A coal-to-methanol system and process enhanced with green hydrogen and green oxygen, and a method for optimizing green hydrogen permeability.

Abstract

This invention provides a coal-to-methanol system and process enhanced with green hydrogen and green oxygen, as well as a method for optimizing green hydrogen permeability. By adjusting the hydrogen-to-carbon ratio with green hydrogen, replacing air separation oxygen production with green oxygen, and achieving synergistic effects of green hydrogen and green oxygen, the system simplifies the process and reduces energy consumption and carbon emissions. At the same time, the optimal green hydrogen permeability is determined through multi-objective optimization, achieving a balance between technical feasibility, low carbon emissions, and economic efficiency. This invention is applicable to new coal-to-methanol plants or low-carbon retrofitting of existing plants.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical and new energy coupling technology, specifically involving a coal-to-methanol system and process enhanced with green hydrogen and green oxygen, and a method for optimizing green hydrogen permeability. Background Technology

[0002] Coal-to-methanol is the core process in the coal chemical industry and the mainstream route for methanol production. However, traditional processes have significant technical bottlenecks that restrict their low-carbon transformation and energy efficiency improvement.

[0003] First, the coal-to-methanol process is complex and energy-intensive. Traditional coal-to-methanol production requires oxygen generation through an air separation unit, followed by methanol production through coal gasification, water-gas shift conversion, acid gas removal, methanol synthesis, and distillation. The water-gas shift unit, in particular, requires the conversion of some CO into H2 and CO2 to adjust the hydrogen-to-carbon ratio, resulting in significant greenhouse gas emissions and increased system energy consumption and equipment investment. Second, existing green-hydrogen coupled coal-to-methanol technologies often focus only on green hydrogen supplementation, failing to fully utilize the green oxygen produced as a byproduct of hydrogen electrolysis. While some technologies attempt to replace air separation with green oxygen, they lack a synergistic enhancement mechanism for green hydrogen to adjust the hydrogen-to-carbon ratio and for green oxygen substitution, leading to a waste of green electricity resources and failing to maximize the benefits of new energy coupling. Furthermore, traditional coal-to-methanol processes rely primarily on the water-gas shift reaction to adjust the hydrogen-to-carbon ratio; this reaction is irreversible, and CO2 emissions are unavoidable. Finally, existing technologies often rely on empirical values ​​or single indicators for selecting green hydrogen penetration rates, and current green hydrogen supplementation technologies lack a synergistic configuration strategy with purchased hydrogen, resulting in unreasonable green hydrogen penetration rate selections and difficulty in balancing economic efficiency and low-carbon emissions.

[0004] In summary, traditional coal-to-methanol processes suffer from problems such as process redundancy, high energy consumption, and large carbon emissions. Existing green hydrogen coupling technologies lack systematic solutions for synergistic enhancement of green hydrogen and green oxygen and multi-objective optimization of permeability. There is an urgent need to develop a new coal-to-methanol process that simplifies the process, improves energy efficiency, and is low-carbon and economical, along with a corresponding method for optimizing green hydrogen permeability. Summary of the Invention

[0005] To address the issues of process redundancy, high energy consumption, and large carbon emissions in existing coal-to-methanol processes, this invention provides a green hydrogen and green oxygen enhanced coal-to-methanol system and process, as well as a green hydrogen permeability optimization method. By adjusting the hydrogen-carbon ratio with green hydrogen, replacing air separation oxygen production with green oxygen, and achieving synergistic effects of green hydrogen and green oxygen, the process is simplified, and energy consumption and carbon emissions are reduced. At the same time, the optimal green hydrogen permeability is determined through multi-objective optimization, achieving a balance between technical feasibility, low carbon emissions, and economic efficiency. This invention is suitable for new coal-to-methanol plants or low-carbon retrofitting of existing plants.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a green hydrogen and green oxygen enhanced coal-to-methanol system, comprising: an electrolytic hydrogen production unit, a coal gasification unit, an air separation unit, an acid gas removal unit, a hydrogen-to-carbon ratio adjustment unit, a methanol synthesis unit, and a methanol distillation unit; the electrolytic hydrogen production unit uses green electricity as its energy source, the green oxygen outlet of the electrolytic hydrogen production unit and the oxygen outlet of the air separation unit are both connected to the oxygen inlet of the coal gasification unit, the crude syngas outlet of the coal gasification unit is connected to the inlet of the acid gas removal unit, the purified syngas outlet of the acid gas removal unit is connected to the syngas inlet of the hydrogen-to-carbon ratio adjustment unit, the hydrogen inlet of the hydrogen-to-carbon ratio adjustment unit is connected to the green hydrogen outlet of the electrolytic hydrogen production unit, the hydrogen inlet of the hydrogen-to-carbon ratio adjustment unit is also used to input purchased hydrogen, the outlet of the hydrogen-to-carbon ratio adjustment unit is connected to the inlet of the methanol synthesis unit, and the methanol outlet of the methanol synthesis unit is connected to the inlet of the methanol distillation tower; the acid gas removal unit is used to remove H2S.

