An energy-saving and efficient blast furnace pulverized coal injection system and control method

Abstract

This invention provides an energy-efficient pulverized coal injection system and control method for blast furnaces. The system includes an auxiliary tank and multiple injection tanks. The auxiliary tank includes a pressure recovery tank and multiple injection pressure stabilizing tanks corresponding to the injection tanks. The pressure recovery tank is connected to each injection tank via a main valve and is used to recover nitrogen from the injection tanks or supply nitrogen to the injection tanks. The pressure recovery tank is also connected to each injection pressure stabilizing tank via a connecting valve and is used to supply nitrogen to the injection pressure stabilizing tanks. Each injection pressure stabilizing tank is connected to its corresponding injection tank via a secondary valve. A piston and a driving device are installed inside each injection pressure stabilizing tank. The driving device pushes the piston, causing the injection pressure stabilizing tank to draw nitrogen from the pressure recovery tank or inject nitrogen into its corresponding injection tank. By using auxiliary tanks, this invention can recover and reuse most of the nitrogen in the injection tanks, reducing nitrogen consumption per ton of coal and improving the pressure stability of the injection tanks.

Description

Technical Field

[0001] This invention relates to the field of blast furnace metallurgical technology, specifically to an energy-saving and efficient blast furnace pulverized coal injection system and control method. Background Technology

[0002] With the increasing steel production capacity and the continuous advancement and improvement of key technologies for pulverized coal injection in blast furnaces, especially with the growing scarcity of high-quality coking coal resources, the role of pulverized coal injection in the steelmaking process is becoming increasingly important. Replacing some coke with pulverized coal injection can, on the one hand, save on coking investment, reduce the number of coke ovens needed, and decrease air pollution caused by coking, thus significantly alleviating the tight supply and demand situation for coking coal. On the other hand, pulverized coal injection is an effective means of adjusting the furnace thermal regime, improving the working condition of the blast furnace hearth, ensuring stable and smooth operation, creating conditions for high blast temperature and oxygen-enriched blast. Pulverized coal gasification releases more hydrogen than coke, improving the reducing power and penetration diffusion capacity of the furnace gas, which is beneficial for ore reduction and improving blast furnace operating parameters.

[0003] With the optimization of blast furnace parameters and the continuous increase in pulverized coal injection rate, the ability to uniformly, stably, and accurately adjust the pulverized coal injection rate is crucial for maintaining stable blast furnace temperature, ensuring smooth furnace operation, and achieving optimal smelting conditions. During high-pressure, high-volume pulverized coal injection, the increased injection rate leads to a continuously rising solid-to-gas ratio in pneumatic conveying, which can easily cause instability in pulverized coal conveying and frequent fluctuations in the injection rate, affecting the stability of the blast furnace. Therefore, improving the stability of dense-phase pulverized coal conveying is particularly important.

[0004] Currently, blast furnace pulverized coal injection systems can be classified into parallel-tank and series-tank injection systems based on the arrangement of the injection tanks. Uninterrupted pulverized coal injection is ensured by sequentially or cross-switching the tanks. For ease of handling injection accidents, a parallel-tank system is typically best with three tanks. Cross-switching improves injection stability. Parallel-tank injection systems require a larger footprint, but injection weighing is simpler, and the investment is lower than that of series-tank systems. Series-tank injection systems consist of two overlapping main tanks. The lower tank, also called the injection tank, is always under high pressure, injecting pulverized coal into the blast furnace. The upper tank, also called the charging tank, is only under high pressure when charging the lower tank; it is under normal pressure during pulverized coal weighing. The switching operation for loading and unloading pulverized coal is achieved through a pressure equalization device connecting the upper and lower tanks. Depending on actual needs, series-tank systems can be single-series or multi-series to meet the requirements of multi-tuyere pulverized coal injection in large blast furnaces. Series-type pulverized coal injection systems have a small footprint, short injection distance, and good injection stability, but their weighing process is complex and the investment is larger than that of parallel-type systems. In China's steel enterprises, blast furnace pulverized coal injection systems mainly control the pulverized coal injection rate by adjusting the opening of the coal flow valve and the gas supply valve, as well as the pressure of the injection tanks. Parallel-type injection systems are more commonly used.

