Method for cross-utilization of raw material gas of synthetic ammonia device and acetic acid device

Abstract

The application discloses a method for cross-device raw material gas synergic utilization of a synthetic ammonia device and an acetic acid device. Crude synthetic gas generated by a space furnace pulverized coal gasification of the synthetic ammonia device is divided into two streams, the first stream is sent into a shift unit, and the second stream is sent to a membrane separation unit of the acetic acid device after being purified by methanol washing; rich CO non-permeation gas and permeation gas are obtained through membrane separation, the rich CO non-permeation gas is used for acetic acid production after being refined and removed, and the permeation gas is returned to the shift unit of the synthetic ammonia device after being compressed, deoiled, washed with water and heated to mix and then be treated by shift. The application replaces the coke gas production process of the acetic acid device by the surplus crude synthetic gas of the synthetic ammonia device, simplifies the preparation process of the acetic acid raw material gas, reduces the production cost, recovers effective components in the permeation gas, activates idle methanol washing equipment of the synthetic ammonia device, and realizes cross-device resource synergic utilization and energy cascade utilization.

Description

Technical Field

[0001] This invention relates to the field of coal chemical industry, specifically a method for the synergistic utilization of feedstock gas between ammonia synthesis unit and acetic acid unit. Background Technology

[0002] Acetic acid is an important basic chemical raw material, widely used in the production of downstream products such as PTA, vinyl acetate, ethyl acetate, and acetic anhydride. Acetic acid production primarily uses methanol and carbon monoxide as raw materials, prepared via a low-pressure carbonyl synthesis method. The preparation and purification of carbon monoxide feed gas is a crucial step in acetic acid production, directly affecting production costs and plant operational stability.

[0003] Currently, acetic acid plants primarily use coke or lump coal as feedstock for carbon monoxide. This feedstock is produced through a pure oxygenation process, followed by purification through multiple steps including pre-desulfurization, decarbonization, pressure swing adsorption (PSA), and fine desulfurization. This complex production process involves air separation, gasification, pre-desulfurization, primary decarbonization, PSA, and fine desulfurization. The process is lengthy, energy-intensive, has low automation, requires a large workforce, and carries significant safety risks. This complexity also prevents the plant from operating stably for extended periods, resulting in high maintenance costs and excessive consumption of auxiliary materials, leading to persistently high acetic acid production costs and weak market competitiveness.

[0004] On the other hand, after producing crude syngas using advanced fluidized bed pulverized coal gasification technology, the ammonia synthesis unit typically uses a low-temperature methanol washing unit to separate and purify the crude syngas. In actual production, due to the influence of the ammonia synthesis production load, the methanol washing unit often has surplus capacity, and some methanol washing towers are idle and unused, resulting in a waste of equipment resources.

[0005] In existing technologies, such as CN102180767A, a method and apparatus for the co-production of methanol, ammonia, and acetic acid from coal and natural gas are disclosed. Syngas is prepared from natural gas and coal respectively, and carbon monoxide and hydrogen are extracted for the production of acetic acid and ammonia. However, this scheme does not involve the direct cross-unit synergistic utilization of crude syngas between the ammonia synthesis unit and the acetic acid unit, nor does it involve the recovery and utilization of membrane separation permeate gas. Another example is CN202122405336.4, which discloses a co-production system for ammonia, methanol, and acetic acid, distributing gas to each unit through a feedstock gas distribution station. However, this also fails to solve the problems of long and energy-intensive coal gasification processes in the acetic acid unit, and does not effectively utilize the surplus methanol washing capacity of the ammonia synthesis unit.

