Method and system for preparing H2 through combined conversion of blast furnace gas and converter gas

Abstract

The invention belongs to the technical field of iron and steel smelting, and relates to a method and system for preparing H2 through combined conversion of blast furnace gas and converter gas. Comprising the following steps: mixing and pressurizing gas: pressurizing converter gas and blast furnace gas respectively, and mixing in proportion; pretreatment: carrying out water washing purification and desulfurization treatment on the mixed gas; heating the purified mixed gas, and mixing with steam; coal gas conversion treatment: carrying out two-stage CO conversion treatment on the mixed coal gas; separation and purification: carrying out heat recovery, gas-liquid separation and washing purification treatment on the converted coal gas; shift gas treatment: carrying out vacuum pressure swing adsorption separation and purification to obtain hydrogen-rich gas with H2 content of more than or equal to 90% and desorbed gas containing CO2 and N2; the desorbed gas is pressurized, liquid CO2 with the purity larger than or equal to 99.5% and nitrogen-rich gas with the purity larger than or equal to 70% are obtained through liquefaction, rectification and purification, the problem that CO and N2 in the blast furnace gas and the converter gas are difficult to efficiently separate due to similar physical properties is solved, the technological process is simplified, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel smelting, and relates to a method and system for jointly converting blast furnace gas and converter gas to prepare H 2 . Background Art

[0002] The iron and steel industry is a basic industry for the development of the national economy. As the production and consumption center of world steel, China currently has the largest steel production in the world. At present, 90% of China's iron and steel industry adopts the blast furnace-converter long process production technology. In the next long period, China will still be based on the blast furnace-converter production process, and most iron and steel enterprises are relatively new and difficult to be phased out in a short time. In addition, due to the differences in the energy structure of China's iron and steel industry and the grade of iron ore resources from other countries, China's main fossil energy is coal, and the grade of iron ore resources is relatively low, and the proportion of the shaft furnace + electric furnace short process technology is relatively low. In this case, from the perspective of energy transformation, the low-carbon transformation of the iron and steel industry is to convert carbon into hydrogen or other energy, but the transformation technology is difficult and the cost is high. Therefore, the iron and steel industry can only improve the utilization efficiency of existing gas resources, optimize the energy structure and support CCUS (carbon capture, utilization and storage) as the main technical direction for the low-carbon transformation of the iron and steel industry.

[0003] In the current comprehensive utilization of gas in iron and steel enterprises, except for special processes such as coke oven gas to hydrogen and LNG with relatively high utilization added value, other thermal energy utilization methods such as using blast furnace gas, converter gas or a blend of the two with coke oven gas as fuel gas for CCPP power generation, etc., have relatively low added value. In view of this, in order to improve the comprehensive utilization value of gas in iron and steel enterprises, research scholars believe that by making full use of the chemical energy of gas and blowing a part of the gas into the blast furnace as a reducing gas, the coke ratio and coal injection volume of the blast furnace can be reduced. This utilization method can not only effectively reduce the operating cost of the blast furnace, but also improve the utilization efficiency of fossil energy and reduce the total consumption and carbon emission of national fossil fuels from the source.

[0004] Based on the above situation, how to conduct high-value comprehensive treatment of blast furnace gas and converter gas by-products of the long process production process to reduce the production cost of iron and steel has always been an important issue concerned by iron and steel enterprises. In addition, how to greatly reduce the carbon emissions of iron and steel enterprises while efficiently utilizing gas resources is also a difficult problem to be solved at present.

[0005] Some solutions have been proposed in the prior art. For example, a hydrogen production process based on desulfurization and pressure swing adsorption is adopted. After the blast furnace gas is desulfurized, pressure swing adsorption is carried out to remove CO 2and CO, removing nitrogen to obtain concentrated coal gas; then the CO is converted into hydrogen-containing shift gas through a steam shift reaction, and finally high-purity hydrogen is obtained through decarbonization pressure swing adsorption separation. Although the process of this technology is clear and easy to implement, it has obvious defects: the steam shift process will generate CO again 2 , which results in the need for two decarbonization operations in the entire process, and the separated CO 2 It cannot be recycled as product gas due to insufficient purity.

[0006] Another study proposed a blast furnace gas hydrogen production process, which uses water vapor shift followed by liquid amine absorption to recover CO 2 The core of this technology is to use precious metal-supported WMoOx catalyst to improve the stability and catalyst life of the water-gas shift reaction. However, its high-pressure water-gas shift unit (reaction pressure is usually ≥3.0MPa) and subsequent atmospheric pressure absorption method to enrich CO 2 There are serious conflicts in the process conditions, and additional decompression and recompression equipment needs to be added, resulting in a significant increase in operating costs.

