CN113736523A - Separating CO from synthetic gas2Method and apparatus of - Google Patents

Abstract

The invention belongs to the technical field of industrial energy conservation, and provides a method for separating CO from synthesis gas₂The synthesis feed gas is passed through gaseous CO₂Cooling, rich in CO₂Methanol desulfurization and low-temperature desorption of gaseous CO₂Cooled, liquid CO₂Evaporative cooling, gas-liquid separation, CO content₂CO removal from methanol liquid₂And removing CO again from the methanol-poor liquid₂And obtaining the purified synthesis gas. The invention provides a method for separating CO from synthesis gas₂The method comprehensively utilizes the energy in the system: the liquid carbon dioxide is used for evaporating and resolving carbon dioxide as a cold source, and cooling steps in the synthetic gas decarburization process saves cooling energy; meanwhile, a part of high-pressure gaseous carbon dioxide is generated, so that the subsequent compression power consumption can be saved; the decarbonization and the desulfurization of the methanol are used in sequence, so that the methanol circulating power consumption can be reduced. The method can effectively reduce and separate CO in the synthesis gas₂The power consumption of the power supply system is reduced,more energy-saving and environment-friendly and has high economical efficiency.

Description

Separating CO from synthetic gas2Method and apparatus of

Technical Field

The invention relates to the technical field of industrial energy conservation, in particular to a method for separating CO in synthesis gas by condensing low-temperature flash evaporation gas₂The method of (1).

Background

CO after syngas shift₂Content 43% of H₂S content is 0.05-0.15%, the currently common desulfurization and decarburization process is low-temperature methanol washing, and synthesis gas is washed with H through low-temperature methanol washing₂S、CO₂Is sequentially absorbed by low-temperature methanol, the synthesis gas is purified, and H is absorbed₂S、CO₂The methanol-rich liquid is flashed to separate CO₂The pressure is 0.25MPa, and the urea removing process is carried out by four-stage compression pressurization to 15MPa by a carbon dioxide compressor. Because the compression ratio is large and the power consumption is high, research on separating the CO from the synthesis gas with low energy consumption₂The method of (1) is very necessary.

Disclosure of Invention

Aiming at the current synthesis gas CO₂The invention provides a method for separating synthesis gas CO, which solves the problem of high separation energy consumption₂Method of condensing CO-rich gas using low temperature flash gas₂Synthesis gas thereby to convert CO₂The liquid is changed into liquid to realize separation, and a large amount of power consumption is saved.

In order to achieve the purpose, the invention adopts the following technical scheme.

Separating CO from synthetic gas₂The method comprises the following steps:

(1) high pressure synthesis of raw gas by high pressure gaseous CO₂And low pressure gaseous CO₂Cooling to-15 to-20 ℃ to obtain low-temperature high-pressure synthesis feed gas, and generating high-temperature low-pressure CO₂And high temperature high pressure CO₂Going to a urea process;

(2) low temperature high pressure synthesis of feed gas to enrich CO₂Desulfurizing methanol to obtain desulfurized synthesis gas and generating methanol-rich liquid; sequentially resolving H by the methanol-rich liquid₂S and CO₂And through a regeneration process, the lean nail is obtainedAlcohol liquid to produce low temperature desorption gaseous CO₂And H₂S；

(3) Low-temp. desorption of gaseous CO from desulfurized synthetic gas₂Cooling to-40 to-45 ℃ to obtain liquid CO₂To produce low pressure gaseous CO₂Returning to the step (1);

(4) entrained liquid CO₂Passing the desulfurized synthesis gas through liquid CO₂Evaporating and cooling to-45 to-50 ℃ to obtain a gas-liquid mixture, and generating low-temperature high-pressure gaseous CO₂Returning to the step (1);

(5) carrying out gas-liquid separation on the gas-liquid mixture to obtain primary decarbonized synthesis gas and generate liquid CO₂Returning to the step (4);

(6) the first decarbonization synthesis gas contains CO₂CO removal from methanol liquid₂Obtaining a second decarbonized syngas to produce a CO-rich₂Methanol is returned to the step (2);

(7) removing CO again from the secondary decarbonized synthetic gas at the temperature of-56-60 ℃ through poor methanol liquid₂Obtaining purified synthesis gas to produce CO-containing₂And (5) returning the methanol liquid to the step (6).

