A steam-enhanced SNCR system and methods of using the same

Abstract

The application discloses a steam enhanced SNCR system and a use method thereof, relates to the technical field of flue gas denitration treatment, and comprises the following steps: S1, a first conveying control unit is used for conveying main steam to a coupling mixer and controlling the flow of the main steam; S2, a second conveying control unit is used for conveying ammonia water and controlling the flow of the ammonia water; S3, a coupling processing unit is used for mixing the main steam and the ammonia water to form a mixture; S4, the second conveying control unit is used for conveying an efficiency improver and controlling the flow of the efficiency improver, and the coupling processing unit is used for mixing the main steam and the ammonia water mixture with the efficiency improver to form a target mixture in a superheated state; and S5, the coupling mixer is used for conveying the target mixture into a lance, and the lance is used for spraying the target mixture into an incinerator. According to the application, water is not added to dilute the ammonia water, and the steam consumption is greatly reduced; the medium-temperature and medium-pressure steam is used to replace the medium-temperature and high-pressure steam in other schemes, so that the requirement for steam quality is reduced; and when the oxygen content is too high, a hydrazine carbohydrazide solution is started to enhance the denitration reaction efficiency.

Description

Technical Field

[0001] This application relates to the technical field of flue gas denitrification treatment, and in particular to a steam-enhanced SNCR system and its usage method. Background Technology

[0002] SNCR, short for Selective Non-Catalytic Reduction, is a catalytic-free denitrification method that uses ammonia or urea as a reducing agent to reduce NOx in flue gas to nitrogen and water at a specific temperature. Due to its low cost, this system is widely used for NOx emission control in various industrial flue gases. Especially in waste-to-energy plants, SNCR systems are common equipment in flue gas treatment systems because of their simplicity and low operating costs. However, in municipal solid waste incinerators, traditional SNCR technology, using compressed air as a medium, often cannot provide sufficient kinetic energy to fully atomize ammonia, nor can it allow ammonia to penetrate deep into the furnace, thus severely limiting its actual denitrification efficiency.

[0003] Existing SNCR systems used in waste-to-energy plants typically use 20% ammonia water, which is further diluted by mixing with water and then injected into the spray gun (0.4MPa~0.5MPa). After that, it is mixed with compressed air, atomized, and sprayed into the furnace through the nozzle.

[0004] In existing technologies and publicly available literature, whether ammonia or urea is used as a reducing agent, the basic method is to prepare it as an aqueous solution, then atomize the diluted solution with compressed air and spray it into the furnace. Another approach is to use steam instead of compressed air for preheating or atomizing ammonia (e.g., patent applications CN201721922888.X, CN202121801117.1, CN201110232337.1, etc.). These approaches do not completely vaporize the reducing agent (ammonia); the ammonia enters the furnace still in droplet form. Some solutions describe using steam to vaporize the reducing agent (e.g., patent applications CN202121412947.5 and CN202020368165.5), but the specific vaporization method is not explained.

[0005] Meanwhile, the publicly available CN117570448A scheme describes a method for premixing and completely vaporizing ammonia water using the thermal energy of high-temperature steam. However, this method uses medium-temperature, sub-high-pressure steam (6.4 MPa, 450℃), which places excessive demands on the steam source. Furthermore, it adds process water to further dilute the ammonia water, resulting in more energy being used to vaporize process water that does not participate in the denitrification reaction, thus increasing steam consumption. Additionally, this scheme does not use synergists to improve denitrification efficiency. Traditional denitrification synergists are injected into the furnace along with ammonia water droplets, without being fully vaporized by steam before being injected. Summary of the Invention

[0006] The purpose of this application is to provide a steam-enhanced SNCR system and its usage method to address the problems of existing technologies that use medium-temperature, sub-high-pressure steam (6.4 MPa, 450°C), which places excessive demands on the steam source; furthermore, the addition of process water to dilute ammonia water results in more energy being used to vaporize process water that does not participate in the denitrification reaction, thus increasing steam consumption; and this solution also does not use synergists to improve denitrification efficiency. Traditional denitrification synergists are injected into the furnace along with ammonia water droplets, without being fully vaporized by the steam before being injected.

[0007] On the one hand, the method of using a steam-enhanced SNCR system provided in this application adopts the following technical solution:

[0008] A method of using a steam-enhanced SNCR system includes the following steps:

[0009] S1. The main steam with a pressure of 4 MPa and a temperature of 400°C is supplied to the coupling mixer through the first conveying control unit, and the flow rate of the main steam is controlled.

[0010] S2. Ammonia water with a concentration of 20% is supplied to the coupling mixer through the second delivery control unit, and the flow rate of the ammonia water is controlled.

