CN114392626A

CN114392626A - Low-temperature treatment system for hazardous waste incineration tail gas

Info

Publication number: CN114392626A
Application number: CN202210044362.5A
Authority: CN
Inventors: 林圣伦; 吴重霖; 黄俊荣; 汤伟; 张育诚
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2022-01-14
Filing date: 2022-01-14
Publication date: 2022-04-26

Abstract

The invention discloses a low-temperature treatment system for hazardous waste incineration tail gas, which comprises: a cooling tower, a washing device, a cyclone demister, a bag-type dust collector and a flue which are connected in series into a whole through pipelines; the tail gas is discharged from a flue after being sequentially treated by a cooling tower, washing equipment, a cyclone demister and a bag-type dust remover; wherein the cooling tower is used for cooling the tail gas, and the cooling temperature is controlled to be 400 +/-100 ℃; the washing equipment is used for removing acid, removing solid precursors in the tail gas, forcibly converting the solid precursors into solid, and forcibly removing dioxin in the tail gas at low temperature; the cyclone demister dehumidifies the tail gas which is washed by the washing equipment and carries water vapor; the bag-type dust collector is added with active carbon which is used for adsorbing fine particles in the tail gas and promoting gaseous pollutants in the tail gas to generate phase transition and ultrafine particulate matters to be coagulated and agglomerated, and the bag-type dust collector is used for filtering the particulate matters in the tail gas; wherein the low temperature is 40-80 ℃.

Description

Low-temperature treatment system for hazardous waste incineration tail gas

Technical Field

The invention relates to the technical field of air pollution control of hazardous waste incineration tail gas, in particular to a low-temperature treatment system of hazardous waste incineration tail gas.

Background

The tail gas generated from the thermal treatment (such as incineration and melting) of hazardous waste often contains air pollutants such as acidity, heavy metals, fine particles and dioxin.

The traditional waste tail gas treatment mode has the defects of large energy consumption, complex procedure, large load and the like. The patent with application number CN201610463180.6 provides a waste incineration treatment system, which is connected in series with a dust remover, an acid removal tower, a demisting tower, an activated carbon box and a soil biofilter. Patent with application number CN201010510764.7 relates to a processing method of dioxin and pollutants in waste incineration tail gas, and the flue gas is processed by alkali liquor absorption in a Raschig ring packed tower, and the processed flue gas ash enters an active carbon collecting tank. The patent with application number CN200810233952.2 discloses a waste incinerator tail gas processing apparatus, including sharp quenching reaction tower and sack cleaner, but the hydrogen chloride in the effective absorption and getting rid of waste incinerator tail gas, acid gas and dioxin such as sulfur dioxide, poisonous and harmful composition such as heavy metal, because the tail gas cooling back is failed the intensive washing, acid gas gets rid of efficiency and can further improve, directly let in the sack cleaner afterwards, can lead to the sack cleaner operation load too big, and along with lime hydrate, the accumulation of solid matter such as reaction auxiliary agent, sack cleaner work efficiency periodicity reduces gradually.

The existing incinerator tail gas treatment system is mainly divided into a wet type and a semi-dry type, the wet incinerator tail gas treatment system is used for carrying out heat treatment on tail gas with high corrosivity and danger, and the process comprises the following steps: tail gas → cooling equipment → dust removing equipment → washing equipment → reheating equipment → flue, namely, the tail gas is firstly subjected to primary cooling through the cooling equipment (such as a heat exchanger), then is subjected to particulate matter removal through the dust removing equipment, is washed through the washing equipment to remove acid, and finally is reheated through the reheating equipment and then is discharged from the flue of the flue; the disadvantages of this system mainly include:

(1) because the dust removal equipment is positioned in front of the washing equipment, the resynthesis of the dioxin can be caused under the condition of poor exhaust gas cooling effect;

(2) dust removal equipment is susceptible to corrosion by acidic gases;

(3) as no further particulate matter removal and filtration operation is performed after washing, the removal effect of acidic pollutants is poor, and the concentration of discharged air pollutants is high;

(4) reheat devices are used to accelerate flue gas flow and eliminate "visible pollution" (i.e., water vapor), which tends to generate additional energy consumption.

