EP3638409B1 - Method and mixing device for controlling the introduction of a pulverulent material into a liquid for a batch mixing method - Google Patents

Description

TECHNICAL AREA

The invention relates to a method for controlling the introduction of a pulverulent substance into a liquid consisting of at least one component for a batch mixing process according to the preamble of claim 1, in which the introduction and treatment of the pulverulent substance quasi under the reaction kinetic conditions of a residence time behavior of a discontinuous working homogeneous reaction vessel takes place as well as a mixing device for carrying out the process.

STATE OF THE ART

With a view to the introduction of a powdery substance into a liquid and its uniform distribution and, if necessary, dissolution in the liquid, mixer technology knows mixing processes that are operated intermittently (so-called batch process) or continuously (so-called inline process).

In the batch process, the mixing of liquid and powdery substance is carried out kinetically in a so-called discontinuously operated reaction vessel (mixing vessel). A certain amount of liquid is placed in the mixing container and powdery substance is added until a desired or systematically predetermined dry substance concentration of the powdery substance is present in the liquid. Powdered substance and liquid are preferably continuously stirred and / or mixed to form a mixed product and the mixed product is homogenized with the aim of uniformly distributing the powdery substance. The powdery substance can be fed in continuously or discontinuously.

In the inline process, the mixing of liquid and powdery substance is carried out kinetically in a so-called continuously operated reaction vessel (mixing vessel). There is steady liquid and the mixing tank powdery substance, the latter either continuously or discontinuously, is supplied and a mixed product corresponding to the supplied amounts of liquid and powdery substance is continuously discharged from the mixing container. Stirring and / or mixing or shearing and homogenizing ensure, according to the theoretical postulate, that the mixed product has the same composition (eg dry matter concentration) at every point and that no temperature differences occur. The dry matter concentration in the discharged mixed product remains unchanged over the duration of the mixing process.

The present invention deals exclusively with mixing processes which are operated in the batch process and here in all possible forms. A related mixing process and the associated mixing device were made known to the public, for example, at the following Internet link: "http://www.gea.com/de/products/High-Shear-Batch-Mixer.jsp".

The above-mentioned mixing devices preferably also include so-called vacuum mixers, which have a mixing container with a stirring and / or shearing and homogenizing device. The free surface of the liquid, which in the mixing container can, for example, have a free fill level with a height of between 0.4 and 4 m, is subject to a negative pressure corresponding to this height range compared to atmospheric pressure of, for example, 0.2 to 0.8 bar, so that the Liquid can on the one hand be freed from gas components more easily during the mixing process and on the other hand has a negative pressure compared to atmospheric pressure in the bottom area of the mixing container under all operating conditions. The powdery substance is introduced into the mixing container via an opening in the container wall below the free fill level. This opening continues in a tubular inlet connection in the direction of the outside of the mixing container, to which a pipeline leading, for example, to a powder storage container is connected. The inlet nozzle and thus the pipeline are designed to be shut off via an inlet valve that controls the supply of the powdery substance, so that on the one hand the mixing device is closed off from its surroundings via this path and on the other hand a quantity of the powdery substance presented in the powder storage container if the liquid is required due to the prevailing Pressure ratios can be fed automatically. A related mixing device with a preferably discontinuous supply of the powdery substance is in the document DE 10 2015 016 766 A1 described, the latter being generic.

A discontinuous supply of the powdery substance, as for example in the DE 10 2015 016 766 A is disclosed, has the advantage that the supply always takes place via the fully open position of the inlet valve designed as a lift valve and thereby the risk of clogging of the inlet valve is minimized. Depending on the duration of the respective open position, more or less large amounts of the powdery substance are introduced into the liquid in bursts, so that there is basically the risk that there is corresponding agglomeration of the powdery substance, which is caused by the stirring and / or shearing and homogenizing -The device must be completely dissolved until the subsequent entry of powdery substance, whereby at the same time a largely uniform distribution of the powdery substance is to be aimed for. In this context, it has been shown that the intermittent supply of the powdery substance is reflected in an increase in the stirring and / or shearing and homogenizing power (drive power for the associated devices), which is necessary to achieve this in this phase of the mixing process to treat temporarily present mixed product. The course of the related drive power, which is proportional to the current consumption of the assigned drive motors, corresponds approximately to a Gaussian normal distribution curve.

What makes the mixing process even more difficult is that the residence time behavior of a discontinuously operated reaction vessel or mixing vessel theoretically postulates the same composition of the mixed product at every point, but in practice, reinforced by the operational discontinuous supply of the powdery substance, it leads to inhomogeneously distributed agglomerations of the powdery substance can occur that have not completely dissolved at all points of the mixing container by the next supply of the powdery substance. As a result, there is a risk of the mixing container becoming blocked due to an excessively high concentration of dry matter.

On the one hand, therefore, it cannot be ruled out that more or less large agglomerations do not completely dissolve and are sustainable in the mixed product. Due to the above-described inhomogeneities of the powdery substance in the mixed product, there is on the other hand the risk of microbiological growth (germ growth), which is conveyed under these thermal conditions, especially when the mixing container is heated. In addition, the latter conditions lead to increased deposits (so-called product fouling) on the heated walls of the mixing container, which on the one hand hinders the transfer of heat and on the other hand shortens the service life of the mixing container until the next cleaning cycle.

Since until now there has been a lack of targeted control mechanisms to avoid inhomogeneities with regard to the distribution and degree of dissolution of agglomerations of the powdery substance and disproportionately large fluctuations in the supply of the powdery substance and to prevent the mixing device from being blocked due to excessive dry substance concentration in the mixing container, so far In order to act supposedly on the safe side, with mixing devices of the type in question, the stirring and / or shearing and homogenizing of the temporarily present mixed product is operated more intensively over the entire duration of the mixing process than is necessary over long periods of time. On the one hand, this too intensive treatment can have a damaging effect on the product and, on the other hand, it is not energy-efficient.

The object of the present invention is to develop a generic method for controlling the introduction of a powdery substance into a liquid consisting of at least one component for a batch mixing process and an associated mixing device for carrying out the process in such a way that the above-mentioned disadvantages of the prior art be eliminated.

SUMMARY OF THE INVENTION

From a procedural point of view, this object is achieved by a method having the features of claim 1. In terms of device technology, the object is also achieved by a mixing device for performing the method with the features of independent claim 9. An advantageous embodiment of the mixing device is the subject of dependent claim 10.

procieedings

With a view to a method according to the invention, the invention is based on a known method for controlling the introduction of a powdery substance into a liquid consisting of at least one component for a batch mixing process, the term "component" being understood to mean here can usually be discrete liquids that are separate from one another and that can also be fed to the mixing process separately from one another. The batch mixing process is typically used for medium to high viscosity mixed products with a medium to high dry matter concentration in the end and also for mixing processes with several liquid components that require little or no further processing in the downstream process. In this case, the powdery substance is introduced and treated, viewed from a reaction kinetic point of view, under the conditions of a residence time behavior of a discontinuously operating homogeneous reaction vessel.

The method is characterized in a manner known per se such that a quantity of liquid is provided and the powdery substance is fed discontinuously into this liquid and the liquid and the powdery substance are continuously stirred and / or mixed to form a mixed product and the mixed product is homogenized. The powdery substance is fed in until a time-dependent course of a dry matter concentration of the powdery substance in the mixed product has grown to a predetermined end value.

