The primary objectives of this work can be summed into two major categories. Firstly, the fundamentals of the combustion of glycerol (in both a refined and unrefined form) were to be investigated, with emphasis of the development of a system capable of reliably and repeatedly combusting glycerol as well as an analysis of the emissions produced during glycerol combustion. Focus was placed on quantifying common emissions in comparison to more traditional fuels and this work showed that the burner developed was able to completely combust glycerol within a relatively wide range of operating conditions. Additionally, focus was placed on examining specific emissions in more detail, namely interesting NOx emissions observed in initial trials, acrolein and other volatile organic emissions, and particulate and ash emissions.
This work showed that the combustion of crude glycerol could result in significantly reduced NOx emissions as a function of the high fuel bound oxygen content within the glycerol fuel. It also showed that when burned properly, the combustion of crude glycerol did not result in excessive emissions of acrolein or any other VOC compared to the combustion from more traditional fuels. Lastly however, this work has shown that in any practical application in which glycerol is being burned, it will be necessary to explore ash mitigation techniques due to the very high particulate matter concentrations produced during glycerol combustion. These emissions are comparable to unfiltered coal combustion and are directly tied to the biodiesel production method.
The second focus of this work was directed to developing a commercialization strategy for the use of glycerol as a fuel replacement. This strategy has identified a 30 month plan for the scaling up of the laboratory scale burner into a pre-pilot scale system. Additionally, financing options were explored and an assessment was made of the economics of replacing a traditional fuel (namely natural gas) with crude glycerol from biodiesel production. This analysis showed that the cost of replacing natural gas with crude glycerol requires a strong function of the market price per unit of energy for the traditional fuel. However, the economics can be improved through the inclusion of a federal tax credit for the use of a renewable fuel. The conclusion of this analysis also shows that the ideal customer for energy replacement via crude glycerol is biodiesel producers who are located in remote regions, where the cost of energy is higher and the cost of crude glycerol is lowest. Lastly, the commercialization strategy analyzed competing technologies, namely traditional natural gas and electric heaters, as well as competing glycerol burners, and concludes with a discussion of the requirements for a pilot demonstration.
Crude Glycerol as Cost-Effective Fuel for Combined Heat and Power to Replace Fossil Fuels, Final Technical Report