Liquid accumulation

To determine if steady state conditions exist, the temperatures and pressures in the column can be tabulated to assure that they are reasonably unchanging. Laboratoiy analyses are usually too slow and expensive for checking lined out conditions. Monitoring reflux accumulator boiloff is often an effective way of noting concentration changes. Simply let a sample of the accumulator liquid boil at atmospheric pressure in a bottle with a thermometer inserted. This method is limited to light hydrocarbons and is not accurate enough for precision fractionation. 

Assume an accumulator having a liquid holdup of 2,000gal. Assume that the liquid leaving as reflux plus distillate is 40GPM. Further assume that the accumulator liquid starts at 2.0 ol % of a key component and that the test conditions produce 0.0 vol. % of the key component. How long will it take for the concentration to reach... 

Undrainable traps that accumulate liquids and absorbent solid wastes should be avoided. Structures should be designed to be self-draining. 

Wliere possible, all flame arresters should be installed so that the elements will be self-draining. If liquid can accumulate in the housing, provision should be made to drain any accumulated liquid that could block the flow of gases through the flame arrester. 

Since much of the vented material will be liquid, separators such as knockout pots or tangential entry separators can provide disengagement and possible recovery. Figure 5 is a typical vapor-liquid separator design found to be effective for these applications. Inlet design superficial vapor velocity is about 100 ft/sec, with sufficient volume provided to accumulate the entire reactor liquid contents. The lip on the outlet vapor line and the horizontal plate to separate the accumulated liquid are important features to prevent re-entrainment. 

The accumulated liquid fills part of the originally free gas volume lowering the porosity of the filter to a certain extent, but typically not totally due to the transport of the liquid, if the liquid is not too viscous. On the contrary, there is no such limitation for accumulated solid particles which can fill the voidage until the filter is clogged. 

In the course of separating the droplets some liquid will be stored within the bed. The accumulated liquid lowers the value of e. However, in contrast to separation of solids the filter will not be blocked as the liquid can move out of the filter, as explained in Section 3.2.1. By introducing the saturation ft the change in bed porosity due to accumulated liquid can be accounted for. 

Pump for transferring the accumulated liquid to subsequent rework, recovery, or disposal. 

Spill or Pool Fire - Is a release of a flammable liquid and or condensed gas that accumulates on a surface forming a pool, where flammable vapors burn above the liquid surface of the accumulated liquid. 

Dikes should be arranged so liquids will flow (with minimum exposure to pipeways) to a low point within the enclosure remote from the equipment producing the spillage. Accumulated liquid can them be easily drained or pumped into a liquid removal system. 

Figure 10,17 Evolution of liquid and solid during fractional melting of initial composition C in Di-Ab-An system. Curves ILC(l) and ILC(2) fractional melting liquids TSC residual solids dotted line fractionally accumulated liquids at quoted degrees of partial melting (from Ottonello and Ranieri, 1977).

However, equation 10.133 is not sufficient to ascribe magmatic evolution to fractional crystallization if it is not supported by petrologic evidence. Adopting the formalism of Shaw (1970), it may be shown that the distribution of hygromagmatophile elements in fractionally accumulated liquids leads to the same sort of linear array. The equation... 

Very high velocities tend to skim the liquid film off the vessel wall and off the liquid at the bottom. The liquid also tends to creep up the wall and down the exit pipe where it is picked up by the exit gas. The skirt shown on Figure 18.9 is designed to prevent reentrainment of the creeping liquid, and the horizontal plate in Figure 18.10 prevents vortexing of the accumulated liquid and pickup off its surface. 

Flooding is an excessive accumulation of liquid inside a column. Flood symptoms include a rapid rise in pressure drop (the accumulating liquid increases the liquid head on the trays), liquid carryover from the column top, reduction in bottom flow rate (the accumulating liquid does not reach the tower bottom), and instability (accumulation is non-steady-state). This liquid accumulation is generally induced by one of the following mechanisms. 

Summing up, if the inventory of the main components can be handled by local control loops, the inventory of impurities has essentially a plantwide character. The rates of generation, mainly in chemical reactors, and of depletion (exit streams and chemical conversion), as well as the accumulation (liquid-phase reactors, distillation columns and reservoirs) can be balanced by the effect of recycles in order to achieve an acceptable equilibrium state. Interactions through recycles can be exploited to create plantwide control structures that are not possible from a standalone unit viewpoint. 

---