A kind of flue gas desulfurization and denitration method of resource
The present invention relates to a kind of flue gas desulfurization and denitration method of resource, specifically, relate to NO and SO in the flue gas
2The method that removes and realize respectively resource.
China is coal-fired big country, and coal accounts for 75% of primary energy total quantity consumed.A large amount of consumption of the energy have caused serious air environmental pollution, and that wherein the most outstanding is SO
xThe acid rain harm that discharging causes, and NO
xDepletion of the ozone layer that causes and photochemical fog." for the first time national pollution sources generaI investigation communique " announced on February 6th, 2010 according to national environmental protection portion shows, in 2007 years, China's SO2 emissions are 2320.00 ten thousand tons, 1166.64 ten thousand tons of flue dust, 1797.70 ten thousand tons of nitrogen oxide, the air contaminant treatment task is very arduous.At present, China's sulfur dioxide (SO2) emissions total amount occupies first place in the world, and acid rain and sulfur dioxide pollution cause economic loss every year is more than 1,000 hundred million yuan.In recent years, country successively puts into effect the multinomial powerful SO of propelling that is intended to
2The policies and regulations of sulfur dioxide (SO2) emissions growth are alleviated in the measure that reduces discharging, and thermal power plant takes active action, or builds the FGD device, or changes clean fuel, or adopts the clean burning technology, or close, stop old, little unit, make the SO that soars for many years
2Total emission volumn is contained tentatively to some extent.Yet nitrogen oxide but highlights day by day, and well-known, the extent of injury of nitrogen oxide goes even farther than sulfur dioxide, even more deep and broad, and the acid rain of Future in China pollutes will be by sulfuric acid type to the compound development of sulfuric acid/nitric acid.Control SO
2With the discharging of nitrogen oxide be extremely urgent.
At present; be placed in status of equal importance in China's desulfurization and denitration; existing mainstream technology has many advantages; can satisfy requirement on environmental protection; but weak point is investment and operating cost height; it is low that desulfurizing byproduct such as calcium sulfate etc. are worth, even also to bring secondary pollution problem, denitration then be unworthy accessory substance N
2, but consume a large amount of reducing agent ammonia and expensive catalysts.Therefore, investment is hanged down in exploitation, the combined desulfurization and denitration technology is the developing direction of pollution that caused by coal burning thing control new technology cheaply.
21 century, the world has entered the epoch of kownledge economy and sustainable development, requires to set up the unity of opposites of development and environment.Along with the mankind's development, many resources are faced with and reduce even depleted stage.Fully make rational use of resources or even waste resource has become contemporary science and technology worker's social responsibility.In theory, any production process does not all have discarded object, has only the resource that is not fully utilized.Also be so aspect atmosphere pollution, be called as the SO of one of atmosphere major pollutants at present
x, but be two important and be badly in need of resources in China.SO
2Be the necessary raw material of producing sulfuric acid, and sulfuric acid is the necessary raw material of producing chemical fertilizer, the title of " father of the female and agricultural of industry " is arranged.Equally, NO
xAlso be the necessary raw material of producing nitric acid, nitric acid is again the important source material of producing NpK complex fertilizer, also is the important source material of industries such as chemical industry, military project, the people be quick-fried.Therefore, carry out SO
xPollution control and recovery technology research are to alleviating acid rain harm, promoting reasonable resources to utilize significant!
Desulfurization in the prior art, denitration technology mainly contain three kinds:
(I) desulfur technology (the removal of nitrogen oxide rate is lower in this technology): as lime-gypsum method (CN1281747), wet ammonia process desulfurizing technology (CN1226459), seawater desulfurizing process (CN1262145), double alkali method desulfurizing technology (CN1475298), semi-dry desulphurization technology (CN101249380), circulating fluidized bed desulfur technology (CN1401411), electron beam desulfur technology (environmental protection, 2004 (9): 15-18) etc.
(II) denitration technology: comprise selective catalytic reduction (SCR), as US 4221768, US4101238, US4048112; With SNCR method (NCSR), as CN1817415, CN101244361.
