CN1091636C - Multi-step process for reucing no and so - Google Patents

Multi-step process for reucing no and so Download PDF

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Publication number
CN1091636C
CN1091636C CN94117013A CN94117013A CN1091636C CN 1091636 C CN1091636 C CN 1091636C CN 94117013 A CN94117013 A CN 94117013A CN 94117013 A CN94117013 A CN 94117013A CN 1091636 C CN1091636 C CN 1091636C
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effluent
slurries
urea
reduce
oxysulfide
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CN1118712A (en
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林美珍
约翰·E·霍夫曼
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Nalco Fuel Tech
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/60—Simultaneously removing sulfur oxides and nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F23J15/006—Layout of treatment plant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J7/00—Arrangement of devices for supplying chemicals to fire
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2215/00—Preventing emissions
    • F23J2215/10—Nitrogen; Compounds thereof
    • F23J2215/101—Nitrous oxide (N2O)
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2215/00—Preventing emissions
    • F23J2215/20—Sulfur; Compounds thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2217/00—Intercepting solids
    • F23J2217/10—Intercepting solids by filters
    • F23J2217/101—Baghouse type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2900/00—Special arrangements for conducting or purifying combustion fumes; Treatment of fumes or ashes
    • F23J2900/15081—Reheating of flue gases
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Treating Waste Gases (AREA)

Abstract

The removal of SOx and particulates, and preferably also NOx, from the combustion gases of a large boiler, is simplified while efficiency is improved. In a primary treatment zone, a slurry comprising an alkaline SOx-reducing composition and preferably a nitrogen-containing composition effective to reduce NOx, is introduced into combustion gases at a temperature of from about 900 DEG to about 1300 DEG C. The gases are cooled by initial contact with steam-generating means, and then by contact with an gas-to-gas heat exchanger. Cooled gases are then subjected to a secondary treatment in which they are first humidified and further cooled by introduction of a water spray or aerosol to reduce the temperature to 100 DEG C. or below. Contact between the SOx-reducing composition and the humidified gases is maintained for a reaction period of at least 2 seconds. Particulate solids are then separated from the gases with a fabric filter. The cleaned gases are reheated by the gas-to-gas heat exchanger prior to discharge to the atmosphere. Reductions of SOx of greater than 80% are achieved, preferably 90 to 95%.

Description

Reduce NO XAnd SO XMultistep method
The present invention relates to a kind of effective minimizing by organic-fuel and the multiple gas with various chemical pollutant of trash burning generation and the method for graininess emission, in the multistep processes of the efficient that improves the pollutant minimizing, the minimizing of chemical pollutant has obtained realization.
The burning of carbon-containing fuel produces nitrogen oxide (NO in Industrial Boiler and other power factory X, X is generally 1 or 2), oxysulfide (SO X, X is generally 1 or 2) and other pollutant, as ammonia (NH 3) and often be called the solid particle of ash content.
Many minimizing burning effluent NO that are used for XMethod developed.They generally can be divided into two classes: optionally with nonselective.In process for selective, (think in this field that these class methods are better), be divided into selective catalytic reduction (SCR) and SNCR method (SNCR) again.
The SCR method generally comprises and makes the effluent that contains nitrogen oxide by an ammonia (NH 3) in the catalytic bed that exists, so that NO XReduction reach 80% or higher.The SNCR method comprises makes reductive NO XInorganic agent enter effluent to reach 50% or higher reduction.
We know that alkaline reagent (as alkaline-earth metal and alkali-metal oxide, hydroxide and carbonate) can reduce the SO in the burning effluent XContent.Yet these materials also produce further particle except being difficult to processing, and these particles enter effluent and make troubles for any particulate abatement device or method in position.The expectation function of these materials is to reduce SO X, they also can reduce SO 3, and SO 3Can improve the operation of " electrostatic precipitator ", and make this deduster become a kind of especially effectively particle removal equipment.
As described, a kind of efficient apparatus that removes degranulation from the burning effluent is the equipment that is called electrostatic precipitator (ESP).In electrostatic precipitator, the burning effluent passes through between the electrode that produces corona discharge.This makes particle charged.After the charging, these particles move on to and are deposited on the passive electrode like this.After coming out from electrostatic precipitator, can not be discharged in the atmosphere basically with the effluent of particle.
