The solid recovered fuel Stabilat Ò : Characteristics and fluidised bed gasification tests G. Dunnu a , K.D. Panopoulos b , S. Karellas c,⇑ , J. Maier a , S. Touliou b , G. Koufodimos d , I. Boukis d , E. Kakaras b,c a Institute of Combustion and Power Plant Technology, University of Stuttgart, Pfaffenwaldring 23, D-70569 Stuttgart, Germany b Institute for Solid Fuels Technology and Applications, Centre for Research and Technology Hellas, 4th km N.R. Ptolemais-Kozani, P.O. Box 95, 50200 Ptolemais, Greece c Laboratory of Steam Boilers and Thermal Plants, National Technical University of Athens, Heroon Polytechniou 9, 15780 Athens, Greece d HELECTOR S.A., Energy and Environmental Applications, 25 Ermou Str., 145 64 N. Kifissia, Greece article info Article history: Received 26 August 2010 Received in revised form 24 August 2011 Accepted 25 August 2011 Available online 9 September 2011 Keywords: Stabilat Ò Gasification Waste-to-energy SRF abstract The solid recovered fuel Stabilat Ò has a low water content which makes it ideal for thermochemical con- version processes such as gasification. The paper presents fuel characterisation and fluidised bed gasifi- cation experiments of the Stabilat Ò solid waste recovered fuel in two experimental facilities, aiming at assessing the product gas quality and bed agglomeration phenomena. The energy content of the gasifica- tion product gas was about 4.3 MJ Nm 3 and the process efficiency reached the value of 64.4%. The amount of HCl measured in the product gas ranged between 61.0 mg Nm 3 (700 °C, k = 0.25) and 37.6 mg Nm 3 (800 °C, k = 0.3). The total tar content was found between 2 and 6 g Nm 3 according to the gravimetric method, while the same range with GC measurements was 4–13 g Nm 3 (N 2 free). No severe loss of fluidisation occurred up to 850 °C while electron microscopy investigation of the bed mate- rial and ash material revealed that some agglomerates were present, due to melting of glass particles inherent in the material while lower amount of ash and original bed material conglomerates. In all cases these phenomena did not cause any severe problems to fluidisation. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The biodegradable part of the Municipal Solid Wastes (MSW) is considered to be a renewable energy source [1] as its properties are similar to the ones of other biomass fuels. Furthermore, the contin- uously growing business of waste recycling applications produce enormous amounts of secondary fuels of high heating value such as the Refuse Derived Fuel (RDF) and Solid Recovered Fuel (SRF). Nevertheless, mature final markets for these fuels have not been developed yet in all EU countries. Moreover, depositing MSW and secondary fuels in landfills has to be abandoned in EU according to directive 1999/31/EU [2]. Therefore there is a great need to de- velop specific processes that best utilise these fuels. The focus of this work is to investigate the thermal utilisation of the secondary fuel from a Waste Treatment Facility technology developed by Herhof GmbH and implemented in more than ten sites worldwide. The technology incorporates an MSW Recycling Plant, and a novel Mechanical Biological Treatment (MBT) of un- sorted MSW with a patented mechanical biological drying step which removes most of the moisture, followed by a mechanical recycling step. Through this process, reusable materials (ferrous metals, aluminium and glass) are separated and can be sold as a genuine high-quality raw material and returned into the material cycle. The remaining organic waste fraction is turned into an SRF marketed product under the name ‘‘Trockenstabilat Ò ’’ or, simply, ‘‘Stabilat Ò ’’, which is delivered after being pressed into hygienic, nearly odour-free, energy resource known as pellets or after being shredded and retained in fluffy form. Nowadays, this product fuel is being utilised as coal substitute in cement plants or large, central waste to energy plants [3]. The overall mass balance of the process is shown in Fig. 1. The Stabilat Ò fuel has a low water content which makes it ideal for thermochemical exploitation processes such as combustion or gasification. Gasification is the conversion of a solid fuel to a mix- ture of combustible gases (mainly H 2 , CO and CH 4 ) through a ther- mochemical process comprised of pyrolysis, partial oxidation and gasification reactions [4–6]. When air is used as gasification med- ium the result is the occurrence of non-combustible gasses CO 2 and N 2 (apart from the above-mentioned combustible species) leading therefore to the production of a low calorific value fuel gas (4– 5 MJ Nm 3 ) [7]. Combustion technologies have several weak- nesses, such as low efficiency of refuse derived combustion steam cycles (20%) and higher capital and operating costs for flue gas treatment associated with stringent emission regulations for diox- ins and furans in the increased volumes of flue gases. Nevertheless the combustion technologies have the advantage of being more mature and have the predominant application examples through- out the world for thermal treatment of waste derived secondary 0016-2361/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2011.08.061 ⇑ Corresponding author. E-mail address: sotokar@mail.ntua.gr (S. Karellas). Fuel 93 (2012) 273–283 Contents lists available at SciVerse ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel