EP0586294B1 - Device for the distribution of cryogenic fluid to apparatuses using them - Google Patents
Device for the distribution of cryogenic fluid to apparatuses using them Download PDFInfo
- Publication number
- EP0586294B1 EP0586294B1 EP19930402120 EP93402120A EP0586294B1 EP 0586294 B1 EP0586294 B1 EP 0586294B1 EP 19930402120 EP19930402120 EP 19930402120 EP 93402120 A EP93402120 A EP 93402120A EP 0586294 B1 EP0586294 B1 EP 0586294B1
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- European Patent Office
- Prior art keywords
- pressure
- valve
- liquid
- piston
- fluid
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B15/00—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts
- F04B15/06—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts for liquids near their boiling point, e.g. under subnormal pressure
- F04B15/08—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts for liquids near their boiling point, e.g. under subnormal pressure the liquids having low boiling points
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C9/00—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2201/00—Vessel construction, in particular geometry, arrangement or size
- F17C2201/01—Shape
- F17C2201/0104—Shape cylindrical
- F17C2201/0109—Shape cylindrical with exteriorly curved end-piece
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2203/00—Vessel construction, in particular walls or details thereof
- F17C2203/03—Thermal insulations
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2205/00—Vessel construction, in particular mounting arrangements, attachments or identifications means
- F17C2205/03—Fluid connections, filters, valves, closure means or other attachments
- F17C2205/0302—Fittings, valves, filters, or components in connection with the gas storage device
- F17C2205/0323—Valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2205/00—Vessel construction, in particular mounting arrangements, attachments or identifications means
- F17C2205/03—Fluid connections, filters, valves, closure means or other attachments
- F17C2205/0302—Fittings, valves, filters, or components in connection with the gas storage device
- F17C2205/0338—Pressure regulators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
- F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
- F17C2223/0146—Two-phase
- F17C2223/0153—Liquefied gas, e.g. LPG, GPL
- F17C2223/0161—Liquefied gas, e.g. LPG, GPL cryogenic, e.g. LNG, GNL, PLNG
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
- F17C2227/01—Propulsion of the fluid
- F17C2227/0121—Propulsion of the fluid by gravity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
- F17C2227/01—Propulsion of the fluid
- F17C2227/0128—Propulsion of the fluid with pumps or compressors
- F17C2227/0135—Pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
- F17C2227/01—Propulsion of the fluid
- F17C2227/0128—Propulsion of the fluid with pumps or compressors
- F17C2227/0135—Pumps
- F17C2227/0142—Pumps with specified pump type, e.g. piston or impulsive type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
- F17C2227/04—Methods for emptying or filling
Definitions
- the present invention relates to a device for transferring cryogenic fluids in industrial establishments between a storage tank and at least one user device.
- Cryogenic fluids are generally transported by truck to their place of use, where they are stored in insulated tanks; from there they are distributed to the user devices by a cryogenic piping or line, under the effect of the pressure which is established in the storage tank by the vaporization of a part of the cryogenic fluid. A balance is established in a few hours between the liquid and gas phases of the tank.
- the circulation is two-phase.
- the two-phase for a given mass flow, increases the pressure losses, makes necessary large diameters of line and accessories, and creates irregularities in operation.
- lines of more than 50 meters may have a random walk, or a very high cost if they are isolated under vacuum in large diameter.
- thermodynamic efficiency of the cryogenic fluid corresponds to the enthalpic variation of the fluid between its initial state, in the reservoir, and its final state, at the outlet of the user device, after vaporization and possible reheating gas produced; it is therefore interesting to find the lowest initial enthalpy, that is to say the lowest equilibrium pressure at the reservoir that can be reached in practice.
- a third aspect is not negligible in terms of yield: maintaining the storage pressure means replacing the volume of liquid drawn off by the same volume of gas; however the insulation of industrial tanks is of high quality, and, in the case of nitrogen, if the contents of a tank are used in less than four days, the heat inputs to the tank will be insufficient to maintain the pressure, and 0.5 to 1.5% of the fluid should be vaporized by a "heater".
- Some examples are known of raising the reservoir relative to the user station in order to benefit from the pressure of the column of fluid.
- Known centrifugal cryogenic pumps are ill suited to small flow rates, variations in flow rate, vaporization by loss of hydraulic efficiency in the event of a reduction in flow rate, causing risks of cavitation.
- Alternative submerged mechanical pumps are known, in installations for filling gas cylinders, pushing the liquid to more than 200 ⁇ 105 Pa in a vaporizer; however, these pumps are not suitable for suctioning the liquid at low pressure.
- the pumping of a cryogenic fluid at low pressure with reciprocating piston, the inlet part of which is immersed in the liquid to be pumped is known from FR-A-2 613 034.
- the object of the present invention is to provide a simple and effective cryogenic fluid pumping device, to raise its pressure to a constant and adjustable level, for variable flows, typically between a zero flow and a maximum depending on the size of the user device, this pumping device being advantageously supplemented by one or more reservoirs for accumulating the fluid under pressure.
- This device allows a new mode of distribution of cryogenic fluids to user devices; taking the case of nitrogen, the filling on delivery will be at the lowest pressure, which constitutes a control of the quality of the fluid, without regulating the pressure at "unloading", an operation which is often a source of installation irregularities; the storage tank, at low pressure, can be lightened, without a pressure regulation system; the lines will be designed for the monophasic, allowing smaller diameters and / or longer lengths at lower costs.
- cryogenic fluid will be understood to mean a liquefied gas such as nitrogen, argon, oxygen, CO2, etc., the user devices being able to be tunnels, baths, runoffs or spraying liquids, etc ..., but also evaporators, as well as carbon dioxide production devices.
- Figures 1 and 2 respectively represent a part of a MOLLIER diagram of nitrogen and CO2, on which have been plotted the points representative of different distribution conditions of this fluid.
- Figure 3 is a partial schematic view of a pumping device according to the invention.
- FIG. 4 is a sectional view of the intake valve and of the piston of the pump in FIG. 3.
- FIG. 5 is an overall diagram of a distribution of carbon dioxide, according to the invention.
- the nitrogen diagram in Figure 1 shows the liquid / vapor equilibrium curve for relative pressures (PR) between zero (atmospheric pressure) and 3 x 105 Pa, along the vertical axis, the enthalpies (H) being carried on the horizontal axis.
- PR relative pressures
- H enthalpies
- liquid nitrogen is normally delivered to its point of use at a pressure of 0.7 x 105 Pa: in fact, nitrogen is less than 0.05 x 105 Pa in the storage facilities of liquefaction.
- Each pumping increases the enthalpy by 0.7 kcal / kg by loss of efficiency of the centrifugal pumps, which corresponds to an increase of 0.22 x 105 Pa in the pressure of the liquid in this pressure zone.
- Transport, heat inputs and mechanical effects combined raises the pressure by 0.07 x 105 Pa for a journey of 100 km.
- the nitrogen pressure in the tank will therefore be tiny, of 0.63 x 105 Pa. Note that the value rounded to 0.7 x 105 Pa translates the good quality of the fluid.
- Nitrogen at 0.7 x 105 Pa is represented in (A1) on the diagram, as well as, in A2, nitrogen in equilibrium at 2 x 105 Pa, very common in the current state of the art; if the point of use is higher than the storage, the pressure will often be 2.6 x 105 Pa, shown in A3).
- Points A'2 or A'3 represent nitrogen at the arrival of a user station, the two-phase often representing 3 to 5% by weight, or 150 to 250% by volume.
- increasing the pressure by pumping from 0.7 to 2.6 x 105 Pa, as shown in A'1 will allow much greater pressure losses and heat inputs, represented by A "1 without formation of vapor.
- one With regard to the comparisons of the initial enthalpies H1, H2, H3, one must establish the variations, therefore the quantities of cold produced in kcal / kg, for 2 final states: one corresponds to the enthalpy of the gas at - 196 ° and atmospheric pressure, when only latent heat is used, such as immersion, i.e. 18.45 kcal / kg; the other corresponds to freezing tunnels, where the gas can exit at - 50 °, with an enthalpy of 55kcal / kg.
- Nitrogen at 0.7 x 105 Pa will produce, in the case of immersion, respectively 7.2% and 9.8% more cold than nitrogen at 2 and 2.6 x 105 Pa, and therefore the 6.7% or 9% of the amount of liquid to be saved will be saved.
- the recovery of the sensible heat of the gas, in tunnels for example, does not depend on the initial enthalpy, and the savings due to the use of nitrogen at 0.7 x 105 Pa will be between 3.7% and 5%, respectively, with respect to nitrogen at 2 x 105 Pa and 2.6 x 105 Pa.
