A method and system for flue gas purification of a waste incinerator

Abstract

The present application belongs to the technical field of waste incineration flue gas purification, and particularly relates to a waste incinerator flue gas purification method and system. The process of the present application is SNCR+semi-dry method+activated carbon+low-temperature oxidation denitration+bag-type dust collector+wet method deacidification. The process system is simple and easy to operate. The low-temperature oxidation denitration is used to replace the low-temperature SCR system, and no additional heat exchange device is needed, thereby saving heating steam, improving project benefits, reducing construction cost and system resistance, and being suitable for compact distribution of old plant modification. The oxidizing agent H2O2 and the magnetic biochar catalyst used in the present application have wide sources and low prices, and are environmentally friendly. The magnetic biochar is used as a catalyst, which can greatly reduce the amount of oxidizing agent and improve the oxidation denitration efficiency. The magnetic biochar is recycled and reused, which can reduce the operation cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste incineration flue gas purification, and particularly relates to a waste incinerator flue gas purification method and system. BACKGROUND

[0002] The waste incineration plant adds a higher-efficiency low-temperature SCR and a wet deacidification process on the basis of the existing combination process of "SNCR + semi-dry method + dry method + activated carbon + bag filter". After these processes, the flue gas can meet the emission standard. The low-temperature SCR can be placed before or after the wet deacidification. Considering that the working temperature window of the developed low-temperature SCR catalyst is usually above 180℃, in order to match the working temperature of the catalyst, a preheating / heat exchange device is often additionally installed, which increases the operation cost of deacidification. In addition, the SCR deacidification unit occupies a large area and has a complex system, which further increases the construction cost and system resistance, causes the production safety to decrease, and is not suitable for the transformation of old plants with compact distribution.

[0003] Nitrogen oxides in flue gas are mainly in the form of NO, which has extremely low solubility. Therefore, in the integrated pollution removal project, pre-oxidation is a very representative pretreatment method, that is, before the flue gas enters the absorption equipment, the NO in the flue gas is converted into high-valence nitrogen oxides which are more easily dissolved by an oxidizing agent, and the HCl and SO2 generated by waste incineration are also absorbed by an alkaline solution. Through this process, efficient integrated desulfurization and denitrification can be achieved, and the use space of the flue gas treatment equipment can be reduced. SUMMARY

[0004] The application provides a waste incinerator flue gas purification method and system, which has the advantages of small occupied area, low investment and operation cost, and is more suitable for the transformation of old plants while achieving ultra-low emission.

[0005] The technical scheme adopted by the application to solve the technical problem is: a waste incinerator flue gas purification method, comprising a incinerator, an SNCR denitration system, a waste heat boiler heating surface, a semi-dry method rotary spraying device, a magnetic biological coke, a bag filter, a gas-gas heat exchanger, a wet deacidification tower and a chimney, and the method specifically comprises the following steps:

[0006] Step S1, primary denitration:

[0007] The flue gas enters the SNCR denitration system from the incinerator for primary denitration;

[0008] Step S2, semi-dry method deacidification:

[0009] The flue gas after the primary denitration in step S1 is heated by the waste heat boiler heating surface and then introduced into the semi-dry method rotary spraying device for deacidification;

[0010] Step S3, magnetic biochar adsorption and oxidation:

[0011] The flue gas after step S2 enters the flue between the semi-dry method rotary spraying device and the bag filter, and the magnetic biochar is sprayed into the flue between the semi-dry method rotary spraying device and the bag filter, which can adsorb dioxin and oxidize NO in the flue gas;

[0012] Step S4, dust removal:

[0013] The flue gas after step S3 adsorption and oxidation enters the bag filter, and the bag filter captures the dust particles and magnetic biochar in the flue gas by using filter material;

[0014] Step S5, flue gas heat exchange:

[0015] The flue gas after step S4 enters the gas-gas heat exchanger and exchanges heat with the clean flue gas after subsequent wet acid removal;

[0016] Step S6, wet acid removal:

[0017] The flue gas after step S5 enters the wet acid removal tower, and reacts with Ca(OH)2 solution in the wet acid removal tower to remove acid gas and solid dust particles to obtain clean flue gas; the clean flue gas discharged after wet acid removal enters the gas-gas heat exchanger, and the flue gas is heated by the gas-gas heat exchanger and discharged from the chimney.

