Straw pellets

A lot of straw in bales and straw pellets are traditionally used for energy production in Denmark within the State subsidy program for the agricultural sector.

Big problem of the straw is its high ash content, high concentration of Chlorine, Potassium and also rather low ash melting temperature. A combination of alkaline media with the low melting temperature leads to sedimentation of the melted ash on the inner surfaces of the pipes and the walls of the boiler, so called “slagging”.Coal fired boilers which are mostly used for co firing of coal with biomass will get  gradually damaged of clinker. One experienced  Danish engineer said to us about  burning straw in such boiler “ we are here dealing  with a programmed destruction of the boiler”.

It has been observed that admixing   to pellets white clay (kaolin) as an  anti-slagging agent allows counter react the tendency of the ash become viscid and form the clinker in alkaline media

Actually same problems arise with olive cake. One of the ways to avoid slagging in this case is using not more than 6-7% of olive cake for co firing.

Totally another issue would be to burn straw in specially constructed biomass dedicated boilers which will allow to use different kinds of biomass products.