Device and method for producing methanol by means of chemical looping

Abstract

A device and method for producing methanol by means of chemical looping. The device comprises a feed gas supply unit, an air supply unit, a chemical looping reaction unit, a synthesis gas treatment unit and a methanol synthesis unit, wherein the chemical looping reaction unit comprises a converter, a reducer and an air oxidizer, which are internally provided with a same oxygen carrier; the feed gas supply unit is connected to the converter; the air supply unit is connected to the air oxidizer; the converter is connected to the synthesis gas treatment unit, and delivers to the synthesis gas treatment unit synthesis gas converted from feed gas; the reducer is connected to the feed gas supply unit, and is configured to return carbon dioxide to the feed gas supply unit; the synthesis gas treatment unit is connected to the converter, and is configured to adjust the composition of the synthesis gas converted from the feed gas; and the methanol synthesis unit is connected to the synthesis gas treatment unit, and is configured to synthesize methanol. The method comprises: a device starting and oxygen carrier and reactor preparing step, a reactor pretreatment step, a feed gas conversion step, an air oxidation step, a reduction step, a synthesis gas treatment step, and a methanol synthesis step.

Description

An apparatus and method for producing methanol via chemical chain reaction Technical Field

[0001] This invention relates to the technical field of chemical chain methanol production, and more particularly to an apparatus and method for producing methanol using a gas containing methane and carbon dioxide as raw materials and employing chemical chain technology. Background Technology

[0002] Methanol, as an important chemical raw material and fuel, has a wide range of downstream applications. In 2023, global methanol production capacity reached 180 million tons, with China accounting for nearly 120 million tons. Global production exceeded 130 million tons, while China's output was close to 100 million tons. There are nearly 30 primary processed chemical products derived from methanol, and over 100 deep-processed products. MTBE (methyl tert-butyl ether), a product of methanol processing, can be used as a high-octane unleaded gasoline additive and can also be used directly as vehicle fuel. Furthermore, methanol can be used directly as a methanol-fueled fuel cell (DFMC) and a hydrogen storage carrier. In recent years, with the rapid progress towards global carbon peaking and carbon neutrality, methanol has received increasing attention as a low-carbon alternative fuel.

[0003] However, globally, almost all methanol is currently produced from fossil fuels (natural gas or coal), especially in China where almost all methanol is coal-based, resulting in high carbon emissions. Producing one ton of methanol requires 1.35 tons of coal and emits approximately 3 tons of carbon dioxide. Currently, the total CO2 emissions from methanol production and use in China exceed 300 million tons per year, accounting for about 10% of the total carbon emissions from the chemical and chemical industries. Globally, green methanol production capacity is only around 500,000 tons, accounting for less than 1%. Given the urgent need to mitigate climate change by reducing CO2 emissions, there is increasing attention being paid to the development of renewable or green methanol.

[0004] Mature methanol production processes mainly involve coal gasification and natural gas. These two processes use fossil-based hydrocarbon feedstocks, resulting in high energy consumption and high carbon emissions. Even after high-cost CO2 capture, they cannot be considered green or renewable methanol.

[0005] Green methanol (or renewable methanol) is produced using renewable energy or renewable raw materials. There are currently three main approaches: (1) using solid biomass to produce green methanol through gasification combined with traditional carbon monoxide hydrogenation, as shown in Figure 1; (2) using biogas as raw material to produce green methanol through reforming combined with carbon monoxide hydrogenation, as shown in Figure 2; (3) using renewable CO2 (such as biomass-derived or air-captured CO2 [DAC]) and green hydrogen (i.e., hydrogen produced by electrolysis of renewable energy power generation) to produce green methanol through carbon dioxide hydrogenation, as shown in Figure 3.

[0006] The process of producing green methanol via biomass gasification is shown in Figure 1. This process is lengthy and complex. In particular, during biomass gasification, for feedstocks with high oxygen content, a large amount of carbon dioxide is generated in the syngas, reducing the gasification efficiency. Furthermore, because biomass is rich in alkali metals (Na, K) or alkaline earth metals (Ca, Mg), it causes serious fire-side problems in the gasifier, such as fouling, slagging, and ash accumulation. In addition, if lignin and hemicellulose are used as biomass feedstocks, a large amount of tar is formed during gasification. This not only wastes carbon resources but also easily binds to and condenses with water, coke, and dust to form a viscous liquid substance that adheres to the flow walls of the gasifier and subsequent equipment. In severe cases, this can cause pipe blockage and corrosion, leading to production malfunctions. Moreover, the acquisition of solid biomass resources is often highly geographically and seasonally dependent. Because freshly acquired biomass has a low density, the transportation cost per unit mass is high, necessitating the establishment of large-capacity warehouses to meet the needs of continuous operation throughout the year. Therefore, ensuring the efficient and economical use of biomass and solving some technical challenges in the biomass gasification process are key to the large-scale commercialization of green methanol production from biomass.

[0007] For example, when using biogas as a feedstock to produce green methanol, as shown in Figure 2, biogas is a mixture of methane and CO2 (typical biogas composition: CH4 60%, CO2 40%). After desulfurization, the CO2 in the biogas first needs to be removed, and the methane needs to be purified to over 97%. Then, steam is introduced for methane steam reforming to generate syngas. Subsequently, the carbon-hydrogen ratio is adjusted through a steam-water change process to suit methanol synthesis. However, this process results in the loss of some methane, and the carbon source of CO2 in the biogas is not utilized, leading to carbon source loss. On the other hand, it requires a large amount of steam, resulting in high energy consumption. Furthermore, although methane steam reforming is one of the important technologies for producing syngas, it is mostly used in large-scale hydrogen production plants. This technology still faces economic and technical optimization issues in the process of miniaturization design and implementation. Currently, there are no small-scale commercial facilities operating using biogas as a feedstock.

[0008] Figure 3 shows the process of producing green methanol by combining renewable CO2 with green hydrogen through carbon dioxide hydrogenation. This requires both the CO2 source and H2 to have green attributes. The CO2 source is mainly DAC captured from the air or produced by biomass combustion and gasification. Currently, there are a series of problems such as high cost and difficulty in technical implementation. In addition, in the process of synthesizing methanol by carbon dioxide hydrogenation, the conversion rate of carbon dioxide and hydrogen reaction is low, the selectivity is not high, the synthesis product contains a lot of non-methanol byproducts with high content, and the separation is difficult, resulting in poor overall economic efficiency.

[0009] Therefore, there is an urgent need to provide an economical, efficient, and low-tech methanol production process and equipment to reduce the difficulty and cost of methanol production, thereby promoting the application of methanol and facilitating carbon emission reduction in vehicle and marine fuels and the chemical industry. Summary of the Invention

[0010] Therefore, the main objective of this invention is to provide an apparatus and method for producing methanol via a chemical chain that is energy self-sufficient, requires no purification of the raw material gas, and can be coordinated with an external hydrogen supply device.

[0011] The present invention solves the technical problem by adopting the following technical solution:

[0012] An apparatus for producing methanol via chemical chain reaction includes a chemical chain reaction unit, a feed gas supply unit, an air supply unit, a syngas treatment unit, and a methanol synthesis unit.

[0013] The chemical chain reaction unit includes a converter, a reducer, and an air oxidizer. These three parts can be converted into each other according to the reaction stage and can be cyclically repeated as a whole.

[0014] The same oxygen carrier is provided in the converter, the reducer and the air oxidizer. The oxygen carrier changes into a metal element or a metal oxide in each reaction stage, and the metal element corresponding to the oxygen carrier plays a catalytic role in the feed gas conversion reaction in the converter.

[0015] The feed gas supply unit is connected to the converter and is used to supply the feed gas required for the reaction to the converter; the air supply unit is connected to the air oxidizer and is used to supply air to the air oxidizer; the converter is connected to the syngas treatment unit and transports the syngas converted from the feed gas to the syngas treatment unit, which is used to treat the syngas; the reducer is connected to the feed gas supply unit and is used to return carbon dioxide to the feed gas supply unit.

[0016] The syngas processing unit is connected to the converter and is used to adjust the composition of the syngas after the feed gas is converted and to pressurize the syngas.

