Converter gas gradient utilization method and system

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a converter gas gradient utilization method and system. The method comprises the following steps: carrying out CO enrichment on the steelmaking converter gas to obtain stable enriched gas with the CO volume fraction greater than or equal to 55%; performing microbial fermentation on the stably enriched coal gas under an anaerobic condition to convert CO of the stably enriched coal gas into ethanol and generate fermentation waste gas of which the calorific value is greater than or equal to 1800kcal / Nm < 3 >; the fermentation waste gas is recycled, stored and subjected to pressure regulation, and pressure-regulated waste gas with the pressure ranging from 0.2 MPa to 0.6 MPa is obtained; the first part of the pressure-regulated waste gas is mixed with low-heat-value coal gas to obtain mixed gas, and the mixed gas serves as fuel to be supplied to a heating furnace; and the second part of the pressure regulating waste gas is directly used as fuel to be supplied to a plate blank cutting procedure. Through the three-stage steps of concentration, biological carbon sequestration and energy gradient utilization, the overall carbon emission intensity of the system is reduced by 25-35%, and meanwhile, the win-win effect of economic benefits and emission reduction is achieved.

Description

Technical Field

[0001] This application belongs to the field of iron and steel metallurgy technology, and in particular relates to a method and system for the cascade utilization of converter gas. Background Technology

[0002] In the existing iron and steel smelting process, converter gas, as a by-product gas in the converter blowing stage, has a production volume of approximately 120-150 m³. 3 / t steel, CO volume fraction is typically between 40-60%, calorific value between 1200-1800 kcal / Nm³ 3 The CO content is significantly higher than that of blast furnace gas. Due to its superior ignition performance and high combustion temperature, this gas has long been used directly as a primary fuel in kilns, hot blast stoves, or power plant boilers. This utilization method only recovers heat and does not involve deep conversion of the chemical energy of CO, resulting in a waste of high-grade carbon resources; at the same time, the direct emission of CO2 after combustion leads to persistently high carbon emission intensity for enterprises. Summary of the Invention

[0003] This application provides a method and system for the cascade utilization of converter gas to solve the following technical problem: how to reduce carbon emissions from converter gas.

[0004] In a first aspect, embodiments of this application provide a method for the cascade utilization of converter gas, including: CO enrichment was carried out on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction ≥ 55%; The stabilized enriched coal gas was subjected to microbial fermentation under anaerobic conditions, converting CO in the stabilized enriched coal gas into ethanol, while generating a product with a calorific value ≥1800 kcal / Nm³. 3 Fermentation waste gas; The fermentation waste gas is recovered, stored, and pressure regulated to obtain pressure-regulated waste gas with a pressure of 0.2 MPa to 0.6 MPa; The pressure-regulating waste gas described in the first part is mixed with low-calorific-value coal gas to obtain mixed fuel gas, and the mixed fuel gas is used as fuel to supply the heating furnace. The pressure-regulating exhaust gas described in Part Two is directly used as fuel to supply the slab cutting process.

[0005] Optionally, the CO enrichment is achieved by pressure swing adsorption or membrane separation, so that the CO volume fraction of the stably enriched coal gas is 55% to 70%.

[0006] Optionally, the oxygen volume fraction under the anaerobic conditions is ≤0.5%.

[0007] Optionally, the calorific value of the low-calorific-value gas is 700 kcal / Nm³. 3 ~1000kcal / Nm 3The calorific value of the mixed gas is 1100 kcal / Nm³. 3 ~1300kcal / Nm 3 .

[0008] Optionally, the volumetric flow rate ratio of the first portion of pressure-regulating waste gas to the low-calorific-value coal gas is 1:2 to 1:4.

[0009] Secondly, embodiments of this application provide a converter gas cascade utilization system, which includes, in sequence along the fluid flow direction: CO enrichment unit, the CO enrichment unit is used to enrich CO in steelmaking converter gas and output stable enriched gas with CO volume fraction ≥55%; An anaerobic biological fermentation unit, which is connected to the CO enrichment unit, is used to convert the CO in the stable enriched coal gas into ethanol and output fermentation waste gas with a calorific value ≥1800kcal / Nm3. The waste gas treatment unit is connected to the anaerobic biological fermentation unit and is used to recover, store and regulate the pressure of the fermentation waste gas and output regulated waste gas with a pressure of 0.2MPa to 0.6MPa. The first fuel utilization unit is connected to the waste gas treatment unit and is used to mix the first part of the pressure-regulating waste gas with low-calorific-value coal gas to form a mixed gas, and supply the mixed gas to the heating furnace. The second fuel utilization unit is connected to the exhaust gas treatment unit and is used to directly supply the pressure-regulating exhaust gas of the second part to the slab cutting process.

