Nalladurai Kaliyan

Natural binders and solid bridge type binding mechanisms in briquettes and pellets made from corn stover and switchgrass.

Corn stover and switchgrass are two important feedstocks considered for producing renewable fuels and energy in the US. Densification of these biomass feedstocks into briquettes/pellets would help reduce the problems and costs of bulk transportation, handling, and storage of biomass feedstocks. In this study, the role of the natural binders in corn stover and switchgrass to make durable particle-particle bonding in briquettes/pellets was investigated by micro-structural analyses. Scanning Electron Microscopy (SEM) images of briquettes made by using a uniaxial piston-cylinder densification apparatus in the laboratory, briquettes made by using a pilot-scale roll-press briquetting machine, and pellets made by using a pilot-scale conventional ring-die pelleting machine were analysed. The SEM images showed that the bonding between particles was created mainly through solid bridges. The solid bridges between particles were made by natural binders in the biomass expressed during the densification process. UV auto-fluorescence images of briquettes and pellets further confirmed that the solid bridges were made mainly by natural binders such as lignin and protein. It was found that activating (softening) the natural binders using moisture and temperature in the range of glass transition is important to make durable particle-particle bonding.

A Corn Stover Supply Logistics System

Published in Applied Engineering in Agriculture, Vol. 26(3): 455‐461, 2010. American Society of Agricultural and Biological Engineers

Factors Affecting Strength and Durability of Densified Products

Effectiveness of a densification process to create strong and durable bonding in densified products such as pellets, briquettes, and cubes can be determined by testing the strength (i.e., compressive resistance, impact resistance, and water resistance), and durability (i.e., abrasion resistance) of the densified products. These tests can indicate the maximum force/stress that the densified products can withstand, and the amount of fines produced during handling, transportation, and storage. In this article, the procedures used for measuring the strength and durability of the densified products are discussed. The effects of constituents of the feed such as starch, protein, fiber, fat, lignin and extractives; feed moisture content; feed particle size and its distribution; feed conditioning temperature/preheating of feed; added binders; and densification equipment variables (forming pressure, and pellet mill and roll press variables) on the strength and durability of the densified products are reviewed. This article will help select process parameters to produce strong and durable densified products from new biomass feedstocks or animal feed formulations. Guidelines for developing standards on criteria for the acceptance levels of strength and durability of the densified products are presented.

Overwintering Mortality of Indianmeal Moth (Lepidoptera: Pyralidae) in Southern Minnesota

Abstract Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), has been classified as one of the most cold-tolerant pests of stored grain. In this study, the supercooling point (SCP) of field-collected, cold-acclimated fifth instars was determined as an index of cold hardiness. In addition, mortality of laboratory-reared and field-collected, cold-acclimated fifth instars exposed to −10°C was measured to understand the ability of P. interpunctella to survive winter conditions. Finally, the overwintering mortality of this species in southern Minnesota was measured in grain bins filled with shelled corn. The SCP of field-collected, cold-acclimated fifth instars was approximately −24°C before their release in grain bins. Mortality of laboratory-reared fifth instars exposed to −10°C reached 100% after only 12 h, whereas the same percentage was achieved after 312 h for field-collected, cold-acclimated individuals. Overwintering mortality of P. interpunctella under field conditions reached 100% in all locations inside the grain bins; however, depth within the grain mass, location inside the grain bin, and the duration of exposure to outdoor conditions significantly affected the rate of mortality. A mathematical model for the overwintering mortality of P. interpunctella is proposed as a first step to forecast early season infestations under field conditions.

Commercial scale tub grinding of corn stover and perennial grasses

Performance of a commercial mobile tub-grinder [463 kW (630 hp)] was studied to produce coarsely ground particles from round-baled, plastic net-wrapped corn stover and native perennial grasses. The effects of grinder screen opening size [25.4 to 127.0 mm (1.0 to 5.0 in.)] and feedstock type on ground particle size, bulk density of ground biomass, throughput, specific energy consumption, and cost of grinding were studied. The bulk density of ground biomass ranged from 69 to 207 kg/m3 with the moisture content of particles ranging from 14% to 39% (w.b.). The throughput of the grinder ranged from 6 to 45 t/h. The specific energy consumption ranged from 93 to 661 MJ/t. The estimated cost of grinding ranged from

A tub-grinding/roll-press compaction system to increase biomass bulk density: Preliminary study

4.39 to

Commercial Scale Grinding of Corn Stover and Perennial Grasses

31.23/t. Increasing the grinder screen opening size increased the ground particle size and throughput, but decreased the bulk density of ground biomass, specific energy consumption, and cost of grinding. High moisture bales (= 25% w.b.) decreased the performance of the grinder. The results from this study would be useful for developing a biomass supply logistics system involving mobile grinding.

Binding Mechanisms of Corn Stover and Switchgrass in Briquettes and Pellets

Transforming biomass into a product with bulk density of 240 kg/m3 (15 lb/ft3) would enhance logistics of truck transport to users throughout the year. We evaluated a system involving tub-grinding followed by roll-press compaction to increase the bulk density of biomass such as corn stover, corn cobs and native perennial grasses. Preliminary experiments were conducted to study the effect of particle size (tub-grinder screen sizes of 19.1, 76.2, and 203.2 mm) on the bulk density of roll-press compacted biomass materials. The bulk density of tub-ground biomass ranged from 50-100 kg/m3 (3-6 lb/ft3). Tub-grinding followed by roll-press compaction increased the bulk density by two- to three-fold, and resulted in densified products with bulk density of 190-240 kg/m3 (12-15 lb/ft3). Additional increases in bulk density appear possible with improved design of the feeding system for the roll-press compaction machine.

Mortality of Indianmeal Moth (Lepidoptera: Pyralidae) Populations Under Fluctuating Low Temperatures : Model Development and Validation

Performances of two commercial grinders [349 and 463 kW (475 and 630 HP)] were studied to produce coarsely ground particles from round-baled, plastic net-wrapped corn stover and native perennial grasses. The effects of grinder screen size [19.1 mm (0.75 in.) to 127.0 mm (5.0 in.)] and feedstock on the particle size, bulk density, throughput, and specific energy consumption were studied. The bulk density of ground biomass ranged from 69 to 207 kg/m3 (4 to 13 lb/ft3). The throughput of the grinders ranged from 5 to 45 t/h. The specific energy consumption ranged from 68 to 804 MJ/t. Increasing the grinder screen size decreased the bulk density and specific energy consumption, but increased the particle size and throughput. High moisture bales (25% or higher moisture content) decreased the performance of the grinders. The results from this study would be useful for developing a biomass supply logistics system involving mobile grinding.

Biomass Integrated Gasification Combined Cycle Systems at Corn Ethanol Plants

Corn stover and switchgrass are two important feedstocks considered for producing renewable fuels and energy in the U.S. Densification of these biomass materials into briquettes or pellets would help reduce the problems and costs of transportation, handling, and storage. The objective of this study was to investigate the binding mechanisms of corn stover and switchgrass in briquettes and pellets. Scanning Electron Microscopy (SEM) images of briquettes made using a roll press briquetting machine, and pellets made using a conventional ring-die pelleting machine were analyzed. The SEM images showed that the bonding between particles was created mainly through solid bridges. The solid bridges between the particles were made by natural binders in the biomass expressed during the densification process. UV auto-fluorescent images of briquettes and pellets further confirmed that the solid bridges were made mainly by the natural binders such as lignin and protein. It was found that activating (softening) the natural binders using moisture and temperature in the range of glass transition is important to make durable particle-particle bonding.