Coke is a vital raw material for iron and steel production. It is produced from coal by heating it in coke ovens at high temperatures to remove volatile matter and impurities. The resulting coke is hard, porous, and has a high carbon content. Coke is then used as a fuel and a reducing agent in blast furnaces to produce pig iron from iron ore.

However, coke production is also an energy-intensive and polluting process. One of the main challenges is how to cool down the hot Coke (about 1000°C) after it is discharged from the Coke ovens. Traditionally, this is done by spraying water on the coke in a process called wet quenching. This method has several disadvantages, such as:

- Loss of water and generation of wastewater that needs to be treated

- Loss of heat and energy that could be recovered and utilized

- Degradation of coke quality and strength due to thermal shock and moisture absorption

- Emission of dust, steam, and harmful gases such as ammonia, hydrogen sulphide, and benzene

To overcome these drawbacks, an alternative method called dry quenching has been developed and adopted by some steel plants. Dry quenching involves cooling the hot coke with an inert gas, usually nitrogen, in a closed chamber. The heat from the coke is transferred to the gas, which then flows to a waste heat recovery boiler to generate steam and electricity. The advantages of dry quenching over wet quenching are:

• Saving water (around 0.5–1.0 m3 per ton of gross coke) and reduction of water pollution

• Recovery of heat and energy (around 0.2–0.3 GJ per ton of gross coke) and reduction of greenhouse gas emissions

• Improvement of coke quality and strength (around 10–15% increase in M40 index and 5–10% decrease in M10 index) and reduction of coke consumption in blast furnaces

• Reduction of dust emissions (around 90%) and improvement of the working environment

According to some estimates, dry quenching can reduce the energy consumption of coke production by 25%, carbon dioxide emissions by 28%, and water consumption by 70%. Dry quenching also enhances the blast furnace's performance by increasing productivity, decreasing the fuel rate, and lowering the slag rate.

Dry quenching is not a new technology; it was first introduced in Japan in the 1970s and then spread to other countries such as China, India, Russia, Germany, and Brazil. However, it still faces some challenges in terms of high capital cost, maintenance cost, operational reliability, and safety issues. Therefore, further research and development are needed to improve the design, operation, and performance of dry quenching systems.

In conclusion, dry quenching is a highly reliable system to reduce air pollution, energy use, water use, and coke consumption in the iron and steel sector. It also improves the quality of Coke and the efficiency of blast furnaces. Dry quenching is an example of how climate technology can contribute to both environmental protection and economic development.