only about 2.5 metres, it took around 20 hours before the fire could be detected by gas analysis located in the top of the silo, clearly indicating the problems of early fire detection of smouldering fires in silos. Gas FillinG tests After the tests were concluded, researchers found that the pellets formed a congealed pile in the top part of the silo and noted that the pyrolysis zone was about 0.5 metres below the ignition source. in diameter and six metres high. A ventila-tion duct was installed close to the base of the silo, which was used to provide ven-tilation to the silo during the “pre-burn” phase and for injection of inert gas dur-ing the extinguishing phase. The silo was filled with wood pellets up to a height of five metres during the tests. Local auto-ignition was simulated using a coiled heating wire placed in the pellets, located centrally in the silo. In these tests, the extension of the pyrolysis zone was mainly downwards, towards the air inlet, while a heat/mois-ture wave with a temperature less than 100 C, slowly moved upwards, seen above. Although the distance from the point of ignition to the pellet surface was The purpose of the second project, con-ducted in 2008, was to investigate how nitrogen should be injected into a real silo during extinction to achieve opti-mal gas distribution. The experiments were performed in a 300 m 3 steel silo with a diameter of six metres, a height of 10.5 metres and filled with about 260 m 3 of wood pellets. In total, five tests were conducted where the gas was in-jected from the centre of the base of the silo, or alternatively, at one point along the silo wall. All tests were conducted in a “cold” silo (no fire), as the main focus was to study the gas distribution in the material. The tests showed that the gas distribution was significantly in-fluenced by the gas flow rate, the loca-tion of the inlet and the properties of Material Handling for Woody Biomass Biomass Handling Equipment Complete Engineered Systems Pulverized Coal Boiler Conversions CFB Boiler Feed Systems UNIT E D STATES STA T ES UNITED CA NADA CANADA SW ED E N SWEDEN Silos Wood Hogs Disc Screens Open Storage Closed Storage Truck Dumpers Chain Conveyors Bucket Elevators Screw Conveyors Screw Reclaimers Pneumatic Conveying SWEDEN: Stockholm Jeffrey Rader AB Domnarvsgatan 11, 163 53 SPÅNGA Stockholm, Sweden Phone: +46 8 56 47 57 47 Fax: +46 8 56 47 57 48 See our Biomass video at www.jeffreyrader.com/videoB USA: CORPORATE HEADQUARTERS Jeffrey Rader Corporation 398 Willis Road Woodruff, SC, USA 29388 Phone: 864.476.7523 Fax: 864.476.7510 CANADA: Montreal, Quebec Jeffrey Rader Canada 2350 Place Trans-Canadienne Dorval, Quebec H9P 2X5 Canada Phone: 514.822.2660 Fax: 514.822.2699 CANADA: Vancouver, BC Jeffrey Rader Canada Unit 2, 62 Fawcett Road Coquitlam, BC V3K 6V5 Canada Phone: 604.299.0241 Fax: 604.299.1491 For information on how Jeffrey Rader Corporation can solve your Biomass Handling needs, visit us at www.jeffreyrader.com/bio2 28 Canadian BIOMASS NOVEMBER/DECEMBER 2011
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