A converter pulverized coal injection system

Abstract

This invention discloses a converter pulverized coal injection system, comprising a pulverized coal silo, a pulverized coal injection tank, a bag filter, and a gas storage tank. The gas storage tank is connected to an external nitrogen or CO2 source. Pulverized coal is conveyed to the pulverized coal silo via nitrogen or CO2 pneumatic conveying. The bag filter is installed on the top of the pulverized coal silo. Pulverized coal in the silo is fed into the pulverized coal injection tank via a pneumatic bell valve. A temperature monitoring device is installed on the top of the pulverized coal silo. The pressure relief pipe of the pulverized coal injection tank is connected to the upper part of the pulverized coal silo. An explosion relief valve is installed on the top of the pulverized coal silo. A fluidizing device is installed in the conical part of the pulverized coal injection tank to fluidize the pulverized coal. The fluidized coal, with a small amount of conveying gas as the carrier gas, is conveyed to the pulverized coal distributor through a first pipeline. After passing through the pulverized coal distributor and the spray gun, pulverized coal is continuously injected and conveyed to the vaporization cooling flue of the converter. This invention can solve the problems of low coal gas recovery, high carbon dioxide emissions, and safety issues existing in the current converter gas recovery technology, achieving safe and efficient recovery of converter gas, and has technological innovation.

Description

Technical Field

[0001] This invention relates to the field of converter steelmaking technology, and more particularly to a converter pulverized coal injection system. Background Technology

[0002] Converter steelmaking plays a dominant role in my country's steelmaking process, and its byproduct, converter gas, is an important secondary energy source for steel enterprises, accounting for 80-90% of the total energy recovery in the entire steelmaking process. It can be used as an important fuel and raw material in industrial production such as metallurgical ladle baking, chemical products, and gas-fired power generation. Therefore, improving the quality and quantity of converter gas recovery is beneficial to increasing steelmaking efficiency and effectively reducing greenhouse gas CO2 emissions, which is of great significance for achieving sustainable development in steel enterprises. However, current converter gas recovery in my country generally suffers from problems such as low gas recovery rate, low CO content in the recovered gas, and high CO2 and O2 content. To further improve and enhance gas recovery technology and strengthen our company's competitiveness, strengthening related research and technological development is urgently needed.

[0003] Currently, the purification and recovery of converter gas mainly adopts wet (OG) and dry (LT) recovery technologies. (1) OG method: The flue gas generated by the converter enters the vaporization cooling flue and the first and second stage Venturi scrubbers through the furnace mouth skirt for washing and purification. The flue gas temperature drops from about 1000℃ at the outlet of the vaporization cooling flue to about 70℃. (2) LT method: The dry purification and recovery system for converter gas was jointly developed by Lurgi GmbH and Thyssen Steel in the 1960s. The converter flue gas enters the vaporization cooling flue through the flue gas hood, and then enters the evaporative cooler. After being cooled by steam injection from 1000℃ to 200℃, it enters the electrostatic precipitator, and the flue gas is fully purified. Compared with the wet (OG) method, the dry method has advantages such as high dust removal efficiency, no secondary pollution and sewage treatment problems, low energy consumption and small footprint. However, the explosion leakage is more prominent in the gas recovery process, which affects the amount of gas recovered to a certain extent. Currently, the purification and recovery of converter gas mainly adopts wet (OG) and dry (LT) recovery technologies, which have problems such as high energy consumption, high pollution, high risk factor, low gas recovery volume and low quality.

[0004] In recent years, the conversion and utilization technology of CO2 in industrial waste gas has attracted much attention. Researchers have studied the conversion of CO2 into alkanes, alcohols, or other organic substances under photocatalytic conditions, as well as the conversion of CO2 into CO or directly into carbon under discharge conditions. However, currently, these methods are limited to laboratory research and are difficult to directly apply to the CO2 conversion and utilization process in converter gas recovery. Coal gasification is one of the efficient and clean ways to convert coal into CO2. It is a process that uses coal or coke as raw material and oxygen or steam as gasifying agent to convert the combustible parts of coal or coke into gaseous fuel through chemical reactions under certain temperature and pressure conditions. However, the coal gasification process requires a large amount of water and involves significant investment.

