EP2279378A2 - Systemes et procedes de conversion de combustible en poudre - Google Patents

Systemes et procedes de conversion de combustible en poudre

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Publication number
EP2279378A2
EP2279378A2 EP09729630A EP09729630A EP2279378A2 EP 2279378 A2 EP2279378 A2 EP 2279378A2 EP 09729630 A EP09729630 A EP 09729630A EP 09729630 A EP09729630 A EP 09729630A EP 2279378 A2 EP2279378 A2 EP 2279378A2
Authority
EP
European Patent Office
Prior art keywords
burner
combustion
explosible
fuel
enclosure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP09729630A
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German (de)
English (en)
Inventor
James K. Mcknight
Edward Bacorn
Ken W. WHITE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP2279378A2 publication Critical patent/EP2279378A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
    • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
    • F23C6/045—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23M—CASINGS, LININGS, WALLS OR DOORS SPECIALLY ADAPTED FOR COMBUSTION CHAMBERS, e.g. FIREBRIDGES; DEVICES FOR DEFLECTING AIR, FLAMES OR COMBUSTION PRODUCTS IN COMBUSTION CHAMBERS; SAFETY ARRANGEMENTS SPECIALLY ADAPTED FOR COMBUSTION APPARATUS; DETAILS OF COMBUSTION CHAMBERS, NOT OTHERWISE PROVIDED FOR
    • F23M9/00—Baffles or deflectors for air or combustion products; Flame shields
    • F23M9/02—Baffles or deflectors for air or combustion products; Flame shields in air inlets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
    • F23C9/003—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for pulverulent fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D1/00—Burners for combustion of pulverulent fuel
    • F23D1/02—Vortex burners, e.g. for cyclone-type combustion apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K2203/00—Feeding arrangements
    • F23K2203/20—Feeding/conveying devices
    • F23K2203/201—Feeding/conveying devices using pneumatic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2221/00—Pretreatment or prehandling
    • F23N2221/10—Analysing fuel properties, e.g. density, calorific
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2225/00—Measuring
    • F23N2225/04—Measuring pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2225/00—Measuring
    • F23N2225/26—Measuring humidity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2239/00—Fuels
    • F23N2239/02—Solid fuels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
    • F23N5/006—Systems for controlling combustion using detectors sensitive to combustion gas properties the detector being sensitive to oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/18—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel

Definitions

  • PCT Patent Application No. PCT/US2007/024044 entitled "POWDERED FUELS, DISPERSIONS THEREOF, AND COMBUSTION DEVICES RELATED THERETO", filed November 16, 2007, which claims priority to U.S. Provisional Application No. 60/859,779, filed November 17, 2006, U.S. Provisional Application No. 60/868,408, filed December 4, 2006, and U.S. Provisional Application No. 60/993,221, filed September 10, 2007.
  • the above-mentioned applications are herein incorporated by reference.
  • the invention pertains to the field of solid fuel combustion. More particularly, the invention pertains to sustained burning of explosible biomass powder with on/off control.
  • the present invention concerns processes, methods, devices, and systems that, taken separately and together, allow for the processing of biomass and other solid fuel materials into an explosible powder and the combustion of the materials for a direct conversion into energy to heat or perform work.
  • This disclosure describes the harnessing of long-feared dust explosions and operating new solid fuel burners to accomplish a unique energy conversion process.
  • the present invention is largely based upon the application and new integration of some advanced yet elegantly simple principles, portions of which exist unconnected in various bodies of knowledge in the fields of fluid mechanics, physics, kinetics, industrial power plant process design, and combustion theory. This technology will soon gain integrated global scientific community attention and be applied in the engineering of fuel source production, distribution, combustion burner design, heating, and other energy conversion applications.
  • a burner of the present invention preferably has numerous features: instant cold start ON- OFF control; stable combustion the moment the powder-air mix is ignited; use in either vertical and horizontal modes; burning solid fuel in a single-phase mode as if it were a vaporized liquid or gas; completeness of combustion within the burner housing itself, rather than in a large high temperature furnace reactor; an ultra-short particle residence time requirement; burning substantially explosible powders; recycle consuming with self- contained management of initially unburned particles; and smaller and simpler than prior art solid fuel systems.
  • the burner and fuel in combination are important to operation of a burner of the present invention, as are the burner itself, the type and quality of fuel, and integration with a Positive Displacement Powder Dispersion (PDPD).
  • PDPD Positive Displacement Powder Dispersion
  • the fuel mixture must be 1) in an environment of adequately high Temperature; 2) for a sufficiently long enough Time; 3) with reasonably Turbulent mixing conditions to provide proper oxidation to complete fuel combustion in the Space allowed (see CE. Baukal, Jr., ed., The John Zink Combustion
  • the selection [of a firing method] for any given installation is governed by a number of variables, of which the principal ones are size, shape, and volume of furnace available to develop the desired capacity. Furnace dimensions establish the maximum length of flame travel available...Quantity of coal to be burned, as well as its volatile matter and sulfur content, fusion temperature of ash, and fineness of pulverization will influence not only method of firing and type of wall construction to be used but also the method of ash disposal.”
  • Coal has been burned both in crushed and pulverized forms for over half a century.
  • moisture, percent volatiles, ash, and BTU value for given types of coal and the type of furnace.
  • a high percent volatiles can cause heating value loss or excess smoking issues for stoker-fired plants, if the specific furnace has inadequate space and time to mix the volatile gases with air and completely combust them.
  • a requirement for an upper limit on volatiles is a typical solution for specific types of furnaces.
  • Solid fuels when burned in suspension, should contain an appreciable quantity of extremely fine dust so as to ensure prompt ignition. The amount of coarser material must be minimized if best combustion results are to be obtained.
  • the fineness to which coals should be pulverized will depend on many factors. Caking coals (sulfur containing bituminous coal, coking coal, forms a fused heavy crust at the surface), when exposed to furnace temperature, will swell and form lightweight, porous coke particles. They may float out of the furnace before they are completely burned. As a result, carbon loss will be high unless pulverization is very fine. Free-burning coals (contains no sulfur and does not cake), on the other hand, do not require the same degree of fineness because the swelling characteristic is absent.”
  • High- volatile coals ignite more readily than those with low volatile content. Therefore, they do not require the same degree of fine pulverization. With the exception of anthracite (called stone coal), however, the low- volatile coals are softer and may be said to have a higher grindability.”
  • the fineness of the product is usually expressed by the percentage of dust that will pass a sieve with specific size openings.
  • the most commonly used sieves are the 50-mesh sieve (210 microns) for determining the oversize and the 200-mesh sieve (74 microns) for determining the fine dust.”
  • Pulverized coal offers benefits for handling with many types of stokers but is a known detriment and avoided for caking types of coal. Coal raw material composition and resulting combustion issues can be compensated for by adjusting the particle size to be finer or coarser. The percentage of volatiles is similarly employed as a trade -off, with a higher volatile percentage enabling a distribution of larger particle size coal to be used.
  • pulverized coal particle size is used to address fuel handling and coal type composition issues.
  • % volatiles consumed in multi-phase combustion combined with large reactor size and residence time common to all furnaces, it is clear that there is no teaching in the art for using only substantially explosible coal powder as a feed stock with a cold, small and low-speed burner design.
  • the main value of having a portion of the overall pulverized size distribution well below 200 microns is for reliable ignition and fast burn only. Further in-depth fluid mechanics comparison of the differences between of our combustion regime and coal power plant furnace techniques may be found later in this disclosure.
  • the patent states that the fines portion is an ignition source, imparting stability to the flame, and that "the presence of the fines portion is the heart of the invention” as it simply "eliminates the requirement for running with supplemental oil.
  • .Hog fuels must be substantially reduced in size to provide an ignition energy source”.
  • the large particle size distribution curve of Fig. Ia depicts a typical hog fuel non-explosible particle size distribution, compared to an explosible powder particle size curve on the left.
  • the stated stability of their two-phase combustion regime has only a 2.5:1 turndown ratio compared to our 10:1 ratio, and their burner cannot tolerate cold secondary air unlike a burner of the present invention.
  • This hog fuel burner system requires a distribution with particle sizes much larger than ours, allowing for up to an estimated 75% of the particles outside the explosible range ("15-85% less than 150 microns") and "65 to 100% less than 1000 microns", meaning 35% could be larger than 1 millimeter (1000 microns), a size that is 4 to 5 times the boundary between explosible and non-explosible wood powders.
  • the present disclosure focuses on combustion of substantially explosible mixtures.
  • Other art including the hog fuel patent just described and co-firing designs, specify the use of a distribution of a mixed particle size fuel, often called “powder”. Only some component segments of the broad, larger fuel particle size distribution are "fine powders" that may, only when used alone, actually be explosible.
  • all of the fuel performs the functions of ignition and combustion temperature maintenance, not simply a portion nor even a significant portion of the overall fuel composite particle size mixture.
  • Substantially all of the fuel has the job of ignition and heating of its neighbors in the entire mixture, even "less burnable” agglomerated clumps or occasional, longer high aspect ratio non-explosible particles having explosible diameters found in the fuel due to manufacturing sieving/separation imperfection.
  • Wood chip up to 3 cm in size were reduced by a hammermill at the plant to a maximum particle size of 4 mm.
  • the particles were sieved and divided and further separated using a dust collector.
  • the particle size distribution of the wood powder is given as 90% less than 800 ⁇ m (a coarse 20 mesh), 99% less than 1000 ⁇ m, and 100% less than 1500 ⁇ m, with a moisture content of less than 8% by weight.
  • a burner system of the present invention operates based on the fluid mechanics driven process of a moving stream of a powdered fuel in an oxidizing gas, feeding a stable stationary deflagrating flame wave with on-off control. Balancing mass flow velocity of an explosible fuel dispersion with deflagrating flame front wave velocity produces a stationary and stable combustion front and zone.
  • the burner system may include both active and passive secondary air, which provides turbulent mixing, particle recirculation, combustion zone support over a wide turndown range, and combustion completion.
  • a de-agglomerization system may be used to break up agglomerate clumps of the powdered fuel to return them to an explosible state.
  • Fig. IA depicts schematically explosible and non-explosible particle size distributions.
  • Fig. IB shows an ideal particle size distribution and a more typical distribution for substantially explosible fuels.
  • Fig. 1C shows three different shapes of substantially explosible powder distributions.
  • Fig. 2A shows schematically particle combustion time versus particle size.
  • Fig. 2B shows schematically heat transfer rate part to gas versus particle size.
  • Fig. 3 shows minimum required ignition energy and flame speed as a function of fuel concentration for an explosible powdered fuel dispersion in an oxidizing gas.
  • Fig. 4 shows graphically two-stage combustion of a stationary deflagrating flame wave front at the interface of a moving stream of premixed solid particles in an oxidizer.
  • Fig. 5A shows basic combustion phenomena observed for two solid fuel particle size distributions.
  • Fig. 5B shows fluid mechanical processes and phenomena observed for two solid fuel particle size distributions.
  • Fig. 6 shows volatile organic compounds (VOCs) from a flue gas analysis
  • Fig. 8 shows schematically a burner in a first embodiment of the present invention.
  • Fig. 9 shows schematically a burner in a preferred embodiment of the present invention.
  • Fig. 1OA shows schematically a horizontal explosible powder fuel dispersion in an embodiment of the present invention with no flame.
  • Fig. 1OB shows a magnified view of Fig. 1OA.
  • Fig. 11 shows schematically velocity and gravity effects on a horizontal explosible powder fuel dispersion with no flame.
  • Fig. 12A-D shows unconfmed free space ignition at four ignition points in a horizontal explosible powder fuel dispersion.
  • Fig. 13 shows a first can embodiment of the present invention.
  • Fig. 14 shows a can embodiment of the present invention with secondary air holes.
  • Fig. 15 shows a small can of the present invention with secondary air holes.
  • Fig. 16 shows stacked cans of the present invention with secondary air holes.
  • Fig. 17 shows stacked cans of the present invention with secondary air holes or slots and with a 1-inch gap between the cans.
  • Fig. 18A shows a first cut-away of a burner can with a sloped bottom and adjustable bottom air holes in an embodiment of the present invention.
  • Fig. 18B shows a second cut-away of the burner can of Fig. 18 A.
  • Fig. 19A shows stacked cans with a multi-holed air ring supplying secondary air.
  • Fig. 19B shows a cut-away of the stacked cans of Fig. 19A.
  • Fig. 2OA shows stacked cans with secondary air from a blower into lower inlet holes.
  • Fig. 2OB shows a cut-away of the stacked cans of Fig. 2OA.
  • Fig. 21 A shows stacked cans with three secondary air nozzles and a 1-inch gap.
  • Fig. 21B shows a cut-away of the stacked cans of Fig. 2OA with a deflagrating flame.
  • Fig. 22A shows a 6-inch stove pipe with no secondary air holes.
  • Fig. 22B shows simplified burner combustion basics for stove pipe of Fig. 22A.
  • Fig. 23A shows a 6-inch stove pipe with secondary air holes.
