WO1986005291A1 - Device for regulating the flow rate of a gas, and application of such device to the gas supply of a reactor - Google Patents

Abstract

The regulation device (D) comprises at least two capillary tubes (C1, C2, C3, C4) mounted in parallel between the upstream side and the downstream side, the inner diameter and the length of such tubes being selected so that the pressure gradient generated by said capillary tubes is sufficient low to avoid the formation of condensates from the gas, control means (B) being further provided to authorize or prevent the circulation of the gas in each capillary.

Description

DEVICE FOR ADJUSTING THE FLOW OF A GAS, AND APPLICATION OF SUCH A DEVICE FOR SUPPLYING GAS TO A REACTOR.

The invention relates to a device for adjusting the flow rate of a gas from gas source dVune près- ^'sion, upstream of the device and may move to an area downstream of the device, lower pressure this device comprising at least two capillary tubes connected in parallel between the upstream and downstream, and control means located downstream of the capillary tubes for self ^• riser or prevent the flow of gas in each re capillai.

A device of this kind is shown, for example, by FR-A-2 172493. The device according to this prior document comprises a pressure reducing agent constituted by a capillary tube, by a diaphragm or by a needle valve with control manual adjustment.

The invention relates to such an adjustment device intended to be used with a corrosive gas, capable of forming condensates during its expansion. The invention relates more particularly, but not exclusively, to a device for regulating the flow of chlorine gas used, in particular for the chlorination of scraping wiper blades of elastomeric material.

The flow control devices proposed to date, which involve throttling devices equivalent to diaphragms or needle valves, have certain drawbacks related to the fact that the gas, when it expands in such throttles, can give rise to condensate, especially if it contains water vapor. When such condensates form, this results in flow instability and, in the case of chlorine or the like, a very corrosive medium, in particular by the formation of hypochlorous acid.

The object of the invention is, above all, to provide a device for adjusting the flow rate of a gas which responds better than up to now the various requirements of the practice and which, in particular, makes it possible to avoid or significantly reduce the formation of condensates, while offering possibilities for precise adjustment of the flow rate. According to the invention, a device for adjusting the flow rate of a gas coming from a source of pressurized gas, located upstream of the device, and which can go towards a zone located downstream of the device, at lower pressure, and which comprises at least two capillary tubes mounted in parallel between the upstream and the downstream, and control means si¬ killed downstream of the capillary tubes to authorize or prevent the circulation of gas in each capillary, is characterized by the fact that in view of its use for regulating the flow rate of a corrosive gas, capable of forming condensate during its expansion, which corresponds to a determined pressure drop (-P), the internal diameter and the length of the tubes capillaries are chosen so that the pressure gradient, i.e. the pressure drop (Δ?) distributed along the length of the tube, is sufficiently low to avoid the formation of condensates from the gas, and that capillary tubes are directly connected to the control means by conduits devoid of any other constriction member, such as a regulator.

The gas source is advantageously formed by a pressurized bottle containing a gas / liquid balance at the temperature considered, the bottle being maintained in a climatic chamber at a constant temperature.

Preferably, when the gas used is chlorine, the internal diameter and the length of the capillary tubes are chosen so that the pressure gradient is at most equal to 1 bar / mm.

In practice, the pressure drop ^ P is between 3 and 10 bars while the length of each capil¬ lar is at least a few millimeters and generally between 10 mm and 200 mm. The control means can be formed by valves operating in completely nothing, in particular with polytetrafluoroethylene coating.

The capillaries generally have an internal diameter of between 0.1 mm and 0.2 mm.

These capillary tubes and the conduits are made of a material that is inert with respect to the corrosive gas. The capillary tubes can be made of glass, while the - conduits are made of polytetrafluoroethylene. The capillary tubes are chosen so as to each determine a flow rate different from that of the other capillaries, the capillary tube of higher rank having in particular a flow twice that of the capillary of immediately lower rank. The device may include four capillaries arranged in parallel, the capillary of rank or lower weight ensuring a flow rate of 0.0625 1 / min, while the following capillaries respectively provide flow rates of 0.125 1 / min, 0.25 1 / min, 0.5 1 / min. A particularly advantageous application of such a flow control device relates to the supply of a reactor for fixing a gas to a solid, in particular for the chlorination of wiper blades of elastomeric material. . Such a reactor and the corresponding treatment process have been described in. Patent application FR 2 537 014 filed on December 6, 1982 at the applicant's ncm under the national registration number FR 82 20405.

In such an application, electromagnetic valves are avar.tagement to authorize or prevent the circulation of gas in each capillary, the control of these solenoid valves being controlled by various parameters such as the speed of movement of the solid to be treated, the temperature ¬ treatment size, the temperature of the gas source, etc. The invention consists, apart from the provisions set out above, in a certain number of other provisions which will be more explicitly discussed below, with regard to a particular embodiment described with reference to the attached drawing, but which is by no means limiting.

