Biodiesel Production Plants
Biodiesel production plants produce biodegradable fuels that can be used in diesel engines.
Biodiesel production results from a chemical process that reacts vegetable oils, seed oils, algae, or animal fats with methanol or ethanol in the presence of a catalyst. A thermochemical process utilizes pyrolysis to decompose cellulosic biomass in the absence of oxygen. This produces a liquid that can be burned like fuel oil or refined into other fuels. Biodiesel is often blended with petroleum diesel. A gasification process produces syngas in a fluidized bed reactor that is then converted to liquid fuels catalytically.
Biodiesel Production Plant Components – Chemical Process
A biodiesel production plant includes the following major components:
Various seeds, beans, or algae are the source of the oils. These crops are delivered to the facility and stored on-site in silos or warehouses. The oil is extracted from the biomass source via chemical or mechanical processes. The fat or oil is combined with an alcohol such as methanol in the presence of a catalyst in a reactor. This reaction occurs at low temperatures (room temperature to about 140 degrees F) and low pressure and produces a crude biodiesel and glycerin. Once the reaction is complete, the glycerin, which is denser, is drawn off the bottom of the settling vessel. Next, the excess alcohol is removed from the biodiesel and from the glycerin and recovered by distillation. The biodiesel is further purified to remove residual catalysts and other contaminants and then dried. The biodiesel and glycerin are then pumped to storage tanks.
Additional processing equipment is necessary to produce the biodiesel. A boiler provides steam for cooking, distillation, evaporation, and other plant uses. A stack is required for the exhaust gas stream. Pollution control equipment (see Biomass Power Plant discussion) would be required, as well as cooling towers to cool plant process water.
Biodiesel Production Plant Components – Pyrolysis Process
In a biodiesel production plant that utilizes pyrolysis, biomass feedstock is fed from a hopper typically as a crushed powder along with nitrogen into a thermal cracker where it is heated to 500 to 700 degrees C in the absence of oxygen. The biomass is converted to pyrolysis vapor, gas, and char. This mixture is fed into a cyclone, which removes the char from the pyrolysis vapor. The vapor next enters a scrubber where it is sprayed with a liquid, which causes it to condense into a pyrolysis oil. The oil is filtered, collected, and run through a series of reactors to upgrade the pyrolysis oil to a more desirable state for processing into transportation fuel. The biodiesel is then pumped to storage tanks. Additional processing equipment (see chemical process) is also required.
Biodiesel Production Plant Components – Gasification Process
In a biodiesel production plant that utilizes gasification, biomass feedstock is fed from a hopper typically as a crushed powder into a fluidized bed reactor. In the reactor, the feedstock mixes with sand as steam bubbles up through the sand at temperatures between 600 and 800 degrees C. The mixture of solids, vapor, and gas then enters a thermal cracker that then forms syngas, a combination of hydrogen and carbon monoxide along with tars and other solids. The solids are removed in cyclones, and a fluidized bed catalytic tar reformer converts the tars to additional syngas. The syngas then enters a scrubber where it is cooled and filtered. The dry gas next moves to a catalytic fuels synthesis unit, which completes the syngas conversion to mixed alcohols or other liquid transportation fuels. The biodiesel is then pumped to storage tanks. Additional processing equipment (see chemical process) is also required.
Biodiesel Production Plant Size
A biodiesel production plant typically requires 15 to 80 acres for all the facilities. The total area of the site is usually larger, landscaped, and serves as an exclusion area to the public.