Wan Zaiton Wan Sulaiman creator author. text monographic eng

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xvii, 170 pages : illustrations ; 30 cm. + 1 CD-ROM Dust explosions associated with rice flour cause loss of life, severe injuries, destruction of properties, premises, and affect the environment. Rice flour poses a particularly high risk due to being highly explosible with elevated pressure and uncertainty of risk due to initial turbulence. Therefore, studying the explosibility and severity of undried and dried commercial rice flour is essential, as no research has combined experimental and Computational Fluid Dynamics (CFD). This study aims to investigate the dust explosion characteristics and effect of initial turbulence inside a Siwek 20 L spherical chamber through laboratory experimentation and simulation. A commercial rice flour sample was analysed in terms of its physicochemical properties to study the impact of moisture, dust concentration, and ignition delay time (tv) on the explosibility and severity of rice flour dust explosions, including the minimum explosibility concentration (MEC), rate of pressure rise (dP/dT), dust deflagration index (Kst), flame propagation velocity (ʋF), and maximum explosion overpressure (Pmax) at different ignition delay times, tv (20 ms, 60 ms, and 100 ms). The findings showed explicitly the impact of initial turbulence, where at an ignition delay time (tv) of 60ms, Pmax for the undried and dried rice flour were 11.25 bar and 8.6 bar, respectively. On the contrary, Pmax obtained at 20 ms for undried rice flour was 10.9 bar, lower than Pmax of dried rice flour, 14.4 bar, while Pmax obtained at 100 ms for undried rice flour was 10 bar, also a bit lower than Pmax of dried rice flour, 10.4 bar. The MEC at tv 60 ms and 1000 ms were higher than the undried rice flour sample, 500 g/m3, while the MEC of dried rice flour at 20 ms was 550 g/m3 . The lower MEC for dried rice flours was attributed to the lower moisture content in the dried rice flour sample (2.47%) after oven drying in comparison with 7.79% moisture for undried rice flour. The rate of pressure rise, and deflagration index (Kst) were observed to increase with the increase in dust concentration until a concentration of 1000 g/m3 but decreased afterwards. The highest value of Kst obtained was 54.83 bar.m/s from dried rice flour at tv = 20 ms. The influence of dust concentration and ignition delay time (tv) in the aspect of dust explosion mechanisms were observed and explained further from a 2D model of the chamber by CFD study using Ansys Fluent software (version 18.2). Low tv at 20 ms entrained the explosibility of rice flour dust to be the lowest in comparison with the explosibility achieved by rice flour dust at tv of 60 ms and 100 ms due to the low concentration of dust at the location of the ignition source (the centre of the chamber). The pattern of rice flour injected at very high pressure (21 bar absolute) was observed to be moving in an upward direction, and after a certain time, dust was distributed and hit on all sides of the wall chamber. Contrary to the explosibility, the Pmax of dried rice flour was found to be the highest at a tv of 20 ms in comparison with the results obtained at 60 ms and 100 ms. This was due to the densely packed dust particles at the centre of the chamber at 20 ms. The turbulence kinetic energy (TKE) of all concentrations studied progressed significantly until 20 ms and decreased gradually afterwards. The velocity vectors also correspond closely to the severity of the rice flour explosion at lower ignition times, where the velocity initially increases until 20 ms and then decreases afterwards, except for the lowest concentration of 500 g/m3 , the highest velocity achieved at 10 ms. In conclusion, the decrease in moisture content and the increase in dust concentration could increase the explosibility and severity of rice flour explosions in general, but the influence of initial turbulence by varying the tv affects the explosibility and severity of rice flour explosions dynamically. Wan Zaiton Binti Wan Sulaiman Faculty of Chemical and Process Engineering Technology Thesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2025 Includes bibliographical references Faculty of Chemical and Process Engineering Technology Dissertations Universities and colleges Dissertations Theses Dissertations THE0010089 (Local) UMPSA 250522 20251125111043.0 eng