DE875915C - Device for the circulation of fluids in digestion containers for fiber material - Google Patents

Description

Device for circulating liquid in digestion containers for fiber material When opening up fibrous material, e.g. B. wood chips, in elongated, vertical Digestion containers in which .the substance is pre-fed in the longitudinal direction of the container it can sometimes be useful to circulate the liquid transversely to the conveying direction to cause thereby in the heating or cooling of the circulated liquid and / or a zone-wise treatment when adding or removing chemicals to achieve the digestion liquid.

This can lead to the heating of the contents of the cooker with a continuous cooking process, in which the digester content is below the vapor tension at the prevailing digester temperature Excessive compression pressure: is held to be of interest. Under these It can be made under certain conditions, different temperatures to certain Keep zones localized. With a vertical, continuous cooker, who works according to the above principle, with entry above and discharge below, it is even possible to have a colder zone on top, an exposure zone in the middle and for example a closure zone with a higher or lower temperature at the very bottom maintain. It may seem paradoxical, a low temperature, preferably below zoo °, for example 80 ° above and a high temperature, preferably r2o to 2oo °, for example r70 ° in the middle and soggar with quite sharp To maintain separation of the zones. But experiments have shown that it is possible is, and theoretically it can be explained as follows: i. As long as the stove is under a compression pressure is maintained which exceeds the evaporation pressure, no vapor bubbles are formed that rise to the top, with the exception of where appropriate of S02 gas. 2. The second form of temperature transfer, namely a flow the warmer liquid to the top, counteracts the fact that the quiver is kept crammed full of chips, just like .es with mechanical feed of the Chips is the case. 3. The third form of temperature transfer, namely slow Heat conduction, is .by the constant even movement of the mass downwards more than compensated for by the cooker.

The importance of this measure is evident by taking it all the way can maintain a colder soaking zone above, the one below hot opening zone or several zones with fairly sharp temperature transitions follows or follow.

There is now a strong lye circulation in the horizontal plane provided to the longitudinal axis of the digester, the heating of the digester contents takes place instead of having this circulating amount of lye the required calories either are supplied directly with live steam or indirectly through a heater, according to which these calories during the passage of the liquor across the cooker to the cooker contents be delivered. The greater the amount of lye in circulation, the smaller the temperature increase is required for the circulating liquor.

In this context it should be emphasized; that a large encircling Lye amount is very easy to maintain by looking at the relevant one anyway Stage of the cooking process (transition from soaking at 8o0 to boiling at z4ob to 1700) has to do with chips that are not yet exposed and the flow of the lye do not offer too much resistance.

Another important advantage is that the sieves are well used due to the compression pressure in the cooker due to the pressure drop prevents the lye from evaporating through the cracks in the sieve. The circulation pump thus works in the most favorable way.

However, it is clear that when the flow is one-sided in the same Direction takes place, the contents of the cooker when the circulating liquor enters from the heater on heated most and least at the outlet at the sieve. This - temperature difference However, the greater the amount in circulation, the smaller it will be. -To such a one To counteract irregularities, the present invention provides for the Läugenurnlaüf e.g. every 2 or 5 minutes or the like to make it reversible. Two or more over . Suction strainers distributed around the circumference of the container with return inlet on the respective opposite side are for this purpose to a circulation circuit via a Switching device connected to switch the circuit of a sieve on the other hand serves.

Appropriately, these screens are arranged at the same height and also the corresponding returns. As a rule, two sieves are sufficient then each can extend over 12o °.

An embodiment of the invention is illustrated in the drawing, the -in Fig. z and 2, the circulating device and a vertical or a horizontal Section of the sieve device in connection with a cooker.

The lye is passed through a sieve which is about z2o ° of the circumference of the digester includes, sucked by means of a circulation pump-2 and continues to flow through a Heater 3 in the cooker at a sieve: diametrically opposite point d. return. The places i and q. : opposite is a sieve 5 with return line to Cooker provided at 6. By simply reversing the direction of flow, like indicated with dashed lines in the drawing, the necessary compensation the temperature via the cross section of the digester. As shown by the rotary valve 7 is, the pump 2 sucks out of the sieve i and, pushes through the heater 3 to q .. If the slide is moved to the other side, like with the dashed channels and lines is indicated, the pump 2 sucks out of the sieve 5 and pushes through the Heater 3 to 6. Of course, there is no obstacle to this, e.g. B. three sieves of To be provided for each 12o °, etc., but the arrangement described above with two groups of sieves of 12o ° each is sufficient to meet practical needs.

In the present case, the inversion takes place, not around the sieves to hold open; as is the case with ordinary periodically charged stoves be. can, but to compensate for the smaller temperature difference that would otherwise would arise between the sieve side and the opposite digester wall which the circulating liquor is introduced.

In addition to the supply of calories through a heater, it is also possible to with - a heat exchanger in a corresponding circulation system at a later one Calories can be extracted to keep the temperature in a limited stage of the digestion Lower zone.

It is also clear that the invention can be used not only to add or remove calories, but also. in addition, new chemicals, e.g. B. acid, alkali, S 02, etc., to be supplied in a sharply defined zone. If necessary, S 02 can also be removed in the same way by relieving the pressure in the circulating lye, after which the lye, which has been partially freed from S O, is pushed back into the system.

Claims (2)

PATENT CLAIMS: i. Device for fluid circulation for the purpose of change .the temperature and / or the composition of the digestion liquid elongated vertical digestion containers for wood chips or similar fibrous material, in which the stock is pre-fed in the longitudinal direction of the container, thereby characterized in that two or more suction strainers distributed over the circumference of the container (1, 5) with return inlet (q. Or 6) on the respective opposite side a circulation circuit with a pump (2) and a heater or heat exchanger (3) are connected via a switching device (7) which is used to switch the circuit serves from one sieve to the other. 2. Device according to claim i, characterized in that that it has two suction strainers, which are each about i2o ° of the container circumference extend and, like the corresponding return inlets, are symmetrically opposite one another. Referenced publications: German patent specification No. 526835.