EP4088077B1 - Procédé et dispositif de détermination de l'encrassement dans un échangeur de chaleur - Google Patents

Procédé et dispositif de détermination de l'encrassement dans un échangeur de chaleur Download PDF

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EP4088077B1
EP4088077B1 EP21711796.9A EP21711796A EP4088077B1 EP 4088077 B1 EP4088077 B1 EP 4088077B1 EP 21711796 A EP21711796 A EP 21711796A EP 4088077 B1 EP4088077 B1 EP 4088077B1
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Prior art keywords
variable
medium
heat exchanger
flow
value
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German (de)
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EP4088077A1 (fr
EP4088077C0 (fr
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Jonas KAUB
Daniel Labisch
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Siemens AG
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Siemens AG
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28G—CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS
    • F28G15/00—Details
    • F28G15/003—Control arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B37/00—Component parts or details of steam boilers
    • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
    • F22B37/56—Boiler cleaning control devices, e.g. for ascertaining proper duration of boiler blow-down
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F2200/00—Prediction; Simulation; Testing

Definitions

  • the invention relates to a method and a device for determining fouling in a heat exchanger according to patent claims 1 and 2 and patent claims 14 and 15.
  • Heat exchangers are technical devices that are used to heat or cool a medium. For this purpose, heat is transferred from a warmer first medium to a colder second medium. Depending on the design, heat exchangers differ in their functional principle. The most common designs are classified into one of the three functional groups: co-current, counter-current or cross-flow heat exchangers.
  • the medium to be heated or cooled is often referred to as the “product medium” and the heating or cooling medium is often also referred to as the “service medium”.
  • the service medium can be, for example, heating steam or cooling water.
  • the service medium usually flows either through a line arrangement which is arranged within the product medium, or flows around a line arrangement through which the product medium flows.
  • the first and the second medium are passed through the heat exchanger, with the two media usually flowing past each other separated by a wall and the heat from the warmer medium being transferred to the colder medium through the wall.
  • a central problem with heat exchangers is so-called "fouling", in which deposits or deposits form on the inner walls of the heat exchanger.
  • the reasons for the formation of such deposits can be physical, chemical or biological. Let them cannot be prevented in many cases, for example due to the given product-related conditions.
  • the coverings inhibit the heat transfer between the media and thereby reduce the efficiency of the heat exchanger. Once a certain level of contamination has been reached, chemical or mechanical cleaning or possibly even replacement of the heat exchanger becomes necessary. This problem is particularly pronounced in large industrial heat exchangers that are used in process engineering plants (e.g. plants in the chemical, petrochemical, glass, paper, metal production or cement sectors) or in power plants, where they are usually designed for a heat transfer capacity of more than 100 kW.
  • a temperature control loop is able to compensate for the effects of contamination to a certain extent, so that the contamination is not immediately recognizable in the initial temperature of the product medium. Due to this lack of knowledge, it is often not possible to clean or replace the heat exchanger as needed.
  • heat exchangers affected by contamination have been cleaned or replaced at regular intervals, i.e. without knowledge of the actual contamination status.
  • the maintenance intervals cannot be adjusted depending on different levels of contamination.
  • the heat exchanger may be cleaned or replaced too early, for example, even though only minor deposits are present by then.
  • this would ensure the efficient operation of the heat exchanger, it would be uneconomical because there would be both direct costs for the maintenance work and indirect costs due to the additional impairment of the ongoing operation of the system in which the heat exchanger is located is used. If appropriate measures are taken too late, excessive deposits inside the heat exchanger will lead to significantly reduced heat transfer.
  • a method for monitoring the effectiveness of a heat exchanger with regard to fouling in which a current heat flow Q ⁇ P of the product medium or Q ⁇ S of the service medium is recorded and compared with at least one reference heat flow Q ⁇ Ref , which has a predetermined degree of contamination, for example the degree of contamination Zero and a maximum permissible degree of contamination of the heat exchanger.
  • the respective reference heat flow Q ⁇ Ref is determined depending on the current operating point of the heat exchanger from a map previously created and saved with the help of a simulation program for different operating points, whereby the operating point of the heat exchanger is determined by the flow rates F P , F s of both media and their temperatures T P,On , T S,On is determined when entering the heat exchanger.
  • the simulation program the operating point dependence of the transferable amount of heat can be pre-calculated, for example at several hundred support points, without having to carry out time-consuming measurements on the real system.
  • a method for monitoring a heat exchanger in which the flow rates, inlet temperatures and outlet temperatures of service and product medium represent process variables, of which on the product side at least one process variable is variable and the inlet temperature is set by the service and the remaining process variables are variable.
