AbstractThere is a strong need for transformative sanitation systems in the areas of the world where open defecation habits and/or inadequate sewage treatment methods and facilities exist. This paper describes an innovative thermally efficient solid waste treatment process as a basis for an off-the-grid, non-sewered toilet in order to address this need. Human feces are combusted in a continuous-cyclic manner using two stages of smoldering and catalytic oxidation. It has been shown that thermal coupling of the two stages creates a self-sustained reactor that can combust wet fecal material containing up to 3.2 parts water to 1 part dry matter – equivalent of water content in healthy human feces – without the need for external heating, known as the ultimate challenge in direct combustion of human feces. Furthermore, it has been shown that air flow rate can be reliably used as a controlling mechanism for fecal destruction rate which means the same reactor could be operated for various and varying input rates. The present work demonstrates the potential for manufacturing low-cost, low-energy consuming sanitation systems that are more easily accessible to communities in need of such systems.
The Discrete Element Method (DEM) is increasingly used to simulate the motion of granular material in engineering devices. The most widely used shape to model granular particles is the sphere due to its simplicity which facilitates computations. However, with increasing advancement and popularity of the DEM approach, a more accurate representation of real granular shapes is becoming intensely important. This paper is an attempt to predict the bulk density of granular particles of cylindrical shape by DEM. The method used to model tube-like particles is the composite method where the tube-like particle is composed of a number of spherical sub-shapes. The results show that the DEM prediction of the bulk density of tube-like particles were accurate provided that a sufficient number of spherical sub-shapes was used to construct the particle. In addition, the bulk density of granular particles in the shape of 32-face polyhedrons was also investigated. It was shown that 32-face polyhedrons can be approximated as spheres provided that the rolling resistance of the shape is taken into consideration.
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