A system for producing liquid ammonia using coke oven gas using combined compression

Abstract

This utility model discloses a system for producing liquid ammonia using coke oven gas through combined compression, comprising a pretreatment unit, an ammonia synthesis unit, and a combined compressor. The combined compressor includes a low-pressure section, a high-pressure section, and a hydrogen-nitrogen compression section. The low-pressure inlet of the low-pressure section is connected to the purified gas exhaust port of the pretreatment unit; the low-pressure exhaust port of the low-pressure section is connected to the second-stage inlet of the pretreatment unit; the high-pressure inlet of the high-pressure section is connected to the second-stage exhaust port of the pretreatment unit; the high-pressure exhaust port of the high-pressure section is connected to the ammonia synthesis unit; and the hydrogen-nitrogen compression inlet and exhaust port of the hydrogen-nitrogen compression section are connected to the ammonia synthesis unit. This utility model adopts a "coke oven gas and synthesis feedstock gas combined compressor" technical solution, reducing the number of equipment purchased and lowering equipment procurement costs. It can effectively resist the corrosion of naphthalene, benzene, and tar, has a long service life, and low subsequent maintenance costs. It has the advantages of shorter construction period, lower cost, and more guaranteed product quality, and can be used for linkage in liquid ammonia production plants.

Description

Technical Field

[0001] This utility model relates to the field of chemical technology, specifically to a system for producing liquid ammonia using coke oven gas through combined compression. Background Technology

[0002] With rapid economic development and population growth, the demand for food is gradually increasing, driving a rapid increase in fertilizer production. As an important intermediate product in fertilizer production, synthetic ammonia production capacity and output are maintaining a relatively rapid growth rate.

[0003] The applicant has discovered that the prior art contains at least the following technical defects:

[0004] The existing process only pre-treats and stores the coke oven gas in a gas holder. To meet the needs of the removal, reaction, and separation processes at different pressures, a "primary screw compressor + secondary and tertiary centrifugal compressor" system is required to allow the coke oven gas to flow between these processes. Traditional processes require 3 to 4 independent compressors, resulting in a large number and variety of compressors, increased equipment investment, large footprint, and significant difficulties in maintenance and handling. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a system for producing liquid ammonia by using coke oven gas through combined compression, thereby solving the problems of numerous and different types of equipment, large investment, large land area, and difficult maintenance caused by the fragmented process in the existing technology.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a system for producing liquid ammonia using coke oven gas by combined compression, comprising a pretreatment device and an ammonia synthesis device, wherein a combined compressor is installed between the pretreatment device and the ammonia synthesis device.

[0007] The combined compressor includes a low-pressure section, a high-pressure section, and a hydrogen-nitrogen compression section.

[0008] The low-pressure air inlet on the low-pressure section is connected to the purified air exhaust port of the pretreatment device.

[0009] The low-pressure exhaust port on the low-pressure section is connected to the second-stage air inlet of the pretreatment device.

[0010] The high-pressure air inlet on the high-pressure section is connected to the two exhaust ports of the pretreatment device.

[0011] The high-pressure exhaust port on the high-pressure section is connected to the ammonia synthesis unit.

[0012] The hydrogen-nitrogen compression inlet and the hydrogen-nitrogen compression outlet on the hydrogen-nitrogen compression section are connected to the ammonia synthesis unit.

[0013] This utility model also has the following technical features:

[0014] The pretreatment device includes a fiber bed pre-purification unit, a gas holder, a primary pre-compressor, and a temperature-switching adsorber, all connected in series.

[0015] The purified gas exhaust port of the variable temperature adsorber is connected to the low-pressure air inlet on the low-pressure section.

[0016] The two-stage air inlet of the variable temperature adsorber is connected to the low-pressure exhaust port on the low-pressure section.

[0017] The two exhaust ports of the variable temperature adsorber are connected to the high-pressure air inlet on the high-pressure section.

[0018] The primary pre-compressor uses a Roots blower.

[0019] The ammonia synthesis unit includes a fine desulfurization unit, a catalytic conversion unit, a converter, an MDEA decarbonization unit, and a methanation unit, all connected in series. The exhaust end of the methanation unit is connected to the hydrogen-nitrogen compression inlet on the hydrogen-nitrogen compression section.