The tail gas treatment process of the semi-dry type incinerator tail gas treatment system comprises the following steps: tail gas → cooling equipment → semi-dry type smoke washing tower → dust collecting equipment → reheating equipment → flue, namely the waste gas is cooled by the cooling equipment (such as cooling tower), then the semi-dry type smoke washing tower is used for deacidification, the waste gas is contacted with an absorbent (such as liquid caustic soda or lime) slurry atomizer, when the small liquid drops reach the inner wall or the bottom of the tower, the moisture is completely evaporated to form a dry powder state, part of the dry powder can be discharged from the bottom of the tower, the rest is delivered to the following dust collecting equipment for treatment, in addition, active carbon is injected in front of the dust collecting equipment, and the adsorption capacity of the active carbon is used for adsorbing air pollutants such as volatile heavy metal, dioxin and the like; the disadvantages of the semi-dry type tail gas treatment mainly include:

(1) because the semi-dry type smoke washing tower needs to ensure that the moisture is evaporated into a dry powder state, the deacidification efficiency is lower;

(2) the dry powder accumulation and the additional addition of the activated carbon of the semi-dry type smoking tower cause the dust removal load to be larger;

(3) there is also the problem of "visible contamination" and the additional energy consumption of the reheating device.

Disclosure of Invention

In view of the above, the invention provides a low-temperature treatment system for hazardous waste incineration tail gas, which can be applied to tail gas treatment of incineration of waste with complex components such as municipal waste, medical waste and the like, and can solve the problem of air pollution prevention and control in the treatment of tail gas emission of waste incineration.

The technical scheme of the invention is as follows: a low-temperature treatment system for hazardous waste incineration tail gas comprises: a cooling tower, a washing device, a cyclone demister, a bag-type dust collector and a flue which are connected in series into a whole through pipelines; the tail gas is discharged from a flue after being sequentially treated by a cooling tower, washing equipment, a cyclone demister and a bag-type dust remover; wherein the cooling tower is used for cooling the tail gas, and the cooling temperature is controlled to be 400 +/-100 ℃; the washing equipment is used for removing acid, removing solid precursors in the tail gas, forcibly converting the solid precursors into solid, and forcibly removing dioxin in the tail gas at low temperature; the cyclone demister dehumidifies the tail gas which is washed by the washing equipment and carries water vapor; the bag-type dust collector is added with active carbon which is used for adsorbing fine particles in the tail gas and promoting gaseous pollutants in the tail gas to generate phase transition and ultrafine particulate matters to be coagulated and agglomerated, and the bag-type dust collector is used for filtering the particulate matters in the tail gas; wherein the low temperature is 40-80 ℃.

Preferably, the washing apparatus comprises: the system comprises a Venturi scrubbing tower, a wet scrubbing tower and a circulating water tank; the cooling tower is connected with the Venturi scrubbing tower through a pipeline, the wet scrubbing tower is connected with the cyclone demister through a pipeline, and the Venturi scrubbing tower and the wet scrubbing tower are both communicated with the circulating water tank; the Venturi scrubbing tower is used for removing coarse particles in the tail gas cooled by the cooling tower and carrying out coarse deacidification on the tail gas; the wet-type washing tower finely removes acid from the tail gas washed by the Venturi washing tower, and the washing temperature is controlled within a preset range; the circulation water tank serves as a container for containing washing water, and supplies the washing water.

Preferably, the inlet temperature of the wet washing tower is kept between 300 and 500 ℃, and the outlet temperature of the wet washing tower is suddenly reduced to 40 to 80 ℃.

Preferably, a fan is arranged on a pipeline between the bag-type dust collector and the flue.

Preferably, the method further comprises the following steps: and the heating buffer tank is connected in series between the cyclone demister and the bag-type dust collector through a pipeline.

