Refrigeration, compression/absorption

The physical processes by which natural gas liquids are recovered include phase separation, cooling, compression, absorption, adsorption, refrigeration, and any combination of these. Obviously the definition already stated excludes refinery light volatiles produced by the destructive decomposition of heavy petroleum fractions and it also excludes liquids that may be produced synthetically from natural gas. These distinctions are of economic importance in considering our basic energy reserves. Both the refinery volatiles and the synthetic liquids represent conversion products from other hydrocarbons and the conversion is usually attended by a considerable loss. Thus it has been stated that only about 47% (17) of the energy of natural gas is realized in the liquid hydrocarbon products of the Fischer-Tropsch type of synthesis. 

Casinghead gasoline the liquid hydrocarbon product extracted from casinghead gas (q.v.) by one of three methods compression, absorption, or refrigeration see also Natural gasoline. 

Compression Refrigeration 224 Refrigerants 226 Absorption Refrigeration 229 Cryogenics 229 References 229... 

The principle of the heat pump, which is the same as that involved in the refrigeration operation, has been known for over 100 years. In the last four decades, heat pump applications have been limited only by economics. Among many types of heat pumps (e.g., vapor compression, absorption, ejector, Brayton cycle, and thermoelectric), only the first found wide application because of its high effideucy and relatively simple construction. 

L. Kairouani, E. Nahdi. Cooling performance and energy saving of a compression -absorption refrigeration system assisted by geothermal energy. App. Th. Eng. 26(2-3), 2006,288-294. 

J. Femandez-Seara, J. Sieres, M. Vazquez. Compression-absorption cascade refrigeration... 

FIGURE 11.20 Technological scheme for the purification of natural gas from sulphur components with concurrent production of methanol by the DMTM (1) gas compression and heating unit, (2) reactor unit, (3) air compression unit, (4) separation unit, (5) rectification unit, (6) receptacle for methanol, (7) receptacle for vat residue, (8) ammonia refrigerator, (9) absorption column, (10) raw gas source, (11) regeneration column, (12) hydrogen sulphide utilization unit, (13) pump, (14) sweet gas consumer. 

Condensable hydrocarbon components are usually removed from gas to avoid liquid drop out in pipelines, or to recover valuable natural gas liquids where there is no facility for gas export. Cooling to ambient conditions can be achieved by air or water heat exchange, or to sub zero temperatures by gas expansion or refrigeration. Many other processes such as compression and absorption also work more efficiently at low temperatures. 

Natural gas Hquids are recovered from natural gas using condensation processes, absorption (qv) processes employing hydrocarbon Hquids similar to gasoline or kerosene as the absorber oil, or soHd-bed adsorption (qv) processes using adsorbants such as siHca, molecular sieves, or activated charcoal. Eor condensation processes, cooling can be provided by refrigeration units which frequently use vapor-compression cycles with propane as the refrigerant or by... 

Conventional refrigeration is based on the evaporation of a refrigerant. The evaporator produces cooling, the compressor generates high-pressure energy, and the condenser rejects heat to the environment. An absorption machine differs from a vapor compressor only in the way the refrigerant is compressed from the evaporator to the condenser. 

The term refrigeration refers to the gas coming into contact with evaporator coils on a dx vapor-compression cycle, coils on an absorption cycle, vortex... 

Vapor compression uses the highest form of energy, namely electrical energy. In absorption refrigeration, the energy input is any source of heat (e.g., electrical energy, bottled gas, kerosene, or solar energy). 

Refrigerant temperatures greater than 32°F suggest the steam jet or lithium bromide absorption system. Between 30°F and —40°F, the ammonia-water absorption or a mechanical compression system is indicated. At less than —40°F, a mechanical compression is used, except in special desiccant situations. The economics of temperature level selection will depend on utility (steam, power) costs at the point of installation and the type of pay-out required, because in some tonnage ranges, the various systems are competitive based on first costs. 

Compression refrigeration cycles are by far the most common and absorption refrigeration only applied in special circumstances. 

The features of absorption refrigeration are that there is a low power requirement relative to compression... 

When should absorption refrigeration be used rather than compression refrigeration There are two important criteria. The first is that absorption refrigeration can only be used... 

Absorption refrigeration is much less common than compression refrigeration. Absorption refrigeration powers by compressing the refrigerant fluid dissolved in a solvent using a pump. 

The thermal compression or absorption refrigeration systems are less common. They do not require a compressor. Their energy source is steam, natural gas, or waste heat. This system requires much more cooling water than the previous one, but may be economical if a large amount of waste heat is available.21 See references 20 and 21 to determine heat and cooling water requirements. 

How does an absorption refrigeration system differ from a vapor compression refrigeration system ... 

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