  • To monitor the heat exchanger without temperature measurement on the service side it is provided to measure the variable process variable(s) of the product medium and the flow of the service medium and to create a map for the mutual dependence of the variable process variable from the measured values obtained in a reference state of the heat exchanger (n) the product medium and the flow of the service medium to be determined and stored.
  • a distance of the measured value tuple formed by them from the map is determined as a measure of a deviation of the current state of the heat exchanger from the reference state.
  • a current K value is determined for each heating surface from a calculated thermal output, a logarithmic temperature difference and the heating surface size.
  • the reference values Kref are stored in a memory depending on the load and possibly depending on the fuel.
  • the reference values Kref can be corrected with correction factors according to some current state variables. For example, a correction is made based on the steam speed. However, it remains unclear how the reference values will be obtained.
  • a so-called “heating surface value FV” is defined as a measure of heating surface contamination. This is defined as the ratio of an actual valuation factor fist to a basic valuation factor fBasis.
  • the actual evaluation factor fist is the ratio of a "measured” heat transfer coefficient Kist to a theoretical heat transfer coefficient KTheory.
  • the “measured” heat transfer coefficient Kist is determined based on the media temperatures and the size of the heating surface.
  • the theoretical heat transfer coefficient KTheory is determined, among other things, based on the geometric data such as pipe dimensions, width and longitudinal pitch, etc. of the heating surface.
  • the basic evaluation factor fBasis is determined and saved from an operating condition that is considered optimal with existing basic contamination, e.g. acceptance test of the steam generator.
  • the calculation of the reference state includes a recalculation of the steam generator with the basic data stored in the system and some current process data, such as feed water, live steam and ZÜ parameters. However, exact details about the process data used are not disclosed.
  • the DE 10 2016 225 528 A1 discloses a method for monitoring a contamination condition in a heat exchanger using an additional temperature sensor which is arranged in or on the heat exchanger wall.
  • the temperature sensor records an operating wall temperature of the heat exchanger.
  • This operating wall temperature is corrected and a deviation between the corrected operating wall temperature and a reference wall temperature is determined.
  • the Correction of the operating wall temperature takes into account changes in measured values that occur due to operating conditions that deviate from reference conditions, such as deviations in the fluid temperatures or in the volume flows of the fluids.
  • Operating wall temperature and reference wall temperature are values that are measured at the same location and/or specified for the same location on the heat exchanger.
  • a value for a variable that characterizes the fouling is determined from a value for a first variable influenced by the fouling and a value of a second variable, one being determined by a change in a property of the first and/or the second medium, in particular a flow of the first and/or the second medium through the heat exchanger, the change in the first variable caused by the second variable is at least partially compensated.
  • variable that characterizes the fouling is preferably a thermal resistance or a thermal conductivity. But it can also be a flow resistance, for example.
  • the invention is based on the knowledge that jumps in the level of the quantity that characterizes fouling can often be explained by changes in the flow of the first and/or the second medium.
  • the reason is that when the flow rate changes, the flow speed and the type of flow at the points of heat transfer from the first to the second medium can also change.
  • the type of flow that then occurs e.g. laminar flow, weakly turbulent flow, strongly turbulent flow
  • changes in the value of the first variable influenced by the fouling can then also occur.
  • the mixing and thus the heat transfer can change depending on the flow speed.
  • a turbulent flow also forms laminar boundary layers at the edge areas, the size and thus influence of which depends, for example, on the flow or flow speed.
  • a change in the first variable caused by a change in a flow of the first and/or the second medium through the heat exchanger is at least partially compensated for by the second variable.
  • a change in the flow of the first and/or second medium causes a corresponding change in the second variable, which is then used to compensate for the influence of the change in flow on the first variable.
  • the invention enables reliable quantification of the fouling resistance even when the flow rate changes for different heat exchangers. No knowledge of material properties or structural properties of the heat exchanger is necessary.
  • the invention works purely based on measurement data. Instead of just using the thermal resistance or the thermal conductivity (or the thermal transmittance (k-value)) or the flow resistance as an indicator for fouling, the invention uses this quantity and at the same time incorporates the influence of the flow dynamics of the two media on the final result.
  • the fouling resistance contained therein is advantageous regardless of the operating point.
  • the invention does not require any special additional measuring instruments (e.g. a temperature sensor on a heat exchanger wall), but rather makes do with the instrumentation usually found in heat exchangers.
  • one of the measurements of flows and inlet/outlet temperatures of the media can also be omitted, so that complete instrumentation is not even required.
  • the invention made it possible to achieve a significantly better result in determining fouling than with a conventional calculation.
  • the results could help a system operator to make a significantly better assessment of the fouling resistance.
