AU724964B2

AU724964B2 - Process and installation for the production of medical quality air

Info

Publication number: AU724964B2
Application number: AU56280/98A
Authority: AU
Inventors: Robert Montausier
Original assignee: Air Liquide Sante International SA
Current assignee: Air Liquide Sante International SA
Priority date: 1997-03-11
Filing date: 1998-02-25
Publication date: 2000-10-05
Anticipated expiration: 2018-02-25
Also published as: DE69813660T2; EP0864818B1; BR9809207A; PT864818E; AR011956A1; AU5628098A; FR2760823B1; ES2198663T3; DE69813660D1; UY24916A1; FR2760823A1; CA2232109C; CA2232109A1; EP0864818A1

Description

SAUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Air Liquide Sante BDcvcloppcment lo Actual Inventor(s): Robert Montausier Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street n. TMelbourne 3000 AUSTRALIA Invention Title: PROCESS AND INSTALLATION FOR THE PRODUCTION OF MEDICAL QUALITY AIR Our Ref 518797 POF Code: 1290/329618 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- The present invention concerns a process and an installation for the production of medicinal quality air from a flow of atmospheric air.

The medicinal quality air, more commonly called "medical air", has a variety of applications in a hospital environment, where it can be used not only as a respiratory assistance gas, for example in operating theatres or in recovery rooms, but also as a source of pneumatic energy for pneumatic apparatus used especially in operating theatres, or else in the pressurisation of compression chambers.

Traditionally, medicinal air is produced in situ from atmospheric air, which must be subjected to stages of treatment and purification in order to eliminate the greater part of the pollutants which it contains, to wit especially the suspended particles (dust, bacteria...), water vapour, carbon dioxide (CO2), carbon monoxide nitrogen oxides (NOx) and sulfur dioxide (SO 2 The quality specifications, which medicinal air has to meet are especially defined in the standards NFS 90140 and NFS 90155. By way of example, at oO.o S 15 atmospheric pressure and 00C, the concentration of water vapour must be below 0.09 grams per m 3 the concentration of carbon dioxide must be below 350 ppm (parts per Se. million by volume), the concentration of carbon monoxide must be below 5 ppm, the concentration of sulfur dioxide must be below 16 x 10" ppm and the concentration of nitrogen oxide and dioxide must be below 25.5 x 10 3 ppm.

There exist in the state of the art several processes and devices which permit the production of purified air.

In a manner known, atmospheric air is directly taken from the atmosphere, compressed by means of a compressor, such as a piston or a diaphragm compressor, and is then directed to at least a first buffer vessel which serves for smoothing out the variations of air pressure caused by the compression. The air taken up by that buffer vessel is subsequently submitted to a purification stage by drying and adsorption of the impurities present (CO2, CO, NOx, SO 2 before being directed to a second buffer vessel located at the outlet of the purification zone, serving on the one hand for smoothing out the variation in oxygen content of the medicinal air produced, that is to say to homogenise the said medicinal air, and on the other hand, storage of the medicinal quality air before the latter is dispatched to one or more user sites, for example a network of gas pipes in a hospital environment.

C:IWINWORDIGAYINODELETEIS18797.DOC In general, this type of device also comprises mechanical filters, placed between the compressor, the first buffer vessel, the purification zone, the second buffer vessel and/or the user sites.

Processes and devices of this type are especially described in the documents US-A-4,670,223, US-A-4,983,190, FR-A-2728803 and EP-A-0716274.

However, these devices of the state of the art have numerous disadvantages and inconveniences.

Thus, the fact that a first buffer vessel has to be interposed between the means of compression and the air purification zone is rather penalising from the point of view of clutter, that is to say of the space occupied by the device producing the medicinal air in the premises of the hospital building in which it is installed.

In fact, it has been shown that one will find again, in this first buffer vessel, the bulk of the condensate of the water vapour contained in the atmospheric air, as well as a not negligible quantity of oil deriving from the compressor.

15 From there, in order to avoid all problems from the collection of condensates of water vapour, and thus a harmful blockage of the conduits by the particles of ice or oil droplets, it is necessary, even obligatory, to place this first buffer vessel inside the building, that is to say into a temperate site, or to maintain it artificially outside the frozen state with the help of, for example, means of heating.

20 One can easily understand that such needs are very penalising, or even unacceptable, both from the point of view of the clutter as from the point of view of the energy costs.

