CN1118712A - 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
CN1118712A
CN1118712A CN94117013A CN94117013A CN1118712A CN 1118712 A CN1118712 A CN 1118712A CN 94117013 A CN94117013 A CN 94117013A CN 94117013 A CN94117013 A CN 94117013A CN 1118712 A CN1118712 A CN 1118712A
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effluent
slurries
reduction
urea
nitrogen
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CN1091636C (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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  • Chemical & Material Sciences (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)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Treating Waste Gases (AREA)

Abstract

The invention relates to a multi-step method used for reducing sulfur oxides and nitrogen oxides in the effusions of the burning of fuels containing carbon. The method includes the following steps: a stabilized serum containing an alkalescent SOx deoxidizing compound and a nitrogen compound which can effectively reduces NOx (except ammonia, in particular to urea or urea hydrolyzed matter or a component of the urea hydrolyzed matter) is introduced; then a later reducing process for sulfur oxides, nitrogen oxides or the two is implemented.

Description

Reductive 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, reduce in the multistep reaction of efficient increase at this pollutant, 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 reduction 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 catalysts selective reducing process (SCR) and selective non-catalytic agent reducing process (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 height to 80% or higher.The SNCR method comprises makes NO xThe reduction inorganic agent enter effluent to reach 50% or higher reduction.
We know that alkaline reagent (as oxide, hydroxide and alkaline-earth metal and alkali-metal carbonate) can reduce the SO in the burning effluent xContent.Yet these materials also further produce particle except being difficult to processing, enter effluent, and they make troubles for any particulate abatement device or method in position.Because these materials are used 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 effective ways that remove degranulation from the burning effluent are to use the equipment as 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, effluent is not with particle basically, can be discharged in the atmosphere.
In some cases, the known technology of electrostatic precipitator is for SO xReduction is competitive.For example, we know SO 3Can strengthen the operation of electrostatic precipitator.And, owing to, need stable slurries and different temperatures window, SO for optimizing operation xReduction technique makes NO xReduce 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 to improve collects operation.
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 SCR nitrogen oxide reduction process or regulate electrostatic precipitator and will in storage, processing and transmittance process, 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 composition, other scheme of effectively removing oxysulfide relates in one or more processes makes water.For example, contain SO xEffluent 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 take away these particles.If contain aforesaid SO in the water xReducing composition, additional oxysulfide reduction 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, then by a spray column absorber.If effluent contacts with mud, just can reach SO in spray column xFurther reduction.Subsequently, effluent is by a demister.Later process relates to simply in the rear end, by in and acidity in the effluent and transform unreacted CaO and become Ca (OH) 2, " humidification " effluent is to increase catching of sulphur.
Yet, back-end process (i.e. the process that in boiler, occurs after the heat exchange first), as an electrostatic precipitator (ESP), a cascade, venturi wet scrubbing tower or humidification (as are used for NO implementing the reduction of full load pollutant xThe SCR of reduction) in, commercial too impracticable, perhaps extremely required degree (for example using cascade, venturi wet scrubbing tower or rear end humidification) is too ineffective reducing pollution content.
Therefore, required is a kind of reliable method that is used for removing from the burning effluent gas pollutant, not relevant with the use of back-end processing poor efficiency and high cost.
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 efficient of process rear end part reach maximum.
Another object of the present invention is by using existing equipment to influence back-end process, realizing to maximal efficiency effective SO xAnd NO xReduction.
A further object of the invention is to implement second level nitrogen oxide or oxysulfide reduction process, and this process is cooperated mutually with first order process, causes the purification reduction 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 alkaline SO xReducing compound and in specific range of temperatures effective reductive NO xNitrogenous composition (except the 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 processing region, this regional temperature is in said specific range of temperatures; Introduce slurries to the treatment region reductive NO xAnd SO x(example: first order process); Use then that product realizes rear end NO in the shunting of slurries or the effluent xOr SO xReduction process (example: second level process).
Following detailed description particularly can make the present invention better understand referring to accompanying drawing, and 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 air preheaters 35.In Fig. 1, electrostatic precipitator 40a is placed in the effluent pipeline 20, like this effluent 14 can proper temperature according to appointment 300 °F from then on pass through.Cascade spray column 40b is placed in the effluent pipeline 20 in Fig. 2, and from then on effluent 14 passes through like this.Venturi wet scrubbing tower 40c is placed in the effluent pipeline 20 in Fig. 3, and from then on effluent 14 passes through like this.Fig. 4 shows that boiler 100 has catalytic bed 40d near saving device 30 and air preheater 35.