Has the advantages that:

1. the low-temperature treatment system is characterized in that a washing device is arranged in front of a cloth bag dust removal device of the existing tail gas treatment system, namely, when the tail gas is washed by a cooling tower and cooled, the temperature of the tail gas is controlled to be reduced to about 400 ℃ by spraying a proper amount of water, then the tail gas enters the washing device, the washing device can remove acid, so that the corrosion of acid substances on subsequent dust removal devices is effectively avoided, solid precursors in the tail gas can be removed, the solid precursors are forcibly converted into solid, and more importantly, the washing device can also forcibly remove dioxin in the tail gas at low temperature; the tail gas washed by the washing equipment enters a cyclone demister, and is finally introduced into a bag-type dust remover (dust removing equipment) for dust removal, and the removal efficiency of particulate matters can be effectively improved by adding activated carbon before dust removal;

meanwhile, the washing equipment, the cyclone demister and the bag-type dust remover have certain removal effects on the tail gas and the particles contained in the tail gas, and the temperature of the washed tail gas is low, so that the phase transformation of a gaseous precursor of condensable particles is facilitated to form filterable particles, and the filterable particles are removed by the bag-type dust remover, so that the removal efficiency of the particles is greatly improved; the cyclone demister can effectively protect the bag-type dust collector from being affected by damp and damaged or reduce the removal effect of pollutants in tail gas.

2. The washing equipment provided by the invention comprises a Venturi washing tower and a wet washing tower, tail gas after water washing and temperature reduction enters the wet washing tower containing alkaline washing liquid such as KOH, NaOH and the like through the Venturi washing tower to be neutralized by alkaline additives, aiming at the temperature (200-400 ℃) of a dioxin generation environment, the inlet temperature of the wet washing tower is kept between 300-500 ℃, and the outlet temperature is controlled between 40-80 ℃, so that dioxin can be concentrated in the washing equipment to be generated and concentrated in a solid phase to be conveniently removed, the memory effect and the resynthesis discharge capacity of a cyclone demister, a bag-type dust collector and the like behind the washing equipment on the dioxin can be eliminated, and the removal efficiency of the dioxin is obviously improved.

3. The heating buffer tank provided by the invention plays a role in heating and buffering when the removal efficiency of the cyclone demister is poor, and can further ensure the drying of tail gas, thereby avoiding visual pollutants and reducing energy consumption (the tail gas of the traditional equipment is easy to carry water vapor when being discharged, and the tail gas needs to be thermally treated before being discharged in order to eliminate white smoke generated in a flue, so that the energy consumption is increased).

Drawings

FIG. 1 is a schematic structural diagram of a low-temperature treatment system for incinerating tail gas according to the present invention.

The method comprises the following steps of 1-a cooling tower, 2-tail gas, 3-Venturi scrubbing tower, 4-wet scrubbing tower, 5-circulating water tank, 6-cyclone demister, 7-heating buffer tank, 8-bag dust remover, 9-fan and 10-flue.

Detailed Description

The invention is described in detail below by way of example with reference to the accompanying drawings.

The embodiment provides a low temperature treatment system of hazardous waste incineration tail gas, can be applied to the tail gas treatment of the complicated waste incineration of compositions such as municipal waste, medical waste, can solve the air pollution prevention and control problem of handling waste incineration tail gas emission.

As shown in fig. 1, the cryogenic processing system comprises: the system comprises a cooling tower 1, a Venturi washing tower 3, a wet washing tower 4, a circulating water tank 5, a cyclone demister 6, a heating buffer tank 7, a bag-type dust remover 8 and a flue 10;

the cooling tower 1 is connected with the Venturi scrubbing tower 3 through a pipeline, the wet scrubbing tower 4, the cyclone demister 6, the heating buffer tank 7, the bag-type dust remover 8 and the flue 10 are connected in series through a pipeline, the Venturi scrubbing tower 3 and the wet scrubbing tower 4 are both communicated with the circulating water tank 5, and the tail gas 2 is discharged from the flue 10 after being sequentially treated by the cooling tower 1, the Venturi scrubbing tower 3, the circulating water tank 5, the wet scrubbing tower 4, the cyclone demister 6, the heating buffer tank 7 and the bag-type dust remover 8;

