Device and method for recycling waste heat of high-temperature flue gas of air cushion furnace

Abstract

The device comprises a smoke exhaust fan pipeline (1) of a heating section of the air cushion furnace and a boiler water return pipeline (2), and is characterized in that a heat exchange assembly is connected between the boiler water return pipeline (2) and the smoke exhaust fan pipeline (1) and comprises a heat exchanger (3), and the heat exchanger (3) is connected with the boiler water return pipeline (2). A hot fluid channel of the heat exchanger (3) is connected with the smoke exhaust fan pipeline (1), and a cold fluid channel of the heat exchanger (3) is connected with the boiler water return pipeline (2). An inlet of the hot fluid channel is a flue gas inlet, and an outlet of the hot fluid channel is a flue gas outlet; an inlet of the cold fluid channel is a water inlet, and an outlet of the cold fluid channel is a water outlet; the system further comprises a PLC control system, energy conservation and consumption reduction are achieved, and the purpose of sustainable development is achieved. The transformation method is scientific in principle, the implementation scheme is simple and easy to implement, and the waste heat recovery effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of heat recovery of air cushion furnaces, and in particular to a device and method for recovering waste heat from high-temperature flue gas of an air cushion furnace. Background Art

[0002] First of all, the automobile plate workshop requires a large amount of thermal energy during the production process. The heating boiler heats water by burning fuel to produce steam or hot water, providing the necessary thermal energy support for the workshop and ensuring the normal operation of the production line.

[0003] For example, the heating boiler in the automobile plate workshop of Ruimin Company consumes 40,000-50,000 cubic meters of natural gas per month. Based on the 24-hour production for 30 days a month, the actual average heating power of the boiler W1 = 40,000 (monthly natural gas volume) * 35,588 * 90% (boiler efficiency) / 24 (hours) / 30 (days) / 3600 (seconds) ≈ 500kW. The on-site boiler outlet pipe temperature is set to 97°C, the actual outlet water temperature is 93-97°C, and the return water temperature is 80-84°C (calculated based on the average value of 82°C, the temperature difference between the return water temperature and the exhaust gas of the heat exchanger needs to be calculated at least 10°C, that is, 92°C). The continuous withdrawal line and the surface line share the nameplate flow rate of the circulating pump of 300m3 / h, so the maximum return water volume of the continuous withdrawal line equipment is 150m3 / h, and the actual operation is about 50-100m3 / h.

[0004] In summary, the heating boiler in the automobile plate workshop needs to consume a large amount of natural gas to heat water.

[0005] Secondly, the exhaust temperature of the air cushion furnace is about 250-300℃ (calculated at 250℃). According to the natural gas consumption of the air cushion furnace, the exhaust gas emission is calculated, and the waste heat that can be used is about:

[0006] W2 = exhaust gas mass flow rate * flue gas temperature difference * flue gas specific heat * flue gas utilization rate =

[0007] [10000*273 / (273+250)*1.2]*(250-92)*1.01*85% / 3600≈236kW.

[0008] In summary, existing devices are unable to recycle waste heat, resulting in a large amount of energy waste. Summary of the invention

[0009] In view of this, an object of the present invention is to provide a device and method for recovering waste heat from high-temperature flue gas of an air cushion furnace, so as to achieve energy saving and consumption reduction.

[0010] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a device for recovering waste heat from high-temperature flue gas of an air cushion furnace, comprising an exhaust fan pipe (1) and a boiler return pipe (2) of a heating section of the air cushion furnace, a heat exchange component being connected between the boiler return pipe (2) and the exhaust fan pipe (1), the heat exchange component comprising a heat exchanger (3), a hot fluid channel of the heat exchanger (3) being connected to the exhaust fan pipe (1), and a cold fluid channel of the heat exchanger (3) being connected to the boiler return pipe (2); the inlet of the hot fluid channel is a flue gas inlet, and the outlet of the hot fluid channel is a flue gas outlet; the inlet of the cold fluid channel is a water inlet, and the outlet of the cold fluid channel is a water outlet; and a PLC control system is also included.

[0011] In a preferred embodiment, the smoke inlet is connected to a smoke inlet pipe (4), and the smoke outlet is connected to a smoke outlet pipe (5). The smoke inlet pipe (4) is provided with a smoke bypass valve (6), a pressure sensor (19), and a smoke inlet temperature sensor (7) in sequence along the direction of smoke flow, and the smoke outlet pipe (5) is provided with a smoke outlet temperature sensor (8) and a smoke exhaust fan (9) in sequence along the direction of smoke flow.

