Drying and gas or vapor contact with solids – Process – Gas or vapor contact with treated material
Reexamination Certificate
2000-05-26
2002-06-25
Walberg, Teresa (Department: 3742)
Drying and gas or vapor contact with solids
Process
Gas or vapor contact with treated material
C034S508000
Reexamination Certificate
active
06408539
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of continuous thermal treatment of a textile product web as well as to a dryer for performing the method.
For continuous thermal treatment of a textile product web, such as drying, drying and/or fixing, it is known to bring the product web in several successive steps in contact with a treatment gas of a corresponding temperature. Such a thermal treatment can be performed in a drying and fixing device disclosed in the German patent document DE A 25 45 440, in particular for textile webs which are fed there by their width.
A dryer, such as a tender dryer, has fields which are arranged one after the other and corresponds to the treatment stages. In each field or in each stage, the treatment gas is guided in a circulating process.
In many cases, heated air is used as the treatment gas. It is also known to use steam as the treatment gas, as disclosed for example in the German patent document DE-A 195 46 344.
A method which utilizes both the advantages of a treatment with heated air and also a treatment with steam, and a corresponding dryer, are disclosed in the German patent document DE-B 95 26 17. In this process for drying of continuous material webs, the product is treated in successive portions of the drying machine alternatingly with heated air and overheated steam. The portions of the drying machine can include several chambers which are also the above mentioned fields. For subdividing the treatment into these portions, the machine is subdivided for example by partitions into successive treatment zones with air or steam as a drying medium.
These processes have however the disadvantage that for different application cases a new dryer is needed. At least, the partitions must be displaced.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for continuous thermal treatment of a textile product web which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a method which includes the steps of bringing a product web in contact with a treatment gas guided in a circulating process, introducing a product web into a steam portion having one or several steam stages in which heat steam is used as a treatment gas, introducing the product web into a steam-air portion which has one or several stages and hot steam and heated air as a treatment gas, passing the product web first through the steam portion and subsequently through the steam air portion, providing an exchange of the treatment gas between the steam stages and the stages, adjusting a relative moisture of the hot steam of the steam stages of the steam portion to the value zero, and performing the adjusting by measuring relative moistures of a first and a last steam stage and changing discharge gas quantities of the first or second steam stages and one further stage.
It is another object of the present invention to provide a dryer which can implement the inventive method.
In keeping with these objects, a dryer is proposed which has a steam-tight housing through which a product web is transportable; at least two successively arranged fields each provided with a circulating device for a treatment gas; moisture sensors arranged in first fields and in at least one rear field; a discharge conduit provided with an adjusting arrangement and arranged at least in a first or a second field and in at least one further field correspondingly; a switching unit through which at least two of said moisture sensors are connected; said switching unit being connected with at least one adjusting device.
When the method is performed and the dryer is designed in accordance with the present invention, various application cases can be realized without significant conversion expenses of the dryer.
In the inventive method for continuous thermal treatment of a textile product web, the product web passes first through one or several steam portions which have steam stages, in which hot steam is used as a treatment gas, and subsequently it passes through one or several air portions which have steam and in which steam and in which hot steam and heated air are used as the treatment gas. Subsequently to the steam-air portion, it can pass in some cases through an air portion with one or several stages in which it is brought into contact with heated air. The number of the steam stages of the steam portion are selected in dependence on the treatment process, wherein for drying there is a tendency for rather more steam stages for drying and fixing and in some cases less steam stages, and for fixing for example only one steam stage is utilized.
A treatment with steam has the advantage that the product web is heated very fast to a temperature of up to 100° C.
With the steam portion during a thermal treatment of a product web, the shrinkage which requires a certain moisture and is enhanced by high temperature of the product web is facilitated. The product web which has approximately input moisture and is heated to 100° C. is dried at this temperature. It has during shrinkage this high temperature at a moisture of approximately 30%. If the treatment gas to the contrary has a lower steam content, then the product web during the drying has a lower cooling limiting temperature corresponding to the steam content. An improved shrinkage during drying has for example an additional shrinkage treatment such as tumbling.
In the inventive method the relative moisture or in other words the volume of the water steam with respect to the volume of the treatment gas is adjusted to the steam stages of the steam portion to the value 1. A relative moisture with the value 1 corresponds to a treatment gas which has up to 100 of saturated, mainly overheated water steam, identified as a hot steam. In guarantees a fast warming of the product web to 100° C.
In principle it is known to adjust the moisture of the treatment gas. In the above mentioned German patent document DE-A 25 45 440 it is described that during drying the steam content which corresponds to the relative moisture is held constant by controlling the fresh air supply in the individual fields. In addition a temperature sensor regulates the discharge air quantity. A steam content of 100° C. adjusted by the regulation of the fresh air supply; is basically not possible. Each fresh air supply would reduce the steam content to the value under 100%. A fresh air supply in the fields operating with hot steam is excluded because of the condensation danger.
This document also discloses a simplifying embodiment, in which during drying the discharge airfans which determine the discharge air quantity are controlled by a steam content sensor. The discharge air fans are connected with several fields. The disadvantage of this method is that the steam content can be regulated only together for the fields connected to one discharge air fan. Thereby the number of the steam fields and correspondingly the number of the steam stages are fixed.
In accordance with the present invention, the relative moisture of the hot steam of the steam stages of the steam portion is adjusted to the value 1, in that the moisture of the treatment gas, in other words the hot steam, of the first and the last steam stage is measured and the discharge gas of the first or the second steam stage and one further stage is changed. This method has the advantage that independently from the number of the steam stages, only two discharge gas quantities are changed.
In a dryer which is suitable for performing the method, corresponding discharge gas conduits only for two fields are needed. It is important that in accordance with the present invention in this open process, or in other words with an exchange of a treatment gas between the stages and thereby between the fields, the discharge gas is discharged only in two fields, while the quantities are changed due to the measured relative moisture.
When compared with a discharge gas control
Stroehrmann Andreas
Voth Marc-Aurel
Babcock-Textilmaschinen GmbH
Fastovsky Leonid M
Striker Michael J.
Walberg Teresa
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