EP0321904B1 - Method for optimizing the flow and temperature of a washing liquid - Google Patents

Description

The invention relates to a method for adjusting the flow rate and temperature of wash water when washing out impurities, such as superfluous chemicals, from cloth webs in textile finishing processes using a wide-washing machine, in which a cloth web is passed through a number of wash basins connected in series and the warm wash water in counterflow Sink is led. Such a method is known from practice.

In such a method, the extent of the washout or the so-called wash effect can be controlled by means of contamination concentration sensors. Such a contamination concentration sensor is, for example, a pH meter or a conductivity sensor that measures the extent of the conductivity of the cloth contaminated with excess chemicals. When entering and dispensing the machine, such a sensor can be pressed onto the cloth. With a cloth of a certain quality, the water flow rate and the water temperature can be set for a certain value of the desired washing action. However, this only applies to a single cloth quality, and with a different cloth quality, a different setting of the water flow rate and the temperature will have to be used in order to achieve the corresponding washing effect.

In general, such an adjustment is carried out with excess water and high temperature, which are dimensioned to such an extent that the desired washing effect is achieved for all fabric qualities. The energy required for this setting for the washing process is used to bring the rinsing or washing water and the cloth to be washed to temperature, to maintain the required temperatures, i.e. Compensate for energy losses that occur and drive the machines.

Practice has shown that the thermal yield of the washing process is often not optimal. The desired washing effect can namely be achieved in various ways, the extreme routes being: a) a lot of water and low temperature and b) little water and a high temperature. In general, too much wash water and too high temperatures are used, which leads to high energy costs. Especially when the temperature rises (too high), the energy losses (and consequently the energy costs) increase exponentially, e.g. because the vaporization is much stronger at high temperature.

The invention aims to remedy the above-mentioned problems and to provide an improved method with which an optimally inexpensive adjustment of the flow rate and temperature of the washing water is achieved while maintaining the desired washing effect, which method can be used for all fabric qualities. This is achieved according to the invention in a method according to claim 1 in such a way that the washing water flow rate and the washing effect are measured by means of a measurement at a water temperature and a corresponding first exchange factor is calculated from this, that the washing water flow rate and the washing effect is measured and a further corresponding second exchange factor is calculated, from which first exchange factor, second exchange factor and corresponding temperatures, the linear relationship M = f (T) is determined, and that, for increasing values of wash water flow rate and desired washing effect, the Corresponding required exchange factors and the required temperatures are determined via the linear relationship mentioned, the costs of the wash water and steam consumption being determined in each case and resulting from this the minimum value of these costs, the corresponding wash water flow rate and the corresponding steam supply are set.

• Figur 1 schematisch eine Darstellung einer Breitwaschmaschine mit drei in Waschkompartimente eingeteilten Waschbecken zeigt ;
• Figur 2 das Prinzip der Mess- und Regelelementen zeigt, die bei dem erfindungsgemässen Verfahren angewandt werden ;
• Figur 3 ein vereinfachtes Schema der angewandten Regeleinheit zeigt;
• Figur 4 ein Schema zur Erläuterung der Bestimmung des auf ein Waschkompartiment anzuwendenden Austauschfaktors zeigt;
• Figur 5 eine Graphik zeigt, als Beispiel des Zusammenhangs zwischen dem Phasenverhältnis und der Temperatur bei einer bestimmten Waschwirkung ;
• Figur6 eine Graphikzeigt, als Beispiel des Zusammenhangs zwischen den Betriebskosten und einer Kombination von Waschwasserdurchflußmenge und Temperatur bei einer bestimmten Waschwirkung ;
• Figur 7 eine Graphik zeigt, als Beispiel des Zusammenhangs zwischen Austauschfaktor und Temperatur;
• Figur 8 ein Ablaufdiagramm der Bestimmung des Zusammenhangs zwischen dem Austauschfaktor und der Temperatur zeigt; und
• Figur 9 ein Ablaufdiagramm der kostenminimalen Einstellung von Waschwasserdurchflußmenge und temperatur zeigt.

