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.

We have investigated Rice straw pellets in Spain, in the area of Valencia where they grow a lot of rice. Moisture content of the pellets was 8%, ash content 12%, Sulphur 0,06%, Chlorine 0,22 %, Nitrogen 0,47%. NCV was 16,4 GJ per mt. Mechanical durability of the pellets was quite low -  88%. Biggest problem with the rice straw is it's very high ash content and also high Chlorine. For example in wood pellets I2 it is accepted only 0,07% of Chlorine and in the rice pellets it was detected 0,22% Chlorine. High chlorine in combination with high ash content   may create slagging (sedimentation) of the ash on the inner walls of the boiler and make it's lifetime shorter. All this makes use of rice straw pellets very limited in coal-fired power plants. Another matter could be biomass dedicated   power plants.

Similar problems as with rice straw are typical for other types of straw because any straw has higher ash content and chlorine. It has been noticed that admixing of molasses as a binding agent makes pellets stronger during the transportation. Adding 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.