Abstract—Development of new highly efficient plasma arc combustion system of pulverized coal is presented. As it is well- known, coal is one of the main energy carriers by means of which electric and heat energy is produced in thermal power stations. The quality of the extracted coal decreases very rapidly. Therefore, the difficulties associated with its firing and complete combustion arise and thermo-chemical preparation of pulverized coal becomes necessary. Usually, other organic fuels (mazut-fuel oil or natural gas) are added to low-quality coal for this purpose. The fraction of additional organic fuels varies within 35-40% range. This decreases dramatically the economic efficiency of such systems. At the same time, emission of noxious substances in the environment increases. Because of all these, intense development of plasma combustion systems of pulverized coal takes place in whole world. These systems are equipped with Non-Transferred Plasma Arc Torches. They allow practically complete combustion of pulverized coal (without organic additives) in boilers, increase of energetic and financial efficiency. At the same time, emission of noxious substances in the environment decreases dramatically. But, the non-transferred plasma torches have numerous drawbacks, e.g. complicated construction, low service life (especially in the case of high power), instability of plasma arc and most important – up to 30% of energy loss due to anode cooling. Due to these reasons, intense development of new plasma technologies that are free from these shortcomings takes place. In our proposed system, pulverized coal-air mixture passes through plasma arc area that burns between to carbon electrodes directly in pulverized coal muffler burner. Consumption of the carbon electrodes is low and does not need a cooling system, but the main advantage of this method is that radiation of plasma arc directly impacts on coal-air mixture that accelerates the process of thermo-chemical preparation of coal to burn. To ensure the stability of the plasma arc in such difficult conditions, we have developed a power source that provides fixed current during fluctuations in the arc resistance automatically compensated by the voltage change as well as regulation of plasma arc length over a wide range. Our combustion system where plasma arc acts directly on pulverized coal-air mixture is simple. This should allow a significant improvement of pulverized coal combustion (especially low-quality coal) and its economic efficiency. Preliminary experiments demonstrated the successful functioning of the system. Keywords—Coal combustion, plasma arc, plasma torches, pulverized coal. I. INTRODUCTION T heat power stations, in combustion of heavily ballasted coals that cannot burn by themselves, especially under conditions of minimum loads, it is necessary to provide a maximum intensification of the pulverized coal flame with fuel oil [1]. In this case, the share of fuel oil in total heat released in a boiler furnace may amount to 30%. Combustion of coal with fuel oil in the above proportions leads to intensive high-temperature corrosion of screens, dramatic decrease in David Gelenidze is with the Andronikashvili Institute of Physics, Georgia (e-mail: d.gelenidze@gtu.ge). burnout of particles of a solid fuel (its unburned part is emitted together with ash and fume), chemical underburning, increase in the amount of pollutant emissions (compared with coal, fuel oil contains twice as much sulfur), and increase in the rate of accidents with steam superheaters. As a result, this causes reduction in the efficiency of boilers [1]. In order to improve the efficiency of coal combustion, new plasma-fuel system for thermal power plants is developed. It is pulverized coal burner equipped with arc plasmatron. It provides fuel oil-free startup of pulverized coal fired boilers, flame stabilization, and as a consequence, the simultaneous decrease of unburned carbon and nitrogen oxides formation due to two-stage combustion [2]. Plasma-fuel systems procedure is based on plasma thermos-chemical activation of coal for burning. It consists in arc plasma heating of air-fuel mixture up to the temperature of coal devolatilization and carbon residue partial gasification. By that initial coal high or low rank from air-coal mixture, hot combustible gas and highly-reacting coke residue is obtained. When mixed with secondary air at furnace, it can be ignited and burn stably without use of fuel oil or natural gas traditionally used for boilers start up and low-rank coals flame stabilization [3]. The use of plasma-fuel systems at thermal power plants decreases the unburned carbon by 40-50%, nitrogen oxides by 50-60%, and carbon dioxide emissions can be reduced by 1-2%. II. PLASMA ASSISTED START-UP OF COAL BURNERS The idea behind a plasma-assisted pulverized coal burner (PAPCB) is to blow plasma torch into the pipe through which pulverized coal in air flows (Fig. 1) [4]. The procedure of plasma assisted start-up of a pulverized coal-fired boiler is similar to the procedure of start-up of a boiler using heavy oil. The essence of plasma assisted start-up procedure is that the plasma assisted pulverized coal burners (PAPCB) with installed plasmatrons are fired first. The remaining pulverized coal burners are started gradually after reaching the required thermal parameters of the furnace and other elements of the boiler [4]. Fuel-air mixture interaction with plasmaflow in a plasma- fuel system (PFS) is given in Fig. 2. Across the plasma flame, coal particles with an initial size of 50-100 mm experience ‘heat shock’ and disintegrate into fragments of 5-10 mm. This increases the active interface of the particles, significantly accelerating the devolatilization (CO, CO 2 , H 2 , N 2 , CH 4 , C 6 H 6 and others) and 3-4 times accelerates the process of oxidation of fuel combustibles [5], [7]. Plasma Arc Burner for Pulverized Coal Combustion Gela Gelashvili, David Gelenidze, Sulkhan Nanobashvili, Irakli Nanobashvili, George Tavkhelidze, Tsiuri Sitchinava A World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering Vol:12, No:6, 2018 278 International Scholarly and Scientific Research & Innovation 12(6) 2018 scholar.waset.org/1307-6892/10009089 International Science Index, Chemical and Molecular Engineering Vol:12, No:6, 2018 waset.org/Publication/10009089