A coupling system for hydrogen production and carbon capture by natural gas dry and wet reforming

Abstract

The present invention relates to a coupling system for hydrogen production and carbon capture by dry and wet reforming of natural gas, comprising: a natural gas steam reforming unit, wherein natural gas and water vapor are preheated by a steam reforming raw gas preheater and then enter a steam reforming converter to react, and the reaction generated gas is cooled by the steam reforming raw gas preheater and then enters a conversion furnace; a hydrogen pressure swing adsorption purification unit, wherein hydrogen is separated from the gas after the reaction in the conversion furnace through a pressure swing adsorber, and the remaining gas enters the steam reforming converter for combustion; a carbon dioxide capture unit, wherein the combustion flue gas of the steam reforming converter and the dry reforming converter flows through the carbon capturer, and the carbon dioxide gas is separated and processed; a natural gas carbon dioxide dry reforming unit, wherein natural gas and part of the carbon dioxide gas captured by the carbon capturer are preheated by a dry reforming raw gas preheater and then enter the dry reforming converter, and the reaction generated gas is cooled by the dry reforming raw gas preheater and then stored or enters the conversion furnace.

Description

Technical Field

[0001] The invention relates to a coupling system for hydrogen production by dry and wet reforming of natural gas and carbon capture, belonging to the technical fields of energy chemical industry and environmental protection. Background Art

[0002] Hydrogen is a recognized clean secondary energy source with high calorific value and no pollution. After combustion, it only produces water. Increasing the proportion of hydrogen in the energy structure is one of the important ways for my country to achieve the "dual carbon" goal. At present, 90% of the world's hydrogen is produced by catalytic reaction using natural gas as raw material. One of the existing methods of hydrogen production: natural gas and water vapor react in the converter under high temperature and catalyst to produce CO, H2 and CO2, and then CO is further oxidized by water vapor in the conversion furnace to increase the production of hydrogen. After the mixed gas generated by the reaction is treated by pressure swing adsorption, high-purity hydrogen products can be separated, and other gases are refluxed to the converter and mixed with air and natural gas for combustion to provide heat to maintain the temperature required for the reforming reaction. According to the calculation of the skid-mounted natural gas hydrogen production device with a daily output of 500kg, the amount of flue gas generated by combustion is 762 standard cubic meters per hour, of which the CO2 content is 15.36%, and the carbon dioxide emissions per hour are about 230kg. The CO2 generated by the natural gas hydrogen production device currently in operation in China is finally directly discharged into the air through pipelines, causing pollution to human health and the environment.

[0003] In order to implement the concept of green and low-carbon development, the flue gas emitted by the skid-mounted natural gas hydrogen production device needs to be treated by carbon dioxide capture. There is no relevant report on how to combine the skid-mounted natural gas hydrogen production device with carbon dioxide capture. Summary of the invention

[0004] In response to the above technical problems, the present invention provides a coupling system for natural gas dry and wet reforming hydrogen production and carbon capture. The method uses the developed skid-mounted wet reforming hydrogen production system to couple the carbon dioxide capture equipment and the process of dry reforming reaction with natural gas after carbon dioxide capture, proposes an optimized design for the utilization of combustion flue gas heat, and a route selection for further increasing the hydrogen production by integrating dry reforming into the gas in the conversion furnace, ultimately achieving the goal of carbon emission reduction and the coordinated utilization of natural gas carbon dioxide to produce "blue hydrogen" and synthesis gas.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A coupling system for natural gas dry and wet reforming hydrogen production and carbon capture, comprising:

[0007] A natural gas steam reforming unit, comprising a steam reforming raw gas preheater, and a steam reforming converter and a shift converter respectively connected to the steam reforming raw gas preheater, wherein natural gas and steam are preheated by the steam reforming raw gas preheater and then enter the steam reforming converter to react, and the reaction product gas is cooled by the steam reforming raw gas preheater and then enters the shift converter;

[0008] A hydrogen pressure swing adsorption purification unit, comprising a pressure swing adsorber, the pressure swing adsorber is connected to the conversion furnace, the gas after the reaction in the conversion furnace is separated into hydrogen of a certain purity through the pressure swing adsorber, and the remaining gas enters the steam reforming conversion furnace for combustion;

