JP2000272905A - Removal of organic impurity in methanol degradation gas by closed tsa method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing organic impurities, without requiring the expense fop a medium, an inlet-outlet treatment apparatus or the like, capable of stably producing highly pure CO gas without reducing the concentration of the CO as in a purified gas by using a methanol-decomposed gas in the system without using the gas introduced from the outside of the system of a TSA process apparatus. SOLUTION: This method for removing organic impurities in a methanol-decomposed gas by a TSA method of alternately carrying out the absorbing step and the heating and desorbing step, and using absorbing columns 6 and 7, carries out the first step for introducing the methanol-decomposed gas discharged from the absorbing column 6 in the heating and desorbing step, to a methanol-absorbing column 10 to allow a part of the organic impurities in the methanol-decomposed gas to be absorbed and removed, and in other hand, for returning the methanol-decomposed gas including the remainder of the organic impurities discharged from the methanol-absorbing column 10 to the absorbing column 7, and the second step for introducing unheated methanol- decomposed gas instead of the heated methanol-decomposed gas to previously cool the absorbing column 6, in order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a methanol decomposition gas generated when carbon monoxide is generated in a methanol decomposition process, wherein dimethyl ether, methyl formate, unreacted methanol and the like contained in the methanol decomposition gas are used. And a method for removing organic impurities by a closed TSA method.

[0002]

2. Description of the Related Art It has been known that carbon monoxide and hydrogen can be obtained by a methanol decomposition process.
The methanol decomposition process is a process in which methanol is decomposed to generate carbon monoxide and hydrogen, and carbon monoxide and hydrogen mixed in the methanol decomposition gas are further converted into CO-
It is separated by PSA or a cryogenic separation device, and each becomes a product gas.

However, in this decomposition process, in addition to carbon monoxide and hydrogen, reaction by-products such as dimethyl ether and methyl formate are generated and remain in the methanol decomposition gas, and unreacted methanol also remains. For this reason, in order to separate the methanol decomposition gas into products such as carbon monoxide and hydrogen, it is necessary to remove these organic impurities from the methanol decomposition gas in advance before separation by CO-PSA or the like. . As a method for removing organic impurities from the methanol decomposition gas, a method using methanol absorption and activated carbon adsorption is known. By passing the methanol decomposition gas through a methanol absorption tower or an activated carbon adsorption tower, the organic impurities are substantially removed. It is possible to obtain a purified gas that does not contain any. However, since the adsorbent used in the adsorption tower has a limited adsorption capacity, after adsorbing to some extent, the adsorbent must be desorbed by heating the adsorbent to regenerate the adsorbent. A TSA method (thermal swing method) has been conventionally known as a method for performing such an adsorbent regeneration step simultaneously with a purified gas production step. In the TSA method, two adsorption towers are used, one of which is used for a purification gas production step, and the other is used for a regeneration step by heating and desorbing the adsorbent. By repeating the process repeatedly in the adsorption tower, the production of the purified gas can be performed without interruption, and the production efficiency is high.

[0004] In the TSA method, a method for regenerating an adsorbent in an adsorption tower is as follows.
Nitrogen gas or purified gas is further purified by CO-PSA to produce a product gas. The residue is heated using an off-gas containing a small amount of organic impurities as a medium, introduced into an adsorption tower to desorb organic impurities and adsorbent. Is known, and then the adsorption tower is cooled.

[0005]

However, if nitrogen gas is used as a medium to be regenerated, it costs much to purchase nitrogen gas or to construct a facility for introducing and discharging nitrogen gas into the system of the TSA process apparatus. There is a problem. Further, when off-gas is used, there is a problem in that construction of a facility for introducing the off-gas into the system of the TSA process apparatus is costly.

Further, nitrogen gas and off-gas contain no or almost no organic impurities. For this reason, the adsorbent in the adsorption tower comes to adsorb CO gas instead of low-concentration organic impurities, and the concentration of CO gas in the obtained purified gas decreases, so that CO-PSA, cryogenic separation equipment, etc. There is a problem that the operation does not work well, the operation is difficult to continue, and the production of high-purity CO gas may be adversely affected.

