PhD defense - T. Pedot

Modelling of the thermal coupling between combustion and fouling inside furnace tubes of a refinery

Delivered by Institut Nationale Polytechnique de Toulouse
Speciality: Energetic and transfer

February 16, 2012 - CERFACS

In industrial refinery furnaces, the efficiency of the thermal transfer to heat crude oil before distillation is often altered by coke deposition inside the process pipes. This leads to increased production and maintenance costs, and requires better understanding and control. Crude oil fouling is a chemical reaction that is, at first order, thermally controlled. In such large furnaces, the predominant heat transfer process is thermal radiation by the hot combustion products, which directly heats the pipes. As radiation fluxes depend on temperature differences, the pipe surface temperature also plays an important role and needs to be predicted with sufficient accuracy. This temperature results from the energy balance between thermal radiation and conduction in the solid material of the pipe, meaning that the thermal behavior of the whole system is a coupled radiation-conduction problem. A comprehensive methodology for coupling is exposed and validated as follows. In this work, the flame is described by an analytical model axisymmétrique with complex chemistry. Coupling with conduction in the pipes is achieved by using a discrete ordinate method (DOM) together with narrow band spectral model for combustion gases radiation. Energy balance confirmed that heat transfer is dominated by thermal radiation. Good agreement with available measurements on a real furnace shows that this approach is able to predict the thermal radiation. Next step, pipe temperature calculation is coupled with a law of fouling. A simple chemical model is used. It is validated using a laboratory experiment. The comparison between the temperatures obtained with the simulation and those measured by thermal probes shows that the simulation is able to capture the evolution of the temperature in the tube accurately. Finally, the whole system, including radiation,conduction and deposition, is coupled. Results are compared to the real furnace and show relatively good agreement in terms of external skin pipe temperature prediction.

O. Colin	IFPEN, Rueil Malmaison	Referee
D. LEMONNIER	CNRS-ENSMA, Poitiers	Referee
D. Escudié	CNRS-CETHIL, Lyon	Member
M. EL HAFI	Ecole des Mines, Albi	Member
F. SER	ONERA, Palaiseau	Member
B. Cuenot	CERFACS, Toulouse	Advisor
E. Riber	CERFACS, Toulouse	co Advisor

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