[0005] Currently, blast furnace pulverized coal injection systems in steel enterprises generally use a configuration of 2-3 injection tanks arranged in parallel, such as... Figure 4 As shown, to recover nitrogen and prevent pulverized coal leakage, many injection tanks have pressure relief valves connected to the pulverized coal silo, and small pressure relief pipes are added to stabilize the injection tank pressure. The pressure relief from the injection tank is then transferred to the pulverized coal silo, essentially introducing nitrogen into the silo to reduce its oxygen content and achieve nitrogen reuse. This method has the following problems: when the pressure relief valve opens instantaneously, the blower on the silo's top filter bag cannot adjust in time, resulting in a large positive pressure in the pulverized coal silo for a short period. This impacts the silo's explosion-proof diaphragm, and if the equipment connected to the silo is not properly sealed, it can cause serious pulverized coal leakage. To reduce the formation of positive pressure in the pulverized coal silo, a multi-stage pressure relief method can be used, i.e., setting up two or more stages of pressure relief valves. When the tank pressure is high, only the small-diameter pressure relief valve is allowed to operate; only when the tank pressure drops to a certain value is the large-diameter pressure relief valve allowed to open. However, this greatly prolongs the depressurization time of the injection tank. With the increasing size of blast furnaces, the volume of the injection tank has also increased from the previous 10m³. 3 Evolved into the current 60m 3 And above. With large-capacity pulverized coal injection tanks employing multi-stage pressure relief, the pressure relief time often takes 15 minutes or longer. Furthermore, the multi-stage pressure relief results in low flow velocity in the pressure relief pipes, frequently leading to blockages. Insufficient pressure relief can cause the pulverized coal injection system to stop. During pulverization system operation, because the negative pressure of the main exhaust fan is much greater than the negative pressure of the filter bags on the silo top, air can be drawn into the pulverized coal silo from the outlet of the filter bags, increasing the oxygen content and posing a safety hazard. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an energy-efficient pulverized coal injection system and control method for blast furnaces. By setting up an auxiliary tank, most of the nitrogen in the injection tank can be recovered and reused, reducing the nitrogen consumption per ton of coal and improving the stability of the injection tank pressure.

[0007] To address the aforementioned technical problems, in a first aspect, the present invention provides an energy-efficient blast furnace pulverized coal injection system, comprising an auxiliary tank and multiple injection tanks. The auxiliary tank includes a residual pressure recovery tank and multiple injection pressure stabilizing tanks corresponding one-to-one with the multiple injection tanks. The residual pressure recovery tank is connected to the multiple injection tanks via main valves and is used to recover nitrogen from the injection tanks or supply nitrogen to the injection tanks. The residual pressure recovery tank is connected to the multiple injection pressure stabilizing tanks via connecting valves and is used to supply nitrogen to the injection pressure stabilizing tanks. The multiple injection pressure stabilizing tanks are connected to their corresponding injection tanks via secondary valves. A piston and a driving device are installed inside each injection pressure stabilizing tank. The driving device is used to push the piston, causing the injection pressure stabilizing tank to draw nitrogen from the residual pressure recovery tank or to inject nitrogen into the corresponding injection tank.

[0008] Furthermore, it includes a pulverized coal bin for supplying pulverized coal to the injection tank, and the residual pressure recovery tank is connected to the pulverized coal bin via a pressure relief pipe.

[0009] Furthermore, the injection tank injects pulverized coal into the blast furnace through the injection valve, the residual pressure recovery tank is connected to the pulverized coal silo through a bell valve, and the residual pressure recovery tank is connected to the injection valve through an emergency pipeline, so that the residual pressure recovery tank can be used as a temporary injection tank.

[0010] Furthermore, it includes a pressurized mixer, a distributor, and a spray gun connected in sequence, the spray gun being used to inject pulverized coal into the blast furnace, and the injection tank being connected to the pressurized mixer via a injection valve.

[0011] Furthermore, a cyclone dust collector is installed on the pipeline connecting the residual pressure recovery tank and the injection tank. The cyclone dust collector is used to prevent coal dust in the injection tank from entering the residual pressure recovery tank.

[0012] Furthermore, the residual pressure recovery tank is arranged vertically to the ground, and the tops of the residual pressure recovery tank and the injection pressure stabilizing tank are set in a hemispherical shape.

[0013] Furthermore, the volume of the residual pressure recovery tank is more than twice the volume of the injection tank.

[0014] Furthermore, the system includes a coal mill, a baghouse, a flue gas furnace, and a coal feeder. The coal mill, baghouse, and pulverized coal silo are connected in sequence. The coal feeder and the flue gas furnace are respectively connected to the coal mill. The flue gas furnace is connected to a gas pipeline and a hot air pipeline. The gas pipeline is used to transport blast furnace gas to the flue gas furnace, and the hot air pipeline is used to transport hot air generated by blast furnace waste heat recovery to the flue gas furnace.

[0015] Secondly, the present invention provides a control method for an energy-efficient and high-performance pulverized coal injection system for blast furnaces, comprising:

[0016] A blowdown blast furnace typically includes at least a first blowdown blast furnace and a second blowdown blast furnace; generally, one blast furnace corresponds to two to three blowdown blast furnaces.

