KR0173399B1 - Method for manufacturing carbon dioxide by pressure swing absorption - Google Patents

Abstract

The present invention provides a method for separating and recovering high-purity CO ₂ from a mixed gas containing CO ₂ by operating an adsorption tower filled with an adsorbent for selectively adsorbing CO ₂ by a pressure swing adsorption method. -When the adsorption amount of CO ₂ is large at the low pressure but the cleaning step is desorption step, since the amount of CO ₂ remaining in the adsorbent after the desorption step is large, it relates to a method for recovering this to increase the efficiency of the process, In addition to the process configuration, adsorption exhaust gas low pressure washing step and adsorption are carried out by introducing a flue gas having a low CO ₂ concentration discharged from the adsorption step of the other tower into the countercurrent to displace the CO ₂ remaining in the adsorption tower after the desorption system. by supplying a high concentration of CO ₂ off-gas discharged from the low pressure off-gas cleaning step to another adsorption tower is over CO ₂ step A low pressure clean flue gas adsorption step was introduced, and a low pressure adsorption flue gas low pressure and a cleaning step were introduced to the tower where the exhaust gas of the adsorption step with a low CO ₂ concentration was introduced into the counter current to direct the adsorption line of CO _{2 to} the inlet of the adsorption tower. The pressure step was added to lower the concentration of CO ₂ in the flue gas discharged from the adsorption step proceeding after the adsorption flue gas reverse compression step. By doing so, it was possible to produce high purity CO ₂ product gas with high recovery rate, and the process configuration devised in the present invention is based on one adsorption tower, and the adsorption exhaust gas reverse pressure step-boosting step-adsorption step-low pressure cleaning flue gas adsorption step is sequentially. -Cleaning step-desorption step-adsorption flue gas low pressure cleaning step.

Description

Pressure fluctuation adsorption high purity carbon dioxide manufacturing method

1 is an equilibrium adsorption isotherm of carbon dioxide and nitrogen on a zeolite molecular sieve.

2 is a three- tower PSA apparatus for producing high purity CO ₂ .

3 is a three-top CO₂ Process diagram of PSA device.

[Purpose of invention]

The present invention provides a recovery rate of carbon dioxide in a method for separating and recovering high purity carbon dioxide from a mixed gas containing CO ₂ by operating an adsorption tower packed with an adsorbent for selectively adsorbing CO ₂ by pressure swing adsorption (PSA). It relates to a process configuration and operation method for increasing.

[Technical field to which the invention belongs and the prior art in that field]

In general, the fixed structure of the apparatus for recovering CO ₂ at high purity by a PSA method using a selective adsorbability is greater adsorbent is packed adsorption column for CO ₂ is sequentially step-up step-by-consists of a desorption step - the adsorption step and the cleaning step . The process is described in detail, by introducing a source gas containing CO ₂ into the desorption adsorption tower to raise the pressure of the tower to the adsorption pressure, while supplying the raw material gas to the adsorption tower after the boosting step is completed, CO ₂ is supplied to the adsorbent. to selectively adsorb and tower exit by introducing a portion of the product CO ₂ gas discharged from the adsorption step, desorption step of the other tower in the adsorption tower adsorption step over to discharge the remaining gas in co-current, such as the direction of flow of the source gas CO ₂ As shown in Fig. ₂ , a vacuum pump is used to purify the pressure of the adsorption tower after the step of desorbing and adsorbing other gases adsorbed to the gas, and to remove the gases other than the CO _{2 in the} adsorption tower cavity to increase the CO ₂ concentration in the adsorption tower. 70 under reduced pressure to about ₂ Torr to remove the CO adsorbed is composed of desorption step that takes the product gas switch each of the adsorption towers with each other This operation is not overlap.

However, as shown in FIG. 1, the adsorption amount of CO _{2 on} the adsorption column such as zeolite molecular sieve is very large even at low pressure of 50 to 70 Torr or less. CO ₂ remains and the efficiency of the process is reduced.

[Technical problem to be achieved]

Therefore, in the present invention, CO ₂ remaining in the process configuration edaga desorbed adsorption step is introduced to the low CO ₂ concentration exhaust gas discharged from the adsorption step of the other tower in the adsorption tower over a counter-current end of the desorption step in order to increase the recovery of CO ₂ a was introduced into a replacement detachable suction-gas low-pressure washing step and the adsorption-gas low-pressure washing with a CO ₂ concentration of the high-gas discharged from the step-fed to another tower adsorption step over a low-pressure cleaning exhaust gas adsorbing step for adsorbing the CO ₂ which, again suction-gas The adsorption step proceeds after the adsorption exhaust gas reverse compression step by introducing the adsorption exhaust gas reverse compression step that introduces the flue gas of the adsorption step with low CO ₂ concentration into the countercurrent to direct the adsorption wire of CO _{2 to} the inlet tower entrance. CO ₂ concentration in the flue gas discharged from the By doing so, it was possible to produce high purity CO ₂ product gas with high recovery rate, and the process configuration devised in the present invention is based on one adsorption tower, and the adsorption flue gas reverse pressure step-boosting step-adsorption step-low pressure cleaning flue gas is sequentially adsorbed. Step-cleaning step-desorption step-sorption exhaust gas low pressure cleaning step.