  • Fig. 23B shows simplified burner combustion basics for stove pipe of Fig. 23 A.
  • Fig. 24A shows flame height for a low primary air flow rate with no secondary air.
  • Fig. 24B shows flame height for a medium primary air flow rate with no secondary air.
  • Fig. 24C shows flame height for a high primary air flow rate with no secondary air.
  • Fig. 25A shows flame height for a low active secondary air flow rate.
  • Fig. 25B shows flame height for a medium active secondary air flow rate.
  • Fig. 25C shows flame height for a high active secondary air flow rate.
  • Fig. 26A shows a cut-away of a 6-inch stove pipe with copper secondary air nozzles.
  • Fig. 26B shows a schematic view of fluid flow with a deflagrating flame for the stove pipe.
  • Fig. 27 shows a 6-inch steel stove pipe burner with four copper active secondary air tubes.
  • Fig. 28 shows agglomerate recirculation and mixing using a 30° cone insert in a 6-inch stove pipe of the present invention.
  • Fig. 29A shows agglomerate recirculation and mixing using four secondary air inlet holes and vibration in a 6-inch stove pipe of the present invention.
  • Fig. 29B is a magnified view of the lower right section of the burner of Fig. 29A.
  • Fig. 3OA shows a wide hole 30° cone combining both recirculation and secondary air in an embodiment of the present invention.
  • Fig. 3OB is a magnified view of the bottom section of the burner of Fig. 3OA.
  • Fig. 31A shows a burner with an ultrasonic agglomerate lump dispersing screen system.
  • Fig. 3 IB is a top view of the ultrasonic agglomerate lump dispersing screen of Fig. 3 IA.
  • Fig. 32 shows a burner of the present invention with a wide 30° cone, baffled passive secondary air, and ultrasonic lump destruction.
  • Fig. 33 shows a burner with a top hat flow reducer mounted at the top of the stove pipe.
  • Fig. 34A show a horizontal four-inch can burner of the present invention.
  • Fig. 34B is a cut-away view of the burner of Fig. 34A.
  • Fig. 35 shows the internal structure of a 4-inch horizontal burner of the present invention with dual coaxial enclosures for passive secondary air management.
  • Fig. 36 shows a 4-inch horizontal burner of the present invention with four active secondary air tubes.
  • Fig. 37A shows graphically a recycle collecting horizontal burner of the present invention, tilted slightly above horizontal for agglomerate and oversize particle collection.
  • Fig. 37B shows graphically a recycle collecting horizontal burner of the present invention, tilted slightly below horizontal for agglomerate and oversize particle collection.
  • Fig. 38 shows a more automated recycle consuming gravity collecting closed loop solid fuel horizontal burner system of the present invention.
  • Fig. 39A shows a recycle agglomerate destructing horizontal burner of the present invention with an ultrasonic driven screen for deagglomeration.
  • Fig. 39B shows an end view of the burner of Fig. 39A.
  • Fig. 4OA shows piping drawing details of the mixing zone and infeed for horizontal burners of the present invention.
  • Fig. 4OB shows an ultrasonic deagglomeration screen in the mixing zone to the piping interconnection for horizontal burners of the present invention.
  • Fig. 41 shows graphically upward vertical, horizontal and downward vertical orientations for a solid fuel explosible powder burner of the present invention.
  • Fig. 42A depicts the internal structure of a large horizontal two-stage burner of the present invention with dual coaxial enclosures for active secondary air management.
  • Fig. 42B adds first-stage active secondary air to the two-stage burner in Fig. 42A.
  • Fig. 43 shows a block diagram of a complete furnace system utilizing an explosible powder burner system and supply for heating.
  • the invention described herein enables the sustained combustion of explosible powder mixed with an oxidizing gas in a dispersed travelling suspension to produce heat or perform work.
  • the combustion technology and systems disclosed herein provide an opportunity for a major reduction in dependence on fossil fuels, leveraging and utilizing local production and distribution of renewable biomass energy fuel to fill in this gap, without the introduction of significant quantities of "new" CO 2 into the atmosphere.
  • No burner system to our knowledge is designed to exclusively handle explosible biomass and other solid fuels suspended in a substantially explosible mixture of an explosible powder with an oxidizing gas, preferably air, with the result of direct energy conversion, in a manner that mimics single -phase combustion of propane or methane gas.
  • a goal for each new burner design of the present invention is to maximize the near-instantaneous combustion of all explosible particles in the moving explosible dispersion stream with a stationary deflagrating flame wave front, while minimizing the amount of agglomerate, particles, and combustible gases (non-CO2/H 2 O) surviving the initial pass that must be burned through recirculation, thereby driving substantially to zero any unburned particles remaining thereafter.
  • a preferred goal for various embodiments of our burner inventions is to establish design and operating process parameters to achieve a heterogeneous combustion regime whereby we have instant ON/OFF and a range of 1Ox linear BTU/hour control, with the combustion process substantially taking place inside our cylindrical stovepipe burners, enclosures that are surprisingly small relative to prior art.
  • inventive techniques are scalable to design burner and Positive Displacement Powder Dispersion (PDPD) system components and combinations to produce a flame from the size of a candle to a megawatt power station burner, yet with substantial apparatus design and configuration differences from current fuel and burner technology art.
  • PDPD Positive Displacement Powder Dispersion
  • a primary, but not limiting, focus is small and medium scale residential and commercial plus industrial applications of this energy conversion technology to reduce our dependence on import and utilization of foreign hydrocarbon-based fuels.
  • a complete burner-PDPD combination of the present invention is convertible and adaptable to various explosible powders, each with their own calorific energy and explosible particle size limit.
  • Tests have been run on flour, pancake mix, confectioner's sugar, and corn starch as well as particle size distributions of various hardwood (74 micron called 200 mesh) and softwood (177 micron called 80 mesh) explosible powders.
  • Bio- scrap such as corn stalks, and field grass, hay, and various woody biomass have also been reduced in test grinding operations using a wide range of commercially-available particle reduction apparatuses and combusted in our burners.
  • Combustion systems of the present invention have a dynamic range of operation (turn-down ratio) far exceeding that typically found in prior art commercial and industrial burners utilizing biomass products with a great similarity to the adjustability of propane (LP) and natural gas burners found in the common stove.
  • LP propane
  • a focus is to utilize powder forms of biomass including, but not limited to, corn stalks, grass, sawdust, bamboo, wood chips, and chemically-cleaned, ultra-clean coal, as a direct replacement for liquid and gaseous fuels.
  • powder forms of biomass including, but not limited to, corn stalks, grass, sawdust, bamboo, wood chips, and chemically-cleaned, ultra-clean coal.
  • PCT/US2007/024044 we disclosed the requirements for these powdered fuels to be explosible and process methods of combustion by a deflagrating flame.
  • the present disclosure reaffirms and relies upon material contained in that application, and further discloses a number of methods, systems, and burner apparatuses to perform combustion, thus enabling the use of more powder fuels to provide energy for heat or to perform work.
  • Burners of the present invention with a range of embodiments and preferably designed for use with an explosible powder combusted in an essentially single phase mode, are surprisingly small and simple. In total, the present invention provides a missing piece to the puzzle of biomass energy harvesting and conversion.
  • the present invention provides methods, systems, and apparatus for one skilled in the art to assemble and utilize this new technology of "harnessing dust explosions" as a means of direct, efficient, and low cost energy conversion of solid fuels.
  • a burner system of the present invention has not been previously known, since there had been no design nor integration combining the critical combustion principles and carburetion techniques for flow control and dispersion with solid fuel burner designs. No significant supply of the proper explosible powder fuel exists either.
  • the vast majority of combustion completion occurs within the confines of an upward firing vertical burner enclosure in one embodiment of the present invention, mimicking a single-phase process.
  • the host unit when combined with a typical industrial or home forced hot air, forced hot water, or forced hot steam type of furnace, the host unit provides only a system for heat exchange and flue gas handling, in essence heat recovery, plus process and environmental control.
  • a burner of the present invention is integrated with such furnaces, sharing of the combustion functions is not necessary.
  • agglomerates as used herein describes large, non-explosible particles of varying sizes and shapes comprised of numerous small particles self-adhering due to mechanical shear and other factors.
  • air as used herein describes a mixture of gases containing free oxygen and able to promote or support combustion.
  • biomass as used herein describes any organic matter available on a renewable or recurring basis, i.e. complex materials composed primarily of carbon, hydrogen, and oxygen that have been created by metabolic activity of living organisms.
  • Biomass may include a wide variety of substances including, but not limited to, agricultural residues, such as grasses, nut hulls, oat hulls, corn stover, sugar cane, and wheat straw, energy crops, such as grasses including but not limited to pampas grass, willows, hybrid poplars, maple, sycamore, switch grass, and other prairie grasses, animal waste from animals, such as fowl, bovine, and horses, sewage sludge, hardwood or softwood residues from industries such as logging, milling, woodworking, construction, and manufacturing, and food products such as sugars and corn starch.
  • the term "blended powdered fuel” as used herein describes a powdered fuel that comprises two or more distinct powdered fuels, each of which may vary in particle
  • burner as used herein is generic to "burner assembly", and "flame holder” and describes a device by which fluent or pulverized fuel is passed to a combustion space where it burns to produce a self-supporting flame.
  • a burner includes means for feeding air that are arranged in immediate connection with a fuel feeding conduit, for example concentric with it.
  • burner is often used instead of “combustion apparatus” and not in the restricted meaning above.
  • burner assembly describes a unitary device or fixture, including a flame holder and associated feeding or supporting elements.
  • char as used herein describes the mostly carbon solid residue that remains when biomass volatiles are driven off during pyrolysis.
  • combustion and “combust” as used herein, without reference to a type of device, i.e., a combustion device, describe the act of deflagration. These terms are distinguishable from the act of simple burning, which is the direct combination of oxygen gas and a burnable substance.
  • combustion area describes a location where combustion occurs, for example, adjacent to a nozzle or inside an engine cylinder.
  • combustion chamber describes a chamber in which fuel is burned to establish a self-supporting fire or flame front and which surrounds that fire or flame. See also combustor and burner.
  • combustion device as used herein describes any system that burns or deflagrates a fuel of any type.
  • combustion devices include internal combustion engines, furnaces, grain dryers, and generators.
  • combustion gases as used herein describes the exhaust gases produced by burning the fuel, including chemical reaction products (e.g. CO 2 , H 2 O, NO x , SO x ), water vapor, and the non-reacting air components (e.g. N 2 ).
  • chemical reaction products e.g. CO 2 , H 2 O, NO x , SO x
  • water vapor e.g. N 2
  • non-reacting air components e.g. N 2 .
  • VOC and TOC are ratings used by the EPA.
  • combustor as used herein describes a combustion chamber with an igniter. While most of the traditional dictionary sources define combustor in the context of jet engines or gas turbines, papers, reports, and products developed by those practicing in the art refer to burners combining a fuel, an igniter, and an oxidizing gas inside a combustion chamber as a combustor.
  • combustion zone describes the part of an apparatus where the reaction takes place between air and fuel.
  • complete combustion describes a combustion reaction in which the oxidizer consumes the fuel, producing a limited number of products. As such, complete combustion of a hydrocarbon in oxygen yields carbon dioxide and water. Complete combustion of a hydrocarbon or any fuel in air also yields nitrogen.
  • controlled stream describes a movement or stream of particles that may be directly controlled and modified, e.g., by feedback modification, based on parameters flow rate, mass transfer rates, power or heat output, temperature regulation, and the like.
  • the stream may be finely or coarsely controlled as the particular application may require.
  • devices such as sensors described herein below, may be used to provide the data necessary to control or modify the stream.
  • the stream may be controlled for the purpose of producing a uniform explosible powder dispersion.
  • deagglomeration describes the act of breaking up or removing large particles comprised of groups of smaller particles self-adhering in clumps.
  • deflagrating and “deflagration” as used herein describe rapid burning with intense heat output and possible sparks in a subsonic combustion that usually propagates through thermal conductivity, e.g., the combusting material heats the next layer of cold material and ignites it. It should be understood that deflagration is distinguished from detonation which is supersonic and propagates through shock compression.
  • devolatization as used herein describes the releasing of combustible volatiles and tar from solid wood or other biomass or combustible fuel during heating and is used interchangeably herein with the term “pyro lysis”.
  • explosive as used herein describes a property of a powder, which, when dispersed under the appropriate conditions as a powder-oxidizing gas mixture, is capable of deflagrating flame propagation after ignition. Explosible powders that form explosible powder dispersions are capable of flame propagation when mixed with the appropriate ratio of an oxidizing gas. Numerous explosible powders, which are distinguishable from “explosive” or ignitable powders, are described in Table A.I of Dust Explosions in the Process Industry (R.K. Eckhoff).
  • gas as used herein describes any substance in the gaseous state of matter, which contains a minimum amount of an oxidizing gas, e.g., O 2 , to produce an explosible powder dispersion, even if insufficient to provide complete combustion, and is used interchangeably herein with the term "oxidizing gas”.
