Nano‐Bonded Wide Temperature Range Designed Refractory Castables

Abstract

Designing high‐performance refractory castables for aluminum and petrochemical applications is not a straightforward target as at their operation temperature range (800°C–1250°C) usual refractory binders show low‐bonding effectiveness and also low sinterability. Taking this into account, colloidal binders can anticipate the castable's densification and inhibit the drawbacks regarding the calcium aluminate hydrates’ decomposition, as the former does not present the typical hydraulic setting of traditional binders. To attain even better results, sintering additives can be incorporated to induce lower temperature densification. Nevertheless, the key issue is to select a suitable additive that is able to generate a transient liquid, leading to densification but with no refractoriness drawbacks, such as low‐hot mechanical properties. Considering these aspects, the objective of this work was to design a novel refractory material able to display a high performance within a wide temperature range. High erosion, hot mechanical and thermal shock resistances were attained pointing out an outstanding potential to increase the refractory lining working life of aluminum and petrochemical equipment units.

High‐Alumina Boron‐Containing Refractory Castables

“…High‐alumina self‐flowing castables were designed according to Alfred's packing model ( q = 0.21) . The compositions comprised coarse tabular alumina (d ≤ 6 mm, Almatis, Frankfurt am Main, Germany) such as aggregates, calcium aluminate cement (CAC, Secar 71, Kerneos, France) as a binder, reactive aluminas (CL370C and CT3000SG, Almatis) and a boron‐based additive (borosilicate, d < 45 μm, SA, under patent application) to speed up the densification of the refractories in the usual temperatures for petrochemical applications (~800°C for FCC risers) . Additionally, an additive‐free composition (TA) was prepared and tested as reference material.…”

“…High‐alumina calcium aluminate cement‐bonded refractory castables are commonly used in risers for fluid catalytic converter (FCC) units. However, most of these materials were originally developed for the steel‐making process and, as a consequence, they do not usually show suitable mechanical strength and thermal shock behavior for the petrochemical application due to their late densification that only effectively takes place above 1200°C …”

“…In this context, there is a limited availability of advanced refractory castables for riser equipment with a good performance within the temperature range of 800°C–1200°C . To minimize this drawback and improve the castables' behavior at lower temperatures, many efforts have been made in recent years, mainly focusing on the sintering additives (i.e., magnesium borate, magnesium fluoride, borosilicates, titania, zirconia, silica, and others) influence on refractory thermo‐mechanical properties.…”

“…Some authors stated that using boron‐based compounds might result in a transient liquid without deteriorating the high‐temperature properties of refractories. Nevertheless, the selection of these materials must be tailored, as the generation of an excessive amount of liquid in the castables' microstructure will affect their refractoriness .…”

Effect of boric acid on properties of high‐alumina phosphate‐bonded plastic refractory materials

“…Nowadays, most studies on refractory materials are limited to investigating their performance improvement at high temperatures (1300–1600 °C) and (rarely) at medium temperatures (700–1100 °C). However, many boilers working at medium temperatures still use refractory materials originally designed, whose strength was relatively low at lower operating temperatures . Therefore, it is vital to design novel refractory materials and enhance the performance of such materials to match their operating temperatures.…”