[0012] In a preferred embodiment, a smoke branch pipe (10) is connected between the smoke inlet pipe (4) and the smoke outlet pipe (5); one end of the smoke branch pipe (10) is connected to the smoke inlet pipe (4) in front of the smoke bypass valve (6); the other end of the smoke branch pipe (10) is connected to the smoke outlet pipe (5) between the smoke outlet temperature sensor (8) and the smoke exhaust fan (9); and a smoke exhaust valve (11) and an air mixing valve (12) are sequentially arranged on the smoke branch pipe (10) along the direction of smoke flow.

[0013] In a preferred embodiment, the water inlet is connected to a water inlet pipe (13), and the water outlet is connected to a water outlet pipe (14).

[0014] In a preferred embodiment, a circulation pump (15) and a water inlet temperature sensor (16) are sequentially arranged on the water inlet pipe (13) along the water flow direction, and a water outlet temperature sensor (17) and an electromagnetic flowmeter (18) are sequentially arranged on the water outlet pipe (14) along the water flow direction.

[0015] In a preferred embodiment, the other end of the water inlet pipe (13) is connected to the boiler return pipe (2), and the other end of the water outlet pipe (14) is connected to the boiler return pipe (2).

[0016] In a preferred embodiment, the number of the circulation pumps (15) is two; the two circulation pumps (15) are arranged in parallel on the water inlet pipe (13).

[0017] The present invention also provides a method for recovering waste heat from high-temperature flue gas of an air cushion furnace, which uses the above-mentioned device for recovering waste heat from high-temperature flue gas of an air cushion furnace, and comprises the following steps:

[0018] Step 1: Before activating the heat exchanger (3), check that the manual valves of the circulating water pipeline are all in a normal open state, and start the circulating pump (15) to ensure that water circulates for 60 to 180 seconds before opening the flue gas bypass valve (6). After ensuring that the flue gas enters the heat exchanger, close the flue gas discharge valve (11) and the air mixing valve (12), and the flue gas enters the heat exchanger (3) to utilize the waste heat for energy saving;

[0019] Step 2: The water outlet temperature sensor (17) records the hot water temperature T1 after heating, the water inlet temperature sensor (16) records the water temperature T2 before heating, and the electromagnetic flowmeter (18) records the cumulative flow rate V of the hot water. The density ρ and specific heat capacity C of water are known, and the heat consumed by heating the water is calculated to be the waste heat that has actually been utilized and recovered;

[0020] m=ρ·V (1)

[0021] W=C·m·(T1-T2) (2)

[0022] but:

[0023] W=C·ρ·V·(T1-T2) (3)

[0024] in:

[0025] ρ—density, Kg / m3;

[0026] V—water flow, m3 / h;

[0027] C—specific heat capacity, J / (Kg·k);

[0028] m—hot water mass, Kg;

[0029] T1—water temperature after heating, °C;

[0030] T2—water temperature before heating, °C;

[0031] 3) Step three, set a flue gas temperature safety threshold T; when the temperature is too high, send an alarm signal to the PLC and force the air mixing valve (12) to open; when the outlet temperature is too high, it indicates that the heat exchange effect is different, and the equipment should be checked to prevent equipment failure and affect production.

[0032] In a preferred embodiment, the smoke inlet temperature sensor (7), the smoke outlet temperature sensor (8), the water inlet temperature sensor (16), the water outlet temperature sensor (17) and the electromagnetic flowmeter (18) respectively convert the detected analog signals into electrical signals, and then the PLC control system receives the electrical signals and compares the received electrical signals with preset parameters and then outputs a control signal to control the valve opening.

[0033] In a preferred embodiment, the PLC control system adjusts the flow of hot water and flue gas by controlling the speed and start and stop of the motor.

[0034] Compared with the prior art, the present invention has the following beneficial effects: the present invention mainly installs a set of heat exchangers between the original exhaust fan pipes to recover waste heat, the heat exchanger is connected to the nearest boiler return water pipe, the boiler return water is taken as the cold end section of the heat exchanger, and then the hot end returns to the boiler return water to achieve interconnection with the original system, thereby reducing the energy consumption of the heating boiler system. By effectively recovering the waste heat of the air cushion furnace flue gas for boiler return water heating, energy saving and consumption reduction are achieved, and the purpose of sustainable development is achieved. The transformation method provided by the present invention has a scientific principle, a simple and easy implementation plan, and a good waste heat recovery effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the structure of a preferred embodiment of the present invention;

[0036] Figure 2 A schematic diagram of structural connection of a preferred embodiment of the present invention;

