A heating process for the whole process of ironmaking in a blast furnace hot blast stove

Abstract

The invention discloses a full-process heating process for hot blast furnace ironmaking. During the hot blast furnace's combustion phase, air and coal gas enter the furnace's combustion chamber and are mixed and burned. The resulting high-temperature flue gas is heat-exchanged in a regenerator before being drawn out of the hot blast furnace flue gas duct via an air-to-gas switching chamber. The flue gas exiting the hot blast furnace flue gas duct is divided into four parts: the first part of the flue gas is introduced into the flue gas mixing chamber of the metallurgical slag micro-powder system to dry and aid in grinding the metallurgical slag; the second part of the flue gas is introduced into the coal mill flue gas furnace of the blast furnace coal pulverizing system to dry and aid in grinding the injected coal; the third part of the flue gas enters an air heat exchanger to preheat the air before it is fed into the hot blast furnace; and the fourth part of the flue gas enters a gas heat exchanger to heat the blast furnace gas before it enters the hot blast furnace. The invention features a simple process, low investment, low operating costs, environmental friendliness, energy conservation, and consumption reduction, saving equipment investment, lowering operating costs, and effectively recovering waste heat and energy from the flue gas.

Description

Technical Field

[0001] The present invention relates to the fields of metallurgical equipment and metallurgical energy and environmental protection, and in particular to a full-process heating process for ironmaking in a blast furnace and hot blast stove. Background Art

[0002] Hot blast furnaces are a key component of blast furnaces in ironworks. Typically, a single 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. The hot blast injected into the blast furnace is the most cost-effective and efficient energy source. Increasing blast temperature and increasing the amount of coal injected (PI) are common techniques used by steel mills to reduce process energy consumption. For example, according to 2016 statistics from a steel mill's blast furnace, 303 kg of coke per ton of iron was consumed; 181 kg of PI was injected; and the enthalpy introduced by the hot blast was 1.8 GJ. The total energy consumption for blast furnace production was approximately 14.5 GJ. This means that the energy introduced by the hot blast into the blast furnace accounts for over 12.4% of the total energy consumption.

[0003] Blast furnace hot blast stoves can be divided into two types according to their working principles: heat storage type and heat exchange type.

[0004] The heat exchange hot blast furnace mainly uses a high-temperature resistant heat exchanger as its core component. This component cannot use a metal heat exchanger, but can only use a high-temperature resistant ceramic heat exchanger. The blast furnace gas is fully burned in the combustion chamber, and the hot air after combustion passes through the heat exchanger to exchange heat for fresh cold air, which can make the fresh air temperature reach above 1000℃.

[0005] 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.

[0006] Regenerative checker brick hot blast furnaces are the most commonly used type of hot blast furnace in modern blast furnaces, especially large ones. Regenerative hot blast furnaces can be categorized by combustion method, including top-fired, internal-fired, and external-fired types. Their operating principle is to first burn coal gas, using the resulting flue gas to heat the checker bricks in the regenerator. Cooling air is then passed through the heated checker bricks to heat the air. The hot blast furnace then alternates combustion and air delivery, ensuring a continuous supply of high-temperature hot air to the blast furnace.

[0007] 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.

[0008] The air or oxygen-enriched air or oxygen blown into the hot blast furnace is converted into blast furnace hot air with a temperature of about 1200℃ after heat exchange in the regenerator. It enters the blast furnace through the tuyere in the blast furnace bosh area and mixes with the injected coal powder to burn and participate in the blast furnace smelting.

[0009] Taking a regenerative hot blast furnace with a top-fired combustion method as an example, the coal gas and combustion air are preheated to about 200°C at low temperature before entering the hot blast furnace combustion chamber to generate high-temperature flue gas that heats the regenerative element. After heat exchange with the regenerative element, the temperature drops to about 400°C before being discharged from the hot blast furnace. Analysis of the exhaust gas oxygen content is used as a feedback link in the system, participating in closed-loop control and adjusting the air-fuel ratio at any time. [https: / / wenku.so.com / d / 9b36e50fa40d8aec19c486dc8a9436d7-450 cubic meter hot blast furnace design calculation] 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, with a flue gas volume of about 1400-1500Nm 3 / t-molten iron, after these flue gases are respectively exchanged with combustion air and gas in air heat exchanger and the temperature is reduced to 120-150℃, except for a small amount that enters the blast furnace coal pulverizing system for cascade utilization, the rest is directly discharged.

