WO2002058833A2

WO2002058833A2 - Method for producing, conveying and dosing a solution, and device for carrying out said method

Info

Publication number: WO2002058833A2
Application number: PCT/EP2002/000308
Authority: WO
Inventors: Günther Amberg; Hubert Kamml
Original assignee: Ecolab Gmbh & Co. Ohg
Priority date: 2001-01-24
Filing date: 2002-01-15
Publication date: 2002-08-01
Also published as: WO2002058833A3; DE10103091A1

Abstract

The invention relates to a method for producing, conveying and dosing a solution. The aim of the invention is to achieve a good dissolution of a powdery or pasty product (P) in a solvent (LM). To this end, the solvent (LM) is heated up directly before it is mixed with the product. When the solution (L) is conveyed, a minimum and maximum level is provided in a mixing container (3) by means of a level control (7) or by returning the solution (L) to the mixing container (3) for a short period. The invention also relates to a method for dosing a product (P) by measuring the conductivity of the solution (L). The invention also relates to devices for carrying out the method.

Description

Process for producing, conveying and metering a solution and device for carrying out the process.

The invention relates to a method for producing a solution by mixing a powdery or pasty product with a solvent in a mixing container. The invention further relates to a method for conveying a solution and a method for metering a product quantity of a solution. Finally, the invention relates to devices for performing these aforementioned methods.

It is known from EP 0 229 038 B1 to determine the product concentration in the solvent stream by means of conductivity measurements in order to determine the concentration of a product dissolved in a solvent stream. Here, a method for dispensing a predetermined amount of a chemical in a solution of unknown or variable concentration is disclosed, in which the determination of the product concentration in the solvent stream is carried out by means of conductivity measurements and temperature measurement. From the measured values, the amount of product dissolved in the solvent stream is then calculated in a computer using known conductivity characteristics for the respective product. The calculated dissolved product quantities are summed up and compared with the maximum product quantity required for the process. As soon as the product quantity determined on the basis of the conductivity measurements corresponds to the product quantity that may be used up to a maximum in the process to be controlled, the solution flow is interrupted. This enables quantity recording and dosing of a product to be carried out for a specific purpose. However, the method is relatively complicated and can only be used with a specific, integrated specific control.

DE 198 52 164 A1 discloses a further development in the sense of simplifying the aforementioned method. With this method, the determined product quantity is not compared with a predetermined one Product quantity or product concentration. Instead, impulses are generated for each calculated product quantity, which are passed on to control or output units. The amount of product that generates a pulse can be freely specified in the computer for any purpose.

The aforementioned methods, namely conductivity-controlled metering systems, have proven themselves well. However, they assume that the product, i.e. powder or paste, is completely uniform in the solvent, e.g. Water is dissolved before the conductivity of the solution is measured. Otherwise the measurement and consequently the dosage will be inaccurate.

The problem can be explained, for example, using the conditions in a conventional washing machine. In conventional powder metering devices on washing machines, e.g. the metered washing powder is mixed with cold water in a dispenser and pumped into the washing machine by means of a centrifugal pump. Since the water only serves as a means of transport, the washing powder does not yet have to be completely dissolved here, it is sufficient to completely dissolve the washing agent in the washing drum first.

It has now been found that washing powder mixed with cold water, due to the short and short-term mechanics in the metering pump, cannot be dissolved to the extent that it is fully recorded during the conductivity measurement.

Proceeding from this, the invention is therefore initially based on the technical problem of finding a mixing process which ensures quick and good mixing of the powder or the paste with the solvent. In addition, the invention has for its object to provide an apparatus for performing this method.

The procedural solution to the problem is characterized in that at least the solvent is heated immediately before the mixing process. Since the volume of the solvent is usually a multiple or even a multiple of the product, namely the powder or the paste, it is sufficient it usually just to heat the solvent. However, this does not rule out that the product can also be heated under special circumstances.

The process according to the invention is characterized in that a rapid and intimate mixing of the product, be it powder or paste, is achieved with the solvent. Since the heating of the effectively small volume takes place immediately before the mixing process, e.g. Heat losses caused by transport or heat loads on lines, containers or other components are avoided.

The heating is expediently carried out electrically. If the heating temperature can be set variably, in particular between 30 and 50 ^° Celsius, the temperature of the solvent can be set to different products to be dissolved, for example different detergent powders. The temperature range mentioned also avoids the formation of water vapors, especially at low ambient temperatures, which lead to undesirable product clumping in the mixing area.