Figure 1 of this drawing is a diagram of an adjustment device according to the invention.

Figure 2, finally, is a diagram of an application of such a device to the supply of a reactor for fixing a gas on a solid.

Referring to the drawing, in particular to FIG. 1, one can see a device D for adjusting the flow rate of a gas, namely chlorine in the example considered, coming from a source of pressurized gas 1, located at upstream of the device D. The gas source is formed by a cylinder 2, under pressure, containing a gas / liquid balance at the temperature considered. This temperature is therefore lower than the critical temperature of the gas. In the case of chlorine, the bottle 2 is advantageously kept in a climatic chamber E, at constant temperature, in particular at a temperature of ^13C C for which the equilibrium pressure gas / liq ide was 5.5 bar absolute and therefore 4.5 relative bars.

The gas can go, in the direction of the arrows F, to a zone A, located downstream of the device D, being at a pressure lower than the pressure of the gas in the source 1. The device D is located a temperature also lower than the critical temperatures of the gas under consideration, chlorine in the example envisaged, and of the vapors, in turn water vapor, conveyed by this gas. As a result, the gas is liable to form condensates when it relaxes from the upstream pressure which prevails in the source 1, to the downstream pressure which prevails in zone A.

The device D comprises several capillary tubes; es C1, C2, C3, C4, mounted in parallel between upstream and downstream. '> In the example shown, four capillary tubes C1-C4 are provided ; it is clear that a different number of capillary tubes can be used as required.

The capillary tubes C1-C4 are mounted in conduits _t1, t2, _t3, t.4, connected in parallel to an inlet pipe 3, transverse, itself connected by a pipe 4 to the source 1. At their other end, the conduits t1-t_4 are connected in parallel to another transverse tube 5, itself connected by a pipe 6 to the zone A of gas use. The capillary tubes C1-C4 are preferably made of glass, while the conduits t -.4 can be made of poly¬ tetrafluoroethylene.

The internal diameter and the length of the C1-C4 capillary tubes are chosen so that the pressure gradient, created by each capillary tube, is sufficiently small to avoid the formation of condensates from the gas.

It has been found, in fact, that for a determined pressure drop ^ P, the formation of condensates is reduced and even eliminated, if this pressure drop AP is distributed along a non-negligible length, so that the pressure gradient is not too high.

Sil_ denotes the length of a capillary, for chlorine, the pressure gradient AP / l is at most equal to 1 bar / mm and preferably less than 0.5 bar / mrn.

The capillaries available on the market generally have an internal diameter which can vary from 0.1 mm to 0.2 mm with an intermediate diameter of 0.15 mm. The length of the capillaries C1-C4 is several millimeters. This length can vary in particular from 10 mm to 200 mm for an ΔP of 3 to 10 bars, for chlorine.

Control means B are further provided for authorizing or preventing the circulation of gas in each capil C1-C4, and therefore in the corresponding conduit Jt1-_t4. These control means B are advantageously formed by valves y_1-y_4 associated with each conduit t -_t4. These valves v1-_4 are of the all-or-nothing type, that is to say that they are either fully open or completely closed. These v1-v4 valves can be manual, or, preferably, electromagnetically controlled (electro¬ valves), in particular with polytetrafluoroethylene coating. The valves y_1-y_4 are arranged downstream of the capillary tubes on each conduit _t1- 4. No throttling member is placed between the capillaries C1-C4 and the valves _y_1-v.

Preferably, the flow rates of each capillary C1-C4 are different. Advantageously, the flow rates are chosen so that, if the capillaries are classified in ascending order of their flow rate, the capillary of higher rank has a flow rate twice that of the capillary of immediately lower rank. For example, the capillary C4 will be the minimum flow capillary, while the capillaries C3, C2 will have progressively increasing flow rates. The capillary C3 assu¬ rera a flow twice that of the capillary C4; the capillary i "e C2 will ensure a flow rate double that of C3, and likewise for C1, with respect to C2.

With four capillaries mounted in parallel e ^ operating in all or nothing, a natural binary four-bit combination is produced. Sixteen different flow rates can thus be obtained by incorporating, in this count, the zero bit obtained when all the capillaries are closed. In the particular application envisaged for supplying a reactor for the chlorination of wiper blades, the maximum desired chlorine flow rate is of the order of 1 1 / min.

Advantageously, for the capillary C4, corresponding to the smallest weight or lower rank, a flow rate of 0.0625 1 / min is chosen. The capillaries C3, C2, C1 will, respectively, have flow rates of 0.125 1 / min; 0.25 1 / min; and 0.5 1 / min. The different flow rates that can be obtained are separated by a quantum of 0.0625 1 / min.

From the foregoing explanations, it is immediately understood that the adjustment of the flow rate is effected, in a way, in digital form, by controlling the opening or closing of the appropriate valves y_1-y_4 to obtain the desired flow rate.