Accordingly, an object of the present invention is to provide a method for removing organic impurities in a methanol decomposition gas by the TSA method, which does not use a gas introduced from outside the TSA process apparatus as a regeneration medium for the adsorption tower. The use of a gas eliminates the need for medium costs and the cost of introduction / emission treatment equipment, etc., and also provides a method for removing organic impurities that can obtain a high-purity purified gas without reducing the CO gas concentration in the purified gas. Is to provide.

[0008]

Under such circumstances, the present inventors have conducted intensive studies and as a result, have found that organic impurities in methanol decomposition gas are further absorbed into two absorption towers alternately performing adsorption and desorption by methanol absorption. A device equipped with a methanol absorption tower for absorbing and removing, a heating means for heating the methanol decomposition gas, and a preliminary adsorption tower provided as necessary, using methanol decomposition gas in the TSA process system as a regeneration medium for the adsorption tower, By circulating this gas through two adsorption towers, a methanol absorption tower, a heating means, and, if necessary, a pre-adsorption tower in a predetermined procedure, it was found that the above object was achieved, and the present invention was completed. Was.

That is, the invention according to claim 1 uses two adsorption towers that alternately perform an adsorption step and a heat desorption step, and one of the adsorption towers is in the adsorption step and passes methanol decomposition gas containing organic impurities. At the very least, organic impurities are adsorbed on the adsorbent to produce purified methanol decomposition gas substantially free of organic impurities, and the other adsorption tower is in a heating / desorption step, and the heated gas is introduced into the adsorption tower. In the method of removing organic impurities in the methanol decomposition gas by the TSA method of desorbing the organic impurities adsorbed on the adsorbent by
The methanol decomposition gas containing the organic impurities discharged from the adsorption tower in the heat desorption step is introduced into the methanol absorption tower to absorb and remove a part of the organic impurities in the methanol decomposition gas, while the methanol decomposition gas is discharged from the methanol absorption tower. A first step of returning the decomposed methanol-containing gas containing the remaining organic impurities to the adsorption tower in the adsorption step, replacing the heated methanol-decomposed gas in the other adsorption tower with an unheated methanol-decomposed gas. A method for removing organic impurities in a methanol decomposition gas by a closed TSA method, wherein a second step of introducing and precooling the other adsorption tower is sequentially performed. Therefore, the methanol decomposition gas in the system can be used as the regeneration medium of the adsorption tower without using a gas introduced from outside the TSA process system, and the cost of the medium and the cost of the introduction / discharge treatment equipment are unnecessary, and Without lowering the CO gas concentration in the purified gas,
A relatively high-purity purified gas having an organic impurity concentration of about several tens of ppm can be obtained.

Further, the invention according to claim 2 is characterized in that, following the second step, the raw material methanol decomposition gas is directly introduced into the other adsorption tower in a direction opposite to the gas flow in the second step. 2. The closed TSA according to claim 1, further comprising a third step of cooling the column and introducing the methanol decomposition gas discharged from the adsorption column to the methanol absorption column.
It is intended to provide a method for removing organic impurities in a methanol decomposition gas by a method. Therefore, in addition to having the same effect as the invention of claim 1, it is possible to cool the bottom of the adsorbent layer, which is insufficiently cooled by the preliminary cooling, and to stabilize the adsorption performance of the adsorption tower. .

Further, in the invention according to a third aspect, the heated methanol decomposition gas used in the thermal desorption step has been previously passed through a pre-adsorption tower to remove at least a part of organic impurities. And subsequent to the second step, the raw material methanol decomposition gas is directly introduced into the other adsorption tower in a direction opposite to the gas flow in the second step to cool the adsorption tower, and discharged from the adsorption tower. Heating the decomposed methanol gas into the pre-adsorption tower to heat and desorb the organic impurities in the pre-adsorption tower, and introducing the decomposed methanol gas discharged from the pre-absorption tower into the methanol absorption tower.
2. A method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to claim 1, wherein a step is provided. Therefore, the same effects as those of the first and second aspects of the present invention can be obtained. In addition, since a methanol decomposition gas containing no organic impurities is used in the heating / desorption step and the pre-cooling step, an organic impurity is not used in the subsequent adsorption step. Can be sufficiently and stably removed. Therefore, it is possible to obtain a highly purified gas having an impurity concentration of 1 ppm or less.

