Products Distribution During Sewage Sludge Pyrolysis in a Sand and Olivine Fluidized Bed Reactor: Comparison with Woody
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ORIGINAL PAPER
Products Distribution During Sewage Sludge Pyrolysis in a Sand and Olivine Fluidized Bed Reactor: Comparison with Woody Waste Sid Ahmed Kessas1 · Thomas Esteves1 · Mehrdji Hemati1 Received: 30 March 2020 / Accepted: 13 August 2020 © Springer Nature B.V. 2020
Abstract The purpose of this article is to improve the understanding on sewage sludge (SS) pyrolysis behavior in a fluidized bed reactor between 700 and 890 °C. The experiments were carried out under a pure nitrogen atmosphere using sand and olivine as bed materials. The results gathered in this paper highlight the impact of temperature and bed materials on various performance criteria. It was observed that the use of olivine as a bed material affects the composition of the syngas, especially the fraction of the light hydrocarbons CH4 and C 2HX. It was also noticed that increasing the pyrolysis temperature yielded more syngas and reduced the condensable species and char quantities. Furthermore, an increase in temperature led to an increase in the fraction of benzene in tars. Comparing different kinds of fuels revealed that SS pyrolysis yields less syngas than pinewood and more syngas than municipal green waste. SS pyrolysis led to significantly higher CH4 and C2HX yields than woody waste, as well as a higher tar quantity. It was also noticed that BTEX compounds account for 70% of the tars produced during the pyrolysis of each of the fuels that were studied at 850 °C. Findings show that the thermal decomposition of SS generates a syngas rich in H2 (25–37 mol%), CO (23–40%), C O2 (6–19%), C H4 (9–21%) and C 2HX (4–17%). The syngas lower heating 3 value is varying between 14,000 and 22,000 kJ/Nm . Graphic Abstract Effect of temperature (700 and 850 °C) on sewage sludge (SS) pyrolysis products distribution in olivine fluidized bed reactor.
Keywords Pyrolysis · Fluidized bed · Sewage sludge · Waste · Syngas · tars.
* Sid Ahmed Kessas sidahmed.kessas@toulouse‑inp.fr 1
Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France
List of symbols d Pellets diameter (cm) d10, d50, d90 Fluidized media size distribution (µm) d3/2 Sauter mean diameter of fluidized media (µm) daf, B Dry ash free basis
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Fdaf,B Mass flow rate of the fuel (daf, B) (kg/h) H2/CO Ratio between H2 and CO molar flow rates in the dry syngas (−) L Wood pellets length (cm) LHV Lower heating value of syngas (kJ/Nm3) MB Molar mass of the waste (daf, B) (kg−1 mol) Ni Molar flow rate of i constituent of syngas (mol/h) P Pressure (mbar) PG Syngas production yield (Nm3/kgdaf,B) PGi Production yield of i component (Nm3/ kgdaf,B) T Bed temperature (°C) U Gas velocity in the reactor (m/s) Umf Minimum fluidization velocity (m/s) V̇ G (t) Volumetric flow rate of the incondensable gases (Nm3/h) ̇Vi (t) Volume flow rate of different incondensable gaseous species (Nm3/h) Vm Molar volume in temperature and pressure at normal conditions (Nm3/mol) XcC Carbon conversion rate into char (−) XcG Carbon
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