[0009] A carbon dioxide capture unit, comprising a carbon capturer, wherein the carbon capturer is connected to the steam reforming converter and the dry reforming converter, and the combustion flue gas of the steam reforming converter and the dry reforming converter flows through the carbon capturer, and the carbon dioxide gas is separated and processed to form carbon dioxide gas with a certain purity;

[0010] The natural gas carbon dioxide dry reforming unit comprises a dry reforming raw gas preheater and the dry reforming converter which are interconnected, wherein the dry reforming raw gas preheater is connected to the carbon trap, and the dry reforming converter is connected to the steam reforming converter. The natural gas and a portion of carbon dioxide gas with a certain purity captured by the carbon trap are preheated by the dry reforming raw gas preheater and then enter the dry reforming converter. The reaction generated gas is cooled by the dry reforming raw gas preheater and can be stored as synthesis gas or enter the conversion furnace to further produce hydrogen.

[0011] The coupling system, preferably, further comprises a steam generating unit, wherein the steam generating unit comprises a steam generator, and the steam generator is respectively connected to the steam reforming feed gas preheater, the steam reforming converter, the shifting furnace, and the dry reforming converter.

[0012] The coupling system, preferably, further comprises a feedwater heater, wherein the feedwater heater is respectively connected to the steam generator and the conversion furnace, and water enters the steam generator after being preheated by the feedwater heater, and then is heated into steam by the combustion flue gas generated by the reaction of the steam reforming converter and the dry reforming converter, and then enters the steam reforming converter and the conversion furnace again, respectively, to provide the water vapor required for the natural gas steam reforming reaction and the carbon monoxide steam reaction.

[0013] The coupling system is preferably configured such that the water inlet of the steam generator is connected to the preheated water outlet of the feed water heater, the water vapor outlet of the steam generator is connected to the steam reforming feed gas preheater and the conversion furnace through regulating valves, the flue gas inlet of the steam generator is connected to the combustion chamber outlet of the steam reforming converter and the combustion chamber outlet of the dry reforming converter, and the flue gas outlet of the steam generator is connected to the air inlet of the carbon collector.

[0014] The coupling system is preferably configured such that the cold source inlet of the steam reforming raw gas preheater is connected to the natural gas raw gas pipe and the water vapor outlet of the steam generator, the cold source outlet of the steam reforming raw gas preheater is connected to the catalytic reaction air inlet of the steam reforming converter, the heat source inlet of the steam reforming raw gas preheater is connected to the catalytic reaction air outlet of the steam reforming converter, and the heat source outlet of the steam reforming raw gas preheater is connected to the air inlet of the conversion furnace.

[0015] In the coupling system, preferably, the air inlet of the combustion chamber of the steam reforming converter is connected to the natural gas raw material gas pipe, the air pipe, and the residual gas pipeline after the pressure swing adsorber separates hydrogen with a certain purity.

[0016] In the coupling system, preferably, the air inlet of the conversion furnace is connected to the heat source outlet of the steam reforming raw gas preheater, the water vapor outlet of the steam generator and the partially cooled reaction gas outlet of the dry reforming raw gas preheater, and the air outlet of the conversion furnace is connected to the heat source inlet of the feed water heater.

[0017] In the coupling system, preferably, the heat source outlet of the feedwater heater is connected to the inlet of the pressure swing adsorber, the cold source inlet of the feedwater heater is connected to normal temperature water, the carbon dioxide gas outlet of the carbon capturer is connected to the carbon dioxide storage and utilization end and the cold source inlet of the dry reforming feed gas preheater, and the remaining gas is discharged through the vent.

[0018] In the coupling system, preferably, the hydrogen outlet of the pressure swing adsorber is connected to the hydrogen storage end for pressurized liquefied storage or direct gaseous utilization of hydrogen, and the remaining gas is connected to the combustion chamber air inlet of the steam reforming converter through a pipeline.