[0020] The high-pressure exhaust port on the high-pressure section is connected to the air inlet of the fine desulfurization unit.

[0021] The exhaust end of the fine desulfurization unit is connected to the first air inlet end of the catalytic conversion unit.

[0022] The ammonia synthesis device further includes an ammonia synthesis unit, the inlet of which is connected to the hydrogen-nitrogen compression exhaust port on the hydrogen-nitrogen compression section.

[0023] The ammonia synthesis unit also includes an air separation unit and an air compressor connected in series, with the exhaust end of the air compressor connected to the second air inlet end of the catalytic conversion unit.

[0024] Compared with the prior art, this utility model has the following technical effects:

[0025] (I) This utility model provides a system for producing liquid ammonia using coke oven gas through combined compression. It adopts the technical solution of "coke oven gas and synthetic raw material gas combined compressor", which reduces the number of equipment purchased and lowers the equipment purchase cost. It can effectively resist the corrosion of naphthalene, benzene and tar, has a long service life, and low post-maintenance investment costs. It has the advantages of shorter construction period, lower cost and more guaranteed product quality, and can be used for linkage in liquid ammonia production plants.

[0026] (II) The present invention provides a system for producing liquid ammonia using coke oven gas through combined compression. It adopts combined compression process technology, oxygen-enriched catalytic conversion technology and low-pressure ammonia synthesis technology. It has the characteristics of advanced process, mature technology, low energy consumption, less waste, and high product quality. After being put into production, it can operate stably and safely for a long time.

[0027] (III) The present invention provides a system for producing liquid ammonia using coke oven gas through combined compression. The system has a small amount of waste emissions and has virtually no impact on the surrounding environment after completion. At the same time, by maximizing the use of coke oven gas by-products from nearby coking plants to produce liquid ammonia, it reduces the impact on the ecological environment of the entire park while also reducing carbon dioxide emissions, which meets the requirements of dual carbon emission reduction.

[0028] (IV) This utility model provides a system for producing liquid ammonia using coke oven gas through combined compression, which is beneficial for the rational use of resources and environmental protection. It plays a significant role in improving product quality, brand awareness, market share, and economic benefits for enterprises. As a raw material for ammonia synthesis, it extends the industrial chain and creates economies of scale. The implementation of this utility model will significantly promote local fiscal revenue, regional economic development, and the improvement of people's living standards, as well as the development of local coal, coking, metallurgy, and transportation industries. It will also improve the regional environment, providing superior conditions and strong guarantees for social prosperity and stability and sustainable economic development.

[0029] (IV) The present invention provides a system for producing liquid ammonia using coke oven gas through combined compression, which is simple in structure, easy to operate, safe and reliable, and highly adaptable. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0031] Figure 2 yes Figure 1 A magnified schematic diagram of the Zhonglian compressor section.

[0032] The meanings of the labels in the attached diagram are as follows:

[0033] 1-Pretreatment unit, 2-Ammonia synthesis unit, 3-Combined compressor.

[0034] 1-1-Fiber bed pre-purification unit, 1-2-Gas holder, 1-3-Primary pre-compressor, 1-4-Variable temperature adsorber, 1-5-Purified gas exhaust port, 1-6-Secondary air inlet, 1-7-Secondary exhaust port.

[0035] 2-1-Fine desulfurization unit, 2-2-Catalytic conversion unit, 2-3-Converter, 2-4-MDEA decarbonization unit, 2-5-Methanation unit, 2-6-Ammonia synthesis unit, 2-7-Air separation unit, 2-8-Air compressor.

[0036] 3-1-Low pressure section, 3-2-High pressure section, 3-3-Hydrogen-nitrogen compression section, 3-4-Low pressure inlet, 3-5-Low pressure exhaust port, 3-6-High pressure inlet, 3-7-High pressure exhaust port, 3-8-Hydrogen-nitrogen compression inlet, 3-9-Hydrogen-nitrogen compression exhaust port.

[0037] The specific content of this utility model will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0038] All components in this invention, such as the fine desulfurization unit and the ammonia synthesis unit, are made from components known in the prior art unless otherwise specified.

