Manfred Rösch discusses a monolithic wear-resistant lining material that’s proving to be a popular choice in the mining industry.
Wear, abrasion and thermal shock cause many operational problems within the different furnace environments, contributing to downtime and cost increases. In the past, the available wear products could withstand one or two of these harsh conditions but not all of them. For example, alumina tiles and basalt have excellent wear and abrasion properties but cannot withstand high temperatures. In some instances, process conditions often create different vapours that creep into and penetrate the joints in the refractory lining, resulting in the lining detaching causing blockages and damage to mechanical parts.
Refraline has now developed a wear-resistant product range of castables in different grades with a triple bonding system to withstand both hot and cold process wear conditions.
With the above challenges and continuous research and development, Refraline has formulated the Ceratuff product range, installed by casting or trowelling and designed to mitigate the above problems.
One key characteristic of the material is its thermal shock resistance. Thermal shock is caused by a rapid change in temperature at a certain point. It can also be extended to the case of a thermal gradient, where different areas of a lining expand at different rates. Refraline’s material (tested according to ASTM C1171-16) is able to withstand 94 thermal cycles in the air. It can be heated to 1,200°C in its cast shape and then be immersed into a drum of cold water without developing a crack from the rapid temperature shock.
Wear resistance is another characteristic. Wear is a process of friction between surfaces that causes the deformation or removal of material on the surfaces due to the effect of mechanical action between the sliding surfaces. The matrix of the lining is crucial as this forms the binding system for the aggregate in the material. If the material has a weak matrix, the wear rate will be very high. The company’s triple bonding system has the strongest matrix resulting in its excellent wear properties.
Having a wear resistant material with a low porosity is key. A material with low porosity will have very high strength. Refraline’s material has low porosity due to the low water requirement and the high-density value of the material.
High compressive strength is another consideration here. A material with a very high compressive strength will have the ability to withstand very harsh wear and abrasion conditions. Silicon carbide is one of the mix components that adds to the strength characteristics of the material because of its hardness. The monolithic product should have a cold crushing strength of 145-160 MPA at 1,200° C
Triple Bonding System
The strength of a refractory material is determined by its matrix and bonding system. The Ceratuff material has a bonding system that has a break-line through larger aggregate in the material matrix. Weaker materials have a break-line through the fine aggregate in the matrix. This is a clear indication that the finer matrix is weaker than, the bigger aggregate.
The material also has a high thermal conductivity of 10W/mK, which means it can effectively transfer heat, resulting in low thermal stress within the lining. Heat transfer is important in many processes, and the temperature profile can be achieved by working out the different required lining materials against their respective thermal conductivity values.
Cyclones, hoppers, ducting and boilers are just a few of the applications for this material. The trowelled installation process involves tack welding expanded metal to the shell at 200mm spacing intervals, followed by the trowelling of a 15-20mm lining. The lining is then left to air dry for 24 hours. The lining can be successfully increased by three to four times, reducing the downtime of the equipment. The advantage of a trowelled lining is that no cuts are required during the installation, and the fact that a trowelled lining can be applied to any shape. Another advantage with a trowelled lining is that there are no joints. Having joints creates vulnerability for attack in a wear lining.
Burner tips, feed chute tips, feed chute liners, muffles, electrode segments and launders are a few of the cast applications for the material. The ability to cast a variety of shapes and sizes to suit the customer’s requirements is a big advantage. The Ceratuff product range has a superior bonding system that enables it to outperform the end-users expectations as well as withstand aggressive operational conditions.
Industry requirements encourage the use of high wear-resistant materials in all tough applications. Having the correct material in wear, abrasion, and thermal shock environments is essential. This will reduce the loss to mechanical parts, lengthen the lifespan of the refractory by three or four times and reduce downtime in the plant.
Manfred Röschis CEO of Refraline