Safety-technical characteristics of forest residue, coal and straw. Final report

摘要

Safety-technical factors related to spontaneous ignition and dust explosions of biomasses were investigated. Parametres of dust explosions and effect of inertisation on the maximum pressure (pmax) and the maximum rate of pressure rise (Kstmax) were studied at elevated initial pressure (1 - 9 bar). The level of inertisation required to prevent dust explosions totally was determined at different initial pressures. The sensitivity of fuels to spontaneous ignition and the effect of pressure on the sensitivity to and temperature of spontaneous ignition were studied on a pressurised dynamic self-ignition equipment. The effect of inertisation on the self-ignition temperature and alternatives of preventing spontaneous ignition by effective inertisation in the pressure ranges of 1 and 25 bar were investigated. As an example of application, results obtained with the laboratory test equipment were extrapolated to bin sizes used in practice. As a factor contributing to spontaneous ignition, the flowability of different fuels in bins and lock-hoppers (stagnant fuel layers are especially sensitive to spontaneous ignition) in continuous flow and in flow stopped for a storage time of 1 hour was also studied. Walker's rotating ring shear equipment and Jenike's linear shear equipment based on shearing the fuel were used in the flowability measurements. The effect of fuel temperature (22 deg C, 40 deg C) on flowability was determined for forest residue chips. Dynamic friction coefficients between fuels and handling equipment were determined for stainless steel and rusty metal surface. As an example of application, results obtained with laboratory test equipment were extrapolated to a bin size of 21 m(sup 3) by calculating the size of the minimum discharge opening required by mass flow of different coals and forest residue chips and the minimum angle of repose of the conical part for a bin of stainless steel. (author)