Where clinker discharges from the kiln and falls into the clinker cooler, chunky material tended to cling to the static cooler grates and/or cooler curbs. Air cannons are commonly used to remedy this phenomenon, but if they experience clogging from backflow, or if they are set in an environment that is too hot to properly maintain them, then accumulations inevitably form.
Operators at the Lehigh-Hanson plant in Leeds (Alabama), the oldest continuously operating cement manufacturer in the state, worked closely with Martin Engineering on an innovative air cannon configuration to resolve such an issue.
“Our cannons were located close to cooler walls where the conditions were very hot and dusty,” said Mike Schutt, production manager for Lehigh Hanson.
With a 24-hour production schedule, 160 tph of raw material is passed through the kiln, reaching approximately 1,900 degC (3,500 degF). Accumulations formed at the discharge point, reaching up to 20ft tall in as little as a single shift. The build-up could stretch back into the kiln and cause serious problems that result in excessive downtime and an increased cost of operation, the operator explained.
Lehigh-Hanson’s initial solution had five cannons with standard OEM piping leading directly to problem areas located near the hottest part of the cooler. The area had an average sustained temperature of 65 degC (150 degF) to 74 degC (165 degF), which made maintenance during operation extremely difficult.
Over time, fine particulates from discharged clinker would migrate up the air cannon discharge pipe. Clinker dust would also settle within the cannon tank, diminishing the tank’s capacity and decreasing the power and effectiveness of the shot.
Previously, workers donned hot suits and were required to remove the entire cannon from the manifold for valve service – one of the most unpleasant projects in the plant. It required at least two workers to perform the maintenance and, due to the heat, they were only able to remain in the area for about five minutes at a time.
“The system broke down so often, we finally just had to leave it and monitor the material build-up until the very last minute, then shut down the system for maintenance,” said Schutt. “This allowed us to get the most production possible, but it caused at least a day of unscheduled downtime a few times per year.”
Technicians installed five 150-litre Martin Hurricane Air Cannons, lifting the units away from the discharge area and up several metres to a pre-existing platform. Located well away from the hot wall and the kiln’s discharge zone, the cannons can be serviced without having workers wear the special high-temperature equipment.
Connected to the existing compressed air system, the Hurricanes supply more force output with less air consumption at half the size of other designs. Each unit fires a shot of air up to 120 PSI (8.27 bar) from a pressurised tank through the long pipes and spreads the airstream across the area of build-up.
To prevent unintentional firing due to drops in pressure, the valve requires a positive signal from the solenoid in the form of an air pulse. Able to be located up to 200ft away from the cannons, the solenoid panel also allows operators to fire manually if needed.