Research & Development

Feedstock purification using water treatment

With the objective to decrease the levels of “show-stopping” impurities (silica, alkali’s, chlorine) Yilkins is developing a technology concept for washing of biomass. This contributes to the purification of the feedstock in a number of ways:With the objective to decrease the levels of “show-stopping” impurities (silica, alkali’s, chlorine) Yilkins is developing a technology concept for washing of biomass.

This contributes to the purification of the feedstock in a number of ways:

  • Inert impurities such as sand, stones, plastics, metals, can be completely removed based on the differences in density versus the biomass;
  • Surface attached impurities such as sand, clay or others, can be washed off the biomass surface;
  • Impurities inside the biomass particles – intrinsic in the biomass – such as salts and other dissolved elements can be removed considerably by intensive contact with hot water.

For some biomass feedstocks – especially waste wood such as shreds, municipal wood waste, toppings – the removal of impurities and surface attached impurities enable its use for upgrading to pellets. In the case of herbaceous biomass (grass, straw, etc) – or in general fast-growing species – the washing to remove in-situ salts is a precondition to its use for upgrading towards pellets.

It is very important to remove the element potassium (K) out of the biomass, since it has a very large (negative) influence on the decomposition characteristics of biomass during torrefaction. Although washing of biomass is not new in itself, continuously operated washing techniques -especially for the removal of adhered and or intrinsic salts – are not readily available, despite the wide offer of washing techniques available for the food industry. By far the biggest drawback of the washing of biomass is that biomass becomes too wet and, in some cases, drenched with water. In addition, water is required and consumed by the process and therefore economics may not be attractive. Washing in combination with the Yilkins technology provides potentially interesting opportunities. The high drying efficiency provides margin for washing and moreover the Yilkins process water is produced at more than 90 degrees C, which can be used for the washing. This way the drawbacks of washing may be minimized.

The concepts under development are:

1. Removal of inert materials by using hot water in a continuously operated plunge pool;

2. Removal of salts by using hot water in a continuously operating, water-based drum washer with plug-flow characteristics.Yilkins has identified partners that produce washing technologies that in many cases were developed for other products. Those washers are being redesigned for use of the hot water produced by the Yilkins drying units, and for the physical characteristics unique to a specific biomass.