WO1987004946A1 - A gas concentrating method and plant - Google Patents

A gas concentrating method and plant Download PDF

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Publication number
WO1987004946A1
WO1987004946A1 PCT/FI1987/000020 FI8700020W WO8704946A1 WO 1987004946 A1 WO1987004946 A1 WO 1987004946A1 FI 8700020 W FI8700020 W FI 8700020W WO 8704946 A1 WO8704946 A1 WO 8704946A1
Authority
WO
WIPO (PCT)
Prior art keywords
gas
adsorbtion
tank
unit
air
Prior art date
Application number
PCT/FI1987/000020
Other languages
French (fr)
Inventor
Samuli Lehtinen
Original Assignee
A-Happi Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from FI860653A external-priority patent/FI76002C/en
Application filed by A-Happi Oy filed Critical A-Happi Oy
Priority to GB08819148A priority Critical patent/GB2207616A/en
Priority to BR8707581A priority patent/BR8707581A/en
Priority to HU871198A priority patent/HUT47455A/en
Publication of WO1987004946A1 publication Critical patent/WO1987004946A1/en
Priority to NO874242A priority patent/NO874242L/en
Priority to DK531787A priority patent/DK531787A/en

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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/106—Silica or silicates
    • B01D2253/108—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2256/00—Main component in the product gas stream after treatment
    • B01D2256/12—Oxygen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/40003—Methods relating to valve switching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/40083—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption
    • B01D2259/40086—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by using a purge gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/402—Further details for adsorption processes and devices using two beds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/41—Further details for adsorption processes and devices using plural beds of the same adsorbent in series

