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Converting from Coal to Biomass: A Case Study

converting from coal to biomass

Biomass has come on strong as an alternative to traditional power sources. Many plants across the nation have considered or actually begun converting from coal to biomass, either as part of a co-firing strategy combining biomass and coal or as a biomass-only setup.

In 2011, one producer got ahead of the curve by implementing a biomass conversion at a decommissioned coal-burning power plant. The company – purchased the facility at Fort Drum, located in Watertown, New York, which was capable of generating 60 MW of electricity. The decision was made to convert the plant into a biomass-fed facility.

ProcessBarron was enlisted to take care of the fuel handling equipment needed to supply the new biomass boilers with biomass fuel.

The Objective

The objective of the fuel handling system was to transport materials – wood scrap from local logging, construction, and demolition – to the plant’s boilers. Capacity would average 1,650 tons of material per day, with a peak of 3,600 tons per day.

The Problem

Converting from coal to biomass is a complex process with many moving pieces. For starters, the project was on an Army installation, so delivery hours were regulated and narrow. The timeline was also abbreviated; the project was slated to last only from August 2012 to April 2013, a brief amount of time for major construction.

The fuel handling system had to be designed in a particular way as well. The plant owners naturally wanted to reuse as much of the original, in-place equipment as possible, in order to reduce costs. This can be difficult, though, because biomass requires specialized equipment. Space constraints were also an issue; the area in question was limited in space.

Additionally, the fuel handling system put into place had to be designed to handle unprocessed material. This includes logging brush, wood from demolitions, and wood scraps from construction sites. As a result, the system had to be able to receive, stack, reclaim, screen, size, convey, and magnetize material so it could be fed into the boiler.

The Solution

Working with the team hired to oversee the project, ProcessBarron engineers began designing a process that would handle fuel, fit within the limited space, and make as much use of existing coal equipment as possible. The process began with two truck dumpers that discharged material into the collection belt conveyor designed by ProcessBarron.

This conveyor feeds another conveyor, which carries to the pre-existing coal stack-out system. The material is stacked and managed on the other side of the property.

After being stacked, the material is sent to a reclaim area equipped with two three-strand drag-chain reclaimers, each of which is capable of maintaining a steady fuel supply at consistent rates for the three boilers. Each reclaimer operates at half speed normally, to provide redundancy and the ability to scale up as capacity increases. The material transported by the reclaimer is then sent to a self-cleaning magnetic separator to remove any ferrous material. Afterward, the material is discharged onto the existing boiler feed belt.

From the feed belt, the material is unloaded onto the pre-existing coal system tripper belt, which takes the material to a series of pre-existing coal bunkers. Both the tripper belt and the boiler feed belt were specially modified by ProcessBarron to handle biomass material. The coal bunkers were retrofitted with flat floors and circular screw reclaimers (CSRs) created with special abrasion-resistant coatings to protect against material wear. Material is then sent from the CSRs to the boiler feed chutes.

The Results

The Utility in the Northeast began production on schedule in May 2013. The plant now supplies Fort Drum with 28 MW of electricity, and the rest of the capacity is sold into the local energy market.

As a result of the biomass conversion enabled by ProcessBarron, Black River is a fully-functioning, successful example of a reclaimed coal facility that now primarily produces energy from biomass, thus satisfying emissions regulations and New York state requirements that 30% of the state’s electricity be generated by renewable energy.

The full case study, along with sources, can be found here.