[0019] The coupling system is preferably configured such that the reaction air inlet of the dry reforming converter is connected to the cold source outlet of the dry reforming raw gas preheater, the reaction air outlet of the dry reforming converter is connected to the heat source inlet of the dry reforming raw gas preheater, the combustion chamber air inlet of the dry reforming converter is connected to the combustion air and natural gas fuel pipelines, the combustion chamber outlet of the dry reforming converter is respectively connected to the combustion chamber air inlet of the steam reforming converter and the flue gas inlet of the steam generator, the cold source inlet of the dry reforming raw gas preheater is connected to the dry reforming reaction raw material natural gas pipeline and the carbon dioxide gas outlet of the carbon capturer, and the heat source outlet of the dry reforming raw gas preheater is connected to the air inlet and synthesis gas output end of the conversion furnace.

[0020] The present invention adopts the above technical solution, which has the following advantages:

[0021] 1. The present invention adds a carbon capture system to the flue gas outlet of the entire hydrogen production device, which greatly reduces carbon emissions and realizes the production of "blue hydrogen".

[0022] 2. The present invention adds a carbon dioxide dry reforming system at the front end of steam reforming. The reaction temperature is higher than that of steam reforming, and the flue gas can be utilized in multiple stages. In addition, the captured carbon dioxide gas can be directly consumed and used in conjunction with natural gas to produce synthesis gas.

[0023] 3. The synthesis gas generated by the increased natural gas carbon dioxide dry reforming system can be further used to produce hydrogen. The carbon monoxide in the synthesis gas reacts with water vapor in the conversion furnace to increase the hydrogen production.

[0024] 4. Steam reforming and carbon dioxide dry reforming share a conversion furnace and a hydrogen pressure swing adsorption purification system, which reduces the construction cost of the entire system and saves the floor space of the skid-mounted equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a coupled system for hydrogen production and carbon capture by dry and wet reforming of natural gas provided in one embodiment of the present invention;

[0026] The marks in the figure are as follows:

[0027] 1-steam generator; 2-steam reforming raw gas preheater; 3-steam reforming converter; 4-conversion furnace; 5-feedwater heater; 6-carbon collector; 7-pressure swing adsorber; 8-dry reforming converter; 9-dry reforming raw gas preheater; 10-supplementary air regulating valve; 11-supplementary natural gas regulating valve; 12-first dry reforming flue gas regulating valve; 13-second dry reforming flue gas regulating valve; 14-dry reforming carbon monoxide conversion regulating valve; 15-dry reforming integrated gas regulating valve; 16-first water vapor regulating valve; 17-second water vapor regulating valve; 18-first pressure swing adsorption valve; 19-second pressure swing adsorption valve. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work are within the scope of protection of the present invention.

[0029] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second", "third", "fourth" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" and the like mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0030] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside", "outside", "inner side", "outside", "below", "above", etc. Such spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0031] Hydrogen is a recognized clean secondary energy source with high calorific value and no pollution. It only produces water after combustion. Increasing the proportion of hydrogen in the energy structure is one of the important ways for my country to achieve the "dual carbon" goal. In order to implement the concept of green and low-carbon development, the flue gas emitted by the skid-mounted natural gas hydrogen production unit needs to be processed by carbon dioxide capture. There is no relevant report on how to combine the skid-mounted natural gas hydrogen production unit with carbon dioxide capture.

[0032] In response to the above technical problems, the present invention provides a coupling system for natural gas dry and wet reforming hydrogen production and carbon capture. The method uses the developed skid-mounted wet reforming hydrogen production system to couple the carbon dioxide capture equipment and the process of dry reforming reaction with natural gas after carbon dioxide capture, proposes an optimized design for the utilization of combustion flue gas heat, and a route selection for further increasing the hydrogen production by integrating dry reforming into the gas in the conversion furnace, ultimately achieving the goal of carbon emission reduction and the coordinated utilization of natural gas carbon dioxide to produce "blue hydrogen" and synthesis gas.

[0033] The present invention is explained in detail below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, the present invention is based on a natural gas steam wet reforming hydrogen production process system, and proposes a technical solution for coupling flue gas carbon dioxide capture and natural gas carbon dioxide dry reforming to produce synthesis gas. It mainly includes: a natural gas steam reforming unit, a hydrogen pressure swing adsorption purification unit, a carbon dioxide capture unit, a natural gas carbon dioxide dry reforming unit, and a steam generator 1 equipped for the above units.