  • This term is intended to encompass gases of singular composition, e.g., O 2 , and mixtures of gases, such as air. This is in contrast to the use of this term as the abbreviated form of the word gasoline, liquefied petroleum gas, or natural gas.
  • heat exchanger as used herein describes a device to transfer thermal energy from the hot exhaust gases to a heat transfer fluid that can be water, air, thermal oil, or an antifreeze solution in a combustion system.
  • heterogeneous combustion describes combustion where the two reactants initially exist in different phases, whether gas-liquid, liquid-solid, or solid-gas. Heterogeneous combustion describes a solid particle oxidizing at its surface.
  • homogeneous combustion as used herein describes combustion where both reactants exist in the same fluid phase, either gas or liquid.
  • incomplete combustion as used herein describes a combustion reaction in which a fuel is incompletely consumed by the combustion. Incomplete combustion produces large amounts of byproducts. For example, incomplete combustion of hydrocarbons may produce carbon monoxide, pure carbon in the form of soot or ash, and various other compounds such as nitrogen oxides.
  • particle size describes the size of a particle, e.g., in terms of what size mesh screen the particle will pass through or by metric description of the size (e.g., in microns). Moreover, certain embodiments of the powdered fuel are defined, in part, by particle size. Particle size may be defined by mesh scales, in which larger numbers indicate smaller particles.
  • particle size distribution describes the prevalence of particles of various size ranges, i.e., the distribution of the particles of various sizes, within a powder sample.
  • particle as used herein describes very fine solid particles, typically ash plus unburned carbon that are entrained by the combustion gases and escape to atmosphere. Usually the main air pollutant from biomass combustion.
  • positive displacement describes a technique using devices that move a known volume of material per unit operation as in per stroke, per index, or per unit time.
  • powder as used herein describes a solid compound composed of a number of fine particles that may flow freely when shaken or tilted.
  • the powder composition, particulate size, or particulate size distribution may be selected based on the application in which the powder is being used.
  • "Powdered” is a substance that has been reduced to a powder.
  • crushed fuel as used herein describes a combustible solid fuel, reduced in mean particle size to a point where the substantial majority of particles are below its particular explosible threshold and is used interchangeably herein with the terms “explosible powder”, “powder”, and “fuel”.
  • the term “powdered fuel dispersion” as used herein describes substantially uniform mixtures of powdered fuel and an oxidizing gas, which are selected to be explosible based on the nature of the powder (e.g., size or composition of the constituent particles) and the ratio of the powder to the oxidizing gas and used interchangeably herein with the term “powder dispersion”.
  • the explosibility of the powdered fuel dispersion may be affected by a number of factors including, for example, the surface area of the powder particles, the energy content of the powder, the concentration of an oxidizer such as oxygen in the powder dispersion, the temperature of the powder and the oxidizer, the heat transfer rate, and the powder particle size.
  • the terms "powdered fuel dispersion” and “powder dispersion” are also intended to cover those dispersions that include an imperfectly distributed mixture made with an imperfect distribution of an explosible powder, provided that such dispersions are explosible.
  • pyrolysis as used herein describes the thermal decomposition of organic fuels (e.g., biomass resources, coal, and plastics) into volatile compounds (e.g., gases and bio-oil) and solids (chars) in the absence of oxygen and usually water.
  • organic fuels e.g., biomass resources, coal, and plastics
  • volatile compounds e.g., gases and bio-oil
  • solids chars
  • Types of pyrolysis are differentiated by the temperature, pressure, and residence (processing) time of the fuel, which determines the types of reactions that dominate the process and the mix of products produced.
  • Slow (conventional) pyrolysis is characterized by slow heating rates (0.1 to 2 0 C per second), low prevailing temperatures (around 500 0 C), and lengthy gas (> 5 seconds) and solids (minutes to days) residence times.
  • Flash pyrolysis is characterized by moderate temperatures (400-600 0 C), rapid heating rates (> 2 0 C per second), and short gas residence times ( ⁇ 2 seconds).
  • Fast pyrolysis thermallysis, using the fast pyrolysis experiment of Nunn et al., 1985) involves rapid heating rates (200 to 10 5 0 C per second), prevailing temperatures usually in excess of 550 0 C, and short residence times.
  • fast pyrolysis thermallysis, using the fast pyrolysis experiment of Nunn et al., 1985
  • rapid heating rates 200 to 10 5 0 C per second
  • prevailing temperatures usually in excess of 550 0 C
  • short residence times Currently, most of the interest in pyrolysis focuses on fast pyrolysis because the products formed are more similar to fossil fuels currently used.
  • secondary air as used herein describes air supplied to the combustible gases liberated by the primary air in order to complete their combustion.
  • secondary air includes tertiary and higher order airs.
  • single-phase combustion as used herein describes combustion where fluid mechanics single temperature and single velocity assumptions can be made. Gases such as propane and methane burn in a single phase regime, whereas gasoline and wood chip combustion is inherently two phase, liquid-gas and solid-gas respectively. Explosible powders, including sufficiently small particles under the proper circumstances and mixed at the molecular level, burn indistinguishably from and as if they were gases in a single- phase regime.
  • stoichiometric as used herein, for example in “stoichiometric combustion” or “stoichiometric mixture”, describes the ratio of the explosible powdered fuel to the oxidizing gas in the powdered fuel/oxidizing gas mixture, i.e., a powdered fuel dispersion of the invention, that is suitable to support deflagration and substantially consume the explosible powder in the mixture or dispersion.
  • the stoichiometric amount of oxidizing gas necessary to consume the explosible powder in the combustion area may be distinguished from the amount of oxidizing gas of the powder dispersion, which is sufficient to create an explosible mixture yet is typically lower than the total amount of oxidizing gas that is ultimately capable of consuming the powder.
  • powders of the present invention may be explosible even without a stoichiometric amount of an oxidizer.
  • turbulent flow as used herein describes fluid flow having the following characteristics: three-dimensional irregularity, diffusivity as in mixing, a large Reynolds number, dissipative in turning kinetic energy into heat, and continuum where the smallest scales are much larger than molecular scale, and is a property of the flow, not the fluid.
  • turn-down ratio as used herein describes a numeric ratio representing highest and lowest effective system capacity. Turn-down ratio is calculated by dividing the maximum system output by the minimum output at which steady, controlled, efficient, pollution-free combustion is sustainable. For example, a 4: 1 turn-down indicates that minimum operating capacity is one-quarter of the maximum.
  • turbulent combustion describes a combustion characterized by turbulent flows.
  • the deflagrating combustion is turbulent combustion, which assists in the mixing process between the fuel and oxidizer.
  • volatiles as used herein describes organic vapors and gases released from biomass during low temperature heating, including that portion of bio fuels that is converted to vapors and gases during pyrolysis, i.e. all components other than residual char.
  • Volatile mass as used herein describes the mass of the powder fuel particles that includes material or compounds, such as water, which vaporize or volatilize at or below the combustion temperature of the powdered fuel.
  • a powdered biomass fuel of the present invention burns like a gas for the following simplified fluid mechanics based reasons: 1) The time scale over which a particle (solid or liquid) interacts with the surrounding gas phase scales with R where R is a length scale (radius) of the particle. 2) As R decreases, the time required for particles to reach equilibrium with the surrounding gas phase goes down with the value of R.
  • a powder-air mix is "explosible" when it supports combustion as a wave process, rather than more common burning in an ideally mixed reactor (i.e. furnace).
  • a granular solid fuel dispersion in an oxidizing suspension is "explosible" when the particles are small enough for single-phase/single-velocity/single-temperature fluid mechanics approximations to accurately describe its behavior, and the dispersion is presented for combustion at an ignitable, hence explosible concentration.
  • An "explosible" solid fuel powder behaves indistinguishably from gaseous or liquid fuels under proper conditions.
  • a granular solid fuel when dispersed in an air suspension, can be made to move as a gas and behave in combustion as a "pseudogas", all without actually being one.
  • Any biomass or chemical solid fuel source can, by reduction to a particle size below its specific critical value, be considered an "explosible" powder.
  • the cost of reducing a solid fuel from a non-explosible form, to a particle size that renders it "explosible”, is small compared to the cost to convert it to a real liquid or gaseous fuel.
  • the particle distribution density in an oxidizing gas that supports dangerous dust explosions is a range of concentration spanning more than two orders of magnitude, from 50 to 100 g/m 3 to 2 to 3 kg/m 3 .
  • Eckhoff Dust Explosions in the Process Industries, 3 rd Edition, RoIfK. Eckhoff, 2003, Elsevier, hereby incorporated by reference
  • this range describes this range as "quite narrow", it actually defines a wide controllable process range for our invention, whereby we perform energy conversion of a dust- like explosible powder with a stationary deflagrating flame wavefront balanced with and surrounding a moving, premixed explosible powdered fuel dispersion in a burner.
  • This section provides a basic description of combustion of an explosible powder with emphasis on deflagration and flame speed.
  • a dust explosion where the dust is stationary in a confined space prior to ignition and the flame wave moves during the explosion
  • the fuel dispersion is moving to an open space and the flame is stationary.
  • a flame is produced when a flammable fuel source, an oxidizer, and a high-temperature environment, such as an ignition source of the present invention, are all present. As long as the three components are present, the flame will continue indefinitely.
  • the deflagration of substantially explosible powders is built on a portion of theory that fluid mechanics scholars and practitioners have not yet explained as a whole.
  • a Positive Displacement Powder Dispersion (PDPD) feed system of the present invention disperses an explosible solid fuel, suspended in an oxidizing gas, horizontally into any open space (see Figs. 1OA, 1OB, and 11), this moving stream, which is initially well above stoichiometric, begins to slow and diverge, becoming ready for ignition.
  • An arc igniter or propane torch flame instantly ignites this explosible mixture with a noticeable "whump" sound a few inches downstream of the PDPD feed nozzle as shown in Fig. 12A.
  • This unconfmed and stationary flame front immediately consumes unburned solid fuel particles in the moving stream, travelling "upstream” at a near equal and opposite velocity of about half a meter to a few meters per second. If the velocity of the flame front remains highly subsonic, this combustion phenomenon is called deflagration, which means “to burn rapidly”. In certain process flow and confinement situations, the flame propagation velocity may increase to near or beyond the speed of sound, producing detonation, a very intense explosion resulting in shock wave generation in the air- fuel mixture and surrounding area. This is not a common event in such an unconfmed environment, as a local, stationary deflagrating flame is our method of combustion in this moving stream, travelling at the flame speed but never far from the ignition zone.
  • deflagrating flames are produced by chemical reactions between "very finely divided fuel and oxidizer particles".
  • the speed with which a deflagrating flame moves through a near-stoichiometric mixture is related to the fuel ignition temperature, its calorific value and particularly to the particle or grain size of both the fuel and oxidizer, which may be in solid, gas, or liquid states.
  • Biomass fuels ground to be explosible powders have a surprisingly high calorific output. In general, it is safe to say that the greater the uniformity of this mixture and the finer the fuel explosible powder is ground (up to a point below ⁇ 80 ⁇ m), the faster the flame speed at which it burns.
  • a particle small enough to be explosible has a large surface- to-volume ratio and burns in a different modality from non-explosible larger particles of the same material with a far lower surface-to-volume ratio.
  • This modality is called single phase combustion.
  • Yarin and Hetsroni Combustion of Two-Phase Reactive Media
  • the particle temperature does not vary with radius, but only with time. "Single temperature" behavior is part of what makes our combustion process appear essentially single-phase. For particles small enough to be explosible, burning occurs at the surface of the particle.
  • Combustion time is short compared to the deflagrating flame front transit time.
  • This type of "flash burn” is near instantaneous, but it can be delayed if the combustion becomes diffusion- limited by the ability of oxygen in nearby air to further support combustion due to lack of supply.
  • the solid fuel burns in air in a single phase process as if it were a gas or vapor fuel for the combustion of substantially explosible powder particles, even though initially these two reactants exist in different solid and gas phases.
  • the reaction between the oxygen and the explosible solid particle at its surface consumes the particle in a flash burn in a single-phase surface reaction.
  • the reaction process is termed homogeneous, since substantial devolatilization produces outgassing of fuel vapor, which reacts with oxygen in the air in the gas phase of a two-phase reaction.
  • homogeneous unless otherwise stated, has nothing to do with the uniformity of the mixture and its lack of gradients in particulate dispersion and temperature.
  • Particles burning in the explosible powder fuel regime do not outgas volatiles.
  • the particle heating rate goes up and combustion time goes down.
  • pyrolysis time (required to outgas volatiles), although it has become extremely short, is still large compared to particle combustion time. That is where the process dividing line is.
  • R.I. Nigmatulin (Dynamics of Multiphase Media: Volume 1) discusses the propagation of a combustion wave in two-phase processes, which is described as "gas- solid combustible particles". This process is defined by interactions amongst hydrodynamic, thermophysical, and chemical processes. His theoretical analysis of the interactions of these phenomena involves a system of equations that treat hydrodynamics, heat and mass exchange, and chemical kinetics in a two-phase medium, with descriptions of assumptions that can be made to reduce it to single phase.
