System for multiple heating furnaces and use method thereof

Abstract

The invention relates to the field of waste heat utilization devices, in particular to a flue gas waste heat recovery system for multiple heating furnaces and a use method of the flue gas waste heat recovery system. The flue gas waste heat recovery system for the multiple heating furnaces comprises at least two heating furnaces (1) and is characterized by further comprising pretreatment units (2), a static pressure air bellow (5), a waste heat boiler (4), a pressure transmitter (51) and an induced draft fan (52), and the number of the pretreatment units (2) is equal to that of the heating furnaces (1); each pretreatment unit (2) comprises an air preheater (21), a coal gas preheater (22), a chimney (23), a smoke exhaust regulating valve (24), a smoke regulating stop valve (25), a smoke inlet regulating valve (26) and a smoke regulating valve (27). The use method of the flue gas waste heat recovery system for the multiple heating furnaces is characterized by comprising the steps of operation, adjustment and maintenance. The work amount is reduced, and the heat energy utilization rate is high.

Description

Technical Field

[0001] The present invention relates to the field of devices for utilizing waste heat, and specifically to a flue gas waste heat recovery system for multiple heating furnaces and its usage method. Background Art

[0002] In industries such as metallurgy, there are relatively abundant flue gas waste heat resources. The dissipation of this part of resources not only pollutes the atmosphere but also wastes energy. How to recover and utilize it with high quality has great economic benefits and good social benefits.

[0003] Currently, in the heating furnace production line of the metallurgy industry, the high-temperature flue gas of the heating furnace is usually introduced into a waste heat boiler to heat the water medium to generate steam for power generation or heating. The main method is to draw out the flue gas of one heating furnace, exchange heat through a waste heat boiler, and then send the flue gas into the chimney for discharge by an induced draft fan. In the case of multiple heating furnaces, waste heat boilers corresponding to the number of furnaces are usually set up. This results in a large construction workload, a large number of new equipment, a large maintenance workload, relatively high operating costs, and a long investment recovery period. Summary of the Invention

[0004] In order to overcome the defects of the prior art and provide a waste heat utilization device with reduced engineering volume and high thermal energy utilization rate, the present invention discloses a flue gas waste heat recovery system for multiple heating furnaces and its usage method.

[0005] The present invention achieves the invention purpose through the following technical solutions: A flue gas waste heat recovery system for multiple heating furnaces includes at least two heating furnaces, and is characterized in that: it further includes a pretreatment unit, a static pressure air box, a waste heat boiler, a pressure transmitter, and an induced draft fan. The static pressure air box is provided with smoke inlets equal in number to the heating furnaces. The number of pretreatment units is equal to the number of heating furnaces. Each pretreatment unit includes an air preheater, a gas preheater, a chimney, a smoke exhaust regulating valve, a flue gas regulating cut-off valve, a flue gas inlet regulating valve, and a flue gas valve. The connection mode between the heating furnace and the pretreatment unit is as follows: two smoke inlets are provided on the chimney. The flue gas outlet of the heating furnace is connected to one smoke inlet of the chimney through a smoke exhaust main pipe that is successively connected in series with an air preheater, a gas preheater, a flue gas valve, and a flue gas regulating cut-off valve. A flue gas inlet regulating valve is connected in series on the smoke exhaust branch pipe. The smoke inlet of the smoke exhaust branch pipe is connected between the flue gas valve and the flue gas regulating cut-off valve on the smoke exhaust main pipe. The smoke exhaust port of the smoke exhaust branch pipe is connected to one smoke inlet of the static pressure air box. The smoke exhaust port of the static pressure air box is connected to the suction port of the induced draft fan through a smoke transmission pipe that is successively connected in series with a pressure transmitter and a waste heat boiler. The other smoke inlet of each chimney is respectively connected to the exhaust port of the induced draft fan through a gas transmission pipe connected in series with a smoke exhaust regulating valve. The pressure transmitter is connected to the induced draft fan through a signal line.