[0035] The natural gas steam reforming unit is based on the transformation of a small skid-mounted natural gas hydrogen production device. After the natural gas and steam are mixed, they are heated in the steam reforming raw gas preheater 2, and the natural gas steam wet reforming reaction is carried out in the steam reforming converter 3. The gas generated by the reaction is cooled by the steam reforming raw gas preheater 2, mixed with water vapor and enters the conversion furnace 4, where carbon monoxide and water vapor react to generate hydrogen and carbon dioxide. The generated gas is cooled by heat exchange in the feed water heater 5 and then enters the hydrogen pressure swing adsorption purification unit.

[0036] The hydrogen pressure swing adsorption purification unit contains multiple pressure swing adsorption towers and matching compressors and program-controlled valves to ensure the continuity of the hydrogen separation process with a certain purity. Figure 1 The pressure swing adsorber 7 is simply shown in the figure, and the specific structure of the entire unit does not involve the core content of this invention and is not included in the figure. Figure 1 The separated hydrogen with a certain purity passes through the second pressure swing adsorption valve 19 for subsequent storage and utilization of hydrogen, and the other mixed gas passes through the first pressure swing adsorption valve 18, mixed with the combustion heating flue gas of the dry reforming converter 8, supplementary natural gas (through the supplementary natural gas regulating valve 11) and supplementary air (through the supplementary air regulating valve 10), and burned in the combustion chamber of the steam reforming converter 3.

[0037] The carbon dioxide capture unit Figure 1 It is embodied as a carbon capture device 6. The carbon capture process can be adopted but not limited to absorption method, adsorption method, membrane separation method and its coupling scheme. The present invention does not involve specific carbon capture technology. The combustion flue gas of the dry reforming converter 8 and the steam reforming converter 3 flows through the carbon capture device 6 after being cooled by the steam generator 1. The carbon dioxide gas undergoes a separation process to form a carbon dioxide gas product with a certain purity, which can be used for liquefaction, storage, transportation and utilization, and other gases are discharged. A part of the carbon dioxide gas passes through the first steam regulating valve 16 and is mixed with natural gas as a reactant for the natural gas carbon dioxide dry reforming reaction.

[0038] The natural gas carbon dioxide dry reforming unit is designed to synergistically utilize natural gas and captured carbon dioxide. After the carbon dioxide gas is mixed with natural gas, it is heated by the dry reforming raw gas preheater 9 and enters the dry reforming converter 8 to react and generate synthesis gas containing carbon monoxide and hydrogen. The synthesis gas can be further purified and stored through the dry reforming synthesis gas regulating valve 15 and used for downstream chemical synthesis reactions, or it can enter the conversion furnace 4 through the dry reforming carbon monoxide conversion regulating valve 14 to react carbon monoxide with water vapor to increase hydrogen production.

[0039] The steam generator 1 is a device that provides steam to the entire system, but it does not belong to the core part of the present invention. Figure 1 Normal temperature water (temperature range is 10-30℃, depending on the season) is preheated by the feed water heater 5 and enters the steam generator 1. After being heated by the flue gas to become steam, it passes through the first steam regulating valve 16 and the second steam regulating valve 17 respectively to provide the steam required for the natural gas steam reforming reaction and the carbon monoxide steam reaction.

[0040] The main process devices included in the present invention are:

[0041] 1. Natural gas steam reforming unit

[0042] Under the action of catalyst and certain temperature, the following chemical reactions mainly occur in the steam reforming converter 3:

[0043]

[0044] The raw gas natural gas and water vapor are preheated by the steam reforming raw gas preheater 2 and then enter the steam reforming converter 3. The reaction generated gas is cooled by the steam reforming raw gas preheater 2 and then enters the conversion furnace 4. Gas heat exchange can be divided into multiple stages according to the specific process. Figure 1 Only one steam reforming raw gas preheater 2 is shown. This reaction is an endothermic reaction, and additional heat required for the reaction should be provided. Air and natural gas are respectively burned in the combustion chamber of the steam reforming converter 3 through the supplementary air regulating valve 10 and the supplementary natural gas regulating valve 11; if the temperature of the combustion flue gas from the natural gas carbon dioxide dry reforming reaction is higher than the temperature of the natural gas water vapor wet reforming reaction, it also enters the combustion chamber of the steam reforming converter 3 through the second dry reforming flue gas regulating valve 13 to further utilize the waste heat; the gas after the reaction in the conversion furnace 4 is separated into a certain purity of hydrogen through the pressure swing adsorber 7, and the remaining gas contains a small amount of hydrogen, unreacted carbon monoxide, water vapor, natural gas and carbon dioxide, etc., and also enters the combustion chamber of the steam reforming converter 3 through the first pressure swing adsorption valve 18 for combustion, thereby improving the energy utilization rate.