[0039] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0040] Example 1:

[0041] This embodiment provides a system for producing liquid ammonia using coke oven gas via combined compression, such as... Figures 1-2 As shown, it includes a pretreatment unit 1 and an ammonia synthesis unit 2, and a combined compressor 3 is installed between the pretreatment unit 1 and the ammonia synthesis unit 2.

[0042] The combined compressor 3 includes a low-pressure section 3-1, a high-pressure section 3-2, and a hydrogen-nitrogen compression section 3-3.

[0043] The low-pressure air inlet 3-4 on the low-pressure section 3-1 is connected to the purified air exhaust port 1-5 of the pretreatment device 1.

[0044] The low-pressure exhaust port 3-5 on the low-pressure section 3-1 is connected to the second-stage air inlet 1-6 of the pretreatment device 1.

[0045] The high-pressure air inlet 3-6 on the high-pressure section 3-2 is connected to the second exhaust port 1-7 of the pretreatment device 1.

[0046] The high-pressure exhaust port 3-7 on the high-pressure section 3-2 is connected to the ammonia synthesis unit 2.

[0047] The second-stage air inlet 1-6 of the pretreatment device 1 is connected to the second-stage exhaust port 1-7 of the pretreatment device 1.

[0048] The hydrogen-nitrogen compression inlet 3-8 and hydrogen-nitrogen compression outlet 3-9 on the hydrogen-nitrogen compression section 3-3 are connected to the ammonia synthesis unit 2.

[0049] Considering the technical and economic advantages of large-capacity dry gas holders in long-term operation, this utility model proposes to adopt a dry gas holder.

[0050] In accordance with the present invention and the characteristics of pyrolysis gas, coke oven gas compression adopts a combined reciprocating compressor. Coke oven gas at 40°C and 50 kPaG from Temperature Swing Adsorption (TSA) devices 1-4 enters the combined compressor and is initially compressed to about 0.55 MPa(G). It then goes back to Temperature Swing Adsorption (TSA) devices 1-4 and enters the combined compressor 3 for secondary compression to a pressure of 2.5 MPa(G). After passing through fine desulfurization, shift conversion, and MDEA decarbonization, it is sent back to the combined compressor 3 for compression and then the syngas is sent to the ammonia synthesis unit 2.

[0051] The conversion of coke oven gas generally adopts a pressurization process to save the power consumption of syngas compression and the investment in conversion system equipment. In order to meet the needs of each process to operate under different pressures (removal, reaction, separation) and the flow of coke oven gas between processes, a coke oven gas compressor must be installed.

[0052] This invention utilizes a combined compressor, reducing the number of devices by more than 50% and energy consumption by 25%. Furthermore, compared to traditional processes, this invention reduces CO emissions by 30%.

[0053] As a preferred embodiment:

[0054] The pretreatment device 1 includes a fiber bed pre-purification unit 1-1, a gas holder 1-2, a primary pre-compressor 1-3, and a variable temperature adsorber 1-4, which are connected in series.

[0055] The purified gas exhaust port 1-5 of the variable temperature adsorber 1-4 is connected to the low-pressure air inlet 3-4 on the low-pressure section 3-1.

[0056] The two-stage air inlet 1-6 of the variable temperature adsorber 1-4 is connected to the low-pressure exhaust port 3-5 on the low-pressure section 3-1.

[0057] The two exhaust ports 1-7 of the variable temperature adsorber 1-4 are connected to the high pressure inlet 3-6 on the high pressure section 3-2.

[0058] The outlet of the primary pre-compressor 1-3 is connected to the purified air inlet of the variable temperature adsorber 1-4.

[0059] As a preferred embodiment:

[0060] The primary pre-compressors 1-3 are Roots blowers.

[0061] As a preferred embodiment:

[0062] The ammonia synthesis unit 2 includes a fine desulfurization unit 2-1, a catalytic conversion unit 2-2, a converter 2-3, an MDEA decarbonization unit 2-4, and a methanation unit 2-5, which are connected in series. The exhaust end of the methanation unit 2-5 is connected to the hydrogen-nitrogen compression inlet 3-8 on the hydrogen-nitrogen compression section 3-3.

