Preparation method and device of synthesis gas with adjustable hydrogen-carbon ratio and high CO concentration and application of synthesis gas

Abstract

The invention provides a preparation method of synthesis gas with adjustable hydrogen-carbon ratio and high CO concentration, and a device and application thereof. The method comprises the following steps: preheating raw material gas; the feed gas comprises natural gas, water vapor and carbon dioxide; the preheated raw material gas flow is subjected to combined reforming under the condition of a reforming catalyst, so that the natural gas reacts with carbon dioxide, the natural gas reacts with water vapor, and the water vapor reacts with the natural gas; the reformed gas stream is decarbonized, and the removed carbon dioxide stream is recycled to the upstream. The technical problems to be solved are how to adjust the hydrogen-carbon ratio of the synthesis gas in a wide range to obtain the synthesis gas with high CO concentration, increase the CO / H2 ratio of the synthesis gas and avoid or reduce the emission of carbon dioxide. The raw material, fuel and steam consumption of CO in unit volume is reduced, and the energy-saving effect is obvious.

Description

Technical Field

[0001] The present invention relates to the field of chemical technology, and in particular to a method for preparing synthesis gas with an adjustable hydrogen-to-carbon ratio and a high CO concentration, a device thereof, and applications thereof. Background Art

[0002] Synthesis gas with high CO concentration has a wide range of applications and can be used to synthesize methanol, acetic acid, FT synthesis, etc. The existing technologies for preparing synthesis gas with high CO concentration by reforming mainly include:

[0003] Steam reforming uses hydrocarbons (such as natural gas and methane) as feedstock, reacting with steam at high temperatures and in the presence of a catalyst to produce synthesis gas. By adjusting reaction conditions and catalyst performance, the CO content can be increased, reaching as high as 30% to 40%. However, the hydrogen-to-carbon ratio of the synthesis gas produced by this method is high, making it difficult to meet the hydrogen-to-carbon ratio requirements of plants such as acetic acid synthesis, FT-H synthesis, and higher alcohols.

[0004] The catalytic partial oxidation method partially oxidizes hydrocarbon fuel with an appropriate amount of oxygen at high temperature to quickly generate synthesis gas mainly composed of CO and H2. Although the synthesis gas prepared by this method has a relatively low hydrogen and carbon content, the ATR partial catalytic oxidation method requires supporting air separation, and its operating costs and energy consumption are relatively high.

[0005] There are also some reports in the existing technology on preparing synthesis gas by dry reforming of CO2 and methane. However, due to the serious carbon deposition of this process, there is no industrial operation record yet. Summary of the Invention

[0006] The main purpose of the present invention is to provide a method for preparing synthesis gas with a high CO concentration and an adjustable hydrogen-to-carbon ratio, as well as its device and application. The technical problem to be solved is how to adjust the hydrogen-to-carbon ratio of the synthesis gas within a wide range to obtain synthesis gas with a high CO concentration. On the one hand, through the recycling of carbon dioxide, the CO / H2 ratio in the product synthesis gas is increased, so that the final product plan downstream of the synthesis gas can be adjusted according to market fluctuations, thereby maximizing the profit of the device. On the other hand, through the recycling of carbon dioxide, carbon dioxide emissions can be avoided or reduced, which is environmentally friendly. At the same time, the recycling of carbon dioxide significantly reduces the water vapor consumption in the reforming reactor, which is equivalent to reducing the raw material, fuel and steam consumption per unit volume of CO, with obvious energy-saving effects, making it more suitable for practical use.

[0007] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions. According to the present invention, a method for preparing a high CO concentration synthesis gas with an adjustable hydrogen-to-carbon ratio is provided, which comprises the following steps:

[0008] Preheating the raw gas; the raw gas includes natural gas, water vapor and carbon dioxide;

[0009] The preheated raw gas stream is subjected to combined reforming under the conditions of a reforming catalyst, so that natural gas reacts with carbon dioxide, natural gas reacts with water vapor, and water vapor reacts with natural gas; the reforming catalyst is selected from nickel-based and / or cobalt-based catalysts;

[0010] The reformed gas stream is decarbonized, and the removed carbon dioxide stream is circulated back to the upstream, and the synthesis gas from which carbon dioxide is removed is a synthesis gas with a high CO concentration.

