Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J3/00—Removing solid residues from passages or chambers beyond the fire, e.g. from flues by soot blowers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
  • F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel 
  • F23L9/02—Passages or apertures for delivering secondary air for completing combustion of fuel  by discharging the air above the fire
• • 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 concerns a method of the kind stated in the preamble of Claim 1.
• the invention also concerns a feeding apparatus for implement ⁇ ing the method.
• Nitrogen oxides are at present the most exposed flue gas components, especially when considering tariff which has been introduced in Sweden for plants larger than 10 MW and with an annual energy production greater than 50 GWh.
• the fuel composition often varies from one operation condition to another, particularly with regard to different types of waste fuels and also wood fuels.
• Examples of ash and/or slag enriched fuels comprise wood fuels, straw, waste such as industrial, municipal, hazardous and chemical waste and also hard coal, lignite, peat, lime sludge and black liquor. Also crematories and cement kilns are included in this category of combustion/gasification systems.
• Al is a term which designates an inorganic and unburnable substance which is originally within the fuel.
• Slag is a term which designates “additives” of inorganic and unburnable substances, such as metals, ceramics, glass, stone etcetera. "Ash” is often considered contained within the term “slag”. Examples of not ash and/or slag enriched fuels are oil, natural gas, LPG and certain biofuels.
• Fuel price is another important parameter for optimization of flue gas or gas parameters. Sulphur content and to a certain degree also nitrogen content in the fuel are directly pro ⁇ portional to the emission level ahead of a flue gas cleaning system. This of cource has the consequence that the fuel price becomes higher when i.e. the nitrogen content in the fuel is lower. Of course also the economical result is influenced by the market price and this will sometimes change quickly.
• the perforated tubes in the combustion or gasification chamber are fed by a fluid comprising a gas or a liquid or possible solid particles.
• gas are air, oxygen, oxygen-enriched air, flue qas, inert gas (C0 2 , N 2 etc) , fuel for reburning (LPG, natural gas, ethanol, etc) N0 X reducing substances (NH 3 , urea etc) and steam with an optimal flow, pressure and temperature.
• liquids are water, NH 3 , urea, ethanol and other organic solution agents, etc.
• solid particles are powder from biofuel including peat, coal and waste (plastic etc) . These can be used as a reburning fuel.
• oxidizing agents e.g. air
• reducing agents e.g. NH 3 or for example LPG
• the tube or the tubes is/are suitably positioned in the combustion/gasification plant to present optimal conditions.
• the tube or tubes can be placed over the grate in connection with the first draught of the boiler.
• under combustion the reverse will apply.
• the tube or tubes can be positioned in the combustion chamber, for instance above the bed in a bubbling bed.
• kilns and furnaces such as these are those that the flue gas emissions of CO, C x H y (hydrocarbons) , NO x , S0 2 , N 2 0, dioxine, PAH among others often are high due to poor combust ⁇ ion optimized plants.
• flue gas cleaning systems e.g. electro- static precipitators or textile filters, SCR, scrubbers etcetera which are positioned after the combustion/gasifica ⁇ tion apparatus, which reduces the emission level in the sub ⁇ sequent stack/gas channel.
• EP-0 286 077 A2 (Mullverbrennungsstrom Wuppertal) describes a method of burning waste in which the flue gas is drawn out of the furnace and made to make a swirling movement by the addition of secondary air.
• the secondary air is fed through nozzles in such a way that the flow of flue gases is slowed down in a uniform temperature zone in the furnace and then allowed to remain there for approximately 8 seconds.
• SE,C,139 072 (Larsson) describes a furnace, especially in a heating boiler or for connection to similar boilers' fire rooms in which intakes for the primary air are located on the side of the furnace, said intakes leading to one or several fixed tubes along the furnace, which in their turn contain a rotatable tube which regulates the outlet area for air by twisting the tube about its axis and/or axial displacement of the tube.
• SE,C,115 046 (Sinding) describes an apparatus for preheating and adjusting the supply of secondary air to furnaces, which apparatus is furnished with concentric tubes positioned close together and extending into a preheating chamber to supply air to the chamber and are mutually rotatable so that its openings can be set at an angle to one another for the adjustment of the area of passage and thereby the air supply.
