Combustion and Flame 155 (2008) 529–537 www.elsevier.com/locate/combustflame Quantitative measurement of atomic sodium in the plume of a single burning coal particle P.J. van Eyk a,∗ , P.J. Ashman a , Z.T. Alwahabi a , G.J. Nathan b a Cooperative Research Centre for Clean Power from Lignite, School of Chemical Engineering, The University of Adelaide, South Australia 5005, Australia b School of Mechanical Engineering, The University of Adelaide, South Australia 5005, Australia Received 21 December 2007; received in revised form 22 May 2008; accepted 29 May 2008 Available online 24 July 2008 Abstract The release of volatile sodium during coal combustion is a significant factor in the fouling and corrosion of heat transfer surfaces within industrial coal-fired boilers. A method for measuring the temporal release of atomic sodium from a single coal particle is described. Laser absorption was used to calibrate laser-induced fluorescence measurements of atomic sodium utilising the sodium D1 line (589.59 nm) in a purpose-designed flat flame envi- ronment. The calibration was then applied to planar laser-induced fluorescence measurements of sodium atoms in the plume from a single Victorian brown coal particle (53 mg) suspended within the flat flame. The peak concen- tration of atomic sodium was approximately 64.1 ppb after 1080.5 s, which appears to correspond to the end of char combustion. To our knowledge this is the first in situ quantitative measurement of the concentration field of atomic sodium in the plume above a burning particle. A simple kinetic model has been used to estimate the rate of sodium decay in the post-flame gases. Comparison of the estimated and measured decay rates showed reasonable agreement.  2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Coal; Sodium; LIF; Fouling 1. Introduction The release of volatile alkali species during coal combustion is a significant factor in the fouling and corrosion of heat transfer surfaces within industrial coal-fired boilers. In particular, alkali species during coal combustion have been shown to form the initial deposit, which accommodates the subsequent build- up of other ash particles. Alkali species also form * Corresponding author. Fax: +61 8 8303 4373. E-mail address: philip.vaneyk@adelaide.edu.au (P.J. van Eyk). complex sulphate compounds that can lead to tube corrosion [1]. Sodium chloride can also be deposited on boiler tubes when very high chlorine content coals are utilised [2], leading to a higher potential for cor- rosion in these furnaces. Volatile alkali constituents have been shown to condense only in the cooler zones of the furnace, thereby allowing a sticky deposit to form on the boiler tubes [1]. Elemental sodium in low-rank coal may occur in several forms. These include water-bound sodium (Na salts in solution), organically bound sodium (e.g., attached to carboxylic acid groups), and within clay minerals. The first two forms will readily va- 0010-2180/$ – see front matter  2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.combustflame.2008.05.012