[0011] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0012] Preferably, in the aforementioned preparation method, the raw gas is selected from marine natural gas with a high carbon dioxide content, biogas from biological fermentation and / or coke oven gas.

[0013] Preferably, the aforementioned preparation method further includes a raw gas purification step before the raw gas preheating step, specifically: heating the carbon dioxide-rich natural gas to 350-380°C, and then performing hydrogenation and desulfurization in sequence to reduce the sulfur content in the natural gas to ≤0.1ppmv.

[0014] Preferably, the aforementioned preparation method further comprises, after the raw gas is purified and before the raw gas is preheated: mixing the desulfurized gas flow with water vapor for pre-conversion to remove high-carbon hydrocarbons.

[0015] Preferably, the aforementioned preparation method further comprises recovering waste heat from the reformed gas flow before the decarbonization treatment.

[0016] Preferably, the aforementioned preparation method further comprises a step of pressurizing the carbon dioxide flow before the carbon dioxide flow is merged into the raw gas flow.

[0017] Preferably, in the aforementioned preparation method, the molar concentration of carbon dioxide in the raw gas stream after being merged into the carbon dioxide stream is 25 to 60 mol%.

[0018] Preferably, in the aforementioned preparation method, a partially removed carbon dioxide stream is introduced into the raw gas stream, and a partially removed carbon dioxide stream is discharged; by controlling the ratio of the carbon dioxide introduced into the raw gas stream to the carbon dioxide discharged, the hydrogen-carbon ratio of the synthesis gas with a high CO concentration can be adjusted between 1.3 and 1.9.

[0019] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions. According to the present invention, a system for producing a high CO concentration synthesis gas with an adjustable hydrogen-to-carbon ratio is proposed, which comprises:

[0020] A first heater is used to heat the carbon dioxide-rich natural gas feedstock to a preset temperature;

[0021] a hydrogenation reactor, arranged in series downstream of the first heater, for hydrogenating the natural gas feedstock;

[0022] a desulfurization reactor, arranged in series downstream of the hydrogenation reactor, for desulfurizing the natural gas feedstock;

[0023] a second heater, arranged in series downstream of the desulfurization reactor, for preheating the natural gas feedstock, water vapor and / or circulating carbon dioxide stream to a preset temperature;

[0024] a reforming reactor, arranged in series downstream of the second heater; a reforming catalyst is arranged inside the reforming reactor for causing a reforming reaction of the raw gas stream;

[0025] a waste heat recovery device, arranged in series downstream of the reforming reactor, for recovering waste heat from the reformed gas stream;

[0026] a decarbonization device, arranged in series downstream of the waste heat recovery device, for removing carbon dioxide from the synthesis gas;

[0027] A compressor is arranged in series downstream of the decarbonization device, and is used to compress the carbon dioxide flow; the outlet of the compressor is connected to the raw gas inlet of the reforming reactor, and is used to send the circulating carbon dioxide flow into the reforming reactor.

[0028] The objectives of the present invention and the technical problems solved therein are achieved by adopting the following technical solutions: According to the present invention, a high CO concentration synthesis gas prepared according to the above preparation method is used in the technical fields of acetic acid synthesis, Fischer-Tropsch synthesis, high carbon alcohol synthesis, or co-production of acetic acid and synthetic ammonia.

[0029] By means of the above technical solution, the present invention provides a method for preparing syngas with a high CO concentration and an adjustable hydrogen-to-carbon ratio, and its device and application have at least the following advantages:

[0030] The method for preparing a high CO concentration synthesis gas with an adjustable hydrogen-carbon ratio proposed in the present invention is a combined reforming method, which allows a preheated mixed gas to flow through a combined reforming catalyst, and at the same time, under external heat and preset pressure conditions, reacts natural gas with CO2, natural gas with water vapor, and water vapor with CO2 to generate synthesis gas; the present invention removes unconverted carbon dioxide from the reformed gas flow flowing out of the reforming reactor through decarbonization treatment to obtain a synthesis gas with a high CO concentration, and partially or completely pressurizes the removed carbon dioxide flow and recirculates it upstream, for example, to merge it into the raw gas flow and re-enter the reforming reactor to further participate in the reaction, so that the carbon dioxide is converted as much as possible. It is a useful synthesis gas that can eliminate or reduce carbon dioxide emissions, and has obvious environmental protection effects. By recycling carbon dioxide back to the reforming reactor, the water vapor consumption in the reforming reactor can be significantly reduced, thereby also increasing the CO / H2 ratio in the product synthesis gas. By increasing the CO ratio in the synthesis gas, it is equivalent to reducing the raw material, fuel and steam consumption per unit volume of CO, with obvious energy-saving effects. By adjusting the ratio of CO2 recycled back to the reforming reactor, the CO / H2 ratio in the product gas can be easily adjusted, so that the final product plan downstream of the synthesis gas can be adjusted according to market fluctuations, so as to maximize the benefits of the device.