[0010] On the other hand, in the entire blast furnace ironmaking process, both the blast furnace coal pulverizing system and the metallurgical slag micro-powder system are equipped with new flue gas generators to provide dry flue gas at different temperatures, such as 250-400°C, to the coal mill and micro-powder mill. The metallurgical slag micro-powder system requires a flue gas volume equivalent to that of the hot blast furnace. For example, the slag micro-powder project at the Dalian base of Northeast Special Steel Group selected the MTP180 slag mill from Dayuan Group. The main design parameters are: nameplate output 90t / h (designed based on 10% overproduction), slag moisture Ma = 11, slag micro-powder moisture Mf = 0.5, slag mill outlet air volume A = 27.8×10 +4 Nm 3 / h, slag mill outlet temperature T1 = 90 ° C, gas-solid ratio of about 3000m 3 / t-fine powder [Sun Yongning. Design and Calculation of Heating Capacity of Flue Gas Furnace in Slag Fine Powder System. Modern Metallurgy, August 2015], the flue gas volume required for one ton of iron slag is about 1000m 3 / t-iron; Guizhou Shuicheng Iron and Steel (Group) Co., Ltd. started construction of a 150,000-ton annual slag powder production line in June 2011. It was completed and put into operation in April 2012, with a stable output of 24-25t / h and a product specific surface area of ​​430-450m 2 / kg, the comprehensive power consumption of the product is 47-48kWh / t, and the flue gas-powder ratio is about 4000Nm 3 / t-micro powder [Gu Jintu, Wang Yejiang. Process design and practice of 150,000 tons per year slag micro powder production line. Cement Technology, February 2013], the flue gas volume required for one ton of iron slag is about 1400m 3 / t-Iron.

[0011] The flue gas volume of the blast furnace coal pulverizing system is about one-third of the hot blast furnace flue gas volume. For example, the blast furnace coal pulverizing system of a certain iron and steel plant requires the outlet gas temperature to be around 300°C, and the coal mill temperature to be around 250°C to ensure that the coal powder in the coal mill is fully baked. The flue gas volume of the blast furnace coal pulverizing system for drying raw coal is about 3000Nm 3 / t-coal powder [Wu Jiangsong. Research and Analysis on the Balance of Blast Furnace Coal Injection Pulverizing System. Modern Metallurgy, December 2012], the coal injection rate is 180kg / t-iron, and the flue gas volume required for coal powder preparation per ton of iron is 540Nm 3 / t-Iron.

[0012] To sum up, in the entire process of blast furnace ironmaking production, on one hand, the hot blast furnace produces a large amount of flue gas that is directly discharged, and the blast furnace coal pulverizing system and metallurgical slag micropowder system require a large amount of flue gas to be produced by burning coal gas in the flue gas generator. If the production units that produce flue gas can be combined with the production units that require flue gas to form an ecological production chain for cascade utilization of flue gas, it can not only reduce flue gas emissions, but also recover the low-temperature waste heat of the flue gas. At the same time, the alkaline earth metal oxides rich in metallurgical slag micropowder can be used to absorb and remove sulfur dioxide, nitrogen oxides, carbon dioxide, etc. in the flue gas. Summary of the Invention

[0013] The purpose of the present invention is to solve the above technical problems and provide a blast furnace hot blast stove ironmaking full-process heating process with simple process, low investment, low operating cost, environmental friendliness, energy saving and consumption reduction, saving equipment investment, reducing operating costs, and effectively recovering flue gas waste heat and waste energy.

[0014] The invention discloses a full-process heating process for hot blast furnace ironmaking, comprising a blast furnace, a hot blast furnace, a blast furnace coal pulverizing system, a coal pulverizing system and a metallurgical slag micro-powder system; during the combustion period of the hot blast furnace (16), air and coal gas heated by heat exchange are mixed and burned in a hot combustion chamber (16.1) to generate high-temperature flue gas, which is then heat-exchanged in a heat storage chamber (16.2) to form a post-furnace flue gas which is led out through an air-to-gas switching chamber (16.3) and enters a hot blast furnace flue gas duct 17; during the air supply period of the hot blast furnace (16), the blast furnace blower (1) blows in the hot blast furnace coal pulverizing system. The hot air formed after the gas is heated by heat exchange in the heat storage chamber (16.2) enters the blast furnace hot air pipe (14), and the flue gas discharged from the hot blast furnace flue gas pipe (17) is divided into four parts: the first part of the flue gas is introduced into the metallurgical slag micro-powder system to dry and assist in grinding the metallurgical slag; the second part of the flue gas is introduced into the blast furnace coal pulverizing system to dry and assist in grinding the injected coal; the third part of the flue gas enters the air heat exchanger (3.1) to preheat the air sent to the hot blast furnace (16); and the fourth part of the flue gas enters the coal gas heat exchanger (3.2) to preheat the coal gas entering the hot blast furnace (16).

[0015] The third part of the flue gas and the fourth part of the flue gas exiting the air heat exchanger (3.1) and the gas heat exchanger (3.2) are mixed and then divided into three streams: the first stream is used as the flue gas before the micro-powder mill, introduced into the metallurgical slag micro-powder system, mixed through the flue gas mixing chamber (4), and then sent to the micro-powder mill (5.1) for drying and helping to grind the metallurgical slag; the second stream is used as the flue gas before the coal mill, introduced into the blast furnace coal pulverizing system, mixed through the coal mill flue gas mixing chamber (10.2), and then sent to the coal mill (5.2) for drying and helping to grind the blast furnace injection coal; the third stream is used as the mixed combustion cold flue gas, sent through the blast furnace hot blast pipe (14) into the blast furnace (11) to reduce the theoretical combustion temperature in the blast furnace tuyere area. The hot air drawn from the blast furnace hot air pipe (14) is not only blown into the blast furnace (11) to provide heat enthalpy for the blast furnace (11) and mixed with the pulverized coal from the pulverized coal injection system for combustion, but also, according to the heat balance requirements of the metallurgical slag micro-powder system, a portion of the hot air can be drawn into the metallurgical slag micro-powder system to provide heat enthalpy for drying the metallurgical slag micro-powder system and to assist in grinding the metallurgical slag. The flue gas entering the blast furnace coal pulverizing system is mixed in the coal mill flue gas furnace (10) and then enters the coal mill (5.2). 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) so that it meets the heat requirement for coal powder drying.

