Feeder gravity

Also as a result of testing or from experience the surface configuration of rollers (e.g. smooth, corrugated, waffled, welded), the type of feeder (gravity or force, e.g. screw, feeder(s)), and the drives, i.e. the size (in kilowatts) and method (single or variable speed, electric or hydraulic, etc.), are chosen. 

There are two types of feeders gravity and force-type feeders. 

The specific equipment used for each step depends on the incinerator type and the physical and chemical characteristics of the wastes the incinerator is designed to bum. Wastes are fed into the incinerator in batches or in a continuous stream. Liquid wastes are often pumped and atomized into fine droplets that bum more easily. Solid wastes may be fed into the incinerator in bulk or in containers using a conveyer, a gravity system, or a ram feeder.8... 

It is the authors experience that with a formulation compressed without a forced feeder in R D, the scale-up in a different country, but by gravity feed and without a forced feeder, was perfect. In a second country, however, all production presses operated with forced feeders, and the target tablet hardness was not achieved. It was possible to conclude that press speed was not the cause of the problem but it was much later (and based on laboratory experiments) that it was possible to conclude that the lubricant was ovennixed on the tablet press, resulting in a softer tablet. Fortunately, the drug was very soluble and no dissolution problem resulted, but slower dissolution could be a problem with a drug of low solubility. 

A variety of feeding arrangements may be employed to ensure that particulate matter of appropriate bulk density is presented to the nip of the rolls. For smoothly flowing materials gravity feed may be used with a control device to adjust feed rate (Fig. 5.4). For fine powders which tend to bridge or stick and are of low bulk density, some form of forced feed (such as the tapered screw feeder shown in Fig. 5.5) must be used to de-aerate, pre-corn-... 

Solids conveying is carried out in two steps the feed hopper and the back (entrance) portion of the screw. The feed hopper is an inverted cone or pyramid, in which solid pellets or powder flow downward from the force of gravity. If they flow poorly ( arcing or bridging ), the problem may be solved by installing a vibrator or a stirrer ( crammer/feeder ) in the hopper, or by coating the particles with a small amount of a chemical that acts as an external lubricant. ... 

Hypochlorinators are most suited for smaller installations. For installations serving about ten people, it is possible to use drip-fed hypochlorinators. For up to 100 people, orifice-controlled feeders using a constant head tank mounted overhead and fed by gravity can be used successfully. The most satisfactory means of feeding hypochlorite solutions is through the use of low capacity proportioning pumps. 

Fresh catalyst is normally delivered in hopper-bottom railroad cars. The catalyst may be withdrawn by gravity flow from the bottom of the car through a hose to a Fuller-Kinyon screw pump and transferred to the hopper by means of an air stream loss of catalyst is prevented by a cyclone on the air discharge from the hopper. Alternatively, the catalyst may be unloaded from the top of the ear by a vacuum lift. In this case, the suction line passes through a separator with bag filters, located above the storage hoppers. The catalyst collects in a chute and flows down through a rotating barrel-valve feeder into a screw conveyor which transfers the catalyst to the hopper (105). 

Once the final blend has been transferred to the press hopper reliably, it is important to ensure that press hopper also provides reliable flow. Most modem presses consist of a small press hopper that is, in essence, a miniature IBC designed to provide a small amount of surge capacity. The press hopper often consists of a cylinder section and a hopper section similar to a larger IBC, but the hopper section may be asymmetric (Fig. 3) as opposed to the symmetric hopper designs commonly used for IBCs. The press hopper is typically flood-loaded from the IBC/chute above via gravity feed. However, in some instances, the material level in the press hopper may be controlled via a feeder at the IBC... 

Limestone is fed to the system through a variable-speed feeder (F-1) which is mounted on top of the tower slurry tank (TK-2). Slurry from this tank is pumped to the absorber section of the tower where it is contacted countercurrently with the flue gas. The reacted slurry then flows by gravity back to the primary tower slurry tank. An agitator mounted on top of the tank maintains a uniform slurry suspension. To prevent the buildup of reaction products, a small stream is bled from the tower slurry tank (TK-2) and sent to the FDS slurry tank (TK-1). 

---