[0010] Optionally, the CO enrichment unit is a pressure swing adsorption device or a gas separation membrane device.

[0011] Optionally, the anaerobic bio-fermentation unit contains immobilized carbon monoxide nutrient bacteria, the concentration of which is ≥10g / L.

[0012] Optionally, the exhaust gas treatment unit includes a water-sealed gas storage tank, a dry gas storage tank, and a variable frequency compressor connected in sequence, wherein the outlet pressure of the variable frequency compressor is 0.2MPa to 0.6MPa.

[0013] Optionally, the first fuel utilization unit includes a gas mixer, which has a low-calorific-value gas inlet, a pressure-regulating exhaust gas inlet, and a mixed gas outlet, wherein the mixed gas outlet is connected to the heater burner. The second fuel utilization unit includes a pressure regulating exhaust gas branch pipe, which is directly connected to the slab cutting burner.

[0014] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for the cascade utilization of converter gas. This method addresses both the "carbon to energy conversion" and "energy utilization" aspects simultaneously, transforming the converter gas that was originally to be burned and released into two high-value-added flows, thereby reducing CO2 emissions at both the source and the end.

[0015] First, carbon is fixed in chemicals: Converter gas is concentrated to CO ≥ 55% using pressure swing adsorption or cryogenic methods to obtain a stable gas source; then, in an anaerobic reactor, carboxyl-trophic bacteria use CO as the sole carbon source to synthesize ethanol via the acetyl-CoA pathway. For every 1 mol of CO converted, 0.5 mol of carbon is fixed, reducing CO2 emissions by an equal amount, while simultaneously obtaining an ethanol solution ≥ 40 g / L, achieving a "carbon-chemical" substitution for fossil fuels.

[0016] Secondly, the remaining energy should be fully utilized: the fermentation exhaust gas still contains combustible components such as CO, H2, and CH4, with a calorific value ≥1800 kcal / Nm³. 3 After being recovered and pressurized to 0.2–0.6 MPa in a gas storage tank, the first portion is blended with low-calorific-value blast furnace gas or coke oven gas to increase the calorific value of the mixed gas to the design range of the heating furnace, replacing the original need for supplemental coke oven gas or natural gas; the second portion is directly sent to slab cutting, replacing propane or liquefied petroleum gas. Both utilization paths efficiently release carbon in the form of "chemical energy," avoiding the increase in CO2 caused by direct combustion.

[0017] Through the three-stage process of "first enrichment, then biological carbon sequestration, and finally energy cascade utilization", the system converts a portion of the carbon in the converter gas into marketable ethanol, and the remaining energy is matched to the heating furnace and cutting process according to grade. The overall carbon emission intensity is reduced by 25-35%, achieving a win-win situation of economic benefits and emission reduction. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0020] In a first aspect, embodiments of this application provide a method for the cascade utilization of converter gas, including: CO enrichment was carried out on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction ≥ 55%; The stabilized enriched coal gas was subjected to microbial fermentation under anaerobic conditions, converting CO in the stabilized enriched coal gas into ethanol, while generating a product with a calorific value ≥1800 kcal / Nm³. 3 Fermentation waste gas; The fermentation waste gas is recovered, stored, and pressure regulated to obtain pressure-regulated waste gas with a pressure of 0.2 MPa to 0.6 MPa; The pressure-regulating waste gas described in the first part is mixed with low-calorific-value coal gas to obtain mixed fuel gas, and the mixed fuel gas is used as fuel to supply the heating furnace. The pressure-regulating exhaust gas described in Part Two is directly used as fuel to supply the slab cutting process.

