Abstract

Heat recovery from bottom ash is more important in municipal waste combustion systems than in any other solid fuel combustion since almost 50% of it comprises of non-combustibles. In this study, an ash cooling system using air as the cooling medium has been modeled for pre-heating the combustion air. Air cooling has several advantages over water cooling methods. The study involves modeling using Gambit tool and is solved with the fluent solver. Municipal solid waste incineration systems have the advantage of being located near the waste collection area apart from the high volume reduction ratio. Improvements in the emission control systems and combustion technology can make incineration a highly feasible disposal method. Low furnace temperature due to heat losses through fuel moisture loss and ash sensible heat loss has been a disadvantage with these systems. In this study, a small percentage of the combustion air is pre-heated in a non-contact type heat exchanger and its effect on the available energy of combustion gases at the evaporator outlet is studied. The study is performed for two different waste samples. Results indicate significant increase in available energy at the evaporator outlet and better relative performance for the lower grade fuel. A comparison is made with similar methods reported in the literature along with a brief discussion on the methodologies adopted. The results confirm the importance of installing ash sensible heat recovery mechanism for waste incineration systems as well as the feasibility of the air based method.

Keywords:

Air pre-heater, ash cooler, heat recovery, incineration, solid waste, waste combustion,

References

1. Alliston, M., A. Rantee and M. Rautanen, 2001. Experience with fuel from biomass to petroleum coke and how their properties affect fluidized bed boiler plant design. Proceeding of the 16th International Conference on Fluidized Bed Combustion. Reno, pp: 201-213.
   
2. Angelo, S., 2012. Co-combustion and its impact on fly ash quality: Pilot-scale experiments. Fuel Process. Technol., 104: 105-114.
   CrossRef    
3. Cheng, Z.H., Y.C. Liu and G. Li, 2005. Application of negative pressure type super-strength steel strip slag cooler. Electr. Equip., 6(2): 43-47.
   
4. Dennis, E.C. and J.K. Albert, 1969. Analysis of Solid Waste Composition, Bureau of Solid Waste Management. US Department of Health, Education and Welfare.
   
5. Ganapathy, V., 2002. Industrial Boilers and Heat Recovery Steam Generators. Marcel Dekker Inc., New York.
   CrossRef    
6. Helemer, W.A. and D.D. Stokke, 1998. A case study of fluidized bed combustion of wood/coal mixtures: Part B-the effect of wood moisture content. Forest Prod. J., 48: 345-356.
   
7. Lara, C., W. Elisabeth, P. Christian, L. Joakim, K.V. Vijay, H. Walter and S. Christoph, 2013. Performance of a pellet boiler fired with agricultural fuels. Appl. Energy, 104: 286-296.
   CrossRef    
8. Liu, Y.C., H.C. Yin and J.P. Liu, 2006. Cold and hot test study on the rolling-cylinder type slag-cooler of CFB boiler. Power Syst. Eng., 22(5): 35-38.
   
9. Lu, X.F., 2006. Equipments and Operation of Large-scale Circulating Fluidized Bed Boiler. China Electric Power Press, Beijing, pp: 125-133.
   PMCid:PMC2196437    
10. Necati, O., 1985. Heat Transfer-A Fundamental Approach. McGrawHill, New York.
    
11. Sami, M., K. Annamalai and M. Wooldridge, 2001. Co-firing of coal and biomass fuel blends. Prog. Energy Combust. Sci., 27: 171-214.
    CrossRef    
12. Sathyanathan, V.T., 2011. Predicting Combustibles in Pulverized Coal Fired Boilers-fly Ash and Bottom Ash, Bright Engineering Hub.
    Direct Link
13. Shu, M.L., J.H. Chen, X.F. Lu and H.Z. Liu, 2007. Investigation on fluidized bed bottom ash coolers in large-scale CFB boilers. Power Syst. Eng., 23(2): 29-31.
    
14. Singh, R.P., V.V. Tyagi, A. Tanu, I.M. Hakimi and K. Richa, 2011. An overview for exploring the possibilities of energy generation from Municipal Solid Waste (MSW) in Indian scenario. Renew. Sust. Energ. Rev., 15: 4797-4808.
    CrossRef    
15. Vincenzo, C., C. Daniele and S. Werner, 2007. Dry ash collection at coal fired power plants and potential for WTE facilities. Proceeding of the 15th North American Waste to Energy Conference. Florida, pp: 692-698.
    
16. Zeng, B., X. Lu, P. Zhao, L. Gan and M. Shu, 2011. Experimental studies and application of a composite fluidized bed bottom ash cooler. Proc. CSEE, 31(29): 27-34.
    

Competing interests

The authors have no competing interests.

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