Further, the invention according to claim 4 is a method for regenerating methanol having absorbed organic impurities in a methanol decomposition gas in the methanol absorption tower, wherein the purified methanol decomposition gas is further purified by a CO-PSA method. 4. A gas stripping method or a distillation method using an off-gas after the separation.
The present invention provides a method for removing organic impurities in a methanol decomposition gas by the closed TSA method described in the above item. Therefore, if the off-gas after purification by the CO-PSA method in the subsequent step can be used, the off-gas is used. In an environment where the heat source is abundant, the heat source can be effectively used, and the scope of the selection of the regeneration method is widened.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a process flow sheet showing a method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to the first embodiment of the present invention. In FIG. 1, 4 is a preliminary adsorption tower filled with an adsorbent, 5 is a heating means, 6 and 7 are adsorption towers filled with an adsorbent, 10 is a methanol absorption tower, and 11 is a methanol regeneration tower. The methanol-decomposed gas generated by the methanol-decomposition process as a raw material is supplied into the system of the methanol-decomposed-gas removing apparatus of the present invention through the raw material main pipe 101 and the branch pipe 102. In the drawings, solid arrows indicate the flow directions of the methanol decomposition gas in the first and second steps, and broken arrows indicate the flow directions of the methanol decomposition gas in the third step (the same applies to FIGS. 2 and 3 hereinafter). is there.). The methanol decomposition gas contains, as organic impurities, unreacted by-products such as methanol, dimethyl ether, and methyl formate in addition to carbon monoxide and hydrogen, which are the target products obtained by decomposing methanol. The content of impurities is usually 0.3 to 0.6% by volume.

(First Step) In FIG. 1, the first step is the operation of valves 1 and 7
3, 64, 71 and 62 are open, valves 74, 64, 7
2 and 61 are closed, and the three-way valve 2a is connected to the pipes 101 and 103.
Are in a communicating state, and the three-way valve 2b is in a communicating state between the pipes 104 and 105. Also, the adsorption tower 7 is in the adsorption step,
Is in the thermal desorption step. Activated carbon is used as an adsorbent filled in the adsorption towers 6 and 7.

A part of the raw material methanol decomposition gas is supplied to the pipe 1
01 and 103, the mixture is introduced into the pre-adsorption tower 4, and a part of the organic impurities in the methanol decomposition gas is adsorbed and removed.
The pre-adsorption tower 4 is filled with an adsorbent such as activated carbon, and the amount of activated carbon can be reduced by removing some of the organic impurities in the methanol decomposition gas. In general, about 12 to 40 parts by weight, preferably about 30 to 40 parts by weight, is sufficient. The clean gas from which organic impurities have been removed in the preliminary adsorption tower 4 is supplied to the pipe 110.
Through the heating means 5 and usually heated to 150 to 250 ° C., preferably 170 to 220 ° C., and then introduced into the adsorption tower 6 in a downward flow as shown in the figure to desorb organic impurities and regenerate the adsorbent. . The methanol decomposition gas discharged from the adsorption tower 6 passes through the pipes 109, 104 and 105, is sequentially cooled by the absorption tower cooler 8 and the absorption tower heat exchanger 9, and is introduced into the methanol absorption tower 10. Unreacted methanol and organic impurities in the methanol decomposition gas discharged from the adsorption tower 6 are usually 0.3 to 1.2% by volume. In the methanol absorption tower 10, some of the organic impurities in the methanol decomposition gas are absorbed and removed by the methanol solution.

The methanol solution of the absorbent is circulated to the cooler 18, the methanol absorption tower 10 and the methanol regeneration tower 11 in this order by the operation of the pump 12.
The organic impurities in the methanol decomposed gas are absorbed and removed by being brought into countercurrent contact with the methanol decomposed gas introduced at 0. The temperature of the methanol solution supplied to the absorption tower 10 is usually -5 to
-15 ° C. The methanol solution having absorbed the impurities in the methanol decomposition gas is stripped by introducing the off-gas 16 in the regeneration tower 11, and the gas containing the organic impurities is discharged to the atmosphere as an off-gas from a discharge pipe 17 provided at the top of the tower. As the off-gas, an off-gas obtained by further purifying a methanol decomposition gas by a CO-PSA method can be used.

