Torrefaction of wheat and barley straw after microwave heating

Hygric properties of porous building materials (II): Analysis of temperature influence

The microwave-assisted torrefaction of woody construction demolition waste (CDW) and grass clippings (GC) from municipal solid waste (MSW) was investigated under nitrogen-activated inert condition with respect to microwave power (250, 500 and 750 W), residence time (15, 30 and 45 min), moisture content (12, 16 and 20% w.b.) for CDW and 64% w.b. for GC. The results show that grinding energy consumption decreases as the microwave power level increases, indicating a significant improvement in the grindability of the material after torrefaction. Depending on the treatment combination, grinding energy savings of about 29–70% and 30–68% resulted after microwave-assisted torrefaction of CDW and GC, respectively. The higher heating value (HHV) increases with increasing microwave power level and torrefaction residence time. For CDW, the HHV increased by about 3–39% having HHV of 25,691 MJ/t. While for GC, the HHV increased by about 8–24%, having HHV of 20,936 MJ/t. This investigation further demonstrates that torrefaction reduced moisture adsorption of CDW and GC, which significantly improves their storage capability in humid locations. The moisture uptake ratios for torrefied CDW were found to be 0.66–0.96 and about 0.92 for torrefied GC, against a moisture uptake ratio of 1.0 for raw CDW and GC. However, biomass subjected to severe torrefaction process conditions produced pellets having poor physical quality. Microwave irradiation can be used effectively for torrefaction of MSW investigated at moderate microwave power level and short torrefaction residence time.

Torrefaction of biomass from municipal solid waste fractions II: Grindability characteristics, higher heating value, pelletability and moisture adsorption

Moisture sorption characteristics and modeling of energy sorghum (Sorghum bicolor (L.) Moench).

Understanding the water sorption characteristics of cereal is extremely essential for optimizing the drying process and ensuring storage stability. Water relation of rough rice was studied at 20, 30, 40 and 50 °C over relative humidity (RH.) between 0.113 and 0.976 using the gravimetric technique. The isotherms displayed the general sigmoid, Type II pattern and exhibited the phenomenon of hysteresis where it was more pronounced at lower temperatures. The sorption characteristics were temperature dependence where the sorption capacity of the paddy increased as the temperature was decreased at fixed (RH). Among the models assessed for their ability to fit the sorption data, Oswin equation was the best followed by the third order polynomial, GAB, Smith, Chung-Pfost, and Henderson models. The monolayer moisture content was higher for desorption than adsorption and tend to decrease with the increase in temperature. Given the temperature dependence of the sorption isotherms the isosteric heats of sorption were calculated using Claussius-Clapeyron equation. The net isosteric heats decreased as the moisture content was increased and heats of desorption were greater than that of adsorption.

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Qiyan Feng

Papers

Equilibrium moisture content and sorption isosteric heats of five wheat varieties in China