A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide

Abstract

The invention discloses a method for reducing blast furnace carbon consumption by burning coal powder through plasma carbon dioxide, comprising: burning coal gas from the top of the blast furnace through CO 2 Separation device, separates carbon dioxide and other gases, and other gases are transported to the hot air furnace; separates CO 2 The gas is used as the carrier gas and oxidant for pulverized coal injection in blast furnaces. It is pressurized by an air compressor and used to transport pulverized coal. A high-frequency induction plasma heater is used, which consists of a plasma generator and a reactor. 2 The pulverized coal as carrier gas enters the plasma generator and CO 2 Gas ionization forms plasma gas with a temperature above 3000K; coal powder and CO 2 The plasma reaction forms high-temperature CO gas; CO carries heat into the blast furnace to participate in the reaction. 2 A method for intensifying the combustion of pulverized coal injected into a blast furnace by using plasma heating as both a carrier gas and an oxidant.

Description

Technical Field

[0001] The present invention relates to the technical field of blast furnace ironmaking, and specifically to a method for injecting pulverized coal into a blast furnace by using plasma-heated CO2 waste gas as a carrier gas to promote pulverized coal combustion, replace part of the injected coal with clean electric energy, and reduce pulverized coal consumption in the blast furnace. Background Art

[0002] In the blast furnace production process, pulverized coal is injected to replace coke to reduce costs. The pulverized coal injected into the blast furnace burns in the oxidation zone in the furnace. A part of the unburned pulverized coal enters the furnace, which may have an adverse effect on the furnace working conditions; the other part of the unburned pulverized coal escapes with the blast furnace gas and fails to be effectively utilized. The factors affecting the combustion rate of pulverized coal mainly include the type of pulverized coal, particle size, oxidation atmosphere, residence time of pulverized coal in the oxidation atmosphere and combustion temperature, among which temperature and oxidation atmosphere are the main factors affecting the combustion of pulverized coal. In blast furnace production, the combustion rate of pulverized coal injection is mainly increased by increasing the oxygen enrichment of the blast and the blast temperature, but it is still difficult to achieve complete combustion of pulverized coal under high coal injection ratio conditions. At present, the carrier gas used for pulverized coal injection in the blast furnace ironmaking process is mainly nitrogen or compressed air. Nitrogen is an inert gas and does not participate in the chemical reaction in the blast furnace, which will reduce the effective gas concentration in the blast furnace. If CO2 is used instead of the original nitrogen or compressed air as the transmission medium, the nitrogen gas volume fraction of the blast furnace top gas will be significantly reduced, and the CO+CO2 volume fraction will increase, which can effectively promote the gas utilization efficiency in the blast furnace.

[0003] Patent document CN107119160A is a method and system for blast furnace coal injection with compressed gas preheating. The compressed gas at room temperature is preheated to 70-80°C through a heat exchanger, which is higher than the saturated steam condensation temperature in the coal powder. Although the precipitation of condensed water is avoided, it is conducive to the smooth flow of the injection pipeline, but it is very limited to improve the combustion efficiency of the coal powder. Patent document CN102382915A uses carbon dioxide as a transmission medium for blast furnace coal injection. CO2 is used instead of N2 and compressed air as the transmission medium for coal powder injection. Although the N2 content fed into the blast furnace can be reduced, CO2 consumes a lot of heat in the blast furnace reaction, and heat supplement is required to maintain the thermal balance of the blast furnace, and it cannot reduce the carbon consumption of blast furnace production. Through literature and patent retrieval, no technical method for using plasma CO2 to promote the combustion of coal powder injection in blast furnaces and reduce the carbon consumption of blast furnaces has been found. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to solve the problem that pulverized coal injected into blast furnace cannot be completely burned under the existing production process conditions, reduce the carbon consumption of blast furnace and reduce the CO2 waste gas emission produced by blast furnace.

[0005] The technical solution of the present invention is a method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide, comprising a pulverized coal injection process in blast furnace production, comprising the following steps:

[0006] (1) The blast furnace top gas is separated into carbon dioxide and other gases through a CO2 separation device, and the other gases are transported to the hot blast furnace; the separated CO2 gas is used as a carrier gas and oxidant for blast furnace pulverized coal injection, and is pressurized by an air compressor for transporting pulverized coal;

[0007] (2) Use a high-frequency induction plasma heater, which consists of a plasma generator and a reactor. Coal powder with CO2 as a carrier gas enters the plasma generator, and the CO2 gas is ionized under high-frequency induction to form a plasma gas with a temperature above 3000K. The reactor mainly reacts with coal powder and CO2 plasma to form high-temperature CO gas.

[0008] (3) CO carries heat into the blast furnace to participate in the reaction.

