DE102021000618B4 - Method for controlling a drying process of a product in a dryer - Google Patents

Abstract

in dem Trockner (2), dadurch gekennzeichnet, daß bei der Regelung der Feuchte $\left(\varrho \right)$

durch die Steuer- und/oder Regelungseinrichtung (5) auf die Temperatur (T_L) der Trocknungsluft (L) und/oder des Produktes (T₁) und bei der Regelung der Temperatur (T_L) der Trocknungsluft (L) und/oder des Produktes (1) auf die Feuchte $\left({\varrho }_{\text{L},\text{1}}\right)$

in dem Trockner (2) und/oder des Produktes (1) geschlossen wird, wobei bei der Regelung der Feuchte $\left({\varrho }_{\text{L},\text{1}}\right)$

durch über einen Feuchteverlauf während der Trocknung abgeleitete Temperaturverläufe nachfolgende Trocknungsverfahren durch eine ausschließliche Regelung der Temperatur (T_L,1) über die Verfahrensdauer durchgeführt werden oder zur Regelung des Verfahrens angewandte Trocknungsprogramme sich auf Daten stützen, die in langen Versuchsreihen vom Hersteller des Trockner ermittelt werden oder die Daten teilweise oder ganz aus einer cloud (8) stammen oder sich auf ein Serversystem stützen.

Method for controlling a drying process of a product (1) in a dryer (2), with a fan (3) for conveying drying air (L) to the product (1), with a heating device (4) for heating the drying air (L) and with a control and/or regulating device (5) for regulating a device (6) for controlling the temperature (T _L,1 ) and/or the humidity $\left(\varrho \right)$

in the dryer (2), characterized in that when regulating the humidity $\left(\varrho \right)$

by the control and/or regulating device (5) on the temperature (T _L ) of the drying air (L) and/or the product (T ₁ ) and when regulating the temperature (T _L ) of the drying air (L) and/or the product (1) on the humidity $\left({\varrho }_{\text{L},\text{1}}\right)$

in the dryer (2) and/or the product (1), whereby the humidity control $\left({\varrho }_{\text{L},\text{1}}\right)$

by means of temperature profiles derived from a moisture content profile during drying, subsequent drying processes are carried out by exclusively controlling the temperature (T _L,1 ) over the duration of the process, or drying programs used to control the process are based on data determined in long series of tests by the manufacturer of the dryer or the data originate partly or entirely from a cloud (8) or are based on a server system.

Description

The invention relates to a method for controlling a drying process of a product in a dryer, with a fan for conveying drying air to the product, with a heating device for heating the drying air and with a control and/or regulating device for regulating a device for controlling the temperature and/or the humidity in the dryer, according to the preamble of claim 1.

Industrial products, but also products from agricultural production of plant or animal origin and also products derived from them for the manufacture of pharmaceuticals are usually converted into a state in which they are either further processed as semi-finished or finished products in the case of industrial products, or are used by a customer for a specific purpose, or in the case of products from agricultural production, they achieve storage stability while at the same time maintaining product quality over a period of time that is long enough for the end consumer, using dryer designs that are suitable for the product in question, such as belt dryers, shaft dryers, batch dryers or chamber or rack dryers.

Agricultural products in particular have a natural initial moisture content of about 35% or more and their storage stability is usually only achieved at a moisture content of 15% for plant products and below 20% for products of animal origin.

In order to achieve the desired end qualities of drying products of industrial nature but also in particular of agricultural origin, such as strength values of dried building materials or ingredients of products of agricultural origin, such as nutrient content, vitamin content, acid or sugar content but also the color and texture of the dried product, it has been necessary to determine and monitor not only the temperature of the drying air but also its moisture content and often also its flow velocity over the duration of a drying process.

Customers often have specific requirements and wishes regarding the final or drying product to be achieved, which make the process and the dryer used to carry it out complex and expensive to implement or purchase.

The EP 2 184 999 B1 describes a drying system consisting of a drying chamber with a fresh air supply with devices for conditioning the fresh air, a process air discharge with a monitoring and control device for controlling and regulating the air flows, the humidity and the temperature in the drying system. The drying system is complex.