[0007] Secondly, this invention provides a coal-to-methanol process enhanced with green hydrogen and green oxygen. Based on the aforementioned green hydrogen and green oxygen enhanced coal-to-methanol system, the process includes: an electrolytic hydrogen production unit simultaneously producing green hydrogen and green oxygen via water electrolysis; raw coal, green oxygen produced by the electrolytic hydrogen production unit, and oxygen generated by the air separation unit are fed into a gasifier in a coal gasification unit for coal gasification reaction to generate crude syngas containing CO and H2; the crude syngas enters an acid gas removal unit to remove H2S; the purified syngas after H2S removal is mixed with green hydrogen produced by the electrolytic hydrogen production unit and purchased hydrogen in a hydrogen-to-carbon ratio adjustment unit to control the hydrogen-to-carbon ratio of the resulting mixed syngas to meet the requirements of the methanol synthesis reaction; the mixed syngas is compressed and heated before being fed into a methanol synthesis unit to synthesize crude methanol; the crude methanol is purified by a methanol distillation unit to obtain refined methanol product.

[0008] Thirdly, the present invention provides a method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process, comprising: Step 1: Given the amount of raw coal used, conduct a full-process simulation of the green hydrogen and green oxygen enhanced coal-to-methanol process to determine the range of green hydrogen permeability in the system. Within the determined range of green hydrogen permeability, conduct variable operating condition simulations to obtain data on green hydrogen consumption, purchased hydrogen, and the corresponding total energy consumption, carbon emissions, and unit product cost under each operating condition, forming a sample library. The green hydrogen permeability is the ratio of green hydrogen produced by the electrolytic hydrogen production unit to the total amount of green hydrogen and purchased hydrogen. The relationship between green hydrogen consumption, purchased hydrogen, and the total energy consumption, carbon emissions, and unit product cost of the system is obtained from the sample library. Step 2: With the objective functions of minimizing total system energy consumption, carbon emissions, and unit product cost, and with green hydrogen consumption and purchased hydrogen consumption as decision variables, and with constraints such as the hydrogen-to-carbon ratio required for methanol synthesis, oxygen supply and demand, equipment operating window, and green hydrogen permeability as constraints, a multi-objective optimization model is constructed by combining the relationship between green hydrogen consumption, purchased hydrogen consumption, total system energy consumption, carbon emissions, and unit product cost. Step 3: Solve the multi-objective optimization model to obtain the amount of green hydrogen used and the amount of purchased hydrogen.

[0009] Preferably, the total energy consumption of the system is... E Represented as:

[0010] in, These represent raw coal consumption, fuel coal consumption, and methanol production capacity, respectively. These are the standard coal conversion coefficients for raw coal, fuel coal, and electricity. It is the total power consumption of the system. It is the lower heating value of coal. It is the amount of waste heat recovered in the system.

[0011] Preferably, the carbon emissions C Represented as:

[0012] in, These represent raw coal consumption, fuel coal consumption, and methanol production capacity, respectively. It refers to the fixed carbon content in raw coal and fuel coal. It is the carbon combustion conversion coefficient; This refers to the amount of hydrogen purchased from outside the system. It is a carbon emission factor of purchased hydrogen.

