Biomass: Types and Uses

• Biomass consists of organic materials derived from plants, trees, and algae.
• Biomass is a renewable organic resource that is sustainable and abundant.
• It fixes CO2 from the atmosphere through photosynthesis.
• Biomass can be converted into liquid and gaseous fuels.
• Biomass contributes 14% of the world's primary energy consumption.
• Biomass contributes 35% of primary energy consumption in developing countries.
• Biomass offers a cost-effective and sustainable energy supply.
• It helps in meeting greenhouse gas emission targets.

Biomass Types:

• Forest Residues include barks, branches, leaves, twigs, and wood.
• Agricultural Residues include rice husk, straw, and wheat straw.
• Plantation Residues include tea, coffee, coconut, and cardamom.
• Industrial Process Waste includes wood chips, sawdust, bagasse, and black liquor.
• Municipal Solid Waste (MSW) is a type of biomass.
• Aquatic and Marine Biomass include sea weeds and algae.
• Energy Crops include jatropha, rapeseed, and palm fruits.

Composition of Biofuels:

• Bagasse contains 33.6% cellulose, 27% hemicellulose, 18.5% lignin, 18.4% extractives, and 2.5% ash.
• Corn cob contains 51.2% cellulose, 14.8% hemicellulose, 31.8% lignin, 1.2% extractives, and 1% ash.
• Rice husk contains 30% cellulose, 25% hemicellulose, 12% lignin, 18% extractives, and 16% ash.
• Rice straw contains 30.2% cellulose, 24.5% hemicellulose, 11.9% lignin, 0% extractives, and 16.1% ash.
• Wheat straw contains 40% cellulose, 28% hemicellulose, 17% lignin, 11% extractives, and 7% ash.
• Wood contains 39% cellulose, 35% hemicellulose, 19.5% lignin, 3% extractives, and 0.3% ash.

Proximate Analysis and Calorific Values of Biofuels include

• Bagasse: 4236 kcal/kg calorific value, 3.8% ash, 78.1% volatile matter, 18.1% fixed carbon.
• Coconut shell: 3649 kcal/kg calorific value, 1.9% ash, 79.9% volatile matter and 18.2% fixed carbon.
• Cotton husk: 4235 kcal/kg calorific value, 4.7% ash, 73.2% volatile matter, and 22.1% fixed carbon.
• Cotton stalk: 3912.2 kcal/kg calorific value, 14.6% ash, 68.5% volatile matter, and 16.9% fixed carbon. Cow dung: 8.4% ash, 74.4% volatile matter, and 17.2% fixed carbon.
• Rice husk: 3300 kcal/kg calorific value, 20% ash, 65% volatile matter, and 15% fixed carbon.
• Rice straw: 3730 kcal/kg calorific value, 15.5% ash, 68.3% volatile matter, and 16.2% fixed carbon.
• Saw dust: 4980 kcal/kg calorific value, 1.5% ash, 75% volatile matter, and 23.5% fixed carbon.
• Wood: 4674 kcal/kg calorific value, 0.5% ash, 87% volatile matter, and 12.5% fixed carbon.
• MSW: 2138.9 kcal/kg calorific value, 48.6% ash, 43.5% volatile matter, and 7.9% fixed carbon.
• 1 cal = 4.18 J

Ultimate Analysis of Biofuels includes:

• Bagasse: 47% Carbon, 6.5% Hydrogen, 0.0% Nitrogen, 42.5% Oxygen, 4% Ash.
• Coir pith: 46.63% Carbon, 4.18% Hydrogen, 1.14% Nitrogen, 32.64% Oxygen, 15.41% Ash.
• Corn cob: 41.44% Carbon, 5.96% Hydrogen, 0.14% Nitrogen, 51.26% Oxygen, 1.2% Ash.
• Cotton pods: 44.19% Carbon, 5.87% Hydrogen, 0.73% Nitrogen, 44.61% Oxygen, 4.6% Ash.
• Cotton stalk: 41.49% Carbon, 6.2% Hydrogen, 1.81% Nitrogen, 47.49% Oxygen, 3.01% Ash.
• Groundnut shell: 33.9% Carbon, 1.97% Hydrogen, 1.1% Nitrogen, 59.93% Oxygen, 3.1% Ash.
• Rice husk: 36.42% Carbon, 4.91% Hydrogen, 0.59% Nitrogen, 35.88% Oxygen, 22.2% Ash.
• Saw dust: 52.28% Carbon, 5.2% Hydrogen, 0.47% Nitrogen, 40.85% Oxygen, 1.2% Ash.
• Water hyacinth: 35.25% Carbon, 4.36% Hydrogen, 1.53% Nitrogen, 53.06% Oxygen, 5.8% Ash.

Bulk Density of Biofuels include

• Charcoal (blocks): 150-170 kg/m3.
• Corn cobs (11% moisture): 304 kg/m3.
• Corn stalks (briquettes 30x30x50 mm): 391 kg/m3.
• Rice hulls (briquettes 30x30x50 mm): 679 kg/m3.
• Saw dust (loose): 177 kg/m3.
• Saw dust (briquettes, 100mm long 75mm): 350-400 kg/m3.
• Straw (bales): 320 kg/m3.
• Straw (loose): 80 kg/m3.
• Wood (hard): 330 kg/m3.
• Wood (soft): 250 kg/m3.

