Deep Utilization of Waste Heat from Blast Furnace Hot Blast Stove Flue Gas Coupled with Desulfurization and Denitrification Process

Abstract

The present invention discloses a coupled desulfurization and denitrification process for deep utilization of flue gas waste heat from a blast furnace hot blast stove. During the hot blast stove's combustion period, air and coal gas enter the hot blast stove's combustion chamber and are mixed and burned. The resulting high-temperature flue gas is heated in a heat storage chamber and then led out of the hot blast stove flue gas duct through an air-to-flue gas switching chamber. Part of the post-furnace flue gas led out of the hot blast stove flue gas duct is passed through an air heat exchanger, a gas heat exchanger, and a blast furnace coal pulverizing system to recover some of the waste heat. The flue gas, along with the remaining post-furnace flue gas, enters the micro-powder mill of a metallurgical slag micro-powder system, where it dries and aids in grinding the metallurgical slag. The slag is then desulfurized and denitrified by chemical absorption of alkaline earth metal oxides in the metallurgical slag micro-powder and adsorption by the metallurgical slag micro-powder. The flue gas then enters the micro-powder bag filter of the metallurgical slag micro-powder system for dust removal before being discharged. The present invention has low investment and operating costs, is environmentally friendly, energy-saving, and consumption-reducing, can effectively recover low-temperature flue gas waste heat, and simultaneously achieves in-situ flue gas desulfurization, denitrification, and carbon dioxide removal.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical energy and environmental protection, and specifically relates to a process for coupling desulfurization and denitrification by deep utilization of waste heat of blast furnace hot blast stove flue gas. Background Art

[0002] The energy required for blast furnace smelting primarily comes from coke added to the furnace top, pulverized coal injected into the tuyeres in the furnace's bosh area, and hot air. For example, according to 2016 statistics from a particular blast furnace, 303 kg of coke was consumed per ton of iron; 181 kg of coal was injected; and 1.8 GJ of heat was introduced by the hot air. The total energy consumption for blast furnace smelting was approximately 14.5 GJ. This means that the energy introduced by the hot air into the furnace accounts for over 12.4% of the total energy consumption. High air temperature is a key technical feature of modern blast furnaces. Increasing air temperature is a key technical measure to increase coal injection rates, reduce coke ratios, and lower production costs.

[0003] In recent years, the hot air temperature of blast furnaces in domestic steel enterprises has been increasing year by year, especially in a batch of newly built large blast furnaces (greater than 2000 cubic meters), the hot air temperature has exceeded 1200℃, reaching the international advanced level.

[0004] Hot blast is supplied to the blast furnace by a hot blast furnace. Hot blast furnaces are a key component of blast furnaces in ironworks. Typically, a blast furnace is equipped with three to four hot blast furnaces. Their function is to continuously provide the blast furnace with high-temperature hot blast exceeding 1000°C. Currently, advanced modern hot blast furnaces can achieve blast temperatures of up to 1300°C. For example, the 5500 cubic meter blast furnace at Caofeidian Jingtang Company utilizes a Kalugin top-fired hot blast furnace.

[0005] Blast furnace hot blast stoves can be divided into two types according to their working principles: heat storage type and heat exchange type.

[0006] Regenerative hot blast furnaces are categorized by their internal heat storage element into spherical hot blast furnaces (referred to as spherical furnaces) and checker brick hot blast furnaces. Based on their combustion method, they can be divided into top-fired, internal-fired, and external-fired types. Increasing the hot blast temperature in hot blast furnaces is a key technology for intensified blast furnace smelting. How to increase blast temperature has been a long-standing research topic in the industry. Common methods include co-firing high-calorific-value gas, increasing the heat exchange area of ​​the hot blast furnace's checker bricks, changing the material and density of the checker bricks, modifying the shape of the heat storage element (such as regenerative balls), and preheating the gas and combustion air through various methods.

[0007] The regenerative checker brick hot blast furnace is the most commonly used type of hot blast furnace in modern blast furnaces, especially large blast furnaces. This heat exchange hot blast furnace primarily utilizes a high-temperature resistant heat exchanger as its core component. This component cannot be made of metal, but must be made of high-temperature resistant ceramic. Blast furnace gas is fully burned in the combustion chamber, and the resulting hot air passes through the heat exchanger, transferring heat to fresh, cool air, raising the fresh air temperature to over 1000°C.

[0008] Taking the top-burning regenerative hot blast furnace as an example, the hot blast furnace has a working cycle of 2.25 hours, 0.75 hours of air supply, and a combustion period of 1.5 hours. The coal gas and combustion air are preheated to 200°C at low temperature and then enter the hot blast furnace combustion chamber to burn and generate high-temperature flue gas to heat the regenerator. After heat exchange with the regenerator, the temperature drops to about 400°C and is discharged from the hot blast furnace. The exhaust gas oxygen content analysis is used as the system feedback link to participate in closed-loop control and correct the air-fuel ratio at any time. Therefore, while the blast furnace hot blast furnace provides high-temperature hot air for the blast furnace, it also produces a large amount of hot blast furnace flue gas [https: / / wenku.so.com / d / 9b36e50fa40d8aec19c486dc8a9436d7-450, cubic meter hot blast furnace design calculation], and its flue gas volume is about 1400-1500Nm 3 Currently, these flue gases are cooled to 120-150°C after being exchanged with combustion air and gas in air and gas heat exchangers, respectively. A small amount is then fed into the blast furnace's coal pulverizing system for cascade utilization, while the rest is directly discharged.

[0009] Because this flue gas is produced by the combustion of a mixture of blast furnace gas and air, the sulfur introduced with the blast furnace gas burns to form sulfur dioxide. Simultaneously, due to the flame temperature exceeding 1300°C, a small amount of nitrogen oxides is also produced in the flue gas. Therefore, directly discharging hot blast furnace flue gas not only releases a large amount of fine coal dust into the atmosphere, but also contains large amounts of carbon dioxide and certain pollutants such as sulfur and nitrate, which are discharged into the atmosphere along with the flue gas. This results in significant waste of resources and energy and pollution to the atmospheric environment.

[0010] With the increasing requirements for environmental protection, many steel companies have implemented desulfurization and denitrification treatment for flue gas. This is particularly uneconomical and not low-carbon because the sulfur component concentration in blast furnace gas is not high. The sulfur dioxide concentration in the flue gas after combustion in the hot blast furnace is low, but it exceeds the ultra-low emission standard (100mg / Nm 3 The hot blast furnace has a large amount of flue gas, and the implementation of the desulfurization and denitrification project requires large investment and occupies a large area. The operating cost of desulfurization and denitrification is high, which further increases the operating costs of steel enterprises. Summary of the Invention

[0011] The purpose of the present invention is to solve the above technical problems and provide a blast furnace hot blast furnace flue gas waste heat coupled desulfurization and denitrification process that has low investment, low operating cost, is environmentally friendly, energy-saving and consumption-reducing, can effectively recover the low-temperature flue gas waste heat discharged from the blast furnace hot blast furnace, and can realize in-situ flue gas desulfurization, denitrification and carbon dioxide removal while recovering the flue gas waste heat.

