Back-flow

Gas Distrihutor The gas distributor has a considerable effect on proper operation of the flmdized bed. Basically there are two types (1) For use when the inlet gas contains solids and (2) for use when the inlet gas is clean. In the latter case, the distributor is designed to prevent Back flow of sohds during normal operation, and in many cases it is designed to prevent back flow during shutdown. In order to provide distribution, it is necessary to restrict the gas or gas and solids flow so that pressure drops across the restriction amount to from 0.5 kPa (2 in of water) to 20 kPa (3 Ibf/iu ). 

Use dedicated exhaust ducts Vent individual pieces of equipment through conservation vents to prevent back flow Install flame arresters at vessel vents, where applicable... 

The most reliable recycle reactors are those with a centrifugal pump, a fixed bed of catalyst, and a well-defined and forced flow path through the catalyst bed. Some of those shown on the two bottom rows in Jankowski s papers are of this type. From these, large diameter and/or high speed blowers are needed to generate high pressure increase and only small gaps can be tolerated between catalyst basket and blower, to minimize internal back flow. 

Check the stripping gas, if applicable, to be sure there is a positive flow of gas. Be sure steam is not back-flowing into the accumulator from the reboiler. 

Temperature—during the back flow, gas at discharge temperature is introduced to the inlet. If more than one cycle occurs, the same gas is reheated and returned, getting hotter with each cycle. 

Load—during the back flow the shaft torque is reduced, then restored with feed forward giving a torsional pulse with each cycle. 

Component stress—during the back flow and forward reversals, all liic components involved with the gas propulsion are loaded diui unloaded, placing blading in a cyclic loading mode. 

Both nonreturn valves corroded, allowing back-flow to take place. 

Ruck-strahler. m. reflector, -strahlung, /. reflection. -strahltmgsmesser, m. reflectome-ter. -strahlverfahren, n. reflection method, -streuung, /. scattering (of rays). -Strom, m. back flow (Elec.) reverse current, return current, -strfimung, /. backflow, reflux. -titrieren, n. back titration, rlicktreiben, v.t. drive back repel. 

Figures 4-65, 4-66, and 4-67 show several units of the bag. The bags may be of cotton, wool, synthetic fiber, and glass or asbestos with temperature limits on such use as 180°F, 200°F, 275°F, 650°F respectively, except for unusual rnaterials. (See Table 4-12A and B.) These units are used exclusively on dry solid particles in a gas stream, not being suitable for wet or moist applications. The gases pass through the woven filter cloth, depositing the dust on the surface. At intervals the unit is subject to a de-dust-ing action such as mechanical scraping, shaking or back-flow of clean air or gas to remove the dust from the cloth. The dust settles to the lower section of the unit and is removed. The separation efficiency may be 99%-i-, but is dependent upon the system and nature of the particles. For extremely fine particles a precoat of dry dust similar to that used in some wet filtrations may be required before re-establishing the pi ocess gas-dust flow.

Mechanically, the pump operates in an oil bath, with the sealing oil lubricating the pump and seals against back flow from the exhaust to the intake/suction. 

Figure 7-11. Safety valve and rupture disk installation using pressure rupturing disk on inlet to safety relief valve, and low pressure disk on valve discharge to protect against back flow/con-osion of fluid on valve discharge side, possibly discharge manifold. By permission, Fike Metal Products Div., Fike Corporation, Inc.

Figure 12-40D. Flow path arrangement Back-to-back flow. (Used by permission Bui. 423, 1992. Dresser-Rand Company.)...

Equation 4-331 is valid for a back-flow valve at the bottom of the casing string such as a float collar. It is also valid for a back-flow valve located at the top of the casing string. 

This answer means that the casing and its contained drilling mud will float when the cementing operation is completed and the back-flow valve is actuated. Thus the casing should be secured down at the well head prior to initiating the cementing operation. 

To ensure proper control and to protect from reversal of hydrocarbons to the regenerator or the back-flow of hot flue gas to the... 

Any discrepancy between the measured and the calculated values for the current in the model for field-induced tunneling can be discussed by (i) a back flow... 

With careful design and exacting construction these types of valves can be extremely efficient. In practice, to ensure absolute minimum back flow through the valve, a single non-return valve assembly usually contains two non-return ball valves connected in series as shown in figure 6. 

Non-return valves are used to prevent back-flow of fluid in a process line. They do not normally give an absolute shut-off of the reverse flow. A typical design is shown in Figure 5.5g. 

The waste hydrochloric acid (HC1) injected at the site was a byproduct of a combustion process at 1633°C (2972°F). When not recovered, the acidic stream was dumped into holding ponds where it was cooled to about 24°C (75°F) before injection. The concentration of injected acid typically varied from 0.5 to 5% HC1, but ranged as high as about 30%. (The pH of injected acid that back-flowed during one blowout incident ranged from 0.5 to 1.3.)... 

A comparison with Burchard s first cumulant calculations shows qualitative agreement, in particular with respect to the position of the minimum. Quantitatively, however, important differences are obvious. Both the sharpness as well as the amplitude of the phenomenon are underestimated. These deviations may originate from an overestimation of the hydrodynamic interaction between segments. Since a star of high f internally compromises a semi-dilute solution, the back-flow field of solvent molecules will be partly screened [40,117]. Thus, the effects of hydrodynamic interaction, which in general eases the renormalization effects owing to S(Q) [152], are expected to be weaker than assumed in the cumulant calculations and thus the minimum should be more pronounced than calculated. Furthermore, since for Gaussian chains the relaxation rate decreases... 

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