A sludge incineration flue gas pollutant synergistic removal system and method

Abstract

The application discloses a sludge incineration flue gas pollutant synergic removal system and relates to the technical field of sludge treatment. The system comprises a circulating fluidized bed boiler for incinerating sludge; the circulating fluidized bed boiler provides a flue for discharging flue gas; an activated carbon adding device is arranged on the flue and used for adding activated carbon into the flue to adsorb dioxin and / or heavy metals in the flue gas; a bag-type dust collector is arranged on the flue and located downstream of the activated carbon adding device and used for removing particulate matters in the flue gas; a desulfurization system is arranged behind the flue and used for desulfurizing the flue gas delivered by the flue; and a chimney is arranged behind the desulfurization system and used for discharging the flue gas after desulfurization. The system is used for sludge incineration treatment and synergic removal of various pollutants contained in flue gas generated by incineration.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, and in particular to a system and method for the synergistic removal of pollutants from sludge incineration flue gas. Background Technology

[0002] Sludge refers to a mixture of organic and inorganic matter containing impurities such as suspended solids, sediments, and microorganisms, generated during various wastewater treatment, pollution control, and waste disposal processes. It has a wide range of sources and complex composition.

[0003] The composition of dyeing and printing sludge is complex. The most commonly used dyes in the dyeing and printing process are disperse dyes, followed by reactive dyes and vat dyes. Many disperse dyes, such as 2,6-dichlorobenzonitrile and 2-nitro-4-chlorodiphenylamine, are chlorine-containing organic compounds. Reactive dyes also contain a large number of chlorine-containing groups. In addition, many auxiliaries are used in the post-processing of these dyes. Dispersants contain a large amount of organic matter, vatants contain many sulfur-containing salts, bleaching agents contain a large amount of chlorine, and dye diluents such as anhydrous sodium sulfate are added to adjust the strength. Since the dye uptake rate during the dyeing and printing process is 70% to 80%, the unuptaken dye enters the wastewater treatment process. In addition to carrying organic matter into the wastewater, it also causes sulfur and chlorine elements to accumulate in the wastewater, and ultimately, a large amount is transferred to the dyeing and printing sludge, giving the sludge characteristics of high sulfur, high chlorine, and high calorific value.

[0004] Traditional landfilling of dyeing and printing sludge can lead to secondary pollution due to the leakage of harmful substances such as heavy metals caused by rainwater erosion. Incineration is the most thorough treatment method; statistics show that sludge volume is reduced by over 80% after incineration. Clean incineration not only saves significant landfill space, but the ash can also be used as new building materials, truly achieving volume reduction, harmlessness, and resource recovery in sludge disposal. Therefore, dyeing and printing sludge incineration combined heat and power (CHP) has become the mainstream treatment method due to its advantages such as small space occupation, volume reduction, harmlessness, and resource recovery.

[0005] However, the flue gas produced by incineration contains various pollutants that are harmful to the environment, such as dioxins, heavy metals, and sulfur. Currently, there is a lack of technologies for the synergistic removal of multiple pollutants from sludge incineration flue gas. Therefore, developing a technology for the synergistic removal of pollutants from sludge incineration flue gas is one of the urgent problems to be solved. Summary of the Invention

[0006] In order to solve at least one of the technical problems mentioned in the background art, the present invention aims to provide a system and method for synergistic removal of pollutants from sludge incineration flue gas, which treats sludge incineration and synergistically removes multiple pollutants contained in the flue gas generated from incineration.

[0007] In a first aspect, the present invention provides a synergistic removal system for pollutants in sludge incineration flue gas, comprising: A circulating fluidized bed boiler for incinerating sludge; the circulating fluidized bed boiler provides a flue to discharge flue gas; An activated carbon addition device is installed on the flue and is used to add activated carbon into the flue to adsorb dioxins and / or heavy metals in the flue gas. A bag filter dust collector is installed on the flue and downstream of the activated carbon addition device to remove particulate matter from the flue gas. The desulfurization system is located behind the flue and is used to desulfurize the flue gas transported by the flue. A chimney is located behind the desulfurization system and is used to discharge the flue gas after desulfurization.