[0017] After the first injection tank completes its injection, the second injection tank begins its injection. Part of the nitrogen in the first injection tank is recovered using an auxiliary tank, and the first injection tank is depressurized. The bell valve is opened, and coal is loaded into the first injection tank, with the coal loading amount ≤ 80% of the tank's volume (ideally to meet the blast furnace's injection volume of approximately 35t per hour). The bell valve is then closed, and the nitrogen recovered from the auxiliary tank is forced into the first injection tank. New nitrogen is then introduced into the first injection tank using a nitrogen charging device until the nitrogen in the first injection tank reaches the working pressure. After the remaining injection tanks have completed their injection, the first injection tank resumes its pulverized coal injection, thus achieving uninterrupted operation.

[0018] Furthermore, the injection pressure stabilizing tank corresponding to the first injection can is the first injection pressure stabilizing tank;

[0019] Methods for recovering a portion of the nitrogen from the first injection tank using an auxiliary tank include:

[0020] Open the main valve connecting the residual pressure recovery tank and the first injection tank, so that some of the nitrogen in the first injection tank is recovered into the residual pressure recovery tank until the pressure in the first injection tank no longer drops, then close the main valve connecting the residual pressure recovery tank and the first injection tank.

[0021] Open the secondary valve connecting the first injection pressure stabilizing tank and the first injection tank, so that some of the nitrogen in the first injection tank is recovered into the first injection pressure stabilizing tank until the pressure in the first injection tank no longer drops, then close the secondary valve connecting the first injection pressure stabilizing tank and the first injection tank.

[0022] The remaining nitrogen in the first injection tank is released into the pulverized coal silo through the pressure relief pipe.

[0023] Furthermore, the method for pressurizing the nitrogen recovered from the auxiliary tank into the first injection tank includes:

[0024] Open the main valve connecting the residual pressure recovery tank and the first injection tank, so that the nitrogen recovered by the residual pressure recovery tank is filled into the first injection tank until the pressure of the first injection tank no longer rises, and then close the main valve connecting the residual pressure recovery tank and the first injection tank.

[0025] Open the secondary valve connecting the first injection pressure stabilizing tank and the first injection tank, start the drive device to control the piston to move, push all the nitrogen in the first injection pressure stabilizing tank into the first injection tank, and close the secondary valve connecting the first injection pressure stabilizing tank and the first injection tank.

[0026] Open the connecting valve between the residual pressure recovery tank and the first injection pressure stabilizing tank, start the drive device to control the piston to move, and draw the nitrogen in the residual pressure recovery tank into the first injection pressure stabilizing tank. Close the connecting valve between the residual pressure recovery tank and the first injection pressure stabilizing tank, open the secondary valve between the first injection pressure stabilizing tank and the first injection tank, start the drive device to control the piston to move, and push all the nitrogen in the first injection pressure stabilizing tank into the first injection tank.

[0027] The nitrogen in the residual pressure recovery tank is repeatedly pumped into the first injection pressure stabilizing tank, and the nitrogen in the first injection pressure stabilizing tank is pushed into the first injection tank until the pressure in the first injection tank meets the requirements and the nitrogen recovery rate meets the requirements.

[0028] Furthermore, after the first injection tank starts injecting coal, whenever the pressure in the first injection tank drops by 'a', the nitrogen in the residual pressure recovery tank is drawn into the first injection pressure stabilizing tank, and the nitrogen in the first injection pressure stabilizing tank is pushed into the first injection tank, so that the pressure in the first injection tank returns to the working pressure.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. By setting up an auxiliary tank, this invention can recover and reuse most of the nitrogen in the injection tank, thereby reducing the nitrogen consumption per ton of coal and lowering the cost of nitrogen.

[0031] 2. This invention utilizes an auxiliary tank to repeatedly replenish the air pressure of the injection tank during the injection process, resulting in smaller pressure fluctuations in the injection tank and improved pressure stability. This, in turn, improves the accuracy of the injection volume and ensures uniform heat distribution in the furnace hearth.

[0032] 3. By setting up a pressure booster mixer, the present invention increases the pressure of the pulverized coal entering the distributor, thereby reducing the pressure requirement of the injection tank, which can reduce the amount of nitrogen in the injection tank and the depressurization time of the injection tank. In addition, it can also improve the service life of the valves and fluidizing plates of the injection tank.

[0033] 4. This invention prevents coal dust from entering the auxiliary tank by setting up a cyclone dust collector, and also facilitates coal dust recovery.

[0034] 5. The residual pressure recovery tank and the pulverized coal silo of the present invention are connected by a pressure relief pipe, so that when the auxiliary tank fails, the nitrogen in the auxiliary tank can be released into the pulverized coal silo.

[0035] 6. The residual pressure recovery tank of the present invention is connected to the pulverized coal silo via a bell valve, and the residual pressure recovery tank is connected to the injection valve via an emergency pipeline, so that when all injection tanks fail, the residual pressure recovery tank can be used as a temporary injection tank. Attached Figure Description

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

[0037] Figure 2 This is a schematic diagram of the auxiliary tank of the present invention;

[0038] Figure 3 This is a block diagram of the coal powder preparation system of the present invention;

[0039] Figure 4 This is a schematic diagram of a blast furnace pulverized coal injection system in the prior art.

