Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
  • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
  • B01D53/0454—Controlling adsorption

Definitions

• This invention relates to apparatus for separating gases from a gaseous mixture and which apparatus includes a unit comprising a vessel containing a separation medium which reversibly retains a first constituent of the mixture preferentially with respect to a second constituent of the mixture.
• a unit comprising a vessel containing a separation medium which reversibly retains a first constituent of the mixture preferentially with respect to a second constituent of the mixture.
• Such a unit is hereinafter referred to as being of the kind specified..
• the proportion of the first constituent in the gaseous phase is reduced . and the proportion of the second constituent in the gaseous phase is correspondingly increased.
• the resulting gaseous phase is called herein the product.
• Zeolites are examples of known separation media used in this way.
• the effectiveness of the separation medium of a unit of the kind specified falls substantially, owing to a cumulation of the first constituent, the effectiveness can be restored by allowing or causing the retention of the first constituent to be reversed, for example by purging the separation medium or by reducing the gas pressure to which the separation medium is subjected.
• separation includes partial separation which results in a change in the proportions of the constituents of ,a gaseous mixture.
• the invention has been developed in connection with apparatus, for separating nitrogen from air so as to provide a supply of oxygen, and the following description
• the kind specified has two pressure vessels and means operable automatically to bring the vessels into opera ⁇ tion alternately, such a unit being hereinafter referred to as a unit of the form specified.
• the arrangement is such that, when the material in one pressure vessel to
• the vessel 20 vent from the vessel to the atmosphere.
• the vessel may be purged by venting air through the vessel to atmos ⁇ phere.
• the vessel is then ready to be brought into operation again when the separation medium in the second .vessel has retained a substantial amount of nitrogen.
• the proportion of nitrogen remaining in the product obtained by treating air in a unit of the form specified depends upon the rate of flow of product from the unit.
• Units of the form specified are supplied in relatively small sizes for use in the home to provide a supply of oxygen for medical purposes. Such units are
• apparatus comprising control means $ a product discharge passage and a plurality of units of the kind specified, wherein each unit of the kind specified has an inlet for the mixture and a product outlet for the product, all of the units which constitute said plurality of units are adapted to deliver the product from their respective product outlets to the product discharge passage and wherein the control means is operable to vary the number of said units in operation at any one time to deliver the product to the product discharge passage in accordance with the demand for the product made on the apparatus.
• a method of separating a gaseous mixture wherein the mixture is fed through a selected number of units of the kind specified to a common dis- charge passage and the number of units of the kind specified through which the mixture passes concurrently is varied according to conditions in the discharge passage.
• provision may be made for purging each of the vessels of each separator unit with product from the other vessel of that unit after the vessel has been vented to atmosphere and before the vessel is reconnected with the product discharge passage.
• FIGURE 1 shows the apparatus diagra maticallyj and t- FIGURE 2 is a diagrammatic illustration of a gas- separating unit of the apparatus of Figure 1.
• the apparatus shown in the accompanying drawings comprises an air reservoir 10, with which there are connected the outlets of a number of electrically Q energisable compressors, two of which are shown at 11 and 12 respectively. A larger number of compressors may be provided.
• control means which includes a
• transducer 13 responsive to changes in .the pressure within the air reservoir 10 to provide an electrical output signal which represents the air pressure.
• One suitable form of transducer provides an output signal having a voltage which represents the air pressure.
• the processor 14 is arranged to control operation of
• the processor 14 provides an alarm signal which operates an audible and/or visible alarm.
• the processor 14 is also provided along lines 16 with signals representing respective output pressures of the compressors 11 and 12. If, when a particular compressor is energised, its output pressure does not promptly rise to a predetermined threshold, the processor again provides the alarm signal. Malfunction of one compressor may result in the pressure in the reservoir 10 being somewhat below the pressure which would be main- tained if that compressor was functioning perfectly but, provided the total number of compressors is adequate, malfunction of a single compressor will not result in the pressure in the reservoir 10 falling to the predetermined minimum value. The pressure in the reservoir can be maintained above this minimum value when a compressor is taken out of service for maintenance or replacement.
• the apparatus further comprises a number of separator units, of which three are shown in the drawing at 17, 18 and 19 respectively.
• Each of these units has a respective air inlet connected with the reservoir 10. This connection may include a common pipe 20 and the separator units may be remote from the reservoir.