In some cases, the known technology of electrostatic precipitator is and SO XMinimizing be at war with.For example, known SO 3Can strengthen the operation of electrostatic precipitator.And, owing to need stable slurries and different temperatures window to be used for optimizing operation, be used to reduce SO XTechnology make NO XMinimizing complicated.
A factor to electrostatic precipitator operation particular importance of having found is the resistivity that is entrained in particle in the effluent.The resistivity of particle must be enough high to promote collection.Yet in many electrostatic precipitator, the resistivity of particle is too high, and its order of magnitude is about 10 13Ohm/cm (ohm-cm) or higher.In these cases, the efficient of particle collection can reduce greatly.The pollution control interests that this reduction meeting grievous injury on collection efficiency is provided by electrostatic precipitator.Usually, desirable electrical resistivity range is about 10 8With about 10 10Between the ohm-cm.
For the particle in " adjusting " effluent with the resistivity that keeps them in desirable scope, used some reagent.These reagent comprise sulfuric acid, sulfur trioxide (SO 3) and phosphoric acid, in these conditioning agents, sulfur trioxide is most preferably also the most frequently used.In addition, the conditioning agent that another kind is used to improve the electrostatic precipitator collection efficiency is an ammonia, and it has been found the collection performance that can improve electrostatic precipitator.
Unfortunately, ammonia is poisonous and unstable.And, must be under high pressure or with dilute aqueous form (NH 4OH) preserve ammonia, this can increase expense.Use ammonia to promote the SCR nitrogen oxides reduction or regulate electrostatic precipitator and may in storage, processing and transportation, produce serious problem, make the SCR method so not desirable, perhaps do not encourage to use a kind of conditioning agent of ammonia as electrostatic precipitator.
Except the slurries that use alkali metal and alkaline earth metal component, other scheme of effectively removing oxysulfide relates in one or more processes makes water.For example, contain SO XEffluent can be by " cascade " in the spray column, the dual purpose that is used to remove oxysulfide and particle.In this arrangement, the effluent of load is by " curtain " or the current or the aqueous solution, and they are from physically taking away these particles.If contain aforesaid minimizing SO in the water XComponent, the minimizing of additional oxysulfide also can realize.In addition, also can use " venturi wet scrubbing tower ".Venturi wet scrubbing tower is a kind of equipment, and wherein the effluent of load deashes and other particle to remove by a variable larynx neck plummet float-Venturi scrubber, and effluent is by a spray column absorber then.If effluent contacts with mud, just can reach SO in spray column XFurther minimizing.Subsequently, effluent is by a demister.Later process relates in the rear end, by in and acidity in the effluent and unreacted CaO changed into Ca (OH) 2, simple " humidification " effluent is to increase catching of sulphur.
Yet, back hold-carrying (i.e. the process of in boiler, carrying out after the heat exchange first), as an electrostatic precipitator (ESP), a cascade, venturi wet scrubbing tower or humidification reduce and (as are used to reduce NO implementing the full load pollutant XSCR) in, commercial too impracticable, perhaps in that reduce to pollute content too ineffective to required degree (for example using cascade, venturi wet scrubbing tower or rear end humidification).
Therefore, required is a kind of being used for to reduce the reliable method that the burning effluent reduces gas pollutant, and not relevant with independent use back-end processing poor efficiency and expensive.
An object of the present invention is by using multi-step system to realize reducing simultaneously effectively SO XAnd NO X, this system makes the maximizing efficiency of process rear end part.
Another object of the present invention is to use existing equipment to implement the back hold-carrying, and effective SO is realized on maximal efficiency ground XAnd NO XMinimizing.
A further object of the invention is to implement the minimizing process of second level nitrogen oxide or oxysulfide, and this process is cooperated mutually with first order process, causes the clean minimizing of nitrogen oxidation and oxysulfide to reach required level jointly.
