Knockout drums vapor-liquid

Types of Equipment The three most commonly used types of equipment for handling emergency relief device effluents are blowdown drums (also called knockout drums or catch tanks), cyclone vapor-liquid separators, and quench tanks (also called passive scruh-hers). These are described as follows. 

Cyclone Separator with Separate Catch Tank This type of blowdown system, shown in Fig. 26-17 and 26-18, is frequently used in chemical plants where plot pan space is hmited. The cyclone performs the vapor-liquid separation, while the catch tank accumulates the hquid from the cyclone. This arrangement allows location of the cyclone knockout drum close to the reactor so that the length of the relief device discharge hne can be minimized. The cyclone nas internals, vital to its proper operation, which will be discussed in the following sections. 

At the central platform, water and hydrocarbon liquids are first removed in knockout drums. Then saturated natural gas, free of any liquid droplets, enters the twin expanders. The gas is cooled below its dewpoint, allowing heavy hydrocarbon components and water vapor to condense in the discharge stream. Turboexpanders were chosen for two main reasons They are more compact than competing methods of controlling the dewpoint and their operating costs are typically lower than those of many alternatives. 

Consideration of All Releases into the System - All releases tied into the closed system must be considered. In addition to PR valve discharges, these may include fuel gas compressor and absorber knockout drum drainage, vapors vented from water disengaging drums, feed diversion streams, closed drainage from equipment, vapor blowdowns and liquid pulldowns. 

Knockout drums are sometimes called catch tanks or blowdown drums. As illustrated in Figure 8-12, this horizontal knockout drum system serves as a vapor-liquid separator as well as... 

Determine the maximum vapor velocity in a horizontal knockout drum to dropout liquid particles with particle diameters of 300 pm, where... 

Bottoms of T-3 proceeds to the top of stripper T-4. Vapor overhead from T-4 is recycled to the middle of T-3. The bottoms product (containing 99.5% oxygen) is sent partly to liquid storage and the remainder to precooler E-l where it is vaporized. Then it is compressed to 150 psig in a two-stage compressor JJ-2 and sent to the battery limits. Compressor JJ-2 has inter- and aftercoolers and knockout drums for condensate. 

Nomographs can be used to quickly size vertical knockout drums, oil separator drums, compressor dry drums, flash drums or any other vertical vapor-liquid separator. 

Remember that a vapor-liquid separator (a drum where entrainment is generated) should have a lower than a knockout drum (a drum where residual entrainment from an external source is further reduced). 

A knockout drum in a flare system is used to prevent hazards associated with burning liquid droplets escaping from the flare stack. Accordingly, the drum must be of sufficient diameter to produce the desired liquid-vapor separation. 

The vapor-liquid separator t5 pe (Fig. 3.96) features an internal knockout drum directly above an orifice redistributor. It consumes more vertical space than the baffle t3q)e, but it has the potential of providing better liquid distribution to the bed below. This device is also most suitable for small columns (386). 

Design methods are discussed elsewhere (417) and are based on limiting the maximum diameter of droplets entrained in the vapor stream. Maximum droplet diameter can be reduced by supplying a knockout facility upstream of the compressor. This can be either an enlargement of the vapor space above the top tray, an in-line liquid separator, or a separate knockout drum. Mist eliminators are effective and can be installed above the top tray or in the drum. If the vapor temperature is higher than the worst ambient conditions, the lines from the knockout facility to the compressor should either be kept short and insulated or be provided with liquid-removal facilities. 

The portion above the high-level trip This portion performs vapor-liquid sepsu-ation uid is sized using a knockout drum-sizing criterion (e.g., 237, 365). If all product is liquid, this portion is not needed. 

No major changes have been made to the SCWO system, but there are some differences between the SCWO unit previously tested and the SCWO units proposed for EDS and for full-scale operation. Changes have also been made to equipment downstream of the SCWO reactor to facilitate processing of the suspended solids in the reactor effluent, especially for aluminum-rich feeds. The effluent flows from the pressure letdown valves to a knockout drum that contains a venturi scrubber, which separates liquid and suspended solids from the uncondensed vapor. The slurry is pumped to an evaporator/crystallizer system that replaces the flash separator in the original design. 

The design of vapor oudets is relatively easy and is less likely to cause problems than liquid oudets fKister. 19901. The main consideration is that the line must be of large enough diameter to have a modest pressure drop. At the top of the column a demister may be used to prevent liquid entrainment. An alternative is to put a knockout drum in the line before any conpressors. 

We wish to make an analysis of column bases with associated reboilers where there is significant liquid holdup. The analysis should take into account the temperature of the entering liquid and the sensible heat effect of the liquid mass. Such an analysis also applies to vaporizers with associated separators or knockout drums. 

The requirement of having low net positive suction head is an advantage. This is advantageous for vessel-emptying applications such as closed-drain drums or flare knockout drums or any applications encountering high-vapor pressure liquids. 

Excessive amounts of foam in a vessel can result in a host of operating and production problems, including reduced product throughput, level control problems, excessive liquid entrainment out the vapor outlet piping, excessive vapor out the liquid underflow piping, and underflow pump cavitation problems. If foaming occurs in a compressor knockout drum it can easily flood a mesh pad or vane (chevron) separator. When this occurs, the foam carryover from the drum can severely damage the gas compressor downstream. 

Knockout pot (drums and accumulators for high ratios of liquid/gas, as in distillation column overheads) use horizontal cylinder size vapor space to provide the residence time for drops to settle out. Vapor volume between 20 and 50% with a minimum of 0.3 m. Design vapor-phase cross-sectional area to allow drops to settle in assigned length of the drum. Assume drops 0.1 to 2(X) pm. The Souders-Brown separation maximum superficial gas velocity is... 

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