The Feed System

The most important component of the feed system in a flood-fed extruder is the feed hopper with possible stirrer and/or discharge screw. A mechanical malfunction of this system can be determined by visual Inspection. If the feed hopper is equipped with a discharge screw (crammer feed), constancy of the drive should be checked. For proper functioning of a crammer feeder, the drive of the crammer feeder should have a torque feedback control to ensure constant feeding and to avoid overfeeding. 

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Extmsion techniques are used to make tubes, rods, gaskets, preforms, etc. Standard mbber equipment may be used to extmde fluorosihcone elastomers. The green strength of fluorosihcones is less than that of typical fluorocarbon elastomers, and this should be considered when designing the feed system. 

The feed system handles the storage, circulation, and temperature control of the whiskey. Siace permeabiUty iacreases with temperature, and considering the heat stabiUty of whiskeys, it is desirable to operate the system above ambient temperatures. Operating at higher temperatures faciUtates temperature control of the process, siace heat losses can be compensated by the addition of heat. 

It is often desired to substitute directiy a more readily available fuel for the gas for which a premixed burner or torch and its associated feed system were designed. Satisfactory behavior with respect to dashback, blowoff, and heating capabiHty, or the local enthalpy dux to the work, generally requires reproduction as neady as possible of the maximum temperature and velocity of the burned gas, and of the shape or height of the dame cone. Often this must be done precisely, and with no changes in orifices or adjustments in the feed system. 

If the substitute fuel is of the same general type, eg, propane for methane, the problem reduces to control of the primary equivalence ratio. For nonaspiring burners, ie, those in which the air and fuel suppHes are essentially independent, it is further reduced to control of the fuel dow, since the air dow usually constitutes most of the mass dow and this is fixed. For a given fuel supply pressure and fixed dow resistance of the feed system, the volume dow rate of the fuel is inversely proportional to. ypJ. The same total heat input rate or enthalpy dow to the dame simply requires satisfactory reproduction of the product of the lower heating value of the fuel and its dow rate, so that WI = l- / remains the same. WI is the Wobbe Index of the fuel gas, and... 

There are direct substitutions of possible interest that would not be feasible without drastic changes in the feed system or pressure. Thus if the available substitute for natural gas is, eg, a manufactured gas containing much CO, there would almost always be a mismatch of the WIs unless the fuel could be further modified by mixing with some other gaseous fuel of high volumetric heating value (propane, butane, vaporized fuel oil, etc). Moreover, if there are substantial differences in eg, as a result of the presence of considerable H2 as well as CO in the substitute gas, the variation in dame height and dashback tendency can also make the substitution unsatisfactory for some purposes, even if the WI is reproduced. Refinements and additional criteria are occasionally appHed to measure these and other effects in more complex substitution problems (10,85). 

Dried product is collected in either cyclones or baghouses depending upon the product-particle size. When primary coUection is carried out in cyclones, secondary collection in a baghouse or scrubber is usually necessary in order to comply with environmental regulations. A rotary valve is used to provide an airlock at the discharge point. Screws are utihzed to combine product from multiple cyclones or large bag-houses. If required, a portion of the dried product is separated from the main stream and returned to the feed system for use as backmix. 

The de-alkalized and degassed water has a pH of 4-5 and (having just passed through an air-blown tower) is laden with oxygen and extremely corrosive. Normal practice is to dose NaOH into the degasser tower sump, at a level sufficient to approach to desired boiler water pH. If this dosing fails, severe corrosion in the degassed water pump, the softener and the feed system will result. 

Filming amines In such situations, one approach is to use the filming type of amine, of which octadecylamine is the most common example. This, and related substances, forms a barrier on the internal surfaces of the feed system offering some protection against corrosive attack. 

There has been renewed interest over the last few years in erosion-corrosion, i.e. essentially velocity-assisted corrosion since it appeared in the feed systems of certain nuclear plant. This prompted extensive experimental investigations . Erosion-corrosion is influenced by many factors-chemistry, flow, temperature, heat flux, and whether one or two phases exist. It also varies with the material, resistance increasing from mild steel, through 1% Cr-Mo to 2% Cr-Mo. 

