Introduction to BOFS > Types of SlagThree types of slag, namely, blast furnace slag, basic oxygen furnace slag, and electric arc furnace slag, are produced in wholly integrated steel mills in the steel industry in Taiwan. The so-called steel slag or steelmaking slag refers to basic oxygen furnace slag and electric arc furnace slag.
A wholly integrated steel mill - GBFS & BOFS
Blast furnace slag (BFS) and basic oxygen furnace slag (BOFS) are by-products of steelmaking in wholly integrated steel mills. When blast furnace slag is cooled in water quickly, water-quenched blast furnace slag is formed, which will become granulated blast furnace slag (GBFS) powder after being ground. When GBFS powder is blended with cement, it can replace general cement and be widely applied in various kinds of construction projects. A small portion of blast furnace slag can be cooled by air naturally to become air-cooled blast furnace slag, which is mostly used as BFS graded materials for road construction. In the wholly integrated steelmaking processes, limestone, dolomite, etc., which are fluxes, are added in molten iron to remove the impurities in it when molten steel is being made in a converter. Basic oxygen furnace slag is the by-product in this production process. It will become graded aggregates after being crushed, magnetically separated, and screened. It is widely utilized for road paving, soil improvement, makeshift pavements, filling materials, land reclamation, etc. A small portion of BOFS graded aggregates can be made into soil improvement agents, lime fertilizers, materials for waste water treatment, etc.
If you would like to delve into relevant domestic and international literature or information regarding basic oxygen furnace slag, you can link to “Literature on BOFS” on our website.
Electric arc furnace (EAF) slagEAF steel mills generally produce carbon steel and stainless steel. The former representative producers are Feng Hsin Steel Co., Ltd., Tung Ho Steel Enterprise Corporation, Hai Kwang Enterprise Corporation, etc., and the latter one is Tang Eng Iron Works Co., Ltd. The main raw materials of EAF steelmaking are scrap iron and scrap steel, which are smelted at high temperature to produce steel products, and the slag that is produced in this production process is called EAF slag. EAF slag must go through the oxidation phase and the reduction phase; therefore, it can be divided into two types, namely, oxidation slag and reduction slag. In addition, the gas and suspended particles that are emitted in this production process are collected by air pollution control equipment. These substances are called collected dust and usually contain heavy metals, such as dioxins, zinc, lead, etc. Therefore, they are categorized as hazardous industrial waste
Since different types of slag have different features, their applicable laws and regulations are also different in terms of their management. In the wholly integrated steelmaking processes, air-cooled blast furnace slag and basic oxygen furnace slag are residual substances from natural minerals after iron is extracted from them. Their composition is simple, and their properties vary only slightly. Basic oxygen furnace slag is one of CSC’s registered products, and it is not considered as industrial waste; therefore, it is not regulated by the Regulations Governing Administration of Reuse of Enterprise Waste promulgated by the Ministry of Economic Affairs (MOEA). Nor is it regulated by the Waste Disposal Act promulgated by the Environmental Protection Agency. However, the utilization of the relevant products of basic oxygen furnace slag should be in accordance with the relevant national standards and outlined construction specifications. The reutilization of basic oxygen furnace slag must follow Item 1: water-quenched basic oxygen furnace slag of the Resource Recycling and Reuse Act promulgated by MOEA.
On the other hand, the composition of EAF slag is more complex, and its properties vary greatly; as a result, oxidation slag and reduction slag are categorized as industrial waste, and the management of its reutilization must follow Item 14: electric arc furnace slag of the Regulations Governing Administration of Reuse of Enterprise Waste.