[0017] The methanol synthesis unit is connected to the synthesis gas treatment unit and is used to synthesize methanol.

[0018] Furthermore, the gas supplied by the raw material gas supply unit is biogas.

[0019] Furthermore, the oxygen carrier contains an active ingredient and selectively contains a secondary active ingredient, an inactive ingredient, or both.

[0020] The active ingredient is one or more of NiO, CeO2, ZnO, and CuO;

[0021] The secondary active ingredient is one or more of Fe2O3, Co3O4, and Mn2O3.

[0022] The inactive component is one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2.

[0023] Furthermore, the oxygen carrier does not contain any active ingredients, but includes secondary active ingredients, and selectively includes inactive ingredients.

[0024] The secondary active ingredient is one or more of Fe2O3, Co3O4, and Mn2O3.

[0025] The inactive component is one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2.

[0026] Furthermore, in the oxygen carrier, the content of active ingredient is 8-40 wt.%, the content of secondary active ingredient is 0-5 wt.%, and the content of inactive ingredient is 60-92 wt.%.

[0027] Furthermore, the raw material gas supply unit includes a raw material gas source, a desulfurization device, a mixer, and a raw material gas blower connected in sequence; the raw material gas source provides the raw material gas required for the reaction, and after the raw material gas is desulfurized by the desulfurization device, it flows into the mixer to mix with CO2 in the tail gas of the chemical looping reaction unit, and then is pressurized by the raw material gas blower and transported to the chemical looping reaction unit.

[0028] Furthermore, the air supply unit includes an air fan, into which outside air enters and is pressurized before being delivered to the chemical chain reaction unit.

[0029] Furthermore, the syngas processing unit includes a syngas control valve, a water-vapor shift device, a purification device, and a syngas compressor. The syngas control valve is connected to the converter and is used to divert the syngas generated by the converter. The water-vapor shift device is connected to the syngas control valve and is used to perform water-vapor shift on the syngas diverted by the syngas control valve, converting CO in the syngas into H2. The purification device is connected to the water-vapor shift device and is used to remove CO2 from the gas after the reaction in the water-vapor shift device. The syngas compressor is connected to the syngas control valve and the purification device and pressurizes the gas inside them.

[0030] In this process, the syngas generated in the converter is divided into three streams by the syngas control valve. The first stream of syngas flows back to the reducer to reduce the oxygen carrier. The second stream enters the water-gas shift device to convert CO in the syngas into H2. After the water-gas shift is completed, the gas enters the purification device, where CO2 is separated out, while H2 is mixed with the third stream of syngas to adjust the ratio of CO and H2 in the third stream of syngas. Then, the gas enters the syngas compressor.

[0031] Furthermore, the syngas processing unit includes a syngas control valve, a hydrogen supply device, and a syngas compressor. The syngas control valve is connected to the converter and is used to control the syngas generated by the converter. The syngas compressor is connected to the syngas control valve, and the hydrogen supply device is connected to the syngas compressor.

[0032] The syngas enters the syngas compressor via the syngas control valve and then enters the methanol synthesis unit;

[0033] The hydrogen supply device is also connected to the reducer. The hydrogen it produces passes through the inlet switching valve and the heat exchanger in sequence before entering the reducer to reduce the oxygen carrier in the oxidized state.

[0034] Furthermore, the hydrogen supply device produces hydrogen by electrolyzing water, and the electrical energy consumed in the process comes from green electricity resources generated by wind power and photovoltaic power generation devices.

[0035] Furthermore, the methanol synthesis unit includes a methanol synthesizer, a heat exchange and steam unit, a condenser, a liquid separator, and a methanol distillation column. The methanol synthesizer is connected to a synthesis gas compressor, and the condenser, liquid separator, and methanol distillation column are sequentially connected to the methanol synthesizer.

[0036] The heat exchange and steam device includes a water pump, a deaerator, and a steam drum. The steam drum is connected to the methanol synthesizer, and the water pump is connected to the steam drum to supply demineralized water. The deaerator is installed on the pipeline between the steam drum and the water pump to remove oxygen from the demineralized water.

[0037] Furthermore, the apparatus for producing methanol via chemical chain also includes a control unit, which controls the inlet switching valve and the outlet switching valve;

[0038] The feed gas supply unit and air supply unit are connected to the air inlets of the three reactors via inlet switching valves. When feed gas / air needs to be supplied to the converter / air oxidizer, the control unit controls the inlet switching valves to connect the feed gas supply unit / air supply unit to the converter / air oxidizer. The three reactors are also connected to the air oxidation tail gas pipeline, the oxygen carrier reduction tail gas pipeline, and the syngas treatment unit via outlet switching valves. After the reaction in the converter / reducer / air oxidizer is completed, the control unit controls the outlet switching valves to connect the converter / reducer / air oxidizer to the syngas treatment unit / oxygen carrier reduction tail gas pipeline / air oxidation tail gas pipeline. The syngas control valve in the syngas treatment unit is connected to the three reactors via inlet switching valves. When reducing gas needs to be supplied to the reducer, the control unit controls the inlet switching valves to connect the syngas control valve to the reducer.

[0039] When a hydrogen supply device is present, the hydrogen supply device is connected to the three reactors through an inlet switching valve. When it is necessary to supply reducing gas to the reducer, the control unit controls the inlet switching valve to connect the hydrogen supply device to the reducer.

[0040] Furthermore, the gas supplied by the raw material gas supply unit is one of the following: natural gas with high CO2 content, industrial tail gas containing CH4 and CO2, or associated gas from CO2-enhanced oilfields.

[0041] The present invention also adopts the following technical solution to solve the technical problem:

[0042] A method for producing methanol via a chemical chain includes the following steps:

[0043] The device startup and oxygen carrier and reactor preparation steps involve first filling the three reactors of the chemical looping reaction unit with the aforementioned oxygen carrier, and then starting the device.

[0044] In the reactor pretreatment step, the three reactors are heated and the system is adjusted to be suitable for the following reactions through a combination of pre-reduction and pre-oxidation: the three reactors of the chemical loop reaction unit switch and cycle repeatedly to carry out the feed gas conversion reaction, air oxidation reaction and reduction reaction.

[0045] In the feed gas conversion step, feed gas is introduced into the converter through the feed gas supply unit. It is first mixed with part of the recycled reduction tail gas. Then, the feed gas undergoes a feed gas conversion reaction under the catalysis of elemental metals. It makes full use of the heat accumulated in the oxygen carrier in the previous pre-oxidation step to generate syngas containing CO, H2, and a small amount of CO2 and H2O. The syngas is discharged from the reactor and is ready to enter the syngas treatment unit or be returned to the reducer.

[0046] In the air oxidation step, after the raw material gas conversion reaction is completed, the reactor is switched to the air oxidizer state and the air oxidation process is carried out. That is, air is introduced into the air oxidizer through the air supply unit. The oxygen in the air oxidizes the metal elemental oxygen carrier to a high oxidation state and releases a large amount of heat. Most of this reaction heat is stored in the oxidized oxygen carrier bed, which stores the heat required for the subsequent raw material gas conversion process in advance.

[0047] In the reduction step, after the air oxidation is completed, the reactor is switched to the reducer state and the reduction process is carried out. That is, a part of the syngas generated by the feed gas conversion reaction is returned to the reducer to reduce the oxygen carrier from the high-valence oxide state to the elemental state. The heat released by the reaction is stored in the oxygen carrier bed. This part of the heat, together with the heat stored in the oxygen carrier in the previous stage of air oxidation, provides the heat required for the next stage of feed gas conversion process.

[0048] In the syngas treatment process, the syngas generated in the converter is divided into three streams by the syngas control valve. The first stream of syngas flows back to the reducer to reduce the oxygen carrier. The second stream enters the water-gas shift converter to convert CO in the syngas into H2. After the water-gas shift is completed, the gas enters the purification device, where CO2 is separated out, while H2 is mixed with the third stream of syngas to adjust the CO and H2 ratio in the third syngas to meet the requirements for methanol synthesis. The mixed syngas then enters the syngas compressor.