With such an embodiment according to the invention, it is possible to tune a wide washing machine in such a way that an economical system is obtained while maintaining the desired washing effect. In practice, this means that the average energy consumption can be reduced by 40 to 50% compared to the known method. The invention will be explained in more detail using an embodiment with reference to the drawings, in which drawings:

• FIG. 1 schematically shows an illustration of a wide washing machine with three wash basins divided into washing compartments;
• FIG. 2 shows the principle of the measuring and control elements which are used in the method according to the invention;
• Figure 3 shows a simplified diagram of the control unit used;
• FIG. 4 shows a diagram to explain the determination of the exchange factor to be applied to a wash compartment;
• FIG. 5 shows a graph as an example of the relationship between the phase ratio and the temperature for a specific washing action;
• Figure 6 shows a graph as an example of the relationship between operating costs and a combination of wash water flow rate and temperature for a particular wash action;
• FIG. 7 shows a graph as an example of the relationship between the exchange factor and the temperature;
• FIG. 8 shows a flow chart of the determination of the relationship between the exchange factor and the temperature; and
• FIG. 9 shows a flowchart of the cost-minimal setting of wash water flow rate and temperature.

Fig. 1 shows schematically a wide washing machine, in which the unnecessary chemicals, such as alkali and reaction products, derived from lye and bleaching treatments, are rinsed out of the cloth. Such a machine has, for example, three wash basins 5, each wash basin being divided into three wash compartments 1 connected in series in order to increase the washing effect. The wash water 2 is passed through the machine in a countercurrent process, the fresh rinse water flowing into the machine on the right-hand side and then flowing through all the compartments. The textile or cloth web 3 to be washed goes into the machine on the left-hand side and is guided on rolls through all compartments. The cloth run can be both vertical and horizontal. After each wash basin, the cloth is pressed through the press plant 4. The pressed water is returned to the wash water flowing through it. The wash water is brought up to temperature and maintained per wash basin, for example by blowing in hot steam. At the same time, a contamination concentration sensor, such as a conductivity sensor, has been attached to the import and possibly to one of the sinks and to the outlet, which is pressed onto the cloth.

In practice, washing water consumption and temperature (i.e. steam supply) are generally selected so that a good rinsing or washing effect is obtained under all circumstances. This almost always means too much wash water and too high temperatures, which leads to high energy costs.

The invention now provides such a method for optimally coordinating the washing water flow rate and temperature, so that energy savings are made possible while maintaining the desired washing effect, for which purpose measures have been taken as shown in FIG. Flow meters W and S are arranged in the two main supply lines for measuring the washing water and steam consumption, and temperature sensors T1 to T6, such as a Pt-100 element, have been installed in the individual wash basins for the temperature measurements. A speedometer V for the speed of the cloth web has also been installed. The valves in the wash water supply lines K1 to K6 can be designed as flow-controlled pneumatic valves. The conductivity sensors G1 to G3 have been installed for the measurement of the contamination of the cloth during import, in one of the sinks and during export.

The control unit 8 shown in FIG. 3 can be a mini computer. The measurement data of the temperature sensors T, the conductivity sensors G and the knives W, S, V are collected by a data logger 6, which forwards them once every ten seconds via an interface 7 of the control unit 8. The control signals in binary code originating from this control unit are converted via an interface 9 into control signals of 4 to 20 mA for the valves generally indicated by 10. Proportional control is used for the water flow rate and PID control for the temperature.

The regulation takes place on the basis of the measurement of the concentration of the impurity in the cloth, for example by means of the conductivity, which corresponds to this concentration of the impurity in proportion. The value of the desired conductivity after n compartments, together with the conductivity measured at the time of import, gives the desired washing effect <p, this is the conductivity C _"of the cloth on export divided by the conductivity C _o on import: <p = C _n / C _o . For this desired washing effect, the optimally inexpensive combination of water flow rate and temperature is calculated, after which this is adjusted via the valves and adjusted in the event of deviations.

In general, it is assumed that each washing compartment has the same washing effect at the same water flow rate and at the same temperature. Since this is not always the case in practice, for example as a result of the dimensions of the compartments and the pressing of the cloth between certain compartments, the average washing effect per compartment is used. FIG. 4 shows a schematic representation of a wide washing machine with a number of compartments, into which the fabric is inserted on the left and out on the right and the contamination of this fabric decreases from left to right. The contamination increases from right to left in the wash water flow. C _o ... C _l-3 , C _1-2 , C _l-1 , C _{l is} the impurity concentration of the cloth, and is K _o ... K _l-3 , R _l-2 , K _I - ₁ , K, the concentration of the impurity in the wash water. The exchange factor M for a washing compartment is defined as the fraction of the liquid coming in with the cloth, which is replaced by washing water.