The inventive solution concept consists in the method that a recipe of the mixed product at least with regard to the predetermined final value associated time-dependent course of a dry matter concentration and the reaction conditions are each given in the form of default data. Furthermore, it is provided that the discontinuous supply of the powdery substance takes place in a manner known per se in pulses by a time sequence of metering pulses. In a preferred embodiment, the reaction conditions provide that the powdery substance is sucked in by a negative pressure (vacuum) in the head space of the mixing container compared to atmospheric pressure. The metering pulses are each characterized by a mass flow of the powdery substance ṁ _P , a duration of the metering pulse Δt1 and a time interval between adjacent metering pulses Δt2.

• Bei dem Verlauf ohne Sättigungscharakter lassen sich im Rahmen der Aufnahmekapazität oder der Löslichkeitsgrenze der Flüssigkeit in gleichen Zeitabständen gleiche Mengen pulverförmiger Stoff dosieren, sodass sich bei vollständiger Homogenisierung des Mischprodukts ein zeitabhängiger näherungsweise linear ansteigender Verlauf einer Trockenstoff-Konzentration einstellt.
• Bei dem Verlauf mit Sättigungscharakter lassen sich im Rahmen der Aufnahmekapazität oder der Löslichkeitsgrenze der Flüssigkeit in gleichen Zeitabständen nur stetig abnehmende Mengen pulverförmiger Stoff dosieren, sodass sich bei vollständiger Homogenisierung des Mischprodukts ein zeitabhängiger degressiv ansteigender Verlauf einer Trockenstoff-Konzentration einstellt.

Der in dem vorgegebenen Endwert endende zeitabhängige Verlauf einer Trockenstoff-Konzentration ist erfindungsgemäß durch die Abfolge eindeutig bestimmter Dosierimpulse definiert.The method results in a time-dependent course of a dry matter concentration c (t), which ends as planned in the specified end value, a distinction being made between the course of a dry matter concentration without saturation character (approximately linear course) or with saturation character (degressive course) .

• In the case of the course without the character of saturation, within the framework of the absorption capacity or the solubility limit of the liquid, the same amounts of powdery substance can be dosed at the same time intervals, so that when the mixed product is completely homogenized, a time-dependent, approximately linearly increasing course of a dry matter concentration is established.
• In the case of the course with a saturation character, only steadily decreasing amounts of powdery substance can be dosed at the same time intervals within the framework of the absorption capacity or the solubility limit of the liquid, so that a time-dependent degressively increasing course of a dry matter concentration occurs when the mixed product is completely homogenized.

The time-dependent course of a dry matter concentration ending in the predetermined end value is defined according to the invention by the sequence of uniquely determined metering pulses.

A significant technical control feature is that a time-dependent current consumption I (t) is determined, which is proportional to the stirring and / or shearing and homogenizing power required for a temporarily present mixed product. The latter always occurs in the form of approximately one Gaussian normal distribution when a defined amount of powdery substance is introduced into the mixing process or the mixing container and treated in pulses.

As soon as the powdery substance is evenly distributed in the absorbing liquid or in the absorbing mixed product, i.e. it has been distributed as homogeneously as possible and possibly dissolved, the time-dependent current consumption I (t) decays, namely to a time-dependent course of a reference current consumption I _o (t) , which is characteristic of the stirring and / or shearing and homogenizing power to be provided on the homogenized mixed product under the conditions of the assigned time-dependent course of a dry matter concentration (c (t)). The related time-dependent course of the reference _{current consumption I o} (t) is stored in the specification data and can be drawn from there, and it is dependent on the recipe of the mixed product and the reaction conditions for the mixing process.

At the end of the time interval between adjacent metering pulses Δt2 and when the time-dependent current consumption I (t) deviates from the respective assigned value in the time-dependent course of a reference current consumption I _o (t) by more than a specified tolerance, with a deviation either upwards or downwards , the duration of the dosing pulse Δt1 for the subsequent dosing pulse is shortened in the first case and lengthened in the second case.

For time-dependent curves of a dry matter concentration c (t) without the character of saturation, a first embodiment of the method provides that these curves are each defined by a fixed duration-time interval ratio V between the duration of the metering pulse Δt1 and the assigned time interval between adjacent metering pulses Δt2 ( V = Δt1 / Δt2 = constant).

In den meisten praxisrelevanten Fällen kann, weil der erste Term der nachfolgenden Relation in der Regel klein gegenüber dem zweiten Term ist, näherungsweise $${\dot{\mathrm{m}}}_{\mathrm{P}}\frac{\mathrm{t}}{\mathrm{\Delta }\mathrm{t}2}\mathrm{\Delta }\mathrm{t}1\ll {\mathrm{m}}_{\mathrm{F}}$$

gesetzt werden, sodass sich nach Gleichung (1a) für den zeitabhängigen Verlauf einer Trockenstoff-Konzentration c(t) mit einer ersten Proportionalitätskonstante $\mathrm{k}1=\frac{{\stackrel{.}{\mathrm{m}}}_{\mathrm{P}}}{{\mathrm{m}}_{\mathrm{F}}}$

näherungsweise ergibt: $$\mathrm{c}\left(\mathrm{t}\right)\approx \frac{{\dot{\mathrm{m}}}_{\mathrm{P}}\frac{\mathrm{t}}{\mathrm{\Delta }\mathrm{t}2}\mathrm{\Delta }\mathrm{t}1}{{\mathrm{m}}_{\mathrm{F}}}=\frac{{\dot{\mathrm{m}}}_{\mathrm{P}}}{{\mathrm{m}}_{\mathrm{F}}}\frac{\mathrm{\Delta }\mathrm{t}1}{\mathrm{\Delta }\mathrm{t2}}\mathrm{t}=\frac{{\dot{\mathrm{m}}}_{\mathrm{P}}}{{\mathrm{m}}_{\mathrm{F}}}\mathrm{Vt}=\mathrm{k}1\mathrm{Vt}$$

The respective course of a dry matter concentration c (t) increases over time t, because the continuously pulsed flow of powdery substance ṁ _P , which in the most general case is a time-dependent flow of powdery substance ṁ _P (t), over the entire period of time t of the mixing process is constant (ṁ _P = constant). The mass flow of powdery substance ṁ _{P is introduced into an unchangeable amount of liquid m F of} the present mixed product in the time period t many times, namely (t / Δt2) times, with an almost unchangeable fill level in the mixing container, the time-dependent course of a dry matter concentration c (t) according to equation (1), as follows: $$\mathrm{c}\left(\mathrm{t}\right)=\frac{{\dot{\mathrm{m}}}_{\mathrm{P.}}\frac{\mathrm{<figure-callout\; id="2"\; label="t\; \Delta \; t"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">t</figure-callout>}}{\mathrm{\Delta }\mathrm{t}}\mathrm{\Delta }\mathrm{t}1}{{\mathrm{m}}_{\mathrm{F.}}+{\dot{\mathrm{m}}}_{\mathrm{P.}}\frac{\mathrm{<figure-callout\; id="2"\; label="t\; \Delta \; t"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">t</figure-callout>}}{\mathrm{\Delta }\mathrm{t}}\mathrm{<figure-callout\; id="1"\; label="\Delta \; t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\mathrm{t}\mathrm{}1}$$

