Ni-supported pigeon pea stalk biochar as a catalyst for ex situ tar cracking in biomass gasification

Tar in producer gas causes detrimental effects on downstream pipelines in gasifier-based power generation systems. Char-supported Ni-based catalysts have been proven to be effective and low-cost solution for tar reduction. Experiments have been conducted with chars derived from various types raw materials available onsite or offsite. This paper investigates the influence of char derived from pigeon pea stalk on the tar reduction of producer gas generated from pigeon pea stalk pellets. The effects of char bed temperature, Ni loading, particle size of char, and gas residence time have also been studied. A laboratory scale downdraft gasifier was used for gasification and an ex situ reactor was used for tar reduction experiments. Taguchi method was used for the optimization analysis of the variables affecting tar reduction efficiency. Experiments showed significant impact of temperature and Ni loading and lesser impact of particle size and gas residence time on reduction of tar in producer gas. Optimum values of operating parameters were 700°C bed temperature, 0.4 mole Ni loading, 1–5 mm char particle size, and 8-s gas residence time. The gas yield due to catalyst activity was enhanced by 3.8