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Process and system for producing biodiesel fuel

Process and system for producing biodiesel fuel description/claims

The present invention relates to an apparatus and process for converting free fatty acids in acid oil or acid fat to fatty acid methyl esters, commonly known as “biodiesel.”

Biodiesel—generally, processed fuel, derived from biological sources of free fatty acids, and that can be used as a substitute, supplement, and/or alternative fuel in un-modified diesel engines or other devices that burn diesel oil.

Feedstock—refers to vegetable oils, animal fats, and other sources of free fatty acids (FFAs) amenable to conversion to biodiesel by transesterification.

Biodiesel fuel—the biodiesel end-product produced by the process and system of the present invention.

Intermediate reaction product—an intermediate-stage product formed of the transesterification reaction prior to removal of glycerine.

Crude biodiesel—an intermediate-stage product produced following by the removal of glycerine from the intermediate reaction product.

Biodiesel is a non-toxic, biodegradable, and renewable diesel-equivalent fuel that is produced from organic feedstocks such as vegetable oils or animal fats through transesterification of free fatty acids (FFAs) into fatty acid methyl esters (FAMEs). This process utilizes a catalyst, an alcohol, and a source of fatty acids such as vegetable oil. The preferred alcohol is methanol, although higher weight alcohols can be used. The methanol is reacted with sodium hydroxide to produce methoxide, which drives the transesterification reaction. The resultant purified liquid is biodiesel. The by-products include methanol and glycerine. Glycerine settles out of the reacted liquid and can easily be isolated.

Conventional methods of transesterification of vegetable oils proceed by mixing methanol and sodium hydroxide with vegetable oil in a tank and heating the mixture to about 66° C. to 71° C. (151° F.-160° F.) This temperature is maintained for hours while mixing paddles stir the mixture, generally at a rotation rate in excess of 100 RPM. During this process the methanol, which has a boiling point of 64.7° C., is vaporized and glycerine precipitates out. Further impurities are removed in a wash tank and a final filtration is performed. The biodiesel fuel that is left has properties very similar to diesel oil but burns with about 70% fewer pollutants.

In order to speed up the trans-esterification reaction, a catalyst is often employed. Typically the catalyst is a base catalyst such as NaOH. However, lower quality (i.e., cheaper) feedstocks have high FFA content and the FFAs tend to form soap with base catalysts, thus reducing yield and presenting significant operational problems.

One approach to solving this problem has been using a large excess of methanol and an acid catalyst. U.S. Pat. No. 6,965,044 to Hammond discloses the use of acid catalysts to avoid these problems. However, the method of Hammond et al. uses 2-4 hour pre-treatment and a 24-hour reaction time. Similarly long process times are found with conventional, base catalysis methods, which take about 3 hours to reach full temperature and several more hours to react. Because of the high cost of the methanol it is necessary to recycle the methanol when using excess amounts, but recovering methanol has been problematic and expensive.

A system with shorter reaction times, using a base catalyst, carried out at lower temperatures, that avoids saponification, and that can produce refined biodiesel fuel from low grade feedstocks is needed. Hammond states that “[t]he base catalyst-catalyzed transesterification reaction, commonly used for generating FAMEs from refined vegetable oils, cannot be used to produce biodiesel from the cheaper starting materials with high FFA content . . . since the FFAs in the materials form soaps with the base catalyst.” As a result of the present process and system, that statement is no longer accurate.

Disclosed and claimed herein is a system and method for producing biodiesel fuel from any feedstock sources of free fatty acids, including low quality sources. The system includes a reaction chamber having a jacket for circulating heating fluid around the chamber; a feedstock pre-treatment assembly; a methoxide reaction tank; a settling tank; a crude biodiesel wash assembly; and, a methanol recovery assembly, also referred to as a methanol recoverer herein.

The method includes the steps of pre-treating the feedstock by heating and, optionally, filtering it; reacting the feedstock in the reaction chamber with a source of esters thereby carrying out transesterfication of the free fatty acids; producing an intermediate reaction product; cooling the intermediate reaction product to allow glycerine to settle out; separating the glycerine from the crude biodiesel; and, washing the crude biodiesel to remove impurities, thereby producing biodiesel fuel.

FIG. 1. is a flow chart of the method of the invention.

FIG. 2. is a schematic diagram of the system of the invention.

• Provisional Patent
• Utility Patent

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