[0037] Figure 3 A schematic diagram of the working process of a preferred embodiment of the present invention;

[0038] In the figure: smoke exhaust fan pipe 1, boiler return water pipe 2, heat exchanger 3, smoke inlet pipe 4, smoke outlet pipe 5, smoke bypass valve 6, smoke inlet temperature sensor 7, smoke outlet temperature sensor 8, smoke exhaust fan 9, smoke branch pipe 10, smoke exhaust valve 11, air mixing valve 12, water inlet pipe 13, water outlet pipe 14, circulating pump 15, water inlet temperature sensor 16, water outlet temperature sensor 17, electromagnetic flowmeter 18, pressure sensor 19. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0042] A device for recovering waste heat from high-temperature flue gas of an air cushion furnace, referring to Figure 1-3 , including the exhaust fan pipe 1 and the boiler return water pipe 2 of the heating section of the air cushion furnace, a heat exchange component is connected between the boiler return water pipe 2 and the exhaust fan pipe 1, and the heat exchange component includes a heat exchanger 3, the hot fluid channel of the heat exchanger 3 is connected to the exhaust fan pipe 1, and the cold fluid channel of the heat exchanger 3 is connected to the boiler return water pipe 2; the hot fluid channel of the heat exchanger is connected to the exhaust fan pipe, and the cold fluid channel of the heat exchanger is connected to the boiler return water pipe to heat the boiler return water. The heat exchanger acts on the heat energy of the high-temperature flue gas discharged from the heating section to the heating return water, and returns it to the heating water after heating, thereby reducing the energy consumption of boiler water heating.

[0043] The inlet of the hot fluid channel is a smoke inlet, and the outlet of the hot fluid channel is a smoke outlet; the inlet of the cold fluid channel is a water inlet, and the outlet of the cold fluid channel is a water outlet; and a PLC control system is also included.

[0044] The smoke inlet is connected to a smoke inlet pipe 4, and the smoke outlet is connected to a smoke outlet pipe 5. The smoke inlet pipe 4 is provided with a smoke bypass valve 6, a pressure sensor 19, and a smoke inlet temperature sensor 7 in sequence along the direction of smoke flow. The smoke outlet pipe 5 is provided with a smoke outlet temperature sensor 8 and a smoke exhaust fan 9 in sequence along the direction of smoke flow.

[0045] A smoke branch pipe 10 is connected between the smoke inlet pipe 4 and the smoke outlet pipe 5. One end of the smoke branch pipe 10 is connected to the smoke inlet pipe 4 in front of the smoke bypass valve 6, and the other end of the smoke branch pipe 10 is connected to the smoke outlet pipe 5 between the smoke outlet temperature sensor 8 and the smoke exhaust fan 9. A smoke exhaust valve 11 and an air mixing valve 12 are sequentially arranged on the smoke branch pipe 10 along the direction of smoke flow.

[0046] The flue gas bypass valve 6, the flue gas discharge valve 11 and the air mixing valve 12 are used to control the flue gas discharge. If the flue gas bypass valve 6 is opened, the flue gas discharge valve 11 is closed and the air mixing valve 12 is closed, it means that the flue gas passes through the heat exchanger 3. Otherwise, it means that the flue gas is discharged from the original flue gas pipeline without passing through the heat exchanger 3.

[0047] The water inlet is connected to a water inlet pipe 13 , and the water outlet is connected to a water outlet pipe 14 .

[0048] The water inlet pipe 13 is provided with a circulation pump 15 and a water inlet temperature sensor 16 in sequence along the water flow direction, and the water outlet pipe 14 is provided with a water outlet temperature sensor 17 and an electromagnetic flowmeter 18 in sequence along the water flow direction. The electromagnetic flowmeter 18 is used to measure the flow of conductive liquid and has a flow accumulation function. The electromagnetic flowmeter 18 controls the flow and boosts the pressure. It is used to measure and control the flow of water and is designed to have a flow rate of 80m 3 / h.

[0049] The other end of the water inlet pipe 13 is connected to the boiler return water pipe 2 , and the other end of the water outlet pipe 14 is connected to the boiler return water pipe 2 .

[0050] The number of the circulating pumps 15 is two; the two circulating pumps 15 are arranged in parallel on the water inlet pipe 13, one for use and one for standby, to ensure that one can operate when enabled, for conveying water from the boiler return pipe to the heat exchanger.