The present invention can realize these and other objects, and a kind of method is provided, and this method comprises the following steps: the preparation of slurries, preferred stabilisation, it contains alkalescence and reduces SO XCompound and in the limiting temperature scope effective reductive NO XNitrogenous composition (be different from ammonia, particularly urea or hydrolysis of urea product or its component at least are as aminoquinoxaline, ammonium carbonate or carbonic hydroammonium and remaining NH 4OH, these will be described in more detail below); Select at least one treatment region, the temperature in this district is in said limiting temperature scope; Slurries are incorporated in the treatment region to reduce NO XAnd SO X(that is first order process); Use the shunting or the product in the effluent of slurries to implement rear end NO then XOr SO XMinimizing method (that is: second level process).
Read following detailed description, particularly referring to accompanying drawing the present invention is better understood, its advantage is more obvious:
Fig. 1 is the schematic diagram of using the present invention and having the boiler of an electrostatic precipitator;
Fig. 2 is the schematic diagram of using the present invention and having the boiler of a cascade spray column;
Fig. 3 is the schematic diagram of using the present invention and having the boiler of a venturi wet scrubbing tower;
Fig. 4 is near the schematic diagram of using the present invention and the boiler of catalytic bed being arranged saving device and air preheater.
A typical case of the present invention is provided with shown in Fig. 1～4, and wherein boiler 100 comprises combustion zone 10, and fuel 12 burnings are to form effluent 14 in this combustion zone.Effluent 14 from the combustion zone 10 by effluent pipeline 20 and flow through and save device 30 and air preheater 35.In Fig. 1, electrostatic precipitator 40a is arranged in the effluent pipeline 20, make effluent 14 can proper temperature according to appointment 300 °F from then on pass through.Cascade spray column 40b is arranged in the effluent pipeline 20 in Fig. 2, makes effluent 14 from then on pass through.Venturi wet scrubbing tower 40c is arranged in the effluent pipeline 20 in Fig. 3, makes effluent 14 from then on pass through.Fig. 4 shows the boiler 100 that catalytic bed 40d is arranged near saving device 30 and air preheater 35.
Be used to introduce nitrogen-containing compound such as urea or hydrolysis of urea product and reduce SO XReagent such as Ca (OH) 2The equipment 50 of stabilisation slurries be placed on the effluent pipeline 20, injection device 60 extends a certain positions in the effluent 14 like this, the temperature of this position effluent 14 is to reductive NO XEffectively.Simultaneously, in Fig. 1, another equipment 70 that is used to introduce water or aforementioned stable slurries is arranged in effluent pipeline 20, makes injection device 80 extend a certain position in the effluent 14, and this position is near the upstream end of electrostatic precipitator 40a; In Fig. 2, slurries and water are introduced in cascade 40b together; In Fig. 3, equipment 70 is introduced slurries among the venturi wet scrubbing tower 40c by injection device 80.
Application of the present invention can realize purpose of the present invention, and the while can reduce or save the installation extras and finish NO XOr SO XBe reduced to desired level.In addition, when the back hold-carrying was the SCR method of minimizing nitrogen oxide, the present invention can reduce or save transportation, storage and the processing to a large amount of ammonias or ammoniacal liquor.Be not convenient to all required ammonia of rear end SCR even method of the present invention provides, the minimizing of this aequum is also showing extremely significant advantage aspect safety and the expense.
The inventive method preferably adopts the single inorganic agent that exists with the aqueous slurry form, and this inorganic agent comprises the reductive NO that contains the nitrogenous composition of non-ammonia XReagent and segmentation (alkalescence of preferred stabilisation reduces SO XThe suspension of reagent.Although reductive NO XReagent can comprise residue or the accessory substance that ammonium hydroxide is reformed as hydrolysis or other degraded or chemistry, " the nitrogenous composition of non-ammonia " speech is meant and comprises that the component that contains at least a composition, this composition contain nitrogen as a kind of element, but is not gaseous ammonia.The alkalescence of segmentation reduces SO XThe suspension of reagent preferably include the material of selecting at least a oxide, hydroxide and the carbonate (hydroxide of preferably magnesium or calcium or carbonate) from alkali metal or alkaline-earth metal.Mixture means each specially and reduces NO XAnd SO XReagent.