An electrically operated instantaneous water heater is used for heating in a space-saving and heat-effective manner. In an optimal manner, it can be attached in the immediate vicinity of the mixing container, in particular in or on the feed line of the solvent, and specifically immediately before it enters the mixing container.

The invention is also based on the object of providing a method for conveying a solution which has been produced by one of the aforementioned methods or with the aid of the aforementioned devices, namely by means of a feed pump connected downstream of the mixing container.

Such a method is that the level of the solution in the mixing tank is controlled by a level control, that the feed pump is followed by a shut-off valve and that the level control that The shut-off valve closes when the minimum solution level is reached and the shut-off valve opens when the maximum solution level is reached. These process steps prevent the mixing container from being temporarily emptied: the consequence would be an intake of air by the feed pump and undesirable foam formation in the solution.

If it is provided in continuation of the invention that the feed pump, e.g. Via the vent pipe, the solution is fed back into the mixing tank via a return line until the maximum level of the solution is reached, then a further intimate mechanical mixing of the product with the solvent is the result. Undissolved residual portions of the product cannot settle or crystallize as sediment on the bottom of the mixing container and lead to impairment of the pump performance or even blockage of the feed pump.

Finally, the invention also enables a method for dosing a product quantity of a solution, produced according to the above method, which is characterized by the method steps: a) cyclically measuring the conductivity of the solution, during the dosing process with the shut-off valve open; b) determining the concentration of the solution by comparing the measured conductivity with the conductivity / concentration characteristics stored in a data memory; c) calculating the amount of product from the determined product concentration of the solution and the known flow rate; d) adding up the calculated product quantities and generating an impulse as soon as a predeterminable product quantity is reached and e) using the impulse to control the dosing process.

In the aforementioned method, an even more precise metering is achieved in that a temperature compensation is included in method step b) or in addition that a correction factor for determining the concentration of products whose characteristics are not stored in the data memory.

In order to protect the finished product solution from sedimentation and crystallization of undissolved product parts, a ring line can be provided, in which the product solution circulates continuously or at intervals as so-called stock liquor, and from which, depending on requirements, several dosing points can be fed via the conductivity meter as required. The use of 8 to 12% product solutions has proven very effective, particularly to counteract product-related gelling or precipitation, even over longer transport distances of the solution.

The aforementioned methods or devices are particularly suitable for use in the mixing and / or metering of detergents, washing or rinsing agents and the like in cleaning machines, washing machines, dishwashers and similar machines.

An embodiment of the invention is described below with reference to the drawing.

The only figure in the drawing shows a schematic representation of devices with the aid of which the methods according to the invention are carried out. The flow of the product, the solvent and the solution is essentially described.

The product, e.g. a powder detergent is designated with P. It enters the cylindrical mixing container 3 via the powder metering device 1 and the line 2.

Furthermore, the solvent LM, here for example water, enters the mixing container 3 directly via the feed valve 4 and an electric instantaneous water heater 5 through the supply line 6. The instantaneous water heater 5 is operated electrically and the temperature of the solvent can be variably adjusted between 30 and 50 degrees Celsius.

The solvent is introduced tangentially into the approximately cylindrical mixing container 3. The mixing container 3 is provided with a level control 7 for the solution L produced with the extreme levels MIN and MAX. Downstream of the mixing container 3 is a feed pump 8, specifically a type of pump with a high level of mechanics, which is connected to the mixing container 3 via the vent pipe 9 and a return line 10. The feed pump 8 is followed by a shut-off valve 11 and a conductivity meter 12. The conductivity meter 12 is connected in terms of control to a computer 13 comprising a data memory, which in turn is connected to the cleaning machine 14, in particular a washing machine. After passing the conductivity meter 12, the solution is passed to the cleaning machine 14.

The function of the devices is as follows:

The powder dosing device 1 doses the washing powder P into the mixing container 3. At the same time, the water LM runs tangentially into the mixing container 3 via the inlet valve 4, the heated instantaneous water heater 5 and the short feed line 6, so that the washing powder P is well distributed in the water LM for formation the solution L is reached. The fine resolution of the washing powder P is further completed by the mechanics of the downstream feed pump 8.

The following conductivity meter 12 of known design is installed directly in front of the dosing point, which has the advantage that any undissolved, even if small, powder constituents may still dissolve completely during transport.