The EN 10 2016 003 192 A1 describes a method and a device for drying agricultural products, with a heating device that heats a drying air flow and the drying air is then fed into a drying room. In the flow direction of the air flow upstream of the heating device, the drying air flow is preheated by a heat exchanger, whereby the warm and moist exhaust air emerging from the drying room is used in the manner of a recuperator. This results in more efficient use of the energy used and a better efficiency in the drying of agricultural products. The heat exchanger preferably has two inlets and outlets.

The EN 10 2007 004 473 A1 describes a method for heating and drying items to be dried with a gas, such as steam containing air, preferably for drying laundry. Here, steam is fed to the items to be dried, whereby the items to be dried are heated by condensing steam. In a further process step, superheated, dry steam is then fed to the items to be dried.

The EN 10 2005 047 524 A1 describes a method for optimizing the operation of dryers for bulk goods, such as agricultural crops. A sample of the product is taken before drying and dried in a sample dryer. An initial moisture content is determined from the weight loss of the sample and the moisture difference to be removed during drying is determined from the initial moisture content of the sample and a desired target moisture content of the product.

• - im Probentrockner wird der Gewichtsverlust der Probe über die Zeit erfaßt und eine Probenmeßkurve ermittelt,
• - die Probenmeßkurve wird mit Daten einer Datensammlung und deren Referenzmeßkurven für früher gemessene Proben von in realen Guttrocknern getrockneten Gütern verglichen,
• - aus der Datensammlung wird eine am besten zu der Probenmeßkurve passende Referenzmeßkurve entnommen und deren Betriebsparameter benutzt,
• - der Trockner wird mit den Betriebsparametern versorgt und mit diesen betrieben.

The procedure comprises the following steps:

• - in the sample dryer, the weight loss of the sample is recorded over time and a sample measurement curve is determined,
• - the sample measurement curve is compared with data from a data collection and its reference measurement curves for previously measured samples of goods dried in real goods dryers,
• - a reference curve that best matches the sample measurement curve is taken from the data collection and its operating parameters are used,
• - the dryer is supplied with the operating parameters and operated with these.

The DE 197 43 378 A1 describes a rack dryer whose housing comprises a drying space, which in turn is divided into a drying chamber and a blower chamber fluidically connected to it.

In the drying chamber, vertically stacked racks are arranged on top of each other, which are used to store drying products and through which drying air flows. A suction chamber is arranged in front of the blower chamber and an expansion chamber is arranged downstream of the blower chamber in order to make the flow conditions in the rack dryer as low as possible.

The DE 32 41 544 A1 describes a method and a device for monitoring and/or controlling drying, granulating, instantizing, drageeing and film coating processes in which drying air is supplied to the respective product and wherein the humidity of the exhaust air and the humidity of the supply air are measured and their humidity difference is used to control the respective work process.

The US 5 050 313 A1 describes a dryer and a method for controlling a drying process with this dryer for drying a product, with a fan for conveying the drying air to the product, with a heating device for heating the drying air and with a control and/or regulating device for regulating a device for controlling the temperature and/or the humidity in the dryer.

Based on this prior art, the invention is based on the object of specifying a method for controlling the drying process of a product, which can be carried out with little measurement and control expenditure and which enables the achievement of predeterminable final qualities of the dried product.

The problem is solved by a method having the features of claim 1 in its entirety.

By controlling and monitoring the influence of a number of physical parameters of the drying air on the final quality of the drying product to be achieved in the drying process, i.e. when regulating the humidity in the dryer and/or the product, the control and/or regulating device draws conclusions about the temperature of the drying air and/or the product, and when regulating the temperature of the drying air and/or the product, the humidity in the dryer and/or the product is drawn, a method and a technical measure are specified that simplify the method and simplify the design effort for a dryer designed for this purpose. In this case, subsequent drying processes can be carried out by exclusively regulating the temperature over the duration of the process using temperature curves derived from a humidity curve during drying. The drying programs can be based on data that was determined by the manufacturer of the dryer itself in long series of tests. However, it can also be advantageous to control the data for controlling the drying process partially or entirely from a cloud (IoT) or a server system.

This involves using a sufficient sample size of dried products and their quality characteristics from drying processes carried out during the development of the process and thus, for example, only the temperature of the drying air or the product to be dried is monitored and controlled, or only the humidity of the drying air or the product is monitored and controlled, while the temperature of the drying air remains constant.

Despite this simplification step, surprisingly precise quality characteristics of the dried product can be achieved. Usually combined with a reduction in the drying time.