wherein, the cooling tower 1 sprays a proper amount of cooling water to the tail gas 2 entering the cooling tower to cool the tail gas 2, and controls the cooling temperature to be about 400 ℃ (300-500 ℃); the Venturi scrubbing tower 3 is used for removing coarse particles in the tail gas 2 cooled by the cooling tower 1 and performing small-amount acid removal (coarse acid removal); washing (fine acid removal) the tail gas 2 washed by the Venturi scrubber 3 by spraying alkaline solutions such as KOH, NaOH and the like in the wet scrubber 4, and controlling the washing temperature within a preset range (such as 60-400 ℃); the circulating water tank 5 is used as a container for containing washing water, and supplies washing water, namely, part of the washing water of the Venturi scrubber 3 and the wet scrubber 4 is added from the outside, and the other part of the washing water is supplied by the circulating washing water in the circulating water tank 5; venturi scrubber 3, wet scrubber 4 and circulating water tank 5 have three functions as a whole: firstly, removing acid, secondly, removing solid precursors in the tail gas 2 and forcibly converting the solid precursors into solids, and thirdly, forcibly removing dioxin in the tail gas 2; the cyclone demister 6 dehumidifies the tail gas 2 which is discharged from the wet washing tower 4 and carries water vapor; activated carbon is added into the bag-type dust collector 8, the activated carbon can adsorb fine particles in the tail gas 2 passing through the bag-type dust collector 8 and promote gaseous pollutants in the tail gas 2 to undergo phase transition and ultrafine particle coagulation and agglomeration, and the bag-type dust collector 8 can effectively filter particles in the tail gas 2 (including particles after phase transition of gaseous pollutants and particles after coagulation and agglomeration of ultrafine particles);

a fan 9 is arranged on a pipeline between the bag-type dust collector 8 and the flue 10 and is used as a power source of the whole low-temperature treatment system;

in the present embodiment, the coarse particles, the fine particles, and the ultrafine particles are relative concepts, and there is no fixed limit.

In this embodiment, the experimental waste liquid and the tail gas 2 generated from the waste incinerator are used, and the tail gas 2 is not limited to the tail gas generated from the incineration facility.

In use, the process flow of the cryogenic treatment system can be summarized as follows: tail gas → water mist cooling → washing equipment washing → cyclone demister dehumidifying → reheating equipment heating → dust removing equipment dust removing → chimney exhaust, namely, the tail gas 2 is firstly cooled by a cooling tower 1 and the temperature is controlled to be reduced to about 400 ℃, the cooled tail gas 2 enters a wet washing tower 4 through a Venturi washing tower 3, the temperature is kept to about 400 ℃, the critical temperature of water is 374 ℃, when the temperature of the tail gas 2 is above 374 ℃, the water exists in a gaseous state, after entering the wet washing tower 4 and a circulating water tank 5, the outlet temperature of the wet washing tower 4 is suddenly reduced to 40-80 ℃, the retention time of the tail gas 2 at the dioxin generation temperature (200-400 ℃) can be reduced, and the generation of dioxin is reduced; in addition, when the temperature of the tail gas 2 entering the wet scrubber tower 4 is lower than the critical temperature of water, a small part of gaseous water begins to condense to form liquid water drops, particulate matters, especially fine particles, in the tail gas 2 become crystals, and are removed in the wet scrubber tower 4 after the condensation process, and the wet scrubber tower 4 can simultaneously remove heavy metals and particulate matters in the tail gas 2; the washed tail gas 2 is introduced into a cyclone demister 6, and water vapor carried in the washing process is removed by the cyclone demister 6 and is used for protecting a bag-type dust collector 8 from being affected with damp or damaged; the heating buffer tank 7 plays a role in heating and buffering when the removal efficiency of the cyclone demister 6 is poor, and the drying of the tail gas 2 can be further ensured; the dried tail gas 2 enters a bag-type dust collector 8, and under the action of activated carbon added in advance in the bag-type dust collector 8, fine particles are captured and the phase conversion of gaseous particles and dioxin into a solid-liquid phase is promoted, so that the bag-type dust collector 8 is facilitated to further remove the particles in the tail gas 2; the purified tail gas 2 is finally extracted with the aid of a fan 9 and is discharged through a flue 10;

table 1 below shows the concentration of the pollutants in the hazardous waste (such as sludge and wastewater) in this example, and table 2 below shows the air pollutant emissions after the present example compares the prior art with the exhaust gas 2 treated by the present invention; as can be seen from table 1, in the wastewater and the bottom residue (sludge) of the wet scrubber tower 4, a considerable amount of heavy metals and particulate matters were found, indicating that the present example can remove a large amount of heavy metals and particulate matters; as shown in Table 2, the present invention has better removal effect on various air pollutants than the prior art;

in addition, dioxin is a pollutant with low solubility, and after the dioxin is treated by the low-temperature treatment system of the embodiment, as shown in table 3, after passing through the venturi scrubber 3, the wet scrubber 4 and the cyclone demister 6, the removal rate (calculated as I-TEQ) is nearly 92.55%, and after passing through the bag-type dust collector 8 sprayed with activated carbon, the removal effect is more as high as 99.976%, and the overall dioxin removal rate is as high as 99.998% or more.