Definitions

  • the invention relates to a gas concentrating method according to the intro ⁇ ductory part of claim 1 and to a gas concentrating plant according to the introductory part of claim 5; especially for separation of oxygen out of air by means of adsorption.
  • the industrial manufacture of oxygen today is mainly carried out in two different ways: by means of distillation or by means of adsorption.
  • Oxygen is also separated out of air by means of a process known as selec ⁇ tive adsorption, which is based on the capability of a certain material, for example natural or synthetic zeolites with theoretical porosity size of 4 A, to hold different molecules, for example oxygen molecules size of which are about 3,8 A, of the air in various ways within its porosity by physical adhesion.
  • selec ⁇ tive adsorption a process known as selec ⁇ tive adsorption, which is based on the capability of a certain material, for example natural or synthetic zeolites with theoretical porosity size of 4 A, to hold different molecules, for example oxygen molecules size of which are about 3,8 A, of the air in various ways within its porosity by physical adhesion.
  • This kind of an adsorption process is usually carried out by so called pre ⁇ ssure swing adsorption - PSA, in which the adsorption material is revieved after every adsorption stage by leading through the adsorption material a regenerating gas flow opposing the feed gas flow to be adsorbed
  • the PSA-plant includes two tanks so that one tank is separating oxygen • whilst the other tank is being regenerated.
  • the equipment associated with the adsorption process has beeb described among others in US-patents 4194890 and 4263018 in GB-patent 2109266 and in Fl-patent application 843014.
  • the main objectives of the present invention are to eliminate the drawbacks and weaknesses associated with known separation methods and to effect a new type of gas adsorbtion plant for gas consentrating especially for producing oxygen out of air.
  • the invention is based on that genious insight that the plant includes as combination; means for compressing and feeding the air into the plant, first adsorbtion means for drying the compressed feed air, and second adsorbtion means for separating the preferred gas component out of the feed air; and that gas flows as well as the different parts of the plant are controlled and regulated by means of pneumatically operating elements.
  • the main advantages due to the present invention are, that the whole plant operates in all surrounding, also in humid and cold conditions, exactly and reliably, which assists the genious use of pneumatic logic and pneumatical ⁇ ly operating elements, and that by using the plant can be achieved an ess ⁇ entially higher attainability of oxygen content than by using plants accor ⁇ ding to the prior art.
  • pneuma ⁇ tic it is intended to mean elements purely operating pneumatically.
  • the power source can therefore be simply compressed air, that the control and regulation means include no electrical components in any form.
  • the control system is of integrated construction, the greater part of its components are arr- anged one one single circuit board which is closed in a sealed case.
  • hybrid circuit board technology in the control system can be achieved the adventages that several millions connections can be made and long work ⁇ ing life attained.
  • the benefit conferred by this solution is that the cont ⁇ rol system is protected from humidity and cold.
  • the require- ments for pneumatic hoses is reduced. Further it can be verified that the use of pneumatics does not cause any risk of sparking nor is electricity needed, whereby the use of the plant is safe.
  • the compressed feed air is dried by means of dual tank adsorbtion drier.
  • the operation of the plant is then fundamentally improved in comparison with earlier known solutions especially in humid conditions.
  • adsorbtion materi ⁇ als such as silica gel or in particular synthetic or natural zeolites.
  • natural zeolites can be mentioned as examples mordenite and morde- nite/clinoptilolite.
  • Suitable synthetics are for example A- and X-type natriumzeolites such as 5A and 13X.
  • zeolite molecular construction together with aluminium or natrium ions may appear also other metallic ions such as gallium or strontium ions.
  • the superior performance values mentioned above are all founded on the use of a dual tank adsorbtion drier in the upstream of the feed air flow of the plant.
  • the drier increases air consumption by about 10 %. which means only slight increase in operational costs when it is possible to increase the yield by about 50 % and at the same time the level of purity can be funda- mentally raised.
  • the output of the plant can be provided with three-way valve which acts as an input devi ⁇ ce for an dual pressure further processing unit which is either in low pre ⁇ ssure daytime use or in pressure boosting use by night for filling pressure bottles to be needed for peak consumption.
  • fig. 1 presents a general arrangement of the first preferred embodiment of the gas concentration plant for separating oxygen out of air
  • fig 2 is the logic drawing of the pneumatically operating valves of said first preferred embodiment
  • fig 3 presents the circuit diagram for the pneumatically operating valves of said first preferred embodiment
  • fig 4 presents a general arrangemang of the second preferred embodiment of the gas concentration plant for separating oxygen out of air
  • fig 5 is the logic drawing of the pneumatically operating valves of said second preferred embodiment
  • fig 6 presents the circuit diagram for the pneumatically operating valves of said second preferred embodiment
  • fig 7 presents shematically the unit for boosting the pressure of the produced oxygen.
  • the air is then led to an aftercooler 2 which may be included with compressor 1.
  • the moisture in the air begins to condensate for which reason condensate drain 3 is coupled to the aftercooler 2.
  • Air then led to a pressure vessel 4 the size of which is determined by the size and type of compressor 1.
  • Air is also condensed in the pressure vessel with cooling of the air so that ensure the faultness operation vessel 4 is provided with the second condensate drain 5.
  • Air is led from the vessel 4 through prefilter 6 for removing water droplets and through fine filter 7 for removing oil from the air into a dual tank type moisture adsorbing drier 14, 15.
  • the prefilter 6 and the fine filter 7 are provided correspondingly with condensate drain 8 and oil drain 9. If the compressor 1 is oil-free the fine filter 7 and drain 9 can be left out of the plant.
  • the compressor is oil lubricated oil separation from the air to be led into the drier 14, 15 is important for the reason that the effiency of the moisture adsorbing material dete ⁇ riorates and useful life essentially reduces if oil is allowed to pass there.
  • first main valve 10 and second main valve 11 correspondingly to one or other of the tanks 14 and 15 which both are filled with moisture adsorbing material such as silica gel or provided with a molecular screen.
  • the main valves 10 and 11 are controlled by microprocessor based programmable auto ⁇ mation 27 which consists according to the invention of a pneumatic logic. If the first tank (or tower) 14 is in drying stage the first main valve 10 stays open and the second main valve 11 connected to the second tank 15 is closed.
  • the second tank 15 is in a regenerating stage during which the moisture gathered there inside is removed.
  • the rege- neration valve 12 connected to the first tank 14 stays closed and regenera ⁇ tion valve 13 connected to the second tank 15 is open.
  • both the regeneration valve 12 and the regeneration valve 13 are connected through sound damper 17 corresp. 16 to open air.
  • the dried air passes through a check valve 20 to a filter 24 because check valves 18 and 21 are in the check direction.
  • the dried air also flows to the filter 24 but passes through the check valve 21 because the check val ⁇ ves 19 and 20 are in the check direction.
  • Said dried air flows to the fil— ter from the tanks 14 and 15 occur in turn whereby one of the tanks is in moisture adsorbing stage whilst the other tank in under regeneration.
  • a small part of the dried air advantageously 10...12 % in heatless types of drier and advantageously 2...4 % in a drier using heat, is used for regene ⁇ rating the other tank.
  • This quantity of dried air is regulated by means of the throttle 23 and is taken from the main dried air flow through filter 22.
  • the tank 15 If the tank 15 is under regeneration the dried air passes from the throttle 23 through the check valve 19, since the throttle 23 reduces the pressure and behind the check valve 18 the pressure is about 700 kPa.
  • the regene ⁇ ration air passes then into the tank 15, since behind the valve 21 the pressure is about 700 kPa and because on the other hand the outflow valve 13 at the bottom of the tank 15 is open and the main valve 11 closed.
  • the regeneration air thus rinses the tank 15t the flow direction being opposite to that adsorbtion flow occuring in the tank 14. In the regeneration the condensation is freed to atmosphere through the noutflow valve 13 and sound damper 16.
  • the pressure in the tank under adsorbtion is higher and essentially cons- tant (e.g. 700 kPa) and the pressure in the tank under regenation is lower decreaces (e.g. from 700 kPa to atmosphere).
  • the valve 13 is closed which inhibits the outflow from the tank 15 where- upon the tank 15 begins to pressurize.
  • both tanks have reached the same pressure the settings of the main valves 10 and 11 are changed over, that is the valve 10 is closed and valve 11 opened.
  • the air coming from the compressor 1 then begins to flow through the tank 15.
  • outflow valve 12 is opened, whereupon the pres- sure in .he tank 14 begins to fall and the regeneration can begin.
  • drying of the air can be continious by alternatively operating the tanks 14 and 15.
  • the function of the filter 24 is to remove from the dried air all dust etc. released into the dried air.
  • pressure reduction unit 25 pressure reduction unit 25 to reduce pressure of the feed air to a suitable value which is ad ⁇ vantageously about 500 kPa.
  • the feed air flow is then equalised in tank 26.
  • the feed air is led after the tank 26 to the dual tank gas adsorbing unit 34"
  • the inflow head of the gas adsorbing unit is correspondingly constructed to that of the dual tank moisture adsorbing unit.
  • the valves 28 and 29 are main valves which alter ⁇ natively allow passage of the feed air into the first tanks 34'or the second tank 35 which tanks are identical.
  • the exiting of nitrogen-rich exhaust gas flow from the tanks 34'and 35 is regulated by outflow valves 30 and 31.
  • the adsorbtion material is elected so that the through-flow of oxygen occurs faster than the flow of nitrogen.
  • suitable material are natural and synthetic zeolites porosity size of which do not exceed 4 A.