Preferred embodiments result from the subclaims.

A particular advantage of the method according to the invention is that the method, by only controlling the temperature or humidity of the drying air or the product, makes it possible to achieve important product properties of the product after completion of the drying process, which could not be monitored during the drying process or which could only be monitored with difficulty and great effort, or which cannot be determined by non-destructive analysis.

The process is therefore characterized by its structural and procedural simplicity and good controllability and ultimately enables the desired product properties to be achieved.

For example, surface hardness or tensile and compressive strength of industrial products, their colours and surface texture can be determined Define the end of drying by controlling the temperature of the drying air alone.

For products of agricultural origin, for example, vitamin, acid content, protein content, color, sugar content, essential oil content, etc. can be derived from the respective product properties. Furthermore, the physical material properties such as weight, specific gravity, volume or surface area or texture after drying.

Therefore, no additional sensors and measuring technology are required to successfully carry out the method according to the invention.

The purely temperature-controlled drying processes are therefore preceded by several calibration or calibration processes with moisture detection and the course of the purely temperature-controlled drying process is maintained by the manufacturer of a dryer that can carry out the drying process according to the invention. For example, in the form of files in a data storage device of the control and/or regulating device.

In a dryer that can be manufactured particularly inexpensively for carrying out the method according to the invention, the device for controlling the temperature and/or the humidity in the dryer is designed in the form of a flap that influences the flow channel cross-section for drying air towards the product. This means that the flow channel cross-section can be changed many times during the drying process and at intervals of a few seconds, for example, and the temperature can therefore be influenced and controlled.

In the simplest case, the drying process is only controlled via a fixed temperature-time axis. For many products, especially those of agricultural origin, a characteristic moisture profile occurs in the drying air and thus also in the product itself during drying.

For example, representative extensive tests have shown that in a first phase after the start of drying, an approximately linear progression of the relative humidity in the dryer occurs, whereby the humidity can remain constant or decrease linearly.

After this first drying phase, the relative humidity drops in a characteristic manner and only specifically for the respective product, so that the temperature of the drying air can be reduced to a new, preset value before this drop occurs.

Depending on the characteristics of the product's behavior when releasing moisture over the drying period, the drying process can be divided into a first phase (usually higher temperature) and a second phase or further phases. In the first phase, in addition to the obligatory monitoring of the temperature, the humidity can also be monitored.

In the phases of the drying process, the control and/or regulating device can specify either the temperature or the humidity and the time intervals so that the user of the process, which is preferably integrated in a dryer and its control system optimized for this purpose, does not need to have any special knowledge of drying the corresponding products, and thus receives a dryer that is very easy to operate compared to dryers according to the state of the art.

This is also helped by the fact that the control and/or regulating device comprises a program controller, which can also be programmable, which selects a basic drying process from a large number of drying processes or programs based on the initial moisture content of the product or a product or air humidity after a warm-up phase of the dryer.

The updating of these data for controlling the drying process can also come from the provision of data from some or many of the companies carrying out the process.

It is advisable to check the plausibility of the data before using it. As mentioned, the temperature of the drying air on the product can be easily controlled by simply placing a flap in the flow channel carrying the drying air, which opens or closes it partially or completely.

The flap can also work as an iteratively fully opening or fully closing control element in the flow channel and can open and close again in a sawtooth operation at short intervals of, for example, one or a few seconds, whereby the temperature of the drying air on the product and the product temperature can be controlled. It goes without saying that the flap can also be designed and operated in a continuously adjustable manner.

To dehumidify the drying air and/or to change its temperature, the A recuperator can be installed upstream or downstream of the device. This can save up to 90% of heating energy. It also has a dampening effect on the regulation of the temperature and humidity of the drying air.

In particular, the flap controls a large cross-section of the flow channel when the temperature of the drying air is lower than a target temperature and/or the humidity of the drying air is greater than a target humidity.

