FI103500B - Method and apparatus for dispensing and mixing liquid substances - Google Patents

Description

103500

The present invention relates to a method for metering and mixing viscous substances according to the preamble of claim 1 in a precise and desired manner.

The invention also relates to apparatus for applying the invention.

It is difficult to accurately dispense and mix high viscous fluids, and especially fluids whose viscosity changes dramatically with temperature change, at a given mixture ratio. For accurate dosing, a flow meter and measuring instruments to compensate for changes in temperature, pressure, and density must be placed in the pipeline. Thus, the pipeline will have four different metering devices that need to be processed 20 to determine the correct dosing volume and mixing ratio. Based on the measurement results obtained, the pipeline pump or the throttle valve is adjusted to maintain the volume flow within the desired range. The devices used to measure volume and mass flow are some of the most prominent parts of the system. Volumetric flow measurements include, but are not limited to, gauge-based differential pressure or centrifugal flow meters, turbine gauges and displacement gauges. Such a system is expensive and complicated and requires careful planning and careful consideration. * 30 uses to operate with reasonable accuracy and reliability.

In addition, the devices used to measure the flow rate only operate accurately within a specific range of viscosity, so that they can reliably handle only products having a viscosity within the narrow operating range of the apparatus. This is a major disadvantage when treating liquids 2 103500 which have a high viscosity variation, for example due to changes in temperature or solids content.

When treating high viscous or viscosity modifying agents, it is very important that the flow in the piping is continuous so that the material to be treated does not solidify in the piping. Examples of such products are bituminous mixtures, adhesives, polymers and various other chemical products and products containing insoluble powders or granules.

Devices which are subject to minimal changes in viscosity must be used for quantity measurement and adjustment. In systems that handle such materials, the return cycle must ensure that a sufficient amount of material is always flowing through the tube. However, carrying out the return cycle results in major difficulties in dispensing the volume, especially if an accurate proportion of the fluids in the various pipelines is to be mixed. When material is taken from the circulating piping, the pressure in the piping decreases and the volume flow drawn is no longer accurate. In such a system, the amount of fluid flowing through the pipeline is measured. These systems lead to costly and complex hardware design and difficult to control control problems. If the system includes several different piping systems for different materials, the equipment will easily become so complex that its reliability does not meet the requirements of a production process equipment. Thus, it would be desirable to provide a method by which materials of varying viscosity could be handled more reliably and, above all, by simple equipment.

3,103,500

There are also problems with calibrating high viscous liquid dispensing devices, for which various methods have been developed. However, these methods as such are not suitable for continuous dosing.

5

EP 26874 describes a calibration device for a metering and mixing device. In this solution, after the removal of the mixing chamber, a throttle valve is provided and the device also has a circulation line 10 back to the storage tank. During calibration, the circulation line is closed as during dispensing, so this device does not have a continuous cycle, which is necessary for handling, among other things, highly solidifying substances.

In the calibrator described in US 3,915,437, the rotation line is throttled by a needle valve. The metering outlet is located after the needle valve, so that the valve does not adjust the pressure in the circulation line at the outlet.

20

GB 1 272 258 describes a paint mixing device in which paint is dispensed by starting the pump and opening the corresponding valve. The amount to be dispensed is adjusted based on the pump run time or valve opening time 25.

It is an object of the present invention to provide a method for accurately dispensing highly viscous materials and compositions.

It is an object of the most preferred embodiment of the present invention to provide a method for preparing a mixture of 1035004 several high viscous materials in which the relative proportions of the various substances are precisely determined.

The invention is based on the fact that the mixture prepared in the mixing tank is circulated by means of a constant volume pump in a circulating pipe having a differential pressure valve for adjusting the pressure in the piping and the mixture outlet being arranged upstream of the valve.

More specifically, the method according to the invention is characterized in what is set forth in the characterizing part of claim 1.

The apparatus according to the invention, in turn, is characterized by what is set forth in the characterizing part of claim 6.

The invention provides considerable advantages.