worin RC und B Konstanten sind, die durch die Art des Waschkompartiments und der Tuchqualität bestimmt werden. M ist ebenfalls von der Grösse der Wasserdurchflußmenge unabhängig. Nach einem einfachen Waschmodell kann eine Funktion für den Zusammenhang zwischen der nicht-ausgewaschenen Fraktion ϕ = C_n/C₀, dem Austauschfaktor M und den Flüssigkeitsflüssen abgeleitet werden. Dieser Zusammenhang lässt sich folgendermassen schreiben :

worin F das Phasenverhältnis ist oder das Volumen des in der Sekunde zugeführten Waschwassers geteilt durch das Volumen des in der Sekunde mit dem Tuch mitgeführten Wassers, und worin P = F - MF + M. dabei wird für das Volumen des in der Sekunde mit dem Tuch mitgeführten Wassers ein fester Durchschnittswert angenommen.With a complete exchange, M = 1 and with no exchange, M = 0. The exchange factor proves to be linear in the working range depending on the temperature:

where RC and B are constants that are determined by the type of wash compartment and the cloth quality. M is also independent of the size of the water flow. According to a simple washing model, a function for the relationship between the non-washed out fraction ϕ = C _n / C ₀ , the exchange factor M and the liquid flows can be derived. This relationship can be written as follows:

where F is the phase ratio or the volume of wash water supplied per second divided by the volume of water carried per second with the towel, and where P = F - MF + M. where is the volume of wash per second with the towel a fixed average value is assumed.

Using the above-mentioned equations (2) and (3), the relationship between the washing action ϕ = C _n / C ₀ , the washing water temperature T and the phase ratio F can be determined, as given as an example for a specific washing action in FIG. This figure shows that a certain desired washing effect can be achieved with a large number of settings for water flow rate A and temperature T. To determine the optimal low cost combination, the cost of steam and water at these settings must be known.

The amount of steam required to heat the wash water and the cloth includes the theoretically required amount of steam to bring the wash water and the cloth up to temperature (linearly depending on the temperature) and the amount of steam required to compensate for the heat loss.

If the total costs for water and steam are set off against the individual combinations of water flow rate and temperature which bring about a certain desired washing effect, the relationship shown in FIG. 6 arises. This figure shows that an optimally inexpensive combination of water flow rate and temperature can be found for each desired washing action.

• 1) Eingeben der Messwerte in die Regeleinheit ;
• 2) Mittelwertberechnung der Messwerte ;
• 3) Berechnen des Austauschfaktors M aus der gemessenen Waschwirkung <p = C_n/C₀ und der Wasserdurchflußmenge ;
• 4) Berechnen des Zusammehangs zwischen dem Austauschfaktor M und der Temperatur T ;
• 5) Bestimmen der optimal kostengünstigen Kombination von Wasserdurchflußmenge und Temperatur bei einer gewünschten Waschwirkung ;
• 6) Anpassen der Einstellpunkte.

Using the earlier data, the following control model can be set up for the control unit:

• 1) Enter the measured values in the control unit;
• 2) mean value calculation of the measured values;
• 3) Calculate the exchange factor M from the measured washing effect <p = C _n / C ₀ and the water flow rate;
• 4) calculating the relationship between the exchange factor M and the temperature T;
• 5) determining the optimally inexpensive combination of water flow rate and temperature for a desired washing effect;
• 6) Adjust the setting points.

worin n = Anzahl der Kompartimente (z.B. 12).By rewriting formula (3) mentioned above, the following equation is obtained for the average exchange factor M:

where n = number of compartments (e.g. 12).

For a washing machine with a number of n compartments, it follows from equation (4) given above that a value of M belongs to a desired washing action and a selected water flow value. In order to be able to calculate the water temperature at which the desired value M (for a desired washing effect) will be achieved for a particular wide-washing machine, the relationship between these two variables must be known. Assuming that this relationship is linear, the directional coefficient (RC) and the axis section (B) of the straight line M = f (T) must first be determined.

• - In einem ersten Messdurchgang wird bei einer bestimmten Temperatur aus den Durchschnittsmesswerten der Leitfähigkeit an der Einfuhr und an der Ausfuhr und aus der Wasserdurchflußmenge der entsprechende M-Wert ermittelt, der eine erste Schätzung des Richtungskoeffizienten RC der Funktion M = f(T) gibt.
• - In einem zweiten Messdurchgang wird bei einer folgenden Temperatur aus den Messwerten der Leitfähigkeit und aus der Durchflußmenge ein zweiter entsprechender M-Wert ermittelt. Aus diesem und dem vorletzten ermittelten M-Wert wird ein neuer Richtungskoeffizient RC errechnet. Auf diese Weise werden immer die jeweils letzten beiden M-Werte verwendet, um die Gerade M = f(T) zu bestimmen.

