The CALDE® FD (Fast Dry) range, developed by Calderys, addresses these challenges by enabling faster, safer, and more energy-efficient dry-out without compromising refractory performance.
Understanding the dry-out challenge in industry furnaces
Cement-bonded castables require a dry-out period postinstallation to remove free water safely from the refractory lining. These castables are structurally sensitive to rapid temperature changes, so dry-out must be very well controlled within a window of four to seven days after installation. This process, if prolonged, results in significant furnace downtime during which the equipment is unavailable for production. Such downtime reduces plant availability and halts production. It also leads to increased energy consumption and higher emissions for the production plant, as auxiliary heating or backup power sources are often required.
The dry-out process is inherently sensitive because rapid moisture removal can cause steam explosions and spalling, potentially causing safety hazards to personnel as well as damage to the refractory lining and equipment. Therefore, balancing dry-out speed with safety and material integrity is a complex challenge for refractory suppliers.
Developing a fast-drying technology
Over the last decade, and despite many new chemical developments, monolithic castables are still composed of a hydraulic bond. This is the case for both chemical binders and non-cement castable binders. Among monolithic castables, the deflocculated dense castables of the low cement castable (LCC) category are of common use.
The dry-out of this kind of castables has always been a challenge. It is particularly the case during the (critical) first heat-up. At the same time, market demand for this product increases steadily, and so does the need for simpler methods and quicker dry-out procedures.
The Calderys Group worked on developing a refractory product that could speed up the dry-out process when relining industrial furnaces. The procedure was a laboratory test setup designed to study and improve the drying process of the cement-bonded castable material for this study. The goal of the laboratory test was to make the drying safer (by preventing damage caused by steam) and to make it faster by removing water more efficiently. The study looks at how different ingredients in the material affected drying, using experiments with two types of monolithic formulations—some with added silica fume and some without.
The result was CALDE® FD. A range of cement-bonded monolithic refractories engineered specifically to accelerate the dry-out process while maintaining the mechanical and thermal performance of traditional castables.
The technology allows for the entire furnace lining to be designed and installed with fast-dry materials, overcoming previous limitations where fast dry products were restricted to localized repairs or specific furnace zones.
Key technical attributes of this innovation include:
- Efficient water removal: CALDE® FD materials are formulated to remove free water rapidly and uniformly, mitigating the risk of steam explosions during dry-out.
- Robustness and stability: the product maintains the standard setting time of conventional castables, allowing quick removal of formwork and continuation to dry-out without delay.
- No additional components: the installation requires no extra equipment, tools, or secondary components, simplifying logistics and reducing site complexity.
- Full furnace application: lining the entire furnace with fast-dry materials, eliminates bottlenecks caused by slower-drying zones.
Overall, the installation of CALDE® FD refractories aligns closely with standard cement-bonded castable procedures, requiring no special tools or equipment. The material’s standard setting time allows for rapid formwork removal, enabling the dry-out phase to begin sooner than with traditional castables.
Calderys reports that using CALDE® FD can reduce dry-out duration by up to 72 hours to reach a temperature of 1,200 °C, a significant operational advantage that translates directly into increased furnace availability.
The production plant’s operations teams benefit from streamlined dry-out processes, reduced downtime, and improved safety which enables better production planning and resource allocation. The seamless integration into existing processes minimizes disruptions and enhances overall efficiency.
The role of CALDE® FD in the utilities sector
While this technology can be used in various industries, it is particularly relevant for boilers and incinerators operators, where continuous operation is critical for power and water supply. The CALDE® FD approach reduces fuel consumption and associated CO2 emissions, supporting sustainability goals. Utility plants, such as those generating power, or waste-to-energy operations, can benefit significantly from this reduction in carbon footprint. The FD technology is integrated seamlessly among the other refractory ranges that serve the above industries.
ALKON® FD: a refractory product range tailored to aluminum producers
Primary and secondary Aluminum producers are always looking to reduce their downtime as much as possible, to improve operational efficiency. The Calderys Group, which has been providing a range of solutions designed specifically for contact with aluminum for decades, has therefore adapted its refractory product range to meet Aluminum producers’ challenges.
This refractory range, ALKON®, is recognized worldwide as the benchmark for refractories in the aluminum industry. The FD technology is fully integrated into this range, enabling full furnace lining with fast-dry materials and thus optimizing the entire dry-out phase of aluminum furnaces.
Copyright Calderys: dry-out duration phase when using CALDE® FD technology (Source: Calderys)
Copyright Calderys: dry-out duration phase when using CALDE® FD technology (Source: Calderys)
Case Study: ALKON® FD used at key aluminum producer in the UAE
This Aluminum producer’s goal was to reduce both the refractory installation and the dry-out time, to optimize the operational workflow. The need for a faster and more efficient lining solution that maintains quality, and safety quickly led to choosing ALKON® FD. Traditionally, relining aluminum casthouse furnaces involves in-situ casting complemented by gunning as a secondary installation technique. This approach is time-consuming, requiring approximately seven days for the dry-out phase alone. Consequently, the furnace remains out of operation for an extended duration. Overall, completing such a project (from the wrecking of the old refractory lining and installation of the new one to the dry-out phase) typically spanned around 23 days.
The proposed combination of materials to address was the following:
- Precast, pre-fired (PCPF) blocks
- ALKON® FD
- Spraycasting products.
The updated method streamlined installation and significantly decreased the dry-out period. This resulted in both time savings and tangible commercial advantages for this Aluminum producer.
Overall, the integration of PCPF blocks, spraycasting, and ALKON® FD products shortened the total project duration by five days, significantly enhancing the furnace’s operational availability. This reduction in relining time—amounting to a 25 % decrease—allowed the customer to resume production more quickly, minimizing downtime and improving productivity.
The Aluminum Casthouse furnace relined with Calderys refractory materials. (Source: Calderys)
The Aluminum Casthouse furnace relined with Calderys refractory materials. (Source: Calderys)
Planning for the future
Many small steps are necessary for a production facility to improve its energy efficiency. One such step lies in the choice of refractory materials and the associated installation method. Adopting fast dry technologies enhances plant availability and aligns with energy transition objectives. Plant operators are reducing their reliance on external solutions (such as external burners) and ensuring more sustainable and economically sound operations. The development and expansion of the CALDE® FD range marks a significant advancement in refractory technology, addressing a longstanding operational bottleneck in industrial furnace management. By enabling faster, safer, and more energyefficient dry-out, the technology supports the operational and sustainability goals of processing industries worldwide. The Group’s approach—offering a full-furnace, fast-dry solution without requiring additional components or process changes—sets a new standard for refractory linings. As industries continue to prioritize uptime, safety, and environmental performance, fast-dry refractory solutions like CALDE® FD will play an increasingly critical role.