[0005] In actual production, the recovery of converter gas is mainly affected by various factors such as equipment level, operating procedures, and raw material quality. Improving and perfecting these factors has the most direct effect on improving the quality of converter gas. However, in the process of gas recovery, problems such as greenhouse gas CO2 emissions and oxygen-free gas recovery have not been solved, and the presence of large amounts of CO2 also affects the unit calorific value of the gas and corrodes equipment such as gas holders. Although metallurgists at home and abroad have conducted a lot of experimental and theoretical research on improving the quality and recovery of converter gas, most of them have focused on smelting process systems and purification and dust removal methods, without fundamentally solving the problems of large greenhouse gas CO2 emissions and ultra-low oxygen recovery of gas. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, this invention provides a converter gas injection system. This novel method utilizes high-temperature converter flue gas to inject pulverized coal, preparing high-quality gas. It adds a pulverized coal injection system to the existing converter gas purification and recovery system, fully utilizing the harmful CO2 components in the high-temperature flue gas. This fundamentally solves the problems of low converter gas recovery efficiency, small recovery volume, and large CO2 emissions, while also addressing the issue of efficient coal gasification. This invention has significant application value for improving the energy resource utilization rate of my country's steel enterprises and provides a useful reference for the steel industry to fully utilize socially recycled resources. It has been verified through industrial trials, demonstrating broad application prospects and significant economic and environmental benefits. This invention solves the problems of low gas recovery volume, large carbon dioxide emissions, and safety issues existing in current converter gas recovery technologies, achieving safe and efficient converter gas recovery, and is technologically innovative.

[0007] A converter pulverized coal injection system provided to achieve the purpose of this invention includes a pulverized coal silo, a pulverized coal injection canister, a bag filter, and a gas storage tank. The gas storage tank is connected to an external nitrogen or CO2 source, and pulverized coal is delivered to the pulverized coal silo via a nitrogen or CO2 pneumatic conveying method. The bag filter is installed on the top of the pulverized coal silo to discharge the nitrogen or CO2 used for conveying pulverized coal, and to depressurize and dehumidify the pulverized coal silo. The pulverized coal in the silo is fed into the pulverized coal injection canister through a pneumatic bell valve. A temperature monitoring device is installed on the top of the pulverized coal silo. The pressure relief pipe of the pulverized coal injection canister is connected to the upper part of the pulverized coal silo. An explosion relief valve is installed on the top of the pulverized coal silo. The system is characterized in that: the conical part of the pulverized coal injection canister is equipped with a fluidizing device, which is used to fluidize the pulverized coal. The fluidized coal is transported to the pulverized coal distributor through a first pipeline with a small amount of conveying gas as the carrier gas. The pulverized coal is then continuously or intermittently injected into the vaporization cooling flue of the converter through the pulverized coal distributor and the spray gun.

[0008] As a further improvement to the above solution, two gas storage tanks are provided. One gas storage tank delivers pulverized coal to the pulverized coal silo via nitrogen or CO2 pneumatic conveying. The other gas storage tank is connected to the nitrogen cooling interface of the pulverized coal gun via a second pipeline. The second pipeline is equipped with a nitrogen shut-off valve for pulverized coal gun cooling and a pressure reducing valve in sequence.

[0009] As a further improvement to the above solution, multiple pulverized coal main pipes are provided between the second pipeline and the first pipeline, and each pulverized coal main pipe is equipped with a purge valve.

[0010] As a further improvement to the above scheme, a return coal pipeline connected to the top of the coal powder silo is provided on the side of the first pipeline near the coal powder distributor, and a return coal valve is provided on the return coal pipeline.

[0011] The beneficial effects of this invention are:

[0012] Compared with existing technologies, this invention mainly utilizes pneumatic injection technology to inject pulverized coal into the converter's vaporization cooling flue through a spray gun. Taking advantage of the high temperature (1200℃-1500℃) and reducing properties of the converter flue gas, the pulverized coal rapidly decomposes into high-calorific-value H2 and carbon. The carbon reacts with a small amount of oxygen in the converter flue gas to generate carbon monoxide, eliminating oxygen in the flue gas and quickly reaching the coal gas recovery standard. Furthermore, the carbon in the pulverized coal reacts with CO2 to generate CO, increasing the absolute value of CO in the coal gas and improving the efficiency, quality, and safety of coal gas recovery. This achieves a safe, efficient, low-consumption, and environmentally friendly converter gas recovery process. The pulverized coal injection process using high-temperature converter flue gas can fundamentally solve problems such as low converter gas recovery efficiency, small recovery volume, large CO2 emissions, and equipment corrosion.

