FR2746914A1 - Device for fluid pressure loss and fluid flow measurement in pipe located in an alcohol fermentation process - Google Patents

Abstract

The device(2) has a diaphragm(10) which includes an orifice(9) of a set diameter. The diaphragm(10) moves between a closed position perpendicular to the axis(3) of the pipe(2) in which the orifice(9) allows a passage for the fluid and the loss of pressure can be thus measured, and an open position, in which the circulation of the fluid or of a cleaning product flows freely, so that the device can be thus dried in situ. The diaphragm(10) is mounted so as to rotate in the pipe(2) and is installed in a valve.

Description

 The invention belongs to the field of measuring fluid flow rates.

 In known manner, such a measurement can be carried out by means of a device installed on a duct, in which the fluid circulates, the flow rate of which must be measured.

This device is generally placed substantially perpendicular to this conduit, which it partially closes.

 The device has, in fact, a diaphragm which partially closes the conduit on which the device is installed, since it has an orifice. The device thus creates a pressure drop which is measured for example by means of a differential pressure sensor. Measuring the pressure drop makes it possible to determine the volume of liquid or gas circulating in the duct and thereby its flow rate.

 Those skilled in the art also know how to size the pressure drop device and calculate the diameter of the diaphragm orifice, in particular as a function of the duct which supports it and the specifications of the differential pressure sensor used to measure the pressure drop. .

 Such a flow measurement device is used in particular for the implementation of the process for forecasting and controlling alcoholic fermentations which is the subject of patent FR-2 606 514.

 This process consists, in fact, in measuring at given time intervals at least one parameter representative of an alcoholic fermentation, so as to determine the evolution of the alcoholic fermentation and to control it, by appropriate modifications of the temperature of the medium. fermentation, to correct any incorrect development of the fermentation process.

 A flow measurement device makes it possible to evaluate the volume of carbon dioxide released which constitutes one of the parameters of alcoholic fermentation.

 In patent FR-2 606 514, the examples illustrating the application of the process all relate to the oenological field.

 In this area, the calculation of the diaphragm has also been the subject of special studies, taking into account the factors specific to the process considered and in particular, the fact that the carbon dioxide is saturated with water vapor and causes volatile products, the risk of condensation of these elements, the volume of fermented must and the maximum foreseeable fermentation speed.

 In the oenological field, several embodiments work with such a flow measurement device and they give users satisfaction.

 Tests have recently been carried out to develop, in the brewing field, an application of the process which is the subject of patent FR-2 606 514.

 These tests showed the limits of such a device for measuring the flow of carbon dioxide.

 In fact, the hygienic constraints imposed on beer production facilities require the practice of regular cyclic cleaning, in particular at the end of each production before the start of production.

 Cleaning an installation requires washing with detergents, rinsing with water and purging with air or CO2. It was found that the diaphragm, installed on the evacuation and collection circuit of the released carbon dioxide, could present, during cleaning, considerable pressure losses.

This forces the operators to dismantle it to avoid hydraulic malfunctions, in particular water hammer and allow the passage of a sufficient flow of cleaning product in relation to the various elements of this cleaning.

 It therefore appeared necessary to develop a new pressure drop device allowing, without prior disassembly, the cleaning of the circuits for liquids or gases whose flow must be measured and in particular the gas evacuation and collection circuits carbon released during brewing fermentation.

 The invention thus relates to a pressure drop device on a conduit for the circulation of a fluid, comprising a diaphragm which has an orifice of determined diameter, characterized in that said diaphragm is movable between a closed position, substantially perpendicular to the axis of the duct, in which only said orifice provides a passage for said fluid, the pressure drop can thus be measured and an open position, in which the circulation of said fluid or of a cleaning product takes place freely, said device can thus be cleaned in place.

 In a first embodiment, the diaphragm is rotatably mounted in the conduit.

 In this case, the diaphragm is advantageously installed on a valve.

