Napier grass is becoming a popular biomass for gasification process to generate electricity in Thailand. Government office also issued the project that subsidizes napier grass as raw material for power plants.
The critical factors for Napier grass for power plants projects are harvesting of the grass, moisture content in the grass, transportation to the preparation factory, and making the dried grass into pellet form or else to be able to use in the reactor of gasification process.
Muddy area can be problem for harvesting and the moisture content in the grass can be as high as 70% (not included the water from rain if the case), causing high cost to dry the grass. Transportation cost and pelletizing cost are also to be considered too. Raw material preparation process includes;
Biomass chipper/cutting Biomass material: Sugar cane stalks or Napier Grass stalks or similar can be mixed and used in most gasifier. Also woody biomass like wood chips or coconut shells can also be used but they might require a chipping or good cutting technology.
Sample of Output chip/strand size required:
Preferred: sum of average chip/strand dimensions (L + W + H) at 50 mm
Maximum: sum of average chip/strand dimensions (L + W + H) at 75 mm
Moisture content input biomass from 50-70% (by weight)
Throughput: minimum 5.0 tph fresh biomass per unit for 1 MWatt power plant size. Auxilliaries: (i) dust collection system. (ii) dust storage system.
Biomass Drying Unit Technology type: Rotary dryer or Columnar type dryer
Fuel: Biomass (grass itself, wood chips, waste wood), LPG, also Drying heat source: ambient air diluted hot gen set exhaust. Direct gen set exhaust will be between 430 and 470 Deg C and we will dilute down temperature with air to required dryer operating temperature.
Chip/strand size input: Expected Average: sum of average chip/strand dimensions (L + W + H) at 50-75 mm
Expected Maximum: sum of average chip/strand dimensions (L + W + H) at 100 mm
Moisture content input biomass (maximum 70% moisture content; target output moisture content at maximum 18-20%
Auxilliaries: (i) feed system (ii) discharge system.
This is just sample idea about the raw material preparation and gasifier related machines.