A control system and method for dynamic air distribution in a flue duct in coordination with SNCR denitration

Abstract

The present invention provides a control system and method for dynamic air distribution in a flue duct in coordination with SNCR denitration. The control system consists of a sensing unit, an execution unit, and a feedback regulation unit; the sensing unit includes temperature, NO concentration, CO concentration, and NH3 concentration detection modules, the execution unit includes a secondary air execution layer, an overfire air execution layer, and an SNCR execution layer, and the feedback regulation unit includes an instruction layer and a data layer. The control method detects parameters through the sensing unit; analyzes data and generates control instructions through the feedback regulation unit, and stores the detected parameters and control instructions; and realizes dynamic regulation of the air distribution state and the reductant injection state through the execution unit. The control system and method have a feedback regulation function to realize dynamic regulation of combustion and denitration and self-correction of the system, and can be widely applied to the technical fields of low-nitrogen combustion and SNCR denitration.

Description

Technical Field

[0001] The present invention belongs to the field of low-nitrogen and low-dioxin combustion of garbage and flue gas denitrification, and particularly relates to a control system and method for dynamic air distribution in a flue duct in cooperation with SNCR denitrification. Background Art

[0002] With the acceleration of the urbanization process in China, the proposal of urban waste classification, and the implementation of the "waste-free city" construction plan, the urban industrial upgrading and the improvement of living quality have led to a sharp increase in urban garbage, and also increased the calorific value of the garbage. Garbage incineration power generation has become the main technology for the treatment of urban domestic waste in China. According to statistics, the average calorific value of garbage in the Yangtze River Delta and Pearl River Delta regions in 2018 was higher than that of domestic waste in other regions of the country, and the calorific value of the incoming furnace garbage was generally higher than 7500 kJ / kg. Due to the substantial increase in the calorific value of domestic waste, the boiler flue gas temperature has increased significantly, the corrosion of the boiler heating surface has intensified, and the furnace wall of the incinerator has been burned out frequently, especially at the front arch of the secondary air burner, and the repair of the castable in the incinerator is frequent.

[0003] The nitrogen oxides generated during the garbage incineration process include NO, NO2, N2O, N2O3, N2O4, and N2O5, etc., among which NO accounts for 90-95% of the total nitrogen oxides generated. NO x The generation mechanism mainly has three types: thermal type, fuel type, and prompt type. According to the in-furnace combustion characteristics during the stable operation of the garbage incinerator, the highest temperature is between 1450-1650K, and the proportion of prompt NO x is extremely small, mainly fuel-type NO x , with a proportion of more than 80%, followed by thermal-type NO x , not exceeding 20%. Experiments show that with the increase of the reaction temperature, the NO x generation reaction rate increases according to an exponential law. When the temperature exceeds 1700K, for every 100K increase in temperature, the reaction rate increases by 6-7 times. Therefore, controlling the incineration temperature in the incinerator is an effective measure to achieve low-nitrogen combustion.

[0004] Dioxin is a colorless, odorless, and highly toxic fat-soluble substance that can damage multiple organs and systems. The main way for urban domestic waste incineration to produce dioxin is during the incineration process of chlorine-containing plastics such as vinyl chloride, which is caused by incomplete combustion of chlorine-containing garbage due to the failure to meet the requirements of an incineration temperature above 850°C and an incineration time above 2s.

[0005] In order to control NO xIn order to reduce the generation of pollutants and dioxins, the patent CN201210510370 proposes to set a four-layer blowing assembly in the first channel of the garbage incinerator to form two groups of tangential circles to make the flue gas spiral up, and the patent CN20110250190 proposes to arrange two layers of burnout air nozzles at the bottom of the incinerator furnace to make the flue gas spiral up, so as to extend the combustion residence time of the flue gas and low nitrogen and low dioxin combustion. In the existing technology for controlling the stratified air distribution of garbage incinerators, there is no method of combining the vertical vortex formed by the secondary air downward blowing with the horizontal vortex formed by the horizontal swirl blowing, and applying this combined blowing method to improve the SNCR denitrification efficiency and the control of the SNCR reducing agent on the water-cooled wall corrosion.

[0006] The waste incinerator distributes the air intake through secondary air and burnout air in stages. Under the condition of maintaining the original excess air coefficient level, the flue gas combustion distribution in the first flue is more uniform, the corrosion of the secondary air burner and the first flue heating surface is reduced, and the incineration temperature in the furnace is effectively controlled, reducing NO x It can also appropriately widen the SNCR reaction temperature range, increase the turbulence in the furnace, increase the residence time of the flue gas at 850℃, and reduce the production of dioxins.

[0007] When using the SNCR method for flue gas denitrification, it is necessary to select an area with a flue gas temperature of 850-1100°C. In a waste incinerator, this is mainly done by arranging one or more groups of fixed spray guns in the first flue. However, as the boiler load changes, it is difficult to ensure that the spray gun arrangement area is within the reaction temperature range of the SNCR. In addition, when using the SNCR method for denitrification, the reducing agent is usually atomized in liquid form and sprayed into the furnace. The effect of denitrification depends largely on the atomization effect of the reducing agent and the degree of mixing between the reducing agent and the flue gas. Patent CN109464900B calculates the elevation of the optimal reaction area and further moves the spray gun through the linear relationship between elevation and temperature, but the application of mobile spray guns has great difficulties in the installation and design of the spray gun. Through the graded air distribution of secondary air and burnout air, the flue gas combustion distribution in the first flue is made more uniform, which can ensure that the combustion temperature of the fixed SNCR spray gun arrangement area is between 850-1100℃ to the greatest extent, and the SNCR reducing agent spray gun is arranged between two layers of burnout air layers, effectively utilizing the high turbulence between the burnout air layers to achieve rapid mixing of the reducing agent and the flue gas. The corrosion of the water-cooled wall by the reducing agent can also be reduced by detecting and analyzing the NH3 concentration near the wall surface of the four water-cooled walls above the SNCR spray gun layer and adjusting the angle of the burnout air gun.