Sole 2 pH and ammonia limits depend on whether or not copper-based alloys as well as ferrous materials are present in the feed system. 

BSI recommended water characteristics for shell boilers (FT boilers) up to 30 bar (435 psig) note that when copper alloys are present in the feed system, the pH should not exceed 9.2 if corrosion of these materials is to be avoided. 

Plants containing copper alloys in either the feed or condensate system should have the pH of the FW limited to 8.5 to 9.2. If the feed system is completely ferrous, the pH should be limited to 9.2 to 9.5. For plants utilizing the FW for spray attemperation or desuperheating, the pH should be controlled with volatile alkalis only. 

Figure 1. Key elements of the TAP reactor (A) and high pressure fixed bed reactor (B) experimental systems. The TAP reactor schematic shows the heated valve manifold and reactor with the elevated pressure attachment located in the main high vacuum chamber. The fixed bed reactor shows the feed system, liquid vaporizer, oxygen disperser, reactor, and waste recovery system.

All the systems must have a means of bringing the solids and the gas stream together. Since the gas is under either vacuum or pressure, some sort of airlock is needed in order to prevent air either from being sucked into the system or from being blown into and through the feeding system. The most common solution is a rotary valve (see Fig. 8-9) driven by a motor. 

While using a screw conveyor to move the solid oxidant, ignition of a polypropylene tube in the feed system occurred. This could not be reproduced, even when likely contaminants were present. 

In this paper we will first describe a fast-response infrared reactor system which is capable of operating at high temperatures and pressures. We will discuss the reactor cell, the feed system which allows concentration step changes or cycling, and the modifications necessary for converting a commercial infrared spectrophotometer to a high-speed instrument. This modified infrared spectroscopic reactor system was then used to study the dynamics of CO adsorption and desorption over a Pt-alumina catalyst at 723 K (450°C). The measured step responses were analyzed using a transient model which accounts for the kinetics of CO adsorption and desorption, extra- and intrapellet diffusion resistances, surface accumulation of CO, and the dynamics of the infrared cell. Finally, we will briefly discuss some of the transient response (i.e., step and cycled) characteristics of the catalyst under reaction conditions (i.e.,... 

Finding (Blue Grass) EFKE-3. The grinding test achieved most of its objectives, particularly those related to safety. Upon completion of the grinding test, questions remained about the design of the feed system and the size of the grinder and motor needed for the full-scale system. 

Sgroi, M., Bollito, G., Saracco, G., Speeehia, S. 2005. BIOFEAT Biodiesel fuel processor for a vehiele fuel eell auxiliary power unit Study of the feed system. J Power Sources 149 8-14. 

The feed system consisted of a reservoir, a plunger-type feed pump, a twin-fluid atomising nozzle (giving a round spray of angle 13° in free air) and a mini-compressor. Inert gas for the twin-fluid nozzle was drawn between the outlet of the heat exchanger and the rotameter... 

One of the most recent applications of the. VADS is in the US Navy s Phalanx ship-board antimissile system. Nine hundred-fifty discarding sabot depleted uranium rounds are carried in the feed system, and search and tracking radar are carried in a dome above the mounting. The gun is controlled automatically by the ship s fire-control computer, and a closed-loop spotting system measures the positons of target and projectile simultaneously to direct the stream of fire (at 3000 rds/minute) on to the target thruout the engagement (Ref 3)... 

Usually the goal is to "dewater the feed system as much as possible that is, to remove solvent to facilitate either re-use or removal of the concentrated solute. Of secondary importance is the possible re-use of the purified solvent (usually water). These two considerations are significant in determining both the process and membrane device to be used. 

Where vibratory bowl feeds are used for the separation and feeding of closures it should be noted that the closures pick up dirt and static electricity unless the feeding system is properly controlled. 

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