CN104084025B - A kind of method of boiler smoke removal of nitrogen oxide - Google Patents

Abstract

The invention discloses a kind of method of boiler smoke removal of nitrogen oxide.First flue gas is passed into Fe ^iIin EDTA solution, complexed absorption NO obtains ferrous sub-acyl complex compound Fe ^iI(NO) EDTA, then by Fe ^iI(NO) EDTA introduces regenerating unit, reduces Fe with metallic iron ^iI(NO) EDTA regenerates Fe ^iIeDTA, NO is converted into the NH of high concentration simultaneously ₃.The present invention removes the NO in flue gas with liquid complexing absorbent, efficiently solve the technical difficulty that NO is difficult to enter liquid phase; Absorb and regenerate and separately carry out, improve NH ₃concentration, can solve NH ₃the problem that absorption plant is too huge; The NH produced ₃ammonium salt can be generated as the raw material of industry, also can be used as reducing agent and enter in other boiler smoke SNCR denitration reactors, the iron oxide hydrate precipitate that iron is formed, can be used as the chemical products such as iron oxide red pigment.

Description

A kind of method of boiler smoke removal of nitrogen oxide

Technical field

The present invention relates to a kind of method of gas cleaning, particularly relate to a kind of method of boiler smoke removal of nitrogen oxide.

Background technology

Main containing NO and NO in industrial waste gas ₂, and the concentration of NO is usually all far away higher than NO ₂, particularly in the NOx of combustion product gases, NO accounts for about 95%, NO ₂the ratio accounted for is less.NO gas-liquid mass transferring resistance is large simultaneously, and in water, solubility is lower, and its processing procedure is very difficult.The discharge capacity of the current NOx of China increases year by year with the speed up to 10%, expects the year two thousand twenty and will reach (2660 ~ 2970) × 104t, therefore carries out the Environmental capacity research of NOx in air extremely urgent.

At present, NOx groundwater pollution control mainly contains three kinds: fuel denitride technology, low NOx combusting technology and gas denitrifying technology.But due to many-sided reason, fuel denitride technology and NOx combustion technology not yet reach comprehensive practical stage, denitrating flue gas remains the topmost method of NOx Environmental capacity.

Gas denitrifying technology is most popular is divided into two classes: selective catalytic reduction (SCR) and SNCR method (SNCR), their reaction mechanism is all be that NOx in flue gas is reduced into harmless nitrogen and water by reducing agent with ammonia, both essential difference are that SCR uses catalyst, reaction temperature is lower, and SNCR does not use catalyst reaction temperatures higher.But these two kinds of methods all also exist certain defect, and SCR method is higher to designing requirement, manufacture and operating cost higher.In denitrification process, owing to containing SO in flue gas ₂, water smoke and grit etc., catalyst " poisoning " etc. can be caused to be unfavorable for the phenomenon of catalytic reaction.SNCR method ammonia consumption is high, and amount of ammonia slip is comparatively large, and the difficulty mixed is large, so its denitration rate can only reach 50 ~ 60%.Simultaneously after these two kinds of methods urea of being or ammonia incomplete reaction, emptying being easy to causes secondary pollution.

In recent years, the wet denitration technical research of liquid complexing absorbing and removing nitrogen oxides in effluent is adopted extensively to carry out.The method utilize liquid complexing agent directly and the NO being insoluble in water in flue gas react, make NO enter liquid phase, thus reach the object of denitrating flue gas.According to lot of domestic and foreign scholar just to the research of liquid complexing absorption process, Fe ^iIeDTA solution is absorbed with extraordinary effect to NO.But up to the present, liquid complexing method is but still difficult to realize industrialization, and its main cause is the Fe needed in denitrification process ^iIeDTA consumption is comparatively large, and price is higher, can increase process operation cost, simultaneously Fe ^iIeDTA is easily oxidized in course of reaction can not the Fe of complexing NO ^iIIeDTA, thus the denitration efficiency that can reduce technique.There is scholar's proposition biocatalytic reduction method afterwards to regenerate Fe ^iIeDTA, but this method implementation process is complicated, drops into practical application and also has a lot of problem to need to solve.Ma Lefan proposes with ferrous chelating agent complexed absorption NO, then reacts reducing/regenerating Fe by the ferrous nitrosyl complex of iron powder and generation ^iIeDTA, its technique adopts Integrated Architecture, and complexed absorption and reducing/regenerating are in same reactor.The defect of this technique is to react the NH generated ₃concentration is lower, and required NH ₃the capacity of absorption plant must be equal to NO complexing device, and equipment investment required like this can increase greatly, can increase the difficulty that whole technological process runs simultaneously.

Summary of the invention

In order to solve the problems of the technologies described above, the invention provides a kind of method of boiler smoke removal of nitrogen oxide.