[0008] However, in the prior art, the flue gas is unevenly distributed in the high-temperature combustion zone, and NO x The large amount of generation, the difficulty in controlling the combustion temperature in the SNCR denitrification area, and the insufficient uniformity of mixing the flue gas and the reducing agent lead to low efficiency. Summary of the Invention

[0009] The present invention aims at a countercurrent grate waste incinerator, and proposes a waste incineration control system and control method for low-nitrogen and low-dioxin combustion and efficient SNCR denitration by combining downward blowing of secondary air, staged air distribution of burnout air and SNCR denitration. Through the staged dynamic adjustment of the air distribution volumes of secondary air and burnout air, and the feedback correction of the control system by storing historical detection and control parameter data, the mixing of vertical and horizontal vortex flows is achieved, the turbulence degree of the flue gas in the furnace is increased, and the combustion temperature is controlled to achieve low-nitrogen and low-dioxin combustion. At the same time, the reaction temperature in the SNCR denitration area is ensured, the SNCR denitration effect is improved, and the corrosion of the water-cooled wall by the reducing agent is reduced. It can be widely applied to the technical fields of low-nitrogen combustion and SNCR denitration.

[0010] The present invention is achieved by at least one of the following technical solutions.

[0011] A control system for dynamic air distribution in the flue and coordinated SNCR denitration, comprising a sensing unit, a feedback adjustment unit and an execution unit;

[0012] The sensing unit includes a temperature and concentration detection module for real-time monitoring of the flue gas temperature detection information, NO concentration detection information, CO concentration detection information, and NH3 concentration detection information in the furnace, and transmitting the detection information to the feedback adjustment unit;

[0013] The feedback adjustment unit includes an instruction layer and a data layer. The instruction layer generates control instructions for the execution unit according to the detection information transmitted by the sensing unit; the data layer is used to store the execution instructions and detection information parameters updated in each cycle, and provide the data called by the instruction layer;

[0014] The execution unit includes a secondary air execution layer, a burnout air execution layer and an SNCR execution layer, and regulates each execution layer according to the control instructions transmitted by the feedback adjustment unit.

[0015] Preferably, the temperature and concentration detection module includes a plurality of sensors for detecting the flue gas temperature, NO concentration, CO concentration, and NH3 concentration, and the sensors are arranged in the incinerator.

[0016] Preferably, the incinerator includes a grate, a furnace chamber, a secondary air burner, a first flue, a second flue, and a third flue; the primary air inlet is below the grate; the furnace chamber is above the grate;

[0017] The secondary air burner is above the furnace chamber, and the first flue is above the secondary air burner; the inlet of the second flue is connected to the outlet of the first flue; the inlet of the third flue is connected to the outlet of the second flue.

[0018] An overfire air lance arrangement area is formed between the overfire air burner and the first flue outlet; at least two or more layers of overfire air layers are arranged at intervals in the overfire air lance arrangement area; an SNCR spray gun arrangement area is provided in the overfire air lance arrangement area, and the SNCR spray gun arrangement area is arranged in the area where the flue gas temperature is 850-1100°C and is located between two layers of overfire air layers, and several layers of SNCR spray gun layers are arranged in the SNCR spray gun arrangement area;

[0019] The several sensors are respectively arranged at the first flue inlet, between the first flue inlet and the first layer of overfire air layer, between every two layers of overfire air layers, and between the overfire air layer and the SNCR spray gun layer. The sensors for detecting NH3 concentration are arranged on the four-sided water-cooled walls above each layer of SNCR spray gun layer and at the first flue outlet;

[0020] In the overfire air lance arrangement area, one layer of overfire air layer is arranged every 2-3m, and one or several blowing components are arranged on the four-sided water-cooled walls of each layer of overfire air layer.

[0021] Preferably, the overfire air execution layer is used to adjust the air distribution volume of the blowing components. The blowing components include several rows of overfire air lances, flow control valves and first signal regulators on the front and rear walls of the overfire air burner. The flow control valves are connected to several rows of overfire air lances and are used to adjust the air output volume of the overfire air lances. The first signal regulator is connected to the first overfire air induced draft fan. According to the control instruction of the feedback adjustment unit, the output power of the overfire air induced draft fan is adjusted to realize the adjustment of the overfire air distribution volume. The two rows of overfire air lances on the front and rear walls of the overfire air lances are arranged staggeredly, and the downward blowing angle of each row of overfire air lances with the horizontal plane is between 20-45°;

[0022] The overfire air execution layer includes a flow control valve and a second signal regulator. The flow control valve is connected to the overfire air lances of each layer and is used to adjust the air output volume of the overfire air lances. The second signal regulator is connected to the second overfire air induced draft fan. According to the control instruction of the feedback adjustment unit, the output power of the overfire air induced draft fan is adjusted to realize the adjustment of the overfire air distribution volume;

[0023] The SNCR execution layer includes a reducing agent flow control valve, an atomizing medium control valve and a third signal regulator. The reducing agent flow control valve and the atomizing medium control valve are respectively installed between the inner and outer interfaces of the reducing agent and atomizing medium conveying pipelines and the SNCR spray guns of each layer and are used to adjust the reducing agent flow rate, atomizing medium flow rate and pressure; the third signal regulator is connected to the input end of the compressor, and the output end of the compressor is respectively connected to the reducing agent and atomizing medium conveying pipelines. According to the control instruction of the feedback adjustment unit, the output power of the compressor is adjusted to realize the adjustment of the flow rate and pressure of the SNCR spray guns.

[0024] Preferably, the overfire air layer is uniformly supplied with air by the secondary air induced draft fan, that is, the secondary air distribution system is used to distribute part of the secondary air to the overfire air, or the overfire air is supplied through an independent induced draft system.