For stable slurry reaching simple and efficient operation, need to use suitable stabilizers.Preferred stabiliser system is that those comprise that hydrophilic lipophilic balance (HLB value) is at least the stronger surfactant of hydrophily about 10 less than about 10 normally hydrophobic surfactant and HLB value, the difference of the HLB value of wherein hydrophobic and hydrophilic surfactant is at least about 3, and preferably about at least 5.The ratio of the weight of hydrophobicity dispersant and the weight of hydrophily dispersant preferably about from 25: 1 in about 1: 1 scope, for example from about 12: 1 by about 2: 1.The general concentration that adopts of dispersant system be from about 1ppm to 20, about 000ppm, preferably from about 250ppm to 1, about 000ppm.
Preferred hydrophobicity dispersant (the HLB value is less than 8) is selected from following material: the block copolymer of ethoxylated phenol ethanol, oxirane and expoxy propane, petroleum sulfonate, organophosphorus ester, aliphatic acid such as oleic acid, castor oil, alkylsulfonate, Marlamid and wherein any two or more mixture.Preferred hydrophily dispersant is selected from following material: alkanolamide, lauryl sulfate, dodecyl benzene sulfonate, amidosulfonic acid salt, phosphate and wherein any two or more mixture.Reductive NO XReagent be a kind of to the non-catalytic reduction of nitrogen oxides effective substances.This method comprises an optionally process of free radical mediated, is exactly the SNCR (SNCR) that often refers to.
With various nitrogenous composition pure and that typical commercial form exists, when introducing, will produce effective gas phase NO with aqueous solution form XReducing agent (as imino group free radical NH).Important nitrogenous composition is a urea; The urea precursor; One or more hydrolysates of urea (as aminoquinoxaline, ammonium carbonate, carbonic hydroammonium); Other ammonium salt; With various urea complexs, comprise the hydrolysis of urea product (most preferably the ratio of aminoquinoxaline and ammonium carbonate/carbonic hydroammonium is about about 10: 1 to 1: 200) that contains the unique texture that ammonium carbonate and carbonic hydroammonium cooperates with aminoquinoxaline; The id reaction of urea or itself and other component, related component, or the product of the mixture of these materials reaction.Also comprise following compounds: ammonium carbonate, ammonium formate, ammonium citrate, ammonium acetate, ammonium oxalate, other ammonium salt are (organic and inorganic, but organic acid particularly), ammonium hydroxide, various stable amine, guanidine, guanidine carbonate, biguanides, dicyandiamidines sulfate, melamine, cdicynanmide, nitrolim, biuret, 1,1 '-mixture of Celogen Az, methylolurea, methylolurea-urea, dimethyl urea, hexa (HMTA) and above-mentioned substance.
Can use reinforcing agent to improve NO XThe validity of reducing agent is promptly improved from its effective temperature window, its service efficiency etc.The reinforcing agent that share with inorganic agent of the present invention can be the appropriate combination of above-mentioned substance, also can be that other component such as oxidation of hydrocarbons and other are listed in the material in this United States Patent (USP) 4,719,092,4,844,878 and 4,877,591 as a reference.
Carrying out the nitrogen oxide reduction with the hydrolysate of urea and unique hydrolysis of urea thing (can be described as ammonium carbonate/carbonic hydroammonium aminoquinoxaline herein) has been listed in this document as a reference disclosed down: the international patent application of von Harpe and Pachaly, be entitled as " hydrolysis of urea method in the pipeline " (" Process for the In-Line Hydrolysis of Urea "), publication number is WO92/02291, and the applying date is 1991.8.1; With von Harpe, Pachaly, Lin, Diep, and the international patent application of Wegrzyn, be entitled as " using the hydrolysis of urea thing to carry out the nitrogen oxide reduction " (" Nitrogen Oxides Reduction Using a UreaHydrolysate "), publication number is WO92/02450, and the applying date is 1991.8.1.
Hydrolysate or the hydrolysis of urea thing of introducing urea in inorganic agent of the present invention have tangible benefit as nitrogenous composition, because they can reduce another kind of pollutant-nitrous oxide (N simultaneously at wide relatively effluent temperature window nitrogen oxides reduction 2O) generation.
In order to provide sufficient hydrolysis of urea thing effectively, and provide ammonia on demand to promote NO with nitrogen oxides reduction XRear end SCR reduction, about at least 25% urea is wanted hydrolysis, more preferably about at least 60% hydrolysis of urea, most preferably about at least 80% hydrolysis of urea.