[0007] There are also technical solutions that attempt to achieve CO separation by coupling water vapor shift and adsorption 2 and H 2 Synchronous enrichment, the specific process includes dry purification (desulfurization and decyanation) of blast furnace gas, heating it to the reaction temperature, mixing it with water vapor and entering the catalytic reactor for transformation coupling reaction to generate CO 2 and H 2 The mixed gas is then separated by a special adsorbent. 2 The remaining gas is purified by molecular sieve to obtain hydrogen. However, there are multiple obstacles in the implementation of this scheme: first, the reaction needs to be carried out at 320-400℃ and 1.0-6.0MPa, while the temperature of the front-end coal gas after purification is only 160-220℃ and the pressure is 0.18-0.30MPa, and a multi-stage high-pressure compressor is required, which leads to a significant increase in equipment investment and energy consumption; second, CO 2 The purity after adsorption separation is only about 95%, which cannot meet the needs of oil recovery and storage (required ≥99%) or chemical synthesis. In addition, the process requires multiple pressure swing adsorption separation and pressurization operations, and a gas expander to recover energy, so the operating cost remains high. At the same time, due to the low CO content of the raw gas (typical blast furnace gas CO content is 22-25%), the H 2 The yield is insufficient and the system energy efficiency is less than 40%.

[0008] Since the main reducing component of converter gas and blast furnace gas produced during the smelting process of the steel industry is CO, but it also contains a large amount of N 2 and CO 2 Components, including CO 2is relatively easy to remove, and there are already mature separation processes. However, CO and N 2 Due to their very similar physical and chemical properties in terms of molecular weight, molecular diameter, boiling point, density, etc., it is difficult to separate them. The current separation process flow is long, the process is complex, and the cost is high. SUMMARY OF THE INVENTION

[0009] In view of this, the purpose of the present invention is to provide a method and system for jointly converting blast furnace gas and converter gas to prepare H 2 to solve the problems that CO and N in blast furnace gas and converter gas in the iron and steel industry are difficult to efficiently separate due to similar physical properties, the process flow is complex and the cost is high, as well as the problems of insufficient CO 2 purity and inability to be directly recycled in traditional processes. 2

[0010] In the first aspect, the present invention provides a method for jointly converting blast furnace gas and converter gas to prepare H 2 , including the following steps:

[0011] Gas mixing and pressurization: Pressurize converter gas and blast furnace gas to 0.5 - 1.0 MPa respectively, and mix the pressurized converter gas and blast furnace gas in proportion;

[0012] Pretreatment: Wash and purify the mixed gas, and perform desulfurization treatment; Heat the purified mixed gas and mix it with steam;

[0013] Gas conversion treatment: Perform two-stage CO conversion treatment on the pretreated mixed gas to obtain converted gas with CO removed;

[0014] Separation and purification: Recover heat, perform gas-liquid separation and wash and purification treatment on the converted gas;

[0015] Converted gas treatment: Use vacuum pressure swing adsorption to separate and purify to obtain a hydrogen-rich gas with H 2 content ≥ 90% and a desorbed gas containing CO 2 , N 2 ;

[0016] Desorbed gas treatment: Pressurize the desorbed gas to 2.0 - 2.5 MPa, and obtain liquid CO with a purity ≥ 99.5% 2 and nitrogen-rich gas with a purity ≥ 70% through liquefaction and rectification purification. The liquid CO 2 is stored and used for industrial applications after storage, and the nitrogen-rich gas is sent to the nitrogen production device after recovering cold energy.

[0017] ​Optionally, in the "gas mixing and pressurizing" step, the converter gas is drawn from the existing converter gas pipeline network, and the blast furnace gas is drawn from the existing blast furnace gas pipeline network; or, the converter gas is drawn from the existing converter gas pipeline network, and the blast furnace gas is drawn from the pipeline located behind the blast furnace top gas wet dust removal system and before the TRT device.

[0018] Optionally, in the "gas mixing and pressurizing" step, the mixing ratio of converter gas and blast furnace gas is 0.5:0.5 to 0:1.

[0019] Optionally, before the "gas shift treatment" step is performed, at least one of the following conditions must be met:

[0020] The dust content of the pre-treated mixed gas is less than 5mg / Nm 3 ;

[0021] The hydrogen sulfide content of the pretreated mixed gas is ≤0.05ppm;

[0022] The temperature of the pretreated mixed gas reaches 180℃~240℃;

[0023] H in the mixed gas components after pretreatment 2 The ratio of O to CO is 1.2:1 to 1.5:1.

[0024] Optionally, in the "gas shift treatment" step, the first-level CO conversion treatment uses an iron-based catalyst to achieve the CO main reaction and high-grade heat energy recovery; the second-level CO conversion treatment uses a copper-based catalyst to complete the deep conversion of residual CO and reaction balance control.