[0013] This new process has the following characteristics:

[0014] (1) The process is simple and efficient. This process adds a pulverized coal injection system to the original gas purification and recovery system;

[0015] (2) Low cost. The anthracite or blended coal used in this process is a common type of coal, which is abundant and inexpensive, and the coal powder preparation and drying technology is mature;

[0016] (3) Full utilization of resources. The injection of pulverized coal into the high-temperature flue gas of the converter can make more efficient use of the waste heat and harmful CO2 of the flue gas. A very small amount of residue enters the subsequent dust removal system together and can be directly used for sintering or preparation of cold-solidified pellets for converter. The residual carbon can improve the reduction performance of cold-solidified pellets;

[0017] (4) The process is safe and reliable. This method solves the problem of oxygen explosion, relaxes the oxygen content limit for recovered coal gas, thereby extending the coal gas recovery period and recovering as much coal gas as possible;

[0018] (5) Environmentally friendly process. The utilization of greenhouse gas CO2, along with improved gas quality, indirectly reduces CO2 emissions. Furthermore, pulverized coal fly ash can also be comprehensively utilized. Converter gas is a byproduct of the steelmaking process and an important secondary energy source. The technology of injecting pulverized coal into high-quality converter gas can solve problems such as low CO content and explosion hazard in the recovered gas. Safe and efficient recovery and utilization of converter gas is of great significance for energy conservation, emission reduction, cost reduction, efficiency improvement, and environmental pollution mitigation in the steel industry.

[0019] The present invention has the following practical application effects:

[0020] (1) Effectively improve the quality of converter gas recovery, achieving an average increase of 10% in gas recovery, an average increase of 10% in CO content in gas, and an average decrease of 40% in CO2 content (based on a CO2 volume fraction of 20%); or an average increase of more than 15% in the calorific value of gas recovered per ton of steel.

[0021] (2) The O2 content in the coal gas is reduced by more than 50%, resulting in a CO2 emission reduction of approximately 8 Nm³ per ton of steel. 3 ;

[0022] Expected economic and social benefits:

[0023] (1) Direct benefits of coal gas recovery

[0024] After the implementation of the new technology:

[0025] 1) After injecting pulverized coal, the CO2 conversion rate is approximately 40% (based on a CO2 volume fraction of 16%), and the O2 conversion rate is approximately 50%. Therefore, the CO content in the coal gas increases by approximately 7 Nm³. 3 / t of steel is equivalent to increasing the amount of gas with the same calorific value by approximately 15Nm³. 3 / t steel (currently, the CO volume fraction of the gas is calculated as 47%, the same below);

[0026] 2) The gas recovery time can be extended by approximately 30 seconds, which can increase the gas volume by approximately 10 Nm³. 3 / t steel (assuming an average CO volume fraction of 35% before and after recovery) is equivalent to 7 Nm³ of gas with the same calorific value. 3 / t steel;

[0027] 3) The amount of H2 generated by the pyrolysis of the injected pulverized coal increases by approximately 5 Nm. 3 / t of steel is equivalent to increasing the amount of gas with the same calorific value by 12Nm³. 3 / t steel;

[0028] It can be seen that the above-mentioned increase of 34 Nm³ in gas consumption per ton of steel corresponds to the same calorific value. 3 / t of steel, the profit from generating electricity per cubic meter of gas is: 0.2 yuan, the profit per ton of steel is approximately: 0.2 * 34 = 6.8 yuan, that is, 6.8 yuan.

[0029] The residual carbon content of pulverized coal per ton of steel is about 3 kg (if the carbon powder is converted by 60%, then 40% of the carbon can be recovered and utilized). The price of carbon powder per kilogram is 1.07 yuan. Therefore, the benefit per ton of steel is about 1.07 * 3 = 3.2 yuan.

[0030] Therefore, the total benefit per ton of steel is approximately: 6.8 + 3.2 = 10 yuan, or 10 yuan.

[0031] The pulverized coal injection rate is approximately 9 kg / t of steel, and the cost of pulverized coal injection per ton of steel is approximately 6.5 yuan (the price of pulverized coal per ton of blast furnace is approximately 600 yuan). The comprehensive economic benefit per ton of steel is: 10 - 6.5 = 3.5 yuan. Based on an annual output of 1.8 million tons of steel per converter, the annual economic benefit is approximately 6 million yuan.

[0032] (2) Environmental benefits

[0033] CO2 emissions are reduced by approximately 8 Nm³ per ton of steel. 3 / t steel, annual CO2 emission reduction is about 30,000 tons, which is about 2.5 million yuan based on the current carbon trading tax.

[0034] It is evident that the project has considerable economic and environmental benefits. Attached Figure Description

[0035] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0036] Figure 1 This is a schematic diagram of the structure of the present invention;

[0037] Figure 2 This is the Gibbs free energy diagram for the reaction process of this invention. Detailed Implementation

[0038] like Figure 1As shown, the present invention provides a converter pulverized coal injection system, comprising a pulverized coal silo 1, a pulverized coal injection tank 2, a bag filter 3, and a gas storage tank 4. The pulverized coal silo 1 is a large-angle steel silo with a volume of 70m³. 3 The maximum storage capacity is 50 tons of pulverized coal. The upper part is square, and the lower conical section is conical. The discharge port of the conical section is equipped with fluidizing nozzles, using nitrogen or CO2 fluidization for easy unloading. The pulverized coal silo 1 is equipped with an electronic weighing device or gauge to measure the amount of pulverized coal inside. The pulverized coal silo 1 is externally insulated, and the discharge port is equipped with a gas-releasing coal device to ensure smooth coal discharge. The injection tank 2 is equipped with a pressure charging valve, a pressure replenishing valve, a pressure relief valve, and a safety valve. A replenishing gas regulating valve is installed on the main injection gas pipeline, and a fluidizing gas regulating valve is installed before the fluidizing device. The opening and closing of each pneumatic valve is controlled by its respective control system. The outlet dust emission concentration of the bag filter 3 is ≤10 mg / Nm³. 3 This meets the national ultra-low emission requirements. Two gas storage tanks (4) are connected to an external nitrogen or CO2 source. One tank delivers pulverized coal to the pulverized coal silo 1 via a nitrogen or CO2 pneumatic conveying method. The other tank connects to the nitrogen cooling interface of the pulverized coal injection gun via a second pipeline 200. A nitrogen shut-off valve 6 and a pressure reducing valve 7 are sequentially installed on the second pipeline 200. A bag filter 3 is installed on the top of the pulverized coal silo 1 to discharge the nitrogen or CO2 used for conveying pulverized coal, for depressurization and moisture reduction in the silo 1. The pulverized coal in the silo 1 is fed into the injection tank 2 via a pneumatic bell valve. A temperature monitoring device is installed on the top of the silo 1. The pressure relief pipe of the injection tank 2 is connected to the upper part of the silo 1. A deflation valve 5 is installed on the top of the silo 1. A fluidizing device is installed at the conical part of the injection tank 2 to fluidize the pulverized coal. The fluidized coal is then transported with a small amount of gas. Carrier gas is transported to the pulverized coal distributor 10 through the first pipeline 100. Pulverized coal is continuously injected into the vaporization cooling flue of the converter through the pulverized coal distributor 10 and the spray gun. Multiple pulverized coal main pipes 300 are provided between the second pipeline 200 and the first pipeline 100. A purge valve 8 is provided on the pulverized coal main pipe 300. A return pulverized coal pipe 400 connected to the top of the pulverized coal silo 1 is provided on the side of the first pipeline 100 near the pulverized coal distributor 10. A return pulverized coal valve 9 is provided on the return pulverized coal pipe 400.

[0039] The pulverized coal injection system employs a single-pipeline, single-distributor direct injection technology. The injection system uses nitrogen or CO2 as the pressurizing gas for injection tank 2, the safety gas for pulverized coal silo 1 and injection tank 2, and the power gas for pneumatic valves; high-pressure N2 or CO2 is used as the transport gas. To prevent blockage of the main pulverized coal pipe 300, a purge valve 8 is installed on it. When the pipe is blocked, the purge valve 8 is opened sequentially, and nitrogen or CO2 is used to purge the blockage section by section. For the medium containing pulverized coal, considering wear resistance requirements, wear-resistant pulverized coal ball valves are used for the pneumatic ball valves. The pulverized coal flow rate can be displayed through the weighing calculation program of injection tank 2, and the pulverized coal injection volume is adjusted under the set tank pressure conditions. One set of 8-branch pulverized coal distributor 10 is provided for pulverized coal injection into the converter.

[0040] This solution displays all data related to pulverized coal injection status on the main screen for easy operation. The screen shows models of the main equipment, pipelines, and control valves in the system. It also displays temperature (pulverized coal silo 1, injection tank 2, etc.); flow rate and pressure (injection tank 2 and air storage tank, etc.); material monitoring (pulverized coal silo 1, injection tank 2); and pressure before the distributor. Each measured value display includes upper and lower limit alarm functions, and simultaneously displays the pulverized coal injection rate, pulverized coal injection rate trend curve, and cumulative pulverized coal injection rate. The main power source is Fuguang Baite; the instrument signals use standard 4-20mA signals, with analog signals electrically isolated by isolators. The instrument selection is as follows:

[0041] (1) The differential pressure and pressure transmitters are intelligent differential pressure and pressure transmitters from the Fuguang Baite brand.