Hydrolysis degree can be determined by measuring electrical conductivity increase, proportion and alkalescence.The electrical conductivity of 10% urea liquid is about 1.2millimhos, and the electrical conductivity of 10% urea liquid of complete hydrolysis is about 120millimhos.As a comparison, the electrical conductivity of 25% urea liquid is about 1.2millimhos and the electrical conductivity of 25% hydrolyzate solution is about 140millimhos.Hydrolysate has higher electrical conductivity and proportion.
Segmentation alkalescence reduces SO XThe stable suspension of reagent preferably include following at least a kind of material: the oxide of alkali metal or alkaline-earth metal, hydroxide and carbonate (hydroxide of preferably magnesium or calcium or carbonate).Many SO that are used for based on calcium and magnesium 2The adsorbent that reduces is known, comprise lime, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide and their mixture, for example the calcium of the lime stone that exists with common mineral forms, dolomite and other form or magnesium carbonate comprise oyster shell, aragonite, calcite, chalk, marble, marl and calcareous tufa.It can be exploited or produce.Yet, having been found that calcium hydroxide when being mixed into slurries (CaO that mainly comprises water mixing) can combine with the collaborative of nitrogenous treating agent in formation, this is preferred.
Adsorbent preferably contains about at least 10% calcium hydroxide, preferably at least about 40%, more preferably all is calcium hydroxide.According to SO in the effluent 2Amount and composition in amount different of nitrogenous treating agent, the amount of calcium adsorbent can change in the present composition.In the preferred composition calcium hydroxide with calcium be the mol ratio of benchmark and baseline sulphur (being the sulphur on the preliminary treatment level) be about 1: 4 by about 4: 1, more preferably about 1: 2 by about 3: 1.In general, calcium hydroxide comprises at least about 10% slurries of the present invention, preferably about 15% and between about 50%.If this slurry constituents is considered to do, for example there are not diluent, calcium hydroxide to account for up to about 97%, more preferably account for about 65% to 97% of the composition that do not comprise diluent.
Nitrogenous treating agent is that the ratio of benchmark and baseline (being preliminary treatment) effluent nitrogen oxide can change about to 3.5 about 0.5 with the nitrogen in the inorganic agent preferably.This ratio can be described as " normalized stoichiometric proportion " or " NSR "." normalized stoichiometric proportion " is meant the concentration NH for example of reduction free radical XFree radical (NH XFree radical, wherein x is an integer, it is considered to by promoting that series reaction causes NO XBe reduced into N 2The part of inorganic agent contribution) with effluent in the ratio of nitrous oxides concentration, be expressed as [NH X]/[NO X].When the chemical formula of reduction reaction can not fine definition, also can select to use inorganic agent and NO XThe mol ratio of concentration replaces NSR; Also can think when NSR one speech used herein is suitable and comprise mol ratio.
Nitrogenous treating agent preferably accounts for about about 3% to 35% (percentage by weight) of the total composition that does not comprise diluent (as water), accounts for about about 1% to 15% of final slurries.When urea adds fashionablely with the form of the aqueous solution, when calculating the amount that adds urea, should not consider the water in the solution.
The adsorbent in the slurries of the present invention and the weight ratio of nitrogenous reagent are generally about 1.5: 1 by about 33: 1, more preferably about 2.7: 1 by about 22: 1.Except nitrogenous reagent and adsorbent, the remainder of said composition comprises water or other diluent that is enough to form slurries.These slurries generally contain about 20% to the solid of about 70% (percentage by weights), the solid of preferred about about 26% to 50% (percentage by weight).
For example, suppose the effluent gas volume be 1,000,000 standard cubic foot (SCF)/hour, SO 2Level be 1000ppm, NO XLevel be 300ppm (as common situation), the Ca that on adsorbent, introduces (OH) 2With slurries and the SO of urea in water 2Mol ratio be 2 (or 384.4 Pounds Per Hours), its NSR is 2 (or 46.75 Pounds Per Hours).The adsorbent of gained and the ratio of urea are 8.22.