• Feeding apparatuses in the shape of a perforated tube which injects into a combustion chamber are known, for example through WO-A1-91/00134 (Fuel Tech Europe) , US-A-4 883 003 (Hoskinson) and SE,C,139 563 (Svenska Maskinverken) .
• FI-B-87014 (Tampella) describes an apparatus for feeding granular lime with the aid of a gas stream to a fire-place.
• a nozzle mounted at the end of a tubular arm to which a means for displacing the nozzle is coupled.
• the lime is fed to a place in the fire-place having a suitable position in the flue gas stream with regard to temperature.
• the preamble of the attached Claim 1 concerns a method of this kind which is deemed to constitute the closest prior art.
• any of the known systems permit an influence or effect on the mixing condition or mixing ratio between the combustion gases and/or between these and the fluid or fluids supplied or fed to the combustion chamber.
• one object of the invention is to mini ⁇ mize inherent disturbances in known methods of combustion and gasification including associated plants, thereby increasing the efficiency and reducing the emission levels in the com ⁇ bustion and gasification processes, respectively.
• Another object is to increase the flexibility of the method and the plant in order to, if so required, make possible a quick and simple adjustment from one desired emission level (e.g. high CO- low NO-concentration) to another (e.g. low CO- high NO-concentration) depending on the economical output.
• one desired emission level e.g. high CO- low NO-concentration
• another desired emission level e.g. low CO- high NO-concentration
• Yet another object is to achieve a method of minimizing dis ⁇ turbances and a feeding apparatus, respectively, which simpli ⁇ fies and cheapens cleaning of the tubes, thereby achieving an increased yield of the combustion and gasification processes, respectively.
• Another object is to accomplish a method and a plant, respect ⁇ ively, which renders it possible to continuously or at least almost continuously operate the combustion process, i.e. with ⁇ out having it to be stopped for soot removal or cleaning of the tubes for example feeding secondary air, and being con ⁇ tained in the combustion or gasification chamber, respective ⁇ ly.
• the same or different fluids can be supplied via the tubes which mutually coact in the way stated.
• a reburning fuel can be supplied which improves the prerequisites for controlling the tempera ⁇ ture profile in the combustion chamber.
• the pipes to change the speed, flowing picture and direction of the fluid are rotated about their longitudinal axis.
• the pipes are displaced and/or rotated at impulse from transmitters positioned outside of the chamber and which sense the state of combustion.
• transmitters for temperature, pressure, flow, present flue gas components etcetera
• optical trans- mitters may be used for the purpose.
• Signals generated by the transmitters can in addition be used to regulate the supply of fluid and solid particles, respec ⁇ tively, to the tubes, said supply possibly being performed by jerks or intermittently.
• the rotation of the perforated tubes can ascertain that the supply, if so desired, takes place at predetermined, varying angles within the combustion chamber.
• the pipes are displaced by holding and drive means positioned outside of the chamber and preferably engaging their ends so that the pipes are complete ⁇ ly withdrawable from the chamber.
• the tubes are withdrawn to an inactive position outside of the chamber at impulse from one or several different transmitters activating the withdrawal mechanism at for instance power failure or failure of cooling fluid supply to the plant.
• the pipes are preferably mounted replaceable at the holder and drive means positioned outside of the chamber. Then a very simple adaption to different operation conditions for the plant will be possible which, thus, can be accomplished by a simple replacement of one or more of the supply tubes. It is realized that the arrrange ent also facilitates preparation and service of the plant which is also made more cheap.
• inventive method can be put into practice on existing as well as new combustion/gasification plants.
• New boilers and furnaces, respectively can be manufactured with a smaller furnace volume due to a more effective mixing of the gases, which reduces costs.
• the best operation possible with optimal emission level at every separate occasion can more simply be obtained than with systems known heretofore.
• a cooling fluid can be added to reduce the tempera ⁇ ture of the jacket of the tube to make slag and other dust deposition of such a kind that the cleaning operation is facilitated or the number of such operations minimized.
• Such a cooling fluid can possibly be supplied separately, possibly intermittently and preferably in connection with withdrawal of the pipes. It is preferably supplied via a ring column around each tube. Due to the cooling, slag and other dust deposition on the tubes become less glass-like or sticky whereby the cleaning operation will be simplified and speeded up.
