Classifications

• • 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
  • B01D53/508—Sulfur oxides by treating the gases with solids
• • 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
  • B01D53/505—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound in a spray drying process
• • 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
  • B01D53/54—Nitrogen compounds
  • B01D53/56—Nitrogen oxides
• • 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
• • 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
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8603—Removing sulfur compounds
  • B01D53/8609—Sulfur oxides
• • 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
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8621—Removing nitrogen compounds
  • B01D53/8625—Nitrogen oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/206—Ammonium compounds
  • B01D2251/2062—Ammonia
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/206—Ammonium compounds
  • B01D2251/2067—Urea
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/40—Alkaline earth metal or magnesium compounds
  • B01D2251/402—Alkaline earth metal or magnesium compounds of magnesium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/60—Inorganic bases or salts
  • B01D2251/604—Hydroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • 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

Definitions

• the invention relates to a process that eliminates constraints on proven NO x and SO 3 reduction technology, by providing a specialized treatment with efficiently controlled reagent introduction for maintaining economy while addressing serious emissions control problems.
• Nitrogen oxides are invariably formed with combustion and are often treated by selective non catalytic reactions (SNCR) or selective catalytic reactions (SCR). Burning other fuels, like No. 6 oil, will create NO x and can cause other problems for boiler operators - including high temperature slagging/fouling and related eutectic corrosion, cold end corrosion/fouling and opacity issues related to carbon particulate and acid mist.
• sulfur in the oil e.g., 1-5%
• SO 3 sulfur trioxide
• SO 3 can condense as sulfuric acid on the back end surfaces (where the temperature has typically been reduced to less than about 150 0 C) and promote corrosion and acid plume.
• SO 3 can be result from oxidation by SCR catalysts.
• SO 3 vapor readily converts to gaseous sulfuric acid when combined with water vapor in the flue gas. As gas and surface temperatures cool through the system the SO 3 , vapors form a fine aerosol mist of sulfuric acid.
• the acid aerosol contains sub-micron particles of acid, which can evade separation or capture in gas cleaning devices and exit the stack. Even relatively low SO 3 concentrations exiting the stack cause significant light scattering and can easily create a visible plume and high opacity reading. As a general rule, every 1 part per million by volume of SO 3 will contribute from 1 to 3 % opacity. Thus, exhaust gas concentrations of only 10 to 20 ppm SO 3 can cause opacity and acid plume problems.
• deposition or formation of acid on any metal surfaces below the acid dew point causes corrosion within the unit, such as at the air heater, duct work and stack liners.
• SCR units are large and costly. To be effective, they must operate at relatively low temperatures and often fill all available space between the combustor and an air heater which uses residual heating capacity of the effluent to heat incoming combustion air. Because of the typical low temperature operation and the presence of significant SO 3 concentrations following an SCR unit, it is sometimes necessary to heat the effluent to avoid corrosion, plume, opacity and related problems. Heating in this manner is a further source of inefficiency, and it would be beneficial if there were a way to avoid it.
• SO 3 has been reduced by introducing an SO 3 treatment agent like magnesium hydroxide at appropriate positions in the duct work. Not all alkaline treatment agents will be useful because SO 3 also reacts with water vapor and ammonia used for the SCR reaction to fo ⁇ n ammonium sulfate and ammonium bisulfate. Both of these ammonia salts can cause fouling and corrosion problems in the system.
• Ammonium bisulfate has a melting point under 300°F and ammonium sulfate at just over 450°F, making both molten or tacky at typical SCR and air heater operating temperatures and making it possible for them to coat, foul and corrode the air heater.
• a yet further but more specific object is to effectively make use of reagents of nano- sized particles of SO 3 reagent and CFD to maximize SO 3 reduction while minimizing chemical consumption.
• the invention provides a process for reducing NO x and SO 3 emissions from combustion of a sulfur containing carbonaceous fuel in the combustion zone of a combustor, comprising: combusting a sulfur containing carbonaceous fuel with an overall excess of oxygen to form combustion gases comprising NO x and SO 2 ; introducing a nitrogen containing NO x control agent into the combustion gases at a point upstream of a selective catalytic reduction catalyst for reduction of NO x ; and following the catalyst and prior to contact with an air heater for heating incoming combustion air, introducing magnesium hydroxide in amounts and with droplet sizes and concentrations effective to form nano-sized particles in the effluent and reduce SO 3 caused by the oxidation of SO 2 in the catalyst.
• the invention provides a process for reducing SO 3 emissions from combustion of a sulfur containing carbonaceous fuel in the combustion zone of a combustor, comprising: combusting a sulfur containing carbonaceous fuel with an overall excess of oxygen to form combustion gases comprising SO 2 ; moving the resulting combustion gases though heat exchange equipment under conditions which cause the oxidation of SO 2 to SO 3 ; and prior to contact with an air heater for heating incoming combustion air, introducing magnesium hydroxide in amounts and with droplet sizes and concentrations effective to form nano-sized particles in the effluent and reduce SO 3 caused by the oxidation of SO 2 .