• Each of the separator units also has a respective product outlet, these being connected with a common product discharge passage which includes an oxygen reservoir 21 having an outlet 22 and an oxygen line 23 leading from the separator units to the reservoir 21.
• This unit comprises two pressure vessels 24, 25 containing a Zeolite or a mixture of Zeolites which constitutes a molecular sieve for retaining nitrogen.
• the vessels 24 and 25 have respective inlets connected to
• valve 26 and respective outlets, spaced from the inlets by the Zeolite, connected with a valve 27.
• the valve 26 has a port connected with the air line 20 and further ports open to the atmosphere.
• the valve can be set in a selected one of three alternative condi-
• the valve 27 also can be set in a selected one of three alternative conditions. In the first of these, the outlet of the vessel 24 is connected with the oxygen line
• the valve 27 may be so arranged that, when in its first condition, oxygen can flow from the outlet of the vessel 24 to both the oxygen line 23 and the vessel 25, in order to purge the vessel 25 with oxygen.
• " 30 when in its third condition, this modified valve would permit flow of oxygen from the outlet of the vessel 25 through the vessel 24 to the atmosphere, in addition to flow from the outlet of the vessel 2S to the oxygen line 23.
• this modified valve in place of the valves 26 and 27, there may be
• 35 provided separate valves for controlling the inlets and outlets of the vessels 24 and 25, in order that purging of a vessel with oxygen flowing from the outlet of the
• OM other vessel can be confined to a period shorter than the period during which oxygen flows from- that other vessel to the oxygen line.
• the controller 28 forms a part of control means which further includes a transducer 29 associated with the oxygen reservoir 21 and adapted to provide an electrical demand signal representing the pressure of oxygen in the reservoir.
• This signal is processed in a processor 30 which provides signals to the controllers of 0 the separator units 17, 18 and 19.
• the arrangement is such that, when the pressure in the oxygen reservoir 21 rises to a predetermined maximum value, the pressure vessels of all of the separator units are isloated from
• the processor 30 When the pressure within the reservoir falls to a first threshold value, the processor 30 provides a signal which turns on one of the separator units, that is to say communication is established between one pressure vessel o of this unit and both the air line 20 and the oxygen line 23. Air then flows into the pressure vessel and oxygen flows from the pressure vessel to the reservoir 21. Whilst that separator unit remains in its On 1 condition, the controller 28 of the unit causes the condition of the valves of that unit to change cyclically between the first and third conditions so that the pressure vessels are used alternately for separating nitrogen from the air. Typically, the cycle time is less than one minute.
• the processor 30 If the pressure in the oxygen reservoir 21 continues to fall and reaches a second threshold value, the processor 30 provides a signal to set a further one of the separator units in an 'on' condition. If the pressure in the oxygen reservoir continues to fall, this procedure is repeated a number of times depending on the number of separator units provided until a predetermined minimum pressure is reached, when the processor 30 provides an alarm signal. It will be understood that the
• OMPI _ reservoir can continue to supply oxygen through its outlet 22 to points of use even when the minimum pressure has been reached.
• each of the transducers 13 and 29 there may be provided a number of pressure-actuated switches, each of these switches providing a demand signal to the associated processor when the pressure in the reservoir concerned falls below a particular value associated with that switch.
• the processor 30 There is provided to the processor 30 along a line 31 from each separator unit 17, 18, 19, when that separator unit is in an 'on* condition, a signal indicat ⁇ ing that cycling of the valves is taking pl.ace.
• the processor 30 monitors these signals and, if cycling of a separator unit ceases whilst that unit is required to be 'on'i the processor provides an alarm signal and also provides a signal which sets the valves of that unit in their second conditions, isolating the pressure vessels of the unit from the air and oxygen lines.
• the analyser 32 there is connected with the oxygen line 23 an analyser 32 through which a sample of gas is bled from the oxygen line and tested for oxygen content.
• the analyser may be a known device, for example one which responds to the paramagnetic character of oxygen.
• the analyser 32 provides a signal to the processor 30 and the latter responds by providing an alarm sign.al and by turning, on all of the separator units. This has the effect of decreasing the rate of product output . from each separator unit and thereby increasing the concentration of oxygen in the gas leaving each separator unit.
• Non-return valves may be provided to prevent reverse flow at various positions in the separator unit. .
• the oxygen reservoir 21 has a volume many times " greater than that of the oxygen line 23 and normally contains sufficient oxygen for several hours supply.
• concentration of oxygen in the gas which flows along the oxygen line 23 can be maintained within a narrow range, for example within the range 94? to 98?.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oxygen, Ozone, And Oxides In General (AREA)
• Separation Of Gases By Adsorption (AREA)

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• 1982
  • 1982-12-01 WO PCT/GB1982/000340 patent/WO1983001908A1/en not_active Ceased
  • 1982-12-01 EP EP19830900056 patent/EP0096685A1/de not_active Withdrawn
  • 1982-12-01 GB GB08320667A patent/GB2122508B/en not_active Expired

Non-Patent Citations (1)

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