Figure 1. Engineered chutes employ special geometries for ease of installation on existing structures, with maintenance doors for easy access.
Westar Energy is the largest electric utility in Kansas, with 19 energy centers providing 7,100 MW of generating capacity to serve more than 689,000 customers. The firm employs about 2,400 people and operates approximately 35,000 miles of transmission and distribution lines. Westar maintains 4 coal-fired facilities, the largest of which is the Jeffrey Energy Center (JEC) near St. Mary’s.
Situated on 10,500 acres of land, JEC is the largest coal-fired power plant in the state, with three generating units producing 1,857 MW, ranking it the 19th largest in the nation. The first unit came online in 1978, and the newest in 1983. All three burn low-sulfur coal (as much as 33,000 tons/day between them) and take advantage of some of the most advanced emission control technologies available.
JEC was named the Powder River Basin Coal Users Group Plant of the Year in 2003, and was the first facility in the 4-state region to receive the OSHA VPP Star designation in 2007. The site includes three wildlife management areas and 7,700 acres that are leased to local farmers.
/> Material handling challenge Over time, operators at JEC began to notice increased dust and spillage around 4 transfer points on 4 of its 42? conveyors. The problem was traced to worn chutes and skirtboard liners, which no longer contained the coal fines as they did when new. A worn-out skirtboard liner plate was exacerbating the problem.
“We have two transfer buildings where the yard feeders deliver incoming material to supply the boilers,” said Josh Olson, a coal handling engineer. “They were wearing out, and we knew we needed to take action. But rather than patching the existing chutes and liners, we wanted to see if we could find a better design solution.”
The ½? thick belts on conveyors 101A, 101B, 301A and 310B travel 550 FPM and have a capacity of approximately 1,000 tons/hour. The load is 4? minus PRB coal, with a moisture content around 28-30 percent and bulk density of 45-55 lbs per cubic foot. Westar contacted Martin Engineering to investigate its options, and technicians came out to assess the situation.
“Chute design has evolved since this system was first installed,” said Jason Illum, a Martin Engineering Territory manager. “Today’s engineered flow chutes employ special geometries that capture and concentrate the material stream as it travels through the chute.
“Every design is tailored to suit the specific material characteristics and conveyor systems of the individual customer, rather than using stock products and attempting to make them work,” he added.
Inertial Flow Transfer Chutes from Martin Engineering provide the dual benefits of minimizing aeration and preventing buildup within the chute, particularly important when dealing with combustible materials.
After reviewing the proposed re-design, Westar engineers visited a nearby facility in which Martin Engineering had installed a similar system.
“We were very impressed by what we saw,” Olson said. “The conveyors delivered excellent belt support, and the material flow was directed to minimize turbulence and maximize dust containment.”
Engineered flow transfers The engineered chutes designed for the Westar facility employ a “chute and spoon” transfer, with the head discharge chute at the top of the system and a spoon receiving chute to place material with minimal impact onto the belt being loaded. Martin Engineering components are custom-designed to suit the characteristics of the conveyed product and the materials used for chute construction.
“The head chute design allowed for external mounting of the head pulley bearings, replacing the old design,” Illum said. “The spoon provides a curved loading chute for a smooth line of descent, consistently feeding the material at a specific speed and direction to minimize impact in the loading zone.”