In most practice-relevant cases, because the first term of the following relation is usually small compared to the second term, approximately $${\dot{\mathrm{m}}}_{\mathrm{P.}}\frac{\mathrm{<figure-callout\; id="2"\; label="t\; \Delta \; t"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">t</figure-callout>}}{\mathrm{\Delta }\mathrm{t}}\mathrm{<figure-callout\; id="1"\; label="\Delta \; t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\mathrm{t}\mathrm{}1\ll {\mathrm{m}}_{\mathrm{F.}}$$

are set so that according to equation (1a) for the time-dependent course of a dry matter concentration c (t) with a first constant of proportionality $\mathrm{k}$$\mathrm{}1=\frac{{\stackrel{.}{\mathrm{m}}}_{\mathrm{P.}}}{{\mathrm{m}}_{\mathrm{F.}}}$

approximately results in: $$\mathrm{c}\left(\mathrm{t}\right)\approx \frac{{\dot{\mathrm{m}}}_{\mathrm{P.}}\frac{\mathrm{<figure-callout\; id="2"\; label="t\; \Delta \; t"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">t</figure-callout>}}{\mathrm{\Delta }\mathrm{t}}\mathrm{\Delta }\mathrm{t}1}{{\mathrm{m}}_{\mathrm{F.}}}=\frac{{\dot{\mathrm{m}}}_{\mathrm{P.}}}{{\mathrm{m}}_{\mathrm{<figure-callout\; id="1"\; label="F.\; \Delta \; t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">F.</figure-callout>}}}\frac{\mathrm{\Delta }\mathrm{t}}{}\frac{\mathrm{}1}{\mathrm{\Delta }\mathrm{t2}}\mathrm{t}=\frac{{\dot{\mathrm{m}}}_{\mathrm{P.}}}{{\mathrm{m}}_{\mathrm{F.}}}\mathrm{Vt}=\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">k</figure-callout>}1\mathrm{Vt}$$

This technical control measure with a fixed duration-time interval ratio V (V = Δt1 / Δt2 = constant) inevitably leads in the same ratio to a corresponding shortening or lengthening of the time interval between adjacent metering pulses Δt2, based on the subsequent metering pulse.

• bei Abweichung der zeitabhängigen Stromaufnahme I(t) von dem jeweils zugeordneten Wert im zeitabhängigen Verlauf einer Referenzstromaufnahme I_o(t) um mehr als die vorgegebene Toleranz nach oben das Zeitdauer-Zeitabstand-Verhältnis V verkleinert und
• bei Abweichung der zeitabhängigen Stromaufnahme I(t) von dem jeweils zugeordneten Wert im zeitabhängigen Verlauf einer Referenzstromaufnahme I_o(t) um mehr als die vorgegebene Toleranz nach unten das Zeitdauer-Zeitabstand-Verhältnis V vergrößert wird.

For time-dependent curves of the dry matter concentration c (t) with a saturation character, a second embodiment of the method provides that these curves are defined by a variable duration-time interval ratio V between the duration of the metering pulse Δt1 and the assigned time interval between adjacent metering pulses Δt2 (V = Δt1 / Δt2 ≠ constant), where

• if the time-dependent current consumption I (t) deviates from the respectively assigned value in the time-dependent course of a reference current consumption I _o (t) by more than the specified tolerance upwards, the duration-time interval ratio V is reduced and
• if the time-dependent current consumption I (t) deviates from the respective assigned value in the time-dependent course of a reference current consumption I _o (t) the time duration / time interval ratio V is increased downwards by more than the specified tolerance.

wie folgt, darstellt: $$\mathrm{c}\left(\mathrm{t}\right)=\frac{{\displaystyle {\sum }_{\mathrm{t}=0}^{\mathrm{t}}\left({\dot{\mathrm{m}}}_{\mathrm{P}}\left(\mathrm{t}\right)\mathrm{\Delta }\mathrm{t}1\right)}}{{\mathrm{\rho }}_{\mathrm{M}}\left(\mathrm{t}\right){\mathrm{V}}_{\mathrm{M}}}=\frac{{\dot{\mathrm{m}}}_{\mathrm{P}}}{{\mathrm{V}}_{\mathrm{M}}}\frac{{\displaystyle {\sum }_{t=0}^t\mathrm{\Delta }\mathrm{t}1}}{{\mathrm{\rho }}_{\mathrm{M}}\left(\mathrm{t}\right)}\approx \mathrm{k}2\frac{{\displaystyle {\sum }_{t=0}^t\mathrm{\Delta }\mathrm{t}1}}{{\mathrm{\rho }}_{\mathrm{M}}\left(\mathrm{t}\right)}.$$

The respective course of a dry matter concentration c (t) increases degressively over time t, because the continuously pulsed flow of the powdery substance ṁ _P , viewed over the entire time t of the mixing process, is constant (ṁ _P = constant), however, the duration of the dosing pulse Δt1 steadily decreases and thus a steadily decreasing amount of powdery substance is dosed. The mass flow of powdery substance ṁ _{P is introduced into an existing almost unchangeable volume of the mixed product V M} (V _M ≈ constant) in the time period t with an almost unchangeable fill level in the mixing container, with a density ρ _{M of} the mixed product corresponding to the time-dependent course of a dry matter concentration c (t) increases and the latter is determined by equation (2) with a second constant of proportionality $\mathrm{k}$$\mathrm{}2=\frac{{\stackrel{.}{\mathrm{m}}}_{\mathrm{P.}}}{{\mathrm{V}}_{\mathrm{M.}}},$

as follows: $$\mathrm{c}\left(\mathrm{t}\right)=\frac{{\displaystyle {\sum }_{\mathrm{t}=0}^{\mathrm{t}}\left({\dot{\mathrm{m}}}_{\mathrm{P.}}\left(\mathrm{<figure-callout\; id="1"\; label="t\; \Delta \; t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>},\right)\mathrm{\Delta }\mathrm{t}\mathrm{}1\right)}}{{\mathrm{\rho }}_{\mathrm{M.}}\left(\mathrm{t}\right){\mathrm{V}}_{\mathrm{M.}}}=\frac{{\dot{\mathrm{m}}}_{\mathrm{P.}}}{{\mathrm{V}}_{\mathrm{M.}}}\frac{{\displaystyle {\sum }_{t=0}^{\mathrm{<figure-callout\; id="1"\; label="t\; \Delta \; t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}\mathrm{\Delta }\mathrm{t}\mathrm{}1}}{{\mathrm{\rho }}_{\mathrm{M.}}\left(\mathrm{t}\right)}\approx \mathrm{<figure-callout\; id="2"\; label="k"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">k</figure-callout>}2\frac{{\displaystyle {\sum }_{t=0}^{\mathrm{<figure-callout\; id="1"\; label="t\; \Delta \; t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}\mathrm{\Delta }\mathrm{t}\mathrm{}1}}{{\mathrm{\rho }}_{\mathrm{M.}}\left(\mathrm{t}\right)}.$$

This technical control measure with a variable duration-time interval ratio V requires the control to be able to shorten or lengthen the duration of the metering pulse Δt1 with an unchanging time interval between adjacent metering pulses Δt2 or to adequately lengthen the time interval between adjacent metering pulses Δt2 with the same duration of the metering pulse Δt1 or shorten it.

