Blast furnace pulverized coal preheating system

Abstract

The invention relates to the field of blast furnace pulverized coal preheating. A blast furnace pulverized coal preheating system comprises a coal injection workshop, a nitrogen heater, a common pulverized coal heater, a compressed nitrogen tank, a blast furnace, an oil storage tank, an expansion tank, a waste heat exchanger, a heat conduction oil pump, a PLC control system and a sound-light alarm device. Pulverized coal discharged from a coal injection workshop is heated in a common pulverized coal heater through waste heat of a blast furnace, and the heated pulverized coal enters the blast furnace to be combusted. The combustion characteristic of the preheated pulverized coal is remarkably improved, and the pulverized coal can be quickly combusted after entering a main combustion chamber of the blast furnace, so that the conventional three-section combustion process of heating, ignition and combustion is broken through.

Description

Technical Field

[0001] The invention relates to the field of blast furnace coal powder preheating. Background Art

[0002] The main process and principle of blast furnace coal powder preheating is to first feed the coal powder (which can be extended to powdered fuel) into the preheating burner, and then preheat the coal powder to above the ignition temperature through the heat release of a small part of the coal powder itself, so as to achieve coal powder modification, form a high-temperature gas-solid mixed fuel containing coal gas and highly active semi-coke, and then enter the main combustion chamber (such as the blast furnace) for combustion. The combustion characteristics of the preheated fuel are significantly improved, and the temperature is higher than the ignition point. Once it enters the main combustion chamber, it burns rapidly, thus breaking through the conventional three-stage combustion process of heating, ignition and combustion. At the same time, due to the strong reducing atmosphere in the preheating device, most of the nitrogen elements precipitated by preheating are reduced to nitrogen, thereby greatly reducing the amount of nitrogen oxides generated in the main combustion chamber.

[0003] The patent with publication number CN113786921A and titled "A blast furnace coal powder preheating system based on raw coal processing technology" uses the flue gas pipeline of the blast furnace to directly preheat the blast furnace coal powder conveying pipeline. This preheating method will cause waste heat from the blast furnace and affect the injection of blast furnace coal powder. The patent with publication number CN118391701A and titled "Coal powder preheating method and system based on oxygen-enriched flue gas from hot blast furnace" uses the flue gas generated by the hot blast furnace to preheat the coal powder in the pulverizer. The utilization rate of heat is low and there will be heat loss in the subsequent injection process.

[0004] With the popularization and development of industrial control systems, automatic control systems have been applied to various fields of industrial production, especially in the steel industry, which requires high system operation stability. It can not only reduce manual operation, but also adapt to the needs of various complex environments. Blast furnace production has high requirements for coal injection stability. How to provide an automatic control system to complete the preheating of coal powder and not affect the use of coal in the blast furnace in the event of an accident? Summary of the invention

[0005] The technical problem to be solved by the present invention is: how to provide a blast furnace coal powder preheating system.

