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RPM Solutions, Inc. Rapid City, SD

Power Engineering June, 2004
New Atomizer Improves FGD Performance

(Reprinted with permission)

LG&E'S Southampton Power Station in Franklin, Virginia uses Flue Gas Desulfurization (FGD) system to control SO2 emissions. A major component of the FGD systems are the notary spray dryer systems, more commonly called atomizers. Atomizers, Figures 1a and b, rotate at 8,000 to 15,000 rpm and inject a lime/fly ash slurry into the combustion gas stream at rates from 50 to 200 gpm. The calcium in the slurry reacts with the sulfur in the combustion gases to form calcium sulfate. Unfortunately, the working environment for the atomizers is corrosive and erosive.

At the Southampton Power Station, the station experienced several recurring problems with the original atomizers. Even though the atomizers were made from stainless steel, they still suffered significant corrosion and premature failure and maintenance.

In the original atomizer design, special tools and/or procedures were needed to install and replace the components. Interference fits also required the installation of the upper and lower wear rings. As a result, the rings were difficult to install, and at times they became damaged during installation and/or removal.

Another problem with the old design was the close clearances between the nozzles and the upper and lower wear rings. In some instances the close clearances caused failure of the wear rings and nozzles during maintenance. The interference fits of the upper and lower wear rings also limited the materials that could be used. In addition, the atomizer was heavy, weighing approximately 130 pounds.

Resolving the Problem

After being awarded a contract to evaluate the problem, RPM Solutions, South Dakota, recommended a redesign of the atomizer. The only real constraint was that the outside geometry of the atomizer had to remain same. According to RPM Solutions, the old head has been chagned from a two-piece to a three-piece design which incorporporates a patented upper where ring.

Incorporated into the new design is the use of titanium alloys for the main structural components. This has resolved the corrosion problem and has also reduced the weight of the atomizer assembly by approximately 50%. As the atomizer only requires a spannerwrench and two Allen wrenches for complete disassembly and reassembly, maintenance is easier and less time consuming.

Because the upper and lowerwear rings are restrained in the new design, the rings could be made from advanced ceramics (silicon carbide). As a result, the wear life of the components is now substantially greater that the original style wear rings. Since incorporating the new design, no premature failures have occurred during installation or removal of the rings. In addition, there have been no nozzle failures during routine a operation. The new design also allows the nozzles to be removed and rotated which further helps to extend the atomizerss life.

Cost Savings

Even though the initial cost of the RPM titanium atomizer was higher than the original stainless steel atomizer, the increased life, lower maintenance costs and down time far out-weighs the higher intial cost. With the new design, the wear life of the upper wear ring, lower wear ring, lid, case, drive plate and nozzles is greater than the original atomizers.

According to Jeff Lanun production manager, LG&E Power Services,Inc., the new style titanium disc has shown exceptional wear characteristics since being put into service in 2002. There has also been a notable reduction in metal wear between the disc taper and output shaft taper, says Robert Reid, a maintenance mechanic at the station. To date, the only maintenance required has been routine cleaning of the nozzles.

Atomizer Design Improves Flue Gas Desulfurization Performance

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