[0031] Furthermore, the present invention proposes a method for preparing high-CO concentration synthesis gas with an adjustable hydrogen-carbon ratio, a device therefor, and an application thereof. It can comprehensively utilize marine natural gas with a high CO2 content, biogas from biological fermentation, or coke oven gas as raw materials to prepare synthesis gas, while reducing the emissions of two greenhouse gases, CH4 and CO2, and has good economic and social benefits.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 1 is a schematic diagram of the process flow for preparing synthesis gas in Example 1 of the present invention;

[0034] Figure 2 Schematic diagram of the process flow for preparing synthesis gas in Example 2 of the present invention;

[0035] Figure 3 Schematic diagram of the process flow for preparing synthesis gas in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0036] To further illustrate the technical means and effectiveness of the present invention in achieving its intended objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail a method for producing high-CO-concentration syngas with an adjustable hydrogen-to-carbon ratio, an apparatus thereof, and its specific embodiments, structures, features, and effectiveness. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0037] The present invention proposes a method for preparing a synthesis gas with a high CO concentration and an adjustable hydrogen-carbon ratio, as shown in the attached Figure 1 To the attached Figure 3 As shown, it specifically includes the following steps:

[0038] First, the raw gas is preheated. The technical effects of the present invention can be achieved by controlling the preheating temperature in this step within the range of 450-600°C. The use of 600°C in the subsequent specific embodiments is for illustrative purposes only and does not limit the technical solution of the present invention. The raw gas of the present invention includes natural gas, water vapor, and carbon dioxide. Specifically, the raw gas can be marine natural gas with a high carbon dioxide content, biogas from biofermentation, and / or coke oven gas, and can include methane, carbon dioxide, and water vapor, or it can include natural gas with a high carbon dioxide content and water vapor.

[0039] The preheated feed gas is passed into a reforming reactor, such as a converter, for reforming; wherein the reforming reactor is loaded with a combined reforming catalyst, preferably the reforming catalyst is selected from a nickel-based and / or cobalt-based catalyst, such as a commercially available nickel-based and / or cobalt-based catalyst from BASF; in the reforming reactor, the gauge pressure of the reforming pressure is controlled to be 1 to 4 MPa; in this step, the technical effect of the present invention can be achieved by controlling the gauge pressure within the range of 1 to 4 MPa; the use of about 2 MPa in the subsequent specific embodiments is only for illustrative purposes and does not constitute a limitation on the technical solution of the present invention.

[0040] The temperature in the reforming reactor is controlled by external heat supply, so that natural gas reacts with carbon dioxide, natural gas reacts with water vapor, and water vapor reacts with natural gas, and the outlet temperature of the reformed gas stream after combined reforming is controlled to be 800-930°C. In this step, the technical effects of the present invention can be achieved by controlling the outlet temperature of the reformed gas stream within the range of 800-930°C. The use of a temperature of approximately 860°C in subsequent specific embodiments is merely illustrative and does not constitute a limitation on the technical solution of the present invention.

[0041] To ensure the purity of the prepared syngas, the present invention preferably includes a raw gas purification step before the raw gas preheating step. Specifically, the carbon dioxide-rich natural gas is heated to 350-380°C, followed by hydrogenation and desulfurization to reduce the sulfur content in the natural gas to ≤0.1 ppmv. The technical effects of the present invention can be achieved by controlling the preheating temperature within the range of 350-380°C. The use of 370°C in the subsequent specific embodiments is merely illustrative and does not constitute a limitation of the technical solution of the present invention. Carbon dioxide-rich natural gas may contain sulfur compounds, such as hydrogen sulfide. To prevent these sulfur compounds from seriously harming the subsequent syngas production and chemical processes utilizing the syngas, the present invention preferably performs a purification treatment by hydrogenation and desulfurization to effectively remove these sulfur impurities and ensure the purity of the syngas. Furthermore, sulfur impurities may also affect the reactivity of active components in the syngas, such as carbon monoxide and hydrogen, reducing the quality and performance of the syngas. After desulfurization, the syngas can react more efficiently in subsequent chemical processes such as methanol and ammonia synthesis, improving product quality and yield. Furthermore, sulfur-containing compounds can react with metals in equipment under certain conditions, causing corrosion. Therefore, strict control of the sulfur content in the feedstock can reduce corrosion and extend the service life of the equipment. Furthermore, sulfur impurities can poison and deactivate reforming catalysts, reducing their activity and selectivity. The present invention preferably removes sulfur impurities through hydrogenation and desulfurization to protect the catalyst and maintain good catalytic performance. The specific hydrogenation and desulfurization processes can be carried out using conventional techniques in the art and are not specifically limited in this invention.

