Separators liquid settling rates

Basic design aspects of three-phase separation are identical to those discussed earlier for two-phase separation. The only additions are that more concern is placed on liquid-liquid settling rates and that some means of removing free water must be added. Liquid-liquid setding rates will be discussed later. Water removal is a function of control methods used to maintain separation and removal from the oil. Several control methods are applicable to three-phase separators and shape and diameter of the vessel will, to a degree, determine types of control used. 

Thickeners, thickeners are primarily used for liquid-solid separation (see Section 10.4). When used for classification, the feed rate is such that the overflow rate is greater than the settling rate of the slurry, and the finer particles remain in the overflow stream. 

Vapor-Liquid Gravity Separator Design Fundamentals The critical factors in the performance of a horizontal separator are the vapor residence time and the settling rate of the liquid droplets. However, two other factors enter into the design—the vapor velocity must be limited to avoid liquid entrainment, and there must be sufficient freeboard within the vessel to allow for a feed distributor. For vertical separators, the design is based on a vapor velocity that must be less than the settling velocity of the smallest droplet that is to be collected, with due allowance for turbulence and maldistribution of the feed. The vapor residence time is a function of the vapor flow rate (mass), vapor density, and volume of vapor space in the separator, based on the following ... 

The majority of the process vessels you see in your plant are gravity, vapor-liquid separators. Their main purpose is to settle out droplets of entrained liquid from the upflowing gas. Factors that affect the settling rate of these droplets are... 

The size of the particle is the most important separation variable because it affects the particle filterability and its settling rate. The smaller the particles, the more difficult it is to separate from the liquid. So the first step is to determine the particle size. Some of the... 

Treatment of a suspension with the necessary chemical will produce a ffster settling system with a more bulky and more permeable sediment, but the final liquid content of the shidge or filter cake may well be significantly hi er than if a nontreated suspension had been settled. The benefits therefore tend to be found in flie enhanced settling rate and increased permeabiUty, and sometimes the sediment is of such bulk as to prove troublesome and expensive in disposal Other solid-liquid separation operations such as dissolved air flotation and centrifiigation have different requirements that must be met by the pretreatment system. 

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