1 MW supercritical water heater for UK nanoparticle manufacturer

Promethean operates what is said to the world’s largest continuous multi-material nanoparticle manufacturing plant in Nottingham, producing more 1,000 tonnes per year of its range of inks and coatings products. Production flexibility is largely down to the wide temperature range achievable with its process. 

For this bespoke heater, Babcock Wanson designed and manufactured a specially wound continuous coil assembly to form the main heating surface using 9 mm thick stainless steel, as opposed to the usual 4 mm carbon steel for a standard industrial water heater. The material and thickness were chosen to meet the pressure and temperature demands of the process to be able to produce supercritical water at up to 250 bar and 450°C. 

Several challenges were faced along the way, including designing the heater with the ability to accept variations in water flow (between 600 and 3,000 kg/h) and heat input within wide parameters, and specifying and installing specialist instruments and controls to work at these temperatures and pressures. 

The resulting heater is now an integral part of the process, which includes return fluid heat recovery to limit the final temperature rise of the fluid to 90°C. This brings it up to 360°C water at 270 bar to take it to the temperature required for the supercritical condition. 

The supercritical water is then pumped into the reactor at the same time as the precursor where it mixes and forms the product. The product leaves the reactor at 350°C, then going through the heat exchanger to cool it down and recover waste heat. 

The entire process is controlled by sophisticated software and is encased in toughened casing for safety.