[0006] For the flue gas waste heat recovery system for multiple heating furnaces, it is characterized in that: the flue gas regulating cut-off valve, the flue gas inlet regulating valve and the flue gas regulating valve are all pneumatic valves or electric valves.

[0007] The usage method of the flue gas waste heat recovery system for multiple heating furnaces is characterized by including operation, adjustment and maintenance steps: Operation: Open the flue gas inlet regulating valve and the exhaust gas regulating valve, close the flue gas regulating cut-off valve, and start the induced draft fan; The flue gas discharged from the heating furnace is sequentially input into the static pressure air box through the main exhaust pipe and the exhaust branch pipe. Under the suction of the induced draft fan, the flue gas in the static pressure air box is input into the waste heat boiler through the flue gas pipe. After releasing heat in the waste heat boiler, the flue gas continues to be input into each chimney for discharge under the suction of the induced draft fan through the gas pipe; Adjustment: Adjust the operating frequency of the induced draft fan to control the flue gas pressure in the static pressure air box; Adjust each flue gas inlet regulating valve to preliminarily adjust the flue gas pressure in the main exhaust pipe and the exhaust branch pipe connecting each heating furnace; Adjust each flue gas regulating valve to adjust the furnace pressure in each heating furnace so that the furnace pressure of the heating furnace is within a reasonable range; Adjust each exhaust gas regulating valve to distribute the flue gas flow rate entering each chimney to ensure normal discharge; Adjust each flue gas regulating cut-off valve to control the flue gas flow rate entering the waste heat boiler, and then control the heat entering the waste heat boiler to meet the requirements of the waste heat boiler.

[0008] Maintenance: Open the flue gas regulating cut-off valve, close the induced draft fan, close the flue gas inlet regulating valve, close the exhaust gas regulating valve. The flue gas discharged from the heating furnace is no longer input into the waste heat boiler but directly input into the chimney for discharge through the main exhaust pipe, and then repair the waste heat boiler and the induced draft fan.

[0009] For the flue gas waste heat recovery system for multiple heating furnaces, it is characterized in that: during adjustment, the opening degree of the flue gas regulating cut-off valve is 20% - 80%.

[0010] In the present invention, the flue gas originally discharged from the heating furnace to the chimney is led out from the flue and sent to a static pressure air box to stabilize the flue gas pressure. After the flue gas is statically pressured by the static pressure air box, the pressure of the flue gas introduced into each heating furnace is stable, which is beneficial to the control of the furnace pressure of the heating furnace. Then, the stabilized flue gas is sent into a waste heat boiler for waste heat recovery. After the flue gas exchanges heat in the waste heat boiler, its temperature drops to 20 °C to more than 40 °C above the flue gas acid dew point, avoiding the condensation corrosion of the system. When extreme waste heat recovery is carried out, the flue gas temperature can drop below the flue gas dew point. At this time, components such as the smoke conveying pipe after the waste heat boiler need to be sprayed with a graphene gold coating or other measures should be taken to avoid dew point corrosion. Finally, through the suction of the induced draft fan to overcome the resistance of the new flue gas pipeline and equipment, the flue gas is sent to the chimney for discharge. The number of chimneys to be connected is checked and determined according to the flue gas volume and temperature after waste heat recovery. A smoke exhaust regulating valve is set before connecting to the chimney to control the flue gas flow into the chimney and ensure the normal discharge of the flue gas.

[0011] The present invention sets an induced draft fan frequency converter, flue gas system pressure and temperature measuring points, and sends the measuring points into a PLC / DCS control system, sets a control station, an operation station, etc. Through the PLC / DCS control program, the above signals and control equipment operate and interlock automatically according to the established program to ensure the safe and stable operation of the system. The waste heat boiler is also equipped with a mechanical safety valve, which automatically discharges overpressure when the waste heat boiler regulating system fails, essentially ensuring the safe operation of the system.