[0011] S3. The main steam from step S1 and the ammonia water from step S2 are mixed by the coupling processing unit in the coupling mixer to form a mixture of main steam and ammonia water.

[0012] S4. A synergist with a concentration of 20% is delivered into the mixture in step S3 through the second delivery control unit, and the mass flow rate of the synergist is controlled. Then, the main steam and ammonia water mixture is mixed with the synergist through the coupling processing unit to form a superheated target mixture.

[0013] S5. Finally, the target mixture from step S4 is transported to the spray gun through the coupling mixer, and the target mixture is sprayed into the furnace area of ​​the waste incinerator for denitrification treatment.

[0014] Further, in step S4, the synergist is carbazide, and the hydrolysis temperature of carbazide is between 135°C and 235°C; when starting from a temperature ≥135°C, the specific enthalpy of the target mixture is 2735~2822 kJ / kg and it remains in a superheated state.

[0015] Furthermore, the safe operating temperature of the carbazide is 176°C, and the corresponding enthalpy of the target mixture is 2822 kJ / kg.

[0016] Further, in step S4, the carbonyl hydrazine and ammonia are first mixed in the second delivery control unit, and then the carbonyl hydrazine solution, ammonia and main steam are mixed in the coupling processing unit to form the target mixture.

[0017] Furthermore, the flow rate of the ammonia water is adjusted according to the NOx concentration inside the waste incinerator;

[0018] The flow rate of the main steam is adjusted based on the target mixture with a specific enthalpy of 2735~2822 kJ / kg and exceeding the saturation temperature;

[0019] The mass flow rate of the carbazide solution ranges from 0 to 4.5 kg / h, and the specific enthalpy of the target mixture formed is in the range of 2735 to 2822 kJ / kg, regardless of whether the carbazide solution is used or not.

[0020] Furthermore, the mass flow rate of the carbonyl hydrazine solution has a linear relationship with the oxygen content at the flue gas outlet of the waste incinerator: when the concentration of the carbonyl hydrazine solution is 20wt%, the mass flow rate of the carbonyl hydrazine solution being put into operation follows the formula: y=ax;

[0021] The mass flow rate of the carbonyl hydrazine solution is y kg / h; the oxygen content at the flue gas outlet of the waste incinerator is x%; a is a proportionality coefficient, and the value of a is obtained based on the calculation of reaction kinetics, with the value of a fluctuating between 0.2 and 1.

[0022] On the other hand, the steam-enhanced SNCR system provided in this application adopts the following technical solution:

[0023] A steam-enhanced SNCR system includes a coupled mixer, a first delivery control unit, a second delivery control unit, and an injection unit;

[0024] The coupling mixer includes a mixer body, with at least two inlet ends and at least one outlet end provided on the outside of the mixer body, and a coupling processing unit is also installed inside the mixer body;

[0025] The first conveying control unit includes a main steam supply device, the output end of which is provided with a main steam pipeline, and the other end of the main steam pipeline is connected to one of the inlet ends;

[0026] The second delivery control unit includes an ammonia delivery control unit and a carbonyl hydrazine solution delivery control unit; the ammonia delivery control unit includes an ammonia supply device, the output end of which is provided with an ammonia pipeline, an ammonia flow meter is provided on the outside of the ammonia pipeline, and one end of the ammonia pipeline is connected to a polymerization pipeline, the other end of which is connected to another inlet end, and the output end of the carbonyl hydrazine solution delivery control unit is connected to one end of the polymerization pipeline;

[0027] The injection unit includes a spray gun installed inside the waste incinerator. The input end of the spray gun is connected to a mixed gas pipeline, one end of which is connected to the outlet end, and a steam flow meter is installed on the mixed gas pipeline.

[0028] Furthermore, the carbonyl hydrazine solution delivery control unit includes a carbonyl hydrazine solution storage tank and a reagent pump. A carbonyl hydrazine solution input pipeline is provided between the carbonyl hydrazine solution storage tank and the input end of the reagent pump, and a carbonyl hydrazine solution output pipeline is provided between the output end of the reagent pump and one end of the polymerization pipeline.

[0029] Furthermore, a first pressure reducing unit is provided inside the mixer body, and a second pressure reducing unit is provided on the mixed gas pipeline.

[0030] Furthermore, when the preset environment of the incinerator meets the following conditions: the oxygen content at the flue gas outlet of the waste incinerator is in the range of 8.5% to 11.5% and is maintained in this range for more than 2 minutes, the carbonyl hydrazine solution delivery control unit is activated and adjusts the mass flow rate of the carbonyl hydrazine solution to regulate the target environment of the waste incinerator; when the preset environment of the waste incinerator does not meet the above conditions, the carbonyl hydrazine solution delivery control unit automatically stops the operation of the carbonyl hydrazine solution.

