Some technical aspects of the rheological properties of high concentration fine suspensions to avoid environmental disasters

The behavior of slurries and suspensions made by mixing solid particles and liquids is very important for various industrial applications. The latest accidental failure events at tailings facilities (Kolontár, Baia Mare) have focused public interest into this field. Nowadays, environmental practice is turning to use dry deposition techniques or at least as high concentration slurries or pastes as possible, to avoid large spills in case of an accidental failure of an embankment. High concentration slurries are becoming widely accepted in many environmentally related operations such as underground backfilling or simple tailings deposition. However, the hydraulic transport of pastes or high density slurries requires higher energy input via pumps, and, in addition, the energy requirement or pressure loss calculation methods are also different because the rheology of pastes differs from that of dilute slurries. At the University of Miskolc, Institute of Raw Materials Preparation and Environmental Processing, Miskolc, Hungary, this topic has been studied for many decades. The fine suspension – coarse mixture flow model was introduced, and it has been determined that the flow behavior of fine suspensions made of solid particles smaller than a limit particle size can be measured and interpreted in almost the same way as for single phase clear liquids. Based on these measured rheological parameters of fine suspensions, the frictional energy loss can be calculated. The aim of this paper is to give a summary and data base about the rheological behavior of different industrial materials based on pilot scale hydraulic loop measurements. An Anton-Paar rotational viscometer and a tube viscometer with three measuring pipe sections,– developed by our institute – were used for testing. The results of measurements of various granular materials, such as sands, fly ashes, perlite, tailings and red mud are presented in connection with environmental applications. Based on these results, empirical relationships are presented, where the parameters are determined by simple function fitting into the data of measurements carried out at discrete concentration values. The rheology of fine suspensions of any concentration up to the measured maximum can be calculated by these relationships

EFFECT OF GRINDING FINENESS OF FLY ASH ON THE PROPERTIES OF GEOPOLYMER FOAM

Present paper deals with the development of geopolymer foam prepared from ground F class power station fly ash. The effect of the fly ash fineness on the rheology of the geopolymer paste and the foam properties have been investigated. The raw fly ash was ground in a ball mill for various duration, 5, 10, 20, 30, 60 and 120 min. Geopolymer paste was prepared from the raw and ground fly ash with NaOH - sodium silicate mixture as alkaline activator. Geopolymer foam production was made using H2O2 as foaming agent. Additionally, the geopolymer material structure was investigated by Fourier transform infrared spectrometer, the foam cell structure was monitored using optical microscopy. The rheological behaviour of the geopolymer paste changed due to the grinding of fly ash (from Bingham plastic to Newtonian liquid). Grinding of fly ash has a significant effect on the physical properties as well as on the cell structure of the geopolymer foam

Szilikát-tartalmú hulladékok együttes hasznosítása = Combined utilization of various silicate bearing wastes

Jelen tanulmány a Föld legnagyobb mennyiségben keletkező ipari hulladékainak jellemzőit és egy hasznosítási lehetőséget ismertet hazai és nemzetközi kutatások eredményein keresztül, nevezetesen erőműi pernye és acélgyártási salakra fókuszálva. A kutatási eredmények azt mutatják, hogy a megfelelő előkészítést alkalmazva és a körülményeket optimálva a nyers alapanyagok eljárástechnikai jellemzőinek (szemcseméret eloszlás, fajlagos felület) megváltoztatásával a geopolimer termékek fizikai és mechanikai tulajdonságai (szilárdság, tömörség) javíthatók. Kutatásaink ugyanis kimutatták, hogy a kémiai aktiválás mellett a mechanikai aktiválás is egy igen hatékony eszköz a tulajdonságok szabályo-zására. Ez azonban megváltoztatja nemcsak a termék fizikai, mechanikai, hanem a szerkezeti, ásványtani jellemzőit is, ezért ezen jellemzők meghatározása is kiemelten fontos feladat többek között a fagyállóság szempontjából

Effect of the milling parameters on the product dispersity and energy consumption in a continuous dry air-transported stirred media mill

Stirred media mills are widely used for the production of ultrafine and nano materials in wet mode, however its application in dry mode is still limited today. The present paper deals with the operation of a continuous dry air-transported stirred media mill. The stirred media mill works in dry continuous mode, and the material is transported inside the mill by air. The mill and the additional systems were designed and built by the research group. The mill was equipped with a measurement and data acquisition system, so the air flow rate and pressure drop in the mill and in the air-solid separation system can be measured continuously. The aim of the research was to investigate the air-transported working principle in case of a horizontal stirred media mill and to install the laboratory scale mill and the additional systems. During the measurements the mill was operated in open circuit mode, the feed model material was limestone. The effect of the feed rate, air flow rate, and tip speed of the rotor on the product particle size was investigated, while the energy consumption of the mill and ventilator was measured as well. As a result of the research work the operation of the mill and the effects of the feed rate, air flow rate and tip speed on the product fineness and specific grinding energy was revealed. The developed laboratory scale dry stirred media milling system can be effectively used for the production of fine ground materials

