The sprawling Koppers complex covers about four city blocks. Several miles of air lines run from the compressor station to various points throughout the operation. Some of the air lines are located as high as 120 feet above ground level. Situated on the Lake Erie shoreline, the Koppers operating and processing equipment is subjected to freezing temperatures, gusty winds and high humidity.

When temperatures dropped below 32ºF, freeze-ups would occur in the distribution lines. Ice would plug the lines and stop the flow of air. This would shut down operation of the air cylinders that actuate vibrators used to keep the coal running freely into chutes over the coke ovens. Frozen lines choked off air to cylinders on the slide gates that regulate material flow. Accurate control of material flow is required to achieve the specified blend of different types of coal. Both product quality and operating efficiency are dependent on the proper functioning of the slide gates. Other pneumatic equipment affected by freeze-ups were vibrators on hoppers and conveyors, as well as oscillators on the rescreen station and the carry car on the feed side of the coke ovens.

When freeze-ups occurred, tasks that normally were automatic had to be performed manually. The result was added man hours for production and increased maintenance time for thawing the blocked lines with blow torches or steam lances.

It was evident to plant management that water in the air supply combined with cold temperature was causing the freeze-ups. A project team quickly determined that drying equipment was needed, but the difficult part was specifying the equipment that would meet the tough requirements. Not only did the dryer have to remove moisture in subfreezing temperatures, it also had to be rugged enough to withstand the dirty, corrosive environment.

Air power at Koppers is supplied by four compressors, one of which is maintained for standby. Two Van Air Freedom Dryers were installed at the Koppers plant. One of the compressed air drying systems that serves the big vibrators and air trestle includes a model D36 Freedom Dryer and a model CA-10 Climate-Cool after-cooler, mounted on the roof over the compressor station. A second system that provides air for coal and coke handling was added later as air usage increased. A Van Air Freedom Dryer model D30 and a model AC-130 air-cooled after-cooler were installed in an unheated room underneath the compressor station. Both Van Air cooling and drying systems automatically compensate for changes in ambient temperature. The air-cooled after-coolers reduce the temperature of the air from the compressors to within 10ºF of the atmospheric air temperature, and the dryer delivers an outlet pressure dew point that is 20ºF lower than the inlet temperature to the dryer. Therefore, no moisture will condense because the dew point temperature of the compressed air is always lower than the ambient temperature.

Since the Van Air drying systems have been installed, no freeze-ups have occurred in compressed air lines or pneumatic equipment.  Savings have been realized in many areas. Manual cleaning of the coal chutes is no longer necessary to dislodge caked materials, and material flow is maintained according to the specified proportions. Maintenance time required to thaw out frozen lines has been eliminated.  The plant’s maintenance superintendent says that “when the second air system was being planned, we didn’t even attempt to run without drying the air. We knew that it was really needed to keep our operation on schedule.”