Sudhagar Mani

Impact of torrefaction on the grindability and fuel characteristics of forest biomass.

Thermal pretreatment or torrefaction of biomass under anoxic condition can produce an energy dense and consistent quality solid biomass fuel for combustion and co-firing applications. This paper investigates the fuel characteristics and grindability of pine chips and logging residues torrefied at temperatures ranging from 225 °C to 300 °C and 30 min residence time. Grinding performance of torrefied biomass evaluated by determining energy required for grinding, particle size distribution and average particle size were compared with raw biomass and coal. Specific energy required for grinding of torrefied biomass decreased significantly with increase in torrefaction temperatures. The grinding energy of torrefied biomass was reduced to as low as 24 kW h/t at 300 °C torrefaction temperature. The gross calorific value of torrefied chips increased with increase in torrefaction temperature. Torrefaction of biomass clearly showed the improved fuel characteristics and grinding properties closer to coal.

ECONOMICS OF PRODUCING FUEL PELLETS FROM BIOMASS

An engineering economic analysis of a biomass pelleting process was performed for conditions in North America. The pelletization of biomass consists of a series of unit operations: drying, size reduction, densifying, cooling, screening, and warehousing. Capital and operating cost of the pelleting plant was estimated at several plant capacities. Pellet production cost for a base case plant capacity of 6 t/h was about

The Potential of C4 Perennial Grasses for Developing a Global BIOHEAT Industry

51/t of pellets. Raw material cost was the largest cost element of the total pellet production cost followed by personnel cost, drying cost, and pelleting mill cost. An increase in raw material cost substantially increased the pellet production cost. Pellet plants with a capacity of more than 10 t/h decreased the costs to roughly

Bulk Density of Wet and Dry Wheat Straw and Switchgrass Particles

40/t of pellets. Five different burner fuels – wet sawdust, dry sawdust, biomass pellets, natural gas, and coal were tested for their effect on the cost of pellet production. Wet sawdust and coal, the cheapest burner fuels, produced the lowest pellet production cost. The environmental impacts due to the potential emissions of these fuels during the combustion process require further investigation.

Binderless Pelletization of Biomass

Unprecedented opportunities for biofuel development are occurring as a result of rising fossil fuel prices, the need to reduce greenhouse gases, and growing energy security concerns. An estimated 250 million hectares (ha) of farmland could be utilized globally to develop a bioenergy industry if efficient and economical perennial biomass crops and bioenergy conversion systems are employed. In temperate zones, C4 or warm-season grass research and development efforts have found switchgrass (Panicum virgatum) and Miscanthus capable of producing biomass yields of 10 to 20 oven dried tonnes (ODT)/ha/yr, while in tropical areas Erianthus and napier grass (Pennisetum purpureum) are producing 25 to 35 ODT/ha/yr. The potential to annually produce 100 barrels of oil energy equivalent/ha with a 25:1 energy output to input ratio appears achievable with high-yielding, N-fixing warm-season grasses grown on marginal lands in the tropics. Commercialization of densified herbaceous plant species has been slow because of the relatively high alkali and chlorine contents of the feedstocks, which leads to clinker formation and the fouling of boilers. This challenge can be overcome by improving biomass quality through advances in plant breeding and cultural management to reduce the chlorine, alkali, and silica content and through the use of new combustion technologies. Warm-season grasses can be readily densified provided suitable grinding and densification equipment and pressure are utilized. The major advantages of producing densified warm-season grasses for BIOHEAT include: it is the most efficient strategy to use marginal farmlands in most temperate and tropical climates to collect solar radiation; it has an excellent energy balance; the feedstocks can be used conveniently in a variety of energy applications; and it is relatively environmentally friendly. Densified warm-season grass biofuels are poised to become a major global fuel source because they can meet some heating requirements at less cost than all other alternatives available today.

