Biomass, municipal wastes, hydrocarbon fuels or coal can be reformed via one or a combination of pyrolysis, combustion and gasification processes. A series of chemical reactions during the course of these processes usually results in the formation of a complex mixture of combustible gases such as CH4, CO, H2, unreacted heavy hydrocarbons; tar and a noncombustible gas, CO2. A combination of all these gases constitutes what is known as pyrolysis gas or pyrogas. The presence of heavy hydrocarbons and tar diminishes the quality of pyrogas from the perspective of its use for power generation or as an intermediate for synthetic fuel production. This drawback therefore necessitates the removal of the unreacted hydrocarbons. Currently, this is accomplished using catalytic partial oxidation, which has extensive drawbacks such as high cost, large size and significant carbon footprint.

As an alternative to the catalytic partial oxidation Drexel’s engineers have developed a new system and method based on non-equilibrium gliding arc plasma for the chemical reformation of pyrogas into synthesis gas, or syngas.  Non-equilibrium gliding arc plasma reforming is a fuel reforming process that eliminates the need for catalysts. Unlike catalytic partial oxidation, gliding arc plasma is characterized by smaller reactors, fast start-up time, higher efficiency and low electrical energy cost to produce plasma: this process consumes only about 2% – 5% of total chemical energy produced within the system.

The reactions used for pyrogas reforming are partial oxidation reaction, steam reforming reaction and dry CO2 reforming reaction. These main reforming reactions produce hydrogen rich synthesis gas which can be used for power generation, utilized for fuel cells to produce electricity and as a building block for production of synthetic fuels via the Fischer Tropsch process. Pyrogas that is coming out of gasifier already has a temperature 600-800C. Therefore, gliding arc plasma serves only as a source of active species and radicals such as O and OH that are necessary to stimulate the desired chemical reactions. Extensive work has been done on reforming hydrocarbons such as methane, ethane, propane, diesel fuel and biofuel.

A laboratory prototype of the pyrogas purifier has been built and successfully tested.