A method and apparatus for coal gas to natural gas

Abstract

The application discloses a method and device for preparing natural gas from coal gas. The method for preparing natural gas from coal gas comprises the following steps: preparing H2 and CO mixed gas, the preparation process comprising the following steps: performing a partial hydrogen production reaction on the coal gas, and separating N2 from the system by a pressure swing adsorption separation method before or after the partial hydrogen production reaction step; and performing a methanation reaction on the H2 and CO mixed gas to prepare natural gas. In the application, N2 is separated from the system before the methanation, so that the cryogenic method is avoided, and the method has the advantages of simple process flow, low equipment investment and low compression power consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and device for producing natural gas, in particular to a process method and device for producing natural gas from coke oven gas, blast furnace gas and converter gas, and belongs to the field of chemical technology. BACKGROUND

[0002] In these industrial production processes, a large amount of coke oven gas (coking), blast furnace gas (ironmaking) and converter gas (steelmaking) will be generated, which are collectively referred to as "three gases". In addition, the smelting processes of other ferrous and non-ferrous metals also produce blast furnace gas, converter gas and tail gas similar to blast furnace gas and converter gas.

[0003] Among the "three gases" in a steel plant, blast furnace gas has the lowest effective gas content but the largest emission amount.

[0004] The main components of blast furnace gas are CO, CO2, N2, H2 and CH4, among which the content of CO is about 25%, the contents of CO2 and N2 are 15% and 55% respectively, and the contents of H2 and CH4 are very small. The calorific value of blast furnace gas is low, only 3300-3800 kJ / Nm3. Since CO2 and N2 in blast furnace gas neither participate in combustion to generate heat nor assist combustion, on the contrary, they absorb a large amount of heat generated in the combustion process, resulting in a low theoretical combustion temperature of blast furnace gas, only about 1300℃. Blast furnace gas is unstable at room temperature and cannot be used as the sole fuel for general industrial furnaces, which need to be mixed with coke oven gas or converter gas with high calorific value. However, the mixed use of blast furnace gas with coke oven gas or converter gas has large fluctuations in calorific value, which not only puts higher requirements on the combustion device, but also has different degrees of impact on product quality. Since most enterprises have surplus blast furnace gas and lack high-calorific-value gas, there is a phenomenon of blast furnace gas emission to different degrees, which not only pollutes the environment but also wastes energy. How to effectively utilize blast furnace gas with low calorific value, high impurity content, huge output, difficult purification and serious environmental pollution is a difficult problem that needs to be solved at home and abroad. At present, blast furnace gas is generally used for combustion, but due to its low calorific value and high non-combustible component content, the combustion efficiency and utilization rate are poor, and a large amount of valuable CO that can be used as chemical raw materials for high-value-added chemical products is wasted. At present, converter gas is generally used for combustion or power generation, but due to its low calorific value, combustion efficiency and utilization rate are poor, and the revenue generated by power generation is much lower than the revenue generated by using it as a chemical raw material to produce high-value-added chemical products.

[0005] The basic principle of pressure swing adsorption (PSA) is to exploit the differences in adsorption properties of gas components on solid materials, achieving gas separation or purification through a periodic pressure swing process. For any type of adsorption, for the same adsorbed gas (adsorbate), at equilibrium, the lower the temperature and the higher the pressure, the greater the adsorption capacity. Conversely, the higher the temperature and the lower the pressure, the smaller the adsorption capacity. If the temperature remains essentially constant, adsorption under pressure, followed by decompression (vacuuming), purging with a weakly adsorbing gas, or low-pressure desorption, is called pressure swing adsorption. Pressure swing adsorption generally includes adsorption and desorption (vacuuming, purging, or both), as well as possible pressure equalization, recharging, forward and reverse discharge, and displacement. Thus, pressure swing adsorption achieves adsorption and desorption by varying pressure. Pressure changes involve energy loss, and current pressure swing adsorption methods do not recover this energy, resulting in wasted energy and reduced economic benefits. Consequently, the cost of using pressure swing adsorption at excessively high pressures is prohibitive. With the development of industry, many gas separations require high pressures. The higher the operating pressure, the higher the energy consumption. Furthermore, during the industrial operation of pressure swing adsorption (PSA), the frequent pressure increase and decrease between numerous devices makes it difficult to effectively recover the energy. Summary of the Invention

[0006] The object of the present invention is to provide a process for preparing natural gas that meets standard requirements from blast furnace gas and converter gas through multiple processing steps, which has a simple process flow, requires less equipment investment, and has low power consumption. This process can not only alleviate the current situation of domestic energy shortage and serious waste of gas, especially blast furnace gas, but also further increase the economic and environmental benefits of gas, especially blast furnace gas, and does not require the use of cryogenic nitrogen separation, which is an uneconomical method.

[0007] The technical solution is:

[0008] A method for producing natural gas from coal gas, comprising:

[0009] (1) preparing a mixture of H2 and CO, the preparation process comprising: performing a partial shift reaction on coal gas to produce hydrogen, and separating N2 from the system by a pressure swing adsorption separation method before or after the partial shift reaction step;

[0010] (2) The H2 and CO mixed gas undergoes a methanation reaction to produce natural gas.

[0011] The coal gas mainly includes blast furnace gas or converter gas; the coal gas may also contain coke oven gas, other tail gas or purge gas, one or a mixture of two or more thereof.

[0012] In one embodiment, a method for preparing a mixture of H2 and CO includes: separating CO and N2 from coal gas by a pressure swing adsorption separation method, and subjecting the gas after the N2 is separated to a partial shift hydrogen production reaction to produce a mixture of CO and H2.

[0013] Wherein, when separating CO and N2 by the pressure swing adsorption separation method, natural gas or H2 is used as flushing gas to obtain a gas containing CO and natural gas, or a gas containing CO and H2, for carrying out the partial shift hydrogen production reaction.

[0014] Natural gas is used as flushing gas, and the natural gas comes from the natural gas finally produced; after the partial conversion hydrogen production reaction, the gas is divided into two parts, one part continues to undergo conversion reaction to completely convert CO into H2, and then H2 is extracted as the flushing gas, and the other part is used to obtain the H2 and CO mixed gas. Alternatively, before the partial conversion hydrogen production reaction, part of the coal gas is taken to undergo conversion hydrogen production reaction, and then H2 is extracted as the flushing gas.

[0015] During flushing with flushing gas, high pressure flushing is used in combination with at least one of low pressure flushing and vacuuming to desorb the gas containing CO and natural gas, or containing CO and H2.

[0016] Before separating CO and N2 by the pressure swing adsorption separation method, a first impurity removal pretreatment is also performed. The first impurity removal pretreatment includes: dust removal, phosphorus removal, arsenic removal, dehydration, dehydrogenation and deoxygenation, desulfurization, CO2 removal, or CH4 removal, or a combination of several steps.

[0017] Furthermore, the first impurity removal pretreatment includes: desulfurization and CO2 removal, and CO2 removal and desulfurization are carried out simultaneously or CO2 removal is carried out after the desulfurization step.

[0018] Furthermore, the first impurity removal pretreatment also includes: CH4 removal and / or dehydrogenation and deoxygenation; CH4 removal is performed after the desulfurization step; dehydrogenation and deoxygenation are performed after the CH4 removal step; and dehydrogenation and deoxygenation are performed before CO2 removal.

[0019] After the partial conversion hydrogen production reaction, the gas is divided into two parts. One part continues to undergo the conversion reaction to completely convert CO into H2, and then removes carbon dioxide to extract H2 as the flushing gas. The other part removes carbon dioxide to obtain the H2 and CO mixed gas, or the other part directly undergoes methanation reaction, and the CO2 produced by the conversion reaction is removed after the methanation reaction.

[0020] The absorption method is used for removing CO2 in the first impurity removal pretreatment, and the absorption liquid is used for removing carbon dioxide after the partial conversion hydrogen production reaction (one step or two steps).

[0021] In another embodiment, the method for preparing the H2 and CO mixture includes: performing a partial conversion reaction on coal gas to produce hydrogen to obtain a gas containing CO, N2 and H2, separating CO by a pressure swing adsorption separation method, and then separating N2 and H2, and using the separated hydrogen as a flushing gas for the CO separation.

[0022] The coal gas is subjected to desulfurization and / or dehydrogenation and deoxygenation before undergoing partial conversion hydrogen production reaction; dehydrogenation and deoxygenation are performed after the desulfurization step; and carbon dioxide is removed before pressure swing adsorption separation of CO after the completion of the partial conversion hydrogen production reaction.

[0023] A device for producing natural gas from coal gas, comprising:

[0024] The first shift reactor is used to partially shift CO in the coal gas to produce hydrogen;

[0025] A first pressure swing adsorption device provided on the upstream side or downstream side of the first shift reactor, for separating N2 from the gas system by a pressure swing adsorption separation method;

[0026] The methanation reactor is used to carry out methanation reaction on a mixture of H2 and CO to produce natural gas.

[0027] In a first embodiment, a first pressure swing adsorption unit is disposed upstream of a first shift reactor. The flushing gas inlet of the first pressure swing adsorption unit is connected to a CH4 or H2 input pipe, wherein the CH4 input pipe is connected to the gas outlet of the methanation reactor. A first impurity removal pretreatment unit is connected upstream of the first pressure swing adsorption unit. The first impurity removal pretreatment unit includes one or a combination of a dust removal unit, a phosphorus removal unit, an arsenic removal unit, a dehydration unit, a dehydrogenation and deoxygenation unit, a desulfurization unit, a CO2 removal unit, a CO removal unit, or a CH4 removal unit. The CH4 or H2 input pipe is used to supply CH4 or H2 flushing gas, respectively, to the first pressure swing adsorption unit. The first impurity removal pretreatment unit is used to remove impurities from the coal gas, such as dust removal, phosphorus removal, arsenic removal, dehydration, dehydrogenation and deoxygenation, desulfurization, CO2 removal, CO removal, or CH4 removal, depending on the unit.

[0028] Furthermore, the first impurity removal pretreatment device includes a desulfurization device and a CO2 removal device, and the CO2 removal device is integrated with the desulfurization device or the CO2 removal device is located at the downstream side of the desulfurization device.

[0029] Furthermore, the first impurity removal pretreatment device also includes a CH4 removal device and / or a dehydrogenation and deoxygenation device; the CH4 removal device is located downstream of the desulfurization device; and the dehydrogenation and deoxygenation device is located downstream of the CH4 removal device. That is, when the CH4 removal device is included, the CH4 removal device is located downstream of the desulfurization device. When the desulfurization device and the CO2 removal device are separated, the CH4 removal device is located downstream of the desulfurization device and upstream of the CO2 removal device. When the dehydrogenation and deoxygenation device is included, the dehydrogenation and deoxygenation device is located downstream of the desulfurization device. When the desulfurization device and the CO2 removal device are separated, the dehydrogenation and deoxygenation device is located downstream of the desulfurization device and upstream of the CO2 removal device. If the CH4 removal device is also included, the dehydrogenation and deoxygenation device is located downstream of the CH4 removal device. For different combinations, it is obvious that the first pressure swing adsorption device is connected to the tail of the first impurity removal pretreatment device (that is, after the last unit of the first pretreatment device is completed).

[0030] The coal gas to natural gas device also includes a first diversion device connected to the first shift reactor, used to divide the gas after partial shift to produce hydrogen into two parts; the first diversion device is connected to the first pressure swing adsorption device through a first pipeline and is connected to the methanation reactor through a second pipeline.

[0031] Furthermore, the first pipeline is equipped with a hydrogen purification device, and / or the second pipeline is equipped with a carbon dioxide removal device. One end of the H2 inlet pipe is connected to the hydrogen purification device on the first pipeline, and the other end is connected to the first pressure swing adsorption device. The first pipeline is also equipped with a second shift reactor upstream of the hydrogen purification device, which is used to further perform the shift reaction on the gas passing through the first pipeline after partial shift hydrogen production. The hydrogen purification device on the first pipeline primarily removes carbon dioxide and purifies hydrogen, and can use pressure swing adsorption or absorption methods.

[0032] The first pressure swing adsorption unit is located upstream of the first shift reactor. In another embodiment, the pipeline of the first impurity removal pretreatment unit or the coal gas source is further connected to a second branch, which is connected to a third shift reactor. A third pressure swing adsorption unit for extracting hydrogen is provided downstream of the third shift reactor. The third pressure swing adsorption unit is connected to the first pressure swing adsorption unit via an H2 input pipe. After a portion of the coal gas is completely converted to hydrogen in the third shift reactor, hydrogen is extracted through the third pressure swing adsorption unit, and the hydrogen is provided as flushing gas to the first pressure swing adsorption unit via the H2 input pipe. The extracted hydrogen can be directly purified hydrogen or / and the downstream gas of the third pressure swing adsorption unit to provide flushing gas at different pressures. The first shift reactor is connected to the methanation reactor to output gas for methanation reaction; or the first shift reactor and the methanation reactor can be implemented by the same device, such as a wide hydrogen-to-carbon ratio methanation unit.

[0033] The second embodiment is that the first pressure swing adsorption device is arranged at the downstream side of the first shift reactor, and the first pressure swing adsorption device comprises a pressure swing adsorption CO extracting device and a pressure swing adsorption N2 and H2 separating device connected in sequence, the pressure swing adsorption CO extracting device is connected with the methanation reactor, and the pressure swing adsorption N2 and H2 separating device is connected with the flushing gas inlet of the pressure swing adsorption CO extracting device through an H2 output pipe. After the coal gas is partially shifted in the first shift reactor, the coal gas enters the pressure swing adsorption CO extracting device, the CO is extracted, and then the coal gas mixed with H2 as flushing gas enters the methanation reactor to perform the methanation reaction. The gas (mainly containing N2 and H2) not adsorbed by the pressure swing adsorption CO extracting device is extracted through the pressure swing adsorption N2 and H2 separating device to serve as flushing gas.

[0034] Further, the pipeline connecting the pressure swing adsorption CO extracting device with the first shift reactor is provided with a CO2 removing device for removing carbon dioxide.

[0035] The first, third pressure swing adsorption devices and the like described above are only numbered and named for the sake of clear description, and the shift reactor is the same. There is no structural limitation. In addition, the naming of the pressure swing adsorption devices involved in the present application also includes some functional naming such as a pressure swing adsorption hydrogen extracting device, a pressure swing adsorption CO and N2 separating device, a pressure swing adsorption CO extracting device and the like, which are all for the sake of clear description of the present application, and not for the main limitation of the structure.

[0036] In addition, in the separation process described above, a plurality of pressure swing adsorption impurity removing unit operations are required. The energy consumption caused by the high operating pressure in the pressure swing adsorption process is large, and the pressure lifting operation is frequently changed. When the pressure difference fluctuation and energy fluctuation are very large, the impact load is very large, which exceeds the allowable fluctuation range of the conventional energy recovery equipment, which can cause the service life of the machine equipment to be shortened, can cause safety and other hidden troubles, and even the machine equipment cannot work normally, so that the energy is difficult to recover and utilize. The present application couples the normal adsorption separation process and the energy recovery process and the pressurization process of a certain gas or liquid together, recovers the energy, has high energy utilization rate, has simple process, and reduces the operation cost of the pressure swing adsorption, thereby expanding the survival space of the pressure swing adsorption from the cost point of view. The energy recovery operation is mainly performed by the coaxial driving energy recovery system composed of an expander, a motor, a compressor or a pump. The device also has the advantages of compact structure, high overall efficiency, low overall equipment cost and operation cost, and good economic benefits.

[0037] In the pressure swing adsorption process described above, the following method can also be used:

[0038] A method for energy recovery in pressure swing adsorption, comprising the following steps: recovering the energy of the gas in the pressure reduction process of pressure swing adsorption by an expander; smoothing the fluctuation of gas pressure at the gas inlet and / or gas outlet of the expander by a fluid buffer device; or, suppressing the fluctuation of the rotating speed of the expander by a rotating resistance device on the rotating shaft of the expander.

[0039] The fluid buffer device is selected from one or a combination of several of the following: a regulating valve or a buffer tank; the rotating resistance device is a flywheel.

[0040] The pressure reduction process refers to a process with pressure change, such as equalization, charging, replacement, flushing with pressure, forward or reverse displacement, etc.

[0041] In one embodiment, the expander drives a generator, and the electricity generated by the generator is used for other devices requiring electricity, or the electricity generated by the generator is used to compress the gas or liquid requiring pressure increase in the pressure swing adsorption process by a compressor.

[0042] The input current of the motor connected to the compressor is controlled to supplement the required electricity; the fluctuation of the electricity input to the motor can be smoothed by a battery pack or a capacitor pack.

[0043] In one embodiment, the electricity generated by the generator is integrated into the power grid, and the power grid is used to smooth the fluctuation of the electricity generated by the expander by using the accommodation capacity; the electricity obtained in the power grid is used for other devices requiring electricity, or the electricity is used to compress the gas requiring pressure increase in the pressure swing adsorption process by a compressor.

[0044] In one embodiment, the rotating shaft of the expander is coaxially connected to the rotating shaft of the motor, and the expander and the motor jointly drive the compressor to work.

[0045] Based on the above method, the following device can also be used:

[0046] A pressure swing adsorption device, comprising:

[0047] 1) at least one high-pressure adsorption tower;

[0048] 2) at least one energy recovery device, the energy recovery device comprising an expander for recovering the energy of the high-pressure gas discharged from the high-pressure adsorption tower;

[0049] The gas inlet and / or gas outlet of the expander is connected to a fluid buffer device;

[0050] Or, a rotating resistance device is provided on the rotating shaft of the expander.