[0031] Compared with the prior art, the beneficial effects of this application are as follows:

[0032] In the method of this application, no process water is added to dilute the ammonia water, which can significantly reduce the steam consumption; at the same time, only medium-temperature and medium-pressure steam (400℃, 4MPa) is used instead of medium-temperature and sub-high-pressure steam (450℃, 6.4MPa) in other schemes, thereby reducing the requirements for steam quality and reducing costs; and when faced with excessive oxygen content in the furnace, the carbonyl hydrazine solution is turned on in a timely manner to enhance the denitrification reaction efficiency.

[0033] Meanwhile, this application also utilizes a denitrification treatment system composed of a coupling mixer, a first conveying control unit, a second conveying control unit, and an injection unit, along with a two-stage decompression method combining a first decompression unit and a second decompression unit. Using main steam at 400℃ and 4MPa as the medium, with the coupling mixer as the core, the main steam is first decompressed, then mixed with ammonia water, and then deheated to form a specific target mixture that is completely maintained in a gaseous state. The obtained mixed gas is drawn out from the coupling mixer, and then subjected to two-stage decompression to ensure a superheated state. Finally, it is sprayed into the furnace area of ​​the waste incinerator through a dedicated spray gun, thereby ensuring superior denitrification effect in the waste incinerator. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a steam-enhanced SNCR system according to an embodiment of this application.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Coupled mixer; 11. Mixer body; 12. Inlet end; 13. Outlet end; 2. First conveying control unit; 21. Main steam pipeline; 3. Second conveying control unit; 31. Ammonia water conveying control unit; 311. Ammonia water pipeline; 312. Polymerization pipeline; 313. Ammonia water flow meter; 32. Carbonyl hydrazine solution conveying control unit; 321. Carbonyl hydrazine solution storage tank; 322. Reagent pump; 323. Carbonyl hydrazine solution input pipeline; 324. Carbonyl hydrazine solution output pipeline; 4. Injection unit; 41. Spray gun; 42. Mixed gas pipeline; 43. Steam flow meter; 44. Second pressure reducing unit. Detailed Implementation

[0037] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0038] On one hand, this application discloses a steam-enhanced SNCR system, which does not use compressed air for atomization and is a denitrification system for controlling nitrogen oxides in municipal solid waste incinerators; see reference Figure 1 In this embodiment, the SNCR system includes a coupling mixer 1, a first delivery control unit 2, a second delivery control unit 3, and an injection unit 4.

[0039] The coupling mixer 1 includes a mixer body 11, an inlet end 12, an outlet end 13, and a coupling processing unit. The inlet end 12 has at least two inlet ends 12, which are respectively installed on the outside of the mixer body 11 to transport external substances (main steam and ammonia water) into the interior of the mixer body 11 along the two inlet ends 12. The outlet end 13 has at least one outlet end 13, which is installed on the outside of the mixer body 11 to discharge the mixture inside the mixer body 11 to a designated location along the outlet end 13.

[0040] The coupling processing unit is installed inside the mixer body 11 to effectively mix the main steam and ammonia water supplied from the two inlet ends 12 into the mixer body 11, thereby forming a main steam and ammonia water mixture. Furthermore, a first pressure reducing unit is integrated inside the mixer body 11. This first pressure reducing unit is used to reduce the pressure of the main steam entering the mixer body 11 while simultaneously creating a local negative pressure area to draw in ammonia water.

[0041] At the same time, refer to Figure 1 In this embodiment, the first delivery control unit 2 includes a main steam supply device and a main steam pipeline 21. The main steam supply device is used to provide main steam with a pressure of 4 MPa and a temperature of 400°C, and a flow meter is also installed on the main steam supply device to control the flow rate of the main steam. One end of the main steam pipeline 21 is connected to the output end of the main steam supply device, and the other end of the main steam pipeline 21 is sealed to one of the inlet ends 12 on the mixer body 11, so as to deliver the main steam into the interior of the mixer body 11 through the main steam pipeline 21.

[0042] Additionally, refer to Figure 1 In this embodiment, the second delivery control unit 3 includes an ammonia delivery control unit 31 and a carbonyl hydrazine solution delivery control unit 32. Specifically, the ammonia delivery control unit 31 includes an ammonia supply device, an ammonia pipeline 311, a polymerization pipeline 312, and an ammonia flow meter 313. The ammonia supply device provides ammonia solution with a concentration of 20%. One end of the ammonia pipeline 311 is connected to the output end of the ammonia supply device. One end of the polymerization pipeline 312 is connected to the end of the ammonia pipeline 311 away from the ammonia supply device, and the other end of the polymerization pipeline 312 is connected to another inlet end 12 on the mixer body 11, so that ammonia solution is sequentially delivered into the interior of the mixer body 11 through the ammonia pipeline 311 and the polymerization pipeline 312. The ammonia flow meter 313 is installed on the outside of the ammonia pipeline 311 to control the flow rate of the ammonia solution.