[0045] 2. Natural gas carbon dioxide dry reforming unit

[0046] Under the action of catalyst and certain temperature, the following chemical reactions mainly occur in the dry reforming converter 8:

[0047]

[0048] The raw natural gas and the captured carbon dioxide of a certain purity are preheated by the dry reforming raw gas preheater 9 and then enter the dry reforming converter 8. The reaction generated gas can be stored as synthesis gas through the dry reforming synthesis gas regulating valve 15 after being cooled by the dry reforming raw gas preheater 9, or can enter the conversion furnace 4 through the dry reforming carbon monoxide conversion regulating valve 14 to further produce hydrogen by reacting the carbon monoxide in the synthesis gas with water vapor. Gas heat exchange can be divided into multiple stages according to the specific process. Figure 1 Only one heat exchanger is shown in the figure. The reaction is an endothermic reaction, and air and natural gas are burned in the combustion chamber of the dry reforming converter 8 to provide a heat source. Since the reaction temperature of the natural gas carbon dioxide dry reforming reaction is generally higher than that of the natural gas water vapor wet reforming reaction, if the combustion flue gas is higher than the wet reforming reaction temperature, it can enter the combustion chamber of the steam reforming converter 3 through the second dry reforming flue gas regulating valve 13, and can also enter the steam generator 1 through the first dry reforming flue gas regulating valve 12 to further utilize the waste heat.

[0049] 3. Shift furnace and pressure swing adsorption unit

[0050] The inlet gas of the shift furnace 4 is the product gas of the natural gas steam reforming reaction, the synthesis gas of the natural gas carbon dioxide dry reforming reaction and the steam at a certain temperature passing through the second steam regulating valve 17. The main reactions are:

[0051]

[0052] This reaction is an exothermic reaction, and the reaction temperature can be maintained by itself without the need for an additional heat source. The gas generated by the reaction in the conversion furnace 4 is cooled by the feedwater heater 5 and enters the pressure swing adsorption unit. Gas heat exchange can be divided into multiple stages according to the specific process. Figure 1 Only one heat exchanger is shown in the figure, where the cold source is water, which enters the steam generation unit 1 after preheating. The pressure swing adsorption unit includes multiple adsorption towers according to the specific process. The pressure and time of adsorption and desorption are adjusted by program-controlled valves inside to ensure the continuous and stable operation of gas separation. Figure 1 In the figure, one adsorption tower is used to briefly represent the entire pressure swing adsorption unit. The separated hydrogen with a certain purity enters the hydrogen storage unit through valve 19, and other gases enter the combustion chamber of the steam reforming converter 3 through the first pressure swing adsorption valve 18 to react with air for combustion.

[0053] 4. Steam generating unit

[0054] The combustion flue gas from the natural gas steam wet reforming reaction and the natural gas carbon dioxide dry reforming reaction enters the steam generator 1 and is used as a heat source to heat the water preheated from the feed water heater 5, and a phase change occurs to generate water vapor. The water vapor passes through the first steam regulating valve 16 and is mixed with the natural gas as the reaction gas for the natural gas steam reforming reaction; it passes through the second steam regulating valve 17 and enters the conversion furnace 4 as the reaction gas for reacting with carbon monoxide to generate hydrogen and carbon dioxide. The flue gas after heat recovery enters the carbon capture unit to separate and recover the carbon dioxide gas in the flue gas.

[0055] 5. Carbon capture unit

[0056] The function of the carbon capture device 6 is to separate the carbon dioxide from the flue gas from the steam generation unit. The system includes two parts: cooling and water separation pretreatment and carbon dioxide separation and purification. The carbon dioxide separation and purification can be carried out by absorption, adsorption, membrane separation or a combination of multiple methods. Figure 1 This unit is only briefly shown in the figure, and the internal equipment and process are not described in detail. The separated carbon dioxide gas with a certain purity can be used for liquefaction storage and utilization, and a part of the carbon dioxide gas is mixed with natural gas through the first steam regulating valve 16 as the reaction gas for the carbon dioxide dry reforming reaction of natural gas. The mixed gas containing only trace amounts of carbon dioxide is directly discharged after leaving the carbon capture unit.

