US 2009/0274986 A1Published application

Merging combustion of biomass and fossil fuels in boilers

OwnerWilliam Arthur Walsh, JR.inventor

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Abstract

A method of injection and combustion control and related injection nozzles and lances are described which facilitate the merging of the combustion of fossil fuels and separately added solid biomass waste product fuels in the form of pelletized chars and fine particulates. The teachings of this inventor's earlier patent, “Variable Gas Atomization,” U.S. Pat. No. 4,314,670, (referred to herein as VGA) are employed. They are applied in a distinctly different manner so as to enable air conveyed and injected solids to be accelerated, propelled and distributed in the combustion zone of fossil or biomass fuel boilers. While the use of an annular nozzle configuration with conically flared exit tips is generally similar, the functions to be performed, and the related conical exit configuration, differ. An assembly of five concentric, annular tubes and conically shaped exit tips is used to deliver air conveyed biomass fuel as an annular stream between two higher velocity air streams, both of which converge so as to accelerate and propel the biomass fuel, and distribute it into the flame zone produced in a conventional fossil fueled boiler. The additional air required for combustion of the biomass fuel is fed to the expanding plume produced by the fuel delivery stream and adjoining air streams. A portion of the combustion air is delivered through the inside of the inner tube in sufficient volume to provide the entrainment flow produced by the expanding air streams. In so doing, it prevents undesirable recirculation of combustion gases and unburned fuel. The remainder of the combustion air is delivered through an additional annular nozzle located on the opposite side of the expanding streams to similarly mix with the fuel.

Claims2

Dependent claims

With a nozzle assembly consisting of a series of circular, cylindrical tubes assembled to provide concentric annular channels for the passage of fluids, the method of injecting, accelerating and propelling solid biomass fuel pellets, which generally have a diameter, or other maximum dimension, shape or surface characteristic that prevents passage through the nozzle, of at least ¼″, or other, finer, solid, biomass fuel particulate matter, together with the additional air required for complete combustion of the injected fuel, into the flame zone of a combustion chamber burning fossil fuel in a manner that provides controlled, merged combustion of the fuels, comprising the following steps:

(a) forming an annular nozzle-exit stream of carrier-air-conveyed solid biomass fuel consisting of pellets and/or other fine particulates;
(b) forming two annular, nozzle-exit streams of air flowing at nozzle exit velocities higher than that of the biomass fuel bearing stream, but less than sonic velocity (upstream delivery pressures less than 15 psig.) adjacent to the biomass conveying stream, one on each side of it, flowing in substantially the same direction but directed so as to immediately converge with it at a small relative angle, and each flowing at a velocity higher than that of the biomass conveying stream;
(c) forming a cylindrical stream of air that exits along the central axis of the annular nozzle at lower velocity than the adjoining air stream, provides a portion of the biomass combustion air, assists in the forming and controlling of the shape and length of the biomass fuel flame zone and furnishes the air for entrainment by the adjacent flow of higher velocity air that would otherwise be re-circulated back along the nozzle axis from the flame zone in the form of undesirable eddy current recirculation of combustion gases and particulates;
(d) forming an annular nozzle exit stream of additional combustion air, located radially outward from the outer of the two compressed-air produced streams, and flowing in substantially the same direction as the other streams but directed so as to immediately converge with them in sufficient quantity to complete the biomass fuel combustion, and to assist in the forming and controlling of the shape and length of the biomass fuel flame zone;
(e) adjustably controlling the widths of the exit streams, the quantities flowing, the acceleration and propulsion of the solid biomass fuel and the shape and length of its flame zone to suit the physical properties of the biomass fuel.

2 more elements

A biomass fuel injection nozzle assembly comprising:

(a) five concentric, circular, cylindrical-tube subassembly members, identified for reference herein as members 1, 2, 3, 4 and 5, in order of their increasing diameters, forming an axially central cylindrical channel and four concentric annular channels;
(b) each subassembly tube being permanently attached at one end to a heavier walled cylindrical section fitted with ports allowing passage of fluids to the respective annular channels and fitted to allow relative axial movement of the respective subassemblies;
(c) each subassembly tube being attached at its opposite end to removable exit nozzles, identified for reference herein as members 6, 7, 8, 9 and 10, in order of their increasing diameters;
(d) the annular channel formed by members 2 and 3 being assigned to delivery of air conveyed biomass fuel pellets or finer particulates;
(e) the annular channels formed by members 1 and 2, and by members 3 and 4, being assigned to delivery compressed air;
(f) the axially central channel formed by member 1 and the annular channel formed by members 4 and 5 being assigned to delivery of combustion air;
(g) the outer and inner surfaces of exit member 8 being equally tapered at a pre-selected angle ranging from 5 and 10 degrees at the nozzle exit tip to an annular exit tip width of 0.04 to 0.06 inches;
(h) the outer surface of member 7 being flared outwardly at its exit end at a pre-selected angle ranging from 5 to 20 degrees relative to the nozzle axis and extending to a diameter equal to that of the inner diameter of the tubular portion of sub-assembly 3;
(i) the inner surface of member 7 being similarly flared at an angle 10 degrees greater than that of its outer surface, and enlarged in diameter sufficiently to form an annular tip width of 0.04 to 0.06 inches;
(j) the outer surface of member 6 being flared outwardly at its exit end at a pre-selected angle ranging from 5 to 10 degrees greater than the angle of the flared inner surface of member 7 and extending to a diameter of 0.1 inches less than that of the inner diameter of the end of member 7;
(k) the inner surface of member 6 being similarly flared at an angle 5 to 15 degrees greater than that of its outer surface, and enlarged in diameter sufficiently to form an annular tip width of 0.04 to 0.06 inches;
(l) the outer diameter of member 9 being decreased at a pre-selected angle ranging from 25 to 30 degrees relative to the nozzle axis at the nozzle exit and decreasing to a diameter equal to that of the outer diameter of the tubular portion of sub-assembly 3;
(m) the inner diameter of member 9 being similarly decreased at an angle of 10 to 20 degrees relative to that of its outer surface and decreased in diameter sufficiently to form an annular tip width of 0.04 to 0.06 inches;
(n) The inner diameter of member 10 being decreased at the nozzle exit end at the same angle as that of the outer end of member 9, to a diameter at its end equal to the outer diameter of the tubular portion of sub-assembly 4;
(o) The outer diameter of member 10 being beveled at its end a 45 degree angle to a radial width at its end of ¼ to ½ inches.

12 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/386,756Filed 22 Apr 2009
Priority: 30 Apr 2008
Published: 5 Nov 2009
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

F23G 5/008
Incineration of waste ; Incinerator constructions; Details, accessories or control therefor: adapted for burning two or more kinds, e.g. liquid…
F23C 1/06
Combustion apparatus specially adapted for combustion of two or more kinds of fuel simultaneously or alternately, at least one kind of fuel…
F23G 7/105
Of field or garden waste or biomasses: of wood waste
F23G 2204/101
Using auxiliary fuel: solid fuel

Family

Application61/125,995Us provisional application · filed 30 Apr 2008
US 7,832,341 B2Related patent
US 2009/0274986 A1This patent

From the US filing history. Foreign family members aren’t listed.

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