 In a second embodiment, the diaphragm is slidably mounted in translation in the duct.

 Furthermore, the diaphragm is movable between the open and closed positions, according to a manual or automatic procedure.

 Preferably, said diaphragm comprises at the edge, a secondary orifice to allow, in the closed position of the device, the evacuation of any condensation and / or cleaning products.

 The invention also relates to a device for measuring the flow rate of a fluid, comprising a pressure drop device according to the invention and a differential pressure sensor, giving the pressure difference between the upstream and downstream of the pressure drop device.

 Furthermore, the pressure drop device according to the invention has made it possible to apply, to the brewing sector, the process for forecasting and controlling alcoholic fermentations which is the subject of patent FR-2 606 514, which was until so difficult due to the constraints associated with cleaning.

 In the oenological field, the measurement of the fermentation speed can be used to control alcoholic fermentation by acting on the temperature.

 In the brewing sector, this parameter is not yet used due to the lack of sufficient knowledge of the relationships that could exist between the speed of fermentation and the quality of the beer.

 On the other hand, brewers are likely to predefine a law of evolution of the density of the fermentation must as a function of time, in order to better control their process.

 This operation has so far been carried out only manually, with reference to density measurements, carried out on samples taken manually, at more or less regular intervals. It therefore essentially comes from the know-how of brewers, established empirically.

 Brewers now want to have automatic processes to control the progress of fermentation.

 The studies which have been carried out have made it possible to develop an automatic control process, using the pressure drop device according to the invention.

 Indeed, this device makes it possible to establish a relationship between the volume of carbon dioxide released during fermentation and the density of the fermentation medium.

 The invention therefore relates to the use of the pressure drop device which has just been described in a brewing installation for determining the density and / or the ethanol concentration of the fermentation medium.

 The invention also relates to an automatic process for controlling the evolution of brewing fermentation, consisting in slaving the temperature of the fermentation medium to the evolution of the density of said medium, the value of which is correlated with that of the pressure drop. , calculated using the pressure drop device according to the invention.

In a first variant, this method consists
- define beforehand an evolution profile of the density of the fermentation medium (dp),
- to calculate, at determined time intervals, the density of the fermentation medium (dc), and
- to adjust the temperature of the fermentation medium, so that the calculated density coincides with the predefined evolution profile.

In a second variant, the automatic control method according to the invention consists
- defining a correspondence table, in which ranges of predetermined values of density of the fermentation medium are associated with setpoint values for fermentation temperature,
- to calculate, in real time or at determined time intervals, the density of the fermentation medium,
- comparing the value of the density calculated with the predetermined values given in the correspondence table, and
- setting a temperature setpoint for the fermentation medium, so that it corresponds to the temperature value associated with the range of predetermined density values in which said calculated density value is located.

 Advantageously, the control method comprises an additional cleaning step during which the pressure drop device is in the open position, a cleaning product then circulating in the duct.

 The pressure drop device according to the invention can also be used in the brewing field to follow the procedure for entering a fermentation tank, that is to say filling this tank by adding must from the stirring and thus, accurately determine the volume started.