[0063] The high-pressure exhaust port 3-7 on the high-pressure section 3-2 is connected to the air inlet of the fine desulfurization unit 2-1.

[0064] The exhaust end of the fine desulfurization unit 2-1 is connected to the first intake end of the catalytic conversion unit 2-2.

[0065] The ammonia synthesis device 2 further includes an ammonia synthesis unit 2-6, the inlet of which is connected to the hydrogen-nitrogen compression exhaust port 3-9 on the hydrogen-nitrogen compression section 3-3.

[0066] The ammonia synthesis unit 2 further includes an air separation unit 2-7 and an air compressor 2-8 connected together, with the exhaust end of the air compressor 2-8 connected to the second air inlet end of the catalytic conversion unit 2-2.

[0067] Liquid ammonia from ammonia synthesis unit 2 is sent to the outside through pipelines.

[0068] The pretreated gas still contains small amounts of impurities such as benzene, naphthalene, and tar. To ensure the reliable operation of subsequent equipment, further purification is required.

[0069] The pre-purification process of this invention adopts temperature swing adsorption (TSA) technology. The removal efficiency of naphthalene by temperature swing adsorbers 1-4 reaches 95%, and the removal efficiency of benzene reaches 98%, ensuring that the service life of the subsequent catalyst is extended to more than 5 years.

[0070] The conversion catalyst and synthesis catalyst used in this invention are susceptible to sulfide poisoning and lose their activity. Therefore, a fine desulfurization unit 2-1 must be used to remove sulfides from the feed gas. Sulfur in the feed gas can exist in various forms of sulfur-containing compounds, such as hydrogen sulfide (H2S), carbon oxysulfide (COS), carbon disulfide (CS2), thiols (RSH), thioethers (RSR), and cyclic sulfides (such as thiophene C4H4S).

[0071] The catalytic conversion unit 2-2 of this invention employs oxygen-enriched catalytic partial oxidation conversion technology. It has the following characteristics:

[0072] a. Hydrocarbons and steam undergo conversion reactions using internal heat, resulting in high thermal efficiency.

[0073] b. No carbon black is precipitated, so there is no need to install separate devices such as filters to remove carbon black.

[0074] c. The flow field and temperature field distribution inside the converter are uniform and reasonable.

[0075] d. The residual methane content at the converter outlet is low, with a dry basis methane content of less than 0.5%.

[0076] e. The conversion unit produces steam as a byproduct, and the heat is utilized efficiently.

[0077] f. The conversion operation temperature is low, ensuring safe and stable production and a short operation cycle.

[0078] In this invention, the effective components of the ammonia synthesis gas are hydrogen and nitrogen, with a hydrogen-to-nitrogen ratio of approximately 3. The purpose of converters 2-3 is primarily to react carbon monoxide in the coke oven gas with water vapor to convert it into carbon dioxide and hydrogen. Then, excess carbon dioxide is removed through a decarbonization section, ensuring that the gas composition meets the requirements for ammonia synthesis.

[0079] The MDEA decarbonization unit 2-4 of this invention uses the active MDEA method for decarbonization. In addition to hydrogen and nitrogen, the process gas after decarbonization also contains small amounts of CO and CO2, which can poison the catalyst in ammonia synthesis and must be completely removed.

[0080] Among the many decarbonization methods, the MDEA method has the advantages of high purification level, low nitrogen and hydrogen loss, poor solution degradation, low volatilization loss, and adaptability to highly acidic feed gas, and is therefore widely used.

[0081] MDEA, also known as N-methyldiethanolamine, is used in decarbonization technology. MDEA decarbonization technology utilizes activated MDEA aqueous solution to absorb carbon dioxide (CO2) from natural gas or syngas under high pressure and ambient temperature. Under pressure reduction and temperature increase, carbon dioxide (CO2) is desorbed from the solution, and the solution is regenerated.

[0082] This invention employs a low-pressure ammonia synthesis process with lower operating pressure and temperature, less stringent material requirements for equipment and pipelines, and easier production management. Both the ammonia synthesis gas and circulating gas compression utilize a combined reciprocating compressor, integrated with the front-end coke oven gas compression. Compared to traditional processes, this invention reduces equipment investment by 35%, floor space by 40%, and liquid ammonia production costs by 200 yuan / ton.

