5..2 Methanol Recovery Design Criteria The EPA specification for methanol is less than 0.2 vol% in the finished biodiesel product. The team is currently researching different methods of separating methanol and methyl esters, which include distillation, centrifugation, and pervaporation. in the pretreatment section of this report and will not be described in detail here. Design Alternatives Distillation Methanol and water are commonly separated by distillation. The Diesel Crew utilized Team Rinnova’s vacuum distillation design, which requires an operating pressure below 1 atm, and found it effective for their purposes. There is over a 60F difference between the boiling points of water and methanol, which makes distillation an attractive and effective choice. However, distillation is the generally the most energy intensive separation technique, and the added energy costs of operating a vacuum tower in a plant may make a different separation technique more feasible. Pervaporation Pervaporation is a technology that is commonly used to separate water from organic solvents. The process takes advantage of differences in polarity and molecular size to pass a smaller and more polar molecule through a selective membrane that is aided by a vacuum. The membrane used is inert, and the only energy requirements are heating the incoming stream (the process is more effective at high temperature) and running the vacuum. Since methanol and water are similar in their polarity, the membrane selection would be particularly important. One downside to pervaporation is that it is usually precedes a distillation column and may not be effective as the only method of separation. If distillation or
5..2 Methanol Recovery Design Criteria The EPA specification for methanol is less than 0.2 vol% in the finished biodiesel product. The team is currently researching different methods of separating methanol and methyl esters, which include distillation, centrifugation, and pervaporation. in the pretreatment section of this report and will not be described in detail here. Design Alternatives Distillation Methanol and water are commonly separated by distillation. The Diesel Crew utilized Team Rinnova’s vacuum distillation design, which requires an operating pressure below 1 atm, and found it effective for their purposes. There is over a 60F difference between the boiling points of water and methanol, which makes distillation an attractive and effective choice. However, distillation is the generally the most energy intensive separation technique, and the added energy costs of operating a vacuum tower in a plant may make a different separation technique more feasible. Pervaporation Pervaporation is a technology that is commonly used to separate water from organic solvents. The process takes advantage of differences in polarity and molecular size to pass a smaller and more polar molecule through a selective membrane that is aided by a vacuum. The membrane used is inert, and the only energy requirements are heating the incoming stream (the process is more effective at high temperature) and running the vacuum. Since methanol and water are similar in their polarity, the membrane selection would be particularly important. One downside to pervaporation is that it is usually precedes a distillation column and may not be effective as the only method of separation. If distillation or