With reference to Figure 7, this relationship is determined as follows:

• - In a first measurement run at a certain temperature, the average measured values of the conductivity at the import and the export and from the water flow rate correspond to the M-value determined, which gives a first estimate of the directional coefficient RC of the function M = f (T).
• - In a second measurement run at a following temperature, a second corresponding M-value is determined from the measured values of the conductivity and from the flow rate. A new direction coefficient RC is calculated from this and the penultimate M-value. In this way, the last two M values are always used to determine the straight line M = f (T).

• 1) bei einer ersten Messung wird für den Achsenschnitt B ein Wert Null angenommen ;
• 2) wenn bei einer folgenden Messung die gemessenen Temperaturen T₁ und T₂ unterschiedlich sind, wird die Gerade folgendermassen bestimmt:
  

• 3) Wenn bei einer folgenden Messung die gemessenen Temperaturen T₁ und T₂ gleich sind oder wenn durch irgendeine Ursache ein negativer RC oder B entsteht, wird die Gerade folgendermassen bestimmt:
  
  darin ist B_o der zuletzt gemessene Wert von Bund wenn dieser zu hoch ist, wird für B_o ein fester Praxiswert angenommen.

The following situations can arise with these calculations, as has also been indicated in the flow chart of FIG. 8:

• 1) in a first measurement, a value of zero is assumed for the axis section B;
• 2) if the measured temperatures T ₁ and T _{2 are} different in a subsequent measurement, the straight line is determined as follows:
  

• 3) If the measured temperatures T ₁ and T _{2 are the} same in a subsequent measurement or if a negative RC or B arises due to any cause, the straight line is determined as follows:
  
  where B _{o is} the last measured value of bundle, if this is too high, a fixed practical value is assumed for B _o .

After the above-mentioned relationship between mouth T has been determined, the corresponding desired exchange factor M and the corresponding temperature T can be calculated starting from an initial value and then from incrementing values of the water flow rate in the flow area and the desired washing action. For these subsequent combinations of water flow rate and temperature, the corresponding costs are calculated and the combination with the minimum costs is selected. This combination of water flow rate and temperature is then adjusted, all as indicated in the flow chart of Figure 9.

In the attached Table I, the results obtained for a series of cloth webs have been given using the old method and the new method. It is clear that while maintaining the required washing effect, considerable energy savings are achieved.

Claims (3)

1. A method of adjusting the flow and temperature of wash water in the washing of impurities out of webs of cloth in textile finishing processes using a full-width washing machine in which a web of cloth is taken though a number of series-connected washing baths and the hot wash water is passed through said baths in countercurrent, characterised in that a first wash water flow and a first washing effect of the water in the baths are measured at a first water temperature while the web of cloth is being taken through the baths, the said first washing effect denoting the ratio of the concentration of the impurity on the web of cloth after washing and before washing ;

in that a first exchange factor is calculated from the said measured first wash water flow and the said first washing effect by means of the following equation :

where M is the exchange factor, F the volume of the wash water supplied per second divided by the volume of water entrained with the cloth per second, n denotes the number of washing compartments and ϕ the ratio of the concentration of the impurity on the web of cloth after washing and before washing, ϕ agreeing with the first washing effect;

in that a second wash water flow and a second washing effect are measured at a second water temperature, the said second washing effect denoting the ratio of the concentration of the impurity on the web of cloth after washing and before washing ;

in that a second exchange factor is calculated from the said second wash water flow and the said second washing effect;

in that coefficients of a linear relationship between the exchange factor and the temperature are calculated from the said first and second exchange factors and from the said first and second water temperatures in accordance with the following equation :

by means of the following equations :

where M₁ denotes the said first exchange factor, M₂ the second exchange factor, T₁ the said first water temperature and T₂ the said second water temperature ;

in that exchange factors M are calculated for progressively increasing values of the wash water flow, on the basis of a required washing effect ϕa, namely :

by means of the following equation

including calculation of the corresponding temperatures T via the relation :

in that the sum of the costs of the wash water flow and of the wash water heating are calculated for incremental values of the wash water flow and the corresponding wash water temperatures in order to compile a table of costs ; in that a wash waterflow and a corresponding wash water temperature are selected from the table of costs to give a minimum cost value ; and in that the wash water flow through the baths and the wash water temperature in the baths are set to the selected flow and water temperature.

2. A method according to claim 1, characterised in that the volume of water entrained with the cloth per second is assumed to be a fixed average.

3. A method according to claim 1 or 2, characterised in that the wash water is heated by steam and adjustment of the wash water temperature is obtained by adjusting the steam supply.

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