Energy and exergy analysis of rice husk high-temperature pyrolysis

Based on a two-stage fixed bed high-temperature pyrolysis system, the influence of temperature (800–1200 °C) on total energy and exergy, as well as exergy and energy efficiency of unreacted carbon, tar and pyrolysis gas were analyzed. The results indicate energy and exergy of each component in the pyrolysis gas as well as the total energy and exergy increase with temperature. Energy value and exergy value contributions of the components in the pyrolysis gas at 800 °C and 900 °C are CO > CH₄ > H₂ > CO₂. From 1000 °C to 1200 °C, the rank turns into CH₄ > CO > H₂ > CO₂. The energy efficiency and exergy efficiency of pyrolysis gas are in the range of 64.57–72.68% and 52.93–60.64%, respectively. The increasing rate of energy value and exergy value of the pyrolysis gas reaches maximum at 1000 °C. The energy efficiency and exergy efficiency of unreacted carbon and tar decrease with temperature. The consumption of energy for tar collection and loss of energy and exergy carried by tar can be reduced by increasing temperature. The loss exergy efficiency increases slightly below 900 °C and decreases from 38.8% to 34.6% above 900 °C.