Process optimization of yellow gypsum synthesized from LD Slag fines – an opportunity for value addition of LD Slag

Abstract

LD slag (steel slag obtained from the Linz-Donawitz steel making process) is an industrial by-product of the steel industry. The present work endeavours to explore the value addition of LD slag, which is a rich source of calcium by the synthesis of yellow gypsum. The yellow gypsum was synthesized by the atmospheric leaching of –60 mesh LD slag fines obtained from the waste recycling plant (WRP) at Tata Steel plant, Jamshedpur, India, using sulphuric acid. Gypsum is an important material which has numerous applications in different sectors such as construction, pottery, agriculture, medicine and for synthesis of other calcium based materials having industrial importance. The present work describes the process flow of synthesis of yellow gypsum in a cost effective manner and its characterization on the basis of different experiments carried out on laboratory scale for optimum utilization of the raw material. The process efficiency was estimated to be about 98.33% and the average cost worked out to be 129 USD/t which was very less as compared to the cost of 311 USD/t for a commercial calcium sulphate product used as a soil conditioner. An Indian patent application bearing application number 572/KOL/2014 has also been filed on the basis of this study.