  • the three possible particle combustion regimes are: heterogeneous - our modality, quasi-homogeneous - the combustion of fuel vapor and gasification by-products, and vapor-phase - the combustion of volatile components.
  • Particle size is the prime criterion determining the regime of combustion. With heterogeneous combustion in a general form, actual burning occurs at both the surface and within the combustible fuel particle. Heat from the combustion chemical reaction is transferred directly to the particles to maintain ignition temperature. Particles of small enough diameter, which are free of or have minimal volatile organics, such as graphite, electrode coal, and other powders, burn this way.
  • Ignition occurs when the particle's surface temperature rises to a certain level.
  • a heterogeneous regime stage of "slow" burning occurs, and if the regime is vapor-phase, the vaporization or gasification stage occurs.
  • the gas heat flux to the particle surface actually penetrates the particles.
  • the major portion of the temperature difference occurs in the gas, so the average temperature of the surrounding gas and the particles just prior to ignition are approximately equal, or single temperature.
  • the Nusselt number a dimensionless ratio describes the heat exchange.
  • Nigmatulin states that there is no F-phase in the regime, along with no fuel vapor, and that the heat of chemical reaction is transferred directly to the particles.
  • the reaction rate constant for this heterogeneous particle combustion regime is given by the Arrhenius law and described by the empirical formula for the dimensionless Nusselt number.
  • Sherwood number describing the diffusion influx of the oxidizer to the particle's surface indicates a diffusion regime of burning, not a kinetic one, since at the wave front of the reaction zone, the process goes from kinetic to diffusion, per Yarin and Hetsroni.
  • a candle flame burns in a single phase combustion process, yet it is common to get smoke and soot from it.
  • a kerosene flame is a single phase combustion process, yet it too produces smoke, some soot and detectable aromatic vapors.
  • Portable kerosene heaters such as the Kerosun® or salamander type heaters prove the point.
  • Most everyone is familiar with the smoke produced when two phase combustion processes are "fuel-rich", running on too little air for a given quantity of fuel.
  • Yard equipment such as lawnmowers, chain saws, snow blowers, and the like smoke profusely when partially choked and running fuel-rich. This smoke signifies that the engine is operating above the proper stoichiometric fuel-to-air ratio (FAR).
  • the first stage comprises the heating side where the cold mix of air and particle reactants is pre-heated by the gas, and initial combustion begins at the stationary deflagrating wave. As particles move into the reaction zone, heating continues, now from particles to gas, and combustion continues until available oxygen is depleted.
  • a powder-air mixture of the present invention may still be explosible, and yet follow the same laws as a single phase methane hydrogen gas mixture in air.
  • the surprising difference is as follows. A powder-air mixture, acting as a single-phase mixture in combustion, is still explosible at several times stoichiometric, whereas a true single phase methane -hydrogen-air mixture, with the same over rich ⁇ equivalence ratio (high fuel to air ratio) is non-explosible. Surprising but true.
  • the burning may be described as a heat transfer process, where particles arriving at the stationary combustion wavefront are warmed up through gas conduction by the proximity of others burning.
  • the turbulence that does occur is usually generated by shear around the outer volume of the moving air-powder dispersion in response to the Bernoulli Effect and gas thermal expansion from combustion.
  • a combustion process of the present invention is simple, since it is profoundly single-phase in behavior.
  • This sole, single-phase burning appearance as a solid combusts like propane, renders moot objections, concerns, and challenges that may be raised about the discovery and uniqueness of our disclosures.
  • Powdered solid fuel of the present invention is transported through a nozzle together with primary air in a dispersion at a low speed above the flame speed, for example twice the flame speed.
  • the stream slows, diverges, and is ignited, forming a stationary standing wave flame front riding on and burning around the fuel-rich core of the flowing explosible powder-air stream.
  • classic techniques include feeding pulverized coal mixed with primary air in a suspension into a furnace/burner at a rate of twenty or more times the flame speed, a process parameter that would not work within our invention disclosure. Only by virtue of sending the coal premix into a reactor with controlled high temperature radiating walls is sustained and complete combustion possible under these conditions. For our invention, burner wall temperatures are not important to initiate and sustain combustion, and no large ideally-stirred reactor is required. These are significant differences.
  • dry pulverized coal may be transported through a nozzle together with primary air at a high speed (up to at least 56 ft/s, according to Y. Kwan et al. in "Advanced Coal-fueled Combustor for Residential Space Heating Applications”), more than an order of magnitude above the flame speed (10 to 30 times greater) into a burner, which is a small reaction chamber emulating a large one.
  • Some designs then continue the combustible flow into the actual furnace, a large reaction chamber where combustion is completed, with ignition initiated by the mechanism of radiation heat transfer (P.M. Krishenik, "Modeling of Combustion Wave Propagation in a Carbon Dust/Gas Mixture”), rather than particle-to-gas heat transfer as is utilized in the case of our combustion burners .
  • Ballester et al. tested a prototype burner with two types of coal, bituminous and lignite, and oak sawdust powder. The design was to burn powder in a regime where heat transfer was primarily radiant as in a high temperature reactor.
  • the large power station- oriented coal combustion experts like all their peers over the years, completely missed the fact that their two coals were pulverized in the 20 to 40 micron range and were in fact of explosible size. Rather, they performed their tests and comparisons with biomass oak dust having particles too large to be explosible ( ⁇ w « 1), by blowing the fuel into a high temperature chamber of 2000 0 F or higher, often at 40 to 60 times the flame speed. In such chambers, the vast majority of the heat transfer is radiant from the chamber walls, thereby igniting and combusting the entire distribution in a two-phase regime, where time and space are not significant limitations, and the value of ⁇ w does not matter much.
  • furnaces and burners designed to emulate their high temperature radiation-based ignition environment have a far narrower operating range and a far smaller turndown ratio than a far smaller burner of the present invention.
  • a burner of the present invention is not required to be integrated with a big furnace-radiating reactor volume for combustion completion. No atomization is required.
  • Our primary air- fuel mixture is fed from the nozzle at just above the flame speed, whereas a coal powder premix is sprayed at 10 to 30 times the flame speed.
  • Our burner is completely standalone for operation, while coal burners must be connected to a large furnace refractory.
  • Our burner is small in size, not burdened by coal combustion design goals and complexity common to large furnaces.
  • the DOE coal combustor required pre-heating the fuel, a quarl and refractory (a
  • Our burner preferably uses a simple spark igniter and continues with self-sustained combustion and no further or external ignition intervention required.
  • the DOE combustor needed oil or gas fuels for a pilot light to initiate and initially sustain ignition, heat the combustor, and stabilize the flame. We require none of those heating functions or hardware. While our burner is self-sustaining through a simple conduction regime, the DOE unit design emulated the radiation heating found in typical coal furnaces to ignite particles continuously. No standard coal combustor would sustain a flame if disconnected from the irradiative furnace reactor! Our burner is standalone. When it comes to size, the DOE combustor needed oil or gas fuels for a pilot light to initiate and initially sustain ignition, heat the combustor, and stabilize the flame. We require none of those heating functions or hardware. While our burner is self-sustaining through a simple conduction regime, the DOE unit design emulated the radiation heating found in typical coal furnaces to ignite particles continuously. No standard coal combustor would sustain a flame if disconnected from the irradiative furnace reactor!
  • DOE burner's "BTUs per hour per cubic foot" is far lower - perhaps one-tenth of the output per cubic foot of a burner of the present invention.
  • combustion of an explosible fuel-air mixture begins instantly in an initially cold burner, is sustained through kinetic particle to gas conductive heat transfer, and is completed substantially within the burner itself, rather than in a large, pre-heated furnace reactor driven by radiation heat transfer, which is typical art for pulverized coal.
  • a preferred use of our burner in many applications is as a single burner. It is not initially intended to be used in vertical banks or arrays of multiple near or below horizontal burners, although there is no intent to be limited by this design goal. It is not intended to burn coal dust slurries. It is designed to operate in a single-phase combustion regimen.
  • Fig. IA shows two curves 10, 11, conceptually depicting two particle size distributions.
  • An important component to our unique powdered fuel energy conversion process is our preferred use of a substantially explosible powder as a fuel, with particle sizes from a few microns up to the neighborhood of 200 microns, as seen in curve 10.
  • Wood particles much larger than 200+ micron limit are not typically explosible, burning more slowly in a common two phase regime.
  • the actual size limit for explosibility varies for different types of biomass and other explosible powders based on a number of variables which include, but are not limited to, particle surface area-to-volume ratios, particle aspect ratio, percent moisture, percent volatiles, calorific value of the powder/dust, temperature, dispersion concentration, particle internal structure morphology, and the like.
  • the term 200+/- microns is used to denote the dividing line between explosible and non- explosible powders generically in this disclosure.
  • the actual particle size diameter for different types of biomass and other powder fuels may be found in a variety of resources (Dust Explosions in the Process Industries, R.K. Eckhoff).
  • a basic measure of the explosibility of a particle distribution is the ability of that distribution, including its largest particles, to flash burn in an explosible mode in the various burners we disclose in tens of milliseconds, emulating a single phase combustion regime commonly seen with propane and other liquid and gaseous fuels.
  • the distribution 11 on the right of Fig. IA includes a wide range of particle sizes, with a predominant membership in the non-explosible range.
  • Wood chips, saw dust, ground waste, hog fuel, coal, and other combustible biomass up to whole trees and hydrocarbon-based fuels have been burned in large furnaces for boilers, power plants, and other common modes for years as cited in numerous references in this disclosure. More recently the literature describes mixed fuel and co-fired burners and combustion schemes for predominantly non-explosible dusts and powders. While a portion of the particle size distribution may fall into the explosible range, today's technology applications tend to produce energy with large mean particle sizes by comparison, often by stated choice to avoid the explosion dangers of particle dust and fines, which fall into the explosible range.
  • Fig. IB depicts an ideal particle size distribution 12 centered around the 50 to 80 micron mean, and a more typical curve 13 found in various types of substantially explosible fuels from biomass and other powdered sources. This curve 13 is skewed heavily to the right, toward a mode larger particles than the mean or median would indicate, yet is still within the explosible region. The skew is primarily based on the manufacturing processes, from sieving to more selective separation techniques utilized.
  • Fig. 1C Three different shapes of substantially explosible powder distributions 15, 16, 17 are depicted in Fig. 1C.
  • the particle size distributions for embodiments of the inventions herein may have a variety of statistical characteristics, based on uses and economics.
  • dispersions are achieved that are explosible regardless of variables such as the surface area of the powder particles, the energy content of the powder, the concentration of an oxidizer such as oxygen, the temperature of the powder and the oxidizer, and the heat transfer rate, provided that sufficient oxidizing gas is present to qualify as explosible in nature. Accordingly, embodiments of inventions herein are capable of deflagrating dispersions of powdered fuel with little or no adjustment required for various powder materials.
  • Fig. 2A depicts the general relationship 20 between particle size of a powder particle and the particle combustion time.
  • Dashed line 14 depicts the explosible limit for the powder - a threshold above which the dispersion is not explosible. This threshold varies from dispersion to dispersion and the other noted factors above. For example, with respect to the concentration of an oxidizer, a first dispersion including a particular powder may not be explosible where the dispersion include air having 20.95% oxygen, while a second dispersion including the same powder may be explosible where the dispersion includes pure oxygen. For methods and apparatus for determining a powder's explosible limit, see W. Bartknecht, Dust Explosions: Course, Prevention, Protection.
  • Fig. 2B shows there is a generally inverse relation 22 between the heat transfer rate and the particle size, with the most predominant portion of the curve existing in the explosible powder region.
  • the heat transfer rate for smaller particles is generally higher than for larger particles.
  • dashed line 14 depicts the explosible limit.
  • the curve of Fig. 2B provides the explanation for why fuels composed primarily of large particles on the order of 500 ⁇ m must remain in a furnace for a significant period of time.
  • Fig. 3 shows a matched set of graphs taken from Eckhoff, the first depicting the minimum required ignition energy 30 as a function of fuel concentration for an explosible powdered fuel dispersed in an oxidizing gas.
  • An explosible powder is only explosible in a concentration range with an oxidizing gas between a lower concentration limit 32 and an upper concentration limit 34. Above the upper critical concentration, the concentration of oxidizing gas is too low to burn all of the fuel. Below the lower critical concentration, the particles are too far apart for enough heat to be transferred from burning particles to unburnt particles to ignite the unburnt particles.
  • the minimum ignition energy required to ignite the particles has a minimum within the explosible concentration range at 36.
  • Fig. 3 also shows schematically the flame speed 38 as a function of fuel concentration for an explosible powdered fuel dispersion in an oxidizing gas. Again, flame speed is relevant only in the explosible particle concentration range between a lower concentration limit 32 and an upper concentration limit 34. This curve is reminiscent of fluid mechanic depiction of the flame speed versus the equivalence ratio ⁇ .
  • the primary process operating in Preheat Zone I 44 is the heating of the dispersed phase.
  • the flame front is the transition line into Reaction Zone II 46 where heating of the gas is the primary dynamic.