Development of polystyrene-geopolymer composite for thermal insulating material and its properties with special regards to flame resistance

As a first part of the research, systematic experimental series were conducted in order to develop an appropriate fly ash-based geopolymer binder focusing on the workability of the paste. In these series, the NaOH molar ratio and water glass/NaOH ratio were investigated and the fineness of the fly ash was optimized presented in a recent paper. Based on these results the effect of metakaolin on the mechanical properties was studied. After developing the appropriate binder, experimental series were carried out using ground polystyrene as light aggregate in various concentration (from 30 V/V% up to 98 V/V%) and geopolymer as a binder in order to develop a heat insulating material. Compressive and flexural strength, specimen density, flammability, freeze-thaw resistance were determined in order to characterize the composite product. As a result of the experimental investigation, it was found that the flexural strength of the composite was found to be ~400 kPa which is as high as the original polystyrene heat insulating panel. Additionally, the flammability was much better than the original pure PS product, the sample was not ignited even at higher PS content (90%). Furthermore, the freeze-thaw resistance of the composite improved compared with the neat geopolymer

Recent trends and activities in hydrogeologic research at the University of Miskolc, Hungary

The Institute of Environmental Management at the University of Miskolc, as a major Hungarian research entity in groundwater management, is dedicated to finding solutions to regional issues of global sustainable water resource management challenges, thus further developing its scope of groundwater management competence. WELLaHEAD is an EU-funded fundamental research program coordinated by the faculty members of the institute, covering a broad spectrum of relevant groundwater related research topics based on Northern Hungarian test sites. The research concept is described in the detailed Research Plan of the project, and after 14 project months some of intermediate results can be presented from three research modules

Recovery of critical and other raw materials from mining waste and landfills

The transition to a more circular economy is essential to develop a sustainable, low carbon, resource efficient, and competitive economy in the EU. In this context Critical Raw Materials (CRM) are defined as those which are of particularly great importance to the EU economy and at the same time there is a high risk of supply disruptions. First and foremost, improving the circular use of CRM is a key strategy in improving the security of supply and not surprisingly is an objective of various policy documents. This report delivers on action #39 of the Circular Economy Action Plan: "Sharing of best practice for the recovery of critical raw materials from mining waste and landfills". It builds on discussions held during two 2018 workshops and gathers together six examples of existing practices for the recovery of critical, precious, and other materials from extractive waste and landfills, highlighting technological innovation and contributions that have been made to a more comprehensive knowledge-base on raw materials. The report also provides various estimates of potential recovery of certain materials compared to their current demand. Lessons learnt from the practices include awareness that it is very unlikely that recovery processes can target one or just a few specific materials of great interest and disregard other elements or bulk matrixes. Especially in case of very low concentrations, most of the mineral resources and other bulk materials in which they are embedded must be valorised in order to increase economic viability and minimise waste disposal. As recovery processes can be very energy intensive, environmental and land use related aspects are also particularly relevant even though environmental gains may also occur and, moreover, land space can be liberated and reused for new purposes and services. Finally, availability of data and information on secondary materials as well as a harmonized legislative framework within the EU appear to be crucial for the large-scale deployment of recovery practices.JRC.D.3-Land Resource

„Hulladékból Energia” Kutatások a ME Nyersanyagelőkészítési és Környezeti Eljárástechnikai Intézetében

The importance of research and development in the field of „Waste-to-Energy” is vital in our modern society trying to establish the circular economy. Such R&D activity has been carrying out at Institute of Raw Materials Preparation and Environmental Processing for decades in several directions. This paper deals with the main results of research on refuse derived fuel from MSW, biogas production, briquetting of biomass, as well as production of fluid fuels.A „hulladékból energia” kutatások és megvalósítások fontosságát a mai modern, körforgásos gazdaság megteremtésére törekvő társadalmakban nehéz túlbecsülni. A Miskolci Egyetem Nyersanyagelőkészítési és Környezeti Eljárástechnikai Intézetben ilyen irányú kutatások már közel két évtizede folynak több irányban. A tanulmány e témakörben végzett kutatásokról, valamint azok eredményeiről számol be: másodlagos tüzelőanyag előállítása települési szilárd hulladékokból, hulladékok biogázosítása, biomassza brikettálása, valamint folyékony üzemanyagok előállítása