[0012] The technical solution includes a blast furnace, a hot blast furnace, a blast furnace coal pulverizing system and a metallurgical slag micro-powder system; during the combustion period of the hot blast furnace, air and coal gas enter the combustion chamber (16.1) of the hot blast furnace (16) and are mixed and burned. The high-temperature flue gas generated is heated by the heat storage chamber (16.2) of the hot blast furnace (16), and then passes through the air-to-gas switching chamber (16.3) of the hot blast furnace (16) and is led out from the hot blast furnace flue gas pipe (17). After the waste heat is recovered by the air heat exchanger (3.1), the gas heat exchanger (3.2), and the blast furnace coal pulverizing system, part of the flue gas from the furnace enters the micro powder mill (5.1) of the metallurgical slag micro powder system together with the remaining flue gas from the furnace to dry and assist in grinding the metallurgical slag. The slag is then desulfurized and denitrified by the chemical absorption of the alkaline earth metal oxides in the metallurgical slag micro powder and the adsorption of the metallurgical slag micro powder. The slag is then discharged into the micro powder bag dust collector (6.1) of the metallurgical slag micro powder system for dust removal.

[0013] The flue gas after entering the blast furnace coal pulverizing system is mixed in the coal mill flue gas furnace (10) and then sent to the coal mill (5.2) to dry and help grind the blast furnace injection coal. After dust removal by the coal powder bag dust collector (6.2), it is introduced into the micro powder grinding flue gas furnace (15) of the metallurgical slag micro powder system for mixed combustion and then enters the micro powder mill (5.1) through the flue gas mixing chamber (4) to dry and help grind the metallurgical slag to further recover the waste heat and waste energy in the flue gas. Desulfurization and denitrification are carried out under the chemical absorption of alkaline earth metal oxides in the metallurgical slag micro powder and the adsorption of the metallurgical slag micro powder.

[0014] The flue gas after heat exchange in the air heat exchanger (3.1) and the gas heat exchanger (3.2) is mixed and divided into three streams: the first stream is used as flue gas before micro-powder grinding and introduced into the flue gas mixing chamber (4) of the metallurgical slag micro-powder system; the second stream is used as flue gas before coal mill and introduced into the blast furnace coal pulverizing system, mixed in the coal mill flue gas furnace (10) and then enters the coal mill (5.2) to participate in drying and assist in grinding the blast furnace coal injection; the third stream is used as mixed combustion cold flue gas and sent into the blast furnace (11) through the blast furnace hot air pipe (14) to reduce the theoretical combustion temperature in the blast furnace tuyere area.

[0015] The pressure in the flue gas duct after the air heat exchanger (3.1) and the gas heat exchanger (3.2) and the hot blast furnace flue gas duct (17) is collected as a feedback link of the system. By adjusting the flow rate of the first flue gas after the furnace introduced into the metallurgical slag fine powder system, the pressure in the flue gas duct after the air heat exchanger (3.1) and the gas heat exchanger (3.2) and the hot blast furnace flue gas duct is stabilized under the premise that the flow rate and thermal enthalpy of the second flue gas after the furnace entering the blast furnace coal pulverizing system meet the stable production requirements of the coal mill.

[0016] By adjusting the flow rate of the remaining part of the post-furnace flue gas entering the metallurgical slag fine powder system, the pressure stability and the balance of the flue gas flow rate in the hot blast furnace flue gas duct (17) are maintained.

[0017] When the temperature of the flue gas entering the coal mill (5.2) is lower than the set temperature, the coal mill flue gas furnace (10) is started, and coal gas and air are introduced for combustion to generate high-temperature flue gas to increase the temperature of the flue gas entering the coal mill (5.2) to meet the set temperature requirement.

[0018] The flue gas and pulverized coal mixture exiting the coal mill (5.2) enters the pulverized coal bag filter (6.2), where the flue gas and pulverized coal are filtered and separated, and the separated pulverized coal enters the pulverized coal bin (12); the separated flue gas is divided into three parts, the first part being used as the pulverized coal carrier gas, which enters the pulverized coal carrier gas tank (12) under the compression action of the pulverized coal carrier gas blower (8.1) of the pulverized coal injection system, and is used as the carrier gas for pulverized coal injection to spray the pulverized coal into the blast furnace (11); the second part is the low-temperature coal-blended flue gas, which is introduced into the blast furnace hot air pipe (14) under the suction action of the blended combustion flue gas blower (8.2); the third part of the return flue gas is first supplemented with coal gas and then enters the micro-powder mill flue gas furnace (15) of the metallurgical slag micro-powder system to be mixed and burned with air or part of the hot air from the blast furnace hot air pipe (17), and the high-temperature flue gas generated then enters the micro-powder mill (5.1) through the micro-powder mill flue gas mixing chamber (4).

[0019] When the amount of flue gas entering the micro powder mill (5.1) is insufficient to meet the flue gas volume required by the micro powder mill (5.1), a portion of the flue gas discharged from the micro powder bag filter (6.1) is circulated into the micro powder mill flue gas furnace (15), and then sent into the micro powder mill through the micro powder mill flue gas mixing chamber (4) to supplement the insufficient flue gas volume.

[0020] The blast furnace coal pulverizing system comprises a coal mill flue gas furnace (10), a coal mill (5.2), and a coal powder bag dust collector (6.2) connected in sequence; the metallurgical slag micro-powder system comprises a micro-powder mill flue gas furnace (15), a micro-powder mill flue gas mixing chamber (4), a micro-powder mill (5.1), and a micro-powder bag dust collector (6.1) connected in sequence.

[0021] In view of the problems existing in the background technology, the inventors have made the following improvements:

[0022] Taking into account the gas phase utilization process of the entire blast furnace ironmaking production process, the functions and roles of each unit in the entire blast furnace ironmaking production process and the working principle of gas phase utilization are analyzed, and the flue gas discharged from different units is utilized in cascade. While recovering the waste heat and waste energy in the flue gas, the pollutants in the flue gas are purified in situ, reducing or even completely eliminating the direct discharge of hot blast furnace flue gas, reducing carbon emissions, reducing environmental protection investment, and reducing operating costs.

[0023] During the blast furnace smelting process, approximately 350kg / t-iron of blast furnace slag is produced. Currently, domestic steel mills process blast furnace slag into fine powder products, and most use a vertical mill production process for slag fine powder, which integrates drying, grinding, and powder selection. For example, the operating parameters of the HRM3700S slag vertical mill are: inlet air temperature: design ≤350°C; outlet air temperature: design 85-100°C, actual 95-105°C. The flue gas volume used for drying, powder selection, and grinding is approximately 3000-4000Nm 3 / t- Slag converted into tons of iron The flue gas volume required to produce slag powder is 1000-1400Nm 3 In actual production, the inlet air temperature of most slag vertical mills (micro powder mills) is controlled at 350-400℃.

[0024] Since metallurgical slag contains a large amount of alkaline earth metal oxides (calcium oxide, magnesium oxide, etc.), and even a certain amount of free calcium oxide, magnesium oxide, etc., and metallurgical slag contains a certain amount of water, during the grinding process, the flue gas dries and aids the grinding of the metallurgical slag in the micro-powder mill, fluidizes the powder selection, and is fully mixed with the metallurgical slag. The sulfur dioxide and carbon dioxide in the flue gas are absorbed by the calcium hydroxide and magnesium hydroxide in the metallurgical slag. Therefore, while the flue gas dries, fluidizes, and aids the grinding of the metallurgical slag, the pollutants in the flue gas are absorbed and removed. In addition, the specific surface area of ​​the produced micro-powder product reaches 430-450m 2 / kg, it has a large adsorption capacity and has an adsorption effect on nitrogen oxides in the flue gas, so the nitrogen oxides in the flue gas are adsorbed and removed while the flue gas dries, fluidizes and aids grinding of metallurgical slag.

