Thermal recuperative incineration of VOCs: CFD modelling and experimental validation

A numerical 2D model of a thermal recuperative incinerator (TRI) used to oxidise volatile organic compounds (VOCs) diluted in an air flow was developed to simulate the coupled equations for flow, heat transfer, mass transfer and progress of chemical reactions. The model was confronted with experimental values obtained on a highly instrumented half-industrial-scale pilot unit run under the same conditions. The model indicates that the flow inside the reactor is close to the ideal situation of a plug flow reactor. Nevertheless, a non-symmetric flow is retrieved despite the symmetrical arrangement of the combustion chamber. The model confirms that the most constraining phenomenon is the oxidation of CO. The formation of CO results of the combustion of the VOCs, and not from the combustion of the methane fed into the burner. The models demonstrated that the CO destruction reaction is controlled by the micro-mixing efficiency in a large part of the reactor, and not by the chemical kinetics of the reaction. This indicates the need for installing additional turbulence devices in order to enhance the turbulence level in a zone established from this modelling. The model establishes that thermal NO is formed in the flame zone of the burner, and is not due to VOC oxidation. These results together indicate that concentrating VOCs in an air flux prior to its treatment by a TRI will limit CO2 emissions and NO emissions together.