“We are running out of oil!” Heard it before, have you? Well look at it this way; we are already close to running out of the light, sweet crude oil that was easy to find. Now we have to go further out into deeper waters to greater depth to find crude oil that is of lower quality, heavily contaminated, and more expensive to get and to process. Power generating turbines are now being designed to burn this nasty crude.

The Biodiesel Opportunity

Among the bio-fuels that have been invented, biodiesel seems the most promising. It is a clean-burning fuel; just follow a city bus in traffic and smell the French fries. Within its evolution the number of biodiesel producers has steadily grown and three distinct segments of producers have emerged:

1. large producers that are well-capitalized and have engineered processing facilities,
2. intermediate producers who are less well-capitalized and are using equipment from various sources, and
3. the low-cost “do-it-your-selvers” operating with equipment they make themselves and do not have the capital, nor the desire to expand production beyond that for their own use.

Allen Filters, Inc. has for over 60 years of its manufacturing history produced equipment that purifies mineral and synthetic oils and proves that they can be reused almost indefinitely. As such, we have made those oils a “renewable resource."

With the advent of diesel production, we have received many requests for the application of our oil purification equipment to the biodiesel process. Allen Filters, Inc. equipment applies the same proven principles of mineral oil purification to the various components of the biodiesel process:

• separation by distillation (vacuum or non-vacuum) in accordance to the boiling points of the individual components and
• recovery by refrigerated condensing of those components that need to be collected and reused.

As such, our equipment performs as follows:

• It removes moisture and solids from the waste vegetable oil, improving the efficiency of the esterification reaction
• It removes moisture and color from crude biodiesel, creating a more valuable fuel
• It removes moisture and color from glycerol and purifies it to pharmaceutical grade, adding the sale of this product to the revenue stream
• It recovers the excess methanol by thermal vaporization and subsequent refrigerate condensation to liquid methanol of a high purity, reducing the overall cost of production

The two types of Allen equipment used in the biodiesel process are the Allen Bioscav and the Allen Biovac. Part one of this series describes the use of the Allen Bioscav in the biodiesel process. These two systems are primarily used by intermediate producers who want to optimize their batch process and produce higher quality, more valuable products.

Figure 1: The Allen Bioscav for Biodiesel

1. Chiller Unit, 2. Refrigerated Condenser, 3. Separator Vessel, 4. Control Box, 5. Duplex Positive Displacement Pump & Motor, 6. Filter, 7. Heater

Waste Vegetable Oil Purification

One of the readily available sources for biodiesel is waste vegetable oil. This type of base material has been reheated several times during the course of its usage and therefore must be treated before it can be used for the biodiesel process. The reheating will cause some of the fatty acids bonded to the glycerol to break away and float freely in the oil. These are the free fatty acids which have to be esterified before transesterification. As the presence of water favors the cleavage of fatty acids in vegetable oil, standard DIN V 51 605 limits the water content to 750 ppm. However, the lower the water content the better the quality of the end product. The actual water content can be determined by Karl Fischer titration.

The Allen Bioscav can be used to filter out the solids and remove free, emulsified, and dissolved water down to 50 ppm total water by circulating the oil through the system multiple times.

Figure 2: Removal of Water and Solids from Waste Vegetable Oil

Methanol Recovery From Biodiesel

The recovery of methanol vapor is accomplished by the refrigerated condensing of the methanol vapor. When the Allen Bioscav is connected to the biodiesel tank—which contains the decanted biodiesel, water, and methanol mixture—the same process of components separation by boiling point is used. The boiling points of the components are:

• Methanol: 148.5 °F (64.7 °C) (evaporates first)
• Water: 212 °F (100 °C) (evaporates next)
• Biodiesel: 955-662 °F (512-350 °C)¹

For methanol separation, the valve at the Separator Vessel manifold is opened to the refrigerated condenser, while the valve to the atmosphere is closed. The PLC's accurate ( ± 0.01 °C) temperature control of the Bioscav is set at slightly above the boiling point of methanol to account for the latent heat of evaporation (the amount of energy required to overcome the cohesive forces between the molecules and expand the gas to a vapor). The biodiesel and the water are not affected since the temperature is lower than either boiling point. The methanol begins to evaporate and is condensed in the refrigerated condenser. Since this is a distillation process, the liquid methanol has a high degree of purity.

Once all the methanol has been evaporated and condensed, the PLC temperature controller can be set to slightly over 212 °F (100 °C) to begin to evaporate the water. The valve to the chiller will be closed while the valve to the atmosphere will be opened. The water vapor will escape from the Separator Vessel to the atmosphere. The vapor is free of contamination by methanol or biodiesel. The final water content of the biodiesel can be verified by Karl Fischer Titration.

Figure 3: Methanol Recovery

Refining of Crude Glycerol

For the subsequent separation of water, residual fatty acids (soap), and salt from crude glycerol, the process temperature is first set at 212 °F (100 °C) or slightly higher and the valve on the Separator Vessel manifold is opened to the atmosphere to allow the water to evaporate. To separate and condense the glycerol, the process temperature is increased to between 554 and 572 °F (290 and 300 °C) and the vapor is routed to the refrigerate condenser. The pH of the glycerol must be kept at 4-5. Foaming will occur at values above pH 5.

Bleaching of Biodiesel

Crude biodiesel will have an orange tint, which can be bleached with activated carbon or fuller's earth adsorption filters. Glycerol can be similarly bleached to a ligther color. The activated carbon or fuller's earth filters can be an optional and integral part of the Bioscav.

Notes

1. Biodiesel has a very high latent heat of evaporation and will not be affected by the removal boiling points of methanol and water.

References

1. Cecil, Steve, Kathy Kiefer, and Jim Walbridge. "New Biodiesel Standards for EN 14105 and ASTM D6584." Analytix: Advances in Analytical Chemistry 4, (2005) 4-5.
2. Kojima, Seiji, Dongning Du, Masayasu Sato, and Enoch Y. Park. "Efficient Production of Fatty Acid Methyl Ester from Waste Activated Bleaching Earth Using Diesel Oil as Organic Solvent." Journal of Bioscience & Bioengineering 98, no. 6 (2004): 420-424.
3. Methanex Corp. Technical Information & Safe Handling Guide for Methanol. Methanex Corp, 2002. http://methanex.com/products/documents/TISH_english.pdf.
4. Sigma-Aldrich. "Standards for Biodiesel Analysis." Analytix: Advances in Analytical Chemistry 4, (2005).
5. Simon, R. "Microorganism Growth in Petrodiesel and Biodiesel." Chemcical Engineering Department, Rice University, 2000.
6. Van Gerpen, J. H., Earl G. Hammond, Lawrence A. Johnson, Stephen J. Marley, Liangping Yu, Inmok Lee, Abdul Monyem. "Determining the Influence of Contaminants on Biodiesel Properties." Final report prepared for The Iowa Soybean Promotion Board, Iowa State University, July 31 1996.
7. Yong, K. C., T. L. Ooi, K. Dzulkefly, W. M. Z. Wan Yunus, and A. H. Hazimah. "Refining of Crude Glycerine Recovered from Glycerol Residue by Simple Vacuum Distillation." Journal of Oil Palm Research 13, no. 2 (2001) 39-44.