[0008] In some embodiments of the first aspect of the present invention, the desulfurization system employs a multi-stage series limestone-gypsum wet desulfurization tower.

[0009] In some embodiments of the first aspect of the present invention, a wet electrostatic precipitator is further provided between the desulfurization system and the chimney for removing gypsum droplets from the flue gas before it is emitted.

[0010] In some embodiments of the first aspect of the present invention, the circulating fluidized bed boiler includes a main furnace, an auxiliary furnace, and a cyclone separator; the main furnace and the auxiliary furnace are arranged side by side and connected at the top; the top of the cyclone separator is connected to the lower part of the auxiliary furnace via a first pipe, and a return material device is provided at the bottom of the cyclone separator, the return material device being connected to the bottom of the auxiliary furnace via a second pipe; the flue is connected to the top of the cyclone separator.

[0011] In some embodiments of the first aspect of the present invention, the flue is provided with an economizer and an air preheater in sequence upstream of the activated carbon addition device.

[0012] In some embodiments of the first aspect of the present invention, an SCR denitrification device is provided on the flue between the economizer and the air preheater.

[0013] In some embodiments of the first aspect of the present invention, the inner wall of the main furnace is provided with an SNCR denitrification device.

[0014] In some embodiments of the first aspect of the present invention, the activated carbon adding device includes: A partition is installed inside the flue and forms a chamber with part of the top wall of the flue. The chamber has an air inlet at the upstream position of the flue and an air outlet at the downstream position of the flue. The tray is rotatably positioned downstream of the air inlet in the chamber. The tray includes a first tray, a second tray, and a groove formed by the first tray and the second tray for placing activated carbon. The second tray is located downstream of the first tray and its length is greater than that of the first tray. An elastic element is disposed between the second support plate and the partition plate to provide the second support plate with elastic force to rotate toward the air inlet.

[0015] In some embodiments of the first aspect of the present invention, an activated carbon inlet is provided directly above the corresponding bracket on the flue, and a sealing door is detachably provided at the activated carbon inlet.

[0016] Secondly, the present invention provides a method for the synergistic removal of pollutants from flue gas during sludge incineration, comprising the following steps: S1. Sludge incineration: The sludge is mixed with coal and added to the circulating fluidized bed boiler for incineration. The temperature of the circulating fluidized bed boiler is maintained between 850℃ and 900℃. The flue gas generated after the sludge is incinerated is discharged through the flue. S2. Activated carbon adsorption: Activated carbon is added into the flue to mix with the flue gas in order to adsorb dioxins and / or heavy metals in the flue gas. S3. Baghouse dust collector: The flue gas after being adsorbed by activated carbon enters the baghouse dust collector, which filters the flue gas and removes particulate matter from it. S4. Desulfurization: Limestone-gypsum wet desulfurization is performed on the flue gas after bag filter dust collection. S5. Emission: The flue gas after desulfurization is emitted through the chimney.

[0017] In some embodiments of the second aspect of the present invention, the activated carbon adsorption in S2 is performed using the activated carbon addition device described in the first aspect.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses a circulating fluidized bed boiler to burn sludge to generate flue gas, which contains various pollutants such as dioxins, heavy metals, particulate matter, sulfur, etc. The flue gas containing pollutants is then passed sequentially through an activated carbon addition device, a bag filter, and a desulfurization system, where activated carbon adsorption, dust removal, and desulfurization are carried out respectively to remove the pollutants synergistically. Finally, the flue gas that meets the emission standards is discharged.