  • the main valve 31 of the second tank 35 is also open, from the beginning of the oxygen production, for a certain time typically between 5...10 seconds advantageously about 8 seconds, whereupon oxygen-rich gas is allowed to flow after the valve 36 through relief valve 41 into the second tank 35 and from there through the outflow valve 31 and sound damper 33 to atmosphere, thus extracting and rinsing the nitrogen-rich gas from the second tank 35.
  • oxygen-rich gas is allowed to flow after the valve 36 through relief valve 41 into the second tank 35 and from there through the outflow valve 31 and sound damper 33 to atmosphere, thus extracting and rinsing the nitrogen-rich gas from the second tank 35.
  • the exhaust of oxygen-rich gas through sound damper 33 is minimised.
  • the outflow valve 31 is closed whereupon outward blowing from the second tank 35 ends and its presurization with oxygen-rich gas begins.
  • the duration of the pressurization is typically between 5...10 seconds advanta ⁇ geously about 7 seconds, after which time the production of oxygen in the first tank 34'is interrupted by closing the valve 36 and at the same time the operation of the tanks 34'and 35 is changed over by opening the main valve 29 and by closing the main valve 28.
  • the second tank 35 then begins to pressurize on feed air inflowing through the main valve 29.
  • the outflow valve 30 is opened whereupon the first tank 34' begins to empty to atmosphere through sound damper 32, whereupon the nitrogen-rich gas is removed from the first tank 34'.
  • the pressure in the second tank 35 has attained its highest value, advantageously about 500 kPa, and at the same time the first tank 34'has emptied for repressurization.
  • the valve 37 is then opened whereby the oxygen production of the second tank 35 may begin.
  • the outflow valve 30 is held open whereby the first tank 34' is under regeneration. Thereafter the outflow valve 30 is closed after which the operation of the first tank 34' proceeds in the manner described above.
  • the duration of one cycle, that is from the begining of the adsorbtion sta ⁇ ge in one tank to the end of the regeneration stage in the other tank is typically between 50 to 100 seconds advantageously about 84 seconds as pre- sented in fig. 2.
  • the dried feed air is led to the single tank gas adsorption drier 34 for separating the oxygen
  • the inflow side of the tank 34 is similarly cons ⁇ compted to that in one of the drier tank 14 or 15.
  • the valve 28 is the main valve which controlls the passage of feed air into the adsorption tank 34 and the flow of nitrogen-rich exhaust gas from the adsorption tank to at ⁇ mosphere is regulated by the outflow valve 30 and happens through a sound damper 32.
  • the adsorption tank 34 is successively either in adsorption stage or in regeneration stage, let us presume that the tank is first in the adsorption stage.
  • the main valve 28 stays then open and outflow valve 30 is closed.
  • the adsorption material existing in the tank 34 is selected, similarly as in the first preferred embodiment, so that the through-flow of oxygen occurs faster that the flow of nitrogen. Suitable materials are natural or synthetic zeolites with approximately 4 A porosity size.
  • the oxygen-rich gas flows onward through the relief valve 41 into the storage tank 45.
  • the exit valve 36 is also at the end of this adsorption stage open for a certain time advantageously about 7 seconds whereupon the flow through relief valve 41 into the storage tank 45 is allowed whereby its pressurization with oxygen-rich gas may begin.
  • the production of oxygen-rich gas is interrupted by shutting the exit valve 36.
  • the regeneration of the adsorption tank 34 is begun by opening the outflow valve 30 and will last between 15 to 30 seconds advantageously about 23 seconds, whereupon the ad ⁇ sorption tank 34 is allowed to empty through the sound damper 32 and the nitrogen-rich gas gathered inside the adsorption tank 34 is allowed to pass out.
  • the adsorption tank 34 has been emptied.
  • both the outflow valve 30 and the exit valve 37 of the storage tank 45 are open for a certain time, typically about 7 seconds, whereupon the oxygen-rich gas is allowed to flow from the storage tank 45 through relief valve 39, filter 42, throttle 43 and relief valve 42 into the adsorption tank 34.
  • valves 30 and 37 are .closed and the main valve 28 is opened, when dried feed air begins to flow into the adsorption tank 34 and it begins to press ⁇ urize.
  • This pressurization up to pressure 500 kPa lasts typically about 11 seconds, after which the operation of the adsorbtion tank 34 proceeds in the previously descriped manner.
  • the duration of the cycle from the begin ⁇ ning of the adsorption stage to the end of the regeneration stage is typi- cally between 30...60 seconds advantageously about 52 seconds.
  • the produced oxygen-rich gas is taken into use from the sorage tank 45 by opening the shut-off valve 46 and by selecting either low-pressure direct-use or high- pressure boosting with the three-way valve 51.
  • direct-use mode (0...500 kPa) oxygen-rich gas is led to the pneumatically controlled pump 49 and further into distribution pipes 50.
  • high-pressure boosting mode pressure of about 500 kPa of the oxygen-rich gas coming from the storage tank 45 is raised by a pneumatically controlled pressure boosting unit 70 to the desi ⁇ red pressure for example for the filling of oxygen bottles as illustrated in fig. 4.
  • the pressure boosting unit 70 can be used for example a system similar to that in fig.
  • the pressure boosting unit here presented consists of;
  • DLE 75-1C a second two-stage working sylinder 72 operating at a higher 10 pressure range of 3,5 MPa...70 MPa.
  • control air unit 75 controlling the operation of the working cylinders 15 71 and 72, the control feed air pressure is typically between 100kPa...l.l
  • Pneumatic timers and directional valves are used in the control of valves 28,29,30,31,36 and 37 both in the first and the second preferred embodi ⁇ ments.
  • a relief valve is also used in the control to halt the working cycle if the pressure in the adsorption unit exceeds the previously set highest
  • control system is integrated, the greater part of the pneumatic components being mounted on a circuit card so that all their interconnect ⁇ ing flow channels are on said circuit card and separate pneumatic hoses are not needed.
  • Said pneumatic components are commercially available through Oy FEST0 Ab existing in Finland and the components are in the following refer-
  • the main valves 28 and 29 as well as the outflow valves 30 and 31 are arranged to operate turn and turn about.
  • the exit val ⁇ ves 36 and 37 are instead arranged to operate in parallel.
  • Said valves are 35 advantageously membran valves (type VLX-2) .
  • the switch chancing operation - of the valves is controlled by a flip-flop valve 52 (type VLL-5-PK-3), which is connected in the operational circuit of impulse valves 53 and 54 (type J-3-3.3), which are provided with one output and a memory.
  • the timer unit of the control system is composed of four timing units 55, 56, 57 and 12 58 (type VUZ) .
  • pneumatically operated mechanical clock devices with which a desired time sequenses of the production cycle can be set. They are regulated in the way shown in the circuit schematics, i.e. through the medium of memory valves 53 and 54 and by direct operation 5 of the membran-type exit valves 36 and 37.
  • the impulse valve 59 (type
  • J-5-3.3 furnished with two outputs controls directly timer units 56 and 58 as well as the operation of flip-flop valve 52.
  • the main valve 28 and the outflow valve 30 are 10" arranged to operate alternatively.
  • the exit valves 36 and 37 are instead arranged to operate in parallel.
  • Said valves are advantageously membran valves (type VLX-2) .
  • Operation of the .valves is controlled by a flip-flop valve 52 (type VLL-5-PK-3), which operates as a changeover switch and is connected to an impulse valve (type J-3-3.3) which is furnished with one 15' output and operation cycle memory.
  • the timer unit of the control system " is composed of four timer units 55, 56, 57 and 58 (type VUZ). These contain pneumatically operating mechanical clock devices with which desired time sequences can be set.
  • the impulse valve 59 (type J-5-3.3) furnished with two outputs controls timer units as wella as the operation of the flip-flop valve 53.
  • the adsorption unit is provided with pressure sensors which are connected to the pressure regulating valve 62 (type VD-3-3.3), whereby as the upper pressure limit is selected advantageously 800 kPa.
  • the pressure regulating valve 62 is connected in parallel to a manually adjustable 30.
  • governing valve 63 type SV-3-M5-N-22-S
  • main shut-off valve 61 type VL/0-3-3.3
  • second coverning valve 64 type SV-3-M5-N-22-S
  • control system is initiated by said goberning valve 63 (64) and there ⁇ after the system operates automatically controlling
  • valves 28, 29, 30, 31, 36 and 38 according to the set sequence shown in fig. 2, or
  • valves 28, 30, 36 and 38 according to the set sequence shown in fig. J.
  • shut-off valve 61 halts the cycle in turn.
  • the cycle can be restarted, however, from governing valve 64 or on pressure drop from governing valve 63.
  • the control system operates completely pneumatically using advantageously compressed air of about 500...600 kPa.
  • the compressed air is obtained th ⁇ rough service equipment from in themselves well-known compressed air sour ⁇ ces, e.g. compressor (not presented in the drawings) and is led into the system through governing valves 63 and 64 as can be seen from fig. 3 and 6.
  • the pneumatic components 52...62 are arranged on one circuit card which is located in a sealed casing 47 (27).
  • the governing valves 63 and 64 are advantageously mounted on the outer side of this ca- sing. As a benefit of this arrangement compressed air hoses are needed only between the governing valves and cicuit card as well as correspondingly between the membran valves and circuit card.
  • a control system assembled from corresponding pneumatic components 52...64 as mentioned above can also be advantageously used to control the operation of the moisture adsorbing unit especially the main valves 10 and 11 as well as the exit valves 12 and 13.
  • the compressos can be substituted for by previoisly obtained comp ⁇ ressed air.
  • the gas ad ⁇ sorbing unit can be adapted for different operational values by changing the operational cycles.
  • two oxygen producing unit can be dup ⁇ licated, whereupon one is perhaps smaller, whereby is attained a two-stage separation wuth which the degree of purity can be raised by flowing through the larger unit a relatively greater quantity of gas. This kind of an ar ⁇ rangement is useful whem an especially high degree of purity is demanded.
  • the plant can instead of oxygen be used for separating of nitrogen or other air components.