[0049] In the methanol synthesis process, the gas from the syngas compressor enters the methanol synthesizer to undergo the methanol synthesis reaction. After the reaction is completed, the gaseous products generated in the methanol synthesizer exchange heat with the syngas and demineralized water that entered the methanol synthesizer before entering the methanol synthesizer. Then, they enter the condenser for condensation. The condensed liquid crude methanol enters the separator, while the non-condensable gas flows back to the inlet of the syngas compressor, mixes with fresh syngas and hydrogen, and then re-enters the methanol synthesizer for the reaction. The liquid crude methanol is then purified by a subsequent methanol distillation column to obtain high-purity methanol.

[0050] Furthermore, the reduction step is as follows: after the air oxidation is completed, the reactor is switched to the state of the reducer and the reduction process is carried out. That is, the hydrogen generated by the hydrogen supply device enters the reducer to reduce the oxygen carrier from the high-valence oxide state to the elemental state. The heat released by the reaction is stored in the oxygen carrier bed. This part of the heat, together with the heat stored in the oxygen carrier in the previous stage of air oxidation, provides the heat required for the reaction in the next stage of raw material gas conversion process.

[0051] The syngas treatment step involves the syngas control valve diverting all the syngas to the syngas compressor in preparation for the methanol synthesis reaction. Before entering the syngas compressor, the syngas is mixed with hydrogen produced by the hydrogen supply device to adjust the ratio of CO and H2 in the syngas entering the syngas compressor.

[0052] The chemical chain conversion methanol production apparatus of this invention uses a mixture of CH4 and CO2 as feedstock. It eliminates the need for pre-separation and purification of CH4 in the feedstock gas, directly performing the chemical chain conversion. This solves the problems of high energy consumption, multiple separation steps, catalyst sintering, and catalyst deactivation due to carbon buildup in traditional methane reforming processes. When the feedstock gas is biogas, the innovative chemical chain conversion technology combined with the mature carbon monoxide hydrogenation methanol synthesis process produces green methanol. This method can maximize the utilization of carbon sources (CH4, CO2) in biomass feedstocks, converting the vast majority of green carbon sources into methanol. It features low technical risk, energy saving and carbon reduction, and good economic efficiency.

[0053] The chemical chain methanol production apparatus of the present invention adopts an in-bed heat storage and heating method (referred to as "internal heating type"), and the reactor temperature is always below 950°C. It does not use the traditional combustion flame radiation heating method (local temperature exceeds 1300°C), which can avoid problems such as catalyst sintering and carbon deposition caused by local high temperature. At the same time, it greatly reduces the material requirements of the reactor and greatly improves the overall economy of the apparatus.

[0054] Furthermore, the chemical looping process for converting the feed gas eliminates the need for excessive water vapor replenishment, significantly saving energy. The composite oxygen carrier material simultaneously achieves stable chemical looping and high reforming catalytic performance, maintaining a methane conversion rate greater than 99.7% while keeping the CO2:CH4 molar ratio between 55:45 and 75:25. It also reduces the partial pressure of inert components like methane in the syngas, thereby decreasing the frequency and flow rate of purge gas emissions from the methanol synthesis section. This eliminates the need for PSA or membrane separation equipment to recover hydrogen from the purge gas, saving investment and reducing the load on the feed gas compressor, thus lowering operating energy consumption. On the other hand, the generated syngas has low CO2 and H2O content, with a total CO and H2 content exceeding 90%. Combined with hydrogen supplementation, this can further significantly reduce investment and operating energy consumption in syngas purification equipment.

[0055] Furthermore, the process of this invention is highly flexible and can be combined with the main process by utilizing external hydrogen sources (such as green electricity hydrogen production), thereby enabling full utilization of the carbon source in the feed gas and increasing methanol production capacity. Attached Figure Description

[0056] Figure 1-3 shows the process flow for producing green methanol in the prior art.

[0057] Figure 4 is a flowchart illustrating the chemical chain methanol production process of the present invention.

[0058] Figure 5 is a flowchart illustrating a chemical chain methanol production process according to another embodiment of the present invention.

[0059] Figure 6 is a time sequence diagram showing the reactions at each stage of the chemical chain reaction cycle of the present invention.

[0060] Figure 7 is a diagram showing the experimental results of biogas conversion in Example 1 of the present invention.

[0061] Figure 8 is a diagram showing the experimental results of biogas conversion in Example 2 of the present invention.

[0062] Figure 9 is a diagram showing the experimental results of biogas conversion in Example 3 of the present invention. Detailed Implementation

[0063] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, it should be understood by those skilled in the art that the present invention is not limited to these specific embodiments, but rather that various equivalent changes, modifications, or substitutions can be made to the present invention without departing from its basic idea and spirit. Therefore, the scope of protection of the present invention should include these equivalent changes, modifications, or substitutions, and be determined according to the scope defined in the appended claims, rather than solely relying on the specific embodiments described herein.

[0064] Figure 4 is a schematic flow diagram of the apparatus for producing methanol via chemical chain reaction according to the present invention. Figure 5 is a schematic flow diagram of the apparatus for producing methanol via biogas coupled with hydrogen supply according to the present invention. Figure 6 is a time sequence diagram of the reactions at each stage of the chemical chain reaction cycle according to the present invention. Below, the structure of the biogas-to-methanol apparatus and related reactions according to an embodiment of the present invention will be described first, with reference to Figures 4 and 5. Next, the method for producing methanol via chemical chain reaction according to an embodiment of the present invention will be described with reference to Figure 6.

[0065] (The overall structure of a chemical chain methanol production apparatus)

[0066] As shown in Figure 4, the apparatus for producing methanol by chemical chain reaction in this invention includes a chemical chain reaction unit, a feed gas supply unit, an air supply unit, a syngas treatment unit, and a methanol synthesis unit.

[0067] The chemical chain reaction unit includes a converter, an air oxidizer, and a reducer, and these three parts can be interchanged according to the reaction stage.

[0068] The feed gas supplied by the feed gas supply unit is one of the following: biogas, natural gas with high CO2 content, associated gas from CO2-enhanced oil fields, or industrial tail gas containing CH4 and CO2. In this embodiment, biogas is used as an example.

[0069] Metal oxides (M) are all provided in the converter, air oxidizer, and reducer. x O y (where M represents a metallic element and O represents oxygen) serves as the oxygen carrier in the reduction-oxidation reaction. The metal M must be selected to act as a catalyst in the feed gas conversion reaction, simultaneously enabling the redox cycle of the chemical chain reaction process, and sufficiently accumulating heat.

[0070] The oxygen carrier includes an active component and may optionally contain a secondary active component or an inactive component, or both.

[0071] The active component is one or more of NiO, CeO2, ZnO, and CuO; the secondary active component is one or more of Fe2O3, Co3O4, and Mn2O3; and the inactive component can be one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2. Here, the main function of the active component is to perform redox cycles and store heat in the exothermic generator during air oxidation, as well as to act as a catalyst in the feed gas conversion reaction after reduction. The main function of the secondary active component is to enhance and stabilize the active component, while the main function of the inactive component is to make the oxygen carrier reaction more stable, prevent sintering, achieve a reasonable pore structure, and achieve a better heat storage structure.

[0072] As an alternative, the oxygen carrier does not contain an active ingredient, but contains a secondary active ingredient, and selectively contains an inactive component. The secondary active ingredient is one or more of Fe2O3, Co3O4, and Mn2O3, and the inactive component can be one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2. The reason for not using the aforementioned secondary active ingredient as the active ingredient in this invention is due to considerations such as cost. However, if cost and other factors are taken into account, or under special conditions, those skilled in the art can certainly use only the secondary active ingredient and not the active ingredient.

[0073] The oxygen carrier is prepared by high-temperature solid-state reaction calcination of the active ingredient, secondary active ingredient, or inactive ingredient. The total content of the active ingredient is 8 wt.%–40 wt.%, the total content of the secondary active ingredient is 0–5 wt.%, and the total content of the inactive ingredient is 60 wt.%–92 wt.%. The high-temperature calcination temperature is 550℃–1250℃, and the average particle size of the shaped oxygen carrier is 1 mm–8 mm.

[0074] The reducer, converter, and air oxidizer can be controlled by a control unit to switch the functions of the three reaction units between each other by controlling multiple pipelines and valves installed on the pipelines. For example, when the three reactors corresponding to the converter, reducer, and air oxidizer are defined as reactor A, reactor B, and reactor C, after the system is preheated and enters the circulation system, initially reactor A performs the function of the converter, reactor B performs the function of the reducer, and reactor C performs the function of the air oxidizer. However, after switching the air intake pipeline by the valve of the control unit, reactor A performs the function of the air oxidizer, reactor B performs the function of the converter, and reactor C performs the function of the reducer. Next, after switching the pipeline again by the valve, reactor A performs the function of the reducer, reactor B performs the function of the air oxidizer, and reactor C performs the function of the converter, and so on, in a continuous cycle.

[0075] Next, the reactions that occur in the converter, reducer, and air oxidizer will be explained.

[0076] After the system has completed preheating and pre-oxidation / reduction, feed gas is introduced into the converter through the feed gas supply unit. It is first mixed with a portion of the recycled reduction tail gas, adjusting the CH4:CO2 ratio in the feed gas to 25:75–50:50. The mixed gas then undergoes a conversion reaction. During the feed gas conversion reaction stage, the oxygen carrier in the reactor has been pre-reduced to its elemental metallic state, and heat has accumulated in the oxygen carrier bed. The feed gas entering the system undergoes a feed gas conversion reaction (process ①) under the catalytic action of the elemental metal, fully utilizing the heat accumulated in the oxygen carrier to generate syngas containing CO, H2, and small amounts of CO2 and H2O. This syngas is discharged from the reactor, ready to enter the syngas treatment unit or be recycled back to the reducer.

[0077] The feed gas conversion reaction that occurs in the converter is as follows: CH4 + CO2 → 2CO + 2H2

[0078] When the oxygen carrier is a Ni-based oxygen carrier, the active component of the oxygen carrier remains unchanged as elemental Ni during process ①.

[0079] The feed gas supply unit includes a feed gas source, a desulfurization device, a mixer, and a feed gas blower connected in sequence. The feed gas source provides the feed gas required for the reaction. After being desulfurized by the desulfurization device, the feed gas flows into the mixer to mix with CO2 in the tail gas of the chemical looping reaction unit. Then, after being pressurized by the feed gas blower, it is delivered to the chemical looping reaction unit.

[0080] In this embodiment, when the raw material gas source is biogas, the supplied biogas includes, but is not limited to, biogas from livestock excrement treatment in animal husbandry, biogas from leachate treatment in waste incineration plants, biogas from municipal solid waste treatment, biogas from landfills, bioethanol, and biogas from food industry waste treatment. The typical composition of the biogas is: CH4 40–75 vol.%, CO2 25–60 vol.%. When the desulfurization device desulfurizes the biogas, conventional chemical absorption desulfurization or chemical adsorption desulfurization can be used. The desulfurizing agent used includes one or more of iron-based desulfurizing agents, zinc-based desulfurizing agents, or modified active desulfurizing agents.

[0081] After the feed gas conversion reaction is completed, the temperature of the oxygen carrier and bed drops to 460–680°C. At this point, the reactor is switched to air oxidizer mode via the control unit and the air oxidation process (process ②) is initiated. Specifically, air is introduced into the air oxidizer through the air supply unit. The oxygen in the air oxidizes the metallic elemental oxygen carrier to a higher valence state, releasing a large amount of heat. Most of the reaction heat is stored in the oxidized oxygen carrier bed, pre-storing the heat required for subsequent feed gas conversion processes. A smaller portion of the heat is discharged with the remaining N2 from the reaction. Hot nitrogen gas exchanges heat with the air entering the reactor through a heat exchanger to preheat the air. After heat recovery, the gas is discharged into the air oxidation tail gas pipeline through the outlet switching valve, and finally, after further heat recovery through a heat exchanger, it is discharged from the system. The reaction temperature of the air oxidation process in the air oxidizer is 650–880°C.

[0082] The reaction that takes place in the air oxidizer is as follows: ②: 2xM + yO2 → 2M x O y

[0083] When the oxygen carrier is a metallic element Ni, the change of the oxygen carrier in process ② is: Ni → NiO.

[0084] The air supply unit includes an air fan. Outside air enters the air fan, is pressurized by the air fan, and then delivered to the chemical looping reaction unit. Preferably, the air fan pressurizes the air to 30–250 kPaG, and the oxygen content in the air is 5–21%.

[0085] After air oxidation is complete, the reactor is switched to the reducer state via the control unit to initiate the reduction process (process ③). A portion of the syngas generated from the feed gas conversion reaction is returned to the reducer to reduce the oxygen carrier from a high-valence oxide state to an elemental state. Alternatively, hydrogen from the hydrogen supply unit enters the reducer to reduce the oxygen carrier from a high-valence oxide state to an elemental state. The heat released by the reaction accumulates in the oxygen carrier bed. This heat, along with the heat accumulated in the oxygen carrier bed during the previous air oxidation process, can provide the heat required for the next stage of feed gas conversion. Simultaneously, CO and H2 are completely oxidized to CO2 and H2O. This tail gas, after being discharged from the reactor, first exchanges heat with the syngas used for reduction in a heat exchanger and preheats it. After heat recovery, it is discharged into the oxygen carrier reduction tail gas pipeline via the outlet switching valve. After passing through a condenser to remove water, the remaining high-concentration CO2 flows into the mixer to mix with the desulfurized feed gas to adjust the ratio of methane and CO2 in the feed gas.

[0086] The reaction that takes place in the reducer is as follows ③: M x O y +yH2→xM+yH2O M x O y +yCO→xM+yCO2

[0087] When the oxygen carrier is an oxide of Ni, the change of the oxygen carrier in process ③ is: NiO → Ni.

[0088] During this process, the temperature of the oxygen carrier reduction reaction bed is 730–930℃.

[0089] The apparatus for the chemical chain production of methanol in this invention will continue to be described with reference to FIG4.

[0090] The syngas processing unit includes a syngas control valve, a water-vapor shift device, a purification device, and a syngas compressor. The syngas control valve is connected to the converter and is used to divert the syngas generated by the converter. The water-vapor shift device is connected to the syngas control valve and is used to perform water-vapor shift on the syngas diverted by the syngas control valve, converting CO in the syngas into H2. The purification device is connected to the water-vapor shift device and is used to remove CO2 from the gas after the reaction in the water-vapor shift device. The syngas compressor is connected to the syngas control valve and the purification device and is used to pressurize the incoming gas.

[0091] In this embodiment, the syngas generated in the converter is divided into three streams by the syngas control valve. The first stream of syngas flows back to the reducer to reduce the oxygen carrier, and the second stream enters the water-gas shift device to convert CO in the syngas into H2.

[0092] The reaction that takes place in the water-vapor shift device is as follows: ④

[0093] After the water-gas conversion is completed, the gas enters the purification device, where CO2 is separated out, while H2 is mixed with the third stream of syngas and then enters the syngas compressor.

[0094] As shown in Figure 5, in another embodiment of the present invention, unlike the above-mentioned chemical chain methanol production device, the syngas processing unit includes a syngas control valve, a hydrogen supply device and a syngas compressor. The syngas control valve is connected to the converter and is used to control the syngas generated by the converter. The syngas compressor is connected to the syngas control valve and the hydrogen supply device is connected to the syngas compressor.

[0095] In this embodiment, the syngas control valve diverts all the syngas to the syngas compressor in preparation for the methanol synthesis reaction. Before entering the syngas compressor, the syngas is mixed with hydrogen produced by the hydrogen supply device, and then pressurized in the syngas compressor.

[0096] Specifically, the hydrogen supplied by the hydrogen supply device is preferably green hydrogen, which can be produced by water electrolysis. The electricity used in the water electrolysis process is green electricity generated by wind power and photovoltaic power generation devices. The power fluctuations caused by the fluctuations of wind and solar resources during wind and solar power generation are adjusted by energy storage facilities to ensure a stable and continuous output of green electricity. Then, the green electricity is used to electrolyze water in the electrolyzer to produce hydrogen, thereby generating green hydrogen.

[0097] On the other hand, the hydrogen supply device is also connected to the reducer. The hydrogen it produces passes through the inlet switching valve and the heat exchanger in sequence before entering the reducer to reduce the oxygen carrier in the oxidized state.