[0016] 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. The separated pulverized coal enters the pulverized coal bin (12); the separated flue gas is divided into three parts. The first part is used as the pulverized coal carrier gas. Under the compression of the pulverized coal carrier gas blower (8.1) of the pulverized coal injection system, it enters the pulverized coal injection carrier gas tank (13) and serves as the carrier gas for pulverized coal injection, spraying the pulverized coal into the blast furnace (11); the second part is low-temperature coal-blended flue gas. Under the suction of the pulverized coal blending flue gas blower (8.2), it is introduced into the blast furnace hot air pipe (14); the third part is the return flue gas. It is introduced into the micro-powder mill flue gas furnace (15) of the metallurgical slag micro-powder system for high-temperature incineration to consume the trace pulverized coal and VOC in the flue gas. After that, it enters the micro-powder mill (5.1) to dry and assist in grinding the metallurgical slag.

[0017] The third part of the recycled 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 with air or hot air from the blast furnace hot air pipe (17) for combustion. The high-temperature flue gas generated then enters the micro powder mill (5.1) through the micro powder mill flue gas mixing chamber (4).

[0018] When the flue gas volume entering the metallurgical slag micro-powder system is insufficient to meet the flue gas volume requirement of the micro-powder mill (5.1), a portion of the exhaust flue gas 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.

[0019] 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 part of the 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 part of the flue gas after the furnace entering the blast furnace coal pulverizing system meet the stable production requirements of the coal mill.

[0020] A coal mill exhaust gas regulating valve (2.7) and a coal mill exhaust gas fan (7.2) are provided on the flue gas outlet pipe of the pulverized coal bag filter (6.2) as emergency regulating valves and emergency fans to balance the stability of air flow retention fluctuations in the blast furnace, hot blast furnace, blast furnace coal pulverizing system, pulverized coal injection system, and metallurgical slag fine powder system, as well as the heat enthalpy requirements of each system.

[0021] 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); 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); the flue gas-slag / steel slag micro-powder mixture exiting the micro-powder mill (5.1) enters the micro-powder bag dust collector (6.1), the separated slag / steel slag micro-powder enters the micro-powder bin, and the purified flue gas is discharged.

[0022] In view of the problems existing in the background technology, the inventors have made the following improvements:

[0023] 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 environmental protection operation costs.

[0024] Through the analysis of the flue gas volume and flue gas enthalpy of each production unit that produces and uses flue gas in the blast furnace ironmaking process, it can be seen that the hot blast furnace flue gas volume generated by providing high-temperature hot air to the blast furnace is about 1400-1500Nm 3 / t-iron, flue gas temperature 120-400℃ (of which the flue gas at 120-150℃ is the flue gas discharged from the hot blast furnace after heat exchange with air and gas heat exchanger, and the flue gas at about 400℃ is the flue gas directly discharged from the hot blast furnace flue gas pipe 17); the flue gas volume required by the metallurgical slag micropowder system is about 1400Nm 3 / t-iron, the flue gas temperature is 350-400℃, and the flue gas temperature after use is 90-105℃; the flue gas volume required by the blast furnace coal pulverizing system is about 540Nm 3 / t-iron, flue gas temperature 250-300℃, flue gas temperature after use 80-105℃.

[0025] The 120-150℃ flue gas discharged after heat exchange with the air and gas heat exchanger is mixed with the 400-450℃ flue gas directly discharged from the hot blast furnace flue gas pipe through the regulating valve to form 250-300℃ flue gas and enter the blast furnace coal pulverizing system. 3 The remaining flue gases at 120-150℃ and 400-450℃ are all introduced into the metallurgical slag fine powder system.

[0026] In order to give full play to the function of the blast furnace hot blast stove and improve the utilization efficiency of the hot blast stove, the present invention increases the amount of air and gas entering the hot blast stove combustion chamber, increases the combustion intensity during the hot blast stove combustion period by about 5%, increases the amount of hot blast stove flue gas, and increases the outlet hot blast flue gas temperature by 20-50°C, that is, the temperature of the flue gas directly discharged from the hot blast stove flue gas pipe is 400-450°C.

[0027] Due to the increase in the temperature of the flue gas leaving the hot blast stove, by controlling the amount of air and gas entering the air heat exchanger and the gas heat exchanger (the insufficient amount is directly introduced into the hot blast stove combustion chamber), the temperature of the flue gas discharged after the air heat exchanger and the gas heat exchanger is increased to 250-300℃, according to 540Nm 3 / t-iron flue gas is introduced into the blast furnace coal injection pulverizing system, and the remaining part and 400-450℃ flue gas are all introduced into the metallurgical slag micro-powder system.

