ITB Journal of Engineering Science (Nov 2012)
The Power Consumption Performance of an Orbiting Screw Solid-Solid Mixer
Abstract
The increasing concentration of CO2 and other greenhouse gasses (GHGs) in the atmosphere warms up the earth's surface and causes drastic changes to the climate. Therefore, reducing energy consumption in order to reduce GHGs emission from the manufactures become urgent, especially in developing new industries such as Slow Release Fertilizer (SRF) urea plant. In this work, mixing in an orbiting screw mixer designed for solid-solid mixing was investigated. Mixing was carried out using urea powder and natural zeolite powder by varying three particle sizes i.e. groups of >50 mesh, >60 mesh and >80 mesh. Mixing process was conducted to examine the influence of orbital and rotation speeds combined with air injection, as well as the particle size of urea-natural zeolite to the specific energy consumption. Achieving a good homogeneity of mixture with a shorter mixing time, thus, power and energy consumption, was one goal of this work. The power consumption was calculated from measured torque of orbital and screw obtained by computerized record. Specific energy consumption was calculated by total power with time tied the homogeneity of the mixture for each particle size group. Experimental results showed that the higher of the orbital and rotation speed, the higher energy consumption. It can be seen that power consumption was dominated by rotation motion of the screw. Smaller particle size required higher power for mixing process due to their cohesiveness. Mixing process used a modified orbiting screw mixer with air injection showed lower power consumption for each particle size group compared with that of no air injection. This paper also developed a derivation of the power equation model of mixing in the orbiting screw mixer. The influence of speed of mixer in an orbiting screw mixer on the power consumption can be expressed by the Power Number.
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