Incineration flue gas SCR denitration system and control method
By introducing the adjustment structure of the main flue and bypass flue in the SCR denitrification system, combining NOx and temperature detection, the pyrolysis of ammonium bisulfate and SCR reaction are achieved in a coordinated manner, which solves the problem of hydrogen sulfate during solid waste incineration. The efficiency reduction and NOx fluctuation caused by ammonium scaling reduce operation and construction costs and improve equipment flexibility and reliability.
Patent Information
- Application Number
- CN202411673863.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-21
- Publication Date
- 2025-01-10
AI Technical Summary
During the incineration of solid waste hazardous waste, the SCR denitrification device has reduced catalyst efficiency due to ammonium bisulfate scaling, and cannot respond to fluctuations in NOx concentration immediately, resulting in high equipment operation costs, increased construction costs and frequent shutdowns and cleaning.
Design a SCR denitrification system including main flue and bypass flue. The main flue valve and bypass flue valve are adjusted through NOx concentration detection sensor and temperature detection sensor, control the flue gas flow and temperature, and realize hydrogen sulfate. The synergistic process of ammonium pyrolysis and SCR reaction reduces heat source consumption and catalyst loss.
It effectively reduces the heat source consumption and catalyst use loss of the SCR device, reduces operation and construction costs, improves the flexibility and reliability of the equipment, and avoids excessive shutdown and cleaning of equipment caused by high temperatures.
Smart Images
Figure CN119281110A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of flue gas denitrification, and in particular to an incineration flue gas SCR denitrification system and a control method. Background Art
[0002] At present, the process flow of solid waste and hazardous waste incineration is generally one-time combustion in a rotary kiln, secondary combustion in a secondary combustion chamber, waste heat recovery from waste heat boiler + SNCR denitrification, rapid cooling of flue gas in a quench tower, deacidification in a dry deacidification device, particulate matter removal by a bag filter, deacidification in a washing tower, particulate matter removal by a wet electrostatic precipitator, denitrification by an SCR device, and chimney emissions. Since solid waste and hazardous waste contain a variety of pollution sources, it is necessary to perform desulfurization, denitrification, dust removal, heavy metal removal, and dioxin removal (reducing dioxin generation and removing generated dioxins) on the flue gas after incineration. There are two processes for flue gas desulfurization: dry deacidification and wet desulfurization. In order to ensure that flue gas emissions meet standards, flue gas desulfurization treatment often adopts dry + wet coordinated treatment.
[0003] There are two types of flue gas denitrification processes after desulfurization: SNCR (selective non-catalytic reduction denitrification technology) and SCR (selective catalytic reduction denitrification technology). SNCR is to spray ammonia source under the condition of flue gas temperature of 850-1050℃ in the boiler, so that NOx in the flue gas reacts with NH3 to generate N2 and H2O, and the denitrification efficiency is 40-60%. SCR is to spray ammonia source under the condition of flue gas temperature of 180-400℃ in the denitrification device, so that NOx in the flue gas reacts with NH3 to generate N2 and H2O, and the denitrification efficiency is 70-95%.
[0004] At present, most solid waste and hazardous waste incineration devices have SNCR denitrification for flue gas denitrification. As NOx emission standards become more stringent, more and more solid waste and hazardous waste incineration devices are equipped with SCR denitrification devices, that is, SNCR+SCR multi-stage denitrification technology.
[0005] Taking into account the operation cost, construction cost, reliability, stability and other factors, the catalyst is mostly selected as medium-temperature or low-temperature SCR catalyst. The temperature of flue gas after wet desulfurization is 50-80℃, which cannot reach the activation reaction temperature of SCR catalyst. Therefore, the current solid waste and hazardous waste incineration flue gas SCR devices are designed with flue gas heating devices, such as GGH heat exchange and external heat source heating. The external heat source heating can use high-temperature steam or (and) burner heating.
[0006] Therefore, the SCR device includes the following parts: GGH, ascending flue, and reactor. After desulfurization, the original flue gas first enters the GGH (heat exchanger) to exchange heat with the high-temperature flue gas after SCR denitrification, and the original flue gas is heated to 120-160°C; then the original flue gas enters the ascending flue, and is heated again to 180-300°C through a steam heater or a natural gas burner. After the flue gas temperature reaches the catalyst activation temperature, it enters the reactor. In the ascending flue, an ammonia source is sprayed into the original flue gas, and NH3 and the flue gas are mixed in the ascending flue. The mixed flue gas undergoes an SCR reaction on the catalyst in the reactor. The high-temperature flue gas after denitrification passes through the GGH and exchanges heat with the original flue gas. The clean flue gas after cooling is discharged from the outlet of the SCR device. The ammonia source in the SCR device is added in excess to ensure the NOx removal efficiency.
[0007] During the incineration of solid waste and hazardous waste, most of the sulfur in the waste is converted into SO2, and 0.5-1.5% will be oxidized to SO3. The catalyst of the SCR device can not only denitrify, but also catalyze the conversion of SO2 into SO3 under high temperature conditions. Under the action of high-temperature catalysts, 1-2% of SO2 will be converted into SO3. The NH3 injected into the SCR device will generate ammonium bisulfate with excess SO3, and it will show strong adhesion. Ammonium bisulfate will adhere to fly ash and deposit on the surface of the catalyst to form scale, block the micropores of the SCR catalyst and even the gas path, causing the catalyst denitrification efficiency to decrease or even deactivate, and increase the flue gas pressure drop. In order to deal with the catalyst fouling and blockage caused by ammonium bisulfate, the flue gas temperature needs to be raised to 350℃ and maintained for 24-48h to fully decompose the ammonium bisulfate. Heating the flue gas inside the SCR device to 350℃ requires a large amount of heat source, which will cause the outer surface of the SCR device to overheat. After the flue gas leaves the SCR device, the ultra-high temperature will not only increase the flue gas volume, but may also exceed the upper temperature limit of the flue, induced draft fan, and chimney. In this case, the system needs to be shut down for manual cleaning.
[0008] The increase in flue gas temperature leads to a larger flue gas volume, which will increase the operating load of the induced draft fan and the operating cost of the system. At the same time, it will also increase the upper limit of the SCR device, outlet flue, induced draft fan, and chimney processing, resulting in the selection of equipment according to a larger flue gas volume, and higher project construction costs. In addition, the high temperature of flue gas places higher requirements on the insulation and anti-corrosion layers of the flue and equipment, which will also lead to an increase in construction costs. In operation, solid waste and hazardous waste materials are volatile, and the NOx concentration in the flue gas after incineration is unstable. It may be low for a long time, or it may exceed the standard for a short time; after incineration, all flue gases are heated and denitrated by the SCR device, and the operating cost of the device is high.
