A high-molecular coupling flue gas recirculation and ammonia reduction system for household garbage incineration

Abstract

The present application belongs to the technical field of waste incineration treatment, and relates to a household garbage incineration polymer coupling flue gas recirculation and ammonia reduction system, which comprises, in sequence, a grate furnace, a waste heat boiler, an economizer, a deacidification tower, a dust collector, an induced draft fan, a chimney, a primary air pipeline leading to a drying section ash bucket of the grate furnace, a secondary air pipeline leading to a flue outlet of the grate furnace, and a recirculation air pipeline; the waste heat boiler is connected with a polymer denitration system; a cyclone separator is arranged between the economizer and the deacidification tower, so that the flue gas can switch paths and enter the deacidification tower after passing through the cyclone separator; the cyclone separator is connected with a leachate concentrate back spraying system; the leachate concentrate back spraying system sprays leachate concentrate into the cyclone separator through a leachate concentrate pipeline to fully react with the flue gas, and absorbs ammonia gas, HCl and SO2 in the flue gas by using the leachate concentrate. The present application couples flue gas recirculation with polymer denitration and leachate back spraying technology, and improves the denitration efficiency to 90%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste incineration treatment, and relates to a high-molecular coupling flue gas recirculation and ammonia reduction system for household waste incineration. BACKGROUND

[0002] With the rapid development of social economy and the continuous improvement of people's living standards, the growth rate of household waste is accelerating, and the environmental pollution problem caused by waste is becoming increasingly serious. Compared with waste composting and waste landfill technology, waste incineration power generation technology is concerned because it meets the requirements of "reduction, harmlessness and resource utilization" for solid waste treatment, and waste incineration power generation has become the leading technology for the treatment of municipal household waste.

[0003] Household waste contains a large amount of C, H, O, N, S and some halogen elements, which will generate harmful components such as NOx, SO2, CO, HCl and dioxin during waste incineration. Among them, the NOx generated by waste incineration is mainly the combustion product of nitrogen-containing organic matter and the reaction product of N2 and O2 in the high-temperature incineration process. NOx includes NO, NO2, N2O and N2O3, and the main components are NO and NO2, of which NO accounts for more than 95%. The NOx generated in the waste incineration process mainly includes fuel-type NOx, thermal-type NOx and rapid-type NOx, of which fuel-type NOx generally accounts for 60% to 80% of the total amount of NOx, thermal-type NOx accounts for 20%, and rapid-type NOx generally does not exceed 5%.

[0004] At present, the removal of NOx in waste incineration flue gas mainly adopts combustion control, SNCR and SCR technology, flue gas recirculation and high-molecular denitration technology, and its main characteristics are as follows:

[0005] Combustion control mainly controls NOx by changing the combustion temperature of the furnace, the oxygen content of the furnace, the ratio of primary and secondary air volume, etc., which can only control the emission limit value of NOx within 400mg / m 3 (per day average), and cannot meet the ultra-low emission requirements of nitrogen oxides NOx.

[0006] SCR technology refers to the reduction of NOx to N2 and water by spraying a reducing agent containing an amino group in the presence of oxygen and a heterogeneous catalyst at a flue gas temperature of 200℃ to 450℃, and the denitration efficiency can reach 80% to 90%.

[0007] SNCR (selective non-catalytic reduction reaction) denitration technology refers to the selective reduction of NOx in flue gas to N2 and water by spraying urea or ammonia water in high-temperature (850℃ to 1100℃) flue gas without catalyst, and the denitration efficiency is generally 30% to 60%. Under normal operating conditions, combined with combustion control, the emission of nitrogen oxides NOx can be controlled within 250mg / m3 The nitrogen oxide NOx emission cannot meet the ultra-low emission requirement.

[0008] The flue gas recirculation is a technology of extracting a part of the flue gas generated by combustion and spraying it into a waste heat boiler for reburning or recycling, and the recirculated flue gas is mostly low-temperature flue gas before and after the incinerator or induced draft fan. The flue gas is basically inert gas, and due to the characteristics of heat absorption and low oxygen content, the recirculation will cause the temperature of the main combustion zone to decrease, thereby reducing the generation of thermal NOx; in addition, it can also reduce the oxygen concentration in the furnace, thereby inhibiting the formation of fuel NOx. At the same time, the flue gas recirculation low-nitrogen combustion technology can also increase the disturbance at the recirculated flue gas injection port and improve the residence time of the flue gas in the furnace.