[0051] The present invention also provides a method for recovering waste heat from high-temperature flue gas of an air cushion furnace, which uses the above-mentioned device for recovering waste heat from high-temperature flue gas of an air cushion furnace, and comprises the following steps:

[0052] Step 1: Before activating the heat exchanger 3, check that the manual valves of the circulating water pipeline are all in the normal open state, and start the circulating pump 15 to ensure that there is water circulation for 60 to 180 seconds before opening the flue gas bypass valve 6. After ensuring that the flue gas enters the heat exchanger, close the flue gas discharge valve 11 and the air mixing valve 12, and all the flue gas enters the heat exchanger 3 for energy-saving waste heat utilization;

[0053] Step 2: The water outlet temperature sensor 17 records the hot water temperature T1 after heating, the water inlet temperature sensor 16 records the water temperature T2 before heating, and the electromagnetic flowmeter 18 records the cumulative flow rate V of the hot water. The density ρ and specific heat capacity C of water are known, and the heat consumed by heating the water is calculated to be the waste heat that has actually been utilized and recovered;

[0054] m=ρ·V 1

[0055] W=C·m·(T1-T2) (2)

[0056] but:

[0057] W=C·ρ·V·(T1-T2) (3)

[0058] in:

[0059] ρ—density, Kg / m3;

[0060] V—water flow, m3 / h;

[0061] C—specific heat capacity, J / (Kg·k);

[0062] m—hot water mass, Kg;

[0063] T1—water temperature after heating, °C;

[0064] T2—water temperature before heating, °C;

[0065] 3) Step three, set a flue gas temperature safety threshold T; when the temperature is too high, send an alarm signal to the PLC and force the air mixing valve 12 to open; when the outlet temperature is too high, it means that the heat exchange effect is different, and the equipment should be checked to prevent equipment failure and affect production.

[0066] After the flue gas inlet temperature sensor 7, the flue gas outlet temperature sensor 8, the water inlet temperature sensor 16, the water outlet temperature sensor 17 and the electromagnetic flowmeter 18 convert the detected analog signals into electrical signals, the PLC control system receives the electrical signals and compares the received electrical signals with the preset parameters, and then outputs the control signal to control the valve opening. The PLC control system adjusts the flow of hot water and flue gas by controlling the speed and start and stop of the motor. Specifically, the PLC control system adopts the Siemens S7-1200PLC control system, sets the program for control, sets the screen for monitoring, and can record and store the use data of the flue gas heat exchanger, which is convenient for statistical calculation of energy-saving effects; the electrical control equipment adopts ABB frequency converter, which is used in conjunction with Siemens PLC, mainly involving the monitoring and adjustment of parameters such as temperature, flow, pressure, etc. in the system to achieve automatic control and optimized operation.

[0067] Detection and signal conversion: ① Install temperature sensors at the inlet and outlet of the heat exchanger and the inlet and outlet of the hot water, and convert the temperature signal into an electrical signal; ② Install a pressure sensor 19 at the flue gas inlet pipe to detect the flue gas pressure difference and convert it into an electrical signal to monitor whether the pressure is normal; ③ Install an electromagnetic flowmeter at the hot water outlet to measure the hot water flow and convert it into an electrical signal as the basis for controlling the heat exchange amount.

[0068] Control unit: Receives signals transmitted by field detection components through PLC and compares them with preset parameters, performs calculations according to logical control, outputs control signals, and then adjusts related equipment, such as valve opening.

[0069] Control of actuators: ① Valve control: PLC controls the opening of the regulating valve according to the control signal, thereby adjusting the flow of hot water and flue gas to achieve the purpose of controlling heat exchange efficiency; ② By controlling the start and stop and speed of the motor, the delivery volume of hot water and flue gas is adjusted. Combined with the frequency converter, the equipment running speed is automatically adjusted according to the actual load to further achieve the purpose of energy saving and stable operation.

[0070] Safety protection and alarm: ① Edit the variable table to set the fault alarm signal. When the device has abnormal operation, such as valve or pump abnormality, an alarm signal will be output to prevent accidents caused by abnormal opening of the equipment. ② Set the flue gas temperature over-high alarm program to ensure that when the temperature exceeds the set upper limit threshold, the alarm is triggered to remind the operator.

Claims

1. A device for recovering waste heat from high-temperature flue gas of an air cushion furnace, comprising a flue gas exhaust fan duct (1) of a heating section of the air cushion furnace and a boiler return water duct (2), characterized in that: A heat exchange component is connected between the boiler return water pipe (2) and the smoke exhaust fan pipe (1), and the heat exchange component includes a heat exchanger (3), the hot fluid channel of the heat exchanger (3) is connected to the smoke exhaust fan pipe (1), and the cold fluid channel of the heat exchanger (3) is connected to the boiler return water pipe (2); the inlet of the hot fluid channel is the smoke inlet, and the outlet of the hot fluid channel is the smoke outlet; the inlet of the cold fluid channel is the water inlet, and the outlet of the cold fluid channel is the water outlet; and a PLC control system is also included.

