Evaluation of Thermal Energy utilization and CFD Modeling of aggregate preheating from Waste Heat for Hot Mix Asphalt production Plant

Abstract

The energy utilization and better sources of energy reduction methods of hot mix asphalt plant are investigated in this thesis based in Ethiopia. In our country, with the increase of high way construction projects asphalt plants are playing vital role. The Asphalt Plant is system of mechanical equipment to produce the Hot Mix which is used for road paving at road construction site. There is a huge amount of fuel consumption of annually used in the production factory sites. The study for energy usage and utilization of waste heat for aggregate preheating is essential for energy reduction in asphalt concrete processing factory. The knowledge of effective plant energy management helps a company in terms of energy, ecology and economics. In this study, evaluation of thermal energy utilization and CFD modeling of aggregate preheating from waste heat for hot mix asphalt production plant with a capacity of 40-60 ton/hr at the humidity of initial materials up to 5% is analyzed based on the site data’s and recorded data’s collected from the production factory in order to reduce the energy usage. The life cycle assessment method and the numerical simulation is used to show the possible techniques of energy consumption reduction. The life cycle assessment investigation involves four categories related to raw material production stage, asphalt mixture production stage, transportation and pavement stage. The annual statistical data analysis shows that, the asphalt mixture production stage consumes 59% energy during the process. The total energy 272.03 MJ/ton is used by the production factory and asphalt mixture production consumes a large amount of energy for the aggregate drying, bitumen heating and storage for mixing process. This result shows that 8.333 kWh electrical energy is used for control and operation of electrical components and 6.33 liter of diesel fuel per tonne of a production. The aggregate moisture content is the main factor influencing the level of energy consumption during a production process. ANSYS FLUENT is used to simulate the utilization of exhaust gas thermal potential to heat the aggregate. By using 2D multiphase gas solid heat transfer model the temperature and heat transfer pattern between the gas and the aggregate is studied. The results are compared analytically and showed that it is possible to reduce the moisture content by heating the particles before entering into the rotary dryer. After pre heating the energy consumption will be reduced by 12.54% per one tonne of a production.