[0025] Preferably, the adjustable range of the angle between each air lance in the overfire air layer and the water wall is 30-50°, which is used to adjust the combustion state and the mixing state of the reducing agent and the flue gas.

[0026] Preferably, the installation height of the SNCR spray gun is selected according to the flue gas temperature of 850-1100°C, and it is arranged between two overfire air layers, and at least two SNCR spray guns are arranged on each layer.

[0027] Preferably, the instruction layer calculates according to the detection information of the flue gas temperature, NO concentration, CO concentration, and NH3 concentration transmitted by the sensing unit, and calls the historical data of the data layer for comparison, generates a control instruction and transmits it to the execution unit and the signal regulator to control the air distribution volume of the secondary air lance and each air lance in the overfire air layer, the spraying parameters of the SNCR spray gun, or selectively turn on / off each air lance and the SNCR spray gun in the overfire air layer.

[0028] The data layer is used to store the control instructions, flue gas temperature distribution, NO concentration distribution, CO concentration distribution, NH3 concentration distribution (ammonia escape), and SNCR denitration efficiency-related data updated in each cycle, and generates a database for the instruction layer to call.

[0029] The control method of the control system for dynamic air distribution in the flue duct and collaborative SNCR denitration includes the following steps:

[0030] The sensing unit detects the flue gas temperature, NO concentration, CO concentration, and NH3 concentration at different elevations in the incinerator;

[0031] The feedback adjustment unit receives the detection data of the sensing unit, and according to the temperature T, temperature change rate △T, NO concentration C NO , NO concentration change rate △C NO , CO concentration C CO , CO concentration change rate △C CO , respectively calculate the fitting function relationship between C NO , C CO and the temperature distribution, and compare the fitting function relationship with the historical function relationship stored in the data layer. Combining the functions of NO x , CO generation characteristics and temperature, calculate the air distribution conditions of the secondary air and the overfire air, and generate a control instruction;

[0032] The execution unit adjusts the air distribution volume of the secondary air and each air lance in the overfire air layer according to the control instruction;

[0033] After the air distribution is adjusted and the incineration state reaches a new stable state, that is, when the set first update time t1 is reached, the sensing unit detects the temperature, NO concentration, and CO concentration at different heights in the furnace again and transmits them to the feedback adjustment unit;

[0034] The feedback adjustment unit determines the combustion effect based on the updated T, △T, C NO , △C NO , C CO , △C CO information. If the control standard is met, it calculates the number of layers of SNCR spray guns to be opened and the flow rate of the reducing agent and the flow rate and pressure of the atomizing medium allocated to each SNCR spray gun, and generates an updated control instruction for the SNCR execution layer. Otherwise, it regenerates the control instruction to adjust the air distribution of each air gun in the secondary air and burnout air layers;

[0035] After the SNCR execution layer executes the update instruction and the denitrification reaction reaches a new stable state, that is, when the set second update time t2 is reached, the sensing unit detects C at the outlet of the first flue NO , C NH3 and above the SNCR spray gun layer NH3 of C, predicts the distribution of the injected reducing agent in the flue through the distribution of NH3 on the four-sided water-cooled wall, transmits it to the feedback adjustment unit, analyzes the denitrification effect, and compares it with the historical function relationship stored in the data layer to further calculate the deflection angle of the burnout air gun and generate a control instruction;

[0036] After the spray gun angle is adjusted and the denitrification and combustion reactions reach a new stable state, that is, when the set third update time t3 is reached, the sensing unit re-detects the temperature, NO concentration, CO concentration, and NH3 concentration, transmits them to the feedback adjustment unit, updates the denitrification state, and stores them in the data layer of the feedback adjustment unit to complete the update of the database;

[0037] The above completes a control cycle for realizing low-nitrogen and low-dioxin combustion and efficient SNCR denitrification through dynamic adjustment of the flow field. According to the different working conditions and furnace types, and whether the actual denitrification effect reaches the set limit value, the execution cycle t0 of this control system and the update time of each stage are adjusted to automatically realize the cyclic feedback control of efficient SNCR denitrification of the waste incinerator.

[0038] Preferably, among the N-layer SNCR spray gun layers, the flow rate of the reducing agent in the k-th layer is calculated according to the following formula:

[0039]

[0040]

[0041]

[0042] β = F(C NO ,C NH3 ,T) (4)

[0043]

[0044] In formula (1), represents the average value of the detection values of all NO concentration sensors below the k-th layer of SNCR spray guns, a is the number of NO concentration detection sensors below the k-th layer of SNCR spray guns, and k ≤ N; X NO(i),k represents the detection value of the i-th NO concentration sensor below the k-th layer of SNCR spray guns, and i ≤ a;

[0045] In formula (2), represents the average value of the detection values of all NH3 concentration sensors above the k-th layer of SNCR spray guns, b is the number of NH3 concentration detection sensors above the k-th layer of SNCR spray guns; X NH3(i),k represents the detection value of the i-th NH3 concentration sensor above the k-th layer of SNCR spray guns, and i ≤ b;

[0046] In formula (3), η is the first correction coefficient; represents the average value of the detection values of all NO concentration sensors below the k-th layer of SNCR spray guns at the initial t0 moment when the sensing unit conducts the first detection each time this invention's control loop is executed; represents the average value of the detection values of all NO concentration sensors below the k-th layer of SNCR spray guns at the t moment when the sensing unit conducts the most recent detection; represents the average value of the detection values of all NH3 concentration sensors above the k-th layer of SNCR spray guns at the initial t0 moment when the sensing unit conducts the first detection each time this invention's control loop is executed; represents the average value of the detection values of all NH3 concentration sensors above the k-th layer of SNCR spray guns at the t moment when the sensing unit conducts the most recent detection;

[0047] In formula (4), β is the second correction coefficient, which is a function of C NO ,C NH3 ,T, and is determined according to on-site test and operation data;

[0048] In formula (5), Q k is the calculated reducing agent flow rate of the k-th layer of SNCR spray guns, and Q V is the volume flow rate of the flue gas at the k-th layer of SNCR spray guns;

[0049] When the following relationship holds, turn off the k-th layer of SNCR spray guns:

[0050] Q k ≤ Q limit (6)

[0051] In formula (6), Q limit is the minimum flow limit value for the opening of the SNCR spray gun layer.

