Centrifugal Sifter Used in Wet Application Improves Safety, Saves Money and Helps Boost Capacity
In addition to making every effort to produce high quality polymer for toner powder, Sybron Chemicals Inc. continues to improve its processing operations. Two bright, young engineers at the Birmingham, NJ, plant took on a processing system that had inherent safety risks, productivity problems, and the appearance of being too costly to improve. The engineers solved these problems through processing design and effective equipment selection.
PROBLEMS BY THE DOZEN
In the old processing lines, after the polymer spheres formed in a reactor, they required washing to remove a suspension. The slurry of polymer beads and wash water flowed into a dewatering tank from which employees had to shovel the wet polymer into a hopper. It emptied onto a conveyor that took the polymer to a heated dryer. Also, a parallel processing line required hoisting and moving an overhead hopper of polymer along a track mounted on a ceiling, centering it over an open hopper and hoping the polymer would fall where it should. Sometimes, spillage was inevitable. Clearly, this posed unnecessary safety risks, a potentially messy processing area and substantial yield loss.
Also, it was difficult to ensure even heating and drying of the polymer as the shoveling created an uneven inflow to the dryer. In addition, the shoveling limited the drying operation to 50% of capacity, restricting productivity.
Excessively wet or over-dry polymer particles presented a risk to product quality. To meet quality standards, the polymer moisture content must be within 0.3% limits, explained the Sybron engineers. To achieve such tight specifications, the company uses a resistance temperature sensor, an electronic controller, and a screw feeder to adjust the rate at which the moist polymer is conveyed into the dryer.
A FEW GREAT CHANGES
When Sybron Chemicals Production Supervisor John Lazevnick and Process Engineer Robert Blantz joined the company and saw this situation, they realized it was an opportunity to make many improvements.
They installed a Kason CENTRI-SIFTER™ Centrifugal Sifter in the summer of '92 to dewater the polymer beads from about 65% water slurry to about 10% surface moisture content. A centrifuge had been purchased by a previous engineer but it was too small for the processing line. A larger one would have cost Sybron Chemicals more than $100,000. Rather than propose such an expensive device, Lazevnick and Blantz sent some polymer samples to Kason's facility for testing. Circular screen separators which are often used for dewatering didn't provide enough force to remove the free water so a CENTRI-SIFTER Centrifugal Sifter was tried. It proved successful so Sybron rented a unit for testing in their line. After experiencing problems with various standard screens, it was determined that modifications were needed.
Using Sybron's design, Kason built a special basket that " extends the support struts farther out from the center, and a diagonal molded plastic strip joins the fabric ends of the nylon screen. The extensions that position the support struts farther out from the center prevent the screen from contacting the struts as the screen bulges repeatedly from the load being pushed by the rotating paddies. The special diagonal molded plastic strip prevents screen failure by allowing some screen flexing due to the incoming slurry. The CENTRI-SIFTER unit presently operates at only a fraction of its capacity because the dryer now limits throughput. Sybron engineers feel that the centrifugal sifter performs better than the centrifuge since the sifter can handle the surges of slurry that the centrifuge couldn't.
By installing this centrifugal sifter, the process was converted from a batch process to a closed loop, continuous process. The potential for contamination is far less had been, improving product quality. Also, yields have been increased since spillage has been eliminated.
Also, manpower requirements decreased by about 25%, permitting plant personnel to accomplish more tasks on other processing lines. The overhead hopper no longer showers the workers and floor with moist polymer or presents a safety hazard. The fluctuation of the moisture content is very rare and thus productivity is higher.
In addition, the second toner polymer dryer became available for other operations as a result of the new processing line configuration. Finally, more than $87,000 was saved by selecting a sifter over a centrifuge.
The CENTRI-SIFTER unit has worked well and Sybron Chemicals has also installed a Kason VIBROSCREEN Circular Screen Separator for classifying dry polymer spheres by diameter. Two screens direct spheres with oversize and undersize diameters away from those that meet diameter size specifications for a specific application. Also, a second CENTRI-SIFTER unit is being tested in a development process.
Clearly, Sybron Chemical's engineers made a good decision and significantly improved quality, safety and productivity. "We are committed to helping our customers succeed, and as a result we are succeeding," says Birmingham Plant Manager Jerry Metzner. Sybron Chemicals also makes top quality resins for ion exchange, and selectively adapted bacteria strains to eliminate undesirable substances in industrial and municipal wastewater.
Screen Tips - Volume 8, Number 3 1993
CENTRI-SIFTER Centrifugal Sifter at Sybon Chemicals Inc. save about $87,000 helps boost capacity and improves safety.