On the other hand, the methanol decomposition gas containing residual organic impurities discharged from the top of the methanol absorption tower 10 is heat-exchanged with the gas introduced into the methanol absorption tower 10 in the adsorption tower heat exchanger 9, and the pipe 107 is connected. Then, it is introduced into the adsorption tower 7 together with a part of the raw material methanol decomposition gas supplied from the pipe 102. In the adsorption tower 7, purified methanol-decomposed gas substantially containing no organic impurities is produced.
-Sent to a PSA or a cryogenic separator (not shown). The amount of organic impurities in the purified methanol decomposition gas is 1 ppm
It is as follows.

In the first step, when the inside of the adsorption tower 6 is sufficiently heated and organic impurities are desorbed from the adsorbent, the procedure shifts to the next second step. The transition is determined by temperature or time. For example, if the temperature in the center or bottom of the adsorption tower 6 is 1
For example, there is a method in which the temperature is raised to 00 ° C. or the temperature is shifted in advance when a predetermined time elapses. The time required for the first step is not particularly limited because it varies depending on the device specifications, but is, for example, 2 to 3 hours.

(Second Step) In the second step, the first
Except that the unheated methanol decomposition gas is introduced instead of the heated methanol decomposition gas in the step, and the other adsorption tower 6 is pre-cooled, the same as the first step, except that the adsorption tower 7 The adsorption tower 6 becomes a pre-cooling step. That is, the clean gas discharged from the preliminary adsorption tower 4 bypasses the heating means 5 (or the heating means 5 is turned off), and the piping 1
08 and is introduced into the adsorption tower 6. Thereby, the temperature of the methanol decomposition gas introduced into the adsorption tower 6 gradually decreases, and the adsorbent in the adsorption tower 6 is gradually cooled. The adsorption tower 6 is usually cooled to 50 to 100 ° C., preferably 70 to 90 ° C. by this pre-cooling. By providing the second step and the third step described below, the pre-cooled adsorbent can smoothly proceed to the adsorption step.

The second step shifts to the next third step when the inside of the adsorption tower 6, particularly the upper part and the central part, are sufficiently cooled.
The transition is determined by temperature or time. For example, there is a method in which the temperature in the tower at the center of the adsorption tower 6 is lowered to 50 ° C., or the flow shifts when a predetermined time has elapsed. The time required for the second step is not particularly limited because it varies depending on the device specifications.
0 minutes to 1 hour.

(Third Step) In FIG. 1, the state of the valve in the third step is a three-way valve 2a in which the pipes 101 and 104 are in communication with each other.
The three-way valve 2b is the same as the first step except that the pipes 103 and 105 are in communication with each other. The adsorption tower 7 is in the adsorption step, and the adsorption tower 6 is in the heat desorption step. That is, the methanol decomposition gas as a raw material at room temperature is directly introduced into the adsorption tower 6 through the pipes 101, 104, and 109 in the upward flow in the drawing, and the adsorbent in the adsorption tower 6 is further cooled. The methanol decomposition gas discharged from the adsorption tower 6 passes through the pipe 108, is heated to 150 to 250 ° C., preferably 170 to 220 ° C. by the heating means 5, and is introduced into the preliminary adsorption tower 4 through the pipe 110. The organic impurities are desorbed by heating to regenerate the adsorbent. The concentration of organic impurities in the methanol decomposition gas discharged from the adsorption tower 6 is usually 1 ppm or less. In addition, the preliminary adsorption tower 4
Organic impurities in methanol decomposition gas discharged from
Usually, it is 0.3 to 1.6% by volume. The methanol decomposition gas discharged from the preliminary adsorption tower 4 passes through the pipes 103 and 105, is sequentially cooled by the absorption tower cooler 8 and the absorption tower heat exchanger 9, and is introduced into the methanol absorption tower 10. The flow of the methanol solution absorbing the organic impurities and the flow of the methanol decomposition gas containing the remaining organic impurities discharged from the methanol absorption tower 10 are the same as those in the first step. In the third step, the adsorbent on the bottom side, which was insufficiently cooled by the preliminary cooling in the second step, is sufficiently cooled, so that an adsorption tower with more stable adsorption performance can be obtained. In addition, while the adsorbent in the preliminary adsorption tower 4 is regenerated, the organic impurities adsorbed in the preliminary adsorption tower 4 are released outside the system.