Be used to introduce nitrogen-containing compound such as urea or hydrolysis of urea product and SO xReducing agent 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 NO xReduction effectively.Simultaneously, in Fig. 1, another equipment 70 that is used to introduce water or aforementioned stable slurries is placed in effluent pipeline 20, and injection device 80 extends a certain position in the effluent 14 like this, 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 venturi wet scrubbing tower 40c by injection device 80 with slurries.
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 back-end process was nitrogen oxide reduction SCR method, the present invention can reduce or save transportation, storage and the processing to a large amount of ammonias or ammoniacal liquor.Do not promote 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 single inorganic agent that the inventive method preferably exists with the aqueous slurry form, this inorganic agent comprises the NO that contains the nitrogenous composition of non-ammonia x(preferred stabilisation) alkaline SO of reducing agent and segmentation xThe suspension of reducing agent.Although NO xReducing agent can comprise residue or the accessory substance of ammonium hydroxide as hydrolysis or other degraded or chemistry reformation, " the nitrogenous composition of non-ammonia " speech is meant and comprises the composition that contains at least a composition, this composition contains nitrogen as a kind of element, but is not the component of gaseous ammonia.The alkaline SO of segmentation xReducing agent suspension preferably includes the material of selecting at least a carbonate from oxide, hydroxide and alkali metal or alkaline-earth metal (hydroxide of preferably magnesium or calcium or carbonate).Mixture is to be each NO specially xAnd SO xReducing agent is designed.
For stable slurry reaching simple and efficient operation, need to use suitable stabilizers.Preferred stabiliser system comprises that hydrophilic lipophilic balance (HLB value) is at least the stronger surfactant of hydrophily about 10 less than about 10 common 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, ethylene oxide and propylene oxide, 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.NO xReducing agent is a kind of to non-catalytic nitrogen oxides reduction effective substances.This process comprise one optionally, free radical is the step of intermediary, is exactly the selective non-catalytic agent reduction (SNCR) that often refers to.
With the pure various nitrogenous composition that exists with common commercial form, 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; The hydrolysate of one or more urea (as aminoquinoxaline, ammonium carbonate, carbonic hydroammonium); Other ammonium salt; With different urea complexs, comprise the hydrolysis of urea product (ratio of preferred 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 with other composition, compositions related, 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 adjust NO xThe validity of reducing agent is promptly 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 composition such as oxidation of hydrocarbons and other are listed in the material on this United States Patent (USP) 4,719,092,4,844,878 and 4,877,591 as a reference.
To be listed in this document as a reference down disclosed: the international patent application of von Harpe and Pachaly to carry out the nitrogen oxide reduction with the hydrolysate of urea and unique hydrolysis of urea thing (can be ammonium carbonate/carbonic hydroammonium aminoquinoxaline herein), be entitled as " hydrolysis of urea method in the pipeline " (" Process for the In-Line Hydrolysis ofUrea "), publication number is WO92/02291, and the applying date is 1991.8.1; And vonHarpe, 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 Reduc-tion Using a Urea Hydrolysate "), 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 important advantage 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 the NO of rear end SCR with nitrogen oxides reduction xReduction, about at least 25% urea is wanted hydrolysis, preferred about at least 60% hydrolysis of urea, more preferably about at least 80%.
Hydrolysis degree can be determined by measuring electrical conductivity increase, proportion and alkalescence.The electrical conductivity of 10% aqueous solution of urea is about 1.2millimhos, and the electrical conductivity of 10% aqueous solution of urea of complete hydrolysis is about 120millimhos.As a comparison, the electrical conductivity of 25% aqueous solution of urea is about 1.2millimhos and the electrical conductivity of 25% hydrolyzate solution is about 140millimhos.Hydrolysate has higher electrical conductivity and proportion.
Segment alkaline SO xThe stable suspension of reducing agent preferably includes following at least a kind of material: oxide, hydroxide and alkali metal or alkaline earth metal carbonate (hydroxide of preferably magnesium or calcium or carbonate).Many SO that are used for based on calcium and magnesium 2The adsorbent of reduction 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 general 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 the about at least 10% calcium hydroxides, 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 do not have diluent, calcium hydroxide to comprise up to about 97%, more preferably do not contain diluent composition about 65% to 97%.
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 " stoichiometric proportion that routinizes " or " NSR "." stoichiometric proportion that routinizes " is meant the concentration NH for example of reduction free radical xFree radical (NH xFree radical, wherein x is an integer, 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 of diluent free (as water), accounts for about about 1% to 15% of final slurries.When urea adds fashionablely with the form of the aqueous solution, the calculating that adds the amount of urea should not considered the water in the solution.
The weight ratio of the nitrogenous reagent in adsorbent and the slurries of the present invention is 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 of enough formation 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 final ratio of adsorbent and urea is 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 use.
