EP0321904A1 - Method for optimizing the flow and temperature of a washing liquid - Google Patents

Abstract

Method for optimising wash liquor flow rate and temperature in the washing of impurities out of cloth webs in the course of textile finishing processes using an open-width washer whereby exchange factors are determined at various temperatures and used to determine the wash liquor flow and steam consumption costs, and these costs are minimised by adjusting wash liquor flow and steam supply rates. <IMAGE>

Description

The invention relates to a method for adjusting the flow and temperature of washing 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 washing water in Counterflow is passed through these sinks, adjusting the flow and temperature of the wash water. Such a method is known from practice.

With 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 inputting and dispensing the machine, such a sensor can be pressed onto the cloth. With a cloth of a certain quality, the water flow and the water temperature can be set for a certain value of the desired washing effect. However, this only applies to a single cloth quality, and with a different cloth quality, a different setting of the water flow and the temperature will have to be used in order to achieve the corresponding washing effect.

In general, such adjustment is carried out with excessive water and high temperature, which is so far are dimensioned so 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, ie to compensate for any energy losses that occur and to 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 aim of the invention is to remedy the above-mentioned problems and to provide an improved method with which the optimally inexpensive setting of the flow 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 in a method of the type mentioned at the outset in such a way that the washing water flow and the washing effect are measured by means of a measurement at a water temperature and a corresponding first exchange factor is calculated therefrom, that the washing water flow is again measured by means of a further measurement at a further temperature 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 values of wash water flow and desired wash effect that are always incremental in the river area, the corresponding required exchange factors and the required temperatures are determined via the linear relationship mentioned, the costs in each case of the wash water flow and steam consumption are determined and the corresponding wash water flow and the corresponding steam supply are set by means of the resulting minimum value of these costs.

• Figur 1 schematisch eine Darstellung einer Breitwaschmaschine mit drei in Waschkompartimente eingeteilten Waschbecken;
• 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 ein Graphik zeigt, als Beispiel des Zusammenhangs zwischen dem Phasenverhältnis und der Temperatur bei einer bestimmten Waschwirkung;
• Figur 6 eine Graphik zeigt, als Beispiel des Zusammenhangs zwischen den Betriebskosten und einer Kombination von Waschwasserfluss 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 Waschwasserfluss 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 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;
• FIG. 6 shows a graph as an example of the relationship between the operating costs and a combination of wash water flow and temperature for a specific washing 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 flow chart of the minimal setting of wash water flow 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 subdivided into three wash compartments 1 connected in series 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 on rolls through all compartments passed through. The cloth run can be both vertical and horizontal. After each wash basin, the cloth is pressed by the press plant 4 and the water squeezed out returns to the washing water flowing through. The wash water is heated and maintained for each wash basin, for example by blowing hot steam in. 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 wash basins and to the export, which is pressed onto the.

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 and temperature that energy saving is made possible while maintaining the desired washing effect, for which purpose measures have been taken as shown in FIG. 2. To measure the washing water and steam consumption, flow meters W and S have been arranged in the two main supply lines and temperature sensors T1 to T6, for example 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. Conductivity sensors G1 to G3 have been installed to measure 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 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 proportionally to this concentration of the impurity. The value of the desired conductivity according to n compartments together with the conductivity measured at import gives the desired washing effect φ, this is the conductivity C _{n of} the cloth when exported divided by the conductivity C _o at import: φ C _n / C _o . For this desired washing effect, the optimally inexpensive combination of water flow and temperature is calculated, after which it is set via the valves and adjusted in the event of deviations.

It is generally assumed that each washing compartment has the same washing effect with the same water flow 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. In Figure 4 is a schematic representation of a wide washing machine with a number of i compartments given, into which the tissue 3 is inserted on the left and led out on the right and the contamination of this tissue decreases from left to right. The contamination increases in the wash water flow 2 from right to left. C _o ... C _i-3 , C _i-2 , C _i-1 , C _{i is} the impurity concentration of the cloth, and is K _o ... K _i-3 , K _i-2 , K _i-1 , K _i 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.
M = (C _i-1 -C _i ) / (C _i-1 -K _i-1 ) (1)

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:
M = RC.T + B (T in ° C) (2)
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 _ = C _n / C ₀ , the exchange factor M and the liquid flows can be derived. This relationship can be written as follows:
C _n / C ₀ = (1 - F) / (1 - F (F / P) ⁿ ) (3)
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.

The relationship between the washing action φ = C _n / C ₀ , the washing water temperature T and the phase ratio F can be determined by means of the above-mentioned equations (2) and (3), as indicated in FIG. 5 as an example of a specific washing action. This figure shows that a certain desired washing effect can be achieved with a large number of water flow and temperature settings. To determine the optimal low-cost combination, the costs of steam and water with 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 keep the wash water and the cloth at 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 offset against the individual combinations of water flow and temperature which bring about a certain desired washing effect, the relationship shown in FIG. 6 arises. This figure shows that an optimally cost-effective combination of water flow and temperature can be found for each desired washing effect.

