Bioelectrochemical treatment of gaseous byproducts

Abstract

The present invention relates to a method for producing electrical energy or hydrogen gas from a gas stream containing one or more gaseous compounds that are oxidatively degradable by microbes, the method comprising contacting the gas stream with an anode of a bioelectrochemical device, said anode containing said microbes which oxidatively degrade one or more of said gaseous compounds while producing electrical energy or hydrogen gas by said oxidative degradation, wherein: (i) said anode is sufficiently porous such that gas is permitted to flow therethrough, (ii) said anode contains on its surface and / or interior portions a proton-conducting medium, and (iii) said anode is in electrical communication with a cathode of the bioelectrochemical device. The invention is also directed to a bioelectrochemical device (e.g., microbial fuel cell) configured to accomplish the above method.

Description

[0001]This invention was made with government support under Contract Number DE-AC05-000R22725 between the United States Department of Energy and UT-Battelle, LLC. The U.S. government has certain rights in this invention.FIELD OF THE INVENTION[0002]The present invention relates to the field of bioelectrochemical treatment of gaseous products. More particularly, the present invention relates to bioelectrochemical (e.g., microbial fuel cell) treatment of sulfide-containing or carbon monoxide-containing gas streams, such as those occurring from a petroleum refining process or syngas-producing process.BACKGROUND OF THE INVENTION[0003]Gaseous streams emanating from industrial processes often contain numerous gaseous byproducts that are processed as waste or directly released into the environment. The gaseous waste is often a significant financial liability since the waste is typically required to be processed by some measure before being released or disposed of. The gaseous waste also pre...

AI Technical Summary

Benefits of technology

[0012]The present invention is directed to a novel method for utilizing gaseous compounds that are oxidatively degradable by microbes (for example, gaseous mercaptan compounds and / or carbon monoxide, i.e., CO) from a gas stream containing such compounds for the purpose of producing energy therefrom (i.e., electricity or hydrogen gas), and in the process, reducing the levels of these byproducts. The method involves treating the gas stream with a bioelectrochemical system or device (i.e., BES) by contact of the gas stream with an anode therein which contains microbes capable of oxidatively degrading one or more gas compounds, preferably mercaptan compounds and / or CO, while producing electrical energy or hydrogen therefrom. The anode is suitably porous to permit flow of the gas stream therethrough such that the gas stream interfaces with the surface of the anode. The anode also contains therein a proton-conducting medium such that protons being produced by the oxidative degradation of the gaseous compounds can migrate from the anode to the cathode. The proton-conducting medium also functions to solubilize the gaseous compounds, such as H2S, other mercaptans or CO, in the gas stream for more efficient processing by microbes on the anode surface. In the use of the device for electricity production, the anode is in electrical communication with a cathode of the device. A cation-permeable material is preferably in direct contact with the anode and cathode and separates the anode and cathode such that the gas stream contacting the anode does not contact the cathode.

[0016]In still another embodiment, the BES device is operated in such a manner that the cathode electrochemically reduces one or more electrochemically reducible species, such as a nitrate, chlorate, or reducible metal species, during microbial consumption of one or more mercaptan compounds or CO at the anode.

[0017]Thus, as will be described in further detail below, the method advantageously provides a method for removing mercaptans (particularly, hydrogen sulfide) and / or CO in a gas stream by a renewable process which is significantly less energy demanding and more cost efficient than current technologies. The method also advantageously converts mercaptans and CO to environmentally benign and / or useful products while producing significantly less waste (or no waste) and using minimal amounts of water.

Problems solved by technology

The gaseous waste is often a significant financial liability since the waste is typically required to be processed by some measure before being released or disposed of.

The gaseous waste also presents an environmental liability since either raw or processed gaseous waste ultimately enters the environment.

These compounds are undesirable in petroleum products for a number of reasons, including their ready conversion to sulfur dioxide (SO2) gas when included in fossil fuels undergoing combustion (as in an automobile or power plant), as well as their ability to function as poisons to noble metal catalysts used in catalytic reforming units and catalytic converters.

The HDS process, the Claus process, and Merox process (and other processes) are energy demanding and rely on fossil fuels.

Usually, extraordinary amounts of water are used in the process, and a large amount of this water is wasted or is contaminated and must be treated as waste.

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