Volatile matter content of fuel

Volatite matter and inherantly bound water in the fuel are given up in pyrolyis zone at the temperatures of 100-150°C forming a vopour consisting of water, tar, oils and gases. Fuel with high volatile matter content produces more tar, causing problems to internal combustion engine. Volatile matters in the fuel determine the design of gasifier for removal of tar. Compared to other biomass materials (crop residue : 63-80 %, Wood : 72-78 %, Peat : 70 %, Coal: upto 40 % ), charcoal contains least percentage of volatile matter (3-30 %)

Ash content of fuel

Mineral contents of fuel which remians in oxidized form after combustion of fuel is called ash. In practice, ash also contain some unburned fuel. Ash content and ash composition have impact on smooth running of gasifier. Melting and agglormeration of ashes in reactor causes slagging and clinker formation. If no measures are taken, slagging or clinker formation lead to excessive tar formation or complete blocking of reactor. In general, no slagging occurs with fuel having ash content below 5 %. Ash content varies fuel to fuel. Wood chips has contains 0.1% ash, while rice hust contains high amount of ash (16-23%)