[0009] Therefore, some devices are equipped with a bypass flue switch valve. When the NOx in the flue gas meets the standard, it can be discharged from the bypass flue without SCR denitrification treatment. However, since the catalyst in the main path of the SCR device is in a cold state at this time, if the NOx concentration increases instantaneously, the SCR device cannot be put into use immediately, and the rapid temperature increase will cause the catalyst to exceed the temperature rise gradient, and the catalyst will crack. Summary of the invention
[0010] The present application provides an incineration flue gas SCR denitrification system and control method, which can be used to solve the technical problem that the NOx concentration increases instantaneously and the SCR device cannot be put into use immediately.
[0011] The present application provides an incineration flue gas SCR denitrification system, the system comprising:
[0012] The flue gas SCR denitrification system includes the main flue, bypass flue and GGH (gas-to-gas heat exchanger);
[0013] Among them, one side of the GGH (gas-to-gas heat exchanger) is the high-temperature section, which includes a high-temperature inlet and a high-temperature outlet;
[0014] The other side of the GGH is the low-temperature section, which includes a low-temperature inlet and a low-temperature outlet. The raw flue gas passes through the low-temperature section, and the clean flue gas passes through the high-temperature section. Heat exchange is carried out in the GGH.
[0015] The main flue inlet is connected to the low-temperature inlet of GGH, and the main flue outlet is connected to the high-temperature outlet of GGH;
[0016] The input port of the bypass flue is connected to the original flue gas inlet of the SCR device, and the outlet of the bypass flue is connected to the clean flue gas outlet of the SCR device; the bypass flue is respectively connected before the low-temperature section of GGH and after the high-temperature section of GGH.
[0017] A main flue valve is installed at the main flue;
[0018] The bypass flue is provided with a bypass flue valve; the bypass flue is used for flue gas bypass circulation, bypassing the GGH, the ascending flue, and the reactor;
[0019] The main flue valve and the bypass flue valve are both regulating valves, and the opening range is 0-100%.
[0020] Furthermore, the main flue includes an ascending flue and a reactor;
[0021] The flue gas in the ascending flue is arranged from bottom to top in sequence with a flue gas heating device, an ammonium bisulfate pyrolysis heating device, an ammonia source dosing device, and an ammonia source distribution device; the flue gas heating device is used to heat the normal operating flue gas to the catalyst activity temperature range of 180-340°C; the ammonium bisulfate pyrolysis heating device is used to heat the ammonium bisulfate pyrolysis flue gas to 350°C.
[0022] A flue gas uniform distribution device, a catalyst and a catalyst cleaning device are respectively arranged from top to bottom in the reactor.
[0023] Furthermore, the main flue valve includes one or two;
[0024] Assuming that two main flue valves are set, one of the first main point and the second main point can be selected for setting;
[0025] The first point includes the original flue gas inlet on the GGH, the connection between the GGH and the ascending flue, the inside of the ascending flue, and between the ascending flue and the reactor; the second main route point includes the connection between the reactor outlet and the GGH, and the clean flue gas outlet of the GGH;
[0026] Assuming that a main flue valve is set, it can be set at any of the 6 points including the first main point and the second main point.
[0027] Furthermore, the system is also provided with a NOx concentration detection sensor; the NOx concentration detection sensor is arranged at the inlet of the flue gas SCR denitrification system and the outlet of the flue gas SCR denitrification system or the chimney; wherein the inlet of the flue gas SCR denitrification system is used to monitor the inlet NOx concentration; the outlet of the flue gas SCR denitrification system is used to monitor the outlet NOx concentration.
[0028] Furthermore, the system is also provided with a temperature detection sensor;
[0029] Temperature detection sensors can be set at any of the following locations as needed: GGH low-temperature inlet, GGH low-temperature outlet, ammonia source dosing device outlet, before the access point of the flue gas heating device of the ascending flue, after the access point of the flue gas heating device of the ascending flue, before each layer of catalyst in the reactor, reactor outlet, GGH high-temperature outlet, and in the bypass flue;
[0030] Among them, a temperature detection sensor must be installed before the uppermost catalyst in the reactor.
[0031] Furthermore, the system is also provided with a pressure detection sensor;
[0032] The pressure detection sensor can be set at any of the following positions as needed: GGH low-temperature inlet, GGH low-temperature outlet, ammonia source dosing device outlet, in front of the flue gas heating device access point of the ascending flue, after the flue gas heating device access point of the ascending flue, in front of each layer of the reactor catalyst, reactor outlet, GGH high-temperature outlet, bypass flue;
[0033] Corresponding pressure detection sensors are also provided before the top catalyst of the reactor and at the reactor outlet;
[0034] The total catalyst pressure drop is obtained by subtracting the pressure before the top catalyst in the reactor and at the reactor outlet to determine the catalyst blockage condition.
[0035] Furthermore, the system is also provided with a flow detection sensor;
[0036] The flow detection sensor is set at any of the following positions as required: GGH low-temperature inlet or GGH high-temperature outlet, bypass flue.
[0037] Furthermore, the main flue is also provided with a main inspection valve;
[0038] Close the main flue valve and main inspection valve, and open the bypass flue valve to 100%, so that the SCR device can be inspected without stopping the system;
[0039] The main line inspection valve is fully open when not in the inspection state;
[0040] The main line inspection valve is a regulating valve or a switching valve.
