Analytical study of the pyrolysis process in a wastewater treatment pilot station

Nowadays, according to new environmental regulations, a reduction of waste volume is required. Because of this limitation, only two ways of elimination will be considered: incineration and land application. In this context, a global energetic study of a wastewater and sewage sludge treatment pilot station is carried out in order to build a real-time simulation tool of incineration processes [1,2]. A part of the investigation was focused on the pyrolysis characteristics. Indeed, thermolysis or pyrolysis kinetics are very complex and depend on many factors, such as sludge composition and its characteristics in the furnace input or such as its previous treatment. The thermal degradation of a complex material in an inert atmosphere or vacuum, causes organic material to change into three phases (liquid, gas and carbon), the proportion of which depends not only on the heat transfer speed, temperature, pressure, turbulence and reactor residence time, but also on the effluent nature (pH, OM%, DM%). Humid or pasty sludge incineration (10–30% DM) in a fluidised bed reactor can be used in conjunction with a natural gas combustion source when sludge auto-combustion is not complete or when the bed temperature is not high enough to destroy all the dangerous components. The modelling of the process in the incinerator is being developed to allow a numerical study of the reactor performance and to better understand the mechanisms of the pyrolysis and locate the different load transformation zones.

Thermal analyses using TG, DSC or MS are very useful techniques for studying the pyrolysis events. Small samples and controlled heat- [1] F. Marias, J.R. Puiggalli and G. Flamant, Modelling for simulation of fluidised bed incineration process, Environment and energy engineering, AIChe. J., 47(6) (2001) 1438–1460. [2] F. Marias, J.R. Puiggalli and G. Flamant, Effects of freeboard volatile release during fluidised bed incineration of a model waste, Trans ICHemE., 79(B) (2001) 244–251. [3] Journal of the Air & Waste Management Association, 272(50) 2000. [4] A.B. Kummer, Pyrolyse von ausgefaultem Klärschlamm in der Wirbelschicht, Eine Entsorgungsalternative (Pyrolysis of digested sewage sludge in a fluidised bed, an alternative disposal method), Ph.D. Thesis, University of Hamburg, Germany, 1989. [5] P.A. Vesilind and T.B. Ramsey, Effect of drying temperature on fuel value of wastewater sludge, Wastewater Management and Research, 14 (1992) 189–196. [6] R. Romer, Thermal treatment of sewage sludge combustion, drying energy recovery, emissions, in: Klarschlamm Entssorgung1, Daten Dioxine, Entewasserung, Entsorgungsvorschlage, Dusseldorf, VDI Gbmh, (1991) 250–271. [7] O.E. Albertson, J.M. Bruno, B. Copeland, J. Crumm, G.G. Homoki, C.M. Koch, B. Low, J. Maberry, M.D. Noriega, R.W. Okey, G.S. Seiler, J.A. Semon, B.C. Waester and R.B. Zang, Sludge incineration: Thermal destruction of residues, Proceedings of the symposium: Water Environment Federation, Alexandria, USA, 1992. [8] R.E. Hidalgo, J.V. Giraldez and J. Ayuso, Uso de las cenizas de incineracion de lodos de depuradoras, Comunicacion I + D., Consejeria de Agricultura y Pesca, 1997. [9] L.J. Alemany, M.A. Larrubia, M.C. Jimenez and J.M. Blasco, Revalorizacion de las cenizas de combustion (Valorisation of the ashes from combustion), Ingenieria Quimica, (1998) 169–174. [10] M. Otero, C. Diez, L.F. Calvo, A.I Garcia and A. Moran, Analysis of the co-combustion of sewage sludge and coal by TG – MS, Biomass & Bioenergy, 22 (2002) 319–329. [11] L. Muhlhaus, Verbrennung von Klärschlamm im Wirbelschichtofen (Combustion of sewage sludge in a fluidised bed), in: VDI - Seminar, Klarschlammentsorgung II, Dusseldorf, 1991. [12] SEGHERSmulti waste degrader. [13] J. Werther and T. Ogada, Sewage sludge combustion, Progress in energy and combustion science, 25 (1990) 55–116. [14] P. Lowe, Development in the thermal drying of sewage sludge, J. CIWEM., 9 (1995) 306–316. [15] R.D. La Nauze, Fundamentals of coal combustion in fluidised beds, Chem. Eng. Res. Des., 63 (1985) 3–33. [16] J. Werther, T. Ogada, V.A. Borodulya and V.I. Dikalenko, Devolatilisation and combustion kinetic parameters of wet sewage sludge in a bubbling fluidised bed furnace, in: Proc. Inst. of Energy’s 2nd International Conference on Combustion and Emission Control, London, UK., (1995) 149–158. [17] T. Ogada and J. Werther, Combustion characteristics of wet sludge in a fluidised bed, release and combustion of the volatiles, Fuel, 75(5) (1996) 617–626. [18] J. Koch and W. Kaminsky, Pyrolysis of a refinery sewage sludge, a material recycling process, Science and Techn. Bd., (1993) 46. [19] W. Kaminsky, H. Schmidt and C.M. Simon, Recycling of mixed plastics by pyroloysis in a fluidised bed. Macromolecular Symposia 152 (2000) 191–200. [20] J. Koch, O. Kock, W. Kaminsky and H. Sinn, Oil sludge recycling by fluid bed pyrolysis, Erdöl. Erdgas. Kohle, 112(6S) (1996) 271–272. [21] M.R. Stammbach, B. Kraaz, R. Hagenbucher and W. Richarz, Energy and Fuel, 3 (1989) 255. [22] J. Piskorz, D.S. Scott and D. Radlein, Composition of oils obtained by fast pyrolysis of different woods. In: Pyrolysis oils from biomass: Producing, analysing and upgrading, American Chemical Society, Washington, DC., (1988) 167–178. [23] G.K. Lee, F.D. Friedrich and E.R; Mitchell, Effect of fuel characteristics and excess combustion air on sulphuric acid formation in a pulverized-coalfired boiler, J. Inst. Fuel, 40 (1967) 397–405. [24] P.J. Collin, R.J. Tyler and M.A. Wilson, Fuel, 59 (1980) 479–86. [25] Chiang, Lo, Tsai, and Chang, J. Air & Waste Management Association, 50 (2000) 273. [26] C. Tullin, J. Andreasson, O. Stahl, M. Hansson, B. Leckner and G. Palchonok, Combustion of single wood particles - fuel - N conversion. [27] F. Winter, M.E. Prah and H. Hofbauer, Temperature in a Fuel Particle Burning in a Fluidized Bed: The Effect of Drying, Devolatilisation, and Char Combustion, The Combustion Institute, 1997. 302–314. [28] B. Waymack and D. Kellogg, Smoldering Combustion Studies using TA/MS. [29] N. Jand and P.U. Foscolo, Pyrolysis and gasification kinetics of biomass particles of different size in a fluidised bed.