[0042] (2) Temperature measurement generally uses thermocouples or resistance thermometers from the Tiankang brand. Wear-resistant resistance thermometers are selected for contact with coal powder.

[0043] (3) Gas flow measurement: For small pipe diameters, orifice plate flow meters are selected;

[0044] (4) Weighing sensors and weighing instruments are selected for material monitoring;

[0045] (5) O2 and CO analysis in the pulverized coal silo is performed using an explosion-proof exhaust gas analyzer;

[0046] (6) Control valve and actuator: The fluidization and pressure replenishment control valve of the injection tank 2 adopts an explosion-proof electric control valve.

[0047] The specific principles of this invention are as follows:

[0048] Utilizing pneumatic injection technology: The process involves a spray gun → pulverized coal injection flue → high-temperature (1200℃-1500℃) converter flue gas + reducing atmosphere → causing carbon in the pulverized coal to react with oxygen in the converter flue gas to generate CO, which then reacts with CO2 to generate CO again → improving the efficiency, quality, and safety of coal gas recovery → achieving safe, efficient, low-consumption, and environmentally friendly production in the converter coal gas recovery process.

[0049] like Figure 2 As shown, the chemical reaction of pulverized coal is: 2C + O2(g) = 2CO(g) → ΔrG1

[0050] C + CO₂(g) = 2CO(g) → ΔrG₂

[0051] C(s) + O2 = CO2 → ΔrG3

[0052] 2CO + O2 = 2CO2 → ΔrG4

[0053] When O2 in flue gas reacts with carbon, some of the carbon continues to react with CO2 in the flue gas to produce CO. Furthermore, the reaction between C and CO2 becomes more readily apparent with increasing temperature. Injecting pulverized coal into the converter gasification flue, allowing it to react with O2 and CO2 in the flue gas under high-temperature conditions to produce CO, thereby improving the amount and quality of recovered coal gas, is theoretically feasible.

[0054] The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments can be combined with each other to form new embodiments. The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the technical solutions of the present invention.

Claims

1. A coal injection system for a converter, comprising a coal powder bin (1), an injection tank (2), a bag filter (3) and a gas storage tank (4), the gas storage tank (4) being connected with a nitrogen or CO2 source, the coal powder being sent to the coal powder bin (1) by nitrogen or CO2 pneumatic conveying, the bag filter (3) being arranged on the top of the coal powder bin (1) to discharge the nitrogen or CO2 used for conveying the coal powder, for pressure relief and moisture reduction of the coal powder bin (1), the coal powder in the coal powder bin (1) being sent to the injection tank (2) through a pneumatic clock valve, a temperature monitoring device being arranged on the top of the coal powder bin (1), a pressure relief pipe of the injection tank (2) being connected with the upper part of the coal powder bin (1), and an explosion venting valve (5) being arranged on the top of the coal powder bin (1), characterized in that: The conical part of the injection tank (2) is provided with fluidization device for fluidizing the pulverized coal, and the fluidized pulverized coal is delivered to the pulverized coal distributor (10) through the first pipeline (100) with a small amount of delivery gas as carrier gas, and then continuously or intermittently injected into the vaporization cooling flue of the converter through the pulverized coal distributor (10) and the injection gun. ​ The gas storage tank (4) is provided with two, one of which sends the pulverized coal to the coal powder bin (1) through nitrogen or CO2 pneumatic conveying; the other gas storage tank (4) is connected with the nitrogen cooling interface of the coal injection gun through the second pipeline (200), and the second pipeline (200) is sequentially provided with an injection gun cooling nitrogen cut-off valve (6) and a pressure reducing valve (7).

2. A coal injection system for a converter as claimed in claim 1, wherein: A plurality of pulverized coal main pipes (300) are arranged between the second pipeline (200) and the first pipeline (100), and the pulverized coal main pipes (300) are provided with purge valves (8).

3. A coal injection system for a converter as claimed in claim 1, wherein: The first pipeline (100) is provided with a return powder pipeline (400) communicating with the top of the coal powder bin (1) on the side close to the pulverized coal distributor (10), and the return powder pipeline (400) is provided with a return powder valve (9).

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