Device and method for removing dioxins from flue gas from solid waste incineration

Abstract

The present invention relates to a device and method for removing dioxins from flue gas from solid waste incineration, which solves the technical problems that activated carbon only adsorbs dioxins but does not decompose them during the process of generating flue gas from solid waste incineration, and the temperature required for the catalyst to catalyze and decompose dioxins is high. The device is provided with an online adsorption part and an offline decomposition part. The online adsorption part is provided with a fluidized bed adsorption tower and a separation device which are connected in sequence. The fluidized bed adsorption tower can mix activated carbon with flue gas containing dioxins, and the separation device can separate the activated carbon adsorbed with dioxins from the clean flue gas; the offline decomposition part is provided with an activated carbon regeneration reactor and an activated carbon conveying device, the activated carbon regeneration reactor is connected with the separation device, the activated carbon conveying device is respectively connected with the activated carbon regeneration reactor and the fluidized bed adsorption tower, and the activated carbon regeneration reactor can decompose the dioxins in the activated carbon adsorbed with dioxins. The present invention can be widely applied to the removal of dioxins from flue gas generated by solid waste incineration.

Description

Technical Field

[0001] The present invention relates to a treatment technology for flue gas generated by solid waste incineration, in particular to a device and method for removing dioxins from flue gas generated by solid waste incineration. Background Art

[0002] Incineration has been increasingly widely used as an effective method of reducing volume and quantity of waste disposal. However, secondary pollution will inevitably occur during the incineration process, especially dioxins, which are highly toxic organic pollutants that are extremely harmful to the environment. At present, the methods for removing dioxins include traditional activated carbon adsorption and SCR reactor technology. The activated carbon adsorption method has a high operating cost, and it only adsorbs dioxins instead of completely decomposing them. The fly ash produced contains dioxins and needs to be sent to a hazardous waste treatment plant for safe treatment to prevent dioxins from escaping again. The SCR reactor technology mainly removes NOx and can also remove dioxins. Under the action of the catalyst, dioxins react with oxygen and are decomposed into non-toxic substances such as CO2, H2O, and HCl for discharge. However, the effect of the catalyst is greatly restricted by the flue gas temperature and the life of the catalyst, and the reaction temperature is relatively high at about 400°C. The flue gas needs to be heated to ensure the maintenance of the catalytic reaction temperature, so that the reheating of the flue gas greatly increases the energy consumption and operating costs. At present, there is an urgent need for a technology that has a good ability to adsorb dioxins and can decompose dioxins under low temperature conditions. Summary of the invention

[0003] In order to solve the technical problems that activated carbon only adsorbs dioxins but does not decompose them in the process of generating flue gas from solid waste incineration, and the temperature required for the catalytic decomposition of dioxins by catalysts is high, the present invention provides a device and method for removing dioxins in the flue gas from solid waste incineration by online adsorption and offline ozone combined with catalysts at low temperature.

[0004] The present invention provides a device for removing dioxins from flue gas from solid waste incineration, which comprises an online adsorption part and an offline decomposition part. The online adsorption part comprises a fluidized bed adsorption tower and a separation device which are connected in sequence. The fluidized bed adsorption tower can mix activated carbon with flue gas containing dioxins, and the separation device can separate the activated carbon adsorbed with dioxins from the clean flue gas. The offline decomposition part comprises an activated carbon regeneration device and an activated carbon conveying device. The activated carbon regeneration device is connected with the separation device, and the activated carbon conveying device is respectively connected with the activated carbon regeneration device and the fluidized bed adsorption tower. The activated carbon regeneration device can decompose the dioxins in the activated carbon adsorbed with dioxins.

[0005] Preferably, the activated carbon regeneration device is provided with an activated carbon regeneration reactor and an ozone generator. The activated carbon regeneration reactor is provided with a heating component, a catalyst layer and an ozone tube. The catalyst layer is filled with a catalyst. The ozone tube is connected to the ozone generator. The activated carbon regeneration reactor promotes the addition of a catalyst to decompose dioxins in the activated carbon at low temperature by ozone.

[0006] Preferably, the heating assembly, the catalyst layer and the ozone tube are arranged in layers, the heating assembly and the ozone tube are arranged alternately, a catalyst layer is arranged between the heating assembly and the ozone tube, the catalyst is in a plate shape, and the catalyst layer thickness is 60 to 100 cm.

[0007] Preferably, the catalyst layer is a VCuCeMnC catalyst.

