ABSTRACT
For a variety of reasons, biofuels derived from a wide range of raw materials, are in higher demand. Biodiesel has several advantages over other biofuels. These include direct substitution for fossil fuels into existing internal combustion engines, an existing distribution network, and a relatively simple conversion technology. In the last few years, many papers have been presented championing one technology over another; however, these papers do not typically address the materials of construction for various components in the production scheme. Many of the raw materials and subsequent co-products are benign to most common materials of construction. Depending on the process scheme, certain process steps may present much more corrosive conditions. For instance, if hydrochloric acid is used in the glycerin loop, the choice of materials of construction is quite limited. This paper presents data for both titanium and zirconium alloys for possible use in biodiesel production. KEY
INTRODUCTON
Dr. Rudolf Diesel, a French native of German parents, received a patent for the compression ignition engine in 1893. Peanut oil was used as fuel for his engine during his exhibit at the World Exhibition in Paris in 1900. Since that time, further development of biodiesel has been sporadic. Only during times when petroleum based fuels were difficult to get or overly expensive was development of alternate fuels continued. The increased emphasis in biodiesel research in the last few years is a prime example. This renewed interest has resulted in biodiesel plants actually producing fuel on a commercially viable basis.
There are four primary ways to make biodiesel1. These include: direct use with blending, microemulsions, thermal cracking (pyrolysis) and transesterification. Tranesterification is by far the most common method of production due to the relative ease of operation and enerally lower costs. The transesterification process will be the focus of this paper. The transesterification process to produce biodiesel is usually based on one of three basic routes when using oil and fats2.
Transesterification of oil using alcohol with a base catalyst.
Esterification of the oil using an acid catalyst with methanol as the alcohol.
Conversion of the oil to fatty acids, and then to alkyl esters utilizing an acid catalyst.
The majority of bio-diesel production is confined to base catalyzed reaction due to several favorable economic factors3.
Operation at low temperatures and pressures.
High conversion rates.
No intermediate steps required for direct conversion to methyl ester.
Commonly available materials of construction are typically used.
References to sodium hydroxide, potassium hydroxide, sulfuric acid, hydrochloric acid, sodium methoxide and methanol show the varied process schemes available to economically produce biodiesel from a variety of starting materials. Common materials of construction can be used for most of the process due to the lower temperatures encountered.
BIODIESEL PRODUCTION METHODS
Biodiesel production processes include batch operation and continuous processing. Basic biodiesel production methods are still in a state of development and new developments occur frequently.