- the system according to the invention adds those resulting from the elimination of the pressure maintenance of the tank: even in the event of rapid emptying, the pressure of 0.7 x 105 Pa will drop only by 0.15 x 105 Pa, or 0.55 x 105 Pa in the end, without drawbacks.
- FIG. 2 represents the states of carbon dioxide, plotted on a diagram, the absolute pressures being represented on the vertical axis, and the enthalpies on the horizontal axis; we will quote the analogies and the differences of CO2 compared to nitrogen.
- a final state of CO2 can be the gas leaving a refrigeration tunnel at atmospheric pressure (PA) and -50 ° C ( HT); another state final will be, after production of snow and its sublimation, the "outlet" of gas at -78.5 ° C, represented by HN.
- the enthalpy variation, or usable cold, essentially corresponds to latent heat; it is therefore all the more interesting to lower the initial enthalpy:
- the usual initial state is the delivery of liquid CO2 at -20 ° C and 20 x 105 Pa, represented in D1), which can be stored completely in the manner of liquid nitrogen, in vacuum-insulated tanks; generally less efficient storages are used, the pressure of which is controlled at 20 ⁇ 105 Pa by a refrigeration unit; in the latter case, centrifugal pumps are known for looping the liquid CO C to keep the line cold, and not for the purpose of obtaining subcooling of the liquid by increasing pressure.
- the gas formed by the losses in efficiency of the pumps and the heat inputs returns at the end of the loop to the tank, where it is condensed by the refrigeration unit.
- the pumping device which is the subject of the invention makes it possible to use CO2 brought in the vicinity of the triple point, either by cooling, or by vaporization and reduction of the pressure, as represented by D3: the pressure can be increased to the point representative of D'3, so that in use (D "3) the risk of solid formation is reduced.
- the pump admits the circulation of fluid loaded with particles, and if the low pressure tank is loaded on its inlet , we could even use a mixture of liquid and solid CO2 at the triple point.
- FIG. 3 schematically illustrates the pumping device according to the invention: an isolated storage tank 1 contains the cryogenic fluid at the lowest possible pressure: for nitrogen, this tank is storage, receiving liquid nitrogen at 0.7 x 105 Pa; for CO2, it is a low pressure tank, generally separate from the delivery tank.
- an isolated storage tank 1 contains the cryogenic fluid at the lowest possible pressure: for nitrogen, this tank is storage, receiving liquid nitrogen at 0.7 x 105 Pa; for CO2, it is a low pressure tank, generally separate from the delivery tank.
- a line 2 is the liquid outlet from the reservoir, which feeds by gravity the pumping device via a stop valve 3; it is desirable to oversize the latter 3 ', and to reduce the horizontal distance during pumping.
- the outlet of tank 1 must be 0.5 to 1 meter higher than the inlet of the pumping device.
- the pumping device comprises at its lower part a small reservoir 4 used to supply liquid devoid of gas to the inlet valve 6 of the pump; for this it is provided with a vent tube 5 connected by an insulated tube to the gas phase (upper part) of the reservoir 1; the tube 5 is also used for cooling the pumping device in the case of the use of CO2. It can alternatively be replaced by a gas eliminator.
- the pump is of the piston and valve type, vertical.
- a tube 7 fixed by flanges to the reservoir 4 carries the cylinder 8 in which the piston 9, itself carrying a discharge valve, is actuated by a rod 10 passing through a set 11 and 11 'of seals, between which gas is injected under pressure from the discharge, through a heating tube 12.
- Only the lower part of the pump is insulated, as shown by the dashed line 13: the liquid leaves the tube 7 is made by a nozzle 14, located just above above the cylinder 8 and the tube and pump fixing flange, so that the upper part of the tube 7 contains a volume of slightly conductive gas, and that the seals 11 and 11 ′ remain at room temperature.
- the piston control rod 10 is connected to a motor 15 giving an adjustable reciprocating movement, a particularly advantageous embodiment using a motor with pneumatic or hydraulic cylinders.
- a motor 15 giving an adjustable reciprocating movement, a particularly advantageous embodiment using a motor with pneumatic or hydraulic cylinders.
- an important characteristic of the movement of the piston is that it must be slow during the ascent, which corresponds to the suction or admission phase of the pumping cycle, compared to the descent movement, which corresponds to the setting. in fluid pressure and in its discharge, and which can be as fast as it is mechanically possible.
- the pressure of the working fluid actuating the engine 15 is regulated by a pressure reducer 17: the ratio of the active sections of the motor cylinder and the pump piston and the pressure setting of the pressure reducer define the maximum pressure to which the cryogenic fluid will be brought.
- a possible adjusting member 18 conditions the flow of working fluid, and therefore the overall duration of an up / down cycle. This duration must be compatible with the operation of the motor fluid distributor 19, actuated by a double timer, or by a timer and a limit switch 21.
- An adjustable unidirectional flow reducer 20 makes it possible to adjust the slow ascent rate (admission), the discharge being free or regulated by the member 18.
- Another limit switch 21 ' can allow the control of the piston ascent rate.
- the detector 21 can be used for counting and determining the instantaneous flow rates, means, or cumulative quantities of cryogenic fluid supplied to an item of equipment.
- Two distribution systems can raise the pressure of counted and regulated quantities of two different liquefied gases, such as nitrogen and oxygen, so that after mixing in the liquid phase, the pressure is greater than the bubble pressure; liquid phase metering can also be used before vaporization and mixing in the gaseous state.
- two different liquefied gases such as nitrogen and oxygen
- FIG. 4 shows the details of the pump and in particular of the piston and of the intake valve: the body of the valve 6 is fixed on the cylinder 8; the valve itself is a flat disc with rounded edges, the lifting of which is limited by a rod 25; it rests on a seat 24, and is guided by the tie rods 26 for assembling the valve bottom 27.
- the disc is preferably made of high density polyethylene or PTFE.
- the piston is constituted by a tubular body 9 fixed on the control rod 10, and provided with windows 22 for passage of the pumped fluid; a hollow screw 28 fixed on the piston of the annular seals 30 with upward-facing lips, made of polyethylene, PTFE, or leather, by tightening spacers 29.
- a ball 31 forms a sealing valve by resting on the screw 28; the rod 10 abuts the lifting of the ball.
- the piston touches the intake valve 23 in order to reduce the "dead volume" of fluid between the piston and the valve: in fact, upon lifting, the acceleration of the valve is several times the gravity, by pressure by below, from the liquid column, and by vacuum from above, due to the upward movement of the piston; we limit this effect and the vaporization, reducing the volume of liquid concerned, by bringing the piston and valve as close as possible.
- the liquid arrives from the storage tank through line 2 and completely fills the pump tank 4 with evacuation of any gas through the vent 5; the liquid descends through the space between the body of the valve 6 and the reservoir 4.
- the valve 23 When the piston is raised, the valve 23 is lifted by pressure difference between the lower and upper faces: the valve must be as light as possible, and in the case of a seat diameter of 80 mm., It will be set to rest on a spider carried by an annular piece 27; the liquid must strictly follow the upward movement of the piston, since any vaporization must be avoided.
- the pressure of the fluid on the discharge side, and the pressure of the gas contained in the tube 7, which are identical, are exerted on the upper face of the piston and on the ball 31.
- the piston rise speed is 0.55 m / s: this is also the nitrogen rise speed.
- the narrowest flow section is in the vicinity of the valve seat; this is also the highest speed of nitrogen, around 1.30 m / s, corresponding to a dynamic pressure of 700 Pa.
- the ascent of the piston is the flow phase through the inlet valve; the piston ascent rate must typically have a maximum value of 0.5 m / s for the rise of the liquid to follow the rise of the piston.
- the rate of rise of the piston conditions the flow rate, and it is desirable that, in a cycle, the descent phase is as brief as mechanically possible, since there is no thermodynamic drawback, and the flow will be optimum in chained cycles.
- the flow rate is proportional to the active surface of the piston, ie the square of its diameter.
- a pressure drop factor of less than 2.86 has been found; multiplied by the dynamic pressure of the highest speed of the fluid in the valve, it indicates its overall pressure drop.
- the same speed must be kept in the smallest section of the valve, namely in the vicinity of the seat, the valve lift being always in practice limited to 5mm; keeping the same fluid speed requires that the diameter of the valve seat be proportional to the square of the piston diameter. If a smaller valve is used, the piston ascent rate must be reduced: the diameter of the piston will be oversized, causing greater pressures of the working fluid.
- the transition times from rise to fall, and vice versa, of the piston are between 25 and 50 ms, and the average speed of the piston is little different from the instantaneous speed during a movement of the cycle. Therefore, the stroke length is not an essential factor of flow, but frequency, with a mechanical interest.
