The principle of oxy-fuel technology is based on the idea of flue gas recirculation into a combustion chamber. Hence a combustion takes place in an O_2/CO_2 mixture instead of air. However, flue gas from coal combustion contains other components, like impurities and steam. Some of those components have to be removed before flue gas enters a combustion chamber, but lately an agree is emerging, that some amount of H_2O in a recycled gas stream is inevitable. The main interest in presented research was to investigate the influence of steam presence on a coal combustion process. Study focused on a determination of particle temperature during oxy-fuel combustion with and without steam addition. The experimental study was supported by numerical simulations aiming to explain the mechanism of observed temperature differences. The experiments were carried out in a laboratory rig developed to investigate a combustion process of single particle of fuel. Tests were performed with particles of a size less than 2 mm, prepared from a bituminous coal. During the test, single particle of coal was introduced to an electrically heated furnace where it was exposed to a flow of hot gases. The composition of the gas stream was changed from a dry oxy-fuel mixture to a wet oxy-fuel mixture, with 35% H_2O concentration. As a result of the experiment, a temperature of coal particle during the combustion process was obtained. Additionally, tests were carried out in air which provided reference data. Results of the experiments revealed that particles burned with higher temperatures in the wet oxy-fuel mixture than in the dry O_2/CO_2 mixture. To explain the observed increase in particle temperature, numerical calculations with the use of Ansys Fluent software were performed. As a result: gasification reactions were selected as a factor that had the greatest impact on the particle temperature during the combustion in tested conditions.
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