A release point closer to the gas/liquid interface results in better calculated droplet-removal performance and a lower entrainment load exiting the gas gravity separation section (mist extractor inlet).
The worst case (most conservative) assumption for the release point is that all droplets are released at the top (inlet) of the gas gravity separation section, as shown by the droplet settling trajectory in Fig. The geometry associated with the droplet settling calculations for a horizontal separator is shown in Fig. 3 - Vertical and horizontal separators showing the gas flow-droplet settling relationships. Use of this factor will allow estimation of the effective actual velocity, which can then be used in the droplet settling calculations for the gas (and liquid) gravity sections. Note also that the calculated effective actual velocity for the gas gravity section will be the velocity at the entrance to the mist extractor section.įig. F values greater than 1.0 imply unused cross-sectional flow area. The quality of the flow distribution is characterized by the factor F, the actual average velocity/ideal plug flow velocity. 2 shows the quality of the flow distribution immediately upon exit of the inlet device ( L/Di=0) and the development of the flow profile with distance downstream of the inlet device.
EXTRACTOR XONOTIC SERIES
The amount of entrainment and the gas velocity profile exiting the inlet device were determined by the method in Part 1 of the series in August 2013.įig. The uniformity of the gas velocity profile through the mist extractor and limits on velocity to prevent re-entrainment are also important factors and will be discussed later. Particularly important are the allowable liquid loading (gal/min/ft 2) of the face area of the mist extractor and the droplet removal capability of the mist extractor. If we think of the gas gravity separation section as a preconditioning step ahead of the mist extractor, then it is clear that the requirements for separation performance of this part of the separator are dependent on the requirements of the selected mist extractor. Even this approach is only semiquantitative in that selection of an appropriate target droplet size is an inherently ill-defined procedure, and provides little indication as to the amount of entrainment remaining. The K smethodology does not readily lend itself to quantification of gas/liquid separation performance, so will not be discussed further.Īfter simplifying assumptions to make the calculations manageable, the droplet settling calculations for sizing the gas gravity separation section (cross-sectional area and length) aim at removing a target liquid-droplet size (e.g., 150 μm) and all droplets larger than the target size. The method, primarily an empirical approach, involves the estimation of an allowable maximum gas velocity to achieve the required degree of droplet separation. Traditionally, the K s method has been most commonly used because it usually provides reasonable results and is easy to use ( K svalues for vertical and horizontal separators are available from many literature sources). The physical process is the separation of liquid droplets from the gas phase. Two approaches to sizing this part of the separator to remove liquid droplets from the gas are the K s method (Souders-Brown equation as shown in Eq.
The gas gravity separation section then provides preconditioning of the gas-and its entrained liquid load-ahead of the mist extractor. However, even in this scenario, a relatively uniform gas velocity distribution should be delivered to the mist extractor to optimize its performance. In low-liquid-loading applications, such as scrubbers, pre-separation of liquid droplets may not be required if the mist extractor can handle the entrainment load. A secondary, but related, function is the improvement/straightening of the gas velocity profile. Available mist extractors have limitations on the amount of entrained liquid (droplets) that can be handled. The primary function of the gas gravity separation section of a separator is to reduce the entrained liquid load not removed by the inlet device. 1 - Parts of a separator (vertical and horizontal).
0 kommentar(er)
