Minnesota CHP plant benefits from air cannon ash cleaning system

By Lisa Gibson | June 23, 2011

Koda Energy in Shakopee, Minn., says it has eliminated labor-intensive air lancing in the biomass boiler ash cleaning process, opting to install a series of air cannons developed by Martin Engineering. While air cannon systems have been in use in industries around the world for decades, the biomass sector is beginning to realize its benefits.

Koda’s 24-megawatt-per-hour combined-heat-and-power plant uses 500 tons per day of agricultural and seed byproducts, wood chips and other biomass materials, but began accruing significant buildup early in its operating life, according to Martin Engineering.Half of the power generated by Koda is sold to Excel Energy and the rest is used by Koda and the adjacent Rahr Malting Co. plant, along with the waste heat. “Efficient material flow is a critical element of biomass-fired boilers, and accumulation or blockages can take a big bite out of the plant’s efficiency,” said James Millis, Martin Engineering service technician. “Ash buildup in the furnace walls and tubes can choke the process, degrading equipment performance and introducing the potential for safety risks during cleanout.”

Koda Energy, a partnership between Rahr Malting and Shakopee Mdewakanton Sioux Community, now has 12 Big Blaster Hurricane Air Cannons, a technology Martin Engineering says has a proven track record around the world for relieving bottlenecks caused by material buildup in high-capacity storage and process vessels. Developed in 1974, Martin’s air cannons are not new technology, but their popularity is spilling over into the biomass sector, according to Rick Felde, spokesperson for Martin Engineering. “Because of the growing popularity of biomass fuels, it’s beginning to garner attention,” he said.

The air cannons help avoid the daily shutdowns and maintenance hours that manual cleaning requires, allowing facilities to run at rated capacity. The automated system is programmed to fire in a prescribed pattern, but can be fired manually if necessary. “You don’t have to stop the process,” Felde said. “You don’t have to invest the manpower and your personnel can focus on the core (elements).”

Martin Engineering’s Hurricane Air Cannon is a positive-acting, internal valve design developed specifically to deliver maximum force output from a direct air path, according to the company. It operates through activation of the solenoid valve, releasing the pressure holding the piston. The piston is instantly forced back by the air pressure stored in the tank, and the blast of air is directed through the nozzle and into the boiler, according to Martin Engineering.

Stacy Cook, Koda’s chief engineer and vice president of operations, said the plant has been able to maintain full boiler output without any hand lancing since the air cannons were installed.

“If they become severe enough, flow problems can bring operations to a complete stop until the problem is corrected,” Millis said. “Although many facilities still use manual techniques to remove boiler build-up, the costs of labor and production shutdowns have prompted some plants to investigate more effective methods for dealing with this type of flow issue.”