[0009] Plasma or plasma gas refers to gas in a plasma state.

[0010] In step (1), other gases are transported to the hot blast furnace for burning the hot blast furnace.

[0011] Step (2), the plasma generator ionizes the gas through high-frequency induction to generate high-temperature plasma gas. The alternating magnetic field in the coil in the plasma generator generates an induced alternating electric field, which transmits energy to the gas in a high-frequency inductive coupling manner, ionizes the gas, generates high-temperature plasma, and the plasma temperature reaches above 3000K; the plasma temperature can reach a higher temperature and there is no problem of electrode loss and gas pollution. Traditional plasma heating uses plasma arc heating, which has the problems of electrode loss and temperature control. The electromagnetic induction method used in the present invention heats the gas to ionize the gas.

[0012] Combined with the research on the reaction between pulverized coal and plasma CO2 in blast furnace, this not only strengthens the combustion of pulverized coal, but also promotes the conversion of CO2. However, the reaction process mechanism is more complicated and has certain operation difficulties. The present invention uses high-frequency induction plasma heating to recycle CO2 in the exhaust gas, strengthen pulverized coal combustion, and convert and utilize CO2 gas.

[0013] The reaction between coal powder and high-temperature CO2 plasma mainly takes place in the reactor. Under the action of high temperature, the volatile matter in the coal powder will be rapidly gasified, and the C in the coal powder will react with the plasma CO2, CO2+C→2CO, to generate high-temperature CO gas.

[0014] Step (3) supplements the heat consumed by direct injection of CO2 into the blast furnace through plasma heating, so that it is converted into CO reducing gas outside the blast furnace, and carries the same amount of heat into the blast furnace to participate in the reaction, thus meeting the heat requirement of the reaction inside the blast furnace. CO2 entering the blast furnace to participate in the reaction consumes carbon, which is not conducive to reducing the carbon consumption of the blast furnace, so it is necessary to convert CO2 into CO to enter the blast furnace to participate in the reaction.

[0015] According to a method of reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide of the present invention, preferably, the other gases in step (1) contain CO and N2, and also contain a small amount of H2.

[0016] According to the method of reducing blast furnace carbon consumption by burning coal powder with plasma carbon dioxide of the present invention, preferably, the coal powder in step (1) is anthracite or bituminous coal, or a mixture of the two.

[0017] More preferably, if the coal powder in step (1) is anthracite, the proportion of anthracite coal powder with a particle size of less than 200 mesh is greater than 80%, and the rest are particle sizes greater than 200 mesh; if it is bituminous coal, the proportion of bituminous coal powder with a particle size of less than 200 mesh is greater than 60%, and the rest are particle sizes greater than 200 mesh. Such a particle size distribution of coal powder can make the coal powder fully combust and decompose.

[0018] Preferably, the anthracite powder or bituminous coal has a moisture content of less than 1.5% and an ash content of less than 9%.

[0019] According to a method for reducing blast furnace carbon consumption by burning coal powder with plasma carbon dioxide of the present invention, preferably, the plasma generator in step (2) comprises a quartz tube, an externally wound coil and a high-frequency power supply. The high-frequency current generated by the high-frequency power supply passes through the coil of the reactor, and the alternating magnetic field in the coil generates an induced alternating electric field.

[0020] According to the method of reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide of the present invention, preferably, the plasma gas temperature in step (2) reaches 3000-3500K.

[0021] According to the method of reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide of the present invention, preferably, the power of the entire plasma heater in step (2) reaches more than 1 MW.

[0022] According to the method of reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide of the present invention, preferably, the temperature of the CO gas generated by the reaction in the reactor in step (2) is controlled at 2000-2500 K. CO is fed into the blast furnace together with the ash remaining after the pulverized coal is burned, and participates in the reaction in the blast furnace.

[0023] Preferably, the CO2 separation method in step (1) adopts physical (PSA) or chemical (amine) gas separation technology to separate part of the CO2 from the blast furnace top gas.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) Compared with the use of N2 or compressed air as carrier gas in the past, the CO2 separated from the blast furnace gas is used as the carrier gas for pulverized coal injection. This not only reduces the N2 content in the blast furnace gas and increases the chemical energy and reaction potential of the reducing gas, but also recycles the CO2 in the blast furnace gas and reduces the CO2 emissions from the blast furnace production process.

[0026] 2) At the same time, CO2 is used as an oxidant to promote the combustion of pulverized coal through plasma heating (clean electricity generation), further reducing the coal consumption of the blast furnace production process. Under plasma heating conditions, the C in the pulverized coal reacts with CO2, and the amount of CO gas generated is twice the amount generated by direct combustion of pulverized coal. Therefore, under the premise of a certain coke ratio, the amount of pulverized coal injected into the blast furnace is only half of the past, and the consumption of pulverized coal injected into the blast furnace has been greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the device of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with specific embodiments.

[0029] like Figure 1 As shown, carbon dioxide is separated from the separator, passes through the plasma generator, and then enters the plasma generator after ionization with pulverized coal using CO2 as carrier gas. Under high-frequency induction, CO2 gas is ionized to form plasma gas with a temperature of more than 3000K; the reactor mainly reacts with pulverized coal and CO2 plasma to form high-temperature CO gas. The high-temperature CO gas further enters the blast furnace for reaction.

[0030] 1) A physical method (PSA) or a chemical method (amine method) is used to separate part of the CO2 from the blast furnace top gas, and the separated CO2 is pressurized and used as a carrier gas for injecting pulverized coal; in this embodiment, the pulverized coal is anthracite, and the proportion of pulverized coal with a particle size less than 200 mesh is greater than 80%.

[0031] 2) If the C in the pulverized coal reacts with O2, 2C+O2→2CO, 1kgC produces 1.87Nm3 of CO gas; if the C in the pulverized coal reacts with plasma CO2, CO2+C→2CO, 1kgC consumes 1.87Nm3 of CO gas. 3 CO2 gas, producing 3.74Nm 3The amount of CO gas produced is twice the amount of gas produced by the combustion reaction of carbon and oxygen.

[0032] 3) 4500m 3 Take the blast furnace as an example, with a daily output of 10,000 tons, a coke ratio of 310 kg / t, a coal ratio of 180 kg / t, and a gas generation of 1,400 m 3 / t. Under the premise of keeping the blast furnace coke ratio unchanged, only 90kg / t of coal powder is consumed to separate 135Nm 3 / t of CO2, after plasma heating and combustion reaction, can generate the same volume and temperature of coal gas as when the pulverized coal is 180kg / t.

[0033] 4) By using clean electricity plasma heating and utilizing plasma CO2 to promote the combustion of pulverized coal injected into blast furnaces, under the existing blast furnace production process, the consumption of pulverized coal injected into blast furnaces can be reduced by 50%, and more than 20% of the CO2 in blast furnace gas can be recycled.

[0034] The present invention proposes a method for intensifying the combustion of pulverized coal injected into the blast furnace by plasma heating using recovered blast furnace gas CO2 as an oxidant, which can not only promote the combustion of pulverized coal injected into the blast furnace, but also realize the recovery and utilization of CO2 in blast furnace gas, thereby reducing the carbon energy consumption of the blast furnace process and reducing carbon emissions.

Claims

1. A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide, comprising a pulverized coal injection process in blast furnace production, characterized in that: The following steps are involved: (1) The blast furnace top gas is separated into carbon dioxide and other gases through a CO2 separation device, and the other gases are transported to the hot blast furnace; the separated CO2 gas is used as a carrier gas and oxidant for blast furnace pulverized coal injection, and is pressurized by an air compressor for transporting pulverized coal; (2) A high-frequency induction plasma heater is used, which consists of a plasma generator and a reactor. Coal powder with CO2 as a carrier gas enters the plasma generator, and the CO2 gas is ionized under high-frequency induction to form a plasma gas with a temperature of more than 3000K. The coal powder and CO2 plasma react in the reactor to form high-temperature CO gas. The plasma generator ionizes the gas through high-frequency induction to generate high-temperature plasma gas. The alternating magnetic field in the coil in the plasma generator generates an induced alternating electric field, which transmits energy to the gas in a high-frequency induction coupling manner, ionizes the gas, and generates high-temperature plasma. (3) CO carries heat into the blast furnace to participate in the reaction.

2. A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 1, characterized in that: The other gases in step (1) contain CO, N2 and H2.

3. A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 1, characterized in that: The coal powder in step (1) is anthracite or bituminous coal, or a mixture of the two.

4. A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 3, characterized in that: The anthracite powder or bituminous coal has a moisture content of less than 1.5% and an ash content of less than 9%.

5. The method of reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 1, characterized in that: The plasma generator in step (2) comprises a quartz tube, an external winding coil and a high-frequency power supply.

6. A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 1, characterized in that: In step (2), the plasma gas temperature is 3000-3500K.

7. A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 1, characterized in that: In step (2), the power of the entire plasma heater is above 1 MW.

8. The method of reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 1, characterized in that: The temperature of the CO gas generated by the reaction in the reactor in step (2) is controlled at 2000-2500K.

9. A method for reducing blast furnace carbon consumption by burning pulverized coal with plasma carbon dioxide according to claim 1, characterized in that: The CO2 separation method in step (1) adopts physical PSA or chemical alcohol amine method coal gas separation technology to separate the CO2 from the blast furnace top gas.

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