  • the diagram emphasizes the continuous gas-particle conductive heat transfer between the Preheat Zone I 44 and the Reaction Zone II 46 as a fresh supply of particle reactants are continuously fed into burners described herein for deflagration.
  • a graphical temperature reaction profile 48 is overlaid inside the burner.
  • the second stage 47 oxygen is depleted somewhere in the reaction Zone II, while hot particles at combustion temperature continue moving.
  • the second stage begins with the introduction of high-speed secondary air 49 at an angle to encourage mixing and a velocity perhaps 10-times the flame speed.
  • Adequate oxidizer drives char burnout to completion, a fast process that occurs in a time related to the particle radius squared (R 2 ), rather than just R as in the first stage.
  • Figs. 5A and 5B present a basic combustion and fluid mechanic summary of phenomena and detail the radically different behavior between combustion of explosible versus non-explosible particles.
  • a list of comparison terms or phrases is overlaid onto the shape of the explosible and non-explosible particle size distribution curves of Fig. IA to emphasize the unique differences between our operation and prior art.
  • Fig. 5A summarizes basic combustion phenomena observed when our disclosed devices and fuels are operating in the explosible regime compared with operation in the non-explosible, more traditional combustion mode.
  • Each item in this overview summary of key combustion regime differences is discussed in detail in other portions of our disclosure. The summary, taken as a whole, makes clear the novel and surprising nature of our disclosure in combustion terms familiar to many including those skilled in the art.
  • Fig. 5B summarizes fluid mechanical processes and phenomena observed when our disclosed devices and fuels are operating in the explosible regime compared with operation in the non-explosible combustion mode broadly utilized today.
  • Each item in this overview summary of key combustion regime differences is discussed in detail in other portions of our disclosure. The summary, taken as a whole, makes clear the novel and surprising nature of this unpracticed combustion regime described in our disclosure using fluid mechanics and combustion dynamics terms familiar to those skilled in the art.
  • a burner system of the present invention preferably includes five sections.
  • Fig. 8 shows schematically a burner in a first embodiment of the present invention.
  • the burner system 80 includes a powdered fuel feed system 82 for feeding a powdered fuel and an oxidizing gas feed system 84 for feeding an oxidizing gas.
  • the powdered fuel and the oxidizing gas mix in a mixing zone 85 fed by the powdered fuel feed system 82 and the oxidizing gas feed system 84.
  • An explosible dispersion directing system 86 fed by the mixing zone 85 directs the explosible dispersion toward the ignition source 88 in the confines of an enclosure (not shown).
  • the ignition source 88 is located downstream from the explosible dispersion directing system and initiates a deflagrating flame for the explosible dispersion.
  • the powdered fuel feed system 82, the oxidizing gas feed system 84, and the mixing zone 85 are collectively termed the positive displacement powder dispersion feed system. Each of these parts is described in detail below.
  • Fig. 9 shows schematically a burner system in a preferred embodiment of the present invention.
  • the powdered fuel feed system 82 includes a powdered fuel storage container 91, a fuel vibrating device 92, a fuel metering device 93, a usage meter 94, and a fuel feed power source 95.
  • the vibrating device 92 vibrates the fuel storage container to reduce clumping of the fuel and to maintain flow of fuel, preferably by gravity, from the storage container 91 to the metering device 93.
  • the fuel supply power source 95 controls the rate of fuel feed by controlling the metering device 93, and the usage meter 94 records the amount of fuel fed the metering device 93.
  • the oxidizing gas feed system 84 includes an oxidizing gas source 96 and a gas metering device 97.
  • the explosible dispersion directing system 86 includes a constriction device 98 and a flame stabilizing system 99 downstream from the nozzle.
  • An agglomerization device 10OA, 10OB, IOOC to break up fuel agglomerates that may have formed during transport or storage of the powdered fuel may be optionally located within or after the fuel metering device 93, within the mixing zone 85, or within the flame stabilizing system 99.
  • a burner system of the present invention is preferably turned on by initiating the powdered fuel feed system to provide powdered fuel at a predetermined feed rate and actuating the ignition source to ignite the fuel and produce a deflagrating flame.
  • the oxidizing gas feed system may be initiated before, at the same time, or after the powdered fuel feed system is initiated, and the oxidizing gas from the oxidizing gas feed system carries the powdered fuel to the combustion enclosure past the ignition source.
  • a burner of the present invention is preferably sustained in the on position by continuing to feed powdered fuel and oxidizing gas at predetermined feed rates, which may vary with time depending on load requirements, to the deflagrating flame.
  • a burner of the present invention is preferably turned off by turning off the powdered fuel feed system.
  • the oxidizing gas feed system is preferably turned off at the same time as the powdered fuel feed system but may be turned off before or after the powdered fuel feed system is turned off. Alternatively, the oxidizing gas feed system may be maintained at a predetermined flow rate, which may vary with time, when the burner is both in the on and off states.
  • the powdered fuel feed system preferably includes a powdered fuel storage container, a fuel vibrating device, a fuel metering device, a usage meter, and a fuel feed power source.
  • the powdered fuel storage container may be any size or shape, preferably with a downward sloping bottom, and made from any structural material.
  • the container is preferably easily accessed for addition of powdered fuel to the system as necessary or fed from remote storage.
  • the fuel vibrating device may be any high frequency device which promotes flow of the powdered fuel from the storage container to the fuel metering device and reduces agglomeration.
  • the fuel metering device may be any device capable of feeding a solid material at an adjustable and controllable rate including, but not limited to, a screw auger, a conveyor, a rotary disk or other metering devices.
  • the usage meter may be any device that counts and records the usage of the fuel metering device, such as the number of turns of a screw auger, to determine the amount of fuel being used by the burner system.
  • the fuel feed power source may be any power source, but is preferably electrical, and either separate or the same power source may be used to run the fuel vibrating device and to drive and control the rate of the fuel metering device.
  • the oxidizing gas system preferably includes an oxidizing gas and a gas metering device.
  • the oxidizing gas for the oxidizing gas feed system may be air, oxygen, or any other composition of gas containing oxygen.
  • the oxidizing gas source may be ambient air, compressed air, or compressed oxygen.
  • the gas metering device may be a valve, a pump, blower or any other device to control the feed rate of the oxidizing gas.
  • the power source to run the oxidizing gas feed system and the power source to run the powdered fuel feed system may be the same or different power sources. Oxidizing gas is separately fed to the burner as a source of secondary air to support one or two stage combustion.
  • the mixing zone is a zone of the burner system which allows the oxidizing gas and the powdered fuel to intersperse after they come together.
  • the mixing zone ideally allows the oxidizing gas to break up and distribute the powdered fuel into its individual particles so that it behaves as a reasonably uniform explosible powder when it reaches the deflagrating flame.
  • the mixing zone may be a chamber, a conduit, educator, or a combination of chambers and conduit.
  • the mixing zone is preferably designed to produce a dispersion by turbulent flow of the oxidizing gas.
  • An ignition source for a burner of the present invention is used to turn the burner on by initiating a deflagrating flame in the fuel-gas dispersion fed by the PDPD system and formed by the flame stabilizing system. Since a burner of the present system preferably stays on until the fuel supply is cut off, the ignition source may be pulsed ON/OFF or continuous.
  • the ignition source is preferably an electric arc ignition source or other spark source such as a conventional spark igniter.
  • the ignition source may, however, alternatively be a gas flame pilot light, a glow plug, or any electronic igniting device.
  • the burner or explosible dispersion directing system, receives the mixed dispersion from the PDPD through the nozzle and delivers it to the ignition source for initiation of the deflagrating wave.
  • the explosible dispersion directing system also controls the process by taking advantage of the fluid mechanics of the dispersion and the deflagrating wave to optimize the burner for the specific application for the burner.
  • the explosible dispersion directing system includes a constricting device and a flame stabilizing system.
  • the constricting device controls the speed and area of the explosible dispersion as it is fed into the flame stabilizing system.
  • the constriction device is a nozzle.
  • the flame stabilizing system is designed to control combustion makeup air system of the powdered fuel and may include an active or a passive secondary air system as well as a de-agglomerization system.
  • Fig. 1OA shows schematically a horizontal explosible powder fuel dispersion in an embodiment of the present invention with no flame.
  • the powder fuel dispersion 100 depicts the fluid dynamical behavior. Flow exiting the eXair air amplifier in much of the cone is initially a directed stream. Turbulence quickly begins circumferentially at the edge of the dispersion flow as stationary air is induced, producing noticeable eddies and drag vortices.
  • the high velocity dispersion jet flow produces a high shear, resulting in turbulence as stationary air flow is induced by the fast moving air-particle mixture. Eddies and waves 104 are immediately apparent surrounding this diverging cone and contribute to a slowing of the air-particle mass flow even before gravity effects become pronounced.
  • Velocities are high near the center of the slowly diverging cone and not immediately amenable to ignition or to sustained burn. There is little or no visible evidence of any particle fall-out in the first several feet after the amplifier nozzle exit.
  • the fine unignited powder which is easily seen without ignition, tends to disperse evenly throughout the room, not just fall to the ground as discharge velocity approaches zero. Particles remaining in a slowly-diverging cloud form a uniform dispersion of fine powder.
  • Fig. 11 depicts the effects of gravity and turbulence on the velocity and momentum of an unignited horizontal dispersion 110 suspended solids blown into stationary air.
  • the first region is characterized by a high velocity flow surrounded by high shear, low pressure room atmosphere and resulting edge flow drag induced turbulence and consequent mixing as predicted by Bernoulli. These phenomena continue for about four feet, abating into the second region of slowing velocities and reduced momentum, where the dispersion appears highly uniform except for some turbulence and thinning at the extreme edges.
  • the dispersed particles enter the third region where the dust-like powder begins to settle 112 under the influence of gravity due to a loss of momentum.
  • Any undesirable oversized, higher mass particles, especially ones within the specified diameter but with aspect ratios greater than 2 stay in a ballistic mode until the end of the third region where they too succumb to gravity.
  • Figs. 12A through 12D show unconfmed free space ignition of a horizontal dispersion as the ignition point location is successively moved away from the nozzle source at four increments.
  • the air-powder premix enters the eXair air amplifier where final dispersion and velocity amplification are completed.
  • the explosible powder dispersion exits the eXair nozzle initially in a fast moving, slowly diverging flow at a concentration several times stoichiometric with a velocity well above the dispersion flame speed.
  • a propane torch applied directly at the nozzle outlet does not ignite the mixture, since the velocity is still above the flame speed, which ranges from about 0.5 to 1+ meters/second.
  • the high solid fuel concentration is likely in the explosible range, but ignition is velocity inhibited.
  • a deflagrating flame erupts at the ignition point 122 of Fig. 12A as shown in the top flame profile.
  • stationary room air is entrained by the fluid mass flow, with turbulent eddys moving forward while slowly rotating back towards the source as a result of shear.
  • the deflagrating flame continues to consume all of the dispersed solid fuel powder suspension in an explosible mode. As velocities and concentration have decreased somewhat, the actual flame front moves upstream 2 to 3 inches from the ignition point and remains essentially stationary. A typical burn at the proper ignition point delivers near complete combustion, with little or no particle fallout.
  • the ignition point 126 of Fig. 12C is just over a foot downstream from the nozzle exit. A noticeable backfire is present, reaching about 4+ inches back towards the source, where it remains stationary as a stream of fresh reactants arrives.
  • the far left "tail" of the flame wavers more with ignition this far out, as the effects of turbulent mixing, the reduction and resupply of oxidizer, and upward gas expansion from particle burning have increased effects on the variability of dispersion uniformity and therefore combustion.
  • the ignition point 128 of Fig. 12D is located about 16 inches downstream, the farthest from the nozzle source in this series of tests. A noticeable change in burning is observed, as the dispersion has become increasingly disturbed in its travels, widening both geometrically as well as in stoichiometric values of air- fuel concentrations. Unburned powder is observed surrounding the deflagrating flame cloud, at concentrations below explosible or temperatures that combine to preclude its combustion consumption. Ignition point 128 is considered to be outside the desirable operation region of our preferred methods and processes, but is included here to round out our disclosure. During these tests, we also observed the usefulness of the eXair air amplifier with horizontal dispersion.
  • the air amplifier turbulence when operating without an ultrasonic deagglomeration function, performs a final destructive breakup and mixing of any remaining particle agglomerate and thereby reduces or eliminates any resulting particulate "fall out” around the burning stream, when compared to a simple pressure- driven stream from the mixing zone to the nozzle.
  • the burner on a gas stove does not need to be confined in order to work well, over a very wide dynamic range. It sends a premixed, close-to-stoichiometric, preheated, well- distributed mix out a flameholder, where it burns cleanly. It helps to have an effectively zero fuel-air density difference, and truly single-phase operation.
  • a horizontal, low-speed jet of explosible powder keeping the powder confined in the combustion zone is a challenge.
  • Our horizontal jet, blowing powder out into free space have worked best with powders of 200 mesh.
  • a vertical jet, blowing up into free space had similar, yet less severe problems, as the effects of gravity are uniformly distributed around the central flow axis, eliminating the asymmetric particle behavior.
