CN112705047A

CN112705047A - Flue gas denitration system of asphalt mixing plant

Info

Publication number: CN112705047A
Application number: CN202011491548.2A
Authority: CN
Inventors: 赵博; 李敬东; 赖文锋; 周伟; 陈洪剑; 韩成涛
Original assignee: Zhejiang Tuna Environmental Science and Technology Co Ltd
Current assignee: Zhejiang Tuna Environmental Science and Technology Co Ltd
Priority date: 2020-12-17
Filing date: 2020-12-17
Publication date: 2021-04-27
Anticipated expiration: 2040-12-17
Also published as: CN112705047B

Abstract

The invention discloses a flue gas denitration system of an asphalt mixing plant, which relates to the field of flue gas denitration, and adopts the technical scheme that: the system comprises a dissolving and storing system, a urea pyrolysis system, a heating and mixing system, a flue gas reaction system and a tail gas heat exchange system, wherein the urea pyrolysis system comprises a pyrolysis device, a second electric heater and a fan, and the second electric heater is arranged on an air pipeline communicated with the pyrolysis device and the fan; the flue gas reaction system comprises a reactor; the heating and mixing system includes heating device and ammonia mixer, ammonia mixer UNICOM pyrolysis device, reactor and flue gas air supply for mix the ammonia and the flue gas of pyrolysis device output, heating device sets up on the flue gas pipeline of UNICOM ammonia mixer and flue gas air supply. The method combines the tail gas characteristic of the asphalt mixing plant and the technical characteristic of low-temperature SCR catalytic reaction, can adjust and control the temperature of the tail gas, and realizes the tail gas denitration treatment of the asphalt mixing plant.

Description

Flue gas denitration system of asphalt mixing plant

Technical Field

The invention relates to the field of flue gas denitration, in particular to a flue gas denitration system and a flue gas denitration process for an asphalt mixing plant.

Background

The asphalt is a waterproof, moistureproof and anticorrosive organic gelled material, and is a black brown complex mixture composed of hydrocarbons with different molecular weights and nonmetal derivatives thereof; when the method is used in industry, half of the tail gas is subjected to stirring and mixing treatment by an asphalt mixing plant, the asphalt mixing plant can generate certain tail gas pollution in the working process, the traditional tail gas treatment method of the asphalt mixing plant comprises a mechanical separation method, a condensation method, an absorption purification method, a filtration method, an adsorption purification method, an electrostatic trapping method, a combustion method, low-temperature plasma generation and the like, the methods can only perform cleaning treatment on dust and organic pollutants in the tail gas, but the tail gas of the asphalt mixing plant also contains pollutants of nitrogen oxides, and the treatment methods cannot treat the nitrogen oxides, so that the flue gas discharged by the asphalt mixing plant has certain pollution.

The utility model discloses a utility model patent that publication number is CN206240311U discloses an asphalt mixture agitated vessel flue waste gas SOx/NOx control device, its technical essential lies in: the device comprises a buffer system, a spraying system and a storage and supply system, wherein the buffer system is provided with an air inlet pipeline, the buffer system is connected with the spraying system through a connecting pipeline, a generator device is arranged in the connecting pipeline, the spraying system comprises an acid spraying tower so as to provide sufficient mixing of the composite absorption liquid and the flue waste gas after the mixing of the buffer system, and a chemical reaction is carried out so as to convert the flue waste gas into clean gas, the spraying system is connected to the storage and supply system so as to store and supply the composite absorption liquid after the mixing and the reaction through the storage and supply system, and the waste gas pollution generated in the production operation process of the conventional asphalt mixture stirring equipment is effectively reduced through denitration treatment; however, in the above scheme, the exhaust gas and the composite absorption liquid are fully reacted, the reaction between the composite absorption reagent and the tail gas is not sufficient, and the tail gas temperature of the asphalt mixing plant is lower, generally about 60 ℃, so that the low-temperature catalytic reaction of the flue gas is not applicable.

Therefore, a new solution is needed to solve this problem.

Disclosure of Invention

The invention aims to solve the problems, and provides a flue gas denitration system for an asphalt mixing plant, which can adjust and control the temperature of tail gas by combining the tail gas characteristics of the asphalt mixing plant and the technical characteristics of low-temperature SCR catalytic reaction, so as to realize tail gas denitration treatment of the asphalt mixing plant.

