Storage of Suspensions
Broder, Michael F.
This material provides recommendations for storing and sparging suspensions in industrial settings. It emphasizes using vertical tanks of mild steel or plastic equipped with air-sparging capabilities. Tank size, typically around 16,000 gallons with a diameter of 12 feet and a height of 20 feet, is deemed satisfactory. Coating the inside of steel tanks with epoxy-based paint can extend their lifespan. The document discusses the advantages of cone-bottom tanks over flat-bottom tanks in resuspending settled materials. It suggests using a foundation made of well-compacted 1/4-inch crushed rock, gravel, or concrete. Proper drainage is essential to prevent the tank bottom from standing in water. For transferring suspensions into and out of storage, a centrifugal pump with a 5-inch inlet, 4-inch outlet, and a 30-hp motor is recommended. Depending on the circumstances, a more powerful motor may be necessary. The transfer lines should be 4-inch black iron or PVC schedule 80 plastic pipes, adequately supported and equipped with expansion joints. The document provides illustrations for recommended designs of air spargers for both flat-bottom and cone-bottom tanks. Sparging, the process of discharging air into the suspension, is crucial to control gel strength, syneresis, and crystal growth. The material suggests sparging each tank once or twice weekly to manage gel strength and syneresis. To prevent excessive crystal growth, especially near the tank walls, frequent sparging is advised during temperature decrease. Daily sparging is recommended in colder seasons until the suspension reaches a similar temperature as the outside air. Once the daily average air temperature stabilizes or rises, the routine sparging schedule can be resumed. Immediate sparging before the withdrawal of suspension from the tank enhances fluidity and corrects any syneresis that may have occurred. The suspension may freeze to a solid mass in regions with temperatures that are frequently below freezing. However, when the outside temperature remains above 40°F for about a week, the suspension becomes fluid and can be sparged. Heating coils can warm frozen breaks, requiring approximately 40 gallons of fuel oil to fluidize 100 tons of material within the tank. These recommendations aim to ensure optimal storage conditions and control the quality of suspensions used in industrial processes.