[0013] Preferably, the unit product cost P Represented as:

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] In the formula, , , , , These represent the costs of raw coal, fuel coal, green hydrogen, purchased hydrogen, and purchased electricity, respectively. The annualized investment cost of the equipment in the system; This refers to the amount of hydrogen purchased from outside the system. The amount of green hydrogen produced by the electrolysis hydrogen production unit is used as the amount of green hydrogen consumed. , , , , These represent the unit prices of raw coal, fuel coal, green electricity, water, purchased hydrogen, and purchased electricity, respectively. It is the unit power consumption for hydrogen production by electrolysis; This is the system's total power consumption; It refers to the amount of electricity generated by the system.

[0020] Preferably, the hydrogen-to-carbon ratio constraint required for methanol synthesis is expressed as follows:

[0021] in, , These represent the number of moles of hydrogen, CO, and CO2 produced by the gasification of raw coal, respectively. These represent the lower and upper limits of the hydrogen-to-carbon ratio required for the reaction process, respectively. This refers to the amount of hydrogen purchased from outside the system. The green hydrogen production from the electrolysis hydrogen production unit is used as the green hydrogen consumption.

[0022] Preferably, the oxygen supply and demand constraint is expressed as follows: When the demand for green oxygen is met:

[0023] When green oxygen cannot meet the demand:

[0024] In the formula, the production capacity of green oxygen is... Calculations based on green hydrogen production:

[0025] The oxygen requirement of the gasifier in the coal gasification unit; This refers to the oxygen production capacity of the air separation unit.

[0026] Preferably, the device operation window constraint is represented as follows:

[0027]

[0028]

[0029] In the formula, , and These represent the rated hydrogen production capacity of the electrolyzer in the electrolysis hydrogen production unit, the rated coal processing capacity of the gasifier in the coal gasification unit, and the rated capacity of the methanol synthesis reactor in the methanol synthesis unit, respectively. These represent the lower and upper limits of the equipment's deviation from its rated load, respectively.

[0030] Preferably, the green hydrogen permeability constraint is expressed as:

[0031] In the formula, This represents the upper bound of green hydrogen permeability.

[0032] Compared with the prior art, the present invention has the following beneficial effects: The green hydrogen and green oxygen enhanced coal-to-methanol system and process of this invention eliminates the water-gas shift unit and air separation unit of the traditional process, and simplifies the acid gas removal unit. By adjusting the hydrogen-to-carbon ratio with green hydrogen and replacing air separation for oxygen production with green oxygen, the coal-to-methanol process is significantly simplified. Adjusting the hydrogen-to-carbon ratio with green hydrogen does not rely on the shift reaction, maximizing the coupling benefits of new energy sources; replacing air separation for oxygen production with green oxygen addresses the dual demands of new energy consumption and the low-carbon transformation of coal chemical industry, resulting in a reduction in the total energy consumption of the system compared to traditional processes.

[0033] This invention, for the first time, constructs a multi-objective optimization model for energy consumption, carbon emissions, and economic efficiency with green hydrogen permeability as the core decision variable. This model achieves synergistic optimization, minimizing total system energy consumption, carbon emissions, and unit product cost, avoiding the limitations of single-index optimization. A joint solution method combining process flow simulation and multi-objective algorithms simplifies the model and verifies the optimization results. The multi-objective optimization model and method of this invention are highly scalable and can be used for the design of new coal-to-methanol plants or the retrofitting of existing plants. It is adaptable to different scenarios, such as the Northwest region with abundant green electricity and the East China cost-sensitive region. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This invention relates to a coal-to-methanol process based on the aforementioned green hydrogen and green oxygen enhanced coal-to-methanol system.

