Performance of Recycled Aggregate Concrete Made with Waste Refractory Brick

Concrete containing recycled aggregates have different properties from concrete containing natural aggregates. This work investigates, firstly, the possibility of using recycled refractory bricks (RBA) as coarse aggregate for concrete, and secondly, finds the ideal replacement percentage of natural coarse aggregate (NCA) by RBA. For this, an experimental study was carried out to assess the physical and mechanical properties of concrete produced with the partial and total replacement of NCA by RBA. Two types of RBA from two different sources were used, RBA-1 obtained from the grinding of new refractory bricks and RBA-2 obtained from refractory bricks used in the furnace recovered from the cement plant. For each type of RBA, two concretes with water/cement (w/c) ratios of 0.59 and 0.38 were tested. These concretes were evaluated by density, water porosity, ultrasonic pulse velocity (UPV) and compressive strength, and compared to those obtained on conventional concretes. The results obtained show that concrete can be manufactured using RBA. Concrete containing 20% ​​RBA shows good quality compared with conventional concrete.

Upgrading the Glass Bead Making Furnace for Ease of Operation: A Case Study of the Masaga Glass Guild

The glass bead making furnace of the Masaga Glass Guild in Bida, Niger State Nigeria was evaluated in comparison to those of Ghana (Krobo) and India (Firozabad); it was discovered that the Masaga furnace falls short of an efficient system for sustainable work that should facilitate appreciable productivity. Furthermore, the furnace is not built with refractory bricks, implying that it has a short life span; the furnace is operated by hand-worked traditional cloth bellows requiring sustained and strenuous efforts over a relatively long period of time; Following this assessment, efforts were directed at modifying the furnace by producing design drawings of the modified furnace, design and production of refractory bricks from the design drawing, constructing the modified furnace structure using the refractory bricks, producing suitable furniture for the furnace and subsequently, devising a suitable mechanical blower device as an alternative to the manually worked bellows for the supply of combustion air. Consequently, a furnace was developed which eliminates the strenuous manual working of the bellows as well as the bellow operator and ensures that a single individual can work unassisted at the furnace in the process of glassware production.

Possible ecological advantages from use of carbonless magnesia refractory bricks in secondary steelmaking: a framework LCA perspective

In the present paper, two types of magnesia-based refractory bricks for the wear lining of a steel ladle furnace are considered, with the aim of comparing their ecological performances. The adopted methodology is the Life Cycle Assessment (LCA) approach from cradle-to-gate of the two brick product systems, in accordance with the European and International Standard EN ISO 14044:2006, and the chosen methodology for the Life Cycle Impact Assessment (LCIA) is ReCiPe 2016, considering the midpoint impact categories and the hierarchist perspective. The conducted study is part of a European industrial research project aimed at investigating the possibility of cleanliness improvement of the steel produced in secondary steelmaking, by reducing the refractory contamination in the steel ladle furnace. The compared refractory bricks consist of a reference, currently used, MgO-C type and a more innovative "carbonless" one, containing magnesia and MA sintered spinel as principal components, on the basis of recipe data provided by the industrial partners of the project. The results attained so far in industrial practice are preliminary, because of the lack of a full-ladle lining experimentation, even though the application of the conceived innovative bricks in the upper part of the slag line of the ladle presents promising aspects. The results of the LCIA comparison between the two brick product systems highlight better performances for all the impact categories, except for "Human carcinogenic toxicity" and markedly for "Mineral resource scarcity." Besides these results, a general framework for shifting the ecological analysis to the steel production is provided. Calculations, referred to the production of one tonne of steel, are therefore performed, involving scenario assumptions not only regarding the refractory consumption but also the forecast operational features of the steel ladle with the "carbonless" lining. In this second set of results, it is clear how the principal contribution to almost all the impact categories is the electrical energy consumption of the ladle, while the contribution from the brick product systems remains important for the above-mentioned worsened impact categories, whose magnitude is strongly dependent on the refractory consumption.

ADVANCED TYPES OF CHECKERWORK OF REGENERATIVE HEAT EXCHANGERS FOR GLASS FURNACES

One of the ways to increase glass furnaces energy efficiency is to apply heat exchangers for flue gases thermal potential utilization. Flue gases losses is up to 25-40 % of the total amount of heat supplied in the furnace. These losses are influences by such factors as fuel type, furnace and burners design and manufactured product type. Regenerative heat exchangers with various types of heat storage packing is more efficient for high-power furnaces. Such types of regenerator checkerwork as Cowper checkerwork, two types of Siemens checkerwork, Lichte checkerwork and combined checkerwork have already been sufficiently researched, successfully applied and widely used for glass furnaces of various designs. All of its are made of standard refractory bricks. Basket checkerwork and cruciform checkerwork that are made of fused-cast molded refractory materials have been widely used recently as well. Further improvement of regenerative heat exchangers thermal efficiency only by replacing the checkerwork does not seem possible unless their size being increased. But this enlarging is not always realizable during the modernization of existing furnaces. From this point of view heat storage elements with a phase transition, where metal salts and their mixtures are used as a fusible agent look promising for glass furnaces. These elements can accumulate additional amount of heat due to phase transition, which allows to increase significantly heat exchanger thermal rating without its size and operating conditions changing. However, it is necessary to carry out additional studies of this type of checkerwork dealing with analysis of complex unsteady heat exchange processes in regenerators and selection of appropriate materials that satisfy the operating conditions of regenerative heat exchangers so that the checkerwork can be widely used for glass furnaces.