466069 Modeling Plasma Gasification of Biomass with Thermodynamic and Kinetic Approach in Series

Monday, November 14, 2016: 8:25 AM
Union Square 19 & 20 (Hilton San Francisco Union Square)
Babita Verma, Chemical Engineering, Indian Institute of Technology Madras, Chennai, India, Rajesh Elangovan, Cognizant Technology solutions, Chennai, India, T. Renganathan, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, India and S. Pushpavanam, Chemical Engineering, Indian Institute of Technology, Madras, Chennai, India

Modeling Plasma gasification of biomass with thermodynamic and kinetic approach in series
 

Babita K. Verma, Rajesh Elangovan, T. Renganathan, S. Pushpavanam*

Department of Chemical Engineering, Indian Institute of Technology Madras,

Chennai 600036, India

*Corresponding author:spush@iitm.ac.in, Tel: +91-44-22574161

Plasma gasification is a promising green technology in which carbon based feed-stocks are converted to synthesis gas. In this process, a plasma arc is used to supply heat to the reactor to sustain the endothermic gasification reactions. Plasma gasification operates at temperatures above 2500 K. Here the reaction rates are very high and this leads to lower residence time as compared to conventional gasification [1]. This drastically reduces the size of gasifiers operating at atmospheric pressure. These advantages motivate the development of accurate mathematical models for plasma gasifiers which can help to analyze the effect of various parameters on the performance.

There are two ways of modeling: Equilibrium and kinetic approach. The purely equilibrium approach does not need information on all reactions which occur at the high temperatures in the reactor here when using the non-stoichiometric approach. The purely kinetic approach requires the consideration of heterogeneous reactions, resistances associated with gas-solid interaction and the formation of radicals. In the present work, the gasifier is modeled as consisting of a high temperature zone followed by a quenching zone where the reactor contents lose heat to the ambient. In the former the reactions are very fast and hence it can be assumed to be at thermodynamic equilibrium. In the quenching zone the reactant mixture cools down and the composition of the gases vary along the reactor length at a finite rate determined by the reaction kinetics. This motivates the reactor to be modeled as being made of two regions namely a plasma gasifier zone (PGZ) which is simulated using a thermodynamic non-stoichiometric approach and a quenching zone (QZ) which is simulated based on a kinetic approach. The schematic representation of the plasma gasifier model [2] is shown in Figure 1

Figure 1. Schematic representation of the plasma gasifier model

The effect of various parameters – gasifier temperature, steam flow rate, air flow rate and feed moisture content – on the performance of the gasifier is studied. Figure 2 shows a typical result i.e. the effect of the gasifier zone temperature on the heat duty and the cold gas efficiency existing in PGZ and QZ region.

Figure 2: Effect of temperature on heat duty and CGE exiting PGZ and QZ region (Air=13.25kg/hr, Steam=3.90 kg/hr, Moisture=10%)

References:

[1]      S. J. Yoon and J. G. Lee, “Syngas Production from Coal through Microwave Plasma Gasification : Influence of Oxygen , Steam , and Coal Particle Size,” Energy & Fuels, vol. 26, pp. 524–529, 2012.

[2]      M. Gorokhovski, E. I. Karpenko, F. C. Lockwood, V. E. Messerle, B. G. Trusov, and  a. B. Ustimenko, “Plasma technologies for solid fuels: experiment and theory,” J. Energy Inst., vol. 78, no. 4, pp. 157–171, Dec. 2005.

 


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