Tom Messer is a 25-year veteran of the cement industry and he has seen the problems that buildups in preheaters can create in production schedules and maintenance plans, and he knows how much these problems can cost a company. So when he had the chance to install the equipment to prevent these choking problems right from plant start-up, he did.

When he came aboard as production manager for the Suwannee American Cement plant near Branford, Fla., Messer knew he wanted high temperature air cannons installed on the preheater inlet and feed shelf. Now co-owned by the Brazilian cement manufacturer Votorantim, the Suwannee plant is designed with an annual capacity of 850,000 tons of clinker. The original owner and now partner Anderson Columbia chose Krupp Polysius to engineer and supply equipment for the $150 million greenfield facility.

The new plant includes a four-stage Prepol MSC-CC precalciner with a 158-ft-long ∞ 13-ft-diam, two-station kiln for producing 2,500 tpd of Type I/II clinker. The finish mill is a Polysius-supplied 6,500-hp, two-compartment mill rated at 140 tph.

Although preheater air cannons were not included in the plant design by Krupp Polysius, Messer knew he would need them. “I've seen the problems that can arise from plugs and choking of the preheater,” Messer explained. “I've seen the high labor costs and the production losses that come from having to shut down the tower to break up a blockage.

“The first cement plant I worked had a full-time position for a preheater attendant, an employee who spent his day wearing a hot suit, cleaning the preheater with air lance. Another plant required cleaning the inlet and feed shelf with high-pressure water spray every eight-hour shift. Of course, that high-pressure spray did tremendous damage to the refractory. These chores were costly and resulted in missed production, manpower expense, and safety hazards. And the worst thing about these jobs is they really didn't solve the problem. The next day, you had to go out and do them all over again.”

Messer knew there was a better way: the installation of a battery of Big Blaster XHV-H Air Cannons from Martin Engineering on the preheater.

Improving material flow

The air cannons utilize the powerful discharge of a reservoir of compressed air to remove material from vessel walls, improve flow, and enhance plant efficiency. They are available in a variety of sizes and mounting arrangements to suit the requirements of each specific application.

For applications on Suwannee's cement kiln preheater, the air cannons were equipped with Martin Engineering's XHV-H valve. Designed for the severe operating conditions of kiln preheaters and other high-temperature applications, the XHV valve features elastomer-free construction and a short piston stroke to shorten the time the valve is open to allow material to blow back into the valve. According to the manufacturer, the valve is guaranteed for 200,000 firings.

Messer and Martin Engineering developed a plan for the installation of 45 air cannons on the brand new preheater. Crews from Martin Engineering's Martin Services group installed the preheater air cannons. In addition, the plant has 11 air cannons installed on the clinker cooler. These are specified in the cooler design by Krupp Polysius. The plant also had air cannons installed on the raw material silos to promote an efficient flow of material as required.

Since the plant started up early in February 2003, the air cannon firing cycle has been adjusted to accommodate changes in operations and materials. Plant officials hope to lock down the schedule within the next few months. After 60 days of operation at the new plant, there have been no problems in keeping the preheater inlet and feed shelf clear. “We haven't had to put an air lance inside the vessel yet,” Messer reported. “The plant has been down a couple of times for other maintenance or start-up issues, and so we've have done visual inspections inside the preheater. We didn't see any buildups whatsoever.”

That was Messer's mission when he ordered the air cannons. “Our goal going in was to provide a system so we would never need to shut the plant down to clean the preheater ducts,” he said. “With the air cannons installed, we're hoping that we'll never need to clean the inlet or the feed shelf with anything other than the air cannons.”