[0006] Therefore, those skilled in the art have provided a method for the synergistic utilization of feed gas between ammonia synthesis units and acetic acid units to solve the problems mentioned in the background art. Summary of the Invention

[0007] This invention addresses the technical problems of complex carbon monoxide feed gas preparation processes, high energy consumption, and high costs in existing acetic acid plants, as well as the idle and wasteful use of methanol washing equipment in ammonia synthesis plants. It provides a method for the synergistic utilization of feed gas between ammonia synthesis plants and acetic acid plants.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for the co-utilization of feed gas between an ammonia synthesis unit and an acetic acid unit includes the following steps:

[0010] Step (1): The crude syngas produced by the pulverized coal gasification of the aerospace furnace of the ammonia synthesis unit is divided into a first crude syngas and a second crude syngas. The first crude syngas is sent to the conversion unit of the ammonia synthesis unit, and the second crude syngas is sent to the membrane separation unit of the acetic acid unit after being purified by methanol washing.

[0011] Step (2): The second crude synthesis gas enters the membrane separation unit of the acetic acid plant for membrane separation to obtain CO-rich non-permeable gas and permeable gas. The CO-rich non-permeable gas is then sent to the acetic acid synthesis unit of the acetic acid plant for acetic acid production after fine removal.

[0012] Step (3): The permeate gas is compressed, deoiled, washed with water, and heated by heat exchange before being returned to the conversion unit of the ammonia synthesis unit. It is then mixed with the first stream of crude synthesis gas and subjected to conversion processing.

[0013] As a further aspect of the present invention: in step (1), before the second crude synthesis gas enters the methanol wash, it sequentially passes through a gas-liquid separator to separate entrained water, a filter tank to remove dust, a secondary heat exchanger to cool down, and a primary heat exchanger to cool down.

[0014] As a further embodiment of the present invention: two filter tanks are provided, one in operation and one on standby, and the tanks are filled with filter media to separate dust entrained in the crude syngas.

[0015] As a further aspect of the present invention: before the membrane separation in step (2), the crude syngas is processed by a gas-liquid separator and a precision filter, wherein the filtration accuracy of the precision filter is 0.01 μm.

[0016] As a further aspect of the present invention: before the permeate gas in step (3) returns to the conversion unit of the ammonia synthesis unit, it undergoes the following heating and humidification treatments in sequence:

[0017] Step (a): Pre-saturate the permeate gas by injecting demineralized water into it;

[0018] Step (b): The pre-saturated permeate gas enters the first-stage heat exchanger and undergoes co-current heat exchange with the aerospace furnace crude syngas from the second-stage heat exchanger, raising the temperature to 145-155°C.

[0019] Step (c): Inject 230°C boiler hot water into the permeate gas after it has been heated by the first-stage heat exchanger to saturate and raise the temperature to 170-180°C.

[0020] Step (d): The gas enters the secondary heat exchanger and exchanges heat with the aerospace furnace crude syngas from the filter tank, raising the temperature to 185-195°C.

[0021] Step (e) involves injecting superheated steam at 320°C to saturate the gas and obtain saturated permeate gas at 190–200°C and 3.5–3.7 MPa.

[0022] As a further embodiment of the present invention: the permeate gas in step (3) is pressurized to 3.5-3.7 MPa by a compressor and then subjected to degreasing and water washing.

[0023] As a further aspect of the present invention: Of the crude syngas produced by the pulverized coal gasification in the ammonia synthesis unit's aerospace furnace, the amount of the second stream of crude syngas sent to the membrane separation unit of the acetic acid unit is... The CO content was 67.64 mol% and the H2 content was 31.61 mol%.

[0024] As a further aspect of the present invention: the amount of permeate gas generated by the membrane separation unit of the acetic acid apparatus is... The H2 content is 65.66 mol and the CO content is 34.10 mol.

[0025] As a further embodiment of the present invention: the CO content in the CO-rich non-permeable gas is ≥98.5 mol%, and the total sulfur content after fine removal is... oxygen content Chloride content CO2 content ≤ 0.3% (V).

[0026] As a further aspect of the present invention: the crude synthesis gas in step (1) is purified by methanol washing using the existing methanol washing tower 9 of the ammonia synthesis unit, which is an idle device of the ammonia synthesis unit.

