Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

Chapter 77.4.5 Plate bank product coolerDescriptionAfter drying and screening, most fertiliser products need additional cooling to avoid potentialcaking in storage. The primary types of coolers that are typically considered are as follows:• rotary drum• fluidised bed• plate bank (or bulk flow) heat exchanger.The rotary drum relies on ambient or chilled air as the cooling medium and is probably the mostcommon unit used in the industry. Although it is fairly expensive from both a capital andoperating perspective, it has proven to be reliable. Fluid bed coolers also use air as the coolingmedium and are commonly used overseas. They are smaller units than rotary drums and have alower capital cost. However, the operating cost is significantly increased due to the need formore airflow at a higher pressure drop.The plate bank exchanger is an additional option that has significant capital and operating costadvantages and has been successfully used in several recent applications. The concept of using aplate bank exchanger to cool a solid product is very simple. The unit consists of a vertical bankof hollow, stainless steel plates. The bulk solids pass through a feed hopper and pass slowlybetween the plates while cooling water is passed countercurrently through the hollow plates.Plate spacing is critical to achieve efficient cooling without causing bridging of the solidmaterial. The cooled material is discharged by a gate mechanism located on the bottom of thecooler. The cooler is designed to run full with the gate opening being controlled by the level inthe feed hopper. A small amount of dry air is used to purge the unit of moisture and preventcaking. Figure 7.3 gives an impression.Figure 7.3: Example for a plate bank cooler warm granules inlet, plate bank, cooling water manifold, cooled granules outlet[55, Piché and Eng, 2005]304 Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers