Process for preparing hydrogen-rich reducing gas by utilizing blast furnace top gas in cooperation with biomass and pulverized coal

Abstract

The invention discloses a process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal, which comprises the following steps: (1) introducing carbon-containing fuel, blast furnace top gas, water vapor and oxygen into a boiling gasifier for gasification reaction to obtain hydrogen-rich reducing gas; (2) introducing the hydrogen-rich reducing gas into a cyclone separator for purification to obtain purified gas; and (3) introducing the purified gas into a user unit 1 and a user unit 2 through a heating furnace and a heat exchanger respectively. According to the method, CO2 in the blast furnace top gas is fully used as a gasifying agent, H2O steam and O2 are used for adjusting the gas composition and temperature, the high-concentration hydrogen-rich reducing gas is cooperatively prepared, CO2 in the blast furnace top gas is recycled, the problem of CO2 emission reduction in blast furnace smelting is effectively solved, low-cost preparation of the hydrogen-rich reducing gas is achieved, and the method is suitable for industrial production. And hydrogen-rich reducing gas with stable yield and low cost can be provided for the ironmaking field.

Description

Technical Field

[0001] The present invention relates to the technical field of ferrous metallurgy, and particularly to a process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal. Background Art

[0002] The iron and steel industry is a major energy consumer and pollutant emitter. Among them, the energy consumption of blast furnace ironmaking accounts for 80% of the total energy consumption of steel production, and the CO 2 emission accounts for more than about 70%. Traditional blast furnaces mainly use pulverized coal to replace part of the coke to reduce the coke ratio and the smelting cost per ton of iron. In order to further achieve low-carbon and green smelting of blast furnaces, the research and development of blast furnace hydrogen-rich smelting technology, replacing carbon with hydrogen and increasing the proportion of hydrogen reduction, can achieve energy conservation and emission reduction. At present, most blast furnace hydrogen-rich smelting projects are still in the research and pilot test stages and have not achieved large-scale industrial production. The bottleneck problems include that the relevant theories of blast furnace hydrogen-rich smelting technology are not perfect at this stage, the injection equipment and technology are not sound, the existing hydrogen production technology has a high cost and limited output, etc. For example, the existing electrolytic water hydrogen production has high purity but high cost; the wind energy and solar energy hydrogen production technologies are not perfect and have low output; the natural gas and coke oven gas hydrogen production processes have high costs and are restricted by the resources of natural gas and coke oven gas. Among them, how to obtain large-scale and inexpensive hydrogen or hydrogen-rich gas for blast furnace hydrogen-rich smelting is one of the key factors restricting the implementation of blast furnace hydrogen-rich smelting technology.

[0003] The top gas recycling technology is also a research and development direction for the low-carbon and green development of blast furnaces. The traditional view is to first remove CO 2 from the top gas and then recycle it. However, the CO 2 removal cost is also relatively high, which limits the recycling of top gas. Biomass energy has a wide variety of raw materials, and after being processed by physical, chemical, biological and other methods, it can be converted into solid, liquid or gaseous fuels. Biomass energy contains carbon and hydrogen elements, and the nitrogen element content is much lower than that of traditional fuels, with the characteristics of low cost, environmental friendliness and carbon neutrality. At present, its use as a fuel or reducing agent in blast furnace, sintering and pelletizing and other production processes has been studied.

[0004] Therefore, how to realize the recycling of top gas and the full utilization of fuel and then prepare hydrogen-rich reducing gas is the current research focus. Summary of the Invention

[0005] The purpose of the present invention is to provide a process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal to solve the problems such as the need to remove carbon dioxide during the recycling process of blast furnace gas and the low yield of hydrogen-rich reducing gas. To effectively solve the above problems, the present invention proposes to use the gasification reaction so that the top gas does not need to remove CO 2And it is used as a gasifying agent to gasify pulverized coal and biomass, and the CO brought in by the top gas of the stack is superimposed to form a hydrogen-rich 2 and CO-rich mixed reducing gas is then blown into the blast furnace. The surplus mixed gas can also be used for injection on the sintering material surface, opening up a new idea for the recycling of top gas in the furnace and avoiding the CO 2 collection process. It also makes full use of the carbon therein, enabling carbon emission reduction; at the same time, using the low-cost and widely sourced biomass green energy as fuel can partially or fully replace the primary pulverized coal energy, broadening the source of gas-making fuel. Through the above technologies, hydrogen-rich reducing gas with stable production and low cost is obtained, providing an effective way for carbon reduction, energy conservation, and emission reduction in ironmaking production.

