Like every other industry, the refractory industry is growing its environmental consciousness. This mindset in the industry is motivated by new efforts and technology. However, space for improvement is always open. We’ll go through some of the refractory industry’s big technical advances.
Issues in the environment:
Refractory materials may generally be known as ‘energy concentrated’ materials, for example – fusion cast materials & manufacturing of high-fired bricks like direct-bonded bricks. The choice to use more monolithic materials and less fired bricks help to save energy in refractory processing. The entire cycle, however, covering both the creation and application of the refractory material, should also be considered, as refractory materials with high energy consumption may be preferred if their application saves energy. Historically, refractory products have been landfilled following withdrawal from use. In terms of energy efficiency and environmental security, progress in the refractory industry has been strongly motivated. Examples of this include energy consumption reduction (production of binders that result in high resistance in low-temperature refractories, creation of spinel grain by mechanical alloy), emission reductions (e.g. conversion of air-powered firing technology into oxygen-powered firing technology, reduced NOx emissions), creation of carbon-containing non-toxic and eco-friendly resins and substitution of the coal tar pitch with other free carbon-free benzo-a-pyrene (BaP) substances for impregnation.
The rise in application of monolithic refractories in the cement industry:
The manufacturing process of high alumina refractory cement in India has been briefly defined and the conditions in the rotary furnace were provided for both dry and wet processes. Modern pyroprocessing ovens have significantly improved efficiency at the expense of significant abuse of refractory materials. Higher capabilities in turn have increased the criticality of refractory equipment, combined with higher thermal load and expensive downtimes. Further aggravation of the operating parameters was the chemical misuse of substitute fuel. Refractory manufacturers have come up with new products with higher heat properties to overcome these challenges. This growth story has played a significant dual role in growing installed cement production capacity by introducing large turn-key projects with a new market strategy. High alumina refractory cement in India was always at the front for the growth of cement technology in the 90s.
Castable containing carbon:
As they consist of oxides, LCCs and ULCCs suffer the same deficiencies as oxide-driven refractory bricks, for example, Al2O3 based castables have low corrosion resistance and spill resistance (especially in basic slag environments) and castables based on MgO have a poor slag penetration and spalling resistance. By adding carbon, the improvement in the properties of oxide bricks indicated that graphite addition to oxide-based castables would enhance the properties. Problems arose, however, as graphite has weak aqueous wettability and dispersion, Al-based antioxidants appear to be hydrated, and after curing and drying, they have lower power. CIREP (Center for Industrial Refractories, École Polytechnique, Montreal) initiated research on C-containing castables for iron and steelmaking applications in 1996. Carbon-containing castables have been hampered by poor water wettability and graphite dispersal capability that lead to badly-flowing castables, requiring a high placing water content that leads to high porosity after desiccation and subsequent decrease in mechanical strength and corrosion resistance. In order to solve these problems, the use of surfactants or dispersants, micropellets of graphite, and graphite coating techniques have been analyzed.
The key requirement is the creation of a bonded coating that is uniform, crack-free, dense, and solid. In MgO-C castables, antioxidants have been found to play a multifunctional role: they protect carbon against oxidation, enhance hot strength, and play a role in the formation and deposition of secondary carbon, which improves the resistance to slag penetration. Trials for the hot repair of the BOF converter and steel ladle slag lines have already been conducted in Brazil with an established MgO-C self-flow castable. It is claimed that this material is compatible with MgO-C bricks and simple slags for steelmaking.
Nanotechnology aims at achieving improved material properties and functions by atomic and molecular scale control of matter. There has been widespread interest in the first papers on nanotechnology and refractories published during UNITECR 2003. The documents covered the creation of the nanostructured matrix in MgO-C. At UNITECR 2007 the nanotechnology papers expanded into refractory aluminum-based materials, ZrO2-C materials, and nano-size MgAl2O4 particles. At UNITECR 2007, nanotechnology papers were extended to include aluminum-based refractory materials, ZrO2-C materials, and the development of nano-sized MgAl2O4 particles. Various nanoscale materials are already being used in refractory goods or have the potential to be used.
The development of nano-graphitized black containing MgO-C bricks means that low-carbon levels can be used in those bricks by lowering the elasticity module, increasing the thermal shock resistance, and the excellent resistance to corrosion and oxidation. Using highly reactive nanoparticles, sintering agents and participants are able to establish a wide range of options through in situ reactions in the matrix-phase formation. The availability, dispersion, storage, price, mixing as well as the health and safety aspects associated with the handling of these very fine materials are related to problems associated with these nanoscale materials.
Refractory containing mgal2o4:
Because of their high refractoriness, mechanical power, thermal impact, and corrosion resistance (MgAl2O4), refractory spinels are finding new applications and creating new spinal refractory forms. It is anticipated that their synthesis techniques can constantly be improved, but new methods such as mechanochemical alloy and molten salt synthesis can become important methods for producing high-quality spinels at lower temperatures and cost. FIRE (The Federation for International Refractory Research and Education) is also currently leading a comprehensive research effort into castables and bricks based on Al2O3-MgO.
Refractories have become a highly advanced industry-focused on innovative methods of implementation, based on an approach of trial and error using mostly natural materials. It has grown as a result of developments in the iron and steel industry in particular. Improved process technology and the need to increase efficiency through longer campaign lives, but also an increasingly better use of resources, the need for environmental conservation, and the reduction, reuse, and recycling of refractory waste material has been a driving force towards change. Refractory materials are becoming readily accessible and the technology is becoming increasingly sophisticated. The evolutionary process is far from complete and continues to evolve through the constant exchange of ideas between the refractory manufacturers’ research teams, the users of refractory materials, the researchers’ contribution at academic institutions, and the raw materials and additives production team.