[0052] The present invention has the following beneficial effects compared with the prior art:

[0053] (1) The combustion control system and control method proposed by the present invention aim at efficient and low-pollution combustion of garbage, reducing the generation of NO x and dioxin pollutants during combustion from the source, strengthening the SNCR denitration efficiency. By blowing the secondary air downward, a local vertical vortex flow can be formed above the front-wall secondary air, and cooperating with the burnout air layer to drive the horizontal vortex flow of the flue gas, realizing the mixing of the local vertical vortex flow flue gas and the upward flow flue gas, prolonging the residence time of the flue gas in the high-temperature zone, making the flue gas mixing more uniform, the combustion more sufficient, and the denitration effect better;

[0054] (2) The addition of the burnout air layer forms a water-cooled wall protection air film in the upper part of the first flue, effectively alleviating the erosion of the upper part of the water-cooled wall of the first flue, the furnace wall at the top of the first flue, the elbow at the outlet of the first flue, and the furnace wall at the inlet of the second flue by the flue gas;

[0055] (3) By dynamically adjusting the air distribution ratio of the secondary air and the burnout air, controlling the incineration temperature, while avoiding the large generation of NO x a reaction space suitable for SNCR denitration is broadened, ensuring that the combustion temperature in the area where the SNCR spray gun is arranged is between 850 - 1100 °C;

[0056] (4) The burnout air is added in multiple layers, and some burnout air layers and SNCR spray gun layers can be selectively opened or closed according to the NO concentration, the temperature of the first flue, and the operating load. Furthermore, the burnout air can be transformed into an independent air box system for air supply, meeting the requirements such as when a part of the tail flue gas is incorporated into the secondary air for flue gas recirculation to achieve lower NO x emissions during system transformation, and being able to use the independent air box system of the burnout air to supplement fresh air to ensure the full combustion of flue gas components such as CO;

[0057] (5) Every time the control system executes a control cycle, a functional relationship is established and stored for the detection parameters before execution, the control instructions, and the detection parameters after execution, realizing the update of the feedback adjustment unit database and the calculation program for feedback correction of the control instructions.

[0058] (6) In summary, the technology of the present invention can effectively improve the uneven distribution in the high-temperature combustion zone and the NO in the local high-temperature zone xIt has the disadvantages of large production volume, easy temperature fluctuation in the SNCR denitration area, and low efficiency due to insufficient uniformity of reductant mixing. The control system and control method have a feedback regulation function to achieve dynamic regulation of combustion and denitration and self-correction of the system, and can be widely applied to the fields of low-nitrogen combustion and SNCR denitration technologies. Brief Description of the Drawings

[0059] Figure 1 is a structural block diagram of a control system and a control method for dynamic air distribution in a flue duct in cooperation with SNCR denitration in an embodiment of the present invention;

[0060] Figure 2 is a schematic flow chart of the association of each unit of a control system and a control method for dynamic air distribution in a flue duct in cooperation with SNCR denitration in an embodiment of the present invention;

[0061] Figure 3 is a method flow chart for the feedback regulation unit to perform control according to limit indexes in an embodiment of the present invention;

[0062] Figure 4 is a structural schematic diagram in an embodiment of the present invention;

[0063] Figure 5a is a flow field schematic diagram of the numerical simulation result in an embodiment of the present invention;

[0064] Figure 5b is a flow field schematic diagram of the numerical simulation result of adding an overfire air layer in an embodiment of the present invention;

[0065] Figure 6a is a contour map of the temperature field of the numerical simulation result in an embodiment of the present invention;

[0066] Figure 6b is a contour map of the temperature field of the numerical simulation result of adding an overfire air layer in an embodiment of the present invention;

[0067] Figure 4 Reference numerals: 1. Grate; 2. Furnace; 3. Secondary air burner; 4. First flue duct; 5. Second flue duct; 6. Third flue duct; 7. Rear arch of the furnace; 8. Secondary air lance; 9. Area for arranging overfire air lances; 10. Area for arranging SNCR spray guns; 11. Outlet of the first flue duct; 12. Outlet of the third flue duct. Detailed Embodiments

[0068] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0069] In the description of the present invention, it should be understood that for the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc., is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0070] In the description of the present invention, the meaning of several is one or more, the meaning of multiple is more than two, greater than, less than, exceeding, etc. are understood not to include the present number, and above, below, within, etc. are understood to include the present number. If the first and second are described only for the purpose of distinguishing technical features, they should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0071] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installation, connection, etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0072] As Figure 1 and Figure 2 shown, this embodiment provides a control system for dynamic air distribution coordination SNCR denitration in a flue, including a sensing unit, a feedback regulation unit, and an execution unit;

[0073] The sensing unit includes a temperature and concentration detection module, which is used to monitor the furnace flue gas temperature detection information, NO concentration detection information, CO concentration detection information, and NH3 concentration detection information in real time, and transmit the detection information to the feedback regulation unit;

[0074] The feedback regulation unit includes an instruction layer and a data layer. The instruction layer is used to generate control instructions for the execution unit; the data layer is used to store the control instructions and detection parameters updated in each cycle, and provide historical data for the instruction layer to call;

[0075] The execution unit includes a secondary air execution layer, an overfire air execution layer, and an SNCR execution layer, and regulates each execution layer according to the control instructions generated by the feedback regulation unit.

[0076] The temperature and concentration detection module includes several sensors for detecting flue gas temperature, NO concentration, CO concentration, and NH3 concentration, and the sensors are respectively arranged in the incinerator.