[0051] The fluid buffer device is selected from one or a combination of a regulating valve or a buffer tank; the rotation resistance device is a flywheel.

[0052] In one embodiment, the high-pressure adsorption tower is connected to the low-pressure adsorption tower via an energy recovery device.

[0053] In one embodiment, the pressure swing adsorption device further includes a generator, and the expander is connected to the generator.

[0054] The generator is connected to other equipment that requires electricity, or the generator drives the compressor to compress the gas or liquid that needs to be pressurized during the pressure swing adsorption process.

[0055] The generator is connected to the power grid, and the role of the power grid is to use its capacity to smooth out the fluctuations in the electrical energy generated by the generator.

[0056] In one embodiment, the pressure swing adsorption device further includes a compressor and a motor, and the rotating shaft of the expander is coaxially connected to the rotating shaft of the motor, and the expander and the motor jointly drive the compressor to work.

[0057] A battery pack or capacitor pack is also installed on the electric motor.

[0058] A buffer tank is further provided at the gas inlet and / or gas outlet of the compressor.

[0059] Compared with the general pressure swing adsorption method, the method and device of the present invention adds an energy recovery process to the pressure swing adsorption method, couples the normal adsorption separation process with the energy recovery process and a certain gas or liquid pressurization process, recovers energy, improves the energy utilization rate of the system, reduces the operating cost of pressure swing adsorption, and expands the survival space of pressure swing adsorption from a cost perspective. The process is simple, the safety factor is high, the unit has a high degree of automation, is easy to operate, and the equipment occupies a small area, ensuring product purity and recovery rate. The operation is flexible and the number and size of tower equipment are reduced.

[0060] Beneficial effects:

[0061] The process concept of the present invention is that, due to national standards for the calorific value of natural gas, the content of non-combustible components such as nitrogen and CO2 needs to be low. However, for blast furnace gas and converter gas, which contain high nitrogen content, the current conventional practice is to synthesize natural gas first and then cryogenically separate methane and nitrogen. However, cryogenic separation is an uneconomical method, with high reinvestment and operating costs. The concept of this method is to separate nitrogen before synthesizing natural gas, thus avoiding the use of cryogenic separation and saving costs. Furthermore, the natural gas synthesis reaction contains nitrogen, and its methanation catalyst can also cause ammonia synthesis to occur, which is detrimental to the methanation reaction and results in a waste of raw materials. Furthermore, the ammonia and water present after the reaction are corrosive to equipment, and subsequent ammonia removal is required, significantly increasing both investment and operating costs. Furthermore, removing nitrogen first can also prevent ammonia synthesis from occurring during the shift reaction using an iron-based catalyst, which is detrimental to the shift reaction, results in a waste of raw materials, is corrosive to equipment, and requires additional equipment to remove it, significantly increasing both investment and operating costs.

[0062] Compared with the prior art, the present invention has substantial characteristics and significant progress in that: the present invention proposes a method for preparing natural gas from blast furnace gas and converter gas through multiple processing steps, which not only provides a new technical route for the comprehensive utilization of coal gas, especially blast furnace gas, but also further improves the economic value of coal gas, especially blast furnace gas; the process for preparing natural gas from blast furnace gas and converter gas disclosed in the present invention (meeting GB17820-2012 and its updated versions) can also co-produce industrial nitrogen, the nitrogen concentration can reach industrial grade requirements and can be recycled and reused; the integrated process for preparing natural gas from blast furnace gas and converter gas disclosed in the present invention is obtained through a large number of experiments, simulation calculations, steel mill field surveys and many years of engineering design experience. Material matching and energy utilization are both considered from the overall process, which optimizes the process flow and reduces equipment investment and overall energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a flow chart of the process for preparing natural gas from coal gas;

[0064] Figure 2 is a process flow chart of the method for preparing natural gas from coal gas in Example 1;

[0065] Figure 3 is a process flow chart of the method for preparing natural gas from coal gas in Example 2;

[0066] Figure 4 is a process flow chart of the method for preparing natural gas from coal gas in Example 3;

[0067] Figure 5is a process flow chart of the method for preparing natural gas from coal gas in Example 4;

[0068] Figure 6 This is a structural diagram of a natural gas preparation device using coal gas;

[0069] Figure 7 This is a structural diagram of an energy recovery device used in a pressure swing adsorption process;

[0070] Figure 8 This is a structural diagram of another energy recovery device used in the pressure swing adsorption process;

[0071] Figure 9 It is a two-tower pressure swing adsorption H2 purification device integrated with an energy recovery device;

[0072] Figure 10 It is a three-tower pressure swing adsorption H2 purification device integrated with an energy recovery device;

[0073] Among them, 1 is the adsorption tower, 2 is the first stage of the turbine expander, 3 is the compressor, 4 is the electric motor, 5 is the air extraction buffer tank, 6 is the vacuum pump, 7 is the reverse bleed buffer tank, 8 is the reverse bleed compressor, 9 is the flywheel, 10 is the capacitor group, 11 is the compressed gas inlet buffer tank, 12 is the compressed gas outlet buffer tank, 13 is the turbine inlet high-pressure buffer tank, 14 is the turbine outlet high-pressure buffer tank, 15 is the turbine inlet low-pressure buffer tank, 16 is the turbine outlet low-pressure buffer tank, 17 is the second stage of the turbine expander, 18 is the incoming gas buffer tank, 19 is the tower top product gas buffer tank, 20 is the first-stage turbine outlet heat exchanger, and 21 is the second-stage turbine outlet heat exchanger. DETAILED DESCRIPTION

[0074] The natural gas production method provided by the present invention primarily utilizes blast furnace gas or converter gas as the raw material or primary raw material, with the primary raw material comprising the majority, for example, 85%, 90%, or 95% by volume or greater. The gas may also contain coke oven gas, other tail gases, or purge gas, one or a combination of two or more thereof. The natural gas described in the present invention is characterized by or primarily composed of methane.

[0075] The gas composition of the above-mentioned coal gas mainly includes: N2, H2, CO, CO2, O2, CH4, H2S, COS, etc. In some typical blast furnace gases, its composition includes, by volume percentage: N2 40-65%, H2 0.5-5%, O2 0.2-5%, CO2 10-30%, CO 10-30%, CH4 0.1-2.0%, H2S 5-400ppm, COS 0.1-100ppm.

[0076] The above raw materials such as coal gas can also be subjected to corresponding pretreatment processes such as impurity removal by conventional methods before entering the process and equipment of this patent; there are no special restrictions on these pretreatment processes.

[0077] A method for producing natural gas from coal gas, comprising:

[0078] (1) preparing a mixture of H2 and CO, the preparation process comprising: performing a partial shift reaction on coal gas to produce hydrogen, and separating N2 from the system by a pressure swing adsorption separation method before or after the partial shift reaction step;

[0079] (2) The H2 and CO mixed gas undergoes a methanation reaction to produce natural gas.

[0080] Partial conversion of coal gas to produce hydrogen means that a portion of the CO in the incoming coal gas undergoes a conversion reaction to produce hydrogen. After this partial conversion, a mixture of CO and H2 can be obtained through some separation methods, rather than purifying CO and H2 separately. The mixed gas can then be subjected to a methanation reaction to produce natural gas. Unlike conventional technologies, the present invention separates N2 before the methanation reaction, avoiding the need for cryogenic methods. The basic principle of CO conversion is:

[0081]

[0082] This is a reversible, exothermic, isovolumetric chemical reaction. From the perspective of chemical reaction equilibrium, increasing the pressure has no effect on the chemical equilibrium. However, lowering the reaction temperature and increasing the amount of water vapor in the reactants favor the reaction toward the production of CO2 and H2. The reactor is a pseudo-isothermal shift reactor with a reaction pressure of 0.1 to 10 MPa (0.2 to 3 MPa in some embodiments) and a reaction temperature of 160 to 550°C (170 to 400°C in some embodiments). The conversion reaction can use catalysts commonly used in the art, such as copper-based and / or iron-based and / or cobalt-molybdenum catalysts, and the catalyst contains copper and / or iron and / or zinc and / or aluminum and / or manganese and / or cobalt and / or molybdenum and / or cerium and / or magnesium and / or chromium and / or potassium and / or vanadium and / or nickel and / or titanium and / or palladium and / or platinum and / or ruthenium and / or rhodium and / or sodium and / or rubidium and / or cesium and / or niobium and / or zirconium and / or rare earth elements and / or alkali metal oxides and / or their sulfides and / or their soluble salts and / or composite metal oxides formed therebetween. The carrier is activated carbon, aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, silica gel, molecular sieve, hydrotalcite, spinel, honeycomb ceramics, monazite, honeycomb metal, metal plate, corrugated filler, corrugated plate, fiber (cloth) material and structure, braid, metal foam, ceramic foam, graphite-based foam, copper and / or iron and / or zinc and / or aluminum and / or manganese and / or cobalt and / or molybdenum and / or cerium and / or magnesium and / or chromium and / or potassium and / or vanadium and / or nickel and / or titanium and / or palladium and / or platinum and / or ruthenium and / or rhodium and / or sodium and / or rubidium and / or cesium and / or niobium and / or zirconium and / or rare earth elements and / or alkali metal oxides and / or their sulfides and / or their soluble salts and / or composite metal oxides formed therebetween, etc. In one embodiment, when the required synthetic natural gas pressure is high, excessively high pressure may require a higher temperature for the conversion reaction so that no liquid appears in the gas and a certain amount of residual gas is retained. When excessively high reaction temperature may adversely affect the conversion reaction catalyst, the conversion reaction may be carried out at an appropriate pressure and temperature, and the subsequent decarbonization and hydrogenation process may be followed by further pressurization to achieve the required synthetic natural gas pressure.

[0083] As a first embodiment, the method for preparing a mixture of H2 and CO includes: separating CO and N2 from coal gas by a pressure swing adsorption separation method, and subjecting the gas after N2 separation to a partial conversion hydrogen production reaction to produce a mixture of CO and H2.

[0084] Before the separation of CO and N2 by pressure swing adsorption, the gas is subjected to a first impurity removal pretreatment, which comprises one or more of the following steps: dust removal, phosphorus removal, arsenic removal, water removal, dehydrogenation and deoxidation, desulfurization, CO2 removal, or CH4 removal. The content of harmful impurities in the purified gas is controlled as follows: sulfides ≤ 1.15 ppm, NH3 ≤ 200 ppm, O2 ≤ 0.4%, H2O ≤ 100 ppm, Cl + ≤ 0.03 ppm, arsenides ≤ 0.1 ppm, tar + dust ≤ 1 mg / Nm 3 , naphthalene ≤ 1 mg / Nm 3 . Further, the content of harmful impurities is controlled as follows: sulfides ≤ 0.1 ppm, Cl + ≤ 0.01 ppm, O2 ≤ 0.2%.

[0085] Further, the first impurity removal pretreatment comprises desulfurization and CO2 removal, which are performed simultaneously or the CO2 removal is performed after the desulfurization step. This is because the blast furnace gas and / or the converter gas contains a small amount of sulfur, which will adversely affect the various catalysts (dehydrogenation and deoxidation, shift, synthesis of methane, and even demethanation catalysts) and adsorbents (CO and nitrogen separation) in the subsequent steps, and even cause them to be inactivated and shorten their service life. Moreover, the content of sulfur is lower than the minimum sulfur content required by some sulfur-tolerant catalysts, so it is necessary to remove it first. In addition, because the blast furnace gas and / or the converter gas has a high initial temperature, this is conducive to the reaction rate and desulfurization effect of the metal oxide desulfurizer.

[0086] The removal of sulfur or various impurities containing sulfur can be carried out by adsorption method, membrane separation method, solid desulfurizer containing oxides or hydroxides of iron, manganese, zinc, copper, nickel, calcium or tin or composite metal oxides formed therebetween, low-temperature methanol washing method, propylene carbonate method, N-methylpyrrolidone method, polyethylene glycol dimethyl ether method, polyethylene glycol methyl propyl ether method, tributyl phosphate method, hot potash method, activated hot potash method, MEA method, DEA method, MDEA method, DIPA method, propylene carbonate method + DIPA, propylene carbonate method + glycolamine, cyclopentane method, cyclopentane + DIPA method, cyclopentane + MDEA method, methanol + secondary amine method, alkyl alcoholamine solution method and MEA method with added activator, DEA method, MDEA method, ammonia water washing method, caustic soda method, ADA method (stretford method), tannin extract method, LO-CAT method, Sulferox method, Sulfint method, Konox method, Bio-SR method, naphthoquinone method (Takahax method), metal phthalocyanine method (PDS method), GV (modified arsenic alkali method), arsenic alkali method, MSQ method, Sulfolin method, EDTA method, wet oxidation method, alkali absorption method, limestone-gypsum method, ammonia method, magnesium method, ammonium phosphate fertilizer method, organic sodium acid-gypsum method, lime-magnesium method, calcium method, dry circulating fluidized bed method, zinc oxide method, urea method, complex absorption method, charged dry absorbent injection method, plasma method, electron beam method, double alkali method, alkali sulfide method, and combinations thereof. The removed sulfur is sent to a sulfur recovery system, and the sulfur in the raw gas is removed to 0.01-0.1 ppm after desulfurization. When using the absorption method, the absorbent has the ability to absorb both sulfur and carbon dioxide, so sulfur and carbon dioxide can be removed simultaneously. When using the absorption method, to achieve better desulfurization results, it is best to add a subsequent fine desulfurization step (for example, desulfurization using a solid desulfurizer). Desulfurization is carried out at 0.2-10 MPa and 20-700°C, and in some embodiments (0.2-3 MPa and 20-400°C, such as 400-280°C for some metal oxide solid desulfurizers, and 20-70°C for the absorption liquid).

[0087] When the incoming gas contains too high an organic sulfur content, the organic sulfur can be converted into H2S through catalytic hydrogenation or catalytic hydrolysis, and then desulfurization is performed to ensure that the sulfur content of the treated gas meets the requirements. When the incoming gas contains sulfur mainly in the form of SO2 and the content is too high, the SO2 can be converted into H2S through catalytic hydrogenation, and then desulfurization is performed to ensure that the sulfur content of the treated gas meets the requirements. The catalyst for the catalytic hydrogenation reaction herein can be a catalyst commonly used in the art, for example, a catalyst containing iron and / or copper and / or cobalt and / or manganese and / or molybdenum and / or zinc and / or aluminum and / or nickel and / or titanium and / or zirconium and / or tungsten and / or cerium and / or their oxides and / or their sulfides and / or their soluble salts and / or composite metal oxides formed therebetween as active components, and one or more of titanium, zirconium, manganese, iron, nickel, cobalt, copper, molybdenum, tungsten, zinc, cobalt, cerium and / or their oxides and silicon, rare earth, alkali metal, alkaline earth metal, transition metal oxides and / or their sulfides as auxiliary agents. The carrier can be activated carbon, aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, silica gel, molecular sieve, honeycomb ceramics, monazite, honeycomb metal, metal plate, corrugated filler, corrugated plate, fiber (cloth) material and structure, braid, metal foam, ceramic foam, graphite-based foam, etc. The catalyst for the catalytic hydrolysis reaction herein comprises magnesium and / or lanthanum and / or barium and / or aluminum and / or titanium and / or zirconium and / or cerium and / or potassium and / or calcium and / or cobalt and / or molybdenum and / or iron and / or copper and / or manganese and / or zinc and / or nickel and / or tungsten metals and / or their oxides and / or their sulfides and / or composite metal oxides formed therefrom as active components, and one or more of titanium, zirconium, nickel, cobalt, molybdenum, cobalt, cerium metals and / or their oxides and silicon, rare earth, alkali metal, alkaline earth metal, transition metal oxides and / or their sulfides as auxiliary agents. The carrier is activated carbon, aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, silica gel, molecular sieve, honeycomb ceramics, monazite, honeycomb metal, metal plate, corrugated packing, corrugated plate, fiber (cloth) material and structure, braid, metal foam, ceramic foam, graphite-based foam, etc.

[0088] If it is not necessary to meet the industrial nitrogen standards, CH4 can also be omitted, and the resulting nitrogen contains a slightly excessive amount of CH4. Furthermore, the first impurity removal pretreatment further includes: removing CH4, which can be achieved by catalytic oxidation, so that the purity of the resulting nitrogen meets the industrial nitrogen standards (GB3864-2008 and its updated versions). Due to the high temperature required for the reaction, it is removed first, that is, after the desulfurization step, CH4 is removed. If desulfurization and decarbonation are separated, CH4 removal is set after desulfurization and before decarbonation, which is beneficial to saving energy and heat exchange equipment, reducing equipment investment and operating costs. In one embodiment, CH4 is removed mainly by removing methane through a catalytic combustion reaction of methane at a certain temperature (200-1000°C, for example, 250-350°C) and pressure (0.1-10MPa, for example, 0.3-1.6MPa) to prevent the catalyst from losing activity. The catalyst used can be a conventional catalyst in the art, for example, a metal containing iron and / or copper and / or cobalt and / or manganese and / or molybdenum and / or zinc and / or aluminum and / or nickel and / or chromium and / or bismuth and / or magnesium and / or titanium and / or barium and / or ruthenium and / or zirconium and / or cerium and / or lanthanides and / or platinum and / or palladium and / or gold and / or rhodium and / or calcium and / or their oxides and / or their soluble salts and / or composite metal oxides formed therefrom as active components. One or more of the metals of titanium, zirconium, manganese, iron, nickel, cobalt, copper, molybdenum, tungsten, zinc, cobalt, cerium, aluminum, chromium, bismuth, magnesium, titanium, barium, ruthenium, zirconium, cerium, lanthanum, platinum, palladium, gold, rhodium, and calcium and / or their oxides and / or their soluble salts and / or composite metal oxides formed therefrom, and oxides of silicon, rare earth, alkali metal, alkaline earth metal, and transition metal can be used as auxiliary agents. The carrier is activated carbon, aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, silica gel, molecular sieve, honeycomb ceramics, monazite, honeycomb metal, metal plate, corrugated packing, corrugated plate, fiber (cloth) material and structure, braid, metal foam, ceramic foam, graphite-based foam, etc. The content of the raw gas after CH4 removal is ≤0.5%, and further CH4 ≤0.1%.