[0040] Reference numerals: 1. Residual pressure recovery tank; 2. First jet pressure stabilizing tank; 3. Second jet pressure stabilizing tank; 4. First jet tank; 5. Second jet tank; 6. First main valve; 7. Second main valve; 8. First valve; 9. Second valve; 10. First connecting valve; 11. Second connecting valve; 12. Piston; 13. Drive device; 14. Sealing gasket. Detailed Implementation

[0041] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0042] like Figure 1 As shown, this embodiment provides an energy-saving and efficient blast furnace pulverized coal injection system, including a coal feeder, flue gas furnace, coal mill, bag filter box, pulverized coal silo, injection tank, injection valve, auxiliary tank, booster mixer, distributor, and injection gun.

[0043] The coal feeder and flue gas furnace are respectively connected to the coal mill. The coal feeder is used to transport raw coal to the coal mill, and the flue gas furnace is used to provide high-temperature gas to the coal mill to dry the pulverized coal. The flue gas furnace is connected to a gas pipeline and a hot air pipeline. The gas pipeline is used to supply the flue gas furnace with blast furnace hot blast stove exhaust gas (i.e., blast furnace gas), and the hot air pipeline is used to supply the flue gas furnace with hot air generated from blast furnace waste heat recovery (the specific source of the hot air is detailed in Chinese invention patent with authorization announcement number CN114774603B). Figure 4 As shown, compared to the existing technology that utilizes blast furnace gas and coke oven gas, this embodiment utilizes hot air above 200°C generated by the waste heat recovery of the blast furnace system to reduce the blast furnace gas consumption of the flue gas furnace and eliminate coke oven gas, thereby reducing the gas consumption for drying pulverized coal.

[0044] In this embodiment, the coal mill is a medium-speed coal mill (i.e., Figure 1 (medium-speed mill).

[0045] In this embodiment, two injection cans are provided (i.e., Figure 1 The injection tanks (1 / 2) include a first injection tank 4 and a second injection tank 5. The coal inlets of the two injection tanks are connected to the pulverized coal silo via two bell valves, and the coal outlets of the two injection tanks are connected to injection valves. The pressure relief ports of the two injection tanks are connected to the pulverized coal silo via two pressure relief pipes, and the two injection tanks are also connected to nitrogen delivery pipes. Figure 1 Not illustrated in the diagram; the jet valve is equipped with a return powder port and a supply powder port. The return powder port of the jet valve is connected to the coal powder silo through a return powder pipe, and the supply powder port of the jet valve is connected to the booster mixer. The booster mixer is connected to the distributor and the spray gun in sequence.

[0046] Understandably, pulverized coal can be fed into the injection tank by opening the bell valve. The pressure in the injection tank is increased to the working pressure through the nitrogen delivery pipeline. Then, the pulverized coal is delivered to the blast furnace through the injection valve, pressurizing mixer, distributor, and injection gun. Because the pressurizing mixer increases the pressure of the pulverized coal entering the distributor, the pressure requirement of the injection tank is reduced, thereby reducing the amount of nitrogen in the injection tank and the depressurization time. In addition, it can also improve the service life of the valves and fluidizing plates in the injection tank. After the pulverized coal in the injection tank is exhausted, the nitrogen in the injection tank can be released to the pulverized coal silo through the depressurization pipeline. However, this would result in nitrogen waste. In this embodiment, by setting up an auxiliary tank, the nitrogen can be recovered and reused.

[0047] like Figure 2 As shown, the auxiliary tank includes a residual pressure recovery tank 1 and two injection pressure stabilizing tanks (i.e., the first injection pressure stabilizing tank 2 and the second injection pressure stabilizing tank 3) corresponding to the two injection tanks. The residual pressure recovery tank 1 is connected to the two injection tanks through the first main valve 6 and the second main valve 7, respectively, and is used to recover nitrogen in the injection tanks or to supply nitrogen to the injection tanks. The residual pressure recovery tank 1 is connected to the two injection pressure stabilizing tanks through the first connecting valve 10 and the second connecting valve 11, respectively, and is used to supply nitrogen to the injection pressure stabilizing tanks. The two injection pressure stabilizing tanks are connected to the two injection tanks through the first valve 8 and the second valve 9, respectively.

[0048] In this embodiment, the volume of the residual pressure recovery tank 1 is twice that of the injection tank. The maximum air pressure of the residual pressure recovery tank 1, which is less than 15m in height, is below 600kPa. The design air pressure of the injection pressure stabilizing tank is 800kPa. The residual pressure recovery tank 1 is arranged vertically to the ground, and its top is hemispherical. The volume of the injection pressure stabilizing tank is half that of the injection tank. The injection pressure stabilizing tank is designed with an air pressure of 800kPa. The injection pressure stabilizing tanks are stacked on a foundation, with four support pillars in the circumferential direction. Each support pillar is secured by eight φ50mm bolts. The top of the injection pressure stabilizing tank is hemispherical.