[0018] As a further preferred embodiment of the present application, in step S3, while spraying magnetic biochar into the flue between the semi-dry method rotary spraying device and the bag filter, H2O2 is also introduced into the flue between the semi-dry method rotary spraying device and the bag filter, and the magnetic biochar reacts with H2O2 in the flue to produce active oxygen radicals to oxidize NO in the flue gas;

[0019] While spraying magnetic biochar into the flue between the semi-dry method rotary spraying device and the bag filter, activated carbon is also introduced, which adsorbs dioxin in the flue gas.

[0020] As a further preferred embodiment of the present application, step S4 and step S5 have step S7 magnetic biochar recycling, which is specifically as follows:

[0021] The dust captured in the bag filter flue gas is magnetically separated, and the magnetic biochar is separated from the dust particles and then sprayed into the flue between the semi-dry method rotary spraying device and the bag filter for reaction.

[0022] As a further preferred embodiment of the present application, the lime slurry, the wet flue gas purification system, the gypsum stabilizer, the belt-driven screen are further included, in step S6, the lime slurry in the wet deacidification tower is sprayed at high speed to react with the acid gas in the flue gas; at the same time, the wastewater in the wet flue gas purification system is removed by the gypsum stabilizer; the liquid returned from the gypsum stabilizer and the belt-driven screen still contains soluble salt, which is introduced into the semi-dry rotary spraying device through the circulating pump.

[0023] As a further preferred embodiment of the present application, the gas-gas heat exchanger comprises a first inlet, a first outlet, a second inlet and a second outlet, wherein:

[0024] The hot flue gas enters the first inlet of the gas-gas heat exchanger from the outlet of the bag filter, and the flue gas after heat exchange enters the wet deacidification tower from the first outlet, and the clean flue gas after the wet deacidification tower enters the gas-gas heat exchanger through the second inlet, and the clean flue gas is heated with the high-temperature flue gas in the gas-gas heat exchanger and then enters the chimney from the second outlet.

[0025] A waste incinerator flue gas purification system is also provided, comprising a wet deacidification tower and an incinerator, an SNCR denitration system, a waste heat boiler heating surface, a semi-dry rotary spraying device, a bag filter, an H2O2 storage tank, a gas-gas heat exchanger, and a chimney arranged in sequence along the flue gas flow direction, wherein:

[0026] The wet deacidification tower is connected with the gas-gas heat exchanger;

[0027] An on-line temperature measuring device is arranged in the incinerator for primary denitration of the SNCR denitration system;

[0028] A plurality of ammonia injection lances are further arranged on the incinerator;

[0029] The semi-dry rotary spraying device is connected with the bag filter through a flue, and the flue is provided with an H2O2 atomizing nozzle, which is in communication with the H2O2 storage tank.

[0030] As a further preferred embodiment of the present application, the gas-gas heat exchanger comprises a first inlet, a first outlet, a second inlet and a second outlet, wherein:

[0031] The outlet of the bag filter is connected with the first inlet through a pipeline;

[0032] The first outlet is connected with the inlet end of the wet deacidification tower;

[0033] The outlet end of the wet deacidification tower is connected with the second inlet;

[0034] The second outlet is connected with the chimney through a pipeline.

[0035] As a further preferred embodiment of the present application, the lime slurry, the wet flue gas purification system, the gypsum stabilizer, the belt-driven screen are further included, in step S6, the lime slurry in the wet deacidification tower is sprayed at high speed to react with the acid gas in the flue gas; at the same time, the wastewater in the wet flue gas purification system is removed by the gypsum stabilizer; the liquid returned from the gypsum stabilizer and the belt-driven screen still contains soluble salt, which is introduced into the semi-dry rotary spraying device through the circulating pump.

