Furnaces – Process – Treating fuel constituent or combustion product
Reexamination Certificate
2000-11-06
2002-04-09
Bennett, Henry (Department: 3749)
Furnaces
Process
Treating fuel constituent or combustion product
C110S346000
Reexamination Certificate
active
06367395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the disposal of animal waste, i.e., manure and is particularly concerned with a method of efficiently burning such waste material in a manner that is environmentally sound.
2. Prior Art
It has been estimated by the United States Department of Agriculture (USDA Report Misc. Pub. 1065, 1968) that nearly two billion tons of manure is generated annually in the United States. Using a density value of fifty pounds per cubic foot it has been calculated that this generated manure is enough to cover about thirty-five thousand square miles, i.e., the State of Indiana, with a one-inch layer annually. The problem is compounded by the fact that manure is produced in concentrated areas, such as feed lots, hog factories and large chicken factories, and in smaller animal processing operations, rather than being uniformly divided over the entire United States. Thus, large quantities need to be processed in local areas or both the large and small quantities need to be collected and transported to distant processing facilities.
Aside from the obvious odor problem associated with the processing of manure, other, not so obvious, problems exist. In many instances manure is mixed with water, as a result of the cleaning out of pens and stalls or by the falling rain and snow. The resulting contaminated water becomes a threat to streams, lakes and underground water supplies and ultimately to the drinking supply. Government agencies in areas of the United States having significant livestock operations are recognizing the dangers to the clean water supply and it has now become more difficult to obtain permits for large livestock operations in such areas. More recently it has become known that manure entering streams and lakes results in growth of organisms that attack and destroy fish in the streams and that even attack other animals and humans causing severe illness.
Even when used as fertilizer the animal wastes often present environmental problems that are costly and difficult to solve. For example, the manure generally contains weed seeds ingested by the animals with their feed grains. Present composting methods do not kill the weed seeds so herbicides are frequently added to the manure and when the manure is used as fertilizer the herbicide chemicals are added to the soil.
It is well recognized that when man creates environmental problems there is a cost associated with the clean-up or avoidance of the problem in the future. Trash dumped in the oceans, manufacturing process pollutants discharged into streams, rivers and lakes, exhaust emissions from automobiles and nuclear wastes are examples of environmental problems that are currently being addressed at great expense to the American taxpayer. Animal wastes represent just one more environmental problem that must be addressed to insure quality life for humans. Clearly, there is a need for methods and systems to dispose of manure, on-site, in a neat, cost effective manner.
At the present time current approaches to animal waste management are as old as the problem itself. Often it is merely spread on the ground as fertilizer or compost. Other times it is dumped into lagoons. Manure spread on the ground or placed in piles or in lagoons not only takes up large amounts of valuable ground space but creates incredible odors. The odors have resulted in the treating of the manure with chemicals to reduce or change the nature of the odors. The use of chemicals results in increased cost in the processing of the manure and the chemicals may not always be environmentally safe.
In most situations manure represents an expense and pollution liability rather than a marketable fertilizer product. In some instances, chicken litter (excreta and bedding material) can be used for cattle feed. In a limited number of areas manure is sold or given away. For most animal operations the manure is simply a nuisance. For producers unable to simply pile up manure there are, at the least, handling and transportation costs involved in moving the manure to a disposal location. Typically, for hogs, manure is produced approximately at the rate of two to three pounds per pound of weight gain. A hog will produce about six hundred pounds of manure over its four and one-half to six month life span. A producer marketing one thousand head per year would have about three hundred tons of raw manure to deal with. Since hog wastes are typically washed out of the hog pens, the total weight to be handled is probably three to four times the raw manure weight, or about one thousand tons. In addition to the costs involved in handling such large quantities of waste, it is noted that there are fewer and fewer locations where sites for the dumping of the large amount of waste can be handled. Consequently, the manure is confined to lagoons and becomes a nuisance to the producer and his neighbors.
There can be no doubt that there is a need for a method and system to dispose of manure, on-site, in a neat and cost effective manner.
SUMMARY OF THE INVENTION
1. Brief Description of the Invention
The present invention provides a method and system to combust manure. More particularly, using coal as fuel for the method of combustion.
2. Objects of the Invention
Principal objects are to provide a method and system for the burning of manure in an economical manner suitable for use by at least medium and large sized size animal operations.
Other objects are to provide for the processing of animal wastes to eliminate the health, safety and nuisance aspects while utilizing the inherent virtues of the material, i.e., its water content and its value as an energy source and as fertilizer. The heat generated by burning the animal waste, in conjunction with coal, can be readily used to create heated air, hot water or steam suitable for heating farm buildings. The animal waste can be collected and stored for such short periods of time as may be necessary to concentrate burning operations according to when the generated heat can be efficiently used for building heating. For larger animal raising operations the heat generated from the burning of the animal waste can efficiently be used in the generation of electricity to be sold or used in the farm operations.
Since most animal wastes contain a significant amount of moisture it is an object of the invention to provide a method and system for burning animal wastes containing high water content, (up to about 75%) and including slurry wastes that have been stored in lagoons or ponds.
3. Features of the Invention
In practicing the method of the invention animal waste is subjected to primary heat exchange to evaporate the bulk of moisture from the waste. The dried waste is then mixed with a combustible supplemental fuel and is burned. Water vapor and gasses separated during the primary heat exchange are processed to recover the water, the gasses and much of the heat used in the primary heat exchange. The recovered gasses are burned with the dried waste and supplemental fuel. Dry ash resulting from the burning of the dried waste, supplemental fuel and recovered gasses is collected for use in producing fertilizer. Exhaust from the burning of the dried waste and supplemental fuel is stripped to provide a clean exhaust suitable for discharge to atmosphere. Fly ash separated from the exhaust is mixed with dry ash in producing fertilizer. Excess heat, i.e. the heat in excess of that amount needed for drying, produced from the burning of the dried waste and supplemental fuel, is discharged to a use location, which may be a boiler, furnace, another system, or a building heating system.
The system used to perform the method of the invention includes a primary heat exchanger that will dry wastes without discharge of repugnant odors to the atmosphere. Preferably, the primary heat exchanger is heated using the heat generated by burning of the dried waste and a supplemental fuel. The primary heat exchanger may be variably constructed, depending upon the specific characteristics of the waste material and appropri
Bennett Henry
Rinehart K. B.
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