Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
1999-11-12
2001-10-02
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Processes
Treatment by living organism
C071S010000, C210S603000, C210S614000, C706S903000
Reexamination Certificate
active
06296766
ABSTRACT:
TECHNICAL FIELD
The invention relates to a digester system that utilizes anaerobic microbes to convert organic material into a biogas and a plant growth media on an industrial scale. More specifically, the present invention relates to a process for monitoring, then analyzing and finally, very precisely controlling a multistage digestion process, to optimize operation of the digester system. The process includes an anaerobic digester, and a control system for the digester that employs pattern recognition.
BACKGROUND OF THE INVENTION
The pre-treatment of cattle feed or roughage, before feeding it to cattle, has long been a subject of research. For instance, during the drought years of the 1930's, there was a need to make cattle feed out of weeds and about anything else that was growing. It was then demonstrated that almost any organic material having any potential as fodder could be made into digestible animal feed. The green fodder could be preserved and converted into animal feed within a silo or similar storage. The process of storing and preserving fodder is known as ensiling.
Ensilage is essentially a partially fermented organic material. Most temperate regions of the planet generate large amounts of organic material, commonly called biomass. Most biomass is considered a waste material and typically disposed of as rubbish. Much of this waste material could be converted into a plant growth media and methane (CH
4
) by first converting it to silage and then processing it through an anaerobic methane producing digester.
The anaerobic digestion process can be fed by an enormous variety of biomass sources. As a result, the process can be used to resolve an equally wide variety of waste disposal problems. If this waste biomass can be efficiently converted into energy, it could be utilized to replace scarce fossil fuels.
Some site specific sources of biomass include:
Dairy farms
Fruit processors
Mint farms
Cheese plants
Potato processors
Hog farms
Cattle feed lots
Egg farms
Poultry farms
Hop farms
Frozen food
processors
Some examples of particular biomass materials include:
Wheat straw
Corn silage
Rice Straw
Food wastes
Grass seed straw
Residential yard
Selected municipal
debris
solid wastes
The physical aspects of an anaerobic digester system are essentially a vessel and all of the necessary accessories and other components to create an environment as close as possible to that in which the anaerobe microorganisms naturally live. The initial digestive chambers of bovines are excellent examples of a well functioning anaerobic digester found in nature. The ingestion of grasses or other similar materials by the bovine ultimately produces a manure mash, which is an excellent fertilizer, and produces a methane gas (CH
4
) emission, as a by-product.
Operating an efficient anaerobic digester roughly patterned after naturally occurring digestive systems, but at an industrial scale, is not a simple task. The feedstocks for such industrial processes are substantially composed of biologically generated material.
A lack of uniform quality of the end product is almost universal in most, if not all, existing industrial scaled anaerobic digesters, and composting operations of a significant scale. This lack in uniformity has led to the dismissal of anaerobic digestion as a viable, reliable methane industrial scale source of methane. To operate even a simple anaerobic digester that substantially mimics the biomass digestive systems found in nature, powerful and sensitive system monitoring methods and controls are needed. This is because in the natural bovine system, hundreds of thousands or even millions of minute and symbiotic organisms have evolved over eons to a self-regulating system.
In the industrial setting, we can observe an example of a high level of sensitivity in the precision of an industrial fermentation process, as typically performed to produce a top quality beer. Typical industrial process control systems use at least one physical parameter, such as pressure, time or temperature for a primary control. When closer control is needed, a second physical parameter is used. Occasionally, a third parameter may also be employed. The use of this “third” parameter or 3
rd
level of control usually results in a process control system with much higher precision than that process's ability to be accurately controlled.
Currently, in most industrial scale anaerobic digesters, the design of various components of the digesters coupled with the control system together allow the temperature to fluctuate anywhere from plus or minus two or three degrees Fahrenheit (F.), up to occasional variations having a range often degrees F., or more. For the digester's anaerobes, even a single degree F change in temperature is at least one hundred times greater than the phenomena that needs to be measured, which is the heat generated by the anaerobes. Therefore, for these conventional industrial digesters, the ten degree “dead band” or noise level of the signal from the phenomena to be measured or controlled, is ten to one hundred times larger than the phenomena's metabolic heat signal that needs to be accurately measured.
A precision control system is of no benefit for these conventional, industrial anaerobic digester systems, because the physical design of the anaerobic digester does not permit “fine tuning” due to the errors produced by the measurement and control system. Therefore, a need exists for both a digester design and a control system for an industrial anaerobic digester, which are better able to monitor and control the anaerobic process.
SUMMARY OF INVENTION
The present invention provides a method for an anaerobic digester system. The method specifically addresses the control difficulties of industrial scale anaerobic digesters, and solves these difficulties by employing a cumulative data base to better monitor and control the anaerobic process, as compared with conventional anaerobic digester systems.
The method of the present invention includes the storing of a feedstock, preferably a biomass, to form a digester feed material. This digester feed material is processed by a digestion process, which mimics the bovine digestion process, in a digester. The process evolves a biogas and forms a digested material. Importantly, the process is monitored, to collect a plurality of digester datum from the digester, and preferably from all stages of the process. These individual points or elements of the datum are telemetered to a cumulative data base for storage and eventual retrieval.
The cumulative data base is “mined” to compile a predictive, feed forward control of an anaerobic digester system. The term mining is employed to describe the process of utilizing an artificially intelligent software application to draw specific relationships from the cumulative data base. This data mining software is a prepackaged and commercially available product, yet highly adaptable to user specific applications. In the present invention, the results of the data mining can be used to construct feedstock correlations between the metabolic activity within the digesters and an analysis of the feedstocks into the digesters. These feedstock correlations can be employed in both feed back and feed forward controls of the anaerobic digester system.
The method of the present invention can further include a recovery of the biogas generated within the digester, with the aid of a biogas recovery system. With the typical biomass feedstock, the biogas formed within the digester is predominantly methane, and the anaerobic digester system is preferably operated to maximize the quantity and quality of methane generated. This biogas formation can be directly related to the metabolic activity within the digesters and optimized with the correlations discovered in the mining of the cumulative data base.
REFERENCES:
patent: 3933628 (1976-01-01), Varani
patent: 4100023 (1978-07-01), McDonald
patent: 4161426 (1979-07-01), Kneer
patent: 4437987 (1984-03-01), Thornton et al.
patent: 4613433 (1986-09-01), McKeown
patent: 4648968
Drodge Joseph W.
Stratton Ballew PLLC
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