[0006] The technical scheme adopted by the present invention is: a blast furnace coal powder preheating system, including a coal injection workshop 1, a nitrogen heater 2, a common coal powder heater 4, a compressed nitrogen tank 5, a blast furnace 6, an oil storage tank and an expansion tank 7, a waste heat exchanger 8, a thermal oil pump 9, a PLC control system, and an audible and visual alarm device. The nitrogen coming out of the compressed nitrogen tank 5 is heated by the nitrogen heater 2 and then divided into four branches. The coal powder coming out of the coal injection workshop 1 is mixed with the nitrogen coming out of the first branch of the nitrogen heater 2 and then enters the common blast furnace feed coal powder pipeline equipped with a normally open coal inlet valve 13. The common blast furnace feed coal powder pipeline is connected to the common coal powder heater 4 through a pipeline equipped with a normally open heating valve 15. The coal powder coming out of the coal outlet pipeline of the common coal powder heater 4 is connected to the common coal powder heater 4 through a pipeline equipped with a normally open coal outlet valve 16. The pipeline of the nitrogen heater 2 is connected to the coal inlet of the blast furnace 6, the second branch of the nitrogen heater 2 enters the common pulverized coal heater 4 and mixes with the pulverized coal in the common pulverized coal heater 4, the third branch of the nitrogen heater 2 is connected to the coal outlet pipeline of the common pulverized coal heater 4 to provide a boost for the pulverized coal coming out of the common pulverized coal heater 4, and the fourth branch of the nitrogen heater 2 is connected to the pipeline at the inlet end of the normally open coal outlet valve 16 to provide a pulverized coal boost for the pulverized coal in the pipeline there; the oil in the oil storage tank and the expansion tank 7 enters the waste heat exchanger 8 by its own gravity and is heated by the waste heat of the blast furnace, the heated oil in the waste heat exchanger 8 enters the common pulverized coal heater 4 through the heat transfer oil pump 9 to heat the pulverized coal therein, and the oil coming out of the common pulverized coal heater 4 circulates into the waste heat exchanger 8 to be heated again; the common A first pressure transmitter 21 is installed on the blast furnace feed pulverized coal pipeline, a first temperature sensor 22 is installed on the oil inlet pipeline of the common pulverized coal heater 4, a second temperature sensor 23 is installed on the oil outlet pipeline of the common pulverized coal heater 4, a second pressure transmitter 24 is installed on the inlet pipeline of the thermal oil pump 9, a third pressure transmitter 25 is installed on the outlet pipeline of the thermal oil pump, a gas flow meter is installed on each branch of the nitrogen heater 2, and a liquid level sensor is installed in the oil storage tank and the expansion tank 7; the pulverized coal inlet pressure in the common pulverized coal heater 4 is obtained through the first pressure transmitter 21, when the pulverized coal inlet pressure is greater than the set pulverized coal pressure, the opening of the normally open coal inlet valve 13 is reduced, and when the pulverized coal inlet pressure is less than the set pulverized coal pressure, the opening of the normally open coal inlet valve 13 is increased. When the coal powder pressure is greater than or equal to the maximum coal powder pressure or less than or equal to the minimum coal powder pressure, an alarm is triggered to remind the staff to perform maintenance; the first temperature sensor 22 measures the oil inlet temperature in the oil inlet pipeline of the commonly used coal powder heater 4. When the oil inlet temperature is less than the set oil inlet temperature, the oil pumping amount of the thermal oil pump 9 is increased; when the oil inlet temperature is greater than the set oil inlet temperature, the oil pumping amount of the thermal oil pump 9 is reduced; when the oil inlet temperature is less than the minimum oil inlet temperature or greater than the maximum oil inlet temperature, an alarm is triggered to remind the staff to perform maintenance; the liquid level sensor measures the liquid level of the oil in the oil storage tank and the expansion tank 7. When the liquid level is equal to or lower than the minimum set value, oil is added to the oil storage tank and the expansion tank 7. When the liquid level is equal to or higher than the maximum set value, the oil addition to the oil storage tank and the expansion tank 7 is stopped.

[0007] The pulverized coal coming out of the coal injection workshop 1 is mixed with the nitrogen coming out of the first branch of the nitrogen heater 2 and is divided into two coal injection branches. One coal injection branch is connected to the coal inlet of the blast furnace 6 through a spare blast furnace feed pulverized coal pipeline equipped with a normally closed coal inlet valve 11 and a normally closed coal outlet valve 12, and the other coal injection branch enters the common blast furnace feed pulverized coal pipeline equipped with a normally open coal inlet valve 13.

[0008] The blast furnace pulverized coal preheating system also includes a standby pulverized coal heater 3. The nitrogen coming out of the compressed nitrogen tank 5 is heated by the nitrogen heater 2 and then divided into five branches. The common blast furnace feed pulverized coal pipeline is connected to two heating branches. One heating branch is connected to the standby pulverized coal heater 3 through a pipeline equipped with a normally closed heating valve 14. The other heating branch is connected to the common pulverized coal heater 4 through a pipeline equipped with a normally open heating valve 15. The pulverized coal coming out of the standby pulverized coal heater 3 and the common pulverized coal heater 4 are merged through a pipeline and then connected to the coal inlet of the blast furnace 6 through a pipeline equipped with a normally open coal outlet valve 16. The nitrogen coming out of the fifth branch of the nitrogen heater 2 is boosted for the pulverized coal coming out of the standby pulverized coal heater 3 after passing through a pipeline equipped with a normally closed booster valve 17.