[0043] Specifically, refer to Figure 1In this embodiment, the carbonyl hydrazine solution delivery control unit 32 includes a carbonyl hydrazine solution storage tank 321, a reagent pump 322, a carbonyl hydrazine solution input pipeline 323, and a carbonyl hydrazine solution output pipeline 324. The storage tank 321 contains a carbonyl hydrazine solution; a reagent pump 322 is installed on one side of the storage tank 321; one end of the carbonyl hydrazine solution inlet pipe 323 is connected to the inlet of the reagent pump 322, and the other end of the carbonyl hydrazine solution inlet pipe 323 is connected to the storage tank 321, so as to draw the carbonyl hydrazine solution in the storage tank 321 into the carbonyl hydrazine solution inlet pipe 323; at the same time, one end of the carbonyl hydrazine solution outlet pipe 324 is connected to the outlet of the reagent pump 322, and the other end of the carbonyl hydrazine solution outlet pipe 324 is connected to one end of the polymerization pipe 312, so as to discharge the carbonyl hydrazine solution in the inlet pipe 323 into the polymerization pipe 312.

[0044] To elaborate, the ammonia water described above is essentially no longer diluted with water in the SNCR system, which significantly reduces steam consumption. This application uses only medium-temperature, medium-pressure steam (400℃, 4MPa) instead of the medium-temperature, sub-high-pressure steam (450℃, 6.4MPa) used in other schemes, thus reducing the requirements for steam quality. Furthermore, when faced with excessively high oxygen content in the furnace, a small amount of carbonyl hydrazine solution is added to the polymerization pipeline 312 at appropriate times to enhance the denitrification reaction efficiency.

[0045] Preferably, the SNCR system of this application is applied to a municipal solid waste incinerator. When the preset environment of the incinerator meets the following conditions: the oxygen content at the flue gas outlet of the waste incinerator is in the range of 8.5% to 11.5% and is maintained in this range for more than 2 minutes, the carbonyl hydrazine solution delivery control unit 32 is activated and the target environment of the waste incinerator is adjusted by regulating the mass flow rate of the carbonyl hydrazine solution. When the preset environment of the waste incinerator does not meet the above conditions, the carbonyl hydrazine solution delivery control unit 32 automatically stops the operation of the carbonyl hydrazine solution.

[0046] The reason for specifying the oxygen content range is that the denitrification reaction also requires a certain oxygen content; too high or too low a content will not achieve optimal efficiency. The solution in this application uses carbamate to address the high oxygen content of most flue gas in the furnace. Too high an oxygen content will cause the carbamate to be consumed prematurely, preventing it from penetrating the furnace with the denitrification agent and thus failing to achieve the expected synergistic effect. With lower oxygen content, the denitrification reaction itself is more efficient, eliminating the need for additional carbamate solution. Furthermore, the requirement to maintain the oxygen content for 2 minutes is the time from when the flue gas composition changes until the sensor can detect that change, thus preventing false triggering.

[0047] In addition, refer to Figure 1 In this embodiment, the injection unit 4 includes a spray gun 41, a mixing gas pipeline 42, and a steam flow meter 43. Multiple spray guns 41 are provided and installed inside the waste incinerator. The input ends of each spray gun 41 are connected to the mixing gas pipeline 42, and the end of the mixing gas pipeline 42 away from the spray gun 41 is connected to the outlet end 13 on the mixer body 11. This allows the mixture inside the mixer body 11 to be transported to the spray gun 41 through the mixing gas pipeline 42, and then the target mixture is sprayed into the waste incinerator using the spray gun 41. The steam flow meter 43 is installed on the mixing gas pipeline 42 to control the flow rate of the mixture.

[0048] Preferably, in this embodiment, a second pressure reducing unit 44 is also installed on the mixed gas pipeline 42. The second pressure reducing unit 44 is located between the steam flow meter 43 and the mixer body 11. By setting the second pressure reducing unit 44, the pressure of the main steam and ammonia water mixture being transported can be reduced, forming a target mixture with a specific enthalpy of 2735~2822kJ / kg and exceeding the saturation temperature.