[0049] A piston 12 and a drive device 13 are installed inside the injection pressure stabilizing tank. The drive device 13 is used to push the piston 12, so that the injection pressure stabilizing tank can extract nitrogen from the residual pressure recovery tank 1 or pressurize nitrogen into the corresponding injection tank. In this embodiment, the drive device 13 includes a motor and five hydraulic push rods. The five hydraulic push rods are arranged according to the four points of a "well" shape and the center point as the five hydraulic push rod action points. The diameter of the hydraulic push rods is ≤10m and the stroke is ≤2m. It is recommended to arrange them on a foundation with a load of 1000kPa. A sealing gasket 14 is installed between the piston 12 and the inner wall of the injection pressure stabilizing tank. The piston 12 is 100mm thick and the sealing gasket 14 is 50mm×50mm (thickness×width). Vaseline or grease is applied to the sealing gasket 14 to help seal it. During the monthly maintenance of blast furnace production, the sealing performance of the sealing gasket 14 needs to be checked and replaced or lubricated with grease.

[0050] like Figure 1 As shown, the residual pressure recovery tank 1 is connected to the pulverized coal silo via a pressure relief pipe. When the residual pressure recovery tank 1 malfunctions, the nitrogen in the residual pressure recovery tank 1 can be released into the pulverized coal silo by opening the pressure relief pipe. In addition, the residual pressure recovery tank 1 is connected to the pulverized coal silo via a bell valve, and the residual pressure recovery tank 1 is connected to the injection valve via an emergency pipeline, so that the residual pressure recovery tank 1 can be used as a temporary injection tank.

[0051] like Figure 1 As shown, a cyclone dust collector is also installed on the pipeline connecting the residual pressure recovery tank 1 and the injection tank. The cyclone dust collector is used to prevent coal dust in the injection tank from entering the residual pressure recovery tank 1.

[0052] The control methods for the aforementioned energy-efficient pulverized coal injection system for blast furnaces include:

[0053] S1. After the pulverized coal in the first injection tank 4 is pulverized, the second injection tank 5 starts to inject, and the nitrogen in the first injection tank 4 is recovered by the auxiliary tank: the first main valve 6 connecting the residual pressure recovery tank 1 and the first injection tank 4 is opened, so that two-thirds of the nitrogen in the first injection tank 4 is recovered to the residual pressure recovery tank 1 (the volume of the residual pressure recovery tank 1 is twice that of the injection tank), until the pressure of the first injection tank 4 no longer drops, and the first main valve 6 is closed;

[0054] Open the first valve 8 connecting the first injection pressure stabilizing tank 2 and the first injection tank 4, so that one-third of the remaining nitrogen in the first injection tank 4 is recovered to the first injection pressure stabilizing tank 2, until the pressure of the first injection tank 4 no longer drops, and then close the first valve 8;

[0055] Considering electricity and recycling efficiency, recycling only needs to be done once. Theoretically, the nitrogen recovered in the first spray tank 4 accounts for about 77% of the original nitrogen.

[0056] The remaining nitrogen in the first injection tank 4 is released into the pulverized coal silo through the pressure relief pipe. At this point, the recovery of nitrogen in the first injection tank 4 and the pressure relief of the first injection tank 4 are completed.

[0057] S2. Load coal into the first injection tank 4 and pressurize the nitrogen recovered from the auxiliary tank into the first injection tank 4: Open the first main valve 6 connecting the residual pressure recovery tank 1 and the first injection tank 4, so that the nitrogen recovered from the residual pressure recovery tank 1 is filled into the first injection tank 4 until the pressure of the first injection tank 4 no longer rises, and then close the first main valve 6.

[0058] Open the first valve 8 connecting the first injection pressure stabilizing tank 2 and the first injection tank 4, start the drive device 13 to control the piston 12 to move, push all the nitrogen in the first injection pressure stabilizing tank 2 into the first injection tank 4, and close the first valve 8.

[0059] Open the first connecting valve 10 connecting the residual pressure recovery tank 1 and the first injection pressure stabilizing tank 2, start the drive device 13 to control the piston 12 to move, draw the nitrogen in the residual pressure recovery tank 1 into the first injection pressure stabilizing tank 2, close the second connecting valve 11, open the first valve 8, start the drive device 13 to control the piston 12 to move, push all the nitrogen in the first injection pressure stabilizing tank 2 into the first injection tank 4;

[0060] The nitrogen in the residual pressure recovery tank 1 is repeatedly pumped into the first injection pressure stabilizing tank 2, and the nitrogen in the first injection pressure stabilizing tank 2 is pushed into the first injection tank 4 until the pressure in the first injection tank 4 meets the requirements and the nitrogen recovery rate meets the requirements. In this embodiment, the process is repeated more than 6 times, so that the gas pressure in the first injection tank 4 reaches about 650 kPa, the nitrogen utilization rate in the residual pressure recovery tank 1 is more than 80%, and the nitrogen recovery and reuse rate in the first injection tank 4 reaches more than 55%.