  • a vertical dispersion allows all powder, especially that which is too dense or coarse, to stay suspended and confined in the jet combustion zone and burn in the stovepipe burner. It should be understood that at very low flow rates, the performance of large burner diameters begins to fall off and destabilize, as the side walls are far enough away to be similar to “free space", not providing the necessary turbulent recirculation.
  • Fig. 13 shows a first can burner embodiment of the present invention.
  • the first sustained burn was accomplished when the air-fuel dispersion generated by the PDPD and dispersion directing system was fed vertically into the first vertical burner 130 enclosure design at a velocity just above the flame speed.
  • This first burner was fabricated from a 6- inch diameter x 6%-inch high coffee can. It produced a tall, rather lazy deep orange deflagrating flame rising several feet above the can with no sensible smoke or soot. It was immediately obvious that further answers would be found buried in the complex relationship between powder-air mix flow, turbulent mixing, available combustion air, dynamics of a burning gas wavefront, gravity effect on explosible and larger burning particles, and actual stream velocity of the air/powder mixture.
  • Both the larger 80-mesh softwood pine and 200-mesh hardwood produced more sparks with a vertical burner than a horizontal dispersion, especially at the top and plume periphery. These sparks were later understood to be the presence of oversized particles in a less than perfect explosible dispersion, plus an occasional larger particle agglomerate.
  • Fig. 14 shows a second can burner 140 of the present invention with four secondary air holes 142 located near the bottom of the burner exterior sidewall.
  • the air holes at or near the burner base provide what we call a supply of passive secondary air to assist with combustion via several processes. External air is pulled or induced into the burner enclosure by the force of a negative draft generated in the combustion process and dispersion in- feed.
  • the amount of passive secondary into the burner through these apertures is related to a number of parameters, including the pressure drop through the burner, the fuel flow combustion rate, and the combustion chamber stack height.
  • the presence of secondary air from the four 1-inch holes on the burner sidewall base improved flame stability inside the burner and allowed for a wider range of air- powder flows without flameout.
  • the structure of the flame above the burner exit was less "lazy" and less tall, as combustion was completed at a decreased distance from the nozzle.
  • Fig. 15 shows a smaller can burner 150 of the present invention with secondary air holes 152.
  • This 4" diameter can is a scaled down version of the original 6" burner. As the nozzle diameter did not decrease proportionately for this embodiment, less of the combustion occurred within the can, appearing more like a torch. A combustion chamber of this size, possibly with a decreased infeed nozzle diameter, would be useful for lesser heat load applications such as a 20,000 BTU/hour residential hot water heater.
  • the fast vertical dispersion jet technique results in a higher initial velocity and greater shear than the target velocity. It introduces turbulence by the dissipation of kinetic energy in the primary fuel-air mix stream. Higher speed primary flow supports the weight of the powder and allows for a closed off bottom, thereby producing recirculation, sustained ignition, and combustion inside combustor. This design allows for a flat bottom, producing an abrupt pressure discontinuity, which is a major driver for recirculation and enables a wide operating range of flows and BTU outputs for a single burner size.
  • Bernoulli's Law which predicts a decrease in pressure in a direction perpendicular to the flow of a gas or fluid. Bernoulli's Equation is a consequence of the conservation of energy as applied to an ideal fluid, dictating that the sum of the pressure, the kinetic and potential energies (both per unit volume) is a constant value at all points along a streamline or laminar flow.
  • the velocity difference as the air-powder stream exits the nozzle into the combustion enclosure means there will be a pressure difference, since moving fluids exert pressure on stationary fluids. Recirculation and turbulence are initiated by the resulting energy transfer from the kinetic high speed air- fuel flow entering this enclosed environment. Likewise, the high speed stream induces the flow into the passive secondary air inlets near the base of many burner embodiments. Once ignition of the air-fuel mix occurs, hot gas expansion adds further kinetic energy into these dynamic processes.
  • Fig. 16 shows two stacked burner cans 160, 162 with secondary air holes 164 at the base of the lower can 162.
  • the addition doubled the combustion chamber length to about 13 inches and reduced the external flame height by providing an environment for further combustion completion.
  • the increased stack height of the combustion chamber increased the vacuum to induce passive secondary air into the 1-inch holes at the burner base, yet the overall mixture combustion became oxygen-starved well below the top exit, indicating further secondary combustion air was needed.
  • Fig. 17 shows the upper 170 of the two stacked cans 170, 172 moved vertically upward to create a one-inch air gap 174 between the upper and lower cans of the combustion enclosure with the lower can having four 1-inch diameter passive secondary air holes 176.
  • This gap 174 provides a second and additional source of passive secondary combustion air beyond the four holes or slots at the base. By providing this additional air through the gap, the flame height was lowered and more combustion of the oxygen- starved mixture was completed within the now 14-inch tall combustion enclosure.
  • Figs. 18A and 18B show a burner can 180 with a sloped bottom 182 and adjustable bottom air holes 184 as an alternative technique for providing a more controlled flow rate of passive secondary air with an axial rather than cross flow orientation.
  • the sloped bottom functioned as intended by returning any unburned particulate back into the air stream.
  • the ability of the bottom holes to control secondary airflow amounts was useful.
  • An apparatus with adjustable slots or holes may be similarly used on the sides of the combustion chamber enclosure as an alternative to this method.
  • the value of the cross flow later called the "sweeper function" of passive secondary air, accomplished in previous prototypes by air inlet holes near the bottom of the enclosure.
  • This cross flow provides greater radial recirculation and increased turbulent mixing, whereas this more axial secondary air flow is useful as a trim control for combustion completion, by providing a certain amount of makeup air for primary combustion air, as well as a trim method to control the deflagrating flame front vertical location and a wider lift area for unburned particles.
  • Fig. 19A diagrammatically shows dual stacked burner cans 190, 191 with a multi- holed air ring 192 supplying active secondary air through a one-inch gap.
  • This burner also has four 1-inch diameter passive secondary air holes 193 on the bottom can 191.
  • An air manifold with holes or slots may be fabricated from materials capable of withstanding temperatures of 1500 0 F or more.
  • a single circle of machined holes may be augmented by an array of holes above and below the plane of the active secondary air module.
  • Passive secondary air preferably entering the enclosure sides near the base, may also enter through the base if internal directing structures such as angled pipes or tubes control the direction of airflow to emulate the paths taken from side entry.
  • a circular manifold may be utilized, comprised of an air channel/reservoir supplying machined holes, all angled identically, both rotationally (coaxially) to produce a light swirl, and at some upward vertical angle across the flow.
  • An alternative, geometric passive method to the production of low speed swirl works by attaching a few stationary predominantly vertical (axial) and slightly angled "vanes" to the sides of the burner wall in protected areas not subject to collisions of high speed particles, for example in the recirculation zone or coaxial air paths (see Fig. 35 and Fig. 42).
  • a second alternative, geometric passive method to produce a low speed swirl may be accomplished by directing the flow of incoming passive or active secondary air at the burner base from each entry orifice at the same angle around the vertical flow axis of the burner. While these air velocities are less than those found in the upper combustion zone with active secondary air, beginning a low speed and gentle swirl early in the rising combustion process does provide containment and stability advantages (see Fig. 42A).
  • Air flow can be provided and controlled by a wide range of common industrial process means.
  • Some burner designs use a "swirler" to support and mix gases and particles in the combustion zone, including many years in burning coal powder. We achieve similar and perhaps more robust benefits by providing primary combustion air through the inlet nozzle as a component of the mixture stream, and supplementing with controlled secondary air.
  • the total primary air flows through the same inlet as the fuel.
  • Most mechanical swirler burners feed a very un- stoichiometric 1-2:1 premix ratio through a centrally located nozzle and then introduce additional primary air circumferentially around the main inlet to spin the swirler.
  • the "support and mixing" functions of a mechanical, air flow driven swirler are much more non-linear than the elegantly simple approaches found in our disclosure, and result in low flow collapse of that function and the subsequent low turn-down ratio performance.
  • the burner of Figs. 2OA and 2OB utilizes similar hardware as the burner of Figs. 19A and 19B, but the active secondary air is fed into the lower 202 of the dual stacked cans 200, 202 of this embodiment by an air ring 204 through the four passive air inlet holes 206 on the sidewalls near the base and a 1-inch gap 208 between them for passive secondary air for the second stage.
  • the use of active, pressurized air flow control through the lower portion of the burner may be advantageous for recirculation, mixing, and improved early combustion completion. Active secondary air benefits operation at lower flow rates and velocities so that the main and recirculating air- fuel dispersion and the return of oversized particles is not inordinately disturbed. Caution must be exercised since flows too high can cause flame out, overwhelm particle recirculation and handling functions, and interfere with the stability of the stationary deflagrating flame wave front.
  • Secondary air such as this, under mechanical control is referred to generically as forced draft.
  • Complete burner systems may be called mechanical-draft burners when the oxidizing gas is supplied under pressure by a blower or air pressure supply device.
  • the supply of active secondary air for this normally passive secondary air situation in our solid fuel burner disclosures constitutes a separate embodiment, and would be delivered by alternate and improved means than that utilized for this simple demonstration.
  • Fig. 21A shows the dual stacked cans 210, 211, separated by a 1-inch gap 212 with the addition of three active secondary air nozzles 213. Holes in the lower can provide passive secondary air.
  • active secondary air we use the term "active secondary air” to describe a method whereby we can control the volume, pressure, and flow from an air source using various control means to aid with accomplishment of the function of combustion completion.
  • the air source may be a high pressure source of compressed air or from any of a variety of blowers or other air moving means.
  • Flows from "passive secondary air” are set by the geometry of the air inlets, internal structures and overall combustion chamber size parameters, and vary with the rate of expansion of gas from combustion of the air-fuel dispersion and its mass flow.
  • three half inch copper lines 215 feed nozzles 213 comprised of an end cap with a l/16th inch hole.
  • each nozzle is aimed toward the center axis of the combustion enclosure upward at a 45 -degree angle.
  • the flow is high speed to accomplish second stage completion.
  • Caps of various nozzle hole sizes and dispersion angles were utilized in tests at numerous flow conditions for primary air, solid fuel mass flow rate and active secondary air flows. For a given air- fuel dispersion mass flow setting, increasing active secondary air flow lowers the height of the flame 216 protruding from the burner exit by completing more combustion within the second stage of the burner enclosure.
  • the vertical position of the deflagration flame wave front shown in Fig. 2 IB is controlled based primarily on fluid mechanics and combustion kinetics process parameters and their mathematical response surfaces.
  • the position of the flame front in the first stage is rather high, indicating a high primary air flow velocity component of the air-fuel explosible dispersion mix.
  • the height of the stationary deflagrating combustion wave is considerably lower.
  • Fig. 22A shows a ruggedized and taller version 220 of the original burner design, fabricated using heavy gage steel nominal 6-inch diameter stove pipe components and cast iron pipe fittings connected to the combustion enclosure.
  • Fig. 22B graphically illustrates the simplified burner combustion system basic processes utilized for the stove pipe burner of Fig. 22A. It is the most general illustration of transition from the flowing fuel dispersion to the deflagrating combustion process.
  • Powdered solid fuel is delivered by the auger 221 at a controlled rate into the turbulent mixing zone 222, in this case a large "T" fitting.
  • High velocity air flows vertically from the eXair amplifier 223, ideally breaking up any remaining agglomerate, and entraining the fine explosible powder particles into a dispersion for delivery vertically into the base of the combustion chamber generically referred to as the burner.
  • the air-fuel dispersion emerges from the nozzle 224, in this case %-inch ID, in stream flow at a velocity about double the flame speed and a concentration approximately four times stoichiometric.
  • the Bernoulli Principle affects the dispersion, slowing the speed and widening the fluid stream 225, decreasing air-fuel equivalence ratio.
  • the recirculation and turbulent mixing are critical to establishing and maintaining support for combustion. Ignition establishes a stationary deflagrating flame wave front at some vertical position above the nozzle, based on the actual process flow settings and fluid mechanic responses.
  • Vigorous combustion in the first stage reaction zone at the flame wave front nearly instantaneously consumes the particles, with the heat of reaction transferred from the gas to the particles by conduction in this narrow zone. Combustion continues until all of the available oxygen arriving in the primary air- fuel stream is consumed. Gas expansion continues, further adding to the turbulence and recirculation, and the unburned dispersion travels upward at combustion temperature, until finally encountering a fresh supply of oxidizer at the burner top, whereby the remaining fuel burns 227 to completion well above the stove pipe burner exit, beyond where we want the second stage to be.
  • Fig. 23 A adds four one -inch passive secondary air holes 232 to the design of Fig. 22A.
  • Fig. 23B graphically illustrates the simplified burner combustion system basic processes with the added benefits of passive secondary air 234 at the burner base.
  • the induced flow of air increases combustion within the enclosures first stage area.
  • the oxidizer supply runs out in all air- fuel mass flow except the lowest flow conditions.
  • the flame 236 height in Fig. 23B is shown lower than that in Fig. 22B, indicating increased combustion completion occurred within the burner enclosure itself.