[0025] Optionally, when performing the primary CO conversion treatment and the secondary CO conversion treatment, at least one of the following conditions must be met:

[0026] The temperature of the converted coal gas after the first-stage CO conversion treatment is ≥300℃;

[0027] The CO content in the converted coal gas after the secondary CO conversion treatment is ≤0.5% (dry basis);

[0028] The pressure drop of the converted coal gas after two-stage CO conversion treatment is ≤0.15MPa.

[0029] Optionally, in the "separation and purification" step, the standard for water washing and purification of the conversion gas is: the methanol content in the conversion gas is ≤20ppm, and the ethanol content is ≤20ppm.

[0030] Optionally, in the "separation and purification" step, the separated hydrogen-rich gas is directly introduced into a low-carbon blast furnace smelting system and used as a reducing agent in blast furnace smelting.

[0031] Second aspect, the present invention provides a system for jointly converting blast furnace gas and converter gas to prepare H 2 using the method for jointly converting blast furnace gas and converter gas to prepare H 2 as described above, which includes a gas mixing and pressurizing unit, a pretreatment unit, a gas conversion treatment unit, a separation and purification unit, a converted gas treatment unit, and a desorbed gas treatment unit connected in sequence;

[0032] The gas mixing and pressurizing unit includes a converter gas compressor and a blast furnace gas compressor. After the outlets of the two are converged, they are jointly connected to the pretreatment unit;

[0033] The pretreatment unit includes a mixed gas water washing tower, a mixed gas preheater, and a mixed gas desulfurizer connected in sequence. The outlets of the converter gas compressor and the blast furnace gas compressor are converged and then connected to the mixed gas water washing tower, and the outlet of the mixed gas desulfurizer is connected to the gas conversion treatment unit;

[0034] The gas conversion treatment unit includes a primary conversion reactor and a secondary conversion reactor; the mixed gas desulfurizer is connected to the primary conversion reactor, the outlet of the primary conversion reactor is connected to the mixed gas preheater, and then connected to the secondary conversion reactor through a boiler heater; the secondary conversion reactor is connected to the separation and purification unit;

[0035] The separation and purification unit includes a heat exchanger, a cooler, a first gas-liquid separator, and a first water washing tower connected in sequence; the outlet of the secondary conversion reactor is connected to the heat exchanger, and the outlet of the first water washing tower is connected to the converted gas treatment unit;

[0036] The converted gas treatment unit includes a second gas-liquid separator and an adsorber; the top outlet of the adsorber is connected to a hydrogen-rich gas buffer, and its bottom outlet is connected with a pressure equalizer, a vacuum pump, and a mixer to desorb the CO 2 , N 2 components adsorbed by the adsorber to form desorbed gas;

[0037] The desorbed gas treatment unit includes a desorbed gas compressor, a desorbed gas dryer, a desorbed gas precooler, a refrigeration unit, a rectification column, and a carbon dioxide storage tank connected in sequence. The outlet of the mixer is connected to the desorbed gas compressor; through pressurization, liquefaction, and rectification purification operations, the desorbed gas is processed into liquid CO 2 with a purity ≥ 99.5% and nitrogen-rich gas with a purity ≥ 70%.

[0038] Optionally, the inlet of the converter gas compressor is connected to the converter gas pipeline network, and the inlet of the blast furnace gas compressor is connected to the blast furnace gas pipeline network or to the pipeline network located after the wet dust removal system of the blast furnace top gas and before the TRT device.

[0039] Optionally, the primary shift reactor is internally provided with an iron-based catalyst bed, and the secondary shift reactor is internally provided with a copper-based catalyst bed.

[0040] Optionally, both the primary shift reactor and the secondary shift reactor have a steam inlet, a demineralized water inlet, and a steam outlet.

[0041] Optionally, the pretreatment unit further includes a first water washing tower circulation pump, which is connected to the first water washing tower in a closed loop to return the water absorbing impurities to the first water washing tower for recycling after treatment.

[0042] Optionally, the separation and purification unit further includes a demineralized water booster pump, which is connected to the heat exchanger to supply demineralized water to the heat exchanger.

[0043] Optionally, the separation and purification unit further includes a second water washing tower circulation pump, which is connected to the second water washing tower in a closed loop to return the water absorbing impurities to the second water washing tower for recycling after treatment.

[0044] The beneficial effects of the present invention are as follows:

[0045] The method and system for jointly converting blast furnace gas and converter gas to prepare H 2 closely conform to the national conditions of our country and the actual situation of the iron and steel industry, and give full play to the unique process advantages of the iron and steel industry. Aiming at the problem of difficult separation of CO and N 2 in converter gas and blast furnace gas generated during the iron and steel smelting process, the present invention adopts the idea of gas component conversion, converting the CO component into H 2 component, thus cleverly avoiding the challenge of difficult separation of CO and N 2 due to their similar physical and chemical properties, and converting it into the relatively easy-to-realize separation of H 2 and N 2 . This transformation not only simplifies the separation process and reduces costs, but also significantly improves the utilization efficiency of solid fossil fuels by converting "carbon" from fuel into a smelting reducing agent.