[0061] Use a nitrogen filling device to fill the first injection tank 4 with new nitrogen until the nitrogen in the first injection tank 4 reaches the working pressure (750 kPa);

[0062] The first injection tank 4 starts injecting pulverized coal, which is expected to take 50 minutes. At this time, the second injection tank 5 is in the injection preparation stage: the residual pressure recovery of the injection tank takes 3 minutes, the pressure relief takes about 1 minute, the coal loading takes about 25 minutes, and the nitrogen recovery and utilization and pressurization stage of the residual pressure recovery tank 1 takes 15 minutes.

[0063] After the first injection tank 4 starts injecting coal, whenever the pressure in the first injection tank 4 drops by 10 kPa, the first connecting valve 10 is opened to draw nitrogen from the residual pressure recovery tank 1 into the first injection pressure stabilizing tank 2. The first connecting valve 10 is then closed, and the first gate valve is opened to push nitrogen from the first injection pressure stabilizing tank 2 into the first injection tank 4, so that the pressure in the first injection tank 4 returns to the working pressure (750 kPa). This continues until the weight change of the first injection tank 4 is minimal, and the injection of the first injection tank 4 ends. At this time, the second injection tank 5 has completed the preparation work for injection and begins to inject. The first injection tank 4 then begins to recover nitrogen, thus achieving uninterrupted operation.

[0064] like Figure 3 As shown, in this embodiment, the target is that the moisture content of the coal powder in the coal powder silo is ≤1.5%, the coal powder is ≤0.075mm, and the particle size is >70%. Combined with the goal of reducing the cost of mixed coal, the feeder speed, medium speed mill speed, and flue gas furnace temperature of the bituminous coal and anthracite silos in the coal powder are adjusted. In the end, the production of coal powder with high fluidity and good injection performance is achieved, which provides a foundation for providing high-quality coal powder for energy-saving and efficient coal powder injection.

[0065] The following description uses two blast furnace pulverized coal injection systems modified according to the present invention as an example:

[0066] 1. 2500m 3 The blast furnace injection system injects 1050 tons of pulverized coal daily at a coal-to-gas ratio of 150 kg / t, with an annual output of 2.2 million tons. Table 1 shows the gas consumption of the injection system. Table 2 shows the cost calculated under standard conditions (25℃, 1 atmosphere) and electricity consumption, based on gas pressure and temperature. Tables 1 and 2 show that the cost of drying, grinding, and injecting pulverized coal, including electricity consumption, is 54.79 yuan / ton. After adopting this invention, the cost of drying, grinding, and injecting pulverized coal, including electricity consumption, is 28.95 yuan / ton, a reduction of 25.86 yuan / ton, resulting in annual cost savings of 8.5272 million yuan. The injection tank volume is 83 m³. 3 A building with a volume of 200m³ was built. 3 One residual pressure recovery tank (Φ8×7.1m) and two tanks with a volume of 50m³ 3 A jet-pressurized pressure tank (Φ5×2.6m) and one booster mixer (utilizing an 83m³) 3 The injection tank was modified, with an investment of 2 million yuan. The nitrogen recovery rate was 59%, and the investment cost was recovered in 90 days. The coal injection difference of each injection gun was reduced from 3.5 kg / min to 0.8 kg / min, and the heat distribution of the furnace hearth was more uniform. The pressure relief pipeline DN300 between the injection tank and the residual pressure recovery tank 1 had a pressure relief time of 2.8 min.

[0067] Table 12500m 3 Blast furnace pulverized coal injection system consumption before and after system use in 2023

[0068]

[0069] Table 22500m 3 Consumption and cost of pulverized coal injection system under standard conditions

[0070]

[0071] Note: The calculation is based on the air injected into the pressurized mixer to supply nitrogen.

[0072] II. 3200m 3 The blast furnace injection system injects 1265 tons of pulverized coal daily at a coal-to-water ratio of 155 kg / t, with an annual output of 2.75 million tons. Table 3 shows the gas consumption of the injection system. Table 4 shows the cost calculated under standard conditions (25℃, 1 atmosphere) and electricity consumption, based on gas pressure and temperature. Tables 3 and 4 show that the cost of pulverized coal drying, grinding, and injection, including electricity consumption, is 51.68 yuan / ton. After adopting the system, the cost of pulverized coal drying, grinding, and injection, including electricity consumption, is 24.81 yuan / ton, a reduction of 26.87 yuan / ton, resulting in annual cost savings of 11.4533 million yuan. The injection tank volume is 83 m³. 3 1 building with a volume of 200m³ 3One residual pressure recovery tank (Φ8×7.1m), two 50m³ injection pressure stabilizing tanks (Φ5×2.6m), and one booster mixer (utilizing an 83m³ capacity). 3 The injection tank was modified with an investment of 2 million yuan. The nitrogen recovery rate was 64.6%. The investment of 2 million yuan was recovered in 50 days. The coal injection difference of each injection gun was reduced from 4.1 kg / min to 0.5 kg / min. The heat distribution of the furnace hearth was more uniform. The pressure relief time of the DN250 pressure relief pipeline between the injection tank and the residual pressure recovery tank was shortened by 3.5 minutes.