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

The following control model can be set up for the control unit using the earlier data

• 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 φ = C _n / C ₀ and the water flow;
• 4) calculating the relationship between the exchange factor M and the temperature T;
• 5) determining the optimally inexpensive combination of water flow and temperature with a desired washing effect;
• 6) Adjust the setting points

worin n = Anzahl der Kompartimente (z.B. 12). Aus der oben bereits gegebenen Gleichung (4) folgt für eine Waschmaschine mit einer Anzahl von n Kompartimenten, dass zu einer gewünschten Waschwirkung und einem gewählten Wasserflusswert ein Wert von M gehört. Um bei einer bestimmten Breitwaschmaschine berechnen zu können, bei welcher Wassertemperatur der gewünschte Wert M (für eine gewünschte Waschwirkung) erreicht werden wird, muss der Zusammenhang zwischen diesen beiden Grössen bekannt sein. Unter der Annahme, dass dieser Zusammenhang linear ist, muss zunächst der Richtungskoeffizient (RC) und der Achsenschnitt (B) der Geraden M = f(T)
bestimmt werden.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 the 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 direction coefficient (RC) and the axis section (B) of the straight line M = f (T)
be determined.

With reference to Figure 7, this relationship is determined as follows:
- In a first measurement run, the corresponding M-value is determined at a certain temperature from the average measured values of the conductivity at the import and export, and from the water flow, which gives a first estimate of the directional coefficient RC of the function M = f (T) .
- In a second measurement run, the conductivity and the Flow determined a second corresponding M-value. 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:
  RC = (M₂ - M₁)/T₂ - T₁) und B = M₂-RC.T₂)
• 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:
  RC = (M₂ - B₀)/T₂.

darin ist B₀ der zuletzt gemessene Wert von B und wenn dieser zu hoch ist, wird für B₀ 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 T₁ and T₂ are different in a subsequent measurement, the straight line is determined as follows:
  RC = (M₂ - M₁) / T₂ - T₁) and B = M₂-RC.T₂)
• 3) If the measured temperatures T₁ and T₂ 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:
  RC = (M₂ - B₀) / T₂.

B₀ is the last measured value of B and if this is too high, a fixed practical value is assumed for B₀.

After the above-mentioned relationship between M and T has been determined, the corresponding desired exchange factor M and the corresponding temperature T can be calculated on the basis of an initial value and then incremental values of water flow in the flow area and the desired washing action. For this subsequent combinations of water flow and temperature, the corresponding costs are calculated and the combination with the minimum costs is selected. This combination of water flow and temperature is then set, 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 by means of the old method and by means of the new method. It is clear that while maintaining the required washing effect, considerable energy savings are achieved. TABLE 1 Average results from five practical trials Normal self-regulation Try the control system number 1 No. 2 No. 3 No. 4 No. 5 Type of cloth cotton cotton cotton cotton cotton cotton cotton Fabric weight g / m² 225 250 260 263 340 195 135 binding Flat twill twill satin satin Flat Flat Temperature in ° C Basin No. 1 95 95 60 59 85 45 45 Basin No. 2 90 90 60 59 85 45 45 Basin No. 3 80 80 60 59 85 45 45 Basin No. 4 70 70 60 59 75 45 45 Basin No. 5 60 60 60 59 70 45 45 Basin No. 6 50 50 50 50 50 45 45 Conductivity of the cloth (µS) enema 420 412 437 2,018 996 346 614 after pool no.3 58 60 75 77 110 55 41 after pool no.6 20th 21st 22 20th 24th 18th 19th Wash water flow (m³ / h) 6.0 6.0 5.8 5.3 8.0 4.0 4.0 Steam consumption (kg / h) 1,360 1,360 864 740 1,650 235 220 Costs (Hfl / h) 88 88 60 52 107 21st 20th Standard time (h.min) 0.57 1.00 0.48 1.53 1.19 1.46 1.48

Claims (3)

1. Method for adjusting the flow and temperature of washing water when washing out impurities, such as superfluous chemicals, from cloth webs in textile finishing processes using a wide-angle washing machine in which a cloth web is passed through a number of wash basins connected in series and the warm washing water is passed through in countercurrent this wash basin is guided, the flow and the temperature of the wash water being set, characterized in that the wash water flow and the wash effect are measured by means of a measurement at a water temperature (T1) and a corresponding first exchange factor (M1) is calculated therefrom that by means of a further measurement at a further temperature (T2), the wash water flow and the wash effect are measured again and a further corresponding second exchange factor (M2) is calculated from which the first exchange factor, second exchange factor and corresponding temperatures, the linear Relationship M = f (T) is determined, and that, for values of wash water flow and desired wash effect that are always incremental in the river area, the corresponding exchange factors required and the temperatures required are determined via the linear relationship mentioned, the costs of the wash water flow and Steam consumption are determined and the corresponding wash water flow and the corresponding steam supply are set by means of the resulting minimum value of these costs. 2. The method according to claim 1, wherein the washing effect is given by the ratio of the concentration of the cloth contamination at the import (Co) and at the export (CD), characterized in that the relationship between the exchange factor (M) and the washing effect (φ = C _n / Co) is reproduced by:

where n is the number of wash compartments and F is the volume of wash water added per second divided by the volume of water carried per second with the cloth. 3. The method according to claim 2, characterized in that the volume of water discharged per second with the cloth is assumed as a fixed average.

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