[0025] In order to achieve in-situ desulfurization and denitrification of hot blast furnace flue gas during the cascade utilization process, all the flue gas discharged from the blast furnace coal pulverizing system is introduced into the metallurgical slag micropowder system (including blast furnace slag micropowder and steel slag micropowder production units). After being processed in the micropowder grinding flue gas furnace of the metallurgical slag micropowder system (mixed with coal gas and incinerated) until the flue gas enthalpy requirements required by the micropowder grinding are met, it is used as drying, fluidization, grinding-aiding and powder selection flue gas for the micropowder grinding to produce slag micropowder and steel slag micropowder products. This not only recycles the fine coal powder and VOC components entrained in the flue gas discharged from the blast furnace coal pulverizing system (the coal is dried and fluidized in the flue gas at 250-300℃, and the highly volatile components in the coal are gasified and enter the flue gas), but also purifies and removes pollutants (sulfur dioxide, nitrogen oxides, carbon dioxide) in the flue gas.

[0026] Further analysis of the steel smelting production process, especially the production units related to blast furnace ironmaking production, shows that there are many gas utilization units. For example, nitrogen is used as a carrier gas to spray coal powder into the blast furnace, and water vapor is added to the blast furnace hot air to reduce the theoretical combustion temperature of the combustion zone in the front area of ​​the blast furnace tuyere.

[0027] In this invention, flue gas from the blast furnace coal pulverizing system replaces nitrogen as the carrier gas for blast furnace coal injection. This method offers all the safety benefits of nitrogen as a carrier gas because the gas originates from the higher-temperature gas phase of the gas-solid mixture within the coal mill, eliminating any explosion hazard. Furthermore, by injecting the flue gas into the blast furnace, the carbon components, trace amounts of pulverized coal, and VOCs in the flue gas are recycled.

[0028] Using flue gas from the blast furnace's coal pulverizing system to replace water vapor as the blending gas to lower the theoretical combustion temperature of the combustion zone in the blast furnace's tuyere area fully replicates the cooling effect of water vapor. First, because the flue gas has undergone a coal drying process, it contains a certain amount of moisture. Upon entering the blast furnace, it reacts with the added water vapor, absorbing heat and lowering the theoretical combustion temperature. Second, the flue gas contains a large amount of carbon dioxide, which undergoes an endothermic reduction reaction upon entering the blast furnace, converting carbon dioxide into carbon monoxide. Third, the addition of flue gas dilutes the oxygen concentration in the injected blast furnace hot air, lowering the theoretical combustion temperature. At the same time, the flue gas temperature is only 85-105°C, far lower than the temperature of the added water vapor, further contributing to lowering the theoretical combustion temperature.

[0029] Furthermore, based on the annual coal injection volume of 100 million tons in blast furnaces nationwide, the amount of pulverized coal carried out by the flue gas of the blast furnace pulverized coal injection system after dust removal is 10mg / Nm 3 The annual emission can reach 30,000 tons / a, and the annual exhaust gas volume is 300 billion Nm 3 (3×10 4 ×10 3 ×10 3 ×10 3 mg / 10mg Nm 3 ), by reusing the flue gas from the blast furnace coal pulverizing system, the amount of flue gas discharged is greatly reduced, and the fine coal powder in the exhaust gas is recovered.

[0030] In order to improve the safety of drying coal with flue gas introduced into the blast furnace coal pulverizing system and to simultaneously increase the temperature of the flue gas exiting the hot blast furnace, the present invention proposes to reduce the air-fuel ratio of air to gas entering the hot blast furnace combustion chamber to control the oxygen content of the flue gas to less than 4% (V / V).

[0031] In order to make full use of the unburned combustible components in the flue gas (the gas is not 100% burned due to the low air-fuel ratio), the flue gas from the micro powder mill flue gas furnace and the first part of the post-furnace flue gas from the hot blast furnace flue gas duct and the flue gas before the micro powder mill are further ignited and burned in the flue gas mixing chamber before entering the micro powder mill.

[0032] The present invention utilizes existing blast furnaces, hot blast furnaces, blast furnace coal pulverizing systems, coal pulverizing injection systems, and metallurgical slag micro-powder systems. Only the connection relationship of the flue gas ducts is changed. This makes the transformation simple, requires little investment, and has significant economic and social benefits. The beneficial effects are as follows:

[0033] (1) Taking advantage of the fact that metallurgical slag powder contains a large amount of alkaline earth metal oxides, combined with the requirements of desulfurization and denitrification of exhaust hot blast furnace flue gas, the exhaust hot blast furnace flue gas is processed and used as the drying flue gas for metallurgical slag powder production. This not only saves the equipment investment for hot blast furnace flue gas purification, but also recovers the waste heat of the flue gas, reducing flue gas emissions by 1000 Nm 3 / t- iron or above;

[0034] (2) Through the gas phase flow balance analysis of each unit in the whole process of blast furnace ironmaking production, the hot blast furnace flue gas flow is equivalent to the powder selection flue gas flow in the metallurgical slag micro-powder vertical mill process. All the hot blast furnace flue gas is directly introduced into the metallurgical slag micro-powder vertical mill, or part of it is introduced into the metallurgical slag micro-powder vertical mill together with the remaining part after cascade utilization, and then cascade utilized again. Under the absorption and adsorption of the metallurgical slag micro-powder, the hot blast furnace flue gas is desulfurized, denitrated and decarbonized, saving the investment and operation costs of hot blast furnace flue gas purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0036] Among them: 1. Blast furnace blower; 2.1. Air heat exchanger-hot flue gas regulating valve; 2.2. Gas heat exchanger-hot flue gas regulating valve; 2.3. Micro powder mill hot flue gas regulating valve; 2.4. Micro powder mill cold flue gas regulating valve; 2.5. Coal mill cold flue gas regulating valve; 2.6. Coal mill cold flue gas regulating valve; 2.7. Flue gas discharge emergency regulating valve; 2.8. Coal mill injection flue gas regulating valve; 2.9. Coal mill co-firing flue gas regulating valve; 2.10. Coal mill-micro powder mill flue gas regulating valve; 2.11 1. Micro powder mill exhaust gas regulating valve; 2.12. Micro powder mill circulating flue gas regulating valve; 2.13. Micro powder mill hot air regulating valve; 2.14. Combustion air regulating valve; 2.15. Gas regulating valve; 2.16. Coal mill hot flue gas regulating valve; 2.17. Coal mill flue gas exhaust regulating valve; 2.18. Coal mill circulating flue gas regulating valve; 3.1. Air heat exchanger; 3.2. Gas heat exchanger; 4. Micro powder mill flue gas mixing chamber; 4.1. Explosion-proof high-energy ignition and reburning chamber; 5.1. Micro powder mill ; 5.2, coal mill; 6.1, micro powder bag filter; 6.2, coal powder bag filter; 7.1, micro powder mill exhaust gas fan; 7.2, coal mill exhaust gas fan (emergency fan); 8.1, coal injection carrier gas fan; 8.2, co-firing flue gas fan; 8.3, coal mill-micro powder mill flue gas fan; 9.1, coal mill air blower; 9.2, coal mill gas blower; 9.3, micro powder mill air blower; 9.4, micro powder mill gas blower; 10, coal mill flue gas furnace; 1 0.1, coal mill flue gas furnace igniter; 10.2, coal mill flue gas mixing chamber; 11, blast furnace; 11.1, blast furnace tuyere; 12, pulverized coal silo; 13, pulverized coal injection carrier gas tank; 14, blast furnace hot blast duct; 15, micro powder mill flue gas furnace; 15.1, explosion-proof high-energy ignition combustion chamber; 15.2, micro powder mill flue gas primary mixing chamber; 16, hot blast furnace; 16.1, hot blast furnace combustion chamber; 16.2, hot blast furnace regenerator; 16.3, air-to-flue gas switching chamber; 17, hot blast furnace flue gas duct. DETAILED DESCRIPTION

[0037] The following is a steel plant with a 2000m 3 Taking a blast furnace as an example, four air and gas dual preheating top-fired hot blast furnaces are used to further explain the present invention. All equipment in the embodiment are commercially available:

[0038] 1. Calculation of flue gas distribution in blast furnace coal pulverizing system

[0039] At present, the coal injection rate of blast furnaces in most domestic ironmaking plants is about 180kg / t-iron. The operating process parameters of the pulverized coal injection production line are as follows:

[0040] Flue gas temperature entering coal powder mill drying: 250-300℃;

[0041] The coal mill outlet temperature during normal pulverizing is 80-85°C;

[0042] Flue gas volume entering coal powder mill: 2000-3000 Nm 3 / t-coal powder (according to 2500 Nm 3 / t-coal powder);

[0043] The dry flue gas volume required for the coal injection per ton of iron in the pulverized coal production line is: 450 Nm 3 / t-Iron.