[0021] The original CO volume fraction of steelmaking converter gas is 40%–60%. CO enrichment is then performed on the converter gas to create stable enriched gas with a CO volume fraction ≥55%. This results in increased CO partial pressure in the stable enriched gas, leading to a linear increase in the microbial fermentation rate with increasing CO partial pressure. This increases the ethanol yield per unit fermenter volume, the amount of CO moles converted to ethanol per unit time, and reduces the amount of carbon emitted through direct combustion of CO per unit time, thus reducing carbon emissions from the converter gas. Alternatively, microbial fermentation of the stable enriched gas under anaerobic conditions reduces CO in the gas to ethanol via the acetyl-CoA pathway by carbon monoxide-loving bacteria. Each mol of CO is fixed as 0.5 mol of ethanol carbon, thus preventing the generation of 1 mol of CO2 per mol of CO, directly reducing emissions by 1 mol of CO2 equivalent, thereby lowering carbon emissions from the converter gas. Microbial fermentation simultaneously generates fermentation waste gas with a calorific value ≥1800 kcal / Nm3 → fermentation waste gas contains unreacted CO, H2, and CH4 → fermentation waste gas calorific value ≥1800 kcal / Nm3 → fermentation waste gas is recovered, stored, and pressure regulated → pressure-regulated waste gas with a pressure of 0.2 MPa to 0.6 MPa is obtained → pressure-regulated waste gas has a stable combustion pressure → the first part of pressure-regulated waste gas is mixed with low-calorific-value coal gas → low-calorific-value coal gas calorific value 700 kcal / Nm3 to 1000 kcal / Nm3 → mixed gas calorific value 1100 kcal / Nm3 to 1300 kcal / Nm3 → the calorific value of the mixed gas increases to the design calorific value range of the heating furnace → the mixed gas replaces the coke oven gas or natural gas that originally needed to be supplemented → the CO2 emissions corresponding to the original coke oven gas or natural gas combustion are avoided → thereby reducing the carbon emissions of converter gas. The second part of the pressure-regulating waste gas is directly used as fuel to supply the slab cutting process → the second part of the pressure-regulating waste gas replaces the original propane or liquefied petroleum gas combustion → the CO2 emissions corresponding to the original propane or liquefied petroleum gas combustion are avoided → thereby reducing the carbon emissions of converter gas. In summary, each technical feature continuously and progressively reduces the carbon emissions of converter gas through two paths: "increasing carbon fixation" or "replacing higher-carbon fuels". CO volume fraction ≥55% includes, but is not limited to: 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%. Calorific value ≥1800 kcal / Nm³ 3Including but not limited to: 1800, 1810, 1820, 1830, 1840, 1850, 1860, 1870, 1880, 1890, 1900, 1910, 1920, 1930, 1940, 1950, 1960, 1970, 1980, 1990, 2000 kcal / Nm3. Pressure 0.2MPa~0.6MPa, including but not limited to: 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60MPa.

[0022] In some embodiments, the CO enrichment is achieved by pressure swing adsorption or membrane separation, so that the CO volume fraction of the stably enriched coal gas is 55% to 70%.

[0023] The process employs pressure swing adsorption (PSA) or membrane separation. PSA operates at an adsorption-desorption pressure of 0.6 MPa–1.2 MPa or a membrane pressure difference of 0.5 MPa–2.0 MPa. This allows for selective permeation or desorption of CO from the steelmaking converter gas, precisely locking the CO volume fraction in the gas to 55%–70%. This 55%–70% range is higher than both the critical inhibition concentration (CIC) of the fermentation bacteria (70%) and the economic equilibrium point (55%). This maintains the fermentation reaction rate at its maximum, maximizing CO conversion per unit fermenter volume and the amount of carbon fixed to ethanol per unit time, thereby minimizing carbon emissions from the converter gas. The CO volume fraction of 55%–70% includes, but is not limited to: 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, and 70%.

[0024] In some embodiments, the oxygen volume fraction of the anaerobic conditions is ≤0.5%.

[0025] Under anaerobic conditions, the oxygen volume fraction is ≤0.5% → ≤0.5% is below the oxygen poisoning threshold of 0.8% for carbon monoxide-producing bacteria → the bacterial ethanol metabolism pathway remains in the reducing direction → CO is prevented from being oxidized to CO2 → every 1 mol of CO is still fixed as 0.5 mol of ethanol carbon → thus preventing the generation of additional CO2 → thus maintaining the reduction in converter gas carbon emissions. Oxygen volume fraction ≤0.5%: 0.50, 0.49, 0.48, 0.47, 0.46, 0.45, 0.44, 0.43, 0.42, 0.41, 0.40, 0.35, 0.30, 0.25, 0.20, 0.15, 0.10, 0.05, 0.02, 0.01%.

[0026] In some embodiments, the calorific value of the low-calorific-value gas is 700 kcal / Nm³.3 ~1000kcal / Nm 3 The calorific value of the mixed gas is 1100 kcal / Nm³. 3 ~1300kcal / Nm 3 .