• the invention also refers to a feeding apparatus for control ⁇ ling the mixing condition or ratio in a combustion or gasifi- cation plant by means of the supplied fluid for optimizing flue gas or gas parameters, the essential features of said feeding apparatus being stated in Claim 8.
• Fig. 1 is a partly cut-away perspective view of a combustion plant for solid fuels having a feeding apparatus in accordance with the invention.
• Fig. 2 is a side view showing a feeding means according to the invention comprising a perforated tube and means for dis- placing, rotation, controlling and cleaning the tube posi ⁇ tioned outside of the combustion chamber.
• the figure shows the feeding means in inserted position in the combustion chamber.
• Fig. 3 is a side view corresponding to Fig. 2 with the feeding means completely withdrawn from the combustion chamber.
• Fig. 4 is a sectional view along the line IV-IV in Fig. 3.
• Fig. 5 is a sectional horizontal view through the combustion chamber and shows three coacting feeding means at one level thereof for increasing the action of intermixing the fluid in the combustion gases.
• Fig. 6 is a schematic vertical sectional view through an alternative embodiment in which a number of different feeding devices for fluid are received in a "revolver-holder" posi ⁇ tioned outside of the combustion chamber for optional, alternative insertion into the combustion chamber.
• the digit 1 denotes a combustion plant comprising a furnace 2 for combustion of solid fuels with a grate 3 and an upper combustion chamber 4.
• the fuel can be fed intermittently or continuously and com ⁇ bustion air in the form of primary air is blown from below and up through the grate 3.
• Secondary air is fed through a number of feeding apparatuses according to the present invention entering the combustion chamber 4 through special ports in the furnace wall 5 and further described below.
• the secondary air is supplied via said feeding apparatuses in order to complete the combustion of formed reaction products in the shape of gas and solid particles.
• Particles in the flue gas above the grate 3 consist of ash, slag and/or unburnt fuel. These can together form bigger particles, so called agglomerates, or be reduced to smaller, more or less clean ash particles. Slag enriched fuels often offer higher concentrations of dust and slag in the flue gas.
• Some of the particles form deposits on the inside of the combustion chamber which is often equipped with tubes 6 with an external insulation. Dust particles also deposit on the tubes 13 where the holes 13a for feeding secondary air are entirely or partially blocked thereby affecting the feed of secondary air, alternatively coating will occur directly on the mantle of the tube.
• the feeding tubes 13 for a fluid are arranged forming a curtain system comprising a number of tubes 13, some of which are parallell, at one or more levels in the combustion chamber 4.
• the tubes 13 are equipped with perforations 13a alongside the mantle surface of the entire tubes.
• the holes can be equally dis- tributed and a row of holes can be positioned on each side of the tubes.
• the through-flow area of the holes 13a determines the flow of the fluid at a given pressure.
• a fluid e.g. secondary air at high pressure
• a fan 10 connected to a collecting box 11, to which flexible tubes 12 are connected, which with quick-couplings are connec ⁇ ted to the end flanges 13b of the tubes 13.
• the opposite ends of the tubes can be plugged or provided with outlet openings (not shown) .
• the tubes 13 are inserted and withdrawn from the chamber 4 in an axial direct ⁇ ion at longer or shorter periods of time. In such a way the emission level of the combustion process can be maintained optimal.
• Figs 2 and 3 illustrate the mechanisms that have been used for displacing the tubes 13 into and out from, respectively, the combustion chamber 4 and for their rotation, guiding and cleaning.
• the tubes 13 are received in a casing 14 supporting some of the stated mechanisms.
• an electric motor 16 is used the output axes of which drives a disc 17.
• An end ⁇ less belt or chain 20 is led around the disc and also around rollers 18, 19.
• To the belt 20 is secured a holder in the shape of a trolley 25 engaging the end of the tube 13 so as to form a bed 25b to make the tube at the same time rotatable around its longitudinal axis.
• the holder 25 is displaceably guided via a guide 26.
• Fig. 2 shows the tube 13 in inserted position in the com ⁇ bustion chamber whereas fig. 3 shows the tube completely with- drawn from the chamber.