The technical purpose of the invention is realized by the following technical scheme: a flue gas denitration system of an asphalt mixing plant comprises a dissolving and storing system, a urea pyrolysis system, a heating and mixing system, a flue gas reaction system and a tail gas heat exchange system, wherein the urea pyrolysis system comprises a pyrolysis device, a second electric heater and a fan, and the second electric heater is arranged on an air pipeline communicated with the pyrolysis device and the fan; the flue gas reaction system comprises a reactor; the heating and mixing system includes heating device and ammonia mixer, ammonia mixer UNICOM pyrolysis device, reactor and flue gas air supply for mix the ammonia and the flue gas of pyrolysis device output, heating device sets up on the flue gas pipeline of UNICOM ammonia mixer and flue gas air supply.

The invention is further configured to: the tail gas heat exchange system comprises a heat exchanger, and the heat exchanger is connected between a flue gas pipeline of the heating device and a flue gas source and a tail gas pipeline of the output end of the reactor and is used for heat exchange of flue gas and tail gas.

The invention is further configured to: the urea dissolving and storing system comprises a urea dissolving tank and a urea storing tank, wherein a stirrer and a first electric heater are arranged in the urea dissolving tank, and the urea dissolving tank is connected with the urea storing tank through a urea pipeline; and a conveying pump and a flowmeter are arranged on a urea pipeline of the urea storage tank and the urea pyrolysis system.

The invention is further configured to: the urea pyrolysis system includes the pyrolysis jar, is equipped with from last flow equalizing layer, the water conservancy diversion layer that down sets gradually, sprays layer and slow flow layer in the pyrolysis jar, the layer that flow equalizes includes two-layer flow equalizing otter board, is provided with a plurality of nozzles one between the two-layer flow equalizing otter board, a nozzle evenly distributed is on the inner wall of pyrolysis jar, and nozzle one all is towards the inside direction of pyrolysis jar.

The invention is further configured to: the flow guide layer comprises an upper flow guide cover and a lower flow guide cover, the upper flow guide cover and the lower flow guide cover are of horn-shaped structures with downward large openings, the upper flow guide cover is positioned above the lower flow guide cover, the top end of the upper flow guide cover is closed, a flow guide gap is formed between the upper flow guide cover and the lower flow guide cover, and the upper end of the lower flow guide cover is provided with an opening; the lower edge of the upper diversion cover is provided with a lower edge extending downwards, the flow blocking net is of an annular structure and is of a honeycomb porous structure, and activated carbon particles are filled in the inner wall of the flow blocking net.

The invention is further configured to: the spray layer is internally provided with a plurality of layers of spray racks, each layer of spray rack is provided with a plurality of second nozzles, the second nozzles are atomizing nozzles, the flow of the second nozzles is smaller than that of the first nozzles, and the second nozzles on each layer of spray racks are distributed in a staggered manner.

The invention is further configured to: the slow flow layer comprises an upper slow flow screen plate and a lower slow flow screen plate, the upper slow flow screen plate is fixedly connected to the inner wall of the pyrolysis tank, and the lower slow flow screen plate is movably connected to the lower portion of the upper slow flow screen plate through a telescopic rod.

The invention is further configured to: go up slow flow otter board and lower slow flow otter board and all include a plurality of intervals and slowly flow the veneer, seted up a plurality of holes on the slow flow veneer, have the slow flow gap between the slow flow veneer in the middle of every layer, go up slow flow otter board and slow flow veneer on the slow flow otter board down and stack up in turn, go up the slow flow gap on slow flow otter board and the slow flow otter board down and misplace each other.

In conclusion, the invention has the following beneficial effects:

according to the invention, low-temperature SCR denitration is adopted, so that nitrogen oxide pollution in tail gas of the asphalt mixing plant is eliminated, and the problem that the tail gas denitration cannot be realized by the asphalt mixing plant is solved; the energy consumption in the heating process is saved and the emission of waste heat is reduced by preheating heat exchange of the flue gas and the tail gas and adopting a GGH heat exchange mode; the delivery of the urea with small flow is adjusted and controlled by adopting a mode of combining a metering pump and a flow meter for control, so that the accuracy and precision of urea supply and delivery are improved, and the loss of materials is reduced; in the pyrolysis process, the small-caliber atomizing spray gun is adopted to realize the uniformity of the urea solution atomizing spray, so that the mixing reaction efficiency of hot air and urea fog drops is improved; the flue gas and the ammonia gas are quickly and fully mixed by the ammonia gas mixer, so that the flue gas and the ammonia gas can be uniformly mixed in a short time, and the uniformity of ammonia gas distribution is improved; the ash blowing device formed by the compressed air pipeline group can clean the fly ash on the surface of the catalyst layer, effectively prevent the catalyst from being blocked and keep the catalytic activity of the catalyst for a long time.