[0044] Regarding the amount of injected carrier gas: the solid-gas ratio is 45.6-51.0 kg / kg [Ao Aiguo, Liu Yu. Research and application of dense phase conveying technology for blast furnace coal injection. Baosteel Technology, 2019, No. 5: 47-51], the solid-gas ratio of most ironmaking plants' blast furnace coal injection is 20-30 kg / kg [Zhang Lei, Xu Feifei, Ren Jiangtao. Design and economic benefit analysis of 1080m3 blast furnace coal injection. Metallurgical Equipment, 2014 Special Issue (1), the nitrogen consumption of pulverized coal injection is 35.5 cubic meters / t (converted to a solid-gas ratio of 22.53 kg / kg), and the solid-gas ratio in the coal mill is 0.27 kg / kg], and the solid-gas ratio is 20-50. Nitrogen is generally used as the carrier gas for injection, so the carrier gas volume is 16-40m 3 / t-coal【Wu Jiangsong. Research and Analysis on the Balance of Blast Furnace Coal Injection Pulverizing System. Modern Metallurgy, December 2012; Li Ping, Chen Long. Laigang Yinshan Steel 3200m 3 Blast furnace coal injection design. Mechanical and Chemical Engineering, Technology Wind May 2018].

[0045] The density of flue gas is about 1.34kg / Nm 3 The density of flue gas is slightly higher than that of nitrogen [Flue gas density under standard conditions - https: / / www.docin.com / p-1569153706.html], and flue gas can replace nitrogen as the carrier gas for pulverized coal injection. The flue gas consumption is slightly lower than that of nitrogen.

[0046] Considering that flue gas contains trace amounts of pulverized coal particles and a small amount of combustible components (during the pulverized coal preparation process, a small amount of volatile components in the coal will evaporate into the flue gas under the heat of the 250-300°C dry flue gas), dense phase conveying of pulverized coal is unnecessary. Instead, the gas-to-solid ratio of pneumatic conveying can be increased, reducing the probability that fluctuations in the injection rate will seriously affect the stable operation of the blast furnace [Yao Xiaowei. Research on Automatic Pressure Setting and Pulverized Coal Flow Regulation for Blast Furnace Coal Injection Tanks. Automation Instrumentation, Vol. 36, No. 7, July 2015: 33-35]. Maintaining sufficient airflow velocity can prevent pulverized coal from depositing in the pipeline and address the frequent gun blockage problem in the blast furnace coal injection system [Fan Jiangbo, Wang Yupeng. Detection and Control System for Pulverized Coal Injection Tanks in Blast Furnaces. China Instrumentation, 2014 Supplement]. The pneumatic conveying of pulverized coal injection and the solid-to-gas ratio of the injection are set at 20 kg / m 3The amount of flue gas introduced into the injection system is about 9-10m3 per ton of iron. 3 / t-iron, accounting for 2-3% of the total flue gas discharged from the blast furnace coal pulverizing system.

[0047] In actual production, the probability of injecting steam into the hot air to reduce the theoretical combustion temperature in the blast furnace tuyere 11.1 area is very low. The injection amount needs to be adjusted according to the actual operating conditions of the blast furnace. At the same time, when flue gas needs to be introduced into the hot air, the blast furnace operation is abnormal. At this time, the amount of pulverized coal injected into the blast furnace also needs to be adjusted accordingly. Therefore, the amount of flue gas introduced into the hot air pipe of the blast furnace coal pulverizing system can be ignored.

[0048] Operating process parameters of slag micropowder production lines [Gu Jintu, Wang Yejiang. Process design and implementation of a 150,000-ton annual slag micropowder production line. Cement Technology, February 2013; Wang Guoqing. Advanced technology for vertical mill slag grinding technology and equipment. China Cement, March 2017; Sun Yongning. Design and calculation of the heating capacity of the flue gas furnace in the slag micropowder system. Modern Metallurgy, August 2015]:

[0049] Hot flue gas temperature entering slag micro powder grinding: 350℃;

[0050] Exhaust gas temperature at the mill: 90-100℃;

[0051] Material temperature entering the mill: 20°C;

[0052] Material temperature out of mill: 90℃

[0053] Flue gas volume entering the mill: 3000-4000 Nm 3 / t-micro powder (according to 3500 Nm 3 / t-coal powder);

[0054] The specific surface area of ​​the slag powder product produced is 430-450m 2 / kg;

[0055] Assuming that 350kg of slag is produced per ton of iron, the amount of dry flue gas required for the slag powder production line to produce slag powder per ton of iron is: 1225 Nm 3 / t-Iron.

[0056] The flue gas volume of the slag micro-powder system is much larger than the flue gas volume discharged by the pulverized coal injection system, so all the remaining flue gas volume of the pulverized coal injection system is introduced into the slag micro-powder system.

[0057] 2. Balance calculation of hot blast furnace flue gas enthalpy and flue gas flow

[0058] A steel plant 2000m 3Statistics of blast furnaces in recent years: coke consumption per ton of iron: 303kg; coal injection amount per ton of iron: 181kg; heat enthalpy brought in by hot air: 1.8GJ / t-iron; comprehensive energy consumption of blast furnace smelting is about 14.5GJ / t-iron.

[0059] Blast furnace utilization coefficient: 2.8-3.0, molten iron output: 230-250t / h (calculated based on 250t / h);

[0060] One ton of iron produces 300-400 kg of slag (calculated at 350 kg / t-iron);

[0061] The coal injection rate per ton of iron is 170-180 kg (calculated at 180 kg / t-iron);

[0062] Hot air temperature: 1150-1200℃

[0063] Hot air volume (oxygen enrichment rate 2-3%): 1100-1200 Nm 3 / t-iron (according to 1150 Nm 3 / t-iron, heat enthalpy brought in by hot air: 1.875-1.85 GJ / t-iron);

[0064] Blast furnace gas production: 1800-2200 Nm 3 / t-iron;

[0065] Blast furnace gas calorific value: 3300-3500 kJ / Nm 3 (According to 3400 kJ / Nm 3 count).

[0066] Air and gas enter the hot blast furnace combustion chamber after heat exchange in the flue gas preheater.

