Within steel production, the preheating of blooms or billets is an essential step before downstream operations such as hot rolling and forging. The walking beam furnaces used for this heating operation need to achieve a uniform target temperature across the entire billet to avoid affecting the quality and yield of the final product. These furnaces represent a substantial portion of energy consumption in steel plants. However, like most furnaces, the walking beam furnaces operate with very low thermal efficiency.
“Typically, only 30 to 60 percent of the heat generated is used to heat billets, while most of the remaining heat is lost through the flue gases that are released into the atmosphere,” Pimpalnerkar explains. “The process also results in high carbon emissions, at around 60 kilograms of CO2 for every ton of steel heated.”
POSSIBLE TO SCALE UP HEATING PROCESS
By replacing the industrial burners with electric heating systems, the thermal efficiency of walking beam furnaces could be increased to more than 90 percent, resulting in substantial cost savings. This is achieved through the absence of flue gases.
Electrification would also remove all direct carbon emissions from the heating process itself, and if the electricity comes from a renewable source, there would effectively be no emissions associated with heating.
The biggest obstacle to electrical furnaces is the perception in the industry that they are only suitable for small-scale heating. Within Kanthal we have our own electrically heated walking beam furnace, which can be scaled up. This is proof that it can be done.
“The biggest obstacle to electrical furnaces is the perception in the industry that they are only suitable for small-scale heating,” says Pimpalnerkar. “But within Kanthal we have our own electrically heated walking beam furnace currently being used in regular production, which can be scaled up. This is proof that it can be done.”
INVESTMENT PAYS OFF
In addition to significantly reducing energy consumption and CO2 emissions, electrical heating has a proven ability to achieve precise target temperatures. This in turn improves the quality of the final product and reduces the number of rejections in downstream operations. In contrast to fossil-fuel-fired heating, electrical heating also allows for controlled atmospheres with low levels of oxygen. As a result, the levels of oxide scale on the surface of the billets can be substantially less.
“For steel producers, electric heating would mean lower production costs, higher yields and a better-quality final product,” Pimpalnerkar says. “Combined with the energy savings and CO2 reductions, it doesn’t take long for electrical heating equipment to repay its investment.”
Key benefits of electric preheating of billets in walking beam furnaces
The preheating of billets is an essential step in steel production for achieving a high-quality end product. However, the fossil-fuel-based heating typically used in walking beam furnaces is inefficient, consuming large amounts of energy and emitting high volumes of CO2.
By electrifying the heating process through Kanthal’s Globar® and Kanthal® Super heating elements, steel producers can achieve much higher thermal efficiency and potentially reduce CO2 emissions to zero. Globar® can achieve temperatures as high as 1,625 degrees Celsius (2,960 degrees Fahrenheit), and Kanthal® Super can reach as high as 1,850 Celsius (3,360 Fahrenheit).
Here are four good reasons to choose Kanthal’s heating elements.
- Thermal efficiency of more than 90 percent
When using conventional gas-heated industrial burners in walking beam furnaces, only 30 to 60 percent of the heat generated is actually used to heat the billets. Most of the remaining heat is lost through the flue gases that are released into the atmosphere. In contrast, because electric heaters do not generate flue gases, the thermal efficiency can be higher than 90 percent. This means a significant reduction in energy consumption and a substantial reduction in costs.
- Zero emissions
Industrial burners that use fossil fuels also produce a high level of CO2 emissions. However, using electric heating can substantially eliminate this problem. In fact, if the electricity derives from a renewable source, the heating can be completely emission free.
- Precise temperature control
Both Globar® and Kanthal® Super enable precise temperature control in the furnace and in turn in the billets. This improves the overall quality of the final steel and reduces costs by minimizing the number of rejections in downstream operations.
- Less oxide scale
Since electric heating has greater flexibility to operate in controlled atmospheres that do not contain high levels of oxygen, there is significantly less oxide scale forming on the surface of billets compared with fuel-fired heating. This reduces time and costs in downstream operations and increases the overall yield.
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