  • An added benefit of this use of passive secondary air is increased flame front stability with improved mass-flow dynamic range of operation, specifically a larger turn-down ratio.
  • Figs. 24A, 24B, and 24C demonstrate the relationship between the carrier gas primary air flow rates at a constant high powder mass flow and the resulting flame height 242, 244, 246 emerging from the burner 240 top for a basic six inch stove pipe burner with no secondary air flow and three settings of low (Fig. 24A), medium (Fig. 24B), and high (Fig. 24C) primary air flow.
  • the low primary air flow shown on the left has the tallest flame height 242. At first this seems counterintuitive. At such a low flow, a high equivalence ratio, very little of the bulk fuel loading is completed inside the burner in the first stage. Therefore, this rather unstable flame completes upon exit at the top exhaust.
  • Figs. 25 A, 25B, and 25C illustrate the relationship of the flame height 251, 252,
  • Fig. 25 A shows the tallest flame height 251, as a low amount of active secondary air is supplied, thereby requiring a substantial portion of the combustion to complete by virtue of room air available to the hot oxygen starved mixture at the top of the burner exit.
  • Fig. 26A shows the configuration and internal combustion structure for a 24-inch tall by 8-inch diameter stove pipe burner 260, with 4 passive secondary air holes 262 and two multi-holed, internal vertical air tubes 264 that provide active secondary air to insure combustion completion in the second stage inside the burner.
  • Fig. 26B graphically illustrates the complete operation of this vertical explosible powdered fuel burner system fed from the positive displacement powder dispersion system's mixing system through to the exhaust outlet of this 8-inch diameter burner, with a focus on the internal combustion processes fluid mechanic and kinetic processes.
  • the lower first zone 266 called the first stage, is a low speed process, with ignition by an igniter 261 and initial combustion near the base; and the second 268 called the second stage, a high speed combustion completion process driven by high speed active secondary air in the upper burner section.
  • annular combustion front at the bottom or initial surface of the flame front. This is a fuel rich zone or volume with the initial fuel-air (fuel-gas) dispersion arriving in the base of the burner at a velocity near double the flame speed.
  • This combustion front does not initially exhibit cross-sectional uniformity. It is predicted and can be observed that most of the initial burning takes place in a hollow, diverging volume characterized by high speed, rich and unignited flow in the center, with lower speed turbulent combustion wrapped around and forming the outside of the burning volume.
  • the powder-air stream is partially burned crossing the ignition wave front of the flame. This burning continues to consume and complete particle combustion until the locally available oxygen is spent. The remainder of the unburned or partially burned fuel suspension, raised above ignition temperature, moves away from the first stage zone combined with nitrogen gas, CO 2 , and zero free oxygen.
  • this superheated fuel rich, oxygen depleted annular powder cloud proceeds into the second stage combustion zone where it encounters a high speed uniform and concentric oxygen rich flow of active secondary air, rapidly burning completely.
  • Room temperature secondary air at reasonably high velocity and/or flow rates can enter this more stable second stage combustion zone, superheated greater than the combustion temperature, with an intense air stream at much higher velocity without flame blow out than is possible in the first stage initial combustion zone.
  • the size of the burner combustion enclosure volume is primarily dictated by the BTU/hour rate planned for normal operation, even though we have a remarkable and uniquely high dynamic range of operation for a solid fuel combustion device, typically a 10:1 turndown ratio. For a burner this large, it makes sense that at low flow rates the width of the 8-inch burner is close enough to "free space" that its performance declines. This 200,000 BTU/hour embodiment is therefore not normally intended for continuous operation in the 10 - 20,000 BTU/hour range.
  • Fig. 27 shows a very robust system of supplying active secondary air to the second stage upper combustion zone of a 6-inch steel stove pipe burner 270.
  • three half inch copper tubes are run on the outside of the burner steel enclosure at a separation of 120 degrees around the vertical axis. Each tube is closed off with an end cap on a 45 -degree street elbow, having a 1/16th inch hole for the nozzle orifice. The three nozzle end caps penetrate the side of the combustion chamber sidewall in a similar manner to the following embodiment.
  • Fig. 27 utilizes four copper active secondary air tubes 272, each 3/8-inch in diameter, running up the outside of the stove pipe combustion enclosure. These tubes are bent at about 75 degrees to the vertical, with nozzle end caps penetrating the enclosure. Both include passive secondary air holes 274 near the base. We found air jets located at or near the circumference of the burner aimed inward at about 15 degrees off the burner flow axis performed well.
  • An explosible dispersion is developed and kept stable by a number of techniques with special emphasis on three: maintaining the turbulent energy level inside burner; feeding the dispersion of individual explosible particles into the combustion chamber at a sufficient velocity with adequate primary and secondary air to insure a non- lazy suspension of all fuel particles for combustion; and avoidance of collision with structures or other particles which encourage agglomeration formation and growth.
  • the explosible dispersion begins at the exit of the auger within the positive displacement powder dispersion delivery means (PDPD), although problems with particle size maintenance issues may begin far upstream of this location and can possibly continue downstream as well.
  • PDPD positive displacement powder dispersion delivery means
  • the powdered fuel is subject to the forces of handling, storage and metering prior to final air- fuel mixing, ignition and combustion. These processes introduce mechanical shear, which combines with humidity and the fibrous nature of biomass, to produce agglomerate, larger particles comprised of many small ones.
  • Fig. 28 shows internal flow and recirculation patterns in a 6-inch steel stove pipe burner 280 fitted with a 30-degree sloped cone insert 281 at the base to perform unburned particle and agglomerate recirculation and mixing.
  • the internal flow and turbulent recirculation patterns are shown by the arrows in this totally enclosed burner without the benefits of passive secondary air.
  • the hole in the bottom of the cone is wide enough to allow the vertical primary air- fuel dispersion to flow upward, unimpeded.
  • any type of particles, from powder to oversized powder particles to agglomerate 282 that is caught up in the recirculation turbulence and falls out of suspension is gently directed back toward the vertical flow stream 283 for re-entrainment.
  • Fig. 29A shows an alternate agglomerate recirculation and mixing embodiment strategy employing four passive secondary air inlet holes 291 combined with vibration 292 in a similar 6-inch stove pipe burner 290.
  • the goal is to compare the effectiveness with the 30-degree cone approach used in Fig. 28.
  • the internal flow and turbulent recirculation patterns are shown by the arrows in this burner with an improvement in vertical flow and stronger recirculation turbulent mixing.
  • a vibration apparatus 292 is attached to the bottom of the burner, causing any particles or agglomerate fallout to dance on the bottom of the burner.
  • This vertical vibration energy when combined with the cross burner "sweeping" function performed by passive secondary air, encourages particle and agglomerate fallout to move toward and be entrained by the high velocity vertical premix dispersion flow.
  • Fig. 29B is a magnified view of the lower right section of the burner of Fig. 29A, showing how the "sweeper" air recirculates unburned "dancing particles" comprised of agglomerate, individual or oversized particles 293.
  • the use of a vibration apparatus 292 encourages this vertical dancing or bouncing, so the wide range of flow from the passive secondary air holes can move any fallout back toward the high premix flow for return to the stationary deflagrating wave for combustion.
  • Fig. 3OA combines the strengths of methods detailed in Fig. 28 and Fig. 29B and improves on them by raising a wide hole version of the 30-degree cone design upwards enough to allow passive secondary air 301 entering from below through four 1-inch holes 302 to assist with lifting and entraining fallout particles 303 gathered by the cone back toward the stationary deflagrating flame wave front.
  • Burner design 300 combines both recirculation and passive secondary air together to further improve functionality. With more oxygen available in the first stage combustion zone, the resulting flame height 306 at the burner top exit is therefore decreased.
  • an embodiment of our system design drops the fuel including some aforementioned agglomerate into a sufficiently turbulent air stream.
  • This turbulence de-agglomerates the substantial majority, dispersing it in a manner sufficient to result in near complete combustion (99.8%+) in a fraction of a second.
  • Fig. 30B is a magnified view of the bottom section of the burner of Fig. 30A, with arrows showing how the recirculation flow patterns above the elevated 30-degree wide mouth cone 304 encourage particles 303 back towards the vertical and rising premix dispersion.
  • These functions combine with flow from the passive secondary air holes 302 which rises coaxially around the dispersion, concentrated by the wide hole in the cone. By focusing and restricting the area for this secondary flow, its ability to lift particles and small agglomerate for recirculation is significantly improved.
  • Fig. 31A shows a burner of the present invention with an ultrasonic agglomerate lump dispersing screen system 311 in the lower section of the burner enclosure.
  • the vertical flowing air- fuel dispersion stream 312 flows through the center of the screen 311 towards the stationary flame wave front 313.
  • some agglomerate may resist complete destruction by the previously disclosed intensely turbulent air stream and configuration of the mixing zone alone. Rather they can become smaller, smoother and more rounded agglomerate.
  • the vast majority of the agglomerate problem may be solved by judicious use of an agglomerate destructor screen, shelf or table-like structure, powered by an ultrasonic transducer driven by advanced signal processing techniques, including a multi-frequency spread spectrum type of signal.
  • the screen does not necessarily have to be quite as fine as the final mesh size of the original individual particles, just with small enough openings to impart adequate energy to the agglomerates to disintegrate them into their original individual particle constituents, which subsequently flow through the screen unimpeded.
  • any agglomerates are formed downstream of this deagglomeration stage through collisions, such as particle-to-particle or with flow conduit walls and fittings, they must be dealt with separately in the burner through various methods described in our unique and inventive methods for agglomerate destruction, collection and recirculation found in this disclosure. These techniques are outlined in descriptions of several burner design configurations which follow, and in combination, constitute further inventive disclosure.
  • a top view example of a general design for an ultrasonic agglomerate lump destructing screen appears like the head of a tennis racket.
  • the hole 314 in the middle is of adequate diameter for the still essentially laminar vertical high speed primary air-fuel dispersion to flow through without particle collisions.
  • the screen is shown mounted by four vibration isolation points 315 inside the 6-inch diameter burner enclosure 310, and connected to an ultrasonic transducer 316.
  • Fig. 32 shows the combination of an elevated 30-degree wide holed cone 322 with an ultrasonic lump destruction screen 324 driven by a transducer 328 to comprise an agglomerate recirculation and dispersion system, augmented by baffled passive secondary air in a 6-inch vertical burner 320.
  • Particles 321 from agglomerate 326 fall through the ultrasonic destructor screen, and through the mechanisms of burner enclosure low frequency vibration and internal air recirculation, find their way to the edge of the cone's central hole 323 where they are swept up and transported as fresh reactant back towards the reaction zone 327 by a combination of eduction from the high speed air- fuel stream and the up-rushing lift from secondary air flow 325 around the flow stream 329.
  • Fig. 33 shows one type of "top hat” flow restricting reducer 332 mounted atop the 6-inch burner of Fig. 27.
  • This 8-inch to 6-inch reducer set atop a 6-inch burner 330 allows a passive or active tertiary air flow 336 to aid with final combustion completion, while still offering some flow restriction on the burner exit throat 334.
  • An alternative embodiment to further restrict outlet flow uses a tight fitting 6-inch to 4-inch reducer 334, thereby eliminating the simple one inch circular tertiary air inlet 336, which can be accomplished by different means if desired.
  • Fig. 34A depicts a early horizontal combustion and powder dispersion feed system using a four inch can burner 340 with passive secondary air.
  • the powder is fed by an auger 344 into a tee fitting where it drops down through conduit 346 and into an inverted tee fitting. There it encounters high pressure air from inlet 347 which breaks up much of the agglomerate from screw feeding, and is turbulently mixed with sufficient primary air to supply the eXair /4-inch air amplifier 348.
  • the dispersion is further improved by this operation, with more agglomerate breakup, then sent in a fuel rich flow dispersion toward the nozzle 343 where it enters the simple combustion enclosure and is ignited.
  • Fig. 34A depicts a early horizontal combustion and powder dispersion feed system using a four inch can burner 340 with passive secondary air.
  • the powder is fed by an auger 344 into a tee fitting where it drops down through conduit 346 and into an inverted tee fitting. There it encounter
  • FIG. 34B is a sectional view of the four-inch burner can 340 showing one of four passive secondary air holes 342 and primary air-fuel connection 343 from the powder dispersion feed system.
  • Fig. 35 diagrams the internal geometric and combustion structure of a 4-inch horizontal burner assembly 350 with novel passive secondary air management accomplished by dual coaxial enclosures 350, 352. Many of these concepts are present in today's high capacity 1 MM BTU/hr horizontal burner.
  • the primary air- fuel mixture is fed into the nozzle located in the 3.5-inch diameter inner enclosure 352 as detailed in Figs.
  • Ignition occurs a few inches downstream from the nozzle and combustion proceeds into the outer 18-inch long six inch diameter steel tube 350.
  • Passive secondary air 359 finds its source in large air inlets 356 and 358, and is guided around the first stage reaction zone protected by enclosure 352 through a circular channel 354 between the inner and outer enclosure.
  • 355 is an angled cowling to direct the secondary air toward the second stage combustion zone.
