Patent Application
20050003515
This invention relates generally to biofilteration, and more specifically to a system for the removal of hydrogen sulfide (H2S) from gaseous fuels such as methane.
In the biofilteration industry typical problems which are focused on include odor control, VOC removal, and the treatment of petroleum hydrocarbons. A fourth problem which has yet to be successfully addressed in the field of biofilteration is the removal of noxious and deleterious sulfur from energy gases.
Organic material can be microbially digested in the absence of oxygen to form biogas containing mostly methane, carbon dioxide, and small amounts of hydrogen sulfide. Specific systems have been developed which allow dairy farmers to collect animal waste and turn it into biogas, which can then be used to generate useful heat and electricity.
These systems have been researched since the early 1970's but economic and operational barriers have curtailed their widespread implementation. Recent emphasis on environmental protection, renewable fuel sources, and distributed generation indicates that these systems will likely become more prevalent.
When methane containing H2S is used as a fuel, such as to run a motor-generator, the combustion converts the H2S to harmful sulfuric acid (H2SO4) which corrodes the generator and dramatically shortens the generator lifetime.
It can therefore be seen that there is a need in the field for a system which will reduce and/or eliminate H2S from methane to provide a “cleaner” methane for use as a fuel.
It is therefore an object of the present invention to overcome the problems of the prior art described above.
It is another object of the present invention to provide a method of H2S removal from fuel gases.
It is another object of the present invention to provide a method of H2S removal from organic gaseous fuel.
It is another object of the present invention to provide a method of H2S removal from methane.
It is yet another object of the present invention to provide a biofilteration system for the removal of H2S from fuel gases.
It is a further object of the present invention to provide a system for H2S removal from fuel gases which utilizes a reactor cartridge.
The invention is directed to a system for removing H2S from methane (CH4) or other suitable gaseous fuel which includes providing at least one biofilter cartridge which sustains microbial activity that will function to consume H2S contained in a stream of methane gas. In one embodiment, a stream of methane gas which contains H2S is transported directly into a biofilter system which contains at least one cartridge containing selected microorganisms which function to biodegrade H2S. The clean methane gas is then recirculated to a source of use.
A suitable reactor cartridge which can be used in the present invention includes an outer housing having a pair of oppositely disposed open ends. The housing which contains an inlet fan and an inlet port connected to a vertical inlet tube positioned at one end which also contains a water inlet and a gas outlet. A water reservoir is attached to the opposite end of the housing, with the reservoir further containing an outlet for the removal of water. In operation, a source of methane which contains H2S to be treated is passed through the inlet and down the vertical tube and reverses direction at the bottom to go up through a suitable source of microorganisms contained in said housing which are selected to degrade the H2S. The treated methane is released through said gas outlet, at the top of the housing and captured for storage or direct use.
For a further understanding of these and objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, wherein:
In the present invention aerobic microorganisms are used to remove hydrogen sulfide from the gas stream and oxidize it back to sulfate, which then combines with water to form sulfuric acid.
Initial testing indicated that cow manure compost, which contains sulfur oxidizing bacteria, can remove hydrogens sulfide (H2S) from a gas stream with removal efficiencies above 80%.
Farm digester gas is not the only source of sulfide contaminated methane rich gas for which biofilteration technology may be suitable. Wastewater treatment plants, landfills, paper mills, and food processing plants are all capable of producing biogas. Additionally, as higher quality natural gas wells are depleted, it may become economical to exploit smaller, remote, sulfur contaminated wells, biofilteration with its modular nature and low operating costs may be the ideal technology for sulfur removal from these gas source.
One embodiment exemplary of the invention is illustrated in
Carrier 11 may comprise any artificial or synthetic such as granular inert plastics, ceramics or crystalline materials which support and act as a carrier for the microorganisms or bacteria. Pearlite functions as an economical and readily available carrier or media. Any suitable microorganism or bacteria which functions to remove or biodegrade H2S can be used. Suitable microorganism include Thiobacillus and Ralstonia. If a natural occurring or biodegradable material is used in place of a synthetic carrier, such as cow manure compost, tree bark or vegetation, then microorganisms indigenous to these materials will function to biodegrade the H2S.
A suitable reactor cartridge 10 which can be used in the present invention includes an outer housing 12 having a pair of oppositely disposed open ends which are closed by a bottom 14 and a top 16. The housing contains an inlet fan or blower 18 and an inlet port 20 connected to a vertical inlet tube 22 positioned at one end which also contains a flush water inlet 24 and a gas outlet 26. A water reservoir 28 is contained in bottom member 14 at the opposite end of the housing, with the reservoir further containing an outlet 30 for the removal of flush water. In operation, a source of methane 19 which contains H2S to be treated is passed through the inlet and down the vertical tube 22 and reverses direction at the bottom to go up through a suitable source of microorganisms contained in said housing which are selected to degrade the H2S. The treated methane is released through said gas outlet, at the top of the housing and captured for storage or direct use. The remote cartridge is also flushed by the down flow of water 25.
While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims including applications and use for cleansing other gaseous fuels of unwanted secondary organic contaminants.