[0027] The calorific value of low-calorific-value coal gas is 700kcal / Nm3~1000kcal / Nm3. Since 700kcal / Nm3~1000kcal / Nm3 is lower than the minimum allowable calorific value of 1100kcal / Nm3 for the heating furnace, the first part of the pressure regulating waste gas is mixed with the low-calorific-value coal gas. The calorific value of the mixed gas is increased to 1100kcal / Nm3~1300kcal / Nm3. Since 1100kcal / Nm3~1300kcal / Nm3 falls into the high-efficiency combustion range of the heating furnace, the combustion efficiency of the heating furnace is ≥88%. The fuel consumption per unit product of the heating furnace decreases, and the CO2 emission per unit product of the heating furnace decreases, thereby reducing the carbon emission of converter gas. Low-calorific-value coal gas has a calorific value of 700 kcal / Nm3 to 1000 kcal / Nm3, including but not limited to: 700, 720, 740, 760, 780, 800, 820, 840, 860, 880, 900, 920, 940, 960, 980, and 1000 kcal / Nm3. Mixed fuel gas has a calorific value of 1100 kcal / Nm3 to 1300 kcal / Nm3, including but not limited to: 1100, 1120, 1140, 1160, 1180, 1200, 1220, 1240, 1260, 1280, and 1300 kcal / Nm3.

[0028] In some embodiments, the volumetric flow rate ratio of the first portion of pressure-regulating waste gas to the low-calorific-value coal gas is 1:2 to 1:4.

[0029] Volumetric flow ratio 1:2 to 1:4 → Pressure regulating exhaust gas with a calorific value of 1800 kcal / Nm3 is mixed with low-calorific-value coal gas with a calorific value of 700 kcal / Nm3 at a ratio of 1:2 to 1:4 → The calorific value of the mixed fuel gas is precisely adjusted to 1100 kcal / Nm3 to 1300 kcal / Nm3 → Combustion rate index ≥35 in the 1100 kcal / Nm3 to 1300 kcal / Nm3 range → The flame stability of the heating furnace is qualified → The heating furnace does not need to be supplemented with coke oven gas or natural gas → The 2.2 kg CO2 emission corresponding to each 1 Nm3 of coke oven gas or natural gas supplementation is avoided → Thus reducing the carbon emission of converter gas. The volumetric flow rate ratio of 1:2 to 1:4 includes, but is not limited to: 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3.0, 1:3.2, 1:3.4, 1:3.6, 1:3.8, and 1:4.0.

[0030] Secondly, embodiments of this application provide a converter gas cascade utilization system, which includes, in sequence along the fluid flow direction: CO enrichment unit, the CO enrichment unit is used to enrich CO in steelmaking converter gas and output stable enriched gas with CO volume fraction ≥55%; An anaerobic biological fermentation unit, which is connected to the CO enrichment unit, is used to convert the CO in the stable enriched coal gas into ethanol and output fermentation waste gas with a calorific value ≥1800kcal / Nm3. The waste gas treatment unit is connected to the anaerobic biological fermentation unit and is used to recover, store and regulate the pressure of the fermentation waste gas and output regulated waste gas with a pressure of 0.2MPa to 0.6MPa. The first fuel utilization unit is connected to the waste gas treatment unit and is used to mix the first part of the pressure-regulating waste gas with low-calorific-value coal gas to form a mixed gas, and supply the mixed gas to the heating furnace. The second fuel utilization unit is connected to the exhaust gas treatment unit and is used to directly supply the pressure-regulating exhaust gas of the second part to the slab cutting process.

[0031] The CO enrichment unit enriches CO in the steelmaking converter gas → outputs stable enriched gas with a CO volume fraction ≥ 55% → the stable enriched gas enters the anaerobic biological fermentation unit → the anaerobic biological fermentation unit converts the CO in the stable enriched gas into ethanol → each 1 mol of CO is fixed into 0.5 mol of ethanol carbon → simultaneously outputs fermentation waste gas with a calorific value ≥ 1800 kcal / Nm3 → the fermentation waste gas enters the waste gas treatment unit → the waste gas treatment unit recovers, stores and regulates the pressure of the fermentation waste gas → outputs pressure-regulated waste gas of 0.2 MPa~0.6 MPa → the pressure-regulated waste gas is divided into the first part for pressure regulation. The first part of the pressure-regulating waste gas enters the first fuel utilization unit and mixes with low-calorific-value coal gas to form a mixed fuel gas with a calorific value of 1100 kcal / Nm3 to 1300 kcal / Nm3. The mixed fuel gas is supplied to the heating furnace to replace coke oven gas or natural gas and avoid CO2 generated by the combustion of coke oven gas or natural gas. The second part of the pressure-regulating waste gas enters the second fuel utilization unit and is directly supplied to the slab cutting process to replace propane or liquefied petroleum gas and avoid CO2 generated by the combustion of propane or liquefied petroleum gas. Thus, the system as a whole reduces the carbon emissions of converter gas.

[0032] In some embodiments, the CO enrichment unit is a pressure swing adsorption device or a gas separation membrane device.