The control-technical measure according to the invention thus essentially consists in both refinements of the method in that the duration of the metering pulse Δt1 and the time interval between adjacent metering pulses Δt2 are selected in such a way that at the respective end of the time interval between adjacent metering pulses Δt2 the time-dependent determined current consumption I (t) for Stirring and / or shearing and homogenizing the temporarily present mixed product _{approximates the time-dependent course of a reference current consumption I o} (t), which is required for the relevant treatment of the homogenized mixed product, within the scope of a practically relevant permissible tolerance.

In order to make the metering of the pulverulent substance as trouble-free as possible, it is proposed for the method that the mass flow of the pulverulent substance is constant over the duration of the metering pulse. This is ensured in particular by the fact that a controllable opening for the supply of the powdery substance only assumes either a fully open position or a closed position.

In order to make the control of the mixing process as manageable as possible, another embodiment of the method provides that the shortening or lengthening of the duration of the metering pulse occurs when a current corridor determined by a permissible current excess or a permissible current shortfall due to an upwardly deviating current consumption or a current consumption deviating downwards is left. The permissible current excess and the permissible current shortfall are each determined by a percentage of the assigned time-dependent course of a reference current consumption. In order for the control to work as sensitively as possible in this regard, it is further proposed that the degree of shortening or lengthening of the duration of the metering pulse is determined as a function of the degree of deviation of the time-dependent current consumption from the assigned course of a reference current consumption.

In order to make the operating data obtained in practice for a specific recipe usable for subsequent mixing processes with the same recipe, another embodiment of the method provides that the control of the introduction of the powdery substance into the at least one liquid is based on further recipe-dependent default data from previous experience Mixing processes are obtained and stored, with these default data a mixing or solution temperature, a pressure above the liquid column from which a reaction pressure results, speeds of devices for stirring and / or shearing and homogenizing and a permissible current exceedance dependent on the assigned time-dependent course of a reference current consumption and are a permissible current shortfall.

In order to make the operating data obtained in practice for a specific recipe usable for subsequent mixing processes with the same recipe, a further embodiment of the method provides that the target-oriented recipe-dependent control parameters, and the duration of the dosing pulse and the time interval between adjacent dosing pulses can be saved and used for subsequent controls of the same recipes.

Mixing device

A mixing device for carrying out the method consists in a manner known per se of a mixing container which has an inlet connection for supplying a liquid, an outlet connection for discharging a mixed product and a stirring device and / or a shearing and homogenizing device. An inlet valve with a valve closing member is arranged on the mixing container. The inlet valve can be adjusted with the valve closing element either between completely closed (closed position) or completely open (open position). A powdery substance is introduced into the liquid with the inlet valve, the valve closing element being able to be moved into the closed or open position with a control device assigned to the inlet valve.

According to the invention, the control device of the mixing device provides recipe-dependent specification data and recipe-dependent control parameters in the form of the duration of the metering pulse and the time interval between adjacent metering pulses. Furthermore, according to the invention, the control device has at least one signal pickup designed as a measuring device, which detects a time-dependent current consumption of the stirring device and / or the shearing and homogenizing device. Equipped with these properties, the control device controls the closed or open position of the valve closing element as a function of the time-dependent power consumption and in relation to the specified data and the control parameters.

Around the inlet valve, designed as a lift valve, which only feeds the powdery substance in its fully open position and thus the susceptibility to clogging Minimized from the start, to be further optimized in this regard and, for example, to avoid dead spaces and cavities in the powder-loaded area of the valve housing of the inlet valve, an advantageous embodiment provides that the valve closing member is designed, at least in its powder-loaded area, as a cylindrical rod of the same diameter on which the same diameter a valve plate is formed. When the inlet valve is in its fully open position, the valve closing member with its valve disk is largely moved out of the fully developed flow of the powdery substance due to this embodiment, so that on the one hand it does not represent a flow obstacle and on the other hand there is a seat seal that is accommodated in the valve disk the vicinity of the wall of a valve housing and thus outside the fully developed flow area of the pipe flow and is therefore only affected by the stagnant flow close to the wall in this edge area.

BRIEF DESCRIPTION OF THE DRAWINGS

Figur 1

in schematischer Darstellung eine Mischvorrichtung für ein Batch-Mischverfahren;

Figur 2

in perspektivischer Darstellung und im Halbschnitt ein Einlaufventil zur Zuführung des pulverförmigen Stoffes in eine Mischvorrichtung gemäß Figur 1 ohne ein Steuerkopfgehäuse;

Figur 3

in einer qualitativen Darstellung für das Verfahren und zur grundsätzlichen Darstellung der erfindungsgemäßen Steuerungsmerkmale eine zeitabhängige Stromaufnahme I(t) für eine Abfolge von Dosierimpulsen mit einer konstanten Zeitdauer des Dosierimpulses Δt1 und mit einem Zeitabstand benachbarter Dosierimpulse Δt2, wobei ein zeitabhängiger Verlauf einer Trockenstoff-Konzentration c(t) ohne Sättigungscharakter zugrunde gelegt ist;

Figur 4

in einer qualitativen Darstellung für das Verfahren eine zeitabhängige Stromaufnahme I(t) für eine Abfolge von Dosierimpulsen mit einer konstanten Zeitdauer des Dosierimpulses Δt1/2 und mit einem Zeitabstand benachbarter Dosierimpulse Δt2/2, wobei der zeitabhängiger Verlauf einer Trockenstoff-Konzentration c(t) gemäß Figur 3 zugrunde gelegt ist;

Figur 5

in einer qualitativen Darstellung für das Verfahren eine zeitabhängige Stromaufnahme I(t) für eine größere Abfolge von Dosierimpulsen mit einer konstanten Zeitdauer des Dosierimpulses Δt1 und mit einem konstanten Zeitabstand benachbarter Dosierimpulse Δt2 zur Realisierung eines zeitabhängigen näherungsweise linear ansteigenden Verlaufs einer Trockenstoff-Konzentration (ohne Sättigungscharakter) entsprechend den Figuren 3 und 4 und

Figur 6

in einer qualitativen Darstellung für das Verfahren eine zeitabhängige Stromaufnahme I(t) für eine Abfolge von Dosierimpulsen mit einer stetig abnehmenden Zeitdauer des Dosierimpulses Δt1 und mit einem konstanten Zeitabstand benachbarter Dosierimpulse Δt2 zur Realisierung eines zeitabhängigen degressiven Verlaufs einer Trockenstoff-Konzentration (mit Sättigungscharakter).