2. The device for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 1, characterized in that: The smoke inlet is connected to a smoke inlet pipe (4), and the smoke outlet is connected to a smoke outlet pipe (5). The smoke inlet pipe (4) is provided with a smoke bypass valve (6), a pressure sensor (19), and a smoke inlet temperature sensor (7) in sequence along the direction of smoke flow. The smoke outlet pipe (5) is provided with a smoke outlet temperature sensor (8) and a smoke exhaust fan (9) in sequence along the direction of smoke flow.

3. The device for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 2, characterized in that: A smoke branch pipe (10) is connected between the smoke inlet pipe (4) and the smoke outlet pipe (5); one end of the smoke branch pipe (10) is connected to the smoke inlet pipe (4) in front of the smoke bypass valve (6); the other end of the smoke branch pipe (10) is connected to the smoke outlet pipe (5) between the smoke outlet temperature sensor (8) and the smoke exhaust fan (9); and a smoke exhaust valve (11) and an air mixing valve (12) are sequentially arranged on the smoke branch pipe (10) along the direction of smoke flow.

4. The device for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 1, characterized in that: The water inlet is connected to a water inlet pipe (13), and the water outlet is connected to a water outlet pipe (14).

5. The device for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 1, characterized in that: The water inlet pipe (13) is provided with a circulation pump (15) and a water inlet temperature sensor (16) in sequence along the water flow direction, and the water outlet pipe (14) is provided with a water outlet temperature sensor (17) and an electromagnetic flowmeter (18) in sequence along the water flow direction.

6. The device for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 5, characterized in that: The other end of the water inlet pipe (13) is connected to the boiler return water pipe (2), and the other end of the water outlet pipe (14) is connected to the boiler return water pipe (2).

7. The device for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 6, characterized in that: The number of the circulating pumps (15) is two; the two circulating pumps (15) are arranged in parallel with each other on the water inlet pipe (13).

8. A method for recovering waste heat from high-temperature flue gas of an air cushion furnace, characterized in that The device for recovering waste heat from high-temperature flue gas of an air cushion furnace as described in any one of claims 1 to 7 comprises the following steps: Step 1: Before activating the heat exchanger (3), check that the manual valves of the circulating water pipeline are all in a normal open state, and start the circulating pump (15) to ensure that water circulates for 60 to 180 seconds before opening the flue gas bypass valve (6). After ensuring that the flue gas enters the heat exchanger, close the flue gas discharge valve (11) and the air mixing valve (12), and the flue gas enters the heat exchanger (3) to utilize the waste heat for energy saving; Step 2: The water outlet temperature sensor (17) records the hot water temperature T1 after heating, the water inlet temperature sensor (16) records the water temperature T2 before heating, and the electromagnetic flowmeter (18) records the cumulative flow rate V of the hot water. The density ρ and specific heat capacity C of water are known, and the heat consumed by heating the water is calculated to be the waste heat that has actually been utilized and recovered; m=ρ·V (1) W=C·m·(T1-T2) (2) but: W=C·ρ·V·(T1-T2) (3) in: ρ—density, Kg / m3; V—water flow, m3 / h; C—specific heat capacity, J / (Kg·k); m—hot water mass, Kg; T1—water temperature after heating, °C; T2—water temperature before heating, °C; 3) Step three, set a flue gas temperature safety threshold T; when the temperature is too high, send an alarm signal to the PLC and force the air mixing valve (12) to open; when the outlet temperature is too high, it indicates that the heat exchange effect is different, and the equipment should be checked to prevent equipment failure and affect production.

9. The method for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 8, characterized in that: The smoke inlet temperature sensor (7), the smoke outlet temperature sensor (8), the water inlet temperature sensor (16), the water outlet temperature sensor (17) and the electromagnetic flowmeter (18) respectively convert the detected analog signals into electrical signals, and the PLC control system receives the electrical signals and compares the received electrical signals with preset parameters, and then outputs a control signal to control the valve opening.

10. The method for recovering waste heat from high-temperature flue gas of an air cushion furnace according to claim 8, characterized in that: The PLC control system adjusts the flow of hot water and flue gas by controlling the speed and start and stop of the motor.

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