[0049] To elaborate, both the first pressure-reducing unit and the second pressure-reducing unit 44 are pressure-reducing valves. Specifically, the highest pressure at the outlet of the first pressure-reducing unit is P1, and the highest pressure at the outlet of the second pressure-reducing unit 44 is P2, where P1 is greater than P2, and the difference between P1 and P2 is between 0.08 MPa and 0.12 MPa.

[0050] More specifically, in this application, the value range of P2 is designed and determined based on the distance the mixture can be sprayed into the furnace, the cross-sectional area of ​​the nozzle 41, and the flow rate of the mixture. P1 is an appropriate increase based on the value of P2. Considering the resistance loss of pipelines and other components, the difference between P1 and P2 cannot be too small; P1 needs to be greater than P2 with a certain design margin, otherwise P2 cannot reach the predetermined value.

[0051] If the difference between P1 and P2 is too large, then the value of P1 will be too large, which will cause the main steam flow rate to increase, potentially resulting in an excessively high temperature of the mixture and an enthalpy value higher than the design range, thus affecting the subsequent commissioning of the carbonyl hydrazine solution.

[0052] Therefore, the solution of this application uses a denitrification treatment system composed of a coupling mixer 1, a first conveying control unit 2, a second conveying control unit 3, and an injection unit 4, and a two-stage decompression method combining a first decompression unit and a second decompression unit 44. It uses main steam at a temperature of 400℃ and a pressure of 4MPa as the medium. With the coupling mixer 1 as the core, the main steam is first decompressed and then mixed with ammonia water and then deheated to form a specific target mixture that is completely kept in a gaseous state. The obtained mixed gas is drawn out from the coupling mixer 1, and then the superheated state is ensured by two-stage decompression. Finally, it is sprayed into the furnace area of ​​the waste incinerator through a dedicated spray gun 41, thereby ensuring a superior denitrification effect in the waste incinerator.

[0053] Specifically, when the enthalpy of the target mixture is too high, the following problems may occur: ① Excessive vaporization causes rapid volume expansion, potentially leading to an explosion risk; ② High temperatures accelerate corrosion of pipes, valves, and other equipment; ③ High temperatures cause complete decomposition of subsequent synergists, thus affecting the denitrification effect. When the enthalpy of the target mixture is too low, it is insufficient to completely vaporize the target mixture to achieve supersaturation, affecting its reactivity with nitrogen oxides and thus impacting the denitrification effect. The first pressure-reducing unit lowers the pressure of the main steam and maintains a constant temperature, thereby effectively achieving rapid jetting and diffusion of subsequent ammonia and synergists, and uniformly improving the performance of these substances.

[0054] Secondly, this application only requires a medium-temperature, medium-pressure steam source. On the one hand, this reduces the quality requirements of the steam source for the entire denitrification system. On the other hand, excessively high temperatures (above 400°C) require more ammonia for cooling, and excessive ammonia can lead to secondary pollution risks such as ammonia escape. Without cooling, the target mixture temperature will be too high, deviating from the required specific enthalpy range. Using excessively high steam pressure may prevent the target mixture from reaching supersaturation at the same specific enthalpy under higher pressure, affecting its reactivity with nitrogen oxides and thus impacting the denitrification effect.

[0055] Furthermore, ammonia water does not need to be diluted with water during use. The 20% concentration of ammonia water used can achieve the denitrification effect of the incinerator, thereby further reducing steam consumption. It should be noted that the fact that ammonia water does not need to be diluted with water does not preclude the option of adding synergist solution later, but the added synergist solution has a negligible impact on the concentration of ammonia water.

[0056] On the other hand, this application discloses a method of using a steam-enhanced SNCR system. In this embodiment, the method includes the following steps:

[0057] S1. The first conveying control unit 2 conveys main steam with a pressure of 4 MPa and a temperature of 400°C into the coupling mixer 1 and controls the flow rate of the main steam.

[0058] S2. Ammonia water with a concentration of 20% is supplied to the coupling mixer 1 through the second delivery control unit 3, and the flow rate of the ammonia water is controlled.

[0059] S3. The main steam from step S1 and the ammonia from step S2 are mixed by the coupling processing unit in the coupling mixer 1 to form a mixture of main steam and ammonia.

[0060] S4. A synergist with a concentration of 20% is supplied to the mixture in step S3 via the second delivery control unit 3, and the mass flow rate of the synergist is controlled. Then, the main steam and ammonia mixture is mixed with the synergist via the coupling processing unit to form a superheated target mixture. Specifically, in step S4, the synergist is carbazide, and the carbazide and ammonia are first mixed in the second delivery control unit 3, and then the carbazide solution, ammonia, and main steam are mixed via the coupling processing unit to form a superheated target mixture. To clarify, the superheated state described above refers to the mixture of main steam, ammonia, and synergist being in a thermodynamic state where the temperature at the corresponding pressure is higher than its saturation temperature.