The technical scheme that the present invention solves the problems of the technologies described above is:

A method for boiler smoke removal of nitrogen oxide, comprises the steps:

(1) in absorber, with Fe ^iIeDTA solution, as absorbing liquid, is reacted by complexed absorption, absorbs pole in flue gas and is insoluble in the NO of water, and the sub-acyl complex compound of the ferrous iron generated after reaction introduces reducing/regenerating device;

(2) in reducing/regenerating device, metallic iron and ferrous nitrosyl complex generation reduction reaction, be reduced to the NH of high concentration by the NO in complex compound ₃, regenerate Fe simultaneously ^iIeDTA is cycled to used in and absorbs NO.

The method of above-mentioned boiler smoke removal of nitrogen oxide, described complexed absorption reaction temperature is 293K ~ 323K, pH is 5.0 ~ 6.5, Fe ^iIthe concentration of EDTA solution is 15 ~ 40mmol/L.

The method of above-mentioned boiler smoke removal of nitrogen oxide, described reduction reaction temperature is 293K ~ 323K, and described ferrous nitrosyl complex sprays on metallic iron, sprinkle density 0.2 ~ 1.0m ³/ (m ²h).

The method of above-mentioned boiler smoke removal of nitrogen oxide, described absorber is sieve-plate tower, rotating stream tray scrubber, spray column or bubble tower.

The method of above-mentioned boiler smoke removal of nitrogen oxide, described reducing/regenerating device is iron filings packed bed or iron powder stirred tank.

The method of above-mentioned boiler smoke removal of nitrogen oxide, described metallic iron is iron powder or iron filings.

Concrete course of reaction is as follows:

Flue gas passes in absorbing liquid, Fe ^iInO in EDTA complexed absorption flue gas:

Fe ^ⅡEDTA+NO→Fe ^Ⅱ(NO)EDTA

Iron powder and ferrous nitrosyl complex react, and make NO be reduced to NH ₃, realize Fe simultaneously ^iIeDTA reducing/regenerating:

2Fe ^Ⅱ(NO)EDTA+Fe+8H+→2Fe ^ⅡEDTA+Fe(OH) ₂+2NH ₃

NH ₃can ammonium salt be generated in acid solution:

NH ₃+H ⁺→NH ₄ ⁺

When there is oxygen in flue gas, can by Fe ^iIeDTA is oxidized to Fe ^iIIeDTA and lose complexing, the existence of iron powder then can address this problem:

Fe ^ⅡEDTA+O ₂→Fe ^ⅢEDTA

Fe+Fe ³⁺→Fe ²⁺

The meeting in the solution of reacted iron powder forms Fe (OH) ₂hydrate, can generate Fe under certain condition ₂o ₃as iron oxide red raw material:

Fe(OH) ₂→Fe ₂O ₃+H ₂O。

Beneficial effect of the present invention is:

(1) the present invention adopts liquid complexing method, removes the NO in flue gas with liquid complexing absorbent, efficiently solves the technical difficulty that NO is difficult to enter liquid phase.

(2) complexed absorption reaction of the present invention and reducing/regenerating reaction are separately carried out in different device, and the ferrous nitrosyl complex that complexed absorption reaction generates is introduced separately into reducing/regenerating device, can solve NH ₃the problem that absorption plant is too huge.

(3) the present invention's complexes absorption used can recycling, and reacted product can comprehensively utilize again, can not produce secondary pollution, and technological operation is simple, and denitration efficiency is high, is easy to industrialization.

(4) process product of the present invention has good value, the NH of generation ₃pass in acid solution and can generate ammonium salt as the raw material of industry, also can enter in SNCR denitration reactor as reducing agent, the iron that reaction consumes can form the hydrate precipitate of iron oxide in the solution, can be used as other chemical products such as iron oxide red pigment.

Accompanying drawing explanation

Fig. 1 is FB(flow block) of the present invention.

Fig. 2 is experimental provision of the present invention and schematic flow sheet: 1, air inlet, 2, absorption tower, 3, absorption cycle groove, 4, regeneration reactor, 5, dehydrator, 6, gas outlet.

Detailed description of the invention

Below in conjunction with specific embodiment, the present invention is described in further details, but the present invention is not limited to this.

Embodiment 1

Fe ^iInO in EDTA complexed absorption simulated flue gas: using the sieve plate absorber of diameter 100mm, high 1200mm as absorber, built-in 2 layers of sieve plate, percent opening 17%.Simulation NO exhaust gas flow 20m ³/ h, containing NO500 × 10 ^-6, absorbing liquid Fe ^iIeDTA concentration is 25mmolL ^-1, internal circulating load is 80L/h, reaction temperature 323K, and the initial pH of complex liquid is 5.5, NO removal efficiency is 97%.Regenerating unit with the iron filings packed-bed reactor of diameter 200mm, high 400mm, sprinkle density 0.2m ³/ (m ²h), the ammonia sulfuric acid absorption of bear again during 313K 5% obtains ammonium sulfate, then the Fe born ^iIeDTA solution circulation is used for absorbing, and denitration efficiency is still about 97%.