In the synthesis raw material gas, CO₂The content is 35-45% v/v, H₂The S content is 0.05-0.15% v/v.

The pressure of the synthesis raw material gas is 5.9-6.2 MPa.

In the step (1), the high-pressure gaseous CO₂The temperature of the mixture is-45 to-53 ℃; the low-pressure gaseous CO₂The temperature is-53 ℃ to-55 ℃. The high temperature low pressure CO₂The pressure of (A) is 0.21-0.25MPa, and the high-temperature high-pressure CO is₂The pressure of (A) is 0.62-0.65 MPa.

In the step (3), the pressure of the desulfurized synthesis gas is 2.1-2.58 MPa.

In the purified synthesis gas, CO₂Content 5ppm, H₂The S content was 0.1 ppm.

Separating CO from synthetic gas₂The apparatus of (1), comprising:

a first cooler, a washing tower and H connected in sequence through pipelines₂S flash column, CO₂Flash column, secondary cooler, CO₂An evaporator andCO₂a separator;

the washing tower is sequentially provided with an upper seal head, a middle seal head and a lower seal head from top to bottom and is sequentially divided into a first washing area, a second washing area, a third washing area and a fourth washing area from bottom to top; the lower end enclosure is in an inverted U shape, the upper end enclosure and the middle end enclosure are flat plates, an air outlet is formed in the center of the upper end enclosure and the middle end enclosure, and a guide plate is arranged above the air outlet; the third washing area is connected with the first washing area through a pipeline; the top of the lower end socket is provided with a pipeline connected with a second cooler; the lower part of the first washing area is provided with a pipeline connected with a first cooler; the lower part of the second washing area is provided with a pipeline and CO₂Connecting a separator; a pipeline is arranged at the upper part of the fourth washing area; the bottom of the washing tower is provided with a pipeline and H₂S, connecting a flash tower; an air outlet pipe is arranged at the top of the washing tower;

said H₂The top of the S flash tower is provided with an air outlet pipe, and the bottom of the S flash tower is provided with a pipeline and CO₂Connecting a flash tower;

the CO is₂An air outlet pipe is arranged at the top of the flash tower and connected with the second cooler, and a discharge pipe is arranged at the bottom of the flash tower;

the second cooler is respectively communicated with CO through pipelines₂The evaporator is connected with the first cooler;

the CO is₂The evaporator is provided with an air outlet pipe and a discharge pipe, the air outlet pipe is connected with the first cooler, and the discharge pipe is connected with the CO₂Connecting a separator;

the CO is₂The bottom of the separator is provided with a discharge port, the top of the separator is provided with an air outlet pipe, and the discharge port is connected with CO₂And the air outlet pipe is connected with the second washing area of the washing tower.

The invention has the following advantages:

the invention provides a method for separating CO from synthesis gas₂The method comprehensively utilizes the energy in the system: the liquid carbon dioxide is used for evaporating and resolving carbon dioxide as a cold source, and cooling steps in the synthetic gas decarburization process saves cooling energy; meanwhile, a part of high-pressure gaseous carbon dioxide is generated, so that the subsequent compression power consumption can be saved; the decarbonization and the desulfurization of the methanol are used in sequence, so that the methanol circulating power consumption can be reduced. TheThe method can effectively reduce and separate CO in the synthesis gas₂The power consumption is more energy-saving and environment-friendly, and the economy is high.

The device of the invention connects the cooler with the carbon dioxide, thus fully utilizing the energy in the system; in the equipment, the desulfurization equipment and the decarburization equipment are integrated in the same washing tower, so that the circulation flow of the methanol is shortened, and the circulation power of the methanol is reduced. The device reduces the equipment number of the synthetic gas decarburization process and reduces the power consumption.

The method and the device can reduce the circulation amount of the low-temperature methanol by over 75 percent and reduce the power consumption of the circulating pump. Separated CO₂Containing a part having a high gas pressure, to make 1Nm per compression³ CO₂The compression work can be saved by 55w, and at least 22 kW.h of electric energy can be saved per ton of urea.

