WO2006016032A1

WO2006016032A1 - Dosing device for introducing an additive into a liquid flow

Info

Publication number: WO2006016032A1
Application number: PCT/FR2005/001655
Authority: WO
Inventors: Gilbert Barras; Matthieu Darbois
Original assignee: Dosatron International
Priority date: 2004-07-15
Filing date: 2005-06-29
Publication date: 2006-02-16
Also published as: ATE383196T1; DE602005004294T2; DK1773479T3; ES2300050T3; PL1773479T3; PT1773479E; EP1773479B1; EP1773479A1; FR2873172B1; FR2873172A1; DE602005004294D1; US20070227961A1

Abstract

The invention relates to a dosing device for introducing an additive (A) in to a main liquid flow (L) in a conduit comprising a reciprocating differential piston pump (2) which is used for collecting and dosing the additive (A) from a container (1) and comprises a first inlet (7) for receiving the main liquid flow which ensures the pump actuation, a second inlet (8) for collecting the additive and an outlet (9) for mixing the additive and the main liquid. The inventive device comprises a Venturi (10) disposed in the conduit and the pump (2) connected in parallel position with respect thereto, wherein the first inlet (7) of the pump is connected to the Venturi input (11) and the outlet thereof is connected to the Venturi throat (12).

Description

ASSAY DEVICE FOR INTRODUCING AN ADDITIVE INTO A LIQUID CURRENT.

The invention relates to a metering device for introducing an additive into a main liquid stream circulating in a pipe, which device comprises a reciprocating differential piston pump for withdrawing the additive from a container and dosing it, this pump having a first inlet for receiving a main liquid flow which drives the pump, a second inlet for withdrawing the additive and an outlet for the admixture of additive and main liquid.

For example, according to EP 1 151 196 or US 6 684 753, differential piston metering pumps are known which operate with reciprocating piston engine technology. The engine liquid, usually water, passes through the pump and drives the piston. The reciprocating movement of the piston makes it possible to operate a second alternative pump, integrated in the first, to take the additive to be dosed and inject it into the main liquid or liquid. This type of metering pump has many advantages:

the volume dosing ratio does not vary with the flow rate or the pressure of the liquid engine; - the metering pump has a large operating range in flow, the upper limitation being related to the maximum allowed frequency;

the dosage remains constant despite variations in flow rate; the operation is not very sensitive to the pressure of the engine liquid;

- A dosage adjustment is possible.

However, the higher values of the flows that a pump can process are relatively limited because the cubic capacity of the pump and its dimensions increase with the maximum flow rate to be treated. Large flows require large pumps whose dimensions are necessarily limited by considerations of maximum size and cost. In addition, the range of dosages is limited especially for obtaining very small dosages, for example of the order of parts per million (ppm). The volumes of additive to be injected at each cycle of the pump then become very small and can not be obtained by a simple mechanical system.

WO 02/02938 proposes a device that allows small dosages. However, this device uses periodic electric control means and solenoid valves, which complicates the installation and increases the cost.

The object of the invention is, above all, to provide a dosing device which makes it possible in a simple and economical way to process high flow rates of main liquid with pumps of reduced dimensions and to increase the permitted range of dosages, in particular to small dosages.

According to the invention, a metering device for introducing an additive into a main liquid stream flowing in a pipe, this device comprising a reciprocating differential piston pump for withdrawing the additive into a container and dosing it, this pump comprising a first inlet for receiving a main liquid flow which drives the pump, a second inlet for withdrawing the additive and an outlet for the admixture of additive and main liquid, is characterized in that it comprises a venturi arranged in the pipe and in that the pump is connected in parallel with the venturi, the first inlet of the pump being connected to the inlet of the venturi while the outlet of the pump is connected to the neck of the venturi.

Thus, only a fraction of the main liquid flow passes through the pump which can maintain reduced dimensions to ensure dosage on a reduced derivative flow which is then mixed with the main stream.

Advantageously, the geometry of the venturi is adjusted to the pressure drop of the pump between first inlet and outlet, to allow to obtain a substantially constant dosage despite the flow variations, and independent of the inlet pressure.

The geometry of the venturi can be adjusted to establish in operation a pressure difference of about 1.5 bar and less than 2 bar between the inlet pressure and the pressure at the neck. In addition, the geometry of the venturi can be adjusted so that the pressure drop created by the venturi is less than 0.5 bar.

An additional pressure drop can be created in the bypass circuit of the pump, in particular by a nozzle, in particular adjustable, preferably disposed at the outlet of the pump.

The venturi can be set so that the ratio of the flow rate through the venturi Qe to the flow rate derivative Qd passing through the pump is equal to R, so that with a pump making it possible to treat a flow rate Qd in an x% dosage, the device makes it possible to treat a flow Qe = Qd.R, according to a dosage close to x / R%. The venturi can be set so that the ratio R is at least ten, or close to ten. Large flows can therefore be treated by smaller pumps.