[0019] 2. The activated carbon addition device of the present invention has a rotatable tray set downstream of the air inlet. The rotation angle of the tray can change with the flow rate of the flue gas entering through the air inlet. When the flow rate is higher, the tray rotates to an angle at which the activated carbon is more likely to flow with the flue gas. Therefore, the effect of automatically controlling the amount of activated carbon added by the flow rate of the flue gas is achieved. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0021] Figure 2 This is a schematic diagram of the circulating fluidized bed boiler structure of the present invention.

[0022] Figure 3 This is a schematic diagram of the activated carbon addition device of the present invention under normal conditions.

[0023] Figure 4 This is a schematic diagram of the activated carbon addition device of the present invention in its working state.

[0024] In the picture: 1. Circulating fluidized bed boiler; 10. Flue; 11. Main furnace; 110. SNCR denitrification device; 12. Auxiliary furnace; 13. First pipeline; 14. Cyclone separator; 15. Return material device; 16. Second pipeline; 17. Economizer; 18. Air preheater; 19. SCR denitrification device; 2. Activated carbon adding device; 21. Partition; 211. Air inlet; 212. Air outlet; 22. Chamber; 23. Tray; 231. First tray; 232. Second tray; 233. Tray; 24. Elastic element; 101. Activated carbon inlet; 102. Sealing door; 3. Baghouse dust collector; 4. Desulfurization system; 5. Wet electrostatic precipitator; 6. Chimney. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: Please see Figure 1 This embodiment provides a synergistic removal system for pollutants in sludge incineration flue gas, comprising a circulating fluidized bed boiler 1, an activated carbon addition device 2, a bag filter 3, a desulfurization system 4, and a chimney 6 connected in sequence.

[0027] The following is a detailed introduction to each part: A circulating fluidized bed boiler 1 is used for incinerating sludge. The circulating fluidized bed boiler 1 includes a main furnace 11, an auxiliary furnace 12, and a cyclone separator 14; The main furnace 11 is the primary incineration area. Sludge and coal are mixed and fed into the main furnace 11, where they are mixed with air for combustion. Figure 2As shown, the two dashed boxes inside the main furnace 11, from bottom to top, represent the dense phase combustion zone and the dilute phase combustion zone, respectively, and the flue gas generated by combustion flows from bottom to top.

[0028] To ensure complete combustion, this scheme adopts the method of adding an auxiliary furnace 12 to increase the flue gas travel. The main furnace 11 and the auxiliary furnace 12 are arranged side by side and connected at the top. Therefore, the flue gas flows downward after entering the auxiliary furnace 12 from the main furnace 11.

[0029] The top of the cyclone separator 14 is connected to the lower part of the auxiliary furnace 12 via the first pipe 13. The flue gas enters the cyclone separator 14 along the first pipe 13. The cyclone separator 14 is used to separate the gas and solids of the flue gas. The separated solid fuel (i.e., coal) is discharged from the bottom of the cyclone separator 14, while the separated flue gas is discharged from the bottom of the cyclone separator 14.

[0030] A return device 15 is provided at the bottom of the cyclone separator 14. The return device 15 is connected to the bottom of the auxiliary furnace 12 via the second pipe 16, specifically located below the first pipe 13, so as to return the separated solid fuel to the auxiliary furnace 12.

[0031] The circulating fluidized bed boiler 1 also provides a flue 10 connected to the top of the cyclone separator 14 to discharge flue gas.

[0032] It is worth mentioning that the flue 10 is equipped with an economizer 17 and an air preheater 18, which are located upstream of the activated carbon addition device 2. The economizer 17 can capture heat energy in the high-temperature flue gas after combustion and transfer it to the outside (such as boiler feedwater). The air preheater 18 preheats the air to make combustion more complete, thereby reducing fuel consumption and also reducing the emission of harmful substances in the flue gas.

[0033] To achieve denitrification, the circulating fluidized bed boiler 1 in this scheme is also equipped with an SCR denitrification device 19 and an SNCR denitrification device 110. Specifically, the SCR denitrification device 19 is located in the flue between the economizer and the air preheater; the SNCR denitrification device 110 is located on the inner wall of the main furnace.