[0042] Optionally, the technical solution of the present invention further comprises mixing the desulfurized gas flow with water vapor for pre-conversion after the raw gas is purified and before the raw gas is preheated, so as to remove high-carbon hydrocarbons; the pre-conversion step here is optional. Figure 1 To the attached Figure 3 Indicated by a dotted box. Removing high-carbon hydrocarbons through pre-conversion can, on the one hand, optimize and stabilize the composition of synthesis gas, reduce the occurrence of some undesirable side reactions, increase the proportion of effective ingredients, and reduce the fluctuation of the composition of synthesis gas; on the other hand, since high-carbon hydrocarbons are easily decomposed to produce carbon at high temperatures, it causes carbon deposition in the equipment, affects the heat transfer efficiency of the equipment, and even blocks the equipment, reducing the service life of the equipment, and high-carbon hydrocarbons may poison or deactivate the catalyst, reducing the performance of the catalyst; the present invention can avoid or reduce carbon deposition in the equipment and maintain catalyst activity through the pre-conversion step. Furthermore, since it takes more energy to bring high-carbon hydrocarbons into the reforming reactor for conversion, removing them in advance can reduce the energy consumption of subsequent processes and improve the efficiency of the entire synthesis gas preparation process. The specific process of pre-conversion can be carried out using conventional technical means in the field, and this is not specifically limited in the present invention.

[0043] The temperature of the reformed gas stream after the reaction reaches as high as 800-930°C, containing a large amount of thermal energy. To better utilize this heat, avoid or reduce energy loss, and achieve cost savings, the present invention preferably recovers the waste heat from the reformed gas stream exiting the reforming reactor. Furthermore, by incorporating a waste heat recovery step into the reformed gas stream, the temperature of the reformed gas stream can be further stabilized, thereby improving the stability of the syngas production process. The specific waste heat recovery method can be performed using conventional techniques in the art and is not specifically limited in this invention.

[0044] Then the reformed gas flow is decarbonized. The purpose of decarbonization is to avoid excessive carbon dioxide content in the synthesis gas, thereby reducing the effective gas components and affecting the quality and application scenarios of the synthesis gas. The decarbonization process can adopt a chemical absorption method, in which the synthesis gas is contacted with a chemical absorbent, and the carbon dioxide and the absorbent react chemically to form a compound to achieve separation; it can also adopt a physical absorption method, which absorbs carbon dioxide based on the difference in solubility of carbon dioxide in different solvents; it can also adopt a pressure swing adsorption method, which utilizes the characteristic that the adsorption capacity of the adsorbent for different gas components changes with pressure, and adsorbs carbon dioxide under high pressure and desorbs it under low pressure to achieve decarbonization. The present invention does not specifically limit the decarbonization process, and conventional decarbonization methods in the field can be used, as long as the carbon dioxide can be effectively removed.

[0045] The product after decarbonization treatment is the synthesis gas with a high CO concentration prepared by the present invention, and its hydrogen-carbon ratio can be flexibly adjusted between 1.3 and 1.9.

[0046] The key to regulating the hydrogen-carbon ratio in the present invention lies in controlling the flow direction of the carbon dioxide flow after decarbonization treatment; when all the removed carbon dioxide is recycled upstream and re-enters the reforming reactor, the hydrogen-carbon ratio of the prepared synthesis gas can be as low as 1.3, as shown in Example 1, the hydrogen-carbon ratio is 1.37; and when all the removed carbon dioxide is vented and not recycled upstream, the hydrogen-carbon ratio of the prepared synthesis gas can reach about 1.9, as shown in Comparative Example 1; and when part of the removed carbon dioxide flow is recycled upstream to merge into the raw gas flow and part of the removed carbon dioxide flow is vented, the hydrogen-carbon ratio of the prepared synthesis gas can be between 1.3 and 1.9, as shown in Example 2, when 50% of the carbon dioxide is recycled upstream and 50% of the carbon dioxide flow is vented, the hydrogen-carbon ratio of the prepared synthesis gas is 1.68.