• the holder 25 is then so adapted that simple replacement of tubes 13 can take part in the withdrawn position.
• An electric motor 27 drives a belt 28 which extends over a number of rollers 29 engaging the periphery of the tubes 13 to turn it around.
• the holder 25 is provided with forked legs 25a supporting the bed 25b in which the tube 13 rests.
• the holder or the trolley 25 is displaceably guided on the guide 26.
• the casing 14 In its forward end the casing 14 is connected to a housing 30 which receives the opposite guide rollers 15 for the tube and also an arrangement of steel brushes 21 between which the tubes pass when being withdrawn and thereafter inserted. These brushes 21 perform an efficient cleaning of the tubes, so that they are released from dust and slag depositions.
• an automatic shaking device spinning tool or similar, not shown
• acoustic sootblower infrasonics or ultrasonics
• Fig. 5 shows how the flow picture of a fluid supplied via adjacent tubes 13 can be changed, in part through displacement of one or more tubes to different positions in the combustion chamber 4 and in part through turning or rotation of one or more of the tubes. Further actuation of such a kind can also be obtained by changing the pressure, speed and/or flow of the supplied fluid. As appears from fig. 5 different intermixing conditions can be obtained as a result of that the flow of fluid from adjacent pipes can amplify or intensify each other, more or less extinct each other or present an action there ⁇ between.
• a reburning-fuel such as ethanol, can be supplied via one, two or all tubes 13, whereby the temperature profile, i.e. the temperature in different zones of the chamber 4, can be controlled to give an optimal combustion process.
• Fig. 6 shows a "revolver arrangement" in which casing 14 is replaced by a casing 14' which is rotatable on a shaft 40 and which receives a number of fluid supply tubes having different spacing and positions for perforations 13a thereon.
• casing 14' is rotated so that the fluid supply tube 13 which is most suitable in the actual situation is inserted into the combustion chamber 4.
• Attached to the ends of the tubes 13 are bellows-shaped hoses 12' for the fluid supply to each tube.
• the tubes 13 may have a length between 1 a 2 and 5 m and a diameter of 120-200 mm.
• the diameter of the perforations 13a may vary from 1 a 2 mm up to 2 a 4 cm and the distance between the perforations can amount to between 10 and 40 cm.
• the regulation of fluid to each tube 13 can further be made via output signals from transmitters for different gas para- meters, gas concentrations, temperatures, pressure, flow etc (not shown) .
• Said transmitters may also be used, e.g. via a computer, to decide when the cleaning or soot removal opera ⁇ tions are to be initiated. As mentioned above there is then no need to stop the combustion process.
• digit 42 denotes a sensor of this kind.
• 43, 44 denote presence of an optical sensor where 44 is a lens.
• At for instance power failure or failure on cooling fluid supply to the plant one or more transmitters are sensing this and give an impulse for withdrawal of the tubes to an inactive position outside of the chamber. This is a very important safety measure within the scope of the inventive concept.
• a plant with a feeding apparatus according to the invention is simple to install and therefore particularly suitable when converting furnaces, combustion and gasification plants which are operating or already existing on the market.
• the tubes need not be oriented horizontally in the combustion chamber.
• One or more of the tubes may, thus, be inclined or extend vertically.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Incineration Of Waste (AREA)
• Gasification And Melting Of Waste (AREA)
• Fluidized-Bed Combustion And Resonant Combustion (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=20391998

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• 1993
  • 1993-12-03 SE SE9304038A patent/SE502283C2/sv unknown
• 1994
  • 1994-12-02 AU AU12080/95A patent/AU1208095A/en not_active Abandoned
  • 1994-12-02 WO PCT/SE1994/001163 patent/WO1995015463A1/en not_active Ceased
  • 1994-12-02 CA CA002177963A patent/CA2177963A1/en not_active Abandoned
  • 1994-12-02 EP EP95903094A patent/EP0730718B1/de not_active Expired - Lifetime
  • 1994-12-02 DK DK95903094T patent/DK0730718T3/da active
• 1996
  • 1996-05-29 FI FI962243A patent/FI120217B/fi not_active IP Right Cessation

Non-Patent Citations (1)

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