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2016-05-19 - Colloque/Présentation - communication orale - Anglais - 2 page(s)

Mosca Gabriele, Lupant Delphine, "In-furnace measurements of MILD combustion of a blend from industrial by-products on a 30 kW chamber" in 24th « Journées d’Etude » of the Belgian Section of the Combustion Institute, Louvain la Neuve, Belgium, 2016

  • Codes CREF : Recherche énergétique (DI2290), Transfert de chaleur (DI2211), Combustion (DI2212)
  • Unités de recherche UMONS : Thermique et Combustion (F704)
  • Instituts UMONS : Institut de Recherche en Energétique (Energie)
Texte intégral :

Abstract(s) :

(Anglais) MILD combustion is a very high efficiency com-bustion technique, successfully applied on industrial furnaces to have very low NOx emissions, stable working conditions and significant energy savings by high air preheating. Thanks to a specific configuration of air and fuel injectors a strong recirculation of flue gases inside the chamber is guaranteed, with consequent high dilution of reactants into the flue gases and a temperature increase above the fuel auto-ignition threshold. The formation of hot-spots is significantly prevented: the result is a reduction of NOx and carbon monoxide emissions [1]. This combustion technique is particularly interesting for alternative fuels such as biogas, gasified waste or by-product gases, for which the generation of a stable flame can be difficult due to their highly varia-ble calorific value. MILD combustion avoids the formation of a flame front because fuel and oxidizer are continually mixed with recirculating combustion products. Therefore the combustion occurs in homogeneous and extended way once the auto-ignition temperature is reached. Without constraints due to the stability of a flame front, it allows larger fuel flexibility compared to conventional burner. Experimental tests have been performed on a 30 kW, laboratory scale furnace, designed to operate in MILD combustion and able to reproduce some of the main features of industrial furnaces (injection system, geometry, variable load). An electrical air preheater is used to get the desired air inlet temperature and a mixing unit supplies the desired composition of the fuel from gas bottles. The chamber is equipped with an optical access which can be used to take images of the main reactions zones by recording the OH* chemiluminescent emissions [2]. However, in the test campaign (TC2015) discussed here this optical access has been closed to simulate conditions as similar as possible to a real furnace. The chamber was designed to work with natural gas and was deeply tested with this fuel [3]. The combustion group of the University of Mons has then decided to start to investigate the behaviour of low calorific, alternative fuels in this particular combustion regime, thanks to the increasing interests of the industrial partners and the community. In 2013 a particular blend (B50: 28% N2, 12% CO2, 14.25% CH4, 32.5% H2, 13.25% CO), obtained by mixing 50% of coke oven gas with 50% of blast furnace gas, has been tested: the effect of the air preheating on its MILD combustion has been investigated in terms of powers balances, combustion efficiency, emissions, shape and position of the reaction zones, and temperatures [4]. In 2015 (TC2015) a further important step has been accomplished: the detailed in-furnace measurements of the MILD combustion of this fuel. Making use of gas sampling and temperature probes, a mapping of 154 internal points of the chamber has been carried out. H2, CO, CH4, O2, CO2, NO concentrations of the sampled volumes (on dry basis) and temperatures have been successfully measured respectively by chromatographic, infrared, paramagnetic, chemiluminescent gas analysers and a suction pyrometer. The knowledge of the temperature and concentration experimental fields on a section of the combustion chamber represents an important goal to help the researchers to understand the real behaviour of the MILD combustion technique and to better validate the performed numerical simulations and the actually used codes for the 30 kW furnace [5].