No abstract

Crude oil is still an attractive fuel for electricity production due to its low extraction costs in relation to other fuels. However, combustion of crude oil in modern gas turbines must meet certain criteria, which mainly include the reduction of harmful gas emissions, the elimination of harmful dust from the exhaust gas, the improvement of turbine efficiency, the limiting of the power degradation process and elimination of hard deposits. Experimental studies are always needed to meet these requirements because of common complexity in CFD crude oil combustion models. This paper presents experimental investigations of the combustion process of crude oil. Using different sorts of crude oil, all experiments are performed in the atmospheric test rig of a top-mounted combustor, which was scaled down from the baseline system. The test rig was optimized for the typical silo gas turbine boundary conditions. The combustion process is described and quantified with the measured temperature and velocity field distributions in the top-mounted combustion chamber for different injector design’s parameters. Additionally, measured profiles of the molar fraction of CO2, are discussed and compared with respect to the injector parameters. Finally, based upon the experimental results gathered, the possibility of fuel flexibility in the top-mounted combustor chamber is discussed.

The paper presents preliminary experimental analyses of combustion processes for crude oil. The research is started from investigation of combustion of gas in a strong swirl flow as is intended to be an introductory step in studying the mechanism of stability and emission of pollutants in combustion of crude oil occurring in gas turbines. The areas of recirculation and pollutant emission in a strong swirl flow have been studied for the following three cases: - isothermal flow without combustion; - combustion of gas mixture with CH4 and N2 differently composed; - combustion of crude oil. All experiments are performed in the atmospheric test rig of a top-mounted combustor, briefly described in the paper. The velocity field in the combustion chamber is measured by laser doppler anemometry. The measured profiles of temperature and molar fraction of NOx, CO, CO2, O2 are discussed for natural gas and crude oil. Depending on the degree of the swirl of the flow and on the temperature of entering air, the distribution of molar fraction of most important chemical species has been established. This allows for better understanding the process of combustion in a strong swirl flow. The established characteristics of the flame blow-out make it possible to calculate the limits of capacity power generation available from a given size of a gas burner. For the burner geometry, similar to that with the know characteristic of gas combustion, the parameters for CO and NOx have been established for crude oil. Also, characteristics have been found for a specially designed oil nozzle with a large spray angle — sufficiently large for the optimum supply of fuel into the area of strong swirl flow with combustion established on the basis of the analysis of the burning of gas. It has been found that in cases of combustion crude oil a relatively small increase of the temperature of air supplied for combustion results in a significant drop in CO emission what has an impact on lower NOx emission.

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.