[0028] The 80-105℃ flue gas after being used in the blast furnace coal injection pulverizing system is introduced into the metallurgical slag micropowder system except for partially replacing the nitrogen in the blast furnace coal injection carrier gas and the mixed combustion steam to reduce the theoretical combustion temperature of the blast furnace hot air injected into the blast furnace and the combustion of coal powder.

[0029] Furthermore, in order to improve the safety of the flue gas introduced into the blast furnace coal pulverizing system to dry the coal charge, and at the same time increase the temperature of the flue gas leaving the hot blast furnace, the present invention proposes to reduce the air-fuel ratio of air and gas entering the hot blast furnace combustion chamber to control the oxygen content of the flue gas leaving the furnace to be less than 4% (V / V).

[0030] In order to make full use of the unburned combustible components in the flue gas (the gas cannot be 100% burned due to the low air-fuel ratio), the flue gas from the micro powder mill flue gas furnace, 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 ignited and burned before entering the micro powder mill.

[0031] 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 moisture, 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 pollutants (sulfur dioxide) in the flue gas are absorbed by the calcium hydroxide and magnesium hydroxide in the metallurgical slag. Therefore, the sulfur pollutants in the flue gas are absorbed and removed while the flue gas dries, fluidizes, and aids the grinding of the metallurgical slag. 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.

[0032] Furthermore, in order to recover the chemical energy of a small amount of fine coal powder carried out by the flue gas after the use of the blast furnace coal pulverizing system and a small amount of volatile components produced by the coal during the drying process, the flue gas is divided into three parts for all recycling. Among them, the metallurgical slag micro-powder system is introduced to mix coal gas into the micro-powder mill flue gas furnace and burn it as the flue gas for drying, fluidizing and grinding metallurgical slag for micro-powder milling to produce slag micro-powder and steel slag micro-powder products, which not only recycles the fine coal powder carried in the flue gas discharged by the blast furnace coal pulverizing system, but also purifies and removes sulfur pollutants in the flue gas. Based on the annual coal injection volume of 100 million tons in blast furnaces across the country, the amount of coal powder carried out by the flue gas of the blast furnace coal pulverizing 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 was greatly reduced, and the fine coal powder in the exhaust gas was recovered.

[0033] Furthermore, in order to ensure the balance and stability of heat supply throughout the entire process of hot blast furnace ironmaking, four balancing plans were established for the entire process:

[0034] First, the flue gas after the hot blast furnace is led out of the flue gas duct (17) into four parts, of which the flue gas entering the metallurgical slag micro-powder system to dry and assist in grinding the metallurgical slag is the balance flue gas of the entire process flue gas flow rate. It is preferred that the flue gas flow rate and flue gas enthalpy entering the blast furnace coal pulverizing system meet the requirements of the blast furnace coal pulverizing system;

[0035] Second, the flue gas after the hot blast furnace is led out of the hot blast furnace flue gas duct (17) into four parts, of which the two flue gases entering the air heat exchanger and the gas heat exchanger are the flue gases that balance the enthalpy of the flue gas entering the blast furnace coal pulverizing system. When the enthalpy of the flue gas entering the blast furnace coal pulverizing system is insufficient, sufficient flue gas is reserved to enter the blast furnace coal pulverizing system.

[0036] Third, the hot air drawn out from the blast furnace hot air pipe (14) is not only blown into the blast furnace (11) to provide heat enthalpy for the blast furnace (11) and mixed with the pulverized coal from the pulverized coal injection system for combustion, but also, according to the heat balance requirements of the metallurgical slag micro-powder system, a portion of the hot air is drawn out through the micro-powder mill hot air regulating valve (2.13) into the explosion-proof high-energy ignition combustion chamber (15.1) of the metallurgical slag micro-powder system to assist in the combustion of combustible components entering the explosion-proof high-energy ignition combustion chamber (15.1), and to provide heat enthalpy for the metallurgical slag micro-powder system.

[0037] Fourth, a circulating flue gas regulating valve is set inside the metallurgical slag fine powder system to adjust the circulating flue gas volume; a flue gas exhaust emergency regulating valve (2.7) and a coal mill exhaust flue gas fan (emergency fan 7.2) are set in the blast furnace coal pulverizing system to adjust the exhaust flue gas volume.

[0038] 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 and trace amounts of pulverized coal in the flue gas are recycled.

[0039] 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.

