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
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L10/00—Use of additives to fuels or fires for particular purposes
  • C10L10/02—Use of additives to fuels or fires for particular purposes for reducing smoke development
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L10/00—Use of additives to fuels or fires for particular purposes
  • C10L10/04—Use of additives to fuels or fires for particular purposes for minimising corrosion or incrustation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
  • F23G5/32—Incineration of waste; Incinerator constructions; Details, accessories or control therefor the waste being subjected to a whirling movement, e.g. cyclonic incinerators
• • 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

Definitions

• the present invention relates to an admixture and mixing process in an incineration unit intended to bring about the reduction of contaminating substances such as soot, hydrocarbons, oxides of nitrogen and, if the fuel contains other substances such as sulphur and chlorine, and metal compounds such as mercury and arsenic, also to bring about a reduction in emissions of acidifying oxides of sulphur and hydrogen chloride, as well as mercury and arsenic compounds, etc., in accordance with the introduction to Patent Claim 1.
• the prior art includes the so-called OFA method, the principle of which is based on the supply of a proportion of the necessary combustion air to the combustion process via separate air ducts at a later point in time situated after the combustion zone, resulting in the following positive effects:
• A) causes fuel-rich/sub-stoichiometric combustion to take place in the hearth and counteracts the oxidation of the nitrogen present in the air and in the fuel.
• the prior art also includes the recycling of the flue-gas into the primary combustion zone and the flame. This method has been found in certain cases to produce a good reduction in NO x , which can be explained by a reduced oxygen content and an associate- ⁇ reduction in the intensity of combustion.
• Another previously disclosed method involves the supply of additional fuel at the end of the flame, in conjunction with which previously formed NO * is reduced. In the case of this method, too, the problem is to obtain reliable, controlled admixture in the flame.
• thermal NO-, reduction (SNCR) for example the DeNO-, and N0 x 0UT processes. These involve the addition of chemicals such as ammonia (NH 3 ) and urea ((NH 2 ) 2 C0).
• the previously disclosed effects include the reduction of N0 X in the range of temperatures between approximately 900 and 1000°C. It is claimed that this temperature range is capable of being extended by the use of special auxiliary chemicals.
• the dosing of the chemical in this case takes place after the actual combustion zone.
• the result of this dosing is greatly dependent on the reliable and controlled admixture of the chemicals.
• the stratified flow in the flame chamber has a marked effect on the result, i.e. on the efficiency, on the consumption of chemicals, on the generation of undesired substances as by-products and on the achievable degree of reduction.
• the principal object of the present invention is to create the necessary conditions for the reduction of environmentally harmful substances, including in existing incineration units, without the need for major and costly conversions.
• the aforementioned object is thus achieved by a method of the kind according to the present invention, which is characterized essentially in that air, flue-gases or residual fuel, etc., and/or reducing agents is/are introduced into the incineration unit in conjunction with the combustion process through asymmetrically positioned ducts, so that rotation of the agents and/or gases which are introduced is achieved in the combustion zone.
• a further object of the invention is to find an arrangement capable of application in conjunction with the execution of the method in accordance with the invention.
• the invention is based on the principle of introducing a proportion of the combustion air during the actual incineration process through ducts which are preferably positioned asymmetrically. This takes place at one or more "levels" of the hearth.
• the asymmetrical positioning of the ducts in conjunction with their appropriate design and the use of an appropriate air velocity, induces rotation of the flue-gases over the entire cross-section of the hearth and provides the opportunity to increase the degree of rotation and turbulence directly upstream of the point of entry of the combustion gases into the convection section of the boiler, thereby providing, amongst other things, better burn-up.
