Monday, April 25, 2011

Bio-Oils to Diesel, Jet Fuel, Gasoline via North Carolina State U.


Researchers at North Carolina State University have devised a refining method for converting triglycerides, or biofats, into drop-in fuels for diesel, gasoline, and jet (turbine) engines. The technology is being developed by a small startup, Avjet Biotech Inc.
The Red Wolf Process (RWP) consists of three main steps: hydrolysis, deoxygenation and hydrocarbon reforming.

Hydrolysis. The first step of the RWP uses the well-established Colgate-Emery reaction (hydrolysis via high-pressure, high-temperature steam) to cleave the three fatty acid chains from the glycerol backbone of the triglycerides. This is accomplished by separately pumping steam and the feedstock oil at high temperature and pressures into a Colgate-Emery reactor. Two product streams exit this reactor, free fatty acids (mixed with water) and sweet water (glycerol mixed with water). Water is removed from the free fatty acid (FFA) stream prior to the next processing step: deoxygenation.

Deoxygenation. The free fatty acid (FFA) and low concentrations of hydrogen are fed into a deoxygenation reactor. This reaction has two steps: 1) remove any degrees of unsaturation from the FFA; 2) catalytically remove oxygen molecules from the FFA. This reaction step results in a saturated, straight chained hydrocarbon with one less carbon than the reacted FFA (i.e. a C18 free fatty acid yields a C17 hydrocarbon). These n-alkanes are a common component of petroleum (which has a wider distribution of alkanes as well as other types of hydrocarbons). The n-alkanes derived using the RWP from the fat-containing oils are in the ranges needed for diesel and jet fuel.

Hydrocarbon reforming. This step converts the n-alkanes to the specifications necessary for jet, diesel and gasoline fuels. Two separate reactions (and reactors) are used to reform the n-alkane into the desired fuels: hydroisomerization and aromatization.

In the hydroisomerization reaction, the n-alkane is branched (no longer a straight chain). Within the hydroisomerization reaction, hydrocarbon cracking also occurs, which shortens the hydrocarbon branch size, which can be controlled to give the desired ranges for jet, diesel and gasoline fuels. Aromatization is a reaction in which the n-alkane is converted into aromatic (or cyclic) hydrocarbons. These aromatics formed are necessary to meet specifications for jet fuel and are also a common component in gasoline to raise the octane rating.

A parallel step to the fuel conversion is the separation of the by-product of hydrolysis, glycerol, from the sweet water. Then the glycerol is combusted to provide energy for the entire process. This step increases the energy efficiency of the process as well as minimizes waste streams.

Red Wolf says that modeling has shown economic viability for smaller plant sizes (10 MGPY and larger). Co-locating fuel processing plants near the feedstock-producing sites, rather than near oil refineries, is therefore advantageous in this schema. This mitigates transportation costs of both the feedstock and the produced fuel. Smaller plants require less land space and capital, and are optimized towards the most economical feedstock of the region. _More details and illustrations at GCC

The process above is not likely to bring high profits to developers and investors unless the price of oil remains inflated, as currently. If oil prices are driven to rise too quickly, too far, the resulting demand destruction and oil price crash will devastate all forms of alternative fuels production which rely upon the high price of crude in order to break even.



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