Anode furnace flue gas denitration heating process

Abstract

The invention discloses a flue gas denitration heating process for an anode furnace, and belongs to the field of flue gas denitration. A flue gas cooling device, a high-temperature bag-type dust collector, a dust collection fan, a desulfurization system, a 1 # gas-gas heat exchanger, a 2 # gas-gas heat exchanger, a denitration reactor and a relay fan are arranged in the process. The heat carried by the anode furnace flue gas and the heat carried by the denitrated tail gas are fully utilized, the heat is transferred to the desulfurized flue gas through the 1 # gas-gas heat exchanger and the 2 # gas-gas heat exchanger for heating, and the flue gas heating energy consumption in the low-temperature SCR denitration process of the anode furnace flue gas is reduced to a great extent. Compared with conventional anode furnace flue gas low-temperature SCR denitration flue gas temperature rising, the flue gas temperature rising energy consumption can be reduced by about 90% or above.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas denitration, and in particular to a flue gas denitration heating process for an anode furnace. Background Art

[0002] SCR (Selective Catalytic Reduction) denitrification technology refers to the process in which a reducing agent (anhydrous ammonia, aqueous ammonia or urea) reacts with NOx in flue gas to generate harmless nitrogen and water in the presence of a catalyst, thereby removing NOx from the flue gas.

[0003] The catalyst used in SCR denitrification requires flue gas: dust content ≤ 10mg / Nm 3 , SO2≤50mg / Nm 3 Therefore, the flue gas needs to be pre-treated with dust removal and desulfurization before the denitrification reaction.

[0004] Since the catalyst used in SCR denitrification requires a flue gas temperature of 220-320°C (median 270°C), and the flue gas temperature after wet desulfurization is generally 50-60°C, in order to meet the needs of SCR denitrification, the low-temperature (50-60°C) flue gas after desulfurization must be heated before the denitrification reaction.

[0005] In the traditional SCR denitrification process, the flue gas heating method generally used is to burn natural gas to heat the pre-denitrification flue gas. This method has the disadvantages of high energy consumption and high operating costs. Summary of the invention

[0006] In order to solve the above technical problems, the present invention designs a process for heating up the flue gas denitrification of an anode furnace.

[0007] The present invention adopts the following technical solution: A process for heating up flue gas denitration of an anode furnace, wherein a flue gas cooling device, a high-temperature bag filter, a dust collecting fan, a wet desulfurization system, a No. 1 gas-gas heat exchanger, a No. 2 gas-gas heat exchanger, an SCR denitration reactor and a relay fan are provided in the process flow, and the steps of the heating process are as follows: S1: After the flue gas at the outlet of the anode furnace is cooled to 400-450℃ by the flue gas cooling device, it enters the high-temperature bag filter to remove dust in the flue gas; S2: The flue gas after dust removal is transported by the dust collecting fan and then passes through the 2# gas-to-gas heat exchanger to remove part of the heat, so as to reduce the heat entering the desulfurization tower; S3: The anode furnace flue gas after heat exchange and cooling in the 2# gas-gas heat exchanger enters the wet desulfurization system for flue gas desulfurization; S4: The desulfurized tail gas at 50-60℃ after desulfurization is first preheated to above 200℃ by 1# gas-gas heat exchanger; S5: The preheated flue gas enters the 2# gas-gas heat exchanger for heat exchange and temperature rises to 250°C. When the heat exchange is insufficient and the flue gas temperature cannot reach 250°C, the natural gas burner on the outlet pipe of the 2# gas-gas heat exchanger is started for supplementary heat to raise the temperature to 250°C. S6: The flue gas after temperature confirmation or supplementary heating enters the low-temperature SCR denitration reactor for denitration treatment; S7: The exhaust gas after low-temperature SCR denitrification enters the 1# gas-to-gas heat exchanger for heat exchange and cooling, and is then sent to the chimney by the relay fan to meet emission standards.

[0008] Preferably, in step S1, the dust content of the flue gas at the bag outlet is ≤30mg / Nm 3 .

[0009] Preferably, in step S3, the SO2 content in the flue gas at the desulfurization outlet is ≤50mg / Nm 3 .

[0010] Preferably, in step S4, the temperature after heating is not lower than the dew point of the flue gas of the anode furnace after desulfurization, so as to avoid the condensation of the flue gas at the outlet of the high-temperature bag filter on the heat exchange surface to form dilute acid and corrode the heat exchange equipment due to the excessively low local temperature of the heat exchange contact surface during the heat exchange between the 2# gas-gas heat exchanger and the flue gas at the outlet of the high-temperature bag filter.