[0036] The activated carbon storage tank is arranged on the flue between the semi-dry method rotary spraying device and the bag-type dust collector, and the activated carbon is stored in the activated carbon storage tank;

[0037] The magnetic separation machine is connected with one outlet of the bag-type dust collector, and the magnetic separation is performed on the dust captured by the bag-type dust collector;

[0038] One end of the collecting bin is connected with the outlet of the magnetic separation machine, and the other end is connected to the flue between the semi-dry method rotary spraying device and the bag-type dust collector;

[0039] The other outlet of the wet method deacidification tower is connected with the gypsum flow stabilizer;

[0040] One outlet of the gypsum flow stabilizer is directly connected with the semi-dry method rotary spraying device, and the other outlet is connected with the belt drive screen;

[0041] The outlet of the belt drive screen is connected with the semi-dry method rotary spraying device.

[0042] As a further preferred embodiment of the present application, the induced draft fan is arranged on the pipeline connected with the chimney at the second outlet.

[0043] As a further preferred embodiment of the present application, the concentration of H2O2 in the H2O2 storage tank is 10-30%wt, the H2O2 atomized by the H2O2 atomizing nozzle is carried into the flue between the semi-dry method rotary spraying device and the bag-type dust collector by compressed gas, and the molar ratio of H2O2 to NO sprayed into the flue between the semi-dry method rotary spraying device and the bag-type dust collector is 1-4.

[0044] Through the above technical scheme, the present application has the following beneficial effects compared with the prior art:

[0045] 1. The process of the present application is SNCR+semi-dry method+activated carbon+low-temperature oxidation denitration+bag-type dust collection+wet method deacidification, and the process system is simple and easy to operate; the low-temperature oxidation denitration is used to replace the low-temperature SCR system, and no additional heat exchange device needs to be installed, thereby saving the heating steam, improving the project benefit, reducing the construction cost and system resistance, and being suitable for the transformation of old plants with compact distribution.

[0046] 2. The oxidant H2O2 and the magnetic biochar catalyst used in the present application have wide sources and low prices, and are environmentally friendly; the magnetic biochar is used as the catalyst, which can greatly reduce the amount of oxidant and improve the oxidation denitration efficiency; the magnetic biochar is recycled and reused, which can reduce the operation cost.

[0047] 3、The H2O2 and magnetic biochar injection area of the application is in the flue before the bag filter 7, and the bag filter 7 is used as an oxidation reactor; the fly ash recovered is screened by the magnetic separation machine 8, the catalyst can be recycled, and the utilization rate of the catalyst is improved.

[0048] 4、The application uses Ca(OH)2 slurry as a wet deacidification absorbent, compared with a system using NaOH as a wet deacidification absorbent, the operation cost is greatly reduced; the wastewater produced in the wet deacidification system is returned to the semi-dry deacidification system; in this way, the salt-containing wastewater is evaporated, and the waste salt is left on the bag filter; therefore, the waste incineration power plant can use the wet flue gas purification system without considering wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0049] The application will be further described below in combination with the drawings and examples.

[0050] Figure 1 It is a schematic diagram of the overall structure of the application.

[0051] In the figure: 1, incinerator; 2, SNCR denitration system; 3, waste heat boiler heating surface; 4, semi-dry rotary spraying device; 5, activated carbon storage tank; 6, H2O2 storage tank; 7, bag filter; 8, magnetic separation machine; 9, material collecting bin; 10, gas-gas heat exchanger; 11, wet deacidification tower; 12, gypsum flow stabilizer; 13, belt drive screen; 14, induced draft fan; 15, chimney; 101, first inlet; 102, first outlet; 103, second inlet; 104, second outlet. DETAILED DESCRIPTION

[0052] The application will be further described below in combination with the drawings and examples. These drawings are all simplified schematic diagrams, and only schematically show the basic structure of the application, and therefore only show the structures related to the application.

[0053] In the description of the application, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and "first", "second" and the like do not represent the importance of the parts, and therefore cannot be understood as a limitation on the application. The specific dimensions used in the embodiment are only for the purpose of illustrating the technical scheme, and do not limit the protection scope of the application.

