Wet Purification Technology And Theoretical Studies Of High Ash Coke Powder

Coke is a kind of by-products in coking and broken process, which size is typically less than 30mm and the ash content is about 30% to 40%. Due to high ash content can't be met the production process, it usually is sold with cheaper or abandoned. With the growing energy shortages, China's coal and coke are in short supply, and the price is high. Coke plays an important role in the preparation of calcium carbide. It is used for conductors in electric arc furnace and heater materials. Coke should have low ash, high activity, resistance and other characteristics of large and medium size for calcium carbide producing. However, it's very expensive the coke with low ash. With the ash content increasing, it not only increases power consumption and carbon consumption, but also would be harm the furnace. Therefore, it is very important to use an effective method to purify high ash coke.In this paper, thermodynamic of the ash content removal is analyzed in chemical demineralization process which based on a lots of related materials about coke and coal ash content removal technology. Thus through the traditional purification of coke combined with hydrometallurgical process, it should reach the purpose of high efficient ash removal. By the Ultimate analysis of coke samples:the main impurities are silicon, aluminum, iron and magnesium oxides in ash content which SiO2 content of 56.86%, Fe2O3 and A12O3 contents were 5.92% and 20.07%.The facile and efficient method to demineralize of high ash coke via pressure hydrometallurgy is introduced. First, the Gibbs free energy of chemical reaction is more negative at the higher temperature in the alkaline leaching process, and the spontaneous reaction becomes better. With the increasing of temperature the Gibbs free energy of chemical reaction becomes greater in the acid leaching process, which is not conducive to the spontaneous reaction. Secondly, the influence of leaching time, leaching temperature, initial concentration, the radio of liquid to solid and particle size on the rate of ash removal are systemically investigated. The optimum conditions of leaching were obtained as follows:(1)In alkali leaching process:the alkali leaching temperature is 200℃, the pressure is 1.2 MPa, the sodium hydroxide initial concentration is 18%, the leaching time is 60 min, (2)In acid leaching process:the initial acid concentration is 12%, the acid leaching temperature is 90℃and the leaching time is 30 min. The results indicate that the ash content could be declined from 28.62% to 3.95% and the efficiency of ash removal achieve 86.20%.The content of carbon in the product is up to 92.90% from 69.20% at the optimum condition.The flow chart of the purification of coke powder can be obtained by the results of high ash removal with hydrometallurgical method. The results of repeatability experiments indicate that the technically of ash removal is feasible through alkali leaching under high pressure and acid leaching under normal atmosphere. The method has better high ash content removal and high recovery ratio of carbon to physical method. The results of expansion testing and economic analysis show that the confirmation experiment indicated the coke should be leached with acid after alkali leaching which can efficiently reduce the ash of coke. After being prilled the product can be potentially useful in the calcium carbide. It has notable economic benefits and broad prospect for industrial application.