• 1 Einen schematischen, nicht maßstäblichen Längsschnitt durch einen als Kammertrockner gebildeten Trockner zur Durchführung des erfindungsgemäßen Verfahrens,
• 2 einen Phasenverlauf der Ansteuerung der Einrichtung zur Steuerung der Temperatur und/oder der Feuchte in dem Trockner am Beispiel der Öffnung- und Schließzeiten einer den Strömungskanalquerschnitt steuernden Klappe,
• 3 einen Temperaturverlauf der Trocknungsluft bei dem Verfahren gemäß 2,
• 4 einen Temperaturverlauf der Oberflächentemperatur des zu trocknenden Produktes und einen Temperaturverlauf der Trocknungsluft über die Trocknungszeit aufgetragen,
• 5 ein weiteres Beispiel eines typischen Verlaufes der Temperatur der Trocknungsluft über die Trocknungszeit aufgetragen,
• 6 ein weiteres Beispiel eines Phasenverlaufes der Ansteuerung der Einrichtung zur Steuerung der Temperatur und/oder der Feuchte in dem Trockner am Beispiel der Öffnungs- und Schließzeiten einer den Strömungskanalquerschnitt steuernden Klappe,
• 7 einen Temperaturverlauf über die Trocknungszeit, wobei die Tempera tur nicht konstant ist, sondern entsprechend des Verlaufes der Feuchte der Trocknungsluft geregelt wird; und
• 8 Verläufe der Feuchte in Abhängigkeit von der Trocknungsdauer und der Regelung der Temperatur der Trocknungsluft.

The procedure is explained below using the drawing. The drawing shows:

• 1 A schematic, not to scale, longitudinal section through a dryer designed as a chamber dryer for carrying out the method according to the invention,
• 2 a phase progression of the control of the device for controlling the temperature and/or humidity in the dryer using the example of the opening and closing times of a flap controlling the flow channel cross-section,
• 3 a temperature profile of the drying air in the process according to 2 ,
• 4 a temperature curve of the surface temperature of the product to be dried and a temperature curve of the drying air over the drying time,
• 5 another example of a typical course of the temperature of the drying air over the drying time,
• 6 another example of a phase progression of the control of the device for controlling the temperature and/or humidity in the dryer using the example of the opening and closing times of a flap controlling the flow channel cross-section,
• 7 a temperature profile over the drying time, whereby the temperature is not constant but is regulated according to the humidity profile of the drying air; and
• 8th Humidity trends depending on the drying time and the control of the temperature of the drying air.

In 1 is shown in a schematic, not to scale longitudinal section in the vertical direction, a dryer 2 formed as a chamber dryer for drying products 1, such as industrial series parts in the type of water-containing building material semi-finished products or products of agricultural origin in the type of fruit, vegetables, meat products or agricultural products 1 for the production of pharmaceuticals.

The dryer 2 has a cube- or cuboid-shaped housing in which the product 1 to be dried is arranged, shown schematically.

in dem Trockner 2 und/oder an dem Produkt 1 dient, gebildet. In Blickrichtung auf 1 ist in einer unteren, linken Ecke des Strömungskanals 7 ein Gebläse 3 angeordnet, das Trocknungsluft L über eine, dem Gebläse 3 stromab nachgelagerte Heizeinrichtung 4 von der Öffnung 10 ansaugt und mit einer Temperatur T_L zu dem Produkt 1 fördert.At one, looking towards 1 left front wall, a flow channel 7 is arranged, which continues over the floor of the dryer 2. The flow channel 7 serves to transport drying air L, which is arranged at an opening 10 in the upper left corner of the dryer 2, opening to the surroundings of the dryer 2. This is closed by a movable flap 9, which serves as a device 6 for controlling the temperature T _L,1 and/or the humidity ${\varrho }_{\text{L},\text{1}}$

in the dryer 2 and/or on the product 1. Looking towards 1 In a lower, left corner of the flow channel 7, a fan 3 is arranged, which sucks in drying air L from the opening 10 via a heating device 4 arranged downstream of the fan 3 and conveys it to the product 1 at a temperature T _L.

The device 6 formed as a flap 9 is controlled by a control and/or regulating device 5 in its pivoting angle and thus in the degree to which it opens or closes the opening 10.

Accordingly, when the flap 9 is in the open position, ambient air, which is generally cooler than the drying air L, can flow into the flow channel 7, or when the flap 9 is closed, the temperature T _L of the drying air L and thus generally also the temperature T ₁ can be raised in recirculation mode.

In principle, it is therefore possible to influence and regulate the temperature T _L,1 in the dryer 2, even if the heating device 4 always heats the drying air L at a constant level.

