DE861539C - Process for the evaporation of encrustation-forming, especially gypsum-containing liquids in multi-stage evaporators - Google Patents

Description

Procedure for. Evaporation of incrustations, in particular liquids containing gypsum in multi-stage evaporators The invention relates to the evaporation of incrustations, especially liquids containing gypsum in multi-stage evaporators to reduce those associated with the incrustations Difficulties, e.g. B. the evaporation of sulphite liquor.

During the evaporation of various encrustation-forming, inter alia. Liquids containing gypsum have been observed in many cases that otherwise the same conditions with regard to temperature etc. cause the incrustation difficulties become lower or relatively benign with increasing dry matter content, if the dry matter content exceeds a certain value, however, that it does become considerably larger if the dry matter content is below this value lies; at the lower dry matter content, the amount of incrustation increases or / and the encrustation is more difficult to dissolve or mechanically to remove.

According to the previously common methods for operating known multi-stage evaporators the liquid to be evaporated will either go through the various stages in series from the lower to the higher temperature level or vice versa. where the The dry matter concentration of the inflowing liquid increases gradually. Included some of the stages work with less dry substance-rich liquid and in unfavorable cases, e.g. B. at a relatively high temperature level, with particularly large incrustation difficulties while using some of the stages more dry substance-rich liquid works and in favorable cases, z. B. at relatively low temperature level, without any particular difficulties regarding Encrustation works. Under these circumstances, however, the system suffers Together, of course, because of the difficulties caused by the incrustations in The aim of the invention is essentially to achieve this at the lower concentration level Eliminate disadvantages.

The invention is essentially characterized by: that new supply of liquid or

Sufite to multi-stage evaporator continuously or only periodically to a greater or lesser extent. 1 parallel to two or more of its stages takes place in which the dry matter content of the liquid content z. B. by Fluid circulation to suitable and possibly for the different stages different values are boosted and kept almost constant at these values, which is closer to the desired final concentration when the liquid leaves the Multi-stage evaporators are located in the same stage as pure series conveying the liquid through this would be the case under otherwise identical conditions.

This can obviously reduce the dry matter content of the liquid in the steps that are otherwise too badly worn by encrustations on any one Value which is most favorable for the restraint of the formation of incrustations is.

In doing so, the increase in the dry matter content is carried out and maintaining it at the desired value expediently by circulating the liquid through the evaporation stages in question.

In certain cases a smaller or larger number can be advantageous of the stages connected in parallel must also be connected in series at the same time.

Since the increasing dry matter content of the liquid, the heat transfer effect more or less, it is generally desirable to use the stated value as much as possible close to the dry matter concentration of e.g. B. with sulfite liquor at least 20 to 25 ° / o or a tried and tested higher value, the incrustation being proportionate becomes low or benign, the benefit of it to an uneconomical degree is eliminated by too much decreased heat transfer effect.

There is a possible and appropriate procedure in certain cases in that all stages are driven with a liquid content, its Dry matter content approximately corresponds to the desired final concentration.

If this causes difficulties, the procedure can also can be changed so that the dry matter content is approximately the same The value of the liquid content in all stages except the last is kept in which it is increased to the desired final concentration.

The devices required to carry out the invention exist only from pipe connections with the necessary shutdown and possibly regulating devices, d. H. from elements known per se in similar systems, which are thus made by the person skilled in the art readily as needed to perform an embodiment of the method according to the invention can be installed in any known type of evaporator.

Modifications to the method are conceivable within the scope of the invention.

Claims (3)

PATENT CLAIMS: 1. Process for the evaporation of incrustation-forming, in particular liquids containing gypsum in multi-stage evaporators, e.g. B. for evaporation of sulphite liquor, characterized in that two or more of these stages, the are expediently provided with liquid circulation systems, from the outside with the Liquid to be thickened or sulphite liquor are fed in parallel. 2. The method according to claim 1, characterized in that at two or more stages at the same time, both parallel and series conveying of the liquid or the sulphite liquor is made. 3. The method according to claim 1 or 2 in the evaporation of sulphite waste liquor up to at least about 50% dry matter, characterized in that so many Stages with liquid circulation systems with the lye to be thickened be fed in parallel that the liquid circulating in these stages reached a dry content of at least 20 to So ° lo.