A more detailed description of the invention can be found in the following description and the attached figures of the drawing and in the claims. While the invention is implemented in the most varied of configurations of a method for controlling the introduction of a powdery substance into a liquid consisting of at least one component for a batch mixing process, a preferred method and a mixing device for performing the method are described in the drawing. Show it

Figure 1

a schematic representation of a mixing device for a batch mixing process;

Figure 2

in a perspective view and in half-section, an inlet valve for feeding the powdery substance into a mixing device according to FIG Figure 1 without a control head housing;

Figure 3

in a qualitative representation for the method and for the basic representation of the control features according to the invention, a time-dependent current consumption I (t) for a sequence of metering pulses with a constant duration of the dosing pulse Δt1 and with a time interval between adjacent dosing pulses Δt2, a time-dependent course of a dry matter concentration c (t) without saturation character being used as a basis;

Figure 4

In a qualitative representation for the method, a time-dependent current consumption I (t) for a sequence of metering pulses with a constant duration of the metering pulse Δt1 / 2 and with a time interval between adjacent metering pulses Δt2 / 2, the time-dependent course of a dry matter concentration c (t) according to Figure 3 is based on;

Figure 5

In a qualitative representation for the method, a time-dependent current consumption I (t) for a larger sequence of metering pulses with a constant duration of the metering pulse Δt1 and with a constant time interval between adjacent metering pulses Δt2 to achieve a time-dependent, approximately linearly increasing course of a dry matter concentration (without saturation character ) according to the Figures 3 and 4 and

Figure 6

In a qualitative representation for the method, a time-dependent current consumption I (t) for a sequence of metering pulses with a steadily decreasing duration of the metering pulse Δt1 and with a constant time interval between adjacent metering pulses Δt2 to achieve a time-dependent degressive course of a dry matter concentration (with a saturation character).

Mixing device (Figures 1 and 2)

A mixing device 1000 has, inter alia, a mixing container 100 which consists of a preferably cylindrical container jacket 100.1, an upper container base 100.2 and a lower container base 100.3. The lower container base 100.3 preferably tapers downwards, mostly in the shape of a cone or in the form of a circular cone, and has an outlet connection 100.4 for a mixed product M at the lower end. _{A liquid F in an amount of liquid m F is placed} in the mixing container 100 via an inlet connection 100 standing mixing device 1000 (eg vacuum mixer) a pressure above the liquid column p, a negative pressure compared to atmospheric pressure, prevails.

An inlet valve 20 is arranged on the container jacket 100.1 or the lower container base 100.3. The inlet valve 20 is used for the discontinuous supply of a powdery substance P with a _{mass flow of powdery substance ṁ P} , which is fed via a feed line 18, into the liquid F or into the mixed product M. The inlet valve 20 is assigned a control device 30, which has a control head housing 14 of the inlet valve 20 communicates via a signal line 22 and, if necessary, the inlet valve 20 is transferred into its open or closed position. In the mixing container 100 there is a stirring device 24 driven by a first drive motor 40 at a rather low first speed n1, preferably arranged centrally and acting mechanically, which preferably extends down into the area of the lower container bottom 100.3. The required stirring effect can also be achieved or supported by fluid mechanical means, for example by pumping the liquid F or the mixed product M through a circulation line (not shown) with preferably tangential entry of the liquid F or the mixed product M into the mixing container 100.

As an alternative or in addition to the stirring device 24, a shearing and homogenizing device 26 driven by a second drive motor 50 with a rather high second speed n2 is preferably provided in the lower region of the lower container bottom 100.3 and preferably eccentrically in this. This preferably sucks in the liquid F or the mixed product M on the one hand from above and on the other hand ejects it in a ring-shaped manner in the area of the lower container bottom 100.3 close to the wall in such a way that a circulation flow directed from the outside inward is preferably formed in the mixing container 100. When passing through the shearing and homogenizing device 26, liquid F and powdery substance P or the mixed product M resulting therefrom are mechanically mixed very intensively and preferably homogenized in the process.

The inlet valve 20 is designed as a lift valve ( Figure 2 ). In a valve housing 2, it has a valve seat 2a and a valve disk cooperating with it 8a, which is formed on a valve closing member 8. As a rule, the valve closing member 8 receives a seat seal 10, which in the closed position of the inlet valve 20, in cooperation with the valve seat 2a, effects the seal. The valve seat 2a has a seat opening 2b through which the powdery substance P supplied from the supply line 18 via a pipe connection 2c is introduced into the liquid F ( Figure 1 ).

The liquid F above the connection point of the inlet valve 20, which is preferably arranged directly in the wall of the mixing container 100, forms a height h with its liquid column ( Figure 1 ), so that the static pressure in the area of the aforementioned connection point and thus also in the area of the seat opening 2b is made up of the pressure above the liquid column p (preferably negative pressure) and the static pressure resulting from the height of the liquid column h. In the case of a vacuum mixer with a negative pressure of, for example, p = 0.2 to 0.8 bar and a height of the liquid column h = 0.2 to 4 m assigned to this pressure range, there is always a negative pressure compared to atmospheric pressure in the area of the seat opening 2b, so that the seat opening 2b is sucked out of the mixing container 100 and thus the powdery substance P is sucked in. The seat opening 2b can be adjusted with the valve disk 8a between completely closed, the closed position, or completely open, the open position. The valve housing 2 is connected via a lantern housing 4 to a drive housing 6 for driving the valve closing member 8. It is preferably a spring / piston drive acted upon by pressure medium, a return spring 12 usually moving the valve closing member 8 into its closed position when the drive housing 6 is not acted upon by pressure medium, preferably compressed air. A valve rod 8b, which engages the valve plate 8a of the valve closing element 8 and is guided through the drive housing 6 and into the control head housing 14, serves on the drive side for the axial guidance of the valve closing element 8. The valve closing element 8 is at least in its powder-loaded area as a cylindrical rod of the same diameter formed on which the valve disk 8a is formed with the same diameter. This structural design avoids cavities and dead spaces in the valve housing 2 in the range of movement of the valve closing member 8 that is exposed to powder, the valve closing member 8 moving with it its end valve disk 8a and the associated seat seal 10 can be withdrawn as far as possible from the area of the valve housing 2 through which there is a full flow.

The control device 30 ( Figure 1 ) has at least one signal pickup 16. The at least one signal pick-up 16 is a measuring device, for example for mixing parameters, such as the pressure above the liquid column p in the mixing container 100, a mixing or solution temperature T of the liquid F, a dry matter concentration c or a time-dependent curve of a dry matter concentration c (t ), Speeds n1, n2 and a time-dependent current consumption I (t) of the stirring and / or shearing and homogenizing device 24, 26. The signal pickup 16 is in Figure 1 shown by way of example for the time-dependent current consumption I (t) of the second drive motor 50 of the shearing and homogenizing device 26. In an analogous manner, additional or alternatively further measuring devices can be provided which determine the other mixing parameters.

Process ( Figures 3 to 6 in conjunction with Figures 1 and 2)

The introduction and treatment of the pulverulent substance P takes place quasi under the reaction kinetic conditions of a residence time behavior of a discontinuously operating homogeneous reaction vessel. The method is characterized in a manner known per se in such a way that a quantity of liquid m _{F is placed} in the mixing container 100 (supply via the inlet connection 100.5) and the powdery substance P of this liquid F via the inlet valve 20 with the flow of powdery substance ṁ _P , which is in In the most general case, a time-dependent mass flow of powdery substance ṁ _P (t) can be supplied discontinuously. The liquid F and the powdery substance P are continuously stirred and / or mixed to form a mixed product M and the mixed product M is homogenized. The pulverulent substance P is supplied until the time-dependent course of a dry substance concentration c (t) of the pulverulent substance P in the mixed product M has grown _{to a predetermined end value c E.}

In the mixing process in question, a recipe of the mixed product M is assigned at least with regard to the predetermined end value c _E time-dependent course of a dry matter concentration c (t) and the reaction conditions are each given in the form of default data D.