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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)
  • Separation Of Gases By Adsorption (AREA)
  • Oxygen, Ozone, And Oxides In General (AREA)
  • Drying Of Gases (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

A gas concentration method and a gas concentrating plant, especially for the separation of oxygen out of air by means of adsorbtion. According to the invention air is first compressed by means of a compressor (1) and dried by means of a dual tank moisture adsorbing unit (14, 15) in order to achieve for the gas adsorbing unit (34', 35) feed air, dew-point of which is about -40°C. The major part of the oxygen-rich gas coming out from the adsorption unit is led forward and the lesser part of said oxygen-rich gas is recycled unit in order to regenerate the adsorbtion unit by removing the nitrogen-rich gas bonded to the adsorption material of the adsorption unit. Said gas flows: compressed and dried feed air flows to adsorption units (14, 15; 34', 35), oxygen-rich gas flows to be recycled and led forward, nitrogen-rich gas flow to be removed from the adsorption unit (34', 35), are controlled and regulated by means of pneumatically operating regulation and control elements (10...13, 28...31, 36, 37, 52...64), whereby the separation of a gas component, advantageously oxygen out of air, is reliably and safely carried out also in humid, cold and/or explosion risky conditions.

Description

A gas concentrating method and plant
The invention relates to a gas concentrating method according to the intro¬ ductory part of claim 1 and to a gas concentrating plant according to the introductory part of claim 5; especially for separation of oxygen out of air by means of adsorption.
The industrial manufacture of oxygen today is mainly carried out in two different ways: by means of distillation or by means of adsorption.
The most significant process today is distillation at high pressure, nor¬ mally 20 ...30 MPa, and low temperature, whereby the the different part components of air (nitrogen, oxygen, argon etc.) are distilled as compress¬ ed liquids separate from each other.
Oxygen is also separated out of air by means of a process known as selec¬ tive adsorption, which is based on the capability of a certain material, for example natural or synthetic zeolites with theoretical porosity size of 4 A, to hold different molecules, for example oxygen molecules size of which are about 3,8 A, of the air in various ways within its porosity by physical adhesion.
This kind of an adsorption process is usually carried out by so called pre¬ ssure swing adsorption - PSA, in which the adsorption material is revieved after every adsorption stage by leading through the adsorption material a regenerating gas flow opposing the feed gas flow to be adsorbed Normally the PSA-plant includes two tanks so that one tank is separating oxygen • whilst the other tank is being regenerated. The equipment associated with the adsorption process has beeb described among others in US-patents 4194890 and 4263018 in GB-patent 2109266 and in Fl-patent application 843014.
The capabilty of zeolite to hold oxygen molecules is reduced remarkably by water vapour. Due to this it has been proposed, among others, in DE-patent applications 1265144 and 1259857 as well as in EP-patent publications 123911 and 128545 to use drier before the adsorbtion stage.
A number of weaknesses are associated with the mentioned gas separation methods. As the principal drawback conserning distillation can be mentioned large size and complicated construction of distillation equipment so that the plant is from outset remarkably costly. In addition the distribution of gas becomes involved and noticeably expensive due to transportation, becau¬ se foor transportation purposes the gas must be compressed and kept in a very high pressure of about 20 MPa althought the working pressure is usu¬ ally about 500 kPa. The compression requires a great deal of energy which raises the the gas production costs. Relating to the disadvantages further can be mentioned there is at all times present a potential risk of explo¬ sion and fire due to the high pressure and to the possibility of gas leaks out of the pressure vessel.
For the time being very few adsorbtion plants have been taken into produc¬ tive use. Up to this date in operation the main drawback associated there¬ with has been the insufficient oxygen content attainability. With the known plants can be achieved oxygen content of about 60 %, however 80 % at the highes. Such content levels are fully insufficient for example in hospital use or for flame cutting etc. which uncompromisingly demand more than 90 % oxygen content.
' Another remarkable drawback is formed by the complicated regulation and control system which the PSA-process demands. In the known plants the equi¬ pments which are used are mainly microprocessor controlled and electrically or magnetically operated functional elements such as solenoid valves which are not, however, suitable for use in humid and/or cold conditions as for example in off-shore of fish-farming plants.
The main objectives of the present invention are to eliminate the drawbacks and weaknesses associated with known separation methods and to effect a new type of gas adsorbtion plant for gas consentrating especially for producing oxygen out of air.
These objects have beeb achieved with the method and the plant according to the invention. The individual distinctive features of the invention are presented in the enclosed claims.
The invention is based on that genious insight that the plant includes as combination; means for compressing and feeding the air into the plant, first adsorbtion means for drying the compressed feed air, and second adsorbtion means for separating the preferred gas component out of the feed air; and that gas flows as well as the different parts of the plant are controlled and regulated by means of pneumatically operating elements.
The main advantages due to the present invention are, that the whole plant operates in all surrounding, also in humid and cold conditions, exactly and reliably, which assists the genious use of pneumatic logic and pneumatical¬ ly operating elements, and that by using the plant can be achieved an ess¬ entially higher attainability of oxygen content than by using plants accor¬ ding to the prior art.
In this context there is cause to emphasise that in using the term pneuma¬ tic it is intended to mean elements purely operating pneumatically. The power source can therefore be simply compressed air, that the control and regulation means include no electrical components in any form. This also conserns said logic, that is the control system, components of which in¬ clude memories and mechanical clock devices operating on compressed air.
According to one preferred empodiment of the invention the control system is of integrated construction, the greater part of its components are arr- anged one one single circuit board which is closed in a sealed case. By using hybrid circuit board technology in the control system can be achieved the adventages that several millions connections can be made and long work¬ ing life attained. The benefit conferred by this solution is that the cont¬ rol system is protected from humidity and cold. In addition the require- ments for pneumatic hoses is reduced. Further it can be verified that the use of pneumatics does not cause any risk of sparking nor is electricity needed, whereby the use of the plant is safe.
According to the advantageous mode of the present invention the compressed feed air is dried by means of dual tank adsorbtion drier. The operation of the plant is then fundamentally improved in comparison with earlier known solutions especially in humid conditions.
For the reliable separation of the preferred gas component especially for the separation oxygen out of air can be used different adsorbtion materi¬ als, such as silica gel or in particular synthetic or natural zeolites. Amongst natural zeolites can be mentioned as examples mordenite and morde- nite/clinoptilolite. Suitable synthetics are for example A- and X-type natriumzeolites such as 5A and 13X. In the zeolite molecular construction together with aluminium or natrium ions may appear also other metallic ions such as gallium or strontium ions.
The most outstanding advantages of the present invention in comparison with the prior art solutions as the following:
1) in comparison with distillation,
- the price of oxygen becomes cheaper (depending on the degree of purity) even down to 1/5...1/10 of the market price today)
- transportation of oxygen in pressure bottles can be avoided - the compression of oxygen to a high pressure can be avoided
2) in comparision with prior art adsorbtion:
- greater attainability of content or purity of the preferred cas component, especially oxygen (=over 90 % to as high as even 98 %) , - higher yield: lnm3 /h oxygen at lnm3 /min/compressed air input, or about 8 % of the theoretical oxygen quantity with content of 92 %, and 2 nm3 /h oxygen at inm3 /min/compressed air input or about 16 % of the theoretical oxygen quantity with content of 87 %.
The superior performance values mentioned above are all founded on the use of a dual tank adsorbtion drier in the upstream of the feed air flow of the plant. The drier increases air consumption by about 10 %. which means only slight increase in operational costs when it is possible to increase the yield by about 50 % and at the same time the level of purity can be funda- mentally raised. To increase the operational possibilities the output of the plant can be provided with three-way valve which acts as an input devi¬ ce for an dual pressure further processing unit which is either in low pre¬ ssure daytime use or in pressure boosting use by night for filling pressure bottles to be needed for peak consumption.
In tests carried out with pneumatically operated and regulated plant in accordance with the invention was established faultless operation in cold marine climate.To assure.the mechanical durability stainless steel is widely used in the plant according to the invention.
The present invention is descriped in the following with aid of individual examples of its preferred embodiments with reference to the accompanying drawings in which, fig. 1 presents a general arrangement of the first preferred embodiment of the gas concentration plant for separating oxygen out of air, fig 2 is the logic drawing of the pneumatically operating valves of said first preferred embodiment,, fig 3 presents the circuit diagram for the pneumatically operating valves of said first preferred embodiment, fig 4 presents a general arrangemang of the second preferred embodiment of the gas concentration plant for separating oxygen out of air, fig 5, is the logic drawing of the pneumatically operating valves of said second preferred embodiment, fig 6 presents the circuit diagram for the pneumatically operating valves of said second preferred embodiment, and fig 7 presents shematically the unit for boosting the pressure of the produced oxygen.
