Successful Reduction of Dust & Spillage

Images: 3 Bilder

Images: 3 Bilder

Fig. 1: This section of existing air-supported conveyor was modified to relieve spillage; it leads to a field-fabricated head chute with Martin Brush Belt Cleaners to further mitigate dust and plugging of the conveyor housing. (Picture: Martin Engineering)

A Minnesota power generating facility has completed the first phase of a program to drastically reduce dust and spillage from its biomass fuel handling system. The project at Hibbing Public Utilities included belt cleaners, new transfer points and modified chutes, settling zones and apron skirts, as well as vibration technology to improve material flow.

The complex project at Hibbing Public Utilities included belt cleaners, new transfer points and modified chutes, settling zones and apron skirts, as well as vibration technology to improve material flow at key points. Company officials have been so satisfied with the upgrades that they are considering additional system enhancements to several other conveyors.

Hibbing Public Utilities

Hibbing Public Utilities (HPU) has been providing electricity to the city of Hibbing (MN), USA, and surrounding area for more than 100 years, and currently owns and operates a cogenerating plant that brings both steam heat and electricity to its service area. In partnership with Virginia Public Utilities, HPU formed a joint company called Laurentian Energy to deliver power from the abundant biomass resources nearby. Under a 20-year contract with Xcel Energy, the firm currently produces about 300,000 MW hours of electricity per year, approximately 70 per cent of it from biomass. The fuel includes wood from open loop sources (such as waste wood, limbs and agricultural waste) and closed loop sources (dedicated crops of trees), with a goal of averaging 75 per cent of the power generated from biomass fuels over the life of the agreement.

The material handling system at the Hibbing site is critical to the plant’s efficiency, but from the time it began operations in 2007, controlling dust and spillage was a challenge. “When construction of the biomass operation was completed, we had three air-supported conveyors and one bucket-type conveyor feeding the material,” explained Assistant General Manager and Director of Power Production Gary Myers. “The boiler can produce up to 135,000 pounds of steam per hour, used to turn three turbo-generators with a combined capacity of 35 MW.”

Cleaning of Cleated Belts

Because of the largely residential area in which the facility is located, controlling carryback and spillage were among the first priorities. After a thorough evaluation of the material handling system, Martin Engineering technicians began by installing primary and secondary belt cleaners on all four conveyors. The primary units on each belt are Martin Brush Belt Cleaners, a unique electric-powered model that provides an effective, cost-efficient solution for residual belt-borne material. The secondary units are SAF-2 Belt Cleaners, a versatile “deflected blade” design that features a gentle pressure to prolong service life and prevent belt damage.

“We installed electric brush cleaners on each conveyor, because they’re very effective on the type of cleated belts used at this facility,” observed Martin Engineering Territory Manager Tom Hines. “The rotating brush delivers good cleaning performance in difficult applications, including belts with ribs, grooves or chevrons, and belts carrying sticky materials or stringy fibers.”

“Part of the problem occurred on the three air-supported conveyors,” Myers recalled. “Some of the sections were at steep angles, and with the variable size and moisture content of the fuel, there were always chips that would fall back down.”

This article is protected by copyright. You want to use it for your own purpose? Infos can be found under www.mycontentfactory.de (ID: 31515760)