Analysis of mixing efficiency by structural factors of livestocks manure compositing machine using DEM

As Korean consumer’s eating habits changed, meat consumption incresed and the number of livestock increased. As a result, the amount of livestock manure has also increased. Livestock manure has been used as fertilizer, but if not properly treated, it can cause environmental problems such as eutrophication and water pollution. Manure is composted mainly through sedimentation, but this method has many problems such as odor, lack of sedimentary area and difficulty to environment control. Vertical composting machine has advantages such as easy odor treatment, sufficient amount of sedimentation, and a suitable environment for composting. However, there is no clear design standard for vertical composting machine. Perfect compost requires a uniform and proper temperature distribution. Uniform mixing of manure in composting machine is affected by the structural factors such as number, length, angle of blades. Due to problems like huge scale, environmental difficulties, it is difficult to evaluate the mixing efficiency of composting machine by field monitoring. So, we conducted a study using discrete element method simulation. This study analyzes the mixing efficiency according to the structural factors of vertical composting machine and presentes pressure and impact load at blades. We determined the sutable rotational speed for the composting machine by performing the speed independence test of blades. The DEM simulation model was varified through field experiment. Using the developed model, we analyzed the mixing efficiency according to various combinations of structural factors. As a result, the length of blades, angle and number of blades respectively had the greatest effect on the mixing efficiency. Since the load on the blade can cause breakage and failure, collision and pressure load were also analyzed. Finally, we present the improved blade design of vertical composting machine.