Post on 24-Mar-2021
BioPro Expo & Marketplace / Atlanta, GA / March 14‐16, 2011
Kanthi Penmetsa and Prof. Philip H Steele
Background Need for energy dense alternative fuels with reduced emissions compared to those for current fossil fuels.
Coal IndustriesElectricity production from coal is 45% in 2010.Increase in demand for coal.Difficult in getting permissions for IGCC due to increase in emissions.Alternatives to reduce emissions.
U.S. coal industry would find it beneficial to combusting torrefied wood as a co‐feed to reduce carbon and other emissions. Coal combustion facilities can only add 5 to 10% of biomass as a cofeed.New biomass fed electrical generation plants cost from $140 to $200 million.A substitute for coal with similar energy, combustion, shipping and handling properties would be an ideal solution for the coal industry.
Torrefied woodReduces biomass weight by 70%Removal of water and hemicellulosic fractionProduced by heating biomass to 250oCProduct looks like char but contains the original cellulose and lignin content.Original biomass energyAnti‐microbial properties and some water resistance
Torrefaction250‐300oC
Biomass Torrefaction gases
Torrefied Biomass
30% Mass and 10% energy
70% Mass and 90% energy
Advantages of torrefied woodCo‐feeding of torrefied wood with charcoal has demonstrated that emissions of SOx and NOx are reduced.Have low alkali metal content and very low chlorine.Acid gas corrosion will not be a problem.
Torrefied wood pelletsA pelletized or briquetted that is waterproof is required.Waterproof torrefied wood pellet has not been achieved to date.MSU tested a combination of two low‐cost biomass derived compounds to produce a high density pellet with high water resistance.Water resistant bond through unique chemical linking action.
Pellet Making processTorrefied wood + Compound (A+B)
Mechanical stirring in glass beaker for 5‐10 mins.
Placed in a Stainless steel press for 5min with heating at 150oC at 300psi
Composition and Images of Pellets Spec.no.
Torrefied wood(%)
Compound A (%)
Compound B (%)
Hardness(psi)
HHV(MJ/kg)
1 70 20 10 702 21.12 70 10 20 1122 21.23 60 20 20 1533 22.2
Spec no ‐ 1 Spec no ‐2
Spec no ‐3
Mechanical Testing
Results of Mechanical TestingSpec.no.
Weight (g)
Radius(cm)
Height(cm)
Volume(cm3)
Density(kg/m3)
Max. load (kg)
Stress(kg/m2)
1 17.38 1.25 3.00 14.73 1180 246 501,891
2 17.00 1.25 3.00 14.73 1154 394 801,915
3 16.80 1.25 3.00 14.73 1141 538 1095,457
Water repellency testPellets Soaked in water for 15 daysPellet has retained the shape without flakingThe weight gain was 1.30%
Pellets after soaking in water
TW Pellet Coal Pellet TW Pellet after soaking in water for 15 days
Economics Torrefied wood costs about $70/ton and with assistance from the USDA biomass Crop Assistance program the cost of torrefied wood is $35/ton.Cost of Compound A is $1.01 per gallon.Cost of Compound B is $0.70 per gallon.Total variable cost of production of pellets is estimated to be $65 per ton.Considering the capital cost, overhead and profit the estimated per‐ton cost is $75.
Conclusions and Future workSuccessful in producing torrefied wood pellets with high mechanical strength.Successful in producing pellets with coal dust feed with the same adhesive.To produce high efficient pellets with zero weight gain when soaked in water.Produce pellets with different biomass feed stocks.