[0089] If the blast furnace gas and / or converter gas contain a high oxygen content (approximately >0.1%, further >0.04%, and typical gases are all greater than this value), it will have an adverse effect on the subsequent shift catalyst, CO and nitrogen separation adsorbent, and even the catalyst in the methanation step, and may even cause them to deactivate and shorten their service life. Therefore, it is necessary to deoxygenate the gas in advance so that the O2 concentration is ≤0.4%, and further ≤0.2%, before entering the pressure swing adsorption separation device for separating CO and nitrogen. Since catalytic deoxygenation is performed in the pure CO, more CO and O2 will react, resulting in CO waste, and the need for additional impurity removal steps and equipment to remove impurities generated by the catalytic reaction. In addition, due to the excessively high oxygen content, the shift catalyst deteriorates, the conversion effect after the shift reactor becomes increasingly poor, the purity of the hydrogen after the shift becomes increasingly low, and the CO content in the purified exhaust gas becomes increasingly high, resulting in unnecessary waste of raw materials and being detrimental to the environment. In addition, due to the excessively high oxygen content, the adsorbent deteriorates, and the separation requirements cannot be met over time. Therefore, dehydrogenation and deoxygenation are performed first in the first pre-desulfurization process (since deoxygenation also occurs during dehydrogenation, the primary purpose is not to remove hydrogen, but to remove H2, resulting in higher nitrogen purity in subsequent steps). This protects the adsorbent and catalyst for subsequent steps, reduces CO waste, and reduces the impurity removal steps for impurities generated after catalytic dehydrogenation and deoxygenation. This shortens the process and reduces investment and operating costs. Furthermore, since the higher temperature of the gas in the first step can meet the reaction temperature of catalytic dehydrogenation and deoxygenation, the investment and operating costs required for heat exchange equipment caused by the need to increase the temperature later are avoided. Therefore, dehydrogenation and deoxygenation are placed after desulfurization. If desulfurization and deCO2 removal are performed sequentially, dehydrogenation and deoxygenation are placed after desulfurization and before deCO2 removal. If a CH4 removal step is present, dehydrogenation and deoxygenation are placed after CH4 removal and before deCO2 removal. Dehydrogenation and deoxygenation are beneficial for increasing nitrogen purity and obtaining industrial nitrogen that meets standards. At the same time, this order of precedence also conforms to the principle of gradual reaction temperature, reducing investment and operating costs for heat exchange equipment.

[0090] Dehydrogenation and deoxygenation can be performed using a selective dehydrogenation catalyst to remove H2 and O2 from blast furnace gas at a pressure of 0.1-10 MPa (0.2-3 MPa in some embodiments) and a temperature of 50-1000°C (80-250°C in some embodiments). When the dehydrogenation and deoxygenation steps are added before the carbon dioxide removal step, the CO concentration in the gas is lower, which improves the selectivity of the catalytic oxidative dehydrogenation and reduces the reaction of CO with oxygen, thereby reducing CO waste. This makes the reaction conditions less stringent and facilitates catalyst selection. The temperature for removing H2 and O2 using catalytic oxidation is ≥100°C. The catalyst may be a catalyst commonly used in the art, for example, a metal containing palladium and / or platinum and / or cobalt and / or manganese and / or copper and / or their oxides and / or sulfides as an active component, and one or more of sodium, potassium, magnesium, titanium, zirconium, vanadium, manganese, iron, nickel, cobalt, copper, molybdenum, tungsten, lanthanum, zinc, silver, palladium, cobalt, or cerium and / or their oxides and / or sulfides and / or complexes formed therefrom as an auxiliary agent. The carrier may be activated carbon, aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, silica gel, molecular sieve, honeycomb ceramics, monazite, honeycomb metal, metal plate, corrugated packing, corrugated plate, fiber (cloth) material and structure, braid, metal foam, ceramic foam, graphite-based foam, etc. As an option, since the O2 content in the incoming gas is very low, it is not necessary to remove O2, so that the O2 concentration is ≤0.4% before entering the pressure swing adsorption separation device for CO and nitrogen. This will not cause rapid deactivation of the adsorbent and catalyst, but it will shorten the service life of the adsorbent and catalyst and increase operating costs.

[0091] CO2 will affect the separation effect of the pressure swing adsorption separation step of CO and nitrogen. Since CO2 has a certain adsorption capacity on the adsorbent used in the CO and nitrogen separation step, the separation coefficients of CO2 and CO, and CO2 and nitrogen are not high. The presence of CO2 will lead to incomplete separation of CO and nitrogen, and it is impossible to obtain high-purity CO and nitrogen. The separated CO and nitrogen gases will contain a relatively large amount of CO2. Therefore, CO2 must be removed first. The step of removing CO2 needs to be before the step of separating CO and nitrogen. The step of removing CO2 is to enable the CO and nitrogen separation step to completely separate CO and nitrogen and obtain high-purity CO and nitrogen respectively. In addition, if CO2 is removed again in a subsequent step, the intermediate stage will need to be pressurized again, and there will be process losses and costs, and an increase in equipment. For the step of removing CO2 from coal gas, pressure swing adsorption, absorption method and a combination thereof can be used. The absorption methods include: water washing method, low-temperature methanol washing method, propylene carbonate method, N-methylpyrrolidone method, polyethylene glycol dimethyl ether method, polyethylene glycol methyl propyl ether method, Catacarb method (catalytic hot alkali method), hot potassium alkali method, activated hot potassium alkali method, improved hot alkali method, hot carbonate method, amino acid salt method, ammonia washing method, combined urea (alkali) method, GV (improved arsenic alkali method), MEA method, DEA method, MDEA method, DIPA method, TEA method, sulfolane method, sulfolane + DIPA method, sulfolane + MDEA method, methanol + secondary amine method, alkyl alcohol amine solution method and MEA method with added active agent, DEA method, MDEA and TEA methods, etc., remove CO2 from the raw gas after decarbonization to 0.01-0.8 Vol%. CO2 removal is carried out under conditions of 0.2-10 MPa and 20-120°C. In some embodiments (0.2-3 MPa and 20-40°C), the removed carbon dioxide can be sold as a carbon dioxide product or used as feed gas for other processes or vented after meeting the venting standard. When the absorption method is used as the decarbonization separation unit, a trace amount of absorption liquid is usually carried out in the gas. It is necessary to add a temperature swing adsorption separation unit after the unit to remove water and some heavy components contained in the gas. The temperature swing adsorption method removes water and heavy components; the adsorbent is a molecular sieve, activated carbon, alumina, silica gel, or a composite bed thereof. The removed tail gas containing a large amount of carbon dioxide can enter the residual pressure recovery device to recover energy when the pressure is greater than 0.15 MPa. After the first impurity removal pretreatment, the coal gas is separated into CO and N2 by pressure swing adsorption. The pressure swing adsorption separation method is used to separate CO and nitrogen, and a catalyst commonly used in the art can be used, such as a copper-based or silver-based adsorbent or a metal organic framework adsorbent (MOFs, ZIFs), or a metal organic polyhedron (MOPs).The carrier can be activated carbon, alumina, silica gel, molecular sieve, honeycomb ceramic, monazite, honeycomb metal, metal plate, corrugated packing, corrugated plate, fiber (cloth) material and structure, woven fabric, metal foam, ceramic foam, graphite-based foam, etc. The CO and nitrogen are separated by pressure swing adsorption, the adsorption pressure of pressure swing adsorption is about 0.02-10 MPa (in some embodiments, 0.2-1.8 MPa), the operating temperature is 0-150°C (in some embodiments, 20-80°C), the volume fraction of the industrial-grade nitrogen extracted by pressure swing adsorption is 99.2%, which can be directly used as a product or sold. When separating CO and nitrogen by pressure swing adsorption, a temperature swing adsorption method needs to be added in front of the unit of pressure swing adsorption to separate and remove water and heavy components. When more than one set of pressure swing adsorption devices are connected in series, the temperature swing adsorption separation unit is added in front of the separation unit of the first set of pressure swing adsorption method. The CO and nitrogen are separated by pressure swing adsorption, and the nitrogen that does not meet the industrial standard can enter the pressure recovery system when the nitrogen pressure is greater than 0.15 MPa to recover the pressure energy carried by the nitrogen. When using pressure swing adsorption, an energy recovery device can be added in the pressure swing adsorption device to recover the pressure energy wasted in the pressure swing adsorption process while completing the pressure swing adsorption separation process.

[0092] In the desorption process of CO in the step of separating CO and N2 by pressure swing adsorption, the present application uses natural gas or H2 as flushing gas to obtain a gas containing CO and natural gas, or a gas containing CO and H2 for the partial reforming reaction to produce hydrogen. The reaction depth of the partial reforming reaction is generally controlled to have a CO / H2 molar ratio of about 1 / 3, such as 1 / 3-4.

[0093] The H2 is obtained by the shift reaction, and the CH4 obtained by the methanation reaction is used as flushing gas. The CO and H2 or CH4 containing mixed gas can be desorbed by multiple (≥1) high-pressure flushing and low-pressure flushing, or high-pressure flushing and low-pressure flushing combined with vacuum pumping, or high-pressure flushing and vacuum pumping. The high-pressure flushing generally refers to a pressure greater than atmospheric pressure, generally 0.2-10 MPa, and in some embodiments, 0.3-3 MPa. The purified H2 or CH4 is generally in this pressure range. The low-pressure flushing generally refers to the use of part of the purified H2 or CH4 to reduce the pressure, or the use of the tail gas (mainly H2 or CH4) of the H2 or CH4 purification device.

[0094] When H2 is used as a flushing gas, one embodiment involves separating the gas into two parts after a partial shift reaction to produce hydrogen. One part (5-80% by volume) undergoes a further shift reaction to completely convert CO to H2, after which carbon dioxide is removed and H2 is extracted as the flushing gas. A portion of the extracted H2 can also be used as a regulating gas to adjust the carbon-hydrogen ratio of the methanation reaction. The other part (20-95%) removes carbon dioxide to obtain the H2 and CO mixed gas, or directly undergoes a methanation reaction. The CO2 generated by the shift reaction then needs to be removed. This method is preferred because CO2 can reduce the concentrations of the reactants CO and H2, which helps reduce the intensity of the reaction, lower the reaction temperature, and extend the life of the catalyst. The ratio of the two parts is determined by the requirements of subsequent processes and the amount and ratio of CO and / or H2 in the incoming gas as a supplementary external gas source. The ratio of CO and H2 is thus adjusted to meet the requirements of subsequent processes.

[0095] When H2 is used as the flushing gas, another embodiment involves separating CO and N2 from coal gas through a pressure swing adsorption separation method. The gas after N2 separation is directly divided into two parts. The CO containing a total volume fraction of 5-80% undergoes a shift reaction to produce hydrogen as the flushing gas, while the remaining CO-containing gas containing a total volume fraction of 20-95% undergoes a partial shift reaction to produce a mixture of CO and H2, which is then subjected to a methanation reaction to produce natural gas. The ratio of the two parts is determined by the subsequent process requirements and the amount and ratio of CO and / or H2 in the incoming gas as a supplementary external gas source. The ratio of CO and H2 is thus adjusted to meet the requirements of the subsequent process (generally, the CO / H2 ratio for methanation is 1 / 3, but wide hydrogen-to-carbon ratio methanation is not limited by this because it contains a shift function).

[0096] When H2 is used as flushing gas, another embodiment is to take part of the coal gas for conversion hydrogen production reaction before the partial conversion hydrogen production reaction, and then extract H2 as the flushing gas. The taken part of the gas is subjected to a second impurity removal pretreatment process before the conversion hydrogen production reaction. The second impurity removal pretreatment process includes the first impurity removal pretreatment step when it is in a mixed state with other gases and a separate pretreatment step. The second impurity removal pretreatment process includes one or a combination of several steps of dust removal, phosphorus removal, arsenic removal, dehydration, dehydrogenation and deoxygenation, desulfurization, CO2 removal, CH4 removal, and heavy component removal. After the part of the gas is purified by the second pretreatment process, the content of harmful impurities in H2 is controlled to be sulfide ≤1.15ppm, NH3 ≤200ppm, O2 ≤0.4%, H2O ≤100ppm, Cl + ≤0.03ppm, arsenic ≤0.1ppm, tar + dust ≤1mg / Nm 3 , naphthalene≤1mg / Nm 3Further harmful impurities content control in sulfide ≤0.1 ppm, Cl + ≤0.01 ppm, O2≤0.2%.

[0097] Taking part of the coal gas can be carried out at the source of the coal gas, in the first impurity removal pretreatment process or after the process. For example: directly separating the incoming gas, separating after desulfurization, separating after CH4 removal, separating after dehydrogenation and deoxidation, separating after CO2 removal, separating after CO and nitrogen separation. However, since some processes and impurity removal processes require both parts of the gas, such as desulfurization, deoxidation (when the oxygen content is relatively high), CH4 removal (when industrial nitrogen is required or environmental protection is required), some processes can be shared (not shared means separate each set of similar devices), and can be implemented in one set of devices, which leads to different positions of the separation point in the process and slightly different subsequent treatment processes. The position of the separation point is affected by the different compositions of the incoming gas and the different product requirements. For example, both parts of the gas need to be desulfurized, and can be separated after desulfurization. If the oxygen content in the incoming gas is relatively low, the branch gas for producing pure H2 gas can directly perform a shift reaction. If industrial nitrogen is required or environmental protection is required, both parts of the gas need to be CH4 removed, and can be separated after CH4 removal. If the oxygen content in the incoming gas is relatively low, the branch gas for producing pure H2 gas can directly perform a shift reaction. If the oxygen content in the incoming gas is relatively high, the branch gas for producing high-purity H2 gas can perform a separate deoxidation step before performing a shift reaction. In this deoxidation step, only the oxygen content is considered, without considering the hydrogen content, without supplementing trace amounts of oxygen, without adjusting the hydrogen-to-oxygen ratio, which can reduce the amount of hydrogen reacting with oxygen and increase the yield of hydrogen. If the oxygen content in the incoming gas is relatively high, both parts of the gas need to be deoxidized, and can be separated after dehydrogenation and deoxidation. Although one-step dehydrogenation and deoxidation slightly increases the amount of hydrogen loss, it reduces the number of devices, reduces the floor area, and reduces investment and operating costs. Separating after CO2 removal can separate the high-content but unnecessary CO2 from the useful gas, increase the content of the useful gas, facilitate subsequent pressurization operations, and reduce pressurization energy consumption. However, the shift reaction and subsequent steps will also generate CO2, which still needs to be removed again. Separating after CO and nitrogen separation can maximize the content of the useful gas, facilitate pressurization operations, and reduce pressurization energy consumption. Since the required high-purity H2 gas has a high pressure, increasing the operating pressure of the shift reaction and subsequent steps will only slightly increase the cost, but can reduce the device volume, improve device utilization, reduce the floor area, and reduce investment costs.

[0098] When natural gas is used as the flushing gas, the natural gas is derived from the final natural gas produced. During the pressure swing adsorption of CO and N2, after separating the N2, a gas containing CO and natural gas is obtained, which is directly subjected to a partial conversion hydrogen production reaction. The appropriate carbon-hydrogen ratio is adjusted by controlling the conversion depth. This method does not require deep conversion hydrogen production and then using H2 as a flushing gas for high-pressure flushing and desorption of CO. Instead, a portion of the produced CH4 is separated and used as a flushing gas for high-pressure flushing and desorption of CO. This method may cause some CH4 loss, but it will shorten the process, reduce equipment, and CH4 as a circulating gas can reduce the concentration of the reactants CO and H2, which helps to reduce the intensity of the reaction, lower the reaction temperature, and extend the life of the catalyst.

