an electric furnace at 450°C for 2 hours to create an adsorbent. In addition, the recovered supernatant liquid and furnace liquid were mixed, and the amount of Na released was determined by flame light analysis, and the ion exchange rate was measured. As a result, the substitution rate was 83.5%. The obtained Cu()-Y type zeolite is 300
Cu()-Y by reduction under CO atmosphere for 60 min at °C
And so.

Put 2 g of the adsorbent prepared in this way into a 20 ml sample bottle and set it in a constant pressure adsorption amount measuring device.
The mixture was heated and evacuated at 10 ^-3 mmHg and 300°C for 2 hours to dehydrate.

Next, put the sample bottle into the silicone oil bath.
Leave it for 20-30 minutes, keeping it at the measurement temperature, and
Gas (purity 99.9% up) was fed into the tank, and the adsorption amount was measured until the saturated adsorption amount was reached to determine the dead volume. The measurement temperature was raised sequentially from about 0°C to about 300°C after measuring the saturated adsorption amount. After measurement, 300℃ again.
Desorption was carried out by heating at 10 ^-3 mmHg for 1 hour, and after cooling, the amount of adsorption was measured in the same manner as above using the gas to be measured. After completing the measurements for each of CO, CO ₂ and N ₂ , the sample was accurately weighed, and this value was used to determine the equilibrium adsorption amount per unit weight.

The results are shown in Figure 1. As mentioned in the previous proposal, the equilibrium adsorption amount of CO ₂ and CO reverses at about 50℃, but in the temperature range from 50℃ to 150℃, the equilibrium adsorption amount of CO and CO ₂ compared to that
CO/CO ₂ is 1.02 to 5.8, but in the temperature range of over 150°C and below 250°C, CO/CO ₂ exceeds 5.8 to 17.1, and the selective adsorption ability of the adsorbent for CO is extremely improved. I understand that.

Example 2 Using a PSA test apparatus equipped with four adsorption towers made of SUS304 and having a length of 2B x 800 mm, the relationship between the CO purity of the recovered gas and the recovery rate with respect to the adsorption operation temperature was determined.
Each tower is equipped with a mantle heater equipped with a temperature controller, so that the temperature inside the tower can be maintained within ±10°C of the set temperature.

Each column was filled with 860 g of 1/16" pellets of Cu()Y-type zeolite (containing 20% granulating agent) prepared under the same conditions as in Example 1, and heated to 300°C. , vacuum desorption was carried out by heating at 50 Torr for about 5 hours.Furthermore, after filling with pure CO gas, about 1/2
min, and was circulated for about 2 hours to reduce to Cu()Y.

The four-column PSA device is capable of repeating the adsorption step, purge step, desorption step, and pressure increase step as a normal method for recovering adsorbate.

Using the above apparatus, separation and purification of a mixed gas assuming a converter gas having the following composition was tested.

Gas composition: CO 74.5% CO ₂ 14.0% H ₂ 1.0% N ₂ 10.5% Setting conditions are adsorption temperature 165±10℃, adsorption pressure 1
Kg/cm ² G, desorption pressure is 50 Torr, and the ratio of purge gas amount to desorption gas amount and raw material gas supply amount are changed to keep the gas flow rate in the column almost constant, and the CO purity of the recovered gas and CO recovery rate are controlled. I sought a relationship with.

An example of the results is: Supply gas amount 0.76/min, purge amount/desorption amount
0.73, the CO recovery rate was 73%, and the recovered gas composition was CO 96.2% CO ₂ 3.0% N ₂ 0.7 H ₂ 0.1. Furthermore, the relationship between product CO purity and CO recovery rate is shown by the broken line in Figure 2.

Example 3 Using the same equipment and conditions as in Example 2, only the adsorption temperature was set at 210±10°C, and the relationship between product CO purity and recovery rate was determined.

An example of the results: Supply gas amount 0.70/min, purge amount/desorption amount
At 0.74, the CO recovery rate was 72%, and the recovered gas composition was CO 98.5% CO ₂ 1.0 N ₂ 0.4 H ₂ 0.1. Furthermore, the relationship between product CO purity and recovery rate is shown by the solid line in Figure 2.

From this result, it was found that by increasing the adsorption temperature compared to Example 1, the product could be improved for the same CO recovery rate.
It can be seen that by improving CO purity and lowering the CO recovery rate to approximately 50%, a product CO purity of 99% or higher can be obtained.

Example 4 Using the same equipment and conditions as in Example 2, only the adsorption temperature was set at 135±10° C., and the relationship between product CO purity and recovery rate was determined.

An example of the results is: Supply gas amount 0.72/min, purge amount/desorption amount
At 0.73, the CO recovery rate was 72%, and the recovered gas composition was CO 93.1% CO ₂ 5.2 N ₂ 1.4 H ₂ 0.3. In addition, the relationship between product CO purity and recovery rate is shown in Figure 2 by the dashed-dotted line.

From this result, when the adsorption temperature is below 150℃, the recovery rate is about 70%, but the product CO purity is 95%.
It can be seen that the recovery rate decreases to about 30% in order to maintain the product CO purity of about 98%.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the relationship between adsorbent temperature and the equilibrium adsorption amount of CO, CO ₂ and N ₂ , and Figure 2 is an explanatory diagram showing the relationship between CO purity of recovered gas and recovery rate at various adsorption operation temperatures. It is a diagram.

[Claims]

1 Average axial ratio of 1.0 or more and less than 3.0, average particle size of 0.1μm
Particles containing iron carbide with a diameter exceeding 5 μm or less. 2 (a) Average axial ratio of 1.0 or more and less than 3.0, average particle size
(b) After or without contacting a carbon-free reducing agent with iron oxyhydroxide or iron oxide having a size exceeding 0.1 μm and 5 μm or less, (b) a reducing carbonizing agent containing carbon or a reducing agent containing no carbon therewith; A method for producing iron carbide-containing particles having an average axial ratio of 1.0 or more and less than 3.0 and an average particle size of more than 0.1 μm and less than 5 μm, the method comprising contacting a mixture with an agent. 3 Iron oxyhydroxide is α-, β- or γ-
FeOOH, iron oxide is α- or γ-Fe ₂ O ₃ or
The manufacturing method according to claim 2, which is Fe ₃ O ₄ . 4. The manufacturing method according to claim 2, wherein the contact temperature in step (a) is 200 to 700°C, and the contact temperature in step (b) is 250 to 400°C. 5 The reducing carbonizing agent containing carbon is CO, CH ₃ OH,
The manufacturing method according to claim 2, wherein HCOOCH ₃ is a saturated or unsaturated aliphatic hydrocarbon having 1 to 5 carbon atoms. 6 Patent claims where the carbon-free reducing agent is _H2