[Configuration and Function of Invention]

Hereinafter, an embodiment of manufacturing high-purity CO ₂ using a PSA apparatus using three adsorption towers filled with an adsorbent for selectively adsorbing CO ₂ based on the _second and third aspects of the present invention will be described in detail. I will explain.

The process configuration and operation method will be described with reference to the first adsorption tower 1A in a vacuum state after the adsorption flue gas low pressure cleaning step in the three tower PSA apparatus of FIG. A low suction-gas CO ₂ concentration in the adsorption step in the adsorption tower 1A H3-gas storage tank in the vacuum pipe 4. The entrance of the tower inside the CO ₂ adsorption front is supplied in counter-current through the valve 22 while increasing the pressure of the column top To the back (sorption exhaust gas reverse pressure step). In the meantime, the second adsorption tower 1B performs the desorption step and the third adsorption tower 1C performs the cleaning step. After closing the valve 22 and ending the adsorption exhaust gas reverse pressure step, the source gas containing CO ₂ is supplied to the first adsorption tower 1A through the source gas supply pipe 2 and the valve 10 by the blower B1 to boost the pressure of the tower to the adsorption pressure. (Boost step). In the meantime, the second adsorption tower 1B performs the desorption step and the third adsorption tower 1C performs the cleaning step. After the boosting step, CO ₂ is adsorbed while continuously supplying raw material gas through valve 10 to the first adsorption tower 1A, and valve 19 is opened at the outlet to send exhaust gas having low CO ₂ concentration to adsorption exhaust gas storage tank H3, and adsorption exhaust gas is stored in the storage tank. It is discharged out through H3 (adsorption step). In the meantime, the second adsorption tower 1B performs the desorption step and the third adsorption tower 1C performs the cleaning step. After the adsorption step is completed, the low pressure clean exhaust gas higher than the CO ₂ concentration in the source gas discharged from the second adsorption tower 1B in the adsorption exhaust gas low pressure cleaning step is discharged to the tube 8, the valve 29, the low pressure clean gas storage tank H1, the tube 9, the valve 30, The valve 10 is introduced into the first adsorption tower 1A to adsorb the CO ₂ , and the remaining gas is sent to the adsorption exhaust gas storage tank H3 through the valve 19 (low pressure washing gas adsorption step). During this time, the third adsorption tower 1C performs a cleaning step. After the valves 10 and 19 are locked and the low pressure clean flue gas adsorption step is completed, high-purity CO ₂ gas is introduced from the product gas reservoir H2 through the tube 7, valve 13, and other adsorption such as CO ₂ is adsorbed to the first adsorption tower 1A. At the same time, the gas is replaced with desorption, and at the same time, gases other than CO _{2 in the} adsorption tower pores are washed out to increase the concentration of CO _{2 in the} adsorption tower. While the first adsorption tower 1A performs the cleaning step, the second adsorption tower 1B receives the adsorption exhaust gas reverse pressure step-up step-adsorption step-low pressure clean exhaust gas adsorption step and the third adsorption tower 1C performs the desorption step-adsorption exhaust gas low pressure cleaning step. Each is performed sequentially. In the first adsorption tower 1A having the cleaning step, the valves 13 and 25 are closed and the valve 16 is opened to enter the desorption step. In this desorption step, the vacuum pump V1 drops the pressure of the first adsorption tower, desorbs the adsorbed CO ₂ , and sends it to the product gas storage tank H2 through tube 6 and valve 28, and some of the CO ₂ gas sent to the product gas storage tank is removed. It is used as the cleaning gas of the two adsorption tower 1B, and the rest is obtained as product gas (desorption step). While the first adsorption tower 1A performs the desorption step, the second adsorption tower 1B sequentially performs the cleaning step, and the third adsorption tower 1C performs the adsorption exhaust gas reverse pressure step-up step-adsorption step. In the first adsorption tower 1A where the valve 28 is closed and the desorption step is completed, the adsorption exhaust gas is introduced from the adsorption exhaust gas storage tank H3 through the tube 4 and the valve 22 to replace and desorb the remaining CO ₂ to the tower 1A. It is exhausted by the vacuum pump through the tube 8, valve 29 is sent to the low pressure wash gas storage tank H1, and then supplied to the third adsorption tower 1C in the low pressure wash gas suction step through the tube 9, valve 30, valve 12 (adsorbed exhaust gas). Low pressure cleaning step). During this time, the second adsorption tower 1B performs a cleaning step.

