Clearing clinkers using gas expansion tech
29 September 2020 | Web Article Number: ME202020502
BABCOCK recently employed gas expansion technology to eliminate clinkers from two ash bunkers and a bottom ash hopper at a coal-fired power plant, putting it back onto the grid and 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. According to Sales Engineer Thaveshen Moodley, this system is highly effective in areas where other tools are not adequate.
He said 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,” said 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 said 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.
He said 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 said that for extremely hard clinkers that require an even tougher application to dislodge the material, Babcock uses 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.