Dryer Energy Reduction
Many chemical processing facilities use a filter belt to separate crystalline material from their mother liquor after a crystallizer. The filter belt offers a continuous separator with extensive opportunity to wash the product free of impurities. While many screening centrifuges have the ability to internally wash products, sometimes a more efficient wash is required and therefore filter belts are commonly used. However, the filter belts produce a damp cake that is typically fed to a rotary drum or fluid bed dryer. The dryer energy usage is directly proportional to moisture in the feed. As energy prices rise, process engineers are working with TEMA Systems to find more economical ways to dry their crystalline products.
TEMA Systems, Inc. has developed a process to reduce the required dryer energy usage by removing up to 50% of the remaining free moisture using a mechanical separator. In some cases dryer feeds can go from 90% solid by mass to 95% solids by mass by passing through a Conturbex Worm Screen Centrifuge. This proportionally reduces the dryer energy usage, but could also allow for additional capacity eliminating a bottleneck at the dryer. The Conturbex is a mechanical separator with a 100 um or larger screen. The only energy that is consumed to power the centrifuge is for a drive motor. A unit that would process 5000 lbs/hr of dry crystal runs with a 30 HP drive motor.
The process works by screw feeding the belt filter cake into the center of the continuously operating Conturbex centrifuge. The screw feeder has a hopper to collect the cake and meter the feed into the Conturbex. The Conturbex Worm Screen Centrifuge then spins the cake at up to 1200g. Driving the free moisture through the screen and continuously discharging solids to the dryer with lower moisture.
The financial payback for adding this additional processing step is often less than one year as the energy costs reduction is significant compared to the cost of the equipment. The Conturbex centrifuge also acts to increase the capacity of the dryer.