Gábor Mucsi

Structural formation and leaching behavior of mechanically activated lignite fly ash based geopolymer

AbstractGeopolymers are inorganic polymers which can be produced by the reaction of aluminium silicate oxides and alkaline silicates in an alkaline medium. Nowadays, silicate bearing wastes, such as fly ash or slag and other by-products of power stations are very common raw materials for geopolymers.In our research a lignite type fly ash was mechanically activated in a high energy density mill (HEM) for different retention time, and geopolymer specimens were produced from these materials. After determining the optimal fly ash fineness, the concentration and composition of the alkaline activator solution were also investigated. The highest compressive strength was reached using fly ash with 2 m2/g specific surface area, activated with a mixture of Na-K silicate (water glass) and NaOH solution. The total dosage of alkaline activators to the fly ash was 40 m/m%, the NaOH activator of 12 M solution represented 25 m/m%, while Na-K silicate 75 m/m%. Then, the leaching properties of the main components and the m...

Grindability of Quartz in Stirred Media Mill

Nowadays, ultrafine grinding in the submicron particle size range is becoming an increasingly conventional process. One of the mostly used ultrafine grinding ways is the size reduction in the so called stirred media mill. This article deals with the experimental investigation of wet grinding of quartz in a stirred media mill. The applicability of the introduced operating Rittinger index and the lower limit size of Rittinger law are studied. Furthermore, the effect of solid concentration of suspension, ball filling ratio, circumferential speed of the stirrer, and size of grinding media on the fineness (median particle size and specific surface area) was examined. Additionally, a relative grindability calculated from the operating Rittinger index is introduced in order to compare the efficiency of stirred media milling. It was found that the grinding conditions greatly affect the applicability of Rittingers law and its lower limit size.

Changeing of fly ash leachability after grinding

Effect of grinding on the reactivity of fly ash used for geopolymer production was tested. Extraction technique using different alkaline and acidic solutions were used for detect the change of the solubility of elements due to the physical and mechano-chemical transformation of minerals in function of grinding time. Both the extraction with alkaline and acidic solution have detected improvement in solubility in function of grinding time. The enhancement in alkaline solution was approx. 100% in case of Si and Al. The acidic medium able to dissolve the fly ash higher manner than the alkaline, therefore the effect of grinding was found less pronounced.

Development of Fly-Ash Based Hydraulic Backfilling Technology for the Final Closure of Underground Mines

The active mining of the Mátraszentimre (Hungary) underground base-metal mine was halted in 1985. So far enormous research and efforts have been taken for the final closure of the mine. The technology of fly-ash based hydraulic backfilling was selected. About 95 000 tons of fly-ash backfilling is necessary to close the mine. A suitable technology have been developed, installed and put into operation. So far about 14 400 tons fly ash have been backfilled.This paper summarizes the main results and elements of the process engineering part of this work. The pozzolanic activity of fly-ash from the Mátra Power Station was examined in order to develop a new hydraulic binder with the addition of lime. As results of the different examinations it had been decided that the backfilling material should be lignite fly-ash from the tailings pond of the nearby Mátra Power Plant. The fly-ash hydraulic transport system of the Mátra Power Station was designed by our institute back in 1998. This system is still operating and now serving the material for backfilling. The knowledge of designing the power station pipeline system was utilized at designing the hydraulic backfilling system. The main technical parameters of the solid – liquid pipe flow were designed based on the Tarján – Faitli: coarse mixture flow in fine suspension flow model then and now as well. The design covered many other aspects of the task such as material characterization and mixing, settling behavior of the backfill, dewatering and mechanical properties of the backfill, water permeability and so on...

Development of hydraulic binder using industrial wastes

This paper is focused on the utilization of landfilled F class fly ash as a main component of hydraulic binder; furthermore quick lime (CaO) and lime kiln dust (LKD) were tested as additives during the experiments. After determination of the material properties, such as particle size distribution, moisture content, real and bulk density and specific surface area, mechanical activation was performed for certain time by laboratory ball mill to improve the pozzolanic activity of fly ash. Than test specimens were produced using different type and composition of hydraulic binder and the compressive strength was measured at 14, 28 and 56 days. Optimal mechanical property was achieved with binder No. II. (containing 80% fly ash, 20% CaO) and No. V. (70% fly ash, 15% CaO and 15% LKD), compressive strength was 4.67 and 4.31 N/mm2 respectively.