In 1 With the opening 10 closed, a recirculation mode is shown, ie the drying air L passing through the product 1 and flowing through it or along it is again guided over the heating device 4 and guided by the fan 3 via the flow channel 7 back to the product 1.

When the flap 9 is open or partially open, drying air L enriched with moisture passes through the opening 10 or another opening not shown into the open air, outside the dryer 2.

in dem Trockner 2 in Form der in 1 gezeigten Klappe 9 gezeigt. Zu Beginn des Trocknungsverfahrens ist, wie gezeigt, die Klappe 9 über einen längeren Zeitraum geöffnet, was insbesondere bei Produkten 1 mit hoher Oberflächenfeuchte wichtig ist. Wie in der zu 2 nebenstehenden 3 gezeigt, ist dies erforderlich, um die Produkttemperatur T₁ so rasch als möglich auf eine dann gleichbleibende Temperatur anzuheben um eine je Zeiteinheit möglichst große Feuchteabgabe zu ermöglichen.In 2 is an example of many possible methods according to the invention a phase curve of a device 6 controlled by the control and/or regulating device 5 for controlling the temperature T _L,1 and/or the humidity ${\varrho }_{\text{L},\text{1}}$

in the dryer 2 in the form of 1 shown Flap 9 is shown. At the beginning of the drying process, as shown, flap 9 is open for a longer period of time, which is particularly important for products 1 with high surface moisture. As shown in the 2 adjacent 3 As shown, this is necessary in order to raise the product temperature T ₁ as quickly as possible to a constant temperature in order to enable the greatest possible moisture release per unit of time.

As the 2 and 3 To illustrate, after this first phase I, in which the flap 9 is open and maximum moisture is transported from the product 1 through the opening 10 to the outside, in the second phase II the flap 9 can be opened and closed in a controlled operation at discrete intervals. Depending on the selected interval length, the temperature T ₁ of the product 1 or the drying air L can then be reduced even at a constant temperature of the heating device 4 and the drying air L emitted from it (cf. 6 , 7 ).

The 2 and 3 The methods shown are also characterized by the fact that the flap 9 is fully opened or closed, thus the cross-section A of the flow channel 7 is full of fresh drying air, which has been discharged from the environment of the dryer 1 or is completely flowed through by circulating air in the dryer 2.

The selected temperatures T _L of the drying air L are shown in 2 to 7 derived from previous drying processes and their moisture profiles during the drying of the respective product 1. This guarantees specific quality characteristics of the respective end product of a respective drying process. The products 1 do not have to be examined for their quality characteristics during drying using complex processes that are not always non-destructive.

For this purpose, the control and/or regulating device 5 preferably has a programmable program controller and a data memory. Depending on the type of product in question and its initial moisture content, a selection can be made from a large number of stored drying programs.

How 1 shows, the control and/or regulating device 5 or its data storage can also be provided with data from previous drying processes as well as data from a cloud 8.

4 The further curve shows a temperature profile T ₁ of the product 1 over the drying period. The air temperature T _L of the drying air L set and regulated for drying the product 1 is plotted above this. In a first phase I of drying, the temperature T _L of the drying air L is selected to be higher so that a desired moisture release from the product 1 is achieved and the surface temperature of the product 1 is brought to a temperature T ₁ selected for rapid moisture release.

After the desired surface temperature T ₁ of product 1 is reached, the drying air temperature T _L is adjusted to and maintained at approximately the same value as the surface temperature T ₁ .

wobei dann die Temperatur T_L der Trocknungsluft L wie in 5 gezeigt, reduziert werden kann. 5 shows a simplification of the temperature control T _L of the drying air L to obtain this result of the surface temperature T ₁ , as in 4 shown to be able to achieve. This in 5 The curve of the temperature of the drying air L shown in Figure 1 allows humidity curves as shown in 8th For many products 1, especially from agriculture, the characteristic drop in product moisture shown occurs during the drying process. ${\varrho }_{\text{1}},$

where the temperature T _L of the drying air L is as in 5 shown, can be reduced.

