Recycled Refractory Brick as Aggregate for Eco-friendly Concrete Production

The amount of construction and demolition waste continues to increase year by year.These wastes have a significant harmful influence on the environment; refractory brick is among of these wastes. this paper concerns the reuse of refractory brick wastes to produce an eco-friendly concrete. To achieve this objective,coarse and fine Natural Aggregates (NA) were partially replaced with recycled Refractory Brick Aggregates (RBA). According to the design of experiment, two families of mixes were prepared and tested: the first mixes was made with coarse and fine NA (as reference concrete) and the second mixes made by replacing 20% of coarse and fine NA by coarse and fine RBA. For each of the mentioned families, three cement dosages of 350 kg/m3 , 400 kg/m3 , 450 kg/m3 were investigated. A series of experiments including water porosity, density, Ultrasonic Pulse Velocity (UPV) and compressive strength were assessed. Observed results indicate that the use of coarse and fine RBA had a relatively influence on the water porosity and UPV of concrete. However, the use of coarse and fine RBA produces a slightly decreased the density of concrete (below 2%). Moreover, the use of coarse and fine RBA in concrete improved the compressive strength. Hence, coarse and fine RBA can be successfully used to produce concrete with acceptable properties.

Study on the corrosion of refractory materials by coal blended with the extraction residue of direct coal liquefaction in a simulated gasification atmosphere

Utilizing the extraction residue (ER) of direct coal liquefaction residue as a gasification feedstock has significant economic value. But the characteristic of high ash and iron in the ER would increase the risk of corrosion of the refractory materials and affect the long-term operation of the gasifier. In this work, corrosion experiments of molten slag derived from a mixture of 20 wt% ER and 80 wt% coal on a high-chromia refractory brick and SiC brick were carried out using a rotary-drum furnace in a simulated gasification atmosphere. The experimental results show that the viscosity of the poured slag is larger as compared to the initial ash sample at the same temperature, which suggests that the viscosity–temperature relationship of the poured slag should be used as the reference for the operation temperature of the gasifier to ensure that the slag can flow during operation. For a high-chromia refractory brick, iron oxides in molten slag could react with Cr2O3 in the refractory matrix but, because the aggregate was not found to be damaged, the damage to the matrix structure was the key factor for causing the corrosion of the high-chromia refractory brick. Metallic iron was observed in the exposed SiC brick, which indicated that the reaction between the iron oxides in the slag and SiC occurred, forming metallic iron and SiO2. The corrosion of a SiC brick by molten slag depended mainly on the dissolution of Al2O3 particles and the reaction between iron oxides in the molten slag and SiC particles. Therefore, the high iron content in coal ash had a serious influence on the corrosion of refractory materials. More efforts need to be made on coal blended with ER as a gasification feedstock in the future.

Combatting lime kiln ringing problems at the Arauco Constitución mill

The lime kiln at the Arauco Constitución mill experienced severe ringing problems requiring it to be shut down for ring removal every 3 to 6 months. The mill controlled the problems by blasting ring deposits off during operation with its existing industrial shotgun and a newly installed Cardox liquid carbon dioxide (CO2) cartridge system. Various ring blasting procedures were tested to determine the optimum ring location and thickness to blast; the optimum depth to insert the CO2 cartridge into the kiln; and the most effective blasting frequency and sequence to employ. The best strategy was found to be the weekly blasting operation that alternated between the liquid CO2 cartridge and the industrial shotgun, with the CO2 cartridge inserted into the ring mass, 20 cm (8 in.) away from the refractory brick surface, and the shotgun aimed at rings at about 28 m (92 ft) from the kiln discharge end. With each blasting event removing considerably more rings than before, it takes a longer time for rings to rebuild, allowing the kiln to run continuously between annual maintenance shutdowns with only a few short (< 4 h) downtimes for ring removal. This substantially reduces the costs associated with ring removal and lime replacement during unscheduled shutdowns.