[0036] Figure 2This invention proposes a method that combines process simulation and multi-objective algorithm for solving problems. Detailed Implementation

[0037] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0038] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0039] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0040] The green hydrogen and green oxygen enhanced coal-to-methanol system of the present invention includes: an electrolytic hydrogen production unit, a coal gasification unit, an air separation unit, an acid gas removal unit, a hydrogen-to-carbon ratio adjustment unit, a methanol synthesis unit, and a methanol distillation unit. The electrolytic hydrogen production unit uses green electricity as its energy source. The green oxygen outlet of the electrolytic hydrogen production unit and the oxygen outlet of the air separation unit are both connected to the oxygen inlet of the coal gasification unit. The crude syngas outlet of the coal gasification unit is connected to the inlet of the acid gas removal unit. The purified syngas outlet of the acid gas removal unit is connected to the syngas inlet of the hydrogen-to-carbon ratio adjustment unit. The hydrogen inlet of the hydrogen-to-carbon ratio adjustment unit is connected to the green hydrogen outlet of the electrolytic hydrogen production unit. The hydrogen inlet of the hydrogen-to-carbon ratio adjustment unit is also used to input purchased hydrogen. The outlet of the hydrogen-to-carbon ratio adjustment unit is connected to the inlet of the methanol synthesis unit. The methanol outlet of the methanol synthesis unit is connected to the inlet of the methanol distillation column.

[0041] Figure 1The process flow of the green hydrogen and green oxygen enhanced coal-to-methanol system is as follows: The electrolytic hydrogen production unit uses green electricity as energy to produce hydrogen through water electrolysis, and simultaneously produces green oxygen with a purity of ≥99%; the raw coal, the green oxygen produced by the electrolytic hydrogen production unit, and the oxygen produced by the air separation unit are fed into the gasifier of the coal gasification unit in a certain proportion to carry out the coal gasification reaction, generating crude syngas containing CO and H2; the crude syngas enters the acid gas removal unit to remove only H2S; the purified syngas after acid gas removal is fed into the hydrogen-carbon ratio adjustment unit in a certain proportion with the green hydrogen produced by the electrolytic hydrogen production unit and purchased hydrogen, and mixed to control the hydrogen-carbon ratio of the mixed syngas to meet the optimal requirements of the methanol synthesis reaction; the mixed syngas is compressed and heated and then sent to the methanol synthesis unit to synthesize crude methanol; the crude methanol is purified by the methanol distillation unit to finally obtain a refined methanol product with a purity of ≥99.7%.

[0042] Existing acid gas removal units remove both CO2 and H2S. Since CO2 has a lower solubility than H2S, ensuring complete CO2 removal requires increasing the solvent volume and complicates the acid gas removal process due to subsequent CO2 and H2S enrichment and utilization. This invention's acid gas removal unit removes only H2S, reducing solvent usage, and does not consider CO2 removal or enrichment. The green hydrogen and green oxygen enhanced coal-to-methanol process of this invention eliminates the water-gas shift unit of the traditional process and simplifies the acid gas removal unit, achieving process simplification through green hydrogen supplementation and green oxygen substitution.

[0043] Figure 2 The present invention proposes a method for jointly solving process simulation and multi-objective algorithms, the detailed steps of which are as follows: Step 1: Given the amount of raw coal used, a full-process simulation of the green hydrogen and green oxygen enhanced coal-to-methanol process is conducted using Aspen Plus. Based on the process simplification objective, the range of green hydrogen permeability in the system is determined. The upper bound of green hydrogen permeability is defined as the permeability when the air separation unit and water-gas shift unit are completely removed, and the lower bound is 0. Within this determined range of green hydrogen permeability, variable operating condition simulations are performed to obtain data on green hydrogen consumption, purchased hydrogen quantity, and corresponding system performance indicators such as total energy consumption, carbon emissions, and unit product cost under each operating condition, forming a sample library. The relationship between green hydrogen consumption, purchased hydrogen quantity, and system total energy consumption, carbon emissions, and unit product cost is then obtained from the sample library.

[0044] Step 2: Using the minimum total system energy consumption, minimum carbon emissions, and minimum unit product cost as objective functions, and unifying the dimensions of the objective function through linear normalization, we determine the boundary values ​​of constraints, such as the range of hydrogen-carbon ratio and the upper limit of equipment load. We then implement the mathematical expression of the model using Python programming and call the Pyomo library to build a multi-objective optimization model.

