Co-combustion of municipal solid biomass wastes and coal at high efficiency has been a challenge in recent time due to the hazardous nature of the waste gases generated in the process. Utilization of bubbling fluidized beds reactors, that use coal, has been called into question due these pollution effects. Measures have been taken to try and solve this problem that originates from the use of coal. In this paper, numerical and experimental models have been adopted for the simulation of the combustion process, within a bubbling fluidized bed reactor, so as to determine temperatures at which coal could be substituted with hydrothermally treated municipal solid waste.
A research team led by Professor Kunio Yoshikawa from Tokyo Institute of Technology and Associate Professor Tamer Ismail from Suez Canal University in Egypt, with Dr. Liang, Dr. Abd El-Salam and Prof. Yuqi Jin investigated the co-combustion characteristics of hydrothermally treated municipal solid waste with coal in a fluidized bed reactor. Their aim was to present models that use composite fuel (coal and municipal solid wastes) at least reactor modification. Their work is now published in the peer-reviewed journal Fuel Processing Technology.
Foremost, experiments had to be conducted using reliable CFD in order to predict crucial results and critical requirements for curbing and ensuring efficiency. The three approaches that were available for numerical simulations were: Euler-Lagrange approach, Euler-Euler approach and Discrete Element Method. Euler-Euler approach was adopted where ratios of 10, 20, 30 and 50% of the hydrothermally treated municipal solid waste were chosen to be tested at 700°C, 800 °C and 900 °C so as to determine the temperatures at which coal could be replaced with the hydrothermally treated municipal solid waste.
The research team had to determine the right temperature and mixture of the system that had the least emissions and yet could be operated at the least cost. They observed that for mixing ratios of 10 and 20% of the HT MSW there was a significant reduction in the CO outflow emission during the co-combustion with coal. Additional mixing of coal with the HT MSW lead to a further decrease in SO2 emission from the combustion. Low levels of HCL were recorded for all the mixtures displaying a positive effect of the mixture. Nitrogen levels were also kept to a minimal as the blending mixing ratios of the HT MSW were increased. Initially, high levels of NO were recorded due to increase in temperature but with the mixing of the HT MSW to 30% level, a significant drop was observed for all temperatures.
This research paper shows that with accurate simulation, trends for co-combustion can be predicted for various emitted gas species in the bed. This research sheds light into a promising way to simulate the combustion of solid waste in bubbling fluidized beds when using minimal coal. This study also reveals the features of a detailed structure for the combustion process inside the solid bed. Finally, it indicates the possibility of accepting the mixing ratio of the hydrothermally treated municipal solid waste, co-combusted with coal up to 30% without major modification of the coal-fired bubbling fluidized beds reactor.
Liang Lu1, T.M. Ismail2, Yuqi Jin3, M. Abd El-Salam4, Kunio Yoshikawa1. Numerical and experimental investigation on co-combustion characteristics of hydrothermally treated municipal solid waste with coal in a fluidized bed. Fuel Processing Technology volume 154 (2016) pages 52–65.Show Affiliations
- Department of Environmental Science and Technology, Tokyo Institute of Technology, G5-8, 4259 Nagatsuta, Midori-Ku, Yokohama 226-8502, Japan
- Department of Mechanical Engineering, Suez Canal University, Ismailia, Egypt
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou 310027, China
- Department of Basic Science, Cairo University, Giza, Egypt
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