Drawings

FIG. 1 is a diagram showing the separation of CO from syngas₂A schematic flow diagram of (a);

FIG. 2 is a diagram showing the separation of CO from syngas₂Schematic diagram of the apparatus of (1); wherein 1-scrubber, 2-second cooler, 3-CO₂Evaporator, 4-first cooler, 5-CO₂Separator, 6-H₂S flash column, 7-CO₂And (4) a flash tower.

Detailed Description

The present invention will be further described with reference to the following examples and drawings, but the present invention is not limited to the following examples.

Example 1 CO in syngas₂Separation of

The apparatus shown in FIG. 1 separates CO from syngas₂The process shown in figure 2 comprises the following steps:

(1) high pressure synthesis raw material gas (wherein, CO) with pressure of 5.9-6.2MPa₂The content is 35-45% v/v, H₂S content of 0.05-0.15% v/v) high-pressure gaseous CO at-45 to-53 DEG C₂And low-pressure gaseous CO at-53 to-55 DEG C₂Cooling to-14.9 deg.C to obtain low-temperature high-pressure synthesis raw material gas, and generating high-temperature low-pressure CO of 0.21-0.25MPa₂And 0.62-0.65MPa of high-temperature high-pressure CO₂Compressing the mixture to 15MPa and then going to a urea process;

(2) low temperature high pressure synthesis of feed gas to enrich CO₂Desulfurizing methanol to obtain desulfurized synthesis gas and generating methanol-rich liquid; sequentially resolving H by the methanol-rich liquid₂S and CO₂And through the regeneration process, obtaining methanol-poor liquid and generating low-temperature desorption gaseous CO₂And H₂S，H₂S, absorbing and recovering S;

(3) the desulfurized synthesis gas with the pressure of 2.1-2.58MPa is subjected to low-temperature desorption of gaseous CO₂Cooling to-40 to-45 ℃ to obtain liquid CO₂To produce low pressure gaseous CO₂Returning to the step (1);

(4) entrained liquid CO₂Passing the desulfurized synthesis gas through liquid CO₂Evaporating and cooling to-45 to-50 ℃ to obtain a gas-liquid mixture, and generating low-temperature high-pressure gaseous CO₂Returning to the step (1);

(5) carrying out gas-liquid separation on the gas-liquid mixture to obtain primary decarbonized synthesis gas and generate liquid CO₂Returning to the step (4);

(6) the first decarbonization synthesis gas contains CO₂CO removal from methanol liquid₂Obtaining a second decarbonized syngas to produce a CO-rich₂Methanol is returned to the step (2);

(7) removing CO again from the secondary decarbonized synthesis gas by using the methanol-poor liquid and the new methanol or the methanol-poor liquid added with the new methanol₂Obtaining purified synthesis gas to produce CO-containing₂Returning the methanol solution to the step (6); purifying the synthesis gas.

Example 2 separation of CO from syngas₂In a device (2)

Separation of CO from syngas as shown in FIG. 1₂Apparatus of, comprising

A first cooler 4, a washing tower 1, H connected in sequence by pipelines₂S flash column 6, CO₂Flash column 7, second cooler 2, CO₂Evaporator 7 and CO₂A separator 3;

the washing tower 1 is sequentially provided with an upper seal head, a middle seal head and a lower seal head from top to bottom and is sequentially divided into a first washing area, a second washing area, a third washing area and a fourth washing area from bottom to top; the lower end enclosure is in an inverted U shape, and the upper end enclosure 1-1 and the middle end enclosure are flat plates and are arranged in the middleThe core is provided with an air outlet, and a guide plate is arranged above the air outlet; the third washing area is connected with the first washing area through a pipeline; the top of the lower end socket is provided with a pipeline which is connected with the second cooler 2; the lower part of the first washing area is provided with a pipeline which is connected with a first cooler 4; the lower part of the second washing area is provided with a pipeline and CO₂The separator 5 is connected; a pipeline is arranged at the upper part of the fourth washing area and is used for feeding methanol; the bottom of the washing tower 1 is provided with a pipeline and H₂S, connecting a flash tower 6; an air outlet pipe is arranged at the top of the washing tower 1 and used for discharging purified synthesis gas;