[0034] Activated carbon addition device 2 is installed on the flue and is used to add activated carbon into the flue 10. The activated carbon has a porous structure and has a strong adsorption capacity for impurities such as dioxins and heavy metals in the flue gas. Thus, by adding activated carbon into the flue 10, dioxins and / or heavy metals in the flue gas can be adsorbed. like Figure 3 and Figure 4 As shown, the activated carbon adding device 2 includes: A partition 21 is disposed within the flue 10, forming a chamber 22 with part of the top wall of the flue 10. The chamber 22 has an air inlet 211 located upstream of the flue 10 and an air outlet 212 located downstream of the flue 10. This allows some flue gas to enter the chamber 22 through the air inlet 211 at the location of the partition 21, and then re-enter the flue 10 through the air outlet 212.

[0035] The tray 23 is rotatably positioned in the chamber 22 downstream of the air inlet 211. The tray 23 includes a first tray 231, a second tray 232, and a groove 233 formed by the first tray 231 and the second tray 232 for placing activated carbon.

[0036] The elastic element 24 is disposed between the second support plate 232 and the partition plate 21, providing the second support plate 232 with elastic force to rotate toward the air inlet 211.

[0037] It is worth mentioning that the first tray 231 and the second tray 232 are in an inverted V-shape. The second tray 232 is located downstream of the first tray 231, and its length is greater than that of the first tray 231. This allows the inner surface of the second tray 232 to be impacted by the flue gas entering through the air inlet 212, causing the tray 23 to rotate. The larger the flue gas volume, the greater the impact and the greater the rotation angle of the tray. This results in the second tray 232 becoming more horizontal and the opening between its top and the top of the flue 10 becoming larger. Therefore, the activated carbon (preferably powdered activated carbon) in the tray 233 is more easily carried by the flue gas and enters the flue 10 through the air outlet 212, and vice versa. This achieves the purpose of automatically controlling the amount of activated carbon added based on the flue gas flow rate.

[0038] In order to ensure that the flue gas entering through the air inlet 211 can hit the second support plate 232, the air inlet 211 is at an angle α with the axis of the flue 10, preferably 15°.

[0039] To facilitate the replenishment of activated carbon, an activated carbon inlet 101 is provided directly above the corresponding support groove 233 on the flue 10, and a sealing door 102 is detachably provided at the activated carbon inlet 101.

[0040] The bag filter 3 is installed on the flue 10 and downstream of the activated carbon adding device 2. It is used to remove particulate matter from the flue gas, including the original particulate matter in the flue gas and the activated carbon added for adsorption.

[0041] The desulfurization system 4 is located downstream of the flue gas 10 and is used to desulfurize the flue gas transported by the flue gas 10. The desulfurization system adopts a multi-stage limestone-gypsum wet desulfurization tower connected in series, which can further improve the desulfurization efficiency. The wet desulfurization efficiency of the two-stage desulfurization tower can reach more than 98.5%.

[0042] The wet electrostatic precipitator 5 is used to remove gypsum droplets from the flue gas before it is emitted. After being treated by the wet electrostatic precipitator 5, the pollutant content in the flue gas is far below the emission standards, and the flue gas from the wet electrostatic precipitator 5 is ultimately emitted to the outside through a chimney. Considering cost, a tube bundle dust collector can be used instead of the wet electrostatic precipitator. Its dust removal effect is slightly inferior to that of the wet electrostatic precipitator, but the result after dust removal by the tube bundle dust collector is still sufficient to achieve the emission standards. Chimney 6 is located behind the wet electrostatic precipitator 5 and is used to discharge the flue gas after dust removal.