[0099] As a second embodiment, the method for preparing the H2 and CO mixed gas comprises: subjecting coal gas to a partial shift reaction to produce hydrogen to obtain a gas containing CO, N2, and H2; separating the CO by pressure swing adsorption separation; and then separating the N2 and H2. The separated hydrogen is used as a flushing gas for the CO separation. Prior to the partial shift reaction to produce hydrogen, the coal gas is subjected to desulfurization and / or dehydrogenation and deoxygenation; the dehydrogenation and deoxygenation are performed after the desulfurization step. In this method, the incoming gas undergoes the previous steps of impurity removal, desulfurization, and deoxygenation, and then undergoes a partial conversion reaction and adjusts the CO / H2 ratio to about 1 / 3. The gas after the reaction is then cooled, first undergoes rough dehydration in a separatory tank, and then undergoes fine dehydration and heavy component steps by temperature swing adsorption. After that, the gas needs to remove the CO2 contained in the gas, and then this part of the gas is sent to a pressure swing adsorption CO, H2 and nitrogen separation device to separate CO and H2 and nitrogen. The gas coming out of the top of the adsorption tower for pressure swing adsorption separation of CO, H2 and nitrogen mainly contains H2 and nitrogen, and then pressure swing adsorption separation of H2 and nitrogen is carried out again. The nitrogen removed from the bottom of the adsorption tower is discharged after being treated to meet the emission standards.

[0100] The gas after the methanation reaction is treated to remove impurities (dehydration, or dehydration and carbon dioxide removal in sequence) to extract natural gas.

[0101] Figure 1 A better process flow is shown, in which coal gas, such as blast furnace gas, is sequentially desulfurized, demethanized, dehydrogenated, deoxygenated, and deCO2-free, and then CO and N2 are separated by pressure swing adsorption. H2 is used as a flushing gas during the pressure swing adsorption to separate the N2 and obtain a mixed gas containing CO and H2. A partial conversion reaction to produce hydrogen is then carried out, and the gas is then divided into two paths. One path undergoes a methanation reaction to remove carbon dioxide to obtain natural gas, and the other path undergoes a further conversion reaction. After the reaction is completed, hydrogen is extracted as the above-mentioned flushing gas.

[0102] The corresponding device for producing H2 / CO raw gas from coal gas is provided, such as Figure 6 ,include:

[0103] A first impurity removal pretreatment device is used to perform a first impurity removal pretreatment on the coal gas raw gas, the first impurity removal pretreatment device comprising a desulfurization device, a CH4 removal device, a dehydrogenation and deoxygenation device and a CO2 removal device connected in sequence;

[0104] The first pressure swing adsorption unit is connected to the gas outlet of the CO2 removal unit. A temperature swing adsorption unit (not shown) is preferably provided between the first pressure swing adsorption unit and the CO2 removal unit. The first pressure swing adsorption unit separates nitrogen from the gas system to produce a mixed gas containing hydrogen and carbon monoxide.

[0105] The first shift reactor is connected to the first pressure swing adsorption unit located upstream of it and is used to partially shift the CO in the gas exiting the first pressure swing adsorption unit to produce H2. The gas outlet of the first shift reactor is connected to a first diverter 301, which separates the partially shifted gas into two streams. The first diverter is connected to the first pressure swing adsorption unit via a first pipeline and to the methanation reactor via a second pipeline. A hydrogen purification unit is located on the first pipeline. One end of the H2 inlet pipe is connected to the hydrogen purification unit on the first pipeline 303, and the other end is connected to the first pressure swing adsorption unit. A second shift reactor is located upstream of the hydrogen purification unit on the first pipeline to further perform a complete shift reaction on the diverted gas. The fully shifted gas is then passed through the hydrogen purification unit to remove carbon dioxide, producing hydrogen. The hydrogen is then fed into the first pressure swing adsorption unit as flushing gas via H2 inlet pipe 304. Another stream of gas enters the methanation reactor via a second pipeline 302 for methanation.

[0106] The gas outlet of the methanation reactor is connected to a CO2 removal and CH4 production device, and natural gas is obtained after removing carbon dioxide for external supply.

[0107] In the above method, some separation steps require the use of pressure swing adsorption separation operations; the purpose of the present invention is to address the relatively large pressure change processes that exist in the fields of normal temperature pressure swing adsorption and very low temperature pressure swing adsorption where the incoming gas pressure is relatively high or needs to be pressurized to a relatively high level in order to achieve the required separation effect. During the frequent pressure increase and decrease operations, the high-pressure gas discharged from the equipment carries relatively high pressure energy, and this process results in a large amount of energy loss. Therefore, an energy recovery device is added in these processes where the pressure changes are relatively large to recover energy, and the recovered energy is used to provide mechanical energy to provide pressure to the gas or liquid.

[0108] The equipment for discharging high-pressure gas referred to here includes various types of industrial pressure swing adsorption equipment. The most common is the adsorption tower, but it can also be other surge tanks or buffer tanks. These equipment contain high-pressure gas, and the pressure reduction process may be pressure equalization, pressure filling, forward or reverse discharge with another adsorption tower or surge tank or buffer tank in a low-pressure state. During these processes, the high-pressure gas in the adsorption saturation adsorption tower is recovered by the energy recovery device to recover the recoverable gas energy and then flows to the adsorption tower or surge tank or buffer tank in a low-pressure state, completing the energy recovery and normal pressure swing adsorption pressure reduction process at the same time. When the energy recovery device here uses an expander, it can convert the pressure energy of the high-pressure gas into mechanical energy. This mechanical energy can be used for various purposes such as driving the compressor rotation, generating electricity for the engine, and supplementing the rotation output of the motor. In the pressure swing adsorption process, the flow rate, pressure and pressure drop of the depressurized gas connected to the energy recovery device are unstable, with periodicity and relatively large fluctuations, which usually makes the energy recovery device almost unable to work normally and stably. Therefore, the energy recovery device needs to be improved accordingly.

[0109] The main design concept of the present invention is to enable the expander to operate normally by smoothing the periodic rapid fluctuations of the gas discharged from the high-pressure device, mainly by smoothing the fluctuations of gas pressure through a fluid buffer device at the gas inlet and / or gas outlet of the expander; another solution is to suppress the fluctuations in the speed of the expander's rotating shaft so that it can operate smoothly, which can be achieved by installing a rotational resistance device on its rotating shaft.

[0110] Based on the above concept, there are several implementation methods as follows:

[0111] A buffer tank of a certain volume is added to the gas that needs energy recovery before it enters the turbine expander in the energy recovery device or after it leaves the energy recovery device. The buffer tank can be used to smooth out the fluctuations in the pressure and flow of the pressurized gas, making it basically stable. The energy of the gas in the pressure swing adsorption can be recovered by the expander first and converted into mechanical energy of the shaft.

[0112] In another embodiment, a regulating valve is installed on the gas pipeline in the energy recovery device. By adjusting the opening of the regulating valve accordingly according to the frequency and magnitude of the pressure change during the pressure change process, the pressure and flow fluctuations of the high-pressure gas entering the expander are suppressed.

[0113] For designs that require increasing the rotational resistance of the expander shaft, in another embodiment, a flywheel of a certain size and a certain mass distribution is installed on the expander shaft to increase the shaft's rotational inertia. The flywheel can be installed on the shaft on the upstream side or downstream side of the expander.

[0114] As can be seen above, when the buffer device or the resistance device is used, the change of the pressure energy can be better suppressed during the process of converting the pressure energy of the gas into mechanical energy by the expander, so that the expander can work normally and stably, and the mechanical energy can be applied to other processes requiring energy consumption.

[0115] In order to better utilize the mechanical energy generated by the expander, the mechanical energy can be used to drive other equipment to work, or the mechanical energy can be converted into electrical energy for reuse.

[0116] In an embodiment, the expander drives the motor to generate electricity. Since the rotation of the expander has certain periodic fluctuation, the generated electricity is integrated into the power grid. The power grid needs to have a large electrical load capacity. The large power grid can accommodate the periodically and rapidly changing current, so that the electricity with periodic fluctuation can be suppressed for utilization. The electricity in the power grid can be transmitted to other electrical equipment, or can drive the compressor in the pressure swing adsorption device to compress the gas or liquid, so that the electricity can be recycled.

[0117] In the pressure swing adsorption process, there is a process of periodically pressurizing the gas. Therefore, in another embodiment, the electricity generated by the expander driving the motor can be used to drive the compressor to work through the motor, to complete the pressurization operation of the gas or liquid, so that the electricity can be recycled.

[0118] Since the overload of the motor connected with the compressor has adverse effects on the reliability, stability, service life, and safety of the equipment, in an embodiment, the motor can be connected with a capacitor bank or a battery bank. When the current fluctuation is large, the capacitor bank or the battery bank can quickly suppress the rapid change of the current, and can enhance the response of the motor system to the rapidly changing rotation energy required by the rotating shaft.

[0119] The above describes an embodiment in which mechanical energy generated by the expander is converted into electrical energy, and the mechanical energy generated by the expander can also be directly used. In this embodiment, the expander, motor, compressor or pump constituting the energy recovery device can constitute a coaxial driving system or a different shaft driving system. The coaxial driving system is such that the mechanical energy converted by the expander is directly supplemented to the shaft system of the compressor or pump, and the insufficient part is supplemented by the motor. For example, the motor is connected to a larger power grid, and on one hand, the motor is driven to operate by electrical energy, and on the other hand, the rotating shaft of the motor is connected to the rotating shaft of the expander, so that the expander can supplement mechanical energy to the motor. This way can directly use the mechanical energy obtained by the expander, and through the joint action of the expander and the motor, the fluctuation of the mechanical energy can be suppressed. The coaxial driving system has the advantages of compact structure, high overall efficiency, low overall equipment cost and operation cost, and good economic benefits.

[0120] For the process of pressure swing adsorption, generally, a high-pressure device (for example, an adsorption tower with a higher pressure) delivers high-pressure gas to a low-pressure device (for example, an adsorption tower with a lower pressure) to reduce the pressure of the high-pressure tower and increase the pressure of the low-pressure tower. Alternatively, the pressure of two gas buffer tanks or the pressure between the adsorption tower and the buffer tank can change. When the fluid buffer device and the expander in the present application are used as the main energy recovery device, the temperature of the gas can decrease after the gas flows through the expander when the gas flows from the high-pressure side to the low-pressure side. This is because the energy recovery process is a pressure reduction process that outputs work to the outside, and the temperature of the gas at the outlet of the expander decreases. When the low-temperature gas enters another tower that needs to be pressurized, the adsorption temperature decreases, which can make the adsorption temperature of the adsorption tower lower than the desorption and regeneration temperature. The low adsorption temperature is beneficial to increase the adsorption amount of the unit adsorbent, and the high desorption and regeneration temperature is beneficial to make the desorption of the adsorbent more thorough, thereby increasing the dynamic adsorption amount of the adsorbent. Alternatively, the gas at the outlet of the expander can be used to output cold energy of a certain temperature to other devices through a heat exchanger.

[0121] In addition, by adding the fluid buffer device before and after the expander, the rapid and periodic fluctuation of the gas pressure can be effectively prevented. Since excessive and frequent impact loads can easily cause the adsorbent to powder and reduce the service life of the adsorbent, and also adversely affect the safety and fatigue service life of the adsorption tower, the use of the control valve, buffer tank and other devices in the pressure swing adsorption device can suppress the rapid fluctuation of the high-pressure gas, thereby prolonging the service life of the adsorbent and being beneficial to the safety and fatigue service life of the adsorption tower.

[0122] Based on the operation of the above energy recovery device, a typical pressure swing adsorption process in the present application is as follows:

[0123] A common pressure swing adsorption industrial process is as follows:

[0124] In the first step, the mixed gas from the upstream enters the adsorption tower in the adsorption stage. Most of the easily adsorbable components are adsorbed by the adsorbent in the adsorption tower, and most of the non-adsorbable components pass through the bed of the adsorption tower. This is the adsorption stage.

[0125] In step 2, the saturated adsorption tower obtained in step 1 is depressurized. This depressurization process may involve pressure equalization with another low-pressure adsorption tower, a surge tank, or a buffer tank, or by placing the gas in a forward or reverse direction. During these processes, the high-pressure gas in the saturated adsorption tower is recovered through an energy recovery device, and then flows back to the low-pressure adsorption tower, surge tank, or buffer tank. This simultaneously completes energy recovery and the normal pressure swing adsorption depressurization process.

[0126] In step 3, it may be necessary to reduce the pressure of the depressurized gas in the adsorption tower, pressure-surge tank, buffer tank, etc. obtained in step 2 again, or to reduce the pressure of the depressurized gas again after certain treatments (such as replacement or re-adsorption, pressure flushing, pressurization, etc.). Similarly, this process may require a treatment method similar to that of step 2. This process may be a process of equalizing the pressure, placing it forward or backward with another adsorption tower, pressure-surge tank, or buffer tank in a low-pressure state. In these processes, the high-pressure gas in the adsorption saturation adsorption tower is recovered by the energy recovery device to recover the recoverable energy and then flows to the adsorption tower, pressure-surge tank, or buffer tank in a low-pressure state. At the same time, energy recovery and the normal pressure swing adsorption depressurization process are completed.

[0127] In step 4, a similar process as step 2 or step 3 may be repeated until the pressure in the adsorption tower drops to a sufficiently low level.

[0128] Step 5: The adsorption tower that has been lowered to a low pressure state in step 4 is subjected to a desorption regeneration process under low pressure. In this process, methods such as vacuuming, purging, vacuuming plus purging, or low-pressure desorption may be adopted.

[0129] In step 6, there may be a need to equalize the pressure of the adsorption tower that has undergone low-pressure desorption by other adsorption towers or pressure-stabilizing tanks or buffer tanks in step 3. In this process, it may take over the high-pressure gas that has been depressurized after energy recovery in step 2 or step 3.

[0130] In step 7, there may be a need to re-pressurize the pressurized gas obtained in step 6 in the adsorption tower, pressure-stabilizing tank, buffer tank, etc., or to subject the pressurized gas to certain treatments (such as replacement or re-adsorption, pressure flushing, pressurization, etc.) before re-pressurizing it. In these possible pressurization processes, the high-pressure gas that has been depressurized after energy recovery in step 2 or step 3 may be taken over.

[0131] In step 8, it may be necessary to pressurize the adsorption tower that has been pressurized in step 7 again to a pressure close to that of the adsorption step using the feed gas or the non-adsorbed gas that has been adsorbed by the adsorption tower.

[0132] Step 9 and the first 8 steps are for a single tower to be operated continuously in a cycle, and for the towers to cooperate with each other and alternately to be operated continuously in a cycle.

[0133] The processes of high-pressure adsorption, pressure reduction energy recovery, pressure reduction, low-pressure desorption, etc. are continuously and cyclically operated for a single tower, and are continuously and cyclically operated for coordination and staggering between towers.

[0134] The rapid, periodic pressure fluctuations during the pressure swing adsorption (PSA) separation process are recovered and converted into usable mechanical energy for the gas pressurization process, saving the electrical energy typically consumed in gas pressurization. Compared to PSA systems without energy recovery, this system can recover 50% of the energy lost due to pressure differentials in conventional PSA systems.

[0135] In addition, the non-adsorbed gas after adsorption by the adsorption tower during the adsorption process may have a relatively high pressure. For venting air or when such a high pressure gas is not needed on the demand side, the high-pressure gas can be connected to a volume recovery and pressurization coupling device for energy recovery. After energy recovery, the gas with reduced pressure can be connected to the demand side or vented again.

[0136] In the present invention, the adsorbent used in the adsorption process can be any type of adsorbent that has an adsorption effect, without special restrictions, and can be molecular sieves, activated carbon, carbon molecular sieves, activated alumina, carbon fiber, etc., as well as their mixed filling and layered filling.

[0137] The present invention provides a method for preparing a supported metal organic framework CO adsorbent, comprising:

[0138] (1) dissolving a total amount of 0.6 to 1 mmol of a divalent copper compound and cerium nitrate at a molar ratio of 100:1 to 1:100 in 15 to 20 mL of deionized water to obtain a divalent copper compound-cerium nitrate mixed solution;

[0139] (2) dissolving 0.3-0.5 mmol of 1,3,5-trimethylbenzene in a mixed solution of ethanol and 8-10 mL of dimethylformamide in a volume ratio of 10:1-1:10, adding commercially available NaY molecular sieves thereto, wherein the molar ratio of the NaY molecular sieves to the divalent copper compound-cerium nitrate is 1:40-50;

[0140] (3) After mixing and stirring the solutions of steps (1) and (2) at room temperature for 5 to 8 minutes, ultrasonically treat the mixture at 150 to 200 W for 8 to 10 minutes, heat the mixture to 230 to 250° C. at a heating rate of 3 to 5° C. / min, and keep the temperature for 20 to 22 hours. Then, cool the mixture to room temperature at a cooling rate of 2 to 5° C. / min to generate a precipitate, centrifuge, and filter; and wash the resulting crystals with anhydrous ethanol;

[0141] (4) Add 3.0 mL of 0.1-0.2 mmol / L AgNO3 ethanol solution to the obtained crystals, irradiate with 80-100 W ultrasound for 1-2 h, immerse in dark for 10-12 h, centrifuge and filter; wash the obtained crystals with anhydrous ethanol for 3 times, irradiate with 100-150 W ultraviolet light for 10-13 h (to make AgNO3 + Oxidized to Ag), centrifuged and washed with anhydrous ethanol, dried at 100-110 ° C, and oxidized with a mixture of O2 / He with an O2 volume fraction of 2-3% at 250-260 ° C for 1-2h (so that Ag and Cu 2+ The reaction generates Ag + and Cu + ), to obtain powder;

[0142] (5) CuCl, AgCl and rare earth powder with a molar ratio of 10:1-2:0.25-0.5 and molar amounts of 1 mmol / 0.1-0.2 mmol / 0.025-0.05 mmol, respectively, were dissolved in 30-40 mL of 0.4-0.5 mol / L hydrochloric acid solution, and 0.225-0.3 g of the powder obtained in step (4) was added. The mixture was ultrasonically irradiated at 100-150 W for 20-30 min, stirred at room temperature for 2-3 h, and the solvent was evaporated with a rotary evaporator and placed in a vacuum drying oven. After drying for 10-12 h, the mixture was activated at 200-220 ° C. in a H2 atmosphere for 4-5 h to obtain a powder material.