[0098] The methanol synthesis unit includes a methanol synthesizer, a heat exchange and steam unit, a condenser, a liquid separator, and a methanol distillation column. The methanol synthesizer is connected to a synthesis gas compressor, and the condenser, liquid separator, and methanol distillation column are connected to the methanol synthesizer in sequence.

[0099] The heat exchange and steam device includes a water pump, a deaerator, and a steam drum. The steam drum is connected to the methanol synthesizer, and the water pump is connected to the steam drum to supply demineralized water. The deaerator is installed on the pipeline between the steam drum and the water pump to remove oxygen from the demineralized water.

[0100] In this embodiment, the syngas in the syngas compressor is heated by a heat exchanger and then enters the methanol synthesizer for methanol synthesis reaction.

[0101] The reaction that takes place in the methanol synthesizer is as follows (⑤): CO + 2H₂ → 2CH₃OH

[0102] The synthesis gas entering the methanol synthesizer may contain a small amount of CO2. This CO2 can control the reaction temperature and improve the conversion rate, which occurs in the following process ⑥: CO2 + 3H2 → CH3OH + H2O

[0103] After the reaction is complete, the gaseous products generated in the methanol synthesizer exchange heat with the gas and demineralized water entering the methanol synthesizer in sequence, and then enter the condenser for condensation. The condensed liquid crude methanol enters the separator, while the non-condensable gas flows back to the inlet of the synthesis gas compressor, mixes with fresh synthesis gas and hydrogen, and then re-enters the methanol synthesizer for reaction. The liquid crude methanol is then purified by the subsequent methanol distillation column to obtain high-purity methanol.

[0104] On the other hand, during methanol synthesis, the temperature in the methanol synthesizer is maintained at 255-270℃. Since the methanol synthesis reaction is exothermic, the heat released can heat and vaporize the water supplied by the pump. The resulting steam, along with the steam generated during the methanol synthesis reaction, is stored in the steam drum. This steam can be supplied to the steam-water conversion unit for further reaction or directly to the steam turbine generator set for power generation. It should be noted that when hydrogen is supplied by a hydrogen supply unit for the methanol synthesis reaction, all the steam in the steam drum is used for power generation in the steam turbine generator set.

[0105] The chemical chain methanol production apparatus of the present invention also includes a control unit, which is used to control or monitor various pipelines, valves (inlet switching valve / outlet switching valve), temperature, pressure, etc. in the apparatus, and to make control adjustments at any time. For example, it can switch gas input and output, switch the reaction of each reactor according to the reaction stage, transfer or recover heat or energy, capture carbon dioxide, cool water vapor, etc.

[0106] Specifically, the feed gas supply unit and the air supply unit are connected to the air inlets of the three reactors via inlet switching valves. When feed gas / air needs to be supplied to the converter / air oxidizer, the control unit controls the inlet switching valves to connect the feed gas supply unit / air supply unit to the converter / air oxidizer. The three reactors are also connected to the air oxidation tail gas pipeline, the oxygen carrier reduction tail gas pipeline, and the syngas treatment unit via outlet switching valves. After the reaction in the converter / reducer / air oxidizer is completed, the control unit controls the outlet switching valves to connect the converter / reducer / air oxidizer to the syngas treatment unit / oxygen carrier reduction tail gas pipeline / air oxidation tail gas pipeline. The syngas control valve in the syngas treatment unit is connected to the three reactors via inlet switching valves. When reducing gas needs to be supplied to the reducer, the control unit controls the inlet switching valves to connect the syngas control valve to the reducer. It should be noted that when a hydrogen supply device is present, the hydrogen supply device is connected to the three reactors through an inlet switching valve. When it is necessary to supply reducing gas to the reducer, the control unit controls the inlet switching valve to connect the hydrogen supply device to the reducer.

[0107] The chemical chain conversion methanol production apparatus of this invention uses a mixture of CH4 and CO2 as feedstock. It eliminates the need for pre-separation and purification of CH4 in the feedstock gas, directly performing the chemical chain conversion. This solves the problems of high energy consumption, multiple separation steps, catalyst sintering, and catalyst deactivation due to carbon buildup in traditional methane reforming processes. When the feedstock gas is biogas, the innovative chemical chain conversion technology combined with the mature carbon monoxide hydrogenation methanol synthesis process produces green methanol. This method can maximize the utilization of carbon sources (CH4, CO2) in biomass feedstocks, converting the vast majority of green carbon sources into methanol. It features low technical risk, energy saving and carbon reduction, and good economic efficiency.

[0108] The chemical chain methanol production apparatus of the present invention adopts an in-bed heat storage and heating method (referred to as "internal heating type"), and the reactor temperature is always below 950°C. It does not use the traditional combustion flame radiation heating method (local temperature exceeds 1300°C), which can avoid problems such as catalyst sintering and carbon deposition caused by local high temperature. At the same time, it greatly reduces the material requirements of the reactor and greatly improves the overall economy of the apparatus.

[0109] Furthermore, the chemical looping process for converting the feed gas eliminates the need for excessive water vapor replenishment, significantly saving energy. The composite oxygen carrier material simultaneously achieves stable chemical looping and high reforming catalytic performance, maintaining a methane conversion rate greater than 99.7% while keeping the CO2:CH4 molar ratio between 55:45 and 75:25. It also reduces the partial pressure of inert components like methane in the syngas, thereby decreasing the frequency and flow rate of purge gas emissions from the methanol synthesis section. This eliminates the need for PSA or membrane separation equipment to recover hydrogen from the purge gas, saving investment and reducing the load on the feed gas compressor, thus lowering operating energy consumption. On the other hand, the generated syngas has low CO2 and H2O content, with a total CO and H2 content exceeding 90%. Combined with hydrogen supplementation, this can further significantly reduce investment and operating energy consumption in syngas purification equipment.

[0110] Furthermore, the process of this invention is highly flexible and can be combined with the main process by utilizing external hydrogen sources (such as green electricity hydrogen production), thereby enabling full utilization of the carbon source in the feed gas and increasing methanol production capacity.

[0111] (Explanation of the chemical chain method for methanol production)

[0112] The method for producing methanol using the chemical chain methanol production apparatus of the present invention will now be described.

[0113] When using the chemical chain methanol production apparatus of the present invention for methanol production, the first step is to start up the apparatus and prepare the oxygen carrier and reactors. Specifically, oxygen carriers, which are oxidized metal oxides, are filled into the three chemical chain reactors (A / B / C) in the chemical chain methanol production apparatus.

[0114] Next, all reactors (A / B / C) are heated to the specified temperature.

[0115] After the three reactors (A / B / C) in the chemical loop reactor unit undergo oxygen carrier pre-reduction preparation, H2 is introduced into the three reactors (A / B / C) to begin the oxygen carrier pre-reduction. Once all reactors have completed pre-reduction, air is introduced into one of the reactors, A, for air oxidation and heat storage. Reactor A, having completed air oxidation and heat storage, is then switched to H2 reduction to continue accumulating heat; simultaneously, air is introduced into another reactor, B, for air oxidation.

[0116] After hydrogen reduction and heat storage, reactor A is introduced with feed gas to convert the feed gas and generate syngas containing CO and H2. At the same time, reactor B switches to oxygen carrier reduction, and the reducing gas is the syngas generated in reactor A. Simultaneously, air is introduced into reactor C for air oxidation.

[0117] Reactor A, which has completed the feed gas conversion, switches to the air oxidation process to perform air oxidation and generate and store heat; reactor B switches to the feed gas conversion process; and reactor C switches to the oxygen carrier reduction process.

[0118] After completing air oxidation, reactor A switches to the oxygen carrier reduction process; after completing feed gas conversion, reactor B switches to the oxygen carrier air oxidation process; reactor C then switches to the feed gas conversion process.

[0119] The subsequent processes of the chemical looping reaction unit are cyclically switched between three reactors (A / B / C).