The discontinuous supply of the powdery substance P takes place over a period of time t in pulses by a time sequence of metering pulses i ( Figures 3 and 4 ), which are each characterized by the mass flow of the powdery substance ṁ _P , a duration of the dosing pulse Δt1 and a time interval between adjacent dosing pulses Δt2. The mass flow of the powdery substance ṁ _P is basically a time-dependent mass flow of powdery substance ṁ _P (t), as already stated above, whereby in the present application subject due to the design and the switching characteristics of the inlet valve 20, approximately from a time-independent and thus constant mass flow of powdery substance ṁ _P is assumed (ṁ _P = constant).

For the duration of the dosing pulse Δt1 according to Figure 3 is, for example, on the second drive motor 50 of the shearing and homogenizing device 26, which is also shown in Figure 3 Time-dependent current consumption I (t) plotted over the corresponding period t is determined or measured. The latter is proportional to a stirring and / or shearing and homogenizing power required for a mixing product M * temporarily present in the mixing container 100 immediately after the dosing pulse i ( Figure 1 ), which is to be applied by the stirring and / or shearing and homogenizing device 24, 26. The course of the time-dependent current consumption I (t) is similar to a Gaussian normal distribution curve, it increases with the intermittent flow of powdery substance ṁ _P , reaches a maximum, and then after dissolution of the powdery substance P, i.e. with a homogenized mixed product that is then reached M to gradually decrease to a time-dependent current consumption I (t) required for this homogenized mixed product M.

According to the invention, this typical behavior is used for control purposes in that a time-dependent course of a reference _{current consumption I o} (t) is used from the default data D, which is characteristic of the stirring and / or shearing and homogenizing power to be provided on the homogenized mixed product M.

If the time interval between adjacent metering pulses Δt2 is not sufficient to _{dissolve, mix in and homogenize a metered amount of powdery substance m P} = ṁ _P Δt1, a time-dependent, upwardly deviating current consumption I * (t) is measured, so that in this state of the temporarily present mixed product M * at the end of the time interval between adjacent dosing pulses Δt2 a new dosing pulse i is not yet displayed. If, under comparable conditions, a time-dependent, downwardly deviating current consumption I ** (t) is determined, this can be an indication that the stirring and / or shearing and homogenizing phase, which is also defined by the time interval between adjacent metering pulses Δt2, is excessively long is or that no adequate amount of powdery substance m _{P was} dosed in this phase.

As soon as the powdery substance P is evenly distributed in the absorbing liquid F or in the absorbing mixed product M, that is, it has been distributed as homogeneously as possible and possibly dissolved, the time-dependent current consumption I (t) subsides, to the time-dependent course of a reference current consumption I _o (t), which is characteristic of the stirring and / or shearing and homogenizing power to be achieved on the homogenized mixed product M under the conditions of the assigned time-dependent curve of the dry matter concentration c (t) (see FIGS. 3 to 5 : approximately linear time-dependent course of a reference current consumption I _o (t); Figure 6 : degressive time-dependent course of a reference current consumption I _o (t)). The time-dependent course of a reference current consumption I _o (t) begins at time t = 0, at which only the pure liquid F is present, with an initial value of a reference current consumption I _o (t = 0) = I ₀ (see FIG Figures 3 to 6 ). The related course of a reference _{current consumption I o} (t) is stored in the specification data D, and it is dependent on the recipe of the mixed product M and the reaction conditions for the mixing process.

At the end of the time interval between adjacent metering pulses Δt2 and when the time-dependent current consumption I (t) deviates from the respective assigned value in the time-dependent course of a reference current consumption I _o (t) by more than a specified tolerance, with a deviation either upwards or downwards (please refer Figures 3, 4 ), the duration of the dosing pulse Δt1 for the subsequent dosing pulse is shortened in the first case and lengthened in the second case. The tolerance consists of a specification of a permissible current exceedance ΔI1 and a permissible current undercurrent ΔI2 ( Figure 3 ).

The case of foreshortening is in Figure 4 shown, whereby in the case example shown, the duration of the dosing pulse Δt1 and thus also the associated time segment of adjacent dosing pulses Δt2 have been halved by way of example (Δt1 / 2; Δt2 / 2). In this metering mode, too, at the end of the period of adjacent metering pulses Δt2 / 2, a check is carried out to determine whether a time-dependent current consumption I * (t), I ** (t) is present within the specified tolerance makes necessary correction in the sense described above.

The shortening or lengthening of the duration of the dosing pulse Δt1 occurs when a current corridor determined by the permissible current exceedance ΔI1 or the permissible current undercurrent ΔI2 due to the time-dependent current consumption I * (t), I ** (t) deviating upwards or downwards. is left. The permissible current excess and the permissible current shortfall ΔI1, ΔI2 are preferably each determined by a percentage of the associated time-dependent course of a reference current consumption I _o (t). Furthermore, the amount of shortening or lengthening of the duration of the metering pulse Δt1 is preferably determined as a function of the amount of deviation of the time-dependent current consumption I (t) from the assigned time-dependent course of a reference current consumption I _o (t). The permissible current excess ΔI1 and permissible current shortfall ΔI2 ultimately determined by the respective formulation of the mixed product M can be part of the specification data D for the mixing process.

In the course of controlling the introduction of the powdery substance P into the at least one liquid F, targeted, recipe-dependent control parameters S, namely the duration of the dosing pulse Δt1 and the time interval between adjacent dosing pulses Δt2, are stored and used for subsequent controls of the same recipes.

The control device 30 of the mixing device 100 is set up according to the invention so that it can provide the recipe-dependent default data D and the recipe-dependent control parameters S in the form of the duration of the metering pulse Δt1 and the time interval between adjacent metering pulses Δt2. The control device 30 also has at least the signal pick-up 16 designed as a measuring device ( Figure 1 ), which records the time-dependent current consumption I (t) of the stirring device 24 and / or the shearing and homogenizing device 26 ( Figures 3, 4 ). According to the invention, the control device 30 controls the closed or open position of the valve closing element 8 ( Figure 2 ) as a function of the time-dependent current consumption I (t) and in relation to the default data D and the control parameters S.

The method results in the time-dependent course of a dry matter concentration c (t), which according to plan _{ends in the specified end value c E} , with the time-dependent course of a dry matter concentration c (t) without saturation character (approximately linear time-dependent course; see Figures 3 to 5 ) or the time-dependent course of a dry matter concentration with saturation character (degressive time-dependent course; see Figure 6 ) is to be distinguished. The time-dependent course of a dry matter concentration c (t) ending in the predetermined end value c _E is defined by the sequence of specific metering pulses i, ie clearly defined by the duration of the metering pulse Δt1 and the time interval between adjacent metering pulses Δt2.