[0027] As a further aspect of the present invention: after the method is implemented, the acetic acid unit is shut down, along with the original pre-desulfurization, primary decarbonization, and pressure swing adsorption processes. Production equipment.

[0028] As a further embodiment of the present invention: the condensate collected by the gas-liquid separator and the condensate tank is depressurized to 0.8 MPa and then sent to the high-pressure flash separator of the gasification device for recycling.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] (1) The present invention directly supplies the crude synthesis gas generated by the aerospace furnace of the ammonia synthesis unit to the acetic acid unit as raw material gas, replacing the original coke gasification process of the acetic acid unit, simplifying the raw material gas preparation process of the acetic acid unit, and significantly reducing the production cost of acetic acid.

[0031] (2) The present invention returns the permeate gas after membrane separation to the conversion unit of the ammonia synthesis plant, effectively recovering effective components such as H2 and CO in the permeate gas, improving resource utilization efficiency. At the same time, the return of the permeate gas increases the H2 content of the crude synthesis gas before entering the conversion system, relieving the pressure on the subsequent conversion system.

[0032] (3) This invention utilizes the existing methanol washing tower 9 (originally idle equipment) of the ammonia synthesis unit to purify and wash the crude synthesis gas, thereby revitalizing the surplus methanol washing capacity of the ammonia synthesis unit, realizing the reuse of equipment resources, and improving resource utilization efficiency.

[0033] (4) This invention uses a counter-flow two-stage heat exchanger to heat the low-temperature permeation gas by utilizing the sensible heat of the high-temperature gas, thereby achieving internal heat transfer, reducing the consumption of external energy (steam), and reducing the water cooling load required for cooling the high-temperature gas, resulting in significant energy saving.

[0034] (5) After the implementation of the present invention, the acetic acid unit can shut down production units such as pre-desulfurization, primary decarbonization, and pressure swing adsorption, saving the consumption of catalyst used in the purification of raw coal gas and the energy consumption of high-power electrical equipment in pressure swing adsorption, reducing the operating cost of the unit, and reducing the workload of equipment maintenance. Attached Figure Description

[0035] Figure 1 This is a flowchart of the method for co-utilizing feed gas between the ammonia synthesis unit and the acetic acid unit according to the present invention. Detailed Implementation

[0036] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for the synergistic utilization of feed gas between an ammonia synthesis unit and an acetic acid unit.

[0039] I. Sources and Distribution of Raw Gas

[0040] The ammonia synthesis unit uses aerospace furnace pulverized coal pressurized gasification technology (HT-L) to produce crude syngas. The aerospace furnace uses dry pulverized coal as feedstock, which is transported to the gasifier via high-pressure carbon dioxide. There, it undergoes a partial oxidation reaction with pure oxygen and superheated steam (approximately 420°C) under high temperature (1400–1700°C) and high pressure (4.0 MPa) conditions to produce syngas mainly composed of carbon monoxide and hydrogen (CO + H2 accounting for approximately 90%).

[0041] The crude syngas produced by the aerospace furnace is divided into two streams: the first stream of crude syngas is fed into the ammonia synthesis unit's conversion unit according to the original process; the second stream of crude syngas (volume) After purification, the second crude syngas stream is sent to the membrane separation unit of the acetic acid plant. The composition of the second crude syngas stream is as follows:

[0042] Table 1 Composition of the second crude syngas stream

[0043]

[0044] II. Purification Treatment of Crude Syngas

[0045] The second stream of crude syngas first enters the newly added gas-liquid separator S-1006 (Φ1800×6175mm, volume). The crude syngas is then separated to remove moisture entrained in it. It then enters a filter tank R-1001A / B (Φ2000×9070mm, volume...). The filter tank is equipped with two units, one operational and one standby, filled with filter media to separate dust entrained in the crude syngas. The crude syngas exiting the filter tank enters the secondary heat exchanger E-1003 (Φ2400×18498mm, heat exchange area...). The gas is cooled by heat exchange with the permeate gas from the acetic acid unit, and then enters the gas-liquid separator S-1003 (Φ1800×6175mm, volume). The condensate is separated and then enters the primary heat exchanger E-1002 (Φ2400×18498mm, heat exchange area). After being cooled by heat exchange with the permeate gas again, it enters the gas-liquid separator S-1002 (Φ1800×6175mm, volume). Separate condensate.