[0009] The polymer denitration technology is to uniformly spray the solid raw material of the polymer denitration agent into the furnace at 850-1100 DEG C by using a pneumatic conveying device. At a suitable temperature window (850-950 DEG C), the chemical bond between the amino group and the polymer is broken, a large amount of ammonia gas is released, the ammonia gas is uniformly mixed with the flue gas in the furnace and reacts with the NOx in the flue gas to generate harmless N2 and H2O, thereby achieving the purpose of removing NOx, and the denitration efficiency is generally 70-80%. When the denitration efficiency of the polymer denitration reaches about 80%, a large amount of ammonia escape will be generated at the rear end of the system, so that due to environmental protection control and other factors, the polymer denitration system can only be operated at a reduced load, and the performance of the polymer denitration cannot be maximized.

[0010] With the increasingly strict control of NOx indicators by the state and local governments, the commonly used SNCR and SNCR+flue gas recirculation methods for waste incineration cannot meet the local emission requirements, and the one-time investment and operation cost of SCR are much higher than those of SNCR, so the polymer denitration technology with less investment and lower operation cost is gradually applied to waste incineration plants. SUMMARY

[0011] Therefore, the present application aims to solve the above problems and provide a household garbage incineration polymer coupling flue gas recirculation and ammonia reduction system.

[0012] To achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0013] The household garbage incineration polymer coupling flue gas recirculation and ammonia reduction system comprises a grate furnace, a waste heat boiler, an economizer, a deacidification tower, a dust collector, an induced draft fan, a chimney, a primary air pipe connected to a drying section ash bucket of the grate furnace and a secondary air pipe connected to a flue outlet of the grate furnace, and a polymer denitration system connected to the waste heat boiler.

[0014] A cyclone separator is arranged in parallel on a pipeline between the economizer and the deacidification tower, so that the flue gas can switch paths and enter the deacidification tower after passing through the cyclone separator; a leachate concentrate back spraying system is connected to the cyclone separator; the leachate concentrate back spraying system sprays leachate concentrate into the cyclone separator through a leachate concentrate pipeline to fully react with the flue gas, and absorbs ammonia, HCl and SO2 in the flue gas by using the leachate concentrate.

[0015] Further, the bottom of the cyclone separator is connected to a fluidized bed through a pipeline, and the salts formed by the reaction of NH3, leachate concentrate, HCl and SO2 and the salts after the drying of the leachate concentrate enter the fluidized bed through the pipeline for fluidization.

[0016] Further, the system further comprises a recirculation air pipeline; the recirculation air pipeline comprises a recirculation air fan, a recirculation front furnace bank branch pipe and a recirculation rear furnace bank branch pipe; the inlet of the recirculation air fan is connected to the air outlet end of the induced draft fan through a recirculation air extraction pipeline; the recirculation front furnace bank branch pipe and the recirculation rear furnace bank branch pipe are both connected to the air outlet end of the recirculation air fan, and the other ends are respectively connected to the two sides of the flue gas outlet of the furnace bank furnace and are located below the secondary air pipeline connection point.

[0017] Further, the air outlet end of the recirculation air fan is further connected to a recirculation tertiary air front main pipeline, the air inlet of the fluidized bed is connected to the recirculation tertiary air front main pipeline, and the air outlet of the fluidized bed is connected to the waste heat boiler through a recirculation tertiary air rear main pipeline; a dust removal device and a NaOH solution spraying port are arranged on the upper part of the fluidized bed; the salts formed by the reaction of NH3, leachate concentrate, HCl and SO2 and the salts after the drying of the leachate concentrate continuously circulate in the fluidized bed, and NH3 in the salts continuously volatilizes under the action of NaOH and returns to the waste heat boiler through the recirculation tertiary air rear main pipeline.

[0018] Further, the flow of the recirculation air introduced into the fluidized bed is controlled by measuring the change of the content of NH3 in the flue gas in the pipeline between the induced draft fan and the chimney; when the content of NH3 is greater than 8 mg / Nm 3 , the flow of the recirculation air in the fluidized bed is increased; and when the content of NH3 is less than 8 mg / Nm 3 , the flow of the recirculation air in the fluidized bed is decreased.

[0019] Further, the recirculation tertiary air rear main pipeline is connected to the waste heat boiler through a branch pipeline.

[0020] Further, flow control valves are arranged on the recirculation front furnace bank branch pipe, the recirculation rear furnace bank branch pipe and the recirculation tertiary air front main pipeline.

[0021] Further, the positions where the recirculation front furnace bank branch pipe and the recirculation rear furnace bank branch pipe are connected to the outlet of the furnace bank furnace are located 0.5-1 meters below the secondary air pipeline connection point.

