Secondary separation and purification device for membrane recovery inert gas in process of preparing ammonia from natural gas

Abstract

The utility model discloses a secondary separation and purification device for membrane recovery inert gas in a natural gas-to-ammonia process, belongs to the field of secondary separation of membrane recovery inert gas, solves the problems of insufficient combustion of methane and generation of carbon monoxide during existing inert gas recovery, and comprises an inert gas preheater, an inert gas conveying pipeline, a washing system, a steam heater and a recovery system, according to the system, through the arrangement of the conveying system, the recycling system and the washing system, non-combustible nitrogen can be separated, the nitrogen is input into the nitrogen recycling system, high-purity methane is separated from the interior of inert gas, and the separated methane is directly input into the incinerator at one end to be fully combusted; the combustion efficiency of methane in the first-section burning furnace is enhanced, methane can be fully burnt, the usage amount of methane is reduced, the content of generated carbon monoxide is reduced, multiple times of separation and purification in inert gas are achieved, and the working quality of equipment is guaranteed.

Description

Technical Field

[0001] This application belongs to the field of membrane recovery and inert gas secondary separation, specifically relating to a membrane recovery and inert gas secondary separation and purification device for a natural gas ammonia production process. Background Technology

[0002] The natural gas-to-ammonia synthesis process can be divided into six steps: Step 1: Natural Gas Desulfurization: Organic sulfur in natural gas is converted into easily absorbed H2S under the action of an iron-manganese catalyst; oxides of iron, manganese, and zinc react with H2S in the gas to form stable sulfides, thereby removing H2S. Step 2: Natural Gas Conversion: Natural gas is converted into crude conversion gas required for subsequent processes and provides nitrogen for the synthesis process. Step 3: Conversion: CO, which is difficult to remove in the previous process, is converted into CO2. Step 4: Carbon Dioxide Removal: Carbon dioxide is removed from the conversion gas using MDEA solution, providing carbon dioxide feedstock for urea. Step 5: Methanation: Residual carbon dioxide and carbon monoxide in the purified gas are converted into a small amount of methane, which is non-toxic to the synthesis catalyst. Step 6: Ammonia Synthesis: Fresh gas prepared in the previous process is synthesized into ammonia through an ammonia synthesis tower, and then condensed into liquid ammonia through an ammonia separator. After metering, it is sent to the liquid ammonia tank area. The remaining gas is cooled by a combined ammonia cooler, pressurized by the integrated compressor circulation section, and then sent back into the system for circulation.

[0003] In the sixth step, the inert gas content of the ammonia separator is approximately 39% NH3, 37% H2, 9% CH4, and 15% N2. The inert gas enters the membrane recovery system, where NH3 is washed, H2 is separated, and the remaining CH4 and N2 are recycled into the primary furnace for combustion and heating. Not only does the excessive N2 inside the primary furnace lead to incomplete combustion of CH4 and the generation of toxic CO gas, but it also reduces the heat generated by the combustion of the same amount of CH4 under the same operating conditions, thus increasing the consumption of CH4 for heating. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of the embodiments of this application and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents, and such simplifications or omissions should not be used to limit the scope of this application.

[0005] To address the problems mentioned in the background section, this application adopts the following technical solution.

[0006] A membrane recovery inert gas secondary separation and purification device for a natural gas to ammonia production process includes an inert gas preheater, an inert gas delivery pipeline, a scrubbing system, a steam heater, and a recovery system. The inert gas preheater has an inert gas delivery pipeline for inputting inert gas at its inlet end. The scrubbing system is connected to the side of the inert gas preheater via a pipeline. A steam heater for heating the gas is connected to the scrubbing system via a pipeline. A recovery system for separating and purifying the gas is installed at the outlet end of the steam heater via a pipeline. The recovery system includes a hydrogen recovery membrane module and a methane recovery membrane module. The hydrogen recovery membrane module is connected to the steam heater via a pipeline, and the methane recovery membrane module is connected to the side of the hydrogen recovery membrane module via a pipeline.

[0007] As a preferred technical solution of this application, the hydrogen recovery membrane module separates the input gas, with hydrogen being input into the methane recovery membrane module through a pipeline, while non-hydrogen gas is input into the compressor for recovery through a pipeline.

[0008] As a preferred technical solution of this application, the outlet of the methane recovery membrane module is divided into two groups, and each group is connected to an incinerator and a nitrogen recovery system via pipelines.

[0009] As a preferred technical solution of this application, the first-stage incinerator performs combustion treatment on the methane separated by the methane recovery membrane module, and the nitrogen recovery system recovers the nitrogen separated by the methane recovery membrane module.