[0143] (6) Weigh a certain amount of the powder material obtained in the above step (5), methyl cellulose and citric acid aqueous solution (the mass ratio of the three is 0.5:0.3-0.4:0.1-0.2), place them in a kneader and stir them evenly, then place the mixture in a centrifugal shot blasting machine for molding, and dry the molded product at 200-250°C to obtain round particles with a diameter of about 2-3 mm, i.e., the supported metal organic framework CO adsorbent molded body.

[0144] The preparation idea of the adsorbent is: Cu and rare earth elements (cerium) are used to make metal organic framework material (Cu / Ce-BTC) together, the rare earth elements (cerium) play a role in stabilizing the structure, and also play a role in resisting sulfur and oxidation. Since the method for making metal organic framework material (MOFs) is not mature, and there are certain defects, the application adds commercially available NaY molecular sieve to fill these defects, increase the adsorption capacity, and metal organic framework is loaded with Ag + and Cu + The adsorbent can improve the CO adsorption capacity and CO adsorption selectivity.

[0145] In step (1), the divalent copper compound is selected from copper nitrate trihydrate, copper sulfate pentahydrate, copper chloride dihydrate and copper acetate tetrahydrate, and preferably copper nitrate trihydrate.

[0146] In step (5), the rare earth powder is one or more of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium or gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium or lutetium.

[0147] The application will be further illustrated below with reference to specific examples. Unless otherwise specified, the methods, adsorbents or catalysts used in the examples can be obtained by conventional means in the art.

[0148] Example 1

[0149] The converter gas (0.2 MPa, 350℃) is first subjected to dust removal, and then subjected to catalytic hydrogenation conversion to convert the sulfur in the gas into hydrogen sulfide (0.2 MPa, 300℃) which is easy to remove. The treated gas is pressurized to 0.4 MPa, cooled to 40℃, and then introduced into a carbon dioxide absorption tower. The carbon dioxide absorption tower uses the DEA absorption method, and simultaneously removes most of the sulfur contained in the gas. The unsaturated DEA absorption liquid after decarburization (i.e. absorption of carbon dioxide) is pressurized and sent to the absorption tower of the decarburization hydrogen extraction device for absorption and decarburization again. Then the absorption liquid is introduced into a secondary decarburization absorption tower using the DEA absorption method, and the absorption liquid is mainly used to remove the carbon dioxide generated by the pseudo-isothermal shift reaction. The saturated DEA solution is regenerated by decompression, releases the contained carbon dioxide, and most of the activated regenerated DEA solution is used as a semi-lean liquid to remove carbon dioxide in the absorption tower. The remaining DEA solution is heated and regenerated in a hot regeneration tower to release the contained sulfur and the remaining small amount of carbon dioxide, and is finally fully activated and regenerated into a lean liquid. The removed carbon dioxide is treated to meet the emission standard and then vented. The gas after the removal of carbon dioxide is sent to a temperature swing adsorption device, and the temperature swing adsorption separation is carried out under the conditions of an adsorption pressure of 0.2 MPa and an operating temperature of 32℃, and then the water and other heavy components are removed. After that, the gas is subjected to fine desulfurization in a fine desulfurization adsorption tower composed of activated carbon, molecular sieve and alumina, and at this time the gas mainly contains CO and nitrogen.

[0150] The part of the gas is sent to a pressure swing adsorption CO and nitrogen separation device for separation of CO and nitrogen. The CO and nitrogen are separated by pressure swing adsorption at similar adsorption pressure (0.2 MPa) and adsorption temperature (32°C). The gas containing a large amount of nitrogen separated at the top is recovered by a pressure recovery device after treatment to reach the discharge standard. The pressure swing adsorption CO and nitrogen separation device uses a combination of multiple (≥1) high pressure flushing and low pressure flushing to desorb the mixed gas containing CO and H2. The flushing gas is obtained from the hydrogen obtained by the DEA absorption decarburization and hydrogen extraction device. This method couples two devices to minimize costs. The flushing pressure of the general pressure swing adsorption is selected near atmospheric pressure, which is beneficial for desorption at low pressure. However, the method used here is to use the hydrogen at the top at its hydrogen extraction pressure and slightly higher than atmospheric pressure to flush and desorb the adsorption device for separating CO and nitrogen twice. Then the mixed gas obtained by flushing at different pressures and different components is fed to the compressor step by step to increase the pressure and then proceed to the next step of isothermal shift. The advantages of this method are: first, the pressure of the hydrogen obtained by the decarburization and hydrogen extraction device is higher than that of the CO and nitrogen separation device. Although the use of high pressure to flush and desorb the CO and nitrogen separation device makes the adsorbent not completely desorbed, it still can make most of the gas desorbed. The gas obtained is high pressure gas, which reduces the energy consumption of the subsequent pressurization. Second, the low pressure flushing process makes the adsorbent completely desorbed. Third, this desorption method can change the gas pressure reduction process into gradual pressure reduction, which can reduce the impact load of the adsorbent, increase the service life of the adsorbent, and reduce the amount of oxygen in the air, reduce the explosion risk of flammable gas (CO, H2 and CH4), and increase safety. Finally, the desorbed mixed gas containing CO and H2 obtained by this method reduces the concentration of CO in the gas, which reduces the conversion depth when adjusting the CO and H2 ratio, reduces the reaction heat release temperature rise, reduces the maximum use temperature of the catalyst, reduces the severity of the conversion conditions, and increases the service life of the catalyst. In summary, this method balances the unit adsorbent circulation adsorption amount and energy consumption, as well as the adsorbent loading amount, adsorbent life, and catalyst life.

[0151] The desorbed mixed gas containing CO and H₂ is then pressurized to 1.2 MPa, mixed with water vapor, and fed into a quasi-isothermal shift reactor for the shift reaction. The reactor uses water cooling to remove the exothermic heat of reaction, with a reaction temperature of 180-450°C. The cooling water is heated to produce 1.2 MPa steam for use in this unit or other units. After the CO / H₂ molar ratio is shifted to 1 / 3, the mixed gas is split into two parts: one-third undergoes deep shift to produce hydrogen. After the CO is fully shifted, the gas phase is further cooled to 40°C and, at 1.2 MPa, enters a gas-liquid separator to remove excess water. The gas then enters a DEA absorption decarbonization and hydrogenation unit, which primarily removes the CO₂ generated by the shift reaction. The absorbent is primarily derived from the DEA absorbent in the previous step, which has completed the decarbonization absorption process in the CO₂ absorption tower. The decarbonization and hydrogenation unit also receives some absorbent from the thermally regenerated lean liquid and the decompression-regenerated semi-lean liquid. The ratio of lean liquid to semi-lean liquid is determined based on actual conditions. The gas then passes through a temperature swing adsorption unit (not shown) to remove trace amounts of water and heavy components removed from the gas during the DEA absorption decarbonization and hydrogenation process. Finally, the purified hydrogen is divided into three parts (the first part is used as a smaller amount of regulating gas, and the second and third parts are used as flushing gas, with the volume ratio of high-pressure flushing to low-pressure flushing being 3:1). The second part of the purified hydrogen is used as high-pressure flushing gas (1.2 MPa) to perform high-pressure flushing and desorption on the pressure swing adsorption device for separating CO and nitrogen, and the third part of the hydrogen is depressurized to atmospheric pressure and used as low-pressure flushing gas to perform low-pressure flushing and desorption on the pressure swing adsorption device for separating CO and nitrogen. Another part of the gas that has undergone partial isothermal conversion is further cooled to 40°C, enters the gas-liquid separator at a pressure of 1.2 MPa to remove excess water contained in the gas, and then enters the secondary decarbonization absorption tower using the DEA absorption method. Its main purpose is to remove the carbon dioxide generated by the quasi-isothermal conversion reaction. The absorption liquid mainly comes from the DEA absorption liquid that completes the decarbonization absorption process of the decarbonization and hydrogenation device in the previous step. Some of the absorption liquid in the secondary decarbonization absorption tower comes from the lean liquid that has undergone thermal regeneration and the semi-lean liquid that has undergone reduced pressure regeneration (the ratio of lean liquid to semi-lean liquid is determined according to actual conditions). The mixed gas after decarbonization in the secondary decarbonization absorption tower passes through the temperature swing adsorption device to remove trace moisture and heavy components contained in the gas when passing through the secondary decarbonization absorption tower of the DEA absorption method, and is then mixed with the first part of hydrogen as the CO / H2 regulating gas to adjust the CO / H2 molar ratio to about 1 / 3. It then enters the quasi-isothermal methanation reactor to synthesize methane. The reactor uses water cooling to remove the reaction heat. The reaction temperature is 250-700°C and the pressure is 1MPa. The cooling water is heated to produce 1.2MPa steam for use in this device or other devices.Finally, after cooling and removing moisture in a gas-liquid separation tank (1MPa, 32°C), and removing trace moisture and heavy components contained in the gas through a temperature-swing adsorption device (1MPa, 32°C), the purified synthetic natural gas (meeting GB17820-2012 and its updated versions) is sent to an intermediate gas storage tank for external transmission.

[0152] In the process and reaction flow of this embodiment, natural gas synthesis primarily considers using the DEA absorption method to remove CO2 three times at two different CO2 concentrations, high and low, and at two different pressures. All three CO2 removal methods employ absorption, and the same absorbent is used for all three CO2 removals. After the absorbent absorbs a certain amount of CO2 in a carbon dioxide absorption tower at a lower pressure during the first CO2 removal process, it is pressurized and then subjected to a second CO2 removal process in a decarbonization and hydrogenation absorption tower at a higher pressure to continue absorbing CO2. Then, during the third CO2 removal process, it continues absorbing CO2 in a secondary decarbonization absorption tower at a higher CO2 concentration. After absorption is complete, the absorbent enters a regeneration tower to complete the activation and regeneration process. Because the first CO2 removal process is performed at a lower pressure, the absorbent generally does not achieve saturation adsorption. However, the higher CO2 pressure obtained after CO conversion allows the absorbent to further absorb CO2. Finally, utilizing the absorbent's higher absorption capacity at higher CO2 concentrations, the absorbent is used again at a higher CO2 concentration to further absorb CO2, thereby reaching saturation. This method helps reduce the amount of absorption liquid circulating, and thus the amount of regeneration liquid circulating, thereby reducing the regeneration process. In this example, the steps are simplified, the process is shortened, and costs are saved. At the same time, the residual pressure recovery system is used to recover the pressure energy contained in the vented gas.

[0153] Example 1 Specific process flow is detailed in Figure 2 The gas components during each step are shown in Table 1.

[0154] Table 1

[0155]

[0156] Example 2

[0157] The incoming blast furnace gas is first dedusted and then desulfurized with a desulfurizer composed of manganese oxide and ZnO at 350°C and 0.3 MPa. As the temperature decreases, a catalytic reaction is carried out at a temperature of 220°C and a pressure of 1 MPa to remove trace amounts of hydrogen and oxygen from the blast furnace gas. The gas is then mixed with water vapor and fed into a multi-stage quenched shift reactor for a shift reaction, generating H2. The reaction depth is adjusted to maintain a CO / H2 molar ratio of approximately 1 / 3. The shift reactor uses intermediate water quenching to remove the exothermic heat of reaction, with a reaction temperature of 180-450°C. The gas phase is then further cooled to 32°C and fed into a gas-liquid separator at 1 MPa to remove excess water. The gas then enters a temperature swing adsorption unit (1 MPa, 32°C) to remove trace moisture and heavy components. The gas then enters a pressure swing adsorption decarbonization unit (1 MPa, 32°C) to remove carbon dioxide. The removed carbon dioxide is treated to meet emission standards and discharged. At this time, the gas components mainly contain CO, H2 and nitrogen.

[0158] This gas is fed into a pressure swing adsorption (PSA) CO, H2, and nitrogen separation unit to separate CO from H2 and nitrogen at an adsorption pressure of 1 MPa and an operating temperature of 32°C. The PSA CO, H2, and nitrogen separation unit uses a combination of multiple (≥1) high-pressure and low-pressure flushes to desorb the gas mixture containing CO and H2. The flushing gas is derived from the hydrogen generated by the PSA hydrogen extraction unit and the downstream gas (primarily H2 with trace amounts of CO) from multiple towers within the unit. This utilizes the hydrogen generated by the PSA hydrogen extraction unit to desorb CO from the CO, H2, and nitrogen separation unit. This method couples the two units, which jointly determine the downstream pressure of the downstream gas and the flushing pressure range of the PSA CO, H2, and nitrogen separation unit, minimizing costs. The PSA flushing pressure is typically selected near atmospheric pressure, facilitating desorption at low pressures. However, the method adopted here is to use the hydrogen at the top of the tower and the downstream gas to flush and desorb the adsorption device for separating CO, H2 and nitrogen twice at the hydrogen supply pressure and slightly higher than the atmospheric pressure; then the multiple streams of flushed mixed gases with different pressures and components are fed step by step to the compressor for pressure boosting.

[0159] The gas exiting the top of the pressure swing adsorption (PSA) CO, H2, and nitrogen separation unit primarily contains H2 and nitrogen. It then enters the PSA hydrogen extraction unit to separate the H2 and nitrogen. The nitrogen removed from the bottom of the PSA hydrogen extraction unit's adsorption tower is treated to meet emission standards and then vented. The H2 exiting the top of the tower is used as high-pressure flushing gas for high-pressure flushing and desorption (1MPa) of the PSA CO, H2, and nitrogen separation unit. The downstream bleed gas from the PSA hydrogen extraction unit is used as low-pressure flushing gas (normal pressure) for low-pressure flushing and desorption of the PSA CO, H2, and nitrogen separation unit.

[0160] The CO and H2 mixture is then pressurized to 1.6 MPa and fed into a pseudo-isothermal methanation reactor for methane synthesis. The reactor is water-cooled to remove the exothermic heat of reaction, with a reaction temperature of 280-700°C. The cooling water is heated to produce 1.6 MPa steam for use in this device or other devices. The resulting gas is then further cooled to 32°C and passed through a gas-liquid separator at 1.6 MPa to remove most of the excess water. It then passes through a temperature swing adsorption device (1.6 MPa, 32°C) to remove trace amounts of water and heavy components. Finally, the purified synthetic natural gas (which complies with GB17820-2012 and its updated versions) is sent to an intermediate gas storage tank for external transport.

[0161] Under the process and reaction flow of this embodiment, not only synthetic natural gas is obtained, but the method also comprehensively balances the life of the conversion catalyst. At the same time, it connects and utilizes a large amount of high-pressure hydrogen and part of the downstream low-pressure process gas such as the exhaust gas generated at the top of another set of equipment for desorption, so that useful gas can be fully utilized and the gas pressurization energy can be reduced.

[0162] Example 2 Specific process flow is detailed in Figure 3 The gas components during each step are shown in Table 2.

