Chemical refining, inadequate to handle waste

The years prior to the global pandemic that we are experiencing were, on a margins’ level, the best in history that biodiesel fuel manufacturers had ever had from waste material. The appearance of new requestors for waste, primarily HVO, as well as the reduction in the collection of oils retrieved, because of the different types of lockdown and the shutdown of the restaurant business, has resulted in a shortage of the quantity that is available, and price levels as never seen before.

The comeback to slim margins must make manufacturers reflect, regarding waste, about the importance of costs and shortages’ control in the business, as well as the optimization in the assessment of by-products.

Many biodiesel plants were originally designed to treat first-use vegetable oils with an acidity range over 1%.

To treat oils with an acidity range over 1%, the simplest and most logical thing to do is to implement chemical refining.

If the refining process is properly carried out, one point of acidity generates two points of decrease. In other words, when we refine a 1% FFA oil with an alkali, we get the acidity plus another point. 98 kilograms of refined oil come out from every 100 kilograms that come in.

We then generate pastes that can be either sold or regained, in an exterior factory or workshop, through acid splitting, which generates acidic waters. The oleins obtained will have an acidity over 50%. If the level of acidity turns out to be less than that, this will mean that we are not carrying out the refining process properly and that we are losing more neutral oil.

Working on oils with a range over 5%, we are generating an incredible amount of decrease on the biggest component of biodiesel cost, superior to 80%. A 6% oil has an oil loss of 12%, a large amount of acidic water and salts, as well as the acidic waters later generated in the acidic esterification if the oleins are recovered.

On standard values, each ton of fatty acids has a cost of 80 euros per ton of refining chemicals, at today’s prices, and generates 460 litres of acidic water and about 360 kilos of salts.

A plant with 300 tons per day, working with a level of 6% acidity, has a chemical cost of € 1,440/day (€ 475,200 per year) and generates 8,280 litres/day of acidic waters (2,732 m3 per year) and 3,83 t / day in salts (1,267 tons per year).

With these levels of soda addition, the refined oil is left with high levels of soaps that can generate emulsions and problems in separations due to the generation of large interfaces that prevent separation.

The specification rate for transesterification is over 50 ppm for soaps, and residual oil refined with soda hardly falls below 1000-3000 ppm.

This situation is aggravated when it comes to plants that have integrated refining and transesterification, since it generates a flow of pastes, fatty acids and salts that completely overflow the circuits for which they were designed.

In this type of plants all of this goes to by-products, specifically glycerin, where we find the following effects:

Higher water contentNeed for greater evaporation capacity and energy.Greater need for water purification.
Higher salts contentClogging and blinding of equipment.Increase of the ebullioscopic constant, higher energy expenditure.Impossibility of fulfilling commercial wealth.Waste management.

At the same time, the addition of a large amount of chemical product, as well as the incredible amount of waste generated, significantly penalizes the emissions of our process, and, consequently, our product is less competitive.

The best solution for these materials to manufacture of biodiesel is deacidification without the use of chemical products, which will result in the following benefits:

  • Direct generation of oleins without using external workshops or generating acidic waters.
  • A lesser amount of oleins. When distilling we will obtain fatty acids over 75% acidity, with which the decrease will be 1.5 points per point of acidity.
  • No generation of salts.
  • No consumption of chemical products.

There is not a single solution available, it depends on each plant and the range of raw materials. From Technoilogy we can analyse each case to provide the most efficient solution.

Feel free to contact us.

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