Batch Pyrolysis of Acid-Treated Rice Straw and Potential Products for Energy and Biofuel Production
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2015, Springer Science+Business Media Dordrecht. Purpose: Rice straw is an abundant but largely unutilized biomass. If rice straws ash content could be reduced by pretreatment, it could be pyrolyzed into energy-dense, soil-enriching products. This paper investigates if acid-pretreatment of rice straw before pyrolysis could improve the char, bio-oil or gas products of pyrolysis. Methods: Rice straw was sonicated in a 5% HCl by volume bath, and the acid-treated straw was slowly pyrolyzed in batches at 500C. Its products were compared with those of untreated rice straw. Results: FTIR analysis showed that both oils were mixtures of alkanes, alkenes, alcohols and aromatics. Less bio-oil was produced after acid pretreatment. After acid pretreatment, the char decreased in ash percentage, increased in acidity and increased in heating value. The gas was rich in CO2 but low in combustible gases like CO, CH4 and H2. Conclusion: This pretreatment did not improve the pyrolysis char, bio-oil, or gas. However, water pretreatment has been reported to remove the alkali ash metals and might improve pyrolysis products. If rice straw is pyrolyzed, the bio-oil can be upgraded to refinery-grade crude oil and the char can improve soil nutrient quality, potentially helping rice farmers in the developing world.