Industrial Furnaces

Industrial furnaces are used in metallurgical production for smelting at high temperatures, in heat treatment, tempering, in some areas such as the food industry, for drying, and for fermentation at low temperatures. The metal industry has a significant share in total industrial energy consumption. These furnaces are used in high-temperature zones:

•enamel cooking: 600°C to 1100°C

•heat treatment of metals: 1100°C

•rolling, extrusion, cooking of ceramic materials, heat treatment, and pressing: 1350°C

•melting and smelting of metals: 1700°C [1]

Furnaces should be operated with minimal fuel and maintenance whereas the design of the furnace should allow for maximum heat transfer to the material in a defined time. To ensure these conditions, these criteria should be considered:

•how much heat will be transferred to the material

•the heat necessary to heat the mass, and the loss

Once these issues are identified, studies should be made on how much of the losses will be minimized, what will be used as a refractor material, and how the temperature of the furnace body will stabilize. The model industrial furnace is used to cure the applied enamel of the tank and boiler that will be used in the heating sector. After the processes of metal forming, welding, degreasing, cleaning, and enameling of the tank and boiler, curing is undertaken in the model furnace. Finally, the tank and boiler are processed in the furnace at 860°C. 

Industrial furnaces are widely used in many industries (metallurgy, mechanical engineering, chemicals, ceramic and building materials). Industrial furnaces using fossil fuels are characterized by heat losses from flue gases with a temperature of 500 °C and above. Recuperators and regenerators are used to partially cool the flue gases and preheat the air supplied to the furnace burners. However, the temperature of the flue gases after cooling remains high and reaches 250–350 °C.

The same characteristics apply to heating boiler plants of large technological facilities and municipalities. These plants consume a significant amount of energy, usually as natural gas, whose price fluctuates depending on supply, demand, and world economic and political conditions. The efficiency of boiler units nowadays is about 0.85–0.90, with the loss of heat via waste gases being about 6–7% or more. The internal use of heat from exhaust gases of boiler units is used for preheating the combustion air supplied to the burner and heating the return circuit water of the heat supply system, but significant heat is still lost to the surroundings.

Since the purpose of boilers is to raise steam for various uses, these boilers do not produce electricity, which means a low energy conversion factor for the fuel. Furthermore, in the event of an emergency power outage and shutdown of their operation, heating mains may be damaged and consumers will lose their steam supply unless an alternative power supply in available on site. One way to use waste gas heat is to generate electricity to meet the boiler house needs such as motor drive of fans, smoke exhaust fans, circulating pumps, etc.