[0073] Table 33200m 3 Blast furnace pulverized coal injection system consumption before and after system use in 2023

[0074]

[0075] Table 43200m 3 Consumption and cost of pulverized coal injection system under standard conditions

[0076]

[0077] Note: The calculation is based on the air injected into the pressurized mixer to supply nitrogen.

[0078] In summary,

[0079] 1) Currently, most blast furnace injection jars have a volume of 60m³. 3 The above applies if the volume of the residual pressure recovery tank 1 is 160m³. 3 For a diameter ≥8m and a height ≤15m, the nitrogen recovery rate of the injection tank is 50-66%. The piston of the injection pressure stabilizing tank operates 15 times per hour, with each round trip lasting 1-2 minutes. The operating time is adjustable according to the tank pressure. The electricity consumption per ton of coal increases by 0.5kWh, and medium-high pressure nitrogen of 500-600kPa can be recovered. Under standard conditions, the nitrogen consumption per ton of coal is reduced by about 60%. After deducting electricity consumption, the nitrogen cost per ton of pulverized coal is reduced by more than 20 yuan.

[0080] 2) Increase the proportion of blast furnace hot blast stove exhaust gas entering the flue gas furnace for pulverized coal drying. Utilize the hot air generated by the waste heat recovery of the blast furnace system at temperatures above 200°C to reduce the amount of gas used for drying ton of coal by more than 20%.

[0081] 3) The initial investment for the residual pressure recovery tank 1 and the booster mixer and their infrastructure is 2-3 million yuan, which can be recovered in six months. It produces 150 kg / t of pulverized coal per ton of iron, and one 2500m³ unit is required. 3 The blast furnace has an annual output of 2.2 million tons and an annual pulverized coal injection capacity of 330,000 tons. The cost per ton of pulverized coal injection has been reduced from 50 yuan to 25 yuan, resulting in an annual cost reduction of 8.25 million yuan. (2500m³) 3 The above blast furnaces are even more efficient. 1000m 3 ~2500m3 The blast furnace can recover its costs within 3 months.

[0082] 4) By employing this invention, the stability rate of the injection tank pressure within ±50 kPa of the target tank pressure fluctuation during the injection process is improved from 75% to 95%, the accuracy of the pulverized coal injection rate in the main injection pipe is improved from ±800 kg / h to ±200 kg / h, the accuracy of the stable injection rate in a single branch pipe is improved from ±100 kg / h to ±60 kg / h, the pulverized coal injection range between each injection gun is reduced from 3 kg / min to 1 kg / min, and the heat distribution in the furnace hearth is more uniform.

[0083] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An energy-efficient and high-performance pulverized coal injection system for blast furnaces, characterized in that: The system includes an auxiliary tank and multiple injection tanks. The auxiliary tank includes a residual pressure recovery tank (1) and multiple injection pressure stabilizing tanks corresponding to the multiple injection tanks. The residual pressure recovery tank (1) is connected to the multiple injection tanks through a main valve and is used to recover nitrogen in the injection tanks or to supply nitrogen to the injection tanks. The residual pressure recovery tank (1) is connected to the multiple injection pressure stabilizing tanks through a connecting valve and is used to supply nitrogen to the injection pressure stabilizing tanks. The multiple injection pressure stabilizing tanks are connected to the corresponding injection tanks through a secondary valve. A piston (12) and a driving device (13) are provided inside the injection pressure stabilizing tank. The driving device (13) is used to push the piston (12) so that the injection pressure stabilizing tank draws nitrogen from the residual pressure recovery tank (1) or pressurizes nitrogen into the corresponding injection tank. The injection tank injects pulverized coal into the blast furnace through the injection valve. The residual pressure recovery tank (1) is connected to the pulverized coal silo through a bell valve. The residual pressure recovery tank (1) is connected to the injection valve through an emergency pipeline, so that the residual pressure recovery tank (1) can be used as a temporary injection tank. It also includes a pressurized mixer, a distributor, and a spray gun connected in sequence. The spray gun is used to inject pulverized coal into the blast furnace. The injection tank is connected to the pressurized mixer through an injection valve. The pressurized mixer is used to increase the pressure of the pulverized coal entering the distributor.

2. The energy-saving and efficient pulverized coal injection system for blast furnaces according to claim 1, characterized in that: It includes a pulverized coal bin for supplying pulverized coal to the injection tank, and the residual pressure recovery tank (1) is connected to the pulverized coal bin via a pressure relief pipe.