Moreover, during the production cycles of the medicinal air and/or as a function of the flow to the users, the assembly of the filter ladders, and in particular the air purification zone, is traversed by air under pressure the instantaneous flow of which is variable. From there, in case of high demand for medicinal air by the user(s), problems of scarcity may supervene due to the impossibility for the assembled production chain of supplying a sufficient quantity of medicinal air. Inversely, when the production of medicinal air is greater than the demand from the users, excess pressures can occur in the whole medicinal air production device, which are susceptible to lead to a premature deterioration of the materials causing a complete C:/WINWORD/GAY/NODELETE/518797.DOC stoppage of the medicinal air production device. It being given that such risks are susceptible to putting patients' lives at risk, one has to try to minimise them.

The above discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia before the priority date of each claim of this application.

The aim of the present invention is therefore to propose a process and a device which overcome, or at least alleviate, one or more disadvantages of the prior art.

The present invention thus concerns a process for the production of medicinal air through a production cycle, each cycle of production comprising at least one compression stage of the atmospheric air at a pressure greater than 15 10 5 Pa by means of at least one source of air compression and at least one purification stage of the compressed atmospheric air, by at least one adsorption stage, the purified medicinal air under pressure being placed in reserve in means of storage/homogenisation, in which: the pressure p of the medicinal air is measured inside the means of storage/homogenisation, the pressure P measured is compared to a threshold pressure Po and a predetermined maximum pressure Pm, and the pressure P is adjusted to a pressure so that: Pm P Po.

The present invention also provides an installation for the production of medicinal air comprising: at least one source of air delivering atmospheric air at a pressure greater than 105 Pa, at least one zone for purification of the compressed atmospheric air which comprises means of adsorption, means of storage/homogenisation containing medicinal air and connected to one or more user sites, MCR:W:\WINWORD\MARY\MMHNODELETE\5628-9

.DOC

means of measurement permitting the measurement of the pressure P of the medicinal air contained in the said means of storage/homogenisation, and means of control comparing the measured pressure P to a given threshold pressure Po and controlling, when P Po, the supply of compressed atmospheric air by the said source of air to the said purification zone.

Advantages of at least the preferred embodiments of the invention are that they: are safe and allow the production of medicinal air of a quality which is essentially constant and acceptable; permit a modular production of medicinal air, that is to say adapted both to periods of high and low demands for medicinal air by the user sites; can be easily connected to the network of pipes which conduct the medicinal air into the heart of a hospital or a clinic; and are completely automatic.

According to the circumstances of each case the process of the invention will be able to comprise one or more of the following characteristics: when P Po, one increases the pressure P by making available the source of air compression during a whole number of production cycles of duration D; one maintains the operation of the source of air compression during a time T corresponding to the minimum number of production cycles of duration D necessary for attaining the desired pressure P; wherein the duration D of one production cycle is between 1 and minutes, for preference between 1 and 15 minutes and especially preferred between 2 and 7 minutes; when P Pm one stops the air compression source; the pressure P corresponds to a spot pressure or to a preset pressure interval; one measures the pressure P more or less continuously or intermittently; the pressures Pm and P 0 are set so that: -1 <Pm

PO

MCR:W:\WINWORD\WARY\MMHNODELETE56280-98

.DOC

The pressure Po is contained within the limits 3 x 10 5 Pa and 8 x 10 5 Pa and/or in so far as the pressure Pm lies within the limits 9 x 105 Pa to 15 x 105 Pa.

The present invention besides concerns an installation for the production of medicinal air which comprises: at least one source of air drawing on atmospheric air at a pressure in excess of 105 Pa; at least one zone for the purification of the compressed atmospheric air which contains means of adsorption; means for storage/homogenisation containing medicinal air and which is connected to one or more user sites; means of measurement permitting the determination of the pressure P of the medicinal air contained in the said means of storage/homogenisation and means of control comparing the pressure P measured at a given S' threshold pressure Po and supplying, when P Po, atmospheric air under pressure from the said source of air to the said purification zone.