[0067] Hot blast furnace production process indicators:

[0068] Hot air furnace flue gas temperature: 300-350℃;

[0069] Hot blast furnace gas consumption 900-1100 Nm 3 / t-iron (710+230+80=1020. This includes the blast furnace gas consumed by production units such as pulverized coal injection and slag powder);

[0070] Air-fuel ratio: 0.7-0.8;

[0071] Preheater combustion air inlet temperature 20-25℃

[0072] Preheater combustion air outlet temperature 140-170℃

[0073] Preheater combustion air inlet temperature 10-15℃

[0074] Preheater combustion gas outlet temperature 140-170℃

[0075] Preheater flue gas inlet temperature 250-350℃

[0076] Preheater flue gas outlet temperature 120-140℃

[0077] [https: / / max.book118.com / html / 2016 / 0612 / 45377018.shtm-Safety Technical Operating Procedures for Hot Blast Furnaces]

[0078] Hot blast stove flue gas energy and flow balance calculation:

[0079] The heat enthalpy brought into the blast furnace by the hot blast is 1.8GJ / t-iron, and the thermal efficiency of the hot blast furnace is 75%. The amount of blast furnace gas required to produce hot blast is:

[0080] 1.8×10 6 ÷3400÷0.75=705.9 Nm 3 / t-iron (according to 710 Nm 3 / t-Iron Meter).

[0081] Based on an air-fuel ratio of 0.7, the air volume is approximately: 500 Nm 3 / t-iron, the total flue gas volume from the hot blast furnace is 1200-1300Nm 3 / t-Iron.

[0082] Since the temperature of the flue gas leaving the hot blast furnace is controlled at 350-400℃, the heat enthalpy of the flue gas between 0-400℃ cannot be absorbed by the hot air blown into the blast furnace. It is necessary to provide more coal gas to the hot blast furnace to provide this part of the heat enthalpy after combustion. The heat enthalpy is about 526kJ / Nm 3 -hot air (400℃×0.3148kcal / ℃×4.18, the initial temperature of the hot air is set to zero degrees), then the enthalpy required for producing one ton of iron is: 0.763GJ / t-iron (526kJ / Nm 3 ×1450 Nm 3 / t-iron, calculated as 0.77 GJ / t-iron).

[0083] The amount of gas required is about 226.5 Nm 3 / t-iron (according to 230 Nm 3 / t-iron), based on an air-fuel ratio of 0.7, the amount of combustion air added is about 160 Nm 3 / t-iron, the total flue gas volume discharged from the hot blast furnace is reduced from the original 1200-1300 Nm 3 / t-Iron increased to 1590-1690 Nm 3 / t-iron (the flue gas volume designed in the reference material: "Design Calculation of 450 cubic meters of hot blast furnace" is about 1400-1500Nm 3 / t-iron, the data difference is about 10%, which is related to the error selection of values ​​such as the selected gas calorific value, gas consumption, and hot blast furnace thermal efficiency, and is within the normal error range [https: / / wenku.so.com / d / 9b36e50fa40d8aec19c486dc8a9436d7].

[0084] Since the flue gas temperature after the preheater drops to 120-140℃, it cannot meet the 240-280℃ temperature requirement of the dry flue gas of the coal pulverizing system [Li Weiguo, Zhu Mingming. Preliminary Practice of Coal Injection in No. 2 Blast Furnace. Baosteel Technology, Issue 6, 1994 (pulverizer inlet flue gas temperature controlled at 260℃); Zhang Lei, Xu Feifei, Ren Jiangtao. 1080m 3 Blast furnace coal injection design and economic benefit analysis. Metallurgical Equipment, 2014 Special Issue (1) (the temperature of the drying flue gas entering the pulverizer is controlled between 240-280℃)], so it is necessary to add blast furnace gas to the hot blast stove combustion chamber 16.1 to supplement the energy required to increase the temperature of the preheater flue gas to between 240-280℃: 1650×120℃×0.3148kcal / ×4.18=0.26GJ / t-iron, so the amount of blast furnace gas entering the combustion chamber is increased by 76.5Nm 3 / t-iron (according to 80Nm 3 / t-iron), increase the combustion air volume by 56Nm 3 / t-Iron.

[0085] After the blast furnace hot blast stove plays the role of providing hot air for the blast furnace, providing dry flue gas for the coal pulverizing production line, and providing drying for the slag micro powder production line, the exhaust temperature is 350-400℃ and the total flue gas volume is 1590-1690 Nm 3 / t - Iron increased to 1726-1826 Nm 3 This indicates that by simply increasing the combustion intensity of the hot blast furnace by 5-10%, increasing the flue gas volume, and raising the outlet hot blast flue gas temperature by 20-50°C, the flue gas volume discharged from the hot blast furnace combustion chamber is sufficient to meet the total dry flue gas demand of the slag fine powder and pulverized coal injection production lines.

[0086] 3. Specific implementation process

[0087] (1) In this embodiment, three hot blast furnaces 16 are connected in parallel. Each hot blast furnace 16 has a working cycle of 2.25 hours, an air supply period of 0.75 hours, and a combustion period of 1.5 hours. The four hot blast furnaces 16 work simultaneously. The air supply time and the combustion time are staggered in order within the working cycle. The gas volume and air volume entering each hot blast furnace 16 are adjusted by regulating valves to ensure continuous delivery of hot blast and stable hot blast temperature.

[0088] (2) Through blower 1, press 1100-1200 Nm 3 Air (or oxygen-enriched air) is blown into the hot blast furnace 16, and after heat exchange in the hot blast furnace regenerator 16.2 to a temperature of 1150-1200°C, it is blown into the blast furnace 11 through the hot blast pipe 14 and the blast furnace tuyere 11.1.

[0089] (3) Press 950-1050 Nm 3 / t-iron blast furnace gas volume Blast furnace gas is introduced into the gas heat exchanger 3.2, preheated to 140-180℃ and directly enters the hot blast furnace combustion chamber 16.1; according to 650-750 Nm 3 Combustion air is introduced into the air heat exchanger 3.1, heated to 140-180°C, and then directly enters the hot blast furnace combustion chamber 16.1, where it is mixed and burned with the incoming blast furnace gas, generating flue gas with a temperature exceeding 1300°C. After heat exchange with the regenerator in the hot blast furnace regenerator 16.2, the flue gas is cooled to 400-450°C. The flue gas is then discharged from the hot blast furnace flue gas duct 17 through the hot blast furnace air-to-flue gas switching chamber 16.3.

[0090] (4) The flue gas discharged from the blast furnace hot blast furnace 16 is divided into four parts: the first part is introduced into the metallurgical slag micro-powder system, enters the explosion-proof high-energy ignition and reburning chamber 4.1, mixes with other gases and burns fully, is further mixed in the micro-powder mill flue gas mixing chamber 4, and then enters the micro-powder mill to dry and help grind the metallurgical slag; the second part is introduced into the coal mill flue gas mixing chamber 10.2 of the blast furnace coal pulverizing system, mixes with other flue gases entering the coal mill flue gas mixing chamber 10.2, and enters the coal powder mill to dry and help grind the injected coal; the third part of the flue gas enters the air heat exchanger 3.1 to preheat the combustion air; the fourth part of the flue gas enters the gas heat exchanger 3.2 to preheat the blast furnace gas.

[0091] (5) After heat exchange in the air heat exchanger 3.1 and the gas heat exchanger 3.2, the third and fourth parts of the flue gas after the furnace are mixed and divided into three streams: one stream is introduced into the metallurgical slag micro-powder system to participate in drying and assist in grinding the metallurgical slag; one stream is introduced into the blast furnace coal injection pulverizing system to participate in drying and assist in grinding the blast furnace injection coal; and one stream is introduced into the blast furnace hot air pipe 14 as a mixed combustion flue gas to reduce the theoretical combustion temperature in the blast furnace tuyere area.