• computational fluid dynamics is employed to determine flow rates and select reagent introduction rates, reagent introduction location(s), reagent concentration, reagent droplet size and/or reagent momentum.
• Figure 1 is a schematic view of one embodiment of the invention.
• Figure 1 is a schematic view of one embodiment of the invention.
• Figure 1 shows a large combuster 10 of the type used for producing steam for electrical power generation, process steam, heating or incineration.
• Fuel (from a source not shown) is burned with air in a combustion zone 20.
• the fuel can be any combustible material, including gas, oil, coal, organic waste or any other combustible material suitable for the combuster.
• the process of the invention has particular advantage with fuels, such as petroleum based products containing sulfur, e.g., in amounts of 500 ppm or more, and 1% to 5% in particular.
• residual, typically heavy fuels e.g., residual fuels like No. 4, 5 and 6 oils.
• the air, supplied by duct 21 is preferably brought in via duct 22 and preheated by a gas-to-gas heat exchanger 23 which transfers heat from duct 24 at the exit end of the combuster.
• Hot combustion gases rise and flow past heat exchangers 25, which transfer heat from the combustion gases to water for the generation of steam.
• Other heat exchangers, including economizer 26 may also be provided according to the design of the particular boiler.
• the combustion gases will contain NO x , which is generated by the heat of combustion alone or due to the presence of nitrogen-containing compounds in the fuel. They will also contain SO x , principally as SO 2 .
• a suitable nitrogenous NO x reduction agent such as ammonia or aqueous urea is introduced from a suitable source 28 through line with valve 30.
• the urea can be introduced at a temperature suitable for SNCR with residual ammonia or other gaseous NO x reducing species passing through the duct to SCR catalyst units 32, 32' and 32".
• Techniques have been developed, inter alia, for SCR using ammonia with a variety of catalysts ⁇ e.g., Kato et al. in U.S. Patent 4,138,469 and Henke in U.S. Patent 4,393,031), hybrids of SCR and SNCR (e.g., Hofmann, et al, U.S.
• Patent 5,139,754 multi-level SNCR injection (e.g., Epperly, et al, U.S. Patent 4,777,024) utilizing urea, a hydrolysate of urea or ammonia, or a related chemical such as any of those described by any of these, which are all incorporated by reference in their entireties.
• PatentNo.4,393,031 disclose the catalytic reduction OfNO x using platinum group metals and/or other metals such as titanium, copper, molybdenum, vanadium, tungsten, or oxides thereof with the addition of ammonia to achieve the desired catalytic reduction.
• one catalyst section could be an oxidation catalyst.
• the NO x reducing catalysts are effective to reduces the NO x to nitrogen (N 2 ) and water (H 2 O) by a reagent comprising ammonia (NH 3 ), urea [(NH 2 )CO(NH 2 )], or the like.
• the effluent containing NO x and some SO 2 is passed over a NO x reducing catalyst which is effective to reduce the NO x in the presence of these reagents. It also strongly promotes the oxidation of SO 2 to SO 3 . It is an advantage of the invention that NO x can be controlled and the SO 3 burden created by an SCR unit or other SO 2 oxidizing source or equipment is also controlled.
• the NO x -reducing reagent is urea or ammonia, stored for use as an aqueous solution, such as in tank 28.
• the urea solution can be at the concentration desired for use or it can be concentrated for dilution at the time of use. It can also be stored dry and hydrated to the desired degree on an as-needed basis.
• the nitrogenous treatment agent is preferably present in a ratio of the nitrogen in the treatment agent to the nitrogen oxides level between about 0.5 and about 3.5.
• the nitrogenous treatment agent is included in an amount of about 3% to about 35% by weight of the total composition, including diluent (i.e., water).
• the solution can be fed to one or more injectors, such as nozzle 31.
• the nozzles can be of conventional design for spraying solutions and can be of the liquid-only or liquid and gas design. Where nozzles of the liquid and gas type are employed, internal mix nozzles are preferred to assure consistency of droplet size. Introduction of the urea under the preferred conditions results in production of ammonia and other species in addition to effecting NO x reduction in the area of introduction.
• the NO x reducing agent containing effluent is most preferably passed over the SCR catalyst while the effluent is at a temperature at least 100 0 C and below about 600 0 C, preferably at least 250 0 C.
• the effluent will preferably contain an excess of oxygen, e.g., from about 1 to about 10%.
• An additional layer or unit of catalyst is effective in reducing ammonia by reacting with NO x to provide NO x reduction and ammonia slip control. Where high solid loading is a concern, this typically requires additional catalyst due to increased pitch size.
• a relatively short duct section 24 which guides the effluent to an air heater 23 and then out duct 34 to stack 36.
• a nozzle 40 or series of such nozzles is provided for introducing magnesium hydroxide slurry from vessel 42.
