Method and apparatus for gas liquefaction with plural work expansion of feed as refrigerant and air separation cycle embodying the same
First Claim
1. In a method of liquefying a low-boiling gas, in which said gas is compressed to a high pressure, is cooled in heat exchange means and is expanded to a low pressure to liquefy at least a portion of the same;
- the improvement comprising compressing a portion of said gas to an intermediate pressure between said high and low pressures, isentropically expanding said intermediate pressure gas at a first temperature and using the isentropically expanded gas to cool a relatively warm portion of said heat exchange means and then recycling said isentropically expanded gas, isentropically expanding a portion of said high pressure gas at a second temperature and using the same to cool a relatively cool portion of said heat exchange means and then again isentropically expanding at least some of the latter portion of gas at a third temperature to said low pressure and returning the same through the heat exchange means to cool the heat exchange means and then recycling the latter gas, said first temperature being higher than said second temperature and said second temperature being higher than said third temperature.
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Abstract
A method of liquefying a low-boiling gas, in which gas is compressed to a high pressure, is cooled in heat exchange structure and is isenthalpically expanded to condense a portion of the same to liquid. The liquid being separated from residual gas and the residual gas is used to cool the heat exchange structure and is then recycled. A portion of the gas is compressed to an intermediate pressure between the high and low pressures, is isentropically expanded at a first temperature and is used to cool a relatively warm portion of heat exchange structure and is then recycled. A portion of the high pressure gas is isentropically expanded at a second temperature and used to cool a relatively cool portion of the heat exchange structure and then again isentropically expanded at a third temperature to that low pressure and returned through the heat exchange structure to cool the same and is then recycled. That first temperature is higher than the second temperature and that second temperature is higher than the third temperature. The gas is preferably nitrogen. The cycle can be part of an air separation unit, whose low pressure nitrogen product is make-up for the liquefaction cycle and whose high pressure nitrogen product is merged with the low pressure cycle gas.
17 Citations
39 Claims
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1. In a method of liquefying a low-boiling gas, in which said gas is compressed to a high pressure, is cooled in heat exchange means and is expanded to a low pressure to liquefy at least a portion of the same;
- the improvement comprising compressing a portion of said gas to an intermediate pressure between said high and low pressures, isentropically expanding said intermediate pressure gas at a first temperature and using the isentropically expanded gas to cool a relatively warm portion of said heat exchange means and then recycling said isentropically expanded gas, isentropically expanding a portion of said high pressure gas at a second temperature and using the same to cool a relatively cool portion of said heat exchange means and then again isentropically expanding at least some of the latter portion of gas at a third temperature to said low pressure and returning the same through the heat exchange means to cool the heat exchange means and then recycling the latter gas, said first temperature being higher than said second temperature and said second temperature being higher than said third temperature.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
- 22. In apparatus for liquefying a low-boiling gas, in which said gas is compressed to a high pressure, is cooled in heat exchange means and is expanded to a low pressure to condense at least a portion of the same to liquid, the improvement comprising means for compressing a portion of said gas to an intermediate pressure between said high and low pressures, means for isentropically expanding said intermediate pressure gas at a first temperature and for using the isentropically expanded gas to cool a relatively warm portion of said heat exchange means and for then recycling said isentropically expanded gas, means for isentropically expanding a portion of said high pressure gas at a second temperature and for using the same to cool a relatively cool portion of said heat exchange means and for then again isentropically expanding at least some of the latter portion of gas at a third temperature to said low pressure and for returning the same through the heat exchange means to cool the heat exchange means and for then recycling the latter gas, said first temperature being higher than said second temperature and said second temperature being higher than said third temperature.
Specification