For the time-dependent course of a dry matter concentration c (t) without saturation character, starting at c (t = 0) = 0 for the pure liquid F ( Figure 5 ), as can be described by the equations (1, 1a) given above (c (t) = k1 V t), provides an embodiment of the method that this course is determined by a fixed time duration-time interval ratio V between the time duration of the dosing pulse Δt1 and the assigned time interval between adjacent dosing pulses Δt2 is defined (V = Δt1 / Δt2 = constant). In the event of deviations from the time-dependent course of a reference _{current consumption I o} (t), the duration of the metering pulse Δt1 is shortened according to the invention with a constant duration-time interval ratio V (as shown in FIG Figure 4 in contrast to Figure 3 is shown qualitatively as an example) or extended. This technical control measure with a Fixed time-duration-time interval ratio V inevitably leads in the same ratio to a corresponding shortening or lengthening of the time interval between adjacent metering pulses Δt2, based on the subsequent metering pulse i.

sieht eine weitere Ausgestaltung des Verfahrens vor, dass dieser Verlauf durch ein variables Zeitdauer-Zeitabstand-Verhältnis V zwischen der Zeitdauer des Dosierimpulses Δt1 und dem zugeordneten Zeitabstand benachbarter Dosierimpulse Δt2 definiert ist (V = Δt1/Δt2 ≠ konstant), wobei

• bei Abweichung der zeitabhängigen Stromaufnahme I(t) von dem jeweils zugeordneten Wert im zeitabhängigen Verlauf einer Referenzstromaufnahme I_o(t) um mehr als die vorgegebene Toleranz nach oben das Zeitdauer-Zeitabstand-Verhältnis V verkleinert und
• bei Abweichung der zeitabhängigen Stromaufnahme I(t) von dem jeweils zugeordneten Wert im zeitabhängigen Verlauf einer Referenzstromaufnahme I_o(t) um mehr als die vorgegebene Toleranz nach unten das Zeitdauer-Zeitabstand-Verhältnis V vergrößert wird.

For the time-dependent course of a dry matter concentration c (t) with saturation character ( Figure 6 ), as can be described by equation (2) given above $\left(\mathbf{c}\left(\mathbf{t}\right)\approx \mathbf{<figure-callout\; id="2"\; label="k"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">k</figure-callout>}2\frac{{\displaystyle {\sum }_{\mathit{t}=0}^{\mathit{<figure-callout\; id="1"\; label="t\; \Delta \; t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}\mathrm{\Delta }\mathbf{t}\mathbf{}1}}{{\mathrm{\rho }}_{\mathrm{M.}}\left(\mathbf{t}\right)}\right),$

Another embodiment of the method provides that this course is defined by a variable time duration / time interval ratio V between the time duration of the metering pulse Δt1 and the assigned time interval between adjacent metering pulses Δt2 (V = Δt1 / Δt2 ≠ constant), where

• if the time-dependent current consumption I (t) deviates from the respectively assigned value in the time-dependent course of a reference current consumption I _o (t) by more than the specified tolerance upwards, the duration-time interval ratio V is reduced and
• if the time-dependent current consumption I (t) deviates from the respectively assigned value in the time-dependent course of a reference current consumption I _o (t), the time-duration-time-interval ratio V is increased by more than the specified tolerance.

The respective course of a dry matter concentration c (t) is over the time period t, starting with c (t = 0) = 0 for the pure liquid F ( Figure 6 ), increasing degressively because the continuously pulsed flow of the powdery substance ṁ _P , viewed over the entire period t of the mixing process, is preferably constant (ṁ _P = const), but the duration of the dosing pulse Δt1 steadily decreases and thus a steadily decreasing one Amount of powdery substance m _{P is} metered in. The mass flow of powdery substance ṁ _{P is introduced into an existing almost unchangeable volume of the mixed product V M} (V _M ≈ constant) in the time period t of the entire mixing process with an almost unchangeable fill level N in the mixing container 100, with a density ρ _{M of} the mixed product M increasing, namely according to the time-dependent course of a dry matter concentration c (t), which grows _{to the predetermined end value c E.}

Figure 6 shows, depending on the time-dependent course of a dry matter concentration c (t), how the respective dosed amount of powdery substance mp = ṁ _P Δt1 steadily decreases, whereby the respectively assigned time-dependent current consumption I (t) is in each case at the end of the time interval between adjacent dosing pulses Δt2 has approximated to the assigned time-dependent course of a reference current consumption I _o (t) or is largely congruent with this. A related course describes a successful mixing process, which on the one hand protects the mixed product M and on the other hand is designed to be energy-efficient. It does not require any control measures in the sense explained above. Only when deviations from the permissible current excess or current shortfall ΔI1, ΔI2 occur, do the control mechanisms, as used in the first method in connection with the Figures 3 and 4 have been described.

These control measures with a variable duration-time interval ratio V require the control device 30 to be able to shorten or lengthen the duration of the metering pulse Δt1 with an unchanging time interval between adjacent metering pulses Δt2 or to adequately adjust the time interval between adjacent metering pulses Δt2 with the same duration of the metering pulse Δt1 lengthen or shorten.

The control measures according to the invention therefore essentially consist in both refinements of the method in that the duration of the metering pulse Δt1 and the time interval between adjacent metering pulses Δt2 are selected in such a way that at the respective end of the time interval between adjacent metering pulses Δt2 the time-dependent determined current consumption I (t) for Stirring and / or shearing and homogenizing the temporarily present mixed product M * _{approximates the time-dependent course of a reference current consumption I o} (t), which is required for the relevant treatment of the homogenized mixed product M, within the scope of a practically relevant permissible tolerance.

LIST OF REFERENCE SIGNS OF THE ABBREVIATIONS USED

1000

Mixing device

100

Mixing tank

100.1

Container jacket

100.2

upper container bottom

100.3

lower container bottom (conical; conical)

100.4

Outlet nozzle

100.5

Inlet connection

20th

Inlet valve

30th

Control device

40

first drive motor

50

second drive motor

2

Valve body

2a

Valve seat

2 B

Seat opening

2c

Pipe connection

4th

Lantern housing

6th

Drive housing

8th

Valve closing member

8a

Valve disc

8b

Valve stem

10

Seat seal

12th

Return spring

14th

Control head housing

16

Signal pickup

18th

Feed line

22nd

Signal line

24

Stirring device

26th

Shearing and homogenizing device

D.

Default data

F.

liquid

Io

Initial value of a reference current consumption (for the homogenized mixed product M; I ₀ (t = 0) = I ₀ )

Io (t)

time-dependent course of a reference current consumption

I (t)

Time-dependent power consumption (for the temporarily present mixed product M *)

I * (t)

time-dependent current consumption deviating upwards

I ** (t)

time-dependent current consumption deviating downwards

ΔI1

permissible current excess

ΔI2

permissible current shortfall

M.

Mixed product

M *

temporarily available mixed product

N

Level

P.

powdery substance

S.