[0008] Preferably, the activated carbon is Mn-modified activated carbon.

[0009] Preferably, the activated carbon conveying equipment is provided with an air lift and a Roots blower, the air lift is connected to the activated carbon regeneration reactor and the fluidized bed adsorption tower respectively, and the air lift is also connected to an activated carbon storage bin.

[0010] Preferably, the online adsorption part is provided with dust removal equipment, draft equipment and a chimney, and the dust removal equipment and separation equipment adopt explosion-proof bag dust collectors.

[0011] Preferably, the bags of the explosion-proof bag filter of the separation equipment adopt catalytic filter bags, and the base material of the catalytic filter bags is a needle-punched fiber structure, and the fibers are made of expanded polytetrafluoroethylene composite catalyst.

[0012] The present invention also provides a method for removing dioxins from flue gas from solid waste incineration, using the above-mentioned device for removing dioxins from flue gas from solid waste incineration, and the specific steps include:

[0013] (1) Flue gas containing dioxins is fully mixed with activated carbon in a fluidized bed adsorption tower, and the activated carbon adsorbs dioxins in the flue gas;

[0014] (2) Separate the activated carbon that adsorbs dioxins from the flue gas and discharge qualified clean flue gas;

[0015] (3) The activated carbon that adsorbs dioxins reacts with ozone and a catalyst to completely decompose the dioxins. The activated carbon is returned to the fluidized bed adsorption tower and steps (2) to (3) are repeated.

[0016] Preferably, in step (3), the catalyst is VCuCeMnC, and the catalyst starts to decompose dioxins at 120°C, and at 220°C, the dioxin decomposition efficiency reaches 95%.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention adopts the combined technology of online adsorption and offline ozone combined with catalyst low-temperature decomposition, which can completely destroy and decompose dioxins, realize the recycling of activated carbon, save the high operating cost of activated carbon, and at the same time, the dioxin emission in the flue gas can stably meet the European standards.

[0019] The invention adopts Mn modified activated carbon, the adsorption efficiency of which is as high as 67%, which is much higher than the adsorption efficiency of 2.4% of common activated carbon, and the adsorption efficiency and adsorption capacity of which are 28 times that of common activated carbon; adopts V-Cu-Ce-Mn-C catalyst, and simultaneously utilizes ozone adsorption to decompose dioxin, thereby realizing multiple decomposition of dioxin, and combining absorption with decomposition, without generating secondary pollution, and completely decomposing dioxin, so that the workers in the factory are in a safe environment, the system resistance is low, and the maintenance is convenient; the invention realizes the low-temperature removal of dioxin in the flue gas of solid waste incineration, an explosion-proof heater is adopted inside the activated carbon regeneration reactor, the temperature can be adjusted between 80 and 240 DEG C, the catalyst can make dioxin begin to decompose at 120 DEG C, and at 220 DEG C, the dioxin decomposition efficiency has reached 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a process flow chart of the present invention;

[0021] Figure 2 This is the internal structure diagram of the activated carbon regeneration reactor.

[0022] Description of the accompanying symbols:

[0023] 0. Solid waste combustion flue gas inlet; 1. First dust removal equipment; 2. Fluidized bed adsorption tower; 3. Second dust removal equipment; 4. Activated carbon storage bin; 5. Air lift; 6. Roots blower; 7. Activated carbon regeneration reactor; 8. Ozone generator; 9. induced draft fan; 10. Chimney; 11. Heating assembly; 12. Catalyst layer; 13. Ozone tube; 20. Injection pipe. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments so that those skilled in the art can easily implement the present invention.

[0025] Example 1: Figure 1As shown, the device for removing dioxins from solid waste incineration flue gas of the present invention comprises an online adsorption part and an offline decomposition part, wherein the online adsorption part is divided into a first dust removal device 1, a fluidized bed adsorption tower 2, a second dust removal device 3, an induced draft fan 9, and a chimney 10; the front end of the first dust removal device 1 is connected to the solid waste combustion flue gas inlet 0, the rear end of the first dust removal device 1 is connected to the lower part of the fluidized bed adsorption tower 2, the upper part of the fluidized bed adsorption tower 2 is connected to the front end of the second dust removal device 3, and the rear end of the second dust removal device 3 is connected to the induced draft fan 9 and the chimney 10 in sequence, which is the path taken by the flue gas; the solid waste incineration flue gas containing dioxins enters the device of the present invention through the solid waste combustion flue gas inlet 0, enters the first dust removal device 1, the fluidized bed adsorption tower 2 and the second dust removal device 3 in sequence through the induced draft fan 9, and becomes qualified flue gas after multiple filtrations and adsorptions and is discharged through the chimney 10.

