Experimental Investigation On The Desulfurization Characteristics Of Petroleum Coke Combustion Blending With Coal In CFB Boiler

With the fast development of the national economy, more and more petroleum is exploited and utilized. As byproducts of solid residuals from the crude refining process, the petroleum coke's yield also increases year by year. The petroleum coke is a kind of inferior fuel, because it is difficult to ignite and burn completely, meanwhile it contains the alkali metals and the sulphur, the nitrogen chemical element which result in pollution and fouling in boiler. For the sake of complete combustion and pollution control, it is a clean and more effective way to burn the petroleum coke blended with coal in circulating fluidized bed (CFB) boiler.Most of the combustion experiments on desulfurization performance of petroleum coke blended with coal on CFB boiler were carried out in laboratory, but a few of those on commercial CFB boilers were reported. In order to instruct and optimize the operation on desulfurization performance of petroleum coke blended with coal on commercial CFB boilers, a systematic combustion experiment on desulfurization performance of petroleum coke blended with coal was conducted on a 220t/h commercial CFB boiler in JinLing Petro-Chemical Co. for the first time. The effects of various parameters, in terms of the Calories ratio of petroleum coke over coal, the bed temperature and Ca/S mole ratio on the SO₂ emission in the flue gas are presented in the paper. The emission characteristics of NO and CO were also verified. Meanwhile, the characteristics of fly ash and bottom ash under different operation conditions were studied. Experimental results show that bed temperature is an important factor influencing desulfuration. With the increase in the bed temperature, the desulphuration efficiency reduces very quickly. 853℃is an optimal temperature at which the SO₂ concentration is the lowest during co-firing of petroleum coke over coal with the Calories ratio of 50:50 in the experiment. The SO₂ concentration in flue gas reduces with increase in Ca /S molar ratio. For the mixed fuel of petroleum coke and coal, the Ca/S molar ratio of 2.5 or so is appropriate. The Calories ratio of petroleum coke over coal has no obvious impact on desulfurization performance. The CO concentration reduces with increase in the bed temperature. The average concentration is 156mg/m³. The bed temperature is an important parameter that influences NO concentration. When the bed temperature increases, the NO concentration increases. With increase in Ca/S molar ratio, the NO concentration reduces. The CaO content and the carbon content in fly ash are higher than those in bottom ash. When the Calories ratio of petroleum coke over coal in the mixed fuel increases, the carbon contents increases. The specific surface area and the specific volume of pores in the fly ash are higher than those in the bottom ash.The main factors that influence desulfurization performance in CFB boiler include operation parameters, design parameters and characteristics of calcium-based sorbents etc. The desulfurization efficiency during the experiment was relatively low, so, further study on properties of limestone and microstructure and the pore size distribution of limestone after calcination was carried out by means of nitrogen adsorption/desorption method. The apparent shape of the limestone after calcination was observed with SEM. Higher content of SiO₂, lower content of CaO, smaller specific surface area and porosity of...