Depending on the circumstances, the installation according to the invention could comprise one or more of the following characteristics: the said source of air is a diaphragm type compressor, a screw or spiral type compressor or a piston type compressor, for preference a screw 20 compressor (rotary compressor); the said means of adsorption are two adsorbers each containing at least one bed of an adsorbent. These two adsorbers function in a cyclic manner, that is to say, MCR:W:\WINWORD\MARY\MMHNODELETE\5628988 .DOC when one adsorber is in the purification stage, the other adsorber is in the regeneration phase, the adsorbent material contained in the adsorbers is chosen from the group formed by the zeolites, activated carbon, silica gel, activated alumina and their mixtures; the means of storage/homogenisation are one buffer vessel; the medicinal air is directed from the means of storage/homogenisation to at least one user site by means of piping or a network of pipes located in a hospital building; the said means of measuring the pressure P are directly connected to means lo of storage/homogenisation or to an expansion of the said means of storage/homogenisation, at the centre of which there is a pressure equal to the ::pressure P; the said means of control include a programmable automatic control; mechanical means of filtration are placed between the source of compressed air, the purification zone, the means of storage/homogenisation and/or the user sites; the means of control stop the source of flow and/or the start of an audio- or visual alarm, when a differential pressure gauge, designed in a manner so as to measure the pressure between the inlet and the outlet of at least the first filter, and connected to the said means of control, detects a pressure difference greater or equal S 20 to one preset value.

The process and the installation for the production of medicinal air according to too• the invention will now be described in greater detail by means of modes of realisation given as examples but in no way limiting, by reference to the attached figures.

Figure 1 represents a first mode of realisation of an installation for the production of medicinal quality air according to the invention implementing a unique line of compression/purification of the air.

Figure 2 represents a second mode of realisation of the invention for the production of medicinal quality air according to the invention implementing two parallel lines of compression/ purification of the air.

Figure 1 represents an installation for the production of medicinal air comprising a rotary compressor 1 (or a screw compressor) taking in the atmospheric C:/WINWORD/GAY/NODELETE/518797.DOC air and compressing it to a pressure within the range of 2 x 105 Pa to 20 x 105 Pa, for preference between 8 x 105 Pa and 15 x 105 Pa.

The air, which has been compressed in this manner, having been directed, by way of piping 11, as far as a purification zone 2 for the atmospheric air, after having crossed mechanical filtration means 7 consisting of a cyclone 7a followed by three filters 7b, 7c and 7d which can, if necessary, be provided with automatic purge vessels. The cyclone 7a and the filter 5b, 5c and 5d permit the purification of the compressed air flow by retaining not only the dust and other solid particles, which can be found there, as well as part of the water vapour contained in the flow of compressed air, but also to retain the droplets of oil given off by the compressor and thus avoiding pollution of the whole installation for the production of medicinal quality air or of the network of hospital piping to which it is connected.

The purification zone 2 of the compressed atmospheric air, already partially purified, contains two adsorber vessels 2a and 2b each containing one or more beds of an adsorbent material, such as alumina, activated carbon, silica gel, zeolites or their mixtures.

As an indication, one will be able to produce medicinal quality air by using a commercial adsorbent of the zeolite type sold by the UOP Company under the label MOLSIV and the reference 13XAPG.

.o Preferentially, the two adsorbers 2a and 2b operate in alternating phases, that is to say, that when one of the adsorbers is in the purification phase, the other is in the regeneration phase. One will be able to refer, for example to EP-A-0716274, which describes such an arrangement.

In the classical manner, the regeneration of the adsorbent beds is done by counter current sweeping by means of a desorbent gas such as medicinal air or nitrogen.

After its passage through the purification zone, the medicinal air is recovered and distributed, via a conduit 12, 14, to a buffer 3 of storage and homogenisation of the medicinal air.

It is desirable to place on conduit 12, at the outlet of the adsorber vessels means for mechanical filtration 8, 8a, 8b in order to retain possible solid particles from the erosion of the adsorber material in the adsorbers themselves.

C:/WINWORD/GAY/NODELETE/S18797.DOC A slide valve 13, placed downstream of conduit 12, permits the regulation of the inlet of air of medicinal quality into buffer 3.

A pressure sensor 5 is placed into the part of conduit 12 downstream from slide valve 13, that is to say part 14 which is referenced in Figure 1. The pressure which s the medicinal air exerts in that part 14 being equal to the pressure existing in buffer 3, this mode of realisation is preferred. However, it is also possible to adjust the pressure sensor 5 in such a manner that the pressure measurement is carried out directly inside the buffer 3. The pressure sensor 5 is, for example, an analogue sensor of the type 4-20 mA, available commercially from the KELLER Company or from the BOURDON-SEDEME Company, gives information on the means of control 4 with regard to the evolution of the pressure being exerted in buffer vessel 3.