[0045] This invention constructs a multi-objective optimization model with green hydrogen penetration rate or green hydrogen usage as the core decision variables, achieving synergistic optimization of minimum total energy consumption, minimum carbon emissions, and minimum unit product cost. The details of the multi-objective optimization model are as follows: (1) Objective function 1) Minimize the total system energy consumption E Total energy consumption includes the energy consumption of raw coal and fuel coal, electricity consumption, minus the energy consumption of waste heat recovery, i.e.

[0046] in, These represent the consumption of raw coal, fuel coal, and methanol production capacity, respectively. These are the standard coal conversion coefficients for raw coal, fuel coal, and electricity. It is the total power consumption of the system. It is the lower heating value of coal. It is the amount of waste heat recovered in the system, which can be determined using pinch analysis technology under given pinch temperature difference conditions, or it can be calculated according to the average proportion of waste heat recovery in the total energy consumption of the coal-to-methanol industry.

[0047] 2) Minimize system carbon emissions C The system's carbon emissions include emissions from coal combustion and implicit emissions from purchased hydrogen, as shown in the following equation:

[0048] in, It refers to the fixed carbon content in raw coal and fuel coal. It is the carbon combustion conversion coefficient; This refers to the amount of purchased hydrogen used in the system. It is a carbon emission factor of purchased hydrogen.

[0049] 3) Minimize unit product cost P Unit product cost includes raw material cost, annualized equipment depreciation, and operating cost, as shown in the following equation:

[0050] The costs of raw coal, fuel coal, green hydrogen, purchased hydrogen, and purchased electricity are calculated using the following formulas:

[0051]

[0052]

[0053]

[0054]

[0055] In the above formula, , , , , These represent the unit prices of raw coal, fuel coal, green electricity, water, purchased hydrogen, and purchased electricity, respectively. This refers to the unit power consumption for hydrogen production via electrolysis. The amount of green hydrogen produced by the electrolysis hydrogen production unit is used as the amount of green hydrogen consumed. It refers to the amount of electricity generated by the system.

[0056] The annualized investment cost of the equipment is calculated using the following formula:

[0057] In the above formula r It's the interest rate. n This refers to the system's lifespan. The formulas for calculating the investment costs of equipment in different units within the system can be directly obtained from existing technologies.

[0058] (2) Constraints 1) Hydrogen-to-carbon ratio constraints required for methanol synthesis The hydrogen-to-carbon ratio of the mixed synthesis gas meets the optimal requirements for methanol synthesis, that is,

[0059] in, , These represent the number of moles of hydrogen, CO, and CO2 produced by the gasification of raw coal, respectively, and can be determined through simulation. These represent the lower and upper limits of the hydrogen-to-carbon ratio required for the reaction process, respectively, which can be adjusted in practice according to the catalyst and reaction conditions used.

[0060] 2) Oxygen supply and demand constraints The production of green oxygen should be balanced with the oxygen demand of the gasifier. Since green oxygen is a byproduct of hydrogen production via water electrolysis, then: When green oxygen can meet the demand:

[0061] When green oxygen cannot meet the demand:

[0062] The production capacity of green oxygen in the above formula Calculations can be made based on green hydrogen production:

[0063] Oxygen requirements of the gasifier The amount of oxygen produced by the air separation unit was obtained from simulation data of the raw coal gasification reaction. It can be calculated by the difference between the oxygen demand of the gasifier obtained from the simulation and the green oxygen supply in the system.

[0064] 3) Equipment operation window constraints To ensure that the loads of core equipment, such as the electrolyzers in the hydrogen electrolysis unit, the gasifiers in the coal gasification unit, and the methanol synthesis reactors in the methanol synthesis unit, do not exceed their permissible operating windows, it is necessary to limit the operating loads of the core equipment, namely:

[0065]

[0066]

[0067] In the above formula, , and These represent the rated hydrogen production of the electrolyzer, the rated coal processing capacity of the gasifier, and the rated production capacity of the methanol synthesis reactor, respectively. These represent the lower and upper limits of the equipment's deviation from the rated load, respectively, and can be determined based on the actual operating conditions.

[0068] 4) Green hydrogen permeability constraint

[0069] In the formula, This represents the upper bound of green hydrogen permeability.