In the third step, when the inside of the adsorption tower 6 is sufficiently cooled, the process proceeds to the next fourth step. The transition is determined by temperature or time. For example, there is a method in which the temperature in the tower at the upper part of the adsorption tower 6 is lowered to 50 ° C., or the method is preset so as to shift when a predetermined time has elapsed.
The time required for the third step is not particularly limited because it varies depending on the device specifications, but is, for example, 1 to 2 hours.

(Fourth Step to Sixth Step) The fourth step is the first step, the fifth step is the second step, the sixth step is the third step, and the one adsorption tower 7 and the other adsorption tower 6 Are the same steps as those in which That is, FIG.
In the middle step, the valves 1, 74, 63, 72 and 61 are open, the valves 73, 63, 71 and 62 are closed and the three-way valve 2
In a, the pipes 101 and 103 are in communication with each other, the three-way valve 2b is in communication with the pipes 104 and 105, the adsorption tower 6 and the preliminary adsorption tower 4 are in the adsorption step, the adsorption tower 7 is in the heat desorption step, and the heating means 5 is in the ON state. It is. In the fifth step, the adsorption tower 6 and the preliminary adsorption tower 4 are in the adsorption step, the adsorption tower 7 is in the preliminary cooling step, and the heating means 5 is in the OFF state. In the sixth step, the adsorption tower 6 is in the adsorption step, the adsorption tower 7 is in the cooling step, the preliminary adsorption tower 4 is in the heating / desorption step, and the heating means 5 is in the ON state.

According to the method of the first embodiment of the present invention, the regeneration medium from which the organic impurities in the methanol decomposition gas have been removed in advance is introduced into the heat desorption step of the adsorption tower. In this, the organic impurities are sufficiently and stably removed. Further, since the concentration of the organic impurities in the obtained purified gas is low and stable, the composition of the purified gas supplied to the CO-PSA for further purifying the purified gas or the cryogenic separation device is small, and the normality of these devices is small. Does not hinder driving.

Next, a method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a process flow sheet showing the second embodiment. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted, and different points will be described. That is, in the second embodiment, the point different from the first embodiment is that in the first embodiment, the preliminary adsorption The point is that the removal of the organic impurities in the introduced methanol decomposition gas is omitted, and the regeneration of the preliminary adsorption tower 4 is omitted. Therefore, the heated or non-heated methanol decomposition gas supplied through the pipe 108 in the heating / desorption step and the pre-cooling step of the adsorption tower 6 in the first step and the second step contains organic impurities as raw material composition It is. Also, the third
The methanol decomposition gas after cooling the adsorption tower 6 in the process passes through the pipe 108, bypasses the heating means 5 (heating means is in an OFF state), passes through the pipes 110, 103, and 105 and absorbs the absorption tower cooler 8 and the absorption tower. The mixture is sequentially cooled by the heat exchanger 9 and introduced into the methanol absorption tower 10. According to the method of the second embodiment, the removing apparatus for performing the method can be simplified. The concentration of organic impurities in the purified gas obtained from the pipe 106 is, for example, several tens of pp.
m, which is higher than that of the first embodiment,
Other than that, the same operation as that of the first embodiment is exerted.

