FR2787345A1 - Air is purified by compressing filtering drying and accumulating when accumulator reaches maximum pressure flow through drier stops and air recycled through compressor - Google Patents

Abstract

Air is purified by successively compressing, filtering out suspended particles, drying and accumulating it. The compression lasts a preset time and starts at a minimum value of the filtered or dried air. When the accumulated air reaches a maximum storage pressure the air flow between the compressor and drier is stopped and the upstream pressure kept at an intermediate value by recycling some of the compressed air through the compressor until the pressure drops to a low value. An Independent claim is included for the following: (a) Installation for performing as above. Preferred Features: The accumulator is upstream or downstream of the drier. During recycling the pressure in the compressor is higher than in the accumulator. The drier has two dehumidifiers in parallel and connected alternately to the compressor outlet. A humidifier is regenerated using some of the purified air while ever the air is not being recycled. The filter has two adsorbers in parallel that are connected alternately. Each adsorber is regenerated using dried air drawn off between the drier and the accumulator.

Description

The present invention relates to a process for producing purified air using

  from unpurified air, as well as an installation implementing this process. By way of illustration, the process of the invention is suitable for the production of dry air, with a constant oxygen content, in particular of the type of that meeting the French standard.

  intended for medical use.

  To obtain purified air, the traditionally used methods include the following stages: (a) compression of an unpurified air flow, and storage in an intermediate capacity or buffer (b) filtration of the compressed air flow, to eliminate particles suspended in said compressed stream (c) drying the compressed air stream, and optionally filtered; expansion of part of the compressed air flow to regenerate the drying means (d) final storage of the dried air flow in a so-called homogenization capacity Traditionally, the compression of the flow of unpurified air is done with a traditional compressor, for example piston, and controlled in all or nothing. This requires implementing between compression and drying an intermediate storage capacity, of relatively large volume, mainly to compensate for the all-or-nothing operation of the compressor, smoothly

  vis-à-vis the installation downstream, in particular vis-

opposite the circuit of use.

  Such an intermediate capacity increases the cost of the installation, and requires a certain occupancy on the ground. The object of the present invention is to remedy this drawback. More specifically, the subject of the invention is a process or installation for producing purified air, making it possible to limit the volume of the intermediate capacity to a minimum value, or even to eliminate it in favor of a capacity having a volume not exceeding not the one strictly necessary to separate the condensates

  compressed air, upstream of the dryer.

  A method according to the present invention, has for this purpose, in combination, the following characteristics: 1) the duration of the compression step (a) is at least equal to a predetermined time, and said step begins at a minimum value final storage pressure, or downstream of drying (c); during the compression step (a), the recycling process according to 3) is inactive, until a maximum value of said final storage pressure is reached; 2) at said maximum value of the final storage pressure (d), the flow of compressed air is interrupted between compression and drying, while the flow of unpurified air remains compressed; 3) from the interruption of the compressed air flow, the latter is maintained, upstream of the interruption, at an upstream pressure, having a value between the high value, for example equal to the discharge pressure of the compressor, at which at least part of the compressed air flow is recycled to compression, and a low value at which recycling of the compressed air flow ceases; 4) once the duration of the compression step

  the process according to 1) to 3) is repeated.

  Preferably, during the recycling step according to 3), the upstream pressure between compression and drying has a value greater than the maximum value of the pressure

of final storage.

  Advantageously, the drying is carried out by means of two charges of a moisture-absorbing material, arranged in parallel, through each of which alternately circulates the compressed air, optionally filtered, and a flow of relaxed and purified air, and the method further comprises the following steps:) as long as the flow of compressed air is not interrupted, the relaxed and purified air for the regeneration of a charge is obtained by expansion of a current taken from the compressed and purified air, downstream of the other charge; 6) as long as the flow of compressed air is interrupted, in addition to the sampling according to 5), an additional stream of compressed and purified air is removed between drying and final storage, and added to the stream of compressed air, between interruption and drying, when the pressure downstream of drying exceeds that upstream of said drying. The invention also relates to an installation for producing purified air from unpurified air, such as atmospheric air, adapted to the course of the

  different steps of the above process.

  This installation is now described by

  reference to the single figure in the appendix.

  It comprises at least one treatment line 3 comprising between an inlet 4 for unpurified air 2 and an outlet 5 for purified air 1. One or each treatment line comprises: (a) a compressor 6 for the non-purified air flow purified, for example a screw compressor (b) possibly at least one filter 71,72 for the filtration of the compressed air flow, to remove particles in suspension in said compressed flow (c) a dryer 8,81,82 of the compressed air flow, and possibly filtered

  (d) a final storage capacity 9 for the dried air flow.