Drawings

FIG. 1 is a schematic structural diagram of a flue gas denitration system of an asphalt mixing plant according to the present invention;

FIG. 2 is a schematic diagram of the dissolving and storing system of the present invention;

FIG. 3 is a schematic diagram of the urea pyrolysis system of the present invention;

FIG. 4 is a schematic diagram of the tail gas heat exchange system and the heating and mixing system of the present invention;

FIG. 5 is a schematic structural view of a flue gas reaction system of the present invention;

FIG. 6 is a schematic structural view of a pyrolysis tank in a second embodiment of the invention;

FIG. 7 is a schematic perspective view of the inside of a pyrolysis tank in a second embodiment of the invention;

fig. 8 is a schematic view of the internal structure of a pyrolysis tank in the second embodiment of the present invention.

Reference numerals: A. a dissolution and storage system; a0, urea pipeline; a1, a urea dissolving tank; a2, a urea storage tank; a3, a stirrer; a4, a first electric heater; a5, a delivery pump; a6, a flow meter; B. a urea pyrolysis system; b0, an air pipeline; b1, a pyrolysis device; b2, a second electric heater; b3, a fan; C. a tail gas heat exchange system; c0, a flue gas pipeline; c1, a heat exchanger; D. a heating and mixing system; d0, a mixing pipeline; d1, a heating device; d2, an ammonia mixer; d3, a tail gas source; E. a flue gas reaction system; e0, a tail gas pipeline; e1, a reactor; e2, catalyst layer; e3, a soot blowing pipeline; e4, a blowing nozzle; 1. a pyrolysis tank; 11. a flue gas inlet; 12. an air outlet; 2. a flow-equalizing layer; 21. a flow equalizing screen plate; 22. a first nozzle; 3. a spraying device; 30. a spray cylinder; 33. a shower pipe; 4. a flow guiding layer; 41. an upper diversion cover; 42. a lower diversion cover; 43. A current blocking net; 44. a lower edge; 45. an opening; 5. a spray layer; 51. a spray rack; 52. a second nozzle; 6. A slow flow layer; 61. an upper slow flow net plate; 62. a lower slow flow net plate; 63. a telescopic rod.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

Referring to fig. 1-5, a flue gas denitration system for an asphalt mixing plant includes a dissolving and storing system a, a urea pyrolysis system B, a heating and mixing system D, a flue gas reaction system E, and a tail gas heat exchange system C.

The dissolving and storing system A comprises a urea dissolving tank A1 and a urea storing tank A2, wherein a stirrer A3 and an electric heater A4 are arranged in the urea dissolving tank A1, and the urea can be stirred and heated to be prepared into a uniform solution; the urea dissolving tank A1 is connected with the urea storage tank A2 through a urea pipeline A0, and the urea dissolving tank A1 and the urea storage tank A2 can flow automatically or can be pumped by a pump; the urea storage tank A2 is communicated with the urea pyrolysis system B through a urea pipeline A0, a delivery pump A5 and a flow meter A6 are mounted on the communicated urea pipeline A0, and urea can be supplied to the urea pyrolysis system B in a pumping mode; the conveying pump A5 is a variable-frequency metering pump, can accurately control the amount of the pumped urea solution, and is matched with the flowmeter A6 for monitoring, so that the accuracy and the precision of urea supply are improved.

The urea pyrolysis system B can heat the input urea solution, and urea is pyrolyzed to form ammonia under the heating action; the system specifically comprises a pyrolysis device B1, an electric heater II B2 and a fan B3, wherein the electric heater II B2 is arranged on an air pipeline B0 communicated with the pyrolysis device B1 and the fan B3, outside air can be input into the pyrolysis device B1 under the action of the fan B3, the air is heated through the electric heater II B2 in the conveying process and then enters the pyrolysis device B1, a spraying mechanism is arranged in the pyrolysis device B1, reagents output from a urea storage tank A2 can be uniformly sprayed to form fog drops, and the urea fog drops can fully contact with hot air to carry out pyrolysis reaction.