Ash Deformation and Ash Fusion Temperatures are as follows:

• Bagasse: Ash Deformation Temperature 1300-1350°C, Ash Fusion Temperature 1420-1450°C.
• Bamboo dust: Ash Deformation Temperature 1300-1350°C, Ash Fusion Temperature 1400-1450°C.
• Corn cob: Ash Deformation Temperature 800-900°C, Ash Fusion Temperature 950-1050°C.
• Cotton coir: Ash Deformation Temperature 1100-1150°C, Ash Fusion Temperature 1150-1200°C.
• Cotton stalk: Ash Deformation Temperature 1320-1380°C, Ash Fusion Temperature 1400-1450°C.
• Groundnut shell: Ash Deformation Temperature 1180-1200°C, Ash Fusion Temperature 1220-1250°C.
• Rice husk: Ash Deformation Temperature 1430-1500°C, Ash Fusion Temperature 1650°C.

Biomass Forms include:

• Pellets - 5-15 mm
• Briquet - 25-50 mm
• Peat briquettes
• Saw dust
• Chips from stem wood
• Wood waste from forest

Biomass Constituents, Features, and Properties:

• Main constituents of biomass: Cellulose, Hemi-Cellulose, Lignin.
• Main Features: High Moisture Content, High Volatile Content (up to 80%), Low ash, Low Sulphur, Low Nitrogen, High Oxygen.
• Calorific Value: up to 20MJ/kg, Low bulk density, Distributed availability.
• Physical properties include skeletal density, bulk density, size distribution, shape distribution, porosity, and internal surface area.
• Thermal properties include specific heat, thermal conductivity, and emissivity.
• Chemical properties include C, H, O, N, S, moisture, volatile matter, fixed carbon, ash content, heating value, heat of pyrolysis, volatile matter heating value, and char heating value.
• Mineral properties include Softening temperature, Fusion temperature, and Slagging potential.

Comparison with Other Fuels:

• In the Van Krevelen Diagram, biomass has low calorific value and is highly reactive.
• Typical Parameter values are listed for both COAL and WOOD:
• Heating value: Coal - 30 MJ/kg, Wood - 20 MJ/kg
• Nitrogen content: Coal - 1.5% , Wood - 0.1%
• Volatile content: Coal - 30%, Wood - 80%
• Char concentration: Coal - 1.5%, Wood - 0.1%

Biomass Advantages

• Traditional fuel
• Universally Available
• Low ash
• Net Zero CO2 (CO2 neutral)
• Low ash
• Ideal for rural and decentralized applications

Biomass Concerns

• Availability in distributed fashion
• Collection and transportation
• Processing: Drying, Briquetting, Pelletizing
• Sustainability threat due to other competitive uses
• Variety of impurities, such as Chlorine, Silica, Sulfur, Phosphorus, Nitrogen
• Variety of ash-forming metals

Formulas

• Proximate
• Moisture
  • Volatile matter
  • Fixed carbon
  • Ash
• Open-petri dish @ 105°C
• Ultimate
  • Elemental analysis
  • C, H, O, N, S

Biomass Technology Pathways:

• Biochemical: Anaerobic Digestion (Bio Gas mainly CH4) , Fermentation (Ethanol).
• Thermochemical: Gasification, Flash Pyrolysis (Biooils), Direct Solid Combustion.
• Mechanical Extraction
  • Vegetable oil

Grate Combustor:

• First combustion system for solid fuels
• Capacity range: 4-300 MWe
• Heat release rate: up to 4MWth/m² -Elements
  • Feeding system.
  • Grate assembly – air/water cooled
  • Secondary air system
  • Ash discharge systems
• Control Possibilities
  • Transportation of the fuel bed along the grate
  • Distribution of primary air
  • Position and velocity of secondary air
  • Position and Velocity of recirculated flue gas
  • Position and velocity of tertiary air

Grate Combustor - Air Supply

• amount
• momentum
• diameter
• spacing
• location
• orientation
• PA-Primary Air
• SA-Secondary Air
• OFA-Over Fire Air

Comparison of Grate Combustors

• Stationary sloping
  • Simple construction
  • Less maintenance
  • Difficult control
  • Risk of avalanching of fuel
• Travelling grate
  • Improved control
  • Better efficiency
  • Relatively higher maintenance
• Reciprocating grate
  • Carbon burn-out better than stationary and travelling grate
• Vibrating grate -Less moving parts
  • Lower maintenance
  • higher reliability
  • Highest efficiency

FBC Technology – Challenges and R&D Issues

• Challenges

  • Bed sintering
  • with high alkali fuels
  • Super heater fouling
  • High temperature corrosion
    • Cl containing fuels -Ash deposition15
  • Fouling
    • Cl containing fuels
      • Bed agglomeration problems -potassium and chlorine containing fuel

• Critical R&D Needs

  • Prediction of degree of ash related problems for various fuels or fuel mixtures
  • Fundamental understanding on the mechanism of interaction of ash and bed materials

###FBC-Active Research Centres

• Chalmers University of Technology, Sweden
• Technical University of Denmark, Denmark
• Canada Centre for Mineral and Energy Technology (CANMET), Canada
• University of Graz, Austria
• University of Umea, Sweden
• University of Stuttgart, Germany
• ECN, Netherlands
• VTT (Technical Research Centre), Finland
• IIT Madras, India