Table 1 concentration of residue contamination of each apparatus of this example

Table 2 comparison of pollutant emissions from this example with the prior art

Contaminants	Unit of	Prior Art	The invention	Reduction benefit of pollutants%
					HCl	mg/Nm3	26.9	4.88	81.8
SO2	mg/Nm3	28.0	17.2	38.8
					Total FPM	mg/Nm3	4.8	0.367	79.2
PM2.5	mg/Nm3	-	0.172	-
					CPM2.5	mg/Nm3	-	0.098	-
NOx	mg/Nm3	62.0	42.9	30.9
					CO	mg/Nm3	41.6	15.0	64.0

TABLE 3 variation of dioxin concentration in exhaust gas

Concentration of PCDD/Fs	Wet type washing tower	Between wet washing tower and bag-type dust collector	Flue duct
				Total amount ng/Nm3	152542.4	12743.1	1.64863
I-TEQ ng/Nm3	3822.048	284.917	0.069

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low temperature treatment system for hazardous waste incineration tail gas is characterized by comprising: a cooling tower (1), a washing device, a cyclone demister (6), a bag-type dust collector (8) and a flue (10) which are connected in series into a whole through pipelines; the tail gas (2) is discharged from a flue (10) after being sequentially treated by a cooling tower (1), washing equipment, a cyclone demister (6) and a bag-type dust remover (8); wherein the cooling tower (1) is used for cooling the tail gas (2), and the cooling temperature is controlled to be 400 +/-100 ℃; the washing equipment is used for removing acid, removing solid precursor in the tail gas (2), forcibly converting the solid precursor into solid, and forcibly removing dioxin in the tail gas (2) at low temperature; the cyclone demister (6) dehumidifies the tail gas (2) which carries water vapor and is washed by the washing equipment; activated carbon is added into the bag-type dust collector (8), the activated carbon is used for adsorbing fine particles in the tail gas (2) and promoting gaseous pollutants in the tail gas (2) to generate phase transition and ultrafine particle coagulation and agglomeration, and the bag-type dust collector (8) is used for filtering particles in the tail gas (2); wherein the low temperature is 40-80 ℃.

2. The system for the low-temperature treatment of hazardous waste incineration tail gas of claim 1, wherein the scrubbing device comprises: a Venturi scrubber tower (3), a wet scrubber tower (4) and a circulating water tank (5); the cooling tower (1) is connected with the Venturi scrubbing tower (3) through a pipeline, the wet scrubbing tower (4) is connected with the cyclone demister (6) through a pipeline, and the Venturi scrubbing tower (3) and the wet scrubbing tower (4) are both communicated with the circulating water tank (5); the Venturi scrubbing tower (3) is used for removing coarse particles in the tail gas (2) cooled by the cooling tower (1) and performing coarse deacidification on the tail gas; the wet-type washing tower (4) finely removes acid from the tail gas (2) washed by the Venturi washing tower (3), and the washing temperature is controlled within a preset range; the circulating water tank (5) is used as a container for containing washing water and provides the washing water.

3. The low-temperature treatment system for hazardous waste incineration tail gas as claimed in claim 2, wherein the inlet temperature of the wet scrubber tower (4) is maintained between 300-500 ℃ and the outlet temperature is suddenly reduced to 40-80 ℃.

4. The low-temperature treatment system for the hazardous waste incineration tail gas as claimed in claim 1, 2 or 3, wherein a fan (9) is arranged on a pipeline between the bag-type dust remover (8) and the flue (10).

5. The system for the low-temperature treatment of hazardous waste incineration tail gas as set forth in claim 1, 2 or 3, further comprising: and the heating buffer tank (7) is connected in series between the cyclone demister (6) and the bag-type dust remover (8) through a pipeline.