DE1043064B - Apparatus for bleaching cellulosic, fibrous material with volatile bleaching agents - Google Patents

Description

The invention relates to an apparatus for bleaching cellulosic, fibrous material with volatile, in the form of solutions or gases to be added bleaching agents, such as chlorine or chlorine dioxide, in a tower with an upstream device for mixing the bleaching agent with the pulp and to convey the substance into the tower.

In the previously known bleaching apparatus of this type, the mixer was equipped with various other devices, upstream such as storage tanks, thickening apparatus, etc. or the pulp was by means of a Screw worm od. The like. Introduced into the tower, so that the feed devices as effective gas barriers served, as is particularly emphasized in the literature. As a result, one has to report Provide special ventilation devices for dangerous overpressure or underpressure in the tower have to.

An open-topped tower is also known in the bleaching of cellulosic, fibrous material without using an upstream mixing device and introducing gaseous bleach into the tower in such a way that it is absorbed by the substance located above the entry point and escapes is prevented. In this known device, however, the tower volume for the bleaching process is not fully exploited, the mixing of fabric and bleach is less good, and one has to be proportionate use narrow tower.

According to the invention, it is now proposed to connect the interior of the tower to the atmosphere via the mixing device to be in contact without pressure, d. H. the mixing device should not act as a gas barrier, but allow free gas passage in both directions. It has surprisingly been found that when using conventional mixers, which, as is known, act in such a way that the substance by beater arms is divided and whirled through, the substance located upstream of the point of entry of the bleach the bleaching gases, such as chlorine and chlorine dioxide, can completely absorb, while inert gas can flow unhindered in both directions and the device is thus effective at the same time Can serve ventilation system, whereby the bleaching apparatus is simplified and cheaper. Simultaneously one achieves an intimate mixing of the same with the pulp even with a high concentration of the pulp Bleaching agent and full utilization of the tower volume for the bleaching process, even with tower diameters of any size. 5c

According to a preferred embodiment of the invention, the volatile bleaching agent is incorporated into the fibrous Ground introduced at a point between two mixers connected in series Bleaching apparatus

of cellulosic, fibrous

Material with volatile bleach

Applicant:

Mo och Domsjö Aküebolag,
örnsköldsvik (Sweden)

Representative: Dr.-Ing. Dr. jur. F. Redies, patent attorney,
Bergisch Neukirchen, Hauptstr. 107

Claimed priority:
Sweden 4 October 1954

Kurt Alfred Jönsson, Hörnefors (Sweden),
has been named as the inventor

and which together form the device for feeding the wood pulp into the bleaching tower.

In order to introduce the heat required to carry out the bleaching process into the reaction mass, one can introduce steam into the feed device at a point which, viewed from the direction of flow of the wood pulp, is above the point where the bleach is introduced.

A preferred embodiment of a bleaching apparatus that is used for carrying out the process suitable according to the invention is given below as an example of the design of the device described according to the invention. The reference numbers relate to the drawing, which is a partial Shows cross-section of the apparatus.

In the drawing, the numbers 1 and 2 designate two mixers of the usual type, which are connected in series between the screw conveyor 3 of a stage located immediately upstream of the bleaching system and the bleaching tower 4. The bleaching agent, for example gaseous chlorine dioxide, is introduced into the apparatus between the two mixers or directly when the wood pulp flow enters the second mixer 2, for example at point b. If heat is required for the process, this can be introduced by means of steam, which steam can be introduced at the outlet of the first mixer, for example at point a .

809 '677/584

The apparatus according to the invention not only enables the bleaching agent to be advantageously introduced in the wood pulp and the good mixing of bleach and wood pulp, but granted in addition, the advantage that the steam in the event of a sudden interruption of the wood pulp supply can go through the upper mixer into the open, while the Chlordioyxdlösung through the lower mixer can flow into the bleaching tower. In cases of this type, the steam does not then lead some of the bleach in the vicinity of the plant, which is what happens with certain previously known processes or apparatus is a significant disadvantage.

Claims (3)

Claims: x5 1. Apparatus for bleaching cellulosic, fibrous material with volatile, in Bleaching agents such as chlorine or chlorine dioxide to be added in the form of solutions or gases a tower with an upstream device for mixing the bleach with the Pulp and for conveying the substance into the tower, characterized in that the bleaching Tower is pressureless through the mixing device with the atmosphere and that the Entry point for the bleach at a point between the front and rear ends the mixing device lies. 2. Apparatus according to claim 1, characterized in that the mixing device consists of two series-connected mixers and that the bleach between the two mixers is introduced. 3. Apparatus according to claim 1 and 2, characterized in that it also includes a device for injecting steam and this opens into the mixing device at one point, which, viewed in the direction of flow of the fibrous material, is upstream of the point of entry of the bleaching agent. Considered publications:
German Patent No. 488 773;
Austrian Patent No. 107,988;
French Patent No. 871,406;
British Patent No. 489,302;
U.S. Patent No. 1,924,860. 1 sheet of drawings © «09 6777584 10. 5 &