Control parameters

T

Mixing or dissolving temperature

V

Duration-time interval ratio (V = Δt1 / Δt2)

VM

Volume of the mixed product

ρM

Density of the mixed product

c

Dry matter concentration

c (t)

Time-dependent course of a dry matter concentration

cE

specified end value (of the time-dependent course)

H

Height of the liquid column

i

Dosing pulse

k1

first constant of proportionality $\left(\mathrm{k}\right)$$\left(\mathrm{}1=\frac{{\stackrel{.}{\mathrm{m}}}_{\mathrm{P.}}}{{\mathrm{m}}_{\mathrm{F.}}}\right)$

k2

second constant of proportionality $\left(\mathrm{k}\right)$$\left(\mathrm{}2\approx \frac{{\stackrel{.}{\mathrm{m}}}_{\mathrm{P.}}}{{\mathrm{V}}_{\mathrm{M.}}}\right)$

mF

Amount of liquid

mP

Amount of powdery substance

ṁP

Mass flow of powdery substance

ṁP (t)

Time-dependent mass flow of powdery substance

n1

first speed

n2

second speed

p

Pressure above the liquid column

t

Time (general) or duration of the mixing process

Δt1

Duration of the dosing pulse

Δt2

Time interval between adjacent dosing pulses

Claims (10)

1. A method for controlling the introduction of a pulverulent material (P) into a liquid (F) consisting of at least one component for a batch mixing method,

   • in which the introduction and treatment of the pulverulent material (P) takes place under the conditions of a dwell time behavior of a discontinuously working homogenous reaction tank such that

   ∘ an amount of liquid (m_F) is presented and the pulverulent material (P) is discontinuously fed into this liquid (F),

   ∘ the liquid (F) and the pulverulent material (P) are constantly stirred and/or mixed to form a mixed product (M) and the mixed product (M) is homogenized, and

   ∘ the pulverulent material (P) is fed in until a time-dependent progression of a dry material concentration (c(t)) of the pulverulent material (P) in the mixed product (M) has grown to a specified end value (c_E),

   characterized in that

   • a formulation of the mixed product (M), at least regarding the time-dependent progression of a dry material concentration (c(t)) associated with the specified end value (c_E), and the reaction conditions are each specified in the form of default data (D),

   • the discontinuous feeding of the pulverulent material (P) takes place in a pulsed manner by a chronological sequence of metering pulses (i) which are each characterized by a volume flow of the pulverulent material (ṁ_P), a duration of the metering pulse (Δt1), and a time interval between neighboring metering pulses (Δt2),

   • the time-dependent progression of a dry material concentration (c(t)) ending in the specified end value (c_E) is defined by the sequence of clearly defined metering impulses (i),

   • a time-dependent current consumption (I(t)) is ascertained which is proportional to a mixing and/or shearing and homogenizing power required for a temporarily present mixed product (M*),

   • a time-dependent progression of a reference current consumption (I_o(t)) is used from the default data (D) which is characteristic of the stirring and/or shearing and homogenizing power to be delivered to the homogenized mixed product (M) under the conditions of the associated time-dependent progression of a dry material concentration (c(t)), and

   • at the end of the time interval between neighboring metering pulses (Δt2) and when the time-dependent current consumption (I(t)) deviates from the respectively associated value in the time-dependent progression of a reference current consumption (I_o(t)) by more than a specified tolerance, either higher or lower, the duration of the metering pulse (Δt1) for the following metering pulse (i) is shortened in the first case and extended in the second case.
2. The method according to claim 1,
   characterized in that
   time-dependent progressions of a dry material concentration (c(t)) without saturation are defined by a fixed duration-to-time interval ratio (V) between the duration of the metering pulse (Δt1) and the associated time interval between neighboring metering pulses (Δt2) (V = Δt1/Δt2 = constant).
3. The method according to claim 1,
   characterized in that
   time-dependent progressions of a dry material concentration (c(t)) with saturation are defined by a variable duration-to-time interval ratio (V) between the duration of the metering impulse (Δt1) and the associated time interval between neighboring metering pulses (Δt2) (V = Δt1/Δt2), wherein

   • when the time-dependent current consumption (I(t)) deviates from the respective associated value in the time-dependent progression of a reference current consumption (I_o(t)) by more than the specified upper tolerance, the duration-to-time interval ratio (V) is reduced, and

   • when the time-dependent current consumption (I(t)) deviates from the respective associated values in the time-dependent progression of a reference current consumption (I_o(t)) by more than the specified lower tolerance, the duration-to-time interval ratio (V) is increased.
4. The method according to one of the preceding claims,
   characterized in that
   the volume flow of the pulverulent material (ṁ_P) over the duration of the metering pulse (Δt1) is constant.
5. The method according to one of the preceding claims,
   characterized in that
   the shortening or the extending of the duration of the metering pulse (Δt1) takes place when a current corridor, determined by a permissible current excess (ΔI1) or a permissible current undershoot (ΔI2), respectively, is departed from by a current consumption that deviates upwards (I*(t)) or a current consumption that deviates downwards (I**(t)), wherein the permissible current excess and the permissible current undershoot (ΔI1, ΔI2) are each determined by a percentage of the associated time-dependent progression of a reference current consumption (I_o(t)).
6. The method according to one of the preceding claims,
   characterized in that
   the measure of the shortening or the extending of the duration of the metering pulses (Δt1) is determined depending on the measure of the deviation of the time-dependent current consumption (I(t), I*(t), I**(t)) from the associated time-dependent progression of a reference current consumption (I_o(t)).
7. The method according to one of the preceding claims,
   characterized in that
   the further formulation-dependent default data (D) on which the control of the introduction of the pulverulent material (P) into the at least one liquid (F) is based are obtained and saved from empirical values from earlier mixing processes, wherein these default data (D) are

   • a mixing or solution temperature (T),

   • a pressure above the liquid column (p),

   • rotational speeds (n1, n2) of apparatuses for stirring and/or shearing and homogenizing, and

   • a permissible current excess (ΔI1) and a permissible current undershoot (ΔI2) dependent on the associated progression of a reference current consumption (I_o(t)).
8. The method according to one of the preceding claims,
   characterized in that
   the expedient formulation-dependent control parameters (S) obtained over the course of controlling the introduction of the pulverulent material (P) into the at least one liquid (F), i.e.

   • duration of the metering pulse (Δt1) and

   • time interval between neighboring metering pulses (Δt2),

   are saved and used for following controls of identical formulations.
9. A mixing device for performing the method according to claim 1, with a mixing container (100) that has an intake connection (100.5) for feeding in for a liquid (F), an outlet spigot (100.4) for discharge for a mixed product (M), and a stirring apparatus (24) and/or a shearing and homogenizing apparatus (26), with an inlet valve (20) arranged on the mixing container (100) with a valve closing member (8), with the valve closing member (8) with which the inlet valve (20) can be adjusted either between fully closed (closed position) or fully open (open position), with the inlet valve (20) through which a pulverulent material (P) is introduced into the liquid (F), with a control apparatus (30) associated with the inlet valve (20) with which the valve closing member (8) can be transitioned to the closed or the open position,
   characterized in that

   • the control apparatus (30) provides formulation-dependent default data (D) and formulation-dependent control parameters (S) in the form of the duration of the metering pulse (Δt1) and the time interval between neighboring metering pulses (Δt2),

   • the control apparatus (30) has at least one sensor (16) formed as a measuring apparatus that detects a time-dependent current consumption (I(t)) of the stirring apparatus (24) and/or the shearing and homogenizing apparatus (26), and

   • the control apparatus (30) controls the closed and open position of the valve closing member (8) depending on the time-dependent current consumption (I(t)) and in relation to the default data (D) and the control parameters (S).
10. The mixing device according to claim 9,
    characterized in that
    the valve closing member (8) is formed, at least in its region that is in contact with powder, as a cylindrical rod with a constant diameter on which a valve disk (8a) is formed with a constant diameter.

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