[0046] After cooling and dust removal, the crude syngas enters the methanol washing tower 9 (C-2209, Φ1860×17150mm) in the ammonia synthesis plant, where acidic gas impurities are removed. Methanol washing tower 9 is an existing, idle piece of equipment in the ammonia synthesis plant, designed at a pressure of 4.2 MPa and a temperature of -65 / 50℃. The purified gas, after reheating, is then sent to the membrane separation unit of the acetic acid plant.

[0047] The condensate collected by the gas-liquid separator and the condensate tank is reduced to 0.8 MPa and then collected in a main pipe, which is sent to the inlet of the high-pressure flash separator of the gasification unit for recycling.

[0048] III. Membrane Separation

[0049] The purified crude syngas enters the membrane separation unit of the acetic acid plant. The membrane separation unit is located at the original desulfurization and decarbonization unit of the acetic acid plant and includes a gas-liquid separator (φ3000mm, H=1000mm, design pressure 4.0MPa), a precision filter (DN700×2400mm, filtration accuracy 0.01μm, one in operation and one on standby), a heater (F=20m²), and a membrane separator adjustment group (membrane core DN200×3000mm, design pressure 4.0MPa).

[0050] After gas-liquid separation and precision filtration, the crude syngas enters a membrane separator for separation, yielding CO-rich non-permeable gas and permeable gas.

[0051] Table 2. Membrane separation product flow rate and composition

[0052]

[0053] CO-rich non-permeable gas (CO content ≥ 98.5 mol%) is sent to the acetic acid unit's 150 purification system. After desulfurization, deoxygenation, and dechlorination, it is sent to the acetic acid synthesis unit for acetic acid production. The purification degree of the purified gas is: total sulfur content... oxygen content Chloride content , content .

[0054] IV. Permeate Gas Return Treatment

[0055] The permeate gas generated by membrane separation (912.37 kmol / h, with H2 content of 65.66 mol% and CO content of 34.10 mol%) is pressurized to 3.5–3.7 MPa and then subjected to the following treatments:

[0056] (1) Pre-saturate the permeate gas by injecting demineralized water into it to improve the heat exchange efficiency of the gas;

[0057] (2) It enters the first-stage heat exchanger E-1002 and exchanges heat with the aerospace furnace crude syngas from the gas-liquid separator S-1003 in parallel flow, raising the temperature to 150°C;

[0058] (3) Inject 230℃ boiler hot water (8.15t / h) to saturate and raise the temperature to 175℃;

[0059] (4) It enters the secondary heat exchanger E-1003 and exchanges heat with the aerospace furnace crude syngas from the filter tank R-1001, raising the temperature to 190°C;

[0060] (5) Inject 320℃ superheated steam (16t / h) to raise the temperature to saturation, and obtain saturated permeate gas at 195℃ and 3.6MPa. Return it to the conversion unit of the ammonia synthesis unit, mix it with the first crude synthesis gas and then perform conversion treatment.

[0061] V. Implementation Results

[0062] After the implementation of this embodiment, the original pre-desulfurization, primary decarbonization, pressure swing adsorption (PSA-CO2), PSA-CO, and PSA-H2 production units of the acetic acid plant were shut down.

[0063] Based on actual operation and testing, the technical effects of this embodiment are as follows:

[0064] (1) Acetic acid production capacity remains unchanged at 360,000 tons / year, acetic acid cost per ton decreases by about RMB122.1, total annual cost decreases by RMB43.957 million, and operating cost decreases by RMB45.935 million;

[0065] (2) Annual electricity consumption decreased by 114.766 million kWh;

[0066] (3) Annual savings of 25,200 tons of lump coal, 75,600 tons of coke, 55,800,000 Nm³ of oxygen, and 7,200 tons of carbon dioxide;

[0067] (4) The overall energy consumption was reduced by 47,169.14 tce / a (equivalent value).