[0120] Figure 6 is a schematic diagram showing the timing of each stage of the chemical chain reaction cycle of the present invention. As shown in Figure 6, reactors A / B / C are heated together during the start-up preparation stage, then undergo pre-reduction together, followed by air oxidation of the reactors. Next, reactor A is reduced while reactor B is oxidized by air. After that, starting from the first cycle (cycle 2-1), reactors A / B / C are switched and cycled repeatedly to carry out the three reaction processes of feed gas conversion, oxygen carrier reduction, and oxygen carrier oxidation.

[0121] After the feedstock gas is converted, the syngas is discharged from the reactor and enters the syngas treatment unit for pretreatment before the methanol synthesis reaction.

[0122] Next, the pretreatment process of the syngas entering the syngas processing unit will be described.

[0123] (1) Has a hydrogen supply device

[0124] At this point, the syngas control valve diverts all the syngas to the syngas compressor in preparation for the methanol synthesis reaction. Before entering the syngas compressor, the syngas is mixed with hydrogen produced by the hydrogen supply unit to adjust the ratio of CO and H2 in the syngas entering the compressor. Specifically, the hydrogen supply unit produces hydrogen by water electrolysis. The electricity used in the water electrolysis process is green electricity generated by wind and solar power generation devices. Energy storage facilities are used to adjust for power fluctuations caused by wind and solar power generation fluctuations, ensuring a stable and continuous output of green electricity. This green electricity is then used in the electrolyzer to electrolyze water and produce green hydrogen.

[0125] (2) No hydrogen supply device

[0126] At this point, the syngas entering the syngas treatment unit is divided into three streams. The first stream is returned to the reactor for oxygen carrier reduction, the second stream enters the syngas compressor to prepare for the methanol synthesis reaction, and the third stream enters the water-gas shift converter to convert all the CO in the synthesis into H2. After the conversion is completed, CO2 and H2O are removed by the purification device, and then it is mixed with the second stream of syngas to adjust the ratio of CO and H2 in the syngas compressor.

[0127] Finally, the methanol synthesis reaction in the methanol synthesis unit is explained.

[0128] Syngas from the syngas compressor is pressurized and then enters the methanol synthesis unit. After heat exchange in the heat exchanger, it enters the methanol synthesizer for reaction. After the reaction is completed, the gaseous products generated in the methanol synthesizer exchange heat with the gas and demineralized water entering the methanol synthesizer in sequence, and then enter the condenser for condensation. The condensed liquid crude methanol enters the separator, while the non-condensable gas flows back to the inlet of the syngas compressor, mixes with fresh syngas and hydrogen, and then re-enters the methanol synthesizer for reaction. The liquid crude methanol is then purified by the subsequent methanol distillation column to obtain high-purity methanol.

[0129] (Example 1)

[0130] The following describes a specific embodiment 1 of the present invention. This embodiment uses the above-described chemical chain methanol production apparatus and the above-described chemical chain methanol production method to produce methanol. The specific parameters are as follows:

[0131] Raw material gas: biogas, flow rate 170 Nm 3 / h, biogas composition (molar ratio) CH4:CO2 = 60:40, reactant gas composition (molar ratio) entering the chemical loop reactor CH4:CO2 = 39.3:60.7

[0132] Oxygen carrier components in the reactor: NiO / Fe2O3 / ZrO composite oxygen carrier

[0133] Reactor bed temperature: 650℃~950℃

[0134] Reactor pressure: 0.18 MPa

[0135] Syngas flow rate: 462 Nm 3 / h

[0136] Syngas composition (molar ratio): CH4:CO2:H2O:H2:CO = 0.1:6.9:5.6:38.3:49.1

[0137] Synthesis gas temperature: 850℃

[0138] The composition (molar ratio) of the synthesis gas entering the methanol synthesis unit is: CO2:CO:H2 = 3.0:29.1:67.9.

[0139] Syngas compressor outlet pressure: 4.5 MPa

[0140] Methanol synthesis catalyst: Cu / Zn / Al based catalyst

[0141] Methanol synthesis reactor temperature: 265℃~272℃

[0142] Methanol synthesis reactor pressure: 4.1 MPa

[0143] Product methanol (99.9% purity) flow rate: 132.1 kg / h

[0144] (Example 2)

[0145] The following describes a specific embodiment 2 of the present invention. This embodiment uses the above-described chemical chain methanol production apparatus and the above-described chemical chain methanol production method to produce methanol. The specific parameters are as follows:

[0146] Raw material gas: biogas, flow rate 6250 Nm 3 / h, biogas composition (molar ratio) CH4:CO2 = 65:35, reactant gas composition (molar ratio) entering the chemical loop reactor CH4:CO2 = 41.3:58.7

[0147] Oxygen carrier composition in the reactor: NiO / CeO2 / MgAl2O3 composite oxygen carrier

[0148] Reactor bed temperature: 620℃~900℃

[0149] Reactor pressure: 0.15 MPa

[0150] Syngas flow rate: 17868 Nm 3 / h

[0151] Syngas composition (molar ratio): CH4:CO2:H2O:H2:CO = 0.1:5.3:4.6:40.5:49.5

[0152] Synthesis gas temperature: 790℃

[0153] The composition (molar ratio) of the synthesis gas entering the methanol synthesis unit is: CO2:CO:H2 = 2.5:30:67.5.

[0154] Syngas compressor outlet pressure: 5.5 MPa

[0155] Methanol synthesis catalyst: Cu / Zn / Al based catalyst

[0156] Methanol synthesis reactor temperature: 262℃~270℃

[0157] Methanol synthesis reactor pressure: 5.2 MPa

[0158] Methanol (99.9% purity) flow rate: 5196.9 kg / h

[0159] (Example 3)

[0160] The following describes a specific embodiment 3 of the present invention. This embodiment uses the above-described chemical chain methanol production apparatus and the above-described chemical chain methanol production method to produce methanol. Unlike embodiments 1 and 2, embodiment 3 uses a hydrogen supply device to supplement hydrogen, and its specific parameters are as follows:

[0161] Raw material gas: biogas, flow rate 342 Nm 3 / h, biogas composition (molar ratio) CH4:CO2 = 60:40, reactant gas composition (molar ratio) entering the chemical loop reactor CH4:CO2 = 38.7:61.3

[0162] Oxygen carrier composition in the reactor: NiO / CeO2 / MgAl2O3 composite oxygen carrier

[0163] Reactor bed temperature: 620℃~900℃

[0164] Reactor pressure: 0.14 MPa

[0165] Syngas flow rate: 930 Nm 3 / h

[0166] Syngas composition (molar ratio): CH4:CO2:H2O:H2:CO = 0.06:7.2:5.7:37.7:49.34

[0167] Synthesis gas temperature: 785℃

[0168] The composition (molar ratio) of the synthesis gas entering the methanol synthesis unit is: CO2:CO:H2 = 3.5:28.7:67.8.

[0169] Syngas compressor outlet pressure: 4.5 MPa

[0170] Methanol synthesis catalyst: Cu / Zn / Al based catalyst

[0171] Methanol synthesis reactor temperature: 262℃~270℃

[0172] Methanol synthesis reactor pressure: 5.2 MPa

[0173] Product methanol (99.9% purity) flow rate: 655 kg / h

[0174] In this embodiment, a hydrogen supply device is provided, which produces hydrogen by water electrolysis, with a hydrogen production capacity of 590 Nm³. 3 / h.

[0175] (Comparative Example 1)

[0176] The following describes Comparative Example 1 (CN116789520A) of the present invention, which uses a mixed catalytic reforming technology of methane + carbon dioxide + water vapor and prepares methanol by mixed hydrogenation of carbon monoxide and carbon dioxide. The specific parameters are as follows:

[0177] Heating method in biogas conversion process: Partial combustion of biogas, with heating achieved through flame radiation.

[0178] The inner or outer wall of the biogas conversion reactor must withstand a maximum temperature greater than 1200℃.

[0179] Biogas conversion water vapor requirement: water-to-carbon ratio ≥ 1

[0180] Process complexity: Complex

[0181] Methanol selectivity: 88%

[0182] Biogas consumption: 1408 Nm 3 biogas / ton of methanol

[0183] Methanol yield: 0.71 kg methanol / ton biogas

[0184] CH4 conversion rate (CH4 → syngas): 97%

[0185] CO2 conversion rate in biogas (CO2 → syngas): 35%

[0186] Carbon source conversion rate (C→methanol) in biogas feedstock: 49.7%

[0187] Is it prone to carbon buildup? Yes

[0188] (Comparative Example 2)

[0189] The following describes Comparative Example 2 of the present invention (Prior Art CN118086017), which first purifies methane in biogas, then catalytically reforms methane and water vapor to finally synthesize methanol. The specific parameters are as follows:

[0190] Heating method in biogas conversion process: Partial combustion of biogas, with heating achieved through flame radiation.