20 The method can replace many expensive and often inaccurate measuring and control devices. The adjustment method is. simple, with little actuators and gauges required, making the system reliable even when the number of lines increases. The method 25 provides systems that can accurately mix mixtures of many difficult-to-handle substances to produce the desired amount of end product. The mixing temperatures of the various blends can be adjusted as desired. The mixing of the partial mixtures prior to the final mixing is prevented, although the flow pipelines may be interconnected without hindrance. Mixtures are continuously flowing in the pipelines, causing no clogging and, at the same time, the fluids are also in the storage tank, reducing the need for mixing in the tank.

As the product to be treated changes, the system can be quickly 5 and simply calibrated to a new mixture, so that the apparatus of the invention is suitable for use over a fairly wide viscosity range, unlike previously known systems. Multiple mixture outlets can be provided in a single pipeline, provided that a constant volume pump output is sufficient to maintain a sufficiently high pressure in the pipeline even if more than one outlet is used. Alternatively, the simultaneous opening of too many outlets can be prevented by software. When handling hot fluids, the invention has the advantage that the piping forms an expansion system, since the circulation circuit and the differential pressure valve are open, so that the thermal expansion of the liquid does not affect the operation. The distance between the mixing point and the storage or mixing tank can be long at moderate mass flows, thus reducing line costs. Thus, the invention is capable of producing and transporting paints and the like to large-scale industrial sites or construction sites. The mixers, tanks and pumps needed for the system, as well as the control equipment, can be assembled into portable containers for easy transport and quick set-up of the system.

The invention will now be explained in more detail with reference to the accompanying drawings.

30

Figure 1 shows a mixing apparatus which may be used in connection with the invention.

6 103500

Figure 2 is a diagrammatic view of one embodiment of the invention. Figure 3 is a schematic view of another embodiment of the invention.

With the exception of features related to the present invention, the apparatus shown in Figure 1 is described in Finnish Patent Application 940882. The main components of the apparatus are a mixing tank 1 with a bottom mixer 3 at its bottom. The tank 1 is suspended from weighing sensors 2. The mixing device 4 is connected to the tank 1 by a feed line 15 at the top of the tank and the return line 16 from the lower part of the tank returns to the mixing device 4. The powder feeding device 5 18. The weighing sensors 2 of the sack 14 are used when a dosing of the sack is required. At the bottom of the tank 1 there are further heating resistors or coils 10 and at its bottom there is a finished product outlet line 19 passing through a filter 8 20 and a pump 7 to, for example, a packing system, or in this case a circulation line 21. plus a control center with weighing and control units 11, 12 and stairs and maintenance-25 levels 13 and the necessary washing connections.

The mixing device 4 in this embodiment is the mixer described in International Application Publication No. WO 92/21436. This mixer consists of a mixing chamber led by a · fluid supply connection and a mixing material supply connection. The mixing chamber has a rotor which is rotated by an electric motor. The powdered matter is fed to the center axis of the rotor

At the inlet and the rotor rotates the liquid in the mixing chamber at high speed, creating a vacuum at the feed point. The powder is rapidly and well absorbed into the liquid and the mixture is rapidly transferred to the outer periphery of the rotor and out through the outlet connection on the side of the mixing chamber. In this device, mixing is quick and efficient because the liquid and powder collide rapidly and the mixing speed in the chamber is extremely high. A more detailed description of this device can be found in the above publication.

10

The exemplary apparatus shown in the figure operates as follows. The tank 1 is first metered with a liquid, such as water, a suitable solvent or other liquid, used as the base raw material for the mixture. The mixing device 4 is started and liquid 15 is supplied to it 15 from the tank 1 via a return line. Subsequently, the powder may be mixed with the powders from the big bag 14 or by the suction line 17 from the small bags 18. The powders are mixed with the liquid in the mixer 4, from where the mixture is conveyed back to the tank 1 via the feed line 15. all additives are mixed with the basic raw material.