[0022] Further, the high polymer denitration system is connected to the front wall and side wall of a flue chamber of a waste heat boiler through a conveying main pipe and upper branch pipes and lower branch pipes connected in parallel on the conveying main pipe; the upper branch pipes, the lower branch pipes and branch pipes on the main pipe after the recirculated third air are arranged alternately in staggered layers.

[0023] The present application has the following advantages:

[0024] The present application couples flue gas recirculation with high polymer denitration and leachate back spraying technology, improves the denitration efficiency to 90%, close to the SCR technology, but the cost is much lower than the SCR, less than half of the cost of the SCR; specifically, the recirculated air is used to stir the flue gas around the high polymer denitration spraying inlet, so that the high polymer denitration agent and the flue gas are mixed more uniformly, and the reaction efficiency is higher; the flue gas recirculation and high polymer denitration two denitration modes are used to superimpose denitration, and the denitration effect is close to the SCR; a bypass is connected between the coal economizer and the deacidification tower, and the leachate concentrate is sprayed, ammonia in the flue gas is absorbed, and the reaction of ammonia, HCl and SO2 is strengthened, so that the deacidification effect is achieved, the load of the deacidification tower is reduced, and the amount of lime is reduced. A part of the salt in the flue gas is separated before the deacidification tower, and the amount of fly ash is reduced. The escaped part of the ammonia in the flue gas is returned to the high polymer denitration reaction area to react with NOx, reducing the consumption of high polymer denitration agent and ammonia escape;

[0025] Other advantages, objects and features of the present application will be in part apparent and in part pointed out hereinafter in the specification, and will be observed by variations now being given or which may be employed in the practice of the application, and which will be within the scope of the application as defined by the appended claims. The objects and other advantages of the present application will be realized and attained by the methods and procedures particularly pointed out in the following description. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to make the objects, technical solutions and advantages of the present application clearer, the preferred embodiments of the present application will be described in detail below with reference to the drawings, in which:

[0027] Figure 1 It is a schematic diagram of the high polymer coupling flue gas recirculation and ammonia reduction system for household garbage incineration in the present application.

[0028] Fig. 1: 1-high molecular de-nitration system; 2-conveying main pipe; 3-upper branch pipe; 4-lower branch pipe; 5-recirculation tertiary air after main pipe; 6-recirculation tertiary air upper branch pipe; 7-recirculation tertiary air middle branch pipe; 8-recirculation tertiary air lower branch pipe; 9-secondary air before branch pipe; 10-exhaust-heat boiler; 11-economizer; 12-secondary air after branch pipe; 13-grate furnace; 14-pipe; 15-cyclone separator; 16-pipe; 17-pipe; 18-permeate thick liquid pipe; 19-pipe; 20-fluidized bed; 21-pipe; 22-deacidification tower; 23-dust collector; 24-inducing fan; 25-chimney; 26-recirculation air extraction pipe; 27-recirculation fan; 28-recirculation main pipe; 29-recirculation grate after branch pipe; 30-recirculation grate before branch pipe; 31-recirculation tertiary air before main pipe; 32-NaOH solution injection port. DETAILED DESCRIPTION

[0029] Other advantages and effects of the present application can be easily understood by those skilled in the art from the description of the embodiments of the present application. The present application can also be implemented or applied in other different embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only schematically illustrate the basic concept of the present application, and the features in the following examples and embodiments can be combined with each other without conflict.

[0030] The drawings are only used for exemplary illustration, and the representation is only a schematic diagram, not a physical diagram, and should not be understood as a limitation of the present application. In order to better illustrate the embodiments of the present application, some components in the drawings may be omitted, enlarged or reduced, and do not represent the actual size of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0031] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back" and the like is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the position relationship in the drawings are only used for exemplary illustration, and should not be understood as a limitation of the present application, and for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0032] Please refer to Figure 1The application discloses a high-molecule coupled flue gas recirculation and ammonia reduction system for household garbage incineration, which comprises a grate furnace 13, a waste heat boiler 10, a coal economizer 11, a deacidification tower 22, a dust remover 23, an air induction fan 24, a chimney 25, a primary air pipe connected to a drying section ash bucket of the grate furnace 13 and a secondary air pipe connected to a flue outlet of the grate furnace 13, and a recirculation air pipe.

[0033] The recirculation air pipe comprises a recirculation air fan 27, a recirculation front grate branch pipe 30 and a recirculation rear grate branch pipe 29.

[0034] The recirculation air fan 27 is connected to an air outlet end of the air induction fan 24 through a recirculation air extraction pipe 26; the recirculation front grate branch pipe 30 and the recirculation rear grate branch pipe 29 are both connected to an air inlet end of the recirculation air fan 27, and connected to two sides of a flue gas outlet of the grate furnace 13 respectively.

[0035] The polymer denitration system 1 accesses the front wall and side wall of a flue gas chamber of the waste heat boiler 10 through the conveying main pipe 2 and the upper branch pipe 3 and the lower branch pipe 4 connected in parallel on the conveying main pipe 2; the recirculation tertiary air main pipe 5 accesses the waste heat boiler 10 in layers through the recirculation tertiary air upper branch pipe 6, the recirculation tertiary air middle branch pipe 7 and the recirculation tertiary air lower branch pipe 8, and the upper branch pipe 3, the lower branch pipe 4, the recirculation tertiary air upper branch pipe 6, the recirculation tertiary air middle branch pipe 7 and the recirculation tertiary air lower branch pipe 8 are arranged alternately in staggered layers, the recirculation air is used to stir the flue gas around the polymer denitration injection port, so that the polymer denitration agent is mixed with the flue gas more uniformly, and the reaction efficiency is higher.

[0036] The positions where the recirculation grate front branch pipe 30 and the recirculation grate rear branch pipe 29 access the outlet of the grate furnace 13 are located 0.5-1 meters below the secondary air pipe access point. The recirculation grate front branch pipe 30, the recirculation grate rear branch pipe 29 and the recirculation tertiary air front main pipe 31 are each provided with a flow control valve.

[0037] During operation, the flow of the recirculation air introduced into the fluidized bed 20 is controlled by measuring the change in the content of NH3 in the flue gas in the pipeline between the induced draft fan 24 and the chimney 25. When the content of NH3 is greater than 8 mg / Nm 3 , the flow of the recirculation air in the fluidized bed 20 is increased, and when the content of NH3 is less than 8 mg / Nm 3 , the flow of the recirculation air in the fluidized bed 20 is reduced.

[0038] Specifically, the recirculation grate rear branch pipe 29 and the recirculation grate front branch pipe 30 are arranged at elevations of 15.8 meters and 15.2 meters respectively below the secondary air front branch pipe 9 and the secondary air rear branch pipe 12 at an elevation of 16 meters. The branch pipe 3 and the lower branch pipe 4 are uniformly arranged on the front wall and the side wall of the waste heat boiler at elevations of 30 meters and 26 meters respectively, and the recirculation tertiary air upper branch pipe 6, the recirculation tertiary air middle branch pipe 7 and the recirculation tertiary air lower branch pipe 8 are uniformly arranged on the front wall and the side wall of the waste heat boiler at elevations of 32 meters, 28 meters and 24 meters respectively.

[0039] When the recirculation system is used, the recirculation air fan 27 is started, and after there is a proper pressure in the recirculation main pipe 28, the valves on the recirculation grate rear branch pipe 29 and the recirculation grate front branch pipe 30 are opened to introduce the recirculation flue gas into the grate furnace 13. According to the air volume and NOx data, the frequency of the recirculation air fan 27 can be appropriately increased or decreased to change the recirculation air volume.

[0040] When the polymer denitration system 1 is running, the polymer denitration agent can be sprayed into the upper branch pipe 3 and the lower branch pipe 4 in one or two layers. The valves on the upper branch pipe 6, the middle branch pipe 7 and the lower branch pipe 8 of the recirculated tertiary air are opened, and the frequency of the recirculated air fan 27 is adjusted to adjust the air volume to the appropriate working condition. For example, when the polymer denitration agent is injected from the polymer denitration upper branch pipe 3, the recirculated flue gas passes through the upper branch pipe 6 and the middle branch pipe 7 of the recirculated tertiary air and enters the waste heat boiler.

[0041] When the leachate concentrate back spraying system is running, the appropriate amount of flue gas at about 250°C is adjusted to enter the cyclone separator 15 by adjusting the valve opening of the pipeline 14 and the pipeline 17, and the leachate concentrate is sprayed through the leachate concentrate pipeline 18 and the branch pipes uniformly distributed around the upper part of the cyclone separator 15. With the spraying of the leachate concentrate and the deceleration of the flue gas, the reaction of ammonia gas with the leachate concentrate, HCl and SO2 is promoted to generate salts which are dried by the flue gas, and other solid impurities in the flue gas are also reduced with the flue gas and settled in the lower part of the cyclone separator 15, and then transported to the fluidized bed 20 through the pipeline 19. In the fluidized bed 20, the impurities are kept for a certain average residence time, and a certain amount of NaOH solution is sprayed into the fluidized bed 20, and the recirculated flue gas is used to promote the fluidization of the impurities, so that the ammonia gas in the impurities is volatilized and mixed with the recirculated tertiary air to return to the waste heat boiler 10. The salts are removed from the pipeline 21 and used for other purposes.