In order to improve the heat utilization efficiency, the fan B3 also can communicate with the tail gas of flue gas reaction system E output, can regard the tail gas that has the waste heat as the air of heating to can reduce the consumption of heating electric energy, can make the further denitration treatment of tail gas again in addition, be favorable to improving the clean degree of tail gas, reduce the pollution of air.

The flue gas reaction system E comprises a reactor E1, specifically an SCR reactor E1, wherein a plurality of SCR catalyst layers E2 are arranged in the reactor E1, and nitrogen oxides in flue gas can be reduced at high temperature to form pollution-free nitrogen and water.

The reactor E1 is internally provided with a soot blower which comprises a soot blowing pipeline E3 arranged above a catalyst layer E2, the soot blowing pipeline E3 is provided with a plurality of blowing nozzles E4, the blowing nozzles E4 face to the catalyst layer E2 and can perform soot blowing treatment on the catalyst layer E2, the blowing nozzles E4 and equipment are cooperatively controlled to blow off ash on the surface of the catalyst before the equipment stops running, and the phenomenon that the active sites on the surface of the catalyst are blocked due to viscosity generated after cooling fly ash is avoided.

The heating and mixing system D comprises a heating device D1 and an ammonia mixer D2, the ammonia mixer D2 is communicated with a pyrolysis device B1, a reactor E1 and a flue gas source, the ammonia mixer D2 is provided with two input ends and an output end, the two input ends are respectively communicated with the pyrolysis device B1 and the flue gas source, the output end is connected with the reactor E1 through a mixing pipeline D0, the ammonia and the flue gas output by the pyrolysis device B1 can be mixed and converged, and the mixed flue gas is input into the reactor E1 through mixing management to perform denitration reaction; the heating device D1 is arranged on a flue gas pipeline C0 communicated with the ammonia mixer D2 and a flue gas source, and can heat input flue gas, heat gas output from an asphalt mixing plant to 200 ℃; the heating device D1 can be a heat-conducting oil smoke heater, can be filled with heat-conducting oil to heat smoke passing through the heat-conducting oil, and has good heat exchange efficiency.

The tail gas heat exchange system C can preheat and recover tail gas output from the tail end of the reactor E1, and specifically comprises a heat exchanger C1, the heat exchanger C1 is connected between a flue gas pipeline C0 of a heating device D1 and a flue gas source and a tail gas pipeline E0 of the output end of the reactor E1, two channels are arranged in the heat exchanger C1, one channel is communicated with the flue gas output from an asphalt mixing plant, the other channel is communicated with the tail gas output from the reactor E1, heat exchange can be carried out between the flue gas and the tail gas, the flue gas can be increased from 60 ℃ to about 160 ℃, energy consumption of the heating device D1 can be reduced, the tail gas can be stabilized from about 200 ℃ to about 105 ℃, and heat emission can be reduced.

In the process of treating the flue gas of the asphalt mixing plant, the urea is dissolved and prepared into a urea solution through the dissolving and storing system A, and the urea is pyrolyzed by the urea pyrolyzing system B to prepare ammonia gas, so that the original liquid ammonia is replaced, and the safety of the whole system is improved; then, the flue gas is heated by a heating and mixing system D, the flue gas and ammonia gas are mixed, and then the mixture is input into a flue gas reaction system E for SCR denitration reaction, so that the pollution of nitrogen oxides in the flue gas is eliminated; and finally, recycling waste heat in the tail gas through a tail gas heat exchange system C, and preheating flue gas generated by the asphalt mixing plant through the waste heat to realize energy conservation and emission reduction.

A flue gas denitration process for an asphalt mixing plant comprises the following steps:

s1: introducing flue gas generated by an asphalt mixing plant into a heat exchanger C1 for preheating, so that the temperature of the flue gas is increased from 60 ℃ to 160 ℃;

s2: the flue gas passes through a heat-conducting oil flue gas heater, hot oil is introduced into the heat-conducting oil flue gas heater to heat the flue gas, so that the temperature of the flue gas is increased from 160 ℃ to 200 ℃;

s3: the heated flue gas and ammonia gas are introduced into an ammonia gas mixer D2, and the ammonia gas and the flue gas are mixed uniformly in a short time, so that the uniformity of ammonia gas distribution is improved to form mixed flue gas;