[0009] Coal powder boosting uses the Venturi acceleration principle for boosting.

[0010] All valves, sensors, heat transfer oil pumps, sound and light alarm devices and other devices in the present invention are connected to the PLC control system through electrical signals, and the blast furnace pulverized coal preheating system is automatically controlled by drawing the PLC control system.

[0011] The waste heat exchanger 8 is a gas-liquid heat exchanger (a gas-liquid heat exchanger in the prior art). The blast furnace tail gas enters the gas channel to heat the oil in the liquid channel. The oil storage tank and the expansion tank 7 are connected to the liquid channel of the waste heat exchanger 8. The liquid level of the oil in the oil storage tank and the expansion tank 7 is higher than the highest liquid level of the oil in the liquid channel of the waste heat exchanger 8, ensuring that the liquid channel of the waste heat exchanger 8 is always full of oil. The oil in the liquid channel of the waste heat exchanger 8 exchanges heat with the blast furnace tail gas in the gas channel to increase the temperature of the oil. The heated oil is pumped into the common pulverized coal heater 4 by the heat transfer oil pump 9 (the common pulverized coal heater 4 is also a gas-liquid heater. The biggest difference from the waste heat exchanger 8 is that the common pulverized coal heater 4 uses liquid to heat gas, while the waste heat exchanger 8 uses gas to heat liquid), and the pulverized coal in the pulverized coal heater 4 is heated. The oil coming out of the pulverized coal heater 4 circulates into the waste heat exchanger 8 for repeated heating and utilization, thereby realizing the heating of pulverized coal by the waste heat of the blast furnace. During the oil circulation process, attention should be paid to the control of the oil inlet temperature of the waste heat exchanger 8. When the oil inlet temperature is lower than the set oil inlet temperature, the oil pumping amount of the thermal oil pump 9 is increased. When the oil inlet temperature is higher than the set oil inlet temperature, the oil pumping amount of the thermal oil pump 9 is reduced. When the oil inlet temperature is lower than the minimum oil inlet temperature or higher than the maximum oil inlet temperature, an alarm is sounded to remind the staff to perform maintenance. The entire control is realized through a PLC control system. The present invention interlocks the oil inlet temperature in the oil inlet pipeline of the common pulverized coal heater 4 measured by the first temperature sensor 22 with the thermal oil pump (frequency conversion), and stably provides heat energy to the pulverized coal in the pulverized coal heater 4.

[0012] The commonly used pulverized coal heater 4 includes a pulverized coal heat exchange chamber 41 and an oil heat exchange chamber 42 for performing heat exchange with the wall of the pulverized coal heat exchange chamber 41. When the pulverized coal enters the commonly used pulverized coal heater 4, as the cross section increases, the pressure decreases. The pulverized coal may gather on the wall of the pulverized coal heat exchange chamber 41, affecting the heat exchange. However, in order to increase the heat exchange area, the cross section of the pulverized coal heat exchange chamber 41 must be increased to better complete the heat exchange. In order to avoid affecting the heat exchange, the nitrogen coming out of a branch of the nitrogen heater 2 is introduced into the pulverized coal heat exchange chamber 41, and the Venturi principle is used to boost the pulverized coal, thereby increasing the pulverized coal outlet speed to avoid blocking the outlet of the pulverized coal heat exchange chamber 41 and affecting the heat exchange.

[0013] The invention adopts boosting in many places to accelerate the coal powder by utilizing the Venturi principle.

[0014] The nitrogen heater 2 heats the compressed nitrogen from the compressed nitrogen tank 5 for use, avoiding direct use of nitrogen with a lower temperature to lower the temperature of the coal powder. In the present invention, the nitrogen heated in the nitrogen heater 2 is divided into multiple paths for boosting, avoiding coal powder accumulation and clogging in the pipeline.