[0033] Pressure swing adsorption (PSA) devices or gas separation membrane devices selectively adsorb or permeate CO from steelmaking converter gas within the range of 0.5 MPa to 2.0 MPa, outputting stable enriched gas with a CO volume fraction ≥ 55%, increasing the CO partial pressure of the stable enriched gas, increasing the reaction rate of the anaerobic bio-fermentation unit, increasing the ethanol yield per unit volume, and increasing the amount of carbon fixed per unit time, thereby reducing carbon emissions from converter gas.

[0034] In some embodiments, the anaerobic bio-fermentation unit contains immobilized carbon monoxide-loving bacteria with a cell concentration ≥10g / L.

[0035] Immobilized carbon monoxide-producing bacteria concentration ≥10 g / L → active biomass per unit volume reactor ≥10 g / L → CO consumption rate per unit volume ≥1.2 g CO / (L·h) → ethanol yield per unit volume ≥0.5 g EtOH / (L·h) → increased fixed carbon per unit time → thereby reducing carbon emissions from converter gas. A concentration ≥10 g / L includes, but is not limited to: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 g / L.

[0036] In some embodiments, the exhaust gas treatment unit includes a water-sealed gas storage tank, a dry gas storage tank, and a variable frequency compressor connected in sequence, wherein the outlet pressure of the variable frequency compressor is 0.2 MPa to 0.6 MPa.

[0037] The water-sealed gas holder provides primary pressure stabilization for the fermentation waste gas → the dry gas holder provides secondary pressure stabilization for the fermentation waste gas → the variable frequency pressurizer provides tertiary pressurization for the fermentation waste gas → outputs pressure-regulated waste gas with a pressure of 0.2MPa to 0.6MPa → the pressure of the pressure-regulated waste gas is stabilized within the required range for the heating furnace and slab cutting burners → incomplete combustion caused by pressure fluctuations is avoided → additional CO2 generated by incomplete combustion is avoided → thereby reducing carbon emissions from converter gas.

[0038] In some embodiments, the first fuel utilization unit includes a gas mixer, which has a low-calorific-value gas inlet, a pressure-regulating exhaust gas inlet, and a mixed gas outlet, the mixed gas outlet being connected to a heater burner; The second fuel utilization unit includes a pressure regulating exhaust gas branch pipe, which is directly connected to the slab cutting burner.

[0039] The gas mixer introduces low-calorific-value coal gas through the low-calorific-value coal gas inlet → the gas mixer introduces the first part of pressure-regulating waste gas through the pressure-regulating waste gas inlet → the gas mixer mixes the low-calorific-value coal gas with the first part of pressure-regulating waste gas → forming a mixed gas with a calorific value of 1100 kcal / Nm3 to 1300 kcal / Nm3 → the mixed gas outlet is connected to the heater burner → the mixed gas replaces coke oven gas or natural gas → avoiding CO2 generated by the combustion of coke oven gas or natural gas → the pressure-regulating waste gas branch pipe is directly connected to the slab cutting burner → the second part of pressure-regulating waste gas replaces propane or liquefied petroleum gas → avoiding CO2 generated by the combustion of propane or liquefied petroleum gas → thereby reducing the carbon emissions of converter gas.

[0040] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0041] I. Implementation Examples Example 1 Step 1: CO enrichment is performed on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction of 55%. Step 2: The stabilized enriched coal gas is fermented under anaerobic conditions with an oxygen volume fraction of 0.5% to convert the CO in the stabilized enriched coal gas into ethanol, while generating fermentation waste gas with a calorific value of 1800 kcal / Nm3. Step 3: Recover, store, and regulate the pressure of the fermentation waste gas to obtain pressure-regulated waste gas with a pressure of 0.20 MPa; Step 4: Mix the first part of pressure-regulating waste gas with low-calorific-value coal gas with a calorific value of 700 kcal / Nm3 at a volume flow ratio of 1:2 to obtain a mixed gas with a calorific value of 1100 kcal / Nm3, and supply the mixed gas as fuel to the heating furnace. Step 5: The second part of the pressure-regulating exhaust gas is directly used as fuel to supply the slab cutting process.

[0042] Example 2 Step 1: CO enrichment is performed on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction of 60%. Step 2: The stabilized enriched coal gas is fermented under anaerobic conditions with an oxygen volume fraction of 0.4% to convert the CO in the stabilized enriched coal gas into ethanol, while generating fermentation waste gas with a calorific value of 1850 kcal / Nm3. Step 3: Recover, store, and regulate the pressure of the fermentation waste gas to obtain pressure-regulated waste gas with a pressure of 0.30 MPa; Step 4: Mix the first part of pressure-regulating waste gas with low-calorific-value coal gas with a calorific value of 800 kcal / Nm3 at a volume flow ratio of 1:2.5 to obtain a mixed gas with a calorific value of 1150 kcal / Nm3, and supply the mixed gas as fuel to the heating furnace. Step 5: The second part of the pressure-regulating exhaust gas is directly used as fuel to supply the slab cutting process.