[0047] In order to enable the prepared synthesis gas to be better applied to subsequent production in the fields of acetic acid synthesis, Fischer-Tropsch synthesis, higher alcohol synthesis or co-production of acetic acid and synthetic ammonia, the present invention preferably controls the molar concentration of carbon dioxide in the raw gas flow after the carbon dioxide flow is merged to be 25-60% mol.

[0048] Before carbon dioxide is recycled and reused, the present invention preferably subject it to pressurization treatment. The reason for its compression treatment is, on the one hand, to improve the transportation efficiency, because uncompressed carbon dioxide is large in volume and will occupy a lot of space in the transportation system such as pipelines, resulting in low transportation efficiency; on the other hand, because the reforming reaction is carried out under certain pressure conditions, its compression is to enable the carbon dioxide to meet the use pressure requirements. The pressure treatment can be carried out by conventional means in the art, as long as the technical purpose of the pressurization can be achieved, and the present invention does not make specific restrictions.

[0049] The present invention also proposes a system for preparing a synthesis gas with an adjustable hydrogen-to-carbon ratio and a high CO concentration, which comprises: a first heater, which is mainly used to heat a natural gas feedstock rich in carbon dioxide so that it can reach the temperature required for the feedstock purification reaction; in a specific embodiment of the present invention, the first heater is used to heat the natural gas rich in carbon dioxide to 350-380°C; the system also comprises a hydrogenation reactor, which is arranged in series downstream of the first heater and is mainly used to hydrogenate the natural gas feedstock; the system also comprises a desulfurization reactor, which is arranged in series downstream of the hydrogenation reactor and is mainly used to desulfurize the natural gas feedstock; after the above-mentioned process, the sulfur content in the natural gas feedstock can reach a level of ≤0.1ppm by volume; the system also comprises a second heater, which is arranged in series downstream of the desulfurization reactor and is mainly used to preheat the natural gas feedstock, water vapor and / or circulating carbon dioxide flow to reach Preset temperature; in a specific embodiment of the present invention, the second heater is used to heat raw gases such as natural gas, water vapor, and carbon dioxide to 450-600°C; the system also includes a reforming reactor, which is arranged in series downstream of the second heater; a reforming catalyst is arranged inside the reforming reactor, and the reforming catalyst is selected from nickel-based and / or cobalt-based catalysts, and the reforming reactor is mainly used to cause the raw gas flow to undergo a reforming reaction here; the system also includes a waste heat recovery device, which is arranged in series downstream of the reforming reactor, and is mainly used to recover waste heat from the reformed gas flow; the system also includes a decarbonization device, which is arranged in series downstream of the waste heat recovery device, and is mainly used to remove carbon dioxide from the synthesis gas; the system also includes a compressor, which is arranged in series downstream of the decarbonization device, and is mainly used to compress the carbon dioxide flow; the outlet of the compressor is connected to the raw gas inlet of the reforming reactor, and is used to send the circulating carbon dioxide flow into the reforming reactor.

[0050] The present invention also proposes an application of the high CO concentration synthesis gas prepared according to the above preparation method in the technical fields of acetic acid synthesis, Fischer-Tropsch synthesis, high carbon alcohol synthesis or co-production of acetic acid and synthetic ammonia.

[0051] The present invention will be further described below with reference to specific embodiments, but this should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0052] Unless otherwise specified, the materials and reagents mentioned below are commercially available products familiar to those skilled in the art. Unless otherwise specified, the methods described are all well-known methods in the art. Unless otherwise defined, technical or scientific terms used shall have the same meanings as those commonly understood by those skilled in the art.

