Optimization of pyrolysis conditions for char production from rice husks and its characterization as a precursor for production of activated carbon

• Response surface methodology was employed to optimize pyrolysis conditions for production of char with maximumyield, fixedcarbon content, and with minimum ash content from Uganda’s New Rice for Africa (NERICA) 1 rice husk variety. The aim wasto obtain rice husk char with more suitable properties as an activated carbon precursor. Mathematical models were developed toexplain the relationships between the experimental responses and the pyrolysis parameters of temperature (400–600 °C), heating rate (10–25 °C min−1), and heating period (60–120 min). The optimized rice husk char was further characterized for elementaland proximate compositions, thermal behavior, specific surface area, as well as surface functional groups. Results from theanalysis of variance (ANOVA) revealed that the quadratic model best fits each of the responses. Pyrolysis temperature had thegreatest influence on each of the responses, followed by heating period, and lastly heating rate. Optimum pyrolysis conditionswere found to be temperature (406 °C), heating rate (10 °C min−1), and heating period (60 min), resulting in char yield, fixedcarbon, and ash contents of 35.26, 55.39, and 35.01% dry basis, respectively. Compared to raw rice husk, the resulting rice huskchar was found more suited as activated carbon precursor, due to its enriched carbon content (60.35%) and specific surface area (123.9 m2 g−1). Thermogravimetric analysis of the rice husk char revealed that thermal activation temperatures higher than 400 °C may be required to considerably devolatilize the char, forming a more porous activated carbon.

Nyckelord

NERICA 1 rice husk

Pyrolysis

Optimization

Char Yield

Fixed carbon

Ash content

Chemical Engineering

Kemiteknik

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