[0163] Table 2

[0164]

[0165] Example 3

[0166] The incoming blast furnace gas (350°C, 0.4 MPa) is first dusted and then desulfurized with a desulfurizer composed of manganese oxide and ZnO at 350°C and 0.4 MPa. As the temperature decreases, a methane catalytic combustion reaction is performed at 290°C and 0.4 MPa to remove trace amounts of methane. Further catalytic reactions are then carried out at a temperature of 220°C and a constant pressure of 0.4 MPa to remove trace amounts of hydrogen and oxygen from the blast furnace gas. The gas then enters a temperature swing adsorption unit (0.4 MPa, 32°C) to remove trace amounts of moisture and heavy components. It then enters a pressure swing adsorption decarbonization unit (0.4 MPa, 32°C) to remove carbon dioxide. The removed carbon dioxide is treated to meet emission standards and then discharged. The gas primarily consists of CO and nitrogen. This gas is fed into a pressure swing adsorption (PSA) CO and nitrogen separation unit for CO and nitrogen separation. Under conditions of an adsorption pressure of 0.4 MPa and an operating temperature of 32°C, a portion of industrial-grade nitrogen with a volume composition of ≥99.2% is extracted and sent to a nitrogen recovery system as a product. The PSA tower utilizes a combination of multiple (≥1) high-pressure flushes and low-pressure flushes, plus vacuum pumping, to desorb a mixed gas containing CO and synthetic natural gas. The flushing gas is derived from the final synthetic natural gas product and multiple, multi-tower effluent (primarily methane) from the PSA decarbonization and methane extraction unit. This method couples two units, which jointly determine the effluent pressure and the flushing pressure of the PSA adsorption unit for CO and nitrogen separation, minimizing costs. The flushing pressure for PSA is typically selected near atmospheric pressure, facilitating desorption at low pressures. However, the method adopted here is to use the hydrogen at the top of the tower and the downstream gas to perform high-pressure flushing and desorption and low-pressure flushing and vacuum desorption on the adsorption device for separating CO and nitrogen at the hydrogen extraction pressure and slightly higher than the atmospheric pressure; then the obtained multiple streams of mixed gases after flushing with different pressures and components are fed step by step to the compressor for pressure boosting. The advantages of using this method are: first, although flushing with flushing gases of different pressures may not completely desorb the adsorbent, most of the gas can still be desorbed, and the gas obtained is high-pressure gas, which reduces the energy consumed in pressurizing them; secondly, the process of simultaneously evacuating and purging with the discharge gas can reduce the vacuum degree of the vacuum pump, save the energy of the vacuum pump, and desorb the adsorbent more thoroughly; thirdly, using this desorption method can change the gas decompression process to a step-by-step decompression, which can reduce the impact load of the adsorbent and increase the service life of the adsorbent. Finally, due to the use of this method, a mixed gas containing CO and synthetic natural gas is desorbed. Since the synthetic natural gas does not participate in the conversion reaction, it can be regarded as an inert component, which reduces the concentration of CO in the gas, lowers the conversion depth, reduces the exothermic temperature rise of the reaction, reduces the maximum operating temperature of the catalyst, reduces the harshness of the conversion conditions, and increases the service life of the conversion catalyst.Similar effects are achieved during the methane synthesis process, reducing the CO concentration in the gas, lowering the depth of the methanation reaction, minimizing the exothermic temperature rise, lowering the maximum operating temperature of the catalyst, reducing the severity of the methanation reaction conditions, and increasing the lifespan of the methanation catalyst. In summary, this method comprehensively balances the cycle adsorption capacity per unit adsorbent with energy consumption, adsorbent loading, adsorbent lifespan, shift catalyst, and methane synthesis catalyst lifespan. It also connects and recycles the downstream gas from another unit, reducing the waste of useful gases such as CO. The mixed gas (CO and methane) is then slightly pressurized to 1 MPa, mixed with water vapor, and fed into a pseudo-isothermal shift reactor for a partial shift reaction. The isothermal shift reactor uses water cooling to remove the reaction heat, with a reaction temperature of 180-450°C. The cooling water is heated to generate 1 MPa steam for use in this unit or other units. By adjusting the depth of the shift reaction to maintain a CO / H2 molar ratio of approximately 1 / 3, the gas then enters a pseudo-isothermal methanation reactor for methane synthesis. The reactor is water-cooled to remove the exothermic heat of reaction, with a reaction temperature of 250-700°C. The cooling water is heated to produce 1 MPa steam for use in this unit or other units. The resulting gas is then further cooled to 32°C and passed through a gas-liquid separator at 1 MPa to remove excess water. It then passes through a temperature swing adsorption unit (1 MPa, 32°C) to remove trace moisture and heavy components. The gas then enters a pressure swing adsorption unit for decarbonization and methane extraction, which primarily produces carbon dioxide generated during the shift reaction. Finally, the purified synthetic natural gas (which complies with GB17820-2012 and its updated versions) is transferred to an intermediate storage tank for external transport.

[0167] Under the process and reaction flow of this embodiment, not only synthetic natural gas is obtained, but industrial-grade nitrogen is also recovered. Furthermore, the resulting natural gas is used as a high-pressure flushing gas and as a process gas such as a portion of the downstream bleed gas from the adsorption decarbonization and methane extraction unit, for low-pressure desorption, thereby fully utilizing the useful gas and reducing gas pressurization energy. Of course, another embodiment employs a process substantially identical to that of this embodiment, but instead of using natural gas as a high-pressure flushing gas and a portion of the downstream bleed gas from the adsorption decarbonization and methane extraction unit for low-pressure desorption, conventional vacuum desorption is employed. This method can also produce natural gas, but it increases energy consumption and is detrimental to the lifespan of the catalyst and adsorbent.

[0168] Example 3 Specific process flow is detailed in Figure 4 The gas components during each step are shown in Table 3.

[0169] Table 3

[0170]

[0171] Example 4

[0172] The incoming blast furnace gas (350°C, 0.4MPa) is first dusted and then desulfurized with a desulfurizer composed of manganese oxide and ZnO at 350°C and 0.4MPa. As the temperature decreases, it undergoes a methane catalytic combustion reaction at 290°C and 0.4MPa to remove trace amounts of methane. Then, a further catalytic reaction is carried out at a temperature of 220°C and a pressure of 0.4MPa to remove trace amounts of hydrogen and oxygen in the blast furnace gas. The gas is then divided into two parts: one part is pressurized to 1MPa, mixed with water vapor, and then enters a quasi-isothermal shift reactor for a shift reaction. The quasi-isothermal shift reactor uses water cooling to remove the reaction heat. The reaction temperature is 180-450°C, and the cooling water is heated to produce 1MPa steam for use in other devices. The gas phase is then further cooled to 32°C and enters a gas-liquid separator at a pressure of 1MPa to remove excess water. It then enters a temperature swing adsorption unit (1MPa, 32°C) to remove trace amounts of water and heavy components. It then enters a pressure swing adsorption hydrogen extraction unit (1MPa, 32°C) to remove impurities such as carbon dioxide and nitrogen, producing H2. The removed carbon dioxide and nitrogen are treated to meet emission standards and then vented. The resulting H2 is used as high-pressure flushing gas (1MPa) to perform high-pressure flushing and desorption on the pressure swing adsorption CO and nitrogen separation unit. The downstream gas from the pressure swing adsorption hydrogen extraction unit is used as low-pressure flushing gas [at normal pressure] to perform low-pressure flushing and desorption on the pressure swing adsorption CO and nitrogen separation unit.

[0173] After dehydrogenation and deoxygenation, the remaining gas enters a temperature swing adsorption unit (0.4MPa, 32°C) to remove trace amounts of water and heavy components, and then enters a pressure swing adsorption decarbonization unit (0.4MPa, 32°C) to remove carbon dioxide. The removed carbon dioxide is treated to meet emission standards and then discharged. At this point, the gas components mainly contain CO and nitrogen. This portion of gas is sent to a pressure swing adsorption CO and nitrogen separation unit for CO and nitrogen separation. Under the conditions of an adsorption pressure of 0.4MPa and an operating temperature of 32°C, industrial-grade nitrogen (volume composition ≥99.2%) is extracted and sent as a product to the nitrogen recovery system. The pressure swing adsorption tower uses a combination of multiple (≥1) high-pressure flushing and low-pressure flushing plus vacuuming to desorb a mixed gas containing CO and H2. The flushing gas comes from the hydrogen obtained from the pressure swing adsorption hydrogen extraction unit and the multiple downstream gases (mainly hydrogen) from multiple towers in the unit. This method couples two units, which jointly determine the discharge pressure of the downstream gas and the flushing pressure of the adsorption unit for pressure swing adsorption (PSA) separation of CO and nitrogen, minimizing costs. The flushing pressure for PSA is typically selected near atmospheric pressure, facilitating desorption at low pressure. However, the method employed here utilizes the overhead hydrogen and downstream gas at their hydrogen extraction pressure and slightly above atmospheric pressure to perform high-pressure flushing and desorption, and low-pressure flushing and vacuum desorption, on the adsorption unit for separation of CO and nitrogen. The resulting multiple flushed gas mixtures, each with varying pressures and components, are then fed stepwise to a compressor for pressure boosting. The mixed gas (CO and H₂) is mixed with water vapor at 1 MPa and fed into a wide hydrogen-to-carbon ratio methanation reactor, where the shift reaction and methanation reactions proceed sequentially. The reactor utilizes multi-stage heat exchange to remove the exothermic heat, with a reaction temperature of 250-700°C. The resulting gas is then further cooled to 32°C and passed through a gas-liquid separator at 1 MPa to remove most of the water. After passing through a temperature swing adsorption unit (1 MPa, 32°C) to remove trace amounts of water and heavy components, it enters a pressure swing adsorption (PSA) decarbonization and methane extraction unit, primarily removing carbon dioxide generated by the shift reaction in the wide hydrogen-to-carbon ratio methanation unit. Finally, the purified synthetic natural gas (compliant with GB17820-2012 and its later versions) is transferred to an intermediate gas storage tank for external transport.

[0174] Under the process and reaction flow of this embodiment, not only synthetic natural gas is obtained, but also industrial-grade nitrogen is recovered, and a wide hydrogen-carbon ratio methanation reaction device is used, which shortens the process, saves energy and investment, and at the same time connects and utilizes a large amount of high-pressure hydrogen and part of the downstream gas and other low-pressure process gases produced at the top of another set of equipment for desorption, so that useful gas can be fully utilized and gas pressurization energy is reduced. The wide hydrogen-carbon ratio methanation reaction device is equivalent to combining a conversion reaction device and a methanation reaction device. The wide hydrogen-carbon ratio methanation reaction device can replace the conversion reaction device and the methanation reaction device under the conditions of the ratio of CO and H2 that meets the conditions. Its wide hydrogen-carbon ratio methanation reaction device can be used in the above various methods.

[0175] Example 4 Specific process flow is detailed in Figure 5 The gas components during each step are shown in Table 4.

[0176] Table 4

[0177]

[0178] Comparative Example 1

[0179] The difference from Example 4 is that the catalytic H2 and O2 removal steps in the blast furnace gas purification process in Example 4 are moved to after the pressure swing adsorption decarbonization and methane extraction unit. Only the O2 content is controlled, and the pure methane obtained after the pressure swing adsorption decarbonization and methane extraction unit is then subjected to catalytic O2 removal. All other aspects are the same as Example 4. O2 removal is necessary because the synthesized natural gas should not contain too high an O2 content, as this would be explosive and have a significant impact on the safety of the natural gas.

[0180] The results showed that the volume composition of the extracted nitrogen in the pressure swing adsorption CO and nitrogen separation device for CO and nitrogen separation was ≤99.2% under the conditions of an adsorption pressure of 0.4 MPa and an operating temperature of 32°C, which was insufficient to meet the demand for industrial-grade nitrogen. The nitrogen was then sent to an energy recovery system to recover the nitrogen pressure energy before being vented. Furthermore, the adsorbent began to deteriorate over time, and after approximately one month, the purity of the purified CO began to decline. After approximately two months, the CO purity decreased significantly (nitrogen concentration greater than 10%, compared to ≤1% in Example 4). Increasing the replacement gas volume was employed to maximize CO purity. After approximately four months, even increasing the replacement gas volume was unable to prevent the decline in CO purity, and the adsorbent no longer met the separation requirements.

[0181] A portion of the gas is pressurized to 1 MPa and mixed with water vapor before entering the quasi-isothermal shift reactor for a shift reaction. The isothermal shift reactor uses water cooling to remove the reaction heat. The reaction temperature is 180-450°C, and as time goes by, the shift catalyst begins to deteriorate. After 6 months, the shift effect of the quasi-isothermal shift reactor becomes worse and worse. It can be seen that after adopting the comparative scheme, the purity of the hydrogen after the shift becomes lower and lower over time, and the CO shift conversion rate is less than 90% (in Example 4, the CO shift conversion rate is ≥99.6%). After the pressure swing adsorption decarbonization and hydrogenation device, the CO content in the purified tail gas generated becomes higher and higher, resulting in unnecessary waste of raw materials and is not conducive to environmental protection.

[0182] A mixture of CO and H2 is mixed with water vapor at 1 MPa and then enters a wide hydrogen-to-carbon ratio methanation reaction unit, where a shift reaction and a methanation reaction are carried out successively. The reactor uses multi-stage heat exchange to remove the reaction heat, and the reaction temperature is 250-700°C. Over time, the shift catalyst in the wide hydrogen-to-carbon ratio methanation reaction unit begins to deteriorate. After 6 months, the shift effect becomes increasingly poor, and the methanation catalyst in the wide hydrogen-to-carbon ratio methanation reaction unit also begins to deteriorate. After 6 months, the shift effect becomes increasingly poor, the content of the obtained methane becomes increasingly low, and the content of CO and H2 in the obtained methane becomes increasingly high (at this time, the embodiment can still ensure the shift quality, with a conversion rate of nearly 100%). After passing through the pressure swing adsorption decarbonization and methane extraction unit, the CO content in the purified tail gas generated becomes increasingly high, resulting in unnecessary waste of raw materials and being detrimental to the environment. Moreover, after 12 months, the calorific value of the obtained synthetic natural gas becomes increasingly low, and even fails to meet the requirements of the GB17820-2012 standard.

[0183] Since catalytic de-O2 is carried out in a higher concentration of CH4, more CH4 will react with O2, resulting in a waste of CH4. In addition, the reaction requires a higher temperature, the gas needs to be heated, and the reaction products after the reaction need to be removed as impurities, which requires the addition of corresponding impurity removal steps and equipment.

[0184] The calorific value of the synthetic natural gas obtained under the process and reaction flow of this embodiment does not meet the requirements of the standard, nor can it meet the requirements of industrial-grade nitrogen. It can also poison the adsorbent, conversion catalyst, and the conversion catalyst and methanation catalyst in the wide hydrogen-to-carbon ratio methanation reaction unit. As time goes by, the adsorbent and catalyst begin to deteriorate until they become unusable. The calorific value of the resulting synthetic natural gas is getting lower and lower, and even does not meet the requirements of the standard. Since catalytic deoxygenation is carried out in pure CH4, more CH4 will react with O2, resulting in a waste of CH4. Moreover, since the reaction products after the catalytic deoxygenation need to be removed as impurities, it is necessary to add corresponding impurity removal steps and equipment.

[0185] Example 5 This example is used to illustrate the energy recovery process in two-tower pressure swing adsorption

[0186] The tail gas also contains trace amounts of impurities such as N2, CO, CO2, CH4, and Ar. To meet the requirements for product hydrogen, a hydrogen separation unit is required for separation and purification. Due to the high operating pressure of the upstream unit, the feed gas pressure entering the H2 pressure swing adsorption separation unit is relatively high. At the same time, the H2 after separation needs to be pressurized to 4.2MPa(G).

[0187] Raw gas conditions:

[0188] Components (dry basis) CO <![CDATA[H2]]> <![CDATA[CO2]]> <![CDATA[N2]]> Ar <![CDATA[CH4]]> <![CDATA[H2S+COS]]> Vol, % 11.179 68.28 10.004 10.227 0.003 0.308 0.1ppm

[0189] Flow rate: 2000Nm 3 / h(dry basis)

[0190] Pressure: 2.2MPa(G)

[0191] Temperature: ≈32℃

[0192] Total H2O, O2, NH3, CH3OH, chlorine, phosphorus, arsenic, fluorine, HCN: ≤0.1ppm

[0193] Separation and purification are performed using a pressure swing adsorption (PSA) purification unit equipped with a specialized H2 separation adsorbent. The separation steps include adsorption, pressure equalization and reduction, reverse pressure release, vacuum pumping, pressure equalization and increase, and final pressure recharge. Energy recovery and pressurization coupling are employed during the pressure swing steps of pressure equalization, reverse pressure release, and final pressure increase, simultaneously completing the specialized H2 separation and purification.

[0194] The coupled energy recovery and pressurization device comprises a screw expander, compressor, and electric motor, along with auxiliary components such as a capacitor bank, regulating valves, a flywheel, multiple buffer tanks, a speed change mechanism, and a control system. A buffer tank of a certain volume is added before and after the pressurized H2 enters and leaves the energy recovery device to smooth out fluctuations in the pressure and flow of the pressurized H2, maintaining a relatively stable flow.

[0195] The device provided in this embodiment is as follows Figure 7 and Figure 8 、 Figure 9As shown, the exhaust pipe of the adsorption tower 1A is connected to the first stage 2 of the expander, and the exhaust direction of the first stage 2 of the expander is connected to the adsorption tower 1B. Buffer tanks 13 and 14 are respectively connected to the pipelines on the inlet and outlet sides of the first stage 2 of the expander. The rotating shaft of the first stage 2 of the expander is connected to the motor 4, and the motor 4 is connected to the compressor 3 for pressurizing the gas. The inlet and outlet of the compressor 3 are also provided with a compressed gas inlet buffer tank 11 and a compressed gas outlet buffer tank 12, respectively. A capacitor group 10 is also connected to the motor 2.

[0196] The following is a further explanation of the operation of the device in conjunction with its operation process:

[0197] During the time period (0-3 minutes), adsorption tower 1A (hereinafter referred to as Tower A) is performing the adsorption process. Valve A5A1 is open, and the raw gas enters the adsorption tower A in the adsorption state through the raw gas pressure-stabilizing tank (18) and regulating valve E4. The unadsorbed gas at the top of the tower passes through the product gas pressure-stabilizing tank (19) and regulating valve E3 as product gas for use by other devices. Adsorption tower 1B (hereinafter referred to as Tower B) is performing the vacuum process. Valve B6 is opened, and Tower B is vacuumed by the reciprocating pump (6) through the air buffer tank (5). No gas passes through the energy recovery device, and no energy is recovered to supply the compressor (3) for gas compression.