[0043] Example 3 Step 1: CO enrichment is performed on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction of 65%. Step 2: The stabilized enriched coal gas is fermented under anaerobic conditions with an oxygen volume fraction of 0.3% to convert the CO in the stabilized enriched coal gas into ethanol, while generating fermentation waste gas with a calorific value of 1900 kcal / Nm3. Step 3: Recover, store, and regulate the pressure of the fermentation waste gas to obtain pressure-regulated waste gas with a pressure of 0.40 MPa; Step 4: Mix the first part of pressure-regulating waste gas with low-calorific-value coal gas with a calorific value of 900 kcal / Nm3 at a volume flow ratio of 1:3 to obtain a mixed gas with a calorific value of 1200 kcal / Nm3, and supply the mixed gas as fuel to the heating furnace. Step 5: The second part of the pressure-regulating exhaust gas is directly used as fuel to supply the slab cutting process.

[0044] Example 4 Step 1: CO enrichment is performed on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction of 70%. Step 2: The stabilized enriched coal gas is fermented under anaerobic conditions with an oxygen volume fraction of 0.2% to convert the CO in the stabilized enriched coal gas into ethanol, while generating fermentation waste gas with a calorific value of 1950 kcal / Nm3. Step 3: Recover, store, and regulate the pressure of the fermentation waste gas to obtain regulated waste gas with a pressure of 0.50 MPa; Step 4: Mix the first part of pressure-regulating waste gas with low-calorific-value coal gas with a calorific value of 1000 kcal / Nm3 at a volume flow ratio of 1:3.5 to obtain a mixed gas with a calorific value of 1250 kcal / Nm3, and supply the mixed gas as fuel to the heating furnace. Step 5: The second part of the pressure-regulating exhaust gas is directly used as fuel to supply the slab cutting process.

[0045] Example 5 Step 1: CO enrichment is performed on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction of 70%. Step 2: The stabilized enriched coal gas is fermented under anaerobic conditions with an oxygen volume fraction of 0.1% to convert the CO in the stabilized enriched coal gas into ethanol, while generating fermentation waste gas with a calorific value of 2000 kcal / Nm3. Step 3: Recover, store, and regulate the pressure of the fermentation waste gas to obtain pressure-regulated waste gas with a pressure of 0.60 MPa; Step 4: Mix the first part of pressure-regulating waste gas with low-calorific-value coal gas with a calorific value of 1000 kcal / Nm3 at a volume flow ratio of 1:4 to obtain a mixed gas with a calorific value of 1300 kcal / Nm3, and supply the mixed gas as fuel to the heating furnace. Step 5: The second part of the pressure-regulating exhaust gas is directly used as fuel to supply the slab cutting process.

[0046] II. Comparative Example Comparative Example 1 (CO enrichment omitted) Step 1: Use steelmaking converter gas with a CO volume fraction of 45% directly as the stable enriched gas; Step 2: The stabilized enriched coal gas is fermented under anaerobic conditions with an oxygen volume fraction of 0.5% to convert the CO in the stabilized enriched coal gas into ethanol, while generating fermentation waste gas with a calorific value of 1550 kcal / Nm3. Step 3: Recover, store, and regulate the pressure of the fermentation waste gas to obtain pressure-regulated waste gas with a pressure of 0.20 MPa; Step 4: Mix the first part of pressure-regulating waste gas with low-calorific-value coal gas with a calorific value of 700 kcal / Nm3 at a volume flow ratio of 1:2 to obtain a mixed gas with a calorific value of 1000 kcal / Nm3, and supply the mixed gas as fuel to the heating furnace. Step 5: The second part of the pressure-regulating exhaust gas is directly used as fuel to supply the slab cutting process.

[0047] Comparative Example 2 (microbial fermentation omitted) Step 1: CO enrichment is performed on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction of 55%. Step 2: The stabilized enriched coal gas is directly combusted to generate combustion exhaust gas with a calorific value of 1200 kcal / Nm3; Step 3: Recover, store, and regulate the pressure of the combustion exhaust gas to obtain pressure-regulated exhaust gas with a pressure of 0.20 MPa; Step 4: Mix the first part of pressure-regulating waste gas with low-calorific-value coal gas with a calorific value of 700 kcal / Nm3 at a volume flow ratio of 1:2 to obtain a mixed gas with a calorific value of 950 kcal / Nm3, and supply the mixed gas as fuel to the heating furnace. Step 5: The second part of the pressure-regulating exhaust gas is directly used as fuel to supply the slab cutting process.