[0191] The inner or outer wall of the biogas conversion reactor must withstand a maximum temperature greater than 1200℃.

[0192] Biogas conversion water vapor requirement: water-to-carbon ratio ≥ 3

[0193] Process complexity: Complex

[0194] Methanol selectivity: >99%

[0195] Biogas consumption: 1620 Nm 3 biogas / ton of methanol

[0196] Methanol yield: 0.62 kg methanol / ton biogas

[0197] CH4 conversion rate (CH4 → syngas): 88–92%

[0198] CO2 conversion rate in biogas (CO2 → syngas): 0%

[0199] Carbon source conversion rate (C→methanol) in biogas feedstock: 43.5%

[0200] Does it easily accumulate carbon deposits: No

[0201] (Comparison between the examples and the comparative examples)

[0202] The table below shows a comparison of the main reaction conditions and final reaction results in the preparation of methanol using the examples and comparative examples.

[0203] As can be seen from the table above, in the preparation of methanol in Examples 1 and 3 of the present invention, since the reactor bed heat storage and heating method is adopted, there is no need to use flame heating. Therefore, the maximum temperature that the converter needs to withstand is much lower than the maximum temperature that the converter needs to withstand in the preparation of methanol in Comparative Examples 1-2.

[0204] Moreover, in Examples 1 and 3 of the present invention, no excess water vapor needs to be added during the entire raw material gas conversion reaction process, which greatly reduces energy consumption. In addition, the methanol selectivity of Examples 1 and 3 of the present invention is greater than 99%, the amount of biogas required to produce 1 ton of methanol is less, the conversion rate of CH4 and CO2 in biogas to syngas is also higher, the total carbon source conversion rate in the raw material biogas is also much higher than that of Comparative Examples 1-2, and the entire device is not prone to carbon accumulation.

[0205] The chemical chain conversion methanol production apparatus of this invention uses a mixture of CH4 and CO2 as feedstock. It eliminates the need for pre-separation and purification of CH4 in the feedstock gas, directly performing the chemical chain conversion. This solves the problems of high energy consumption, multiple separation steps, catalyst sintering, and catalyst deactivation due to carbon buildup in traditional methane reforming processes. When the feedstock gas is biogas, the innovative chemical chain conversion technology combined with the mature carbon monoxide hydrogenation methanol synthesis process produces green methanol. This method can maximize the utilization of carbon sources (CH4, CO2) in biomass feedstocks, converting the vast majority of green carbon sources into methanol. It features low technical risk, energy saving and carbon reduction, and good economic efficiency.

[0206] The chemical chain methanol production apparatus of the present invention adopts an in-bed heat storage and heating method (referred to as "internal heating type"), and the reactor temperature is always below 950°C. It does not use the traditional combustion flame radiation heating method (local temperature exceeds 1300°C), which can avoid problems such as catalyst sintering and carbon deposition caused by local high temperature. At the same time, it greatly reduces the material requirements of the reactor and greatly improves the overall economy of the apparatus.

[0207] Furthermore, the chemical looping process for converting the feed gas eliminates the need for excessive water vapor replenishment, significantly saving energy. The composite oxygen carrier material simultaneously achieves stable chemical looping and high reforming catalytic performance, maintaining a methane conversion rate greater than 99.7% while keeping the CO2:CH4 molar ratio between 55:45 and 75:25. It also reduces the partial pressure of inert components like methane in the syngas, thereby decreasing the frequency and flow rate of purge gas emissions from the methanol synthesis section. This eliminates the need for PSA or membrane separation equipment to recover hydrogen from the purge gas, saving investment and reducing the load on the feed gas compressor, thus lowering operating energy consumption. On the other hand, the generated syngas has low CO2 and H2O content, with a total CO and H2 content exceeding 90%. Combined with hydrogen supplementation, this can further significantly reduce investment and operating energy consumption in syngas purification equipment.

[0208] Furthermore, the process of this invention is highly flexible and can be combined with the main process by utilizing external hydrogen sources (such as green electricity hydrogen production), thereby enabling full utilization of the carbon source in the feed gas and increasing methanol production capacity.

[0209] (Results of biogas conversion)

[0210] Figures 7-9 show the biogas conversion experimental results of Examples 1, 2, and 3 of the present invention (water vapor is difficult to detect; the data are the residual components after syngas is cooled and dehydrated). As can be seen from the figures, the CH4 concentration at the syngas outlet in Examples 1, 2, and 3 is maintained at a very low level (below 0.1 vol.%), and the methane conversion rate is above 99%. At the same time, the CO2 concentration in all the generated syngas is below 8%, which means that most of the CO2 in the raw gas can be converted and utilized.

Claims

1. An apparatus for the chemical chain production of methanol, characterized in that, The apparatus for producing methanol via chemical chain reaction includes a feed gas supply unit, a chemical chain reaction unit, an air supply unit, a syngas treatment unit, and a methanol synthesis unit. The chemical chain reaction unit includes a converter, a reducer, and an air oxidizer. These three parts can be converted into each other according to the reaction stage and can be cyclically repeated as a whole. The same oxygen carrier is provided in the converter, the reducer and the air oxidizer. The oxygen carrier changes into a metal element or a metal oxide in each reaction stage, and the metal element corresponding to the oxygen carrier plays a catalytic role in the feed gas conversion reaction in the converter. The feed gas supply unit is connected to the converter and is used to supply the feed gas required for the reaction to the converter; the air supply unit is connected to the air oxidizer and is used to supply air to the air oxidizer; the converter is connected to the syngas treatment unit and transports the syngas converted from the feed gas to the syngas treatment unit, which is used to treat the syngas; the reducer is connected to the feed gas supply unit and is used to return carbon dioxide to the feed gas supply unit. The syngas processing unit is connected to a converter and is used to adjust the composition of the syngas after the feedstock gas is converted, and to pressurize the syngas. The methanol synthesis unit is connected to the synthesis gas treatment unit and is used to synthesize methanol.

2. The apparatus for chemical chain methanol production according to claim 1, characterized in that, The raw material gas supplied by the raw material gas supply unit is biogas.

3. The apparatus for chemical chain methanol production according to claim 1, characterized in that, The oxygen carrier contains an active ingredient and selectively contains a secondary active ingredient, an inactive ingredient, or both. The active ingredient is one or more of NiO, CeO2, ZnO, and CuO; The secondary active ingredient is one or more of Fe2O3, Co3O4, and Mn2O3. The inactive component is one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2.

4. The apparatus for chemical chain methanol production according to claim 1, characterized in that, The oxygen carrier does not contain any active ingredients, but includes sub-active ingredients, and selectively includes inactive ingredients. The secondary active ingredient is one or more of Fe2O3, Co3O4, and Mn2O3. The inactive component is one or more of ZrO2, MgO, Y2O3, MgAl2O4, CaAl2O4, CaO, Al2O3, and TiO2.

5. The apparatus for chemical chain methanol production according to claim 3, characterized in that, The oxygen carrier contains 8–40 wt.% of active ingredients, 0–5 wt.% of secondary active ingredients, and 60–92 wt.% of inactive ingredients.

6. The apparatus for chemical chain methanol production according to claim 1, characterized in that, The raw material gas supply unit includes a raw material gas source, a desulfurization device, a mixer, and a raw material gas blower connected in sequence. The raw material gas source provides the raw material gas required for the reaction. After being desulfurized by the desulfurization device, the raw material gas flows into the mixer to mix with CO2 in the tail gas of the chemical looping reaction unit. Then, after being pressurized by the raw material gas blower, it is transported to the chemical looping reaction unit.

7. The apparatus for chemically chain-based methanol production according to claim 6, characterized in that, The air supply unit includes an air fan. Outside air enters the air fan, is pressurized by the air fan, and is then delivered to the chemical chain reaction unit.