[0043] Example 2: This invention provides a method for the synergistic removal of pollutants from sludge incineration flue gas, comprising the following steps: S1. Sludge incineration: The sludge is mixed with coal and added to the circulating fluidized bed boiler for incineration. The temperature of the circulating fluidized bed boiler is maintained between 850℃ and 900℃. The flue gas generated after the sludge is incinerated is discharged through the flue. S2. Activated carbon adsorption: Activated carbon is added into the flue gas to mix with the flue gas and adsorb dioxins and / or heavy metals in the flue gas. The activated carbon adsorption in this step uses the activated carbon adding device as described in Example 1, which will not be described again here.

[0044] S3. Baghouse dust collector: The flue gas after being adsorbed by activated carbon enters the baghouse dust collector, which filters the flue gas and removes particulate matter from it. S4. Desulfurization: Limestone-gypsum wet desulfurization is performed on the flue gas after bag filter dust collection. S5. Emission: The flue gas after desulfurization is emitted through the chimney.

[0045] In other embodiments, the flue gas is subjected to wet electrostatic precipitator before being discharged in step S5.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A system for the synergistic removal of pollutants from sludge incineration flue gas, characterized in that, include: Circulating fluidized bed boilers are used for incinerating sludge; The circulating fluidized bed boiler provides a flue to discharge flue gas; An activated carbon addition device is installed on the flue and is used to add activated carbon into the flue to adsorb dioxins and / or heavy metals in the flue gas. A bag filter dust collector is installed on the flue and downstream of the activated carbon addition device to remove particulate matter from the flue gas. The desulfurization system is located behind the flue and is used to desulfurize the flue gas transported by the flue. Chimneys are located behind the desulfurization system and are used to discharge the flue gas after desulfurization. The activated carbon addition device includes: A partition is installed inside the flue and forms a chamber with part of the top wall of the flue. The chamber has an air inlet at the upstream position of the flue and an air outlet at the downstream position of the flue. The tray is rotatably positioned downstream of the air inlet in the chamber. The tray includes a first tray, a second tray, and a groove formed by the first tray and the second tray for placing activated carbon. The second tray is located downstream of the first tray and its length is greater than that of the first tray. An elastic element is disposed between the second support plate and the partition plate to provide the second support plate with elastic force to rotate toward the air inlet.

2. The synergistic removal system for pollutants in sludge incineration flue gas according to claim 1, characterized in that, The desulfurization system employs a multi-stage series limestone-gypsum wet desulfurization tower.

3. The synergistic removal system for pollutants in sludge incineration flue gas according to claim 2, characterized in that, A wet electrostatic precipitator is also installed between the desulfurization system and the chimney to remove gypsum droplets from the flue gas before it is emitted.

4. The synergistic removal system for pollutants in sludge incineration flue gas according to claim 1, characterized in that, The circulating fluidized bed boiler includes a main furnace, an auxiliary furnace, and a cyclone separator; the main furnace and the auxiliary furnace are arranged side by side and connected at the top; the top of the cyclone separator is connected to the lower part of the auxiliary furnace via a first pipe, and a return material device is provided at the bottom of the cyclone separator, which is connected to the bottom of the auxiliary furnace via a second pipe; the flue is connected to the top of the cyclone separator.

5. The synergistic removal system for pollutants in sludge incineration flue gas according to claim 4, characterized in that, The flue is located upstream of the activated carbon addition device and is equipped with an economizer and an air preheater in sequence.

6. The synergistic removal system for pollutants in sludge incineration flue gas according to claim 5, characterized in that, An SCR denitrification device is installed on the flue between the economizer and the air preheater.

7. The synergistic removal system for pollutants in sludge incineration flue gas according to claim 4, characterized in that, The inner wall of the main furnace is equipped with an SNCR denitrification device.

8. The synergistic removal system for pollutants in sludge incineration flue gas according to claim 1, characterized in that, An activated carbon inlet is provided directly above the corresponding support groove on the flue, and a detachable sealing door is provided at the activated carbon inlet.

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