[0068] (5) Annual CO2 emissions decreased by 29,265.44 tons;

[0069] (6) The idle methanol washing tower 9 of the synthetic ammonia plant was revitalized, realizing the reuse of equipment resources.

[0070] Example 2

[0071] The difference between this embodiment and Embodiment 1 lies in the different process parameters.

[0072] The volume of the second crude syngas stream is When the permeate gas returns to the ammonia synthesis unit, the first-stage heat exchanger is heated to 148°C, and after injecting 230°C boiler hot water, the temperature rises to 172°C. The second-stage heat exchanger is heated to 188°C, and after injecting 320°C superheated steam, saturated permeate gas at 192°C and 3.55MPa is produced and returned to the ammonia synthesis unit's conversion unit.

[0073] Example 3

[0074] The difference between this embodiment and Embodiment 1 lies in the different process parameters.

[0075] The volume of the second crude syngas stream is When the permeate gas returns to the ammonia synthesis unit, the first-stage heat exchanger is heated to 155°C, and after injecting 230°C boiler hot water, the temperature is raised to 180°C. The second-stage heat exchanger is heated to 195°C, and after injecting 320°C superheated steam, saturated permeate gas at 200°C and 3.65MPa is produced and returned to the ammonia synthesis unit's conversion unit.

[0076] Comparative Example 1

[0077] The acetic acid unit uses a traditional coke gasification process to produce CO feedstock gas. It uses coke, pure oxygen, and... The raw material is used to prepare coal gas (CO content 65-70%). After being buffered in a gas holder, the coal gas enters the pre-desulfurization process to remove dust, coal tar, and hydrogen sulfide. The purified coal gas is then compressed and enters the carbon dioxide PSA process for desulfurization. The purified gas will be processed in the "new three sets of pressure swing adsorption" section. After separation of other impurities, the pure CO is sent to the acetic acid synthesis process after fine desulfurization.

[0078] Compared to Example 1, this comparative example has a longer production process, involving multiple steps such as air separation, gasification, pre-desulfurization, primary decarbonization, and pressure swing adsorption. It also has higher energy consumption, lower automation, and requires more manpower. Calculations show that the cost per ton of CO feedstock gas produced using this traditional process is approximately RMB 122.1 higher than that of acetic acid in Example 1.

[0079] Comparative Example 2

[0080] The crude synthesis gas from the aerospace furnace of the ammonia synthesis unit is directly supplied to the acetic acid unit, but the membrane separation permeate gas is not returned to the ammonia synthesis unit conversion unit. Instead, the permeate gas is directly discharged or treated by combustion.

[0081] While this comparative example simplifies the feed gas preparation process for the acetic acid unit, a significant amount of H2 (approximately 65.66 mol%) and CO (approximately 34.10 mol%) in the permeate gas is not recovered and utilized, resulting in resource waste. Furthermore, direct emission of the permeate gas does not meet environmental protection requirements. Compared to Example 1, Comparative Example 2 loses approximately 912.37 kmol / h of effective gas annually (equivalent to an annual H2 loss of approximately 4.79 million kcal / h). CO approximately 2.49 million ), resource utilization has decreased significantly.

[0082] The method for synergistic utilization of feedstock gases between ammonia synthesis and acetic acid plants provided by this invention is technically mature and reliable, and has been successfully implemented in the ammonia synthesis plant of Henan Junhua Development Co., Ltd. and the acetic acid plant of Henan Shunda New Energy Technology Co., Ltd. This method simplifies the feedstock gas preparation process for the acetic acid plant, significantly reduces acetic acid production costs, and simultaneously revitalizes idle equipment resources in the ammonia synthesis plant. It achieves synergistic resource utilization and energy cascade utilization across plants, demonstrating good industrial practical value and promising prospects for widespread application.

