Carbonized anthracite is also called calcined anthracite in the coal industry. It is widely used due to high carbon fixed content, low sulfur, stable carbon additive effect, and cost-effectiveness. The water treatment industry has used calcined anthracite extensively in industries such as metallurgy and hydroelectricity. It is also widely used by the papermaking, pharmaceutical, chemical and pharmaceutics industries. It is also an important raw material for steel-making, as it is able to provide the steel with carbon, which can improve its hardness and strength.
Southern Coal manufactures calcined coke in three rotary-kilns that heat anthracite between 900 to 1000 degrees centigrade. In the calcination, the volatile part of anthracite is burned off. The resultant electrical forging coal has a higher carbon content. In the production of Soderberg and cathode block carbons and electrodes for pre-baking, it is often used.
As aggregates, calcined coal can be used in the production of concrete. This is a very popular and cost-effective way to utilize it. This method reduces the amount of cement clinker needed to produce concrete, which is beneficial for both environmental and resourceful aspects. The feasibility and potential to substitute traditional coarse or fine aggregates in concrete with calcined Coal Gangue has been investigated by numerous studies.
Another way to utilize calcined coal is to make it into metakaolin, which is an admixture that can be used in the production of cement to replace part of the clinker. This can enhance the durability and long-term strength of concrete. It also is an environmentally-friendly method, since it doesn't produce waste or pollutants.
Coal gangue is a secondary product of the coal mining process and is currently disposed of in landfills, which leads to severe environmental pollution. Researchers propose that the coal waste be turned into valuable products including aggregates as well as alumina. Coal gangue is abundant in alumina, which can be utilized as a substitute for cement clinker. The hydration response speed can be increased and the concrete's strength improved by using this substitution (Yuetal, 2012).
The present study was designed to upcycle coal gangue fine aggregates by substituting fly ash with thermally activated calcined coal gangue. CGF, which is a fine aggregate of coal gangue without any grinding, was calcined in a range between 500-900 degrees Celsius to boost its reactivity. The X-ray diffraction and scanning electron microscopy analyses showed that calcined CGF can fully substitute fly ash in the preparation of alkali-activated slag materials (AASM). The 3 d and the 7 d compression strengths of AASM for both with and without CGF have been determined. As compared with the control sample, replacement of fly ash for calcined CGF did not have a significant impact on the microstructure development of AASM. Moreover, the substitution of CGF can effectively improve the performance of AASM. The research presented here provides an effective and new way of recycling coal gangue.
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