said H₂The top of the S flash tower 6 is provided with an air outlet pipe, and the bottom is provided with a pipeline and CO₂The flash tower 7 is connected;

the CO is₂An air outlet pipe arranged at the top of the flash tower 7 is connected with the second cooler 2, and a discharge pipe for discharging lean solution is arranged at the bottom of the flash tower;

the second cooler 2 is respectively communicated with CO through pipelines₂The evaporator 3 is connected with the first cooler 4;

the CO is₂The evaporator 7 is provided with an air outlet pipe and a discharge pipe, the air outlet pipe is connected with the first cooler 4, and the discharge pipe is connected with the CO₂The separator 5 is connected;

the CO is₂The bottom of the separator 5 is provided with a discharge port, the top is provided with an air outlet pipe, and the discharge port is connected with CO₂And the evaporator 3, and the air outlet pipe is connected with the second washing area of the washing tower 1.

The device is used for separating CO in the synthesis gas₂The flow is as follows:

(1) the high-pressure synthesis raw material gas is subjected to high-pressure gaseous CO in a first cooler 4₂And low pressure gaseous CO₂Cooling to-15 deg.C to obtain low-temperature high-pressure synthesis raw material gas, and generating high-temperature low-pressure CO₂And high temperature high pressure CO₂Going to a urea process;

(2) the low-temperature high-pressure synthesis raw gas is enriched with CO in the first washing zone of the washing tower 1₂Desulfurizing methanol to obtain desulfurized synthesis gas and generating methanol-rich liquid; the methanol-rich liquid passes through H in turn₂S flash column 6 and CO₂H is respectively analyzed out by the flash tower 7₂S and CO₂And through the regeneration process, obtaining methanol-poor liquid to generate low temperatureResolving gaseous CO₂And H₂S，H₂S entering a sulfur recovery process;

(3) the desulphurised synthesis gas is subjected to cryogenic desorption of gaseous CO in a second cooler 2₂Cooling to-40 to-45 ℃ to obtain liquid CO₂To produce low pressure gaseous CO₂Flows through the first cooler 4 through a pipeline;

(4) entrained liquid CO₂In CO₂In the evaporator 3, liquid CO₂Evaporating and cooling to-45 to-50 ℃ to obtain a gas-liquid mixture, and generating low-temperature high-pressure gaseous CO₂Flows through the first cooler 4 through a pipeline;

(5) gas-liquid mixture in CO₂The separator 5 performs gas-liquid separation to obtain a first decarbonized synthesis gas and liquid CO₂Inflow of CO₂In the evaporator 3;

(6) the primary decarbonized synthesis gas flows from bottom to top through the second and third scrubbing zones of the scrubbing tower 1 and the cold CO-containing gas flows from top to bottom₂CO removal from methanol liquid₂Obtaining a second decarbonized syngas to produce a CO-rich₂Methanol flows into the first scrubbing zone of the scrubbing tower 1 through a pipeline;

(7) the second decarbonized synthesis gas flows through the first washing area of the washing tower 1 from bottom to top to remove CO again through cold methanol-poor liquid flowing from top to bottom, new methanol or methanol-poor liquid added with new methanol₂The obtained purified synthesis gas enters the ammonia synthesis process from the top, and the produced CO-containing gas₂The methanol liquid flows downwards through the second and third scrubbing zones of the scrubbing tower 1.

Claims (8)

1. Separating CO from synthetic gas₂The method is characterized by comprising the following steps:

(1) high pressure synthesis of raw gas by high pressure gaseous CO₂And low pressure gaseous CO₂Cooling to-15 deg.C to-20 deg.C to obtain low-temperature high-pressure synthesis raw material gas, and generating high-temperature low-pressure CO₂And high temperature high pressure CO₂Going to a urea process;

(2) low temperature high pressure synthesis of feed gas to enrich CO₂Desulfurizing methanol to obtain desulfurized synthetic gas and generate rich methanolLiquid; sequentially resolving H by the methanol-rich liquid₂S and CO₂And through the regeneration process, obtaining methanol-poor liquid and generating low-temperature desorption gaseous CO₂And H₂S；