[0015] In order to prevent the common blast furnace feed coal powder pipeline from being blocked due to accidents, the present invention additionally prepares a spare blast furnace feed coal powder pipeline, on which a normally closed coal inlet valve 11 and a normally closed coal outlet valve 12 are installed. When the common blast furnace feed coal powder pipeline is blocked, the normally closed coal inlet valve 11 and the normally closed coal outlet valve 12 are opened to avoid the blast furnace being unable to spray coal.

[0016] In order to prevent accidents that may cause the outlet of the conventional pulverized coal heater 4 to be blocked and the blast furnace cannot use coal, a spare pulverized coal heater 3 is prepared in the present invention. The spare pulverized coal heater 3 can be directly heated by electric heating or other heating methods. When the outlet of the conventional pulverized coal heater 4 is blocked, the spare pulverized coal heater 3 is switched to heat the coal.

[0017] The present invention provides a blast furnace coal powder preheating system, which can automatically control the preheating of coal powder, and when an accident occurs, it will not affect the use of coal in the blast furnace. The present invention uses oil as a heat transfer medium, and uses the waste heat of the blast furnace (waste heat of blast furnace tail gas, etc.) to heat the coal powder coming out of the coal injection workshop 1 in a common coal powder heater 4, and the heated coal powder enters the blast furnace for combustion. The combustion characteristics of the preheated coal powder are significantly improved, and it can burn quickly when entering the main combustion chamber of the blast furnace, thereby breaking through the conventional three-stage combustion process of heating, ignition and combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 It is a schematic diagram of the oil circulation pipeline; Figure 3 It is a schematic diagram of the connection between the oil storage tank, the expansion tank and the waste heat exchanger; Figure 4 It is a schematic diagram of the internal structure of a pulverized coal heater; Among them, 1. Coal injection workshop, 2. Nitrogen heater, 3. Standby pulverized coal heater, 4. Common pulverized coal heater, 5. Compressed nitrogen tank, 6. Blast furnace, 7. Oil storage tank and expansion tank, 8. Waste heat exchanger, 9. Thermal oil pump, 11. Normally closed coal inlet valve, 12. Normally closed coal outlet valve, 13. Normally open coal inlet valve, 14. Normally closed heating valve, 15. Normally open heating valve, 16. Normally open coal outlet valve, 17. Normally closed booster valve, 21. First pressure transmitter, 22. First temperature sensor, 23. Second temperature sensor, 24. Second pressure transmitter, 25. Third pressure transmitter, 41. Coal powder heat exchange chamber, 42. Oil heat exchange chamber. DETAILED DESCRIPTION

[0019] like Figure 1-4As shown, a blast furnace coal powder preheating system includes a coal injection workshop 1, a nitrogen heater 2, a common coal powder heater 4, a standby coal powder heater 3, a compressed nitrogen tank 5, a blast furnace 6, an oil storage tank and an expansion tank 7, a waste heat exchanger 8, a thermal oil pump 9, a PLC control system, and an audible and visual alarm device. The nitrogen coming out of the compressed nitrogen tank 5 is heated by the nitrogen heater 2 (existing technology) and then divided into five branches. The coal powder coming out of the coal injection workshop 1 (coal powder mixed gas, existing technology) is mixed with the nitrogen coming out of the first branch of the nitrogen heater 2 (first boost) and then divided into two branches. Coal injection branch, one coal injection branch is connected to the coal inlet of the blast furnace 6 through a spare blast furnace pulverized coal feed pipeline equipped with a normally closed coal inlet valve 11 and a normally closed coal outlet valve 12 (when the other coal injection branch cannot be fed with coal due to an unexpected situation, coal is fed to ensure continuous production of the blast furnace. When the spare blast furnace pulverized coal feed pipeline is used, the normally open coal inlet valve 13 is closed, and the normally closed coal inlet valve 11 and the normally closed coal outlet valve 12 are opened), and the other coal injection branch enters the common blast furnace pulverized coal feed pipeline equipped with a normally open coal inlet valve 13, and a first pressure transmitter 21 is installed on the common blast furnace pulverized coal feed pipeline.