  • the invention can advantageously be applied not only to the heat balances, but also to the consideration of the pressure differences and thus the flow resistances.
  • the second variable is a variable that is unaffected by fouling.
  • the first variable influenced by the fouling is a heat transfer resistance or a heat transfer conductivity (or a heat transfer coefficient, often also referred to as a “k value”).
  • the thermal resistance or thermal conductivity (or the k value) can be obtained particularly easily from measured values of temperatures of the first medium and the second medium are determined at an inlet and an outlet of the heat exchanger.
  • Changes in the flow of the first and/or second medium through the heat exchanger can lead to changes in the flow speed and type of flow and thus to changes in the heat transfer coefficient ⁇ 1.2 .
  • the second size X is therefore a size that is unaffected by fouling.
  • the second variable is therefore a measure of the heat transfer coefficient between the first medium and the wall, the thermal conductivity of the wall and the heat transfer coefficient between the second medium and the wall.
  • variable influenced by the fouling is a flow resistance of the first or second medium through the heat exchanger.
  • a flow resistance can be determined particularly easily from measured values of pressures of the first medium and the second medium at an inlet and an outlet of the heat exchanger.
  • Method 1 at the time of a flow change, in particular a sudden change, the value of the second variable is changed in such a way that the value of the variable characterizing the fouling remains constant.
  • an initial value of the first variable can be determined (or "learned") and the second variable can be set to an initial value that corresponds to the initial value of the first variable.
  • the two sizes then compensate each other completely. If then in further operation of the heat exchanger the value of the first variable due to fouling and due to. As flow changes increase, the flow changes cause a corresponding change in the second variable, which leads to a corresponding compensation for the first variable.
  • This method is particularly suitable for operating the heat exchanger with operating phases in which the flow is constant in parts and then changes suddenly.
  • this corresponds to the relatively common case where the flow of the product medium is regulated, with the setpoints being constantly specified.
  • a constant flow change can only be processed piecemeal. However, continuous adjustment could then occur via interpolation between the piecemeal changes.
  • the advantage is that changes to the medium after cleaning have no influence on the result and no learning data is required.
  • Method 2 a function can be defined which assigns a value for the second variable to a value for a flow through the heat exchanger of the first and/or the second medium.
  • This function can be determined or “learned” in a time interval after the heat exchanger is put into operation for the first time or after the heat exchanger has been cleaned of fouling.
  • the function is preferably formed by a regression of measured values of the flow and associated values of the second variable in the time interval.
  • the regression can be, for example, a linear regression (when only the flow of one of the two media changes) or a 3D regression (when the flow of both media changes).
  • This method can also take constant changes into account, is relatively resistant to deviations in normal operation and requires several cleanings (and then several different flow changes) to "teach" the function. It also allows comparisons between the quality of cleanings.
  • Value ranges for the flow are defined, each of which has a Value for the second size is assigned.
  • the assignment of the values of the second variable to the flow is advantageously determined or "learned" in a time interval after the heat exchanger has been put into operation for the first time or after the heat exchanger has been cleaned of fouling.
  • the transitions between values of the second size can be filtered slightly at the range boundaries so that they do not change too much. It is also possible to interpolate between the different learned points instead of quantizing to create a "smoother" transition.
  • the time interval for defining the function or the area-wise value assignments depends on the speed of the fouling processes and can, for example, be between a few hours (for fast fouling processes, which, for example, lead to weekly cleaning of the heat exchanger) and a few days (for slow fouling processes, which lead, for example, to monthly cleaning of the heat exchanger).
  • method 1 can be used whenever a flow change occurs and the jump height and compensation height can be taken into account as a new learning point in methods 2 and 3. This means that learning points in a dirty state are also possible.
  • a characteristic curve for a relationship between the second variable and the flow of one of the two media is determined, with a characteristic curve of a mathematical derivative of the first variable according to the flow of the medium being determined in a first step to determine the characteristic curve and in a second step, the characteristic curve obtained in the first step is integrated again with respect to the flow of the medium.
  • This method takes advantage of the fact that the quantity that characterizes fouling follows a slow and fairly consistent trend.
  • the relationship between the first variable and the flow is constantly shifting, so that no direct estimate of the relationship is possible. There is therefore the problem of estimating a characteristic curve (static relationship) between two variables. In addition to the static relationship, an additive trend also affects the dependent variable.
  • the basic idea for solving this problem is to estimate the derivative of the first quantity according to the flow (e.g. (d 1/k)/dF)), from which the fouling can be eliminated.
  • the integration of the derivative then provides the actual connection again, although the absolute value is obviously lost.
  • this is not necessary in the application, as only relative flow changes need to be compensated.