[0198] During the (3-4 min) period, the pressure of Tower A and Tower B is equalized. Valve A2B3E2 is opened, and the high-pressure gas in Tower A is used to increase the pressure of Tower B. First, at the moment valve A2B3E2 is opened, the pressure in the pipeline, the pressure difference between the inlet and outlet of the expander (3), and the flow rate all change greatly, which will cause a relatively large impact load. Excessive impact load will affect the smooth and safe operation of the equipment and shorten the life of the equipment. Therefore, the pressure difference and flow rate between the inlet and outlet of the expander 3 are adjusted by regulating valve E5E10. At the moment valve A2B3E2 is opened, the opening of regulating valve E5E10 is reduced to hold back the pressure of the corresponding adsorption tower, thereby reducing the impact of the impact load on the expander. The buffer tank (13) (14) connected to the inlet and outlet pipelines of the expander is also used for buffering. When the pressure in the pipeline connected to the buffer tank is higher than the pressure set by valve E6E7, valve E6E7 opens, and the buffer tank is connected to the pipeline, so that the gas is diverted into the buffer tank, reducing the amount of gas entering the expander and reducing the impact of the impact load, thereby gaining the required time for the action of the expander regulating mechanism, so that the regulating control mechanism actuates the slide valve of the screw expander, and adjusts the flow rate, internal pressure ratio, and internal volume ratio through the expander to be suitable for the external pressure ratio and flow rate of the inlet and outlet of the expander after the valve is opened. At the same time, the pressure energy acting on the expander drives the shaft to rotate and is converted into mechanical energy of the shaft. Due to the impact load formed when the valve is opened, the shaft speed is likely to exceed the set required speed. The change in shaft speed is not conducive to forming a joint force with the motor to jointly drive the compressor to complete the compression process of another gas. By adding a flywheel of a certain size and a certain mass distribution to the shaft to increase the shaft's rotational inertia, the acceleration obtained by the shaft is reduced under the same torque, which is conducive to the stability of the shaft speed at a certain required speed. The expander's rotating shaft is connected to the motor (4), which can drive the motor to rotate. However, since the mechanical energy output by the expander will change periodically due to the frequent changes in the pressure swing adsorption process, it will cause the motor to operate unstably. Therefore, the current required by the motor needs to be connected to the overall power grid. The large power grid's ability to accommodate periodic and rapidly changing current is used to apply a control device to achieve stable driving of the motor. Under the action of impact loads, the flow rate of current input by the power grid to the motor may decrease rapidly, and even cause the direction of current transmission to change. Therefore, by connecting the motor and the capacitor group (10) to smooth the rapid change in current flow rate caused by the impact load, the motor system's response ability to the rapidly changing rotation energy required by the rotating shaft can be enhanced, reducing the impact on the power grid. As the operating time increases, as the gas in tower A gradually flows to tower B, the pressure of tower A gradually decreases, the pressure of tower B gradually increases, the pressure difference between the two towers gradually decreases, the pressure difference of the gas between the expander inlet and outlet gradually decreases, and the flow rate also gradually decreases. This process gradually changes. Increase the opening of the regulating valve E5E10 to reduce the resistance loss at the valve.As the pressure in the expander inlet and outlet pipelines gradually changes, the gas flows from the buffer tank to the outlet. When the pressure in the pipeline connecting to the buffer tank falls below the pressure set by valves E6 and E7, valves E6 and E7 close, disconnecting the buffer tank from the pipeline. Since compressed gas requires a relatively stable pressure and flow rate, this means the required shaft power for compression must also be relatively stable. Therefore, buffer tanks are connected to both the compressor inlet and outlet to account for potential pressure and flow fluctuations. Over time, the pressure differential between the expander inlet and outlet gradually decreases, and so does the flow rate. Consequently, the shaft power output of the expander decreases, requiring the shaft power output of the motor to increase. Consequently, the current input from the power grid must be adjusted through the control system to compensate for the shaft power required by the compressed gas. The current required by the motor is connected to the overall power grid. Leveraging the grid's ability to accommodate rapidly changing currents, a control device is used to ensure stable motor drive. Simultaneously, the control mechanism adjusts the screw expander's sliding valve to regulate the flow rate, internal pressure ratio, and internal volume ratio through the expander, maintaining high expander efficiency.

[0199] Since the energy recovery process is an expansion process that reduces pressure and outputs work to the outside, the temperature of the gas at the expander outlet will drop. The temperature drop is determined by the pressure difference between the inlet and outlet of the expander. The gas at the expander outlet outputs a certain temperature of cold to the outside through the heat exchanger (20)(21) for use by other devices. The gas at the expander outlet enters Tower B, and the pressure of Tower B is equalized and increased. After heat exchange and recovery of a certain amount of cold, the temperature of the gas is lower than the temperature of the gas at the inlet of the expander. The entry of low-temperature gas reduces the temperature of Tower B. For Tower B, in the next step of the pressurization process, there is also a similar process of the entry of low-temperature gas that reduces the temperature of Tower B. This will cause the adsorption temperature of Tower B to drop in the next step of adsorption, which will cause the adsorption temperature of the adsorption tower to be lower than the desorption regeneration temperature. The low temperature during adsorption is conducive to increasing the adsorption capacity of the unit adsorbent, and the high temperature during desorption regeneration is conducive to making the desorption of the adsorbent more thorough and increasing the dynamic adsorption capacity of the adsorbent. At the same time, because the gas is energy-recovered through the expander, the pressure increase or decrease process of the adsorption tower tends to be slower. Compared with pressure swing adsorption devices that do not use energy recovery, the impact load of the gas on the adsorption tower during the pressure equalization process is reduced. Excessive and frequent impact loads can easily cause the adsorbent to pulverize, shortening its lifespan and adversely affecting the safety and fatigue life of the adsorption tower. Therefore, the use of an energy recovery device in a pressure swing adsorption device can extend the service life of the adsorbent and is also beneficial to the safety and fatigue life of the adsorption tower.

[0200] During the time period of (4-5 minutes), Tower A is in reverse discharge and Tower B is in the pressurization process. Valve A4E13 is opened, and the high-pressure gas in Tower A recovers the pressure energy and coldness through the energy recovery system, and then goes to other combustion devices through the reverse discharge buffer tank (7) and the reverse discharge compressor (8). Similar to the operation of the energy recovery system in the pressure equalization process, the impact load formed at the moment of valve opening is alleviated by the buffering effect of the regulating valve group E6E8E9, the buffer tank (13)(15)(16), the flywheel, and the capacitor group (10). The access to the large power grid and the adjustment of the expander slide valve can also play a certain buffering role on the impact load. Similarly, similar to the operation of the energy recovery system in the pressure equalization process, as the operating time increases, the pressure of the gas in Tower A gradually decreases, the pressure difference of the gas between the inlet and outlet of the expander gradually decreases, and the flow rate also gradually decreases. Therefore, the shaft power output by the expander is also gradually decreasing, and the shaft power output by the motor needs to gradually increase. The current input from the power grid needs to be gradually increased through the adjustment of the control system to supplement the shaft power required by the compressed gas. The current required by the motor needs to be connected to the overall power grid. The large power grid has the capacity to accommodate the periodically rapidly changing current. The control device is used to complete the smooth driving of the motor. The capacitor group also contributes to the smooth driving of the motor through the input and output of the current. At the same time, the slide valve of the screw expander is adjusted by adjusting the control mechanism so that the flow rate, internal pressure ratio, and internal volume ratio of the expander are suitable for the external pressure ratio and flow rate of the expander inlet and outlet after the valve is opened, so that the expander maintains a high efficiency. Similarly, the heat exchanger at the outlet of the expander outputs a certain temperature of cold water for use by other devices. The operation of the energy recovery system in the pressure equalization process is similar. Because the energy recovery system is added during the process of excessive pressure change, the service life of the adsorbent is extended, and it is also beneficial to the safety and fatigue service life of the adsorption tower. The valve E1E2B3 is opened, and the high-pressure gas in the product gas pressure regulating tank (19) is pressurized to the B tower after the pressure energy and cold water are recovered by the energy recovery system, so that the pressure of the B tower is increased to a pressure close to that of the adsorption step. During this process, the energy recovery system's response to the impact load of the open valve, the smooth driving of the system by changes in the grid input current, the cooling provided by the heat exchanger, and the slide valve's regulation of the expander's flow rate, internal pressure ratio, and internal volume ratio are similar to the sequential discharge process of Tower A. After recovering a certain amount of cooling through heat exchange, the temperature of the gas is lower than that at the expander inlet. The entry of the cooler gas lowers the temperature of Tower B.

[0201] During the time period of (5-8 minutes), Tower B is evacuated. Valve A6 is opened and Tower A is evacuated by the reciprocating pump (6). Tower B is in the adsorption state. The raw gas enters the adsorption tower B in the adsorption state through the raw gas pressure-stabilizing tank (18) and the regulating valve E4; the unadsorbed gas at the top of the tower passes through the product gas pressure-stabilizing tank (19) and the regulating valve E3 as product gas for use by other devices. Because the temperature of the gas after energy recovery received by Tower B during the previous pressure equalization, pressure boosting and charging process is lower than the gas temperature at the inlet end of the expander, the adsorption temperature of Tower B will be reduced. During the adsorption step of B, the adsorption temperature of the adsorption tower will be lower than the vacuum desorption regeneration temperature. The low temperature during adsorption is conducive to increasing the adsorption capacity of the unit adsorbent, and the high temperature during desorption regeneration is conducive to making the adsorbent desorb more thoroughly, thereby increasing the dynamic adsorption capacity of the adsorbent. During this period, no gas passes through the energy recovery device, and no energy is recovered to supply the compressor (3) for gas compression.

[0202] During the 8-9 minute period, Towers B and A are equalizing the pressure. Valves B2 and A3 are opened, and the high-pressure gas in Tower B is used to increase the pressure in Tower A. This process is similar to the equalization process during the 3-4 minute period. Towers A and B work together and alternate in a continuous cycle.

[0203] During the time period of (9-10 minutes), Tower A is pressurized and Tower B is in the reverse discharge process. Valve E1, E2, B3, the high-pressure gas in the product gas pressure stabilizing tank (19) recovers the pressure energy and cold energy through the energy recovery system, and then pressurizes Tower A, raising the pressure of Tower A to a pressure close to that of the adsorption step. Valve B4, E13 is opened, and the high-pressure gas in Tower A recovers the pressure energy and cold energy through the energy recovery system, and then passes through the reverse discharge buffer tank (7) and the reverse discharge compressor (8) and goes to other combustion devices. This process is similar to the process of Tower A in the reverse discharge and Tower B in the (4-5 minutes) period, where Tower A is in the reverse discharge and Tower B is pressurized. Towers A and B cooperate with each other and alternate to perform continuous and repetitive operations.

[0204] At this point, the adsorption tower has completed a complete adsorption-regeneration cycle and is ready for the next cycle. The operation of Tower B is the same as Tower A. Each adsorption tower alternates between the various steps. For a single tower, the operation is continuous and repetitive. For towers, the operation is continuous and repetitive.

[0205] PSA recovers the periodic, rapid pressure fluctuations during H2 separation, converting them into usable mechanical energy for H2 pressurization and external cooling, saving the electricity consumed in H2 pressurization. Compared to PSA systems without energy recovery, this system can recover 46% of the energy lost due to pressure differentials in conventional PSA systems.

[0206] Table 5 Timing chart of the two-tower pressure swing adsorption purification H2 cycle operation steps

[0207]

[0208] Example 6 This example is used to illustrate the energy recovery process in three-tower pressure swing adsorption

[0209] The tail gas also contains trace amounts of impurities such as N2, CO, CO2, CH4, and Ar. To meet the requirements for product hydrogen, a hydrogen separation unit is required for separation and purification. Due to the high operating pressure of the upstream unit, the feed gas pressure entering the H2 pressure swing adsorption separation unit is relatively high. At the same time, the H2 after separation needs to be pressurized to 4.2MPa(G).

[0210] Raw gas conditions:

[0211]

[0212]

[0213] Flow rate: 2000Nm 3 / h(dry basis)

[0214] Pressure: 2.2MPa(G)

[0215] Temperature: ≈32℃

[0216] Total H2O, O2, NH3, CH3OH, chlorine, phosphorus, arsenic, fluorine, HCN: ≤0.1ppm

[0217] The H2 is separated and purified by a pressure swing adsorption purification device equipped with a special adsorbent for H2 separation. The separation steps include: adsorption, pressure equalization and reduction, reverse pressure release, vacuuming, pressure equalization and boosting, and final pressure boosting. In the steps involving pressure changes: pressure equalization, reverse pressure release, and final pressure boosting, an energy recovery and pressurization coupling device is used to recover energy and simultaneously complete the special separation and purification of H2. The energy recovery and pressurization coupling device is a system composed of a turbine expander, a compressor, an electric compressor, and its auxiliary capacitor group, a regulating valve group, a flywheel, multiple buffer tanks, and also includes a complex system such as a gearbox and a control system. A buffer tank of a certain volume is added before the pressurized H2 enters the compressor in the energy recovery device and after it leaves the energy recovery device to smooth out the fluctuations in the pressure and flow of the pressurized H2 and keep it basically stable.

[0218] like Figure 10 shown.

[0219] The energy recovery process in each operating step of the apparatus coupling pressure swing adsorption and energy recovery and pressurization has a similar process. For the valve opening moment in the operating step conversion process in the operating process, the pressure in the pipeline is large, the pressure difference of the regulating expander inlet and outlet is large, so a large impact load is caused, which affects the smooth and safe operation of the equipment and the service life of the equipment. Therefore, by adjusting the valve E2E5, the pressure difference and flow rate of the expander inlet and outlet are adjusted, the opening of the regulating valve E2E5 is reduced at the moment of valve opening, the corresponding adsorption tower is pressurized to reduce the impact of the impact load on the expander. The buffer tank (13) (14) (15) (16) connected to the expander inlet and outlet pipelines is also used for buffering, when the pressure in the pipeline connected to the buffer tank is higher than the pressure set by the valve E6E7E8E9, the valve E6E7E8E9 is opened, the buffer tank is connected to the pipeline to make the gas flow into the buffer tank, reducing the amount of gas entering the expander to reduce the impact of the impact load, and the required time for the action of the expander regulating mechanism is ensured, so that the deflection angle of the inlet guide vane of the turbine expander or the opening of the adjustable nozzle is adjusted, the flow rate and pressure difference through the expander are adjusted to adapt to the pressure difference and flow rate at the inlet and outlet of the expander after the valve is opened. The pressure energy acting on the expander drives the shaft to rotate and is converted into mechanical energy of the shaft. Since the impact load formed when the valve is opened is easy to drive the shaft speed to accelerate, the change of the shaft speed is not conducive to the formation of the resultant force with the motor to drive the compressor to complete the compression process of another gas. By increasing the flywheel with a certain size and mass distribution on the rotating shaft, the moment of inertia of the shaft is increased, so that the acceleration obtained by the rotating shaft is reduced under the same torque. The current required by the motor needs to be connected to the overall power grid, and the large power grid has the capacity to accommodate the periodically rapidly changing current. The control device is used to complete the smooth driving of the motor. Under the action of the impact load, the current flow input by the power grid to the motor may rapidly decrease, or even change the direction of the current flow, so the motor and the capacitor bank are connected to suppress the rapid change of the current flow caused by the impact load, which can strengthen the response ability of the motor system to the rotating energy required by the rotating shaft and reduce the impact on the power grid. With the increase of the running time, the gas in the high-pressure tower gradually flows to the low-pressure tower or the pressure tank, the pressure of the high-pressure tower gradually decreases, the pressure of the low-pressure tower gradually increases, the pressure difference between the two towers gradually decreases, the pressure difference between the inlet and outlet of the expander gradually decreases, and the flow rate also gradually decreases. This process gradually changes. The opening of the regulating valve E2E5 is increased to reduce the resistance loss at the valve. With the gradual change of the pressure in the pipeline at the inlet and outlet of the expander, the gas gradually changes from flowing into the buffer tank to flowing out of the buffer tank, when the pressure in the pipeline connected to the buffer tank is lower than the pressure set by the valve E6E7E8E9, the valve E6E7E8E9 is closed, and the buffer tank is no longer connected to the pipeline.Since the compressed gas requires a relatively stable pressure and flow rate, the required shaft power for the compressed gas must also be relatively stable. Therefore, buffer tanks are connected to the compressor inlet and outlet to mitigate potential pressure and flow fluctuations. Over time, the pressure differential between the expander inlet and outlet gradually decreases, and so does the flow rate. Consequently, the expander's shaft power output also decreases, requiring the motor's shaft power to gradually increase. Consequently, the grid current needs to be adjusted through the control system to gradually increase to meet the shaft power requirements of the compressed gas. The current required by the motor needs to be connected to the overall grid. Leveraging the grid's ability to accommodate rapidly fluctuating currents, a control device is employed to ensure stable motor drive. Simultaneously, the control mechanism adjusts the deflection angle of the turbine expander's inlet guide vanes or the opening of the adjustable nozzle, regulating the flow rate and pressure differential through the expander to maintain high efficiency. Because the energy recovery process involves an expansion process that reduces pressure and outputs work, the temperature of the gas at the expander outlet decreases. The extent of this temperature drop is determined by the pressure differential between the expander inlet and outlet. The gas at the expander outlet then flows through a heat exchanger to deliver cooling at a specific temperature for use by other devices. The gas at the outlet of the expander enters the low-pressure tower, and during the process of increasing the pressure of the low-pressure tower, the temperature of the gas after heat exchange and recovery of a certain amount of cold is lower than the temperature of the gas at the inlet of the expander. The entry of the low-temperature gas reduces the temperature of the low-pressure tower. For the low-pressure tower, the pressure increase process in the next step also involves a similar process of the entry of low-temperature gas, which reduces the temperature of the low-pressure tower. This will cause the adsorption temperature of the low-pressure tower to decrease during the adsorption step after the pressure increase is completed, which will cause the adsorption temperature of the adsorption tower to be lower than the desorption regeneration temperature. The low temperature during adsorption is conducive to increasing the adsorption capacity per unit adsorbent, and the high temperature during desorption regeneration is conducive to making the adsorbent desorb more thoroughly and increasing the dynamic adsorption capacity of the adsorbent. At the same time, since the gas recovers energy through the expander, the pressure increase or decrease process of the adsorption tower tends to be slow, which reduces the impact load of the gas on the adsorption tower during the pressure equalization process compared to a pressure swing adsorption device that does not use energy recovery. Excessive and frequent impact loads will make the adsorbent easy to pulverize, reducing the life of the adsorbent, and also have an adverse effect on the safety and fatigue service life of the adsorption tower. Therefore, the use of an energy recovery device in a pressure swing adsorption device will extend the service life of the adsorbent, and is also beneficial to the safety and fatigue service life of the adsorption tower.