[0020] The commonly used blast furnace feeding pulverized coal pipeline (the pipeline after the normally open coal inlet valve 13) is connected to two heating branches for preheating the pulverized coal. One heating branch is connected to the spare pulverized coal heater 3 through a pipeline equipped with a normally closed heating valve 14 (when the commonly used pulverized coal heater 4 cannot work normally, the spare pulverized coal heater 3 is used for heating to ensure the preheating of the pulverized coal and the high quality of steel smelting. When the spare pulverized coal heater 3 is working, the normally closed heating valve 14 is opened, the valve on the outlet pipeline of the spare pulverized coal heater 3 is opened, and the normally open heating valve 15 is closed. The spare pulverized coal heater 3 can be electrically heated. Such a heater already exists in the prior art and will not be explained here). The other heating branch is connected to the commonly used pulverized coal heater 4 through a pipeline equipped with a normally open heating valve 15. A valve is installed on the outlet pipeline of the commonly used pulverized coal heater 4. After the pulverized coal from the spare pulverized coal heater 3 and the commonly used pulverized coal heater 4 are merged through the pipeline, they are connected to the coal inlet of the blast furnace through a pipeline equipped with a normally open coal outlet valve 16.

[0021] The nitrogen coming out of the fifth branch of the nitrogen heater 2 passes through a pipeline equipped with a normally closed booster valve 17 to boost the coal powder coming out of the standby coal powder heater 3 (the coal powder boosting in the present invention utilizes the Venturi acceleration principle for boosting, and the normally closed booster valve 17 is opened only when the standby coal powder heater 3 is in use. At this time, the normally open heating valve 15 is closed, and the second branch and the third branch of the nitrogen heater 2 are also closed). The pulverized coal coming out of the common pulverized coal heater 4 (the pulverized coal coming out of the outlet pipe of the common pulverized coal heater 4) is connected to the coal inlet of the blast furnace 6 through a pipe equipped with a normally-open coal outlet valve 16, the second branch of the nitrogen heater 2 enters the common pulverized coal heater 4 and mixes with the pulverized coal in the common pulverized coal heater 4, the third branch of the nitrogen heater 2 is connected to the coal outlet pipe of the common pulverized coal heater 4 to provide a boost for the pulverized coal coming out of the common pulverized coal heater 4, and the fourth branch of the nitrogen heater 2 is connected to the pipe in front of the normally-open coal outlet valve 16 to boost the pulverized coal in the pipe (high-speed nitrogen uses the Venturi acceleration principle to boost the pulverized coal, and the pulverized coal is a nitrogen flow carrying the pulverized coal).

[0022] The commonly used blast furnace feed pulverized coal pipeline is connected to two heating branches, one heating branch is connected to the standby pulverized coal heater 3 through a pipeline equipped with a normally closed heating valve 14, and the other heating branch is connected to the commonly used pulverized coal heater 4 through a pipeline equipped with a normally open heating valve 15. The fifth branch of the nitrogen heater 2 is used to boost the pulverized coal coming out of the standby pulverized coal heater 3 through a pipeline equipped with a normally closed booster valve 17.

[0023] The oil in the oil storage tank and the expansion tank 7 enters the waste heat exchanger 8 by its own gravity and is heated by the waste heat of the blast furnace. The heated oil in the waste heat exchanger 8 enters the common pulverized coal heater 4 through the thermal oil pump 9 to heat the pulverized coal therein. The oil coming out of the common pulverized coal heater 4 circulates into the waste heat exchanger 8 and is heated again.

