Diversified Energy Corporation has successfully demonstrated a glycerol combustion system for which it holds an exclusive worldwide license from the developer, North Carolina State University. The system efficiently burns the glycerol byproduct generated during the manufacture of biodiesel; energy created through the combustion of glycerol can then be used for process heating applications or electricity generation.
|Glycerol combustion system prototype in action. Click to enlarge.|
The university has built and tested a 100,000 Btu/hour prototype burner with pure glycerol, crude glycerol from a biodiesel process, and glycerol with water. Diversified Energy is now seeking commercialization partners for market introduction.
The manufacture of biodiesel through transesterification results in approximately one pound of crude glycerol byproduct for every nine pounds of biodiesel produced. As the biodiesel industry has expanded, so has the supply of crude glycerol/ Glycerol is expected to reach in excess of 350,000 tons/year in the US and 600,000 tons/year in Europe.
Crude glycerol contains artifacts from the biodiesel process such as catalysts, alcohol, and soap and is therefore costly to refine into higher grade, pure glycerol. As a consequence, crude glycerol market prices have collapsed and the biodiesel industry is struggling with viable options for the glut of glycerol on hand.
The combustion of glycerol will produce 16 MJ of heat per kilogram of glycerol burned which could be provided back to the biodiesel process, another co-located system, or converted into other energy forms like electricity. However, the combustion of glycerol has been challenging because of technical, safety, and cost obstacles.
By nature, glycerol has a high viscosity, high auto-ignition temperature, and low heating value. It is difficult to flow the product into a burner, hard to ignite, and even more challenging to maintain a flame. In addition, if the glycerol is not completely combusted it is possible to generate toxic gases.
The patent-pending process from NC State University is based on a novel spray atomization swirl burner architecture that overcomes the technical and safety issues. This is coupled with pre-heating the combustion chamber, maintaining heat retention, maximizing radical retention, and carefully interacting air and fuel flows. The system is extendable to any liquid fuel having an ambient viscosity of greater than 20 centistokes.