(III) while desulphurization denitration technology: as CN1454700, CN1147416, CN1843574, CN1923341, CN101053747, CN101337152, CN101485957, CN101352648, CN101306308, CN1311052, CN101053750 etc.
In the technology (I), mainly based on desulfurization, the denitration rate is generally lower.Lime-gypsum method is maximum a kind of technology of using in the present state inner desulfurization technology, desulfuration efficiency is higher, the energy by-product gypsum, but because China is a plaster of paris resource-rich country, and the gypsum of desulfurization by-product is being compared nuance in addition qualitatively with the plaster of paris, as color and luster, content of beary metal etc., going back that therefore domestic desulfurated plaster really uses is few, and most of desulfurated plasters are among the stacking.A large amount of constructions along with the power plants desulfurizing item, the desulfurated plaster discharge capacity increases severely, how handling this a part of gypsum well also will be a very important problem, store up if take to abandon, need to build special slag field, not only invest hugely, take a large amount of soils, also easily cause the pollution to surrounding environment of dust, underground water, the operating cost of handling gypsum simultaneously is also very high.The ammonia process of desulfurization, belong to the resource desulfur technology, sulfur in smoke is reclaimed the production ammonium sulfate fertilizer, but ammonium sulfate uses as chemical fertilizer certain limitation is arranged, long-term use can make soil compaction, and under the waterflooding condition, soil meeting severe depletion of oxygen, after ammonium sulfate was used, sulfate ion wherein can be reduced into sulfide, and the too high root system of plant that makes of sulfide concentration accumulation is injured and death.Ammonium sulfate fertilizer uses better in the salt-soda soil.Therefore, if a large amount of desulfurizing items adopts ammonia process, might cause the market problem of thiamine fertilizer.Other desulfur technology is used also less relatively at present in industry.
In the technology (II), the denitration efficiency of SCR is higher than NCSR, and the denitration efficiency of SCR can reach more than 80%, and most of technology of using in the denitrification apparatus are SCR at present.But the major defect of SCR method is that catalyst is easily poisoned, and exists ammonia leakage and investment cost, operating cost to cross problems such as height.According to (China Power, 2006,39 (3): 86～89) measuring and calculating, utilize the SCR method remove-ton NOx expense reached more than 9800 yuan! High operating cost will hinder the enthusiasm of enterprise's denitration, and the researcher is exploring new denitration technology both at home and abroad.
In the technology (III), be meant in a process, use with a kind of method the SO in the flue gas
2Technology with NOx removes simultaneously that is to say, no matter the product behind the desulphurization denitration has or not use, contains SO in the product simultaneously
3 -/ SO
4 -Or NO
2 -/ NO
3 -, be a kind of mixture.CN1454700 adopts microwave to be radiated in the absorption sensitizer layer of being made up of Ni, Fe, Co, Mn metal or metal oxide the SO in the flue gas
2Be reduced into sulphur, NOx is reduced into N
2, but there is microwave leakage problem etc. in this process unit complexity.CN1147416 discloses and has used TiO
2SO in the absorption flue gas
2With the technology of NOx, adsorb saturated TiO
2Realize regeneration in the dilute sulfuric acid by being immersed in, but this method is not illustrated TiO
2The SO of middle absorption
2With the place to go of NOx in its regenerative process, well-known, dilution heat of sulfuric acid be not can and SO
2With NOx reaction.CN1843574 discloses and has utilized sodium chlorite and additive to form absorbent solution, with SO in the flue gas
2Be oxidized to SO
4 -, NO is oxidized to NO
3 -, generate the mixture of ammonium sulfate and ammonium nitrate then with the ammoniacal liquor effect; But the consumption of sodium chlorite is big in this technology, and absorbent pH value is lower, and is big to the corrosivity of equipment.CN1923341 discloses and has utilized ozone simultaneous oxidation SO
2With the method for NO, the oxidisability of utilizing ozone is with SO