The output of the feed pump 8 must necessarily be greater than that of the incoming water LM including the powder P. To ensure this, the shut-off valve 11 is connected downstream of the feed pump 8. Dosing then proceeds as follows:

The feed valve 4, the powder metering device 1, the feed pump 8 and the shut-off valve 11 work simultaneously. That is, the conveyed solution L is detected by the conductivity meter. If the quantity of solution in the mixing tank 3 reaches the minimum level MIN due to the output of the feed pump 8, the shut-off valve 11 closes until the maximum level MAX is reached. Then the shut-off valve 11 opens again. So that there is always a solution column in the mixing container 3, which prevents the penetration of air into the feed pump 8.

If the shut-off valve 11 is closed, the conductivity meter 12 remains out of operation. If the shut-off valve 11 opens again, the conductivity meter 12 measures again. If the desired amount of product is then detected by the conductivity measuring device 12, the metering process is ended.

In order to mix the above-mentioned solution column well, pumping around the solution L is carried out via the vent pipe 9 and the return line 10 when the shut-off valve 11 is shut off. Pumping is carried out over a controllable period of approx. 5 to 20 seconds. When the pumping is finished, the level in the mixing tank is raised to the maximum level by adding water. 8 to 12% product solutions have proven to be optimally coordinated.

LIST OF REFERENCE NUMBERS

1 powder dosing device

2 line 3 mixing containers

4 inlet valve

5 instantaneous water heaters

6 supply line

7 level control

8 feed pump

9 vent connection

10 return line

11 shut-off valve

12 conductivity meter

13 computers, data storage

14 cleaning machine

P product, powdery or pasty

LM solvent, water

L solution

MIN minimum level in 3

MAX maximum level in 3

Claims

claims

1. A method for producing a solution by mixing a powdery or pasty product (P) with a solvent (LM) in a mixing container (3), characterized in that at least the solvent (LM) is heated immediately before the mixing process.

2. The method according to claim 1, characterized in that the heating is carried out electrically.

3. The method according to claim 1 or 2, characterized in that the heating takes place to a temperature between 30 and 50 ° Celsius.

4. The method according to any one of claims 1 to 3, characterized in that the heating temperature is variably adjustable.

5. Apparatus for performing the method according to one of claims 1 to 4, characterized in that a water heater (5) is used for heating.

6. The device according to claim 5, characterized in that the flow heater (5) in or on the feed line (6) of the solvent (LM) is arranged immediately before it enters the mixing container (3).

7. A method for conveying a solution which was produced by a method according to one of claims 1 to 4 or with the aid of the devices according to claim 5 or 6, by means of a feed pump (8) connected downstream of the mixing container (3), characterized in that the Standing height of the solution (L) in the mixing container (3) by a

Level control (7) is controlled that the feed pump (8) is followed by a shut-off valve (11) and that the level control (7) closes the shut-off valve (11) when the minimum standing height (MIN) of the solution (L) is reached and opens the shut-off valve when the maximum standing height (MAX) of the solution (L) is reached.

8. The method according to claim 7, characterized in that when the shut-off valve (11) the feed pump (8) feeds the solution (L) via a return line (10) into the mixing container (3) until the maximum standing height (MAX) of the solution (L) is reached.

9. A method for dosing a product amount of a solution (L), produced according to claim 7 or 8, characterized by the method steps: f) cyclical measurement of the conductivity of the solution (L), during the dosing process with the shut-off valve 11); g) determining the concentration of the solution (L) by comparing the measured conductivity with the conductivity / concentration characteristics stored in a data memory (13); h) calculating the amount of product from the determined product concentration of the solution and the known flow rate; i) Sum up the calculated product quantities and generate one

Impulse, as soon as a predeterminable product quantity is reached and j) use the impulse to control the dosing process.

10. The method according to claim 9, characterized in that a temperature compensation is included in step b).

11. The method according to claim 9 or 10, characterized in that in step b) a correction factor for determining the concentration of products is additionally included, the characteristics of which are not stored in the data memory.

12. Device for performing the method according to one of claims 9 to 11, characterized in that a ring line is provided in which circulates the product solution as a so-called stock liquor continuously or at intervals and from which several dosing points are fed as required via the conductivity meter.

13. The method according to any one of claims 9 to 11, characterized by the use of 8 to 12% product solutions.

14. The method or device according to any one of claims 1 to 13, characterized by the use in the mixing and / or metering of detergents or detergents in cleaning machines, washing machines, dishwashers and similar machines.