279645 Co-Fire Pellets Consisting of Coal and Pyrolysis-Derived Binder

Thursday, November 1, 2012: 1:50 PM
336 (Convention Center )
Andrew Friend1, Robert Brown1 and R. Christoper Williams2, (1)Center for Sustainable Environmental Technologies, Iowa State University, Ames, IA, (2)Department of Civil, Construction, and Environmental Engineering , Iowa State University, Ames, IA

The goal of this research is to allow utilities with coal-fired plants to meet renewable energy mandates and reduce greenhouse gas emissions through the utilization of a co-fire pellet consisting of coal and a fast pyrolysis-derived binder.  In the past decade, carbon dioxide and other greenhouse gases (GHGs) have been subjected to intense study for their contribution to climate change.  Electrical utilities are facing federal, state, and local mandates for renewable power production.  At the same time, utilities are also facing existing and upcoming regulations that demand emissions reduction from their current sources of power generation.  In order to meet these mandates and regulations in a timely and inexpensive manner, electrical utilities are adding more “green” options to their power portfolios.  Biomass is a near term option due to its low cost and easy integration into the existing coal-fired infrastructure. 

Biomass co-firing is heralded as a simple and inexpensive way to reduce CO2 and other greenhouse gas emissions from power plants.    However, there are many practical difficulties in storing and co-firing two fuels with large differences in heating value, bulk density, moisture content, and ash composition as often occurs for coal and biomass.  This can lead to reductions in boiler capacity and combustion efficiency, increases in emissions of regulated pollutants, and loss of markets for coal ash.

Our approach to solving several of the problems of conventional co-firing is to create a pellet from coal and a co-product of fast pyrolysis.   These pellets have many advantages over both traditional coal combustion and co-firing with biomass.  Co-fire pellets have approximately the same or greater heating value than the coal used in the pellets.  They can be handled with existing coal infrastructure, injected into stoker-grate boilers or pulverized for use in PC boilers with little loss in boiler capacity or ash properties.  They also contain substantially lower alkali levels than biomass, allowing for a wide utilization of annual or perennial biomasses without fear of boiler corrosion or fouling.  Greenhouse gas emissions are much lower for the co-fire pellets than for coal because the biomass contributes relatively little net carbon dioxide emissions.  Co-fire pellets allow electrical utilities to harness all the advantages of biomass co-firing without experiencing the downsides.  They have the potential for utilities to meet both their renewable energy mandates and their emission reduction regulations without expensive facility retrofits.

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