[Effects of the Invention]

Thus desorption to remove the CO ₂ remaining in the column after the step, introduction of the suction-gas low-pressure washing step to recover and introduce in this step the CO ₂ concentration, high gas a low-pressure cleaning exhaust gas absorption step than the raw material gas that is discharged from the CO ₂ It is possible to obtain high purity CO ₂ at a high recovery rate by adsorbing and recovering and introducing an adsorption exhaust gas reverse compression step to lower the concentration of CO ₂ in the exhaust gas discharged from the adsorption step.

Example 1

Zeolite 13X as the adsorbent in a 0.5 liter filling 3 tapsik PSA unit _{25 vol.% CO 2/74} vol.% N 2/1 vol. By supplying a mixed gas consisting of% O ₂ The process of the present invention shown in FIG. 3 Table 1 shows the results when operating with the configuration and when operating with the conventional process consisting of the boost step, the adsorption step, the cleaning step and the desorption step. As shown in Table 1, at a CO ₂ concentration of 99 vol.%, The conventional process yields 60% recovery and productivity 0.948 N1 / (kg.min), whereas the process of the present invention yields 80% recovery and productivity 1.087 N1 (kg.min). Recovery and productivity increased by 33% and 14.7%, respectively. At 95 vol.% Of CO ₂ concentration, the existing process has a recovery of 71% and a productivity of 1.146 N1 (kg.min). The process of the present invention has a recovery of 90%, a productivity of 1.25 N1 (kg.min) and a recovery of 27% and a productivity of 5.4. There was an improvement of about%.

The recovery rate = (CO ₂ amount in the product gas / raw material gas in the CO ₂ amount) × 100 and the productivity is the amount of product gas produced per unit time per unit adsorbent.

Claims (2)

From a mixed gas containing CO ₂ to a pressure change adsorption using adsorption towers packed with an adsorbent which selectively adsorbs the CO ₂ A method for separation and recovery of high purity CO _2, (1): the mixed gas as a raw material gas Adsorption step of supplying to the inlet of the adsorption tower to adsorb CO ₂ , a strongly adsorbent gas, and discharge the weakly adsorbent gas to the exit of the tower. (2): Adsorption flue gas to the inlet of the adsorption tower after the adsorption step is completed Adsorption flue gas (2) is introduced with a flue gas having a higher CO ₂ concentration than the source gas discharged from the low pressure cleaning step to adsorb CO ₂ and discharge the weak adsorbent gas toward the exit of the tower. Low pressure wash gas adsorption step. (3): To the inlet of the adsorption tower where the low pressure clean exhaust gas adsorption step is completed, a portion of the high-purity CO ₂ gas discharged from the desorption step shown in (4) is introduced to wash out the gas other than the CO ₂ remaining in the tower to the exit of the tower. A washing step to increase the CO ₂ concentration in the tower while discharging. (4): Desorb the CO ₂ adsorbed by dropping the pressure of the adsorption tower after the cleaning step is removed from the inlet side of the tower to recover high purity CO ₂ , and use some of it as the cleaning gas for the cleaning step. Desorption step to take. (5): Adsorbent exhaust gas having a low CO ₂ concentration discharged from the step (1) or (2) is introduced to the outlet of the adsorption tower after the desorption step is completed, and the remaining CO ₂ is replaced and desorbed after the desorption step is completed. Low pressure cleaning step for adsorption exhaust gas discharged to the inlet. (6): Adsorbent exhaust gas The exhaust gas discharged in the step (1) or (2) or (3) is introduced from the outlet side of the adsorption tower after the low pressure cleaning step, and the CO ₂ adsorption wire in the tower is directed to the inlet of the tower. Adsorption flue gas reverse pressure step to increase the pressure of the tower, (7): Continuous process while repeating the process consisting of the stepping up step of raising the pressure of the tower to near the suction step pressure by introducing raw gas to the inlet of the column where the adsorption flue gas reverse pressure step is completed. a pressure swing adsorption process for producing high purity CO _2, characterized in that the recovery of high purity CO _2. The process according to claim 1, wherein the exhaust gas discharged from the cleaning step 3 is introduced instead of the boosting step 7 by the source gas to raise the pressure of the adsorption tower to the vicinity of the adsorption step pressure. Method of recovering CO ₂ .