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During the mixing, the mixture in the container can be mixed with a side mixer 3 to keep it fluid and, if necessary, the mixture is heated by a heater 10. After mixing the additives, the base stock is added to the container 1 until the correct mixing ratio and product amount is achieved. At the same time, the temperature of the final product is desired to be packaged. The finished end product can be removed from the container for immediate use or packaged for delivery to customers.

The present invention relates to the further subdivision of a mixed material into applications or the mixing of a plurality of pumpable mixtures into a ready-to-use or packaging end product. Fig. 2 shows a detail of a system where 5 partial products circulate in circulating lines 21 leaving the mixing system. The system has four lines and at the system operating point illustrated in Fig. 2, each line has a branch closed by a shut-off valve 27. The junctions are connected to the mixing valve 28. Each of the lines 21 is supplied with a mixing device or other required ingredient by means of a constant volume pump 7. The pressure in the line is adjusted by the differential pressure valve 26 positioned after the junctions. The flowrate through each line is determined by the desired mixture ratio of the final product so that the flowrate ratio of the lines corresponds to the mixture ratio of the final product. The adjustment is made by changing the frequency of the drive motor of the constant volume pump 7, while at the same time adjusting the differential pressure valve or automating the line pressure to the desired level. When the volume flow and pressure for each line are set, the shut-off valves 27 can be opened, whereby the differential pressure valves 26 close or remain in their desired control position and the blends 25 flow to the mixing valve 28. The desired final product can now be taken from mixing valve 28. When the mixing valve 28 is closed, the shut-off valves 27 can be closed, whereby the differential pressure valves 26 open and rotation of the component mixtures continues in the circuits 21. Further, the outlet valves of each lin 30 are provided with non-return valves 31 for flow direction.

• · 9 103500

The flow rate circulating in the circulation line 21 is determined by the rotational speed of the constant volume pump 7. The speed is preferably controlled by an electric motor controlled by the frequency converter. For each material to be pumped, the RPM of the pump 7 and the setting of the differential pressure valve can be determined such that the flow rate and line pressure are desired. Since the volume flow rate provided by the constant volume pump 7 changes linearly with the speed, it is preferable to use a linear valve 10 as a differential pressure valve 10, whereby the setting value of the valve 26 corresponding to a single flow rate is sufficient. The setpoint for other volume flows is derived from this. These values must be determined whenever the viscosity of the medium to be pumped changes. The determination can be made during the installation of the system, whereby the values are determined during the test run, or most preferably, a calibration unit can be used, which allows the setting values to be determined whenever the fluid being pumped and whenever necessary.

One preferred calibration unit is shown in connection with the mixing apparatus of Figure 1. It has a calibration tank 24 separated from the mixing tank 1 and passing a line to be closed from the constant volume pump 7 by means of a shut-off valve 22. There is a constant differential pressure valve 23 in line 25 between the Sul valve 22 and the calibration tank 24. The calibration tank 24 is disposed above the mixing tank separated from the weighing system of the mixing tank 1 and exits the shut-off valve 25 to the mixing tank 1. Otherwise, the shut-off valve 22 is opened, whereby the mixture to be pumped through the constant pressure differential valve 23 flows into the calibration tank 24. The mixture is pumped into a calibration tank of 10 103500 sealing tanks 24 for a predetermined period of time, or the amount of hertz supplied to a motor using pump 7 to obtain a quantity pumped at a constant speed over a constant pressure difference. The amount is readily obtained by the mixing tank weighing system 5 as a mass flow from the tank, or alternatively the calibration tank 24 can be weighed. After calibration, the calibration tank 24 is emptied through line 25 to the mixing tank 1.

10 If the mass flow rate provided by the constant volume pump is 100 kg / h and the adjustable range of the frequency converter is 100 Hz, the change in one hertz corresponds to the change in mass flow rate 1 kg / h. If such pumps are placed in five circuits, the following exemplary products are provided.

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Table 1.