[0061] More specifically, when the oxygen content in the furnace increases (i.e., the oxygen content reading at the flue gas outlet is greater than 8.5%), the reagent pump 322 is turned on, and its output flow rate is adjusted to 3.4~4.6 kg / h, allowing the solution to be continuously pumped into the ammonia water pipeline 311 at this low flow rate. When the conditions are not met, the reagent pump 322 is turned off, thereby saving the amount of reagent used. To address the situation of excessively high oxygen content in the furnace, a small amount of carbonyl hydrazine solution can be added to the ammonia water pipeline to enhance the denitrification reaction efficiency.

[0062] Preferably, in existing publicly available methods for using carbamate, it is mixed with ammonia or urea solution and then injected into the furnace using compressed air. However, in the method of this application, the specific denitrification process is as follows: carbamate is vaporized into a gas by contacting ammonia and high-temperature steam, and then injected into the furnace of the incinerator in molecular form along with the steam at high speed. Simultaneously, the hydrolysis temperature of this carbamate is between 135°C and 235°C; when the temperature starts at ≥135°C, the specific enthalpy of the target mixture is 2735~2822 kJ / kg and remains in a superheated state; specifically, the safe operating temperature of this carbamate is 176°C, corresponding to an enthalpy of 2822 kJ / kg for the target mixture.

[0063] More specifically, starting from 135℃ (i.e., the target mixture specific enthalpy value corresponding to the temperature ≥135℃ in this application scheme is 2735~2822kJ / kg), carbonyl hydrazine has begun to partially hydrolyze into hydrazine, which reduces the reaction steps and time after entering the furnace, and the reaction activity is significantly increased compared to other disclosed schemes; by using hydrazine to create a local reducing atmosphere or consume local excess oxygen in the furnace, the denitrification efficiency of ammonia water under excess oxygen content conditions is improved.

[0064] S5. Finally, the target mixture from step S4 is transported to the spray gun 41 through the coupling mixer 1, and the target mixture is sprayed into the furnace area of ​​the waste incinerator by the spray gun 41 for denitrification treatment.

[0065] Therefore, the use of carbonyl hydrazine in this application has the following effects: on the one hand, carbonyl hydrazine, as an enhancer, helps to improve the denitrification efficiency; and on the other hand, carbonyl hydrazine is injected into the incinerator by the main steam instead of compressed air, which can further improve the denitrification efficiency.

[0066] On the other hand, in this application's SNCR system, carbazide is first mixed with ammonia water before being introduced into the coupling mixer 1, rather than being directly introduced into the coupling mixer 1 through a single pipe, nor is it introduced separately into another coupling mixer 1 connected to the spray gun 41 unit. This ensures the uniformity of the state of carbazide and ammonia water, while reducing equipment complexity. Furthermore, since carbazide hydrolyzes instantaneously at 235°C, if it directly comes into contact with the 400°C main steam, it will decompose instantly, posing an explosion risk. Therefore, in this application's scheme, carbazide must first be mixed with ammonia water, utilizing the endothermic process of ammonia water vaporization to prevent the instantaneous hydrolysis of carbazide from causing drastic volume changes.

[0067] The flow rates of ammonia water, main steam, and carbonyl hydrazine solution are described in detail below:

[0068] Specifically, in this embodiment, the flow rate of ammonia water is adjusted according to the NOx concentration inside the waste incinerator; the flow rate of main steam is adjusted according to the target mixture with a specific enthalpy of 2735~2822 kJ / kg and exceeding the saturation temperature; the mass flow rate of the carbamate solution is in the range of 0~4.5 kg / h, and regardless of whether the carbamate solution is activated, the specific enthalpy of the target mixture formed is in the range of 2735~2822 kJ / kg.

[0069] More specifically, in the operating environment of a 500-ton / day municipal solid waste incinerator, the mass flow rate of the carbonyl hydrazine solution has a certain linear relationship with the oxygen content at the flue gas outlet of the waste incinerator: when the concentration of the carbonyl hydrazine solution is 20wt%, the mass flow rate of the carbonyl hydrazine solution in operation follows the following formula: y=ax;

[0070] The mass flow rate of the carbonyl hydrazine solution is y kg / h; the oxygen content at the flue gas outlet of the waste incinerator is x%, and the achievable range of y is 0~4.6 kg / h, which does not change with the ammonia flow rate but only depends on the oxygen content; a is a proportionality coefficient, and the value of a is obtained based on the calculation of reaction kinetics. The value of a fluctuates between 0.2 and 1, and the optimal value of a in this application is 0.4.