[0092] (6) When the flue gas drawn from the air heat exchanger 3.1 and the gas heat exchanger 3.2 into the blast furnace coal pulverizing system enters the coal mill 5.2 through the coal mill flue gas mixing chamber 10.2, and its temperature is lower than 250°C, or lower than the flue gas temperature actually controlled by the coal mill 5.2, the coal mill hot flue gas regulating valve 2.16 is opened to introduce the hot blast furnace flue gas of about 400°C into the coal mill flue gas mixing chamber 10.2. The amount of flue gas entering is adjusted by the coal mill hot flue gas regulating valve 2.16 and the coal mill cold flue gas regulating valve 2.5 so that the temperature of the mixed flue gas reaches 250-300°C, meeting the flue gas enthalpy requirement entering the coal mill 5.2.

[0093] (7) When the amount of hot blast furnace flue gas at about 400°C introduced through the coal mill hot flue gas regulating valve 2.16 is not enough to increase the thermal enthalpy of the flue gas entering the coal powder mill 5.2, the coal mill flue gas furnace 10 is started to generate high-temperature flue gas and mix it with the flue gas entering the coal mill flue gas mixing chamber 10.2 to reach the thermal enthalpy required by the coal powder mill 5.2, and the flue gas enters the coal powder mill 5.2 to dry and help grind the blast furnace injection coal.

[0094] (8) The flue gas drawn out from the air heat exchanger 3.1 and the gas heat exchanger 3.2 is fully mixed with the flue gas drawn directly from the hot blast furnace through the micro powder mill flue gas mixing chamber 4 to form a mixed flue gas at 350-400℃, which dries and helps grind the metallurgical slag. When the mixed flue gas temperature is lower than 350℃, or lower than the flue gas temperature actually controlled by the micro powder mill production, or is insufficient to provide the flue gas enthalpy required by the micro powder mill 5.1, the high-temperature flue gas generated by the micro powder mill flue gas furnace 15 can be introduced into the micro powder mill flue gas mixing chamber 4 together to form a higher temperature flue gas to meet the flue gas enthalpy required by the micro powder mill 5.1.

[0095] (9) The flue gas and pulverized coal mixture from the pulverized coal mill 5.2 enters the pulverized coal bag filter 6.2, where the flue gas and pulverized coal are filtered and separated. The separated pulverized coal enters the pulverized coal bin 12; the separated flue gas is divided into three parts. The first part is the pulverized coal carrier gas, which is injected through the coal mill flue gas regulating valve 2.8 at a speed of 20-40m 3 The flue gas volume of the pulverized coal is adjusted, and under the compression of the coal injection carrier gas blower 8.1, it enters the pulverized coal injection carrier gas tank 13, serves as the carrier gas for the pulverized coal injection, and injects the pulverized coal into the blast furnace 11 through the blast furnace tuyere 11.1. The second part is the coal mill mixed combustion flue gas, which is introduced into the blast furnace hot blast duct 14 under the suction of the mixed combustion flue gas blower 8.2. The amount of mixed combustion flue gas entering the blast furnace hot blast duct 14 is regulated by the coal mill mixed combustion flue gas regulating valve 2.9 according to the temperature in the blast furnace tuyere 11.1 area in the blast furnace 11. The third part is the return furnace flue gas, which passes through the coal mill-micro powder mill flue gas regulating valve 2.10 and is introduced into the micro powder mill flue gas furnace 15 for recycling under the suction of the coal mill-micro powder mill flue gas blower 8.3.

[0096] (10) Before the return flue gas drawn from the blast furnace coal pulverizing system and entering the metallurgical slag microsystem enters the micro-powder mill flue gas furnace 15, coal gas is added to the return flue gas through the micro-powder mill coal gas blower 9.4. The return flue gas mixed with coal gas first enters the explosion-proof high-energy ignition combustion chamber 15.1 of the micro-powder mill flue gas furnace 15, and is mixed and burned with the air blown in by the micro-powder mill air blower 9.3 or the hot air introduced by the micro-powder mill hot air regulating valve 2.13, generating high-temperature flue gas that enters the micro-powder mill flue gas primary mixing chamber 15.2 for mixing and uniform heating, and then enters the explosion-proof high-energy ignition reburning chamber 4.1 to fully mix and burn with the hot blast furnace flue gas directly from the hot blast furnace 16 and the flue gas directly from the heat exchanger (air heat exchanger 3.1 and gas heat exchanger 3.2), burning out the combustible components in the flue gas, and is further mixed in the micro-powder mill flue gas mixing chamber 4 before entering the micro-powder mill.

[0097] (11) Mixed with the metallurgical slag in the mill, dried and ground to form a flue gas-slag / steel slag powder mixture, the temperature of which drops to 90-100 ° C. Under the suction action of the exhaust fan 7.1 of the micro powder mill, the mixture enters the micro powder bag filter 6.1, and the slag / steel slag powder is separated and enters the micro powder bin. The flue gas is desulfurized and denitrified by the chemical absorption of the alkaline earth metal oxides in the metallurgical slag powder and the adsorption of the metallurgical slag powder, and then discharged to the outside.

[0098] (12) When the amount of flue gas entering the micro powder mill 5.1 is insufficient to meet the flue gas volume requirement of the coal powder mill 5.1, a portion of the exhaust flue gas is circulated into the micro powder mill flue gas primary mixing chamber 15.2 through the adjustment of the micro powder mill exhaust flue gas regulating valve 2.11 and the micro powder mill circulating flue gas regulating valve 2.12, and is further mixed in the micro powder mill flue gas mixing chamber 4 before entering the micro powder mill, and the remaining flue gas is directly discharged.

[0099] (13) In order to improve the safety of the flue gas entering the blast furnace coal pulverizing system during the drying and grinding process of the coal, the air-fuel ratio of air and gas entering the hot blast furnace combustion chamber is reduced, and the oxygen content of the flue gas after the furnace is controlled to be less than 4% (V / V).

[0100] (14) The amount of flue gas drawn out from the blast furnace coal pulverizing system into the metallurgical slag micro-powder system accounts for more than 95% of the total flue gas volume. It is also a flue gas that is balanced in terms of the flue gas volume and flue gas enthalpy of the blast furnace coal pulverizing system. The amount of this flue gas drawn out is adjusted according to the flue gas and flue gas enthalpy conditions in the blast furnace coal pulverizing system and the metallurgical slag micro-powder system. Under the premise that the coal mill mixed combustion flue gas and the injected carrier gas are normally drawn out, the adjustment process is as follows:

[0101] ① When the flue gas in the blast furnace coal pulverizing system has sufficient enthalpy and a surplus, but the flue gas volume is insufficient, close the mill flue gas exhaust regulating valve 2.17 and open the mill circulating flue gas regulating valve 2.18 to introduce some flue gas into the mill flue gas mixing chamber 10.2 for recycling. Simultaneously, increase the amount of combustion air and gas entering the mill flue gas furnace 10 via the mill air blower 9.1 and mill gas blower 9.2.

[0102] ② When the flue gas enthalpy and flue gas volume in the blast furnace coal pulverizing system are both surplus, open the coal mill circulating flue gas regulating valve 2.18 and the flue gas discharge emergency regulating valve 2.7 to introduce part of the flue gas into the coal mill flue gas mixing chamber 10.2 for recycling, and at the same time increase the discharge volume of the first part of the flue gas;

[0103] ③ When the flue gas enthalpy in the blast furnace coal pulverizing system is insufficient and the flue gas volume is surplus, close the coal mill circulating flue gas regulating valve 2.18 and the flue gas discharge emergency regulating valve 2.7 to increase the extraction volume of the first part of the flue gas;

[0104] ④ When the flue gas enthalpy and flue gas volume in the blast furnace coal pulverizing system are insufficient, close the flue gas discharge emergency regulating valve 2.7;

[0105] ⑤ When the flue gas enthalpy and flue gas volume in the blast furnace coal pulverizing system are both surplus and other adjustment measures are ineffective, start the coal mill exhaust gas fan (emergency fan) 7.2, open the coal mill exhaust gas regulating valve 2.17, and exhaust the flue gas until the system flue gas volume is balanced.