  • a first characteristic curve for a relationship between the second variable and the flow of the first medium and a second characteristic curve for a relationship between the second variable and the flow of the second medium are simultaneously determined, the characteristic curves being determined in
  • a characteristic curve of a mathematical derivative of the first variable is determined for each of the two media according to the flow of the respective medium and in a second step the characteristics obtained in the first step are integrated again in relation to the flow of the respective medium.
  • the “derived variables” can be, for example, statistical variables such as mean values, minimums and maximums of measured values.
  • a computer program according to the invention comprises instructions which, when the program is executed on a computer, cause the computer to carry out a method according to the invention described above.
  • a corresponding computer program product comprises a storage medium on which a program is stored with instructions which, when the program is executed on a computer, cause the computer to carry out a method according to the invention described above.
  • FIG 1 shows, by way of example and in a simplified representation, a heat exchanger 1 for transferring heat or cold from a service medium S to a product medium P.
  • the heat exchanger 1 is shown by way of example as a countercurrent heat exchanger, but other designs of heat exchangers are also possible.
  • the product medium P flows through a line 2.
  • the flow F P or the flow rate or the volume flow
  • the temperature T P,A before entering are measured by means of a flow sensor 4 and a temperature sensor 5 measured the heat exchanger 1.
  • a further temperature sensor 6 arranged behind the heat exchanger 1 in the flow direction measures the temperature T P,Aus of the product medium P emerging from the heat exchanger 1.
  • the product medium P is heated or cooled by means of a service medium S, which is supplied to the heat exchanger 1 from a heating or coolant supply.
  • a service medium S which is supplied to the heat exchanger 1 from a heating or coolant supply.
  • the flow F S (or the flow rate or the volume flow) of the service medium and its temperature T S,Ein are measured by means of a flow sensor 7 and a temperature sensor 8 before entering the heat exchanger 1.
  • a further temperature sensor 9 arranged behind the heat exchanger 1 in the flow direction measures the temperature T S,Aus of the service medium S emerging from the heat exchanger 1.
  • the flow measurement value F P and the temperature measurement values T P,In , T P,Out of the product medium P and the flow measurement value F S and the temperature measurements T S,In , T S,Off of the service medium S are transmitted to a device 10 for determining fouling. If individual process variables of the product medium P or the service medium S, for example its inlet temperature T P,On or T S,On , are fixed based on given framework conditions and can therefore be assumed to be unchangeable, they do not need to be measured.
  • the current fouling resistance can be calculated from the difference between the current heat transfer resistance 1/ k is and the heat transfer resistance 1/ k should , which was determined in the clean state.
  • a relative value for k can only be calculated using the measured values of the inlet and outlet temperatures as well as the flow rates of the two media.
  • FIG 2 shows an example of a typical course of the 1/k value over time t for an industrial heat exchanger.
  • Vertical lines show the cleaning times. In some areas a decrease of 1/k' caused by fouling can be seen. However, there are jumps in level at the points marked with an arrow, which make it difficult to accurately evaluate the fouling resistance.
  • the determination of the fouling resistance can be made more precisely by taking flow changes in the product and/or service medium into account during the evaluation.
  • the second variable X is therefore a measure of the heat transfer coefficient between the first medium and the wall, the thermal conductivity of the wall and the heat transfer coefficient between the second medium and the wall.
  • changes in the first variable caused by flow changes are at least partially compensated for with the aid of a second variable, here a value of the variable X.
  • FIGS. 3 to 10 Three procedures or methods are now presented as to how the flow can be taken into account:
  • FIG 3 shows an example of a course of 1/k, X and R f over time t.
  • the value of X is constant and results in a constant difference between 1/k and R f .
  • X new X old - (1/ k old - 1/ k new ).
  • FIG 4 shows an example of a course of 1/k, X and R f over time t.
  • This method is particularly suitable for operating the heat exchanger with operating phases in which the flow is constant in parts and then changes suddenly.
  • a constant flow change can only be processed piecemeal. However, continuous adjustment could then occur via interpolation between the piecemeal changes.
  • changes to the medium after cleaning have no influence on the result and no learning data is required.
  • FIG 6 shows an example of an application of linear regression using the example of the industrial heat exchanger FIG 2 .
  • the relative fouling resistance R f for the industrial heat exchanger is determined FIG 2 calculated and plotted together with the values X determined using linear regression over time t, the result is an in FIG 7 shown course.
  • the function f can be calculated using a linear regression (if only the flow of one of the two media changes, see FIG 6 ) or a 3D regression (if the flows of both media change) of measured values of flows and associated values of the second variable can be formed in the time interval after an initial commissioning or cleaning.
