Furnaces – Utilizing powdered fuel – Having rotary flow means
Reexamination Certificate
1999-07-29
2001-08-07
Ferensic, Denise L. (Department: 3749)
Furnaces
Utilizing powdered fuel
Having rotary flow means
C110S261000, C110S262000, C110S265000, C110S263000, C110S210000, C110S214000
Reexamination Certificate
active
06269755
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is in the field of industrial burners and incinerators and, more particularly, relates to new industrial burners for combustion of particulate fuels such as wet or dry sawdust and many types of varying moisture content biomass fuels including, agricultural products, wood waste, bagasse, poultry waste, and other cellulosic materials, and especially in the wood products manufacturing or processing operations, including combustion of smoke or other combustible gases produced by processes relating to such products and other gases, such as industrial off-gases, and specifically operating with high turndown ratios and high heat release ratios.
2. Related Art
In the general field of burners and incinerators for industrial purposes, there are myriad different configurations, wherein there has for many years been an increasing focus on efficiency and output. Thus, there have been proposals for swirling or cyclonic combustion and combustion chambers of unusual geometries, as well as many proposals for controlling the entry of air and fuel into the combustion chamber for contributing to swirling or other patters of combustion motion. There have been various burners proposed for burning, as feed stocks, organics or biomass materials, including so-called green (high moisture content) sawdust, solid cellulosic or wood-containing waste, waste wood, and fragments of wood, and all of which may herein be referred to as wood products.
In burners useful for burning such materials, there has been insufficient emphasis on achieving efficiency and flexibility which can result from achieving a high turndown ratio (which may for convenience be abbreviated “TDR”). Turndown ratio is the maximum firing rate of the burner divided by the minimum firing rate of the burner. Prior constructions have not achieved sufficiently high TDRs.
The provision of a high TDR for a burner capable of carrying out combustion of wood products is highly desirable, as such a burner would be capable of being operated over a great dynamic range. If, for example, in a manufacturing or materials handling operation which creates such wood products, which are to be combusted (as for heating or energy extraction for other processes or purposes), the use of a burner having a limited TDR can require that burner operation be terminated if wood product supply rates are insufficient to achieve the minimum firing rate of the burner. Or, if combustion of wood products at low feed rates is to be carried out, an auxiliary fuel such as natural gas, liquefied petroleum (LP) gas, propane, or fuel oil, may have to be fed into the burner for maintaining combustion. But, on the other hand if the burner is designed for burning wood products at low feed rates, its output may be insufficient to handle high feed rates when wood products to be combusted are being produced at high volumes. Further, if TDR can be increased, much less auxiliary fuel will be required to initiate burner operation.
As an example, in a wood products manufacturing or processing operations, very substantial quantities of green sawdust are created during sawing, planing, shaping, etc., but the rate of production of sawdust will be dependent upon the various wood-handling processes, which vary in rate, time of operation, and volume, so that sawdust may be produced at a highly variable rate.
If the sawdust is to be combusted by a burner for the purpose of extracting heat for other uses (such as heating, boiler operation, drying, etc.), the use of a burner having a high TDR enables its operation on continuous basis or at least for longer periods of operation, as desired.
In the wood products industry, as including also the production of charcoal, there is a need also for dealing with smoke and other gases produced during operations. For example, in cooperage operations where barrels are produced for aging of beverages, such as wines or brandies, etc., some types of barrels require that they be charred, as for the aging of various kinds of whiskeys. Charring operations produce smoke which may need to be combusted. So also, in charcoal kilns, the off-gases are sources of environmental pollution, and may also need to be combusted, i.e., by oxygenation combustion.
It would be desirable to combine a burner, capable of burning wood products for the above-noted purposes, with features for combustion of off-gases in the wood products industry.
Present burners in the wood products industries have not met the needs for these kinds of combustion, and have not achieved satisfactory TDR and efficiencies for acceptable usage in the wood products industries.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides various burner embodiments for burning particulate fuel such as so-called green (high moisture content) sawdust, various feed stocks, organics or biomass materials, including solid cellulosic or wood-containing waste, waste wood, and fragments or wood, and all of which may herein be referred to as wood products or particulate organic fuels or materials.
The invention is also concerned with such burners which are capable of combustion of gases, such as off-gases produced in the wood products industry, or other gases which are to be oxygenated or burned for conversion to a condition environmentally non-polluting.
Burners of the present invention achieve high efficiency and flexibility, particularly achieving a very high turndown ratio (TDR).
The inventive burners specifically achieve a high TDR while carrying out combustion of wood products. Burners of the invention are capable of being operated over a great dynamic range.
The new burners are especially useful in wood products manufacturing or processing operations, such as stave and barrel-forming (cooperage) operations which create very substantial quantities of green sawdust.
The new burners, because of their high TDR, efficiency and dynamic range, can be used in operation on continuous basis or for longer periods of operation, and at greatly variable output different as may be desired.
The new burners disclosed are capable of combustion of a high-moisture, low-Btu value fuels not only providing high turndown ratio but also achieving a high heat release ratio, meaning beat output per volume per unit of time. This allows a smaller size burner of the present invention than would be required in a prior art burner, and so the invention results in a burner of lower cost than heretofore.
Another feature of the presently inventive burners is the capability for designing the burners to a desired scale, as according to the intended mode of usage and industry segment in which the burners will serve. Thus, the present burners are easily scalable.
A further advantage of the inventive burners is their use of electronic controls using programmable logic controllers, for achieving precise, efficient, safe and reliable control and operation in all modes of usage.
Yet another feature of the inventive burners is a gas combustor for combustion of smoke and various combustible gases, including off-gases in the wood products industry, such as for example gases produced during cooperage operations and gases produced during the operation of charcoal kilns, as well as other industrial off-gases.
The presently inventive burners achieve satisfactory TDR and efficiencies for acceptable usage in the wood products industries.
In addition, burners of the present invention are economical in construction and operation and are easily installed and operated.
Briefly, the present invention relates to various burner configurations. Each burner of the disclosure exhibits a high turndown ratio for combustion of a principal fuel. The burner includes, or comprises, consists, of or consists essentially of a housing defining an upright combustion chamber lined with refractory material and generally circular in horizontal section, a main combustion region within an upper end of the combustion chamber, an initial combustion zone at a lower end of the combustion chamber of reduced-sized cross-section
Boswell John J.
Eichmeyer Dale R.
Ferensic Denise L.
Gilster Peter S.
Greensfelder Hemker & Gale, P.C.
Independent Stave Company, Inc.
Rinehart K. B.
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