Plates operating range

The term in equation 42 is called a Souders-Brown capacity parameter and is based on the tendency of the upflowing vapor to entrain Hquid with it to the plate above. The term E in equation 43 is called an E-factor. and E to be meaningful the cross-sectional area to which they apply must be specified. The capacity parameter is usually based on the total column cross section minus the area blocked for vapor flow by the downcomer(s). Eor the E-factor, typical operating ranges for sieve plate columns are... 

The cross-flow plate (Fig. 14-16 ) utilizes a hquid downcomer and is more generally used than the counterflow plate (Fig. 14-16Z ) because of transfer-efficiency advantages and greater operating range. The liquid-flow pattern on a cross-flow plate can be controlled by placement... 

One way of calculating the number of equilibrium stages (or number of theoretical plates, NTP) for a mass exchanger is the graphical McCabe-Thiele method. To illustrate this procedure, let us assume that over the operating range of compositions, the equilibrium relation governing the transfer of the pollutant from the... 

Column type Operating range (PEO/PEG equivalent) Guaranteed minimum efficiency (plates/meter)... 

The principal factors to consider when comparing the performance of bubble-cap, sieve and valve plates are cost, capacity, operating range, efficiency and pressure drop. 

Operating range. This is the most significant factor. By operating range is meant the range of vapour and liquid rates over which the plate will operate satisfactorily (the... 

The lower limit of the operating range occurs when liquid leakage through the plate holes becomes excessive. This is known as the weep point. The vapour velocity at the weep point is the minimum value for stable operation. The hole area must be chosen so that at the lowest operating rate the vapour flow velocity is still well above the weep point. 

Stable operating range). Some flexibility will always be required in an operating plant to allow for changes in production rate, and to cover start-up and shut-down conditions. The ratio of the highest to the lowest flow rates is often referred to as the turn-down ratio. Bubble-cap plates have a positive liquid seal and can therefore operate efficiently at very low vapour rates. 

Figure 2. (Top) Detail of the MULVFS pump unit and filter-holder assembly. The filter holder consists of three stages. The upper two plates are baffles necessary to prevent particles from being redistributed on the filters during recovery. The next plate supports the 53-gm mesh Nitex prefilter, and the bottom plate supports the pair of 1-pm micro quartz-fiber filters and seals to the pump intake. (Bottom) Pressure vs. flow rate curves for the MULVFS and LVFS pump units. Horizontal bars indicate operating ranges of the two systems during filtration.

---