A customer approached Caloris because they were having spray dryer yield issues, evidenced by heavy loading of their scrubber. The system was being fed at 1300 lbs/hr of feed at 45% total solids, indicating that there should be 615 lbs/hr of powder being produced. We found that they were packaging at only about 450 lbs/hour — a yield of only 73%. Instruments were verified, but it was quickly evident that the powder was escaping the cyclones and going to the wet scrubber and therefore onward to wastewater.
The customer had slowed the dryer production rate down recently to accommodate a new product, which meant they had slowed the dryer airflow down. The client was not only losing product, but the situation was compounded by the lost production, creating high wastewater processing loads.
After a site visit to inspect the spray dryer and measure the performance of the cyclones, our engineer verified the operating conditions and the performance of the cyclones.
Cyclones are designed to operate with a certain airflow and, therefore, differential pressure, resulting in the high efficiency needed to capture 99% of the spray dried material. This efficiency drops off exponentially when the airflow is reduced.
At this plant, an experiment was carried out to achieve an airflow closer to the original design, in the hopes of correcting the spray dryer yield issues. The experiment proved that capture rate in the cyclones, and therefore yield, increased with the increase in airflow.
Over a period of continuing support, our engineer worked with the client to optimize the operating parameters for the new product so that yield was at target. Loading of the wet scrubber and also wastewater loading is now minimized as well.