2Be oxidized to SO
3, NO is oxidized to NO
3, then with alkali lye absorb, crystallization, form the mixture of sulfate and nitrite, nitrate, but this mixture is as if without separation, be no much use.CN101053747 by hydrogen peroxide or ozone with the SO in the flue gas
2With the NO oxidation, absorb with ammoniacal liquor then, form ammonium sulfate and ammonium nitrate mixture at last, use as chemical fertilizer.Although last desulphurization denitration accessory substance can be used as the chemical fertilizer use in this technology, added value is relatively low.CN101337152 is then by the ozone SO in the flue gas just
2With the NO oxidation, water absorbs then, forms sulfuric acid and nitric acid weak solution at last, and separates the single product that forms sulfuric acid and nitric acid by chemical method.But how this technology also unspecifiedly separates the nitration mixture of sulfuric acid and nitric acid, the worker of chemical field knows, with the mixed solution separating difficulty of sulfuric acid and nitric acid is very big, and in desulphurization plant, form dilute acid soln, corrosivity to equipment is very large, and equipment investment and maintenance cost will be very big.CN101485957 then discloses desulfurization and denitration has been carried out in two equipment, uses alkali lye the SO in the flue gas
2Absorption is got off, and with ozone sulfite oxidation is become sulfate again in liquid phase; In denitration device, use ozone the NO oxidation, absorb the mixture that forms nitrite/nitrate with alkali lye then.Though this technology is carried out desulfurization, denitration respectively in two equipment, realized separating of sulphur resource and nitrogen resource, high more a lot of with ozone deoxidation sulphite than cost with air oxidation.CN101352648 then absorbs SO with cobalt amine complex solution absorption of N O, bivalent metal oxide or carbonate alkalescence desulfurizing agent
2Method realize desulphurization denitration simultaneously.This is a kind of pure SO that removes
2With the method for NOx, do not have to realize resource.CN101306308 and CN101352648 are similar, and knowledge has replaced to the ferrous ammonium complex solution to cobalt amine complex solution.CN1311052 then discloses the complex compound that forms with divalence cobalt and ammonia NO has been oxidized to NO
2, generate ammonium nilrite, the SO in the flue gas with the ammoniacal liquor reaction then
2Generate ammonium sulfite with ammonia react, in liquid phase, be oxidized to ammonium sulfate, formed the mixture of ammonium sulfate and ammonium nilrite/ammonium nitrate, reach the purpose of desulphurization denitration.The same with CN101053747, the accessory substance of desulphurization denitration can only use as chemical fertilizer, and added value is lower.CN101053750 then discloses at photochemical catalyst TiO
2Effect under, by UV-irradiation, the NO in the flue gas is oxidized to NO
2Be reduced into N by sodium sulfite
2Be reduced into N
2This saying is worth discussion, because in the file of this patent, does not have NO in the relevant reaction equation
2Generate N with the sodium sulfite reaction
2Reaction, in aforesaid each desulphurization denitration patent, mostly be NO
2Absorbed by alkali lye, form nitrite/nitrate, with SO
2The sulphite that absorbs the back generation mixes.
China is the country of an a lack of sulfur, the annual need from external a large amount of imported sulphur with preparation SO
2Or sulfuric acid, and China is a SO
2Discharging big country in the existing desulfur technology, is SO mostly
2Absorb and form the solid waste gypsum, the ammonium sulfate of the low fertilizer efficiency of a small amount of desulfur technology generation.In the desulfurizing and denitrifying process, also be the SO in the flue gas mostly simultaneously
2Absorb the mixture of formation sulfate and nitrate with NOx, be difficult to form the resource product of high added value.
In sum, in the existing desulfurizing and denitrifying process, the part that still has some deficits, desulphurization denitration technology remain further to be improved.
Summary of the invention
The object of the invention is, overcomes the defective that prior art exists, and provides a kind of and can remove SO from flue gas
2With NOx, can reclaim SO again
2, NOx resource desulphurization denitration technology.