8. The apparatus for chemical chain methanol production according to claim 1, characterized in that, The syngas processing unit includes a syngas control valve, a water-vapor shift device, a purification device, and a syngas compressor. The syngas control valve is connected to the converter and is used to divert the syngas generated in the converter. The water-vapor shift device is connected to the syngas control valve and is used to perform water-vapor shift on the syngas diverted by the syngas control valve, converting CO in the syngas into H2. The purification device is connected to the water-vapor shift device and is used to remove CO2 from the gas after the reaction in the water-vapor shift device. The syngas compressor is connected to the syngas control valve and the purification device and pressurizes the gas inside them. In this process, the syngas generated in the converter is divided into three streams by the syngas control valve. The first stream of syngas flows back to the reducer to reduce the oxygen carrier. The second stream enters the water-gas shift device to convert CO in the syngas into H2. After the water-gas shift is completed, the gas enters the purification device, where CO2 is separated out, while H2 is mixed with the third stream of syngas to adjust the ratio of CO and H2 in the third stream of syngas. Then, the gas enters the syngas compressor.

9. The apparatus for chemical chain methanol production according to claim 1, characterized in that, The syngas processing unit includes a syngas control valve, a hydrogen supply device, and a syngas compressor. The syngas control valve is connected to the converter and is used to control the syngas generated by the converter. The syngas compressor is connected to the syngas control valve, and the hydrogen supply device is connected to the syngas compressor. The syngas enters the syngas compressor via the syngas control valve and then enters the methanol synthesis unit; The hydrogen supply device is also connected to the reducer. The hydrogen it produces passes through the inlet switching valve and the heat exchanger in sequence before entering the reducer to reduce the oxygen carrier in the oxidized state.

10. The apparatus for chemically chain-based methanol production according to claim 9, characterized in that, The hydrogen supply device produces hydrogen by electrolyzing water, and the electrical energy consumed in the process comes from green electricity resources generated by wind power and photovoltaic power generation devices.

11. The apparatus for chemically chain-based methanol production according to claim 1, characterized in that, The methanol synthesis unit includes a methanol synthesizer, a heat exchange and steam unit, a condenser, a liquid separator, and a methanol distillation column. The methanol synthesizer is connected to a synthesis gas compressor, and the condenser, liquid separator, and methanol distillation column are connected to the methanol synthesizer in sequence. The heat exchange and steam device includes a water pump, a deaerator, and a steam drum. The steam drum is connected to the methanol synthesizer, and the water pump is connected to the steam drum to supply demineralized water. The deaerator is installed on the pipeline between the steam drum and the water pump to remove oxygen from the deoxygenated water.

12. The apparatus for chemically chain-based methanol production according to claim 1, characterized in that, The apparatus for producing methanol via chemical chain also includes a control unit, which controls the inlet switching valve and the outlet switching valve. The feed gas supply unit and air supply unit are connected to the air inlets of the three reactors via inlet switching valves. When feed gas / air needs to be supplied to the converter / air oxidizer, the control unit controls the inlet switching valves to connect the feed gas supply unit / air supply unit to the converter / air oxidizer. The three reactors are also connected to the air oxidation tail gas pipeline, the oxygen carrier reduction tail gas pipeline, and the syngas treatment unit via outlet switching valves. After the reaction in the converter / reducer / air oxidizer is completed, the control unit controls the outlet switching valves to connect the converter / reducer / air oxidizer to the syngas treatment unit / oxygen carrier reduction tail gas pipeline / air oxidation tail gas pipeline. The syngas control valve in the syngas treatment unit is connected to the three reactors via inlet switching valves. When reducing gas needs to be supplied to the reducer, the control unit controls the inlet switching valves to connect the syngas control valve to the reducer. When a hydrogen supply device is present, the hydrogen supply device is connected to the three reactors through an inlet switching valve. When it is necessary to supply reducing gas to the reducer, the control unit controls the inlet switching valve to connect the hydrogen supply device to the reducer.

13. The apparatus for chemically chain-based methanol production according to claim 1, characterized in that, The feed gas supplied by the feed gas supply unit is one of the following: natural gas with high CO2 content, industrial tail gas containing CH4 and CO2, or associated gas from CO2-enhanced oilfields.

14. A method for producing methanol via chemical chain reaction, characterized in that, Using the apparatus for the chemical chain production of methanol according to any one of claims 1-13, and comprising the following steps: The device startup and oxygen carrier and reactor preparation steps involve first filling the three reactors of the chemical looping reaction unit with the aforementioned oxygen carrier, and then starting the device. In the reactor pretreatment step, the three reactors are heated and the system is adjusted to be suitable for the following reactions through a combination of pre-reduction and pre-oxidation: the three reactors of the chemical loop reaction unit switch and cycle repeatedly to carry out the feed gas conversion reaction, air oxidation reaction and reduction reaction. In the feed gas conversion step, feed gas is introduced into the converter through the feed gas supply unit. It is first mixed with part of the recycled reduction tail gas. Then, the feed gas undergoes a feed gas conversion reaction under the catalysis of the metal elemental oxygen carrier. It makes full use of the heat accumulated in the oxygen carrier in the previous pre-oxidation step to generate syngas containing CO, H2, and a small amount of CO2 and H2O. The syngas is discharged from the reactor and is ready to enter the syngas treatment unit or be returned to the reducer. In the air oxidation step, after the raw material gas conversion reaction is completed, the reactor is switched to the air oxidizer state and the air oxidation process is carried out. That is, air is introduced into the air oxidizer through the air supply unit. The oxygen in the air oxidizes the metal elemental oxygen carrier to a high oxidation state and releases a large amount of heat. Most of this reaction heat is stored in the oxidized oxygen carrier bed, which stores the heat required for the subsequent raw material gas conversion process in advance. In the reduction step, after the air oxidation is completed, the reactor is switched to the reducer state and the reduction process is carried out. That is, a part of the syngas generated by the feed gas conversion reaction is returned to the reducer to reduce the oxygen carrier from the high-valence oxide state to the elemental state. The heat released by the reaction is stored in the oxygen carrier bed. This part of the heat, together with the heat stored in the oxygen carrier in the previous stage of air oxidation, provides the heat required for the next stage of feed gas conversion process. In the syngas treatment process, the syngas generated in the converter is divided into three streams by the syngas control valve. The first stream of syngas flows back to the reducer to reduce the oxygen carrier. The second stream enters the water-gas shift converter to convert CO in the syngas into H2. After the water-gas shift is completed, the gas enters the purification device, where CO2 is separated out, while H2 is mixed with the third stream of syngas to adjust the CO and H2 ratio in the third syngas to meet the requirements for methanol synthesis. The mixed syngas then enters the syngas compressor. In the methanol synthesis process, the gas from the syngas compressor enters the methanol synthesizer to undergo the methanol synthesis reaction. After the reaction is completed, the gaseous products generated in the methanol synthesizer exchange heat with the syngas and demineralized water that entered the methanol synthesizer before entering the methanol synthesizer. Then, they enter the condenser for condensation. The condensed liquid crude methanol enters the separator, while the non-condensable gas flows back to the inlet of the syngas compressor, mixes with fresh syngas and hydrogen, and then re-enters the methanol synthesizer for the reaction. The liquid crude methanol is then purified by a subsequent methanol distillation column to obtain high-purity methanol.

15. The method for producing methanol via chemical chaining according to claim 14, characterized in that, The reduction step is as follows: after the air oxidation is completed, the reactor is switched to the state of the reducer and the reduction process is carried out. That is, the hydrogen generated by the hydrogen supply device enters the reducer to reduce the oxygen carrier from the high-valence oxide state to the elemental state. The heat released by the reaction is stored in the oxygen carrier bed. This part of the heat, together with the heat stored in the oxygen carrier in the previous stage of air oxidation, provides the heat required for the reaction in the next stage of raw material gas conversion process. The syngas treatment step involves the syngas control valve diverting all the syngas to the syngas compressor in preparation for the methanol synthesis reaction. Before entering the syngas compressor, the syngas is mixed with hydrogen produced by the hydrogen supply device to adjust the ratio of CO and H2 in the syngas entering the syngas compressor.

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