Refrigeration – Cryogenic treatment of gas or gas mixture – Liquefaction
Reexamination Certificate
1999-03-23
2001-03-06
Doerrler, William (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Liquefaction
C062S912000, C062S913000, C062S613000
Reexamination Certificate
active
06196021
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the manufacture of merchant liquid nitrogen, oxygen, argon, carbon monoxide and plant air utilizing the refrigeration capacity of high pressure gas expansion.
BACKGROUND
Traditionally industrial gases used in larger quantities as a utility have been compressed and sent down pipelines under high pressure to transport the gas to one or more industrial gas customers. The high pressure in the pipeline is used for transport and gas storage. When the gas has arrived at it's use point, the pressure of the industrial gas is reduced by passing it through one or more control valves and/or pressure regulators to it's final pressure for consumption. Typically, one or more of the industrial gas customers will need the gas at a much lower pressure than is required by the transportation pipeline. The available energy and the chilling effect from the reduction in the pressure of the industrial gas to be consumed is wasted in the control valves and pressure regulators for the gas sent to the customers. Furthermore, due to the nature of the pipeline controls, some of the industrial gas manufactured and compressed into the pipeline must be vented to the atmosphere through control valves and pressure regulators when the customer demand does not closely match the design capacity of the pipeline compressors. Centrifugal pipeline compressors, due to seasonal cooler ambient temperatures also experience large increases in capacity. The available energy and chilling capacity in this gas is also wasted.
While industrial gas companies have compressed industrial gas into merchant liquid units for many years, none have attempted to recover the potential merchant capacity inherent in the high pressure transportation pipelines supplying lower pressure industrial gas customers. The letdown liquefaction units described herein will opportunistically take advantage of the ability of the pressure reduction already occurring to make merchant liquid products, which include liquid nitrogen, liquid oxygen, liquid air, liquid carbon monoxide and liquid argon.
SUMMARY OF THE INVENTION
While a number of industrial gas companies have taken advantage of excess capacity, pressure reduction inside their air separation units to make extra merchant liquid gases, none have utilized the inherent capacity of pressure letdown stations outside the air separation unit cold boxes as in the present invention. The present invention is a recognition of the need to utilize such capacity of the pressure letdown stations to make such extra merchant liquid gases.
Among the objects and advantages of the present invention is to provide systems for producing merchant liquid gases such as nitrogen, oxygen, argon, carbon monoxide and plant air by employing the refrigeration capabilities of higher pressure industrial gas expansion, plant air expansion and/or natural gas expansion, and the energy recovered from letting down pressure through a letdown liquefaction process instead of a control valve or a pressure regulator.
It is among the further objects and advantages of the present invention to provide systems for producing liquid merchant gases with reduced power consumption by recovering both refrigeration and energy from the high pressure industrial gas stream.
An additional object and advantage of the present invention to provide systems for producing liquid merchant gases with additional liquid reflux generated by the inventive novel systems that increases the amount of product argon and oxygen produced in an air separation unit.
A further object and advantage of the present invention is to provide systems for producing liquid merchant gases with reduced capital expenditure resulting from recovering both refrigeration and energy from an industrial gas stream.
An additional object and advantage of the present invention is to provide systems for producing liquid merchant gases that utilize excess gaseous production capacity under pressure which is currently wasted by venting to atmosphere. The systems take advantage of overcapacity commonly found in the industrial gas business.
An additional object and advantage of the present invention is to provide systems for producing liquid merchant gases that provide supplemental storage capacity to the transport pipelines as liquid product.
A system for recovering refrigeration and energy from a relatively high pressure air or an air component gas supplied to a letdown station having a lower pressure output stream according to the present invention comprises heat exchanger means for receiving and cooling a pressurized air or air component gas and first expander means responsive to cooled pressurized gas at an output of the heat exchanger means applied thereto for expanding and further cooling the pressurized gas and for supplying a first portion of the further cooled pressurized gas to said heat exchanger means for the cooling of the received pressurized gas and for liquefying a second portion of the further cooled pressurized gas.
The heat exchanger means preferably has an input for receiving the pressurized air or gas upstream the letdown station and an output for supplying the first portion downstream the letdown station and storage means for storing the second portion.
One embodiment includes separator means responsive to the expanded cooled gas for separating the first and second portions.
A further embodiment further includes an air separation means and means for supplying a third portion of the liquefied gas to the air separation means for assisting in separating air into component gases.
The pressurized gas is preferably selected from the group consisting of air, nitrogen, argon, carbon monoxide and oxygen.
The pressurized gas is air in a further embodiment and further includes adsorbing means for drying and removing carbon dioxide from the pressurized air and for supplying the dried air to the heat exchanger means.
A further embodiment includes means for regenerating the adsorbing means with the first portion of the gas outputted from the heat exchanger means.
A still further embodiment includes means coupled to the expander means for generating power. Preferably a further embodiment includes compressor means coupled to the expander means for compressing at least one of the received gas applied to the heat exchanger means and supplied first portion.
A preferred embodiment further includes means responsive to pressurized natural gas applied to an input thereto for cooling applied natural gas and applying the cooled natural gas to the heat exchanger means for cooling the air or air component.
In a still further embodiment, means are provided for dividing the pressurized natural gas into a first relatively large stream and a relatively smaller second stream, the heat exchanger means comprising cascaded heat exchangers, a first portion of the cascaded heat exchangers for successively cooling and liquefying the smaller second stream, second expander means for expanding and cooling the natural gas larger first stream at an output of a second portion of the heat exchangers and for applying the expanded cooled natural gas first larger stream to a third portion of the cascaded heat exchangers for cooling the natural gas second smaller steam, and means for applying the liquefied natural gas to the first portion of the cascaded heat exchangers for cooling the smaller second stream and for applying the pressurized air or air component gas to a fifth portion of the heat exchangers including the first portion of the cascaded heat exchangers for cooling the air or air component by the cooled natural gas.
Preferably separation means are included for separating cold vapor from liquid in the liquefied air or air component gas, and means for applying the cold vapor to the fifth portion of heat exchangers for cooling the air or air component gas.
In a further embodiment, the first expander means is for expanding and liquefying a portion of the air or air component at the output of a sixth portion of the cascaded heat exchangers, the means for sepa
Carella Byrne Bain Gilfillan
Doerrler William
Squire William
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