[0083] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for the co-utilization of feed gas between an ammonia synthesis unit and an acetic acid unit, characterized in that, Includes the following steps: Step (1): The crude syngas produced by the pulverized coal gasification of the aerospace furnace of the ammonia synthesis unit is divided into a first crude syngas and a second crude syngas. The first crude syngas is sent to the conversion unit of the ammonia synthesis unit, and the second crude syngas is sent to the membrane separation unit of the acetic acid unit after being purified by methanol washing. Step (2): The second crude synthesis gas enters the membrane separation unit of the acetic acid plant for membrane separation to obtain CO-rich non-permeable gas and permeable gas. The CO-rich non-permeable gas is then sent to the acetic acid synthesis unit of the acetic acid plant for acetic acid production after fine removal. Step (3): The permeate gas is compressed, deoiled, washed with water, and heated by heat exchange before being returned to the conversion unit of the ammonia synthesis unit. It is then mixed with the first stream of crude synthesis gas and subjected to conversion processing.

2. The method for co-utilizing feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 1, characterized in that, In step (1), the second crude synthesis gas passes through a gas-liquid separator to separate entrained water, a filter tank to remove dust, a secondary heat exchanger to cool, and a primary heat exchanger to cool before entering the methanol wash.

3. The method for co-utilizing feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 2, characterized in that, Two filter tanks are provided, one in operation and one on standby. They are filled with filter media to separate dust entrained in the crude syngas.

4. The method for co-utilizing feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 1, characterized in that, Before the membrane separation in step (2), the crude syngas is processed by a gas-liquid separator and a precision filter, the precision filter having a filtration accuracy of 0.01 μm.

5. The method for co-utilizing feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 2, characterized in that, Before the permeate gas in step (3) returns to the conversion unit of the ammonia synthesis unit, it undergoes the following heating and humidification treatments in sequence: Step (a): Pre-saturate the permeate gas by injecting demineralized water into it; Step (b): The pre-saturated permeate gas enters the first-stage heat exchanger and undergoes co-current heat exchange with the aerospace furnace crude syngas from the second-stage heat exchanger, raising the temperature to 145-155°C. Step (c): Inject 230°C boiler hot water into the permeate gas after it has been heated by the first-stage heat exchanger to saturate and raise the temperature to 170-180°C. Step (d): The gas enters the secondary heat exchanger and exchanges heat with the aerospace furnace crude syngas from the filter tank, raising the temperature to 185-195°C. Step (e) involves injecting superheated steam at 320°C to saturate the gas and obtain saturated permeate gas at 190–200°C and 3.5–3.7 MPa.

6. The method for co-utilizing feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 5, characterized in that, The permeate gas mentioned in step (3) is pressurized to 3.5-3.7 MPa by a compressor and then subjected to oil removal and water washing.

7. A method for the co-utilization of feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 1, characterized in that, Of the crude syngas produced by the pulverized coal gasification in the ammonia synthesis unit's aerospace furnace, the amount of the second stream of crude syngas sent to the membrane separation unit of the acetic acid unit is... The CO content was 67.64 mol% and the H2 content was 31.61 mol%.

8. The method for co-utilizing feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 1, characterized in that, The amount of permeate gas generated by the membrane separation unit of the acetic acid apparatus is The H2 content is 65.66 mol and the CO content is 34.10 mol.

9. A method for the co-utilization of feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 1, characterized in that, The CO-rich non-permeable gas contains ≥98.5 mol% CO, and the total sulfur content after fine removal is [not specified]. oxygen content Chloride content CO2 content ≤ 0.3% (V).

10. A method for the co-utilization of feed gas between an ammonia synthesis unit and an acetic acid unit according to claim 1, characterized in that, The crude synthesis gas in step (1) is purified by methanol washing using the existing methanol washing tower 9 of the ammonia synthesis unit, which is an idle device of the ammonia synthesis unit.

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