[0048] Comparative Example 3 (omitting the mixing of pressure-regulating exhaust gas and low-calorific-value coal gas, and using all pressure-regulating exhaust gas for slab cutting) Step 1: CO enrichment is performed on the steelmaking converter gas to obtain stable enriched gas with a CO volume fraction of 55%. Step 2: The stabilized enriched coal gas is fermented under anaerobic conditions with an oxygen volume fraction of 0.5% to convert the CO in the stabilized enriched coal gas into ethanol, while generating fermentation waste gas with a calorific value of 1800 kcal / Nm3. Step 3: Recover, store, and regulate the pressure of the fermentation waste gas to obtain pressure-regulated waste gas with a pressure of 0.20 MPa; Step 4: Directly supply all the pressure-regulating exhaust gas as fuel to the slab cutting process; Step 5: The heating furnace continues to burn coke oven gas separately.

[0049] III. Results Data Experimental methods for evaluating results: 1. Ethanol Yield Determination: The fermentation broth from the anaerobic biological fermentation unit was taken, and the ethanol mass was determined using the distillation-gravity method according to GB / T394.2-2008 "General Test Methods for Alcohol". The yield was converted to per 100 Nm³. 3 The number of kilograms of CO converted into ethanol.

[0050] 2. CO2 Reduction Measurement: By comparing the Example 2 with Comparative Example 2 (direct combustion baseline), the total flue gas volume and CO2 concentration difference were measured using a Continuous Emission Monitoring System (CEMS, compliant with HJ75-2017), and the number of kilograms of CO2 emissions reduced per 100 Nm3 of original converter gas were calculated.

[0051] 3. Measurement of natural gas replacement volume in the heating furnace: Install an ultrasonic flow meter (accuracy ±1%) at the gas inlet of the heating furnace, record the cumulative volume of natural gas reduced due to the mixing of gas, and convert it to per 100 Nm³. 3 The number of cubic meters of natural gas replaced by the original converter gas.

[0052] 4. Measurement of propane substitution during slab cutting: Install a mass flow meter (accuracy ±0.5%) at the gas inlet of the slab cutting process, and record the cumulative mass of propane reduced due to the use of the second-stage pressure-regulating exhaust gas, converting it to per 100 Nm³. 3 The number of kilograms of propane replaced by the original converter gas.

[0053] 5. Calculation of the overall carbon emission reduction rate: The sum of the carbon equivalent of ethanol fixation, the carbon equivalent of natural gas substitution, and the carbon equivalent of propane substitution is divided by the total carbon emissions in the baseline scenario (Comparative Example 2), expressed as a percentage.

[0054] Table 1. Results data for both the examples and comparative examples.

[0055] As shown in Table 1, the inventiveness of the technical solution of this application includes: 1. The development of carbon fixation pathways from scratch: Comparative Example 2 did not undergo microbial fermentation, and the ethanol yield was 0 kg / 100 Nm³. 3 CO and CO2 reduction was 0 kg; however, in Examples 1–5, due to the introduction of the "CO enrichment-anaerobic microbial fermentation" step, the ethanol yield instantly jumped to 22.5–30.0 kg / 100 Nm³. 3 CO directly resulted in a reduction of 45–60 kg of CO2 equivalent, thus achieving a "carbon → chemicals" route rather than "carbon → CO2" for the first time in the field of converter gas in steel plants.

[0056] 2. A step-by-step increase in carbon fixation efficiency: In Comparative Example 1, due to the omission of CO enrichment, the bacterial cells were limited by CO partial pressure, and the ethanol yield was only 15.2 kg; Examples 1–5, by locking the CO volume fraction at 55–70%, increased the yield of the same strain by 48–97%, proving that the combination of "CO enrichment" and "microbial fermentation" is not a simple superposition, but produces a synergistic amplification effect, thus exceeding the conventional understanding of fermentation inlet gas concentration by industry technicians.

[0057] 3. Additional emission reductions resulting from energy cascade utilization: Although Comparative Example 3 retains the fermentation step, it omits the sub-step of "mixing pressure regulating waste gas with low-calorific-value coal gas", and the amount of natural gas replaced by the heating furnace is 0 Nm³; Examples 1–5 introduce this mixing step, which replaces an additional 38–50 Nm³ of natural gas / 100 Nm³ of converter gas, thereby increasing the overall carbon emission reduction rate from 22% to 6–17 percentage points. For the first time, the low-calorific-value coal gas from steel plants is included in carbon emission reduction by the method of "re-co-firing fermentation tail gas".

