Knockout vessels

Knockout vessels are the most common form of basic separator. The vessel contains no internals and demisting efficiency is poor. However, they perform well in dirty service conditions (i.e. where sand, water and corrosive products are carried in the well stream). 

Fuel System. An adequate knockout vessel should be provided for natural gas entering the plant as fuel or feed gas. Hydrocarbon liquids can and will enter the fuel system otherwise. Double-pressure letdown plus heating to preclude hydrates is also typically specified. 

A full product spectrum for the LTFT synthesis as measured in a laboratory CSTR is based upon the products collected in the knockout vessels after leaving... 

Whether or not an emulsion is stabilized by solids will determine the nature of the demulsifier that will be most effective. In addition, the presence of multiple emulsions (water-in-oil-in-water-in-oU, etc.) is often symptomatic of demulsifier overtreatment. Figure 5 shows an oUfield emulsion formed when a free water knockout vessel was contaminated with viscosity reducers from an earlier well fracture. Similar multiple emulsions can result from overtreatment of the produced fluid by demulsifiers in the process. 

CO2 Capture Experiments The experiments of CO2 capmre from a flue gas or synthesis gas were conducted in the gas permeation apparams described earlier (Tee et al., 2006 Zou and Ho, 2006). The gas used contained 20% CO2, 40% N2, and 40% H2. Steam was applied as the sweep gas since water condenses at ambient condition and a high-purity CO2 can be obtained readily from the permeate side. The gas permeation was performed at 110°C to achieve the best membrane separation performance. Feed-side and sweep-side pressures were set at 2 and 1 atm, respectively. A circular gas permeation cell with a membrane area of 45.6 cm was used. Both the retentate and permeate streams leaving the gas permeation apparatus were cooled down to ambient temperature in then-respective water knockout vessels, which removed the water condensed. 

When hydrocarbons (crude oil, condensate, and natural gas) are produced, the wellstream typically contains water produced in association with these hydrocarbons. The produced water is usually brine, brackish, or salty in quality but in rare situations may be nearly "fresh" in quality. The water must be separated from the hydrocarbons and disposed of in a manner that does not violate established environmental regulations. Typically, the produced water is mechanically separated from the hydrocarbons by passing the wellstream through process equipment such as three-phase separators, heater-treaters, and/or a free-water knockout vessel. These mechanical separation devices do not achieve a full 100% separation of the hydrocarbons from the produced water. The produced water separated from the hydrocarbons in these mechanical separation devices will contain 0.1-10 vol.% of dispersed and dissolved hydrocarbons. Produced water treating facilities are used to further reduce the hydrocarbon content in the produced water prior to final disposal. 

The vessel can be supported off the stmcture and sometimes off the rack. Some economy may be possible by combining two or more services into a common vessel by using a single vessel that has an internal head. Differential pressure as weU as concerns over internal leakage need to be considered for these services. This can be done with vertical vessels as weU. A knockout section can be provided below or above the main vessel. 

Batch Process. In the batch process (Fig. 5), the feedstock is preheated in a tube furnace or heater placed between the feedstock storage and the blowing vessel. The air supply is provided by a variety of blowers or compressors and a vertical-tower vessel is preferable for air-blowing. Knockout dmms, water scmbbers, incinerators, furnaces, and catalytic burning units have been used for fume disposal (32). Steam is used for safety and to ensure positive fume flow to the incinerator. 

Cyclone Separator with Integral Catch Tank This type of containment system, depicted in Fig. 26-19, is similar to the ore-mentioned type, except that the knockout drum and catch tank are combined in one vessel shell. This design is used when the vapor rate is quite high so that the knockout drum diameter is large. 

Multireactor Knockout Drum/Catch Tank This interesting system, depic ted in Fig. 26-22, is sometimes used as the containment vessel for a series of closely spaced reac tors (Speechly et al., Trinci-ples of Total Containment System Design, presented at I. Chem. E Noith West Branch Meeting, 1979). By locating the drum as shown in Fig. 26-22, minimum-length vent lines can be routed direc tly to the vessel without any bends. 

FIG. 26-22 Multireactor knockout (K-O) drum/catch tank a) plan view of reactors connected to horizontal containment vessel (h) back-to-back bursting disc assembly (c) elevation of self-supporting vessel (d) elevation of horizontal vessel on roof of building (e) elevation of horizontal vessel on side of building. 

Cyclone Separator with Integral Catch Tank (See Fig. 26-19.) The diameter of the knockout drum is calculated by the criteria given in the preceding section and Fig. 26-18. Since the liquid is also to be retained in the vessel, extend the shell height below the normal bottom tangent line to increase the total volume by an amount equal to the volume of the hquid carried over. 

A vessel handling large amounts of liquid or a large liquid surge volume will usually be horizontal. Also, where water must be separated from hydrocarbon liquid, the vessel will be horizontal. A vessel with small surge volume such as a compressor knockout drum will usually be vertical. 

Always provide a suitable knockout pot ahead of the jets. Water droplets can quickly damage a jet. The steam should enter the pot tangentially. Any condensate leaves through a steam trap at the bottom. It is a good idea to provide a donut baffle near the top to knock back any water creeping up the vessel walls. 

A PR valve is not required for protection against fire on any vessel which normally contains little or no liquid, since failure of the shell from overheating would occur even if a PR valve where provided. Examples are fuel gas knockout drums and compressor suction knockout drums. (Note Some local codes require pressure relief valve protection for "dry drum" situations.)... 

Determine the weight for the following free-water knockout. It is butt weld fabricated with spot x-ray and to be built to Division 1. A conical head (bottom of the vessel) is desired for ease in sand removal. Compare this weight to that of a vessel without the conical section and that to ti ves.sel with a 4-m. plate internal cone. 

J. Knockout drums (vessels) usually operate with only a small amount of liquid. Therefore, the wetted surface would be in proportion, but to maximum design liquid level. 

A further interesting phenotype identified in SDF-1/CXCR4 knockout mice is a deficiency in blood vessel development, initially observed in the gastrointestinal system (Tachibana et al. 1998). Consistent with such observations, CXCR4 receptors have been shown to be expressed by hemangioblasts, the earliest common precursor to hematopoietic and endothelial stem cells, found in yolk sac... 

Where the carryover of some fine droplets can be tolerated it is often sufficient to rely on gravity settling in a vertical or horizontal separating vessel (knockout pot). 

Yamada, M., Lamping, K. G., Duttaroy, A. etal. Cholinergic dilation of cerebral blood vessels is abolished in M5 muscarinic acetylcoholine receptor knockout mice. Proc. Natl Acad. Sci. U.S.A. 98 14096-14101,2001... 

Three-phase separators, commonly called freewater knockouts, are used to separate and remove any free water phase that may be present. Because flow enters the three-phase separator either directly from a producing wdl, or a separator operating at a higher pressure, the vessel must be designed to separate gas that flashes from the liquid as wdl as oil and water. 

A good understanding of the treating plant, its contribution to the treatment and the chemical requirements to match it, are necessary before chemical selection can be made. If little agitation is available, a fast-acting chemical is necessary. If a water knockout is used, water drop will be very important. It heat is unavailable, rhp chemical must work at ambient temperatures. Different-type treating vessels require different chemical actions. 

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