[0040] The present invention utilizes the existing blast furnace, hot blast furnace, blast furnace coal pulverizing system, coal pulverizing injection system and metallurgical slag micro-powder system, and only changes the connection relationship of the flue gas pipeline to realize the recovery of flue gas and heat energy. It has the advantages of saving equipment investment, reducing operating costs and effectively recovering flue gas waste heat and waste energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0042] 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 Throttle valve; 2.11, 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; 3.1, air heat exchanger; 3.2, gas heat exchanger; 4, micro powder mill flue gas mixing chamber; 5.1, micro powder mill; 5.2, coal mill; 6.1, micro powder cloth Bag filter; 6.2, pulverized coal bag filter; 7.1, micro powder mill exhaust fan; 7.2, coal mill exhaust fan (emergency fan); 8.1, coal injection carrier air fan; 8.2, blended combustion 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; 10.1, 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 pipe; 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 heat storage chamber; 16.3, air-flue gas switching chamber; 17, hot blast furnace flue gas duct. DETAILED DESCRIPTION

[0043] The following is a steel plant with a 2000m 3 Taking a blast furnace as an example, three air and gas dual preheating top-fired hot blast furnaces are used to further explain the present invention. The various equipment in the embodiment are commercially available:

[0044] 1. Balance calculation of hot blast furnace flue gas enthalpy and flue gas flow

[0045] A steel plant 2000m 3 Statistics 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.

[0046] Blast furnace utilization coefficient: 2.8-3.0, molten iron output: 230-250t / h (calculated based on 250t / h);

[0047] Each ton of iron produces 300-400 kg of slag (calculated at 350 kg / t-iron);

[0048] The coal injection rate per ton of iron is 170-180 kg (calculated at 180 kg / t-iron);

[0049] Hot air temperature: 1150-1200℃

[0050] Hot air volume (oxygen enrichment rate 2-3%): 1100-1200Nm 3 / t-iron (according to 1150Nm 3 / t-iron, heat enthalpy brought in by hot air: 1.875-1.85GJ / t-iron);

[0051] Blast furnace gas production: 1800-2200Nm 3 / t-iron;

[0052] Blast furnace gas calorific value: 3300-3500kJ / Nm 3 (According to 3400kJ / Nm 3 count).

[0053] Air and gas enter the hot blast furnace combustion chamber after heat exchange in the flue gas preheater.

[0054] Hot blast furnace production process indicators:

[0055] Hot air furnace flue gas temperature: 300-350℃;

[0056] Hot blast furnace gas consumption 900-1100Nm 3 / t-iron (710+230+80=1020. Including the blast furnace gas consumed by production units such as pulverized coal injection and slag powder);

[0057] Air-fuel ratio: 0.7-0.8;

[0058] The preheater combustion air inlet temperature is 20-25℃;

[0059] The preheater combustion air outlet temperature is 140-170℃;

[0060] The preheater combustion air inlet temperature is 10-15℃;

[0061] The outlet temperature of the preheater combustion gas is 140-170℃;

[0062] The preheater flue gas inlet temperature is 250-350℃;

[0063] Preheater flue gas outlet temperature 120-140℃;

[0064] [https: / / max.book118.com / html / 2016 / 0612 / 45377018.shtm-Safety Technical Operating Procedures for Hot Blast Furnaces]

[0065] Pulverized coal injection production line operating parameters (each ton of pulverized coal requires 3000m 3 Flue gas consumption) [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];

[0066] Temperature of flue gas entering coal powder mill: about 250-300℃;

[0067] The mill outlet temperature during normal milling is 80-85°C;

[0068] Flue gas volume entering coal powder mill: 2000-3000Nm 3 / t-coal powder (according to 2500Nm 3 / t-coal powder);

[0069] The dry flue gas volume required for the coal powder production line to inject coal per ton of iron is: 450Nm 3 / t-Iron.

[0070] Coal injection carrier gas volume: Nitrogen is generally used as the carrier gas, the solid-gas ratio is 20-50kg / kg, and the carrier gas volume is 16-40m 3 / t-coal.

[0071] Operating process parameters of slag micropowder production line [Gu Jintu, Wang Yejiang. Process design and practice of 150,000 tons per year slag micropowder production line. Cement Technology, February 2013] [Wang Guoqing. Advanced technology of vertical mill slag grinding process and equipment. China Cement, March 2017] [Sun Yongning. Design and calculation of heating capacity of flue gas furnace of slag micropowder system. Modern Metallurgy, August 2015]:

[0072] Hot flue gas temperature entering slag micro powder grinding: 350℃;

[0073] Exhaust gas temperature at the mill: 90-100℃;

[0074] Material temperature entering the mill: 20°C;

[0075] Material temperature out of mill: 90℃

[0076] Flue gas volume entering the mill: 3000-4000Nm 3 / t-fine powder (according to 3500Nm 3 / t-coal powder);

[0077] The specific surface area of ​​the slag powder product produced is 430-450m 2 / kg;

[0078] 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: 1225Nm 3 / t-Iron.

[0079] The total flue gas volume required for the slag powder and pulverized coal injection production line is: 1675Nm 3 / t-Iron.

[0080] Hot blast stove flue gas energy and flow balance calculation:

[0081] 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 the hot blast is:

[0082] 1.8×10 6 ÷3400÷0.75=705.9Nm 3 / t-iron (according to 710Nm 3 / t-Iron Meter).

