This invention relates to gas producing and handling systems and, in particular, to such systems which produce a combustible gas for burning in an internal combustion engine coupled to an electrical generator.
There are presently many instances where a combustible gaseous fuel, such as methane, is produced as a by-product of other processes, such as in anaerobic digesters. It has long been known that anaerobic digesters can be utilized in decomposing organic waste, such as animal manure, so that the resulting decomposed matter is less offensive and less damaging to the environment. Anaerobic decomposition produces various gaseous by-products including carbon dioxide and combustible methane gas. Until the last decade, because the cost of petroleum and other energy sources has been relatively low, it has not been economically feasible to attempt to collect and utilize the methane produced by the digesters to produce energy such as in electricity. Because of the events of the last decade, particularly concerning the supply of petroleum fuels, the cost of producing energy has increased to an extent where it is now economically feasible to attempt to utilize the methane produced by the anaerobic digesters to produce a usable form of energy. Typically, the methane gas produced by the anaerobic digesters fuels an internal combustion engine which drives a generator for producing electricity. Also, the methane gas can be used as fuel in appliances converted from operation on natural gas.
A major problem encountered in attempts to utilize the methane gas produced by the digester concerns the need to store the gas when the total amount of gas being produced by the digester is either not used fully by the various appliances utilizing the gas or is not being combusted in the internal gas engine for driving the electrical generator. Prior attempts to overcome this problem have included furnishing a large storage tank with the digester or, at times, including a compressor to compress the gas in volume for easier storage. Another recent example of an attempt to overcome the storage problem is a digester having an expansible cover secured over the decomposing matter. As more gas is produced, the cover expands to a greater volume to store the gas and vice verse. A major problem with this manner of storage aside from the fact that the expansible bag can be punctured and leak is that most users enclose the digester in a suitable building to protect the bag, thereby increasing the expense of the system.
The gas storage problem encountered by prior digesters which use methane gas in an engine coupled to a generator for the production of energy is two-fold. First, the associated generator is a synchronous generator which must be rotated at a certain predetermined speed or revolutions per minute (rpm) so that alternating electrical current produced thereby is compatible with utilization by the appliances of the user. Secondly, the consumption of fuel by the generator is determined by the demand placed on it. As a result, the consumption and production rates of gas are different resulting in a need for a storage vessel for any excess gas produced and not contemporaneously consumed by the engine.
There are many other types of potential gas supplies which presently are not being utilized but, which also have the attendant problem of fuel storage.