(3) Low-temp. desorption of gaseous CO from desulfurized synthetic gas₂Cooling to-40 to-45 ℃ to obtain liquid CO₂To produce low pressure gaseous CO₂Returning to the step (1);

(4) entrained liquid CO₂Passing the desulfurized synthesis gas through liquid CO₂Evaporating and cooling to-45 to-50 ℃ to obtain a gas-liquid mixture, and generating low-temperature high-pressure gaseous CO₂Returning to the step (1);

(5) carrying out gas-liquid separation on the gas-liquid mixture to obtain primary decarbonized synthesis gas and generate liquid CO₂Returning to the step (4);

(6) the first decarbonization synthesis gas contains CO₂CO removal from methanol liquid₂Obtaining a second decarbonized syngas to produce a CO-rich₂Methanol is returned to the step (2);

(7) removing CO again from the secondary decarbonized synthetic gas at the temperature of-56-60 ℃ through poor methanol liquid₂Obtaining purified synthesis gas to produce CO-containing₂And (5) returning the methanol liquid to the step (6).

2. The method of claim 1, wherein the high pressure synthesis feed gas comprises CO₂The content is 35-45% v/v, H₂The S content is 0.05-0.15% v/v.

3. The process of claim 1, wherein the pressure of the high pressure synthesis feed gas is in the range of from 5.9 to 6.2 MPa.

4. The method according to claim 1, wherein in step (1), the high-pressure gaseous CO is₂The temperature of the mixture is-45 to-53 ℃; the low-pressure gaseous CO₂The temperature is-53 ℃ to-55 ℃.

5. The method according to claim 1, wherein in step (1), the high-temperature low-pressure CO is used₂The pressure of (A) is 0.21-0.25 MPa; the high temperature high pressure CO₂The pressure of (A) is 0.62-0.65 MPa.

6. The method of claim 1, wherein in step (3), the pressure of the desulfurized syngas is from 2.1 to 2.58 MPa.

7. The method of claim 1, wherein the CO is purified from the syngas₂Content 5ppm, H₂The S content was 0.1 ppm.

8. Separating CO from synthetic gas₂The device is characterized by comprising a first cooler, a washing tower and a second cooler which are sequentially connected through a pipeline₂S flash column, CO₂Flash column, secondary cooler, CO₂Evaporator and CO₂A separator;

the washing tower is sequentially provided with an upper seal head, a middle seal head and a lower seal head from top to bottom and is sequentially divided into a first washing area, a second washing area, a third washing area and a fourth washing area from bottom to top; the lower end enclosure is in an inverted U shape, the upper end enclosure and the middle end enclosure are flat plates, an air outlet is formed in the center of the upper end enclosure and the middle end enclosure, and a guide plate is arranged above the air outlet; the third washing area is connected with the first washing area through a pipeline; the top of the lower end socket is provided with a pipeline connected with a second cooler; the lower part of the first washing area is provided with a pipeline connected with a first cooler; the lower part of the second washing area is provided with a pipeline and CO₂Connecting a separator; a pipeline is arranged at the upper part of the fourth washing area; the bottom of the washing tower is provided with a pipeline and H₂S, connecting a flash tower; an air outlet pipe is arranged at the top of the washing tower;

said H₂The top of the S flash tower is provided with an air outlet pipe, and the bottom of the S flash tower is provided with a pipeline and CO₂Connecting a flash tower;

the CO is₂An air outlet pipe is arranged at the top of the flash tower and connected with the second cooler, and a discharge pipe is arranged at the bottom of the flash tower;

the second cooler is respectively communicated with CO through pipelines₂The evaporator is connected with the first cooler;

the CO is₂The evaporator is provided with an air outlet pipe and a discharge pipe, the air outlet pipe is connected with the first cooler, and the discharge pipe is connected with the CO₂Connecting a separator;

the CO is₂The bottom of the separator is provided with a discharge port, the top of the separator is provided with an air outlet pipe, and the discharge port is connected with CO₂And the air outlet pipe is connected with the second washing area of the washing tower.

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