[0220] Simply put, a buffer tank and regulating valve assembly are incorporated into the pressure swing adsorption (PSA) coupled energy recovery and pressurization system to smooth out fluctuations in gas pressure or flow within the pipeline. A turbine expander recovers the energy of the PSA gas, converting it into mechanical energy for the shaft. A flywheel of a defined size and mass distribution is incorporated into the energy recovery system to increase the shaft's moment of inertia, thereby smoothing out the periodic and rapid fluctuations in the shaft's rotational energy. The control system then determines the required output of the electric compressor based on the system's total energy needs, controlling the motor output. The electric compressor or electric pump then provides energy to supplement the remaining energy required to complete the H2 supercharging process. The electric motor is connected to a capacitor bank. When current fluctuates significantly, the battery pack can quickly smooth out the rapid current fluctuations, enhancing the motor system's response to the rapidly changing shaft rotational energy demand. The motor's current needs to be connected to the overall power grid, leveraging the grid's ability to accommodate periodic and rapid current fluctuations. A control device is then used to smoothly drive the motor. This recovers the periodic, rapid changes in pressure energy during the pressure swing adsorption (PSA) H2 separation process and converts them into conventional, usable mechanical energy to power the H2 pressurization process, saving the electrical energy consumed in H2 pressurization. Compared to a PSA system without an energy recovery device, it can recover 46% of the energy lost due to pressure differentials in conventional PSA systems. For the PSA process, according to the three-tower PSA H2 purification cycle operating steps (Appendix 1), each adsorption tower alternates through the aforementioned steps, with a single tower performing a repetitive, continuous operation, and towers coordinating and alternating to perform a repetitive, continuous operation.

[0221] The reverse venting and exhaust air are used as waste gas to the waste gas flare network in the plant area, and the H2 with a purity of ≥99.9% is obtained through the H2 adsorption separation device, which is 1300Nm 3 / h, the rest is about 0.03% CO, about 0.03% CO2, about 0.03% N2, about 0.01% Ar+CH4; reverse venting and air extraction 700Nm 3 / h, of which CO is about 31.94%, CO2 is about 28.59%, N2 is about 29.22%, H2 is about 9.37%, and CH4 is about 0.88%.

[0222] The process of separating H2 by pressure swing adsorption is explained using Tower A as an example:

[0223] (a) Adsorption (0-2 min): At a pressure of 2.2 MPa, valve A4 is opened to allow the feed gas to enter the fixed bed for adsorption. Adsorption ceases before the adsorption front reaches the bed outlet, leaving a fresh bed between the adsorption front and the bed outlet. The H2 obtained at the top of the tower is discharged as product gas through the open valve A1 at the top of the tower. The adsorption pressure is close to the feed gas pressure.

[0224] (b) Adsorption (2-3 min): while A column is adsorbing, the top of A column is connected to B column which is under pressure, and the partial H2 from the top of A column is used to pressurize B column, and the energy is recovered by the energy recovery and pressurization coupling device, the valves A1, A4 are opened, the valves A2 of A column, B3 of B column, E3, E6, E7 are opened, when the pressure in the tank connected by E6 is lower than 1.9 MPa, E6 is closed, when the pressure in the tank connected by E7 is lower than 1.4 MPa, E7 is closed. The regulating valve groups E2, E5 are used to adjust the pressure and the gas flow in the pipeline, so that the fluctuation of the turbine expander (2) is reduced. The buffer tanks connected by E6, E7 and the regulating valve groups E2, E5 can buffer the flow and the pressure difference of the gas through the turbine expander at the moment when the valves are just opened, so that the instantaneous output of the turbine expander is reduced.

[0225] (c) Desorption (3-4 min): A column is connected to C column which is under vacuum, and the pressure is equalized, and the energy is recovered by the energy recovery and pressurization coupling device, the valves A2 of A column, C3 of C column, E3, E6, E9 are opened, when the pressure in the tank connected by E6 is lower than 1.9 MPa, E6 is closed, when the pressure in the tank connected by E9 is lower than 0.4 MPa, E7 is closed. The regulating valve groups E2, E5 are used to adjust the pressure and the gas flow in the pipeline, so that the fluctuation of the turbine expander is reduced. The buffer tanks connected by E6, E9 and the regulating valve groups E2, E5 can buffer the flow and the pressure difference of the gas through the turbine expander at the moment when the valves are just opened, so that the instantaneous output of the turbine expander is reduced. For column A, it is a process of pressure reduction, and for column C, it is a process of pressure increase. After pressure equalization, the pressure of A column is slightly higher than half of the original pressure (1.1 MPa), and the purity of the equalization gas and the product gas flowing out of the top is basically the same.

[0226] (d) Reverse (4-5 minutes): Column A is connected to a near-ambient pressure reverse venting buffer tank for the reverse venting step. The reverse venting circuit also recovers energy during this step, requiring energy recovery and pressurization coupling. Column A's bottom valves A3, E1, E4, E8, and E9 are opened. When the gas pressure in the tank connected to E8 falls below 0.9 MPa, E8 closes. When the gas pressure in the tank connected to E9 falls below 0.4 MPa, E9 closes. Control valve groups E2 and E5 are used to gradually adjust the pressure and gas flow in the pipeline, thereby reducing fluctuations in the turbine expander's operation. The buffer tank connected to valves E8 and E9 and control valve groups E2 and E5 buffer the gas flow and pressure differential through the turbine expander at the moment the valves are opened, thereby reducing the turbine expander's transient output. After the pressure equalization and decompression process is complete, the impurity front in the adsorption bed has reached the adsorption tower outlet. At this point, the adsorption tower pressure is reduced to near-ambient pressure (0.11 MPa) in the reverse direction of adsorption. During this process, the impurities adsorbed in the adsorption tower begin to be desorbed from the adsorbent in large quantities. The reverse bleed gas passes through the reverse bleed gas buffer tank (7) and the reverse bleed gas compressor (8) and then goes to other combustion devices.

[0227] (e) Vacuuming (5-6 min): After the inversion step, the adsorption tower is evacuated to allow for more thorough regeneration of the adsorbent and complete desorption. Open valve A5 at the bottom of tower A and use a vacuum pump (6) to reversely evacuate the bed until the pressure inside the tower is reduced to -0.09 MPa.

[0228] (f) Equalization (6-7 minutes): Tower A, which is in a vacuum state, is connected to Tower B, which has completed the adsorption process, for the equalization step. This is a pressurization process for Tower A, and a depressurization process for Tower B. Valve A3 at the bottom of Tower A and valves B2, E3, E6, and E9 at the top of Tower B are opened. This step requires energy recovery and pressurization coupling to recover energy. The process is similar to the equalization step (c), except that Tower A becomes a low-pressure tower that receives gas and is equalized and increased in pressure. After equalization, the pressure in Tower A is slightly lower than half the pressure of the adsorption step (0.9 MPa). The purity of the equalized gas is basically the same as the purity of the product gas flowing out of the top of Tower B.

[0229] (g) Idle (7-8 min): The valves at the top and bottom of Tower A are closed, there is no gas entering or leaving Tower A, and Tower A is in a waiting state.

[0230] (h) Pressurization (8-9 minutes): Tower A, after equalization, is connected to the top outlet of Tower C. Tower A is pressurized with some H2, raising the internal pressure of Tower A to near the adsorption pressure (2.1 MPa). Valve A3 at the bottom of Tower A and valves C2, E3, E6, and E7 at the top of Tower C are opened. This step, which involves energy recovery and pressurization coupled with a device, recovers energy. This process is similar to the adsorption process in (b), except that Tower A becomes the pressurized low-pressure tower that receives gas.

[0231] At this point, the adsorption tower has completed a complete adsorption-regeneration cycle and is ready for the next cycle. The operation process of the other three towers is the same as Tower A. Each adsorption tower alternates the above steps. For a single tower, the operation is repeated continuously. For other towers, the operation is repeated continuously.

[0232] The specific operating steps, operation times, and timings are shown in Table 6. The control and operation of the valve opening status of each tower during this period are shown in Table 79. The timing table (Table 6) and the valve opening control table (Table 7) indicate that the energy recovery system is in continuous operation, with pressure equalization, reverse discharge, and pressure charging processes alternating in a continuous cycle. The energy recovery system operates continuously, recovering energy from these three operating steps, preventing the energy recovery system from idling, facilitating safe and stable operation of the machine, and avoiding adverse effects on the machine and energy loss.

[0233] Table 6 Three-tower pressure swing adsorption purification H2 cycle operation steps sequence table

[0234]

[0235] Table 7 Valve opening control table of each tower

[0236]

[0237] Example 7

[0238] A method for preparing a supported metal organic framework CO adsorbent is as follows:

[0239] (1) Copper nitrate trihydrate and cerium nitrate hexahydrate (a total of 0.6 mmol) were dissolved in 15 mL of deionized water at a molar ratio of 19:1 to obtain a blue, clear copper nitrate-cerium nitrate mixture;

[0240] (2) 0.3 mmol of 1,3,5-pyromellitic acid (H3BTC) was dissolved in a mixed solution of ethanol and 8 mL of dimethylformamide (DMF) in a volume ratio of 1:1, and commercially available NaY molecular sieves were added thereto. The molar ratio of NaY molecular sieves to copper nitrate-cerium nitrate was 1:50.

[0241] (3) After mixing and stirring the solutions of steps (1) and (2) at room temperature for 5 minutes, ultrasonically control the mixture at 150W for 8 minutes, heat the mixture to 250°C at a heating rate of 3-5°C / min, and keep the temperature for 20 hours. Then, cool the mixture to room temperature at a cooling rate of 2°C / min to generate a precipitate, centrifuge, and filter. Wash the resulting crystals with anhydrous ethanol three times.

[0242] (4) Add 3.0 mL of 0.1 mmol / L AgNO3 ethanol solution to the obtained crystals, irradiate with 80W ultrasound for 1 hour, immerse in dark for 12 hours, centrifuge and filter; wash the obtained crystals with anhydrous ethanol 3 times, irradiate with 100W ultraviolet light for 10 to 13 hours (to make Ag + Oxidized to Ag), centrifuged and washed with anhydrous ethanol, dried at 110 ° C, and oxidized with a mixture of O2 / He with an O2 volume fraction of 2% at 250 ° C for 1 h (to make Ag and Cu 2+ The reaction generates Ag + and Cu + ), flow rate 50ml·min -1 , obtain powder;

[0243] (5) CuCl, AgCl with a molar ratio of 10:1:0.25 and a molar weight of 1 mmol / 0.1 mmol / 0.025 mmol, respectively, and rare earth powder (a mixture of yttrium, lanthanum, and cerium, with a mass ratio of 1:1:2) were dissolved in 30 mL of 0.4 mol / L hydrochloric acid solution, and 0.225 g of the powder obtained in step (4) was added. The mixture was ultrasonically irradiated at 100 W for 20 min, stirred at room temperature for 2 h, and the solvent was evaporated using a rotary evaporator and placed in a vacuum drying oven. After drying for 12 h, the mixture was activated at 220 ° C. in a H2 atmosphere for 5 h to obtain a powder material.

[0244] (6) Weigh a certain amount of the powder material obtained in step (5), methyl cellulose, and a 5% citric acid aqueous solution (the mass ratio of the three, excluding water, is 10:0.3:0.2), place them in a kneader and stir them evenly. Then, place the mixture in a centrifugal shot blasting machine for molding. The molded product is dried at 200°C to obtain round particles with a diameter of about 2 mm, i.e., the supported metal organic framework CO adsorbent molded body.

[0245] Comparative Example 7-1

[0246] In step (1), the solution contains only copper nitrate and no cerium nitrate or rare earth powder (yttrium, lanthanum, cerium). Other conditions are the same as those in Example 1.

[0247] Comparative Example 7-2

[0248] In step (2), no NaY molecular sieve is included, and the rest is the same as in Example 1.

[0249] Comparative Example 7-3

[0250] In step (5), no AgCl is added, only Cu + CO was adsorbed, and the other procedures were the same as in Example 1.

[0251] result:

[0252] The adsorption capacity of each adsorbent for carbon monoxide was tested using the physical and chemical adsorption instrument ASAP 2020. The adsorption capacity of the adsorbent in Example 7 for carbon monoxide was 72 L / g when the operating conditions were 25°C and the pressure was 0.1 MPa. The adsorption capacities of comparative examples 7-1 to 7-3 were 67 mL / g, 64 mL / g, and 59 mL / g, respectively. The adsorption capacity of conventional commercially available adsorbents was between 20 and 50 mL / g. The adsorption capacity of the adsorbent of the present invention was greatly improved compared with the existing commercially available adsorbents.

[0253] When the sulfide accumulates to 0.2% sulfur by weight of the adsorbent, the adsorption capacity of Example 7 decreases by 4%, the adsorption capacity of Comparative Example 7-1 decreases by 21%, and the adsorption capacity of Comparative Examples 7-2 to 7-3 decreases by 5%, respectively. The adsorbent of Example 7 has good sulfur resistance.

Claims

1. A method for producing natural gas from coal gas, characterized in that: include: (1) preparing a mixture of H2 and CO, the preparation process comprising: performing a partial shift reaction on coal gas to produce hydrogen, and separating N2 from the system by a pressure swing adsorption separation method before the partial shift reaction step; When separating CO and N2 by the pressure swing adsorption separation method, H2 is used as a flushing gas to obtain a gas containing CO and H2 for the partial shift hydrogen production reaction; After the partial conversion hydrogen production reaction, the gas is divided into two parts, one part continues to undergo the conversion reaction to completely convert CO into H2, and then H2 is extracted as the flushing gas, and the other part is used to obtain the H2 and CO mixed gas. Alternatively, before the partial conversion hydrogen production reaction, part of the coal gas is taken to undergo the conversion hydrogen production reaction, and then H2 is extracted as the flushing gas; when flushing the flushing gas, a high-pressure flushing desorption method is used, combined with at least one of low-pressure flushing and vacuuming, to desorb the mixed gas containing CO and natural gas, or containing CO and H2; high-pressure flushing desorption refers to a high-pressure gas with a feed flushing gas pressure of 0.3 to 10 MPa; Before separating CO and N2 by the pressure swing adsorption separation method, a first impurity removal pretreatment is also performed. The first impurity removal pretreatment includes one or a combination of dust removal, phosphorus removal, arsenic removal, dehydration, dehydrogenation and deoxygenation, desulfurization, CO2 removal, or CH4 removal. The CO2 removal method in the impurity removal pretreatment is pressure swing adsorption. The impurity removal pretreatment process can co-produce industrial nitrogen. (2) The H2 and CO mixed gas undergoes a methanation reaction to produce natural gas.

2. The method for producing natural gas from coal gas according to claim 1, characterized in that: The coal gas mainly includes blast furnace gas or converter gas; the coal gas may also contain coke oven gas, other tail gas or purge gas, one or a mixture of two or more thereof.

3. The method for producing natural gas from coal gas according to claim 1, characterized in that: The first impurity removal pretreatment includes: desulfurization and CO2 removal, and CO2 removal and desulfurization are carried out simultaneously or CO2 removal is carried out after the desulfurization step.

4. The method for producing natural gas from coal gas according to claim 3, characterized in that: The first impurity removal pretreatment further includes: CH4 removal and / or dehydrogenation and deoxygenation; CH4 removal is performed after the desulfurization step; and dehydrogenation and deoxygenation are performed after the CH4 removal step.

5. The method for producing natural gas from coal gas according to claim 1 or 4, characterized in that: After the partial conversion hydrogen production reaction, the gas is divided into two parts. One part continues to undergo the conversion reaction to completely convert CO into H2, and then removes carbon dioxide to extract H2 as the flushing gas. The other part removes carbon dioxide to obtain the H2 and CO mixed gas, or the other part directly undergoes methanation reaction, and the CO2 produced by the conversion reaction is removed after the methanation reaction.

6. The method for producing natural gas from coal gas according to claim 1, characterized in that: The method for preparing the H2 and CO mixed gas includes: performing a partial conversion reaction on coal gas to produce hydrogen to obtain a gas containing CO, N2 and H2, separating CO by a pressure swing adsorption separation method, and then separating N2 and H2. The separated hydrogen is used as a flushing gas for the CO separation.

7. The method for producing natural gas from coal gas according to claim 6, characterized in that: The coal gas is subjected to desulfurization and / or dehydrogenation and deoxygenation before undergoing partial conversion hydrogen production reaction; dehydrogenation and deoxygenation are performed after the desulfurization step; after the partial conversion hydrogen production reaction is completed, carbon dioxide is removed before pressure swing adsorption separation of CO.

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