Refrigeration – Cryogenic treatment of gas or gas mixture – Liquefaction
Patent
1994-12-02
1996-07-16
Capossela, Ronald C.
Refrigeration
Cryogenic treatment of gas or gas mixture
Liquefaction
62621, F25J 300
Patent
active
055355943
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the cooling of fluids, and applies particularly to the liquifying of natural gas. It concerns in the first place a process for cooling a fluid, especially for liquifying natural gas, of the incorporated integral cascade type, in which a coolant mixture composed of constituents of different volatilities is compressed in at least two stages and after at least each of the intermediate compression stages the mixture is partially condensed, at least some of the condensed fractions, as well as the high pressure gas fraction being cooled, then being depressurised, put into a heat exchange relation with the fluid to be cooled, and then compressed again.
The pressures dealt with below are absolute pressures.
The liquifying of natural gas using a cooling cycle called "incorporated cascade" utilising a mixture of liquids has long been proposed.
The coolant mixture is constituted by a certain number of fluids which include, among others, nitrogen and hydrocarbons such as methane, ethylene, ethane, propane, butane, pentane, etc.
The mixture is compressed, liquified then supercooled at the high pressure of the cycle which generally lies between 20 and 50 bars. This liquifying can be put into effect in one or several stages with the condensed liquid being separated at each stage.
The liquid or liquids obtained is or are, after supercooling, depressurised to the low pressure of the cycle, generally lying between 1.5 and 6 bars, and vaporised in counter current with the natural gas to be liquified and the cycle gas to be cooled.
After reheating to about ambient temperature, the coolant mixture is once again compressed to the high pressure of the cycle.
For the operation to be possible it is necessary to have available a fluid capable of condensing at ambient temperature at the high pressure of the cycle. This poses a particular difficulty because the mixture and the pressures are generally optimized for the cold part of the liquifying installation and do not lend themselves well to a cooling which performs equally well in the hot part, that is to say lying between the ambient temperature (generally of the order of +30.degree. C. to +40.degree. C. in natural gas production regions) and an intermediate temperature of the order of -20.degree. C. to -40.degree. C.
Thus numerous existing installations require, for the hot part, a separate cooling cycle of propane or a propane-ethane mixture. Thus a relatively low consumption of specific energy is obtained, but at the price of a large increase in the complexity and cost of the installation.
SUMMARY OF THE INVENTION
The object of the invention is to eliminate the separate cooling cycle, and thus to utilise a single compressor group, that is to say a so-called "integral incorporated cascade" cooling cycle, in such a way as to permit a specific energy of the process to be obtained with, at the same time, a relatively reduced investment.
To this effect, the object of the invention is a cooling process of the type mentioned above, characterised in that the gas issuing from the penultimate compression stage is distilled in a distillation apparatus the head of which is cooled with a liquid having a temperature significantly lower than the ambient temperature, in order to form on one hand the condensate of this penultimate stage, and on the other hand a vapour phase which is delivered to the last compression stage.
In the interests of clarity, the "ambient temperature" will be defined as the thermodynamic reference temperature corresponding to the temperature of the cooling fluid (notably water) available on the site and utilised in the cycle, increased by the temperature difference, fixed by construction, at the exit of the machinery of the cooling apparatus (compressors, heat exchangers, etc.). In practice, this difference is in the region of 3.degree. C. to 10.degree. C., and preferably of the order of 5.degree. to 8.degree. C.
It will henceforth equally be noted that the cooling temperature at the head of the distillat
REFERENCES:
patent: 3747359 (1973-07-01), Streich
patent: 4274849 (1981-06-01), Garier et al.
patent: 4334902 (1982-06-01), Paradowski
patent: 4339253 (1982-07-01), Caetani et al.
patent: 4586942 (1986-05-01), Gauthier
patent: 4809154 (1989-02-01), Newton
Capossela Ronald C.
Gaz de France (Service National)
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