[0057] Specific Example 1

[0058] like Figure 1 As shown, the water inlet of the steam generator 1 is connected to the preheated water outlet of the feedwater heater 5; the steam outlet of the steam generator 1 is connected to the first steam regulating valve 16 and the second steam regulating valve 17; the flue gas inlet of the steam generator 1 is connected to the combustion chamber outlet of the steam reforming converter 3 and the first dry reforming flue gas regulating valve 12; the flue gas outlet of the steam generator 1 is connected to the air inlet of the carbon capture device 6;

[0059] The cold source inlet of the steam reforming raw gas preheater 2 is connected to the natural gas raw gas and the first steam regulating valve 16; the cold source outlet of the steam reforming raw gas preheater 2 is connected to the catalytic reaction air inlet of the steam reforming converter 3; the heat source inlet of the steam reforming raw gas preheater 2 is connected to the catalytic reaction air outlet of the steam reforming converter 3; the heat source outlet of the steam reforming raw gas preheater 2 is connected to the air inlet of the conversion furnace 4;

[0060] The combustion chamber air inlet of the steam reforming converter 3 is connected to the supplementary air regulating valve 10, the supplementary natural gas regulating valve 11, the second dry reforming flue gas regulating valve 13 and the first pressure swing adsorption valve 18; the air inlet of the conversion furnace 4 is connected to the heat source outlet of the steam reforming raw gas preheater 2, the second water vapor regulating valve 17 and the dry reforming carbon monoxide conversion regulating valve 14; the air outlet of the conversion furnace 4 is connected to the heat source inlet of the feed water heater 5;

[0061] The heat source outlet of the feedwater heater 5 is connected to the inlet of the pressure swing adsorber 7; the cold source inlet of the feedwater heater 5 is connected to water at room temperature; the carbon dioxide gas outlet of the carbon capture device 6 is connected to the carbon dioxide storage and utilization end and the first water vapor regulating valve 16, and the remaining gas is discharged through the vent; the hydrogen outlet of the pressure swing adsorber 7 is connected to the second pressure swing adsorption valve 19 for pressurized liquefied storage or direct gaseous utilization of hydrogen, and the remaining gas is connected to the combustion chamber air inlet of the steam reforming converter 3 through the first pressure swing adsorption valve 18;

[0062] The reaction air inlet of the dry reforming converter 8 is connected to the cold source outlet of the dry reforming raw gas preheater 9; the reaction air outlet of the dry reforming converter 8 is connected to the heat source inlet of the dry reforming raw gas preheater 9; the air inlet of the combustion chamber of the dry reforming converter 8 is connected to the combustion air and natural gas fuel; the outlet of the combustion chamber of the dry reforming converter 8 is connected to the first dry reforming flue gas regulating valve 12 and the second dry reforming flue gas regulating valve 13; the cold source inlet of the dry reforming raw gas preheater 9 is connected to the dry reforming reaction raw natural gas and the first water vapor regulating valve 16; the heat source outlet of the dry reforming raw gas preheater 9 is connected to the dry reforming carbon monoxide conversion regulating valve 14 and the dry reforming integrated gas regulating valve 15.

[0063] The entire system of the present invention separates and purifies carbon dioxide in combustion flue gas on the basis of hydrogen production by steam reforming of natural gas, and consumes part of carbon dioxide on site through natural gas carbon dioxide dry reforming reaction. On the product side, the system can provide hydrogen of a certain purity, carbon dioxide of a certain purity and synthesis gas. The overall process flow of the system is relatively simple and easy to operate, and it occupies a small area. It can be designed and constructed in a skid-mounted manner. One skid is a natural gas hydrogen production system, and the other skid is a carbon capture system, which effectively reduces the overall cost. At the same time, the entire process fully considers heat recovery and utilization to improve the economic efficiency of the overall system operation.