[0083] Methanation unit 2-5 uses a catalytic oxidation conversion process to convert methane and a small amount of multi-carbon hydrocarbons in coke oven gas into carbon monoxide and hydrogen.

[0084] Temperature Swing Adsorption (TSA) regenerated gas is centrally recovered and sent to the coking furnace as fuel. Ammonia synthesis off-gas is purified after ammonia recovery and CO2 removal, and then pressure-regulated by a buffer tank before being used as fuel for the conversion preheater.

[0085] The oxygen generated at the exhaust end of the air separation unit 2-7 and the air compressed by the air compressor 2-8 are connected through a pipeline and flow into the intake end of the catalytic conversion unit 2-2 through a pipeline, where a conversion reaction occurs.

[0086] The specific working process of this utility model:

[0087] A process for producing liquid ammonia using coke oven gas via combined compression includes the following steps:

[0088] Step 1: The raw material gas from outside the interface, with a temperature of 40℃ and a pressure of atmospheric pressure, enters the fiber bed pre-purification unit 1-1 for pretreatment to remove tar and dust from the pyrolysis gas, with a removal rate greater than 80%, and naphthalene is removed to ≤50mg / Nm³. 3 The pre-purified gas from the fiber bed pre-purification unit 1-1 enters the gas holder 1-2. The raw material gas from the gas holder 1-2 is pressurized to 50 kPa (G) by the Roots blower and enters the first stage of the temperature swing adsorption (TSA) device 1-4 for crude deoiling and crude naphthalene removal, removing impurities such as tar and naphthalene from the gas.

[0089] Step 2: The raw gas after crude oil and naphthalene removal enters the low-pressure section of the combined compressor 3, is compressed to 0.6–0.8 MPa(G), and then re-enters the fine removal section of the Temperature Swing Adsorption (TSA) unit 1-4 to remove benzene and naphthalene. The regeneration gas of the Temperature Swing Adsorption (TSA) unit 1-4 comes from the ammonia synthesis off-gas; if the off-gas is insufficient, it is supplemented by purified coke oven gas.

[0090] Step 3: The purified gas after passing through the Temperature Swing Adsorption (TSA) unit 1-4 is pressurized to 2.5 MPa (G) by the high-pressure section of the combined compressor 3 and enters the fine desulfurization unit 2-1. The fine desulfurization unit 2-1 uses zinc oxide desulfurizing agent, and the temperature is controlled at 280-320℃, with the total sulfur at the outlet ≤0.1 ppm. After desulfurization, it is sent to the catalytic conversion unit 2-2.

[0091] Step 4: The methane in the coke oven gas is converted into carbon monoxide and hydrogen using a catalytic oxidation conversion process. Catalytic conversion unit 2-2 uses a high-temperature resistant nickel-based catalyst, with a reaction temperature of 850–900℃, a pressure of 2.5 MPa, and a water-to-carbon ratio of 3.0–3.5. The converted gas enters converter 2-3, where CO is converted into H2. Then, after CO2 is removed by the MDEA decarbonization unit 2-4, it enters the methanation unit 2-5.

[0092] Step 5: The raw material gas from the methanation unit 2-5 is used as the raw material gas for ammonia synthesis. It is compressed and pressurized to 15 MPa(G) by hydrogen and nitrogen in the combined compression unit 3, and then enters the ammonia synthesis unit 2-6 to react and obtain the product liquid ammonia. The liquid ammonia product is finally sent out of the boundary area.

[0093] The advantages of this utility model are:

[0094] System innovations:

[0095] (1) Integrated combined compressor: integrates the low-pressure section (0.6-0.8MPa), high-pressure section (2.5MPa) and hydrogen-nitrogen compression section (15MPa) of coke oven gas, reducing the number of equipment and reducing pipeline losses.

[0096] (2) Multi-stage purification synergy: fiber bed pre-purification (tar + dust removal rate > 80%) and TSA deep purification (naphthalene ≤ 50 mg / Nm 3 Benzene ≤10mg / Nm 3 This combination is adapted to high-impurity coke oven gas.

