A heat exchanger is a piece of equipment used to transfer heat from one gas or liquid to another colder fluid. The exchanger ensures this transfer happens without the two substances mixing. For example, a car’s radiator receives coolant which has been pumped through the engine, drawing heat from it, then transfers that heat through tubes and fans to the outside air.
Heat exchangers are very important in the mining industry, maintaining conditions in a mine and keeping the equipment operational and the workplace safe and comfortable for the workers. Temperatures in deep mines can reach 50°C. As the normal human body temperature is around 37°, it is dangerous not to regulate these working conditions. At a 3° rise, the body begins to become fatigued and sluggish, while a rise of 4° causes it to shut down completely. That’s why it’s critical for working temperatures to remain between 28 and 30°C, which is achieved using a large network of heat exchangers.
On the surface, draglines are the largest moving machines in the world, weighing around 3500 to 5500t and able to dig up 200 to 300t of earth in one scoop. Instead of the usual diesel engines, these vehicles are powered through high voltage grids, causing the internal temperature to rise due to the amount of electrical energy. A heat exchanger is used to extract this excessive heat and regulate the machine’s internal temperature so that no dangerous malfunctions occur.
A dragline’s heat exchanger also has to withstand the temperatures of the environment, whether a desert where the temperature can reach 50°C or a snowy area where it can drop to -50°. Overall, the job of the heat exchanger is to maintain an optimal temperature regardless of the external temperature.
Extracted ore is impure and needs to be transported to where it can be refined, usually in large haul trucks capable of carrying up to 275t of ore. While these trucks’ engines are diesel-electric, they can still get extremely hot and therefore require a heat exchange to operate safely.
Further, the chemical reactions necessary to refine ores like copper or iron also require high and specific temperatures, so a heat exchanger becomes crucial to ensure this process is kept stable.
The exchanger transfers heat from the hottest part of the furnace, where the impure ore is to be processed, while recycling any excess heat for the continuous reaction. A common process happens in an autoclave where crushed copper ore is refined through its reaction with sulphuric acid. At the wrong temperature, this reaction can fail or become unbalanced.
Even though heat exchangers have a common purpose, they greatly vary in terms of structure and fluid flow. Complex and extensive research is being conducted to come up with more efficient heat transfer methods.