[0054] In order to meet the increasingly stringent emission standards, waste incineration power plants often use the process of "dust removal + wet acid removal + low temperature SCR". After these processes, the flue gas can meet the emission standard. However, the temperature of the flue gas after wet acid removal drops significantly. Considering that the working temperature window of the currently developed low-temperature SCR catalyst is above 180℃, in order to match the working temperature of the catalyst, a preheating / heat exchange device is often additionally installed, which increases the operation cost of denitrification. In addition, the SCR denitrification unit occupies a large area and the system is complex, which will further increase the construction cost and system resistance, causing the production safety to decrease, and is not suitable for the transformation of old plants with compact distribution. In view of the above problems, the application uses H2O2 as an oxidant and magnetic biological coke as a catalyst to improve the efficiency of oxidative denitrification while reducing the amount of H2O2. The oxidative denitrification reaction zone is set in the dust remover. On the one hand, the flue gas from the rotary spray device meets the temperature window of oxidative denitrification; on the other hand, the flue gas in the dust remover is disturbed violently, which enhances the mass transfer and heat transfer efficiency and accelerates the NO oxidation reaction rate. The "non-selective catalytic reduction denitrification technology + semi-dry acid removal + low-temperature oxidative denitrification + bag filter + wet acid removal technology" developed in the application can effectively reduce the plant area and investment cost, simplify the process flow while ensuring to meet the requirements of ultra-clean emission.

[0055] Embodiment 1

[0056] The embodiment provides a preferred embodiment, a waste incinerator flue gas purification system, as shown in Figure 1 The system comprises a wet acid removal tower 11 and an incinerator 1, an SNCR denitrification system 2, a waste heat boiler heating surface 3, a semi-dry rotary spray device 4, a bag filter 7, an H2O2 storage tank 6, a gas-gas heat exchanger 10 and a chimney 15 arranged in sequence along the flue gas flow direction, wherein:

[0057] The above-mentioned wet acid removal tower 11 is connected with the gas-gas heat exchanger 10. Specifically, the gas-gas heat exchanger 10 comprises a first inlet 101, a first outlet 102, a second inlet 103 and a second outlet 104, the outlet of the bag filter 7 is connected with the first inlet 101 through a pipeline; the first outlet 102 is connected with the inlet end of the wet acid removal tower 11; the outlet end of the wet acid removal tower 11 is connected with the second inlet 103; and the second outlet 104 is connected with the chimney 15 through a pipeline.

[0058] The above-mentioned incinerator 1 is arranged with an online temperature measuring device for primary denitrification of the SNCR denitrification system 2. Preferably, the online temperature measuring device can adopt acoustic wave temperature measurement and optical temperature measurement.

[0059] The above-mentioned incinerator 1 is also arranged with a plurality of spray guns for spraying ammonia, the arrangement of the plurality of spray guns is according to the corresponding working conditions, and the ammonia spraying amount of the spray guns is automatically adjusted according to the temperature measured by the online temperature measuring device.

[0060] The semi-dry method rotary spraying device 4 is connected with the bag-type dust collector 7 through a flue, and an H2O2 atomizing nozzle is arranged on the flue, and the H2O2 atomizing nozzle is communicated with the H2O2 storage tank 6. Preferably, the concentration of H2O2 in the H2O2 storage tank 6 is 10-30%wt. Specifically, the H2O2 atomized by the H2O2 atomizing nozzle is carried into the flue between the semi-dry method rotary spraying device 4 and the bag-type dust collector 7 by compressed gas. Preferably, the molar ratio of H2O2 to NO sprayed into the flue between the semi-dry method rotary spraying device 4 and the bag-type dust collector 7 is 1-4.

[0061] The embodiment further comprises an activated carbon storage tank 5, a magnetic separation machine 8, a material collecting bin 9, a gypsum flow stabilizer 12 and a belt-driven screen 13. The activated carbon storage tank 5 is arranged on the flue between the semi-dry method rotary spraying device 4 and the bag-type dust collector 7, and the activated carbon storage tank 5 stores activated carbon. The magnetic separation machine 8 is connected with an outlet of the bag-type dust collector 7, and the magnetic separation machine 8 is used for magnetic separation of the dust captured by the bag-type dust collector 7. One end of the material collecting bin 9 is connected with the outlet of the magnetic separation machine 8, and the other end of the material collecting bin 9 is connected with the flue between the semi-dry method rotary spraying device 4 and the bag-type dust collector 7. The other outlet of the wet method deacidification tower 11 is connected with the gypsum flow stabilizer 12. One outlet of the gypsum flow stabilizer 12 is directly connected with the semi-dry method rotary spraying device 4, and the other outlet of the gypsum flow stabilizer 12 is connected with the belt-driven screen 13. The outlet of the belt-driven screen 13 is connected with the semi-dry method rotary spraying device 4.