[0026] The off-line decomposition part includes an activated carbon regeneration reactor 7, an ozone generator 8, an air lift 5, a Roots blower 6 and an activated carbon storage bin 4. The upper part of the activated carbon regeneration reactor 7 is connected to the lower part of the second dust removal equipment 3, the activated carbon regeneration reactor 7 is connected to the ozone generator 8, the lower part of the activated carbon regeneration reactor 7 is connected to the air lift 5, the outlet of the air lift 5 is connected to the fluidized bed adsorption tower 2, and the air lift 5 is also connected to the Roots blower 6 and the activated carbon storage bin 4. This part is the path taken by the activated carbon; the solid activated carbon that fully absorbs dioxins in the fluidized bed adsorption tower 2 enters the second dust removal equipment 3 at the same time as the flue gas, the activated carbon is separated from the flue gas, the solid activated carbon enters the activated carbon regeneration reactor 7, and the dioxins are decomposed at low temperature by ozone combined with a catalyst. The regenerated activated carbon is returned to the fluidized bed adsorption tower 2 through the air lift 5 to continue to adsorb dioxins. The activated carbon storage bin 4 is used for initial startup or to make up for the amount of activated carbon consumed by the system.

[0027] The first dust removal device 1 and the second dust removal device 3 use explosion-proof bag dust collectors, and the dust removal method uses pulse spraying. The dust collector filtration wind speed is 0.6-0.7m / min, and the bag material is three-proof material.

[0028] The fluidized bed adsorption tower 2 adopts the fluidized bed material distribution technology. The regenerated activated carbon is sprayed into the fluidized bed adsorption tower 2 by the roots blower 6 to the air lift 5 to generate airflow. The activated carbon enters the fluidized bed adsorption tower 2 and adopts multi-point injection feeding to spray the activated carbon evenly and uninterruptedly into the adsorption tower, and forms a material layer at the position of the injection pipe 20 of the entire fluidized bed adsorption tower 2. The activated carbon rises with the flue gas airflow to form a high-density bed layer in the upper part of the fluidized bed adsorption tower 2, where the flue gas and the activated carbon are fully contacted. The flue gas and the activated carbon enter the second dust removal equipment 3 at the same time for gas-solid separation, the clean flue gas is discharged through the chimney 10, and the activated carbon particles fall into the activated carbon regeneration reactor 7.

[0029] The heating assembly 11, the catalyst layer 12, and the ozone tube 13 are arranged in layers inside the activated carbon regeneration reactor 7. The heating assembly 11 and the ozone tube 13 are arranged alternately. The catalyst layer 12 is arranged between the heating assembly 11 and the ozone tube 13. The catalyst layer 12 has a thickness of 60 to 100 cm. The catalyst adopts VCuCeMnC catalyst, which is in the shape of a plate. The heating assembly 11 adopts an explosion-proof heater, and the temperature can be adjusted between 80 and 240°C. The ozone tube 13 is connected to the ozone generator and is made of stainless steel. The ozone tube 13 is connected to the ozone generator 8. The ozone tube is connected to the ozone generator. When the adsorbed activated carbon enters the activated carbon regeneration reactor, the low-temperature decomposition of dioxins is achieved under the conditions of catalyst adsorption + ozone promotion.

[0030] The activated carbon uses Mn modified activated carbon, which has many pores and large specific surface area. Dioxins are strongly adsorbed in the micropores on the surface of the activated carbon, with high adsorption efficiency. The adsorption capacity is 28 times that of ordinary activated carbon.

[0031] The induced draft fan 9 adopts a centrifugal fan, and the motor adopts frequency conversion control.

[0032] Example 2: This example is different from Example 1 in that a catalytic filter bag is used as the filter bag in the second dust removal equipment 3. When the dioxin content in the flue gas is high, the flue gas can be further decomposed into CO2, H2O and HCl by the catalytic filter bag after the flue gas passes through the dust removal equipment 2 after being adsorbed by activated carbon. The catalytic filter bag is used to deeply purify the dioxins and improve the overall purification capacity of the system.

