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RESEARCH PAPERS

# Effect of Fuel Properties on the Bottom Ash Generation Rate by a Laboratory Fluidized Bed Combustor

[+] Author and Article Information
Peter L. Rozelle

Department of Energy and Geo-Environmental Engineering, The Pennsylvania State University, 110 Hosler Building, University Park, PA 16802

Sarma V. Pisupati

Department of Energy and Geo-Environmental Engineering, The Pennsylvania State University, 110 Hosler Building, University Park, PA 16802spisupati@psu.edu

Alan W. Scaroni

Department of Energy and Geo-Environmental Engineering, The Pennsylvania State University, 110 Hosler Building, University Park, PA 16802

J. Energy Resour. Technol 129(2), 144-151 (Aug 22, 2006) (8 pages) doi:10.1115/1.2719205 History: Received June 20, 2005; Revised August 22, 2006

## Abstract

The fluidized bed combustion (FBC) process, used in power generation, can handle a variety of fuels. However, the range of fuels that can be accommodated by an FBC boiler system is affected by the ability of the fuel, sorbent, and ash-handling equipment to move the required solids through the boiler. Of specific interest is the bottom ash handling equipment, which must have sufficient capacity to remove ash from the system in order to maintain a constant bed inventory level, and must have sufficient capability to cool the ash well below the bed temperature. Quantification of a fuel’s bottom ash removal requirements can be useful for plant design. The effect of fuel properties, on the rate of bottom ash production in a laboratory FBC test system was examined. The work used coal products ranging in ash content from $20to40+wt.%$. The system’s classification of solids by particle size into flyash and bottom ash was characterized using a partition curve. Fuel sizing was compared to the partition curve, and fuels were fractionated by particle size. Fuel fractions in the size range characteristic of bottom ash were further analyzed for distributions of ash content with respect to specific gravity, using float sink tests. The fuel fractions were then ashed in a fixed bed. In each case, the highest ash content fraction produced ash with the coarsest size consist (characteristic of bottom ash). The lower ash content fractions were found to produce ash in the size range characteristic of flyash, suggesting that the high ash content fractions were largely responsible for the production of bottom ash. The contributions of the specific gravity fractions to the composite ash in the fuels were quantified. The fuels were fired in the laboratory test system. Fuels with higher amounts of high specific gravity particles, in the size ranges characteristic of bottom ash, were found to produce more bottom ash, indicating the potential utility of float sink methods in the prediction of bottom ash removal requirements.

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## Figures

Figure 1

Size classification of particles to the bottom ash and flyash streams

Figure 2

Example of a partition curve

Figure 3

Laboratory fluidized bed combustion system

Figure 4

Methods used to prepare fuels for combustion tests

Figure 5

Effect of the laboratory concentration process on bottom ash production

Figure 6

Classification fartition curve for the laboratory fluidized bed combustor

Figure 7

Camparison of predicted and measured bottom ash removal rates

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