- the pump described above, with piston diameter 45 mm, valve seat 40 mm, stroke 100 mm, can be industrially used at a rate typically of around 125 to 130 cycles / min, corresponding to a flow rate of 1100 to 1200 liters / hour of cryogenic fluid, suitable for many applications.
- a double flow pump i.e. 2200 to 2400 liters / hour, would have a piston diameter multiplied by ⁇ 2, or approximately 65 mm, a valve seat diameter proportional to the flow rate, ie 80 mm, and an operating rate of about 125 to 130 cycles / min. if the stroke is 100 mm, and about 85 cycles per minute, if the stroke is 150 mm.
- the present device provides a solution by the use of accumulators under pressure, either at the point of use, or online.
- the reservoir 1 receives the CO2 from a delivery reservoir 32, at a pressure P1 of the order of 20 ⁇ 105 Pa, via a line 33; a float 34 controls a filling means 35 to keep a constant level; the liquid at 20 ⁇ 105 Pa is introduced into the tank by means of a phase separator 36.
- a demister 37 placed in the tank 1, is located at the intake of a single-stage compressor 38 associated with a gas-gas exchanger 39.
- the compressor 38 raises the pressure of the CO2 gas in the tank 1 from 6 to 22 ⁇ 105 Pa, to reliquefy it by the condenser 40, connected at 41 and 42 to a refrigeration circuit (not shown).
- the tank pressure can be lowered by refrigeration to -53 ° C.
- the discharge line 14 of the pumping device ensures a flow of liquid CO2 at -53 ° C, at a pressure of 10 x 105 Pa, for example, (therefore sub-cooled relative to the equilibrium temperature at 10 x 105 Pa, which is - 40 °), until the use represented by a solenoid valve 48.
- a gas trap 53 for example with float 54, ensures that the line is kept cold, even if it is not there is no traffic.
- the gas at 10 x 105 Pa, leaving the trap 53 is brought through a pipe 55, to the gas phase of the tank 1, or to the reliquefaction. This arrangement advantageously replaces the technique of keeping cold by loop of liquid with circulation pump.
- an isolated accumulator tank 43 allows operation if the average flow rate is lower than the nominal flow rate of the pumping device: the latter fills the accumulator 43 up to the level defined by a detector 44; as long as the level is not reached, a valve 45 in a line connecting the upper parts of the tanks 1 and 43, is open, and the gas repelled by the liquid in the tank 43 joins the tank 1, passing through a spillway 46 set to maintain an upstream pressure of 8 x 105 Pa for example; this spillway can also be replaced by simple rolling.
- the pumping device 7 When the accumulator tank 43 is full, without use, the pumping device 7 maintains the pressure at zero flow, by the adjustment established on the pressure of its working fluid.
- a solenoid valve 49 for pressurizing the accumulator tank 43 disposed in a line connecting the upper parts of the tanks 43 and 32 is also opened; the pressure of the pressurization gas coming from the storage tank 32 is adjusted by the pressure reducer 50 which ensures, for example, a downstream pressure of 11 x 10, Pa, so that the fluid reaching use 48 comes first from the accumulator 43; on the contrary, it will be possible to adjust the downstream pressure of the regulator 50 to a value lower than the pumping pressure, for example 9.5 x 105 Pa, so that the flow rate of the pumping device is used as a priority, and the accumulator 43 only as a backup.
- a level control 47 can be used in the accumulator tank 43 stopping the supply of fluid supplied for use 48 in the event of excessive draining of the accumulator, the size of the latter having to be adapted to Requirement ; one can also use a pressure switch P3 to check that the pressure in the accumulator 43 is always at a certain level above that of the triple point.
- This accumulator system can optionally be adapted to fluids such as liquid nitrogen; in this case, the evacuation of the gas from the accumulator takes place in the atmosphere, and the pressurization can be carried out by increasing the size of the vaporizer 12 of FIG. 3, and by connecting it to the solenoid valve 49.
- valve 56 For the record, the usual safety and purging devices have been shown, respectively a valve 56 and a valve or solenoid valve 57; a drain valve for the pump reservoir 4 must also be provided when the installation is stopped.
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- General Engineering & Computer Science (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
- Jet Pumps And Other Pumps (AREA)
Description
La présente invention concerne un dispositif de transfert de fluides cryogéniques dans des établissements industriels entre un réservoir de stockage et au moins un appareil utilisateur.The present invention relates to a device for transferring cryogenic fluids in industrial establishments between a storage tank and at least one user device.
Les fluides cryogéniques sont généralement transportés par camion à leur lieu d'utilisation, où ils sont stockés dans des réservoirs isolés; de là ils sont distribués aux appareils utilisateurs par une tuyauterie ou ligne cryogénique, sous l'effet de la pression que l'on établit dans le réservoir de stockage par la vaporisation d'une partie du fluide cryogénique. Il s'établit en quelques heures l'équilibre entre phases liquide et gazeuse du réservoir.Cryogenic fluids are generally transported by truck to their place of use, where they are stored in insulated tanks; from there they are distributed to the user devices by a cryogenic piping or line, under the effect of the pressure which is established in the storage tank by the vaporization of a part of the cryogenic fluid. A balance is established in a few hours between the liquid and gas phases of the tank.
Ce mode opératoire a l'avantage de la simplicité, mais il présente plusieurs inconvénients:This procedure has the advantage of simplicity, but it has several disadvantages:
Lorsque le liquide cryogénique circule dans la tuyauterie il subit à la fois des pertes de charge et des entrées de chaleur, rompant l'équilibre et causant sa vaporisation: la circulation est diphasique. Le diphasique, pour un débit massique donné, augmente les pertes de charge, rend nécessaires de gros diamètres de ligne et d'accessoires, et crée des irrégularités de fonctionnement. Pour l'azote, par exemple, des lignes de plus de 50 mètres pourront avoir une marche aléatoire, ou un coût très élevé si elles sont isolées sous vide en gros diamètre.When the cryogenic liquid circulates in the piping it undergoes both pressure losses and heat inputs, breaking the balance and causing its vaporization: the circulation is two-phase. The two-phase, for a given mass flow, increases the pressure losses, makes necessary large diameters of line and accessories, and creates irregularities in operation. For nitrogen, for example, lines of more than 50 meters may have a random walk, or a very high cost if they are isolated under vacuum in large diameter.
Un autre inconvénient a trait au rendement thermodynamique du fluide cryogénique: le froid utilisable correspond à la variation enthalpique du fluide entre son état initial, dans le réservoir, et son état final, à la sortie de l'appareil utilisateur, après vaporisation et réchauffage éventuel du gaz produit; il est donc intéressant de rechercher l'enthalpie initiale la plus basse, c'est à dire la pression d'équilibre au réservoir la plus basse que l'on puisse atteindre en pratique.Another drawback relates to the thermodynamic efficiency of the cryogenic fluid: the usable cold corresponds to the enthalpic variation of the fluid between its initial state, in the reservoir, and its final state, at the outlet of the user device, after vaporization and possible reheating gas produced; it is therefore interesting to find the lowest initial enthalpy, that is to say the lowest equilibrium pressure at the reservoir that can be reached in practice.
Un troisième aspect n'est pas négligeable sur le plan du rendement: maintenir la pression au stockage, c'est remplacer le volume de liquide soutiré par le même volume de gaz; or l'isolation des réservoirs industriels est de grande qualité, et, dans le cas de l'azote, si on utilise le contenu d'un réservoir en moins de quatre jours, les entrées de chaleur au réservoir seront insuffisantes pour maintenir la pression, et on devra vaporiser 0,5 à 1,5 % du fluide par un "réchauffeur".A third aspect is not negligible in terms of yield: maintaining the storage pressure means replacing the volume of liquid drawn off by the same volume of gas; however the insulation of industrial tanks is of high quality, and, in the case of nitrogen, if the contents of a tank are used in less than four days, the heat inputs to the tank will be insufficient to maintain the pressure, and 0.5 to 1.5% of the fluid should be vaporized by a "heater".
Les inconvénients ci-dessus, et la pratique paradoxale de réchauffer un fluide dont on utilise le froid, afin d'élever sa pression, sont néanmoins acceptés parce qu'il n'existe pas d'autre moyen pratiquement utilisable de distribution du fluide cryogénique à l'appareil utilisateur.The above drawbacks, and the paradoxical practice of heating a fluid which is used cold, in order to raise its pressure, are nevertheless accepted because there is no other practically usable means of distributing the cryogenic fluid to the user device.
