No abstract

Problems related to rare earth metals leaching from coal ash and theirs ion-exchange concentration from sulfuric solutions, in particular the characteristics of scandium, yttrium and lanthanum sorption by different ion exchange resins have been considered in this work. It has been shown that the best way to leach rare earth metals from coal ash is a complex acid and biological treatment of ash waste. Kinetics related to the process of scandium, yttrium and lanthanum acid leaching from ash and slag waste of CHPP in Kumertau has been investigated. Subsequent metal solutions concentration was achieved using ion exchange resins. The results of experimental studies related to the processes of rare-earth metals (in particularly scandium) ion exchange concentration by cation exchange resin in the Naform PC-100 have been presented, as well as the results of experimental studies related to rare earth metals (scandium including) sedimentation process, using special sedimentators. Dependences of rare earth metals (in particular scandium) sedimentation efficiency against pH value have been constructed, and recommendations for pH values, that are optimal for rare earth metals sedimentation, have been given. Based on obtained experimental results it was created and tested an experimental laboratory prototype of plant for rare earth metals (scandium, yttrium and lanthanum including) extraction from located near Moscow brown coal basin’s slag heaps, and from ash dumps of Russian Federation’s energy enterprises. This plant’s process flow diagram as well as its operation description has been presented. The created plant was tested in modes previously fulfilled in laboratory conditions. At the same time, carried out integrated exploration have showed the prospects for implementation of developed technical solutions for processing of ash dumps of Russian Federation’s various energy enterprises.

The article covers theoretical basics of floatation process and main stages of flotators’ evolution. special attention is paid to flotation as multistage process as well as to definition of constants with theoretical and the experimental methods. Authors demonstrate that use of theoretical bases of multistage flotation model allows to significantly stimulating floatation process. Leading foreign and domestic innovations in floatation sewage treatment and active sludge thickening are presented. Promising research in constructing multi-tool floatation apparatus (flotation combine) is described. The article provides variants of multi-tool flotators’ design, examples of its integration into operation, and the test data confirming its high effectiveness for sewage treatment and active sludge thickening. Methods of stimulating thickening with carbon dioxide and chemical agents are used for wastewater sludge (including active sludge).

Urgency of the problem of sludge treatment and disposal in recent times is noted in this paper. Questions related to sludge and other waste treatment by centrifugation both with pre-treatment, and without it, have been considered. It has been demonstrated that the treatment is more effective at heating of above-noted waste, and by reagents adding. As a result of use of centrifuges at a stage of above-noted waste treatment it is possible to reach rather high degree of separation into liquid and firm phases which can be used in various directions. Further dewatering is possible by using a proposed drying scheme with a closed circuit of heat transfer fluid. The scheme includes a unit for heat transfer fluid preparation, a drying chamber, a device for a finished product unloading, a cleaning system for used drying agent, a unit for additional cleaning of heat transfer fluid, dual-circuit system of pneumatic transport for the finished product. The proposed scheme contributes to exclusion of sludge’ toxic substances from getting into the environment. Experimental studies of activated sludge suspension thickening process after secondary clarifiers in centrifuges of different types have been carried out. Tests were conducted on laboratory and industrial direct-flow and counter-flow centrifuges. Optimal parameters and modes for centrifugation and thermo-reactant treatment were selected. Effectiveness of preliminary thermo-reactant treatment at a predetermined optimal centrifugation mode for activated sludge has been confirmed. The solids content in the concentrate of microbial biomass at the load 10–13 m3/h reached 9–10 % DIA. At the maximum capacity was used one nozzle with 6 mm diameter. Minimum specific dosage of flocculent is about 2 kg per 1 ton of dry product.