Other advantages and characteristics of the invention will appear on reading the following nonlimiting description, made with reference to the appended drawings in which
FIG. 1 is a schematic sectional view of the pressure drop device according to the invention, in place on a pipe for the circulation of a fluid, along the axis of said pipe,
FIG. 2 is a schematic plan view of the pressure drop device according to FIG. 1,
FIG. 3 is a schematic view of an industrial tank for implementing the automatic control methods according to the invention, in the brewing sector,
FIG. 4 represents the evolution curves as a function of the fermentation time (t) respectively, of the pressure drop (Delta P) created by the device according to the invention (-I-), of the circulation speed of the carbon dioxide in the device (-o-) and the cumulative volume of carbon dioxide (-),
FIG. 5 illustrates the correlation between the cumulative volume of carbon dioxide released (VCO2) and the density of the must during fermentation (d), for musts of different initial density (do),
FIG. 6 represents three correlation curves between the cumulative volume of carbon dioxide released (VCO2), and the concentration of ethanol (E) produced during fermentation, for musts of initial concentration of ethanol substantially equal,
- Figure 7 represents the evolution curves as a function of the fermentation time (t), the density (d) measured (*) or calculated (---), the ethanol concentration (E) measured (-) or calculated (-) as well as the fermentation speed (VF) (-x-),
- Figure 8 illustrates the implementation of the first variant of the control method according to the invention and represents the evolution curves as a function of time (t), of the predefined density (dp) of the fermentation medium (- -), the calculated density (dc) of the fermentation medium (-x-) and the temperature (T) (-)
- Figures 9 and 10 illustrate the second variant of the control method according to the invention: Figure 9 is a table establishing a correspondence between the desired fermentation temperature (or set temperature) and a range of density values of the medium of fermentation and FIG. 10 illustrates the result obtained, namely the curves of evolution of the density (d) of the fermentation medium (-o-) and of the temperature (T) of the medium (-), as a function of the time of fermentation (t), and
- Figure 11 illustrates an example of monitoring a procedure for intoning a fermentation tank, carried out by means of a pressure drop device according to the invention.

 The elements common to the different figures will be designated by the same references.

 Figure 1 shows a sectional view of the pressure drop device 1 according to the invention, attached to a conduit 2 for the circulation of a fluid. The arrow F gives, by way of example, the direction of circulation of this fluid inside the duct 2.

 The references 4, respectively 5 denote pipes connected to the pipe 2, placed upstream, respectively downstream of the device 1. These pipes are connected to a differential pressure sensor which is not illustrated in the figures.

 With reference also to FIG. 2, the device 1 for pressure drop according to the invention comprises a diaphragm 10 intended to be placed inside the duct 2, as well as first and second parts 11 and 12 intended to be rotatably mounted in the wall 6 of the conduit.

 In this exemplary embodiment, the diaphragm 10 consists of a central part 7 having the shape of a disc of given thickness and held in an annular element 8 of greater thickness. The diameter of this diaphragm 10 substantially coincides with the internal diameter of the duct 2.

 Significantly at its center, the central part 7 has a main orifice 9. The center of this orifice 9 practically coincides with the axis 3 of the conduit 2, when the pressure drop device 1 is fixed to the conduit.

 On either side of a diameter of the diaphragm 10, the first and second parts 11 and 12 of the device are fixed. They are intended to be placed in recesses, respectively 13 and 14, formed in external protrusions, respectively 15 and 16 of the wall 6 of the conduit.

 Means not shown in the figures, allow the rotation of the first part 11 in its recess 13 and consequently, the rotation of the diaphragm 10 in the duct 2 and of the second part 12 in its recess 14. Sufficient play must therefore be provided between the first part 11, respectively the second part 12 and its recess 13, respectively 14.

 When the diaphragm 10 is mounted in rotation, it can advantageously be installed on a manual or automatic valve of any type, in particular: gate valve, butterfly valve, valve, sphere or ball. In this case, the first and second parts 11 and 12 are elements of such a valve.

 However, the diaphragm 10 is not necessarily mounted in rotation, to be movable between an open position and a closed position. I1 can also be mounted sliding in translation between the inside and the outside of the duct 2 (the embodiment is not illustrated). This translational movement can be obtained automatically or manually.

The operation of the pressure drop device according to the invention is as follows
When the device is in the closed position as illustrated in FIG. 1, that is to say when the diaphragm 10 is substantially perpendicular to the axis 3 of the duct, it closes the duct 2, the passage of the liquid or of the circulating gas in the duct being possible only through the orifice 9. The device causes a pressure drop between the area of the duct located upstream of the device and that located downstream of the device.

 The differential pressure sensor allows the measurement of the pressure drop and thus, the calculation of the volume of liquid or gas circulating in the duct or its flow.

