Alcohol Instead of Alkaline Neutralisation
04 January 2006 14:18
Greater efficiency in biodiesel production
With a newly developed process for pre-treating oils and fats used in the production of biodiesel, Westfalia Separator Food Tec has now added a financially interesting note to the process of recovering biodiesel. The new process involving alcohol neutralisation enables very high quality biodiesel to be produced efficiently by removing unwanted escort substances, and also enables those valuable substances to be recovered. It makes a huge financial difference, for example, if soapstock can be used to obtain up to 1.5% free fatty acids as a marketable product rather than dispose of it as a waste product.
Efficiency is decisive
The market for biodiesel is expanding. A corresponding EU directive provides that at least 2% bio fuels will be marketed by the end of 2005; this figure will be 5.75% by the end of 2010. In Australia and Asia as well as South America, particularly in Brazil, the governments are discovering and promoting bio fuels as a substitute for mineral oil fuels.
The production of biodiesel from seed oils such as rapeseed and soy or from spent oils and fats is based on alkaline transesterification with the addition of methanol as a catalyst with the by-product glycerine. If this transesterification process is to proceed with a high degree of efficiency, the oils and fats have to be pre-treated so that they are cleaned of free fatty acids, gums and dirt. In the past, alkaline neutralisation has been used, involving a process whereby the oils are pre-cleaned with acid and lye treatment. However, this process results in soapstock, a waste product which contains significant fatty acids and which represents a loss of raw materials. In addition, disposal of such soapstock is expensive. A further problem with the existing method has been the need to integrate a washing stage using a lot of wash water, and vacuum drying involving the use of considerable quantities of steam and energy.
Recovery of fatty acid
All of this is no longer necessary in the new process of alcohol neutralisation. This process combines degumming and neutralisation of the free fatty acids in a single process stage. This functions as follows:
In a first stage, the gums are conditioned with an acid-alcohol mixture. In the second stage, that of actual alcohol neutralisation, the fatty acids are finally degummed and simultaneously neutralised in the form of soap. For this purpose, the glycerine-alcohol-lye phase from the interesterification stage is used as the catalyst. This means that there is no need for additional lye as is the case in alkaline neutralisation. An additional effect is that the separated soap in the subsequent process can be recovered as fatty acids, thus providing increased added value.
Effluent- and waste-free
And the main advantage: the alcohol neutralisation process does not produce any effluent or waste. Vacuum drying is not needed at all, as the oil is dried by extracting the water with the glycerine phase. The yield of the process is boosted by the fact that the 1% to 1.5% fatty acids normally contained in the crude oil are recovered. In a 100,000 tonne installation, this represents up to 1500 tonnes of free fatty acids, which with a market price of more than EUR 200 per tonne, provides a major contribution to overall cost effectiveness. The degumming process is more thorough. Instead of the normal figure of 6ppm to 8ppm phosphorus, which is a parameter for gums, the residual phosphorus content of alcohol neutralisation is between 1ppm and 3ppm; it is perfectly degummed, which means that the quality of the biodiesel is improved.
One of the major factors in the success of the method is the use of a methanol phosphoric acid mixture for acid conditioning. The glycerinemethanol-lye phase, which comes from interestification, contains large quantities of alcohol as a result of the alcohol surplus in the interestification process. Approximately half of this alcohol surplus from the first interestification phase is recovered simply by using the new method. This is because this percentage is transferred to the oil phase and does not need to be recovered subsequently by distillation. Accordingly, the oil contains significant quantities of one of the reaction partners for interestification: methanol.
Self-cleaning
The key component in the process is a self-cleaning RSE centrifuge with an explosion-protected design in line with the ATEX regulations. A further key factor is the use of a dynamic mixer from the Westfalia Separator ZA mixer series to achieve very intense mixing of the methanol-phosphoric acid mixture with the oil during conditioning. Westfalia Separator Food Tec is able to offer process lines for the new method of alcohol neutralisation in a range between 25 tonnes per day and 1200 tonnes per day for much more efficiency in the production of biodiesel.
For more information on this company:
Westfalia Separator Food Tec - Separators, Clarifiers, Decanters and Complete Processing Lines for the Food Industry
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