[0064] The present invention is a supplementary design for a small skid-mounted natural gas steam reforming hydrogen production equipment. The steam reforming part has not been greatly changed, and a flue gas inlet is added at the inlet of the combustion chamber of the steam reforming converter. The added flue gas inlet is the combustion flue gas of the natural gas carbon dioxide dry reforming reaction. Since the temperature of the dry reforming reaction is higher than that of the wet reforming, the flue gas can provide heat for the wet reforming reaction, thereby realizing efficient utilization of energy.

[0065] The newly added carbon capture unit determines the process plan and process flow according to the carbon dioxide capture rate and the purity of the carbon dioxide gas product. Commonly used carbon capture processes include chemical absorption, adsorption and membrane separation. Since the volume fraction of carbon dioxide in the flue gas is less than 20%, cryogenic distillation is not applicable to this condition. The above three carbon capture methods can achieve a carbon dioxide capture rate of 90% and a carbon dioxide gas product purity of 95%, greatly reducing the total amount of carbon dioxide emitted by the natural gas skid-mounted production of "grey hydrogen" and converting it to the natural gas skid-mounted production of "blue hydrogen". In addition, the captured carbon dioxide gas can be directly used in the natural gas carbon dioxide dry reforming hydrogen production reaction, realizing the integration of carbon dioxide capture and utilization.

[0066] The newly coupled natural gas CO2 dry reforming unit can achieve the coordinated utilization of natural gas and CO2, consume part of the captured CO2 gas on site, and give the entire system product diversity. The synthesis gas generated by the dry reforming reaction can be further purified and separated for the manufacture of high value-added chemical products such as methanol; the carbon monoxide in the synthesis gas can also be further reacted with water vapor in the conversion furnace to increase the production of hydrogen. The system can change the process at any time according to market conditions to achieve optimal benefits.

[0067] The present invention is based on carbon dioxide capture technology. It captures carbon dioxide generated in the process of hydrogen production from natural gas steam reforming reaction and carbon dioxide in combustion flue gas used for reaction heating. While ensuring clean flue gas emissions, the captured carbon dioxide is reused in natural gas carbon dioxide dry reforming. Supplementary heating is designed and the cascade utilization of reaction heating is optimized. The synthesis gas generated by the dry reforming reaction can be used for chemical preparation or to further increase hydrogen production. Under the coupling of multiple processes, a technical system for the synergistic utilization of natural gas and carbon dioxide capture to produce "blue hydrogen" and synthesis gas is established.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coupling system for natural gas dry and wet reforming hydrogen production and carbon capture, characterized in that: include: A natural gas steam reforming unit, comprising a steam reforming raw gas preheater (2) and a steam reforming converter (3) and a shift converter (4) respectively connected to the steam reforming raw gas preheater (2); natural gas and steam are preheated by the steam reforming raw gas preheater (2) and then enter the steam reforming converter (3) to react; and a reaction product gas is cooled by the steam reforming raw gas preheater (2) and then enters the shift converter (4); A hydrogen pressure swing adsorption purification unit, comprising a pressure swing adsorber (7), wherein the pressure swing adsorber (7) is connected to the conversion furnace (4), and the gas after reaction in the conversion furnace (4) is separated into hydrogen of a certain purity through the pressure swing adsorber (7), and the remaining gas enters the steam reforming conversion furnace (3) for combustion; A carbon dioxide capture unit, comprising a carbon capturer (6), wherein the carbon capturer (6) is connected to the steam reforming converter (3) and the dry reforming converter (8), and the combustion flue gas of the steam reforming converter (3) and the dry reforming converter (8) flows through the carbon capturer (6), and the carbon dioxide gas is separated and processed to form carbon dioxide gas with a certain purity; A natural gas carbon dioxide dry reforming unit, comprising a dry reforming raw gas preheater (9) and a dry reforming converter (8) which are interconnected, wherein the dry reforming raw gas preheater (9) is connected to the carbon trap (6), and the dry reforming converter (8) is connected to the steam reforming converter (3), the natural gas and a portion of carbon dioxide gas of a certain purity captured by the carbon trap (6) are preheated by the dry reforming raw gas preheater (9) and then enter the dry reforming converter (8), and the reaction generated gas is cooled by the dry reforming raw gas preheater (9) and can be stored as synthesis gas or enter the shift converter (4) to further produce hydrogen; The combustion chamber air inlet of the steam reforming converter (3) is connected to a natural gas raw material gas pipe, an air pipe, and a residual gas pipeline after the pressure swing adsorber (7) separates hydrogen with a certain purity; The combustion chamber air inlet of the dry reforming converter (8) is connected to the combustion air and natural gas fuel pipelines, and the combustion chamber outlet of the dry reforming converter (8) is connected to the combustion chamber air inlet of the steam reforming converter (3).