  • This method can also take into account constant changes, is relatively resistant to deviations in normal operation, but also requires several cleanings (and then several different flows) to "learn" the function f. It also allows comparisons between the quality of cleanings.
  • the X values learned after initial commissioning or cleaning can be used to create value ranges for the flow. Within such a range, each flow value is assigned a learned X value. To ensure that the transitions between two X values are not too abrupt, this X value can be filtered slightly over time.
  • the assignment of the values of the second variable to the flow rates is advantageous in a time interval after one The first time the heat exchanger is put into operation or after the heat exchanger has been cleaned of fouling.
  • the transitions between values of the second size can be filtered slightly at the range boundaries so that they do not change too much. It is also possible to interpolate between the different learned points instead of quantizing to create a "smoother" transition.
  • This method also represents a way in which the analysis of a relationship between flow and reference value could be implemented. This requires a rough idea of what the characteristic curve of the ⁇ value could look like depending on the flow velocity. Here, boundary conditions for the later characteristic curve or function could already be found, such as monotonicity of the curve.
  • the first values for the analysis are obtained and recorded in a clean state after cleaning.
  • New values are added during runtime. These are weighted with the previous values in a certain area and the characteristic curve is updated.
  • the weighting factor can be the number of previous points in an area or the current fouling resistance.
  • the fouling resistance or the X-value could first be determined for the heat exchanger using method 1 and then, in the medium term, the the variance of Method 2 or the number of data points in Method 2). In the long term, only method 2 should be sufficient.
  • Method 1 To calculate the final X value, you can interpolate between the different sampling points in order to avoid a jump-like progression (see dashed line in FIG 9 ).
  • a combination of Method 1 and Method 4 therefore offers particular advantages.
  • a characteristic curve for a relationship between the second variable and the flow of one of the two media is determined, with a characteristic curve of a mathematical derivative of the first variable according to the flow of the medium being determined in a first step to determine the characteristic curve is determined and in a second step the characteristic curve obtained in the first step is integrated again in relation to the flow of the medium.
  • This method takes advantage of the fact that the quantity that characterizes fouling follows a slow and fairly consistent trend.
  • the relationship between the first variable and the flow is constantly shifting, so that no direct estimate of the relationship is possible. There is therefore the problem of estimating a characteristic curve (static relationship) between two variables.
  • An additive trend also acts on the dependent variable.
  • the basic idea for solving this problem is to estimate the derivative of the first quantity according to the flow (e.g. (d 1/k)/dF)), from which the fouling can be eliminated.
  • the integration of the derivative then provides the actual connection again, although the absolute value is obviously lost.
  • this is not necessary in the application, as only relative flow changes need to be compensated.
  • the absolute value is irrelevant, so that no initial value has to be taken into account during the integration.
  • a special feature of this method is that the actual task of determining fouling initially takes a back seat and the effect of fouling is compensated for in order to estimate the X-F characteristic curve. Only then is the fouling determined using the characteristic curve from 1/k.
  • a characteristic curve can be easily implemented, so that nothing stands in the way of online evaluation.
  • FIGS. 10 to 12 show a simulation of an industrial heat exchanger with a flow rate variation.
  • FIG 10 shows a time course of (simulated) measured values of the flow F P of the product medium and the flow F S of the service medium through the heat exchanger.
  • FIG 11 shows the associated (simulated) measured values for the temperature T P,In of the product medium at the inlet and the temperature T P,Out of the product medium at the outlet of the heat exchanger.
  • (simulated) measured values of the temperature T S,In of the service medium at the inlet and the temperature T S,Out of the service medium at the outlet of the heat exchanger are shown.
  • FIG 12 shows the associated calculated relative values for 1/k and the fouling resistance R f .
  • the 1/k value shows a significant dependence on flow changes, regardless of which side of the heat exchanger. A superimposed trend can still be seen in the idealized data. Depending on the severity of the fouling, however, no reliable statement can be derived from the 1/k value alone.
  • the estimated fouling curve is obtained (shown with an upward offset for better visibility). Except for the measurement noise, a linear trend can be seen. Fouling can thus be determined very reliably. It should be noted that at the beginning both flow rates were changed independently of one another, so that both flow characteristics could gradually be well estimated independently of one another.
  • a first characteristic curve for a relationship between the second variable and the flow of the first medium and a second characteristic curve for a relationship between the second variable and the flow of the second medium are simultaneously determined, in order to determine the Characteristic curves in a first step, a characteristic curve of a mathematical derivative of the first variable is determined for each of the two media according to the flow of the respective medium and in a second step, the characteristics obtained in the first step are integrated again in relation to the flow of the respective medium.
  • n D equations can then be summarized in matrix notation, whereby the respective flow at the support points must be taken into account.
