This article was originally published in expanded form in the Proceedings Book of the 4th Industrial Furnaces & Refractory Symposium (EFRS) 2012 held in Izmir, Turkey. Presented by: B. Hiot (author, Technical support AMEA), S. Roodsari (GM Russia & Ukraine), M. Artukmaç (GM Türkiye) – Calderys

Monolithic refractories are successfully replacing bricks in various industries. This is due to the cost savings made possible, through shorter delivery time, higher performance, reduced installation time and higher energy saving. These savings allow steelmakers to remain competitive in a globalised market. For the particular case of Reheat Furnaces, Calderys has optimized monolithic concepts, enabling complete lining solutions. To lower costs for clients, Calderys has developed innovative concepts to revitalize four crucial elements of the Reheat Furnace:
    1. Castable refractory lining
    2. Precast roof
    3. Precast skids and posts
    4. Precast blocks

1) Quick Dry No Cement Castable (QD™)

Calderys has developed a patented range of castables, Quick Dry No Cement Castables (QD™), which can be dried 50% faster than standard castables in the market, giving shorter shut downs. This reduced drying time comes from a specific bonding system that is neither hydraulic (no cement) nor chemical (no organic additives). This gives the castable the ability to be quickly and safely dried, reducing the overall downtime of installations, i.e. optimizing the availability.

Example of QD™ compared to Low Cement Castable in reheating furnace after complete revamping:
The time saving is in the range of 50% which represents an important amount of energy and time.

Dry-out curves
Dry-out curves

Quick Dry No Cement Castable (QD™) vs. Low Cement Castable

One Spanish client operating a Walking Hearth Furnace began using bauxite-based CALDE™ CAST NB 82 QD™ for repairs and found that they save 2-3 days of production each time, avoiding long and costly stoppages. Andalusite-based CALDE™ CAST NA 55 QD™ is also gaining strong Reheat Furnace references worldwide, with particular appreciation for its thermal shock resistant qualities.

More information on Calderys QD™ refractory products

2) Precast Diamond Roof

Ramming plastics and cast in-situ solutions have been widely used to line reheat furnaces but recently, energy saving and productivity have become more and more critical. Therefore, Calderys has developed the Precast Diamond Roof that both decreases installation time and improves thermal efficiency of the furnace thanks to its specific shape.

Diamond Roof concept

There are 3 sources of energy consumption in a reheating furnace:

  • • Heat absorbed by slabs,
  • • Heat taken away by the exhaust system, and
  • • Heat conduction
By increasing the radiant surface by 9% compared to a flat roof (using the diamond concept), we have enabled a better repartition and homogenization of the heat, which results in a reduction in fuel consumption of up to 7%.

Diamond Roof: Single element and furnace thermal state

Calderys is able to propose a tailored solution with minimum shutdown time, optimum insulation and efficient performance for years. International presence and local production facilities allows us flexibility for answering the demands of our customers. Building on the success of the Diamond Roof, Calderys is now engaged in the extension of this concept to the walls.

More information on Calderys roof options for the Reheat Furnace

3) Precast skids and posts

Calderys proposes high quality precast solutions for skids and posts to decrease installation time.

Posts: The CALDE™ BLOCK POST system does not need any additional anchoring and fixing mortar. The self-keeping applied rings get held in position by a special designed upper-ending-ring which is cast in-situ. This system is adaptable to all pipe diameters. In our standard design, we consider an insulating layer made of ceramic fiber blanket but on request for higher insulating properties, we propose vacuum formed ceramic fiber. This system has high strength and is very stable over time.

Skids: The CALDE™ BLOCK SKID system is a very robust system suitable for slab or heavy products, even in pusher furnaces where the vibrations are important. The precast shape is welded onto the skids and ramming product is installed on the top.

CALDE™ BLOCK POST system (different designs available)
CALDE™ BLOCK SKID system (different designs available)

More information on Calderys skids & posts for the Reheat Furnace

4) Precast Blocks

In reheating pusher furnaces, high alumina electrofused blocks are currently used in the discharging area as rails or as full hearth. These blocks are expensive and the delivery time is quite long. For years, no castable was able to compete against electrofused blocks. A new generation of silica-free products has been developed by Calderys, offering a real alternative with performances very similar to electrofused blocks.

Calderys proposes their cost-effective alternative: a sandwich precast block with CALDE™ CAST LT 90 SP G8 on the hot face and CALDE™ CAST LX 68 on the back face.

Calderys Precast blocks

CALDE™ CAST LT 90 SP G8 is a low cement castable, based on tabular alumina and preformed spinel. This product exhibits outstanding hot mechanical/abrasion and corrosion resistance due to:

  • • High quality raw materials – Tabular alumina and preformed spinel
  • • Dense - low porosity - fine matrix
  • • Silica and iron oxide free, improving steadily the corrosion resistance
  • • Dense macrostructure due to particular grain size distribution
  • • Excellent dimensional stability at high temperature

CALDE™ CAST LX 68 is a low cement castable, corundum based. This product, used on the back face, has been chosen for its high strength and good dimensional stability.

For more details on Reheat Furnace solutions, please contact your experts at Calderys!

About Calderys

Our mission is to help you meet your ever increasing production and productivity targets, whilst protecting the safety of your people and the integrity of your equipment. Our focus is to deliver safe, reliable and high performing refractory solutions customized to your needs. Our international production and sales facilities allow us to develop and deliver customized solutions based on monolithic and ready shape monolithic refractory materials worldwide in a fast, efficient, and safe manner.

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Roof Precast Solutions

Case studies 01

Calderys has developped a complete range of precast materials for reheat furnace roofs to meet the need for significant operational savings on installation time and energy.

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Skids & Posts Precast Solutions

Case studies 01

The CALDE™ range of precast products for skids and posts for reheat furnaces can lead to significant operational savings on installation time and energy.

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Project Management Testimony

Case studies 01

Blending technical knowledge with practical experience, our dedicated project managers provide the organization and coordination needed to support installation and special projects worldwide.

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