[0046] By implementing the present invention, the iron and steel smelting industry can significantly reduce the consumption of solid fuels during the smelting process, which not only helps to reduce energy consumption, but also reduces carbon emissions from the source, promoting the iron and steel smelting industry towards a green, low-carbon, and efficient development path. At the same time, the present invention utilizes the gas shift reaction, vacuum pressure swing adsorption to separate and purify hydrogen, and combines with a cryogenic separation system, which can not only produce a hydrogen-rich gas with a relatively high H 2 content at low cost as a reducing agent for low-carbon blast furnace smelting or hydrogen-based shaft furnace smelting, but also produce high-purity liquid carbon dioxide, providing valuable resources for fields such as oil displacement, storage, or chemical synthesis.

[0047] In addition, the implementation of the present invention also realizes the recycling of the by-product gas generated in the iron and steel smelting process. The hydrogen-rich gas is used as a reducing agent for blast furnace smelting, effectively reducing the coke ratio and the amount of pulverized coal injection in the blast furnace, and further reducing the carbon emission per ton of steel. At the same time, through the vacuum pressure swing adsorption and cryogenic separation processes, the present invention can also separate hydrogen-rich gas, liquid high-purity carbon dioxide, and nitrogen-rich gas, and these products all have broad application prospects and market values.

[0048] In summary, the present invention not only solves the problem of difficult separation of CO and N in the iron and steel smelting process 2 but also improves the energy utilization efficiency, reduces carbon emissions, and provides strong technical support for the green development of the iron and steel smelting industry.

[0049] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0051] Figure 1 FIG. 1 is a schematic structural diagram of a system for jointly converting blast furnace gas and converter gas to prepare H 2 of the present invention;

[0052] Figure 2 FIG. 2 is a schematic structural diagram of a system for jointly converting blast furnace gas and converter gas to prepare H 2 of the present invention.

[0053] Reference numerals:

[0054] 1 - Converter gas compressor; 2 - Blast furnace gas compressor; 3 - First water washing tower; 4 - First water washing tower circulation pump; 5 - Mixed gas preheater; 6 - Mixed gas desulfurizer; 7 - Primary conversion reactor; 8 - Secondary conversion reactor; 9 - Heat exchanger; 10 - Cooler; 11 - Demineralized water pressurizing pump; 12 - First gas-liquid separator; 13 - Second water washing tower; 14 - Second water washing tower circulation pump; 15 - Second gas-liquid separator; 16 - Adsorber; 17 - Hydrogen-rich gas buffer; 18 - Equalizer; 19 - Mixer; 20 - Vacuum pump; 21 - Desorbed gas compressor; 22 - Desorbed gas dryer; 23 - Desorbed gas precooler; 24 - Refrigeration unit; 25 - Rectification tower; 26 - Carbon dioxide storage tank; 27 - Boiler heater. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0056] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be understood as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0057] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and cannot be understood as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0058] In the prior art, for the comprehensive utilization of blast furnace gas and converter gas produced as by-products in iron and steel smelting, although a process of water-gas shift combined with adsorption separation has been proposed, there are still significant defects: First, since CO and N 2 have similar physical properties such as molecular weight and boiling point, separation requires multi-stage compression and adsorption, with a complex process and high energy consumption; Second, in the traditional process, the separation purity of CO 2 is only about 95%, which is difficult to meet the requirements of oil displacement or chemical synthesis, and the two decarbonization operations result in low efficiency; Third, the process conditions of high-pressure water-gas shift and subsequent atmospheric pressure absorption conflict, and additional decompression and recompression equipment need to be added, resulting in a sharp increase in operating costs; Fourth, when using blast furnace gas alone, the CO content is insufficient, and the H 2 production rate after conversion is low, and the system energy efficiency is relatively low.

[0059] In response to the above problems, the present invention proposes a "component conversion - efficient separation" technical route: converting CO in the gas into H 2 through two-stage conversion reactions, avoiding the separation of CO and N 2Separation problems, and matching vacuum pressure swing adsorption and cryogenic distillation technology to achieve H 2 , high purity CO 2 Specifically, CO is converted by mixing converter gas with high CO content with blast furnace gas and combining iron-based and copper-based catalysts with graded temperature control reactions; then CO is absorbed by vacuum pressure swing adsorption. 2 With N 2 , get H 2 The purity of hydrogen-rich gas is ≥90%, and the desorbed gas is pressurized, liquefied and distilled to obtain liquid CO with a purity of ≥99.5%. 2 This process transforms the traditional "fuel utilization" into a "reducing agent + carbon resource" co-production model through the reconstruction of coal gas components, cascade utilization of thermal energy and optimization of separation processes, thus improving energy efficiency, reducing carbon emissions and providing an efficient solution for the low-carbon transformation of the steel industry.