As can be seen from figures 1 and 4 compressor 1 takes in suction air from normal air surroundings and feeds a certain air quantity in time unit (= 100%) at certain pressure (normally 700...750 kPa) . The air is then led to an aftercooler 2 which may be included with compressor 1. The moisture in the air begins to condensate for which reason condensate drain 3 is coupled to the aftercooler 2. Air then led to a pressure vessel 4 the size of which is determined by the size and type of compressor 1.
Air is also condensed in the pressure vessel with cooling of the air so that ensure the faultness operation vessel 4 is provided with the second condensate drain 5. Air is led from the vessel 4 through prefilter 6 for removing water droplets and through fine filter 7 for removing oil from the air into a dual tank type moisture adsorbing drier 14, 15. The prefilter 6 and the fine filter 7 are provided correspondingly with condensate drain 8 and oil drain 9. If the compressor 1 is oil-free the fine filter 7 and drain 9 can be left out of the plant. If the compressor is oil lubricated oil separation from the air to be led into the drier 14, 15 is important for the reason that the effiency of the moisture adsorbing material dete¬ riorates and useful life essentially reduces if oil is allowed to pass there.
As mentioned above purified air is led to the drier, for producing of feed air the dewpoint of which would be about -40 °C, in turn with the aid of first main valve 10 and second main valve 11 correspondingly to one or other of the tanks 14 and 15 which both are filled with moisture adsorbing material such as silica gel or provided with a molecular screen. The main valves 10 and 11 are controlled by microprocessor based programmable auto¬ mation 27 which consists according to the invention of a pneumatic logic. If the first tank (or tower) 14 is in drying stage the first main valve 10 stays open and the second main valve 11 connected to the second tank 15 is closed. During the adsorbing stage of the first tank 14 the second tank 15 is in a regenerating stage during which the moisture gathered there inside is removed. When the first tank 14 is in moisture adsorbing stage the rege- neration valve 12 connected to the first tank 14 stays closed and regenera¬ tion valve 13 connected to the second tank 15 is open. To avoid noise it is advantageous that both the regeneration valve 12 and the regeneration valve 13 are connected through sound damper 17 corresp. 16 to open air.
On coming out of the first tank 14 the dried air passes through a check valve 20 to a filter 24 because check valves 18 and 21 are in the check direction. On coming out of the second tank 15 the dried air also flows to the filter 24 but passes through the check valve 21 because the check val¬ ves 19 and 20 are in the check direction. Said dried air flows to the fil— ter from the tanks 14 and 15 occur in turn whereby one of the tanks is in moisture adsorbing stage whilst the other tank in under regeneration. A small part of the dried air, advantageously 10...12 % in heatless types of drier and advantageously 2...4 % in a drier using heat, is used for regene¬ rating the other tank. This quantity of dried air is regulated by means of the throttle 23 and is taken from the main dried air flow through filter 22.
If the tank 15 is under regeneration the dried air passes from the throttle 23 through the check valve 19, since the throttle 23 reduces the pressure and behind the check valve 18 the pressure is about 700 kPa. The regene¬ ration air passes then into the tank 15, since behind the valve 21 the pressure is about 700 kPa and because on the other hand the outflow valve 13 at the bottom of the tank 15 is open and the main valve 11 closed. The regeneration air thus rinses the tank 15t the flow direction being opposite to that adsorbtion flow occuring in the tank 14. In the regeneration the condensation is freed to atmosphere through the noutflow valve 13 and sound damper 16.
The pressure in the tank under adsorbtion is higher and essentially cons- tant (e.g. 700 kPa) and the pressure in the tank under regenation is lower decreaces (e.g. from 700 kPa to atmosphere). After a predetermined time, advantageously 9 minutes, after the drying stage had began in the tank 14, the valve 13 is closed which inhibits the outflow from the tank 15 where- upon the tank 15 begins to pressurize. When both tanks have reached the same pressure the settings of the main valves 10 and 11 are changed over, that is the valve 10 is closed and valve 11 opened. The air coming from the compressor 1 then begins to flow through the tank 15. After a certain time, advantageously 9 seconds, outflow valve 12 is opened, whereupon the pres- sure in .he tank 14 begins to fall and the regeneration can begin. Thus drying of the air can be continious by alternatively operating the tanks 14 and 15.
The function of the filter 24 is to remove from the dried air all dust etc. released into the dried air. After the filter 24 pressure of the feed air is reduced by pressure reduction unit 25 to a suitable value which is ad¬ vantageously about 500 kPa. The feed air flow is then equalised in tank 26.
In the first preferred embodiment of the present invention the feed air is led after the tank 26 to the dual tank gas adsorbing unit 34"| 35 for conti¬ nious separation of oxygen out of the feed air. The inflow head of the gas adsorbing unit is correspondingly constructed to that of the dual tank moisture adsorbing unit. The valves 28 and 29 are main valves which alter¬ natively allow passage of the feed air into the first tanks 34'or the second tank 35 which tanks are identical. Correspondingly the exiting of nitrogen-rich exhaust gas flow from the tanks 34'and 35 is regulated by outflow valves 30 and 31.
Let us presume that the first tank 34'is in the adsorbtion stage. The main valve 28 and the out flow valve 31 stays then open and the main valve 29 and the outflow valve 30 are closed, whereupon the feed air flows into the tank 34' According to the invention the adsorbtion material is elected so that the through-flow of oxygen occurs faster than the flow of nitrogen. As mentioned before suitable material are natural and synthetic zeolites porosity size of which do not exceed 4 A. On the exit the valve being open oxygen passes, because the check valves 40 and 39 are in check direction, through the check valve 38 to the filter 42. Thereafter the flow of oxygen- rich gas is regulated by throttle 44 and the oxygen-rich gas is stored into tank 45. While the first tank 34'is producing oxygen, that is when the valve 36 stays open for a certain time between 10 to 30 seconds advantageously about 15 seconds, the main valve 31 of the second tank 35 is also open, from the beginning of the oxygen production, for a certain time typically between 5...10 seconds advantageously about 8 seconds, whereupon oxygen-rich gas is allowed to flow after the valve 36 through relief valve 41 into the second tank 35 and from there through the outflow valve 31 and sound damper 33 to atmosphere, thus extracting and rinsing the nitrogen-rich gas from the second tank 35. Naturally the exhaust of oxygen-rich gas through sound damper 33 is minimised..
On completion of the set time, which for extracting the nitrogen-rich gas is between 15 to 30 seconds advantageously 24 seconds as can be seen from fig. 2, the outflow valve 31 is closed whereupon outward blowing from the second tank 35 ends and its presurization with oxygen-rich gas begins. The duration of the pressurization is typically between 5...10 seconds advanta¬ geously about 7 seconds, after which time the production of oxygen in the first tank 34'is interrupted by closing the valve 36 and at the same time the operation of the tanks 34'and 35 is changed over by opening the main valve 29 and by closing the main valve 28. The second tank 35 then begins to pressurize on feed air inflowing through the main valve 29.
After this, typically over about 11 seconds, the outflow valve 30 is opened whereupon the first tank 34' begins to empty to atmosphere through sound damper 32, whereupon the nitrogen-rich gas is removed from the first tank 34'. Typically about 16 seconds after opening the main valve 29 the pressure in the second tank 35 has attained its highest value, advantageously about 500 kPa, and at the same time the first tank 34'has emptied for repressurization.
The valve 37 is then opened whereby the oxygen production of the second tank 35 may begin. At the end of the oxygen production advantageously about 8 seconds the outflow valve 30 is held open whereby the first tank 34' is under regeneration. Thereafter the outflow valve 30 is closed after which the operation of the first tank 34' proceeds in the manner described above. The duration of one cycle, that is from the begining of the adsorbtion sta¬ ge in one tank to the end of the regeneration stage in the other tank is typically between 50 to 100 seconds advantageously about 84 seconds as pre- sented in fig. 2.
The operational schematics of the main valves 28 and 29, for the compressed feed air, of the outflow valves 30 and 31, for the nitrogen-rich exhaust gas, and of the exit valves 36 and 37, for the oxygen-rich production gas, are presented as a combination in fig. 2, whereby the reference "1" means that the valve is open and whereby the reference "0" means that the valve is closed. The operational times given in this schematics are steplessly regulated for producing oxygen-rich gas with desired purity.
According to the second preferred embodiment of the invention presented in fig. 4 the dried feed air is led to the single tank gas adsorption drier 34 for separating the oxygen The inflow side of the tank 34 is similarly cons¬ tructed to that in one of the drier tank 14 or 15. The valve 28 is the main valve which controlls the passage of feed air into the adsorption tank 34 and the flow of nitrogen-rich exhaust gas from the adsorption tank to at¬ mosphere is regulated by the outflow valve 30 and happens through a sound damper 32.