[0012] The present invention has the following beneficial effects: In the present invention, the flue gas of multiple heating furnaces is led out, aggregated into a static pressure air box to stabilize the pressure in each pipeline, and sent into a waste heat boiler through a main pipe to recover the waste heat of the flue gas. Finally, an induced draft fan sends the flue gas after waste heat recovery into the chimney for discharge. Compared with the traditional method, when multiple heating furnaces need waste heat recovery, adopting the present invention only requires setting a set of waste heat boiler and supporting fan systems, etc., without the need to set multiple units, reducing the maintenance workload, lowering the operating cost, and reducing the total investment.

[0013] The present invention adopts the big data and intelligent manufacturing technology of the PLC / DCS control system. The control system can be set separately or interlocked and embedded into the main control system of the heating furnace; the control program can online control the furnace pressure index of each heating furnace and dynamically adjust parameters such as the flue gas flow rate extracted into the waste heat boiler of each heating furnace. It effectively and accurately controls the air pressure in the flue gas pipeline and reduces the impact on the production of the heating furnace. On the premise of not affecting the normal operation of the heating furnace, following the principle of cascade utilization, high temperature is used for high-temperature applications, and low temperature is used for low-temperature applications, making full use of the "exergy" of energy, reducing the waste gas temperature to above the flue gas acid dew point, and it can be reduced below the flue gas acid dew point under extreme waste heat recovery, improving the thermal energy utilization efficiency. At the same time, there is no need to change the existing waste gas pipeline process and existing waste gas pipeline facilities, that is, the existing pipelines, air preheaters, gas preheaters, regulating valves, chimneys, etc. of the waste gas system are retained. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be further described below with specific embodiments. Embodiment

[0016] A flue gas waste heat recovery system for multiple heating furnaces includes at least two heating furnaces 1, a pretreatment unit 2, a static pressure air box 5, a waste heat boiler 4, a pressure transmitter 51 and a draft fan 52, as Figure 1 shown, the specific structure is as follows: The static pressure air box 5 is provided with smoke inlets equal in number to the heating furnaces 1; The number of pretreatment units 2 is equal to that of the heating furnaces 1. Each pretreatment unit 2 includes an air preheater 21, a gas preheater 22, a chimney 23, a smoke exhaust regulating valve 24, a flue gas regulating cut-off valve 25, a flue gas inlet regulating valve 26 and a flue gas regulating valve 27; The connection mode between the heating furnace 1 and the pretreatment unit 2 is as follows: Two smoke inlets are provided on the chimney 23. The flue gas outlet of the heating furnace 1 is connected to one smoke inlet of the chimney 23 through a smoke exhaust main pipe 61 that is successively connected in series with an air preheater 21, a gas preheater 22, a flue gas regulating valve 27 and a flue gas regulating cut-off valve 25. A flue gas inlet regulating valve 26 is connected in series on a smoke exhaust branch pipe 62. The smoke inlet of the smoke exhaust branch pipe 62 is connected between the flue gas regulating valve 27 and the flue gas regulating cut-off valve 25 on the smoke exhaust main pipe 61. The smoke exhaust port of the smoke exhaust branch pipe 62 is connected to one smoke inlet of the static pressure air box 5; The smoke exhaust port of the static pressure air box 5 is connected to the suction port of the draft fan 52 through a smoke transmission pipe 63 that is successively connected in series with a pressure transmitter 51 and a waste heat boiler 4. The other smoke inlet of each chimney 23 is respectively connected to the exhaust port of the draft fan 52 through a gas transmission pipe 64 connected in series with a smoke exhaust regulating valve 24. The pressure transmitter 51 is connected to the draft fan 52 through a signal line.

[0017] In this embodiment: The flue gas regulating cut-off valve 25, the flue gas inlet regulating valve 26 and the flue gas regulating valve 27 are all selected as pneumatic valves or electric valves.

