The Technology Of Preparation Of Aluminium Sulfate From Coal Fly Ash

Coal fly ash (CFA) is a castoff of coal combustion in power plants. It's letting not only occupies large area, but also causes environment pollution. So how to dispose and utilize CFA has become an urgent and arduous task. Generally speaking, the main composition of CFA is alumina and silicon oxide. The content of alumina and silicon oxide is about 42% and 48% in CFA which is from somewhere of Shanxi province, and the content of others is lower observably. Therefore, CFA has a value of using synthetically.First of all, the row CFA that is used in the experiments of this article is analyzed and detected roundly by chemical and physical method. Then the technology of preparing aluminium sulfate from CFA by sulfuric acid is proposed:CFA→sulfuric acid sintering→leaching→filtration→evaporation→crystallization→desiccation→aluminium sulfate. The residue is used as a raw for preparing silica. In this process, sulfuric acid can use circularly and fly ash can be utilized comprehensively. It doesn't bring waste and is also neighborly to environment.Second, Equipment is selected based on the requirement of technology, by considering strongpoint, shortcoming the used condition of equipment, we confirm standard and type that is in accord with this technology.Third, the workshop is disposed by the flow we have confirmed. In the field, we assemble, dispose and install the equipment reasonably.Forth, the industrialized experiment is carried, and every part of technology is analyzed and studied in detailed. The conclusions are drawn as follows:1. The effect of temperature and time of sintering, ratio of acid vs ash and granularity of CFA on the extracting efficiency of Al2O3 in activated CFA are studied. The optimum processing conditions of the system are defined by the orthogonal experiment based on single factor experiments:sintering temperature is 260℃, sintering time is 90min, the ratio of acid vs ash is 1.2:1 and granularity of CFA is 68μm. The Al2O3 extracted rate can be stabilized about 87% under these conditions.2. The materiel sintered by sulfuric acid is leached by adding distilled water. The leaching conditions are got:temperature is between 85℃, water at amount of 300L/(100kg materiel) and time is 60min. The product crystal aluminium sulphate that was gotten by decompression condensing and pexitropy was conformed to corresponding national standard:HG/T2225-2001. Finally, economic benefit is analyzed and environment is evaluated by calculating materiel equation and energy equation. We can know:This technology' synthetical benefit of economy and environment is better, resource is used synthetically and material is used circularly, no contamination is let, so this technology is a "grassy" industry and has a good social benefit, according with the requirement of industrial manufacture.