[0010] As a preferred technical solution of this application, the device further includes a conveying system, which includes a demineralized water pump, a demineralized water tank, and a conveying pipeline. The demineralized water tank contains demineralized water. The demineralized water pump is connected to the side of the demineralized water tank through a pipeline. The demineralized water pump conveys the demineralized water inside the demineralized water tank. The conveying pipeline is installed at the outlet end of the demineralized water pump and is connected to an inert gas preheater.

[0011] As a preferred technical solution of this application, a flow meter for detecting the flow rate of demineralized water and a regulating valve for controlling the opening and closing of the conveying pipeline are installed outside the conveying pipeline.

[0012] As a preferred technical solution of this application, the desalinated water in the desalination tank is fed into the inert gas preheater through the desalination water pump and the conveying pipeline, and the desalinated water is fed into the washing system through the inert gas preheater.

[0013] As a preferred technical solution of this application, the washing system includes an inert gas scrubbing tower and an ammonia separator. The inert gas scrubbing tower is connected to the side of the inert gas preheater through a pipeline. The inert gas scrubbing tower washes the inert gas, and the washed gas is input into the ammonia separator through a pipeline.

[0014] As a preferred technical solution of this application, the bottom of the ammonia separator is equipped with an ammonia recovery system for recovering the ammonia-removed water inside the ammonia separator.

[0015] As a preferred technical solution of this application, the top of the ammonia separator is connected to a steam heater via a pipe, and the top of the steam heater is connected to a steam delivery pipe.

[0016] Compared to existing technologies, the beneficial effects of this application are as follows:

[0017] In this application, by setting up a conveying system, a recovery system, and a washing system, non-combustible nitrogen can be separated and fed into the nitrogen recovery system. High-purity methane is then separated from the inert gas. The separated methane is directly fed into a single-stage incinerator for complete combustion, which enhances the combustion efficiency of methane in the incinerator. This allows for more complete combustion of methane, reducing the amount of methane used and decreasing the amount of carbon monoxide produced, thus reducing the probability of harm to the surrounding environment and personnel. This achieves multiple separations and purifications of the inert gas, ensuring the working quality of the equipment itself. Attached Figure Description

[0018] Figure 1 This is a floor plan of the overall structure of this application.

[0019] Figure 2 This is a floor plan of the recycling system structure for this application.

[0020] Figure 3 This is a plan view of the conveying system structure of this application.

[0021] Figure 4 This is a schematic diagram of the washing system in this application.

[0022] The correspondence between the labels and component names in the attached figures is as follows:

[0023] 1. Inert gas preheater; 2. Inert gas conveying pipeline; 3. Scrubbing system; 31. Inert gas scrubbing tower; 32. Ammonia separator; 33. Ammonia water recovery system; 4. Steam heater; 5. Recovery system; 51. Hydrogen recovery membrane module; 52. Methane recovery membrane module; 53. Combined compressor; 54. Primary incinerator; 55. Nitrogen recovery system; 6. Conveying system; 61. Demineralized water pump; 62. Demineralized water tank; 63. Conveying pipeline. Detailed Implementation

[0024] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments. The following embodiments are provided in this application.

[0027] Depend on Figure 1 The diagram shown is a structural schematic of a membrane recovery inert gas secondary separation and purification device for a natural gas ammonia production process in this embodiment. It includes an inert gas preheater 1, an inert gas conveying pipeline 2, a washing system 3, a steam heater 4, and a recovery system 5. The inert gas preheater 1 has an inert gas conveying pipeline 2 for inputting inert gas installed at its inlet end. The washing system 3 is connected to the side of the inert gas preheater 1 via a pipeline. The washing system 3 is connected to the steam heater 4 for heating the gas via a pipeline. The steam heater 4 is connected to the outlet end of the steam heater 4 via a pipeline, and the recovery system 5 for separating and purifying the gas is installed thereon. The recovery system 5 includes a hydrogen recovery membrane module 51 and a methane recovery membrane module 52. The hydrogen recovery membrane module 51 is connected to the steam heater 4 via a pipeline, and the methane recovery membrane module 52 is connected to the side of the hydrogen recovery membrane module 51 via a pipeline.

[0028] In operation, the inert gas conveying pipeline 2 introduces inert gas into the inert gas preheater 1. The inert gas preheater 1 performs preliminary treatment on the introduced gas. Then, the gas is introduced into the washing system 3 for filtration and further treatment. After treatment, some impurities in the inert gas can be effectively removed. The steam heater 4 further heats the gas processed in the washing system 3. Subsequently, the hydrogen recovery membrane module 51 and the methane recovery membrane module 52 separate the introduced gas. The separated gas is then introduced into the corresponding downstream equipment for further processing and recycling.