[0018] When this embodiment is used, it includes operation, adjustment and maintenance steps: Operation: Open the flue gas inlet regulating valve 26 and the smoke exhaust regulating valve 24, close the flue gas regulating cut-off valve 25, and start the draft fan 52; The flue gas discharged from the heating furnace 1 sequentially passes through the main exhaust pipe 61 and the exhaust branch pipe 62 and is input into the static pressure air box 5. Under the suction of the induced draft fan 52, the flue gas in the static pressure air box 5 is input into the waste heat boiler 4 through the smoke transmission pipe 63. After releasing heat in the waste heat boiler 4, the flue gas continues to be input into each chimney 23 for discharge under the suction of the induced draft fan 52; Adjustment: Adjust the operating frequency of the induced draft fan 52 to control the flue gas pressure in the static pressure air box 5; Adjust each flue gas inlet regulating valve 26 to preliminarily adjust the flue gas pressure in the main exhaust pipe 61 and the exhaust branch pipe 62 connecting each heating furnace 1; Adjust each flue gas regulating valve 27 to adjust the furnace pressure in each heating furnace 1 so that the furnace pressure of the heating furnace 1 is within a reasonable range; Adjust each exhaust regulating valve 24 to distribute the flue gas flow entering each chimney 23 to ensure normal discharge; Adjust each flue gas regulating cut-off valve 25. The opening degree of the flue gas regulating cut-off valve 25 is between 20% and 80% to control the flue gas flow entering the waste heat boiler 4, and then control the heat entering the waste heat boiler 4 to meet the requirements of the waste heat boiler 4.

[0019] Maintenance: Open the flue gas regulating cut-off valve 25, close the induced draft fan 52, close the flue gas inlet regulating valve 26, close the exhaust regulating valve 24. The flue gas discharged from the heating furnace 1 is no longer input into the waste heat boiler 4 but directly discharged into the chimney 23 through the main exhaust pipe 61, and then repair the waste heat boiler 4 and the induced draft fan 52.

[0020] In this embodiment, the flue gas originally discharged from the heating furnace 1 to the chimney 23 is led out from the flue and sent to the static pressure air box 3 to stabilize the flue gas pressure. After the flue gas is statically pressured by the static pressure air box 3, the flue gas pressure introduced into each heating furnace 1 is stable, which is beneficial to the control of the furnace pressure of the heating furnace 1; then the stabilized flue gas is sent into the waste heat boiler 4 for waste heat recovery. After the flue gas exchanges heat in the waste heat boiler 4, the temperature drops to above 20°C to 40°C of the flue gas acid dew point, avoiding flue gas condensation and corrosion of the system. When extreme waste heat recovery is carried out, the flue gas temperature can drop below the flue gas dew point. At this time, components such as the smoke transmission pipe 63 after the waste heat boiler 4 need to be sprayed with a graphene gold coating or other measures to avoid dew point corrosion; finally, after being sucked by the induced draft fan 52 to overcome the resistance of the new flue gas pipeline and equipment, the flue gas is sent to the chimney 23 for discharge. The number of chimneys to be connected is checked and determined according to the flue gas volume and temperature after waste heat recovery. A smoke exhaust regulating valve 24 is set before connecting to the chimney 23 to control the flue gas flow entering the chimney 23 to ensure normal flue gas discharge.

[0021] In this embodiment, an induced draft fan frequency converter, pressure and temperature measuring points of the flue gas system are set, and the measuring points are sent to the PLC / DCS control system. Control stations, operation stations, etc. are set. Through the PLC / DCS control program, the above signals and control equipment operate and interlock automatically according to the established program to ensure the safe and stable operation of the system. The waste heat boiler is also equipped with a mechanical safety valve, which automatically discharges overpressure when the regulation system of the waste heat boiler fails, essentially ensuring the safe operation of the system.