 When the device is in the open position, that is to say when it no longer closes the duct and the fluid can circulate freely inside it, no pressure drop measurement can be carried out.

On the other hand, in this open position, cleaning of the duct can be carried out, in particular by circulating therein suitable liquids (detergents, rinsing water, etc.). The device can therefore be cleaned without disassembly.

 This pressure drop device will therefore be advantageously used in the brewing sector. It will, in fact, by rotation or translation, the complete opening of the evacuation and carbon dioxide collection circuits which equip the brewing tanks, and thus their cleaning, without it being necessary to dismantle the device beforehand.

 The diameter of the main opening 9 of the diaphragm 10, will be calculated to be equivalent to that of a static diaphragm. Conventionally, this calculation will take into account the specifics of the differential pressure sensor used to measure the pressure drop.

 It is important to correctly determine the diameter of the main orifice, so that the pressure drop measurement created in the duct can be properly exploited.

 Preferably, the central part 7 of the diaphragm 10 of the pressure drop device has a secondary orifice 17. This orifice is placed on the periphery of the central part 7. I1 is intended for the evacuation of any condensation products and / or cleaning.

In an exemplary embodiment, the secondary orifice has a diameter equal to approximately 1 / 20th of that of the main orifice 9.

 In this exemplary embodiment, so that this secondary orifice effectively fulfills its evacuation function, it is aligned with the first and second parts 11 and 12.

 Furthermore, the pressure drop device will be fixed in the duct 2 so that the orifice 17 is in the low position of the duct.

 This secondary orifice is of particular interest when the pressure drop device is used in the brewing sector. It makes it possible, in fact, to avoid any accumulation of water, reagent and beer and thus contributes to fulfilling the cleanliness constraints which are required during the manufacture of beer.

 FIG. 3 illustrates the mounting of the pressure drop device according to the invention, on the carbon dioxide evacuation circuit, at the outlet of a brewing fermentation tank.

 The reference 20 designates a fermentation tank, mounted on a base 21 and having a filling and draining valve 22, located under the cylindrical-conical part of the tank.

 On the shell of the tank is mounted a heat exchanger 23 receiving a pipe 24, connected to a cooling group, a coolant whose flow is regulated by a valve 25. The coolant returns to the coolant group by driving 26.

 It is an external exchanger of the double jacket type.

 The carbon dioxide produced in the tank 20 is captured by a pipe 30, on which is fixed a device for measuring the pressure drop 27, comprising a differential pressure sensor as well as a pressure drop device according to the invention.

 On the conduit 30 are also provided successively and upstream of the device 27, a sensor 28 for measuring the pressure of the dome of the tank as well as a valve 29 for regulating this dome pressure.

 Also provided are a temperature sensor 31 and a pressure sensor 32 at the bottom of the tank.

 This set was produced and installed in a brewery, on a 2,500 hectoliters tank, used to ensure the alcoholic fermentation of musts from brewing.

 Thanks to the pressure drop device according to the invention, the process for monitoring and controlling the alcoholic fermentation of the type described in patent FR 2 606 514 could advantageously be applied to the brewing sector.

 FIG. 4 shows an example of an evolution curve, as a function of the fermentation time, of the pressure drop Delta P (~ -) created by the device according to the invention on the evacuation and collection pipe for carbon dioxide. released by a tank, of the type illustrated in Figure 3.

 This evolution curve was obtained during an industrial fermentation test.

 FIG. 4 also shows the curves of evolution of the speed V (-o-) of circulation of carbon dioxide in the device according to the invention as well as of the cumulative volume (VCO2) of carbon dioxide released (-), as a function of the time (t). These last two curves are obtained by calculation, from the pressure drop curve (Delta P).

 FIG. 5 establishes the correlation which exists between the cumulative volume of carbon dioxide released VCO2 and the density d of the must during fermentation. This latter value can thus also be obtained by means of the pressure drop device according to the invention.