3. The energy-saving and efficient pulverized coal injection system for blast furnaces according to claim 1, characterized in that: A cyclone dust collector is installed on the pipeline connecting the residual pressure recovery tank (1) and the injection tank. The cyclone dust collector is used to prevent coal dust in the injection tank from entering the residual pressure recovery tank (1).

4. The energy-saving and efficient pulverized coal injection system for blast furnaces according to claim 1, characterized in that: The system includes a coal mill, a baghouse, a flue gas furnace, and a coal feeder. The coal mill, baghouse, and pulverized coal silo are connected in sequence. The coal feeder and the flue gas furnace are respectively connected to the coal mill. The flue gas furnace is connected to a gas pipeline and a hot air pipeline. The gas pipeline is used to transport blast furnace gas to the flue gas furnace, and the hot air pipeline is used to transport hot air generated by blast furnace waste heat recovery to the flue gas furnace.

5. A control method for an energy-saving and efficient pulverized coal injection system for a blast furnace according to any one of claims 1 to 4, characterized in that: include: The spray tank includes at least a first spray tank (4) and a second spray tank (5); After the first injection tank (4) finishes injection, the second injection tank (5) starts injection. Part of the nitrogen in the first injection tank (4) is recovered by the auxiliary tank, and the pressure in the first injection tank (4) is released. Coal is loaded into the first injection tank (4), and the nitrogen recovered by the auxiliary tank is pressed into the first injection tank (4). New nitrogen is charged into the first injection tank (4) by the nitrogen charging device until the nitrogen in the first injection tank (4) reaches the working pressure. After the other injection tanks finish injection, the first injection tank (4) starts injection of pulverized coal again, thereby achieving uninterrupted operation. The first injection pressure stabilizing tank corresponding to the first injection pressure stabilizing tank (4) is the first injection pressure stabilizing tank (2); Methods for recovering a portion of the nitrogen in the first injection tank (4) using an auxiliary tank include: Open the main valve connecting the residual pressure recovery tank (1) and the first injection tank (4) to recover some of the nitrogen in the first injection tank (4) back to the residual pressure recovery tank (1) until the pressure of the first injection tank (4) no longer drops, and then close the main valve connecting the residual pressure recovery tank (1) and the first injection tank (4). Open the secondary valve connecting the first injection pressure stabilizing tank (2) and the first injection tank (4) to allow some of the nitrogen in the first injection tank (4) to be recovered back into the first injection pressure stabilizing tank (2) until the pressure of the first injection tank (4) no longer drops, and then close the secondary valve connecting the first injection pressure stabilizing tank (2) and the first injection tank (4). The remaining nitrogen in the first injection tank (4) is released into the pulverized coal silo through the pressure relief pipe.

6. The control method according to claim 5, characterized in that: The method of pressurizing the nitrogen recovered from the auxiliary tank into the first injection tank (4) includes: Open the main valve connecting the residual pressure recovery tank (1) and the first injection tank (4) so ​​that the nitrogen recovered by the residual pressure recovery tank (1) is filled into the first injection tank (4) until the pressure of the first injection tank (4) no longer rises, and then close the main valve connecting the residual pressure recovery tank (1) and the first injection tank (4). Open the secondary valve connecting the first injection pressure stabilizing tank (2) and the first injection tank (4), start the drive device (13) to control the piston (12) to move, push all the nitrogen in the first injection pressure stabilizing tank (2) into the first injection tank (4), and close the secondary valve connecting the first injection pressure stabilizing tank (2) and the first injection tank (4). Open the connecting valve between the residual pressure recovery tank (1) and the first injection pressure stabilizing tank (2), start the drive device (13) to control the piston (12) to move, and draw the nitrogen in the residual pressure recovery tank (1) into the first injection pressure stabilizing tank (2). Close the connecting valve between the residual pressure recovery tank (1) and the first injection pressure stabilizing tank (2), open the secondary valve between the first injection pressure stabilizing tank (2) and the first injection tank (4), start the drive device (13) to control the piston (12) to move, and push all the nitrogen in the first injection pressure stabilizing tank (2) into the first injection tank (4). Repeatedly pump nitrogen from the residual pressure recovery tank (1) into the first injection pressure stabilizing tank (2), and push nitrogen from the first injection pressure stabilizing tank (2) into the first injection tank (4) until the pressure in the first injection tank (4) meets the requirements and the nitrogen recovery rate meets the requirements.

7. The control method according to claim 6, characterized in that: After the first injection tank (4) starts injecting coal, whenever the pressure in the first injection tank (4) drops by a, the nitrogen in the residual pressure recovery tank (1) is drawn into the first injection pressure stabilizing tank (2), and the nitrogen in the first injection pressure stabilizing tank (2) is pushed into the first injection tank (4), so that the pressure in the first injection tank (4) returns to the working pressure.

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