[0071] Based on the above description, the oxygen content at the flue gas outlet of the waste incinerator ranges from 8.5% to 11.5%, meaning that when x = 8.5~11.5%, y = 3.4~4.6 kg / h. Specifically, the value of 'a' is derived from reaction kinetic calculations and is 0.4 under the limitations of this application. However, this value varies under different furnace environments (e.g., flue gas throughput, initial NOx concentration, primary air volume, flue gas velocity, etc.) and can fluctuate between 0.2 and 1. When 'a' is too large, it will result in excessive carbonyl hydrazine input, an overly strong reducing atmosphere, and inhibited denitrification efficiency; when 'a' is too small, the amount of carbonyl hydrazine input is insufficient to cope with the excess oxygen in the furnace, and it will not have an synergistic effect.

[0072] Example 1:

[0073] Taking a 500-ton / day incinerator as an example, the flow rates of ammonia water and main steam can be adjusted. Please refer to Table 1 below for detailed plans.

[0074]

[0075] As can be seen from Table 1, only schemes 1-2 and 1-3 can achieve the requirement of a specific enthalpy of the mixture in this application of 2735~2822kJ / kg.

[0076] Example 2:

[0077] In this embodiment, a 500-ton / day furnace is still used as an example. During the test, the furnace temperature fluctuation did not exceed 5%, the ammonia water flow rate was 50 kg / h, and the main steam flow rate was 300 kg / h. The addition of carbonyl hydrazine solution was manually controlled under different test conditions. Please refer to Table 2 below for detailed procedures.

[0078]

[0079] As shown in Table 2 above, in schemes 2-1, 2-2, 2-7, and 2-8, the oxygen content of the outlet flue gas did not meet the conditions for automatically starting the injection of carbohydrazine solution; therefore, the experiment was changed to manual control. When the oxygen content was low, the NOx conversion values ​​of schemes 2-1 and 2-2 were both low, and the denitrification efficiency was not significantly different. On the contrary, after using carbohydrazine solution, the reducing atmosphere it created was too strong, which inhibited the reaction between ammonia and NOx, thus leading to a decrease in the denitrification reaction efficiency. Therefore, when the oxygen content is low, carbohydrazine solution should not be turned on.

[0080] When the oxygen content is too high, a comparison of schemes 2-7 and 2-8 reveals that while the carbamate solution can increase denitrification efficiency after being turned on, the high oxygen content causes it to be consumed instantly upon entering the furnace. It cannot penetrate the furnace with the gasified ammonia, thus limiting its synergistic effect. Using carbamate in this situation not only wastes the reagent but also fails to significantly control NOx emissions. Schemes 2-3 to 2-6 represent common high-oxygen conditions in the furnace flue gas. Comparing their effects, the carbamate solution can improve denitrification efficiency by approximately 5%.

[0081] Example 3:

[0082] Taking a 500-ton / day furnace as an example, the ammonia flow rate is maintained at 50 kg / h, and the main steam flow rate is maintained at 300 kg / h. When the oxygen content (x) is approximately 10%, according to the formula for calculating the flow rate of the carbamate solution (y=ax) recorded above, the flow rate of manually adding a 20wt% concentration carbamate solution is y under different values ​​of a. Please refer to Table 3 below for detailed plans.

[0083]

[0084] As shown in Table 3 above, in the four schemes, the denitrification efficiency did not reach its maximum value when the proportionality coefficient 'a' was too large (i.e., schemes 3-3 and 3-4) or too small (i.e., scheme 3-1). In scheme 3-2, the denitrification efficiency reached its maximum when the proportionality coefficient 'a' was 0.4.

