Simulation and Modelling of Zinc Recovery Process from Steel Scrap
Date
2020-12-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-1334-610X
Type
Thesis
Degree Level
Masters
Abstract
This research project addressed a practical problem besetting electric arc furnace (EAF) steelmakers and environmentalists for many years. EAF dust is generated during the EAF steelmaking process, and it is designated as a hazardous waste in most industrialized countries because it contains zinc, which is hazardous for the environment. The purpose of this research was to develop a pre-treatment step that removes zinc coatings from galvanized steel scrap, leaving steel products with low or no zinc content, which can be used as a cheap source of feed materials for steel making industries that produce zinc-free EAF dust. Also, zinc consuming industries can use the recovered zinc to bridge the gap between the supply of and demand for zinc.
The zinc recovery process involves three major stages, namely: leaching, solvent extraction and electrowinning. A metallurgical simulator (METSIM) was used to simulate these processes. The leaching of the zinc coating from the galvanized scrap was carried out with sodium hydroxide because it cannot leach iron, which is the major component of the galvanized steel scrap. Sodium zincate was produced from this process, and black steel is recovered as a solid from the solid-liquid separator, which can be fed in the EAF to produce new steel. In the solvent extraction, 8-hydroxyquinoline (LIX-26) was used as an extractant because of its ability to extract zinc. Zinc quinoline and sodium hydroxide were produced as extract and raffinate, respectively. Concentrated sulfuric acid was used to strip the extract to produce zinc sulphate transferred to the electrowinning section. In electrowinning, metallic zinc was recovered from zinc ion deposited at the cathode and oxygen gas evolved from the stream.
This process's feed rate is 400 mt/yr of galvanized steel scrap with a feed component of 320 mt/yr and 80 mt/yr of iron and zinc, respectively. The amount of zinc recovered at the end of the process is 72.59 mt/yr, and the percentage is 90.74%. With this amount of zinc recovery, the steelmakers will be able to recycle the galvanized steel scrap with zero or minimal pollutants caused by zinc; also, the recovered zinc as a by-product will be used for other purposes in the zinc consuming industry.
Description
Keywords
Leaching, Solvent extraction, Electrowinning
Citation
Degree
Master of Science (M.Sc.)
Department
Chemical and Biological Engineering
Program
Chemical Engineering