[0060] Specifically, the present invention provides a method for preparing H by combining blast furnace gas and converter gas for conversion. 2 The method is implemented by the following steps:

[0061] S1: Gas mixing and pressurization

[0062] The converter gas and blast furnace gas are pressurized to 0.5-1.0MPa by the converter gas compressor and blast furnace gas compressor respectively, and then mixed. By adjusting the mixing ratio (0.5:0.5-0:1), the CO content fluctuation in the raw gas can be flexibly matched to optimize the subsequent reaction efficiency. Among them, blast furnace gas is preferably taken from the pipeline after wet dust removal and before the TRT device to avoid pressure loss caused by TRT residual pressure power generation and reduce compression energy consumption. This step increases the density and reaction activity of the gas by pressurization, providing stable pressure conditions for subsequent processes.

[0063] S2: Preprocessing

[0064] The mixed gas enters the water scrubber, preheater and desulfurizer in sequence. The water scrubber removes dust, tar and acidic impurities in the gas by circulating water spraying, reducing the risk of subsequent equipment blockage; the preheater heats the gas to 180℃~240℃ to meet the active temperature requirements of the desulfurizer; the desulfurizer uses iron oxide or activated carbon-based catalyst to convert H 2 The sulfur content is reduced to ≤0.05ppm to avoid sulfide poisoning the conversion catalyst. At the same time, steam is added to the pretreated gas to control the H 2 The O / CO molar ratio is 1.2:1 to 1.5:1, which provides sufficient water vapor for the CO shift reaction and inhibits the occurrence of side reactions.

[0065] S3: Gas shift treatment

[0066] The pre-treated coal gas first enters the primary shift reactor. Under the action of an iron-based catalyst (Fe-Cr series), the main reaction (CO + H 2 O → CO 2 + H 2 ) is completed at 200 - 300 °C. The CO conversion rate reaches 80% - 90%, and high-grade heat energy is released (the temperature of the coal gas after the reaction is ≥ 300 °C). The steam is recovered by the waste heat boiler for the system's own use. Subsequently, the coal gas enters the secondary shift reactor and undergoes deep conversion at 180 - 220 °C under the action of a copper-based catalyst (Cu-Zn-Al series), reducing the residual CO content to ≤ 0.5% (dry basis). The two reactors achieve optimized reaction equilibrium through staged temperature control, avoiding the problem of catalyst sintering and deactivation caused by temperature rise in a single-stage reaction.

[0067] S4: Separation and purification

[0068] After the shift coal gas recovers waste heat through a heat exchanger, it is cooled to below 40 °C by a cooler. The condensate water and trace organic impurities (methanol, ethanol) are removed by a gas-liquid separator and a water wash tower to ensure that the impurity content in the coal gas is ≤ 20 ppm. The purified coal gas enters the vacuum pressure swing adsorption unit, and a composite adsorbent of molecular sieve and activated carbon is used to selectively adsorb CO 2 and N 2 , obtaining hydrogen-rich gas with a H 2 purity ≥ 90%. The adsorption stage reduces energy consumption through multi-column equalization operation, and the desorption stage uses a vacuum pump to suck and release the adsorbed CO 2 and N 2 , forming desorbed gas containing CO 2 (60% - 75%) and N 2 (25% - 40%).

[0069] S5: Treatment of desorbed gas

[0070] After the desorbed gas is compressed to 2.0 - 2.5 MPa, moisture is removed through a dryer, and CO 2 is pre-cooled to below -30 °C for liquefaction. Then, through a distillation column, liquid CO 2 with a purity ≥ 99.5% (for oil displacement or chemical synthesis) and nitrogen-rich gas (N 2 ≥ 70%) are separated. The nitrogen-rich gas is cooled to -150 °C by a cold energy recovery system and then returned to the nitrogen production unit to achieve cascaded utilization of cold energy. This process breaks through the separation bottleneck of the close boiling points of CO 2 and N 2 through cryogenic distillation, and at the same time reduces the liquefaction energy consumption by more than 30%.

[0071] Through the above method, the present invention efficiently converts CO in the coal gas into H 2 , and synergistically solves the problem of separating CO 2 from N 2Separation problems are finally solved, and a hydrogen recovery rate of ≥85% and a CO 2 capture rate of ≥90% are achieved. Moreover, the comprehensive energy consumption of the system is reduced by 25% - 40% compared with the traditional process. The hydrogen-rich gas can be directly used for hydrogen-rich smelting in blast furnaces, replacing 20% - 30% of coke consumption, reducing the carbon emissions per ton of steel by more than 15%, and having both economic and environmental benefits.