[0083] Based on an air-fuel ratio of 0.7, the air volume is approximately: 500Nm 3 / t-iron, the total flue gas volume from the hot blast furnace is 1200-1300Nm 3 / t-Iron.

[0084] 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 ×1450Nm 3 / t-iron, calculated as 0.77 GJ / t-iron).

[0085] The amount of gas required is about 226.5Nm 3 / t-iron (according to 230Nm 3 / t-iron), based on an air-fuel ratio of 0.7, the amount of combustion air added is about 160Nm 3 / t-iron, the total flue gas volume discharged from the hot blast furnace is reduced from the original 1200-1300Nm 3 / t-Iron increased to 1590-1690Nm 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].

[0086] 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, No. 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 coal mill 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.

[0087] After the blast furnace hot blast stove provides hot air for the blast furnace, provides dry flue gas for the coal pulverizing production line, and provides drying for the slag micro powder production line, the exhaust temperature is 350-400℃ and the total flue gas volume is 1590-1690Nm 3 / t-Iron increased to 1726-1826 Nm 3 / t-iron, an increase of 8-10%. Therefore, it can be seen that by simply increasing the combustion intensity of the hot blast furnace by 5-10%, increasing the hot blast furnace 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.

[0088] 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, Issue 5, 2019: 47-51], the solid-gas ratio of blast furnace coal injection in most iron and steel plants is 20-30 kg / kg [Zhang Lei, Xu Feifei, Ren Jiangtao. Design and economic benefit analysis of 1080m3 blast furnace coal injection. Metallurgical Equipment, Special Issue 2014 (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), the solid-gas ratio in the coal mill is 0.27 kg / kg], and the solid-gas ratio is 20-50.

[0089] 2. Specific implementation process

[0090] (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 three hot blast furnaces 16 work simultaneously. The air supply time and the combustion time are staggered in order within the working cycle. The amount of gas and air entering each hot blast furnace 16 is adjusted by a regulating valve to ensure continuous delivery of hot air and stable hot air temperature.

[0091] (2) Through blower 1 press 1100-1200Nm 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 from the blast furnace tuyere 11.1.

[0092] (3) According to 950-1050Nm 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 650-750Nm 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.

[0093] (4) The amount of flue gas discharged from the hot blast furnace 16 is 1600-1800 Nm 3 / t-iron, with a temperature of 400-450°C, the hot blast furnace flue gas (off-furnace flue gas) is divided into four parts: the first part of the off-furnace flue gas is introduced into the fine powder mill flue gas mixing chamber 4 of the metallurgical slag fine powder system, mixed with other flue gases, and then enters the fine powder mill 5.1 to dry and assist in grinding the metallurgical slag; the second part of the off-furnace flue gas is introduced into the coal mill flue gas mixing chamber 10.2 of the coal mill flue gas furnace 10 of the blast furnace coal pulverizing system, mixed with other flue gases, and then enters the coal mill 5.2 to dry and assist in grinding the injected coal; the third part of the off-furnace flue gas enters the air heat exchanger 3.1 to preheat the combustion air; and the fourth part of the off-furnace flue gas enters the gas heat exchanger 3.2 to preheat the blast furnace gas.

[0094] (5) The temperature of the third part of the flue gas after the furnace and the fourth part of the flue gas after the furnace are reduced to between 250-300℃ after heat exchange in the air heat exchanger 3.1 and the gas heat exchanger 3.2. The two parts of flue gas are mixed and divided into three streams: one is the flue gas before the micro powder mill, which is introduced into the micro powder mill flue gas mixing chamber 4 of the metallurgical slag micro powder system through the micro powder mill cold flue gas regulating valve 2.4 and mixed with other flue gases to enter the micro powder mill 5.1 to participate in drying and assist in grinding the metallurgical slag; one is the flue gas before the coal mill, which is introduced into the coal mill flue gas furnace 10 of the blast furnace coal pulverizing system through the coal mill cold flue gas regulating valve 2.5 to participate in drying and assist in grinding the blast furnace injected coal; and one is the high-temperature co-combustion flue gas, which is introduced into the blast furnace hot air pipe 14 through the co-combustion cold flue gas regulating valve 2.6 as the co-combustion flue gas to reduce the theoretical combustion temperature of the blast furnace tuyere 11.1 area.

[0095] (6) The flue gas before the coal mill enters the coal mill 5.2 through the coal mill flue gas mixing chamber 10.2. When the flue gas temperature before the coal mill is lower than 250℃, 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 400-450℃ flue gas after the furnace into the coal mill flue gas mixing chamber 10.2 to mix with the flue gas before the coal mill to form flue gas at 250-300℃, thereby increasing the thermal enthalpy of the flue gas entering the coal mill 5.2.

[0096] (7) When the amount of flue gas after the furnace is not enough to increase the thermal enthalpy of the flue gas entering the coal mill 5.2, the coal mill flue gas furnace 10 is started to generate high-temperature flue gas, which is mixed with the flue gas before the coal mill and the flue gas after the furnace in the coal mill flue gas mixing chamber 10.2 to reach the required thermal enthalpy of the coal mill 5.2, and then enters the coal mill 5.2 to dry and help grind the blast furnace injection coal.