This adjustment is obtained without the formation of condensate at the level of the capillaries C1-C4 due to the reduced pressure gradient. FIG. 2 illustrates, in summary, the application of such a device to the supply of a reactor 7, diagrammatically shown, for the chlorination of wiper blades, made of elastomeric material, traveling in the form of 'a continuous ribbon 8. The reactor 7, as described in patent FR 2 537 014 already cited, consists for example of a tube slightly inclined relative to the vertical, provided at its upper part with a suitable sealing device ¬ required 9 allowing the passage of the ribbon 8. At its lower part, the tube 7 plunges into a tank 10 containing liquid, in particular water, to form a liquid seal. The reaction gas, chlorine in the example envisaged, is introduced into the lower part of the reactor 7 by a tube 11. The ribbon 8, the surface of which has been treated in the reactor 7 by reaction with chlorine, leaves the reactor 7 by plunging into the tank 10 and then emerging from this tank.

In such an application, the electromagnetic valves _1-y_4 of the device D for adjusting the flow rate are advantageously controlled from a computer 12 which receives information on various operating parameters such as the speed of travel of the ribbon 8 , supplied by a sensor 13, the temperature inside the reactor 7 supplied by a temperature measurement probe 14. It can be the same for any parameter that one wishes to take into consideration. From the information provided by the various sensors and probes, the computer 12 determines, by example from a pre-established program or law, the required chlorine flow rate and therefore controls the closing or opening of each of the valves y_1-_4.

It is clear that the numerical examples of bit rate given in the above description are indicative and not limiting. Higher flow rates could be obtained with different combinations of capillaries.

Claims

1. Device for adjusting the flow rate of a gas pro¬ coming from a source of pressurized gas, located upstream of the - device, and being able to go towards an area, located downstream of the device, at lower pressure device comprising at least two capillary tubes (C1, C2, C3, C4) mounted in parallel between upstream and downstream, and control means (B) located downstream of the capillary tubes to authorize or prevent the circulation of gas in each capil- lalre, characterized in that, with a view to its use for regulating the flow rate of a corrosive gas, capable of forming condensates during its expansion, which corresponds to a determined pressure drop (ϋP), the internal diameter and the length of the capillary tubes are chosen such that the pressure gradient, that is to say the pressure drop (_ & P. distributed along the length of the tube, is sufficiently low to avoid the formation of condensate from the gas, and that the tubes capillaries (C1, C2, C3, C4) are directly connected to the control means (B) by conduits (t1, t2, t3, t4) devoid of any other throttling member, such as a regulator.

2. Device according to claim 1, characterized in that the gas source (1) is formed by a bottle (2) under pressure containing .a gas / liquid balance at the temperature considered, the bottle (2) being maintained in a climatic chamber at a constant temperature.

3. Device according to claim 1 or 2, for adjusting a chlorine flow rate, characterized in that the internal diameter and the length of the capillary tubes are chosen so that the pressure gradient (-ΔP / 1) or at most equal to 1 bar / mm.

4. Device according to any one of claims 1 to 3, because ctérized by the fact that the control means (B) are closed by valves (v1-v4) operating all or nothing, in particular with polytetrafluoro¬ thylene coating.

5. Device according to any one of the preceding claims, characterized in that each capillary (C1-C4) has a length of at least a few millimeters, in particular from 10 mm to 200 mm.

6. Device according to any one of the preceding revendica¬ tions, characterized in that the capillai¬ res have an internal diameter between 0.1 mm and 0.2 mm.

7- Device according to any one of the preceding revendica¬ tions, characterized in that the capillary tubes (C1-C4) as well as the conduits (t1-t4) are made of an inert material with respect to the corrosive gas.

8. Device according to claim 7, characterized in that the capillary tubes (C1-C4) are made of glass, while the conduits (t1-t4) are made of polytetrafluorethy¬ lene.

9. Device according to any one of the preceding revendica¬ tions, characterized in that the capillary tubes (C1-C4) are chosen so as to deterr.iner each a flow different from that of the other capillai¬ res tubes, the tube capillary of higher rank having in particular a flow twice that of the capillary of rank immediately lower.

10. Device according to claim 9, characterized in that it comprises four capillaries dispensed in parallel, the capillary of rank or lower weight assu¬ rant a flow rate of 0.0625 1 / min, while the following capillaries respectively provide flow rates of 0.125 1 / min; 0.25 1 / min; 0.5 1 / min.

11. Application of a device according to any one of the preceding claims to the supply of a reactor (7) for fixing a gas to a solid, in particular for the chlorination of scraper blades d elastomer wiper.

12. Application according to claim 11, charac¬ terized in that it provides electro¬ magnetic valves (v1-v4) to allow or prevent the flow of gas in each capillary (C1-C4), the control of these solenoid valves (v1-v4) being controlled by various parameters such as the speed of movement of the solid (8) to be treated, the treatment temperature, the temperature of the gas source.