MECHANICAL PROPERTIES OF CORN STOVER GRIND

Bulk density is a major physical property in designing the logistic system for biomass handling. The size, shape, moisture content, individual particle density, and surface characteristics are few factors affecting the bulk density. This research investigates the effects of true particle lengths ranging from 6 to 50 mm and moisture contents ranging from 8% to 60% wet basis (wb) on the bulk density of wheat straw and switchgrass. Three types of particle densities of straw and switchgrass measured were: a hollow particle density assuming a hollow cylindrical geometry, a solid particle density assuming a solid cylindrical geometry, and a particle density measured using a gas pycnometer at a gas pressure of 40 kPa. The bulk density of both loose-fill and packed-fill biomass samples was examined. The calculated wet and dry bulk density ranged from 24 to 111 kg m-3 for straw and from 49 to 266 kg m-3 for switchgrass. The corresponding tapped bulk density ranged from 34 to 130 kg m-3 for straw and 68 to 323 kg m-3 for switchgrass. The increase in bulk density due to tapping the container was from 10% for short 6-mm particles to more than 50% for long 50-mm particles. An equation relating the bulk density of stems as a function of moisture content, dry bulk density, and particle size was developed. After the validation of this bulk density equation, the relationship would be highly useful in designing the logistics system for large-scale transport of biomass to a biorefinery. The bulk density and particle density data of uniform particles would be important, if straw and switchgrass is used for pulping and paper making.

Grinding Performance and Physical Properties of Selected Biomass

A cost-effective pelletized biomass is a key to the success of bio-based industry. Low production costs along with safe handling of biomass will make biomass competitive with fossil fuels. Recent advances in biochemical treatments and force-deformation research point to a possible breakthrough in the age-old pelleting/cubing. The structure of lignocellulosic biomass consists of complex molecules of cellulose, hemicellulose and lignin. Modifying the structure of cellulose-hemicelluloselignin matrix can enhance binding characteristics of lignocellulosic biomass. Furthermore. The research reported in this paper demonstrates that by optimizing a combination of physico-chemical treatments of biomass before and during its densification will improve the hardness and durability of pelletized biomass.

Torrefaction of sorghum biomass to improve fuel properties

Mechanical properties of corn stover grind are important because of the need for accurate input data in the mathematical modeling of densification processes and the design of densification equipment. Mechanical properties of corn stover grind such as particle size distribution, bulk and particle densities, compressibility, particle stiffness, wall friction, and adhesion on steel surfaces were determined with two hammer mill screen sizes (3.18 and 6.35 mm) used in grinding at three different moisture contents (7%, 11%, and 15% w.b.). Compression tests were conducted for each combination of hammer mill screen size and moisture content to establish pressure-density data at different applied pressures. Mechanical properties such as compressibility, initial bulk modulus, porosity index, and particle stiffness were determined from the pressure-density data. Shear tests were conducted to determine the coefficient of friction between the steel plate and corn stover grind at different moisture contents and normal pressures.

Antimicrobial and Physicochemical Characterization of Biodegradable, Nitric Oxide-Releasing Nanocellulose–Chitosan Packaging Membranes

Biomass residues such as straws, corn stover and energy crop - switchgrass were ground using a hammer mill with three different screen sizes (3.175 mm, 1.588 mm and 0.794 mm) for densification. Energy required for grinding these materials was measured at two different moisture contents. Among the four materials, switchgrass had the highest specific energy requirement to grind using a hammer mill. Corn stover used the least specific energy. Physical properties of ground samples such as moisture content, geometric mean diameter, particle size distribution, bulk and particle densities were determined. Second or third order polynomial models were developed relating bulk and particle densities of ground samples to geometric mean diameter within the range of 1.428 to 0.178 mm. Switchgrass had the highest calorific value and the lowest ash content among the materials used in the experiment.

Compaction of Corn Stover

Torrefaction of energy sorghum and sweet sorghum bagasse was investigated at three different temperatures (250, 275 & 300°C) for 30min to determine product yields and its compositions. The torrefied solid yield ranged from 43% to 65% for sweet sorghum bagasse and 51-70% for energy sorghum. The energy density of both torrefied sorghums increased between 1.6 and 1.4 folds. Besides water, the acetic acid, with a maximum yield of 101.90gL-1 was the dominant compound in the aqueous fraction of liquid products. The aqueous fraction from sweet sorghum bagasse contained furfural and furan carboxyl aldehydes, while ketones and alcohols were dominant from energy sorghum as other key compounds. Phenolic type chemicals and furan derivatives were the major compounds in the oil fraction of the liquid product, accounted up to 58wt%. The condensable liquid products can be further upgraded into high-value platform chemicals.