Background of the Invention Rotating calcining kilns are utilized for calcining various materials including so-called green coke. Particulate green coke is fed into one end of an inclined rotating generally cylindrical kiln, and burners near the discharge end of the kiln provide heat for transforming green coke into calcined coke as the coke moves through the calciner. In order to obtain uniformity in calcining, it is conventional to provide lifters (mixers) in at least part of the calciner interior. The calciner interior typically is lined with refractory material to protect the calciner shell from the high calcining temperature. Mixers comprised of reinforced refractory material are typically located in a pattern on the calciner interior. These mixers project into the kiln interior beyond the surface of the refractory lining and assist in the mixing and tumbling of the particulate material being calcined, resulting in a more uniformly calcined material than would be obtained in the absence of the mixers.

Mixers formed of refractory material are satisfactory up to a point, but over a period of several months to one or two years these mixers degrade by spalling and crumbling, resulting in reduced calcining efficiency between shutdowns for repair. In the past, when calciners have been shut down for scheduled maintenance, repair of refractory mixers has been required.

Background Art In addition to the refractory mixers discussed above, a cast metal lifter is available from Fuller

Mineral Processing, Inc. of Bethlehem, PA. This lifter includes a rather complex anchoring system including multiple support posts extending through the kiln shell.

Summary of the Invention According to the present invention, a fabricated steel lifter is provided for replacement of the conventional refractory mixer. The steel lifter is adapted for attachment to the kiln shell, and is configured to effectively mix the kiln contents and to have a longer life than refractory mixers.

Accordingly, it is an object of the invention to overcome the deficiencies of refractory mixers in rotary calcining kilns. It is a further object to provide a mixer that can be easily fabricated and installed, and that will be much more durable than existing mixers.

The Drainas Figure 1 is a cut away view of a calciner showing a pattern of mixers on the interior of the calciner.

Figure 2 is a rear elevation, partially cut away, showing a fabricated lifter in accordance with the invention.

Figure 3 is a side elevation, partially cut away, showing a fabricated lifter in accordance with the invention.

Figure 4 is a perspective view showing a fabricated lifter in accordance with the invention.

Description of the Preferred Embodiment As seen in Figures 2,3, and 4, a fabricated lifter shown generally at 10 includes a base plate 12 attached by welds 14 to kiln shell 16. Base plate 12 includes a vent hole (not shown) for preventing gas pressure build up under base plate 12. An anchor post 20 is affixed to base plate 12 by welds 22, and extends into

the kiln interior, preferably just past the thickness of the refractory lining of the kiln shell.

A sole plate 24 is attached to anchor post 20 by welds 26, and includes a shorter section 28 and a longer section 30.

A face plate 32 is attached to the short section of the sole plate 28 by welds 34, and extends at an incline back over anchor post 20.

A pair of gussets 34 and 36 in the shape of triangular plates are affixed to sole plate 24 and face plate 32 to provide rigidity and support to the lifter, particularly to the face plate 32.

As seen best in Figure 2, gussets 34 and 36 are positioned outside the diameter of anchor post 20 and in combination with face plate 32 provide protection from radiant heat for the connection of the anchor post to the sole plate.

As seen in Figure 4, the sole plate 24 overlies refractory material 40 lining the interior of the kiln.

It will be apparent that variations from the structure shown in Figures 2 and 3 could be utilized.

For example, the acute angle between the face plate and sole plate could be more or less than as shown, and the shape of the various segments of the lifter could be changed. For example, the face plate could have a plow shape to enhance mixing of the kiln contents.

The lifter of this invention is fabricated from a weldable alloy suitable for high temperature service.

A preferred alloy composition for the lifter is a nickel-based alloy comprising about 45 percent nickel, 25 percent chromium, 18 percent iron, 1.25 percent silicon and 3 percent each of molybdenum, columbium and tungsten.

Operation In utilizing the lifter of the invention, a group of lifters are positioned in a pattern on the interior of a kiln 18 as shown in Figure 1. The face plates 32 of lifters 10 are inclined back from the

direction of kiln rotation so that the front surfaces 38 of face plates 32 contact particulate material being calcined.

A lifter in accordance with the invention is fabricated of a weldable alloy adapted to withstand the severe operating conditions. In a commercial kiln, the base plate 12 might be an eight inch diameter circle of one inch thickness, the anchor post 20 a 2.5 inch diameter rod, the face plate 32 about one square foot of one inch plate, the gussets 34 and 36 might be equilateral triangles of one inch plate, and the sole plate 24 a one inch plate about 20 by 12 inches. The bottom of sole plate 24 overlies the top of refractory lining (not shown) between the kiln shell and the bottom of sole plate 24.

Example 1 In this example, lifters substantially as described above and shown in Figures 2 and 3 were installed in a commercial coke calcining kiln. After three months of continuous operation, the kiln interior was inspected, and the lifters showed no significant degradation. Conventional cast refractory lifters in similar circumstances typically exhibit significant degradation.