[0041] The present application also provides an incineration flue gas SCR denitrification system and a control method, which is used to control the system provided in the present application. When the operating conditions change, as the NOx concentration changes, the adjustment method of the main flue valve and the bypass flue valve is shown in Table 1:
[0042] Table 1: Changes of various parameters after NOx concentration changes
[0043]
[0044] Under the condition of ensuring that NOx emission meets the standard, when the NOx concentration in the flue gas increases or decreases, the main flue valve and the bypass flue valve opening are adjusted to control different flue gas volumes to pass through the main flue for heating and denitrification and direct discharge through the bypass flue; under the condition of ensuring that the inlet temperature of the SCR reactor is stable, as the flue gas volume increases or decreases, the heat source consumption of the flue gas heating device increases or decreases accordingly;
[0045] When the catalyst is clogged by ammonium bisulfate fouling, a small amount of flue gas is controlled to pass through the main path of the SCR device by adjusting the opening of the main flue valve and the bypass flue valve while ensuring that NOx emissions meet the standards; the main flue gas of the SCR device is heated to 350°C through a heating device or an ammonium bisulfate pyrolysis heating device to achieve efficient pyrolysis of ammonium bisulfate, while removing NOx through the SCR reaction; after pyrolysis of ammonium bisulfate, the flue gas leaves the SCR device, mixes with the bypass flue gas, and is discharged through the induced draft fan and chimney. When a small amount of flue gas is heated to the pyrolysis temperature of 350°C, less heat source is consumed.
[0046] Furthermore, the main valve opening and the bypass valve opening are adjusted according to the NOx concentration, and the adjustment range is shown in the following table:
[0047]
[0048]
[0049] The main valve opening and the bypass valve opening are adjusted according to the outlet NOx concentration and the inlet NOx concentration so that the outlet NOx concentration meets the emission standards.
[0050] The present invention reduces the main flue gas volume, can reduce the heat source consumption for flue gas heating, catalyst loss, etc., and save the operating cost of the device; low main flue gas volume will also reduce the total exhaust flue gas temperature, the lower the working flue gas volume will be, and the construction cost of devices such as induced draft fans and chimneys will also be lower.
[0051] Since the amount of main flue gas is small, the flue gas temperature is relatively low after mixing with the bypass flue gas, and the operating flue gas volume is also relatively low. The low-temperature flue gas is not easy to exceed the upper limit of the operating temperature of the flue, induced draft fan and chimney, and can also effectively reduce the construction cost of the flue, induced draft fan and chimney, while saving the operating cost of the equipment; the low flue gas temperature will also have lower requirements for the insulation and anti-corrosion layer of the flue and equipment, which can reduce the insulation and anti-corrosion construction cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0052] Figure 1 This is a schematic diagram of the solid waste and hazardous waste incineration process flow chart of the prior art;
[0053] Figure 2 A schematic diagram of the SCR process flow provided in the embodiment of the present application;
[0054] Figure 3 A schematic diagram of the SCR process flow provided for the first embodiment;
[0055] Figure 4 A schematic diagram of the SCR process flow provided for the second embodiment. DETAILED DESCRIPTION
[0056] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.
[0057] The flue gas SCR denitrification system includes the main flue, bypass flue and GGH (gas-to-gas heat exchanger);
[0058] Among them, one side of the GGH (gas-to-gas heat exchanger) is the high-temperature section, which includes a high-temperature inlet and a high-temperature outlet;
[0059] The other side of the GGH is the low-temperature section, which includes a low-temperature inlet and a low-temperature outlet. The raw flue gas passes through the low-temperature section, and the clean flue gas passes through the high-temperature section. Heat exchange is carried out in the GGH.
[0060] The main flue inlet is connected to the low-temperature inlet of GGH, and the main flue outlet is connected to the high-temperature outlet of GGH;
[0061] The input port of the bypass flue is connected to the original flue gas inlet, and the outlet of the bypass flue is connected to the clean flue gas outlet; the bypass flue is respectively connected before the GGH low temperature section and after the GGH high temperature section.
[0062] A main flue valve is installed at the main flue;
[0063] The bypass flue is provided with a bypass flue valve; the bypass flue is used for flue gas bypass circulation, bypassing the GGH, the ascending flue, and the reactor;
[0064] The main flue valve and the bypass flue valve are both regulating valves, and the opening range is 0-100%.
[0065] The main flue includes an ascending flue and a reactor;
[0066] The flue gas in the ascending flue is arranged from bottom to top in sequence with a flue gas heating device, an ammonium bisulfate pyrolysis heating device, an ammonia source dosing device, and an ammonia source distribution device; the flue gas heating device is used to heat the normal operating flue gas to the catalyst activity temperature range of 180-340°C; the ammonium bisulfate pyrolysis heating device is used to heat the ammonium bisulfate pyrolysis flue gas to 350°C.
[0067] A flue gas uniform distribution device, a catalyst and a catalyst cleaning device are respectively arranged from top to bottom in the reactor.
[0068] The main flue valve includes one or two;
[0069] Assuming that two main flue valves are set, they are set at any one of the first main point and the second main point; the first point includes the original flue gas inlet on the GGH, the connection between the GGH and the ascending flue, the inside of the ascending flue, and between the ascending flue and the reactor; the second main point includes the connection between the reactor outlet and the GGH, and the clean flue gas outlet of the GGH;
[0070] Assuming that a main flue valve is set, it can be set at any of the 6 points including the first main point and the second main point.
[0071] The flue gas SCR denitrification system is provided with a NOx concentration detection sensor; the NOx concentration detection sensor is arranged at the inlet of the flue gas SCR denitrification system and the outlet of the flue gas SCR denitrification system or the chimney; wherein the inlet of the flue gas SCR denitrification system is used to monitor the inlet NOx concentration; the outlet of the flue gas SCR denitrification system is used to monitor the outlet NOx concentration.
[0072] The flue gas flow velocity in the main flue is 3-15m / s according to the equipment requirements. The main flue is square in shape according to the site layout, catalyst shape, etc. The flue gas flow material is carbon steel and 304.
[0073] The flue flow velocity in the bypass flue is 11-15m / s; the bypass flue cavity adopts a circular flue; the flue gas flow material is carbon steel and 304.
[0074] The temperature detection sensor is set at any of the following positions as needed: GGH low-temperature inlet, GGH low-temperature outlet, ammonia source dosing device outlet, in front of the flue gas heating device access point of the ascending flue, after the flue gas heating device access point of the ascending flue, in front of each layer of catalyst in the reactor, reactor outlet, GGH high-temperature outlet, and in the bypass flue; among them, a temperature detection sensor must be set in front of the uppermost catalyst in the reactor.
[0075] GGH is used for heat exchange between raw flue gas and clean flue gas, and is an air-to-air plate heat exchanger or a heat pipe heat exchanger.