[0011] Preferably, the heat exchange in the 1# gas-gas heat exchanger is to heat the denitrified tail gas with a temperature of 250°C after denitrification with the desulfurized tail gas with a temperature of 50-60°C at the outlet of the desulfurization tower, so as to increase the temperature of the flue gas after desulfurization and reduce the temperature of the flue gas after denitrification. The flue gas after desulfurization absorbs heat in the 1# gas-gas heat exchanger, saving the energy consumption required for heating; the flue gas at the outlet of the denitrification reactor releases heat in the 1# gas-gas heat exchanger, reducing its own temperature and avoiding damage to the emission chimney.

[0012] Preferably, the heat exchange in the 2# gas-gas heat exchanger is to exchange the high-temperature flue gas at the outlet of the dust collecting fan with the desulfurized tail gas preheated by the 1# gas-gas heat exchanger, and the flue gas after desulfurization is heated for a second time, while cooling the flue gas after dust removal. The desulfurized tail gas absorbs heat in the 2# gas-gas heat exchanger, saving the energy consumption required for heating; the flue gas at the outlet of the dust collecting fan releases heat in the 2# gas-gas heat exchanger, reducing the evaporation of water vapor in the desulfurization process; the reduction of water content in the tail gas after desulfurization also reduces the energy consumption required for heating the desulfurized tail gas.

[0013] Preferably, an instrumentation control valve is provided on the pipeline between the dust collecting fan outlet and the desulfurization tower inlet of the wet desulfurization system. The flue gas volume of the high-temperature flue gas at the dust collecting fan outlet entering the 2# gas-gas heat exchanger can be adjusted by adjusting the opening of the instrumentation control valve. When the inlet flue gas temperature of the SCR denitration reactor is lower than the required temperature of the SCR denitration reaction (250°C), the valve is closed to increase the amount of high-temperature flue gas entering the 2# gas-gas heat exchanger; when the inlet flue gas temperature of the SCR denitration reactor is higher than the required temperature of the SCR denitration reaction (250°C), the valve is opened to reduce the amount of high-temperature flue gas entering the 2# gas-gas heat exchanger.

[0014] The control method of the inlet flue gas temperature of the SCR denitrification reactor is as follows: ① When the inlet flue gas temperature of the SCR denitrification reactor is lower than the required temperature of the denitrification reaction (250℃), first close the instrumentation and control valve on the pipeline between the dust collection fan outlet and the desulfurization tower inlet to increase the amount of high-temperature flue gas entering the 2# gas-to-gas heat exchanger; when the instrumentation and control valve on the pipeline between the dust collection fan outlet and the desulfurization tower inlet is fully closed, and the inlet flue gas temperature of the denitrification reactor is still lower than the required temperature of the denitrification reaction (250℃), open the natural gas burner on the cold side outlet pipeline of the 2# gas-to-gas heat exchanger to supplement heat, and heat the inlet flue gas of the denitrification reactor to the required temperature of the denitrification reaction (250℃).

[0015] ② When the inlet flue gas temperature of the SCR denitration reactor is higher than the required temperature of the denitration reaction (250℃), first turn off the natural gas heating burner on the cold side outlet pipe of the 2# gas-to-gas heat exchanger. When the natural gas heating burner is completely closed and the inlet flue gas temperature of the denitration reactor is still higher than the required temperature of the denitration reaction (250℃), open the instrumentation and control valve on the pipeline from the dust collection fan outlet to the desulfurization tower inlet to reduce the amount of high-temperature flue gas entering the 2# gas-to-gas heat exchanger until the inlet flue gas temperature of the SCR denitration reactor meets the required temperature of the denitration reaction (250℃).

