Lime Kilns Cut Gas Costs by $200,000 per Year with Marinite Insulation
Products: Marinite I; Marinite P
Industry: Pulp & Paper
Application: Rotary Kiln Insulation
The insulation requirements were stringent.
TRP&P’s corporate process engineer was “looking for several qualities in the insulation. The ideal material would possess a thermal conductivity low enough to justify the cost of the insulation: crushing strength, or modulus of rupture, at least 1200 psi in the hotter zones, and at least 800 psi in the colder ones; and the ability to withstand temperatures of at least 800°F at the brick/insulation interface in the burn zones, and l000°F in
the cooler areas.”
“In addition, the insulation had to be economical and light in weight so the kiln would not exceed its load limit and tax the kiln supports and drive system.” (The light weight would also facilitate handling, resulting in easier installation.)
A thorough evaluation of insulation alternatives.
In its search for an insulation that would meet these multiple requirements, over one-half dozen materials were evaluated.
Several fiber-based boards were considered, but none had the crush-resistance of Marinite I and P insulation. A foreign-made insulation was also investigated, but not used because it required a thickness more than two times that of Marinite to provide the same insulating capability. That extra thickness would reduce the kiln volume and throughput, and result in higher weight, which would
push a kiln over its load-carrying limit .
Marinite installation was customized for each kiln zone.
TRP&P’s two kilns measure 9′ ID x 250′ long, and
10 1/2′ ID x 270′ long. In each kiln, temperatures range from 2500°F in the burn zone to 300°F at the charge end. The kilns operate continuously for several months at a time. The Marinite was installed between the refractory brick and shell when worn bricks were being replaced during regularly-scheduled maintenance shutdowns. Factory pre-cut into 4″ x 4′ strips from 4′ x 8′ panels,
Marinite was laid in place without any adhesive. After a 4′ section was placed, liner brick was installed over it in normal fashion.
Marinite I and P were used in 170 lineal feet of each kiln. At the charge end. where temperatures can be as low as 300°F each kiln contains a 95′ to 100′ long section of 1′ thick Marinite I placed behind 70% alumina refractory brick.
Following the Marinite I installation is a section containing approximately 35′ of 1′ thick Marinite P, where brick hot face temperatures range from 1300°F to 1800° F.
The next segment, just before the burn zone, where temperatures rise to 2000°F is a short section (18′ and 13′ kilns 1 and 2, respectively) of 1/2″ thick Marinite P, all behind the alumina brick.
In the burn zone. where temperatures peak at 2500°F basic brick is used with no insulation because the interface temperatures would be too high for the Marinite.
From the end of the burn zone to the discharge outlet ( 18′ and 27′ in the two kilns , respectively), l/2″ Marinite P backs up the alumina brick.
Narrower thicknesses of Marinite are used in the hotter kiln zones to avoid brick and insulation interface temperatures above 1800°F.
The energy savings from Marinite insulation become even more significant as the brick wears down. In the burn zone, the difference between new 6″ brick with no insulation and new 6″ brick backed by 1/2″ Marinite P is approximately 1200 Btu/ft2/hr in savings.
This contrasts sharply with the difference between worn 3″ brick with no insulation and worn 3″ brick backed by 1/2″ Marinite P, which showed a savings of 2800 Btu/ft2/hr.
The heat loss reduction achieved by Marinite behind worn brick is almost 2 1/2 times greater than with the new.
5-month paybacks, and more.
Since installation. Marinite I and P have provided a heat-loss reduction totaling more than 6.3 million Btu/hr, with combined savings of more than $200.000 per year in natural gas costs, 5-month paybacks and returns on investment of 228% and 255%.
Because of their high thermal insulating values and good mechanical strength. Marinite I and P insulating boards have met the requirements of Tennessee River Pulp & Paper. and continue to function well in both kilns.
1. The cold rolled steel kiln shell was prepared prior to application of the insulation. First. it was cleaned of all dirt and debris. Then, where the shell was out of round or partially oxidized, depressions were filled in with mortar.
2. Next. factory pre-cut 4 ‘ x 4’ strips of Marinite structural insulating board were laid in place dry, without adhesive, on the cleaned surface . Although the Marinite was pre-cut for on-the-job efficiency, it was also easily cut on site, as needed.
Beginning at the very bottom o f the shell – at 6 o’clock – the boards were laid up both sides to 3 and 9 o’clock. Where welds or bolts were in the way, the Marinite was grooved with a bricklayer’s scotch to fit over the irregular surface.
4. With the bottom half of the shell completed , a jig was moved into position, and one row of kiln liner brick was put loosely into place. Then Marinite boards were slid between brick and shell surface.
5. Finally, the jig was tightened, and key brick and board were inserted, assuring a tight seal. Additional rows of brick were added to complete one 4′ long section.
6. With one 4′ long section completed, the whole process was repeated in the next 4′ section, and then the next, until the entire shell was insulated.
Limitation of Liability
THAN THE LIMITED LIABILITY SET FORTH ABOVE.
6901 South Pierce Street
Littleton. CO 80123
Phone: (303) 978-1199
Marinite Plant Location
Iron Hourse Park
North Billerica, MA 01862
Other Plant Locations:
P.O. Box 190
Zelienople, PA 16063