Boilers
How industrial boilers work
A boiler is a pressurised vessel in which heat generated through combustion is transferred to water to produce hot water or steam. The two traditional configurations for industrial boilers are water tube and fire tube designs. In both cases, the boiler shell is a large steel cylinder lined with a high-temperature refractory material and fitted with a network of tubes.
In a water tube boiler, hot combustion gases pass around water-filled tubes. In contrast, fire tube boilers contain the combustion gases within the tubes, while the surrounding shell holds the water. Water tube boilers, though more costly to manufacture, provide greater surface area for heat transfer and produce steam more quickly. Fire tube boilers hold more water, take longer to reach steaming temperature, but are more stable under varying loads. The choice between the two depends on application-specific requirements.
The Benson boiler and supercritical steam technology
In 1922, engineer Mark Benson patented a new design for a supercritical steam generator, proposing to raise the pressure and temperature of water to its critical point, where it becomes a supercritical fluid. This design eliminated bubble formation in steam generation and became known as the Benson boiler.
This concept revolutionised power generation and remains at the core of many modern thermal power stations. The supercritical process has been refined to increase efficiency and lower emissions in fossil-fuel-powered generators.
Ultra-supercritical steam and material challenges
Building on this technology, ultra-supercritical (USC) steam systems now reach temperatures of 600°C (1112°F), pressures of 300 bar, and enable coal-fired plants to operate at 46% thermal efficiency. Future advanced ultra-supercritical designs aim to exceed 700°C (1292°F) and achieve 50% efficiency.
As operating temperatures and pressures rise, so too do the demands placed on construction materials. These extreme environments require new refractory linings, insulation materials and advanced heat-resistant alloys to ensure safe and efficient operation.