[0024] A first pressure transmitter 21 is installed on the common blast furnace feed pulverized coal pipeline, a first temperature sensor 22 is installed on the oil inlet pipeline of the common pulverized coal heater 4, a second temperature sensor 23 is installed on the oil outlet pipeline of the common pulverized coal heater 4, a second pressure transmitter 24 is installed on the inlet of the thermal oil pump 9, a third pressure transmitter 25 is installed on the outlet of the thermal oil pump, a gas flow meter is installed on each branch of the nitrogen heater 2 (all gas flow meters are connected to the PLC control system), and a liquid level sensor is installed in the oil storage tank and the expansion tank 7; the pulverized coal pressure in the common pulverized coal heater 4 is obtained through the first pressure transmitter 21, when the pulverized coal pressure is greater than the set pulverized coal pressure, the opening of the normally open coal inlet valve 13 is reduced, when the pulverized coal pressure is less than the set pulverized coal pressure (such as 1.5 atmospheres), the opening of the normally open coal inlet valve 13 is increased, when the pulverized coal pressure is greater than the maximum pulverized coal pressure (such as 1.7 atmospheres) or less than the minimum pulverized coal pressure When the pressure (such as 1.3 atmospheres) is lower than the set oil inlet temperature (such as 230°C), the first temperature sensor 22 measures the oil inlet temperature in the oil inlet pipeline of the common pulverized coal heater 4. When the oil inlet temperature is lower than the set oil inlet temperature (such as 230°C), the oil pumping amount of the heat transfer oil pump is increased. When the oil inlet temperature is higher than the set oil inlet temperature (such as 250°C), the oil pumping amount of the heat transfer oil pump is reduced. When the oil inlet temperature is lower than the minimum oil inlet temperature (such as 200°C) or higher than the maximum oil inlet temperature (such as 270°C), the alarm is sounded to remind the staff to perform maintenance. The liquid level sensor measures the liquid level of the oil in the oil storage tank and the expansion tank 7. When the liquid level is equal to or lower than the minimum liquid level setting value (the lower liquid level in the oil storage tank and the expansion tank 7 may cause the liquid channel of the waste heat exchanger 8 to be unable to be filled with oil and affect heat exchange), the oil is added to the oil storage tank and the expansion tank 7. When the liquid level is equal to or higher than the maximum liquid level setting value, the oil is stopped from being added to the oil storage tank and the expansion tank 7. The oil used in the present invention is a grease with a boiling point higher than 300°C.

[0025] The waste heat exchanger 8 is a gas-liquid heat exchanger (a gas-liquid heat exchanger in the prior art). The blast furnace tail gas (about 300°C) enters the gas channel to heat the oil in the liquid channel. The oil storage tank and the expansion tank 7 are connected to the liquid channel of the waste heat exchanger 8. The liquid level of the oil in the oil storage tank and the expansion tank 7 is higher than the highest liquid level of the oil in the liquid channel of the waste heat exchanger 8, ensuring that the liquid channel of the waste heat exchanger 8 is always full of oil. The oil in the liquid channel of the waste heat exchanger 8 exchanges heat with the blast furnace tail gas in the gas channel to increase the temperature of the oil. The heated oil is pumped into the common pulverized coal heater 4 by the heat transfer oil pump 9 (the common pulverized coal heater 4 is also a gas-liquid heater. The biggest difference from the waste heat exchanger 8 is that the common pulverized coal heater 4 uses liquid to heat gas, while the waste heat exchanger 8 uses gas to heat liquid), and heats the pulverized coal in the pulverized coal heater 4. The oil coming out of the pulverized coal heater 4 circulates into the waste heat exchanger 8 for repeated use, thereby realizing the heating of pulverized coal by the waste heat of the blast furnace. During the oil circulation process, attention should be paid to the control of the oil inlet temperature of the waste heat exchanger 8. When the oil inlet temperature is lower than the set oil inlet temperature, the oil pumping amount of the thermal oil pump 9 is increased. When the oil inlet temperature is higher than the set oil inlet temperature, the oil pumping amount of the thermal oil pump 9 is reduced. When the oil inlet temperature is lower than the minimum oil inlet temperature or higher than the maximum oil inlet temperature, an alarm is sounded to remind the staff to perform maintenance. The entire control is realized through a PLC control system. The present invention interlocks the oil inlet temperature in the oil inlet pipeline of the common pulverized coal heater 4 measured by the first temperature sensor 22 with the thermal oil pump (frequency conversion), and stably provides heat energy to the pulverized coal in the pulverized coal heater 4.

[0026] The pulverized coal from the coal injection workshop 1 is mixed with the nitrogen from the first branch of the nitrogen heater 2 and enters the common pulverized coal feeding pipeline for blast furnaces equipped with a normally open coal inlet valve 13. The common pulverized coal feeding pipeline for blast furnaces is connected to the common pulverized coal heater 4 through a pipeline equipped with a normally open heating valve 15. The pulverized coal from the common pulverized coal heater 4 is connected to the coal inlet of the blast furnace 6 through a pipeline equipped with a normally open coal outlet valve 16. The pulverized coal heater 4 can adopt the existing heat exchange type pulverized coal heating equipment.

