Feeders, granular solids

When the solid is one of the reactants, such as in ore roasting, the flow must be continuous and precise in order to maintain constant conditions in the reactor. Feeding of free-flowing granular solids into a fluidized bed is not difficult. Standard commercially available sohds-weighiug and -conveying equipment can be used to control the rate and dehver the solids to the feeder. Screw conveyors, dip pipes, seal legs, and injectors are used to introduce the solids into the reactor... 

Sanitizers. Spa and hot-tub sanitation is dominated by chlorine- and bromine-based disinfectants. Public spas and tubs usually employ automatic feeders, eg, CI2 gas feeders, to maintain a disinfectant residual. Private or residential spas and tubs can use automatic chemical feeding or generating devices, or they can be sanitized manually with granular or liquid products. The most widely used products for private spa and tub sanitation are sodium dichloroisocyanurate and bromochlorodimethylhydantoin. Granular products are normally added before and after use, whereas solids, eg, stick-bromine, are placed in skimmers or feeders. Bromine generating systems can also be used and are based on oxidation of bromide ions (added to the water as sodium bromide) by peroxymonosulfate, chloroisocyanurates, hypochlorites, or ozone to generate the disinfectant HOBr. 

Sanitizer and Chemical Feeders. Feeders dispense the chemicals in gaseous, liquid, and solid (both granular and compacted) forms. Many health departments requite that pubUc pools have approved feeding devices for the daily application of all chemicals, including sanitizers. A slurry feeder for diatomaceous earth (DE) on diatomite filter installations may also be required. 

Rotary, star valve feeder Used especially as solids feeders for dilute phase pneumatic conveying to provide an air lock and to feed solids. Seal/wear depends on Ap and abrasiveness of powder. For pressure systems keep Ap < 80 kPa for vacuum systems Ap < 40 kPa. Provide an air vent to take the air loss away from the gravity flow of the solids and to control the filling of the star. For granular particles, prefer an offset-feed rotary valve for cohesive particles, more difficult to handle prefer a blow-through rotary valve. Cohesive particles will tend to seal a rotary valve and minimize air leakage. Not recommended for abrasive powders. 

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