Heat Flux Evaluation in a Test Furnace Equipped With High Temperature Air Combustion (HTAC) Technique

High Temperature Air Combustion has already been applied in various industrial furnaces. Steel producers use most of the revamped furnaces. These are: • Batch and continuous heating furnaces in which HRS burners with open flames were used, • Batch and continuous heat treatment furnaces in which HRS burners with radiant tubes were used. Apart from steel industry the HTAC systems were applied to melt aluminium or to incinerate odour, vapour gases for example in pulp and paper industry. In all these applications very high fuel savings (sometimes as high as 60%), reduction of NOx and production increase (by 20–50%) was achieved. Progress in applications of the HTAC increased also needs of more information and data required by furnace and process designers. For this reason study in larger scale where at least one set of regenerative burner systems is installed are very much needed. Aim of such studies is not only to verify furnace performance with respect to the known general advantages of HTAC but are focused on specific problems related to furnace and high-cycle regenerative burners operation, process and product properties or type of fuels used. Parallel to the semi-industrial tests numerical models of furnaces have to be developed and verified. In this work, mainly results of heat flux measurements as well as results of numerical modeling of heat transfer in the HTAC test furnace are presented. Results were obtained for propane combustion at firing rate equal to 200 kW. The general code, STAR-CD, was employed in this work to analyse the HTAC test furnace numerically. HTAC test furnace at Royal Institute of Technology (KTH) with capacity of 200 kW was used in this work. The furnace is equipped with two different high-cycle regenerative systems (HRS). In both systems the “honeycomb” regenerator is used. The two-burner system is made of two pairs (four burners) of high cycle-regenerative burners with switching time between 10 and 40 seconds. HTAC test furnace is equipped with four air-cooled tubes to take away heat from the furnace. The total radiative heat flux measured in the HTAC furnace shows very uniform distribution over the whole combustion chamber. For total radiative heat flux, the values are in the range of 110–130 kW/m² as measured by means of the total radiative heat flow meter at the furnace temperature 1100 C. Average total radiation flux on the top furnace wall is as high as 245.5 kW/m2 as well as total incident radiation flux. Total radiation heat flux on the air-cooled tube surface is very uniform along and around the tubes. Average radiant heat flux taken away by air cool tube is 35.46 kW/m2.