[0029] From the appendix Figure 2 As shown, this is a schematic diagram of the recovery system 5 in this embodiment. The hydrogen recovery membrane module 51 separates the input gas. Hydrogen is input into the methane recovery membrane module 52 through a pipeline, while non-hydrogen is input into the compressor 53 through a pipeline for recovery.

[0030] During use, the hydrogen recovery membrane module 51 utilizes its own structure to separate the input gas. The permeated gas, hydrogen, is directly input into the methane recovery membrane module 52 through a pipeline, where the hydrogen is recovered. Meanwhile, the non-permeated gas is directly input into the methane recovery membrane module 52 through a pipeline, where the methane recovery membrane module 52 further filters the input gas.

[0031] From the appendix Figure 2 As shown, this is a schematic diagram of the structure of the recovery system 5 in this embodiment. The outlet of the methane recovery membrane module 52 is divided into two groups, and is respectively connected to a section incinerator 54 and a nitrogen recovery system 55 through pipelines. The section incinerator 54 performs combustion treatment on the methane separated by the methane recovery membrane module 52, and the nitrogen recovery system 55 recovers the nitrogen separated by the methane recovery membrane module 52.

[0032] In use, the methane recovery membrane module 52 further filters and separates the input gas. The methane in the gas is discharged through the outlet at the bottom of the methane recovery membrane module 52 and fed into the first-stage incinerator 54 for treatment, while the nitrogen in the gas is recovered and reused through the nitrogen recovery system 55.

[0033] From the appendix Figure 3 As shown, this is a schematic diagram of the conveying system 6 in this embodiment. The device also includes a conveying system 6, which includes a demineralized water pump 61, a demineralized water tank 62, and a conveying pipe 63. The demineralized water tank 62 contains demineralized water. The demineralized water pump 61 is connected to the side of the demineralized water tank 62 through a pipe. The demineralized water pump 61 conveys the demineralized water inside the demineralized water tank 62. The conveying pipe 63 is installed at the outlet end of the demineralized water pump 61 and is connected to the inert gas preheater 1.

[0034] During operation, the demineralized water pump 61 pumps the demineralized water in the demineralized water tank 62 into the inert gas preheater 1 through the conveying pipe 63. After processing and treatment by the inert gas preheater 1, the heated demineralized water is then fed into the washing system 3.

[0035] From the appendix Figure 3 As shown, it is a structural schematic diagram of the conveying system 6 in this embodiment. The conveying pipe 63 is equipped with a flow meter for detecting the flow rate of demineralized water and a regulating valve for controlling the opening and closing of the conveying pipe 63 itself. The demineralized water in the demineralized water tank 62 is input into the inert gas preheater 1 after passing through the demineralized water pump 61 and the conveying pipe 63, and the demineralized water is input into the washing system 3 after passing through the inert gas preheater 1.

[0036] During use, the total amount of demineralized water delivered by the demineralized water pump 61 is monitored in real time by installing a flow meter, ensuring that the ratio of demineralized water to gas is reasonable, which facilitates the subsequent washing system 3 components to wash the gas.

[0037] From the appendix Figure 4 As shown, it is a schematic diagram of the structure of the washing system 3 in this embodiment. The washing system 3 includes an inert gas washing tower 31 and an ammonia separator 32. The inert gas washing tower 31 is connected to the side of the inert gas preheater 1 through a pipeline. The inert gas washing tower 31 washes the inert gas, and the washed gas is input into the ammonia separator 32 through a pipeline.

[0038] In operation, the inert gas scrubbing tower 31 receives the demineralized water pumped by the demineralized water pump 61, and the receiving port is installed at the top side of the inert gas scrubbing tower 31. The gas input into the inert gas preheater 1 is input from the bottom of the inert gas scrubbing tower 31, so that the input gas is discharged from the inert gas scrubbing tower 31 after countercurrent flushing and input into the ammonia separator 32 for further processing. The ammonia separator 32 can separate the ammonia components in the gas to ensure the stability of the equipment operation.

[0039] From the appendix Figure 4 As shown, it is a structural schematic diagram of the washing system 3 in this embodiment. The ammonia separator 32 is equipped with an ammonia recovery system 33 at the bottom to recover the ammonia water inside the ammonia separator 32. In use, the 32 separates the ammonia components in the gas, and the separated ammonia gas is directly input into the ammonia recovery system 33 through a pipeline to achieve the screening and treatment of the gas itself.

[0040] From the appendix Figure 1 and Figure 4 As shown, the top of the ammonia separator 32 is connected to the steam heater 4 via a pipe, and the top of the steam heater 4 is connected to a steam delivery pipe. During use, after the ammonia component in the gas is separated in the ammonia separator 32, the remaining gas is directly input into the steam heater 4 through the pipe to assist the operation of subsequent components. The steam delivery pipe connected to the top of the steam heater 4 facilitates the heating and processing of the input gas by the steam heater 4.

[0041] Working principle: The inert gas from the ammonia separator enters the inert gas preheater 1 through the inert gas delivery pipe 2, and then enters the inert gas scrubbing tower 31. After being regulated and countercurrently absorbed with the demineralized water from the demineralized water pump 61, it exits from the top of the inert gas scrubbing tower 31, and then passes through the ammonia separator 32 for separation. After that, it is fed into the steam heater 4, and then the gas is fed into the hydrogen recovery membrane module 51. The hydrogen permeate is discharged on the permeate side, and the remaining gas is obtained on the non-permeate side. After the hydrogen is separated, it returns to the system compressor 53. The process gas that comes out then passes through the methane recovery membrane module 52. The methane permeate is discharged on the permeate side, and nitrogen is obtained on the non-permeate side. After the methane is separated, it goes to the first-stage incinerator 54, and the separated nitrogen is transported to the nitrogen recovery system 55 for recycling.

[0042] The above description, in conjunction with specific embodiments, provides a further detailed explanation of this application. It should not be construed that the specific implementation of this application is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of this application, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted in this application.

Claims

1. A membrane recovery inert gas secondary separation and purification device for a natural gas-to-ammonia process, characterized in that, include: The inert gas preheater (1), inert gas delivery pipeline (2), washing system (3), steam heater (4) and recovery system (5) are provided. The inert gas preheater (1) is equipped with an inert gas delivery pipeline (2) for inputting inert gas. The side of the inert gas preheater (1) is connected to the washing system (3) through a pipeline. The washing system (3) is connected to the steam heater (4) for heating the gas through a pipeline. The outlet of the steam heater (4) is equipped with a recovery system (5) for separating and purifying the gas through a pipeline. The recovery system (5) includes a hydrogen recovery membrane module (51) and a methane recovery membrane module (52). The hydrogen recovery membrane module (51) is connected to the steam heater (4) through a pipeline. The methane recovery membrane module (52) is connected to the side of the hydrogen recovery membrane module (51) through a pipeline.

2. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 1, characterized in that: The hydrogen recovery membrane module (51) separates the input gas, with hydrogen being piped into the methane recovery membrane module (52) and non-hydrogen being piped into the compressor (53) for recovery.

3. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 2, characterized in that: The outlet of the methane recovery membrane module (52) is divided into two groups, and is connected to a section of incinerator (54) and nitrogen recovery system (55) respectively through pipelines.

4. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 3, characterized in that: The incinerator (54) performs combustion treatment on the methane separated by the methane recovery membrane module (52), and the nitrogen recovery system (55) recovers the nitrogen separated by the methane recovery membrane module (52).

5. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 1, characterized in that: The device also includes a conveying system (6), which includes a demineralized water pump (61), a demineralized water tank (62), and a conveying pipe (63). The demineralized water tank (62) contains demineralized water. The demineralized water pump (61) is connected to the side of the demineralized water tank (62) through a pipe. The demineralized water pump (61) conveys the demineralized water inside the demineralized water tank (62). The conveying pipe (63) is installed at the outlet of the demineralized water pump (61) and is connected to the inert gas preheater (1).

6. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 5, characterized in that: The external part of the conveying pipeline (63) is equipped with a flow meter for detecting the flow rate of demineralized water and a regulating valve for controlling the opening and closing of the conveying pipeline (63) itself.

7. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 6, characterized in that: The desalinated water in the desalinated water tank (62) is fed into the inert gas preheater (1) after passing through the desalinated water pump (61) and the conveying pipe (63), and the desalinated water is fed into the washing system (3) after passing through the inert gas preheater (1).

8. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 1, characterized in that: The washing system (3) includes an inert gas scrubbing tower (31) and an ammonia separator (32). The inert gas scrubbing tower (31) is connected to the side of the inert gas preheater (1) through a pipeline. The inert gas scrubbing tower (31) washes inert gases, and the washed gas is input into the ammonia separator (32) through a pipeline.

9. The membrane recovery inert gas secondary separation and purification device for natural gas ammonia production process according to claim 8, characterized in that: The ammonia separator (32) is equipped with an ammonia recovery system (33) at the bottom for recovering the ammonia-removed water inside the ammonia separator (32).

10. A membrane recovery inert gas secondary separation and purification device for a natural gas ammonia production process according to claim 9, characterized in that: The top of the ammonia separator (32) is connected to the steam heater (4) via a pipe, and the top of the steam heater (4) is connected to a steam delivery pipe.

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