Realize the technical scheme of the object of the invention:
The inventor thinks, in order to reclaim SO
2Can adopt the method for absorbent absorption, desorb, from flue gas, remove SO
2And prepare liquid SO
2, realize the SO in the resource type treating flue gas
2Problem, and realize value maximization.SO with the sodium sulfite solution absorption
2Method claim the Wellman-Lord method again, its principle is:
Absorption process: Na
2O → 2NaHSO
Side reaction: Na
3+ 1/2 O
But, the main cause that sodium sulfite absorption desorption method is difficult to promote is: (1) alkaline consumption height: lost absorbability owing to some sodium sulfite is oxidized to sodium sulphate, oxygenation efficiency is about 10%, so the sodium sulfite that needs additional alkali such as soda ash to fall with replenish lost:
Like this, 1 ton of SO of every recovery
2Replenish 0.3 ton of soda ash.(2) steam consumption height.Desorption process need be used Steam Heating, 1 ton of SO of every desorb
2Approximately need the water of about 10 tons of evaporations,, need to consume 11 tons of steam,, also will consume the steam about 7 tons if adopt double effect evaporator if adopt single effect evaporator.The desulphurization cost height has just limited applying of this method.
At some oxygen in the flue gas, the situation of the easy oxidation of sodium sulfite, the inventor finds to add the oxidation that high-efficiency anti-oxidant can suppress to press sodium sulphate effectively by a large amount of experiments, the oxygenation efficiency of sodium sulfite can drop to below 1.5%, thereby greatly reduces alkaline consumption.At former Arbiso process desorb SO
2The time steam consumption high problem, adopted the indirect steam pressurization that 2nd effect evaporator is steamed to heat the back reuse, make the live steam consumption reduce to 3 tons of/ton SO
Because more than the NOx95% in the flue gas is NO, and NO is insoluble in water, be difficult to absorb with absorbent, therefore adopt NO is oxidized to NO
2After absorb with alkali lye again, thereby reach the purpose of denitration.Utilize ozone O
3The reaction mechanism of oxidation NO is very complicated, still lacks further investigation at present.Key reaction has:
Absorb with alkali lye, just can form nitrate.Therefore, remove SO
2After flue gas enter denitrating tower, feed O in the tower bottom
3Gas, tower top spray into alkali lye and absorb, and the denitration rate can reach more than 90%.Nitrate crystallizable separating out after being accumulated to finite concentration in the solution after filtration, drying obtains the higher nitrate product of purity, thereby realized the resource of denitrification process.
The exhuast gas desulfurization method of denitration of the said resource of the present invention, it comprises the steps:
(1) flue gas from boiler enters desulfurizing tower from the bottom, and absorbent sprays into from the top of desulfurizing tower, in desulfurizing tower, and absorbent sodium sulfite and SO
2Reaction generates sodium hydrogensulfite.
(2) enter 1st effective evaporator after the rich solution of desulfurizing tower bottom and the lean solution heat exchange in the step (1), after the heating vaporization, contain SO from multi-effect evaporator
2Gas phase enter 2nd effect evaporator heating; After the compressed machine supercharging of the gas phase of 2nd effect evaporator, enter 1st effective evaporator with fresh steam.
(3) evaporimeter steam condensate (SC) and the SO in the step (2)
2Mixture enters knockout drum, and gas phase can make liquid SO with compressor compresses after condenser condenses
2Product enters storage tank.Liquid then with mix from second lean solution of imitating after with the rich solution heat exchange after enter desulfurizing tower and recycle.
(4) flue gas that comes out of the cat head in the step (1) enters in the denitrating tower, from the O of ozone generator
3Also enter in the denitrating tower, NO is by O in desulfurizing tower
3Be oxidized to NO
2, absorbed by the denitrfying agent that sprays into from denitrating tower top, form nitrate.
When (5) nitrate reaches finite concentration in step (4) absorption liquid, can crystallization separate out, can obtain the higher nitrate of purity by filtering.
(6) step (5) is filtered the filtrate that obtains and is turned back to denitrating tower top with the denitrfying agent that replenishes.