[0077] The incinerator includes a grate 1, a furnace chamber 2, a secondary air burner 3, a first flue 4, a second flue 5, and a third flue 6; the lower part of the grate 1 is the primary air inlet; the furnace chamber 2 is located above the grate 1;

[0078] There is a rear arch 7 on the furnace chamber 2; the secondary air burner 3 is located above the furnace chamber 2, and the first flue 4 is located above the secondary air burner 3; the inlet of the second flue 5 is connected to the outlet of the first flue 4; the inlet of the third flue 6 is connected to the outlet of the second flue 5.

[0079] A burnout air lance arrangement area 9 is formed between the secondary air burner 3 and the outlet of the first flue 4; at least two or more layers of burnout air layers are arranged at intervals in the burnout air lance arrangement area 9; the SNCR lance arrangement area 10 is located in the burnout air lance arrangement area 9 and is arranged in the area where the flue gas temperature is 850 - 1100 °C, and one or more layers can be selectively arranged.

[0080] The several sensors are respectively arranged at the inlet of the first flue 4, between the inlet of the first flue 4 and the first layer of burnout air layer, between every two layers of burnout air layers, and between the burnout air layer and the SNCR lance layer. The sensors for detecting the NH3 concentration are arranged on the four-sided water-cooled walls above each layer of SNCR lance layer and at the outlet of the first flue 4.

[0081] As Figure 4 shown, the garbage enters above the grate through the feed inlet, and the primary air is blown in from the primary air inlets below each stage of the grate 1. The garbage completes four processes of moisture evaporation, devolatilization, volatile combustion, and burnout of fixed carbon in the furnace chamber under the heating of the primary air, gas-phase combustion radiation, and countercurrent flue gas at the rear of the furnace chamber. Under the restriction of the rear arch 7, the furnace chamber flue gas flows reversely into the secondary air burner 3 along the fold angle of the rear arch 7. The front and rear wall secondary air lances 8 are blown downward at an angle of 20 - 45° with the horizontal plane for counterblowing. Under the action of the secondary air, as Figure 5a shown, the flue gas converges and burns in the middle of the secondary air burner, rises along the first flue 4 and gradually spreads out, and forms a negative pressure in the area above the front and rear wall secondary air. Since the outlet of the first flue is located on one side of the rear wall, when the flow field tends to be stable, the flue gas is more inclined to rise along the rear wall. As Figure 5a shown, therefore, a locally larger vertical vortex is generated above the front wall secondary air, and a locally smaller vertical vortex is formed above the rear wall secondary air.

[0082] The secondary air execution layer is used to adjust the air distribution volume of the blowing components on the front and rear walls of the secondary air burner 3. The blowing components include several rows of secondary air lances 8, flow control valves, and a first signal regulator located on the front and rear walls of the secondary air burner. The flow control valves are connected to several rows of secondary air lances 8 and are used to adjust the air output volume of the secondary air lances. The first signal regulator is connected to the first secondary air induced draft fan and adjusts the output power of the secondary air induced draft fan according to the control instruction of the feedback adjustment unit to realize the adjustment of the secondary air distribution volume. The two rows of air lances on the front and rear walls of the secondary air lance 8 are arranged staggeredly, and the downward blowing angle of each row of secondary air lances with the horizontal plane is between 20 - 45°.

[0083] The burnout air layer is arranged in the area 9 between the secondary air burner 3 and the outlet of the first flue 4. One layer of burnout air is arranged every 2 - 3 m. One or more blowing components are arranged on the water-cooled walls on all four sides at the arrangement position of each layer of burnout air (i.e., at the same height). The adjustable range of the angle between the burnout air lance and the water-cooled wall in the burnout air execution layer is 30 - 50°, which is used to adjust the combustion state and the mixing state of the reducing agent and the flue gas. Driven by the burnout air, the flue gas forms a horizontal vortex flow above the first flue, mixes the locally vertically vortex-flowing flue gas above the secondary air burner 3 with the rising flue gas, and forms an enclosing air layer in the upper part of the first flue 4, effectively converging the flue gas to burn in the middle area of the flue.

[0084] The burnout air layer is uniformly supplied with air by the secondary air induced draft fan, that is, using the secondary air distribution system to distribute part of the secondary air to the burnout air; it can also be supplied with air by configuring an independent induced draft system.

[0085] Preferably, the burnout air execution layer includes a flow control valve and a second signal regulator. The flow control valve is connected to the burnout air lances of each layer and is used to adjust the air output of the burnout air lances. The second signal regulator is connected to the second secondary air induced draft fan and adjusts the output power of the secondary air induced draft fan according to the control instruction of the feedback adjustment unit to achieve the adjustment of the burnout air distribution volume.

[0086] The SNCR execution layer controls the reducing agent flow control valve, the atomizing medium control valve and the third signal regulator. The reducing agent flow control valve and the atomizing medium control valve are respectively installed between the inner interface and the outer interface of the reducing agent and the atomizing medium conveying pipelines and the SNCR spray guns of each layer to adjust the reducing agent flow rate, the atomizing medium flow rate and the pressure. The third signal regulator is connected to the input end of the compressor. The output end of the compressor is respectively connected to the reducing agent and the atomizing medium conveying pipelines and adjusts the output power of the compressor according to the control instruction of the feedback adjustment unit to achieve the adjustment of the flow rate and pressure of the SNCR spray guns.

[0087] The start cycle of the sensing unit is adjusted according to the actual operating conditions. The temperature and NO concentration detection sensors of the sensing unit are arranged in the area 9 where the burnout air lances are arranged, specifically at the entrance of the first flue 4, between the entrance of the first flue 4 and the first layer of burnout air layer, between every two layers of burnout air, and between the burnout air layer and the SNCR spray gun layer. The sensors for detecting the NH3 concentration are arranged on the water-cooled walls on all four sides above each layer of SNCR spray guns and at the outlet of the first flue 4.