[0076] The pressure detection sensor is set at any of the following positions as needed: GGH low-temperature inlet, GGH low-temperature outlet, ammonia source dosing device outlet, before the access point of the flue gas heating device of the ascending flue, after the access point of the flue gas heating device of the ascending flue, before each layer of catalyst in the reactor, reactor outlet, GGH high-temperature outlet, bypass flue; and pressure detection sensors are respectively set before the top catalyst in the reactor and at the reactor outlet; the total pressure drop of the catalyst is obtained by subtracting the pressure before the top catalyst in the reactor and at the reactor outlet.
[0077] The flow detection is arranged at the following positions of the SCR device: GGH low-temperature inlet or GGH high-temperature outlet, bypass flue.
[0078] In an SCR flue gas denitrification method, when the operating conditions change, during the monitoring process, as the NOx concentration changes, the adjustment method of the main flue valve and the bypass flue valve is shown in Table 1.
[0079] Table 1: Changes of various parameters after NOx concentration changes
[0080]
[0081] Among them, the bypass flue gas flow and main flue gas flow are detected by flow detection sensors; the main and bypass flue gas mixed temperature is detected by temperature detection sensors; NOx concentration is detected by NOx concentration detection sensors; system pressure drop is detected by pressure detection sensors. The system pressure drop is the pressure difference between the GGH raw flue gas inlet and the GGH clean flue gas outlet.
[0082] Under the condition of ensuring that NOx emission meets the standard, when the NOx concentration in the flue gas increases or decreases, by adjusting the opening of the main flue valve and the bypass flue valve, different flue gas volumes are controlled to pass through the main road of the SCR device for heating and denitrification and the SCR device bypass flue direct discharge. The main flue gas volume of the SCR device is heated to 180-300℃ by a conventional flue gas heating device, and the SCR reaction is carried out to remove NOx. The main flue gas after denitrification is mixed with the bypass flue gas and discharged through the induced draft fan and chimney.
[0083] Reducing the main flue gas volume can reduce the heat source consumption for flue gas heating, catalyst loss, etc., saving equipment operating costs; low main flue gas volume will also reduce the total exhaust flue gas temperature, the operating flue gas volume will also be lower, and the construction cost of induced draft fans, chimneys and other equipment will also be lower.
[0084] When the catalyst is clogged by ammonium bisulfate fouling, a small amount of flue gas is controlled to pass through the main path of the SCR device by adjusting the opening of the main flue valve and the bypass flue valve while ensuring that NOx emissions meet the standards. The main flue gas of the SCR device is heated to 350°C through a conventional heating device and (or) an ammonium bisulfate pyrolysis heating device to achieve efficient pyrolysis of ammonium bisulfate, while removing NOx through the SCR reaction. After pyrolysis of ammonium bisulfate, the flue gas leaves the SCR device, mixes with the bypass flue gas, and is discharged through the induced draft fan and chimney. When a small amount of flue gas is heated to the pyrolysis temperature of 350°C, less heat source is consumed. Since the amount of main flue gas is small, the flue gas temperature is relatively low after mixing with the bypass flue gas, and the operating flue gas volume is also relatively low. The low-temperature flue gas is not easy to exceed the upper limit of the operating temperature of the flue, induced draft fan and chimney, and can also effectively reduce the construction cost of the flue, induced draft fan and chimney, while saving the operating cost of the equipment; the low flue gas temperature will also have lower requirements for the insulation and anti-corrosion layer of the flue and equipment, which can reduce the insulation and anti-corrosion construction cost.
[0085] Corresponding to different working conditions, the opening degrees of the main flue valve and the bypass flue valve are shown in Table 2.
[0086] Table 2: Valve adjustment table for different working conditions:
[0087]
[0088]
[0089] As shown in Table 2, once the outlet NOx concentration does not meet the emission standards, adjustments need to be made. If the outlet NOx concentration meets the emission standards, the system pressure drop, main flue valve opening, and bypass flue valve opening can all be maintained as they are.
[0090] Specifically, when the outlet NOx concentration exceeds the standard, there is no need to continue observing the inlet NOx concentration. Instead, the main flue valve opening should be gradually increased, while the bypass flue valve opening should be gradually reduced until the outlet NOx concentration meets the standard.
[0091] If the outlet NOx concentration meets the standard, the status quo can be maintained, the main flue valve opening can reach 0, and the bypass flue valve opening is 100%, which means that the flue gas does not pass through the main flue, so there is no catalyst consumption and ammonia consumption.
[0092] The various operating conditions are described in detail below.
[0093] Working condition 1: When the hazardous solid waste material is stable and does not contain N element or is very low (specifically N element that will produce NOx during combustion), after full combustion, the NOx in the flue gas can be kept up to standard for a long time (100% of the time up to standard operation), the flue gas bypass valve is opened, the regulating valve opening is 100%, the main flue valve is closed, and all the flue gas is directly discharged from the bypass flue, and the main flow from the SCR device is stopped. The heat source consumption of flue gas heating can be completely eliminated, and the service life of the catalyst can be extended. At this time, the flue gas temperature is the lowest, the operating flue gas volume is the smallest, and the flue gas resistance is the smallest, which effectively reduces the power load of the induced draft fan.
[0094] Working condition 2, when hazardous solid waste materials are unstable and contain 0-0.5% N elements (specifically N elements that produce NOx when burned), after sufficient combustion, the NOx in the flue gas can be kept up to standard for a long time (90-99% of the time up to standard operation). When NOx occasionally exceeds the standard, the flue gas bypass valve is opened, the valve opening is adjusted to 20-99%, and the main flue valve opening is 1-50%. Most of the flue gas is discharged from the bypass flue of the SCR device, and a small part of the flue gas is discharged from the main road through the SCR device main road denitrification treatment. The flue gas after denitrification is mixed with the bypass flue gas and then discharged. The main flue gas passes through a conventional flue gas heating device to heat this part of the flue gas to the catalyst activation temperature range; when NOx does not exceed the standard, no ammonia source can be added; when the NOx concentration increases and exceeds the standard, a small amount of ammonia source is added to achieve standard emissions. It can effectively reduce the heat source consumption of flue gas heating and extend the service life of the catalyst. At this time, the flue gas temperature is low, the operating flue gas volume is low, and the flue gas resistance is small, which effectively reduces the power load of the induced draft fan.
