The Engineering Design Of The Preparation Of White Carbon Black From Leached Coal Gangue

Coal gangue is one of the largest industrial solid waste production. A great amount of coal waste is open-air stack-stored near the coal mines, occupying much land and leading to a series of environmental problems. At present, coal gangue are mainly utilized in an extensive way such as backfilling, power generation, construction and building materials. Coal gangue contains large amounts of SiO2, Al2O3, therefore, the recovery of valuable elements from coal waste to produce high value-added products with minimal environmental impact is an important way to reduce the coal waste environmental problem. However, the industrialization of aluminum extracting faces enormous difficulties due to high material and energy consumption, large quantity of waste discharge and serious secondary pollution. Considering the main component in the acid-leached slag of coal gangue is silica (60-90wt.%), it is of great importance to prepare high value-added silica products from the slag to solve the problem above-mentioned. In this way the solid waste would be further reduced.This thesis summarizes the previous research results achieved by our research group about white carbon black prepared by acid-leached slag of coal gangue. Analyze and proposed the issues it may encounter with industrialization such as difficult discharge of Na2OnSi02 prepared by sintering method and unstable quantity of amorphous silica, and focuses on the process optimization and engineering issues of the preparation of white carbon using slag from acid leaching of coal gangue based on the previous study:the development of a novel approach called low-temperature co-melting method for preparation of sodium silicate (Na2OnSi02), the co-melting mechanism between sodium carbonate and silica in the feedstock and the effects of aluminum on the co-melting temperature. The main contents and results are as follows:(1)Some suggestions have been proposed aim at the issues it would be faced with industrialization. ①Sodium Silicate shows high viscosity at the temperature between 790℃ and 850℃,consequently it may very likely cling to the internal face of equipment during the reaction occur at a static solid phase. Use dynamic sintering method with converter solve the problem of which the difficult discharge of Na2O-nSiO2. ②he content of impurity aluminum oxide in the feedstock affect the solubility of SiO2 and the modulus of the prepared sodium silicate. In addition, the extraction yield of alumina is different from different region. Getting quality stable product via adding silica to raw material to control the aluminum content to ensure the route’s stability.③The centrifugal spray dryer is used to improve the quality of white carbon black. Feed content is 20%, the inlet temperature of spray dryer is 300℃, and outlet is 110℃.(2) The annual output of 3000 tons of white carbon black project has been design. Primarily, the process flow has been determined, on this basis, the material balance for each unit operation and main equipment was calculated. The calculation shows, one ton product can be produce by 0.68 tons of acid leaching slag of coal gangue, and consumed 0.68 tons of quartz sand,0.99 tons of Na2CO3, and discharge 0.35 tons of waste residue which can be used to make brick. According to the calculation of material balance and energy balance, main reactors have been designed or determined and draw a process flow diagram.