[0053] Example 1

[0054] This embodiment is an implementation case in which the carbon dioxide stream removed in the synthesis gas preparation process is pressurized and recycled back to the upstream working condition. In this embodiment, the hydrogen-carbon ratio of the product synthesis gas is about 1.37. The process is as shown in the attached figure. Figure 1 The material flow is shown in Table 1. The specific steps are as follows:

[0055] The combined reforming reactor is a pipeline reactor filled with 40 cubic meters of BASF's nickel- and / or cobalt-based catalyst. The CO2-rich raw natural gas is preheated to 370°C, hydrogenated, and desulfurized to reduce the sulfur content to 0.1 ppmv. After mixing with steam, it enters a pre-conversion reactor (optional) to remove higher hydrocarbons. It is then mixed with recycled CO2 and preheated to 600°C before entering the combined reforming reactor for a reaction at 2 MPa. The post-reaction process gas temperature can reach approximately 860°C. The post-reaction process gas undergoes a waste heat recovery process to maximize heat recovery before entering a decarbonization unit to remove CO2 to meet the CO2 content requirements of downstream equipment. All removed CO2 is returned to the combined reforming inlet for further reaction. Throughout the entire process, no CO2 from the raw natural gas needs to be discharged, except for some CO2 emitted from the flue gas during the natural gas preheating process, virtually 100% of the carbon in the raw natural gas is utilized.

[0056] Example 2

[0057] This embodiment is an implementation case in which a portion of the carbon dioxide stream (about 50%) removed in the synthesis gas preparation process is pressurized and recycled to the upstream working condition. In this embodiment, the hydrogen-carbon ratio of the product synthesis gas is about 1.68. The process is as shown in the attached figure. Figure 2 The material flow is shown in Table 1. The specific steps are as follows:

[0058] The combined reforming reactor is a pipeline reactor filled with 40 cubic meters of BASF's nickel- and / or cobalt-based catalyst. The CO2-rich raw natural gas is preheated to 370°C, hydrogenated, and desulfurized to reduce the sulfur content to 0.1 ppmv. After mixing with steam, it enters a pre-conversion reactor (optional) to remove higher carbon hydrocarbons. It is then mixed with recycled CO2 and preheated to 600°C before entering the combined reforming reactor for a reaction at 2 MPa. The post-reaction process gas temperature can reach approximately 860°C. The post-reaction process gas undergoes a waste heat recovery process to maximize heat recovery before entering a decarbonization unit to remove CO2 to meet the CO2 content requirements of downstream equipment. 50% of the removed CO2 is returned to the combined reforming inlet for further reaction. In addition to the CO2 emitted from the flue gas during the natural gas preheating process, some excess carbon in the raw natural gas must be discharged as CO2.

[0059] Comparative Example 1

[0060] This embodiment is an implementation case in which the carbon dioxide stream removed in the synthesis gas preparation process is completely vented. In this embodiment, the hydrogen-carbon ratio of the product synthesis gas is about 1.9. The process is as shown in the attached figure. Figure 3 The material flow is shown in Table 1. The specific steps are as follows:

[0061] The CO2-rich raw natural gas is preheated to 370°C, hydrogenated, and desulfurized to reduce the sulfur content to 0.1 ppmv. The natural gas is then mixed with steam and fed into a pre-reforming reactor (optional) to remove higher-carbon hydrocarbons. The gas is then preheated again to 600°C and fed into a combined reforming reactor where a reaction occurs at 2 MPa. The post-reaction process gas temperature can reach approximately 860°C. The post-reaction process gas undergoes a waste heat recovery process to recover as much heat as possible before entering a decarbonization unit to remove CO2 to meet the CO2 content requirements of downstream equipment. All removed CO2 is vented to the atmosphere.

[0062] Table 1

[0063] project Implementation Case 1 Implementation Case 2 Implementation Case 3 <![CDATA[Raw natural gas consumption, Nm 3 / h]]> 56303 58335 58335 <![CDATA[Fuel gas natural gas consumption, Nm 3 / h]]> 17584 16290 13107 <![CDATA[Total output of syngas (CO + H2), Nm 3 / h]]> 100000 100000 100000 <![CDATA[The content of CO in syngas, Nm 3 / h]]> 42205 37314 33531 <![CDATA[Content of H2 in syngas, Nm 3 / h]]> 57795 61861 63799 <![CDATA[H2 / CO]]> 1.37 1.68 1.90 Energy consumption per thousand standard cubic meters of synthesis gas, GJ 17.64 17.10 16.73 <![CDATA[Thousand standard cubic meters of syngas emissions, t CO2]]> 0.476 0.554 0.617

[0064] It can be seen from the above embodiments that the ratio of CO to H2 in the synthesis gas product can be adjusted by implementing the technical solution of the present invention; at the same time, due to the comprehensive utilization of CO2, the CO2 emission intensity is reduced by about 30%; Comparative Example 1 is a case under non-circulating CO2 conditions and can be used as a comparative condition.