The means of control 4 which comprise a programmable automatic control of the type MICRO 612, which is sold commercially by the MODICON Company especially controls the operation of compressor 1 and the opening and, if need be, the 15 closure of the slide valve 13, as a function of the pressure measurements transmitted to it by the pressure sensor 5. Thus, as far as the pressure exerted inside buffer 3 is Sgreater than a given threshold pressure value Po, for example, P 0 15 x 105 Pa, because of a small demand for medicinal air by the user sites 6, the means of control 4 stop the compressor 1 and close the slide valve 13. In this case, the quantity of S 2o medicinal air enclosed in buffer vessel 3 is sufficient to supply the demands of the user sites 6. The stopping of compressor 1 and the closure of slide valve 13 remain unaltered as long as the pressure. inside the buffer vessel 3 remains greater than the said value of threshold pressure Po.

On the other hand, when the pressure exerted inside the buffer vessel 3 becomes lower than the said threshold value Po, for example lower than 3 x 105 Pa, the controller 4 will start up the compressor 1 and subsequently open slide valve 13, during the number of cycles, that is to say the time periods necessary to attain a maximum pressure Pm which permissible in buffer vessel 3.

If at the end of this number of cycles, the pressure exerted inside buffer vessel 3 is within the minimum threshold value P 0 and the maximum pressure value Pm, then the controller 4 will stop the compression and close the slide valve 13.

C:/WINWORD/GAY/NODELETE/518797.DOC However, if at the end of this production cycle of medicinal air, the pressure inside buffer 3 does not correspond to the anticipated pressure, because of a large demand for medicinal air by the user sites 6, for example, the controller 4 will maintain the compressor operating and slide valve 13 open, that is to say, in other terms, it will continue the production of medicinal air.

Finally, when the pressure sensor 5 detects a pressure inside the buffer 3 which is greater than a maximum value Pm permissible, then the controller 4 will stop the compressor 1 and close slide valve 13, as long as the pressure exerted in buffer 3 does not again fall to a pressure which makes it necessary to restart the installation io for the production of medicinal air.

For preference, the operation of the installation for the production of medicinal air is based on purification cycles. A purification cycle corresponds essentially to the oo** duration D during which the adsorbent contained in the adsorbers 2a, 2b can carry out an efficient purification of the air without having to be regenerated, that is to say, 15 the time T for complete saturation of the adsorbent by adsorption on the latter of the impurities (CO2, CO, NOx, SO 2 contained in atmospheric air to be purified.

*•This duration D depends both on the type of adsorbents used and on the concentration of pollutants present in the air.

A production cycle generally lasts from 1 to 30 minutes and, for preference S 20 from 2 to 7 minutes.

In other terms, it being given that the adsorbers operate in an alternating fashion, that is to say that while adsorber 2a is in the purification stage, the adsorber 2b is in the regeneration stage, and conversely, the duration D of one purification cycle corresponding equally to the time required for the complete regeneration of the adsorbent situated in the adsorber in the purification stage.

For the greater security of the installation, it is desirable that a differential pressure gauge 10 be installed (analogue sensor or differential pressure sensitive switch) between the inlet and the outlet of the filter 7b and which is connected to the controller 4, in order to detect any harmful break in the oil separator located in the outlet of the compressor, which break could cause a pollution of the network.

In effect, if such a break would occur, the blockage of the filter 7b which would result from it, would immediately be detected by the said differential pressure gauge C:/WINWORD/GAY/NODELETE/518797.DOC which would transmit that information by way of the controller 4 which would soon shut down the compressor 1, triggering an audio and/or visual alarm.

In order to avoid any contamination of the network 6 by micro-organisms, it is desirable to install a bacterial filter 9 between the buffer 3 and the said network 6.

Moreover, when the plant is shut down, it is equally possible to maintain under pressure that part of the installation which is between the compressor 1 and the slide valve 13, the latter being in conformity with the information given in FR-A-2728803.

Figure 2 represents an installation for the production of medicinal air according to the invention, which comprises two production lines for the production of medicinal air, which are connected to a single buffer vessel 3, the internal pressure of which is measured by means of pressure sensor 5, which in this case is also connected to controller 4, which controls the compressors and the opening and closing of the slide *ooo valves 13 and 13'.

.In fact, that installation comprises two units which are identical to those oo 15 described in Figure 1, connected to each other.