[0016] The beneficial effects of the present invention are: (1) By using a high-temperature bag filter as the dust collection equipment + wet desulfurization system, the dust removal efficiency in the anode furnace flue gas is improved, ensuring that the dust at the inlet of the SCR denitrification reactor is ≤30mg / Nm 3 the achievement of its objectives; (2) By using a wet desulfurization system to desulfurize the anode furnace flue gas, the SO2 inlet of the SCR denitrification reactor is guaranteed to be ≤50mg / Nm 3 the achievement of its objectives; (3) In the No. 1 gas-gas heat exchanger, the high-temperature flue gas at the outlet of the SCR denitration reactor is used as a heat source to preheat the flue gas at the outlet of the desulfurization tower, thereby eliminating the damage to the subsequent chimney caused by the high temperature of the flue gas at the outlet of the SCR denitration reactor and obtaining the heat required in the flue gas preheating process; and because the SO2 content of the flue gas at the outlet of the SCR denitration reactor is low and the dew point temperature is high, the dew point corrosion caused by the local excessively low temperature on the heat exchange surface of the No. 1 gas-gas heat exchanger is effectively eliminated; (4) In the 2# gas-gas heat exchanger, the high-temperature flue gas at the outlet of the dust collecting fan is used as the heat source to further heat the desulfurized tail gas preheated by the 1# gas-gas heat exchanger. By recovering the heat brought by the high-temperature flue gas at the outlet of the dust collecting fan, heat is provided for further heating of the desulfurized tail gas preheated by the 1# gas-gas heat exchanger. The desulfurized tail gas preheated by the 1# gas-gas heat exchanger is used as the cold source to cool the high-temperature flue gas at the outlet of the dust collecting fan, thereby reducing the heat brought into the desulfurization system by the flue gas at the outlet of the dust collecting fan, effectively inhibiting the evaporation of water vapor during the desulfurization process, and reducing the water content of the flue gas after desulfurization. This method is conducive to raising the dew point of the tail gas after desulfurization and avoiding dew point corrosion, and reducing the total amount of flue gas at the outlet of the desulfurization, which is conducive to reducing the heat required for flue gas heating. (5) A natural gas burner is installed on the inlet flue gas pipeline of the SCR denitration reactor. When the system heat source is insufficient and the inlet flue gas temperature of the SCR denitration reactor cannot be raised to 250°C, the natural gas burner can be turned on to supplement the heat of the inlet flue gas of the SCR denitration reactor, thus ensuring the reliable operation of the temperature-raising system, i.e., the SCR denitration reaction device, under all working conditions; (6) By installing an instrumentation control valve on the pipeline between the dust collecting fan outlet and the desulfurization tower inlet, the flue gas temperature entering the SCR denitrification reactor can be automatically controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the process of the present invention; In the figure: 1- flue gas cooling device, 2- high temperature bag filter, 3- dust collecting fan, 4- wet desulfurization system, 5- 1# gas-gas heat exchanger, 6- 2# gas-gas heat exchanger, 7- SCR denitrification reactor, 8- natural gas burner, 9- instrumentation control valve, 10- relay fan, 11- high temperature bag filter inlet thermometer, 12- desulfurization flue gas 1# gas-gas heat exchanger outlet thermometer, 13- SCR denitrification reactor inlet flue gas thermometer. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example: Figure 1As shown: a denitrification and heating process of flue gas from an anode furnace, in which a flue gas cooling device 1, a high-temperature bag filter 2, a dust collecting fan 3, a wet desulfurization system 4, a 1# gas-gas heat exchanger 5, a 2# gas-gas heat exchanger 6, an SCR denitrification reactor 7 and a relay fan 10 are arranged.

[0019] When this process is used, the flue gas from the anode furnace is cooled to 400°C by the flue gas cooling device 1 and then enters the high-temperature bag filter 2. The temperature is displayed by the inlet thermometer 11 of the high-temperature bag filter; In the high-temperature bag filter 2, the dust in the anode furnace flue gas is collected. After dust removal, the dust content in the flue gas at the outlet of the high-temperature bag filter 2 is ≤30mg / Nm 3 ; The outlet flue gas of the high-temperature bag filter 2 enters the 2# gas-gas heat exchanger 6 for heat exchange under the promotion of the dust collecting fan 3. In the 2# gas-gas heat exchanger 6, the high-temperature flue gas at the outlet of the dust collecting fan transfers part of its own heat to the desulfurized tail gas at the outlet of the 1# gas-gas heat exchanger 5, raising the flue gas temperature of the desulfurized tail gas to about 250°C. The temperature is displayed by the thermometer 12 at the outlet of the desulfurized flue gas 1# gas-gas heat exchanger. At the same time, the temperature of the flue gas itself at the outlet of the dust collecting fan 3 is reduced.

[0020] In order to accurately control the inlet flue gas temperature of the SCR denitrification reactor 7, the control system automatically adjusts the opening of the instrumentation control valve 9 on the pipeline from the outlet of the dust collection fan 3 to the inlet of the wet desulfurization system 4 according to the temperature display of the inlet flue gas thermometer 13 of the SCR denitrification reactor, so as to achieve the purpose of controlling the inlet flue gas temperature of the SCR denitrification reactor 7 at 250°C.

[0021] The anode furnace flue gas cooled by the 2# gas-gas heat exchanger 6 enters the desulfurization system 4 for wet spray desulfurization. In the wet desulfurization system 4, the anode furnace flue gas has its temperature reduced and SO2 removed. The SO2 content of the desulfurized tail gas at the outlet of the wet desulfurization system 4 is ≤50mg / Nm 3 .

[0022] After being discharged from the wet desulfurization system 4, the desulfurized tail gas enters the 1# gas-gas heat exchanger. In the 1# gas-gas heat exchanger 5, the desulfurized tail gas is heat-exchanged with the denitrified tail gas at the outlet of the SCR denitrification reactor 7. The low-temperature desulfurized tail gas absorbs the heat of the high-temperature denitrified tail gas, and the temperature rises to about 200°C, achieving waste heat heating. The high-temperature denitrified tail gas releases heat and reduces its own temperature.