[0006] To achieve the above object, the present invention provides a process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal, comprising the following steps:

[0007] (1) Pass the carbon-containing fuel, blast furnace top gas, steam, and oxygen into a fluidized gasification furnace for gasification reaction to obtain hydrogen-rich reducing gas;

[0008] (2) Pass the hydrogen-rich reducing gas into a cyclone separator for purification to obtain purified gas;

[0009] (3) Pass the purified gas into user unit 1 and user unit 2 through a heating furnace and a heat exchanger respectively.

[0010] The gasification reaction in step (1) of the present invention is as follows:

[0011] H 2 O + C = H 2 + CO ΔH = +131.273 kJ / mol (1)

[0012] CO 2 + C = 2CO ΔH = +172.4 kJ / mol (2)

[0013] 0.5O 2 + C = CO ΔH = -110.5 kJ / mol (3)

[0014] O 2 + C = CO 2 ΔH = -393.51 kJ / mol (4)

[0015] Preferably, in step (1), the carbon-containing fuel includes biomass and pulverized coal. The particle size requirement for biomass is that the particle size fraction <0.074 mm is greater than 85 - 90%, and for pulverized coal, the particle size fraction <0.074 mm is greater than 85 - 90%; the ratio of biomass to pulverized coal is 0% - 100%. The ratio of biomass to pulverized coal is determined according to the composition and temperature requirements of the hydrogen-rich reducing gas proposed by the user unit.

[0016] Preferably, in step (1), the biomass and pulverized coal are mixed in the biomass-blended coal unit.

[0017] Preferably, in step (1), using the energy-quality balance model, based on the volume ratio and temperature of H and CO in the hydrogen-rich reducing gas, the addition amounts of the biomass and pulverized coal, as well as the injection amounts of the blast furnace top gas, steam, and oxygen are determined. 2 and CO in the hydrogen-rich reducing gas, the addition amounts of the biomass and pulverized coal, as well as the injection amounts of the blast furnace top gas, steam, and oxygen are determined.

[0018] The energy-quality balance model in the present invention includes a material balance model and a heat balance model. First, based on the law of conservation of mass, according to the physical and chemical reactions occurring in the furnace, carbon, hydrogen, and oxygen balance equations are established, and the component and mass of the syngas product are obtained by solving the combined balance equations. Secondly, based on Hess's law, without considering the reaction process in the furnace, taking the energy possessed and consumed by the material in the initial and final states as the calculation basis, the input and output values of the system heat are calculated. According to the law of conservation of energy, the temperature of the syngas can be determined. The idea of the above mass-energy balance model is a common calculation idea or theoretical method in the metallurgy and chemical industries. For the above calculation process, an Excel software can be used to compile a balance calculation model to achieve interlock calculation. By changing the mass, composition, or temperature of the raw fuels, the calculation can be performed immediately to obtain the component, mass, and temperature of the syngas, and the adjustment of the composition and temperature can be realized.

[0019] By changing the ratio (biomass and pulverized coal) and flow rate (blast furnace top gas, steam, and oxygen) of each substance in the raw fuels in the present invention, it is equivalent to adjusting the content of carbon, hydrogen, and oxygen in the reactants. When the content of each element in the input reactants changes, the content of carbon, hydrogen, and oxygen in the reaction product (hydrogen-rich reducing gas) and their distribution in the species will also change, thereby realizing the adjustment of the ratio of hydrogen and carbon monoxide in the syngas. At the same time, when the input elements change, the influence on the heat will also change accordingly, which is equivalent to adjusting the heat and temperature carried by the output product.

[0020] Preferably, in step (1), by volume, the composition of the hydrogen-rich reducing gas is: H 2 35.62% - 62.23%, CO 40.12 - 11.22%, CO 2 4.32 - 1.53%, N 2 12.28 - 8.02%, H 2 O 7.66 - 16.99%.

[0021] Preferably, in step (1), the operating temperature of the fluidized gasifier can reach 1300 - 1500 °C, and the temperature of the hydrogen-rich reducing gas is 200 - 1000 °C.

[0022] Preferably, in step (2), the operating temperature of the cyclone separator can reach up to 1000 - 1200 °C.

[0023] In the present invention, the cyclone dust collector is used to remove a small amount of unburned pulverized coal from the hydrogen-rich reducing gas output from the fluidized gasifier. It can operate in a high-temperature environment of 1000-1200°C, and can meet the requirement of minimizing heat loss during the dust removal process of the hydrogen-rich reducing gas. Since the gasification reaction rate is fast and the residence time of biomass and pulverized coal in the fluidized gasifier is limited, a small amount of unburned pulverized coal particles will be entrained in the produced hydrogen-rich reducing gas. After these unburned pulverized coal particles are collected by the cyclone dust collector, they can be returned to the coal blending unit, improving the conversion rate of solid fuel carbon.

[0024] Preferably, in step (3), the user unit 1 is the tuyere injection of the blast furnace.

[0025] Preferably, in step (3), the user unit 2 is the injection at the middle and lower part of the tuyere of the blast furnace hearth or the injection on the sintering material surface or other production units using gaseous fuel.

[0026] Therefore, the present invention adopts the above process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal, and has the following beneficial effects:

[0027] (1) In the process of the present invention, CO in the top gas of the blast furnace is used as a gasification agent, and at the same time, CO and CO in the top gas of the blast furnace are recycled. CO reacts with biomass and pulverized coal to generate CO, which enters the product reducing gas together with the original CO in the top gas, realizing the low-cost recycling of the top gas of the blast furnace, solving the emission reduction problem of CO in the blast furnace process, and improving the effective conversion rate and utilization rate of carbon in the top gas of the blast furnace. 2 as a gasification agent, and at the same time, CO and CO in the top gas of the blast furnace are recycled. 2 CO 2 reacts with biomass and pulverized coal to generate CO, which enters the product reducing gas together with the original CO in the top gas, realizing the low-cost recycling of the top gas of the blast furnace, solving the emission reduction problem of CO in the blast furnace process, and improving the effective conversion rate and utilization rate of carbon in the top gas of the blast furnace. 2

[0028] (2) In the process of the present invention, H2O vapor is used as a gasification agent, and the concentration of H2 in the hydrogen-rich reducing gas is adjusted by changing the injection amount of H2O vapor; the outlet temperature of the hydrogen-rich reducing gas is adjusted by adjusting the flow rate and temperature of the introduced O2 gas. 2 O vapor is used as a gasification agent, and the concentration of H in the hydrogen-rich reducing gas is adjusted by changing the injection amount of H 2 O vapor; the outlet temperature of the hydrogen-rich reducing gas is adjusted by adjusting the flow rate and temperature of the introduced O 2 gas. 2

[0029] (3) After the hydrogen-rich reducing gas is injected into the tuyere of the blast furnace in the user unit 1 of the process of the present invention, while playing the advantageous role of hydrogen-rich smelting, the top gas of the blast furnace with a high H2 content can also be obtained, improving its reduction potential and recycling value. 2 content of the top gas of the blast furnace, improving its reduction potential and recycling value.

[0030] (4) The process of the present invention makes full use of the characteristics of high hydrogen and carbon content of biomass energy, and partially or completely replaces pulverized coal as the gasification fuel, which can reduce the consumption of primary coal resources.

[0031] (5) The hydrogen-rich reducing gas prepared by the process of the present invention has the characteristics of stable production, large quantity and low cost, and can meet the large demand of blast furnace production for hydrogen-rich reducing gas.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0033] Figure 1 is a schematic process flow diagram of the present invention;

[0034] In the figure: 1. Biomass and coal mixing unit; 2. Fluidized gasification furnace; 3. Cyclone separator; 4. Heat exchanger; 5. Heating furnace. Detailed Embodiments

[0035] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution, and detailed implementation methods and specific operation processes are given, but the present invention is not limited to this embodiment.