• the system offers the opportunity for the admixture of recirculated flue-gases (0- 100%). This results in better admixture, better mixing and better rotation.
• Combustion causes the emission of undesirable compounds. This is true of all combustion of wood, peat and fossil fuels, such as oil, gas and coal, cellulose waste and household refuse, etc.
• the invention relates to a method for achieving admixture and mixing by rotation, e.g. for ROFA.
• the invention also proposes that the method should give effective admixture, for example of over fire air added by ROFA.
• the invention also relates to the creation of admixture and/or mixing using this method by the combustion of, for example, the reburning fuel and recirculated flue-gases.
• IV. The invention also relates to the application of the method for the introduction of reducing agents, e.g. lime, ammonia substances and active carbon, etc., in the gas flow.
• the invention relates to the application of. the method in accordance with I-IV at all stages of an incineration and cleaning process, not only in the supply air, drying and pyrolysis stages, but also in the primary and secondary combustion and reburning stages, and also subsequently in the flue-gas system.
• VI. The invention relates to the application of the method in order to permit and/or facilitate (preparation, homogenization) the ability of other methods, e.g. ROFA, to realize their inherent NO., reduction potential (the DeNO.. or N0 X OUT processes) .
• the invention relates to the application of the method in other contexts, including outside the area of combustion, where there is a requirement for reliable admixture and mixing of substances, primarily in gas flows.
• Figs. 1-5 show examples of various types of incineration installations
• Figs. 6-8 show sections through incineration installations with an arrangement of gas delivery openings.
• one or more separate techniques are used simultaneously in respect of NO-, reduction, for example.
• a very good combined result is achieved in this way.
• rotating over fire air in itself leads to more effective combustion, resulting in better efficiency.
• Chemicals such as ammonia substances, introduced via the rotating over fire air, flue-gas or similar, produce more effective admixture, lower chemical consumption and a broader area of application, thanks to the temperature-reducing effect of the method through the increased absorption of heat in the hearth.
• the method in accordance with the present invention for bringing about the reduction of, for example, the oxides of nitrogen in an incineration unit 1, l 1 , l 2 , l 3 , 1* ... l n of the desired type, to which air 2 or some other gas is supplied, takes place, in the first place, by the introduction of agents 3 which exhibit a nitrogen-reducing, f nction into the combustion zone 4, 4 1 , 4 2 , 4 3 , 4* ... 4 n of the incineration unit in question, or at a later stage in conjunction with said gas supply during the actual combustion process. It is also possible to introduce agents 3 which bring about the reduction of sulphur or the reduction of some other substance into said zone 4-4 n - or at a later stage.
• the reducing agent 3 should preferably be introduced together with air 2, flue-gas 5, residual fuel 6 or the like, so that the desired penetration and impulse for rotation and mixing are achieved.
• the introduction performed in this way is of a nature such that rotation of the introduced reducing agent 3 and the gas 2 , 5, 6 is achieved in the combustion zone 4- 4 n , preferably by the introduction of reducing agent 3 and gas 2, 5, 6 asymmetrically on opposite sides 7-8; 9-10 of the combustion zone 4-4*, causing deflection of and turbulence in the mixture of gaseous substances 2, 5, 6, resulting in effective admixture through rotation.
• the introduction of gas in the form of at least air 2 preferably takes place from one or more points 11 at identical, smaller or, preferably, successively increasing relative spacings, which act at a successively greater distance A, B, C, etc. , along the combustion zone 4-4 n , preferably via ducts 11, for .
• Said ducts 11 can be positioned on essentially opposite sides 7-8; 9-10 of the incineration plant 1-1" in question, for example on two, three or four walls or similar, having a circular cross-section, as shown in Fig. 8, or having a cross-section of some other form.
• a reducing agent 3 is added preferably in the form of a suitable chemical which brings about the desired reduction of the oxides of nitrogen, or a reduction in sulphur, or pwerforms some other function, for example one of the following: ammonia (NH 3 ), urea ((NH 2 ) 2 C0), lime products, sodium carbonates and active carbon, and in one or more of the following forms: liquid, spray or powder.