  • F s n s , m T c ⁇ t 1 ... ⁇ t m A ⁇ R n D x n p + n s + 1
  • the absolute values of the characteristics are unknown due to the integration. Due to the simpler parameterization, the modeling is only carried out qualitatively, i.e. 1/k is determined without exact material data or properties of the heat exchanger. This means that only relative changes in the k value can be calculated. However, the specific characteristics can be used exactly for relative changes in flow rates.
  • FIGS. 13 - 15 show a simulation of an industrial heat exchanger with varying flow rates.
  • FIG 13 shows a time course of (simulated) measured values of the flow F P of the product medium and the flow F S of the service medium through the heat exchanger.
  • FIG 14 shows the associated (simulated) measured values for the temperature T P,In of the product medium at the inlet and the temperature T P,Out of the product medium at the outlet of the heat exchanger.
  • (simulated) measured values of the temperature T S,In of the service medium at the inlet and the temperature T S,Out of the service medium at the outlet of the heat exchanger are shown.
  • FIG 15 shows the calculated relative values for 1/k and the fouling resistance R f .
  • the 1/k value shows a significant dependence on flow changes, regardless of which side of the heat exchanger. A superimposed trend can still be seen in the idealized data. Depending on the severity of the fouling, however, no reliable statement can be derived from the 1/k value alone.
  • the estimated fouling curve Rf is obtained. Except for the measurement noise, a linear trend can be seen. Fouling can therefore be determined very reliably, even if both flow rates change at the same time.
  • the methods enable reliable quantification of the fouling resistance even when the flow rate changes for different heat exchangers. No knowledge of material properties or structural properties of the heat exchanger is necessary. The methods all work purely based on data. So far only the pure k value has been used as an indicator for fouling. These methods use this size and at the same time incorporate the influence of the flow dynamics of the two media on the final result.
  • the methods can not be applied to the heat balances, but also to the consideration of the pressure differences and thus the flow resistance.
  • the method according to the invention can be provided as a stand-alone application in a process plant or integrated into a process control system of a process plant. It can also be provided in a local or remote computing system ("cloud"), e.g. by a service provider as "Software as a Service”.
  • cloud e.g. by a service provider as "Software as a Service”.
  • the evaluation device 30 comprises a processor unit 31, a memory 32 for storing the received measurement data, and a memory 33 in which a program 34 with instructions is stored, which can be executed using the Processor unit 31 one of the methods described above is carried out.
  • the processor unit 31 stores the measured values M received from the device 20 in the memory 32.
  • FIG 1 Device 10 shown can, for example, be provided as a stand-alone application in a process plant or integrated into a process control system of a process plant.
  • the device 100 shown for detecting fouling can be provided by a local or remote computer system (“cloud”), for example in order to offer the detection of fouling by a service provider as “Software as a Service”.
  • the receiving device 20 is located on site in the process system of the heat exchanger 1 and the evaluation device 30 is located on a local or remote computer system (“cloud”).
  • the receiving device 20 stores the received measured values in a memory 21 and sends (for example at regular time intervals, event-controlled or upon request by the evaluation device 30) the measured values M (or variables derived therefrom) by means of a transmitting device 22, for example via the Internet or Intranet, to the evaluation device 30.
  • the evaluation device 30 comprises a processor unit 31, a memory 32 for storing the received measurement data, and a memory 33 in which a program 34 with instructions is stored, when executed by means of the processor unit 31 one of the methods described above is carried out.
  • the processor unit 31 stores the measured values M received from the device 20 via an interface 36 in the memory 32, as well as, if necessary, for other input variables that are received via a separate interface 37.
  • the values for the fouling resistance R f determined with the program 34 and/or a signal which signals the need for cleaning are output via an interface 38.
  • the interfaces 36, 37 and 38 can also be provided by a single common interface, for example to the intranet or an intranet.

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Claims (16)

  1. Procédé de détermination de l'encrassement dans un échangeur de chaleur (1), dans lequel on transmet de la chaleur d'un premier milieu (S) à un deuxième milieu (P),
    dans lequel on détermine une valeur d'une grandeur (Rf ) caractérisant l'encrassement, à partir d'une valeur d'une première grandeur (k) influencée par l'encrassement et d'une valeur d'une deuxième grandeur (X), dans lequel on compense, au moins en partie par la deuxième grandeur (X), une variation de la première grandeur (k), provoquée par une variation du débit (FS, FP) du premier milieu (S) et/ou du deuxième milieu (P) dans l'échangeur de chaleur (1), dans lequel la première grandeur (k) est une résistance au passage de la chaleur ou une conductibilité au passage de la chaleur (respectivement un coefficient de passage de la chaleur (valeur k)) et dans lequel on détermine la première grandeur (k) et la deuxième grandeur (X) à partir de valeurs de mesure de plusieurs des grandeurs de mesure suivantes :
    - des températures (TP,Ein, TP,Aus , TS,Ein , TS,Aus ) du premier milieu (S) et du deuxième milieu (P) à l'entrée et à la sortie de l'échangeur de chaleur (1) et
    - des débits (FP, FS ) du premier milieu (S) et du deuxième milieu (P) dans l'échangeur de chaleur (1),
    caractérisé en ce que, lors de la détermination de la première et de la deuxième grandeurs, on n'utilise ni des propriétés de matière du premier milieu (S) et du deuxième milieu (P), ni des propriétés de construction de l'échangeur de chaleur (1).