  • 355a is similar to 355 and has the same function, but has a less abrupt angle.
  • Airflow 357 is our classic passive secondary air feeding the first stage. The remaining combustion takes place at the exit of the long tube horizontal burner, sourced by outside air, and the flame 351 curls upward as final gas expansion takes place.
  • This embodiment is easily extensible to the use of active secondary air through inlets 356 and 358, and controlled by choice of the gap 354 between the two enclosures.
  • Fig. 36 shows a 4-inch diameter horizontal burner 360, fabricated in steel with four active secondary air tubes 362 intended for prototype testing as a direct retrofit into an oil- fired furnace. It utilizes passive secondary air through four holes 363 to achieve a tall, horizontal version of the vertical burner in Fig. 27. This burner has been highly tested and is ready for prototype trials in a formerly oil-fired furnace, delivering 200,000 BTU/hour.
  • Fig. 37A graphically depicts a basic recycle collecting horizontal burner 370, tilted up 372 preferably by about 3 to 5 degrees above horizontal for agglomerate and oversized particle collection.
  • a vibrator or ultrasonic transducer 374 causes high-frequency vibration of the burner, which allow agglomerates and oversized particles 376 to move back in the burner toward an opening and into a collection vessel 378.
  • the unburned fuel collected in the collection vessel 378 may be reprocessed to an explosible form or discarded.
  • Fig. 37B graphically depicts a basic recycle collecting horizontal burner 370, tilted downward 373 preferably by about 3 to 5 degrees below horizontal for front end agglomerate and oversized particle collection.
  • a vibrator or ultrasonic transducer 374 causes high-frequency vibration of the burner, which allow agglomerates and oversized particles to move forward in the burner toward an opening 377 and into a collection vessel 378.
  • the opening 377 is preferably at the end of the burner but may be located back from the end slightly.
  • the opening 377 may also be formed as a spout to better direct the agglomerates and oversized particle to the collection vessel 378.
  • the collection vessel 378 is preferably large enough to require only occasional emptying. Unburned fuel collected in the collection vessel 378 may be reprocessed to an explosible form or discarded.
  • Fig. 38 shows a more automated recycle consuming gravity collecting closed loop solid fuel horizontal burner system with agglomerate and oversized particle reprocessing and reintroduction into the air- fuel dispersion.
  • the burner 380 is tilted upward 382, preferably by about 3 to 5 degrees.
  • a vibrating or ultrasonic transducer 384 causes high-frequency vibration of the burner, which nudge agglomerates and oversized particles to move back in the burner toward a recycle system.
  • the particles fall toward a recycling device 386, which sends the particles along a recycle path 388 feeding into the main powdered fuel dispersion stream, or into the mixing system.
  • the recycle system preferably provides agitation or grinding to break the agglomerates into small particles.
  • Fig. 39A shows a recycle agglomerate destructing horizontal burner 390 using an ultrasonic driven screen 394 for deagglomeration.
  • the burner is preferably tilted up 392 by about 3 to 5 degrees.
  • An ultrasonic transducer 396 causes high-frequency vibration of the screen 394 to break up agglomerates falling onto it and vibration of the burner 390, which allows de-agglomerated particles to move back in the burner toward an active secondary air flow source 398, which recycles the particles back toward the main powdered fuel dispersion stream.
  • Fig. 39B shows an end view of the recycle agglomerate destructing horizontal burner 390 showing the presence of the ultrasonic screen 394 across the lower portion of the burner and a trough for particle collection and movement.
  • Fig. 4OA shows a piping drawing detail of a preferred mixing zone and infeed for horizontal burners.
  • a horizontal auger 403 feeds powdered fuel which mixes with oxidizing gas entering at hole 401.
  • the dispersion then travels down a vertical conduit 405 to a horizontal conduit 404, where additional oxidizing gas is added at point 402 before the dispersion travels through an eXair amplifier 400.
  • the burner of Fig. 4OB adds an ultrasonic deagglomeration screen with an ultrasonic transducer 406 in the mixing zone 405 to the piping interconnection drawing of Fig. 4OA for horizontal burners.
  • Fig. 41 graphically shows a wide range, upward vertical to horizontal to downward vertical orientations possible for the disclosed solid fuel explosible powder burners.
  • About a 0-degree orientation burner 410, about an 45-degree orientation burner 412, about a 90- degree orientation burner 414, about a minus 90-degree orientation burner 416, and about a minus 45-degree orientation burner 418 of the present invention are shown in Fig. 41.
  • Downward burners have to fight gravity to keep the combustion reactants suspended and under control. Explosible mixture feed velocity is lowered to maintain the stationary deflagration wave at about the same location. More work is performed by combustion gas expansion and its tendency to rise. Active secondary air near the burner base becomes important for first stage turbulent mixing at lower dispersion stream infeed velocities. Downward burners require a finer with the least oversize fuel particles, unless used in a "sloppy fuel" application.
  • Fig. 42A depicts our current IMM BTU/hr burner slated for test on a grain drier.
  • This coaxial unit uses an inner first stage combustion enclosure 420 with passive secondary air holes 421.
  • Active secondary air 422 is fed through one or more supply hoses 422ato a circular plenum 423 formed by larger outer enclosure 424 and an outer collar 423. Heading for the second stage combustion completion zone, the active secondary air is fed through an angled directing slot in circular insert 425 a and emerges at speeds up to 1Ox times the powder flame speed to mix the hot particles and supply necessary oxidizer for combustion completion.
  • Optional swirl vanes circumferentially mounted in the coaxial air channel as in Fig. 35 may be used for additional second stage combustion zone support.
  • Fig. 42B is uses the Fig. 42A design and simply adds active secondary air to the first stage burner enclosure sides near the nozzle end to promote better control of the recirculation and flame support functions.
  • One or more supply hoses 428 feed the oxidizing and support air 421 into a collar or plenum 428a for distribution.
  • Fig. 43 is a system level block diagram of a furnace for heating with explosible powder fuel.
  • a PDPD system comprised of an oxidizing gas feed 4310, a powder fuel feed 4312 with hopper 4314 and a mix zone 4316, feeds the dispersion to the burner 4318, which exhausts into the furnace heat exchanger4320. Flue gas 4321 continues through a heat recovery exchanger 4322, then a particle filtration system 4324 where air entrained ash is removed and stored 4326 for disposal. The flue gas exhausts to atmosphere 4335.
  • a heating fluid 4328 circulates through the furnace heat exchanger 4230, then to the main heat load 4330, returning low temperature fluid back through a heat recovery exchanger 4322.
  • the burner system, external powder storage 4332 and flue gas particle filtration systems 4324 comprise a unique to adaptation to a furnace for explosible powder fuel direct energy conversion to produce heat.
  • Fuel parameters must be mentioned since they impact on techniques to maintain a completely explosible combustion regime and ties to burner design choices and operation.
  • Particle size is important, and the "quality" of that distribution determines the ability of the burner combustion process to run most efficiently and cleanly in the explosible zone, our claimed region of operation.
  • the primary focus is on minimizing oversize particles, ones with a diameter/length over the explosibility threshold for that material (-200 microns for wood), when it comes to the particle size distribution's upper/outer limit composition as a percentage of the entire distribution.
  • a mixed flow of 200 and 100 micron diameter particles will be explosible, if the air-fuel equivalence ratio is in the correct range. With particles on the large side close to the explosible transition line, getting a proper dispersion of air and powder is more difficult. As a rule of thumb, as particle size is slowly reduced, explosible behavior shows up long before it becomes easy to keep the population of particles in suspension.
  • burner systems and methods disclosed herein may be applied for heating or energy purposes to a variety of device applications including, but not limited to, furnaces, engines, boilers, grain dryers, clothes dryers, hot water heaters, combined furnace/water heaters, hot air balloons, space heaters, wood burning stoves, gas fireplaces, gas turbines and electrical generators, forced hot air heating systems, forced hot water heating systems, forced steam heating systems, and radiant heating systems.
  • Additional devices include ovens, absorption chillers, ammonia cycle refrigeration, patio heaters, heating torches, controllable fire pits, continuous water heaters, booster and inline water heaters, yellow flame gas log sets, inserts, freestanding stoves and built in zero clearance fireplaces, radiating stoves and furnaces, outdoor wood boilers, industrial furnaces and boilers, corn stoves, pellet stoves, coal stoves, entertainment controllable torches, pyrotechnic type displays, and steam engines by replacing or supplementing existing combustion devices with powder burning devices.
  • an apparatus for combustion of a fluent fuel may be made to many self-contained devices, but are often part of, or used in connection with, heat-consuming apparatus, such as heating furnaces and boilers.
  • our burner apparatus may be considered a subsystem detail of a larger end product entity.
  • a burner of the present invention may be adapted for use in any types of furnaces, boilers, and other heating systems such as but not limited to those today typically fueled by oil, natural gas, and LP gas.
  • a burner of the present invention may also be adapted for use in an existing system of any of the applications mentioned above.
  • burner technology means, methods, and apparatuses are also intended to be adapted to existing heat exchange furnace and other systems, or designed for installation in new heat exchange furnaces and other systems, as described above.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combustion Of Fluid Fuel (AREA)

Abstract

L'invention porte sur un brûleur brûlant, de préférence exclusivement, des combustibles solides sensiblement explosifs et, de préférence, a une commande de thermostat MARCHE-ARRET, ne gaspille pas d'énergie en préchauffant l'enceinte ou une alimentation en air externe, permet d'obtenir une combustion stable dès l'allumage du mélange poudre-air dans le brûleur, est utilisé dans le mode vertical vers le haut à l'exception de rattrapages de brûleur à pétrole, brûle un combustible solide dans un régime à unique phase comme s'il s'agissait d'un liquide vaporisé ou d'un gaz, est conçu pour achever la combustion à l'intérieur du boîtier de brûleur lui-même plutôt que dans une enceinte de four grande et à haute température qu'il alimente, a une exigence de temps de résidence ultra-court, est un brûleur à consommation recyclée avec une gestion auto-contenue de particules initialement non brûlées, est bien plus petit et plus simple et a un coût plus faible, a une plage dynamique/débit moyen plus large, est plus efficace en termes de caractère complet de la combustion et en termes de rendement thermique, et fonctionne avec un mélange air-combustible approximativement à la vitesse de flamme.
EP09729630A 2008-04-07 2009-04-07 Systemes et procedes de conversion de combustible en poudre Withdrawn EP2279378A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US4299608P 2008-04-07 2008-04-07
US7424408P 2008-06-20 2008-06-20
PCT/US2009/039820 WO2009126660A2 (fr) 2008-04-07 2009-04-07 Systèmes et procédés de conversion de combustible en poudre

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EP2279378A2 true EP2279378A2 (fr) 2011-02-02

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EP (1) EP2279378A2 (fr)
KR (1) KR101547583B1 (fr)
AU (1) AU2009233850B2 (fr)
CA (1) CA2720970A1 (fr)
WO (1) WO2009126660A2 (fr)

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CN102012028A (zh) * 2010-12-28 2011-04-13 东莞市嘉品电器有限公司 喷气式燃气炉的燃气混合系统
CN102410534B (zh) * 2011-10-25 2013-12-25 无锡中阳新能源科技有限公司 一种太阳能塔热气流发电辅助热力装置
WO2013082146A1 (fr) * 2011-11-28 2013-06-06 Scott Laskowski Brûleur de combustible de biomasse non catalytique et procédé associé
JP6188658B2 (ja) * 2014-09-24 2017-08-30 三菱重工業株式会社 燃焼バーナ及びボイラ
JP6632226B2 (ja) 2015-06-12 2020-01-22 三菱日立パワーシステムズ株式会社 バーナ、燃焼装置、ボイラ及びバーナの制御方法
CN106369630A (zh) * 2016-08-30 2017-02-01 济南同智创新能源科技股份有限公司 一种应用于火炬系统的安全节能燃烧控制系统和方法
CN106766973B (zh) * 2016-12-20 2019-04-26 四川金象赛瑞化工股份有限公司 一种氧化炉工艺联锁控制方法
CN108488784B (zh) * 2018-01-30 2020-10-02 中国神华能源股份有限公司 一种煤粉燃烧锅炉系统以及煤粉燃烧锅炉运行方法
RU2686138C1 (ru) * 2018-02-26 2019-04-24 Общество с ограниченной ответственностью "Новые физические принципы" Способ получения сильно перегретого пара и устройство детонационного парогенератора (варианты)
CN111239053A (zh) * 2018-11-28 2020-06-05 中国科学院大连化学物理研究所 一种动态质量重置法检测化合物临界聚合浓度的方法
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EP4341611A2 (fr) * 2021-05-19 2024-03-27 ClearSign Technologies Corporation Brûleur à faible émission de nox et à haute performance et système associé
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KR20110091437A (ko) 2011-08-11
KR101547583B1 (ko) 2015-08-27
WO2009126660A3 (fr) 2010-01-07
CA2720970A1 (fr) 2009-10-15
AU2009233850A1 (en) 2009-10-15
AU2009233850B2 (en) 2014-04-10
WO2009126660A2 (fr) 2009-10-15

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