s4: introducing the mixed flue gas into an SCR reactor E1, rectifying by a fairing to enable the mixed flue gas to flow from top to bottom in the SCR reactor E1, passing through each catalyst layer E2 in the SCR reactor E1, reducing nitrogen oxides in the flue gas by ammonia under the catalytic action of an SCR catalyst to generate pollution-free nitrogen and water to form tail gas, wherein the temperature of the tail gas is about 200 ℃;

s5: tail gas is output from an outlet at the lower end of an SCR reactor E1, is conveyed into a heat exchanger C1 through a tail gas pipeline E0, and exchanges heat with low-temperature flue gas generated by an asphalt mixing plant, so that the low-temperature flue gas is increased from about 60 ℃ to about 160 ℃, and the tail gas is cooled from about 200 ℃ to about 105 ℃, thereby realizing the recovery of heat energy, reducing the energy consumption of a system and reducing the emission of waste heat; the inlet of the reactor E1 is provided with a sampling port for uninterrupted NO measurement_X、O₂(ii) a The outlet of the reactor E1 is provided with a sampling port for uninterrupted NO measurement_X、O₂、NH₃Dynamically adjusting the contents of the two groups of gases introduced into the ammonia gas mixer D2 according to the tail gas treatment condition;

s6: the asphalt mixing plant is frequently started and stopped, when the asphalt mixing plant stops running, the denitration device continuously runs for a period of time, the flue gas in each pipeline and the reactor E1 is treated, and then the denitration device stops running; before the operation is stopped, blowing off ash on the surface of the catalyst layer E2, opening a valve, blowing ash to a blowing nozzle E4 for a period of time through a compressed air soot blowing pipeline E3, blowing off fly ash on the surface of a catalytic base layer, and avoiding the fly ash from generating viscosity after being cooled, so that the active sites on the surface of the catalyst are easily blocked, and the activity of the surface of the catalyst layer E2 can be always kept;

in step S3, ammonia gas introduced into the ammonia gas mixer D2 is prepared by the urea pyrolysis system B, which includes the following steps:

t1: adding urea particles and hygroscopic water into a urea dissolving tank A1, stirring and heating simultaneously to accelerate the dissolution of urea, keeping the temperature of liquid in a urea dissolving tank A1 to be more than or equal to 40 ℃, spinning urea crystals to prepare 40% urea solution, and automatically flowing the prepared urea solution into a urea storage tank A2 for storage;

t2: conveying the urea solution into a pyrolysis device B1 through a variable frequency metering pump, spraying in a pyrolysis device B1, and monitoring the flow rate of urea through the variable frequency metering pump and a flowmeter A6;

t3: the fan B3 inputs the outside air or the tail gas output from the S5 into the second electric heater B2 for heating, and the temperature of the heated tail gas reaches about 600 ℃ after being heated by the second electric heater B2 to form hot air;

t4: hot air is introduced into the pyrolysis device B1 and enters from the upper end of the heating device D1, a urea solution is sprayed into an inner cavity of the pyrolysis device B1 through an atomizing nozzle, the hot air and urea fog drops are mixed with each other, the urea is pyrolyzed into ammonia, and the pyrolyzed ammonia mixed gas flows out from the lower end of the pyrolysis device B1 and is introduced into an ammonia mixer D2; the amount of hot air introduced is adjusted, and 5% ammonia is contained in the ammonia mixed gas formed by pyrolysis, so that the subsequent denitration reaction is utilized, and the material consumption is reduced under the condition of ensuring effective denitration.

According to the invention, low-temperature SCR denitration is adopted, so that nitrogen oxide pollution in tail gas of the asphalt mixing plant is eliminated, and the problem that the tail gas denitration cannot be realized by the asphalt mixing plant is solved; the energy consumption in the heating process is saved and the emission of waste heat is reduced by preheating heat exchange of the flue gas and the tail gas and adopting a GGH heat exchange mode; the delivery of the small-flow urea is regulated and controlled by adopting a mode of combining a metering pump and a flowmeter A6, so that the accuracy and precision of urea supply and delivery are improved, and the loss of materials is reduced; in the pyrolysis process, the small-caliber atomizing spray gun is adopted to realize the uniformity of the urea solution atomizing spray, so that the mixing reaction efficiency of hot air and urea fog drops is improved; the flue gas and the ammonia gas are quickly and fully mixed by the ammonia gas mixer D2, so that the flue gas and the ammonia gas can be uniformly mixed in a short time, and the uniformity of ammonia gas distribution is improved; the soot blower composed of the group of the compressed air pipeline B0 can clean the fly ash on the surface of the catalyst layer E2, effectively prevent the catalyst from being blocked and keep the catalytic activity of the catalyst for a long time.