[0042] The system in the embodiment can improve the denitration efficiency to 90%, close to the SCR technology, but the cost is much lower than the SCR.

[0043] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should be covered by the claims of the present application.

Claims

1. A polymer-coupled flue gas recirculation and ammonia reduction system for municipal solid waste incineration, comprising a grate furnace, a waste heat boiler, an economizer, a deacidification tower, a dust collector, an induced draft fan, and a chimney arranged sequentially, as well as a primary air duct leading to the ash hopper of the grate furnace drying section and a secondary air duct leading to the flue gas outlet of the grate furnace; characterized in that: The waste heat boiler is connected to a polymer denitrification system, which transports polymer denitrification agent to the waste heat boiler through pipelines to carry out the denitrification reaction. A cyclone separator is installed in parallel on the pipeline between the economizer and the deacidification tower, allowing the flue gas to switch paths and enter the deacidification tower after passing through the cyclone separator. A leachate concentrate return spraying system is connected to the cyclone separator. The leachate concentrate return spraying system sprays leachate concentrate into the cyclone separator through a leachate concentrate pipeline to fully react with the flue gas, using the leachate concentrate to absorb ammonia, HCl, and SO2 in the flue gas.

2. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 1, characterized in that: The bottom of the cyclone separator is connected to a fluidized bed via a pipe. The salt formed by the reaction of NH3 with leachate concentrate, HCl and SO2, as well as the salt after the leachate concentrate has been dried, enter the fluidized bed through the pipe for fluidization.

3. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 2, characterized in that: It also includes a recirculating air duct; the recirculating air duct includes a recirculating fan, a recirculating grate front branch pipe, and a recirculating grate rear branch pipe; the inlet of the recirculating fan is connected to the outlet of the induced draft fan through a recirculating exhaust pipe; one end of the recirculating grate front branch pipe and the recirculating grate rear branch pipe are connected to the outlet of the recirculating fan, and the other end is connected to both sides of the flue gas outlet of the grate furnace, and is located below the secondary air duct access point.

4. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 3, characterized in that: The outlet of the recirculation fan is also connected to the pre-recirculation tertiary air main pipe. The inlet of the fluidized bed is connected to the pre-recirculation tertiary air main pipe, and the outlet of the fluidized bed is connected to the waste heat boiler through the post-recirculation tertiary air main pipe. The upper part of the fluidized bed is equipped with a dust removal device and a NaOH solution nozzle. The salt formed by the reaction of NH3 with leachate concentrate, HCl and SO2, as well as the salt after the leachate concentrate is dried, continuously circulates in the fluidized bed. Under the action of NaOH, the NH3 in the salt continuously volatilizes and returns to the waste heat boiler through the post-recirculation tertiary air main pipe.

5. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 4, characterized in that: The flow rate of recirculated air introduced into the fluidized bed is controlled by measuring the change in NH3 content in the flue gas in the pipeline between the induced draft fan and the chimney. When the NH3 content is greater than 8 mg / Nm³, the flow rate is controlled. 3 At this time, increase the flow rate of the recirculated air in the fluidized bed to less than 8 mg / Nm³. 3 At all times, reduce the flow rate of recirculated air in the fluidized bed.

6. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 4, characterized in that: The main recirculation air pipe is connected to the waste heat boiler in layers via branch pipes.

7. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 4, characterized in that: The recirculating grate front branch pipe, the recirculating grate rear branch pipe, and the recirculating tertiary air front main pipe are all equipped with flow control valves.

8. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 3, characterized in that: The recirculating grate front branch pipe and the recirculating grate rear branch pipe are connected to the grate furnace outlet at a location 0.5 to 1 meter below the secondary air duct connection point.

9. The municipal solid waste incineration polymer-coupled flue gas recirculation and ammonia reduction system according to claim 6, characterized in that: The polymer denitrification system is connected to the front wall and side wall of the flue gas chamber of the waste heat boiler through the main conveying pipe and the upper and lower branch pipes connected in parallel to the main conveying pipe; the upper and lower branch pipes are arranged alternately with the branch pipes on the main recirculation tertiary air pipe.

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