On connaît quelques exemples de surélévation du réservoir par rapport au poste utilisateur pour bénéficier de la pression de la colonne de fluide. Les pompes cryogéniques centrifuges connues s'accommodent mal de petits débits, de variations de débit, de la vaporisation par pertes de rendement hydraulique en cas de réduction du débit, entraînant des risques de cavitation. On connaît des pompes mécaniques alternatives immergées, dans les installations de remplissage de bouteilles de gaz, poussant le liquide à plus de 200 x 10⁵ Pa dans un vaporiseur; ces pompes ne sont toutefois pas adaptées à l'aspiration du liquide à faible pression. Le pompage d'un fluid cryogénique à pression basse à piston à mouvement alternatif, dont la partie admission est immergée dans le liquide à pomper est connu du FR-A-2 613 034.Some examples are known of raising the reservoir relative to the user station in order to benefit from the pressure of the column of fluid. Known centrifugal cryogenic pumps are ill suited to small flow rates, variations in flow rate, vaporization by loss of hydraulic efficiency in the event of a reduction in flow rate, causing risks of cavitation. Alternative submerged mechanical pumps are known, in installations for filling gas cylinders, pushing the liquid to more than 200 × 10⁵ Pa in a vaporizer; however, these pumps are not suitable for suctioning the liquid at low pressure. The pumping of a cryogenic fluid at low pressure with reciprocating piston, the inlet part of which is immersed in the liquid to be pumped is known from FR-A-2 613 034.
L'objet de la présente invention est de proposer un dispositif de pompage de fluide cryogénique simple et efficace, pour élever sa pression à un niveau constant et réglable, pour des débits variables, typiquement entre un débit nul et un maximum dépendant de la taille de l'appareil utilisateur, ce dispositif de pompage étant avantageusement complété par un ou plusieurs réservoirs d'accumulation du fluide sous pression.The object of the present invention is to provide a simple and effective cryogenic fluid pumping device, to raise its pressure to a constant and adjustable level, for variable flows, typically between a zero flow and a maximum depending on the size of the user device, this pumping device being advantageously supplemented by one or more reservoirs for accumulating the fluid under pressure.
Ce dispositif permet un nouveau mode de distribution des fluides cryogéniques aux appareils utilisateurs ; en prenant le cas de l'azote, le remplissage à la livraison se fera à la plus basse pression, ce qui constitue un contrôle de la qualité du fluide, sans régulation de la pression au "dépotage", opération qui est souvent source d'irrégularités de marche de l'installation; le réservoir de stockage, à basse pression, pourra être allégé, sans système de régulation de pression; les lignes seront conçues pour le monophasique, permettant de plus petits diamètres et/ou de plus grandes longueurs à des moindres coûts. Au sens de la présente invention, on entendra par fluide cryogénique, un gaz liquéfié comme l'azote, l'argon, I'oxygène, le CO₂, etc..., les appareils utilisateurs pouvant être des tunnels, bains, ruissellements ou pulvérisation de liquides, etc..., mais aussi des évaporateurs, ainsi que des appareils de production de neige carbonique.This device allows a new mode of distribution of cryogenic fluids to user devices; taking the case of nitrogen, the filling on delivery will be at the lowest pressure, which constitutes a control of the quality of the fluid, without regulating the pressure at "unloading", an operation which is often a source of installation irregularities; the storage tank, at low pressure, can be lightened, without a pressure regulation system; the lines will be designed for the monophasic, allowing smaller diameters and / or longer lengths at lower costs. Within the meaning of the present invention, the term “cryogenic fluid” will be understood to mean a liquefied gas such as nitrogen, argon, oxygen, CO₂, etc., the user devices being able to be tunnels, baths, runoffs or spraying liquids, etc ..., but also evaporators, as well as carbon dioxide production devices.
Un ensemble de schémas et dessins permet de décrire le dispositif et son fonctionnement:A set of diagrams and drawings makes it possible to describe the device and its operation:
Les figures 1 et 2 représentent respectivement une partie d'un diagramme de MOLLIER de l'azote et du CO₂, sur lesquels ont été portés les points représentatifs de différentes conditions de distribution de ce fluide.Figures 1 and 2 respectively represent a part of a MOLLIER diagram of nitrogen and CO₂, on which have been plotted the points representative of different distribution conditions of this fluid.
La figure 3 est une vue schématique partielle d'un dispositif de pompage selon l'invention.Figure 3 is a partial schematic view of a pumping device according to the invention.
La figure 4 est une vue en coupe du clapet d'admission et du piston de la pompe de la figure 3.FIG. 4 is a sectional view of the intake valve and of the piston of the pump in FIG. 3.
La figure 5 est un schéma d'ensemble d'une distribution de dioxyde de carbone, suivant l'invention.FIG. 5 is an overall diagram of a distribution of carbon dioxide, according to the invention.
Le diagramme de l'azote de la figure 1 montre la courbe d'équilibre liquide/vapeur pour des pressions relatives (PR) entre zéro (pression atmosphérique) et 3 x 10⁵ Pa, suivant l'axe vertical, les enthalpies (H) étant portées sur l'axe horizontal.The nitrogen diagram in Figure 1 shows the liquid / vapor equilibrium curve for relative pressures (PR) between zero (atmospheric pressure) and 3 x 10⁵ Pa, along the vertical axis, the enthalpies (H) being carried on the horizontal axis.
On peut considérer que l'azote liquide est normalement livré à son point d'utilisation à une pression de 0,7 x 10⁵ Pa : en effet, l'azote est à moins de 0,05 x 10⁵ Pa dans les stockages des usines de liquéfaction. Chaque pompage élève l'enthalpie de 0,7 kcal/kg par perte de rendement des pompes centrifuges, ce qui correspond à une élévation de 0,22 x 10⁵ Pa de la pression du liquide, dans cette zone de pressions. Le transport, entrées de chaleur et effets mécaniques confondus, élève la pression de 0,07 x 10⁵ Pa pour un trajet de 100 km. En comptant deux pompages, et pour une distance de transport de 200 km, la pression de l'azote dans le réservoir sera donc infime, de 0,63 x 10⁵ Pa. On notera que la valeur arrondie à 0,7 x 10⁵ Pa traduit la bonne qualité du fluide.It can be considered that liquid nitrogen is normally delivered to its point of use at a pressure of 0.7 x 10⁵ Pa: in fact, nitrogen is less than 0.05 x 10⁵ Pa in the storage facilities of liquefaction. Each pumping increases the enthalpy by 0.7 kcal / kg by loss of efficiency of the centrifugal pumps, which corresponds to an increase of 0.22 x 10⁵ Pa in the pressure of the liquid in this pressure zone. Transport, heat inputs and mechanical effects combined, raises the pressure by 0.07 x 10⁵ Pa for a journey of 100 km. By counting two pumps, and for a transport distance of 200 km, the nitrogen pressure in the tank will therefore be tiny, of 0.63 x 10⁵ Pa. Note that the value rounded to 0.7 x 10⁵ Pa translates the good quality of the fluid.
L'azote à 0,7 x 10⁵ Pa est représenté en (A1) sur le diagramme, ainsi que, en A2, l'azote en équilibre à 2 x 10⁵ Pa, très fréquent dans l'état actuel de la technique ; si le point d'utilisation est plus élevé que le stockage, la pression sera souvent de 2,6 x 10⁵ Pa, représentée en A3).Nitrogen at 0.7 x 10⁵ Pa is represented in (A1) on the diagram, as well as, in A2, nitrogen in equilibrium at 2 x 10⁵ Pa, very common in the current state of the art; if the point of use is higher than the storage, the pressure will often be 2.6 x 10⁵ Pa, shown in A3).
Les points A'2 ou A'3 représentent l'azote à l'arrivée d'un poste utilisateur, le diphasique représentant souvent 3 à 5 % en poids, soit 150 à 250 % en volume. Par contre, augmenter par pompage la pression de 0,7 à 2,6 x 10⁵ Pa, comme représenté en A'1, permettra de beaucoup plus grandes pertes de charge et entrées de chaleur, représentées par A"1 sans formation de vapeur.Points A'2 or A'3 represent nitrogen at the arrival of a user station, the two-phase often representing 3 to 5% by weight, or 150 to 250% by volume. On the other hand, increasing the pressure by pumping from 0.7 to 2.6 x 10⁵ Pa, as shown in A'1, will allow much greater pressure losses and heat inputs, represented by A "1 without formation of vapor.