Example two

The embodiment discloses another flue gas denitration system of an asphalt mixing plant, and as shown in fig. 6-8, on the basis of the first embodiment, a urea pyrolysis system in a denitration device is specifically optimized.

The urea pyrolysis system comprises a pyrolysis tank 1, wherein a flue gas inlet 11 and a gas outlet 12 are respectively arranged at the upper end and the lower end of the pyrolysis tank 1, so that high-temperature flue gas can be introduced into the pyrolysis tank 1 to form a flow direction from top to bottom; the inside from last down has set gradually the homoflow layer 2, water conservancy diversion layer 4, has sprayed layer 5 and has slowed down the flow layer 6 in pyrolysis tank 1, can evenly stably pass through pyrolysis tank 1 to the high temperature flue gas, maintains in the pyrolysis tank 1 high temperature flue gas can with urea spray the liquid uniform contact, improve urea pyrolysis efficiency.

The flow equalizing layer 2 comprises two layers of flow equalizing net plates 21, each flow equalizing net plate 21 comprises a plurality of flow equalizing single plates which are arranged in parallel, each flow equalizing single plate is provided with a plurality of holes, each flow equalizing single plate comprises a middle sunken part and parallel parts on two sides, the directions of the openings 45 of the sunken parts on the adjacent flow equalizing single plates are opposite, the parallel parts of the adjacent flow equalizing single plates are overlapped up and down, and gaps are formed at the overlapped parts; after entering the pyrolysis tank 1 from the flue gas inlet 11, the high-temperature flue gas is quickly blocked by the two flow equalizing screen plates 21, the bundled flue gas is scattered and passes through gaps and holes between the flow equalizing single plates, and the holes are distributed in a densely distributed state, so that the flue gas can be subjected to homogenization treatment; moreover, a double-layer flow equalizing net plate 21 structure is adopted, so that the flue gas can be homogenized more repeatedly;

a plurality of first nozzles 22 are arranged between the two layers of flow equalizing mesh plates 21, the first nozzles 22 are uniformly distributed on the inner wall of the pyrolysis tank 1, and the first nozzles 22 face the inner side direction of the pyrolysis tank 1, so that pyrolysis reaction can be generated at the position between the two layers of flow equalizing mesh plates 21, and because the descending flow rate of the blocking flue gas of the flow equalizing mesh plates 21 at the two sides is slow, a high-temperature flue gas mixed urea atomized liquid mixture can stay for a longer time between the two layers of flow equalizing mesh plates 21, and the pyrolysis efficiency and the pyrolysis sufficiency are improved; this nozzle 22 is small-bore atomizing nozzle, can realize the atomizing of low discharge urea solution and spray, and the stable and accurate control that urea can be realized to cooperation measuring pump and flowmeter avoids the insufficient condition of reaction that excessive urea solution produced, improves the utilization ratio of urea.

The lower side of the flow equalizing layer 2 is provided with a flow guide layer 4, the flow guide layer 4 comprises an upper flow guide cover 41 and a lower flow guide cover 42, the upper flow guide cover 41 and the lower flow guide cover 42 are both of horn-shaped structures with large openings facing downwards, the upper flow guide cover 41 is positioned above the lower flow guide cover 42, the top end of the upper flow guide cover 41 is sealed, a flow guide gap is formed between the upper flow guide cover 41 and the lower flow guide cover 42, the upper end of the lower flow guide cover 42 is provided with an opening 45, the edge of the lower end of the lower flow guide cover is hermetically connected with the inner wall of the pyrolysis tank 1, so that a zigzag flow guide channel is formed in the flow guide layer 4, a flue gas mixture needs to enter the flow guide gap between the upper flow guide cover 41 and the lower flow guide cover 42 from the lower edge of the upper flow guide cover 41 and then flows out from the opening 45 on the lower flow guide cover 42, the path;

the lower edge of the upper flow guide cover 41 is provided with a downwardly extending lower edge 44, the edge position of the flow guide gap is provided with a flow blocking net 43, the flow blocking net 43 is of an annular structure and surrounds the outer side position of the lower edge 44, the flow blocking net 43 is of a honeycomb porous structure, and the inner wall of the flow blocking net 43 is filled with activated carbon particles; when the flue gas enters the flow guide gap, the flue gas needs to pass through the flow blocking net 43, and the porous structure can filter and absorb part of impurities in the flue gas and further delay the flow velocity of the flue gas.