These slurries most preferably are that the concentrated solution by calcium hydroxide slurry and nitrogenous treating agent mixes with required ratio.If these slurries are not to prepare the back to introduce effluent at once, preferably add suitable stabilizers, this depends on how long these slurries are placed before introducing.
These slurries of near then small part are introduced, and for example inject, and be able to effectively reduce in the effluent pending under the condition of pollutant level.Slurries generally are to introduce effluent when the temperature of effluent changes to 2200 left and right sides scopes about 1500 °F.Do like this, the effect of the even mixing of slurries and enough infiltrations just can guarantee.Described injection is designed to exist the nozzle of part to carry out from being installed in, so that the slurries on the cutting plane of varying level are evenly distributed in the effluent.
In order to reduce pollutant effectively, need slurries on required effluent cross section, evenly to distribute, so must select nozzle to make it effective to this purpose.Experienced technical staff can understand, is effective for some conventional spout of this purpose.The suitable single-nozzle that is used to inject aqueous slurry comprises Turbotak Nozzle.Other suitable nozzle is described in following open part as a reference to some extent: international patent application is entitled as " method and apparatus that is used for reducing the combustion gas pollutant levels " (" Process and Apparatus for MinimizingPollutant Concentrations in Combustion Gases "), application number is PCT/EP91/00952, applicant Chawla, von Bergrnan and Pachaly, the applying date is 1991.5.21, and DRP DE-2627880 C2,1982.11.11 announces.
In some cases, the amount of water or other diluent may have shock chilling function to adsorbent and nitrogenous reagent in the slurries of the present invention.That is to say that evaporation can make coming into force of chemical treatments be deferred to processing the required time of diluent to occur under than the lower temperature of anticipation temperature.When amount of solid in the slurries is lower than about 38%, when preferably being lower than about 28% (percentage by weights), (but not being inevitable) may appear in this situation.Under these circumstances, the injection of slurries should be carried out under higher effluent temperature, to compensate this quenching.
Above-mentioned slurries inject effluent, the minimizing that can make effluent sulphur oxide content the most nearly about 75%, more generally about about 40% to 70%.Even now is enough sometimes, but also need further reduce SO sometimes XIn these cases, can adopt back-end processing with further minimizing oxysulfide.Because the SO that reduces by the rear end logos XAmount relatively low (that is, can additionally increase by 30% at most), can adopt existing equipment and a whole set of SO of minimizing in this rear end logos XDevice compare, so just greatly reduce cost.
The treatment step that oxysulfide is reduced in this rear end is to make this slurries shunting, and the slurries of q.s are used for aforesaid NO XAnd SO XMinimizing, and a part of slurries are introduced in the water in the cascade particulate abatement device, as shown in Figure 2.Like this, when effluent passed through cascade, oxysulfide and slurry constituents reaction had further reduced oxysulfide.The processing that another is so as shown in Figure 3, relates to a venturi wet scrubbing tower.Part NO X/ SO XSlurries are introduced in the spray column of venturi wet scrubber, make the further minimizing of oxysulfide and remove degranulation.
As shown in Figure 1, when in boiler electrostatic precipitator being arranged, slurries can improve the minimizing of oxysulfide like this introducing in the effluent near the electrostatic precipitator upstream end.Effluent preferably about 70 °F to 1350 left and right sides temperature ranges by electrostatic precipitator, more preferably about 250 °F and in 850 left and right sides scopes.With in the electrostatic precipitator, operating temperature can be up to about 1500 °F in some experiments.
Sometimes, for the ideal that obtains the oxysulfide minimizing increases progressively increase, needed is to adopt humidifying method, and wherein water spray adds in the effluent.This water spray that can carry out in Fig. 1,2 or 3 device can comprise above-mentioned slurries or only comprise water that this depends on required extra minimizing SO XAmount.In any therein situation, change into Ca (OH) with the acidity of gas and with unreacted lime stone or CaO in the water 2To increase capturing of sulphur.
Be used for increasing the mechanism of oxysulfide regardless of selection, can use method of the present invention to provide to reach about 70% or be higher than the clean minimizing (reaching 40% to 70% minimizing) of the effluent sulphur oxide content about 95%, and not influence the minimizing of nitrogen oxide than the leading section branch that only uses this method.