Next, a method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a process flow sheet showing the third embodiment. 3, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted, and different points will be described. That is, the third embodiment is different from the second embodiment in that the three-way valve 2a, the three-way valve 2b, and unnecessary piping related thereto are omitted in the second embodiment. , The third in the first and second embodiments
The point is that the cooling step of the adsorption tower using the raw material methanol decomposition gas in the step is omitted. According to the method of the third embodiment, a removing apparatus for performing the method can be simplified. Further, the concentration of organic impurities in the purified gas obtained from the pipe 106 is higher than that of the first and second embodiments, but otherwise, the same operation as the first and second embodiments is performed. Play.

The method for removing organic impurities by the closed TSA method of the present invention is not limited to the above embodiment, and various modifications or additions can be made without departing from the gist of the present invention. For example, in the method of regenerating methanol in the regenerator 11, organic impurities in the methanol solution may be removed by distillation using the regenerator 11 as a distillation column other than the stripping method. FIG. 4 is a process flow sheet when the regeneration tower 11 is a distillation tower in FIG. That is, in FIG. 4, a part of the methanol solution regenerated in the regeneration tower 11 and extracted from the bottom is heated by the reboiler 19,
It is returned to the regeneration tower 11 to maintain the temperature at the bottom of the regeneration tower. On the other hand, the remaining methanol solution extracted from the bottom is heat-exchanged with the methanol solution charged into the regeneration tower 11 by the heat exchanger 20, cooled by the cooler 18, and fed to the methanol absorption tower 10. Examples of the heat source 14 of the reboiler 19 include a heating medium oil, steam, and the like. In addition, piping 1
The off-gas released from 7 can be used as fuel for the heating medium heater.

The method for removing organic impurities by the closed TSA method of the present invention can be used for removing organic impurities in a methanol decomposition gas generated in a methanol decomposition process. Further, the purified gas produced by the removal method of the present invention is supplied to a CO-PSA apparatus or a cryogenic separation apparatus to be further purified and separated, and the further purified and separated gas is used as a high-purity gas in various organic chemicals. Used as raw material or reducing gas.

[0029]

Next, the present invention will be described more specifically with reference to examples. Example 1 Organic impurities in a methanol decomposition gas (hereinafter, also referred to as “raw material gas”) using an apparatus having the following specifications represented by the process flow sheet of FIG. 1 and according to the above-described first embodiment. Was removed. After one cycle of the first to sixth steps, the composition of the purified gas produced was, as a result of analysis, determined to be 66.6% hydrogen, 32.9% carbon monoxide, and carbon dioxide and methane as remaining gases. The concentration of organic impurities such as dimethyl ether, methyl formate and unreacted methanol was 1 ppm or less. From this result, it can be seen that the produced purified gas has a lower concentration of carbon monoxide than the composition of the raw material methanol decomposition gas, and only impurities have been removed.

(Organic impurity removal apparatus by closed TSA method) Material gas composition: 66.1% hydrogen, 32.7% carbon monoxide
%, Carbon dioxide 0.3% and methane 0.2% as residual gas, 870 ppm of dimethyl ether, 20 ppm of methyl formate, 0.5% of unreacted methanol ・ Supply amount of raw material gas: 42 m ³ / min ・ Adsorption Tower: activated carbon; Shirasagi pellets (manufactured by Takeda Pharmaceutical Co., Ltd.), the amount of activated carbon per unit is 3,700 kg. Preliminary adsorption tower: activated carbon; Shirasagi pellets (manufactured by Takeda Pharmaceutical Co., Ltd.), the amount of activated carbon per unit is 2, 000 kg ・ Temperature of heated methanol decomposition gas; 190 ° C. ・ First step: Required time 2.3 hours, temperature at bottom of adsorption tower 1
Switch to the second step at 00 ° C., and the ratio of the source gas supplied to the pipe 101 side in the source gas is 80%. ・ The second step: the required time is 0.5 hour, the temperature at the bottom of the adsorption tower is 5
Switch to the third step at 0 ° C. Third step: required time 1.2 hours, temperature 5 at the top of adsorption tower
Switch to 4th step at 0 ° C

[0031]

According to the method for removing organic impurities by the closed TSA method of the present invention, T is used as a regeneration medium for an adsorption tower.
By using methanol decomposition gas in the system without using gas introduced from outside the SA process system, there is no need for medium cost and introduction / discharge treatment facilities, etc., and the CO gas concentration in the purified gas is reduced. Without this, high-purity CO gas can be stably produced.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to a first embodiment of the present invention.

