Production of pure nitrogen
AssigneeCostain Petrocarbon Limited
InventorRonald D. Openshaw
Life of this patent
Estimating the term…
Abstract
A process and apparatus for the production of nitrogen from air by the cryogenic fractionation of the air at superatmospheric pressure and which permits the production of variable quantities of nitrogen from a constant supply of air at superatmospheric pressure by periodically distilling less than all of the air which is supplied at superatmospheric pressure and work expanding a stream of air at superatmospheric pressure provided from the balance of said supply whereby to produce additional refrigeration for the process, and recovering condensed nitrogen vapor thereby formed in excess of that required for reflux.
Claims17
An Apparatus for the production of nitrogen by compressing a supply of air to superatmospheric pressure and after removing water vapour and carbon dioxide cooling it and subjecting the compressed air to separation by cryogenic distillation wherein the condensation of a portion of the nitrogen vapour recovered overhead to provide reflux for the distillation and optionally some liquid nitrogen as product is effected by indirect heat exchange with evaporating oxygen-containing liquid residue of the distillation and refrigeration for the process is provided by work expanding evaporated oxygen-containing liquid residue recovered from the reflux condenser, said apparatus further includes means designed for regulating the output of nitrogen in accordance with a variable demand of nitrogen gas by increasing the output of liquid nitrogen in periods of reduced demand for nitrogen gas, said means comprising valve, conduit and work expansion means for periodically diverting from the distillation a portion of the air supplied at superatmospheric pressure, work expanding it and passing the work-expanded stream in indirect heat exchange with the feed to the distillation to provide additional refrigeration and means for recovering and optionally storing the excess condensed nitrogen vapour so obtained.
A process for the production of nitrogen gas and liquid from air comprising:
- cooling and distilling a supply of air at superatmospheric pressure to produce a nitrogen rich vapor stream and an oxygen-containing liquid residue;
- recovering a first portion of said vapor as product nitrogen gas;
- condensing a second portion of said vapor by indirect heat exchange with oxygen-containing liquid residue which has been expanded to an intermediate pressure, thereby providing reflux for the distillation and optionally some liquid nitrogen as product and providing refrigeration for the process by work-expanding evaporated oxygen-containing liquid residue recovered from said indirect heat exchange;
- regulating the output of nitrogen gas and liquid in accordance with a variable demand of nitrogen gas whereby the output of liquid nitrogen is increased in periods of reduced demand for nitrogen gas by periodically distilling less than all of the air which is supplied at superatmospheric pressure and work-expanding a stream of air at superatmospheric pressure provided from the balance of said supply whereby to produce additional refrigeration for the process;
- and
- recovering condensed nitrogen vapor thereby formed in excess of that required for reflux.
An apparatus for the production of nitrogen gas and liquid from air which comprises:
- a distillation column;
- means for introducing a flow of compressed air into said distillation column whereby a nitrogen-rich gas stream is recovered at the top of the distillation column and an oxygen-containing liquid stream is recovered at the bottom of the distillation column;
- a valve means;
- means for introducing at least a portion of said oxygen-containing liquid stream recovered from the bottom of the distillation column to the valve means for expansion therein;
- means for effecting an indirect heat exchange between a portion of the nitrogen-rich gas stream recovered from the top of the distillation column and the expanded oxygen-containing liquid stream recovered from the value means whereby the expanded oxygen-containing liquid stream is evaporated and the portion of the nitrogen-rich gas stream recovered from the top of the distillation column is condensed and returned to the distillation column as reflux and a portion thereof optionally recovered as a liquid nitrogen product;
- a work expansion means;
- means for passing the evaporated oxygen-containing liquid stream through the work expansion means;
- means for passing the work-expanded oxygen-containing stream in indirect heat exchange with the flow of compressed air to be introduced into the distillation column to refrigerate the flow of compressed air, and recovering the work-expanded oxygen-containing stream;
- means for recovering a portion of the nitrogen-rich gas stream recovered at the top of the distillation column as a gaseous nitrogen product;
- and
- means designed for regulating the output of nitrogen gas and liquid in accordance with a variable demand for nitrogen gas whereby the output of liquid nitrogen is increased in periods of reduced demand for nitrogen gas, said means including:
- means for periodically diverting a portion of the flow of compressed air to be introduced into the distillation column, combining the diverted compressed air stream with the evaporated oxygen-containing liquid stream, passing the combined stream through the work expansion means, passing the combined work-expanded stream in indirect heat exchange with the flow of compressed air to be introduced into the distillation column to refrigerate the compressed air, and recovering the combined stream.
An apparatus for the production of nitrogen gas and liquid from air which comprises:
- a distillation column;
- means for introducing a flow of compressed air into said distillation column whereby a nitrogen-rich gas stream is recovered at the top of the distillation column and an oxygen-containing liquid stream is recovered at the bottom of the distillation column;
- a valve means;
- means for introducing at least a portion of said oxygen-containing liquid stream to the valve means for expansion therein;
- means for effecting an indirect heat exchange between a portion of the nitrogen-rich gas stream recovered from the top of the distillation column and at least a portion of the oxygen-containing liquid stream recovered from the bottom of the distillation column whereby the oxygen-containing liquid stream is evaporated and the portion of the nitrogen-rich gas stream recovered from the top of the distillation column is condensed and returned to the distillation column as reflux and a portion thereof optionally recovered as a liquid nitrogen product;
- a first work expansion means;
- means for passing the evaporated oxygen-containing stream through the first work expansion means;
- means for passing the work-expanded oxygen-containing liquid stream in indirect heat exchange with the flow of compressed air to be introduced into the distillation column to refrigerate the flow of compressed air, and recovering the work-expanded oxygen-containing stream;
- means for recovering a portion of the nitrogen-rich gas stream recovered at the top of the distillation column as a gaseous nitrogen product;
- and
- means designed for regulating the output of nitrogen gas and liquid in accordance with a variable demand for nitrogen gas whereby the output of liquid nitrogen is increased in periods of reduced demand for nitrogen gas, said means including:
- means for periodically diverting a portion of the flow of compressed air to be introduced into the distillation column, passing the diverted stream of compressed air through a second work expansion means, combining the diverted stream of compressed air which has been work-expanded with the work-expanded oxygen-containing stream and passing the combined stream in indirect heat exchange with the flow of compressed air to be introduced into the distillation column to refrigerate the flow of compressed air, and recovering the combined stream.
Dependencies are inferred from the claim text.