Except the minimizing that can reach oxysulfide, above-mentioned slurries are introduced and can be made also in the effluent that the minimizing of amount of nitrogen oxides reaches about 75% in the effluent, and more commonly about about 50% to 70%.Sometimes be enough although it is so, but also need further to reduce NO sometimes XIn these cases, can further reduce the rear end logos of nitrogen oxide.Because NO by this rear end logos minimizing XMeasure relatively low (that is, can additionally increase by 10% at most), in the rear end logos, utilize existing equipment, greatly reduce cost.
The more important thing is because this rear end logos relates generally to the installation of SCR, and with all obtain NO by SCR XThe required catalytic bed of reduction compare, the reduction relatively small amount nitrogen oxide mean the catalytic bed that needs are much smaller.If only needing increases about 10%, catalytic bed may diminish to (shown in Fig. 1～3) on the economizer or air preheater that is installed in boiler, and does not need common big SCR device.
For example, reduce 90% NO if desired X, the initial part of this method can reduce about 50% the nitrogen oxide to 70%, so just the burden of catalysed partial can be dropped to from 90% to be less than about 80%.This variation of 10% means that the space velocity ratio of catalyst volume (the effluent flow velocity with) has improved nearly 2 times, and in other words, the required catalyst volume of given outflow logistics reduces 50%.Because catalyst is a part the most expensive in this method, so this minimizing has increased the practicality and the economy of this method widely.
And, use less catalyst to reduce the treating capacity of used catalyst.As well known in the art, the processing of used catalyst is difficult, because it has caused the concern of environment aspect.Because typical SCR catalyst is a heavy metallic oxide, handles not only cost height but also regulation strictness.By making catalyst volume reduce 50% or more, these worries can significantly reduce.
As mentioned above, the SCR of this method part need contain ammonia in effluent.Yet, use the upstream SNCR part of slurries that many required ammonia can be provided, even be not whole.More particularly, the introducing of slurries guarantees the SCR aspect that in the effluent ammonia arranged and can support this method.
The existence of capacity ammonia, to small part, can guarantee that wherein effluent temperature is meant the temperature when nitrogenous treating agent contained in the slurries is introduced by the introducing ratio that changes effluent temperature, particular composition and inorganic agent, this variation of temperature for example can realize by regulating the introducing position.Should regulate these parameters so that ammonia amount required in the effluent to be provided.This can be used in this United States Patent (USP) U.S.4 as a reference, 780,289, U.S.4,830,839 and/or U.S.5,017,347 described method and technology realize, wherein used nitrogen oxide also commercial weight to the curve of the effluent temperature of processing scheme and plateau with at reductive NO XThe amount of time control secondary pollutant such as ammonia.
" nitrogen oxide also commercial weight convection current goes out the thing temperature curve " is meant and implements processing scheme when introduce inorganic agent in effluent in one section effluent temperature scope and introduce the curve that data point that the also commercial weight (generally recently representing with the baseline percentage) of measuring nitrogen oxide in temperature place produced plots at each." plateau " is meant NO in one section temperature range XAlso commercial weight be essentially maximum place nitrogen oxide also the commercial weight convection current go out zone in the curve of thing temperature, and preferably include at least two data points (certainly, those of ordinary skill in the art knows that plateau is not necessarily flat owing to the influence of " data discrete " and the generation of other real data).Processing scheme is the condition of pointing in the effluent when introducing (for example injecting) inorganic agent and inorganic agent introducing, composition (being the composition or the chemical formulation of inorganic agent) as inorganic agent, the inorganic agent diluent is (promptly when used inorganic agent is formed solution, the inorganic agent component concentrations), relative amount of inorganic agent component (promptly constituting the relative weight ratio or the mark of the chemical formulation component of inorganic agent) or the like.
The effluent that contains ammonia is by reducing the catalyst of effluent nitrous oxides concentration in the presence of ammonia.Such catalyst for example, comprises activated carbon, charcoal or coke, vanadium oxide, tungsten oxide, titanium oxide, iron oxide, cupric oxide, manganese oxide, chrome green, and noble metal such as platinum group metal be the mixture of platinum, palladium, rhodium and iridium or these materials for example.Other catalyst material of being familiar with those of ordinary skills commonly used in the art also can use.These catalyst materials generally are installed on the holder as pottery or zeolite, although other holder known in the art also can use.The effluent that contains ammonia most preferably effluent be about 230 °F and 950 left and right sides temperature ranges in the time pass through catalyst.