The adsorption tank 34 is successively either in adsorption stage or in regeneration stage, let us presume that the tank is first in the adsorption stage. The main valve 28 stays then open and outflow valve 30 is closed. The adsorption material existing in the tank 34 is selected, similarly as in the first preferred embodiment, so that the through-flow of oxygen occurs faster that the flow of nitrogen. Suitable materials are natural or synthetic zeolites with approximately 4 A porosity size. On the exit valve 36 36 being open the oxygen-rich gas passes through check valve 38 to fil¬ ter 42, the gas flow being thereafter being regulated by means of the throttle 43. The oxygen-rich gas flows onward through the relief valve 41 into the storage tank 45.
On adsorption tank 34 beginning to produce oxygen-rich gas, that is when the valve 28 is being held open for a time of 10...30 seconds advantage¬ ously about 18 seconds, the exit valve 36 is also at the end of this adsorption stage open for a certain time advantageously about 7 seconds whereupon the flow through relief valve 41 into the storage tank 45 is allowed whereby its pressurization with oxygen-rich gas may begin. After this pressurization during which the pressuremin of the tank 45 has risen to a value of advantageously 500 kPa the production of oxygen-rich gas is interrupted by shutting the exit valve 36.
After this, typically after over about 11 seconds, the regeneration of the adsorption tank 34 is begun by opening the outflow valve 30 and will last between 15 to 30 seconds advantageously about 23 seconds, whereupon the ad¬ sorption tank 34 is allowed to empty through the sound damper 32 and the nitrogen-rich gas gathered inside the adsorption tank 34 is allowed to pass out. After a certain time, typically after about 16 seconds, the adsorption tank 34 has been emptied. At the end of the regeneration stage both the outflow valve 30 and the exit valve 37 of the storage tank 45 are open for a certain time, typically about 7 seconds, whereupon the oxygen-rich gas is allowed to flow from the storage tank 45 through relief valve 39, filter 42, throttle 43 and relief valve 42 into the adsorption tank 34. After this the valves 30 and 37 are .closed and the main valve 28 is opened, when dried feed air begins to flow into the adsorption tank 34 and it begins to press¬ urize. This pressurization up to pressure 500 kPa lasts typically about 11 seconds, after which the operation of the adsorbtion tank 34 proceeds in the previously descriped manner. The duration of the cycle from the begin¬ ning of the adsorption stage to the end of the regeneration stage is typi- cally between 30...60 seconds advantageously about 52 seconds.
The operational schematics of the main valve 28, for the feed air, of the outflow valve 30, for the nitrogen-rich exhaust gas, of the exit valves 36 and 37 for both to oxygen-rich production gas and oxygen-rich regeneration gas, are presented in fig. 5. The operational times given in this schema¬ tics are stepplessly regulated for producing oxygen-rich gas with desired purity.
According to both the first and second preferred embodiment the produced oxygen-rich gas is taken into use from the sorage tank 45 by opening the shut-off valve 46 and by selecting either low-pressure direct-use or high- pressure boosting with the three-way valve 51. In direct-use mode (0...500 kPa) oxygen-rich gas is led to the pneumatically controlled pump 49 and further into distribution pipes 50. In high-pressure boosting mode pressure of about 500 kPa of the oxygen-rich gas coming from the storage tank 45 is raised by a pneumatically controlled pressure boosting unit 70 to the desi¬ red pressure for example for the filling of oxygen bottles as illustrated in fig. 4. As the pressure boosting unit 70 can be used for example a system similar to that in fig. 7, with which the pressure can be boosted up to even 70 MPa. Components for such a system are commercially available from SCHMIDT, KRANTZ AND CO. GmbH and the components are referred to in the following by 5 using the company codes in brackets. The pressure boosting unit here presented consists of;
- a first two-stage working sylinder 71 (DLE 5-30) operating at a lower pressure range of 200 kPa...32 MPa,
- a second two-stage working sylinder 72 (DLE 75-1C) operating at a higher 10 pressure range of 3,5 MPa...70 MPa.
- an intermediate tank 74 acting as a pressure accumulator and furnished with a relief valve 73, and which tank 74 is fitted between serially and sequentially operating working cylinders 71 and 72,
- a control air unit 75 controlling the operation of the working cylinders 15 71 and 72, the control feed air pressure is typically between 100kPa...l.l
MPa,
- a first shut-off valve 76 which effects the first working cylinder 71,
- a second shut-off valve 77 and pressure regulating valve 78 which both effect to the second working cylinder 72.
•20
Pneumatic timers and directional valves are used in the control of valves 28,29,30,31,36 and 37 both in the first and the second preferred embodi¬ ments. A relief valve is also used in the control to halt the working cycle if the pressure in the adsorption unit exceeds the previously set highest
25 value. The control system is integrated, the greater part of the pneumatic components being mounted on a circuit card so that all their interconnect¬ ing flow channels are on said circuit card and separate pneumatic hoses are not needed. Said pneumatic components are commercially available through Oy FEST0 Ab existing in Finland and the components are in the following refer-
30 red by using the product codes in brackets of said company.
As can be seen from fig. 3 the main valves 28 and 29 as well as the outflow valves 30 and 31 are arranged to operate turn and turn about. The exit val¬ ves 36 and 37 are instead arranged to operate in parallel. Said valves are 35 advantageously membran valves (type VLX-2) . The switch chancing operation - of the valves is controlled by a flip-flop valve 52 (type VLL-5-PK-3), which is connected in the operational circuit of impulse valves 53 and 54 (type J-3-3.3), which are provided with one output and a memory. The timer unit of the control system is composed of four timing units 55, 56, 57 and 12 58 (type VUZ) . These are provided with pneumatically operated mechanical clock devices with which a desired time sequenses of the production cycle can be set. They are regulated in the way shown in the circuit schematics, i.e. through the medium of memory valves 53 and 54 and by direct operation 5 of the membran-type exit valves 36 and 37. The impulse valve 59 (type
J-5-3.3) furnished with two outputs controls directly timer units 56 and 58 as well as the operation of flip-flop valve 52.
As can be seen from fig. 6 the main valve 28 and the outflow valve 30 are 10" arranged to operate alternatively. The exit valves 36 and 37 are instead arranged to operate in parallel. Said valves are advantageously membran valves (type VLX-2) . Operation of the .valves is controlled by a flip-flop valve 52 (type VLL-5-PK-3), which operates as a changeover switch and is connected to an impulse valve (type J-3-3.3) which is furnished with one 15' output and operation cycle memory. The timer unit of the control system" is composed of four timer units 55, 56, 57 and 58 (type VUZ). These contain pneumatically operating mechanical clock devices with which desired time sequences can be set. They are regulated as shown in the circuit schema¬ tics, i.e. through the medium of the memory valve 53 and by direct opera- 20 tion ofthe membran-type exit valves 36 and 37. The impulse valve 59 (type J-5-3.3) furnished with two outputs controls timer units as wella as the operation of the flip-flop valve 53.
To assure the certain and exact operation of the gas adsorption unit of 25- both the first and the second preferred embodiments illustrated in figures 1 and 4 the adsorption unit is provided with pressure sensors which are connected to the pressure regulating valve 62 (type VD-3-3.3), whereby as the upper pressure limit is selected advantageously 800 kPa. The pressure regulating valve 62 is connected in parallel to a manually adjustable 30. governing valve 63 (type SV-3-M5-N-22-S) together with the main shut-off valve 61 (type VL/0-3-3.3), which in turn is connected to the "or"-valve 60 (type OS-6/3-3.3) to which is also connected a second coverning valve 64 (type SV-3-M5-N-22-S) .
35 The control system is initiated by said goberning valve 63 (64) and there¬ after the system operates automatically controlling
- the valves 28, 29, 30, 31, 36 and 38 according to the set sequence shown in fig. 2, or
- the valves 28, 30, 36 and 38 according to the set sequence shown in fig. J.
5.'
If the pressure of the gas adsorbtion unit rises excessively the shut-off valve 61 halts the cycle in turn. The cycle can be restarted, however, from governing valve 64 or on pressure drop from governing valve 63.
The control system operates completely pneumatically using advantageously compressed air of about 500...600 kPa. The compressed air is obtained th¬ rough service equipment from in themselves well-known compressed air sour¬ ces, e.g. compressor (not presented in the drawings) and is led into the system through governing valves 63 and 64 as can be seen from fig. 3 and 6.
As mentioned earlier the pneumatic components 52...62 are arranged on one circuit card which is located in a sealed casing 47 (27). The governing valves 63 and 64 are advantageously mounted on the outer side of this ca- sing. As a benefit of this arrangement compressed air hoses are needed only between the governing valves and cicuit card as well as correspondingly between the membran valves and circuit card.
A control system assembled from corresponding pneumatic components 52...64 as mentioned above can also be advantageously used to control the operation of the moisture adsorbing unit especially the main valves 10 and 11 as well as the exit valves 12 and 13.
The invention has heretofore only been described with the aid of a couple of preferred embpdiments. It is naturally not here desired to limit the present invention in any way but that the present invention and/or its manifold individual variations are possible within the enclosed claims.
Thus other parts of the plant can differ from the aforementioned represen- tation. The compressos can be substituted for by previoisly obtained comp¬ ressed air. Whilst the plant in its entirety remains the same the gas ad¬ sorbing unit can be adapted for different operational values by changing the operational cycles. In addition two oxygen producing unit can be dup¬ licated, whereupon one is perhaps smaller, whereby is attained a two-stage separation wuth which the degree of purity can be raised by flowing through the larger unit a relatively greater quantity of gas. This kind of an ar¬ rangement is useful whem an especially high degree of purity is demanded. By changing the gas adsorbtion material the plant can instead of oxygen be used for separating of nitrogen or other air components.