Be introduced into to these slurries of small part then, for example inject, 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.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 carry out the pollutant reduction effectively, need slurries on required effluent cross section, evenly to distribute, so nozzle must be selected for this purpose, be effective.Experienced technical staff can understand, is effective for some conventional spout of this purpose.The suitable single-nozzle that is used for the liquid slurry injection comprises Turbotak board 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 Apparatusfor Minimizing Pollutant Concentrations in CombustionGases "), application number is PCT/EP 91/00952, applicant Chawla, vonBergman 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%, preferably be 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 when higher effluent temperature, to compensate this quenching.
Above-mentioned slurries inject into effluent, the reduction that can make effluent sulphur oxide composition 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 oxidation of reduced sulfur thing.Because by back-end processing reduction SO xAmount relatively low (can increase by 30% at most), existing equipment can be used for back-end processing and a whole set of SO xReduction apparatus is compared, and so just greatly reduces cost.
This rear end oxysulfide processing procedure is to make this slurries shunting, and the slurries of q.s are used for aforesaid NO xAnd SO xReduction, and a part of slurries are introduced in the interior water of cascade particulate abatement device, as shown in Figure 2.Like this, when effluent passes through cascade, oxysulfide and further reduction of slurry constituents reaction.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 reduction of oxysulfide and remove degranulation.
As shown in Figure 1, when in boiler electrostatic precipitator being arranged, slurries can increase the reduction of oxysulfide like this introducing 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 reduction increases progressively growth, needed is to adopt humidifying method, and wherein water spray adds to effluent.This water spray that can carry out in Fig. 1,2 or 3 device can comprise above-mentioned slurries or singly be water that this depends on required additional reduction 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, method of the present invention can provide the pure reduction that can reach about 70% or be higher than the effluent sulphur oxide content about 95% (more only using the leading section branch of this method to reach 40% to 70% reduction), and does not influence the reduction of nitrogen oxide.
Except reaching the reduction of oxysulfide, above-mentioned slurries are introduced effluent can make also that the reduction 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 reductive NO sometimes xIn these cases, can carry out the back-end processing of nitrogen oxides reduction.Because the NO that reduces by this back-end processing xMeasure relatively low (can increase by 10% at most), existing equipment can be utilized in back-end processing, can reduce cost greatly.
The more important thing is because this back-end processing relates generally to the installation of SCR, and with whole NO xReduction obtain required catalytic bed by SCR and compare, need the nitrogen oxide of the relatively small amount of reduction to mean the catalytic bed that needs are less.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% to 70% nitrogen oxide, so just the burden of catalyst member 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, in other words, to given effluent flow velocity, can cause required catalytic amount to reduce 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 is introduced in the slurries 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, and 780,289, U.S.4,830,839 and/or U.S.5,017,347 described methods and technology realize, wherein used nitrogen oxide also commercial weight to the effluent temperature curve of treatment state and plateau with at reductive NO xThe amount of time control secondary pollutant such as nitrogen.
" nitrogen oxide also commercial weight convection current goes out the thing temperature curve " is when introducing inorganic agent and reach treatment state and introduce the also curve that plots of the data point that produced of commercial weight (generally recently representing with the baseline percentage) of temperature survey nitrogen oxide at each to effluent in one section effluent temperature scope." plateau " be meant nitrogen oxide also the commercial weight convection current go out in the thing temperature curve NO in one section temperature range xAlso commercial weight keeps peaked zone substantially, preferably includes at least two data points (certainly, the those of ordinary skill in this field knows that plateau is not necessarily flat owing to the influence of " data discrete " and the generation of other real data).Treatment state is meant the condition when inorganic agent is introduced effluent (for example injecting) 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 inorganic agent is used to form solution, the inorganic agent component concentrations), relative amount of inorganic agent component (promptly constituting the relative weight ratio or the mark of the component of inorganic agent chemical formulation) 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, copper monoxide, 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 known holder also can use in the field.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 reduction of nitrogen oxide and do not influence the acquisition of oxysulfide reduction.
Above-mentioned explanation is how to implement the present invention in order to allow those of ordinary skills know, and the variation that experienced workman just can understand after not planning to describe the tangible modification of all that in detail and reading the present invention.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 claim key element 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 (10)

