Title

Toward a Cleaner Coal

Document Type

Article

Publication Date

6-1-2011

Abstract

Toward a Cleaner Coal

The Fort Union Region offers a unique combination of material and energy resources that are essential for the growth of local and global economies, including coal, oil shale deposits, natural gas, and biomass. An understanding of clean and efficient methods of utilizing energy resources within North Dakota is critical to the growth of future economies. The Red River Valley Research Corridor has on-going research geared toward understanding and developing technologies that utilize these resources.

Power plants located in North Dakota primarily use lignite coal mined within the state to generate steam and power that services communities in North Dakota and the surrounding states. A challenge for these plants is that coal contains varying amounts of incombustible mineral matter that ends up as ash during combustion and gasification.

Managing Ash

The importance of managing ash in boiler systems has to be emphasized because the behavior of mineral matter during combustion and gasification influences slagging and fouling chemistry and control of particulate emissions. Some of the potential issues associated with ash transformations include deposition on heat transfer surfaces that reduce the overall performance of radiant and convective heating surfaces, corrosion of furnace elements, and particulate matter that is difficult to collect.

The University of North Dakota has worked with the North Dakota Experimental Program to Stimulate Competitive Research (ND EPSCoR) which was established by the National Science Foundation. The ND EPSCoR research is focusing on the formation mechanisms of ash in various size modes.

Minerals present in coal, either in association with organic or inorganic species, contribute to the formation of ash species of varying particle sizes. The mechanisms of formation of ash particles in conventional combustion systems have been found to be heavily dependent upon fuel composition and combustion conditions. UND's laboratory scale furnace is designed to scale up bench, industrial and utility scale boilers so that ash formation mechanisms can be investigated to determine the subsequent impacts on pollution control devices.

The Combustor

The furnace is a 19-kilowatt laboratory scale down-fired combustor capable of burning fossil-based biomass, and waste fuels. Various sampling ports along the length of the furnace can be selectively used to capture ash during the various stages of combustion. The mechanisms leading to the formation of ash particles for various elemental and mineral species can then be determined.

This research will be focused on understanding the impact of blending coal with biomass on ash formation mechanisms and trace elements mobility and leachability. Other factors to be studied include furnace design and combustion system tuning. Preliminary work under investigation include loss of ignition testing of coal and biomass, particle size distribution of ashes generated from coal/biomass blends and chemistry and morphology of ash particles. Future work will be investigations into trace element evolution from biomass sources, oxidation of mercury from taconite pellets and carbon capture technologies using regenerable sorbents.

Cleaner Coal

Anticipated benefits of these studies include advancement of technologies that aid in reduction of emissions of fine particulates, heavy metals and green-house gases that result from use of Fort Union resources. Further, these studies are expected to advance the state of knowledge of current technologies and better position North Dakota as a global technology and resource supplier.

Through the use of advanced carbon-capture technologies, the goal of making coal a cleaner resource for combustion or gassification is within our reach.

By Dennis Sisk, Ph.D. Student in the Department of Chemical Engineering

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