For small dosages, the ratio R may be greater than one hundred. The pump may be provided to allow a volume ratio between injected additive flow and engine liquid flow through the pump less than or equal to one thousandth (1/1000) while the volume dilution of the mixture exiting the pump in the main flow venturi crossing is less than one percent (1%) so that the volume dosage in the main flow is less than or equal to 10 ^{~ 5} or 10 ppm (10 parts per million).

Advantageously, the venturi and the pump form a together, and connection means are provided at the inlet and the outlet of the venturi for insertion and connection to two sections of the pipe.

The invention consists, apart from the arrangements described above, in a certain number of other arrangements which will be more explicitly discussed hereinafter with reference to an exemplary embodiment described with reference to the appended drawing, but which is in no way limiting. In this drawing: Fig. 1 is a diagram, partly outside, partly in section, of an installation with a metering device according to the invention.

Fig. 2 is a simplified schematic view with part torn off the pump of the device, and Fig.3 shows in section on a larger scale a detail of a variant.

Referring to Fig. 1, there can be seen a dosing device D for introducing a liquid additive A in a main liquid stream L, water in the example in question. The liquid additive A is contained in a container 1.

Device D comprises a metering pump 2 arranged with its vertical axis. The pump 2 is of a known type, in particular manufactured and marketed by the applicant company DOSATRON INTERNATIONAL. An example of such pumps is described in EP 1 151 196 or US 6 684 753. As schematically illustrated in FIG. 2, in a general manner, the pump 2 comprises a reciprocating differential piston 3 which drives a piston 4 of smaller diameter, ensuring the pumping and injection of the additive A. The piston 4 slides in a chamber cylindrical auxiliary pump 5 connected by a sampling tube 6 to the container 1. The tube 6 immersed in the additive to be taken. The pump 2 comprises a first inlet 7 for receiving a flow of main liquid, generally water, which drives the differential piston 3. The pump 2 comprises a second inlet 8 located at the bottom of the auxiliary pump body 5 for the removal of the additive A, and an outlet 9 for the mixture of additive A and main liquid L. Conventional means with valves or analogues are provided for controlling the reciprocating movements of the piston 3. These known means are not shown or described.

Device D comprises a venturi 10 which has an inlet section 11, a neck 12 of reduced section and an outlet section 13.

The pump 2 is connected in parallel with the venturi 10, the first inlet 7 of the pump being connected by a pipe 14 to the inlet 11 of the venturi while the outlet 9 of the pump is connected by a pipe 15 to the neck 12 of the venturi .

The cross sections of the different parts of the venturi are preferably circular, but could have a different shape, for example rectangular.

It is recalled that a venturi makes it possible to lower the pressure of a flow of fluid in the neck, in particular to make it lower than atmospheric pressure. The flow of a liquid in a pipe not involving change of altitude is governed by the Bernoulli equation: P + pV ^2/2 = constant.

With P = static pressure of the liquid,

V = velocity of the liquid and p = density of the liquid.

The pressure difference (Pe -Pc) between the inlet and the neck of the venturi is related to the geometry (section variation) and the flow rate Qe of liquid. By designating Se as the cross section of the inlet 11 and by Sc the cross section at the neck 12 of the venturi, we obtain:

Entry speed: Ve = Qe / Se Speed at the neck: Vc = Qe / Sc.

hence Pc-Pe = -l / 2p.Qe ² . (1 / Sc ² -1 / Se ² ). A variation of the inlet pressure shifts the operating range of the venturi, the range of which decreases as the inlet pressure increases. Advantageously, the pressure difference between the inlet 11 and the neck 12 of the venturi is adjusted to the pressure drop between the inlet 7 and the outlet 9 specific to the pump in normal operation. By way of non-limiting example, this pressure drop can be of the order of 1.5 bar and remains less than 2 bar.

The geometry of the venturi is designed to create a reduced pressure drop, less than 0.5 bar, between inlet and outlet of the venturi.

The venturi 10 and the pump 2 may form an assembly, and connection means Re and Rs are provided at the inlet and the outlet of the venturi for insertion and connection to two sections of the pipe Te, Ts.

The operation of the device results immediately from the foregoing explanations.

The derivative flow which passes through the pipe 14 and into the pump 2 allows the operation of the metering pump between the inlet pressure Pe of the venturi 10 and the pressure Pc at the neck. The venturi 10 is set so that the ratio R of the flow rate Qe passing through the venturi 10 to the flow rate Qd passing through the metering pump 2 is at least equal to 10 (ten). Thus, the main flow does not pass into the metering pump 2. This allows the use of a small pump 2 for dosing an additive product A in a large flow of main liquid. For example, to ensure a 1% dosage in a flow rate of 20 m / h, with a ratio R equal to ten can be used a standard pump of maximum flow rate of 2.5 m / h, ensuring a dosage of 10%. The invention thus makes it possible to treat large flows of main liquid with relatively small dosing pumps.

In addition, the dilution effect between the flow passes through the pump 2 and the main flow that passes into the venturi 10 allows to obtain very small dosages with significant accuracy. The ratio R to ensure small dosages can be at least 100 (one hundred). A metering pump 2 allowing a volume ratio between flow rate of additive A injected and flow rate Qd of engine liquid passing through the pump equal to one thousandth (1/1000), combined with a dilution of at least one percent (1%) allows a volume dosage of additive A in the main flow rate Qe less than 10 ^{~ 5} , ie 10 ppm (10 parts per million).

