Hoppers discharge aids

A range of devices designed to facilitate flow of powders from silos and hoppers are commercially available. These are known as discharge aids or silo activators. These should not, however, be employed as an alternative to good hopper design. 

Discharge aids may be used where proper design recommends an unacceptably large hopper outlet incompatible with the device immediately downstream. In this case the hopper should be designed to deliver uninterrupted mass flow to the inlet of the discharge aid, i.e. the slope of the hopper wall and inlet dimensions of the discharge aid are those calculated according to the procedure outlined in this chapter. 

Vertical filters are not convenient for the removal of dry cake, although they can be used in this service if they have a bottom that can be retracted to permit the cake to fall into a bin or hopper below. They are adapted rather to wet-solids discharge, a process that may be assisted by leaf vibration, air or steam sparging of a filter full of water, sluicing from fixed, oscillating, or traveling nozzles, and blowback. They are made by many companies, and they enjoy their widest use for filter-aid precoat filtration. 

Live bottom hoppers. These devices replace the lower section of the silo discharge cone. Typically, they are approximately one-third of the silo diameter. They consist of an upper section bolted to the cone and a lower section secured to the upper by connecting links and flex collars. The lower section vibrates to break up bridging and aid product discharge. 

When referring to optional materials, this generally refers to the material of construction of the discharge cone and the receiving hopper. These are available in a number of materials from food quality stainless steel to mild steel. When selecting for a food application, it is also important to ensure that the rubber seal materials are also compliant with regulations. Apart from the mechanical flow aids, some sysfems are also available with pneumatic... 

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