 Each of the three curves corresponds to a different initial density. Thus, the first curve (1) corresponds to an initial density d0 = lO0P, the second curve (+) to an initial density d0 = 11.50P and the third curve (X) to an initial density d, = 13.50P.

 The initial density value is an indicator of the sugar content of the must considered.

 A general law of the type: d = a.VCO2 + b.d0 + c describes all of these results. The experimental results obtained during the numerous tests carried out allowed the identification of the parameters a, b, c.

 FIG. 6 shows three curves of evolution of the cumulative volume of carbon dioxide released VCO2, as a function of the concentration of ethanol E produced during the fermentation. Each of these three curves (V,, *) corresponds to an initial ethanol concentration substantially equal to 0.5.

 It will be noted that for each of these curves, the final values of the cumulative volume of carbon dioxide released VCO2 and of the ethanol concentration are different.

These values are all the more important the higher the initial density of the must considered.

A general law can also describe all the results obtained in this regard. This general law is written in the form: E = a VCO2 + B.Eo + Y. The experimental results also made it possible to identify the parameters a, B and y
As illustrated in FIG. 7, the use of these two general laws makes it possible to describe the evolution of the density of the fermentation medium (d) and of the ethanol concentration (E), as a function of the progress of the fermentation.

 Figure 7 shows the evolution of the density measured experimentally (*) as a function of time, as well as the evolution of the density (---) as a function of time, calculated from the general law defined above.

 The example illustrated in Figure 7 shows that the adequacy between the calculated values and those measured experimentally is excellent.

 The same conclusion is necessary with regard to the ethanol concentration of the fermentation medium.

 Indeed, the experimental results reported in Figure 7 compare the changes as a function of the fermentation time (t) of the ethanol concentration measured in the laboratory (A), calculated () from the general law defined above.

 Figure 7 also shows the evolution of the fermentation speed (VF) (-x-) as a function of the fermentation time (t), which is calculated at all times by derivation, with respect to time, of the volume of carbon dioxide. VCO2 produced.

 As will now be explained, the pressure drop device according to the invention, which can be cleaned in place, without being dismantled, allows the control of alcoholic fermentation in the brewing sector.

 As indicated above, the fermentation speed is not yet used in breweries for the control of alcoholic fermentation, since brewers do not know enough about the relationships that may exist between the fermentation speed and the quality of the beer.

 On the other hand, the brewers have defined, empirically, laws of evolution or fall in the density of the fermentation medium as a function of time. These evolution laws are used to better control the fermentation process.

 From the measurements obtained thanks to the pressure drop device according to the invention, an automatic process has been developed for monitoring the evolution of brewing fermentation. This process consists in slaving the temperature of the fermentation medium to the evolution of the density of this medium.

 The first variant of the control method according to the invention consists in following a profile of evolution of the density (dp) predefined by the operator, by acting adequately on the fermentation temperature.

 This process consists of a direct and permanent control of the fermentation temperature.

 The implementation of this method is illustrated in FIG. 8.

 This figure shows the evolution curve, as a function of the fermentation time (t), of the density as desired by the operator (dp) (---).

 This figure also shows the evolution of the real density, calculated by application of the process (dc) (-x-), as a function of time (t), the calculation being carried out from the pressure drop measurements made possible by the device according to the invention.

 Finally, Figure 8 shows the evolution imposed on the temperature of the fermentation medium (T) as a function of time (t) (-) to ensure the control of the fermentation.

 Thus, the method consists in constantly acting on the temperature of the fermentation medium so that the density, calculated at determined time intervals, follows, as closely as possible, the density predefined by the operator.

 In practical terms, in the brewing sector, no means of heating the tanks is provided. The temperature of the fermentation medium naturally rises during the fermentation. On the other hand, cooling means are provided.

 In the example illustrated in Figure 8, we observe that the initial density is slightly higher than the desired density, as defined in the profile.

 However, the situation recovers fairly quickly due to the rapid start of alcoholic fermentation.

Thus, after approximately 20 hours of fermentation, the predefined and measured densities are very good. A significant reduction in temperature, which went from around 10.5 ° C to 90 ° C, made it possible to achieve this result.

 Between the 20th and the 115th hour of fermentation, the match between the actual density of the must and the predefined density is excellent. This is made possible by maintaining the temperature of the fermentation medium at around 90C until about the 50th hour of fermentation, then gradually increasing this temperature to 120C, this value being obtained after about 80 hours of fermentation. Beyond 115 hours of fermentation, the attenuation limit is reached and the alcoholic fermentation is finished.

 When the fermentation is complete, the curves illustrated in FIG. 8 show a significant difference between the density predefined by the operator which is of the order of 2.80P, and the real density of the beer which is approximately 3, 7 "P. This is due to an insufficient knowledge of the richness of the must in fermentable sugars.

 The final cooling of the beer takes place after 145 hours of fermentation. This cooling could be carried out earlier and automatically controlled according to the process, since the fermentation has been completed for more than 30 hours when it begins.

 Another variant of the control process according to the invention consists in acting, sequentially, on the temperature of the fermentation medium, as a function of the values of the density of the fermentation medium, calculated at determined time intervals or in real time. and from the pressure drop measurements given by the device according to the invention.

 It is first of all advisable to define a correspondence table, in which ranges of predetermined values of density of the fermentation medium are associated with reference values of fermentation temperature.

 An example of such a correspondence table is illustrated in FIG. 9.

 During the implementation of the process for monitoring the progress of fermentation, the density is calculated at fixed time intervals or in real time, using the pressure drop device according to the invention.

 Each calculated density value is compared to the predetermined density value ranges listed in the mapping table. The method then consists in fixing a set value for the temperature of the fermentation medium, corresponding to the temperature value associated with the predetermined density range in which the calculated density lies.

 The implementation of this second variant of the control method according to the invention will be illustrated with reference to the example shown in FIGS. 9 and 10.

 In this example, the initial density of the wort do is lloP and the fermentation temperature is set at 90C.

 The alcoholic fermentation then starts and the fermentation temperature is automatically regulated at 90C until the density of the wort measured reaches the value of 90P.

DBP

 The temperature of 12 "C is maintained until a density of 4.60P is obtained. At this time, a new setpoint is fixed for the temperature, at 9" C.

 When the density reaches the attenuation limit (40P), coinciding with the end of the alcoholic fermentation, the temperature is fixed at 8 "C.

 This second variant of the control method according to the invention is not limited to the example illustrated in FIGS. 9 and 10. In particular, the table of correspondence between the ranges of density and temperature values can be more or less large. , so as to define a greater or lesser number of steps for modifying the fermentation temperature.

 The two variants of the process for controlling the evolution of brewing fermentation which have just been described are intended to illustrate the possibilities of density control during fermentation. They also show the numerous ways of studying and improving the process which result from the implementation and correct use of the pressure drop device according to the invention.

 The pressure drop device according to the invention can also be used to follow the procedure for entering a fermentation tank, such as tank 20 illustrated in FIG. 3.

 The seasoning generally gives rise to several successive additions of must (corresponding to as many brews), made over several hours or several days. In this second case, the alcoholic fermentation starts even before the end of the seasoning.

 The pressure drop device according to the invention makes it possible to display these successive additions of wort which result in a displacement of gas substantially equal to the volume of wort introduced.

 We can refer to figure 11 which represents the curve (- -) of evolution of the pressure drop (Delta P) according to the duration of entonnement (t).

 FIG. 11 also illustrates the curve (-X-) of evolution of the dome pressure (p) as a function of the duration of entonnement (t). The pressure values are determined for example by means of the sensor 28, illustrated in FIG. 3.

 By taking into account the temperature measurements of the must, given for example by the sensor 31 of FIG. 3, and the pressure measurements of the dome of the tank, to correct the volume of gas displaced during filling, it is possible to calculate the volume of wort actually sown (V).