[0088] According to the temperature, NO concentration, and CO concentration detected by the sensing unit at different elevations in the furnace, the feedback adjustment unit instructs the layer according to the temperature T, the temperature change rate △T, and the NO concentration C NO and the NO concentration change rate △CNO 、CO concentration C CO 、CO concentration change rate △C CO , calculate C NO 、C CO and the fitting function relationship with the temperature distribution respectively, and compare the fitting function relationship with the historical function relationship stored in the data layer. Combine with NO x 、the function relationship between the generation characteristics of CO and temperature, calculate the air distribution conditions of the secondary air and burnout air, generate control instructions, and further transmit them to the execution unit.

[0089] As Figure 3 shown, the calculation process of the instruction layer is as follows:

[0090] According to the distribution of T, C NO 、C CO in the first flue 4, judge whether the combustion control standard is reached. When the combustion control standard is not reached, recalculate the air distribution volume of the secondary air and burnout air according to the detection information, and generate control instructions to act on the execution unit;

[0091] Wait until T, C NO 、C CO reach the control index, and further judge whether the flue gas exceeds the set emission limit according to C NO 、C NH3 at the outlet of the first flue 4;

[0092] When C NO and C NH3 both exceed the limit, it means that the SNCR denitration effect is not ideal, and the temperature field and flow field distribution in the SNCR spray gun layout area should be changed by adjusting the air distribution volume of the secondary air and burnout air; when C NO exceeds the standard while C NH3 does not exceed the standard, it means that the reductant injection amount is too small, and the reductant dosage should be calculated; when C NH3 exceeds the standard while C NO does not exceed the standard, it means that the reductant injection amount is too much, and the reductant dosage should be calculated;

[0093] Further generate control instructions to act on the execution unit, and wait until the update time to re-detect the data and judge the limit value of the instruction layer.

[0094] The execution unit adjusts the air distribution volume of each air gun in the secondary air and burnout air distribution layer according to the received control instructions. Wait until the first update time t1, and the sensing unit detects the temperature, NO concentration, and CO concentration at different elevations in the furnace again, and transmits them to the feedback adjustment unit;

[0095] The feedback adjustment unit is based on the updated T, △T, C NO 、△C NO 、CCO , △C CO Based on information such as etc., judge the combustion effect. If the control standard is met, calculate the number of layers of SNCR spray guns to be opened, the reducing agent flow rate and compressed air pressure allocated to each SNCR spray gun, as well as the atomizing medium parameters (flow rate, pressure), and generate an updated control instruction for the SNCR execution layer. Otherwise, regenerate the control instruction to adjust the air distribution volume of each air gun in the overfire air and burnout air distribution layers;

[0096] When the second update time t2 is reached, the sensing unit measures C at the outlet of the first flue NO , C NH3 and C above the SNCR spray gun layer NH3 . Detect the distribution of NH3 on the four-sided water-cooled wall, predict the distribution of the injected reducing agent in the flue, transmit it to the feedback adjustment unit, analyze the denitrification effect, and compare it with the historical function relationship stored in the data layer. Further calculate the deflection angle of the burnout air gun and generate a control instruction;

[0097] After the spray gun angle is adjusted, when the third update time t3 is reached, the sensing unit re-measures the temperature, NO concentration, CO concentration, and NH3 concentration, and transmits them to the feedback adjustment unit to judge the denitrification effect. If the set standard is met, store them in the data layer of the feedback adjustment unit to complete the update of the database. Otherwise, through the instruction layer of the feedback adjustment unit, recalculate and generate an instruction based on the detection data of C NO , C NH3 .

[0098] Through numerical simulation verification, the flow field and temperature field without the burnout air layer are as shown in Figure 5a and Figure 6a . The flow field and temperature field after adding the burnout air are as shown in Figure 5b and Figure 6b . In Figure 5b , the flow field distribution of the first flue is uniform, and the flue gas flow rate in the central area of the flue is the largest. In Figure 5a , when the burnout air is added, the phenomenon that the flue gas rises close to the rear wall is significantly improved, and at the same time, the phenomenon that the flue gas scours the rear wall at the inlet of the second flue is also significantly improved; From Figure 6a and Figure 6b , it can be seen that there is a large correlation between the temperature distribution of the flue gas and the flow field distribution. The high-temperature area of Figure 6a is close to the rear wall of the first flue, and the high-temperature area of Figure 6b is concentrated in the center of the flue. According to the density of the isotherms, it can be analyzed that the temperature distribution of Figure 6b is more uniform. Figure 5a The arrows in represent the secondary air injection direction, the burnout air injection direction, respectively. The two large arrows on Figure 5a represent that affected by the downward secondary air, the flue gas forms a vertical vortex flow. Figure 5bThe arrow in the figure indicates the approximate layout of the overfire air (OFA) / burnout air.

[0099] In summary, through numerical simulation, the control method of this waste incinerator is feasible. Compared with the existing control systems, the control system for dynamic regulation of air distribution and coordinated SNCR denitrification in the flue gas of the waste incinerator in this embodiment has at least the following advantages:

[0100] (1) It can meet the automatic adjustment of different air distribution volumes and SNCR reductant injection amounts under different load conditions, different fuel calorific values and other variables. By dynamically regulating the air distribution ratio of the overfire air and burnout air and performing feedback correction through segmented and multiple parameter detections, the temperature in the SNCR denitrification area of the first flue can be controlled between 850 - 1100 °C, ensuring the reaction area of SNCR denitrification and reducing the generation of thermal NO x and selecting an appropriate SNCR spray gun layer to reduce ammonia escape and save the usage amount of the reductant.

[0101] (2) There are two layers of burnout air above and below the SNCR spray gun. By controlling the air volume of the burnout air, the full mixing of the reductant and the flue gas can be achieved, maximizing the denitrification efficiency. Through the detection and analysis of the NH3 concentration near the wall surface of the four - sided water - cooled wall above the SNCR spray gun layer to understand the distribution of the reductant in the flue, and feedback - correcting the adjustment of the blowing angle of the burnout air gun, the corrosion of the water - cooled wall by the reductant can be effectively avoided.

