Method for removing phosphine from carbon monoxide gas by low temperature methanol absorption

Abstract

The application discloses a method for removing phosphine from carbon monoxide gas by using a low-temperature methanol absorbent, and comprises the following steps: introducing the CO gas containing PH3 into the bottom of an absorption tower, and making the CO gas contact with the methanol in the absorption tower in a countercurrent mode; controlling the temperature and pressure of the methanol; absorbing the PH3 in the CO gas into the methanol; discharging the purified CO gas from the top of the absorption tower and sending the CO gas to a next working section; introducing the methanol rich in PH3 and part of CO in the absorption tower into a flash tower, flashing out the CO and recycling the CO; introducing the methanol rich after the flashing into a hot regeneration tower, desorbing the PH3 by hot regeneration, obtaining lean methanol, and recycling the lean methanol by cooling and pressurizing and then introducing the lean methanol into the absorption tower again; and discharging the PH3 from the top of the hot regeneration tower and recycling the PH3. The method can realize deep purification and recycling of the PH3, and can solve the problems of low PH3 removal efficiency, high cost and secondary pollution in the phosphorus furnace tail gas.

Description

Technical Field

[0001] This invention relates to the field of phosphorus and coal chemical technology, and in particular to a method for removing phosphine from carbon monoxide gas using a low-temperature methanol absorbent. Background Technology

[0002] CO gas is an important chemical feedstock gas, used in the production of various chemical products such as synthetic ammonia, dimethyl ether, and methanol. The tail gas from the electric furnace process for producing yellow phosphorus, and the gas from the phosphorus coal gasification reactor (application number 202110736690.7), contains 80%–90% CO gas, but it also contains PH3 gas, which needs to be removed before further utilization. Currently, industrial methods for purifying PH3 from CO gas mainly include combustion and adsorption. Combustion can achieve a phosphorus removal rate of over 90%, but a small amount of PH3 and phosphoric acid mist is released into the atmosphere during the process, causing environmental pollution. This method converts PH3 into inexpensive phosphoric acid, resulting in low economic efficiency and severe equipment corrosion. Due to its relative simplicity, most companies directly burn the yellow phosphorus tail gas after pretreatment, leading to a waste of carbon and phosphorus resources and a carbon effect. Adsorption, represented by activated carbon, can purify the PH3 content to below 1 mg / Nm³, but this technology requires significant investment, has low activated carbon capacity, high regeneration energy consumption, and a small gas processing capacity. Due to current limitations in exhaust gas purification technology, only a few yellow phosphorus companies can deeply purify yellow phosphorus exhaust gas to obtain CO syngas for the production of downstream products. Summary of the Invention

[0003] The technical problem to be solved by this invention is how to provide a method that can achieve deep purification and recycling of PH3, and solve the problems of low PH3 removal efficiency, high cost, and secondary pollution in phosphorus furnace tail gas.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for removing phosphine from carbon monoxide gas using a low-temperature methanol absorbent, characterized by comprising the following steps:

[0005] CO gas containing PH3 is introduced into the bottom of the absorption tower and comes into countercurrent contact with methanol in the absorption tower. The temperature and pressure of the methanol are controlled to absorb the PH3 in the CO gas into the methanol. The purified CO gas is discharged from the top of the absorption tower and sent to the next stage for use.

[0006] The methanol-rich material that has absorbed PH3 and some CO in the absorption tower enters the flash evaporation tower, where CO is flashed out and recycled.

[0007] After flash evaporation, the rich methanol enters the thermal regeneration tower, where PH3 is desorbed through thermal regeneration to obtain lean methanol. The lean methanol is then cooled and pressurized before being recycled back into the absorption tower, while PH3 is discharged from the top of the tower for recovery.

[0008] A further technical solution is to control the methanol temperature in the absorption tower at -50℃ to -20℃ and the absorption tower pressure at 2 MPa to 8 MPa.

[0009] A further technical solution involves ensuring that the PH3 content in the CO synthesis gas purified by the absorption tower is less than 0.1 mg / Nm³. 3 .

[0010] A further technical solution is that after the methanol-rich methanol enters the flash distillation tower, more than 99% of the CO is flashed out and recovered, and the pressure of the flash distillation tower is controlled at 0.6 MPa ~ 1.4 MPa.

[0011] A further technical solution is as follows: the flash-evaporated rich methanol enters the thermal regeneration tower, and PH3 is desorbed from the rich methanol by changing the methanol temperature. The temperature of the thermal regeneration tower is controlled at 80~150 ℃, and the desorption rate of phosphine is greater than 98%.

[0012] The beneficial effects of adopting the above technical solution are as follows: 1) By controlling the temperature and pressure of methanol, CO gas and PH3 can be separated efficiently. The method is simple and highly efficient. 2) PH3 is physically absorbed by methanol, which has a large absorption capacity, can handle a large volume of gas, is simple to operate, has good stability, and a short process. 3) Methanol can be recycled, and the desorbed PH3 can be further recovered and reused without secondary pollution, making it a green process. Attached Figure Description

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0014] Figure 1 This is a schematic diagram of the structure of the device used in the method described in the embodiments of the present invention;

[0015] Wherein: 1-Absorption tower; 2-Flash tower; 3-Thermal regeneration tower. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0018] like Figure 1 As shown in the figure, this invention discloses a method for removing phosphine from carbon monoxide gas using a low-temperature methanol absorbent, comprising the following steps:

[0019] CO gas containing PH3 is introduced into the bottom of the absorption tower 1, where it comes into countercurrent contact with methanol inside the absorption tower 1. The temperature and pressure of the methanol are controlled to absorb the PH3 in the CO gas into the methanol. The purified CO gas is discharged from the top of the absorption tower 1 and sent to the next stage for use. The methanol rich in PH3 and some CO absorbed in the absorption tower 1 enters the flash evaporation tower 2, where CO is flashed off and recycled. The flash-evaporated methanol rich in PH3 enters the thermal regeneration tower 3, where PH3 is desorbed through thermal regeneration to obtain lean methanol. The lean methanol is cooled and pressurized and then re-enters the absorption tower for recycling. PH3 is discharged from the top of the thermal regeneration tower 3 for recycling.

