Finding innovative solutions for its customers is all in a day’s work for Babcock, which recently employed safe and highly effective gas expansion technology to eliminate clinkers from two ash bunkers and a bottom ash hopper at a coal-fired power plant. By combining the gas expansion technology with equipment developed and assembled locally, Babcock was able to safely and effectively remove the clinkers. As a result, the power station could put power back onto the grid, alleviating potential load shedding.
The gas expansion technology makes use of the Cardox CO₂ system which Babcock applies in conjunction with various cylinders designed for different applications. This system is highly effective in areas where other tools are not adequate.
Thaveshen Moodley, Sales Engineer at Babcock, explains that at the heart of the system is a reusable high-strength steel cylinder containing a charge of liquid carbon dioxide (CO₂) and a safety heater. Once energised by a small electric charge, the safety heater instantly converts the liquid CO₂ to gas, causing the volume and pressure of the carbon dioxide to increase.
The instantaneous build-up of pressure then breaks a rupture disc, releasing CO₂ through a special discharge nozzle. The gas expunged is 600 times its original volume, while the nozzle creates a powerful force on the CO₂ in the cylinder at pressures of up to 40 000 psi (3 000 bar). This pressure has the power to break surrounding material such as concrete, coal, and other rock-hard materials.
“The cylinders are also ideal for high temperature production areas and where hazardous, flammable or combustible materials are stored,” says Moodley. The cylinders can be re-used, and after being fired can be rebuilt, filled and fired again. After recovery the cylinder is recharged with liquid carbon dioxide and the heater, washer and rupture disc are replaced.
Moodley explains that the build-up of clinkers is formed through the fusion of ash in high temperature areas of boilers. In the bottom ash hopper, this occurs when there is some kind of failure in the bottom ash removal system, which causes bridging of ash at the throat of the hopper, and clinker formation to start. This ash is collected in an ash hopper, and non-combustible elements and minerals found in the coal interact at high temperatures and fuse together to form clinkers.
Babcock’s gas expansion technology can be safely used in feed mills and grain-handling plants where grain dust can be volatile and dangerous, and is suitable and effective when used in preheater systems, feeder systems, kilns, paper and pulp mills, waste handling sites and storage systems, steam boilers, and coal bunkers.
It is also safe and effective in clearing blockages and hang-ups from bulk materials handling storage vessels where it powerfully but gently breaks rock, concrete and other materials that have fused and hardened. Storage vessel walls are not damaged in the process, and the system does not present a fire hazard.
Moodley says that for extremely hard clinkers that require an even tougher application to dislodge the material, Babcock utilises a remote-operated drilling machine, similar to a mechanical excavator or heavy-duty drilling machine. If space allows, the machine is rigged and lifted into position on the clinker, and secured with multiple lifelines, which is then operated via remote control to hammer and drill away at the clinker.
Babcock supports southern Africa’s energy infrastructure through engineering design, maintenance and a host of other services. Major industrial customers include companies in the power and petrochemical sector, and the paper and the pulp industry.