[0102] (3) This control system and control method have the function of a feedback - correction system program. By analyzing the optimal operating conditions existing in the operation optimization process, referring to its control process and adjustment range, and applying them to the correction of key control parameters, with the accumulation of historical data, the optimization and adjustment function of the control system is enhanced, and it has a wide application prospect.

[0103] The above - mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above - mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A control system for dynamic air distribution in a flue duct in coordination with SNCR denitration, characterized in that, It includes a sensing unit, a feedback regulation unit, and an execution unit; The sensing unit includes a temperature and concentration detection module, which is used to monitor the detection information of the flue gas temperature, NO concentration, CO concentration, and NH3 concentration in the furnace in real time, and transmit the detection information to the feedback regulation unit; the temperature and concentration detection module includes several sensors for detecting the flue gas temperature, NO concentration, CO concentration, and NH3 concentration, and the sensors are arranged in the incinerator; The incinerator includes a grate (1), a furnace chamber (2), a secondary air burner (3), a first flue (4), a second flue (5), and a third flue (6); the lower part of the grate (1) is the primary air inlet; the furnace chamber (2) is located above the grate (1); a rear furnace arch (7) is provided on the furnace chamber (2); The secondary air burner (3) is located above the furnace chamber (2), and the first flue (4) is located above the secondary air burner (3); the inlet of the second flue (5) is connected to the outlet of the first flue (4); the inlet of the third flue (6) is connected to the outlet of the second flue (5); A burnout air lance arrangement area (9) is formed between the secondary air burner (3) and the outlet of the first flue (4); more than two layers of burnout air layers are arranged at intervals in the burnout air lance arrangement area (9); an SNCR spray gun arrangement area (10) is provided in the burnout air lance arrangement area (9), and the SNCR spray gun arrangement area (10) is arranged in the area where the flue gas temperature is 850 - 1100 °C and is located between two layers of burnout air layers, and several layers of SNCR spray gun layers are provided in the SNCR spray gun arrangement area (10); The flue gas temperature sensors, NO concentration sensors, and CO concentration sensors of the sensing unit are arranged at the inlet of the first flue (4), between the inlet of the first flue (4) and the first layer of burnout air layer, between every two layers of burnout air layers, and between the burnout air layer and the SNCR spray gun layer, and the sensors for detecting the NH3 concentration are arranged on the four - side water - cooled walls above each layer of SNCR spray gun layer and at the outlet of the first flue (4); In the burnout air lance arrangement area (9), a burnout air layer is arranged every 2 - 3 m, and one or several blowing components are arranged on the four - side water - cooled walls of each burnout air layer; the burnout air layers are uniformly supplied with air by a secondary air induced draft fan, that is, using a secondary air distribution system to distribute part of the secondary air to the burnout air, or supplying air through a configured independent induced draft system; The feedback regulation unit includes an instruction layer and a data layer. The instruction layer generates control instructions for the execution unit according to the detection information transmitted by the sensing unit; the data layer is used to store the execution instructions and detection information parameters updated in each cycle and provide the data called by the instruction layer; The execution unit includes a secondary air execution layer, a burnout air execution layer, and an SNCR execution layer, and regulates each execution layer according to the control instructions transmitted by the feedback regulation unit; The secondary air execution layer is used to adjust the air distribution volume of the blowing component. The blowing component includes several rows of secondary air nozzles (8) located on the front and rear walls of the secondary air burner, a secondary air flow control valve, and a first signal regulator. The secondary air flow control valve is connected to several rows of secondary air nozzles (8) and is used to adjust the air output volume of the secondary air nozzles. The two rows of secondary air nozzles on the front and rear walls of the secondary air nozzles (8) are arranged staggeredly, and the downward blowing angle of each row of secondary air nozzles with the horizontal plane is between 20° and 45°; The adjustable range of the angle between each air gun of the overfire air layer and the water wall is 30° - 50°, which is used to adjust the combustion state and the mixing state of the reducing agent and the flue gas.

2. The control system for dynamic air distribution in flue ducts in coordination with SNCR denitration according to claim 1, wherein, The first signal regulator is connected to the first secondary air induced draft fan, and according to the control instruction of the feedback adjustment unit, adjusts the output power of the first secondary air induced draft fan to realize the adjustment of the secondary air distribution volume; The overfire air execution layer includes an overfire air flow control valve and a second signal regulator. The overfire air flow control valve is connected to each layer of overfire air nozzles and is used to adjust the air output volume of the overfire air nozzles. The second signal regulator is connected to the second secondary air induced draft fan, and according to the control instruction of the feedback adjustment unit, adjusts the output power of the second secondary air induced draft fan to realize the adjustment of the overfire air distribution volume; The SNCR execution layer includes a reducing agent flow control valve, an atomizing medium control valve, and a third signal regulator. The reducing agent flow control valve and the atomizing medium control valve are respectively installed between the inner and outer interfaces of the reducing agent and the atomizing medium conveying pipelines and each layer of SNCR spray guns, and are used to adjust the reducing agent flow rate, the atomizing medium flow rate and pressure; The third signal regulator is connected to the input end of the compressor, and the output end of the compressor is respectively connected to the reducing agent and the atomizing medium conveying pipelines. According to the control instruction of the feedback adjustment unit, the output power of the compressor is adjusted to realize the adjustment of the flow rate and pressure of the SNCR spray gun.

3. The control system for dynamic air distribution in flue ducts in coordination with SNCR denitration according to claim 1, wherein The layout height of the SNCR spray gun is selected according to the flue gas temperature of 850 - 1100 °C and is arranged between two layers of overfire air layers, and at least two SNCR spray guns are arranged on each layer.