[0095] Working condition 3: When hazardous solid waste materials are unstable and contain 0-1% N elements (specifically N elements that produce NOx when burned), after full combustion, when NOx in flue gas often exceeds the standard (1-90% of the time is up to standard), open the flue gas bypass valve, adjust the valve opening to 10-90%, and the main flue valve opening to 10-90%. Most of the flue gas can be discharged from the SCR device bypass, or it can be denitrified from the main road of the SCR device. Finally, the flue gas is mixed and sent to the induced draft fan and chimney. The main flue gas passes through a conventional flue gas heating device to heat this part of the flue gas to the catalyst activation temperature range; when NOx does not exceed the standard, a small amount of ammonia source is added to maintain the reliability of the ammonia source addition device, and at the same time, the instantaneous excess of NOx is alleviated in advance; when the NOx concentration increases and exceeds the standard, ammonia source is added according to the amount to achieve standard emissions. It can reduce catalyst loss and flue gas heating heat source consumption. At this time, the flue gas temperature is low, the operating flue gas volume is low, and the flue gas resistance is small, which effectively controls the power load of the induced draft fan.
[0096] Working condition 4: When the hazardous solid waste material is slightly stable and contains 0.5-2% N element (specifically N element that will produce NOx when burned), after full combustion, when the NOx in the flue gas continues to exceed the standard without SCR denitrification treatment (100% of the time exceeds the standard, exceeding the emission concentration by 1-100%), the flue gas bypass valve is opened to 1-50% and the main flue valve is opened to 10-99%. Most of the flue gas is denitrified by the main road of the SCR device, and the remaining small part of the flue gas is directly discharged from the bypass flue of the SCR device. Finally, the flue gas is mixed and sent to the induced draft fan and chimney. The main flue gas passes through a conventional flue gas heating device to heat this part of the flue gas to the catalyst activation temperature range; an ammonia source is added to achieve standard emissions. It can reduce catalyst loss and flue gas heating heat source consumption. At this time, the flue gas temperature is slightly lower, the operating flue gas volume is slightly lower, and the flue gas resistance is slightly smaller, and the power load of the induced draft fan is slightly lower.
[0097] Working condition 5: When the hazardous solid waste material is stable and contains more than 1% N element (specifically N element that will produce NOx when burned), after full combustion, all NOx in the flue gas needs to be denitrated by SCR to ensure that the outlet meets the standard (100% of the time exceeds the standard, and the emission concentration exceeds 100%), the flue gas bypass valve is closed, the main flue valve is 100% open, and all flue gas undergoes denitration reaction from the main SCR device. After denitration, the flue gas is sent to the induced draft fan and chimney, and stops flowing inside the bypass flue. The main flue gas passes through a conventional flue gas heating device to heat this part of the flue gas to the catalyst activation temperature range; an ammonia source is added to achieve standard emissions.
[0098] Working condition 6: When the pressure difference before and after the reactor in the main circuit of the SCR device or the pressure difference of the single-layer catalyst bed exceeds the design value, it indicates that ammonium bisulfate scale blockage occurs on the catalyst surface, and ammonium bisulfate high-temperature decomposition treatment is required. Open the bypass valve of the SCR device to 10-90% and the main flue valve to 99-10%. While ensuring that the NOx of the exhaust gas meets the standard, minimize the amount of flue gas entering the main circuit of the SCR device. The flue gas entering the main circuit of the SCR device is heated to 350℃ for 24-48h under the action of a conventional flue gas heating device and (or) ammonium bisulfate pyrolysis heating device to achieve complete decomposition of ammonium bisulfate. Under the condition of 350℃, the SCR reaction can be carried out simultaneously, and NOx can be removed with the same high efficiency. During the pyrolysis of ammonium bisulfate, the opening of the main valve and the bypass valve are adjusted accordingly according to the NOx concentration to keep a low gas volume passing through the SCR device. After the high-temperature flue gas from the main route leaves the device, it is mixed with the bypass flue gas and cooled before being discharged through the induced draft fan and chimney.
[0099] Condition 7: When the NOx in the flue gas at the outlet of the SCR device continues to exceed the standard, gradually increase the main flue valve opening, and gradually reduce the flue gas bypass valve opening, increase the amount of flue gas treated by the main denitrification of the SCR device, and reduce the amount of flue gas directly discharged from the bypass flue of the SCR device. Finally, the flue gas is mixed and sent to the induced draft fan and chimney. The main flue gas passes through a conventional flue gas heating device to heat this part of the flue gas to the catalyst activation temperature range; add an ammonia source to achieve flue gas denitrification. When the NOx in the flue gas at the outlet of the SCR device reaches the emission concentration limit, it can be switched to condition 1-6.
[0100] When the NOx concentration in the inlet flue gas of the SCR device is not detected, control can be performed only based on the outlet NOx. When the outlet flue gas NOx concentration meets the standard, gradually reduce the main valve opening, and gradually increase the bypass valve opening, reduce the amount of flue gas treated by the main denitrification process of the SCR device, and increase the amount of flue gas directly discharged from the bypass flue of the SCR device; until the NOx concentration in the outlet flue gas of the SCR device reaches the standard emission value.
[0101] Compared with the original high-temperature pyrolysis process, the heat source consumption for flue gas heating can be greatly reduced. The exhaust temperature is low and it is not easy to exceed the upper temperature limit of the flue, induced draft fan and chimney. The low working condition flue gas volume can also effectively reduce the construction cost of the flue, induced draft fan and chimney, and save the operating cost of the device; the low flue gas temperature will also have lower requirements for the insulation and anti-corrosion layer of the flue and equipment, which can reduce the cost of insulation and anti-corrosion construction. As shown in Table 3, it is a comparison table of the effects of the present invention and the prior art.
[0102] Table 3: Effect comparison table
[0103] Serial number name Original pyrolysis system The pyrolysis system 1 Pyrolysis flue gas flow 100％ part 2 Bypass flue gas flow 0 part 3 Heat source consumption of flue gas heating device big Small 4 Ammonia consumption big Small 5 Catalyst service life High consumption Low consumption 6 Main bypass flue gas mixed temperature high Low 7 Ammonium bisulfate blockage cleaning effect good good 8 Thermal insulation and anti-corrosion cost of the device high Low 9 Construction costs high Low 10 System pressure drop high Low 11 Running costs high Low
[0104] Furthermore, the flue gas heating device can be a steam heat exchanger, which uses high-temperature steam to indirectly heat the flue gas, or the flue gas heating device can be a burner, and the fuel is natural gas, fuel gas, fuel oil and other raw materials, and the high-temperature combustion generates a large amount of heat, which is directly mixed with the flue gas to achieve the flue gas heating effect. The flue gas heating device is one or more, and can be a combination of a steam heat exchanger and a burner.