[0085] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method of using a steam-enhanced SNCR system, characterized in that: The steam-enhanced SNCR system includes a coupling mixer (1), a first delivery control unit (2), a second delivery control unit (3), and an injection unit (4); The coupling mixer (1) includes a mixer body (11), with at least two inlet ends (12) and at least one outlet end (13) provided on the outside of the mixer body (11), and a coupling processing unit is also installed inside the mixer body (11); the first delivery control unit (2) includes a main steam supply device, with a main steam pipeline (21) provided at the output end of the main steam supply device, and the other end of the main steam pipeline (21) being connected to one of the inlet ends (12); The second delivery control unit (3) includes an ammonia delivery control unit (31) and a carbonyl hydrazine solution delivery control unit (32); the ammonia delivery control unit (31) includes an ammonia supply device, the output end of which is provided with an ammonia pipeline (311), an ammonia flow meter (313) is provided on the outside of the ammonia pipeline (311), and one end of the ammonia pipeline (311) is connected to a polymerization pipeline (312), the other end of the polymerization pipeline (312) is connected to another inlet end (12), and the output end of the carbonyl hydrazine solution delivery control unit (32) is connected to one end of the polymerization pipeline (312); The injection unit (4) includes a spray gun (41) installed in the waste incinerator. The input end of the spray gun (41) is connected to a mixed gas pipeline (42). One end of the mixed gas pipeline (42) is connected to the outlet end (13), and a steam flow meter (43) is installed on the mixed gas pipeline (42). The mixer body (11) is also provided with a first pressure reducing unit inside, and the mixed gas pipeline (42) is also provided with a second pressure reducing unit (44); The method of using the steam-enhanced SNCR system includes the following steps: S1. The first conveying control unit (2) conveys main steam with a pressure of 4 MPa and a temperature of 400°C into the coupling mixer (1) and controls the flow rate of the main steam; wherein, the highest pressure value at the outlet of the first pressure reducing unit is P1. S2. Ammonia water with a concentration of 20% is supplied to the coupling mixer (1) through the second delivery control unit (3), and the flow rate of the ammonia water is controlled; wherein, process water is not added to further dilute the ammonia water; S3. The main steam from step S1 and the ammonia water from step S2 are mixed by the coupling processing unit in the coupling mixer (1) to form a mixture of main steam and ammonia water. S4. The second delivery control unit (3) delivers a synergist with a concentration of 20% into the mixture in step S3 and controls the mass flow rate of the synergist. Then, the main steam and ammonia mixture are mixed with the synergist through the coupling processing unit to form a superheated target mixture. The synergist is a carbazide solution, and the mass flow rate of the carbazide solution has a linear relationship with the oxygen content at the flue gas outlet of the waste incinerator: when the concentration of the carbazide solution is 20wt%, the mass flow rate of the carbazide solution is given by the following formula: y=ax; where the mass flow rate of the carbazide solution is y kg / h; the oxygen content at the flue gas outlet of the waste incinerator is x%; and a is a proportionality coefficient, and the value of a is obtained based on the calculation of reaction kinetics, and the value of a fluctuates between 0.2 and 1. The target mixture has a specific enthalpy of 2735~2822 kJ / kg and remains in a superheated state; S5. Finally, the target mixture from step S4 is transported to the spray gun (41) through the coupling mixer (1), and the target mixture is sprayed into the furnace area of ​​the waste incinerator by the spray gun (41) for denitrification treatment; wherein, the highest pressure value at the outlet of the second pressure reducing unit (44) is P2, and P1 is greater than P2, and the difference between P1 and P2 is between 0.08MPa and 0.12MPa.

2. The method of using a steam-enhanced SNCR system according to claim 1, characterized in that: In step S4, the carbonyl hydrazine and ammonia are first mixed in the second delivery control unit (3), and then the carbonyl hydrazine solution, ammonia and main steam are mixed in the coupling processing unit to form the target mixture.

3. The method of using a steam-enhanced SNCR system according to claim 2, characterized in that: The flow rate of the ammonia water is adjusted according to the NOx concentration inside the waste incinerator; The flow rate of the main steam is adjusted based on the target mixture with a specific enthalpy of 2735~2822 kJ / kg and exceeding the saturation temperature; The mass flow rate of the carbazide solution ranges from 0 to 4.5 kg / h, and the specific enthalpy of the target mixture formed is in the range of 2735 to 2822 kJ / kg, regardless of whether the carbazide solution is used or not.

4. The method of using a steam-enhanced SNCR system according to claim 1, characterized in that: The carbonyl hydrazine solution delivery control unit (32) includes a carbonyl hydrazine solution storage tank (321) and a reagent pump (322). A carbonyl hydrazine solution input pipeline (323) is provided between the carbonyl hydrazine solution storage tank (321) and the input end of the reagent pump (322). A carbonyl hydrazine solution output pipeline (324) is provided between the output end of the reagent pump (322) and one end of the polymerization pipeline (312).

5. The method of using a steam-enhanced SNCR system according to claim 4, characterized in that: When the preset environment of the incinerator meets the following conditions: the oxygen content at the flue gas outlet of the waste incinerator is in the range of 8.5% to 11.5% and is maintained in this range for more than 2 minutes, the carbonyl hydrazine solution delivery control unit (32) is activated and the target environment of the waste incinerator is adjusted by regulating the mass flow rate of the carbonyl hydrazine solution; when the preset environment of the waste incinerator does not meet the above conditions, the carbonyl hydrazine solution delivery control unit (32) automatically stops the operation of the carbonyl hydrazine solution.

Images