[0033] The bottom material of the catalytic filter bag is a needle-punched structure. The fiber is composed of expanded polytetrafluoroethylene composite catalyst, which plays a supporting role. The catalyst can catalytically decompose dioxins under the condition of oxygen participation. This coated catalytic felt can decompose dioxins through catalytic oxidation reaction with oxygen participation in the temperature range of 180-260℃.

[0034] The present invention also provides a method for removing dioxins from solid waste incineration flue gas, the specific steps of which include:

[0035] (1) Flue gas containing dioxins is fully mixed with activated carbon in fluidized bed adsorption tower 2, and the activated carbon adsorbs dioxins in the flue gas;

[0036] (2) Separate the activated carbon that adsorbs dioxins from the flue gas and discharge qualified clean flue gas;

[0037] (3) The activated carbon that adsorbs dioxins reacts with ozone and the catalyst to completely decompose the dioxins. The activated carbon is returned to the fluidized bed adsorption tower 2 and steps (2) to (3) are repeated.

[0038] In order to improve the dioxin removal effect, the activated carbon uses Mn-modified activated carbon. When the Mn-modified activated carbon is separated from the qualified flue gas, the catalytic filter bag bottom material can also be used as the separation equipment material to catalytically decompose the dioxins that are not adsorbed by the Mn-modified activated carbon.

[0039] In step (3), after the dioxins attached to the Mn-modified activated carbon react with the catalyst through ozone, the ozone-promoted catalytic decomposition technology is used in the dioxin decomposition process. The catalyst is VcuCeMnC, which starts to decompose the dioxins at a low temperature of 120°C. At 220°C, the decomposition efficiency reaches 95%.

[0040] The invention realizes the removal of dioxins in the flue gas from the incineration of solid wastes, has reasonable design, good adsorption effect, can completely decompose dioxins, has low decomposition temperature, high reliability and low operating cost.

[0041] The present invention adopts online adsorption / offline ozone + catalyst low temperature decomposition technology. The online adsorption adopts fluidized bed adsorption and bag dust removal combined technology to achieve full combination of activated carbon and flue gas and realize gas-solid separation of adsorbed activated carbon through bag dust removal; offline ozone + catalyst low temperature decomposition, rationally utilize ozone to promote dioxin decomposition under the condition of catalyst low temperature, thoroughly remove dioxin, and regenerate the adsorbed activated carbon at the same time, return it to the system to continue to adsorb dioxin, saving the high operating cost of activated carbon, and when the dioxin content in the flue gas is high, the filter bag in the dust removal equipment 2 can adopt catalytic filter bag to realize the catalytic decomposition of the remaining dioxin in the flue gas again, and the dioxin emission in the flue gas can stably reach the European standard. At the same time, the present invention has the advantages of high dioxin decomposition efficiency, high reliability, convenient installation, low maintenance and operation cost, and can achieve ultra-low dust emission.

[0042] 1. Test on the ability of catalyst to adsorb dioxin and ozone to promote dioxin decomposition

[0043] Five groups of tests were conducted, in which the catalyst was loaded into a reactor using a fixed bed, and a gas containing a certain concentration of dioxins was passed through the reactor, while ensuring that the reaction was carried out under a certain reaction atmosphere.

[0044] The reaction experimental conditions are shown in Table 1 below:

[0045]

[0046] Test results:

[0047] Table 2 Dioxin content at each location

[0048] Unit: ng TEQ / Nm3

[0049] Location 1 2 3 4 5 Occurrence source 1.46 1.46 1.46 1.46 1.46 Wall residue 0.56 0.3 1.56 1.13 0.18 Catalyst residue 4.63 3.12 0.13 0.05

[0050] From the dioxin content at various locations in the test in Table 2, it is obvious that the V-Cu-Ce-Mn-C catalyst has the best effect in adsorbing dioxins and promoting the decomposition of dioxins by ozone. The residual dioxin concentration on the vessel wall is the lowest, and the catalyst residue is the least.

[0051] 2. Test of adsorption capacity of Mn-modified activated carbon

[0052] The experiment tested the dioxin adsorption capacity of ordinary activated carbon and Mn-modified activated carbon; the activated carbon was loaded into the reactor using a fixed bed, and a gas containing a certain concentration of dioxins was passed through the reactor. The dioxin content in the reactor wall and exhaust gas was detected, and the adsorption efficiency and capacity of the activated carbon were calculated.