[0105] Furthermore, the ammonium bisulfate pyrolysis and heating device is a steam heat exchanger or a burner; the steam heat exchanger uses high-temperature steam to indirectly heat the flue gas; the fuel of the burner includes natural gas, fuel gas, fuel oil and other raw materials, which burn at high temperatures to generate a large amount of heat, which is directly mixed with the flue gas to achieve the flue gas heating effect. The ammonium bisulfate pyrolysis and heating device is one or more.
[0106] Furthermore, according to the outlet NOx concentration, while ensuring that NOx emissions meet the standards, the amount of flue gas flowing through the main path of the SCR device is minimized; the main flue valve and bypass flue valve are set to be interlocked with the NOx concentration in the flue gas.
[0107] Furthermore, the main flue valve and the bypass flue valve are set to be interlocked with the flue gas volume and the NOx concentration in the flue gas.
[0108] Furthermore, the temperature of the flue gas entering the catalyst is interlocked with the conventional flue gas heating device to ensure that the temperature of the flue gas entering the catalyst reaches the catalyst active temperature range of 180-340°C.
[0109] Furthermore, the temperature of the flue gas entering the catalyst is interlocked with the ammonium bisulfate pyrolysis heating device to ensure that the temperature of the flue gas entering the catalyst reaches 350°C.
[0110] Furthermore, if there is a requirement for the exhaust gas temperature of the SCR device, the exhaust gas temperature after the SCR device is interlocked with the main flue valve and the bypass flue valve.
[0111] Furthermore, if there are requirements for the exhaust gas temperature and NOx concentration of the SCR device, the flue gas temperature and NOx concentration after the SCR denitrification device are interlocked with the main flue valve and the bypass flue valve.
[0112] For the specific contents of the above interlocking adjustment settings, please refer to Table 1 and Table 2, which will not be repeated here.
[0113] Furthermore, the main flue valve and the bypass flue valve are regulating valves with an opening of 0-100%; they are any one of a single-axis flue baffle, a multi-axis flue baffle, a louvered baffle, a rotary flue baffle, a plug-in flue baffle, a butterfly valve, and a gate valve; and the actuator is any one of electric, pneumatic or hydraulic drive.
[0114] Furthermore, a main inspection valve is added to the main flue of the SCR device, the main flue valve and the main inspection valve are closed, and the bypass flue valve is opened 100%, so that the SCR device can be inspected without stopping the system. The main inspection valve is fully open when not in the inspection state; the main inspection valve can be a regulating valve or a switch valve, the inspection valve driving mechanism is any one of electric, pneumatic, hydraulic drive or manual, and the valve form is any one of a single-axis flue baffle, a multi-axis flue baffle, a shutter baffle, a rotary flue baffle, a plug-in flue baffle, a butterfly valve, and a gate valve.
[0115] Furthermore, in order to prevent the appearance of white smoke plumes at the chimney outlet due to the flue gas temperature being too low, a flue gas heating device is added to the bypass flue; or a flue gas heating device is added to the main flue before the SCR device and the bypass flue to heat the flue gas in advance during normal operation, or for the purpose of chimney whitening.
[0116] Furthermore, when the incineration flue gas is not subjected to a wet deacidification process, GGH can be retained or removed.
[0117] The SCR flue gas denitrification system provided by the present invention is suitable for removing non-high-concentration NOx, and is particularly suitable for situations where the NOx concentration fluctuates.
[0118] Furthermore, during the SCR flue gas denitrification process, catalysts can be added to improve the denitrification efficiency of the main flue gas entering the SCR device. While ensuring the total flue gas denitrification efficiency, the flue gas volume entering the main flue of the SCR device can be reduced and the flue gas volume entering the bypass flue can be increased, thereby reducing the heat source for flue gas heating and the outlet flue gas temperature.
[0119] The effects of the present invention are further described below in conjunction with two embodiments.
[0120] First embodiment
[0121] A company in Yantai, Shandong Province uses a 35,000 tons / year solid waste comprehensive utilization device for the incineration of solid waste and hazardous waste within the group. The process flow includes: rotary kiln, secondary combustion chamber, waste heat boiler, quenching tower, dry deacidification tower, bag filter, wet deacidification device, SCR device, induced draft fan and chimney.
[0122] The SCR device has a primary steam heater, GGH, a secondary steam heater, an ammonia injection device, an ammonia source uniform distribution device, a flue gas uniform distribution device, a catalyst, etc. The catalyst is a low-temperature catalyst, the flue gas heating device is a steam indirect heater, and the GGH is an air-to-air plate indirect heat exchanger. The SCR device has no bypass, no heating device for ammonium bisulfate pyrolysis, and does not take into account the high-temperature pyrolysis process requirements of ammonium bisulfate.
[0123] The flue gas from the wet deacidification device has a temperature of 50-80℃. It first passes through the first-level steam heater to heat up to 120-140℃, then passes through the GGH heat exchange to heat up to 160-190℃, and then passes through the second-level steam heater to heat up to 200-240℃, enters the catalyst for NOx removal reaction, and the flue gas temperature after denitrification is 190-220℃. Finally, it passes through the GGH to cool down to 150-170℃ and is discharged to the induced draft fan and chimney.
[0124] The interior of the induced draft fan is equipped with fiberglass anti-corrosion, which can withstand temperatures up to 170°C, and the interior of the chimney is equipped with high-temperature anti-corrosion, which can withstand temperatures up to 250°C.
[0125] After the SCR device has been running for a long time, ammonium bisulfate will scale on the surface of the catalyst of the SCR device, blocking the catalyst channel. Since the possibility of ammonium bisulfate blocking the catalyst was not considered in the original design of the SCR device, there is no heating device for the thermal decomposition of ammonium bisulfate, and only manual cleaning is used when the device is shut down.
[0126] In order to solve the above problems, it is necessary to transform the SCR denitrification device. The transformation contents are as follows:
[0127] 1. Add an SCR device bypass between the first-stage steam heater and the GGH raw flue gas inlet, connect the bypass flue to the GGH clean flue gas outlet, and set a flue valve on the bypass;
[0128] 2. Add a burner after the secondary steam heater in the ascending flue, use natural gas as the fuel heat source, consider the need for airflow mixing and distribution, and add two natural gas burners in a symmetrical arrangement;
[0129] 3. Add a main flue valve to the flue between the natural gas burner and the catalyst;
[0130] 4. Set up interlocking adjustment between the NOx concentration at the outlet of the SCR device, the flue gas temperature, the main flue valve, and the bypass flue valve.