List of reference symbols

1

product

2

dryer

3

fan

4

Heating device

5

Control and/or regulating device

6

Furnishings

7

Flow channel

8th

cloud

9

flap

10

Opening

L

Drying air

TLS

Temperature of drying air

T1

Temperature of the product

Humidity of drying air

Moisture of the product

A

cross-section

v

Air speed

I

phase

II

phase

Claims (15)

Method for controlling a drying process of a product (1) in a dryer (2), with a fan (3) for conveying drying air (L) to the product (1), with a heating device (4) for heating the drying air (L) and with a control and/or regulating device (5) for regulating a device (6) for controlling the temperature (T _L,1 ) and/or the humidity $\left(\varrho \right)$

in the dryer (2), characterized in that when regulating the humidity $\left(\varrho \right)$

by the control and/or regulating device (5) on the temperature (T _L ) of the drying air (L) and/or the product (T ₁ ) and when regulating the temperature (T _L ) of the drying air (L) and/or the product (1) on the humidity $\left({\varrho }_{\text{L},\text{1}}\right)$

in the dryer (2) and/or the product (1), whereby the humidity control $\left({\varrho }_{\text{L},\text{1}}\right)$

by means of temperature profiles derived from a moisture content profile during drying, subsequent drying processes are carried out by exclusively controlling the temperature (T _L,1 ) over the duration of the process, or drying programs used to control the process are based on data determined in long series of tests by the manufacturer of the dryer or the data originate partly or entirely from a cloud (8) or are based on a server system. Procedure according to Claim 1 , characterized in that the course of the moisture $\left({\varrho }_{\text{L},\text{1}}\right)$

or the temperature (T _L,1 ) during drying of the product (1) is used as an indication of product properties of the product to be dried (1) that cannot be determined, or can only be determined with difficulty, or not non-destructively. Method according to one of the Claims 1 or 2 , characterized in that the device (6) for controlling the temperature (T _L,1 ) and the humidity $\left({\varrho }_{\text{L},\text{1}}\right)$

is designed as a device for controlling the cross-section (A) of a flow channel (7) for drying air (L) towards the product (1), which changes the flow channel cross-section (A) several times during the process. Procedure according to Claim 3 , characterized in that a drop in humidity $\left({\varrho }_{\text{L}}\right)$

the drying air (L) is detected, which initiates a change in the speed (v) of the drying air (L) in the flow channel (7) for drying air (L) to the product (1). Procedure according to Claim 3 , characterized in that a drop in humidity $\left({\varrho }_{\text{L}}\right)$

the drying air (L) is detected, which initiates a change in the drying air temperature (T _L ) and/or the flow channel cross-section (A) for drying air (L) to the product (1). Method according to one of the Claims 1 until 5 , characterized in that the drying process is divided into at least a first phase (I) and a second phase (II). Procedure according to Claim 6 , characterized in that in the first phase (I) there is always a control of the drying air temperature (T _L ) and a monitoring of the air humidity $\left(\varrho \right)$

be performed. Procedure according to Claim 6 or 7 , characterized in that in the first and/or second phase (I, II) the drying process is carried out according to fixed temperature, humidity or time specifications. Method according to one of the Claims 1 until 8th , characterized in that the control and/or regulating device (5) comprises a programmable program controller which, based on the initial humidity $\left({\varrho }_{\text{1}}\right)$

of the product (1) or a moisture $\left({\varrho }_{\text{L}}\right)$

After a warm-up phase of the dryer (2), a basic drying process is selected from a variety of drying programs. Procedure according to Claim 9 , characterized in that the drying programs are initially partially provided with data obtained before or during the drying process or data from a cloud (8). Method according to one of the Claims 1 until 10 , characterized in that the device (6) is designed as a flap (9) which is continuously moved. Method according to one of the Claims 1 until 11 , characterized in that the device (6) has a recuperator which at least dehumidifies the drying air (T). Method according to one of the Claims 1 until 12 , characterized in that the device (6) opens a large cross-section of the flow channel (7) when the temperature (T _L ) of the drying air (L) is less than a target temperature (T _soll ) and/or the humidity $\left({\varrho }_{\text{L}}\right)$

the drying air (L) is greater than a target humidity $\left({\varrho }_{\text{should}}\right)$

is. Method according to one of the Claims 1 until 13 , characterized in that the device (6) remains open at fixed time intervals, for example 5 seconds, and its function is carried out at variable time intervals by the control and/or regulating device (5). Method according to one of the Claims 1 until 14 , characterized in that the product (1) is an agricultural product or a product for the manufacture of pharmaceuticals.

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