[0058] 4. Table 1 shows that when the CO volume fraction, fermentation calorific value, pressure, and flow rate ratio are all taken at the upper limit of the claims (Example 5), the overall carbon emission reduction rate reaches the maximum value of 39%. Any parameter deviating from the upper limit (Example 1 or Comparative Example 1) will cause the reduction rate to decrease monotonically, proving that the claimed numerical range is not a conventional choice, but a "critical range" screened through creative experiments.

[0059] In summary, this application achieves emission reduction through a three-in-one coupling of "CO enrichment - anaerobic fermentation - waste gas cascade combustion" for the first time in the same system through "chemical fixation + fuel substitution" dual-path emission reduction, and all performance indicators show a step-like increase.

[0060] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for the stepwise utilization of converter gas, characterized in that The application relates to a steelmaking converter gas CO enrichment method and device. The application comprises the following steps: The stable enriched coal gas is subjected to microbial fermentation under anaerobic conditions, so that CO in the stable enriched coal gas is converted into ethanol, and fermentation exhaust gas with a calorific value ≥1800kcal / Nm 3 is generated. CO enrichment is carried out on the steelmaking converter gas to obtain stable enrichment gas with a CO volume fraction of greater than or equal to 55%; The fermentation waste gas is recovered, stored and pressure-regulated to obtain pressure-regulated waste gas with a pressure of 0.2-0.6 MPa; The first part of the pressure-regulated waste gas is mixed with low-calorific-value gas to obtain mixed gas, and the mixed gas is used as fuel for a heating furnace; 2. The method of claim 1, wherein, The second part of the pressure-regulated waste gas is directly used as fuel for a slab cutting process.

3. The method of claim 1, wherein, The CO enrichment is carried out by pressure swing adsorption or membrane separation, and the CO volume fraction of the stable enrichment gas is 55-70%.

4. The method of claim 1, wherein, The low-calorific-value gas has a calorific value of 700 kcal / Nm 3 ~ 1000 kcal / Nm 3 The mixed gas has a calorific value of 1100 kcal / Nm 3 ~ 1300 kcal / Nm 3 .

5. The method of claim 1, wherein, The oxygen volume fraction in the oxygen-free condition is less than or equal to 0.5%.

6. A converter gas cascade utilization system characterized by comprising: The volume flow ratio of the first part of the pressure-regulated waste gas to the low-calorific-value gas is 1:2-1:

4. The application comprises the following steps in sequence along the fluid flow direction: A CO enrichment unit is used for carrying out CO enrichment on the steelmaking converter gas and outputting stable enrichment gas with a CO volume fraction of greater than or equal to 55%; An anaerobic biological fermentation unit is in communication with the CO enrichment unit and is used for converting CO in the stable enrichment gas into ethanol and outputting fermentation waste gas with a heat value of greater than or equal to 1800 kcal / Nm3; A waste gas treatment unit is in communication with the anaerobic biological fermentation unit and is used for recovering, storing and pressure-regulating the fermentation waste gas and outputting pressure-regulated waste gas with a pressure of 0.2-0.6 MPa; A first fuel utilization unit is in communication with the waste gas treatment unit and is used for mixing the first part of the pressure-regulated waste gas with low-calorific-value gas to form mixed gas and supplying the mixed gas to a heating furnace; 7. The system of claim 6, wherein, A second fuel utilization unit is in communication with the waste gas treatment unit and is used for directly supplying the second part of the pressure-regulated waste gas to a slab cutting process.

8. The system of claim 6, wherein, The CO enrichment unit is a pressure swing adsorption device or a gas separation membrane device.

9. The system of claim 6, wherein, The anaerobic biological fermentation unit is internally provided with immobilized carboxydotrophic bacteria, and the bacterial concentration of the carboxydotrophic bacteria is greater than or equal to 10 g / L.

10. The system of claim 6, wherein, The waste gas treatment unit comprises a water-sealed gas storage tank, a dry gas storage tank and a variable-frequency pressure regulator in sequence, and the outlet pressure of the variable-frequency pressure regulator is 0.2-0.6 MPa. The first fuel utilization unit comprises a gas mixer provided with a low-calorific-value gas inlet, a pressure-regulated waste gas inlet and a mixed gas outlet, and the mixed gas outlet is in communication with a heating furnace burner; The second fuel utilization unit comprises a pressure-regulated waste gas branch pipeline, and the pressure-regulated waste gas branch pipeline is directly in communication with a slab cutting burner.

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