Key points
Many industrial facilities rely on fossil fuels for heating or melting glass, plastics and metals as well as processes like annealing and drying as well as a variety of other applications. However, continuing to use fossil fuels presents a number of challenges related to increased costs related to growing scarcity and instability of supplies.
There are also environmental and sustainability concerns related to the associated CO2, NOX and SOX emissions that require investment to meet stringent regulations.
Furthermore, with conventional fossil fuel heating systems it can also be difficult to ensure precise temperature control, while the equipment tends to be low in efficiency, expensive to install and maintain and the working environment is both hazardous and noisy.
Fortunately, electrical heating presents a superior alternative that offers reduced energy costs with less dependance on geopolitics and market fluctuations and higher efficiency.
The elimination of flammable gases also offers a safer working environment that eliminates CO2, NOX and SOX emissions and the costs associated with controlling them, and electric heating can be entirely sustainable when powered by renewable energy.
Electric heating systems also have a reduced need for maintenance that results in lower operating costs and with advanced controllers, facilities can automate heat control, ensuring consistent temperatures and minimising energy waste.
Traditional electric furnace control
Traditional electric furnaces have historically used power supplies based on variable-reactance transformers (VRTs) and saturable-core reactors. However, these technologies generally operate at a low power factor (PF), indicating inefficient electricity usage.
To address this limitation, a modern alternative is to adopt thyristor-based systems, which offer several benefits including lower peak power demand, load management and ease of use.
Reducing peak power demand
Modern thyristor-based heating controllers feature highly accurate inputs and outputs. Combined with advanced control algorithms, they maximise energy efficiency and overcome common heating issues. As electricity constitutes a significant operational expense for many facilities, substantial cost savings can be achieved.
For instance, numerous industrial facilities employ multiple heating elements. Without control, this setup can lead to high peak power demand, resulting in increased energy costs and potential grid instability. However, by implementing a setup with programmable logic controllers (PLCs) and several proportional–integral–derivative (PID) controllers, the load can be optimised.
In this configuration, maintaining good power quality remains essential. Modern controllers like ABB's DCT880 offer a range of control methods such as phase-angle control, full wave/burst control, half wave control, and I-, I2-, U-, U2-, and P control.
This ensures the suitability of the equipment for demanding applications with short rise times or challenging hot-cold ratios.
Electric Heating Power Optimisation
Even with the use of full wave/burst mode, there is still an impact on the grid. For example, simultaneous on-off switching of several DCT880 units would create large cyclic power peaks, resulting in an unstable energy supply.
To address this, the DCT880 incorporates a feature called Power Optimiser. By placing the peaks in series, it creates a steady load for the grid. This approach proves particularly effective in heating applications, where differences in timing do not affect the heating element.
The diagram above illustrates the contrast in curve volatility between before and after implementing the power optimiser feature. As a result, the peak power draw in this example has been reduced to below fifty percent of the installed capacity.
The diagram above shows eight heat consumers operating at power levels of 100 kilowatts (kW) and 200 kW. During a one-second cycle, these consumers utilise between 30 percent and 70 percent of the maximum available power. This uneven consumption pattern results in a peak after 300 milliseconds (ms) and a low point after 600 ms.
This graph (above) demonstrates the operation of the same eight heat consumers in a mathematically optimised solution, facilitated by the Power Optimiser. With this optimisation, power consumption remains constant at 500 kW, ensuring a steady load on the grid.
This optimised performance can also be achieved in challenging mid-load scenarios. For instance, when multiple devices operate at over half utilisation, a peak can occur at some point during the cycle. However, by splitting some of the on-cycles and toggling a consumer on and off twice within one optimisation cycle, optimal consumption can still be achieved.
Thyristor control in action
An excellent example of thyristor control in action is demonstrated by Norwegian unbleached pulp producer Vafos Pulp. At their Kragerø plant, they previously relied on oil for the drying process. Concerned about carbon emissions, they decided to replace their nine-megawatt (MW) oil-fired boiler with electric heaters in 2022.
To ensure maximum safety, operational efficiency and minimal downtime, Vafos selected five ABB DCT880 power controllers, each rated at 2.2 MW. These controllers were mounted in containers at the Kragerø facility.
With the power controllers, Vafos achieved precise control over the drying process compared to when oil was used. Moreover, the switch to electricity eliminated the need for on-site oil storage. The DCT880 Power Optimiser facilitated a steady load on the local electricity grid, minimising disruptions.
Thanks to Vafos utilising renewable electricity from hydropower, their shift away from oil resulted in an annual reduction of approximately 14,000 tonnes of CO2. This reduction is equivalent to removing 7,000 combustion-engine cars from the road.
Significant long-term savings with Electric Heaters
While a precision electrical heating control system may entail higher upfront costs compared to cheaper alternatives, it delivers a lower total cost of ownership (TCO) due to the substantial energy savings it enables. Additionally, electronic control systems contribute to delivering a superior product by providing precise and rapid temperature control.
Conclusion
Thyristor power control technology offers a key solution for achieving precise, sustainable and efficient electric heating. By implementing advanced controllers like the ABB DCT880, facilities can optimise energy usage, reduce peak power demand, and contribute to a greener future. The ease of use, flexible interfaces, and comprehensive control capabilities of these controllers make them an ideal choice for an array of industrial applications.