[0023] The desulfurized tail gas at the outlet of the 1# gas-gas heat exchanger 5 then enters the 2# gas-gas heat exchanger 6, and the temperature is further increased to about 250°C due to the high temperature flue gas at the outlet of the dust collecting fan 3.

[0024] When the temperature of the desulfurized tail gas at the outlet of the 2# gas-gas heat exchanger 6 is lower than 250°C, close the instrument control valve 9. When the instrument control valve 9 is fully closed, if the temperature of the flue gas thermometer 13 at the inlet of the SCR denitrification reactor is still lower than 250°C, open the natural gas burner 8 for supplementary heat and temperature increase.

[0025] After the inlet flue gas temperature of the SCR denitration reactor 7 reaches 250° C., it enters the SCR denitration reactor 7 for denitration reaction.

[0026] In the SCR denitration reactor 7, the desulfurized tail gas undergoes a denitration reaction to remove nitrogen oxides in the flue gas.

[0027] The denitrification tail gas discharged from the SCR denitrification reactor 7 enters the 1# gas-gas heat exchanger 5 for heat exchange, transferring part of its own heat to the desulfurization tail gas at the outlet of the wet desulfurization system 4, thereby reducing its own temperature.

[0028] After the denitrification tail gas is cooled in the 1# gas-to-gas heat exchanger 5, it is relayed by the fan 10 and discharged through the tail gas chimney in compliance with the emission standards.

[0029] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A process for heating up flue gas denitration of anode furnace, characterized in that: The process flow is equipped with a flue gas cooling device, a high-temperature bag filter, a dust collecting fan, a wet desulfurization system, a 1# gas-gas heat exchanger, a 2# gas-gas heat exchanger, an SCR denitrification reactor and a relay fan. The steps of the heating process are as follows: S1: After the flue gas at the outlet of the anode furnace is cooled to 400-450℃ by the flue gas cooling device, it enters the high-temperature bag filter to remove dust in the flue gas; S2: The flue gas after dust removal is transported by the dust collecting fan and then passes through the 2# gas-to-gas heat exchanger to remove part of the heat, so as to reduce the heat entering the desulfurization tower; S3: The anode furnace flue gas after heat exchange and cooling in the 2# gas-gas heat exchanger enters the wet desulfurization system for flue gas desulfurization; S4: The desulfurized tail gas at 50-60℃ after desulfurization is first preheated to above 200℃ by 1# gas-gas heat exchanger; S5: The preheated flue gas enters the 2# gas-gas heat exchanger for heat exchange and temperature rises to 250°C. When the heat exchange is insufficient and the flue gas temperature cannot reach 250°C, the natural gas burner on the outlet pipe of the 2# gas-gas heat exchanger is started for supplementary heat to raise the temperature to 250°C. S6: The flue gas after temperature confirmation or supplementary heating enters the low-temperature SCR denitration reactor for denitration treatment; S7: The exhaust gas after low-temperature SCR denitrification enters the 1# gas-to-gas heat exchanger for heat exchange and cooling, and is then sent to the chimney by the relay fan to meet emission standards.

2. The anode furnace flue gas denitrification and heating process according to claim 1 is characterized in that: In step S1, the dust content of the flue gas at the bag outlet is ≤30mg / Nm 3 .

3. The anode furnace flue gas denitrification and heating process according to claim 1 is characterized in that: In step S3, the SO2 content in the flue gas at the desulfurization outlet is ≤50mg / Nm 3 .

4. The anode furnace flue gas denitrification and heating process according to claim 1 is characterized in that: In step S4, the temperature after heating is not lower than the dew point of the anode furnace flue gas after desulfurization.

5. The anode furnace flue gas denitrification and heating process according to claim 1 is characterized in that: The heat exchange in the 1# gas-to-gas heat exchanger is to heat the denitrified tail gas with a temperature of 250°C after denitrification with the desulfurized tail gas with an outlet temperature of 50-60°C of the desulfurization tower, thereby heating up the flue gas after desulfurization and cooling down the flue gas after denitrification.

6. The anode furnace flue gas denitrification and heating process according to claim 1 is characterized in that: The heat exchange in the 2# gas-to-gas heat exchanger is to exchange the high-temperature flue gas at the dust collecting fan outlet with the desulfurized tail gas preheated by the 1# gas-to-gas heat exchanger, thereby heating the desulfurized flue gas for a second time and cooling the dust-removed flue gas.

7. The anode furnace flue gas denitrification and heating process according to claim 1 is characterized in that: An instrumentation control valve is provided on the pipeline from the dust collecting fan outlet to the desulfurization tower inlet of the wet desulfurization system. The opening of the instrumentation control valve is adjusted to adjust the volume of the high-temperature flue gas after dust collection entering the 2# gas-to-gas heat exchanger.

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