[0020] The above method will be explained in detail below with specific parameters. Example 1

[0021] Will contain 3000 mg / m 3 PH3-containing CO gas is introduced into the bottom of the absorption tower, where it comes into countercurrent contact with methanol inside the tower. The methanol temperature is controlled at -20 °C, and the absorption tower pressure is 2 MPa. The mass content of PH3 in the CO synthesis gas after purification by the absorption tower is less than 0.1 mg / Nm³. 3 The methanol-rich product, having absorbed PH3 and some CO in the absorption tower, enters the flash distillation tower. The pressure in the flash distillation tower is controlled at 1.4 MPa, and 99% of the CO is flash-evaporated and recycled. The flash-evaporated methanol-rich product then enters the thermal regeneration tower, where the temperature is controlled at 80 ℃, and the desorption rate of PH3 is 98%. Example 2

[0022] Will contain 4000 mg / m 3 PH3-containing CO gas is introduced into the bottom of the absorption tower, where it comes into countercurrent contact with methanol inside the tower. The methanol temperature is controlled at -30 °C, and the absorption tower pressure is 3 MPa. The mass content of PH3 in the CO synthesis gas after purification by the absorption tower is less than 0.1 mg / Nm³. 3 The methanol-rich material, having absorbed PH3 and some CO in the absorption tower, enters the flash distillation tower. The pressure in the flash distillation tower is controlled at 1.2 MPa, and 99.2% of the CO is flash-evaporated and recycled. The flash-evaporated methanol-rich material then enters the thermal regeneration tower, where the temperature is controlled at 100 ℃, and the desorption rate of PH3 is 98.5%. Example 3

[0023] Will contain 5000 mg / m 3PH3-containing CO gas is introduced into the bottom of the absorption tower, where it comes into countercurrent contact with methanol inside the tower. The methanol temperature is controlled at -35 ℃, and the absorption tower pressure is 4 MPa. The mass content of PH3 in the CO synthesis gas after purification by the absorption tower is less than 0.1 mg / Nm³. 3 The methanol-rich material, having absorbed PH3 and some CO in the absorption tower, enters the flash distillation tower. The pressure in the flash distillation tower is controlled at 0.8 MPa, and 99.5% of the CO is flash-evaporated and recycled. The flash-evaporated methanol-rich material then enters the thermal regeneration tower, where the temperature is controlled at 120 ℃, and the desorption rate of PH3 is 99.3%. Example 4

[0024] Will contain 8000 mg / m 3 PH3-containing CO gas is introduced into the bottom of the absorption tower and comes into countercurrent contact with methanol inside the tower. The methanol temperature is controlled at -50 °C, and the absorption tower pressure is 8 MPa. The mass content of PH3 in the CO synthesis gas after purification by the absorption tower is less than 0.1 mg / Nm³. 3 The methanol-rich material, having absorbed PH3 and some CO in the absorption tower, enters the flash distillation tower. The pressure in the flash distillation tower is controlled at 0.6 MPa, and 99.9% of the CO is flash-evaporated and recycled. The flash-evaporated methanol-rich material then enters the thermal regeneration tower, where the temperature is controlled at 150 ℃, and the desorption rate of PH3 is 100%.

[0025] In summary, the method described achieves efficient separation of CO gas and PH3 by controlling the temperature and pressure of methanol. The method is simple and highly efficient. PH3 is physically absorbed by methanol, which has a large absorption capacity, can handle large gas volumes, is simple to operate, has good stability, and a short process flow. Methanol can be recycled, and the desorbed PH3 can be further recovered and reused, resulting in no secondary pollution; it is a green process.

Claims

1. A method for removing phosphine (PH3) from a carbon monoxide (CO) gas in a low temperature methanol absorbent, characterized in that Comprising the following steps: CO gas containing PH3 is introduced into the bottom of the absorption tower (1) and contacted with methanol in the absorption tower (1) in countercurrent, the temperature and pressure of the methanol are controlled, PH3 in the CO gas is absorbed into the methanol, and the purified CO gas is discharged from the top of the absorption tower (1) and sent to the next section for use; The methanol rich in PH3 and part of CO in the absorption tower (1) enters the flash tower (2), CO is flashed out and recycled; The flashed methanol rich enters the hot regeneration tower (3), PH3 is desorbed by hot regeneration, and lean methanol is obtained, the lean methanol is cooled and pressurized to enter the absorption tower again for recycling, and PH3 is discharged from the top for recycling; The temperature of the methanol in the absorption tower (1) is controlled at -50℃ to -20℃, and the pressure of the absorption tower (1) is controlled at 2 MPa to 8 MPa; The mass content of PH3 in the CO synthesis gas purified by the absorption tower (1) is lower than 0.1 mg / Nm 3 ; After the methanol rich enters the flash tower (2), more than 99% of the CO is flashed out and recycled, and the pressure of the flash tower (2) is controlled at 0.6 MPa to 1.4 MPa; The flashed methanol rich enters the hot regeneration tower (3), PH3 is desorbed from the methanol rich by changing the methanol temperature, the temperature of the hot regeneration tower (3) is controlled at 80-150 ℃, and the desorption rate of PH3 is greater than 98%.

Images