En ce qui concerne les comparaisons des enthalpies initiales H1, H2, H3, on doit établir les variations, donc les quantités de froid produites en kcal/kg, pour 2 états finaux: l'un correspond à l'enthalpie du gaz à - 196° et pression atmosphérique, lorsque seule la chaleur latente est utilisée, comme en immersion, soit 18,45 kcal/kg; l'autre correspond aux tunnels de congélation, ou le gaz peut sortir à - 50°, avec une enthalpie de 55kcal/kg.With regard to the comparisons of the initial enthalpies H1, H2, H3, one must establish the variations, therefore the quantities of cold produced in kcal / kg, for 2 final states: one corresponds to the enthalpy of the gas at - 196 ° and atmospheric pressure, when only latent heat is used, such as immersion, i.e. 18.45 kcal / kg; the other corresponds to freezing tunnels, where the gas can exit at - 50 °, with an enthalpy of 55kcal / kg.
Le tableau suivant permet la comparaison:
L'azote à 0,7 x 10⁵ Pa produira, dans le cas d'immersion, respectivement 7,2 % et 9,8 % plus de froid que l'azote à 2 et 2,6 x 10⁵ Pa, et donc l'on économisera 6,7 % ou 9 % de la quantité de liquide à utiliser.Nitrogen at 0.7 x 10⁵ Pa will produce, in the case of immersion, respectively 7.2% and 9.8% more cold than nitrogen at 2 and 2.6 x 10⁵ Pa, and therefore the 6.7% or 9% of the amount of liquid to be saved will be saved.
La récupération de la chaleur sensible du gaz, dans les tunnels par exemple, ne dépend pas de l'enthalpie initiale, et l'économie due à l'emploi d'azote à 0,7 x 10⁵ Pa sera entre 3,7 % et 5 %, respectivement, par rapport à l'azote à 2 x 10⁵ Pa et 2,6 x 10⁵ Pa.The recovery of the sensible heat of the gas, in tunnels for example, does not depend on the initial enthalpy, and the savings due to the use of nitrogen at 0.7 x 10⁵ Pa will be between 3.7% and 5%, respectively, with respect to nitrogen at 2 x 10⁵ Pa and 2.6 x 10⁵ Pa.
A ces économies, le système selon l'invention ajoute celles résultant de la suppression du maintien en pression du réservoir: même en cas de vidange rapide, la pression de 0,7 x 10⁵ Pa ne chutera que de 0,15 x 10⁵ Pa, soit 0,55 x 10⁵ Pa en final, sans inconvénients.To these savings, the system according to the invention adds those resulting from the elimination of the pressure maintenance of the tank: even in the event of rapid emptying, the pressure of 0.7 x 10⁵ Pa will drop only by 0.15 x 10⁵ Pa, or 0.55 x 10⁵ Pa in the end, without drawbacks.
Au contraire, les rapports des masses volumiques, en kg/m3 du gaz et du liquide en équilibre à 2 et 2,6 x 10⁵ Pa sont, respectivement: 12,8 / 756,5 = 0,017 et 15,1 / 746 = 0,02, ce qui signifie qu'il faudra vaporiser 1,7 % ou 2 % du liquide, pour maintenir la pression à 2 ou 2,6 x 10⁵ Pa.On the contrary, the density ratios, in kg / m3 of gas and liquid in equilibrium at 2 and 2.6 x 10⁵ Pa are, respectively: 12.8 / 756.5 = 0.017 and 15.1 / 746 = 0 , 02, which means that 1.7% or 2% of the liquid will have to be vaporized to maintain the pressure at 2 or 2.6 x 10⁵ Pa.
La figure 2 représente les états du dioxyde de carbone, portés sur un diagramme, les pressions absolues étant figurées sur l'axe vertical, et les enthalpies sur l'axe horizontal; on citera les analogies et les différences du CO₂ par rapport à l'azote.FIG. 2 represents the states of carbon dioxide, plotted on a diagram, the absolute pressures being represented on the vertical axis, and the enthalpies on the horizontal axis; we will quote the analogies and the differences of CO₂ compared to nitrogen.
La différence majeure est la pression du point triple (PT), à 5,18 x 10⁵ Pa. Un état final du CO₂ peut être le gaz sortant d'un tunnel de réfrigération à la pression atmosphérique (PA) et -50°C (HT); un autre état final sera, après production de neige et sa sublimation, la "sortie" de gaz à -78,5°C, représenté par HN.The major difference is the pressure of the triple point (PT), at 5.18 x 10⁵ Pa. A final state of CO₂ can be the gas leaving a refrigeration tunnel at atmospheric pressure (PA) and -50 ° C ( HT); another state final will be, after production of snow and its sublimation, the "outlet" of gas at -78.5 ° C, represented by HN.
La variation enthalpique, ou froid utilisable, correspond essentiellement à la chaleur latente ; il est donc d'autant plus intéressant d'abaisser l'enthalpie initiale:The enthalpy variation, or usable cold, essentially corresponds to latent heat; it is therefore all the more interesting to lower the initial enthalpy:
L'état initial habituel est la livraison de CO₂ liquide à -20°C et 20 x 10⁵ Pa, représenté en D1), qui peut être stocké tout à fait à la manière de l'azote liquide, en réservoirs isolés sous vide; généralement on utilise des stockages moins performants, dont on contrôle la pression à 20 x 10⁵ Pa par un groupe frigorifique; dans ce dernier cas, on connaît des pompes centrifuges de circulation en boucle du C0₂ liquide, pour maintenir en froid la ligne, et non dans le but d'obtenir un sousrefroidissement du liquide par augmentation de pression. Le gaz formé par les pertes de rendement des pompes et les entrées de chaleur, revient en bout de boucle au réservoir, où il est condensé par le groupe frigorifique.The usual initial state is the delivery of liquid CO₂ at -20 ° C and 20 x 10⁵ Pa, represented in D1), which can be stored completely in the manner of liquid nitrogen, in vacuum-insulated tanks; generally less efficient storages are used, the pressure of which is controlled at 20 × 10⁵ Pa by a refrigeration unit; in the latter case, centrifugal pumps are known for looping the liquid CO C to keep the line cold, and not for the purpose of obtaining subcooling of the liquid by increasing pressure. The gas formed by the losses in efficiency of the pumps and the heat inputs, returns at the end of the loop to the tank, where it is condensed by the refrigeration unit.
Le plus fréquent est l'emploi d'une ligne simple, et dans ce cas, le CO₂ parvenant à l'utilisation est représenté par D'1, ce qui permet un fonctionnement normal ; I'intérêt de la diminution de l'enthalpie et de la pression initiale, a motivé des distributions de CO₂ liquide à 8 x 10⁵ Pa et -45°C, représenté par D2 : à l'arrivée à l'utilisation, représentée par D'2, la proximité de la pression du point triple impose des précautions particulières. On peut dire que même sous 10 ou 11 x 10⁵ Pa les risques de bouchage par le CO₂ solide (plugging) existent.The most frequent is the use of a single line, and in this case, the CO₂ arriving at the use is represented by D'1, which allows normal operation; The interest of the reduction in the enthalpy and the initial pressure, motivated distributions of liquid CO₂ at 8 x 10⁵ Pa and -45 ° C, represented by D2: on arrival at use, represented by D '2, the proximity of the pressure of the triple point requires special precautions. We can say that even under 10 or 11 x 10⁵ Pa the risks of plugging by solid CO₂ (plugging) exist.
Le dispositif de pompage objet de l'invention, permet d'utiliser du CO₂ amené au voisinage du point triple, soit par refroidissement, soit par vaporisation et abaissement de la pression, comme représenté par D3 : la pression peut être augmentée jusqu'au point représentatif D'3, de sorte qu'à l'utilisation (D"3) le risque de formation de solide soit réduit. La pompe admet la circulation de fluide chargé de particules, et si le réservoir basse pression est en charge sur son entrée, on pourra même utiliser un mélange de CO₂ liquide et solide au point triple.The pumping device which is the subject of the invention makes it possible to use CO₂ brought in the vicinity of the triple point, either by cooling, or by vaporization and reduction of the pressure, as represented by D3: the pressure can be increased to the point representative of D'3, so that in use (D "3) the risk of solid formation is reduced. The pump admits the circulation of fluid loaded with particles, and if the low pressure tank is loaded on its inlet , we could even use a mixture of liquid and solid CO₂ at the triple point.