Claims

1. A gas concentration method by means of adsorbtion, especially for the separation of oxygen out of air, characterized in that the method consists of successive stages in which
- air is compressed to a pressure, which is essentially higher than normal atmospheric pressure,
- the water condensed in assosiation with the compression is removed, and the compressed air is possibly dried, - the compressed air is led into a adsorbtion unit, which contains adsorb¬ tion material, advantageously natural or synthetic zeolites, suitable for the separation of gas into part components,
- at least a major part of the product gas, abundantly containing oxygen, coming out from the adsorbtion unit is led forward, advantageously to a storage means or user point, and
- a lesser part of the product gas, abundantly containing oxygen, is cycled into the adsorbtion unit in order to regenerate the adsorbtion unit by re¬ moving the gas, abundantly containing nitrogen, bonded to the adsorbtion material in the adsorbtion unit, and that said gas flows:
- compressed air to be led into the adsorbtion unit,
- major part of the product gas, abundantly containing oxygen, coming out from the adsorbtion unit,
- lesser part of the product gas, abundantly containing oxygen, to be cycl- ed into the adsorbtion unit,
- waste gas, abundantly containing nitrogen, to be removed from the adsorb¬ tion unit, are controlled and regulated by means of pneumatically operating elements, whereby the separation of a gas component, advantageously oxygen, out of air is reliably and safely carried out by means of adsorbtion also in hu¬ mid, cold and/or explosion risky conditions.
2. Method according to the claim 1 which method is carried out by means of a dual tank adsorbtion unit, characterized in that the starting moment and the flowing time of said lesser part of the product gas flow, which is led from the upper part or outflow pipe of one adsorbtion tank through the ot¬ her adsorbtion tank for regenerating the same, are defined, controlled and regulated by means of pneumatically operating elements.
3. Method according to the claim 1 which method is carried out by means of a single tank adsorbtion unit, characterized in that the starting moment and the flowing time of said lesser part of the product gas flow, which is led from the intermediate storage through the adsorbtion tank for regene- rating the adsorbtion tank, are defined, controlled and regulated by means of pneumatically operating elements.
4. Method according to anyone of the preceeding claims 1...3, characterized in that the compressed air, from which the condensed water is separated, is led into at least dual tank drier which includes moisture adsorbing mate¬ rial, advantageously silica gel or molecular screen, in order to to dry the air to a suitable degree of humidity, advantageously so that the dewpoint of the compressed air after drying is about -40 °C, and that
- the flow of the compressed air into one moisture adsorbing drying tank, - major part of the dried air flow from one moisture adsorbing drying tank into one adsorbing tank,
- lesser part of the dried air flow from one moisture adsorbing drying tank into the other moisture adsorbing tank for regenerating the same by re¬ moving the moisture bonded to the moisture adsorbing material, and - the outflow of air with bound humidity from the moisture adsorbing tank under regeneration are controlled and regulated by means of pneumatically operating elements.
5. Cas concentrating plant, especially for separating oxygen out of air, characterized in that the plant includes as a combination at least:
- an air feeding device (1), advantageously a compressor, for the compression of feed air,-
- separation means (2...9), advantageously applied in combination with said air feeding device, for removing from said feed air at least condensed wa- ter caused of the air compression,
- a moisture adsorbtion drier consisting of advantageously two successively in moisture adsorbtion stage operating tanks (14,15), each of which contains either suitable moisture adsorbing material advantageously silica gel or includes a molecule sieve, said drier being sited after said water separation means (2...9) and optimised in ratio to the drying material, cycle times and other optional parametres for the production of dried compressed air, the dew-point of which is advantageously about -40 °C,
- a gas adsorbtion unit (34;34',35) which contains material suitable for separation of gas by means of adsorbtion into part components, advantage- ously natural or synthetic zeolite for the separation of oxygen and nitro¬ gen existing in the feed air from each other,
- tank means (45;47) to storage the gaseous product, advantageously oxygen- rich gas, obtained from said gas adsorbtion unit, - pipework, which connects said parts of the plant into a flow connection with each other and is applied for conduction of gas flows between said feedeing device (1), said separation means (2...9), said moisture adsorb¬ tion drier (14,15), said gas adsorbtion unit (34';34',35) and said tank means (45;47), and - pneumatically operating regulation and control elements (10...13,28...31, 36,37, 52...64) in order to control the gas flows in said parts of the plant as well as in said pipework, and optionally
- means for further processing of separated gas components, advantageously oxygen-rich gas, which means are sited after said tank means (45;47) and include advantageously a pneumatic pressure boosting unit (70) and a pres¬ sure bottle (80) to storage the gaseous product under high pressure.
6. Gas concentrating plant according to the claim 5, characterized in that the gas adsorbtion unit consists of a single tank (34) which is successi¬ vely either in adsorbtion stage, in which the out flow time of oxygen-rich gas is between 10...30 seconds advantageously about 18 seconds, or in re¬ generation stage, in which the out flow time of nitrogen-rich gas is bet¬ ween 15...30 seconds advantageously about 23 seconds, whereby the duration of the whole cycle from the begining of the adsorbtion stage to the end of regeneration stage is between 30...60 seconds advantageously 52 seconds.
7. Gas concentrating plant according to the claim 5, characterized in that the gas adsorbtion unit consists of two tanks (34',35), which are succes- sively in adsorbtion stage, in which the out flow time of oxygen-rich gas is between 10...30 seconds advantageously about 15 seconds, or in regene¬ ration stage, in which the out flow time of nitrogen-rich gas is between 15...30 seconds advantageously 24 seconds, whereby duration of the whole cycle from the begining of the adsorbtion stage in one tank to the end of the regeneration stage in the other tank is between 50...100 seconds advan¬ tageously 84 seconds.
8. Gas concentrating plant according to any one of the preceeding claims 5...7, characterized in that the pneumatic regulation elements for feed air, oxygen-rich gas and nitrogen-rich gas consist of several pneumatic membran valves (10...13,28...31,36,37) and that the control elements for operating said pneumatic membran valves (10...13,28...31, 36,37) include at least pneumatic timers (55...58) and pneumatic impulse valves (53,54,59).
9. Gas concentrating plant according to any one of the preceeding claims 5...8, characterized by the pressure regulating valve (62) connected on one hand to pressure sensors, which are located in each tank of the gas adsorb¬ tion unit (34;34',35) and the moisture adsorbtion unit (14,15), and on the other hand to a main shut-off valve (61) of the pneumatic control system (52...64), that said pneumatic control system is integrated in a common tightly closed casing so that the greater part of its components (52...64) are adapted inside said casing, and that said pressure regulating valve (62) is adapted to halt the working cycle if the pressure in the tank of either gas adsorbtion unit or moisture adsorbtion unit exceeds a predeter¬ mined highest value, advantageously about 800 kPa in a tank of moisture adsorbing unit or about 500 kPa in a tank of gas adsorbing unit.
10. Gas concentrating plant according to any one of the preceeding claims "5...9, characterized in that said pressure boosting unit (70), for boosting the pressure of the produced oxygen-rich gas up to 70 MPa, consists of:
- a first, two-stage, working cylinder (71) operating in a lower pressure area,
- a second, two-stage, working sylinder (72) operating in a higher pressure area,
- an intermediate tank (74) furnished with a relief valve (73) fitted in series between said cylinders (71,72) operating successively,
- a control air unit (75),
- a first shut-off valve (76) which affects to the first working cylinder (71), and
- a second shut-off valve (77) and a pressure-regulating valve (78) which affect to the second working cylinder (72).
PCT/FI1987/000020 1986-02-12 1987-02-06 A gas concentrating method and plant WO1987004946A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
GB08819148A GB2207616A (en) 1986-02-12 1987-02-06 A gas concentrating method and plant
BR8707581A BR8707581A (en) 1986-02-12 1987-02-06 GAS CONCENTRATING PROCESS AND INSTALLATION
HU871198A HUT47455A (en) 1986-02-12 1987-02-06 Method and apparatus for concentrating gas
NO874242A NO874242L (en) 1986-02-12 1987-10-09 PROCEDURE FOR CONCENTRATION OF GAS, AND APPARATUS FOR EXECUTION OF THE PROCEDURE.
DK531787A DK531787A (en) 1986-02-12 1987-10-12 PROCEDURES FOR CONCENTRATION OF GAS AND PLANT THEREOF