  This installation further comprises a control means 10 arranged to perform the following functions: 1) triggering the operation of the compressor 6 at a minimum value of the final storage pressure 9, or downstream of the drying 8, for an operating time of the compressor at least equal to a predetermined time; 5 during the operation of compressor 6, the recycling process according to 3) is inactive, until a maximum value of said final storage pressure is reached; 2) with a valve 11 disposed between the compressor 6 and the dryer 8, for example between the filter and the dryer, isolating said compressor from said dryer, at said maximum value of the final storage pressure, or downstream of drying; and this without stopping the compressor 6; 3) with a recycling conduit 12 connecting a connection 14 upstream of the shut-off valve 11 and the compressor 6, said connection being provided with a recycling valve 13, maintain the pressure upstream of said connection at a value between the high value, for example equal to the discharge pressure of the compressor 6, at which the recycling valve 13 is open, and a low value at which said recycling valve is closed; 4) once the operating time of the

  compressor elapsed, repeat the process according to 1) to 3).

  According to a preferred variant of the installation, this comprises a capacity 15 disposed between the nozzle 14 downstream of the compressor and upstream of the dryer and the shut-off valve 11, on which the upstream pressure is sensed for controlling the recycling valve 13, said capacity having a volume not exceeding that strictly necessary for separating the condensates from

  compressed air, upstream of the dryer 8.

  The compressor 6 is advantageously a screw compressor, and the recycling duct 12

  communicates with the compressor input.

  In accordance with a variant of the installation, the dryer 8 for the compressed and possibly filtered air flow comprises two columns 81, 82 each comprising a charge of an adsorbent material, arranged in parallel, and the control means 10 is arranged to circulate alternately in each column said compressed air flow, and a relaxed and purified air flow, said installation being further arranged to perform the following functions: 5) when the interrupt valve 11 remains open, make circulate 14 through the regenerating column 82, by means of a nozzle 151,152 and an expansion member 16 of the air obtained at the outlet of the column 82 purifying the air in humidity; 6) when the interruption valve 11 remains closed, circulate through a bypass duct 18 a supplementary stream of compressed and purified air, between a nozzle 19 disposed between the dryer 8 and the final storage capacity 9, and a point introduction 20 into the compressed air, disposed between the shut-off valve 11 and the dryer 8, when the pressure downstream of the dryer 8 exceeds

  at 21 the pressure upstream of said dryer 8.

  The final storage capacity 9 can be arranged on the bypass duct 18 upstream or downstream of the

dryer.

  The operation of the installation is now described. In normal operation, for example until a pressure of approximately 10 bar is detected by the sensor 23 in the capacity 9, the valves 11, 24 and 27 which are solenoid valves are on, and the valves 13,

  26 and 29 which are solenoid valves, are non-conducting.

  The unpurified air 2, such as atmospheric air, is introduced into the treatment line 3 through the inlet 4, is compressed in a compressor 6, fills the capacity, is at least partially purified in the capacity 15 and the filters 71, 72, and enters the dryer 8 where it alternately passes through the charge 81 or 82 of adsorbent material, after which the air flow passes through the filter 22, to be stored under pressure in the capacity 9. A portion compressed air is taken at the outlet of the adsorbent charge 81, expanded in the member 16 and passes under low pressure the charge 82 during regeneration. When the pressure in the capacity 9, detected by the sensor 23, reaches 11 bar, the solenoid valve 11 becomes non-conducting, the solenoid valve 13 becomes active, and the flow of compressed air is interrupted. When the maximum pressure of the compressor is detected in capacity 15, the air flow is recycled to said compressor. As long as the pressure downstream of the dryer 8 is higher than the pressure upstream, part of the air flow circulates in the bypass duct 18 of the nozzle

  19 to the inlet conduit 20, fitted with an anti-flap valve

  return 21, in order to then regenerate the charge 82. This guarantees the production at the outlet of the dryer of an air

sleek high quality.