• a suitable chemical which brings about the desired reduction of the oxides of nitrogen, or a reduction in sulphur, or pwerforms some other function, for example one of the following: ammonia (NH 3 ), urea ((NH 2 ) 2 C0), lime products, sodium carbonates and active carbon, and in one or more of the following forms: liquid, spray or powder.
• the quantity or level of the reducing chemical 3 required in order to be able to meet and achieve the desired degree of reduction is appropriately metered into preferably rotating over fire air and/or gas via the supply of supply air and/or gas and/or the supply of residual fuel 3; 5; 6.
• the arrangement is preferably executed in such a way that air ducts 11 are so arranged as to act at mutually separate levels 12, 13, 14, 15, 16, 17 on the mutually opposing walls 7-8; 9-10 of an incineration unit 1-1" and/or are displaced laterally in pairs in relation to one another.
• Illustrated as examples of an appropriate incineration unit to which the invention is applicable are a soda recovery boiler in Fig. 1; an oil-gas-powder boiler with a top-mounted vertically acting burner in Fig. 2; a solid fuel boiler for wood fuels or household refuse in Fig. 3; an oil-gas-powder boiler with one or more side-mounted burners in Fig. 4; and a CFB boiler, i.e. a boiler with a circulating fluidized bed, in Fig. 5, although other types of boiler and designs are suitable to utilize the present invention.
• an appropriate level of ammonia (concentrated or diluted) or an ammonia-based preparation such as urea or lime products, or sodium carbonates for sulphur reduction, or other suitable chemicals, can be introduced into the rotating over fire air in powder, spray or liquid form.
• the necessary quantity of an ammonia substance, etc. is metered by a control system via the intended number of ducts.
• the process is suitable for installations of all types, both small and large, for example of the following types: grate-fired/solid fuel; liquid gas-fuelled via burners; fluidized bed; circulating fluidized bed; soda recovery; engines; gas turbines, and afterburning in cyclones, etc.
• the process is applicable to different types of fuels, such as heating oil; fuel oil; natural gas; household refuse; bio-fuels; powder fuels, and cellulose waste, etc.
• the process is also applicable to the controlled supply and admixture of reburning fuel.
• the design of the ducts 11 can be executed in various ways, for example as ordinary openings, nozzles, sprinklers, and vaporizers, etc., and preferably circular or rectangular in form.
• the supply of chemicals, etc. can also take place in various ways, for example by being mixed into the air 2, flue-gas 5 or equivalent (e.g. steam) before it is introduced into the incineration plant 1-1", or by being introduced separately from the supply of air or gas to the plant 1-1" and not mixed with the air until it is inside the actual combustion area 4-4", or as a combination of these.
• Combustion air 2 or recirculated flue-gas 5 (carrier gas), a reducing agent 3 and, where appropriate, residual fuel 6 are introduced for combustion via asymmetrically positioned air ducts 11 in the walls 7-10 of the boiler.
• the air ducts 11 are dimensioned with reference to, amongst other things, the cross-sectional area of the hearth, so that sufficient penetration and impulse for the desired admixture, mixing and rotation are achieved.
• the underlying principle of the flow is that air 2 or flue-gas 5 or residual fuel 6 are introduced into the hearth in the form of jets via ducts 11.
• the jets are deflected on the opposite side (in the case of rectangular section - 90 degrees). This deflection is followed by strong turbulence resulting in thorough admixture.
• rotation 18 corkscrew movement of the entire cross-section is obtained, resulting in higher unit volume velocity.
• the creation of turbulence is a physical consequence of the change in direction.
• N0 X reduction is thus now achieved with the help of ammonia or some other suitable substance due, amongst other things, to the lower flame temperature and the larger area at an appropriate temperature, i.e. through the displacement of the thermal balance towards the hearth.

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

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• 1992
  • 1992-05-18 SE SE9201554A patent/SE501418C2/sv not_active IP Right Cessation
• 1993
  • 1993-05-18 WO PCT/SE1993/000436 patent/WO1993023147A1/en not_active Ceased
  • 1993-05-18 AU AU40994/93A patent/AU4099493A/en not_active Abandoned
  • 1993-05-18 EP EP93910538A patent/EP0642380A1/de not_active Ceased

Non-Patent Citations (1)

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