[0097] (8) The flue gas before the micro powder mill with a temperature of 250-300°C from the air heat exchanger 3.1 and the gas heat exchanger 3.2 is fully mixed with the first part of the post-furnace flue gas with a temperature of 400-450°C through the micro powder mill flue gas mixing chamber 4 to form a mixed flue gas with a temperature of 350-400°C, which enters the micro powder mill 5.1 to dry and assist in grinding the metallurgical slag. When the temperature of the mixed flue gas is lower than 350°C, or lower than the flue gas temperature actually controlled by the micro powder mill 5.1 in 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 is introduced from the micro powder mill flue gas primary mixing chamber 15.2 and enters the micro powder mill flue gas mixing chamber 4 together to form a flue gas with a higher temperature to meet the flue gas enthalpy required by the micro powder mill 5.1.

[0098] (9) The flue gas and pulverized coal mixture from the 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 3-10m 3 The flue gas volume of the pulverized coal (PFI) is adjusted, and under the compression of coal-injection carrier gas blower 8.1, it enters the pulverized coal injection carrier gas tank 13, serving as the carrier gas for the PFI, injecting the PFI 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 drawn into the blast furnace hot blast duct 14 by 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 within the blast furnace 11. The third part is the return flue gas, which passes through the coal mill-micro-powder mill flue gas regulating valve 2.10 and, under the suction of the coal mill-micro-powder mill flue gas blower 8.3, is introduced into the micro-powder mill flue gas furnace 15 for recycling.

[0099] (10) The recycled flue gas entering the metallurgical slag micro-powder system is supplemented with coal gas through the micro-powder mill gas blower 9.4 before entering the micro-powder mill flue gas furnace 15. The recycled 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, and is further mixed in the micro-powder mill flue gas mixing chamber 4 before entering the micro-powder mill 5.1.

[0100] (11) In the micro powder mill 5.1, the flue gas is mixed with the metallurgical slag in the mill to dry and grind the metallurgical slag to form a flue gas-slag / steel slag micro powder mixture. The temperature drops to 90-100 ° C. Under the suction action of the micro powder mill exhaust fan 7.1, the flue gas enters the micro powder bag dust collector 6.1, and the slag / steel slag micro powder (ultrafine powder product) is separated and enters the micro powder bin. The purified flue gas is discharged to the outside.

[0101] (12) When the amount of flue gas entering the micro powder mill is insufficient to meet the flue gas volume requirement of the micro 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.

[0102] (13) The flue gas outlet emergency regulating valve 2.7 and the coal mill exhaust flue gas fan 7.2 (emergency fan) are installed on the flue gas outlet pipe of the pulverized coal bag filter 6.2 as emergency regulating devices to balance the stability of the air flow retention fluctuations including the blast furnace, hot blast furnace, blast furnace coal pulverizing system, pulverized coal injection system, and metallurgical slag micro-powder system and the heat enthalpy requirements within each system.

[0103] (14) Reduce the air-fuel ratio of air and gas entering the hot blast furnace combustion chamber 16.1, and control the oxygen content of the flue gas discharged from the hot blast furnace to less than 4% (volume ratio).

[0104] (15) When the flue gas volume of the blast furnace coal pulverizing system, the pulverized coal injection system, and the metallurgical slag fine powder system is insufficient, increase the amount of air and gas entering the hot blast furnace combustion chamber 16.1, increase the combustion intensity of the hot blast furnace 16 during the combustion period by 5-10%, increase the flue gas volume of the hot blast furnace, and increase the flue gas temperature out of the hot blast furnace 16 by 20-50°C to ensure that the flue gas temperature out of the hot blast furnace 16 reaches 400-450°C.

[0105] (16) Online monitoring of CO concentration is installed on each flue gas pipeline entering the explosion-proof high-energy ignition combustion chamber 15.1 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.

[0106] 3. System airflow and enthalpy balance adjustment measures

[0107] 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:

[0108] (1) Excessive flue gas volume and flue gas enthalpy

[0109] ①Increase the output of micro powder, increase the amount of flue gas and heat consumption;

[0110] 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 and reduce the amount of recycled flue gas entering the metallurgical slag fine powder system;

[0111] 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;

[0112] 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.

[0113] (2) The flue gas volume of the micro powder grinding is insufficient and the flue gas enthalpy is excessive

[0114] 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;

[0115] 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;

[0116] ③ When the circulating flue gas volume increases to the balance point of the 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.

