Mar-2023

Decarbonisation of industrial process heating - electric heaters

Electricity is a potential carbon-free solution to process heating, but since not all heat sources are created equal, electrical heating equipment must be uniquely designed.

Brian Stubenbort
Armstrong Chemtec Group

Article Summary

Industrial titans are racing to decarbonise their facilities to meet government, investor, and public demands alike. The unavoidable fact is that most manufacturing processes require heating. As seen in Figure 1, process heating makes up approximately 70% of all process energy input. Furthermore, 95% of the heating energy is derived from either steam or fuels, which contribute to carbon emissions.

Sustainability and EHS managers across all sectors have correctly identified the third energy source, electricity, as a potential carbon-free solution to process heating. The electrification revolution has inspired the application of electricity in areas of process heating previously unconsidered. Further environmental benefits are gained when electrical generation for process heating is provided by a renewable power source. Using renewable power for electric heaters eliminates both Scope 1 and Scope 2 emissions.

If the solution to decarbonise process heating is so obvious, why has there been a delay in implementing electric process heating? The answer may not be as straightforward as expected. Firstly, using electric heaters for industrial heating has historically been avoided as industries found a more economical solution for heating through the combustion of readily available fossil fuels. However, as environmental pressure regarding fossil fuel usage continues to build, the cost-benefit analysis has progressively tilted towards the use of electricity. Secondly, first-time users of electric heat quickly discover that not all heat sources are created equal.

Unlike the relatively forgiving heat transfer environment of combustion and steam, electrical heating equipment must be uniquely assessed and designed. If the constant flux of electrical heat is not continuously transferred to the process, damage can quickly occur, degrading the process fluid and rendering the heater useless. Experience in the design and implementation of electric heaters to a specific process is not only required but is frequently absent, and therefore this has hindered the transition to electrification.

Immersion heaters
Current industrial exposure to electric heaters is mainly confined to immersion heaters (see Figure 2) or some version of resistance heating, such as strip heaters, finned heaters, cartridge heaters, and band heaters. At first glance, immersion heaters resemble shell and tube heat exchangers. These types of heaters all use an electrically insulated internal resistance wire that heats. The heat is then transferred through thermally conductive but electrically insulating material to the skin of the device or the heating element. In a similar manner to an electric stove, the high skin temperature is used to transfer the heat.

Immersion heaters are readily available off the shelf from global vendors and are typically offered in various standard sizes in an attempt to best match the process duty. A recurring cause of premature failure of immersion heaters has resulted from the selection of standard sizes to match process requirements instead of being individually custom designed for the process duty. Often, electric heater vendors are experts in electrical heat design but lack process engineering expertise. Compounding this issue is that the typical immersion heater purchaser has expert knowledge of their process but is not an electric heat expert. The mismatch results in a serious knowledge gap that can result in premature (and sometimes instantaneous) equipment failure.

The installation of an electric heater in a new or existing process must be meticulously evaluated. This can only be accomplished by suppliers who are experts in both process heat transfer and electrical heating equipment manufacturing. The marriage between these two core competencies is a proven method for ensuring a successful startup of the capital equipment and achieving an extended lifespan. The higher initial equipment cost when compared with fired heaters, due to its design, is recuperated on the backend when the equipment’s lifespan is measured in years or decades instead of in days or months.

Process electrification requirements
Unfortunately, due to limiting factors, such as but not limited to coking, maximum temperature, and proper mixing, immersion heaters are not well suited for some processes. Therefore, other electric heating methods must be utilised to fulfil process electrification requirements. Industry has allocated billions of dollars of funding for the research and development of process electrification. One of the best examples is the electrification studies of ethylene crackers. Even the transition to hydrogen is drawing R&D funding for electric heat as it is heavily reliant on electric heat to eliminate its carbon footprint.

Investment funding currently flowing into this research could be significantly optimised by focusing on pilot testing for end-user proof of concept and leveraging already proven technologies. The Armstrong Chemtec Group has been designing electric process heaters for over 40 years. As a company specialising in heat transfer, we have custom-designed thousands of electric heaters with proven operational reliability.

Current publications suggest that electrical process heating above 1000°C is experimental. This is not the case, as several of our technologies operate at process temperatures over this suggested limit. Radiant and impedance heating technologies are particularly well suited for solving many process electrification challenges. Along with regular duties, these heaters can also be designed for high-temperature, high-pressure, and two-phase cases. Depending on the particular design, electric heaters can be supplied for both direct and indirect service. Furthermore, electric heaters can be made from many different metallurgies, ensuring thermal, chemical, and mechanical compatibility with the process.