[0027] The pulverized coal heater 4 includes a pulverized coal heat exchange chamber 41 and an oil heat exchange chamber 42 for performing heat exchange with the wall of the pulverized coal heat exchange chamber 41. As the cross section of the pulverized coal entering the pulverized coal heater 4 increases, the pressure decreases, and the pulverized coal may gather in the pulverized coal heat exchange chamber 41. However, in order to increase the heat exchange area, the cross section of the pulverized coal heat exchange chamber 41 must be increased to better complete the heat exchange. In order to avoid blocking the outlet of the pulverized coal heat exchange chamber 41, the nitrogen coming out of the first branch of the nitrogen heater 2 carries the pulverized coal coming out of the pulverized coal heat exchange chamber 41 (using the Venturi principle), thereby increasing the pulverized coal outlet speed and avoiding blocking the outlet of the pulverized coal heat exchange chamber 41 and affecting the heat exchange.

[0028] The nitrogen heater 2 heats the compressed nitrogen from the compressed nitrogen tank 5 for use, so as to prevent the nitrogen with a lower temperature from lowering the temperature of the coal powder. In the present invention, the nitrogen heated in the nitrogen heater 2 is divided into multiple paths for boosting, so as to prevent the coal powder from accumulating and clogging in the pipeline.

[0029] In order to prevent the common blast furnace feed coal powder pipeline from being blocked due to accidents, the present invention additionally prepares a spare blast furnace feed coal powder pipeline, on which a normally closed coal inlet valve 11 and a normally closed coal outlet valve 12 are installed. When the common blast furnace feed coal powder pipeline is blocked, the normally closed coal inlet valve 11 and the normally closed coal outlet valve 12 are opened to avoid the blast furnace being unable to spray coal.

[0030] In order to prevent accidents that may cause the outlet of the conventional pulverized coal heater 4 to be blocked and the blast furnace cannot use coal, a spare pulverized coal heater 3 is prepared in the present invention. The spare pulverized coal heater 3 can be directly heated by electric heating or other heating methods. When the outlet of the conventional pulverized coal heater 4 is blocked, the spare pulverized coal heater 3 is switched to heat the coal.