Claims (8)

  1. Method for producing purified air (1) from unpurified air (2), for example atmospheric air, said method comprising at least the following steps: (a) compression (6) of a flow unpurified air (b) possibly filtration (71,72) of the compressed air flow, to remove particles in suspension in said compressed flow (c) drying (8,81,82) of the compressed air flow, and optionally filtered (d) storage (9) of the dried air flow characterized in that, in combination: 1) the duration of the compression step (a) is at least equal to a predetermined time, and said step begins at a minimum value of the final storage pressure, or downstream of drying (c); during the compression step (a), the recycling process according to 3) is inactive, until a maximum value of said final storage pressure (d) is reached; 2) at said maximum value of the final storage pressure (d), the flow of compressed air is interrupted (11) between compression (6) and drying (8), while the flow of unpurified air ( 2) remains compressed; ) from the interruption of the compressed air flow, the latter is maintained, upstream of the interruption (11), at an upstream pressure, having a value between a high value, at which at least part of the compressed air flow is recycled to compression (6), and a low value at which recycling of the compressed air flow stops; ) once the duration of the compression step   the process according to 1) to 3) is repeated.   2. Method according to claim 1, characterized in that, during the recycling process according to 3), the upstream pressure between the compression (6) and the drying (8) has a value greater than the maximum value of the pressure final storage (9).   3. Method according to claim 1, characterized in that the drying (8) is carried out by means of two charges (81,82) of a moisture-absorbing material, arranged in parallel, through each of which circulate alternately l compressed air, possibly filtered, and a relaxed and purified air flow, process according to which:) as long as the compressed air flow is not interrupted (11), the relaxed and purified air for regeneration d 'A charge (82) is obtained by expansion of a current (14) taken from the compressed and purified air, downstream of the other charge (81); 6) as long as the flow of compressed air is interrupted, in addition to the sampling according to 5), a current (18) of additional compressed and purified air is sampled between drying (8) and final storage (9), and added to the compressed air stream, between the interruption (11) and the drying (8), when the pressure downstream of the drying exceeds that upstream of said drying.   4. Installation for producing purified air (1) from unpurified air (2), for example atmospheric air, said installation comprising at least one treatment line (3) comprising between an inlet (4) d air and a purified air outlet (5): (a) a compressor (6) for an un purified air flow (b) possibly at least one filter (71,72) for the filtration of the flow of compressed air, to remove particles suspended in said compressed stream (c) a dryer (8,81,82) from the compressed air stream, and optionally filtered (d) a final storage capacity (9) of the stream dried air characterized in that said installation comprises a control means (10) arranged to perform the following functions: 1) triggering the operation of the compressor (6) at a minimum value of the final storage pressure (9), or downstream of the drying (8), for an operating time at least equal to a predetermined time; during the operation of the compressor (6), the recycling process according to 3) is inactive, until a maximum value of said final storage pressure is reached; 2) with a valve (11) disposed between the compressor (6) and the dryer (8), for example between the filter (71,72) and the dryer (8), isolate said compressor from said dryer, at said maximum value of final storage pressure, or downstream of drying; and this without stopping the compressor (6); 3) with a recycling duct (12) connecting a nozzle (14) upstream of the shut-off valve (11) and the compressor (6), said nozzle being provided with a recycling valve (13), maintain the pressure upstream of said tap at a value between a high value at which the recycling valve (13) is open, and a low value at which said recycling valve is closed; 4) once the operating time of the   compressor elapsed, repeat the process according to 1) to 3).   5. Installation according to claim 4, characterized in that a capacity (15) is disposed between the nozzle (14) and the shut-off valve (11), on which the upstream pressure is captured, for piloting the valve 13, said capacity having a volume not exceeding that strictly necessary to separate   the compressed air condensates, upstream of the dryer (8).   6. Installation according to claim 4, characterized in that the compressor (6) is a screw compressor, and the recycling conduit (12)   communicates with the input of said compressor.   7. Installation according to claim 1, according to which the dryer (8) of the compressed and possibly filtered air flow comprises two columns (81, 82) each comprising a load of an adsorbent material, arranged in parallel, and the control means (10) is arranged to circulate alternately in each column said compressed air flow, and a relaxed and purified air flow, characterized in that said installation is arranged to perform the following functions:) when the valve (11) remains open, circulate (14) through the regenerating column (82), by means of a nozzle (151,152) and an expansion member (16) of the air obtained at the outlet of the column (82) purifying the air in humidity; 6) when the interruption valve (11) remains closed, circulate by a bypass duct (18) an additional stream of compressed and purified air, between a nozzle (19) disposed between the dryer (8) and the capacity final storage (9), and an introduction point (20) in the compressed air, disposed between the shut-off valve (11) and the dryer (8), when the pressure downstream of the dryer (8) exceeds (21) the pressure upstream of said dryer (8). 8. Installation according to claim 7, characterized in that the final storage capacity (9) is disposed on the bypass duct (18) upstream or downstream of the dryer (8).