[0131] When the scale of ammonium bisulfate blocks the catalyst and needs to be pyrolyzed, the bypass flue valve is opened at 40-60% and the main flue valve is opened at 40-90%. The main flue gas of the SCR device is heated to above 350°C through GGH, secondary steam heater, and ammonium bisulfate pyrolysis heating device (2 natural gas burners), and the temperature is kept constant for 48 hours to achieve full decomposition and cleaning of the scale on the catalyst surface. The flue gas after pyrolysis is also treated by catalyst denitrification, and then cooled to 220-240°C through GGH, and then mixed with the bypass flue gas to cool to 160-170°C, discharged to the induced draft fan for pressurization, and discharged from the chimney.
[0132] The exhaust temperature does not exceed the upper temperature limit of the induced draft fan, so there is no need to re-purchase the induced draft fan or replace the anti-corrosion, saving project transformation costs.
[0133] The exhaust gas temperature is low, the flue gas volume is small, the power load of the induced draft fan is low, and the operating cost is saved. It is expected that the power consumption of flue gas transmission of the SCR device will be saved by 20-50%.
[0134] The amount of flue gas is small, and the amount of natural gas used for heating is small, saving 40-80% of natural gas consumption.
[0135] The NOx concentration in the flue gas of this plant is low, and NOx may exceed the standard under fluctuation conditions. In actual operation, the NOx concentration at the outlet of the SCR device is interlocked with the main flue valve and the bypass flue valve to ensure that the bypass flue valve is opened at 50-80% and the main flue valve is opened at 20-50% when the outlet meets the standard. Most of the flue gas passes through the bypass, and the remaining flue gas enters the main road. After heating and denitrification, it is discharged from the main road. The flue gas is mixed and discharged to the induced draft fan and chimney.
[0136] The exhaust gas temperature is as low as 140-155℃, the flue gas volume is small under working conditions, the power load of the induced draft fan is low, and the operating cost is saved. It is expected that the power consumption of flue gas transmission of the SCR device will be saved by 30-70%.
[0137] The flue gas volume is small, and the steam consumption of the secondary steam heater can be reduced by 50-80%, saving operating costs. Before the flue gas bypass, the steam consumption of the primary steam heater is not reduced.
[0138] Second embodiment
[0139] A 25t / d solid waste and hazardous waste incineration device for a company in Ningxia is used for internal solid waste and hazardous waste incineration treatment. The process flow includes rotary kiln, secondary combustion chamber, waste heat boiler, quenching tower, dry deacidification tower, bag filter, wet deacidification device, induced draft fan, wet electrostatic precipitator, SCR device and chimney. The local particulate matter emission concentration is extremely strict, so a wet electrostatic precipitator is installed.
[0140] The SCR device includes GGH, flue gas heating device, ammonia spraying device, ammonia source uniform distribution device, flue gas uniform distribution device, catalyst, etc. The catalyst is a low-temperature catalyst, the flue gas heating device is a natural gas heater, and the GGH is a heat pipe gas-to-gas indirect heat exchanger. The SCR device has a bypass, and the main valve and bypass valve are switch valves without the function of opening adjustment; there is no heating device for ammonium bisulfate pyrolysis, and the high-temperature pyrolysis process requirements of ammonium bisulfate are not considered.
[0141] The flue gas from the wet electrostatic precipitator has a temperature of 50-80℃. It first passes through the GGH and is heated to 120-140℃. Then it passes through the natural gas burner and is heated to 200-220℃. It enters the catalyst for NOx removal reaction. The flue gas temperature after denitrification is 190-210℃. Finally, it passes through the GGH and is cooled to 130-150℃ before being discharged to the induced draft fan and chimney.
[0142] The inside of the chimney is made of fiberglass for corrosion protection and is temperature resistant to 200°C.
[0143] After the SCR device has been running for a long time, ammonium bisulfate scales on the surface of the SCR device catalyst, blocking the catalyst channel. The design did not consider the possibility of ammonium bisulfate blocking the catalyst, and no heating device for ammonium bisulfate pyrolysis was equipped. When the catalyst is blocked, it can only be cleaned manually when the device is shut down.
[0144] In order to solve the above problems, it is necessary to transform the SCR denitrification device. The transformation contents are as follows:
[0145] 1. Replace the original main flue valve and bypass flue valve from on-off valve to regulating valve;
[0146] 2. Set up interlocking adjustment between the NOx concentration at the outlet of the SCR device, the flue gas temperature, the main flue valve, and the bypass flue valve;
[0147] 3. No additional ammonium bisulfate pyrolysis heating device is installed, and the original natural gas burner is reused, and the temperature of the flue gas entering the catalyst is linked to the load setting of the natural gas burner.
[0148] When the ammonium bisulfate scale blocks the catalyst and needs to be pyrolyzed, the bypass flue valve is opened at 50-80% and the main flue valve is opened at 20-50%. The main flue gas of the SCR device is heated to above 350°C through the GGH and natural gas burner, and kept at a constant temperature for 48 hours to achieve full decomposition and cleaning of the scale on the catalyst surface. At the same time, the flue gas is treated by catalyst denitrification, and then cooled to 200-260°C through the GGH, and then mixed with the bypass flue gas to cool to 120-180°C, and discharged from the chimney.
[0149] The exhaust temperature is lower than the upper temperature limit of the chimney's anti-corrosion resistance, so the chimney does not need to replace anti-corrosion, saving project renovation costs.
[0150] There is no need to add new ammonium bisulfate heating equipment, and the original natural gas combustion can be reused, saving project transformation costs.
[0151] The exhaust gas temperature is low, the operating flue gas volume is small, the power load of the induced draft fan is low, and the operating cost is saved. It is expected that the power consumption of flue gas transmission of the SCR device will be saved by 30-60%.
[0152] The amount of flue gas is small, and the amount of natural gas used for heating is small, which can save 50-80% of natural gas consumption.
[0153] The NOx concentration in the flue gas of this plant is relatively low, and NOx may exceed the standard under fluctuation conditions. In actual operation, the NOx concentration at the outlet of the SCR device is interlocked with the main flue valve and the bypass flue valve to ensure that the bypass flue valve is opened at 70-90% and the main flue valve is opened at 10-30% when the outlet meets the standard. Most of the flue gas passes through the bypass, and a small amount of flue gas enters the main road. After heating and denitrification, it is discharged from the main road. The flue gas is mixed and discharged to the induced draft fan and chimney.