La figure 3 illustre schématiquement le dispositif de pompage selon l'invention : un réservoir isolé de stockage 1 contient le fluide cryogénique à la plus basse pression possible: pour l'azote, ce réservoir est le stockage, recevant l'azote liquide à 0,7 x 10⁵ Pa; pour le CO₂, il s'agit d'un réservoir basse pression, distinct généralement du réservoir de livraison.FIG. 3 schematically illustrates the pumping device according to the invention: an
Une ligne 2 est la sortie liquide du réservoir, qui alimente par gravité le dispositif de pompage via une vanne d'arrêt 3 ; il est souhaitable de surdimensionner cette dernière 3', et de réduire la distance horizontale au pompage. La sortie du réservoir 1 doit être en surélévation de 0, 5 à 1 mètre par rapport à l'entrée du dispositif de pompage.A
Le dispositif de pompage comporte à sa partie inférieure un petit réservoir 4 servant à alimenter en liquide dépourvu de gaz le clapet d'admission 6 de la pompe; pour cela il est muni d'un tube évent 5 relié par un tube isolé à la phase gazeuse (partie haute) du réservoir 1 ; le tube 5 sert également à la mise en froid du dispositif de pompage dans le cas de l'utilisation du CO₂. Il peut, en variante être remplacé par un éliminateur de gaz.The pumping device comprises at its lower part a
La pompe est du type à piston et clapets, verticale. Un tube 7 fixé par brides au réservoir 4 porte le cylindre 8 dans lequel le piston 9, portant lui-même un clapet de refoulement, est actionné par une tige 10 passant dans un jeu 11 et 11' de garnitures d'étanchéité, entre lesquelles on injecte du gaz sous pression du refoulement, par un tube réchauffeur 12. Seule la partie inférieure de la pompe est isolée, comme figuré par le tireté 13 : la sortie du liquide du tube 7 se fait par un piquage 14, situé juste au-dessus du cylindre 8 et de la bride de fixation du tube et de la pompe, de sorte que la partie haute du tube 7 contient un volume de gaz peu conducteur, et que les étanchéités 11 et 11' restent à température ambiante.The pump is of the piston and valve type, vertical. A tube 7 fixed by flanges to the
La tige 10 de commande du piston est reliée à un moteur 15 donnant un mouvement alternatif réglable, une réalisation particulièrement avantageuse utilisant un moteur à vérins pneumatiques ou hydrauliques. En effet, une caractéristique importante du mouvement du piston est qu'il doit être lent pendant la montée, qui correspond à la phase d'aspiration ou d'admission du cycle de pompage, par rapport au mouvement de descente, qui correspond à la mise en pression du fluide et à son refoulement, et qui peut être aussi rapide qu'il est mécaniquement possible.The
La pression du fluide moteur actionnant le moteur 15 est régulée par un détendeur 17 : le rapport des sections actives du vérin de moteur et du piston de pompe et le réglage de pression du détendeur définissent la pression maxima à laquelle sera porté le fluide cryogénique. Un organe de réglage éventuel 18 conditionne le débit de fluide moteur, et donc la durée globale d'un cycle montée/descente. Cette durée doit être compatible avec le fonctionnement du distributeur de fluide moteur 19, actionné par une minuterie double, ou par une minuterie et un contact de fin de course 21. Un réducteur de débit unidirectionnel réglable 20 permet d'ajuster la vitesse lente de remontée (admission), le refoulement étant libre ou réglé par l'organe 18. Un autre détecteur de fin de course 21' peut permettre le contrôle de la vitesse de remontée du piston.The pressure of the working fluid actuating the engine 15 is regulated by a pressure reducer 17: the ratio of the active sections of the motor cylinder and the pump piston and the pressure setting of the pressure reducer define the maximum pressure to which the cryogenic fluid will be brought. A possible adjusting
Le fonctionnement de la pompe est volumétrique, en liquide franc: le détecteur 21 peut servir au comptage et à la détermination des débits instantanés, moyens,ou quantités cumulées de fluide cryogénique fournis à un équipement.The operation of the pump is volumetric, in free liquid: the
Deux systèmes de distribution peuvent élever la pression de quantités comptées et régulées de deux gaz liquefiés différents, tels azote et oxygéne, de sorte qu'après leur mélange en phase liquide, la pression soit supérieure à la pression de bulle; le comptage en phase liquide peut également être utilisé avant vaporisation et mélange à l'état gazeux.Two distribution systems can raise the pressure of counted and regulated quantities of two different liquefied gases, such as nitrogen and oxygen, so that after mixing in the liquid phase, the pressure is greater than the bubble pressure; liquid phase metering can also be used before vaporization and mixing in the gaseous state.
La figure 4 montre les détails de la pompe et notamment du piston et du clapet d'admission: le corps du clapet 6 est fixé sur le cylindre 8; le clapet proprement dit est un disque plat à bords arrondis, dont la levée est limitée par une tige 25; il repose sur un siège 24, et est guidé par les tirants 26 d'assemblage du fond de clapet 27. Le disque est de préférence en polyéthylène haute densité ou en PTFE.FIG. 4 shows the details of the pump and in particular of the piston and of the intake valve: the body of the
Le piston est constitué par un corps tubulaire 9 fixé sur la tige de commande 10, et muni de fenêtres 22 de passage du fluide refoulé; une vis creuse 28 fixe sur le piston des joints annulaires 30 à lèvres orientées vers le haut, en polyéthylène, PTFE, ou en cuir, par serrage d'entretoises 29. Une bille 31 fait clapet d'étanchéité en reposant sur la vis 28 ; la tige 10 fait butée à la levée de la bille.The piston is constituted by a
En position basse, le piston touche le clapet d'admission 23 afin de réduire le "volume mort" de fluide entre piston et clapet: en effet, à la levée, l'accélération du clapet est de plusieurs fois la pesanteur, par pression par dessous, de la colonne de liquide, et par dépression par dessus, du fait du mouvement vers le haut du piston; on limite cet effet et la vaporisation,en réduisant le volume de liquide intéressé, en amenant au plus près piston et clapet.In the low position, the piston touches the
Le liquide arrive du réservoir de stockage par la ligne 2 et emplit totalement le réservoir de pompe 4 avec évacuation du gaz éventuel par l'évent 5 ; le liquide descend par l'espace entre le corps du clapet 6 et le réservoir 4.The liquid arrives from the storage tank through
A la remontée du piston, le clapet 23 est donc levé par différence de pression entre faces inférieure et supérieure: le clapet doit être aussi léger que possible, et dans le cas d'un diamètre de siège de 80 mm., on le fera reposer sur un croisillon porté par une pièce annulaire 27 ; le liquide doit suivre rigoureusement le mouvement de remontée du piston, car toute vaporisation doit être évitée. La pression du fluide côté refoulement,et la pression du gaz contenu dans le tube 7, qui sont identiques, s'exercent sur la face supérieure du piston et sur la bille 31.When the piston is raised, the
A la descente, le clapet d'admission 23 se referme, le liquide contenu entre piston et clapet voit sa pression s'élever au-dessus de la pression de refoulement, de sorte que le liquide passe par la vis 28 et le clapet à bille 31 ; les pressions sont peu différentes, et l'effort sur la tige 10 est faible.On descent, the
La difficulté du pompage cryogénique par pompe alternative réside dans la nécessité d'éviter toute vaporisation: toute dépression vaporise immédiatement du liquide par effet "flash"; au contraire, la compression ne recondense pas immédiatement le gaz formé, car il faut un transfert de chaleur entre gaz et liquide: la compression doit donc comprimer le gaz avant d'élever la pression du liquide, et pour un volume critique de gaz, le processus empire jusqu'à la compression-détente de gaz, sans débit de liquide. A titre d'information, la vaporisation des fluides à l'équilibre, en poids %, et la correspondance en volume , pour des exemples azote et CO₂, et pour une dépression de 1000 Pa, sont:
- . 0,1 % d'azote à pression atmosphérique,
formant 17,5 % de gaz - . 0,07 % d'azote à 0,7 x 10⁵ Pa relatif,
formant 7,1 % de gaz, - . 0,019 % de CO₂ à 6,8 x 10⁵ Pa abs.,
1,2 % de gaz.formant
- . 0.1% nitrogen at atmospheric pressure, forming 17.5% gas
- . 0.07% nitrogen at 0.7 x 10⁵ relative Pa, forming 7.1% gas,
- . 0.019% CO₂ at 6.8 x 10⁵ Pa abs., Forming 1.2% gas.
A titre d'exemple, pour une pompe ayant un diamètre intérieur de 45,3 mm, une course de 100 mm, un clapet de diamètre 54 mm recouvrant un siège de 40 mm et une levée du clapet de 5 mm, les observations suivantes ont été effectuées :For example, for a pump having an internal diameter of 45.3 mm, a stroke of 100 mm, a valve with a diameter of 54 mm covering a 40 mm seat and a 5 mm valve lift, the following observations were made:
Il n'y a pas de réduction de volume d'azote pompé par cycle jusqu'à une cadence de 165 cycles par minute, si la hauteur de l'azote liquide au-dessus du clapet est égale ou supérieure à 250 mm. d'azote, ou 2000 Pa. Le débit est alors de 1400 litres/heure.There is no reduction in the volume of nitrogen pumped per cycle up to a rate of 165 cycles per minute, if the height of the liquid nitrogen above the valve is equal to or greater than 250 mm. nitrogen, or 2000 Pa. The flow rate is then 1400 liters / hour.