FIG. 2 is a flow sheet showing a method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to a second embodiment of the present invention.

FIG. 3 is a flow sheet showing a method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to a third embodiment of the present invention.

FIG. 4 is a process flow sheet showing a case where the regeneration tower is a distillation tower in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 61-64, 71-74 Valve 2a, 2b Three-way valve 4 Pre-adsorption tower 5 Heating means 6, 7 Adsorption tower 8 Absorption tower cooler 9 Absorption tower heat exchanger 10 Methanol absorption tower 11 Regeneration tower 12 Absorption tower circulation pump 14 Heat transfer oil 15 Cooling water 16 Off-gas from CO-PSA 17 Off-gas from regeneration tower 18 Methanol cooler 19 Reboiler 20 Heat exchanger 101-110 Piping

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takahiro Kobe 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo Co., Ltd. Cosmo Engineering Co., Ltd. (72) Inventor Masahiko Heijo 2-5 Higashishinagawa, Shinagawa-ku, Tokyo -8 Tennoshu Parkside Building Cosmo Engineering Co., Ltd. (72) Kazuhiko Takadono 2-5-2, Marunouchi, Chiyoda-ku, Tokyo Sanshi Gas Chemical Co., Ltd. (72) Tomofumi Ando 2-chome, Marunouchi, Chiyoda-ku, Tokyo 5-2 F-term (reference) in Mitsubishi Gas Chemical Co., Ltd. 4G040 FA04 FB01 FC02 FD02 FE06

Claims (4)

[Claims] 1. An adsorption step and a heat desorption step are alternately performed.
Using the base adsorption tower, one of the adsorption towers is in the adsorption step, and the methanol decomposition gas containing organic impurities is passed through, the organic impurities are adsorbed by the adsorbent, and the purified methanol decomposition substantially free of organic impurities is used. As well as producing gas,
The method for removing organic impurities in methanol-decomposed gas by a TSA method in which the other adsorption tower is in a heat desorption step and a heated gas is introduced into the adsorption tower to desorb organic impurities adsorbed on the adsorbent, The methanol decomposition gas containing the organic impurities discharged from the adsorption tower in the process is introduced into the methanol absorption tower to absorb and remove a part of the organic impurities in the methanol decomposition gas, while the residual gas discharged from the methanol absorption tower is removed. A first step of returning a methanol decomposition gas containing organic impurities to the adsorption tower in the adsorption step, introducing an unheated methanol decomposition gas into the other adsorption tower in place of the heated methanol decomposition gas. Organic impurities in a methanol decomposition gas by a closed TSA method, wherein a second step of pre-cooling the other adsorption tower is sequentially performed. How to remove things. 2. Following the second step, a raw material methanol decomposition gas is directly introduced into the other adsorption tower in a direction opposite to the gas flow in the second step to cool the adsorption tower. 3. A method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to claim 1, wherein a third step of introducing the methanol decomposition gas discharged from the reactor into the methanol absorption tower is provided. 3. The method according to claim 2, wherein the heated methanol decomposition gas used in the heating and desorbing step is one in which at least a part of organic impurities has been removed by passing through a pre-adsorption tower in advance, and Then, the methanol decomposition gas as a raw material is directly introduced into the other adsorption tower in a direction opposite to the gas flow in the second step to cool the adsorption tower, and the methanol decomposition gas discharged from the adsorption tower is heated. A third step of introducing into the pre-adsorption tower, heating and desorbing organic impurities in the pre-adsorption tower, and introducing the methanol decomposition gas discharged from the pre-absorption tower to the methanol absorption tower. Item 1. A method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to Item 1. 4. A method for regenerating methanol having absorbed organic impurities in a methanol decomposition gas in the methanol absorption tower, wherein a gas stream using an off-gas after purifying the purified methanol decomposition gas by a CO-PSA method. The method for removing organic impurities in a methanol decomposition gas by a closed TSA method according to any one of claims 1 to 3, wherein the method is a ripping method or a distillation method.