Embodiment 2

Fe ^iInO in EDTA complexed absorption simulated flue gas: using the sieve plate absorber of diameter 100mm, high 1200mm as absorber, built-in 2 layers of sieve plate, percent opening 17%.Simulation NO exhaust gas flow 20m ³/ h, containing NO400 × 10 ^-6, absorbing liquid Fe ^iIeDTA concentration is 25mmolL ^-1, internal circulating load is 80L/h, reaction temperature 323K, and the initial pH of complex liquid is 5.5, NO removal efficiency is 98%.Regenerating unit with the iron filings packed-bed reactor of diameter 200mm, high 400mm, sprinkle density 0.4m ³/ (m ²h), the ammonia sulfuric acid absorption of bear again during 303K 5% obtains ammonium sulfate, then the Fe born ^iIeDTA solution circulation is used for absorbing, and denitration efficiency is still about 98%.

Embodiment 3

Fe ^iInO in EDTA complexed absorption simulated flue gas: using the sieve plate absorber of diameter 100mm, high 1200mm as absorber, built-in 2 layers of sieve plate, percent opening 17%.Simulation NO exhaust gas flow 20m ³/ h, containing NO500 × 10 ^-6, absorbing liquid Fe ^iIeDTA concentration is 30mmolL ^-1, internal circulating load is 100L/h, reaction temperature 323K, and the initial pH of complex liquid is 6.0, NO removal efficiency is more than 97%.Regenerating unit with the iron filings packed-bed reactor of diameter 200mm, high 400mm, sprinkle density 0.6m ³/ (m ²h), the ammonia sulfuric acid absorption of bear again during 293K 5% obtains ammonium sulfate, then the Fe born ^iIeDTA solution circulation is used for absorbing, and denitration efficiency is still about 96%.

Embodiment 4

Fe ^iInO in EDTA complexed absorption simulated flue gas: using the sieve plate absorber of diameter 100mm, high 1200mm as absorber, built-in 2 layers of sieve plate, percent opening 17%.Simulation NO exhaust gas flow 20m ³/ h, containing NO500 × 10 ^-6, absorbing liquid Fe ^iIeDTA concentration is 20mmolL ^-1, internal circulating load is 60L/h, reaction temperature 313K, and the initial pH of complex liquid is 6.0, NO removal efficiency is 98%.Regenerating unit is with the iron powder stirred tank reactor of diameter 200mm, high 400mm, and speed of agitator 60 revs/min, the ammonia sulfuric acid absorption of bear again during 293K 5% obtains ammonium sulfate, then the Fe born ^iIeDTA solution circulation is used for absorbing, and denitration efficiency is still about 97%.

Embodiment 5

Fe ^iInO in EDTA complexed absorption simulated flue gas: using the sieve plate absorber of diameter 100mm, high 1200mm as absorber, built-in 2 layers of sieve plate, percent opening 17%.Simulation NO exhaust gas flow 20m ³/ h, containing NO500 × 10 ^-6, absorbing liquid Fe ^iIeDTA concentration is 20mmolL ^-1, internal circulating load is 60L/h, reaction temperature 323K, and the initial pH of complex liquid is 5.5, NO removal efficiency is 98%.Regenerating unit is with the iron powder stirred tank reactor of diameter 200mm, high 400mm, and speed of agitator 80 revs/min, the ammonia sulfuric acid absorption of bear again during 313K 5% obtains ammonium sulfate, then the Fe born ^iIeDTA solution circulation is used for absorbing, and denitration efficiency is still about 97%.

Claims (6)

1. a method for boiler smoke removal of nitrogen oxide, comprises the steps:

(1) in absorber, with Fe ^iIeDTA solution, as absorbing liquid, is reacted by complexed absorption, absorbs pole in flue gas and is insoluble in the NO of water, and the sub-acyl complex compound of the ferrous iron generated after reaction introduces reducing/regenerating device;

(2) in reducing/regenerating device, metallic iron and ferrous nitrosyl complex generation reduction reaction, be reduced to the NH of high concentration by the NO in complex compound ₃, regenerate Fe simultaneously ^iIeDTA is cycled to used in and absorbs NO;

Described ferrous nitrosyl complex sprays on metallic iron, and sprinkle density is 0.2 ~ 1.0m ³/ (m ²h).

2. the method for boiler smoke removal of nitrogen oxide according to claim 1, described complexed absorption reaction temperature is 293K ~ 323K, pH is 5.0 ~ 6.5, Fe ^iIthe concentration of EDTA solution is 15 ~ 40mmol/L.

3. the method for boiler smoke removal of nitrogen oxide according to claim 1, described reduction reaction temperature is 293K ~ 323K.

4. the method for boiler smoke removal of nitrogen oxide according to claim 1, described absorber is sieve-plate tower, rotating stream tray scrubber, spray column or bubble tower.

5. the method for boiler smoke removal of nitrogen oxide according to claim 1, described reducing/regenerating device is iron filings packed bed or iron powder stirred tank.

6. the method for boiler smoke removal of nitrogen oxide according to claim 1, described metallic iron is iron powder or iron filings.