[0065] The technical features in the claims and / or the specification of the present invention may be combined, and the manner of combination is not limited to the combination obtained by reference in the claims. The technical solutions obtained by combining the technical features in the claims and / or the specification are also within the scope of protection of the present invention.

[0066] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing synthesis gas with an adjustable hydrogen-to-carbon ratio and high CO concentration, characterized in that: It includes the following steps: Preheating the raw gas; the raw gas includes natural gas, water vapor and carbon dioxide; The preheated raw gas stream is subjected to combined reforming under the conditions of a reforming catalyst, so that natural gas reacts with carbon dioxide, natural gas reacts with water vapor, and water vapor reacts with natural gas; the reforming catalyst is selected from nickel-based and / or cobalt-based catalysts; The reformed gas stream is decarbonized, and the removed carbon dioxide stream is circulated back to the upstream, and the synthesis gas from which carbon dioxide is removed is a synthesis gas with a high CO concentration.

2. The preparation method according to claim 1, characterized in that The raw gas is selected from marine natural gas with high carbon dioxide content, biogas from biological fermentation and / or coke oven gas.

3. The preparation method according to claim 1 or 2, characterized in that The raw gas preheating step also includes a raw gas purification step, specifically: heating the carbon dioxide-rich natural gas to 350-380° C., and then performing hydrogenation and desulfurization in sequence to reduce the sulfur content in the natural gas to ≤0.1 ppmv.

4. The preparation method according to claim 3, characterized in that After the raw gas is purified and before the raw gas is preheated, the process further includes: mixing the desulfurized gas flow with water vapor for pre-conversion to remove high-carbon hydrocarbons.

5. The preparation method according to claim 1, characterized in that The decarbonization process also includes recovering waste heat from the reformed gas stream.

6. The preparation method according to claim 1, characterized in that The method further comprises the step of pressurizing the carbon dioxide stream before the carbon dioxide stream is merged into the raw gas stream.

7. The preparation method according to claim 1, characterized in that The molar concentration of carbon dioxide in the raw gas stream after being merged into the carbon dioxide stream is 25 to 60 mol%.

8. The preparation method according to claim 1, characterized in that The partially removed carbon dioxide stream is introduced into the raw gas stream, and the partially removed carbon dioxide stream is discharged. By controlling the ratio of the carbon dioxide introduced into the raw gas stream to the discharged carbon dioxide, the hydrogen-carbon ratio of the synthesis gas with high CO concentration can be adjusted between 1.3 and 1.

9.

9. A system for producing synthesis gas with an adjustable hydrogen-to-carbon ratio and high CO concentration, characterized in that: It includes: A first heater is used to heat the carbon dioxide-rich natural gas feedstock to a preset temperature; a hydrogenation reactor, arranged in series downstream of the first heater, for hydrogenating the natural gas feedstock; a desulfurization reactor, arranged in series downstream of the hydrogenation reactor, for desulfurizing the natural gas feedstock; a second heater, arranged in series downstream of the desulfurization reactor, for preheating the natural gas feedstock, water vapor and / or circulating carbon dioxide stream to a preset temperature; a reforming reactor, arranged in series downstream of the second heater; a reforming catalyst is arranged inside the reforming reactor for causing a reforming reaction of the raw gas stream; a waste heat recovery device, arranged in series downstream of the reforming reactor, for recovering waste heat from the reformed gas stream; a decarbonization device, arranged in series downstream of the waste heat recovery device, for removing carbon dioxide from the synthesis gas; A compressor is arranged in series downstream of the decarbonization device, and is used to compress the carbon dioxide flow; the outlet of the compressor is connected to the raw gas inlet of the reforming reactor, and is used to send the circulating carbon dioxide flow into the reforming reactor.

10. Use of the synthesis gas with high CO concentration produced by the production method according to any one of claims 1 to 8 in the technical fields of acetic acid synthesis, Fischer-Tropsch synthesis, higher carbon alcohol synthesis, or co-production of acetic acid and synthetic ammonia.

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