• An important feature of the invention is the discovery that if the particle size of the magnesium hydroxide in the slurry is carefully controlled to have a mean diameter of under 8 microns, preferably under 5 microns, e.g., from about 3 to 4.5 'microns, the heat available in the effluent in duct 24, while low, will still be high enough to vaporize the water from the slurry and leave micro sized particles of active chemical to react with the SO 3 sufficiently to actually decrease the tendency of the SO 3 to form ammonium sulfate and bisulfate compositions, increase the pH of the effluent and decrease the tendency of the effluent to corrode the air heater or cause acid plume from the stack.
• the SO 3 and/or MgO reactants will be captured to some to an extent on the heat transfer surfaces of the air heater 23, which will then carry the captured reactant to increase the opportunity for gas to solid contact to occur.
• the capture of either of the two reactants on the heat transfer surfaces will increase the apparent rate of reaction by increasing gas/solid reactant contact.
• Any configuration of surface can be employed for the heat transfer surfaces of the air heater 23, but those characterized by heat transfer surfaces receptive to adherence of MgO, such as those available from Ljungstrom as recuperative air heaters, are believed especially effective.
• Any surface material can be employed for the heat transfer surfaces of the air heater 23, but those characterized by coated or uncoated steel, are believed especially effective.
• the temperature of the surfaces is believed to be optimally maintained within the range of from about 150 to about 350 °C.
• the magnesium hydroxide reagent is preferably prepared from brines containing calcium and other salts, usually from underground brine pools or seawater. Dolomitic lime is mixed with these brines to form calcium chloride solution and magnesium hydroxide which is precipitated and filtered out of the solution.
• This form of magnesium hydroxide can be mixed with water, with or without stabilizers, to concentrations suitable for storage and handling, e.g., from 25 to 65% solids by weight.
• it is diluted as determined by computational fluid dynamics (CFD) to within the range of from 0.1 to 10%, more narrowly from 1 to 5%.
• CFD computational fluid dynamics
• suitable chemicals can be substituted for the magnesium oxide/hydroxide described in detail above. Generically, they should be capable of spraying in fine droplet form, drying to an active powder within the available duct work and reacting with the SO 2 and/or SO 3 in the effluent.
• suitable alternative chemicals are oxides or hydroxides of calcium, potassium, sodium, and/or other alkali and alkali earth metals.
• the invention will preferably take advantage of CFD to project flow rates and select reagent introduction rates, reagent introduction location(s), reagent concentration, reagent droplet size and reagent momentum.
• CFD is a well understood science, but is not always utilized when it can be of benefit, such as in this case, where space limitations are so extreme. It is essential to obtain the correct concentrations, rates and introduction rates for the proper form of magnesium hydroxide to enable chemical reductant to be added with effect and without fouling in the short (e.g. , often under 25 feet, and 10 to 20 feet in cases) duct 24 following an SCR unit.
• the implementation of CFD to the invention can be accomplished as set out in U. S. Patent Application No. 10/754072.
• Particulate removal equipment (not shown) can be employed to remove particulates prior to passing the effluent up the stack.
• the invention provides a process for reducing SO 3 emissions from combustion of a sulfur containing carbonaceous fuel in the combustion zone of a combustor wherein downstream conditions or equipment other than an SCR catalyst can cause the oxidation of SO 2 to SO 3 .
• the sulfur containing carbonaceous fuel is combusted with an overall excess of oxygen to form combustion gases comprising SO 2 and is moved though heat exchange equipment under conditions which cause the oxidation of SO 2 to SO 3 ; and prior to contact with an air heater for heating incoming combustion air, introducing magnesium hydroxide in amounts and with droplet sizes and concentrations effective to form nano-sized particles in the effluent and reduce SO 3 caused by the oxidation OfSO 2 .
• the schematic of Fig. 1 is equally applicable, but the catalyst 32 is optional.
• combustion catalysts and or effluent treatment chemicals can be added to the fuel, combustion zone or otherwise as described, for example in U. S. Patent Application No. 10/754072, filed January 8, 2004.
• a suitable reagent such as magnesium hydroxide is introduced from vessel 50 through line 52 and nozzle 54.
• the entire disclosure of the above-noted U. S. Patent Application No. 10/754072 is incorporated herein by reference.

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• 2006
  • 2006-02-06 WO PCT/US2006/003976 patent/WO2006086251A2/en not_active Ceased
  • 2006-02-06 CA CA2596893A patent/CA2596893C/en not_active Expired - Fee Related
  • 2006-02-06 CN CN2006800106705A patent/CN101522287B/zh not_active Expired - Fee Related
  • 2006-02-06 ES ES06720288.7T patent/ES2527422T3/es active Active
  • 2006-02-06 KR KR1020077019723A patent/KR101169831B1/ko not_active Expired - Fee Related
  • 2006-02-06 EP EP06720288.7A patent/EP1848524B1/en not_active Not-in-force
  • 2006-02-06 BR BRPI0607004-3A patent/BRPI0607004A2/pt not_active Application Discontinuation
  • 2006-02-06 RU RU2007131784/15A patent/RU2007131784A/ru not_active Application Discontinuation
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  • 2006-02-06 AU AU2006212947A patent/AU2006212947B2/en not_active Ceased
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