2. The coupling system according to claim 1, characterized in that: The coupling system further comprises a steam generating unit, wherein the steam generating unit comprises a steam generator (1), and the steam generator (1) is respectively connected to the steam reforming raw gas preheater (2), the steam reforming converter (3), the shift converter (4), and the dry reforming converter (8).

3. The coupling system according to claim 2, characterized in that: The coupling system further comprises a feedwater heater (5), wherein the feedwater heater (5) is connected to the steam generator (1) and the shift converter (4) respectively. Water is preheated by the feedwater heater (5) and then enters the steam generator (1). Water is then heated to steam by the combustion flue gas generated by the reaction of the steam reforming converter (3) and the dry reforming converter (8), and then enters the steam reforming converter (3) and the shift converter (4) again, respectively, to provide water vapor required for the natural gas steam reforming reaction and the carbon monoxide steam reaction.

4. The coupling system according to claim 3, characterized in that: The water inlet of the steam generator (1) is connected to the preheated water outlet of the feed water heater (5); the water vapor outlet of the steam generator (1) is connected to the steam reforming raw gas preheater (2) and the conversion furnace (4) through regulating valves; the flue gas inlet of the steam generator (1) is connected to the combustion chamber outlet of the steam reforming conversion furnace (3) and the combustion chamber outlet of the dry reforming conversion furnace (8); and the flue gas outlet of the steam generator (1) is connected to the air inlet of the carbon capture device (6).

5. The coupling system according to claim 4, characterized in that: The cold source inlet of the steam reforming raw gas preheater (2) is connected to the natural gas raw gas pipe and the water vapor outlet of the steam generator (1); the cold source outlet of the steam reforming raw gas preheater (2) is connected to the catalytic reaction air inlet of the steam reforming conversion furnace (3); the heat source inlet of the steam reforming raw gas preheater (2) is connected to the catalytic reaction air outlet of the steam reforming conversion furnace (3); and the heat source outlet of the steam reforming raw gas preheater (2) is connected to the air inlet of the conversion furnace (4).

6. The coupling system according to claim 5, characterized in that: The air inlet of the conversion furnace (4) is connected to the heat source outlet of the steam reforming raw gas preheater (2), the water vapor outlet of the steam generator (1) and the partially cooled reaction gas outlet of the dry reforming raw gas preheater (9), and the air outlet of the conversion furnace (4) is connected to the heat source inlet of the feed water heater (5).

7. The coupling system according to claim 6, characterized in that: The heat source outlet of the feed water heater (5) is connected to the inlet of the pressure swing adsorber (7), the cold source inlet of the feed water heater (5) is connected to normal temperature water, the carbon dioxide gas outlet of the carbon capture device (6) is connected to the carbon dioxide storage and utilization end and the cold source inlet of the dry reforming feed gas preheater (9), and the remaining gas is discharged through the vent.

8. The coupling system according to claim 7, characterized in that: The hydrogen outlet of the pressure swing adsorber (7) is connected to the hydrogen storage end for pressurized liquefied storage or direct gaseous utilization of hydrogen, and the remaining gas is connected to the combustion chamber air inlet of the steam reforming converter (3) through a pipeline.

9. The coupling system according to claim 8, characterized in that: The reaction air inlet of the dry reforming converter (8) is connected to the cold source outlet of the dry reforming raw gas preheater (9), the reaction air outlet of the dry reforming converter (8) is connected to the heat source inlet of the dry reforming raw gas preheater (9), the flue gas inlet of the steam generator (1) is connected, the cold source inlet of the dry reforming raw gas preheater (9) is connected to the dry reforming reaction raw natural gas pipeline and the carbon dioxide gas outlet of the carbon capture device (6), and the heat source outlet of the dry reforming raw gas preheater (9) is connected to the air inlet of the conversion furnace (4) and the synthesis gas output end.

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