Throughout this mode of realisation, in case of untimely stoppage of one of the S.two units or production lines for air, medicinal air would nevertheless be produced and directed toward the user sites 6 by taking the second production unit into service, the two units being controlled by the same control 4 and the medicinal air produced being oo S 20 directed to the same buffer 3.

In the same way, if the demand for medicinal air would be greater than the capacity of one production line, the second line would start up in order to meet the needs of this excess consumption.

Throughout the description and claims of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives or components or integers.

C:/WINWORDGAY/NODELETEI518797.DOC

Claims

1. A process for the production of medicinal air through a production cycle, each cycle of production comprising at least one compression stage of the atmospheric air at a pressure greater than 105 Pa by means of at least one source of air compression and at least one purification stage of the compressed atmospheric air, by at least one adsorption stage, the purified medicinal air under pressure being placed in reserve in means of storage/homogenisation, in which: the pressure p of the medicinal air is measured inside the means of storage/homogenisation, 1- the pressure P measured is compared to a threshold pressure Po and a predetermined maximum pressure Pm, and the pressure P is adjusted to a pressure so that: Pm P P.

2. A process according to claim 1, wherein when P Pc, one increases the 15 pressure P by bringing about the start up of the source of air compression during a whole number of production cycles of duration D. :i

3. A process according to claim 2, wherein one maintains the operation of •the source of air compression during a time T which corresponds to the minimum S* number of production cycles of duration D necessary for attaining the desired pressure P.

4. A process according to either one of claims 2 or 3, wherein the duration D of one cycle of production lies within the limits of 1 to 30 minutes, for preference between 2 and 7 minutes.

5. A process according to claim 1, wherein when p pm one stops the 25 source of air compression.

6. A process according to any one of claims 1 to 5, wherein the pressure P, when Pm P Pc, corresponds to a spot pressure or to a period of prefixed pressure.

7. A process according to any one of claims 1 to 6, wherein one measures the pressure P essentially continuously or in a sequential manner.

8. A process according to any one of claims 1 to 7, wherein one fixes the pressures Pm and so that: 1 Fm 1$ c.PO W:\mary\MMHNODEL\5280-98.dc

9. A process according to any one of claims 1 to 8, wherein the pressure P 0 lies within the range 3 x 105 Pa to 8 x 10 5 Pa and/or in that the pressure Pm lies within the range 9 x 105 Pa to 15 x 105 Pa.

An installation for the production of medicinal air comprising: at least one source of air delivering atmospheric air at a pressure greater than 10 5 Pa, at least one zone for purification of the compressed atmospheric air which comprises means of adsorption, means of storage/homogenisation containing medicinal air and connected to one or more user sites, means of measurement permitting the measurement of the pressure P of the medicinal air contained in the said means of storage/homogenisation, and means of control comparing the measured pressure P to a given threshold pressure Po and controlling, when P Po, the supply of compressed 15 atmospheric air by the said source of air to the said purification zone.

11. An installation according to claim 10, wherein the said source of air is a screw compressor, piston compressor or a spiral or diaphragm compressor.

12. An installation according to claim 10, wherein the said means of 20 adsorption, which comprise at least two adsorbers, each containing at least one 20 bed of at least one adsorbent material.

13. An installation according to claim 10, wherein the storage/homogenisation means are a buffer vessel.

:14. An installation according to claim 10, wherein the said means of control include a programmable automatic control.

15. An installation according to any one of claims 10 to 14, wherein the means of mechanical filtration are installed between the source of compressed air, the purification zone, the means of storage/homogenisation and/or the user sites.

16. An installation according to any one of claims 12 to 15, wherein the control controls the stoppage of the source of flow and/or the triggering of an audio and/or visual alarm, when a differential pressure gauge, designed in such a manner as to measure the pressure between the inlet and the outlet of at least the first filter and W:\maryXMMHNODEL56280-98.doc connected to the said control, detects pressure difference greater or equal than a prefixed value.

17. A process according to claim 1 substantially as hereinbefore described with reference to any of the figures and/or examples.

18. An installation according to claim 10 substantially as hereinbefore described with reference to any of the figures and/or examples. DATED: 19th February, 1998 PHILLIPS ORMONDE FITZPATRICK A Attorneys for: G se AIR LIQUIDE SANTE DEVELPPEEMENT C* So 0 s o C:/WINWORD/GAY/NODELETE/518797.DOC