The lower side of the flow guide layer 4 is provided with a spraying layer 5, and the spraying layer 5 mainly sprays urea fog drops to supplement and adjust the content of ammonia in the high-temperature flue gas; a plurality of layers of spraying frames 51 are arranged in the spraying layer 5, generally, the spraying frames can be three layers, each layer of spraying frame 51 is provided with a plurality of second nozzles 52, the second nozzles 52 atomize nozzles, the flow of the second nozzles 52 is smaller than that of the first nozzles 22, and the second nozzles 52 can spray finer fog drops, so that high-temperature flue gas can further pyrolyze urea and further utilize the high-temperature flue gas, the second nozzles 52 in each layer can work independently and adjust the flow, the adjustment can be carried out according to the residual condition of nitrogen oxides in tail gas, and the content of ammonia in the pyrolyzed mixed flue gas can be adjusted; and the second nozzles 52 on each layer of spraying frame 51 are distributed in a staggered manner, and the mutually wrong structures can increase the uniformity of urea fog drops sprayed by the second nozzles 52 in the pyrolysis tank 1, so that the urea pyrolysis degree in the flue gas is more uniform, and the urea can be fully contacted with the flue gas for pyrolysis.

A plurality of spraying devices 3 are arranged between the flow equalizing layer 2 and the flow guiding layer 4, each spraying device 3 comprises a spraying cylinder 30 and a spraying cylinder connected with the spraying cylinder, one end of each spraying pipe 33 is connected with the spraying cylinder, and the other end of each spraying pipe extends into the pyrolysis tank and is provided with a third nozzle for spraying urea solution; the spraying cylinder 30 can temporarily store urea, and has the function of pressure buffering, so that the stability of urea spraying is improved.

The lower side of the spraying layer 5 is provided with a circulation layer which regulates the flow and the flow velocity of the flue gas flowing out of the gas outlet 12; the slow flow layer 6 comprises an upper slow flow screen plate 61 and a lower slow flow screen plate 62, the upper slow flow screen plate 61 is fixedly connected to the inner wall of the pyrolysis tank 1, the lower slow flow screen plate 62 is movably connected to the lower part of the upper slow flow screen plate 61 through a telescopic rod, and the telescopic state of the telescopic rod is adjusted by a barrel so that the distance between the lower slow flow screen plate 62 and the upper slow flow screen plate 61 can be adjusted, the gap between the lower slow flow screen plate and the upper slow flow screen plate can be adjusted, and the passing space of high-temperature flue gas can be;

the upper slow flow net plate 61 and the lower slow flow net plate 62 both comprise a plurality of spaced slow flow single plates, the slow flow single plates are connected through a support, a plurality of holes are formed in the slow flow single plates, a slow flow gap exists between the slow flow single plates in each layer, and the slow flow single plates on the upper slow flow net plate 61 and the lower slow flow net plate 62 are alternately laminated, so that the slow flow gaps on the upper slow flow net plate 61 and the lower slow flow net plate 62 are staggered; when the upper slow flow net plate 61 and the lower slow flow net plate 62 are close to each other, the slow flow gap between the slow flow single plates of each layer is blocked by the slow flow single plate of the other layer, so that the flue gas channel between the two slow flow net plates is reduced, the retention time of the flue gas in the pyrolysis tank 1 can be prolonged, on one hand, the pyrolysis sufficiency of urea fog drops in high-temperature flue gas can be increased, and the urea can be fully pyrolyzed; on the other hand, the amount of discharged flue gas can be controlled, so that the flue gas can be fully reacted in the reactor, and the treatment effect of nitrogen oxides in the flue gas is improved.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims

1. The flue gas denitration system of the asphalt mixing plant is characterized by comprising a dissolving and storing system (A), a urea pyrolysis system (B), a heating and mixing system (D), a flue gas reaction system (E) and a tail gas heat exchange system (C), wherein the urea pyrolysis system (B) comprises a pyrolysis device (B1), a second electric heater (B2) and a fan (B3), and the second electric heater (B2) is arranged on an air pipeline (B0) communicated with the pyrolysis device (B1) and the fan (B3); the flue gas reaction system (E) comprises a reactor (E1); heating and hybrid system (D) include heating device (D1) and ammonia gas blender (D2), ammonia gas blender (D2) UNICOM pyrolysis device (B1), reactor (E1) and flue gas source for mix the ammonia and the flue gas of pyrolysis device (B1) output, heating device (D1) set up on UNICOM ammonia gas blender (D2) and flue gas pipeline (C0) of flue gas source.

