Ethylene compression

Figure 31. Example of ethylene compression and reaction plant.

SYNS ACETENE ATHYLEN (GERMAN) BICARBURETTED HYDROGEN ELAYL ETHENE ETHYLENE, compressed (DOT) ETHYLENE, refrigerated liquid (DOT) LIQUID ETHYLENE OLEFIANT GAS... 

The original ICI process for polymerising ethylene, developed in the 1940s, produces low density polyethylene (LDPE) with a density in the range 910-935 kgm. Ethylene, compressed to pressures between 1400 and 2400 bar at a temperature between 200 and 250 °C, is above the critical point where liquids and gases can be distinguished. When it is polymerised using a free... 

Synonyms Acetene Bicarburretted hydrogen Ethene Ethylene, compressed Ethylene, refrigerated liq. 

Ethylene, chlorotrifluoro-, polymers. See Chlorotrifluoroethylene polymer Ethylene, compressed. See Ethylene Ethylene cyanide. See Succinonitrile Ethylene cyanohydrin CAS 109-78-4 El NECS/ELINCS 203-704-8 Synonyms 2-Cyanoethanol Hydracrylonitrile 3-Hydroxypropionitrile Classification Nonaromatic nitrile Empiricai C3H5NO Formuia N=CC2H40H... 

DOT Label FLAMMABLE GAS TC Shipping Name Ethylene, compressed... 

In the LDPE autoclave process, the general process design (e.g., ethylene compression, high and low pressure product separation and ethylene recycling) is very similar to the LDPE tubular process. Instead of the jacketed tube reactor, however, the autoclave process employs a high-pressure stirred tank reactor. The reactor is designed to allow a residence time of 30-60 s (typical reactor volumes are around 1 m for large plants). The autoclave is usually operated in an adiabatic manner the reaction heat is removed by the fresh ethylene... 

ETHYLENE, compressed 197 72 NITRfXJEN, refrigerated liquid (cryogenic... 

Synonyms Acetone Bicarburrelled hydrogen Elhene Ethylene, compressed Ethylene, refrigerated liq. Liquid ethylene Olefiant gas Empirical CjHj Formula H2C CH2... 

Trade Names AClyn 201 A AClyn 246A Ethylene carboxylic acid. See Acrylic acid Ethylene chloride. See Ethylene dichloride Ethylene, compressed. See Ethylene Ethylenediamine... 

In addition to these mechanical problems there are two aspects of the compression process which relate specifically to ethylene. Eirst, there is a tendency for small amounts of low molecular weight polymer to be formed and, second, the gas may decompose into carbon, hydrogen, and methane if it becomes overheated during compression. Cavities in which the gas can collect and form polymer, which hardens with time or in which the gas can become hot, need to be avoided. 

Ethylene Stripping. The acetylene absorber bottom product is routed to the ethylene stripper, which operates at low pressure. In the bottom part of this tower the loaded solvent is stripped by heat input according to the purity specifications of the acetylene product. A lean DMF fraction is routed to the top of the upper part for selective absorption of acetylene. This feature reduces the acetylene content in the recycle gas to its minimum (typically 1%). The overhead gas fraction is recycled to the cracked gas compression of the olefin plant for the recovery of the ethylene. 

The reactor outlet is flashed to remove ethylene which is then compressed and recycled a-olefins are separated from the solvent that contains the catalyst, treated to remove catalyst, and then distilled into commercial fractions. Most of the catalyst in the solvent is recycled but a portion is purged. The catalyst in the purge stream is recovered by reducing the oxidized nickel with boron hydride. 

Ghdants are needed to faciUtate the flow of granulation from the hopper. Lubricants ensure the release of the compressed mass from the punch surfaces and the release/ejection of the tablet from the die. Combinations of siUcas, com starch, talc (qv), magnesium stearate, and high molecular weight poly(ethylene glycols) are used. Most lubricants are hydrophobic and may slow down disintegration and dmg dissolution. 

Vinyl Acetate—Ethylene Copolymers. In these random copolymers, the ratio of ethylene to vinyl acetate (EVA) is varied from 30—60%. As the vinyl acetate content increases, the oil and heat resistance increases. With higher ethylene content the physical strength, tensile, and tear increases. The polymers are cured with peroxide. The main properties of these elastomers include heat resistance, moderate oil and solvent resistance, low compression set, good weather resistance, high damping, exceUent o2one resistance, and they can be easily colored (see Vinyl polymers, poly(VINYL acetate)). 

EPDM is a terpolymer of ethylene, propylene, and a small amount (<10%) of an unsaturated diene third monomer to provide a cure site. Unlike the elastomers previously discussed, the unsaturation in EPDM is not in the main chain, but it is pendent to the chain. Peroxide cure gives superior aging resistance and low compression set. 

In contrast to other polymers the resistance to water permeation is low due to the hydrolysis of the poly(vinyl acetate) (163,164). Ethylene copolymers have been developed which have improved water resistance and waterproofness. The polymer can be used in the latex form or in a spray-dried form which can be preblended in with the cement (qv) in the proper proportion. The compressive and tensile strength of concrete is improved by addition of PVAc emulsions to the water before mixing. A polymer-soHds-to-total-soHds ratio of ca 10 90 is best. The emulsions also aid adhesion between new and old concrete when patching or resurfacing. 

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