[0072] Based on the above method, the present invention also provides a system for jointly converting converter gas and blast furnace gas to prepare H 2 . The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The structure of the system is as shown in Figure 1 and Figure 2 . It should be noted that Figure 2 the structure shown in Figure 1 is a continuation of the structure shown in

[0073] . The two are combined to form the complete structure of the system. Specifically, the system includes a gas mixing and pressurizing unit, a pretreatment unit, a gas shift treatment unit, a separation and purification unit, a shift gas treatment unit, and a desorbed gas treatment unit. The converter gas and blast furnace gas to be processed are respectively pressurized to 0.5 - 1.0 MPa by a converter gas compressor 1 and a blast furnace gas compressor 2 and then mixed. The mixing ratio can be adjusted to 0.5:0.5 - 0:1 according to the gas component requirements. By mixing different ratios of gases, it can flexibly adapt to the fluctuations in the raw gas components, optimize the subsequent reaction conditions, and at the same time make full use of the high reducibility of CO in the blast furnace gas to provide a sufficient reactant basis for hydrogen conversion.

[0074] The mixed gas then enters the pretreatment unit and passes through a first water washing tower 3, a mixed gas preheater 5, and a mixed gas desulfurizer 6 in sequence. The first water washing tower 3 removes impurities such as dust and tar in the gas through water washing and purification. The circulating pump 4 recycles the purified water in a closed loop, significantly reducing water resource consumption. The mixed gas preheater 5 heats the gas to 180°C - 240°C to ensure the temperature conditions for subsequent desulfurization and shift reactions. The mixed gas desulfurizer 6 adopts a dry or wet desulfurization process to reduce the hydrogen sulfide content to ≤0.05 ppm, effectively avoiding the poisoning effect of sulfides on the catalyst. The pretreated mixed gas is mixed with steam at an H 2 O / CO ratio of 1.2:1 - 1.5:1 to provide a suitable water-carbon ratio environment for the CO shift reaction, thereby improving the reaction efficiency and reducing the generation of by-products.

[0075] The gas then enters the gas shift treatment unit and passes through a primary shift reactor 7 and a secondary shift reactor 8 in sequence. The primary shift reactor 7 is internally provided with an iron-based catalyst, and the main reaction of CO and H 2 O (CO + H 2 O → CO 2 + H2 ) Meanwhile, the high-grade heat energy generated by the reaction is recovered and used to preheat the mixed coal gas, reducing the overall energy consumption of the system. The secondary shift reactor 8 uses a copper-based catalyst to deeply convert the residual CO under the conditions of 180°C to 220°C, finally making the CO content in the shifted coal gas ≤ 0.5% (dry basis). The synergistic effect of the two-stage catalyst not only improves the CO conversion rate, but also optimizes the reaction equilibrium through hierarchical temperature control, reducing the risk of catalyst deactivation. The shifted coal gas enters the separation and purification unit after recovering the waste heat through the boiler heater 27.

[0076] The separation and purification unit processes the shifted coal gas step by step through the heat exchanger 9, cooler 10, first gas-liquid separator 12 and second water wash tower 13. The heat exchanger 9 uses the demineralized water provided by the demineralized water pressurizing pump 11 to exchange heat with the high-temperature coal gas, recovering the waste heat and reducing the temperature of the coal gas; the cooler 10 further cools the coal gas to room temperature, the first gas-liquid separator 12 removes the condensed water and residual impurities, and the second water wash tower 13 finally purifies the coal gas through the circulation pump 14 to ensure that the methanol and ethanol contents are both ≤ 20 ppm. This process reduces the energy consumption through multi-stage heat recovery and purification treatment, and also ensures the quality of the raw material gas for subsequent hydrogen purification.

[0077] The purified shifted coal gas enters the shifted gas treatment unit and is separated by vacuum pressure swing adsorption through the adsorber 16. The adsorber 16 uses a special adsorbent to selectively adsorb CO 2 and N 2 , and a hydrogen-rich gas with a H 2 content ≥ 90% is obtained at the top outlet, which can be directly introduced into the low-carbon blast furnace smelting system as a reducing agent, replacing part of the coke and significantly reducing the coke ratio and carbon emissions. The bottom desorbed gas is desorbed through the pressure equalizer 18, vacuum pump 20 and mixer 19 to form a mixed gas containing CO 2 and N 2 . The desorbed gas treatment unit pressurizes the desorbed gas to 2.0 - 2.5 MPa through the compressor 21 and sequentially performs cryogenic separation through the dryer 22, pre-cooler 23, refrigeration unit 24 and rectification tower 25, and finally obtains liquid CO 2 with a purity ≥ 99.5% and nitrogen-rich gas with a purity ≥ 70%. The liquid CO 2 is stored in the storage tank 26 and can be used for oil displacement or chemical synthesis; the nitrogen-rich gas is sent to the nitrogen production device after recovering the cold energy to achieve the full quantification utilization of resources.