2. The flue gas denitration system of the asphalt mixing plant according to claim 1, wherein the tail gas heat exchange system (C) comprises a heat exchanger (C1), and the heat exchanger (C1) is connected between the heating device (D1) and the flue gas pipeline (C0) of the flue gas source and the tail gas pipeline (E0) at the output end of the reactor (E1) for heat exchange between the flue gas and the tail gas.

3. The flue gas denitration system of the asphalt mixing plant according to claim 1, wherein the dissolving and storing system (A) comprises a urea dissolving tank (A1) and a urea storing tank (A2), a stirrer (A3) and an electric heater I (A4) are arranged in the urea dissolving tank (A1), and the urea dissolving tank (A1) is connected with the urea storing tank (A2) through a urea pipeline (A0); and a delivery pump (A5) and a flow meter (A6) are arranged on a urea pipeline (A0) of the urea storage tank (A2) communicated with the urea pyrolysis system (B).

4. The flue gas denitration system of the asphalt mixing plant according to claim 3, characterized in that the urea pyrolysis system comprises a pyrolysis tank (1), wherein a flow equalizing layer (2), a flow guiding layer (4), a spraying layer (5) and a flow buffering layer (6) are arranged in the pyrolysis tank (1) from top to bottom in sequence, the flow equalizing layer (2) comprises two layers of flow equalizing net plates (21), a plurality of first nozzles (22) are arranged between the two layers of flow equalizing net plates (21), the first nozzles (22) are uniformly distributed on the inner wall of the pyrolysis tank (1), and the first nozzles (22) face the inner side direction of the pyrolysis tank (1).

5. The flue gas denitration system of the asphalt mixing plant according to claim 4, wherein the flow guide layer (4) comprises an upper flow guide cover (41) and a lower flow guide cover (42), the upper flow guide cover (41) and the lower flow guide cover (42) are both in a horn-shaped structure with a large opening facing downwards, the upper flow guide cover (41) is positioned above the lower flow guide cover (42) and the top end of the upper flow guide cover is closed, a flow guide gap is formed between the upper flow guide cover (41) and the lower flow guide cover (42), and an opening (45) is formed at the upper end of the lower flow guide cover (42); the lower edge of the upper flow guide cover (41) is provided with a lower edge (44) extending downwards, the flow blocking net (43) is of an annular structure, the flow blocking net (43) is of a honeycomb porous structure, and the inner wall of the flow blocking net (43) is filled with activated carbon particles.

6. The flue gas denitration system of the asphalt mixing plant according to claim 5, wherein a plurality of layers of spray racks (51) are arranged in the spray layer (5), a plurality of second nozzles (52) are arranged on each layer of spray rack (51), the second nozzles (52) are atomizing nozzles, the flow rate of the second nozzles (52) is smaller than that of the first nozzles (22), and the second nozzles (52) on each layer of spray racks (51) are distributed in a staggered manner.

7. The flue gas denitration system of the asphalt mixing plant according to claim 6, wherein the slow flow layer (6) comprises an upper slow flow screen plate (61) and a lower slow flow screen plate (62), the upper slow flow screen plate (61) is fixedly connected to the inner wall of the pyrolysis tank (1), and the lower slow flow screen plate (62) is movably connected to the lower portion of the upper slow flow screen plate (61) through a telescopic rod (63).

8. The flue gas denitration system of the asphalt mixing plant according to claim 7, wherein the upper slow flow screen (61) and the lower slow flow screen (62) comprise a plurality of spaced slow flow veneers, the slow flow veneers are provided with a plurality of holes, a slow flow gap exists between the slow flow veneers in each layer, the upper slow flow screen (61) and the lower slow flow screen (62) are alternately stacked, and the slow flow gaps on the upper slow flow screen (61) and the lower slow flow screen (62) are mutually staggered.