A Fast, Friendly Furnace Fix

October 1, 2001
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A new furnace lining has been designed to save energy while increasing installation speed and lining performance for a range of high-temperature applications.

An installer applies the new insulation system as a veneer over an existing hard refractory material.
In this era of high energy costs and competitive production schedules, companies operating older kilns are looking for fast, inexpensive ways to make their kilns more energy efficient. The conventional solutions are to build a new kiln or undergo weeks of downtime to update the old kiln. Today, however, companies have new options, especially where furnace insulation is concerned.

A new monolithic ceramic or soluble fiber insulation system* was recently developed for repairing/upgrading existing furnace linings or installing new full-thickness linings in a fraction of the time required for conventional blanket or module linings. The system offers energy savings, installation speed, and lining performance for upgrades of existing fiber linings, linings over hard refractory, and furnace lining patches or refits.

Energy Savings

The primary benefit of the new system is that the end user realizes energy savings immediately after the product is installed and the furnace is put back into service. When installed as a lining upgrade or lining over existing refractory, the system has demonstrated a substantial improvement in thermal performance, saving thousands of dollars in energy costs. The typical payback period in terms of energy savings for an installation with this technology is less than six months. Applying several inches of the new system over a partially deteriorated furnace lining can extend the furnace lining life and improve furnace efficiency. The new system can also be used as a hot face veneer or full-thickness lining in kilns and furnaces operating at temperatures up to 2450?F.

When the new system is installed as a full thickness lining, a trowel is used to smooth the hotface surface.

Installation Speed

The new insulation system is designed to be installed quickly and easily by trained contractors using patented installation machinery. It is composed of specially conditioned bulk ceramic or soluble fibers with an inorganic binder and an organic foaming binder. The fibers and binders are combined within a patented mixing chamber to create a homogeneous foam/fiber mixture. The installation machinery propels this mixture through a feed hose and nozzle, and the material is then gunned onto the target surface.

The new system can be installed at rates in excess of 1000 board feet per hour, which, depending on the application, can be two to six times faster than traditional installation techniques. When compared to repairing existing furnace linings that would otherwise require complete removal prior to a traditional installation, the time savings is even greater.

Additionally, unlike traditional construction techniques that could often require five or more installers, only a three-person installation crew is required with this new technology, thereby reducing labor requirements.

Lining Performance

The interlocking network of fibers in the new system is designed to provide a strong, uniform monolithic structure with excellent thermal insulating properties, low heat loss, low heat storage, and excellent resistance to chemicals and thermal shock. Perhaps even more importantly, the system is specially designed to control airborne fiber levels. Unlike “sprayable fiber” technologies, which feed dry fiber and binder in separate streams that are partially combined once the product leaves the installation nozzle, the fiber in the new system is completely coated within the foaming binder solution while in the mixing chamber, significantly reducing the potential for airborne fiber release into the surrounding environment.

Measurable airborne fiber levels with the new system depend on a number of factors, including weather conditions, the size of the job, the type of fiber applied, and the condition of any existing furnace linings. However, average real-time exposures to airborne fiber levels with this technology are similar to or less than those experienced during conventional blanket or module installations. Also, because the new system is installed much faster than conventional methods, the duration of exposure is significantly decreased.

In addition to the patented mixing chamber and proprietary binder system, a dust collection hood is located on top of the fiber feed hopper to further control the release of airborne fiber. A vacuum is drawn on the fiber hopper hood, which keeps the bulk fiber chamber under negative pressure during operation. Additionally, limit switches installed on the binder mixing chamber prevent discharge of fiber prior to complete mixing with the foam binder.

From faster, safer installation to proven energy performance, this new technology provides a new option for companies looking to increase their furnace efficiency.

For More Information

For more information about this new furnace lining system, contact Unifrax Corp., 2351 Whirlpool St., Niagara Falls, NY 14305-2413; (716) 278-3800; fax (716) 278-3900; e-mail info@unifrax.com; or visit www.unifrax.com.

*Foamfrax™ Insulation, supplied by Unifrax Corp., Niagara Falls, N.Y.



SIDEBAR: Case Study: New Lining Repairs Refractory Erosion

The sidewall lining on the throat section of a rotary calciner operating in 1500¿F (815¿C) conditions had begun to exhibit erosion in areas tangent to the end wall burners. Due to flame impingement, the existing ceramic fiber modules had become grooved 3 to 4-in. deep at these locations.

The available repair options were a full lining replacement or pinning layers of blanket over the existing module lining. Given both the material and labor costs associated with these options, a 3-in. veneer of the new monolithic ceramic fiber insulation system was chosen for this unit.

The new lining installation was completed in four hours, and the unit was put into service immediately after installation, resulting in reduced furnace downtime and increased productivity. The additional lining thickness of the new system served to lower heat loss and heat storage values. Additionally, the upgrade extended the service life for the calciner and avoided a complete lining replacement.

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