                                     ! " #$ " % &" !      " #$ " !  ’ ( ) *+ ’$ %’ ( ! ,-  $.  / ’ ’’/  /  $/ 0$/ " 0’ The purpose of this study was to investigate the effect of particle size distribution on the mechanical properties of granular sulphur and its relation to silo blockage at South Pars Gas Complex Phases 2 & 3. Solid elemental sulphur is a relatively hard, friable crystalline material that tends to break up into smaller particles when subjected to force or stress of any magnitude. Conglomeration of the dust so produced clogs storage silos, making truck loading difficult. Grain size selection is based on the “friability value” and “maximum entropy” for granules in a static state. The model of the behavior of confined granular sulphur is based on the principle of continuum mechanics. Granules were formed by feeding liquid sulphur and water to a rotating granulation drum. Sample granules were classified into different size fractions (300 µm – 4.75 mm) by sieve analysis, and friability tests were done by the Fines 28-inch tumbler S5-77 test. Friability and granule size data collected over four years were studied. The implication of field analysis and laboratory tests is that the granule size should be controlled during sulphur solidification while ensuring that only granular material with the correct mechanical characteristics is stored in the silo and shipped.  Liquid sulphur from the sulphur recovery unit is stored in a heated tank, from which it is sent to the sulphur solidification unit for conversion to solid sulphur granules using the Enersul (Procor) GX™ drum granulation process. The GX™ process functions by accretion: small granules build up layer by layer by repeated coating with liquid sulphur, followed by cooling to solidify the superficial layer of liquid sulphur, until the desired size range is reached [1]. Ultimately the sulphur granules are loaded onto trucks for export. The site has two 210-tones silos for intermediate storage of the granular solid sulphur between the GX™ plant and the export truck loading facilities [2]. There was a problem with conglomeration in the outlet of silo, which was causing difficulties during truck loading. The operator had to hit the silo with a hammer to get the sulphur granules to move, which was not only hazardous for the operator but also risked damaging the silo body and the check valve. The SUDIC (Sulphur Development Institute of Canada) specification for limiting operating problems during transportation and storage is still the industry standard. Our unit is designed to a more stringent specification than that, so we concentrated our investigation on the operation method. In this article field observations and operational problems are described and the most probable explanation (checked against laboratory results and the SUDIC specification) is presented.        Stress distribution within a silo filled with granular sulphur is rather unusual “Fig. 1”. The reason is the shear stresses acting between the granular sulphur and the silo walls, even when the granular sulphur is at rest. Owing to the shear stresses, the silo walls carry a part of the weight of the bulk solid [3]. Applied Mechanics and Materials Online: 2011-10-24 ISSN: 1662-7482, Vols. 110-116, pp 83-90 doi:10.4028/www.scientific.net/AMM.110-116.83 © 2012 Trans Tech Publications, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 130.203.136.75, Pennsylvania State University, University Park, USA-06/03/16,14:38:52)