Claims

1. A blast furnace coal powder preheating system, characterized in that: The invention comprises a coal injection workshop (1), a nitrogen heater (2), a common pulverized coal heater (4), a compressed nitrogen tank (5), a blast furnace (6), an oil storage tank and an expansion tank (7), a waste heat exchanger (8), a thermal oil pump (9), a PLC control system, and an audible and visual alarm device. The nitrogen from the compressed nitrogen tank (5) is heated by the nitrogen heater (2) and then divided into four branches. The pulverized coal from the coal injection workshop (1) is mixed with the nitrogen from the first branch of the nitrogen heater (2) and then enters a common blast furnace feed pulverized coal pipeline equipped with a normally open coal inlet valve (13). The common blast furnace feed pulverized coal pipeline is connected to the common pulverized coal heater (4) through a pipeline equipped with a normally open heating valve (15). The pulverized coal from the coal outlet pipeline of the common pulverized coal heater (4) is connected to the common pulverized coal heater (4) through a pipeline equipped with a normally open heating valve (15). A pipeline with a normally open coal outlet valve (16) is connected to the coal inlet of the blast furnace (6); a second branch of the nitrogen heater (2) enters the common pulverized coal heater (4) to mix with the pulverized coal in the common pulverized coal heater (4); a third branch of the nitrogen heater (2) is connected to the coal outlet pipeline of the common pulverized coal heater (4) to provide a boost for the pulverized coal coming out of the common pulverized coal heater (4); a fourth branch of the nitrogen heater (2) is connected to the pipeline at the inlet end of the normally open coal outlet valve (16) to provide a pulverized coal boost for the pulverized coal in the pipeline; the oil in the oil storage tank and the expansion tank (7) enters the waste heat exchanger (8) by its own gravity and is heated by the waste heat of the blast furnace; the heated oil in the waste heat exchanger (8) enters the common pulverized coal heater (4) through a heat transfer oil pump (9) to heat the coal therein The pulverized coal is heated, and the oil from the common pulverized coal heater (4) is circulated into the waste heat exchanger (8) to be heated again; a first pressure transmitter (21) is installed on the common blast furnace feed pulverized coal pipeline, a first temperature sensor (22) is installed on the oil inlet pipeline of the common pulverized coal heater (4), a second temperature sensor (23) is installed on the oil outlet pipeline of the common pulverized coal heater (4), a second pressure transmitter (24) is installed on the inlet pipeline of the thermal oil pump (9), a third pressure transmitter (25) is installed on the outlet pipeline of the thermal oil pump, a gas flow meter is installed on each branch of the nitrogen heater (2), and a liquid level sensor is installed in the oil storage tank and the expansion tank (7); the pressure of the common pulverized coal heater (2) is obtained through the first pressure transmitter (21). 4) the coal inlet pulverized coal pressure, when the coal inlet pulverized coal pressure is greater than the set coal inlet pulverized coal pressure, the opening of the normally open coal inlet valve (13) is reduced, when the coal inlet pulverized coal pressure is less than the set coal inlet pulverized coal pressure, the opening of the normally open coal inlet valve (13) is increased, when the coal inlet pulverized coal pressure is greater than or equal to the maximum coal inlet pressure or less than or equal to the minimum coal inlet pressure, an alarm is sounded to remind the staff to perform maintenance; the first temperature sensor (22) measures the oil inlet temperature in the oil inlet pipeline of the common coal pulverized heater (4), when the oil inlet temperature is less than the set oil inlet temperature, the oil pumping amount of the heat transfer oil pump (9) is increased, when the oil inlet temperature is greater than the set oil inlet temperature, the oil pumping amount of the heat transfer oil pump (9) is reduced, when the oil inlet temperature is less than the minimum oil inlet temperature or greater than the maximum oil inlet temperature, an alarm is sounded to remind the staff to perform maintenance;The liquid level sensor measures the liquid level of the oil in the oil storage tank and the expansion tank (7). When the liquid level is equal to or lower than the minimum set value, the oil is added to the oil storage tank and the expansion tank (7). When the liquid level is equal to or higher than the maximum set value, the oil is stopped from being added to the oil storage tank and the expansion tank (7).

2. A blast furnace coal powder preheating system according to claim 1, characterized in that: The pulverized coal from the coal injection workshop (1) is mixed with the nitrogen from the first branch of the nitrogen heater (2) and then divided into two coal injection branches. One coal injection branch is connected to the coal inlet of the blast furnace (6) through a spare blast furnace feed pulverized coal pipeline equipped with a normally closed coal inlet valve (11) and a normally closed coal outlet valve (12), and the other coal injection branch enters a regular blast furnace feed pulverized coal pipeline equipped with a normally open coal inlet valve (13).

3. A blast furnace coal powder preheating system according to claim 1, characterized in that: The blast furnace coal powder preheating system also includes a standby coal powder heater (3). Nitrogen from a compressed nitrogen tank (5) is heated by a nitrogen heater (2) and then divided into five branches. A common blast furnace feed coal powder pipeline is connected to two heating branches. One heating branch is connected to the standby coal powder heater (3) through a pipeline equipped with a normally closed heating valve (14). Another heating branch is connected to a common coal powder heater (4) through a pipeline equipped with a normally open heating valve (15). The coal powders from the standby coal powder heater (3) and the common coal powder heater (4) are combined through a pipeline and then connected to a coal inlet of a blast furnace (6) through a pipeline equipped with a normally open coal outlet valve (16). Nitrogen from the fifth branch of the nitrogen heater (2) is boosted for the coal powder from the standby coal powder heater (3) after passing through a pipeline equipped with a normally closed boosting valve (17).

4. A blast furnace coal powder preheating system according to claim 1, characterized in that: Coal powder boosting uses the Venturi acceleration principle for boosting.

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