[0070] 5) Purity constraints To meet the purity requirements for raw materials and products during the production process, the following constraints are imposed:

[0071]

[0072]

[0073] in, For the purity of green hydrogen, For the purity of green oxygen, This refers to the purity of the methanol output from the methanol distillation column.

[0074] Step 3: The NSGA-Ⅲ algorithm is used to solve the multi-objective optimization model to obtain the green hydrogen consumption, the amount of purchased hydrogen, the total power consumption of the system, the power generated by the system, the raw coal consumption, and the fuel coal consumption. The algorithm parameters are set, and Pareto optimal solution set is generated through non-dominated sorting and congestion calculation. In the calculation, the priority of the objective function can be adjusted according to the actual situation, or the calculation weight of different objectives can be set to ensure the diversity and optimality of the solution.

[0075] Step 4: Based on the actual application scenario, such as the abundance of green electricity resources, carbon price level, and raw coal cost, select the optimal green hydrogen permeability from the Pareto optimal solution set; substitute the optimal permeability parameter into the Aspen Plus model for simulation verification to confirm that the methanol production capacity, energy consumption, carbon emissions and other indicators meet the design requirements and all constraints are met.

[0076] This invention is the first to construct a three-objective optimization model encompassing energy consumption, carbon emissions, and economic efficiency, avoiding the limitations of single-index optimization. It provides personalized solutions through Pareto optimal solutions, adapting to different green energy resource endowments and market conditions. The method of this invention can be used for the design of new coal-to-methanol plants or the retrofitting of existing plants, and is suitable for different scenarios such as the Northwest region with abundant green energy resources and the East China cost-sensitive region.

[0077] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A coal-to-methanol system with green hydrogen and green oxygen enhancement, characterized in that, include: The system comprises an electrolytic hydrogen production unit, a coal gasification unit, an air separation unit, an acid gas removal unit, a hydrogen-to-carbon ratio adjustment unit, a methanol synthesis unit, and a methanol distillation unit. The electrolytic hydrogen production unit uses green electricity as its energy source. The green oxygen outlet of the electrolytic hydrogen production unit and the oxygen outlet of the air separation unit are both connected to the oxygen inlet of the coal gasification unit. The crude syngas outlet of the coal gasification unit is connected to the inlet of the acid gas removal unit. The purified syngas outlet of the acid gas removal unit is connected to the syngas inlet of the hydrogen-to-carbon ratio adjustment unit. The hydrogen inlet of the hydrogen-to-carbon ratio adjustment unit is connected to the green hydrogen outlet of the electrolytic hydrogen production unit. The hydrogen inlet of the hydrogen-to-carbon ratio adjustment unit is also used to input purchased hydrogen. The outlet of the hydrogen-to-carbon ratio adjustment unit is connected to the inlet of the methanol synthesis unit. The methanol outlet of the methanol synthesis unit is connected to the inlet of the methanol distillation column. The acid gas removal unit is used to remove H2S.

2. A green hydrogen and green oxygen enhanced coal to methanol process, characterized in that, The coal-to-methanol system enhanced with green hydrogen and green oxygen as described in claim 1 comprises: an electrolytic hydrogen production unit that simultaneously produces green hydrogen and green oxygen through water electrolysis; raw coal, green oxygen produced by the electrolytic hydrogen production unit, and oxygen produced by the air separation unit are fed into a gasifier in a coal gasification unit for coal gasification reaction to generate crude syngas containing CO and H2; the crude syngas enters an acid gas removal unit to remove H2S; the purified syngas after H2S removal is mixed with green hydrogen produced by the electrolytic hydrogen production unit and purchased hydrogen in a hydrogen-to-carbon ratio adjustment unit to control the hydrogen-to-carbon ratio of the mixed syngas to meet the requirements of the methanol synthesis reaction; the mixed syngas is compressed and heated before being fed into a methanol synthesis unit to synthesize crude methanol; the crude methanol is purified by a methanol distillation unit to obtain refined methanol product.