4. The control system for dynamic air distribution in flue ducts cooperating with SNCR denitration according to claim 1, characterized in that, The instruction layer calculates according to the detection information of the flue gas temperature, NO concentration, CO concentration, and NH3 concentration transmitted by the sensing unit, and compares with the historical data of the data layer, generates a control instruction and transmits it to the execution unit and the signal regulator to control the air distribution volume of the secondary air nozzles and each air gun of the overfire air layer, the spraying parameters of the SNCR spray gun, or selectively turn on / off each air gun of the overfire air layer and the SNCR spray gun; The data layer is used to store the control instructions, flue gas temperature distribution, NO concentration distribution, CO concentration distribution, NH3 concentration distribution, and SNCR denitration efficiency related data updated in each cycle, and generates a database for the instruction layer to call.

5. A control method for a control system of a dynamic air distribution in a flue duct in coordination with SNCR denitration as claimed in claim 1, characterized in that, It includes the following steps: The sensing unit detects the flue gas temperature, NO concentration, CO concentration, and NH3 concentration at different elevations in the incinerator; The feedback adjustment unit receives the detection data of the sensing unit and adjusts the temperature T, temperature change rate △T, NO concentration C at different elevations. NO , NO concentration change rate △C NO , CO concentration C CO , CO concentration change rate △C CO , calculate C NO , C CO The fitting function relationship with the temperature distribution is compared with the historical function relationship stored in the data layer, combined with NO x , the functional relationship between CO generation characteristics and temperature, calculate the air distribution conditions of secondary air and burnout air, and generate control instructions; The execution unit adjusts the air distribution volume of each air gun of the secondary air and the overfire air layer according to the control instruction; After the air distribution is adjusted and the incineration state reaches a new stable state, that is, when the set first update time t1 is reached, the sensing unit detects the temperatures, NO concentrations, and CO concentrations at different elevations in the furnace again and transmits them to the feedback adjustment unit; The feedback adjustment unit makes a judgment on the combustion effect based on the updated T, △T, C NO , △C NO , C CO , △C CO information. If the control standard is met, it calculates the number of layers of SNCR spray guns to be opened and the flow rates and pressures of the reducing agent and atomizing medium allocated to each SNCR spray gun, and generates an updated control instruction for the SNCR execution layer. Otherwise, it regenerates the control instruction to adjust the air distribution of each air gun in the overfire air and burnout air layers; After the SNCR execution layer finishes executing the update instruction and waits for the denitration reaction to reach a new stable state, that is, when the set second update time t2 is reached, the sensing unit performs the detection of C at the outlet of the first flue NO , C NH3 and above the SNCR spray gun layer C NH3 The detection of is carried out. Through the distribution of NH3 on the four-sided water-cooled wall, the distribution of the injected reducing agent in the flue is predicted, transmitted to the feedback adjustment unit, the denitration effect is analyzed, and compared with the historical function relationship stored in the data layer, and further calculate the deflection angle of the burnout air lance to generate a control instruction; After the spray gun angle is adjusted and the denitrification and combustion reactions reach a new stable state, that is, when the set third update time t3 is reached, the sensing unit re-detects the temperatures, NO concentrations, CO concentrations, and NH3 concentrations, transmits them to the feedback adjustment unit, updates the denitrification state, and stores them in the data layer of the feedback adjustment unit to complete the update of the database; The above completes a control cycle for achieving low-nitrogen and low-dioxin combustion and efficient SNCR denitrification through dynamic flow field adjustment. According to the different working conditions and furnace types, as well as whether the actual denitrification effect reaches the set limit value, the execution cycle t0 of this control system and the update time of each stage are adjusted to automatically realize the cyclic feedback control of efficient SNCR denitrification in the waste incinerator.

6. The control method of a control system for dynamic air distribution in a flue duct in coordination with SNCR denitration according to claim 5, characterized in that, In the N-layer SNCR spray gun layer, the reducing agent flow rate of the k-th layer is calculated according to the following formula: β = F(C NO , C NH3 , T)(4) In formula (1), represents the average value of the detection values of all NO concentration sensors below the k-th layer of SNCR spray guns, a is the number of NO concentration detection sensors below the k-th layer of SNCR spray guns, and k ≤ N; X NO(i),k represents the detection value of the i-th NO concentration sensor below the k-th layer of SNCR spray guns, and i ≤ a; In formula (2), represents the average value of the detection values of all NH3 concentration sensors above the k-th layer of SNCR spray guns, and b is the number of NH3 concentration detection sensors above the k-th layer of SNCR spray guns; X NH3(i),k represents the detection value of the i-th NH3 concentration sensor above the k-th layer of SNCR spray guns, where i ≤ b; In formula (3), η is the first correction coefficient; represents the average value of the detection values of all NO concentration sensors below the k-th layer of SNCR spray guns at the initial time t0 when the sensing unit conducts the first detection each time the control loop of the present invention is executed; represents the average value of the detection values of all NO concentration sensors below the k-th layer of SNCR spray guns at time t when the sensing unit conducts the most recent detection; represents the average value of the detection values of all NH3 concentration sensors above the k-th layer of SNCR spray guns at the initial time t0 when the sensing unit conducts the first detection each time the control loop of the present invention is executed; represents the average value of the detection values of all NH3 concentration sensors above the k-th layer of SNCR spray guns at time t when the sensing unit conducts the most recent detection; In formula (4), β is the second correction coefficient, which is a function of C NO , C NH3 , and T, and is determined according to on-site test and operation data; In formula (5), Q k is the reducing agent flow rate of the k-th layer of SNCR spray guns calculated, and Q V is the volume flow rate of the flue gas at the k-th layer of SNCR spray guns; When the following relationship holds, the k-th layer SNCR spray gun is closed: Q k ≤Q limit (6) In formula (6), Q limit is the minimum flow limit value for the opening of the SNCR spray gun layer.

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