For example, a pump 2 allowing a volume ratio of 1/1500 (0.07%) between the flow rate of additive A taken and the flow rate Qd corresponds, in practice, substantially to the lowest dosage mechanically obtained with such a pump. By adjusting the venturi 10 to have a Qe / Qd ratio equal to 133 (Qe = 20 m ³ / h while Qd = 150 1 / h), the volume ratio of the additive A dosage in the main flow becomes equal to: (0.07% / 133), a ratio of 5.10 ^{~ 6} or 5 ppm.

FIG. 3 illustrates an additional possibility of adjusting the flow rate of the pump by creating an additional pressure drop in the circuit derived from the pump. Preferably, this pressure drop is created by a nozzle 16 installed at the outlet 9 of the pump. The nozzle 16 has a calibrated through hole. For a pressure difference given between the neck and the venturi inlet, the frequency of the pump 2 and thus the flow rate derived in the pump 2 will be even lower than the orifice of the nozzle 16 is reduced. The pump 2, in the absence of any nozzle 16, generally allows a flow rate adjustment between a maximum value M and a minimum value M / p, with p close to three, for example. By arranging a nozzle 16, the adjustment range is increased towards the lower values, according to the diameter of the calibrated orifice of the nozzle.

The nozzle 16 may be adjustable, in particular by means of a needle, which makes it possible to vary the dosage, in particular particularly in the case of a dosing pump which has no adjustment.

In a variant, at least two different nozzles, connected in parallel on one or more bypass, can be provided with one or more selection valves, which makes it possible to obtain at least two dosing ranges.

The combination of venturi and metering pump allows a pressure independent operating range. This combination also makes it possible to obtain a substantially constant dosage and not simply an injection that would vary as a function of pressure and flow rate variations.

Tests carried out in flows from 25 m ³ / h to

40 m ³ / h under a pressure of 8 bar to 10 bar, especially for watering in the agricultural field, have been satisfactory with the use of a DOSATRON doser

INTERNATIONAL DI 1500 operating at 1.1 m ³ per hour, obtaining an additive dosage of 50 ppm in the main flow, then 4 ppm with a different jet 16.

The invention makes it possible to overcome the pressure limitation of the venturi.

Claims

A metering device for introducing an additive (A) into a main liquid stream (L) flowing in a pipe, comprising a reciprocating differential piston pump (2) for withdrawing the additive (A) into a container ( 1) and metering it, said pump having a first inlet (7) for receiving a main liquid flow which drives the pump, a second inlet (8) for withdrawing the additive and an outlet (9) for the admixture of additive and main liquid, characterized in that it comprises a venturi (10) arranged in the pipe and in that the pump (2) is connected in parallel with the venturi (10), the first inlet (7) the pump being connected to the inlet (11) of the venturi while the outlet (9) of the pump is connected to the neck (12) of the venturi.

2. Device according to claim 1, characterized in that the geometry of the venturi (10) is adjusted to the pressure drop of the pump (2) between first inlet (7) and outlet (9).

3. Device according to claim 1 or 2, characterized in that the geometry of the venturi (10) is adjusted to establish in operation a pressure difference of about 1.5 bar and less than 2 bar between the inlet pressure and the pressure at the collar.

4. Device according to one of claims 1 to 3, characterized in that the geometry of the venturi (10) is adjusted so that the pressure drop created by the venturi is less than 0.5 bar.

5. Device according to any one of the preceding claims, characterized in that an additional pressure drop (16) is created in the circuit derived from the pump.

6. Device according to claim 5, characterized in that the additional pressure drop is created by a nozzle (16)

7. Device according to claim 6, characterized in that the nozzle (16) is disposed at the outlet (9) of the pump.

8. Device according to claim 6 or 7, characterized in that the nozzle is adjustable.

9. Device according to one of the preceding claims, characterized in that the venturi (10) is set so that the ratio of the flow rate (Qe) passing through the venturi derivative flow (Qd) through the pump (2) is equal to ( R), so that with a pump for processing a flow rate (Qd) in an x% assay, the device can process a rate Qe = Qd.R, in a dosage close to x / R%.

10. Device according to claim 9, characterized in that the venturi (10) is set so that the ratio (R) of the flow rate (Qe) through the venturi derivative flow (Qd) through the pump (2) is equal to ten , or neighbor of ten.

11. Device according to one of claims 1 to 7, characterized in that the pump (2) is provided to allow a volume ratio between injected additive flow and engine liquid flow through the pump less than or equal to one thousandth ( 1/1000), while the volume dilution of the mixture exiting the pump in the main flow through the venturi is less than one percent (1%) so that the volume dosage in the main flow is less than or equal to 10 ^{~ 5} or 10 ppm

(10 parts per million).

Device according to one of the preceding claims, characterized in that the venturi (10) and the pump (2) form an assembly, and connecting means (Re, Rs) are provided at the inlet and the outlet of the venturi for insertion and connection to two sections (Te, Ts) of the pipe.