Suppressing dust

A high-volume coal transshipping company servicing the Powder River Basin (PRB) has adopted atomised mist dust suppression to raise air quality and keep site equipment free of particulate accumulation. After successful deployment of a DustBoss^® Ring (DB-R) on its barge-loading conveyor, Hendricks River Logistics (HRL) added another unit to its larger conveyor, which feeds the stockpile area, thus reducing the amount of fugitive dust at the work site. Effective dust management has been cited by company officials as an important component of the facility’s environmental stewardship and regulatory compliance.  

Located on the Mississippi River, just north of Keokuk, Iowa, HRL exclusively serves two utilities along the Mississippi River. Trains as long as 123 cars, loaded with sub-bituminous coal, take the 5.5 day round trip to HRL’s site. The train enters a 3 mile spur track off of the main BNSF line. Each car is unloaded using a rotary dumper, a large cylindrical framework with its own track, which braces onto the car with hydraulic clamps, then turns the car and track nearly 160°, emptying the contents into a large hopper. The rotary dumping sequence takes about two to three minutes per car, allowing the facility to process approximately 3000 short tph from its receiving area.

The coal is loaded onto conveyor belts leading to the stockpile. “We generally do about 1.6 to 1.7 million t of production per year,” said Shawn Duer, general manager of HRL. “PRB coal is inherently dusty, so we knew from the beginning that we needed some form of dust control.”

Duer’s team researched trade magazines for their options and spoke to several sources before deciding on a DustBoss. “We initially purchased the DB-R for our 48 in. wide barge loading conveyor belt, and it did such an excellent job that we decided to get another one for our other main discharge point,” Duer said.

The main discharge belt leads 1000 ft (304 m) uphill from the rotary dumper. The belt is 60 inches wide with a material volume of as much as 3000 short tph, feeding into the 14-acre stockpile that is managed by bulldozer. The large 72 in. DB-R is a stainless steel circular manifold with 38 misting nozzles mounted on the conveyor 3 ft under the discharge point, pumping 23.94 gal./min (90.62 l/min) of atomised water. The DB-R creates a circular curtain of 50 – 200 micron sized droplets, which travel with the dust, absorb the particles and pull them to the ground with little or no pooling or runoff. Pressure is adjustable to match the fluctuations in volume of fugitive dust dispensed from the belt. The size of the mist droplets does not change regardless of the pressure.

“Visiting the site, we noticed the main discharge point was high enough for air currents to carry dust a long distance,” said Carl Harr, who handles Technical Sales for Dust Control Technology, manufacturer of the DustBoss line of products. “It does twice the volume of the barge loader, but since it’s located on a hill, it creates greater potential for migration, so adding a new DB-R in that location was an excellent choice.”

According to Duer, it has been historically faster and cheaper to transport coal by barge. The PRB coal burning utility clients of HRL are located on or near the Mississippi River, so the barges offload directly to the plant.

HRL has fleeting for 80 barges. The conveyor leading from the stockpile to the dock is 1100 ft (335 m) long, loading barges at a rate of 1500 short tph. Coal is directly discharged onto the barge through a 54 in. DB-R, a stainless steel circular manifold containing 30 specialised nozzles, which pumps 18.90 gal./min (71.54 l/min) of atomised water. This helps keep the dock, equipment and barges cleaner, with less fugitive material settling on the water.

“Currently we only deal in PRB coal,” Duer concluded. “We try to run the most efficient and environmentally compliant operation possible. DustBoss is an essential part of that.”

Edited by Sam Dodson

Read the article online at: https://www.worldcoal.com/handling/21102014/suppressing-dust-on-the-mississippi-river-1431/