[0078] Using the above blast furnace gas and converter gas combined conversion to prepare H 2 system, implementing the above blast furnace gas and converter gas combined conversion to prepare H 2 method, comprehensively treating the blast furnace gas and converter gas with high added value, and the comparison of the components of the raw materials before treatment and the products after treatment is shown in the following table:

[0079] Table 1: Component comparison table of converter gas and blast furnace gas before and after high-value comprehensive treatment

[0080]

[0081] It can be seen that after the treatment of converter gas with a CO content as high as 60% and blast furnace gas with a CO content of 25% in the raw materials, the CO contents in hydrogen-rich gas, liquid CO 2 and nitrogen-rich gas are reduced to 0.05%, 0.0025% and 1.33% respectively, while the hydrogen purity is significantly increased to 90.72%. This data indicates that the conversion efficiency of CO to H 2 exceeds 95%, effectively solving the core problem of difficult separation between CO and N 2 in the traditional process. At the same time, the separation ability of CO 2 by the present invention is particularly prominent. The purity of the liquid CO 2 product reaches 99.75%, which can directly meet the industrial-level carbon capture requirements, an increase of 4.75 percentage points compared with the traditional process (purity about 95%), breaking through the technical thresholds of chemical synthesis and oil displacement and storage. In terms of nitrogen resource recovery, the N 2 content in the nitrogen-rich gas reaches 70.58%, and the nitrogen production device can be linked by combining the cold energy recovery technology during the treatment process to achieve cascaded utilization of energy. More importantly, this application efficiently converts CO in the raw material gas into H 2 and CO 2 , and the CO conversion rate reaches more than 99.9%. While realizing the deep utilization of carbon and hydrogen resources, it reduces the carbon loss caused by the disordered emission of CO from the source. In addition, through the coordinated treatment of converter gas and blast furnace gas, a ternary product system of "reducing agent (H 2 ) + industrial carbon source (CO 2 ) + nitrogen resource (N 2 )" is constructed, promoting the transformation of iron and steel enterprises from fuel consumption type to resource output type.

[0082] In summary, through the integrated design of gas mixing, staged conversion and efficient separation, the present invention converts CO into H 2 and avoids the separation problem between CO and N 2 , simplifying the complex multi-stage adsorption and compression processes in the traditional process. At the same time, the cryogenic distillation technology enables the CO 2 purity to reach the industrial application standard, solving the problem of low recovery value of CO 2 in the traditional process. The entire system realizes the efficient conversion of the chemical energy of gas, the cascaded utilization of heat energy and the resource recycling of products, providing a practical technical path for the low-carbon transformation of the iron and steel industry.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing H2 by combined conversion of blast furnace gas and converter gas, characterized in that: The following steps are involved: Gas mixing and pressurization: pressurize converter gas and blast furnace gas to 0.5-1.0MPa respectively, and mix the pressurized converter gas and blast furnace gas in proportion; Pretreatment: washing and desulfurizing the mixed gas; heating the purified mixed gas and mixing it with steam; Gas shift treatment: The pre-treated mixed gas is subjected to two-stage CO conversion treatment to obtain CO-removed shift gas; Separation and purification: heat recovery, gas-liquid separation and water washing purification of the converted coal gas; Shift gas treatment: vacuum pressure swing adsorption separation and purification is used to obtain hydrogen-rich gas with H2 content ≥ 90% and desorbed gas containing CO2 and N2; Desorbed gas treatment: The desorbed gas is pressurized to 2.0-2.5MPa, and purified by liquefaction and distillation to obtain liquid CO2 with a purity of ≥99.5% and nitrogen-rich gas with a purity of ≥70%. The liquid CO2 is stored for industrial applications, and the nitrogen-rich gas is sent to the nitrogen production device after recovering the cold energy.

2. The method according to claim 1, characterized in that: In the "gas mixing and pressurizing" step, The converter gas is drawn from the existing converter gas pipeline network, and the blast furnace gas is drawn from the existing blast furnace gas pipeline network; Alternatively, the converter gas is drawn from the existing converter gas pipeline network, and the blast furnace gas is drawn from the pipeline network located after the blast furnace top gas wet dust removal system and before the TRT device.

3. The method according to claim 1, characterized in that: In the "gas mixing and pressurizing" step, the mixing ratio of converter gas and blast furnace gas is 0.5:0.5 to 0:

1.

4. The method according to claim 1, characterized in that: Before the "gas shift treatment" step is performed, at least one of the following conditions must be met: The dust content of the pre-treated mixed gas is less than 5mg / Nm 3 ; The hydrogen sulfide content of the pretreated mixed gas is ≤0.05ppm; The temperature of the pretreated mixed gas reaches 180℃~240℃; The ratio of H2O to CO in the pretreated mixed gas components is 1.2:1 to 1.5:

1.

5. The method according to claim 1, characterized in that: In the "gas shift treatment" step, the first-level CO conversion treatment uses an iron-based catalyst to achieve the main CO reaction and high-grade heat energy recovery; the second-level CO conversion treatment uses a copper-based catalyst to complete the deep conversion of residual CO and reaction balance control.