Wherein, in said desulfurization absorbent sodium sulfite solution, add high-efficiency anti-oxidant, said antioxidant is to be made up of a kind of in hydroquinones soluble in water, catechol, resorcinol, tert-butyl catechol, alpha-Naphthol, betanaphthol, p-phenylenediamine (PPD), dimethyl-p-phenylenediamine, sodium thiosulfate, vulcanized sodium, sodium dithionate, the thiourea dioxide or two or more mixture, and said antioxidant concentration is 0.001%～0.5%.
Said denitrfying agent is a kind of in sodium carbonate, potash, ammonium carbonate, carbonic hydroammonium, sodium acid carbonate, saleratus, NaOH, potassium hydroxide, liquefied ammonia or the ammoniacal liquor.
Said desulfurizing tower is spray column, plate column or packed tower.
Said denitrating tower is spray column, plate column or packed tower.
Adopt technique scheme can obtain liquid SO
2, desulfurization degree can reach more than 96%, and the denitration rate can reach more than 90%, and nitrate content is more than 96%.
Description of drawings
Fig. 1 is the exhuast gas desulfurization method of denitration schematic flow sheet from resource.
The part symbol description is as follows among Fig. 1:
The 3-desulfurizing tower, the 5-ozone generator, 7-denitrating tower, 11-filter, 17-poor rich liquid heat exchanger, 23-first single-effect evaporator, 26-first are imitated gas-liquid separator, 30-second single-effect evaporator, the 36-second effect gas-liquid separator, 40-condensate liquid gas-liquid separator, 44-SO
2Gas condenser, 48-liquid SO
The specific embodiment
Referring to accompanying drawing 1, the present invention is achieved in that
From the flue gas of boiler fan from managing 1 bottom that enters desulfurizing tower 3, from lean solution-sodium sulfite (containing a small amount of sodium hydrogensulfite) absorption liquid (containing antioxidant) of rich or poor heat exchanger 17 from managing 2 tops that enter desulfurizing tower 3.Rich solution-the solution of sodium bisulfite of desulfurizing tower 3 bottoms (containing a small amount of sodium sulfite) enters heat exchanger 17 from managing 16, by from be from managing 24 live steam and from managing 18 thermals source that enter first single-effect evaporator, 23, the first single-effect evaporators 23 through pump 21 after the heating of pipe 19 lean solution from the indirect steam of compressor 38.After rich solution is vaporized by 23 heating of first single-effect evaporator, enter first and imitate gas-liquid separator 26, gas phase enters second single-effect evaporator 30 from managing 27 as thermal source, the liquid major part then enters first single-effect evaporator 23 from managing 28 through pump 21 circulation, and a part of liquid enters second single-effect evaporator 30 through pump 32 from managing 29.Condensate liquid in first single-effect evaporator 23 enters the condensate liquid gas-liquid separator 40 from managing 34.After rich solution in second single-effect evaporator 30 is vaporized, gas enters the second effect gas-liquid separator 36 from managing 31, after gas-liquid separation, gas phase enters first single-effect evaporator 23 from managing 37 compressed machines 38, the liquid major part then enters second single-effect evaporator 30 through pump 32 circulation from managing 42, and a part of liquid is extracted out through pump 20 from managing 39 as lean solution.Condensate liquid in second single-effect evaporator 30 enters the condensate liquid gas-liquid separator 40 gas phase SO from managing 35
2From manage 43 enter condenser 44 condensers after, be compressed into liquid SO from managing 45 by compressor 46
2, enter the storage tank 48 from managing 47.Liquid in the condensate liquid gas-liquid separator 40 from manage 41 with mix from pipe 39 liquid, extract out through pump 20.
Through removing SO
2Flue gas come out from the top of desulfurizing tower 3, from managing 4 bottoms that enter denitrating tower 7, from the O of ozone generator 5
3Enter pipe 4 from managing 6, the denitrfying agent of circulation enters the top of denitrating tower 7 from managing 15 with being mixed from pipe 9 additional denitrfying agent.In denitrating tower inside, NO is oxidized to NO
5, it is soluble in water to be absorbed formation nitrate by denitrfying agent, when nitrate concentration reaches one regularly, can crystallization separate out, enter filter 11 and carry out Separation of Solid and Liquid from the bottom of denitrating tower 7 from managing 10, solid is discharged by pipe 12, and drying can get the nitrate product of purity more than 95%.Filtrate from manage 13 by pump 14 through managing 15 tops that pump into denitrating tower 7, recycle.Through the flue gas after the denitration from the top of denitrating tower from managing 8 chimneys that enter boiler.
