Feeder valve

Even though 15 psi is possible from a blower, most positive-pressure systems are limited to 10-12psi differential pressure because of limits of the rotary air lock feeder valves (deflections in shaft and bearings and increased blowback air). 

The fuel solids are fed into the fluidized bed by means of a screw conveyor with a specially designed feeder valve. The feed port is located 5 inches above the gas distribution plate. The 2 -inch screw is constructed of carbon steel with a Type 310 stainless steel coating on the wearing surfaces. The construction details of this feeder and the auxiliary solid feed hopper system have been described by Burton and Bailie (2). The feeding unit has performed successfully in smoothly feeding 15-60 lbs of solids/hr into the fluidized bed. 

The rotary lock, star or feeder valve and the screw conveying discharge device, shown in Figs. 11.1.1a and 11.1.1b and 11.1.2, are two devices often used to seal against high differential pressures existing between the cyclone and the underflow. These devices are very suitable for some cyclone applications such as the flour mill application shown in Fig. 11.1.3. However, rotary valves do require motors that render them unsuitable for use inside of vessels... 

Volumetric Feeders. Examples of volumetric feeders are screws, belts, rotary valves, louvered, and vibratory. 

Rotary V lve Feeders. Devices known as rotary valve feeders are commonly used for circular or square configured outlets. These are particularly useful when discharging materials to a pneumatic conveying system where a seal is required to prevent air flow through the hopper outlet. The discharge rate is set by the speed of rotation of the vanes or pockets of the valve. 

Ga.s Eeeders. Chlorine gas is usually fed from a chlorine cylinder equipped with a pressure gauge, reducing valve, regulating valve, feed-rate indicator, and aspirator-type injector for dissolving the chlorine gas in water. The feeder can be manually, or more desirably automatically, controlled utili2ing continuous amperometric or potentiometric measurement of the free chlorine residual. The chlorine solution is normally introduced into the return line to the filter. 

Proprietary designs for rotary valve feeders (star valves) capable of continuous feeding of certain pelleted and granular materials into low velocity, dense phase systems, having system pressures up to 200 kPa (2 bars) have been developed. 

FIG. 17-16 Solids-flow-control devices, a) Slide valve, (h) Rotary valve, (c) Table feeder, (d) Screw feeder, (e) Cone valve, (f ) L Valve. 

FIG. 21-1 Typical feed arrangements for screw conveyors, a) Plain spouts of chutes, (h) Rotary cutoff valve, (c) Rotary-vane feeder, (d) Bin gate, (e) Side inlet gate. (FMC Corporation, Matetial Handling Systems Division. )... 

Charge solids materials by means of a closed system (e.g., hopper and rotary airlock, screw feeder, double-dump valve system, etc.)... 

Operator exposure Charge liquids and solids materials by means of a to fumes or inerts. closed system (e.g., hard piping, hopper and rotary airlock, screw feeder, double-dump valve system, etc.) Provide local ventilation Use proper personnel protective equipment (PPE) ACGIH 1986 CCPS G-22 CCPS G-23 CCPS G-29... 

Material Choke A mass of bulk solids or powders in a rotary valve or screw feeder that prevents a flame from being transmitted. 

At the downstream end of the pipeline it is necessary to disengage the solids front the gas and this is most usually carried out in cyclone separators (See Volume 2, Chapter 8). However, there may be a carry-over of tine particles which must be eliminated before the gas is vented, and gas filters or electrostatic precipitators may be used for this purpose (See again Volume 2, Chapter 8). At the upstream end, the particles must be introduced using some form of positive feeder, such as a rotary valve or a blow tank. 

Rotary valves have been specified for the receivers of the vacuum pneumatic conveying systems (RV-601 and RV-602) and for the feeders (RV-40 1) and receivers (RV-501) of the positive-pressure system transferring powder from the dryers to the extruders. Perry72 gives some recommended sizes for rotary valves. The power required by all these valves will probably not exceed 2 kw and will be ignored. 

Equipment for solids transport which is usually needed in fluidized bed processes will also add to the overall attrition rate. In screw feeders or rotary valves, the particles can be crushed or sheared between the vanes and the housing. The contribution of pneumatic conveying lines is discussed in Sec. 6. 

The rate of feed of solids may be controlled using screw feeders, rotating tables or vibrating feeders, such as magnetically vibrated troughs. Volumetric rates may be controlled by regulating the speeds of rotation of star feeders or rotary vaned valves. 

Fig.8.1. Schematic representation of iuminescent sorter 1-funnei 2-vibrational feeder 3-frame 4-conveyer for concentrate 5-conveyer for waste 6-luminescence excitation source 7-collecting optics 8-optical filter 9-detector 10-air valve (Moskrousov and Lileev 1979)... 

Figure 5.3. Basic equipment arrangements of pneumatic conveying systems, (a) Vacuum system with several sources and one destination, multiple pickup (b) pressure system with rotary valve feeder, one source and several destinations, multiple discharge (c) pressure system with Venturi feed for friable materials (d) pull-push system in which the fan both picks up the solids and delivers them [after F. J. Gerchow, Chem. Eng. [17 Feb. 1975, p. )].

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