[0062] The embodiment further comprises an induced draft fan 14, and the induced draft fan 14 is arranged on a pipeline through which the second outlet 104 is connected with a chimney 15.

[0063] The embodiment is provided with a fly ash outlet at the bottom of the bag-type dust collector 7, and the fly ash outlet is connected with the magnetic separation machine 8. The average magnetic induction intensity of the magnet surface of the magnetic separation machine 8 is 80-400mT. The magnetic biochar separated after the magnetic separation is sprayed into the flue.

[0064] The embodiment further comprises a waste incinerator flue gas purification method, and the method specifically comprises the following steps:

[0065] Step S1, primary denitration:

[0066] The flue gas from the incinerator 1 enters the SNCR denitration system 2 for primary denitration. Specifically, the SNCR denitration system 2 is based on different temperature measuring devices to realize real-time rapid online temperature measurement (acoustic wave temperature measurement and optical temperature measurement), and the ammonia injection amount is automatically adjusted under different working conditions through reasonable spray gun arrangement.

[0067] Step S2, semi-dry deacidification:

[0068] The flue gas after the primary denitration in step S1 is heated by the waste heat boiler heating surface 3 and then enters the semi-dry method rotary spraying device 4 for deacidification.

[0069] Step S3, magnetic biochar adsorption and oxidation:

[0070] The flue gas after step S2 enters the flue between the semi-dry method rotary spraying device 4 and the bag filter 7, and the magnetic biochar is sprayed into the flue between the semi-dry method rotary spraying device 4 and the bag filter 7, which can adsorb dioxin and oxidize NO in the flue gas;

[0071] Specifically, it further comprises an H2O2 storage tank 6, which is in communication with the flue between the semi-dry method rotary spraying device 4 and the bag filter 7. In step S3, while spraying the magnetic biochar into the flue between the semi-dry method rotary spraying device 4 and the bag filter 7, H2O2 is introduced into the flue between the semi-dry method rotary spraying device 4 and the bag filter 7, and the Fenton reaction occurs between the magnetic biochar and H2O2 in the flue, and the active oxygen free radicals generated by the reaction oxidize NO in the flue gas. (H2O2 and magnetic biochar can only partially react in the flue, and due to the high flow rate of the flue gas, the unreacted powder is carried into the bag filter 6 with the flue gas, and is recovered by the magnetic separation machine 8 and then sprayed into the flue by compressed air.)

[0072] At the same time, while spraying the magnetic biochar into the flue between the semi-dry method rotary spraying device 4 and the bag filter 7, activated carbon is introduced, which adsorbs dioxin in the flue gas.

[0073] Further, the magnetic biochar in step S3 can act as both a dioxin adsorbent and a Fenton reaction catalyst. The H2O2 solution is atomized into small droplets with a diameter of 10-50 μm by an ultrasonic atomization device, and the droplets are gasified by the flue gas waste heat.

[0074] Step S4, dust removal:

[0075] The flue gas after step S3 adsorption and oxidation is introduced into the bag filter 7, which captures dust particles and magnetic biochar in the flue gas by using filter material;

[0076] Step S5, flue gas heat exchange:

[0077] The flue gas after step S4 is introduced into the gas-gas heat exchanger 10 and exchanged with the clean flue gas after subsequent wet desulfurization;

[0078] Specifically, hot flue gas enters the first inlet 101 of the gas-to-gas heat exchanger 10 from the outlet of the bag filter 7. After heat exchange, the flue gas enters the wet desulfurization tower 11 from the first outlet 102. After passing through the wet desulfurization tower 11, the clean flue gas passes through the second inlet 103 to the gas-to-gas heat exchanger 10. After exchanging heat with the high-temperature flue gas in the gas-to-gas heat exchanger 10, the clean flue gas enters the chimney 15 from the second outlet 104.

[0079] Step S6, Wet deacidification:

[0080] The flue gas after step S5 is fed into the wet deacidification tower 11, where it undergoes a gas-liquid reaction with the Ca(OH)2 solution to remove acidic gases and solid dust particles, resulting in clean flue gas. The clean flue gas discharged after wet deacidification is fed into the gas-to-gas heat exchanger 10, where it is heated and then discharged through the chimney 15.