3. A green hydrogen permeability optimization method for the green hydrogen green oxygen enhanced coal-to-methanol process of claim 2, characterized in that, include: Step 1: Given the amount of raw coal used, conduct a full-process simulation of the green hydrogen and green oxygen enhanced coal-to-methanol process to determine the range of green hydrogen permeability in the system. Within the determined range of green hydrogen permeability, conduct variable operating condition simulations to obtain data on green hydrogen consumption, purchased hydrogen, and the corresponding total energy consumption, carbon emissions, and unit product cost under each operating condition, forming a sample library. The green hydrogen permeability is the ratio of green hydrogen produced by the electrolytic hydrogen production unit to the total amount of green hydrogen and purchased hydrogen. The relationship between green hydrogen consumption, purchased hydrogen, and the total energy consumption, carbon emissions, and unit product cost of the system is obtained from the sample library. Step 2: With the objective functions of minimizing total system energy consumption, carbon emissions, and unit product cost, and with green hydrogen consumption and purchased hydrogen consumption as decision variables, and with constraints such as the hydrogen-to-carbon ratio required for methanol synthesis, oxygen supply and demand, equipment operating window, and green hydrogen permeability as constraints, a multi-objective optimization model is constructed by combining the relationship between green hydrogen consumption, purchased hydrogen consumption, total system energy consumption, carbon emissions, and unit product cost. Step 3: Solve the multi-objective optimization model to obtain the amount of green hydrogen used and the amount of purchased hydrogen.

4. The method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process according to claim 3, characterized in that, The system total energy consumption E is represented as: wherein, respectively represent raw coal consumption, fuel coal consumption and methanol production capacity; respectively are the conversion standard coal coefficients of raw coal, fuel coal and electric energy; is the total power consumption of the system, is the low calorific value of coal, is the waste heat recovery amount in the system.

5. The method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process according to claim 3, characterized in that, The carbon emissions C is represented as: wherein, respectively represent raw coal consumption, fuel coal consumption and methanol production capacity; is the content of fixed carbon in raw coal and fuel coal, is the carbon combustion conversion coefficient; is the amount of purchased hydrogen in the system, is the carbon emission factor of purchased hydrogen.

6. The method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process according to claim 3, characterized in that, The unit product cost P is represented as: In the formula, , , , , respectively represent the cost of raw coal, fuel coal, green hydrogen, purchased hydrogen, and purchased electricity; is the annual investment cost of the equipment in the system; is the amount of purchased hydrogen in the system; is the green hydrogen production of the hydrogen production unit by electrolysis, as the green hydrogen consumption; , , , , respectively represent the unit price of raw coal, fuel coal, green electricity, water, purchased hydrogen, and purchased electricity, is the unit power consumption of hydrogen production by electrolysis; is the total power consumption of the system; is the amount of electricity generated by the system.

7. The method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process according to claim 3, characterized in that, The hydrogen-to-carbon ratio constraint required for methanol synthesis is expressed as follows: in, , These represent the number of moles of hydrogen, CO, and CO2 produced by the gasification of raw coal, respectively. These represent the lower and upper limits of the hydrogen-to-carbon ratio required for the reaction process, respectively. This refers to the amount of hydrogen purchased from outside the system. The amount of green hydrogen produced by the electrolysis hydrogen production unit is used as the amount of green hydrogen consumed.

8. The method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process according to claim 3, characterized in that, The oxygen supply and demand constraints are expressed as follows: When the demand for green oxygen is met: When green oxygen cannot meet the demand: In the formula, the production capacity of green oxygen is... Calculations based on green hydrogen production: The oxygen requirement of the gasifier in the coal gasification unit; This refers to the oxygen production capacity of the air separation unit.

9. The method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process according to claim 3, characterized in that, The device operation window constraint is represented as follows: In the formula, , and These represent the rated hydrogen production capacity of the electrolyzer in the electrolysis hydrogen production unit, the rated coal processing capacity of the gasifier in the coal gasification unit, and the rated capacity of the methanol synthesis reactor in the methanol synthesis unit, respectively. These represent the lower and upper limits of the equipment's deviation from its rated load, respectively.

10. The method for optimizing the green hydrogen permeability of the green hydrogen and green oxygen enhanced coal-to-methanol process according to claim 3, characterized in that, The green hydrogen permeability constraint is expressed as follows: In the formula, This represents the upper bound of green hydrogen permeability.

Images