Separation method and apparatus
AssigneePraxair Technology, Inc.
InventorsHenry Edward Howard, Richard John Jibb
Life of this patent
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Abstract
Separation method and apparatus for separating a gaseous mixture, for example, air, in a cryogenic rectification plant in which a compressed stream is divided into subsidiary streams that are extracted from a main heat exchanger of the plant at higher and lower temperatures. The two streams are then combined and expanded in a turboexpander to generate refrigeration for the plant. The flow rates of the two streams are adjusted to control inlet temperature of a turboexpander supplying plant refrigeration and to minimize potential deviation of the turboexpander exhaust from a saturated vapor state. Control of the expansion ratio can advantageously be applied to allow variable liquid production from the rectification plant.
Claims13
A separation method comprising:
- separating a compressed gaseous mixture within a cryogenic rectification plant by purifying the compressed gaseous mixture cooling the compressed gaseous mixture by indirect heat exchange with mixture component streams after having been purified and rectified within a separation unit having at least one column to produce the mixture component streams;
- discharging at least one liquid stream from the separation unit enriched in one mixture component of the gaseous mixture;
- dividing at least part of the compressed gaseous mixture after partial cooling thereof during the indirect heat exchange into a first subsidiary stream and a second subsidiary stream and withdrawing the first subsidiary stream and the second subsidiary stream from the indirect heat exchange at higher and lower temperatures, respectively;
- combining the first subsidiary stream and the second subsidiary stream after withdrawal from the indirect heat exchange to produce a combined stream;
- expanding at least part of the combined stream with the performance of work within a turboexpander to supply refrigeration to the cryogenic rectification plant and introducing at least part of an exhaust of the turboexpander into the separation unit;
- and
- controlling temperature of the combined stream such that the exhaust stream is at least at about its saturation temperature by controlling flow rates of the first and second subsidiary streams.
A separation apparatus comprising:
- at least one compressor to compress a gaseous mixture, thereby to produce a compressed stream and a purification unit to purify the compressed stream;
- a main heat exchanger connected to the purification unit having flow passages for subjecting the compressed stream to indirect heat exchange with mixture component streams;
- a separation unit having at least one distillation column to rectify the gaseous mixture contained in the compressed stream, thereby to produce the mixture component streams;
- the separation unit having a liquid outlet to discharge a liquid stream enriched in one mixture component of the gaseous mixture;
- the main heat exchanger connected to the separation unit such that the mixture component streams flow from cold to warm ends thereof;
- the main heat exchanger configured to discharge a first subsidiary stream and a second subsidiary stream at higher and lower temperatures, respectively, the first subsidiary stream and the second subsidiary stream made-up of the gaseous mixture;
- a turboexpander to expand at least part of a combined stream with the performance of work to supply refrigeration, the combined stream formed from a mixture of the first subsidiary stream and the second subsidiary stream and the turboexpander connected to the separation unit such that at least part of an exhaust stream of the turboexpander is introduced into the at least one distillation column;
- and
- a flow control network configured to mix the first subsidiary stream and the second subsidiary stream and thereby to form the combined stream, the flow control network having valves to control flow rates of the first subsidiary stream and the second subsidiary stream and therefore, the temperature of the combined stream to ensure that the exhaust stream from the turboexpander has an outlet temperature at least at about equal to saturation temperature.
Dependencies are inferred from the claim text.