  2. Procédé de détermination de l'encrassement dans un échangeur de chaleur (1), dans lequel on transmet de la chaleur d'un premier milieu (S) à un deuxième milieu (P),
    dans lequel on détermine une valeur d'une grandeur (Rf ) caractérisant l'encrassement, à partir d'une valeur d'une première grandeur (k) influencée par l'encrassement et d'une valeur d'une deuxième grandeur (X), dans lequel on compense, au moins en partie par la deuxième grandeur (X), une variation de la première grandeur (k), provoquée par une variation du débit (FS, FP) du premier milieu (S) et/ou du deuxième milieu (P) dans l'échangeur de chaleur (1), dans lequel la première grandeur est une résistance à l'écoulement et dans lequel on détermine la première grandeur (k) et la deuxième grandeur (X) à partir de valeurs de mesure de plusieurs des grandeurs de mesure suivantes :
    - des pressions du premier milieu (S) et du deuxième milieu (P) à l'entrée et à la sortie de l'échangeur de chaleur (1),
    - des débits (FP, FS ) du premier milieu (S) et du deuxième milieu (P) dans l'échangeur de chaleur (1), caractérisé en ce que, lors de la détermination de la première et de la deuxième grandeurs, on n'utilise ni des propriétés de matière du premier milieu (S) et du deuxième milieu (P), ni des propriétés de construction de l'échangeur de chaleur (1).
  3. Procédé suivant la revendication 1 ou 2, dans lequel, à l'instant (t0) d'une variation de débit, on fait varier la valeur de la deuxième grandeur (X), de manière à ce que la valeur de la grandeur (Rf ) caractérisant l'encrassement reste constante.
  4. Procédé suivant la revendication 3, dans lequel, après une première mise en fonctionnement et respectivement après un nettoyage de l'échangeur de chaleur (1), on détermine une valeur (k0) initiale de la première grandeur (k) et on règle la valeur de la deuxième grandeur (X) à une valeur (X0) initiale, qui correspond à la valeur (k0) initiale de la première grandeur (k).
  5. Procédé suivant l'une des revendications précédentes, dans lequel il est défini une fonction (f), qui a une valeur d'un débit du premier milieu (S) et/ou du deuxième milieu (P) associée respectivement à une valeur de la deuxième grandeur (X).
  6. Procédé suivant la revendication 5, dans lequel on détermine la fonction (f) dans un intervalle (T) de temps, après une première mise en fonction ou après un nettoyage de l'échangeur de chaleur (1) pour en supprimer l'encrassement.
  7. Procédé suivant la revendication 5 ou 6, dans lequel on forme la fonction (f) par une régression, en particulier par une régression linéaire ou en 3D, de valeurs de mesure associées du débit (F) et de valeurs associées de la deuxième grandeur (X) dans l'intervalle (T) de temps.
  8. Procédé suivant l'une des revendications précédentes, dans lequel des plages de valeurs du débit (F) sont définies, auxquelles est associée respectivement une valeur de la deuxième grandeur (X) .
  9. Procédé suivant la revendication 8, dans lequel on détermine les associations des valeurs de la deuxième grandeur (X) au débit (F) dans un intervalle (T) de temps, après une première mise e fonctionnement ou après un nettoyage de l'échangeur de chaleur (1) pour en supprimer l'encrassement.
  10. Procédé suivant l'une des revendications précédentes, dans lequel on détermine une courbe caractéristique d'une relation entre la deuxième grandeur (X) et le débit (F) de l'un des deux milieux (S, P), dans lequel, pour la détermination de la courbe caractéristique, on détermine, dans un premier stade, une courbe caractéristique d'une dérivée mathématique de la première grandeur (k) en fonction du débit (F) du milieu (S ou P) et, dans un deuxième stade, on intègre la courbe caractéristique obtenue dans le premier stade à nouveau par rapport au débit (F) du milieu (S ou P).