[0081] Specifically, this implementation scheme also includes lime slurry, a wet flue gas purification system, a gypsum flow stabilizer 12, and a belt-driven screen 13. In step S6, the lime slurry in the wet deacidification tower 11 is sprayed at high speed to neutralize the acidic gases in the flue gas. Simultaneously, the wastewater in the wet flue gas purification system passes through the gypsum flow stabilizer 12 to remove wet gypsum CaSO4•2H2O. The liquid returning from the gypsum flow stabilizer 12 and the belt-driven screen 13 still contains soluble salts and is pumped into the semi-dry rotary spray device 4 via a circulating pump. The flue gas exiting the semi-dry rotary spray device 4 is at a temperature of 140–160°C. In this way, the saline wastewater is evaporated, while the waste salt remains on the bag filter 7.

[0082] This implementation scheme also includes a magnetic separator 8. Between step S4 and step S5, there is a step S7 for the recovery of magnetic bio-coke. Specifically, step S7 involves the magnetic separator 8 performing magnetic separation on the dust captured in the flue gas of the bag filter 7. The separated magnetic bio-coke is collected in the collection bin 9, and then the separated magnetic bio-coke is sprayed into the flue between the semi-dry rotary spray device 4 and the bag filter 7 for reaction.

[0083] In this implementation plan, regarding the acquisition of magnetic biochar: Magnetic biochar can be obtained using rice husks, bamboo shavings, pine wood, etc., as raw materials. The biomass raw materials are impregnated in a ferric chloride solution for 2-5 hours, and then dried in an oven at 105℃. The dried sample is placed in a tube furnace and heated to 500-1000℃, and the precursor is pyrolyzed for 0.5-3 hours under a CO2 protective gas flow rate of 0.1-0.5 L / min. -1 After cooling to room temperature in a protective gas atmosphere, magnetic biochar was obtained.

[0084] Magnetic biochar and H2O2 injected into the flue gas undergo Fenton reaction to produce active oxygen free radicals, and NO is oxidized by active oxygen free radicals in bag filter 7. The oxidized high-valence nitrogen oxides are absorbed by alkaline liquor in wet desulfurization tower 11. The main reaction equations are as follows:

[0085] Fenton reaction:

[0086]

[0087]

[0088] Oxidation process:

[0089]

[0090]

[0091] Absorption process:

[0092]

[0093]

[0094]

[0095]

[0096] As shown in Figure 1 , wet desulfurization tower 11 adopts a single-tower double-circulation structure. The flue gas enters from the lower part of wet desulfurization tower 11, first contacts the slurry sprayed by the lower-circulation spraying device in wet desulfurization tower 11 in a reverse direction, and then is cooled and washed to remove part of SO2 and high-valence nitrogen oxides. The flue gas then enters the upper-circulation zone through the guide vanes of the liquid collector. The flue gas here contacts the liquid slurry sprayed by the upper-circulation spraying device in a reverse direction, and then is washed to remove the remaining SO2 and high-valence nitrogen oxides. The desulfurized clean flue gas is discharged from the upper part of wet desulfurization tower 11 after removing the mist by a mist eliminator.

[0097] Low-temperature oxidation denitration: a technology for realizing denitration by oxidizing NO in flue gas into high-valence nitrogen oxides and then neutralizing and absorbing the high-valence nitrogen oxides by alkaline reagents. In this example, the oxidizing agent is atomized into small droplets by an ultrasonic atomization device, and is injected into the flue gas between the semi-dry method rotary spraying device and the bag filter. The small droplets of the oxidizing agent are gasified by using the residual heat of the flue gas. At the same time, magnetic biochar is used as a gas-phase Fenton catalyst, and is injected into the flue gas between the semi-dry method rotary spraying device and the bag filter. The gasified oxidizing agent is catalytically decomposed into active oxygen free radicals by the magnetic biochar. The active oxygen free radicals oxidize NO into high-valence nitrogen oxides, which are removed by the subsequent wet desulfurization device.