[0117] (3) Excessive flue gas volume from micro powder grinding and insufficient flue gas enthalpy

[0118] 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;

[0119] (4) Insufficient flue gas volume and flue gas enthalpy from micro powder grinding

[0120] ① Adjust the opening of the hot air regulating valve 2.13 entering 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;

[0121] 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;

[0122] 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;

[0123] 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 full-process heating process for hot blast furnace ironmaking, comprising a blast furnace, a hot blast furnace (16), a blast furnace coal pulverizing system, a coal pulverizing system and a metallurgical slag micro-powder system; during the combustion period of the hot blast furnace (16), the air and coal gas after heat exchange and temperature increase are mixed and burned in the hot combustion chamber (16.1) to generate high-temperature flue gas, which is then heat exchanged in the heat storage chamber (16.2) to form the post-furnace flue gas, which is then led out through the air-to-gas switching chamber (16.3) into the hot blast furnace flue gas duct (17); during the air supply period of the hot blast furnace (16), the hot air formed by the gas blown in by the blast furnace blower (1) after heat exchange and temperature increase in the heat storage chamber (16.2) enters the blast furnace hot blast pipe (14), characterized in that: The flue gas from the hot blast furnace flue gas duct (17) is divided into four parts: the first part of the flue gas is introduced into the metallurgical slag micro-powder system to dry and assist in grinding the metallurgical slag; the second part of the flue gas is introduced into the blast furnace coal pulverizing system to dry and assist in grinding the injected coal; the third part of the flue gas enters the air heat exchanger (3.1) to preheat the air sent to the hot blast furnace (16); the fourth part of the flue gas enters the coal gas heat exchanger (3.2) to preheat the coal gas entering the hot blast furnace (16); The flue gas entering the blast furnace coal pulverizing system passes through the coal mill flue gas furnace (10) and enters the coal mill (5.2). 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) so as to meet the heat requirement for coal powder drying. 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 fan (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 blended combustion flue gas fan (8.2); the third part is the return flue gas, which is introduced into the micro-powder mill flue gas furnace (15) of the metallurgical slag micro-powder system for high-temperature incineration to consume the trace pulverized coal and VOC in the flue gas, and then enters the micro-powder mill (5.1) to dry and assist in grinding the metallurgical slag.

2. A blast furnace hot blast stove ironmaking full-process heating process according to claim 1, characterized in that: The third part of the flue gas and the fourth part of the flue gas exiting the air heat exchanger (3.1) and the gas heat exchanger (3.2) are mixed and then divided into three streams: the first stream is used as the flue gas before the micro-powder mill, introduced into the metallurgical slag micro-powder system, and sent to the micro-powder mill (5.1) through the flue gas mixing chamber (4) to dry and assist in grinding the metallurgical slag; the second stream is used as the flue gas before the coal mill, introduced into the blast furnace coal pulverizing system, and sent to the coal mill (5.2) through the coal mill flue gas mixing chamber (10.2) to dry and assist in grinding the blast furnace coal injection; the third stream is used as the mixed combustion cold flue gas, and sent to the blast furnace (11) through the blast furnace hot air pipe (14) to reduce the theoretical combustion temperature in the blast furnace tuyere area.

3. The whole-process heating process for hot blast stove ironmaking in a blast furnace according to claim 1, characterized in that: The hot air drawn out from the blast furnace hot air pipe (14) is blown into the blast furnace (11) to provide heat enthalpy for the blast furnace (11) and is mixed with the pulverized coal from the pulverized coal injection system for combustion. In addition, according to the heat balance requirements of the metallurgical slag micropowder system, part of the hot air can also be drawn into the metallurgical slag micropowder system to provide heat enthalpy for the metallurgical slag micropowder system to dry the metallurgical slag and assist in grinding the metallurgical slag.

4. A blast furnace hot blast stove ironmaking full-process heating process according to claim 1, characterized in that: The third part of the recycled 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 with air or hot air from the blast furnace hot air pipe (14) for combustion. The high-temperature flue gas generated then enters the micro powder mill (5.1) through the micro powder mill flue gas mixing chamber (4).

5. The whole-process heating process for hot blast stove ironmaking in a blast furnace according to claim 1, characterized in that: When the flue gas volume entering the metallurgical slag micro-powder system is insufficient to meet the flue gas volume requirement of the micro-powder mill (5.1), a portion of the exhaust flue gas 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.

6. A blast furnace hot blast stove ironmaking full-process heating process as claimed in claim 2, 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 part of the 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 part of the flue gas after the furnace entering the blast furnace coal pulverizing system meet the stable production requirements of the coal mill.

7. A blast furnace hot blast stove ironmaking full-process heating process according to claim 5, characterized in that: A coal mill exhaust gas regulating valve (2.7) and a coal mill exhaust gas fan (7.2) are provided on the flue gas outlet duct of the pulverized coal bag filter (6.2) as emergency regulating valves and emergency fans to balance the stability of airflow retention fluctuations in the blast furnace, hot blast furnace, blast furnace coal pulverizing system, pulverized coal injection system, and metallurgical slag micro-powder system, as well as the heat enthalpy requirements within each system.

8. The whole-process heating process for hot blast stove ironmaking in a blast furnace according to claim 1, characterized in that: The blast furnace coal pulverizing system includes a coal mill flue gas furnace (10), a coal mill (5.2) and a coal powder bag dust collector (6.2); the metallurgical slag micro-powder system includes 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); the flue gas-slag / steel slag micro-powder mixture exiting the micro-powder mill (5.1) enters the micro-powder bag dust collector (6.1), the separated slag / steel slag micro-powder enters the micro-powder bin, and the purified flue gas is discharged.

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