Claims

1. A flue gas waste heat recovery system for multiple heating furnaces, comprising at least two heating furnaces (1), characterized in that: It also includes a pre-treatment unit (2), a static pressure wind box (5), a waste heat boiler (4), a pressure transmitter (51) and an induced draft fan (52), The static pressure wind box (5) is provided with smoke inlets having the same number as that of the heating furnace (1); The number of pretreatment units (2) is equal to that of the heating furnace (1), and each pretreatment unit (2) comprises an air preheater (21), a coal gas preheater (22), a chimney (23), a smoke exhaust regulating valve (24), a smoke regulating shut-off valve (25), a smoke inlet regulating valve (26) and a smoke regulating valve (27); The heating furnace (1) and the pretreatment unit (2) are connected in the following manner: two smoke inlets are provided on the chimney (23); the smoke outlet of the heating furnace (1) is connected to a smoke inlet of the chimney (23) through a smoke exhaust main pipe (61) which is connected in series with an air preheater (21), a gas preheater (22), a smoke regulating valve (27) and a smoke regulating shut-off valve (25); a smoke inlet regulating valve (26) is connected in series on a smoke exhaust branch pipe (62); the smoke inlet of the smoke exhaust branch pipe (62) is connected between the smoke regulating valve (27) and the smoke regulating shut-off valve (25) on the smoke exhaust main pipe (61); and the smoke exhaust port of the smoke exhaust branch pipe (62) is connected to a smoke inlet of a static pressure bellows (5); The smoke exhaust port of the static pressure wind box (5) is connected to the air intake port of the induced draft fan (52) through a smoke delivery pipe (63) connected in series with a pressure transmitter (51) and a waste heat boiler (4), and the other smoke inlet of each chimney (23) is connected to the exhaust port of the induced draft fan (52) through a gas delivery pipe (64) connected in series with a smoke exhaust regulating valve (24), and the pressure transmitter (51) is connected to the induced draft fan (52) through a signal line.

2. The flue gas waste heat recovery system for multiple heating furnaces according to claim 1, characterized in that: The smoke regulating cut-off valve (25), the smoke inlet regulating valve (26) and the smoke regulating valve (27) are all pneumatic valves or electric valves.

3. The method for using the flue gas waste heat recovery system for multiple heating furnaces according to claim 1 or 2, characterized in that: Includes operation, adjustment and maintenance steps: Operation: Open the smoke inlet regulating valve (26) and the smoke exhaust regulating valve (24), close the smoke regulating shut-off valve (25), and start the induced draft fan (52); The smoke exhausted from the heating furnace (1) is sequentially input into the static pressure wind box (5) through the smoke exhaust main pipe (61) and the smoke exhaust branch pipe (62). The smoke in the static pressure wind box (5) is input into the waste heat boiler (4) through the smoke conveying pipe (63) under the suction of the induced draft fan (52). After the smoke releases heat in the waste heat boiler (4), the smoke is further input into each chimney (23) through the gas conveying pipe (64) under the suction of the induced draft fan (52) for discharge. Regulation: regulating the operating frequency of the induced draft fan (52) to control the flue gas pressure in the static pressure wind box (5); Regulating each smoke inlet regulating valve (26) to preliminarily regulate the smoke pressure in the smoke exhaust main pipe (61) and the smoke exhaust branch pipe (62) connected to each heating furnace (1); Regulating each flue gas regulating valve (27) to adjust the furnace pressure in each heating furnace (1) so that the furnace pressure of the heating furnace (1) is within a reasonable range; Adjusting each smoke exhaust regulating valve (24) to distribute the smoke flow entering each chimney (23) to ensure normal exhaust; Each flue gas regulating shut-off valve (25) is adjusted to control the flue gas flow entering the waste heat boiler (4), thereby controlling the heat entering the waste heat boiler (4) to meet the demand of the waste heat boiler (4).

4. Maintenance: Open the flue gas regulating shut-off valve (25), shut down the induced draft fan (52), shut down the flue gas inlet regulating valve (26), shut down the exhaust gas regulating valve (24), and the flue gas discharged from the heating furnace (1) is no longer input into the waste heat boiler (4) but directly input into the chimney (23) through the exhaust pipe (61) for discharge, and then the waste heat boiler (4) and the induced draft fan (52) are repaired.

5. The flue gas waste heat recovery system for multiple heating furnaces as claimed in claim 3 is characterized in that: During regulation, the opening degree of the flue gas regulating cut-off valve (25) is between 20% and 80%.

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