[0098] The temperature range of low temperature in the low temperature oxidation denitration of the embodiment is 140-160 DEG C; lower than the requirement of low temperature SCR catalyst working temperature window 180 DEG C above.

[0099] In summary, the process of the application is SNCR+semi-dry method+activated carbon+low temperature oxidation denitration+bag filter dust removal+wet deacidification; the low temperature oxidation denitration is used to replace the low temperature SCR system. The application uses hydrogen peroxide as the oxidant, magnetic biochar as the catalyst and dioxin adsorbent; the preparation of magnetic biochar adopts CO2 activation process. The injection area of H2O2 and magnetic biochar of the application is in the flue before the bag filter dust collector 7, and the bag filter dust collector 7 is used as the oxidation reactor. The application uses the magnetic separation machine 8 to screen the fly ash recovered, and the catalyst can be recycled, thereby improving the utilization rate of the catalyst. The application uses Ca(OH)2 slurry as the wet deacidification absorbent.

[0100] Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have meanings consistent with meanings in the context of the present technology, and should not be interpreted with idealized or overly formal meanings unless defined as such.

[0101] The meaning of "and / or" described in the application means that each single existence or both existences are included.

[0102] The meaning of "connection" described in the application can be direct connection between components or indirect connection between components through other components.

[0103] Based on the above ideal embodiments according to the application, the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the application. The technical scope of the application is not limited to the contents of the specification, and the technical scope must be determined according to the scope of claims.

Claims

1. A method for cleaning flue gas from a waste incinerator, characterized in that: The method comprises a burning furnace (1), an SNCR denitration system (2), a waste heat boiler heating surface (3), a semi-dry method rotary spraying device (4), magnetic biological coke, a bag-type dust collector (7), a gas-gas heat exchanger (10), a wet method acid removal tower (11), and a chimney (15), and specifically comprises the following steps: Step S1, primary denitration: The flue gas from the burning furnace (1) enters the SNCR denitration system (2) for primary denitration; Step S2, semi-dry method acid removal: The flue gas after the primary denitration in step S1 is heated by the waste heat boiler heating surface (3) and then enters the semi-dry method rotary spraying device (4) for acid removal; Step S3, magnetic biological coke adsorption and oxidation: The flue gas after step S2 enters the flue duct between the semi-dry method rotary spraying device (4) and the bag-type dust collector (7), and magnetic biological coke is sprayed into the flue duct between the semi-dry method rotary spraying device (4) and the bag-type dust collector (7), which can adsorb dioxin and oxidize NO in the flue gas; Step S4, dust removal: The flue gas after the adsorption and oxidation in step S3 enters the bag-type dust collector (7), which captures dust particles and magnetic biological coke in the flue gas by using filter material; Step S5, flue gas heat exchange: The flue gas after step S4 enters the gas-gas heat exchanger (10) to exchange heat with clean flue gas after subsequent wet method acid removal; Step S6, wet method acid removal: The flue gas after step S5 enters the wet method acid removal tower (11) to react with Ca(OH)2 solution, remove acid gas and solid dust particles, and obtain clean flue gas; the clean flue gas after the wet method acid removal enters the gas-gas heat exchanger (10), and the flue gas is heated by the gas-gas heat exchanger (10) and then discharged from the chimney (15); In step S3, while spraying magnetic biological coke into the flue duct between the semi-dry method rotary spraying device (4) and the bag-type dust collector (7), H2O2 is also sprayed into the flue duct, and a Fenton reaction occurs between the magnetic biological coke and H2O2, producing active oxygen radicals to oxidize NO in the flue gas; In step S3, while spraying magnetic biological coke into the flue duct between the semi-dry method rotary spraying device (4) and the bag-type dust collector (7), activated carbon is also sprayed into the flue duct to adsorb dioxin in the flue gas; Step S7, magnetic biological coke recycling, is provided between step S4 and step S5, and specifically comprises the following: The dust captured in the flue gas of the bag-type dust collector (7) is magnetically separated, and the magnetic biological coke is separated from the dust particles and then sprayed into the flue duct between the semi-dry method rotary spraying device (4) and the bag-type dust collector (7) for reaction. The lime slurry, the wet flue gas purification system, the gypsum stabilizer (12), and the belt drive screen (13) are further included. In step S6, the lime slurry in the wet deacidification tower (11) is sprayed at high speed to react with the acid gas in the flue gas; meanwhile, the wastewater in the wet flue gas purification system passes through the gypsum stabilizer (12) to remove wet gypsum (CaSO4•2H2O); the liquid flowing back from the gypsum stabilizer (12) and the belt drive screen (13) still contains soluble salt, which is introduced into the semi-dry rotary spraying device (4) through a circulating pump.