[0154] The exhaust gas temperature is as low as 110-130℃, the flue gas volume is small under working conditions, the power load of the induced draft fan is low, and the operating cost is saved. It is expected that the power consumption of flue gas transmission of the SCR device will be saved by 40-70%.
[0155] The amount of flue gas is small, and the consumption of natural gas burners can be saved by 50-80%, saving operating costs.
[0156] It should be noted that the above content only illustrates the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.
[0157] The above-described embodiments of the present application do not constitute a limitation on the protection scope of the present application.
Claims
1. An incineration flue gas SCR denitrification system, characterized in that: The system comprises: The flue gas SCR denitrification system includes the main flue, bypass flue and GGH; Among them, one side of the GGH is the high-temperature side, which includes a high-temperature inlet and a high-temperature outlet; The other side of GGH is the low temperature side, which includes a low temperature inlet and a low temperature outlet. The inlet of the main flue is connected to the low temperature inlet of GGH, and the outlet of the main flue is connected to the high temperature outlet of GGH. The input port of the bypass flue is connected to the original flue gas inlet of the SCR device, and the outlet of the bypass flue is connected to the clean flue gas outlet of the SCR device; the bypass flue is respectively connected before the low temperature section of GGH and after the high temperature section of GGH; A main flue valve is installed at the main flue; The bypass flue is provided with a bypass flue valve; The main flue valve and the bypass flue valve are both regulating valves, and the opening range is 0-100%.
2. The system according to claim 1, characterized in that The main flue includes an ascending flue and a reactor; In the ascending flue, flue gas is arranged from bottom to top in sequence, including a flue gas heating device, an ammonium bisulfate pyrolysis heating device, an ammonia source dosing device, and an ammonia source uniform distribution device; A flue gas uniform distribution device, a catalyst and a catalyst cleaning device are respectively arranged from top to bottom in the reactor.
3. The system according to claim 2, characterized in that The main flue valve includes one or two; Assuming that two main flue valves are set, one of the first main point and the second main point can be selected for setting; The first point includes the original flue gas inlet on the GGH, the connection between the GGH and the ascending flue, the inside of the ascending flue, and between the ascending flue and the reactor; the second main route point includes the connection between the reactor outlet and the GGH, and the clean flue gas outlet of the GGH; Assuming that a main flue valve is set, it can be set at any of the 6 points including the first main point and the second main point.
4. The system according to claim 3, characterized in that The system is also provided with a NOx concentration detection sensor; the NOx concentration detection sensor is arranged at the inlet of the flue gas SCR denitrification system and the outlet of the flue gas SCR denitrification system or the chimney; wherein the inlet of the flue gas SCR denitrification system is used to monitor the inlet NOx concentration; the outlet of the flue gas SCR denitrification system is used to monitor the outlet NOx concentration.
5. The system according to claim 1, characterized in that The system is also provided with a temperature detection sensor; Temperature detection sensors can be set at any of the following locations as needed: GGH low-temperature inlet, GGH low-temperature outlet, ammonia source dosing device outlet, before the access point of the flue gas heating device of the ascending flue, after the access point of the flue gas heating device of the ascending flue, before each layer of catalyst in the reactor, reactor outlet, GGH high-temperature outlet, and in the bypass flue; Among them, a temperature detection sensor must be installed before the uppermost catalyst in the reactor.
6. The system according to claim 1, characterized in that The system is also provided with a pressure detection sensor; The pressure detection sensor can be set at any of the following positions as needed: GGH low-temperature inlet, GGH low-temperature outlet, ammonia source dosing device outlet, in front of the flue gas heating device access point of the ascending flue, after the flue gas heating device access point of the ascending flue, in front of each layer of the reactor catalyst, reactor outlet, GGH high-temperature outlet, bypass flue; Corresponding pressure detection sensors are also provided before the top catalyst of the reactor and at the reactor outlet; The total catalyst pressure drop is obtained by subtracting the pressure before the top catalyst in the reactor and at the reactor outlet.
7. The system according to claim 1, characterized in that The system is also provided with a flow detection sensor; The flow detection sensor is set at any of the following positions as required: GGH low-temperature inlet or GGH high-temperature outlet, bypass flue.
8. The system according to claim 3, characterized in that The main flue is also equipped with a main inspection valve; Close the main flue valve and main inspection valve, and open the bypass flue valve to 100%, so that the SCR device can be inspected without stopping the system; The main line inspection valve is fully open when not in the inspection state; The main line inspection valve is a regulating valve or a switching valve.
9. A control method for an incineration flue gas SCR denitration system, the method being used to control any system in claims 1 to 8, characterized in that: When the working conditions change, as the NOx concentration changes, the adjustment methods of the main flue valve and the bypass flue valve are shown in Table 1: Table 1: Changes of various parameters after NOx concentration changes Under the condition of ensuring that NOx emission meets the standard, when the NOx concentration in the flue gas increases or decreases, the main flue valve and the bypass flue valve opening are adjusted to control different flue gas volumes to pass through the main flue for heating and denitrification and direct discharge through the bypass flue; under the condition of ensuring that the inlet temperature of the SCR reactor is stable, as the flue gas volume increases or decreases, the heat source consumption of the flue gas heating device increases or decreases accordingly; When the catalyst is clogged by ammonium bisulfate scaling, a small amount of flue gas is controlled to pass through the main path of the SCR device by adjusting the opening of the main flue valve and the bypass flue valve while ensuring that NOx emissions meet the standards; the main flue gas of the SCR device is heated to 350°C by a heating device or an ammonium bisulfate pyrolysis heating device to achieve efficient pyrolysis of ammonium bisulfate, while removing NOx by SCR reaction; the flue gas after pyrolysis of ammonium bisulfate leaves the SCR device, mixes with the bypass flue gas, and is discharged through the induced draft fan and chimney.
10. The method according to claim 9, characterized in that The main valve opening and bypass valve opening are adjusted according to the NOx concentration. The adjustment range is shown in the following table: The main valve opening and the bypass valve opening are adjusted according to the outlet NOx concentration and the inlet NOx concentration so that the outlet NOx concentration meets the emission standards.