  11. Procédé suivant l'une des revendications précédentes, dans lequel on détermine, en même temps, une première courbe caractéristique d'une relation entre la deuxième grandeur (X) et le débit (F) du premier milieu (S ou P) et une deuxième courbe caractéristique d'une relation entre la deuxième grandeur (X) et le débit (F) du deuxième milieu (P ou S), dans lequel, pour la détermination des courbes caractéristiques, on détermine, dans un premier stade pour chacun des deux milieux (S, P) respectivement une courbe caractéristique d'une dérivée mathématique de la première grandeur (k) en fonction du débit (F) du milieu (S ou P) respectif et, dans un deuxième stade, on intègre les courbes caractéristiques obtenues dans le premier stade à nouveau en fonction du débit (F) du milieu (S ou P) respectif.
  12. Procédé suivant l'une des revendications précédentes, dans lequel la grandeur (Rf ) caractérisant l'encrassement est une résistance au passage de la chaleur.
  13. Procédé suivant l'une des revendications précédentes, dans lequel on ne détermine que des variations relatives de la grandeur (Rf ) caractérisant l'encrassement, de la première grandeur (k) et de la deuxième grandeur (X).
  14. Installation (10, 100) pour effectuer le procédé suivant l'une des revendications 1 et 3 à 13, comprenant
    - un dispositif (20) de réception de valeurs (M) de mesure ou de grandeurs, qui s'en déduisent, de l'échangeur de chaleur (1), et
    - un dispositif (30) d'analyse, qui est agencé pour déterminer, à partir des valeurs (M) de mesure ou des grandeurs, qui s'en déduisent, une valeur d'une grandeur (Rf ) caractérisant l'encrassement, à partir d'une valeur d'une première grandeur (k) influençant l'encrassement et d'une valeur d'une deuxième grandeur (X), dans lequel on compense au moins en partie, par la deuxième grandeur (X), une variation de la première grandeur (k) provoquée par une variation d'un débit (FS, FP) du premier milieu (S) et/ou du deuxième milieu (P) dans l'échangeur de chaleur (1), et dans lequel on détermine la première grandeur (k) et la deuxième grandeur (X), à partir de valeurs de mesure de plusieurs des grandeurs de mesure suivantes
    - des températures (TP,Ein, TP,Aus, TS,Ein, TS,Aus ) du premier milieu (S) et du deuxième milieu (P) à l'entrée et à la sortie de l'échangeur de chaleur (1), et
    - des débits (FP, FS ) du premier milieu (S) et du deuxième milieu (P) dans l'échangeur de chaleur (1),
    et sans utiliser, lors de la détermination de la première et de la deuxième grandeurs, des propriétés de matière du premier milieu (S) et du deuxième milieu (P) et des propriétés de construction de l'échangeur de chaleur (1).
  15. Installation (10, 100) pour effectuer le procédé suivant l'une des revendications 2 à 13, comprenant
    - un dispositif (20) de réception de valeurs (M) de mesure ou de grandeurs, qui s'en déduisent, de l'échangeur de chaleur (1), et
    - un dispositif (30) d'analyse, qui est agencé pour déterminer, à partir des valeurs (M) de mesure ou des grandeurs, qui s'en déduisent, une valeur d'une grandeur (Rf ) caractérisant l'encrassement, à partir d'une valeur d'une première grandeur (k) influençant l'encrassement et d'une valeur d'une deuxième grandeur (X), dans lequel on compense au moins en partie, par la deuxième grandeur (X), une variation de la première grandeur (k) provoquée par une variation d'un débit (FS, FP) du premier milieu (S) et/ou du deuxième milieu (P) dans l'échangeur de chaleur (1), dans lequel la première grandeur est une résistance à l'écoulement et dans lequel on détermine la première grandeur (k) et la deuxième grandeur (X), à partir de valeurs de mesure de plusieurs des grandeurs de mesure suivantes
    - des pressions du premier milieu (S) et du deuxième milieu (P) à l'entrée et à la sortie de l'échangeur de chaleur (1),
    - des débits (FP , FS ) du premier milieu (S) et du deuxième milieu (P) dans l'échangeur de chaleur (1),
    et sans utiliser, lors de la détermination de la première et de la deuxième grandeurs, des propriétés de matière du premier milieu (S) et du deuxième milieu (P) et des propriétés de construction de l'échangeur de chaleur (1).
  16. Programme d'ordinateur comprenant des instructions qui, lorsque le programme est réalisé sur un ordinateur, font que l'ordinateur effectue le procédé suivant l'une des revendications 1 à 13.
EP21711796.9A 2020-03-09 2021-03-05 Procédé et dispositif de détermination de l'encrassement dans un échangeur de chaleur Active EP4088077B1 (fr)

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