Metallurgical Slag Treatment and Utilization
Metallurgical slag is classified into two major categories: non-metallic materials and waste products. Non-metallic materials consist of non-conductive slag, such as alumina as well as other minerals. Waste products are generated from the thermal processes involved in the production of metal, and include oxides, metals, and other compounds driven off from the metal. Metallurgical slag is a byproduct from the engineering and metal processing stages of manufacturing. This type of slag is produced from the thermal decomposition of metal or minerals in the form of vapor, liquid, and solid particles. Metallurgical slag, which is also referred to as metal sludge, is made up of various minerals as well as metals, including iron, copper, nickel, chromium, zinc, lead, and cobalt. The presence of various metal compounds in the slag indicates that there is a potential for metal recovery, as well as potential for additional uses.
Metallurgical slag is typically categorized into three different types: ferrous slag, non-ferrous slag, and refractory slag. Ferrous slag is a byproduct of ferrous metal production through smelting and refining processes. This type of slag consists of calcined lime and ash as well as metallic elements such as iron, copper, nickel, chromium, zinc, lead, and cobalt. Non-ferrous slag is a byproduct of refining processes aimed at producing metals or minerals from non-ferrous ore or from secondary raw materials. Refractory slag is the slag produced from processes involving refractory materials. These types of slag contain components such as alumina, zirconia, and other oxides.
Metallurgical slag can be treated for reuse, either as a raw material in other manufacturing processes or as a part of concrete and cement production. Metallurgical slag can be used for either “treat-and-use” or “treat-and-throw” operations. Treat-and-use operations involve the physical and chemical treatment of slag, so that it can be used as a raw material in other manufacturing processes. Treat-and-throw operations involve chemical treatment of slag, so that it can be used as a filler material in concrete and cement production.
The most common treatment used to reclaim air-cooled metallurgical slag for reuse is grinding. Grinding reduces the size of slag particles, allowing them to be more easily separated from the metals and minerals that make it up. Slag grinding plants will also utilize flotation to separate the slag from the metals and minerals it contains. This process involves introducing a surfactant to a slag/water mixture, so that the metals and minerals can be selectively bonded to the surfactant and removed.
Metallurgical slag can be used in several industrial processes. Slag is a good replacement for traditional soil amendments, as it is made up of non-toxic, non-volatile particles that are beneficial to the growth of plants. Slag can also be used as a road base material, as the particles it contains are durable and provide significant stability to roadways. In addition to its use in construction, slag can also be used as a raw material in engineering, manufacturing, and metallurgical processes.
By utilizing metallurgical slag in various ways, industries are able to reduce their costs, as well as reduce their negative environmental impact. Treating and making use of metallurgical slag helps to eliminate the need for disposing of the material in landfills. Additionally, by using metallurgical slag, resources required for other types of raw materials can be saved. As industries continue to become more aware of the potential of metallurgical slag and look for ways to save costs and reduce their environmental impact, metallurgical slag treatment and utilization is likely to gain in importance.