[0053] Test results:

[0054] 1) Ordinary activated carbon adsorption capacity data table 3

[0055] Ordinary activated carbon Reactor inlet Activated carbon adsorption Reactor wall Concentration (ng) 2.11*4＝8.44(100％) 0.2(2.4％) 6.5(77％) Toxicity (ngI-TEQ) 0.25*4＝1 0.02(2.4％) 0.82(82％)

[0056] 2) Mn modified activated carbon adsorption capacity data table 4

[0057]

[0058] It can be clearly seen from the test results in Table 3 and Table 4 that the adsorption efficiency of Mn-modified activated carbon is 67%, and the adsorption efficiency of ordinary activated carbon is 2.4%. The adsorption efficiency of Mn-modified activated carbon is high, and the adsorption capacity is 28 times that of ordinary activated carbon.

[0059] In the description of the present invention, it is necessary to understand that the orientation indications or positional relationships are based on the orientations or positional relationships shown in the drawings and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0060] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the scope of the claims of the present invention shall be within the scope of protection of the present invention.

Claims

1. A device for removing dioxins from flue gas from solid waste incineration, characterized in that: An online adsorption part and an offline decomposition part are provided, wherein the online adsorption part is provided with a fluidized bed adsorption tower and a separation device which are sequentially connected, wherein the fluidized bed adsorption tower can mix the activated carbon with the flue gas containing dioxins, and the separation device can separate the activated carbon adsorbed with dioxins from the clean flue gas; The offline decomposition part is provided with an activated carbon regeneration device and an activated carbon conveying device, the activated carbon regeneration device is communicated with the separation device, the activated carbon conveying device is communicated with the activated carbon regeneration device and the fluidized bed adsorption tower respectively, the activated carbon regeneration device can decompose the dioxins in the activated carbon adsorbed with dioxins; the activated carbon regeneration device is provided with an activated carbon regeneration reactor and an ozone generator, the activated carbon regeneration reactor is provided with a heating component, a catalyst layer and an ozone tube, the catalyst layer is filled with a catalyst, the ozone tube is communicated with the ozone generator, the activated carbon regeneration reactor promotes the addition of a catalyst to decompose the dioxins in the activated carbon adsorbed with dioxins at low temperature by ozone; the heating component, the catalyst layer and the ozone tube are arranged in layers, the heating component and the ozone tube are arranged alternately, a catalyst layer is arranged between the heating component and the ozone tube, the catalyst is in the shape of a plate, and the catalyst layer has a thickness of 60 to 100 cm; the activated carbon is Mn modified activated carbon; the catalyst is a VCuCeMnC catalyst.

2. The device for removing dioxins from solid waste incineration flue gas according to claim 1, characterized in that: The activated carbon conveying equipment is provided with an air lift and a Roots blower. The air lift is connected to the activated carbon regeneration reactor and the fluidized bed adsorption tower respectively. The air lift is also connected to an activated carbon storage bin.

3. The device for removing dioxins from solid waste incineration flue gas according to claim 1, characterized in that: The online adsorption part is also provided with dust removal equipment, draft equipment and a chimney, and the dust removal equipment and the separation equipment adopt explosion-proof bag dust collectors.

4. The device for removing dioxins from solid waste incineration flue gas according to claim 3, characterized in that: The bags of the explosion-proof bag filter of the separation equipment adopt catalytic filter bags, the bottom material of the catalytic filter bags is a needle-punched fiber structure, and the fibers are made of expanded polytetrafluoroethylene composite catalyst.

5. A method for removing dioxins from flue gas from solid waste incineration, characterized in that: The device for removing dioxins from solid waste incineration flue gas as claimed in any one of claims 1 to 4 is used, and the specific steps include: (1) Flue gas containing dioxins is fully mixed with activated carbon in a fluidized bed adsorption tower, and the activated carbon adsorbs dioxins in the flue gas; (2) Separate the activated carbon that adsorbs dioxins from the flue gas and discharge qualified clean flue gas; (3) The activated carbon that adsorbs dioxins reacts with ozone and the catalyst to completely decompose the dioxins. The activated carbon is returned to the fluidized bed adsorption tower and steps (2) to (3) are repeated.

6. The method for removing dioxins from solid waste incineration flue gas according to claim 5, characterized in that: In the step (3), the catalyst is VCuCeMnC. The catalyst starts to decompose dioxins at 120°C, and the dioxin decomposition efficiency reaches 95% at 220°C.

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