Tower pressure raising

Another reason to raise tower pressure is to permit higher reflux rates. If the pressure controller in Fig. 3.1 is set too low, then during hot weather, when condenser capacity becomes marginal, the level in the reflux drum will be lost. If we then raise the pressure set point, the drum will refill—but why ... 

Raising the tower pressure also increases the reflux drum pressure, raising, in turn, the temperature at which the vapors condense. The rate of condensation is then calculated from the following ... 

As the hot-vapor bypass valve opens, the condensate level in the shell side of the condenser increases to produce cooler, subcooled liquid. This reduces the surface area of the condenser exposed to the saturated vapor. To condense this vapor, with a smaller heat-transfer area, the pressure of condensation must increase. This, in turn, raises the tower pressure. This then is how opening the hot bypass pressure-control valve increases the tower pressure. 

The formation of cross-linked aromatic rings can be reduced by lowering the coke drum pressure, raising the coke drum outlet temperature, improving the vacuum tower operation, and by adding steam to the coke drum. 

Another test for seal leg backup into Ihe precondenser requires raising the pressure in the seal drum by 0.5 psi. If liquid had been backed up in the condenser, the vacuum tower pressure will go up by 1 in. Hg. If Ihe condenser was running properly drained, the vacuum tower pressure will remain unaffected. 

A.djustingTrocess to Optimi AT. At first glance, there appear to be only three or four utiUty levels (temperatures), and these can be 50°C apart. Different ways to increase the options include using multieffect distillation, which spreads the AT across two or three towers using waste heat for reboil and recovering energy from the condenser. To make these options possible, the pressure in a column may have to be raised or lowered. 

A vital part of the process system for each of the plants includes a turboexpander-compressor set. This turbomachinery string has two main functions. The first function reduces the pressure and temperature of the incoming gas to facilitate separation of the methane. The second function raises the pressure of the methane after it leaves the fractionation tower and is transferred directly to the customers through an underground pipeline. 

The cold-water temperature should be taken from the basin or the suction side of the pumps (not the pressure side, as the energy input can raise the temperature, nor from the water falling through the tower). 

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