Fixed-bed pyrolysis of walnut shell: Parameter effects on yields and characterization of products

- Walnut shell was pyrolyzed to study parameter effects on product yields.
- Reaction temperature was found to be the most effective parameter.
- Maximum liquid yield was obtained at 500 °C, 30 min and 150 ml min−1 as 48.2%.
- Liquid product was a low-grade fuel with an energy content of 4799 kcal kg−1.
- Solid product was a valuable fuel which can replace with conventional fossil fuels.

Fixed-bed pyrolysis experiments of walnut shell have been conducted in a well-swept tubular reactor to investigate the effects of various process parameters on product yields. For this purpose, pyrolysis temperature, reaction time and sweeping gas (N2) flow rate were set in the ranges of 350-650 °C, 10-50 min and 50-450 ml min−1, respectively. The heating rate was fixed at 40 °C min−1. Maximum liquid yield was obtained at 500 °C, 30 min and 150 ml min−1 as 48.2%. The liquid product was characterized by FTIR and GC-MS analyses, and shown to be a highly oxygenated complex mixture with 32 identified compounds whose carbon distribution was between C2-C10. In addition, the solid product was analyzed by means of FTIR, SEM and BET surface area which showed that solid product, as produced, was not appropriate for activated carbon applications. However, the higher heating value of solid product was higher than that of sub-bituminous coal, indicating a valuable solid fuel.