[0106] (15) The flue gas introduced into the blast furnace coal pulverizing system after the heat exchanger is the flue gas that maintains the balance of the flue gas volume in the flue gas duct after the heat exchanger. The amount of flue gas introduced changes with the fluctuation of the flue gas volume in the duct, which leads to fluctuations in the flue gas volume entering the coal mill 5.2. In order to control the flue gas volume entering the coal mill 5.2 and the stability of the flue gas enthalpy, the amount of combustion air and gas entering the coal mill flue gas furnace 10 is adjusted by the coal mill air blower 9.1 and the coal mill gas blower 9.2. The adjustment measures are shown in item (14) above.

[0107] (16) The two streams of flue gas directly drawn out from the hot blast furnace 16 and entering the metallurgical slag powder system and the flue gas directly drawn out from the heat exchanger (air heat exchanger 3.1 and gas heat exchanger 3.2) and entering the metallurgical slag micro-powder system are flue gases that maintain the balance of the flue gas volume in the hot blast furnace flue gas duct 17 and the flue gas duct after the heat exchanger. The drawn-out volume changes with the fluctuation of the flue gas volume in the duct, thereby causing the fluctuation of the flue gas volume entering the micro-powder mill 5.1. In order to control the flue gas volume and flue gas enthalpy stability entering the micro-powder mill 5.1, the micro-powder mill air blower 9.3 and the micro-powder mill hot air regulating valve 2.13 are used to adjust the amount of oxygen-enriched air or oxygen entering the explosion-proof high-energy ignition combustion chamber 15.1 and the amount of hot air from the blast furnace to control the flue gas volume generated by the micro-powder mill flue gas furnace 15 and ensure the balance of the drying and grinding flue gas volume entering the micro-powder mill 5.1. The control process is as follows:

[0108] ① When the flue gas enthalpy in the metallurgical slag micro powder system is sufficient and there is a surplus, but the flue gas volume is insufficient, increase the amount of oxygen-enriched air or oxygen blown into the explosion-proof high-energy ignition combustion chamber 15.1 by the micro powder mill air blower 9.3, and reduce the amount of blast furnace hot air regulated by the micro powder mill hot air regulating valve 2.13 entering the explosion-proof high-energy ignition combustion chamber 15.1;

[0109] ② When the flue gas in the metallurgical slag micro-powder system has sufficient heat enthalpy and a sufficient flue gas volume, maintain the amount of oxygen-enriched air or oxygen blown into the explosion-proof high-energy ignition combustion chamber 15.1 by the micro-powder mill air blower 9.3, and reduce the amount of blast furnace hot air regulated by the micro-powder mill hot air regulating valve 2.13 entering the explosion-proof high-energy ignition combustion chamber 15.1;

[0110] ③ When the flue gas enthalpy in the metallurgical slag micro-powder system is insufficient and the flue gas volume is surplus, reduce the amount of oxygen-enriched air or oxygen blown into the explosion-proof high-energy ignition combustion chamber 15.1 by the micro-powder mill air blower 9.3, and increase the amount of blast furnace hot air regulated by the micro-powder mill hot air regulating valve 2.13 entering the explosion-proof high-energy ignition combustion chamber 15.1;

[0111] ④ When the flue gas enthalpy and flue gas volume in the metallurgical slag micro-powder system are insufficient, add gas to the introduced flue gas through the micro-powder mill gas blower 9.4, reduce the amount of oxygen-enriched air or oxygen blown into the explosion-proof high-energy ignition combustion chamber 15.1 by the micro-powder mill air blower 9.3, increase the amount of blast furnace hot air regulated by the micro-powder mill hot air regulating valve 2.13 entering the explosion-proof high-energy ignition combustion chamber 15.1, and at the same time open the micro-powder mill post-circulation flue gas regulating valve 2.12 to introduce circulating flue gas.

[0112] (17) Online monitoring of CO concentration is installed on each flue gas pipeline entering the explosion-proof high-energy ignition and reburning chamber 4.1 upstream of the micro-powder mill flue gas mixing chamber 4. The CO concentration analysis in the flue gas is used as the feedback link of the system. The amount of air blown into the explosion-proof high-energy ignition combustion chamber 15.1 by the micro-powder mill air blower 9.3 or the amount of hot air introduced by the micro-powder mill hot air regulating valve 2.13 is adjusted according to the CO concentration value.

[0113] 4. System airflow and thermal enthalpy balance adjustment measures

[0114] Through the above implementation, all flue gas generated by the hot blast furnace 16, the explosion-proof high-energy ignition combustion chamber 15.1 of the blast furnace coal pulverizing system, and the flue gas generated by the coal mill flue gas furnace igniter 10.1 during emergency conditions in the blast furnace coal pulverizing system are all discharged through a single outlet of the pulverizing system and out through the chimney. There is a balance between the flue gas volume and flue gas enthalpy between these systems. The balance solution is as follows:

[0115] (1) Excessive flue gas volume and flue gas enthalpy from micro powder grinding

[0116] ① Increase the output of micro powder, increase the amount of flue gas and heat consumption;

[0117] ② Install a flue gas discharge emergency regulating valve 2.7 and a coal mill exhaust flue gas fan (emergency fan) 7.2 on the flue gas duct after the coal mill 5.2. When the flue gas from the fine powder mill 5.1 is excessive, open the flue gas discharge emergency regulating valve 2.7 and the coal mill exhaust flue gas fan (emergency fan) 7.2 to discharge part of the flue gas, thereby reducing the amount of recycled flue gas entering the metallurgical slag fine powder system;

[0118] ③ Close the hot air regulating valve 2.13 for the micro powder mill, stop supplying hot air to the micro powder mill flue gas furnace 15 to support combustion, and blow air into the micro powder mill air blower 9.3 to support combustion;

[0119] ④ Adjust the combustion air regulating valve 2.14 to reduce the air-fuel ratio and reduce the amount of hot blast furnace flue gas generated.

[0120] (2) The flue gas volume of the micro powder grinding mill is insufficient and the flue gas enthalpy is excessive

[0121] ① Close the flue gas exhaust emergency regulating valve 2.7 and the coal mill exhaust gas fan (emergency fan) 7.2 to increase the amount of recycled flue gas entering the metallurgical slag fine powder system;

[0122] ② Adjust the opening of the exhaust gas regulating valve 2.11 and the circulating gas regulating valve 2.12 after the micro-powder grinding to increase the circulating gas volume;

[0123] ③ When the circulating flue gas volume increases to the balance point of flue gas enthalpy, if the flue gas volume is still insufficient, close the hot air regulating valve 2.13 for the micro powder mill, stop supplying hot air to the micro powder mill flue gas furnace 15 to assist combustion, and blow air into the micro powder mill air blower 9.3 to assist combustion.

[0124] (3) Excessive flue gas volume from micro powder grinding and insufficient flue gas enthalpy

[0125] Increase the amount of blast furnace gas introduced by the micro powder mill gas blower 9.4, adjust the opening of the micro powder mill hot air regulating valve 2.13, increase the amount of hot air entering the micro powder mill flue gas furnace 15, reduce the amount of air blown in by the micro powder mill air blower 9.3, and increase the flue gas temperature leaving the micro powder mill flue gas furnace 15;

[0126] (4) The amount of flue gas from the micro powder grinding mill is insufficient, and the flue gas enthalpy is insufficient.

