Modeling and pilot plant runs of slow biomass pyrolysis in a rotary kiln

Pyrolysis of biomass in a rotary kiln finds application both as an intermediate step in multistage gasification as well as a process on its own for the production of biochar. In this work, a numerical model for pyrolysis of lignocellulosic biomass in a rotary kiln is developed. The model is based on a set of conservation equations for mass and energy, combined with independent submodels for the pyrolysis reaction, heat transfer, and granular flow inside the kiln. The pyrolysis reaction is described by a two-step mechanism where biomass decays into gas, char, and tar that subsequently undergo further reactions; the heat transfer model accounts for conduction, convection and radiation inside the kiln; and the granular flow model is described by the well known Saeman model. The model is compared to experimental data obtained from a pilot scale rotary kiln pyrolyzer. In total 9 pilot plant trials at different feed flow rate and different heat supply were run. For moderate heat supplies we found good agreement between the model and the experiments while deviations were seen at high heat supply. Using the model to simulate various operation conditions reveals a strong interplay between heat transfer and granular flow which both are controlled by the kiln rotation speed. Also, the model indicates the importance of heat losses and lays the foundation for scale up calculations and process optimization.

[1]  K. Umeki,et al.  Mass loss rates for wood chips at isothermal pyrolysis conditions: A comparison with low heating rate powder data , 2017 .

[2]  Frank Kreith,et al.  CRC Handbook of Thermal Engineering , 1999 .

[3]  Tony Howes,et al.  Solid transport in a pyrolysis pilot-scale rotary kiln: preliminary results—stationary and dynamic results , 2005 .

[4]  Kunio Yoshikawa,et al.  Pyrolysis gasification of dried sewage sludge in a combined screw and rotary kiln gasifier , 2011 .

[5]  Ingrid J. Paredes,et al.  The effect of operating conditions on the residence time distribution and axial dispersion coefficient of a cohesive powder in a rotary kiln , 2017 .

[6]  S. H. Tscheng,et al.  Convective heat transfer in a rotary kiln , 1979 .

[7]  Qiang Yao,et al.  A Mathematical Model of Heat Transfer in a Rotary Kiln Thermo‐Reactor , 2005 .

[8]  H. Baum,et al.  Experimental and theoretical investigation of heat and mass transfer processes during wood pyrolysis , 2010 .

[9]  Peter McKendry,et al.  Energy production from biomass (Part 3): Gasification technologies. , 2002, Bioresource technology.

[10]  M. Godinho,et al.  Performance of rotary kiln reactor for the elephant grass pyrolysis. , 2016, Bioresource technology.

[11]  Eckehard Specht,et al.  Mean residence time and hold-up of solids in rotary kilns , 2006 .

[12]  Ningbo Gao,et al.  Modeling and Simulation of Oil Sludge Pyrolysis in a Rotary Kiln with a Solid Heat Carrier: Considering the Particle Motion and Reaction Kinetics , 2014 .

[13]  Frank P. Incropera,et al.  Fundamentals of Heat and Mass Transfer , 1981 .

[14]  Fernando J. Muzzio,et al.  Measurement of residence time distribution in a rotary calciner , 2013 .

[15]  F. Fantozzi,et al.  Rotary Kiln Slow Pyrolysis for Syngas and Char Production From Biomass and Waste—Part I: Working Envelope of the Reactor , 2007 .

[16]  B. Acharya,et al.  Torrefaction of Poplar in a Continuous Two-Stage, Indirectly Heated Rotary Torrefier , 2016 .

[17]  C. Blasi,et al.  Experimental Analysis of Reaction Heat Effects during Beech Wood Pyrolysis , 2013 .

[18]  Larry L. Baxter,et al.  Effects of particle shape and size on devolatilization of biomass particle , 2010 .

[19]  Rosana Moriana,et al.  A single model-free rate expression describing both non-isothermal and isothermal pyrolysis of Norway Spruce , 2015 .

[20]  Qing Yang,et al.  Torrefaction of cedarwood in a pilot scale rotary kiln and the influence of industrial flue gas. , 2015, Bioresource technology.

[21]  Ramiar Sadegh-Vaziri,et al.  A Medium-Scale 50 MWfuel Biomass Gasification Based Bio-SNG Plant: A Developed Gas Cleaning Process , 2015 .

[22]  Leteng Lin,et al.  Decomposition of benzene using char aerosol particles dispersed in a high-temperature filter , 2017 .

[23]  Ramiar Sadegh-Vaziri,et al.  Numerical investigation of the outward growth of ZnS in the removal of H2S in a packed bed of ZnO , 2017 .

[24]  Baptiste Colin,et al.  Wood chips flow in a rotary kiln: Experiments and modeling , 2015 .

[25]  Hua Wu,et al.  Parametric sensitivity in chemical systems , 1999 .

[26]  G. Braccio,et al.  Simulation of olive pits pyrolysis in a rotary kiln plant , 2011 .

[27]  Thomas Nussbaumer,et al.  Mechanisms and kinetics of homogeneous secondary reactions of tar from continuous pyrolysis of wood chips , 2002 .

[28]  Rosana Moriana,et al.  Pyrolysis of kraft pulp and black liquor precipitates derived from spruce: Thermal and kinetic analysis , 2016 .

[29]  H. Hofbauer,et al.  Rotary kiln pyrolysis of straw and fermentation residues in a 3 MW pilot plant – Influence of pyrolysis temperature on pyrolysis product performance , 2012 .

[30]  Steffen Heidenreich,et al.  New concepts in biomass gasification , 2015 .

[31]  Magnus Pettersson,et al.  Performance of an effectively integrated biomass multi-stage gasification system and a steel industry heat treatment furnace , 2016 .

[32]  Sushil Adhikari,et al.  A review on biomass gasification syngas cleanup. , 2015 .

[33]  Morten Grønli,et al.  Mathematical Model for Wood PyrolysisComparison of Experimental Measurements with Model Predictions , 2000 .

[34]  John Howard Perry,et al.  Chemical Engineers' Handbook , 1934 .

[35]  A. D. Damodaran,et al.  Residence time distribution and material flow studies in a rotary kiln , 1990 .

[36]  J. Bellan,et al.  A Generalized Biomass Pyrolysis Model Based on Superimposed Cellulose, Hemicelluloseand Liqnin Kinetics , 1997 .

[37]  C. Courson,et al.  Overview and Essentials of Biomass Gasification Technologies and Their Catalytic Cleaning Methods , 2016 .

[38]  G. San Miguel,et al.  Slow pyrolysis of olive stones in a rotary kiln: Chemical and energy characterization of solid, gas, and condensable products , 2015 .

[39]  F. Marias,et al.  Modelling of a rotary kiln for the pyrolysis of aluminium waste , 2005 .