Preparation And Application Of Ceramsite By Using Coal Slime,Fly Ash And Coal Gangue

Slime, fly ash and coal gangue are the larger emissions of industrial solid waste in China. At present the primary treatment methods include landfills and open dumps, it will bring environmental pollution and waste of resources with massive production and the lower use ratio. Therefore, exploring a new way of slime, fly ash and coal gangue source reuse seem to be particularly important.In this study, slime was used as principal material to sinter ceramsite, selecting the best technique conditions for the slime ceramsite produce by experiment. Then in slime ceramsite prepared on the basis of fly ash and coal gangue as additives. The best mass ratio of raw materials was selected. And the impact of main factors, such as preheat temperature, preheat time, sinter temperature and sinter time, on the characteristics of ceramsite were studied. Experiment was carried out to determine the best technique conditions for the ceramsite of slime as principal material, fly ash and coal gangue as additives. Treating ammonia wastewater with slime ceramsite and mixed burning ceramsite as adsorbed media, respectively, and the results showed that the application of ceramsite as adsorbed media in wastewater treatment was feasible.Based on the water absorption and bulk density, the best preparation conditions for the slime ceramsite was determined as follows:the dry temperature was105±2℃, the dry time was1h, the preheat temperature was450℃, the preheat time was20min, the sinter temperature was900℃, and the sinter time was15min. Under the optimized preparation conditions, the characteristics of ceramsite were obtained as follows:the water absorption was48.9%, the bulk density was1023kg/m3, the surface area was17.1m2/g, and the solubility in hydrochloric acid was0.54%. By orthogonal experiments and variance analyses, the optimum weight ratios of raw materials were coal slime60%, fly ash10%-15%, coal gangue20%. And the optimized preparation conditions were dry temperature was105±2℃, dry time was1h, preheat temperature and time were450℃,25min, sinter temperature and time were900℃,20min.Under the optimized preparation conditions,the characteristics of ceramsite were obtained as follows:the water absorption was63.5%, the bulk density was920kg/m3, the surface area was20.8m2/g, and the solubility in hydrochloric acid was0.67%. XRD analysis indicates that the slime ceramsite and the mixed burning ceramsite with the crystal structure of oxide and silicate structures, the main crystals are quartz (SiO2) and also contains a small amount of heavy metal compounds. SEM analysis indicates that two kinds of ceramisite have good adsorption properties with high specific surface area, rougher surfaces and porous. The contents of metal elements in the lixivium of the two kinds of ceramsite were within the content range defined in the hazardous waste identification standards (GB5085.3-2007) and the Integrated Wastewater Discharge Standard (GB8978-1996). Which indicated that the application of ceramsite was safe and feasible in the wastewater treatmentThe effects of ceramsite was used as the adsorbed media to treat the simulated ammonia wastewater and actual sewage were very good. The simulated ammonia wastewater removal efficiency was maintained at between40%-44%, and the ammonia removal efficiency of actual sewage in35%. The mixed burning ceramsite ammonia removal efficiency is higher than the slime ceramsite, due to it has a larger surface area and more adsorption capacity. The above results indicated that the use of slime, fly ash and coal gangue are feasible to prepared ceramsite, and can be used for ammonia wastewater treatment, So the resource reuse of slime, fly ash and coal gangue could be achieved.