 Thus, FIG. 11 shows the evolution curve () of the volume of wort actually sown (V), as a function of the duration of sowing (t).

The interest for brewers of such a determination is twofold
First of all, the volumes of intoned wort and, consequently, of beer produced are known with precision.

 In addition, the initial volume of wort is, like its initial density, an essential data for the implementation of the process for controlling the evolution of brewing fermentation. In fact, an erroneous volume (poorly evaluated) leads to determinations of density, ethanol concentration and fermentation rate which are also erroneous.

 A variant of the method for determining the volume of intoned wort described above consists in using the pressure difference between the bottom of the tank (the value of the pressure at the bottom of the tank being for example given by the sensor 32 illustrated in the Figure 3) and the dome (the value of the dome pressure of the tank being determined as previously by the sensor 28 of Figure 3).

 The reference signs inserted after the technical characteristics mentioned in the claims have the sole purpose of improving the understanding of the latter and should not limit their scope.

Claims (13)

 1. A pressure drop device on a conduit (2) for the circulation of a fluid, comprising a diaphragm (10) which has an orifice (9) of determined diameter, characterized in that said diaphragm (10) is movable between a closed position, substantially perpendicular to the axis (3) of the duct (2), in which only said orifice (9) provides a passage for said fluid, the pressure drop can thus be measured and an open position, in which the circulation of said fluid or of a cleaning product takes place freely, the device thus being able to be cleaned in place.  2. Pressure drop device according to claim 1, characterized in that said diaphragm (10) is rotatably mounted in the conduit (2).  3. Pressure drop device according to claim 2, characterized in that said diaphragm (10) is installed on a valve.  4. Pressure drop device according to claim 1, characterized in that said diaphragm (10) is slidably mounted in translation in the conduit (2).  5. Pressure drop device according to one of claims 1 to 4, characterized in that said diaphragm (10) is movable between the open and closed positions, according to a manual or automatic procedure.  6. Device according to one of claims 1 to 5, characterized in that said diaphragm (10) comprises, at the edge, a secondary orifice (17) to allow, in the closed position of the device, the evacuation of any products of condensation and / or cleaning.  7. Device for measuring the flow rate of a fluid, comprising a pressure drop device (1) according to one of claims 1 to 6 and a differential pressure sensor, giving the pressure difference between the upstream and the downstream of said pressure drop device (1).  8. Use of the pressure drop device according to one of claims 1 to 6 in a brewing installation, to determine the density (d) and / or the ethanol concentration (E) of the fermentation medium.  9. Automatic process for controlling the evolution of brewing fermentation, consisting in slaving the temperature of the fermentation medium to the evolution of the density of said medium, the value of which is correlated with that of the pressure drop, calculated using the pressure drop device according to one of claims 1 to 6.  10. Automatic control method according to claim 9, consisting of  - define beforehand an evolution profile of the density of the fermentation medium (dp),  - to calculate, at determined time intervals, the density of the fermentation medium (dc), and  - to adjust the temperature of the fermentation medium, so that the calculated density coincides with the predefined evolution profile.  11. Automatic control method according to claim 9, consisting of  - defining a correspondence table, in which ranges of predetermined values of density of the fermentation medium are associated with setpoint values for fermentation temperature,  - to calculate, in real time or at determined time intervals, the density of the fermentation medium,  - comparing the value of the density calculated with the predetermined values given in the correspondence table, and  - to set a temperature set point of the fermentation medium, so that it corresponds to the temperature value associated with the range of predetermined density values in which said calculated density value is located.  12. Method according to one of claims 9 to 11 characterized in that it comprises an additional cleaning step during which said pressure drop device is in the open position, a cleaning product then circulating in the conduit (2).  13. Use of the pressure drop device according to one of claims 1 to 6 in a brewing installation, to follow the entonnement of a fermentation tank (20) and thus, to accurately determine the volume entonnée.