Averaging pressure control

If a smooth flow to the next step in the process is needed, a reflux drum, with averaging level control of distillate, should be employed. If the column top product is a vapor, takeoff should be by averaging pressure control. As an alternative, vapor may be taken off on flow control cascaded from top composition control while column pressure is controlled by heat input. 

FIG. 8-78 Generic depictions of average pressure at subsequent cross sections throughout a control valve, FiS selected for illustration are 0,9 and 0,63 for low and high recovery, respectively. Internal pressure in the high-recovery valve is shown as a dashed line for flashing conditions [Pg.788]

The hydrocarbon yields shown represent those expected averaged over the useful life of the ZSM-5 catalyst. Finished gasoline contains C4 s for vapor pressure control. For an 82.7 kPa (12 psi) RVP (Reid Vapor Pressure) finished gasoline, the yield is 86 wt% of hydrocarbons and the clear Research octane number is 93. Additional gasoline could be made by alkylating the propene and butenes produced with isobutane. As the amount of alkylate would be low, its manufacture would most likely be considered only for very large plants. 

Sharp splits. Boyd (58, 59) developed a double differential temperature control scheme, which is essentially an average temperature control scheme that compensates for pressure and differential pressure variations. The scheme overcame the problem described in the previous section and was demonstrated to maintain tight control on both... 

For the tribological measurements, the radial position of the slider during the tests was halfway between the inner and outer diameters of the disk, and the pivot-to-center distance was adjusted so that the slider skew angle was close to 0°. The disk rotation was started with the slider suspension on the load/unload ramp just off the edge of the disk. The slider was accessed to the test radius. The pressure control and measurement of the frictional displacement were performed with The National Instruments LabView software on a PC with interface cards. Average displacement and peak amplitude were recorded after each pressure decrement/incre-ment (4000 samples at 20 kHz for 200 ms). The pressure inside the tester was varied linearly from ambient (100 kPa) to 15 kPa and back up to ambient over about 3 min in approximately 1-kPa increments. At the end of the test, the slider was translated back to the load/unload ramp before stopping the disk rotation. 

As an additional compensation for rapid temperature transients the reactor outlet temperature is measured at the inlet to each of the five steam generator cells, averaged, and used to adjust the set point for the steam pressure controller. This will effectively anticipate the response required to maintain a constant inlet coolant temperature to the reactor. 

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