__Tl__T2__T3__T4__T5__T6__T7 LI__10__20___100___45__ 20 _L2__40__17__40____10__ L3__25__13____100___50 L4__15__21__40_____50 L5__10__20__20____45 __100 100 100 100 100 100 25

As can be seen from the table above, five different mixing lines already provide a variety of end products. Using a line with each line rotating through multiple application points provides, for example, a paint mixing system suitable for large 30 construction sites, which can be used for various purposes at • · 11 103500 dyes, mixing material at different points in the application point as needed.

In the example of Fig. 3, no circulating lines are used, but a supply line 21 is provided from the four constant volume pumps 7 to the operating point 5, from which the return lines 29 leave via the differential pressure valves 26 back to the mixing tank. The feed lines 21 are connected to a static mixer 30 and a valve 28 is provided in the line exiting the mixer 30. to set the temperature and energy content of the final 15 product.

In addition to the above, the present invention has other embodiments. This method is suitable for all materials that need to be recycled in the distribution pipeline to avoid solidification and clogging. As long as the return flow and circulation are arranged, the mesh shape can be freely designed and, for example, multiple outlet lines can be placed in the same container. As such, there is also a list of possible 25-ways to branch out the line from the constant volume pump, but for ease of adjustment, it is preferable to use lines with one pump and one differential pressure valve. There is no need to limit the number of withdrawals. The operation of the pressure relief valve can be controlled automatically.

30 When the mixture is drawn from the line, the differential pressure valve may close, in whole or in part, depending on how the system is to be controlled and the volume flow 103500 12 is to be circulated in the line. The method may be applied as part of any mixing system and the dosing mixture or liquid may be taken from a source other than a storage or mixing tank, for example, a production line or other source.

Claims (9)

A method for dosing and mixing liquid substances, wherein 5 - at least one dosing substance is continuously pumped from a cold (1) to a circulation line (21) leading back (1) to the cold, and 10 - substance. is withdrawn from the circulation line (21) from at least one outlet connection, characterized in that - a constant volume pump (7) is used for the pumping of the substance, - the current in the circulation line (21) is throttled to a set point by means of a pressure differential valve (26) arranged in the line (21) in the flow direction after the outlet, and - the pressure in the circulation line (21) is kept at the set value by controlling the pressure differential valve (26). Method according to claim 1, characterized in that the blank is withdrawn from the circulation line (21) in an amount corresponding to the amount input by the constant volume pump (7) and the pressure differential valve (26) is switched off for the time of the outlet or left in a desired control position. 35 Method according to claim 2, characterized in that at least two substances are pumped at least into two circulation lines (21); substance is taken simultaneously from each of the lines and the blends are mixed, thereby obtaining, as a mixing ratio, the ratio of the circulation lines (21) to the volumetric flows. 5 Method according to any of the preceding claims, characterized in that the system is calibrated for the part of this line by pumping over a fixed period of substance by means of the constant-pressure differential valve (23) during a change of the substance intended for pumping to the circulation line (21). ) and by weighing the amount passed through the valve (23). Process according to Claim 3 or 4, characterized in that the substances for mixing are conducted from the circulation line (21) into a static mixer (30), in which the temperature of the mixture is controlled to the desired level. Apparatus for dispensing and mixing together 20 liquid substances, comprising - at least one cold (1) containing for dispensing substance, 25 - at least one source (1) outgoing and to the same recirculating line (21), - one pump (7 ) for continuous circulation in the line of the substance in each circulation line (21), and 30. - an outlet connection for extracting material from: the circulation line (21), characterized in that the 35 pump is a constant volume pump (7), and • <103500 - a pressure differential valve (26) is arranged in the circulation line (21) in the flow direction after the outlet. . Device according to claim 6, characterized in that the device comprises a plurality of lines (21) each having a constant volume pump (7) and a pressure differential valve (26). 8. Apparatus according to claim 6 or 7, characterized in that it comprises a calibration device comprising an outlet line with a constant pressure differential valve (23), and a container (24) and weighing means for detecting the amount of substance pumped into the container (24). Device according to any of claims 6-8, characterized in that it comprises at least one plate type mixer (3), in which the blank taken out of the lines can be fed and of which plates a part consists of heating plates and part of cooling plates. . «·