La vitesse de montée du piston est 0,55 m/s : c'est également la vitesse de montée de l'azote. La section la plus étroite d'écoulement est au voisinage du siège du clapet; c'est là aussi la plus grande vitesse de l'azote, d'environ 1,30 m/s, correspondant à une pression dynamique de 700 Pa . La perte de charge globale du clapet est inférieure à 2000 Pa, le coefficient de perte de charge du clapet est donc inférieur à 2000/700 = 2,86 valeur due aux particularités de la configuration décrite par la figure 4: arrondis des profils, et taille du siège.The piston rise speed is 0.55 m / s: this is also the nitrogen rise speed. The narrowest flow section is in the vicinity of the valve seat; this is also the highest speed of nitrogen, around 1.30 m / s, corresponding to a dynamic pressure of 700 Pa. The overall pressure drop of the valve is less than 2000 Pa, the coefficient of pressure drop of the valve is therefore less than 2000/700 = 2.86 value due to the particularities of the configuration described in FIG. 4: rounding of the profiles, and seat size.
Les observations effectuées ont permis d'établir des relations caractéristiques du pompage des fluides cryogéniques à l'équilibre par pompes alternatives:The observations carried out made it possible to establish characteristic relationships for the pumping of cryogenic fluids at equilibrium by alternative pumps:
La remontée du piston est la phase de débit à travers le clapet d'entrée; la vitesse de remontée du piston doit avoir typiquement une valeur maximum de 0,5 m/s pour que la montée du liquide suive la montée du piston. Pour une pompe donnée, la vitesse de montée du piston conditionne le débit, et il est souhaitable que, dans un cycle, la phase de descente soit aussi brève que mécaniquement possible, car il n'y a pas d'inconvénient thermodynamique, et le débit sera optimum en cycles enchaînés.The ascent of the piston is the flow phase through the inlet valve; the piston ascent rate must typically have a maximum value of 0.5 m / s for the rise of the liquid to follow the rise of the piston. For a given pump, the rate of rise of the piston conditions the flow rate, and it is desirable that, in a cycle, the descent phase is as brief as mechanically possible, since there is no thermodynamic drawback, and the flow will be optimum in chained cycles.
Pour des cycles optimisés, le débit est proportionnel à la surface active du piston, soit au carré de son diamètre.For optimized cycles, the flow rate is proportional to the active surface of the piston, ie the square of its diameter.
En fonction de la géométrie du clapet et des arrondis dans les sections de changement de direction du fluide, un facteur de perte de charge inférieur à 2,86 a été trouvé; multiplié par la pression dynamique de la plus grande vitesse du fluide dans Ic clapet, il indique sa perte de charge globale. Pour conserver la même perte de charge, on devra garder la même vitesse dans la plus petite section du clapet, à savoir au voisinage du siège, la levée du clapet étant toujours en pratique limitée à 5mm ; la conservation de la même vitesse du fluide impose que le diamètre du siège du clapet soit proportionnel au carré du diamètre du piston. Si un clapet plus petit est utilisé, la vitesse de remontée du piston devra être réduite: le diamètre du piston sera surdimensionné, entraînant de plus grandes pressions du fluide moteur.Depending on the geometry of the valve and the rounding in the fluid direction change sections, a pressure drop factor of less than 2.86 has been found; multiplied by the dynamic pressure of the highest speed of the fluid in the valve, it indicates its overall pressure drop. To keep the same pressure drop, the same speed must be kept in the smallest section of the valve, namely in the vicinity of the seat, the valve lift being always in practice limited to 5mm; keeping the same fluid speed requires that the diameter of the valve seat be proportional to the square of the piston diameter. If a smaller valve is used, the piston ascent rate must be reduced: the diameter of the piston will be oversized, causing greater pressures of the working fluid.
Les temps de passage de montée à descente, et inversement, du piston sont compris entre 25 et 50 ms, et la vitesse moyenne du piston est peu différente de la vitesse instantanée au cours d'un mouvement du cycle. De ce fait, la longueur de course n'est pas un facteur essentiel de débit, mais de fréquence, avec un intérêt d'ordre mécanique.The transition times from rise to fall, and vice versa, of the piston are between 25 and 50 ms, and the average speed of the piston is little different from the instantaneous speed during a movement of the cycle. Therefore, the stroke length is not an essential factor of flow, but frequency, with a mechanical interest.
La pompe décrite ci-dessus, de diamètre de piston 45 mm, siège de clapet 40 mm, course 100 mm, peut être industriellement utilisée à une cadence typiquement d'environ 125 à 130 cycles/mn, correspondant à un débit de 1100 à 1200 litres/heure de fluide cryogénique, convenant à de nombreuses applications.The pump described above, with piston diameter 45 mm,
Une pompe de débit double, soit 2200 à 2400 litres/heure, aurait un diamètre de piston multiplié par √2, soit environ 65 mm, un diamètre de siège de clapet proportionnel au débit, soit 80 mm, et une cadence de fonctionnement d'environ 125 à 130 cycles/mn. si la course est de 100 mm, et environ 85 cycles par minute, si la course est 150 mm.A double flow pump, i.e. 2200 to 2400 liters / hour, would have a piston diameter multiplied by √2, or approximately 65 mm, a valve seat diameter proportional to the flow rate, ie 80 mm, and an operating rate of about 125 to 130 cycles / min. if the stroke is 100 mm, and about 85 cycles per minute, if the stroke is 150 mm.
Ces exemples montrent que la pompe alternative est adaptée à une installation dont le débit instantané, qui doit être inférieur au débit maximum de la pompe, ne sera pas très élevé ou différent du débit moyen d'utilisation. On connait des cas de débits instantanés importants, pour des débits moyens petits. En CO₂ notamment, on a à injecter quelques kg de neige en quelques secondes, correspondant à 2000 ou 3000 kg/h de débit instantané de liquide, pour un débit moyen de quelques centaines de kg/h ; d'autre part une chute de pression au voisinage du point triple cause des bouchages catastrophiques.These examples show that the alternative pump is suitable for an installation whose instantaneous flow rate, which must be less than the maximum flow rate of the pump, will not be very high or different from the average flow rate of use. We know cases of large instantaneous flows, for small average flows. In CO₂ in particular, we have to inject a few kg of snow in a few seconds, corresponding to 2000 or 3000 kg / h of instantaneous flow of liquid, for an average flow of a few hundred kg / h; on the other hand, a pressure drop near the triple point causes catastrophic blockages.
Le présent dispositif apporte une solution par l'emploi de réservoirs accumulateurs sous pression, soit au point d'utilisation, soit en ligne.The present device provides a solution by the use of accumulators under pressure, either at the point of use, or online.
