Synergistic recycling of biochar from sawdust pyrolysis and waste coke breeze to produce metallurgical quality biocoke with syngas as a by-product

Abstract

Waste coke breeze and sawdust were synergistically utilized as two solid waste resources to produce a high-quality metallurgical biocoke product and a combustible syngas as a by-product in this study. The experiments of the sawdust pyrolysis were carried out to prepare biochar and bio-syngas. A sawdust biochar with high fixed carbon content (88.23%) and low volatile content (4.98%) was obtained by sawdust pyrolysis at 900 °C for 40 min. Meanwhile, a bio-syngas with 87.7% combustible gases was obtained as a by-product. The carbon valid conversion ratio (to combustible gases and biochar) in sawdust was 89.6%. The obtained biochar was first used as an auxiliary filler for coke breeze(as aggregate) to produce a metallurgical quality formed biocoke product (a metallurgical coke substitute). The cracks and pores inside the formed coke product can be filled with a suitable amount of sawdust biochar powder, improving its internal structure and performance. A formed biocoke product, which met the Chinese secondary metallurgical coke standard, was produced with the mass ratio (biochar to coke breeze) of 2:8 by carbonization under a nitrogen atmosphere for 30 min. This study provides an efficient and high-value-added way of using sawdust and coke breeze resources. And it offers an essential research reference for recycling bioresources and solid waste fuels.