[0097] Technological innovation points:

[0098] (1) Oxygen-enriched catalytic conversion: Low oxygen concentration (21%~25%) is used for catalytic oxidation, with a methane conversion rate of >99% and a by-product steam utilization rate of 85%.

[0099] (2) Waste heat recovery system: TSA regenerated gas and ammonia synthesis off-gas are recovered to the coking furnace, improving the overall thermal efficiency by 15%.

[0100] This invention enables 99% of the carbon resources in coke oven gas to be converted into liquid ammonia, reducing CO emissions by approximately 20,000 tons per year, which aligns with low-carbon economic policies.

[0101] The above technical solutions are only preferred embodiments of this utility model, but the protection scope of this utility model is not limited thereto. Any changes or substitutions that can be conceived by those skilled in the art without creative effort within the technical scope disclosed in this utility model are covered within the protection scope of this utility model.

Claims

1. A system for producing liquid ammonia using coke oven gas with combined compression, comprising a pre-treatment device (1) and an ammonia synthesis device (2), characterized in that, A combined compressor (3) is installed between the pretreatment unit (1) and the ammonia synthesis unit (2); The combined compressor (3) includes a low-pressure section (3-1), a high-pressure section (3-2), and a hydrogen-nitrogen compression section (3-3); The low-pressure air inlet (3-4) on the low-pressure section (3-1) is connected to the purified air exhaust port (1-5) of the pretreatment device (1); The low-pressure exhaust port (3-5) on the low-pressure section (3-1) is connected to the second-stage air inlet (1-6) of the pretreatment device (1); The high-pressure air inlet (3-6) on the high-pressure section (3-2) is connected to the second exhaust port (1-7) of the pretreatment device (1); The high-pressure exhaust port (3-7) on the high-pressure section (3-2) is connected to the ammonia synthesis unit (2); The hydrogen-nitrogen compression inlet (3-8) and hydrogen-nitrogen compression exhaust outlet (3-9) on the hydrogen-nitrogen compression section (3-3) are connected to the ammonia synthesis unit (2).

2. The system for producing liquid ammonia using coke oven gas via combined compression as described in claim 1, characterized in that, The pretreatment device (1) includes a fiber bed pre-purification unit (1-1), a gas holder (1-2), a primary pre-compressor (1-3), and a temperature-switching adsorber (1-4) connected in series. The purified gas exhaust port (1-5) of the temperature-changing adsorber (1-4) is connected to the low-pressure air inlet (3-4) on the low-pressure section (3-1); The two-stage air inlet (1-6) of the temperature-changing adsorber (1-4) is connected to the low-pressure exhaust port (3-5) on the low-pressure section (3-1); The two exhaust ports (1-7) of the variable temperature adsorber (1-4) are connected to the high pressure inlet (3-6) on the high pressure section (3-2).

3. A system for producing liquid ammonia using coke oven gas via combined compression as described in claim 2, characterized in that, The primary pre-compressor (1-3) mentioned above uses a Roots blower.

4. A system for producing liquid ammonia using coke oven gas via combined compression as described in claim 1, characterized in that, The ammonia synthesis unit (2) includes a fine desulfurization unit (2-1), a catalytic conversion unit (2-2), a converter (2-3), an MDEA decarbonization unit (2-4), and a methanation unit (2-5) connected in series. The exhaust end of the methanation unit (2-5) is connected to the hydrogen-nitrogen compression inlet (3-8) on the hydrogen-nitrogen compression section (3-3). The high-pressure exhaust port (3-7) on the high-pressure section (3-2) is connected to the air inlet of the fine desulfurization unit (2-1); The exhaust end of the fine desulfurization unit (2-1) is connected to the first intake end of the catalytic conversion unit (2-2); The ammonia synthesis device (2) further includes an ammonia synthesis unit (2-6), the inlet of which is connected to the hydrogen-nitrogen compression exhaust port (3-9) on the hydrogen-nitrogen compression section (3-3); The ammonia synthesis unit (2) further includes an air separation unit (2-7) and an air compressor (2-8) connected in series, with the exhaust end of the air compressor (2-8) connected to the second air inlet end of the catalytic conversion unit (2-2).

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