2. The method according to claim 1, wherein: The gas-gas heat exchanger (10) comprises a first inlet (101), a first outlet (102), a second inlet (103), and a second outlet (104), wherein: The hot flue gas enters the first inlet (101) of the gas-gas heat exchanger (10) from the outlet of the bag-type dust collector (7), the flue gas after heat exchange enters the wet deacidification tower (11) from the first outlet (102), and the clean flue gas after passing through the wet deacidification tower (11) enters the gas-gas heat exchanger (10) through the second inlet (103), and the clean flue gas after heat exchange with the high-temperature flue gas in the gas-gas heat exchanger (10) enters the chimney (15) from the second outlet (104).

3. The system for flue gas cleaning of a waste incinerator according to any of claims 1-2, characterized in that: The system comprises a wet deacidification tower (11), a incinerator (1), an SNCR denitration system (2), a waste heat boiler heating surface (3), a semi-dry rotary spraying device (4), a bag-type dust collector (7), an H2O2 storage tank (6), a gas-gas heat exchanger (10), and a chimney (15) arranged in sequence along the flue gas flow direction, wherein: The wet deacidification tower (11) is connected with the gas-gas heat exchanger (10); The incinerator (1) is provided with an online temperature measuring device for primary denitration of the SNCR denitration system (2); The incinerator (1) is further provided with a plurality of spray guns for spraying ammonia; The semi-dry rotary spraying device (4) is connected with the bag-type dust collector (7) through a flue, and the flue is provided with an H2O2 atomizing nozzle, which is in communication with the H2O2 storage tank (6); The gas-gas heat exchanger (10) comprises a first inlet (101), a first outlet (102), a second inlet (103), and a second outlet (104), wherein: The outlet of the bag-type dust collector (7) is connected with the first inlet (101) through a pipeline; The first outlet (102) is connected with the inlet end of the wet deacidification tower (11); The second inlet (103) of the outlet end of the wet deacidification tower (11) is connected; The second outlet (104) is connected with the chimney (15) through a pipeline; The system further comprises an activated carbon storage tank (5), a magnetic separation machine (8), a material collecting bin (9), a gypsum stabilizer (12), and a belt drive screen (13), wherein: The activated carbon storage tank (5) is arranged on the flue between the semi-dry rotary spraying device (4) and the bag-type dust collector (7), and the activated carbon storage tank (5) stores activated carbon; The magnetic separation machine (8) is connected with one outlet of the bag-type dust collector (7) to perform magnetic separation on the dust captured by the bag-type dust collector (7); One end of the material collecting bin (9) is connected with the outlet of the magnetic separation machine (8), and the other end is connected to the flue between the semi-dry rotary spraying device (4) and the bag-type dust collector (7). Another outlet of the wet deacidification tower (11) is connected with the gypsum flow stabilizer (12); One outlet of the gypsum flow stabilizer (12) is directly connected with the semi-dry rotary spraying device (4), and another outlet is connected with the belt drive screen (13); The outlet of the belt drive screen (13) is connected with the semi-dry rotary spraying device (4).

4. A system for flue gas cleaning in a waste incinerator according to claim 3, characterized in that: The induced draft fan (14) is arranged on a pipeline, in which the second outlet (104) is connected with the chimney (15).

5. A system for flue gas cleaning in a waste incinerator according to claim 4, characterized in that: The H2O2 concentration in the H2O2 storage tank (6) is 10-30%wt; the H2O2 atomized by the H2O2 atomizing nozzle is carried into the flue between the semi-dry rotary spraying device (4) and the bag-type dust collector (7) by compressed gas; the molar ratio of H2O2 to NO sprayed into the flue between the semi-dry rotary spraying device (4) and the bag-type dust collector (7) is 1-4.

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