Treatment of Blast Furnace Wastewater and Utilization of LD Slag from Steel Industry

Abstract

Steel industries are one among the major industries which contribute to the world's economic growth. However, waste generation.within the industry is enormous due to its high production rates. Large quantity of water is used in the steel industry for different processes like cooling operations, dust scrubbing and descaling. Nanofiltration (NF) is been used as a tertiary treatment system for the blast furnace (BF) wastewater in TATA Steel Ltd., India. The volume of the reject stream varies between 20-30 % of feed steam. This membrane reject stream contain concentrated monovalent and divalent ions (3- 4 times of feed). Available technologies for the treatment of NF reject are not efficient and economically viable due to high energy and space requirement (eg. Solar concentrator). Therefore, there is an urge for a more efficient, economical and facile technique for the treatment of membrane reject stream. Similarly, around 2 - 4 tontres of waste per tonne of steel are being generated within the industry. Linz Donawitz (LD) slag is one among the wastes in integrated steel industry. Globally, production of LD Slag is around 47 MT per annum. Hence there is a need for use of the LD slag in much persuading way through either conversion of slag into useful material or recycling as process material. Taking all these issues into considerations, the main objectives of this work are divided into two sections. First section deals with the treatment of highly saline wastewater from blast furnace unit of steel industry. And the second section deals with the utilization of LD slag which is a by-product of steel industry.