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FI860653A FI76002C (en) 1986-02-12 1986-02-12 Gas amplification method and apparatus
FI860653 1986-02-12
FI861189 1986-03-20
FI861189A FI76003C (en) 1986-02-12 1986-03-20 FOERSTAERKNINGSFOERFARANDE OCH -ANORDNING FOER GAS.

Publications (1)

Publication Number Publication Date
WO1987004946A1 true WO1987004946A1 (en) 1987-08-27

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CN102705204A (en) * 2012-07-05 2012-10-03 昆山宝宏机械有限公司 Oxygen-making and nitrogen-making air compressor
WO2017184855A1 (en) 2016-04-20 2017-10-26 Carleton Life Support Systems, Inc. Moisture resistant molecular sieve beds
CN114392632A (en) * 2022-01-30 2022-04-26 浙江省生态环境科学设计研究院 Nitrogen-protected organic waste gas condensation and recovery treatment method for degreasing process

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CN100391555C (en) * 2005-04-22 2008-06-04 欧阳才峰 Medical health care oxygen machine with molecular sieve PSA
NZ619142A (en) 2007-04-20 2015-08-28 Invacare Corp Product gas concentrator and method associated therewith
NZ722551A (en) 2012-03-09 2018-01-26 Invacare Corp System and method for concentrating gas
CN103723682A (en) * 2013-12-13 2014-04-16 科迈（常州）电子有限公司 Household oxygenerator with two oxygen tanks
CN106955560A (en) * 2017-04-18 2017-07-18 湖南泰瑞医疗科技有限公司 Air-treatment main frame and oxygen generation system
US20230012016A1 (en) * 2019-11-27 2023-01-12 ResMed Asia Pte. Ltd. Oxygen tank with improved oxygen storage
AU2021309952A1 (en) 2020-07-16 2023-03-16 Ventec Life Systems, Inc. System and method for concentrating gas
US11915570B2 (en) 2020-07-16 2024-02-27 Ventec Life Systems, Inc. System and method for concentrating gas

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CN102705204A (en) * 2012-07-05 2012-10-03 昆山宝宏机械有限公司 Oxygen-making and nitrogen-making air compressor
WO2017184855A1 (en) 2016-04-20 2017-10-26 Carleton Life Support Systems, Inc. Moisture resistant molecular sieve beds
US10252212B2 (en) 2016-04-20 2019-04-09 Carleton Life Support System, Inc. Moisture resistant molecular sieve beds
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CN114392632A (en) * 2022-01-30 2022-04-26 浙江省生态环境科学设计研究院 Nitrogen-protected organic waste gas condensation and recovery treatment method for degreasing process

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BR8707581A (en) 1988-12-06
FI76003C (en) 1988-09-09
JPH01501529A (en) 1989-06-01
DE3790099T1 (en) 1989-01-19
YU20387A (en) 1988-10-31
CN87102164A (en) 1987-11-25
SE8802881D0 (en) 1988-08-12
NL8720055A (en) 1988-12-01
ES2002568A6 (en) 1988-08-16
HUT47455A (en) 1989-03-28
DK531787D0 (en) 1987-10-12
SE8802881L (en) 1988-08-12
EP0294382A1 (en) 1988-12-14
GB8819148D0 (en) 1988-10-12
GB2207616A (en) 1989-02-08
FI76003B (en) 1988-05-31
PT84283A (en) 1987-03-01
FI861189A (en) 1987-08-13
AU7027887A (en) 1987-09-09
DK531787A (en) 1987-10-12
FI861189A0 (en) 1986-03-20

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