After catalytic bed, can obtain the further minimizing of nitrogen oxide and do not influence the minimizing of the oxysulfide of gained.
Above-mentioned explanation is how to implement the present invention and the variation of experienced personnel with regard to understanding after not planning to describe in detail the tangible modification of all that and reading the present invention in order to allow those of ordinary skills know.Yet these tangible modification of place and variation are will be included within the scope of the invention that is defined by following claims.Claims have comprised to realizing key element required for protection and the step in effective any arrangement of the present invention or the order, unless definite explanation does not comprise in the literary composition.

Claims (11)

1, be used to reduce the effluent sulphur oxide of carbon-containing fuel burning and the multistep method of amount of nitrogen oxides, comprise:
The preparation slurries contain alkalescence and reduce the compound of oxysulfide and the nitrogenous composition except that ammonia in these slurries, they are effective to nitrogen oxides reduction in the limiting temperature scope;
In the burning effluent, select temperature at least one treatment region in the limiting temperature scope;
These slurries are incorporated in this treatment region, to reduce nitrogen oxide and oxysulfide; And
Implement the back hold-carrying to reach nitrogen oxide or oxysulfide or further minimizing that the two is common.
2, the method for claim 1, wherein, nitrogenous composition comprises aqueous solution of urea heating and pressurization time enough, the hydrolysis of urea thing that generates down to this urea of small part hydrolysis, this hydrolysate comprises the complex that aminoquinoxaline and carbonic hydroammonium/ammonium carbonate form, and wherein the ratio of aminoquinoxaline and carbonic hydroammonium/ammonium carbonate is 10: 1 to 1: 200.
3, the process of claim 1 wherein that the reagent that reduces oxysulfide comprises at least a material of the oxide, hydroxide and the carbonate that are selected from alkali metal and alkaline-earth metal.
4, the method for claim 1, wherein said composition comprises a stabiliser system, this stabiliser system comprises having less than the common hydrophobic surfactant of 10 HLB value and have the stronger surfactant of hydrophily that is at least 10 HLB value, and wherein hydrophobic surfactant and hydrophilic surfactant active's HLB value differs and is at least 3.
5, the method for claim 4, wherein said hydrophobic surfactant and hydrophilic surfactant active's HLB value differs and is at least 5.
6, the process of claim 1 wherein that this back hold-carrying comprises a cascade, wherein contain this slurries as in the current of this cascade.
7, the process of claim 1 wherein that this back hold-carrying comprises a venturi wet scrubbing tower with spray column, wherein these slurries are introduced in the spray column of this venturi wet scrubbing tower.
8, the process of claim 1 wherein that this back hold-carrying comprises makes water, slurries or the two carry out the humidification of effluent together.
9, the process of claim 1 wherein that this back hold-carrying comprises the catalyst that is used for nitrogen oxides reduction in the presence of ammonia, effluent passes through from this catalyst.
10, the method for claim 9, wherein these slurries are introduced the catalytic reduction that ammonia that limiting temperature scope in this effluent should make the introducing of these slurries make to exist in this effluent promotes nitrogen oxide.
11, the process of claim 1 wherein that this back hold-carrying comprises an electrostatic precipitator, wherein these slurries are injected in this effluent in the upstream of this electrostatic precipitator.
CN94117013A 1994-06-30 1994-10-11 Multi-step process for reucing no and so Expired - Fee Related CN1091636C (en)

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CN100344378C (en) * 2005-11-30 2007-10-24 曹志德 Desulfur denitrogen catalyst of fuel coal, fuel oil boiler smoke and its desulfur denitrogen method
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US4167578A (en) * 1977-09-22 1979-09-11 Combustion Engineering, Inc. Method for removing sulfur and nitrogen compounds from a gas mixture

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Publication number Priority date Publication date Assignee Title
US4167578A (en) * 1977-09-22 1979-09-11 Combustion Engineering, Inc. Method for removing sulfur and nitrogen compounds from a gas mixture

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