1, be used for the effluent sulphur oxide of reduction of carbonaceous fuel combustion and the multistep method of nitrogen oxide component, comprise:
The preparation slurries contain the compound of alkaline reduction oxysulfide and the nitrogenous composition except that ammonia in these slurries, they are effective to nitrogen oxides reduction in the limiting temperature scope;
In having the limiting temperature scope, select at least one treatment region in the burning effluent of a certain temperature;
Introduce these slurries to this treatment region, with nitrogen oxides reduction and oxysulfide; And
Implement back-end process and reach the common further reduction of nitrogen oxide or oxysulfide or the two.
2, the method for claim 1, wherein, nitrogen component 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 about about 10: 1 to 1: 200.
3, the process of claim 1 wherein that the reducing agent of oxysulfide comprises at least a material of the carbonate that is selected from oxide, hydroxide and 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 left and right sides HLB values and have the stronger surfactant of hydrophily that is at least 10 left and right sides HLB values, wherein hydrophobic surfactant and hydrophilic surfactant active's HLB value differs and is at least about 3, preferably is at least about 5.
5, the process of claim 1 wherein that this back-end process comprises a cascade, wherein contain this slurries as in the current of this cascade.
6, the process of claim 1 wherein that this back-end process comprises a venturi wet scrubbing tower with spray column, wherein these slurries are introduced in the spray column of this venturi wet scrubbing tower.
7, the process of claim 1 wherein that this back-end process comprises makes water, slurries or the two carry out the humidification of effluent together.
8, the process of claim 1 wherein that this back-end process comprises the catalyst that is used for nitrogen oxides reduction in the presence of ammonia, this effluent passes through from this catalyst.
9, the method for claim 8, this limiting temperature scope when wherein these slurries are introduced this effluent are meant that the introducing of these slurries in this scope can make the ammonia that exists in this effluent promote the catalytic reduction of nitrogen oxide.
10, the process of claim 1 wherein that this back-end process comprises an electrostatic precipitator, wherein these slurries are injected into 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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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
CN102213126A (en) * 2011-05-24 2011-10-12 辽宁润迪精细化工有限公司 Low-temperature urea reducing agent composition
CN102213124A (en) * 2011-05-24 2011-10-12 辽宁润迪精细化工有限公司 Ultralow-temperature urea reducing agent composition

Family Cites Families (1)

* Cited by examiner, † Cited by third party
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

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
CN102213126A (en) * 2011-05-24 2011-10-12 辽宁润迪精细化工有限公司 Low-temperature urea reducing agent composition
CN102213124A (en) * 2011-05-24 2011-10-12 辽宁润迪精细化工有限公司 Ultralow-temperature urea reducing agent composition
CN102213124B (en) * 2011-05-24 2013-02-06 辽宁润迪精细化工有限公司 Ultralow-temperature urea reducing agent composition
CN102213126B (en) * 2011-05-24 2013-02-06 辽宁润迪精细化工有限公司 Low-temperature urea reducing agent composition

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