Contain SO like this
2Obtain improvement with the flue gas of NOx, reclaimed liquid SO
2, the nitrate product, becoming useless is the mixture of single useful products rather than sulphur and nitrogen, has realized the value maximization of exhuast gas desulfurization denitration resource process, greatly reduces the desulphurization denitration expense.
To originally being further elaborated, its purpose only is better to understand content of the present invention below by embodiment.Therefore, the cited case does not limit protection scope of the present invention:
Flue gas condition: 15000Nm
3/ h, SO
2Concentration 2000ppm (5714mg/Nm
3), NO concentration 460ppm (616mg/Nm
3), 150 ℃ of temperature.
Absorption liquid (lean solution) is formed: sodium sulfite 16.78%, sodium hydrogensulfite 11.45%, antioxidant hydroquinones 0.03%, vulcanized sodium 0.02%.
Flue gas enters desulfurizing tower (desulfurizing tower is the plate ripple arranged packing tower), and lean solution sprays in the tower from tower top, and flow is 2t/h.Through after the desulfurization, the rich solution at the bottom of the desulfurization Tata consists of: sodium sulfite 8.69%, sodium hydrogensulfite 23.37%.SO in the flue gas of tower top outlet
2Content is 190mg/Nm
3, desulfurization degree is 96.6%.
Rich solution discharges SO after the 2nd effect evaporator desorb
2, after condensation, compression, obtain liquid SO
282.8kg/h.Solution after the desorb is lean solution, forms the same.
2After flue gas enter denitrating tower, denitrating tower is a spray column, has produced the O of 14.8kg/h from ozone generator
3Enter in the flue gas, spray into 5% ammonia spirit 500kg/h from the top of denitrating tower.Through after the denitration, NO concentration is 49mg/Nm from the flue gas of denitrating tower tower top discharge
3, the denitration rate is 92%.After the ammonium nitrate that produces is accumulated to finite concentration, separate out from the crystallization of denitration Tata still, dry after filtration, obtain ammonium nitrate 23.4kg/h, content 96.5%.
Flue gas condition: 54200Nm
3/ h, SO
2Concentration 1560ppm (4457mg/Nm
3), NO concentration 650ppm (875mg/Nm
3), 140 ℃ of temperature.
Absorption liquid (lean solution) is formed: sodium sulfite 13.58%, sodium hydrogensulfite 5.6%, antioxidant dimethyl-p-phenylenediamine 0.01%, sodium dithionate 0.03%.
Flue gas enters desulfurizing tower (desulfurizing tower spray column), and lean solution sprays in the tower from tower top, and flow is 5.5t/h.Through after the desulfurization, the rich solution at the bottom of the desulfurization Tata consists of: sodium sulfite 5.6%, sodium hydrogensulfite 24.96%.SO in the flue gas of tower top outlet
2Content is 89mg/Nm
3, desulfurization degree is 98.0%.
Rich solution discharges SO after the 2nd effect evaporator desorb
2, after condensation, compression, obtain liquid SO
2236kg/h.Solution after the desorb is lean solution.
2After flue gas enter denitrating tower, denitrating tower is the guide float-valve tower, in adorn 3 blocks of column plates, produced the O of 84.7kg/h from ozone generator
3Enter in the flue gas, spray into 5%KOH solution 2600kg/h from the top of denitrating tower.Through after the denitration, NO concentration is 61.2mg/Nm from the flue gas of denitrating tower tower top discharge
3, the denitration rate is 93.0%.After the potassium nitrate that produces is accumulated to finite concentration, separate out from the crystallization of denitration Tata still, dry after filtration, obtain potassium nitrate product 148.6kg/h, content 97.5%.