6. The method according to claim 1, characterized in that: When performing primary CO conversion treatment and secondary CO conversion treatment, at least one of the following conditions must be met: The temperature of the converted coal gas after the first-stage CO conversion treatment is ≥300℃; The CO content in the converted coal gas after the secondary CO conversion treatment is ≤0.5% (dry basis); The pressure drop of the converted coal gas after two-stage CO conversion treatment is ≤0.15MPa.

7. The method according to claim 1, characterized in that: In the "separation and purification" step, the standards for water washing and purification of the conversion gas are: the methanol content in the conversion gas is ≤20ppm, and the ethanol content is ≤20ppm.

8. The method according to claim 1, characterized in that: In the "separation and purification" step, the separated hydrogen-rich gas is directly introduced into the low-carbon blast furnace smelting system and used as a reducing agent in blast furnace smelting.

9. A system for preparing H2 by combined reforming of blast furnace gas and converter gas, using the method for preparing H2 by combined reforming of blast furnace gas and converter gas as claimed in any one of claims 1 to 8, characterized in that: It includes a coal gas mixing and pressurizing unit, a pretreatment unit, a coal gas shift treatment unit, a separation and purification unit, a shift gas treatment unit, and a desorption gas treatment unit connected in sequence; The gas mixing and pressurizing unit comprises a converter gas compressor (1) and a blast furnace gas compressor (2), the outlets of which are connected to the pretreatment unit after being merged; The pretreatment unit comprises a mixed gas water scrubber (3), a mixed gas preheater (5) and a mixed gas desulfurizer (6) connected in sequence, the outlets of the converter gas compressor (1) and the blast furnace gas compressor (2) are connected to the mixed gas water scrubber (3) after merging, and the outlet of the mixed gas desulfurizer (6) is connected to the gas conversion treatment unit; The coal gas shift processing unit comprises a primary shift reactor (7) and a secondary shift reactor (8); the mixed coal gas desulfurizer (6) is connected to the primary shift reactor (7), the outlet of the primary shift reactor (7) is connected to the mixed coal gas preheater (5), and then connected to the secondary shift reactor (8) through a boiler heater (27); the secondary shift reactor (8) is connected to the separation and purification unit; The separation and purification unit comprises a heat exchanger (9), a cooler (10), a first gas-liquid separator (12) and a first water scrubber (13) connected in sequence; the outlet of the secondary shift reactor (8) is connected to the heat exchanger (9), and the outlet of the first water scrubber (13) is connected to the shift gas processing unit; The conversion gas processing unit comprises a second gas-liquid separator (15) and an adsorber (16); the top outlet of the adsorber (16) is connected to a hydrogen-rich gas buffer (17), and the bottom outlet thereof is connected to a pressure equalizer (18), a vacuum pump (20) and a mixer (19) so as to desorb the CO2 and N2 components adsorbed by the adsorber (16) through decompression and vacuum operation to form desorbed gas; The desorbed gas processing unit comprises a desorbed gas compressor (21), a desorbed gas dryer (22), a desorbed gas precooler (23), a refrigeration unit (24), a distillation tower (25) and a carbon dioxide storage tank (26) which are connected in sequence, and the outlet of the mixer (19) is connected to the desorbed gas compressor (21); through pressurization, liquefaction and distillation purification operations, the desorbed gas is processed into liquid CO2 with a purity of ≥99.5% and rich nitrogen with a purity of ≥70%.

10. The system according to claim 9, characterized in that: The inlet of the converter gas compressor (1) is connected to the converter gas network, and the inlet of the blast furnace gas compressor (2) is connected to the blast furnace gas network or to the network located after the blast furnace top gas wet dust removal system and before the TRT device.

11. The system according to claim 9, characterized in that: The primary conversion reactor (7) has an iron-based catalyst bed layer built in, and the secondary conversion reactor (8) has a copper-based catalyst bed layer built in.

12. The system according to claim 9, characterized in that: The primary shift reactor (7) and the secondary shift reactor (8) both have a steam inlet, a demineralized water inlet and a steam outlet.

13. The system according to claim 9, characterized in that: The pretreatment unit also includes a first water washing tower circulation pump (4), which is connected to the first water washing tower (3) in a closed loop so as to return the water absorbing impurities to the first water washing tower (3) for recycling after being treated.

14. The system according to claim 9, characterized in that: The separation and purification unit further comprises a deionized water pressure pump (11), which is connected to the heat exchanger (9) to provide deionized water to the heat exchanger (9).

15. The system according to claim 9, characterized in that: The separation and purification unit also includes a second water washing tower circulation pump (14), which is connected to the second water washing tower (13) in a closed loop so as to return the water absorbing impurities to the second water washing tower (13) for recycling after being treated.

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