High Pressure Process for

Linde process A high-pressure process for the production of liquid oxygen and nitrogen by compression to about 200 bar (20MN/m ) followed by refrigeration and fractionation in a double column. 

A sophisticated model of the high-pressure process for polyethylene is described in... 

In the high-pressure process for the production of polyethylene, ethylene is compressed in a two-step process. In the primary step, the gas is compressed in a two-stage compressor to 25 to 30 MPa. This is followed by compression in a hypercompressor to 150 to 320 MPa. 

Meanwhile, Wacker Chemie developed the palladium-copper-catalyzed oxidative hydration of ethylene to acetaldehyde. In 1965 BASF described a high-pressure process for the carbonylation of methanol to acetic acid using an iodide-promoted cobalt catalyst (/, 2), and then in 1968, Paulik and Roth of Monsanto Company announced the discovery of a low-pressure carbonylation of methanol using an iodide-promoted rhodium or iridium catalyst (J). In 1970 Monsanto started up a large plant based on the rhodium catalyst. 

Cashman A high-pressure process for extracting gold from arsenic-bearing ores, concentrates, and flue dusts. 

Mitsui-Toatsu A high-pressure process for making urea from ammonia and carbon dioxide. Invented in 1967 by Toyo Koatsu Industries. 

These give off significant quantities of gas when evacuated, especially if they had been exposed to excess gas pressure before evacuation. The second, technically more important case deals with high pressure processes for the manufacture of foams U2). 

James Watt s steam engine (around 1785) working with several bar steam pressure only, innovated the world s energy supply and induced an industrial revolution. This steam engine represented one of earliest high pressure processes for power generation. 

ExxonMobil has produced LDPE by both high pressure processes since the late 1960s. Schuster and Kaus have described the workings and advantages of ExxonMobil high pressure processes for LDPE (3). 

Figure 7.1 Schematic process flow diagram for autoclave high pressure process for production of low density polyethylene. (Reprinted with permission of John Wiley Sons, Inc., Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley and Sons, Inc., h edition, 2006).

Cited from Forbes and O Beirne, op. cit. (25), p. 456. Royal Dutch/Shell, in common with ICI and Standard Oil of New Jersey, also became closely involved with I.G. Farben in negotiations over high pressure processes for coal to oil conversion. This and other aspects of high pressure industrial chemistry during the interwar period are reviewed in Anthony S. Travis, The High Pressure Chemists (Wembley Brent Schools Industry Project, 1984). 

The instabilities possible in tubular reactors have had a major influence on the process design. A model of the high pressure process for polyethylene is available in the hteratin-e (2) and there are even more sophisticated proprietary models. The highpressure process for polyethylene uses a single tube about 4.5 cm in diameter and several miles long to avoid thermal runaway and tube-to-tube... 

Examination of the data between 1952 through 1956 in Table 5.4 illustrates the enormous growth in the high-pressure process for the manufacture of polyethylene as a result of the court decision. Ihe polyethylene production for 1954 was 195 million pounds, which increased to 375 million pounds in 1955, and is particularly interesting because the 92% annual growth that took place in the manufacture of polyethylene came three years after the antitrust court decision, which is approximately the amoxmt of time necessary to license the ICl technology and construct a new polyethylene plant in order to begin production. Moreover, in 1956,... 

Make the reactor longer or add reactors in series. Capacity can be increased in the high-pressure process for LDPE by adding an extra mile to the tubular reactor. Adding stirred-tank or stirred-tube reactors in series is sometimes used to scale up polystyrene processes. For incompressible fluids, scaling in series is lim-... 

Tubular reactors are rarely scaled in series because of pressure limitations. The great exception to this statement is the high-pressure process for LDPE, where reactor lengths are measured in kilometers. The diameter of the tube is strictly limited to about 5 cm to avoid thermal runaway. A few tubes in parallel, possibly with separate ethylene compressors, can be used to achieve greater capacity, but conventional shell-and-tube designs present a serious problem of tube-to-tube instability. 

Process for the direct decaffeination of aqueous coffee extract solutions Process for extracting caffeine from solutions thereof in carbon dioxide under high pressure Process for the extraction of caffeine supercritical solutions Decaffeination process Method for decaffeinating coffee with a supercritical fluid Method for decaffeinating coffee with a supercritical fluid... 

Supercritical extraction processes show similar requirements with regard to high pressure fluid machinery as do high pressure processes for reactions. However, since the principal solvent is usually CO2 the corrosion and erosion aspects are less demanding than is the case in reaction processing. Also the temperature will not usually be high since a limit to the allowable temperature is often set by the properties of the components and the required quality of the products. 

The necessity to monitor high-pressure processes for design optimization, safety, and controlling will most probably not vanish in the future on the contrary, the need to enhance efficiencies will lead to heighten the need for sensors. Maintenance intervals are increasing while on-site manpower is consequently reduced, thus... 

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