[0127] ① Adjust the opening of the hot air regulating valve 2.13 for the micro powder mill to increase the amount of hot air entering the micro powder mill flue gas furnace 15, reduce the amount of air blown in by the micro powder mill air blower 9.3, and increase the flue gas temperature leaving the micro powder mill flue gas furnace 15;

[0128] ② Adjust the opening of the combustion air regulating valve 2.14 and the gas regulating valve 2.15 to increase the heat load of the hot blast furnace 16, thereby increasing the hot blast furnace flue gas volume and the flue gas temperature after the furnace;

[0129] ③ Close the flue gas exhaust emergency regulating valve 2.7 and the coal mill exhaust gas fan (emergency fan) 7.2 to increase the amount of recycled flue gas entering the metallurgical slag fine powder system;

[0130] ④ Adjust the opening of the exhaust gas regulating valve 2.11 after micro powder grinding and the circulating flue gas regulating valve 2.12 after micro powder grinding to increase the circulating flue gas volume.

Claims

1. A blast furnace hot blast stove flue gas waste heat deep utilization coupled desulfurization and denitrification process, comprising a blast furnace, a hot blast stove, a blast furnace coal pulverizing system and a metallurgical slag micro-powder system; during the hot blast stove combustion period, air and coal gas enter the combustion chamber (16.1) of the hot blast stove (16) and are mixed and burned, and the generated high-temperature flue gas is heated by the heat storage chamber (16.2) of the hot blast stove (16), and then is led out from the hot blast stove flue gas duct (17) through the air and flue gas switching chamber (16.3) of the hot blast stove (16), characterized in that: Part of the flue gas after the furnace is led out from the hot blast furnace flue gas duct (17) to recover waste heat through the air heat exchanger (3.1), the gas heat exchanger (3.2), and the blast furnace coal pulverizing system. The flue gas after the heat exchange in the air heat exchanger (3.1) and the gas heat exchanger (3.2) is mixed and divided into three streams: the first stream is used as the flue gas before the micro-powder grinding and is introduced into the micro-powder grinding flue gas mixing chamber (4) in the metallurgical slag micro-powder system; the second stream As the flue gas before the coal mill, it is introduced into the blast furnace coal pulverizing system, passes through the coal mill flue gas furnace (10) and enters the coal mill (5.2) to participate in drying and help grind the blast furnace injection coal, and then passes through the coal powder bag dust collector (6.2) for dust removal, and is introduced into the fine powder mill flue gas furnace (15) of the metallurgical slag fine powder system for mixed combustion; the third stream is sent into the blast furnace (11) through the blast furnace hot air pipe (14) as the mixed combustion cold flue gas to reduce the theoretical combustion temperature in the blast furnace tuyere area; The flue gas after heat exchange from the air heat exchanger (3.1) and the gas heat exchanger (3.2), the flue gas after mixed combustion from the micro powder grinding flue gas furnace (15) of the metallurgical slag micro powder system, and the remaining flue gas from the hot blast furnace flue gas duct (17) all enter the explosion-proof high-energy ignition and reburning chamber (4.1) of the metallurgical slag micro powder system for full mixing and combustion, and then enter the micro powder grinding flue gas mixing chamber (4) for further mixing and enter the micro powder grinding mill (5.1) to dry and assist in grinding the metallurgical slag, and desulfurize and denitrify under the chemical absorption of alkaline earth metal oxides in the metallurgical slag micro powder and the adsorption of the metallurgical slag micro powder, and then enter the micro powder bag dust collector (6.1) of the metallurgical slag micro powder system for dust removal before being discharged.

2. The blast furnace hot blast stove flue gas waste heat deep utilization coupled desulfurization and denitrification process according to claim 1, characterized in that: The pressure in the flue gas duct after the air heat exchanger (3.1) and the gas heat exchanger (3.2) and the hot blast furnace flue gas duct (17) is collected as a feedback link of the system. By adjusting the flow rate of the first flue gas after the furnace introduced into the metallurgical slag fine powder system, the pressure in the flue gas duct after the air heat exchanger (3.1) and the gas heat exchanger (3.2) and the hot blast furnace flue gas duct is stabilized under the premise that the flow rate and thermal enthalpy of the second flue gas after the furnace entering the blast furnace coal pulverizing system meet the stable production requirements of the coal mill.

3. The blast furnace hot blast stove flue gas waste heat deep utilization coupled desulfurization and denitrification process according to claim 1, characterized in that: By adjusting the flow rate of the remaining part of the post-furnace flue gas entering the metallurgical slag fine powder system, the pressure stability and the balance of the flue gas flow rate in the hot blast furnace flue gas duct (17) are maintained.

4. The blast furnace hot blast stove flue gas waste heat deep utilization coupled desulfurization and denitrification process according to claim 1, characterized in that: When the temperature of the flue gas entering the coal mill (5.2) is lower than the set temperature, the coal mill flue gas furnace (10) is started, and coal gas and air are introduced for combustion to generate high-temperature flue gas to increase the temperature of the flue gas entering the coal mill (5.2) to meet the process temperature requirements of the blast furnace coal pulverizing system.

5. The blast furnace hot blast stove flue gas waste heat deep utilization coupled desulfurization and denitrification process according to claim 1, characterized in that: The flue gas and pulverized coal mixture exiting the coal mill (5.2) enters the pulverized coal bag filter (6.2), where the flue gas and pulverized coal are filtered and separated, and the separated pulverized coal enters the pulverized coal bin (12); the separated flue gas is divided into three parts, the first part being used as the pulverized coal carrier gas, which enters the pulverized coal carrier gas tank (13) under the compression of the pulverized coal carrier gas blower (8.1) of the pulverized coal injection system, and is used as the carrier gas for pulverized coal injection to spray the pulverized coal into the blast furnace (11); the second part is the low-temperature coal-blended flue gas, which is introduced into the blast furnace hot air pipe (14) under the suction of the co-combustion flue gas blower (8.2); the third part of the return flue gas is first supplemented with coal gas and then enters the micro-powder mill flue gas furnace (15) of the metallurgical slag micro-powder system to be mixed and burned with air or part of the hot air from the blast furnace hot air pipe (14), and the high-temperature flue gas generated then enters the micro-powder mill (5.1) through the micro-powder mill flue gas mixing chamber (4).

6. The blast furnace hot blast stove flue gas waste heat deep utilization coupled desulfurization and denitrification process according to claim 5, characterized in that: When the amount of flue gas entering the micro powder mill (5.1) is insufficient to meet the flue gas volume required by the micro powder mill (5.1), a portion of the flue gas discharged from the micro powder bag filter (6.1) is circulated into the micro powder mill flue gas furnace (15), and then sent into the micro powder mill through the micro powder mill flue gas mixing chamber (4) to supplement the insufficient flue gas volume.

7. The blast furnace hot blast stove flue gas waste heat deep utilization coupled desulfurization and denitrification process according to claim 1, characterized in that: The blast furnace coal pulverizing system comprises a coal mill flue gas furnace (10), a coal mill (5.2), and a coal powder bag dust collector (6.2) connected in sequence; the metallurgical slag micro-powder system comprises a micro-powder mill flue gas furnace (15), a micro-powder mill flue gas mixing chamber (4), a micro-powder mill (5.1), and a micro-powder bag dust collector (6.1) connected in sequence.

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