Stepped pyrolysis: A novel approach for enhanced adsorbency and carbon in Pigeon pea stalk char

Abstract

This article introduces a novel technique, stepped pyrolysis, for thermal degradation of biomass. The differential thermogram (DTG) of pigeon pea stalk was deconvoluted into their intrinsic bioconstituents and these deconvoluted peaks were used to decide the different stages or steps to finalize the thermal protocol to be executed for stepped pyrolysis. The stepped pyrolysis and traditional pyrolysis of pigeon pea stalk were conducted and the characterisation of outputs was done. The obtained result for the char produced by the stepped pyrolysis method showed a reduction of 5% in the volatile matter and an increment of 5% in fixed carbon content, over the product of traditional pyrolysis. The stepped pyrolysis increased the iodine number by 17% while reducing the methylene blue values by 31% as compared to the traditional pyrolysis. A significant reduction in activation energy by 21% for FWO, 18% for KAS, and 26% for Starink methods were recorded for stepped, over traditional pyrolysis. The pyrolysis reaction mechanism of stepped and traditional pyrolysis methods followed the second-order (F2) and two-dimensional diffusion model (D2). The stepped pyrolysis method produced a better quality product with more micropores and carbon-rich char than the traditional method.