[0036] Taking biomass (by mass percentage, fixed carbon 16.94%, ash 0.34%, volatile matter 77.71%) and pulverized coal (by mass percentage, fixed carbon 82.28%, ash 10.1%, volatile matter 6.94%), blast furnace top gas (by volume percentage, CO2 2.55%, CO 2 22.82%, N 2 50.23%) as an example, with the total amount of solid fuel being 100 kg and the addition amount of top gas being 100 m 3 , and the addition amount of oxygen being 20 kg, by varying the ratio of biomass to pulverized coal and the addition amount of steam, the composition and temperature of the hydrogen-rich reducing gas produced by the present invention are calculated.

[0037] According to the law of conservation of mass, taking the mass and chemical composition of biomass, pulverized coal and top gas as input conditions, the masses of carbon, hydrogen and oxygen elements brought in by the three substances are calculated respectively; secondly, according to reaction equations (1) to (4), carbon, hydrogen and oxygen balance equations are established, and the combined balance equations are solved to obtain CO and H of the generated products 2 . At the same time, there is a water gas reaction CO 2 +H 2 =CO+H 2 O in the system. When the reaction reaches equilibrium, there will still be a certain amount of CO 2 , H 2O. The above calculation process is programmed into a calculation model using Excel software, which is the material balance model in this specification. By using the Excel table nesting function, only the input of a certain mass of biomass, pulverized coal, water vapor, and oxygen is required to calculate the composition and mass of the syngas product; conversely, the H in the product can also be controlled by adjusting each input quantity. 2 / CO.

[0038] On the basis of the material balance, according to Hess's law, taking the energy possessed and consumed by the material in the initial and final states as the calculation basis, calculate the income and output values of the system heat. According to the law of conservation of energy, the temperature of the synthesis gas can be determined. The above calculation process is programmed into a heat balance model using Excel software, and the interlocking calculation of the material balance model and the heat balance model is realized.

[0039] Example 1

[0040] A process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal includes the following steps:

[0041] (1) Mix 30 kg of biomass and 70 kg of pulverized coal (the ratio of biomass to pulverized coal is 3:7) in the biomass-blended coal unit to obtain a carbon-containing fuel; among them, the particle size requirement of biomass is that the particle size greater than 0.074 mm is more than 85 - 90%, and the particle size of pulverized coal greater than 0.074 mm is more than 85 - 90%;

[0042] Feed 100 kg of carbon-containing fuel, 100 m 3 blast furnace top gas, 100 kg of water vapor, and 20 kg of oxygen into the fluidized gasifier for gasification reaction. The temperature of the blown O 2 is 500 °C to obtain hydrogen-rich reducing gas; the total amount of hydrogen-rich reducing gas is 522.1 m 3 , and the components of the hydrogen-rich reducing gas include, by volume ratio: H 2 47.59%, CO 27.14%, CO 2 3.30%, H 2 O 11.57%, N 2 10.40%, and the gas temperature is 708.76 °C;

[0043] (2) Feed the hydrogen-rich reducing gas into a cyclone separator for purification to obtain purified gas;

[0044] (3) Feed the purified gas into User Unit 1 and User Unit 2 through a heating furnace and a heat exchanger respectively. User Unit 1 is for injection at the blast furnace tuyere, and User Unit 2 is for injection at the middle and lower part tuyeres of the blast furnace hearth or for injection on the sintering material surface or for other production units using gaseous fuels.

[0045] Example 2

[0046] A process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal, comprising the following steps:

[0047] (1) Mix 50 kg of biomass and 50 kg of pulverized coal (the ratio of biomass to pulverized coal is 1:1) in a biomass-blended coal unit to obtain a carbon-containing fuel; wherein the particle size requirement of the biomass is that the particle size fraction <0.074 mm is greater than 85-90%, and the particle size fraction of the pulverized coal <0.074 mm is greater than 85-90%;

[0048] Feed 100 kg of the carbon-containing fuel, 100 m 3 blast furnace top gas, 130 kg of steam and 20 kg of oxygen into a fluidized-bed gasifier for gasification reaction, with the temperature of the blown O 2 being 500 °C to obtain hydrogen-rich reducing gas; the total amount of hydrogen-rich reducing gas is 629.9 m 3 , and the composition of the hydrogen-rich reducing gas by volume includes: H 2 60.77%, CO 12.82%, CO 2 1.73%, H 2 O 16.42%, N 2 8.26%, and the gas temperature is 578.3 °C;

[0049] (2) Pass the hydrogen-rich reducing gas into a cyclone separator for purification to obtain purified gas;

[0050] (3) Pass the purified gas through a heating furnace and a heat exchanger into User Unit 1 and User Unit 2 respectively. User Unit 1 is for injection into the blast furnace tuyere, and User Unit 2 is for injection into the middle and lower part tuyeres of the blast furnace shaft or injection onto the sintering material surface or other production units using gaseous fuels.

[0051] Example 3

[0052] A process for preparing hydrogen-rich reducing gas by using blast furnace top gas in cooperation with biomass and pulverized coal, comprising the following steps:

[0053] (1) Mix 10 kg of biomass and 90 kg of pulverized coal (the ratio of biomass to pulverized coal is 1:9) in a biomass-blended coal unit to obtain a carbon-containing fuel; wherein the particle size requirement of the biomass is that the particle size fraction <0.074 mm is greater than 85-90%, and the particle size fraction of the pulverized coal <0.074 mm is greater than 85-90%;

[0054] Feed 100 kg of the carbon-containing fuel, 100 m 3 blast furnace top gas, 100 kg of steam and 20 kg of oxygen into a fluidized-bed gasifier for gasification reaction, with the temperature of the blown O 2 being 500 °C to obtain hydrogen-rich reducing gas; the total amount of hydrogen-rich reducing gas is 451.6 m 3, the composition of the hydrogen-rich reducing gas by volume includes: H 2 40.28%, CO 35.07%, CO 2 3.97%, H 2 O 9.12%, N 2 11.56%, and the gas temperature is 910.5 °C;

[0055] (2) Pass the hydrogen-rich reducing gas into a cyclone separator for purification to obtain purified gas;

[0056] (3) Pass the purified gas into User Unit 1 and User Unit 2 through a heating furnace and a heat exchanger respectively. User Unit 1 is for tuyere injection in a blast furnace, and User Unit 2 is for injection at the middle and lower part of the blast furnace shaft tuyere or injection on the sintering material surface or other production units using gaseous fuels.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended 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 they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder, characterized in that: The following steps are involved: (1) introducing carbon-containing fuel, blast furnace top gas, water vapor and oxygen into a boiling gasifier for gasification reaction to obtain hydrogen-rich reducing gas; (2) passing the hydrogen-rich reducing gas into a cyclone separator for purification to obtain purified gas; (3) The purified gas is introduced into user unit 1 and user unit 2 through the heating furnace and the heat exchanger respectively.

2. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 1, characterized in that: In step (1), the carbon-containing fuel includes biomass and coal powder, the particle size of biomass is required to be greater than 85-90% of the particle size <0.074mm, and the particle size of coal powder is required to be greater than 85-90% of the particle size <0.074mm; the ratio of biomass to coal powder is 0% to 100%.

3. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 2, characterized in that: In step (1), biomass and coal powder are mixed in a biomass-coal mixing unit.

4. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 3, characterized in that: In step (1), the amount of biomass and pulverized coal added and the amount of blast furnace top gas, water vapor and oxygen injected are determined according to the volume ratio and temperature of H2 and CO in the hydrogen-rich reducing gas using an energy-mass balance model.

5. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 4, characterized in that: In step (1), the composition of the hydrogen-rich reducing gas is, by volume ratio, 35.62% to 62.23% H2, 40.12% to 11.22% CO, 4.32% to 1.53% CO2, 12.28% to 8.02% N2, and 7.66% to 16.99% H2O.

6. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 1, characterized in that: In step (1), the operating temperature of the boiling gasifier can reach 1300-1500°C, and the temperature of the hydrogen-rich reducing gas is 200-1000°C.

7. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 1, characterized in that: In step (2), the operating temperature of the cyclone separator can reach a maximum of 1000-1200°C.

8. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 1, characterized in that: In step (3), user unit 1 is blast furnace tuyere injection.

9. The process for preparing hydrogen-rich reducing gas by using blast furnace top gas in combination with biomass and coal powder according to claim 1, characterized in that: In step (3), user unit 2 is other production units that perform blowing at the lower tuyere of the blast furnace body or sintering material surface blowing or use gas fuel.

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