Dans l'installation de distribution de CO₂ selon la figure 5, on reconnait le réservoir basse pression 1 alimentant par la ligne 2 le réservoir 4 du dispositif de pompage schématisé par son tube 7. Le réservoir 1 est maintenu par un pressostat P2 à une pression de 6 x 10⁵ Pa, par exemple, l'équilibre du CO₂ étant à -53°CIn the CO₂ distribution installation according to FIG. 5, we recognize the
Le réservoir 1 reçoit le CO₂ d'un réservoir de livraison 32, à une pression P1 de l'ordre de 20 x 10⁵ Pa, par une ligne 33 ; un flotteur 34 commande un moyen de remplissage 35 pour garder un niveau constant; le liquide à 20x 10⁵ Pa est introduit dans le réservoir au moyen d'un séparateur de phases 36. Un dévésiculeur 37, disposé dans le réservoir 1, est situé à l'aspiration d'un compresseur monoétagé 38 associé à un échangeur gaz-gaz 39. Le compresseur 38 élève la pression du gaz CO₂ dans le réservoir 1 de 6 à 22 x 10⁵ Pa, pour le reliquéfier par le condenseur 40, relié en 41 et 42 à un circuit de réfrigération (non représenté). En variante, la pression du réservoir peut être abaissée par réfrigération à -53°C.The
La ligne de refoulement 14 du dispositif de pompage assure un débit de CO₂ liquide à -53°C, à une pression de 10 x 10⁵ Pa, par exemple, (donc sous-refroidi par rapport à la température d'équilibre à 10 x 10⁵ Pa, qui est - 40°), jusqu'à l'utilisation représentée par une électro-vanne 48. Un purgeur de gaz 53, par exemple à flotteur 54, assure le maintien en froid de la ligne, même s'il n'y a pas de circulation. Le gaz à 10 x 10⁵ Pa, sortant du purgeur 53, est ramené par une tuyauterie 55, à la phase gazeuse du réservoir 1, ou à la reliquéfaction. Cette disposition remplace avantageusement la technique de maintien en froid par boucle de liquide à pompe de circulation.The
Pour obtenir des débits instantanés supérieurs au débit nominal du dispositif de pompage, un réservoir accumulateur isolé 43 permet le fonctionnement si le débit moyen est inférieur au débit nominal du dispositif de pompage : celui-ci remplit l'accumulateur 43 jusqu'au niveau défini par un détecteur 44 ; tant que le niveau n'est pas atteint, une vanne 45 dans une ligne reliant les parties hautes des réservoirs 1 et 43, est ouverte, et le gaz repoussé par le liquide dans le réservoir 43 rejoint le réservoir 1, en passant par un déverseur 46 réglé pour maintenir une pression amont de 8 x 10⁵ Pa par exemple; on peut aussi remplacer ce déverseur par un simple laminage.To obtain instantaneous flow rates greater than the nominal flow rate of the pumping device, an
Lorsque le réservoir accumulateur 43 est plein, sans utilisation, le dispositif de pompage 7 maintient la pression à débit nul, par le réglage établi sur la pression de son fluide moteur.When the
Lorsque l'électrovanne d'utilisation 48 est ouverte, on ouvre également une électrovanne 49 de pressurisation du réservoir accumulateur 43 disposé dans une ligne reliant les parties hautes des réservoirs 43 et 32 ; la pression du gaz de pressurisation venant du réservoir de stockage 32 est réglée par le détendeur 50 qui assure par exemple une pression aval de 11 x 10⁵ Pa, de sorte que le fluide atteignant l'utilisation 48 vienne en priorité de l'accumulateur 43 ; on pourra au contraire régler la pression aval du détendeur 50 à une valeur inférieure à la pression du pompage, par exemple à 9,5 x 10⁵ Pa, pour que le débit du dispositif de pompage soit utilisé en priorité, et l'accumulateur 43 seulement en appoint.When the operating solenoid valve 48 is open, a
Pour éviter des fausses manoeuvres, on pourra utiliser dans le réservoir accumulateur 43 un contrôle de niveau 47 arrêtant la fourniture de fluide fourni à l'utilisation 48 en cas de vidange excessive de l'accumulateur, la taille de celui-ci devant être adaptée à la demande ; on peut également utiliser un pressostat P3 pour vérifier que la pression dans l'accumulateur 43 est toujours à un certain niveau au-dessus de celle du point triple.To avoid false operations, a
Ce système d'accumulateur peut être éventuellement adapté à des fluides tels que l'azote liquide; dans ce cas, I'évacuation du gaz de l'accumulateur se fait à l'atmosphère, et la pressurisation peut être réalisée en augmentant la taille du vaporiseur 12 de la figure 3, et en le raccordant à l'électrovanne 49. On pourra placer un clapet anti-retour sur la tuyauterie de refoulement pour éviter un retour au dispositif de pompage, et surtout, pour créer une perte de charge supplémentaire et privilégier la mise en pression de l'accumulateur 43.This accumulator system can optionally be adapted to fluids such as liquid nitrogen; in this case, the evacuation of the gas from the accumulator takes place in the atmosphere, and the pressurization can be carried out by increasing the size of the
Pour mémoire, des organes habituels de securité et de purge ont été représentés, respectivement une soupape 56 et une vanne ou électrovanne 57 ; on doit également prévoir une vanne de vidange du réservoir 4 de la pompe, à l'arrêt de l'installation.For the record, the usual safety and purging devices have been shown, respectively a valve 56 and a valve or
Claims (7)
- Device for distributing a cryogenic fluid to the means for using it, this fluid being stored at low pressure in a storage reservoir (1) supplying a pumping device with a piston (9) having a reciprocating movement, the inlet part (6) of which is immersed in the liquid to be pumped, characterized in that the pumping device comprises operating means ensuring a slow upward movement of the piston, corresponding to aspiration of the fluid, preferably less than 0.5 m/s, and a rapid downwards movement corresponding to delivery under pressure.
- Device according to claim 1, characterized in that movement of the piston (9) is obtained by the action of at least one jack.
- Device according to claim 1 or 2, characterized in that the pumping device comprises an inlet valve (23) and in that the piston (9) in the lowest position of its stroke, comes into contact with the valve (23).
- Device according to claim 3, characterized in that the pumping device is connected in a liquid tight manner to a reservoir (4) surrounding the inlet valve (23), and comprising a vent (5) for evacuating gas.
- Device according to one of claims 1 to 4, characterized in that it comprises a means for counting the cycles of the pumping device, so as to obtain an evaluation of the volume flow rates of the fluid used in an installation.
- Device according to one of claims 1 to 5, characterized in that it comprises at least one insulated reservoir (43) connected to the delivery of the pumping device, this reservoir being filled by evacuating gas through a valve (45), and being emptied during the periods of use, with pressurization by means of a regulated inflow of gas above the accumulated liquid, controlled by a valve (49).
- Distribution device according to one of claims I to 6, characterized in that the fluid is carbon dioxide, pressurized by the pumping device, and is conveyed through an insulated pipe (14) kept full of liquid by at least one gas trap (53), the gas leaving from these traps being led again (55) to the storage reservoir (1).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9210449A FR2695188B1 (en) | 1992-09-01 | 1992-09-01 | Device for distributing cryogenic fluids to their devices of use. |
FR9210449 | 1992-09-01 |
Publications (2)
Publication Number | Publication Date |
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EP0586294A1 EP0586294A1 (en) | 1994-03-09 |
EP0586294B1 true EP0586294B1 (en) | 1996-03-20 |
Family
ID=9433122
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP19930402120 Expired - Lifetime EP0586294B1 (en) | 1992-09-01 | 1993-08-30 | Device for the distribution of cryogenic fluid to apparatuses using them |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0586294B1 (en) |
DE (1) | DE69301882T2 (en) |
ES (1) | ES2088247T3 (en) |
FR (1) | FR2695188B1 (en) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5537828A (en) * | 1995-07-06 | 1996-07-23 | Praxair Technology, Inc. | Cryogenic pump system |
US5858934A (en) * | 1996-05-08 | 1999-01-12 | The Lubrizol Corporation | Enhanced biodegradable vegetable oil grease |
DE19646664A1 (en) * | 1996-11-12 | 1998-05-14 | Linde Ag | Compress CO¶2¶ or nitrous oxide |
DE19839233A1 (en) * | 1998-08-28 | 2000-03-02 | Linde Ag | Installation for compression of fluidized gas involves compressor with cylinder and piston, storage tank for fluidized gas and evaporator, piston moving in cylinder at speed between 1 and 250 mm/s. |
DE19915853A1 (en) * | 1999-04-08 | 2000-10-12 | Linde Tech Gase Gmbh | Pump system for pumping cryogenic liquids |
GB9913071D0 (en) * | 1999-06-04 | 1999-08-04 | Boc Group Plc | Cryogenic refrigeration of goods |
SE519091C2 (en) * | 2000-05-03 | 2003-01-14 | Aga Ab | Device and process for pumping liquid gas, pumping system for pumping liquid gas and system and process for cyclic production of polymer products |
US20150192116A1 (en) * | 2012-05-31 | 2015-07-09 | Cern - European Organization For Nuclear Research | Cryogenic Cooling Pump and Method |
WO2015153631A1 (en) * | 2014-04-01 | 2015-10-08 | Trinity Cryogenics, Llc | Dual pressure-retaining manway system |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
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GB573383A (en) * | 1943-05-27 | 1945-11-19 | Air Prod Inc | Improvements in the transference of and manufacture of liquid oxygen |
DE3710363C1 (en) * | 1987-03-28 | 1988-12-01 | Deutsche Forsch Luft Raumfahrt | Method and device for conveying a liquid |
FR2672942A1 (en) * | 1992-02-14 | 1992-08-21 | Ebara International Corp | Method and apparatus for pumping liquefied gases |
-
1992
- 1992-09-01 FR FR9210449A patent/FR2695188B1/en not_active Expired - Fee Related
-
1993
- 1993-08-30 ES ES93402120T patent/ES2088247T3/en not_active Expired - Lifetime
- 1993-08-30 EP EP19930402120 patent/EP0586294B1/en not_active Expired - Lifetime
- 1993-08-30 DE DE69301882T patent/DE69301882T2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
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FR2695188A1 (en) | 1994-03-04 |
DE69301882D1 (en) | 1996-04-25 |
DE69301882T2 (en) | 1996-09-19 |
ES2088247T3 (en) | 1996-08-01 |
FR2695188B1 (en) | 1994-10-28 |
EP0586294A1 (en) | 1994-03-09 |
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