Pseudo-Component Approach to Distillation Design for Desulfurization of Biodiesel Produced from Brown Grease

Greenhouse gas emissions have become a critical problem. A factor in environmental degradation is coupling world population growth and waste management, including wastewater management. An example of the coupling between energy, population, waste and the environment is FOG (fats, oils and grease), a mixture of fat, wastewater, and suspended solids. This work focuses on converting FOG to biodiesel by extracting the brown grease from FOG and conducting a series of reactions and separations. This operation is a solution for both greenhouse gas emissions and sewer clogs, and also reduces the feedstock cost of biodiesel production. High sulfur content is the biggest challenge of brown grease biodiesel. Sulfur content in fuels is restricted because sulfur is converted to sulfur dioxide, causing significant environmental and health problems.

An industrially feasible process is described to convert brown grease to biodiesel that is green, safe, and effective. The three major steps in the process are esterification, transesterification and vacuum distillation. Several acid catalysts in esterification and base catalysts in transesterification were evaluated. A two-step vacuum distillation was designed to reduce sulfur content to approximately 10 ppm, which exceeds the commercial standard in the USA. A successful demonstration project applied this technique at the Greater New Haven Water Pollution Control Authority (GNHWPCA) and a commercial project in Danbury, CT is in construction. A more effective and energy saving desulfurization process will be developed to complete this investigation. Some ideas and preliminary phenomenon will be presented to introduce advanced desulfurization.