DE1619709A1 - Method and arrangement for vaporizing materials - Google Patents

Description

Method and arrangement for vaporizing materials The invention relates to a method and an arrangement for evaporating materials by means of a thin film evaporator. A Silm evaporator is a special one Evaporator that has a central rotor that has a relatively thin layer of the material to be processed on a heated or cooled wall of the evaporator applies. The material goes through the evaporator quickly, usually in some Hours, with the steam being discharged in the desired quality at the same time. Consequently film evaporators are very suitable for materials that are sensitive to heat and which are at least partially decomposed in the usual evaporators, since the Treatment time in it is much longer.

Examples of film evaporators are known from American patents 2 927 634, 3 253 643 and 3 261 391. They can be vertical or horizontal.

Because of the mechanical stirring and blending of the thin film which caused by the rotor, such pilm evaporators are also suitable for evaporation or another treatment of materials that are or become viscous during treatment with minimal contamination of the heat transfer surfaces.

Usually evaporators without movable plates cannot be used for this purpose. because very viscous materials quickly adhere to the heat exchanger in such a way that that the heat transfer practically ceases and the material burns or scorches will.

Film evaporators are expensive and difficult to manufacture because they are small Tolerances are allowed. This makes a film evaporator cost around five or ten Times as much as an ordinary vaporizer per unit of carmia transfer area.

Accordingly, it is desirable to have as much of the evaporation as possible to be allowed to happen in the evaporator of conventional design, as far as this is safe and can be practically carried out before evaporation in the film evaporator is continued This is particularly advantageous when processing large quantities of yeast materials must be, because of the great cost of the Pilm evaporator, which is relatively small and can be cheap. So far this has been medium-sized when working or little eals in a film evaporator because of the way that combined Procedure must be derived, in no way possible.

In the known evaporation arrangements of the type described is the mixture of steam and concentrate coming out of the evaporator to a steam separator out, wel 1 is connected to a compressor vacuum system, wherein the steam condenses and the condensate is pumped to the film evaporator and a compressor is also connected.

The purpose of the invention is to simplify the process and the arrangement.

According to the invention, these simplifications would be made by a method realized, which is characterized in that the material in a pre-evaporator is evaporated, and this pre-evaporated material together with its steam directly is led to a film evaporator of the Rotortyfs, in which a further evaporation and separation takes place. A pre-evaporator without moving parts is preferred of the direct current type is applied. illerin steep: Fi. 1 a scheme of a well-known Arrangement; Fig. 2 is a diagram of an arrangement according to the invention.

In the two figures, the same parts are denoted by the same numbers.

The example of the known arrangement in Figure 1 has a container 1, which by means of a line and a pump 3 with a pre-evaporator 4 of known type is connected, which a supply and discharge pipe 5 and 6 for a heating means e.g. B. Has steam. The pre-evaporator 4 is connected by means of a line 7 connected to a vapor separator 8, which by means of a vapor discharge pipe 9 with a vacuum condenser 10 with a supply 11 for water or another Coolant is connected. The vacuum condenser 10 is provided with a drain 12, wherein a regulator 28 for the pre-evaporator. is appropriate. The steam separator 8 has an outlet 14 for the condensate, which by means of a pump with a Film evaporator 16 is connected.

A rotor (not shown) in the film evaporator 16 is driven by a motor 17. This evaporator 16 has a heating jacket 18 and a Inlet 19 and an outlet 20 for steam. The film evaporator 16 is also provided with a vapor discharge 21, which with a vacuum condenser 22 with a Inlet 23 and an outlet for water is connected. The capacitor 22 is also connected to a vacuum device (not shown) connected to 25. There is also an outlet for the condensate 29.

As shown in Figure 1, it is in practice common, to use a regulating device 28 for the evaporation process in the pre-evaporator 4, while the vapors and the product from the pre-evaporator 4 in a single vapor separator be introduced, and the partially treated product carefully and simultaneously from the vapor separator 4 into the film evaporator 16 by means of a pump 15. Such a combined method can be largely justified by for the film evaporation unit with regard to heat utilization and steam treatment its maximum power can be used almost or entirely. But this takes No longer to ride for edits on a smaller scale, with the film evaporator no longer used to its maximum performance in terms of steam treatment will. According to the invention, a large amount of pre-evaporation-film evaporation combinations can be used the mixture of steam and product from the pre-evaporator as a whole directly into the Film evaporator are performed. The3 enables an important simplification and cost savings of the method and the arrangement, since the vapor separator 8, the regulating element 28 and transport pumps 15 can be omitted.

The arrangement according to the invention then has the appearance of the figure 2, in which it is indicated that the pre-evaporator 4 is connected directly to the film evaporator 16 is connected by means of a direct pipe 27, so that the starting material is fed into the pre-evaporator 4 are pumped, and then as described in the above-mentioned patents treat f t be In the case of evaporation, the general intention is to the concentration of one or more relatively non-volatile substances from the removal as vapor from e.g. letting alcohol or another solvent or mixture to separate from it. With all evaporation there is a tendency to be part of the non-volatile Add residue. If the backlog is an important product, it's over Economic reasons necessary, taking the residue with you as completely as possible to prevent. If the vapors, such as alcohol, are e.g. the most important priiiuu it is also important to avoid carrying the residue with the steam, so as not to contaminate the vapors and not to reduce their economic value. The problem of entrainment with the film evaporator must therefore be fully apprehensive and is often the limit; Factor of such an arrangement.

If entrainment is not the limiting factor, it is pre-evaporation in a common, cheap vaporizer advantageous, especially when this step can be carried out more easily and by omitting the steam separator according to the invention, Regulating elements and the pump less complicated and less expensive devices must be applied.

The phenomenon of carrying along vaporizers of all kinds is high Measures depend on the steam speed in the arrangement before the steam of the evaporator comes in iien vacuum condenser. The higher this speed over a certain value increases, the greater the phenomenon of entrainment. the Speed is on your part depending on the known influencing Factors such as the weight of the steam, the molecular weight, the temperature, the Pressure and the free surface area in the evaporator.

The propensity to take away can be expressed using a formula: where S = the steam speed in bp / h; Vo = the volume of 1 / b / under the prevailing circumstances, and A = the surface area of the free area of the evaporator.

It follows that by increasing the surface area of the free section more steam can be processed if the phenomenon of entrainment occurs, so that a greater capacity can be achieved, provided that the thermal Capacity is sufficient. This means that a pre-evaporator is used, in order to create such thermal properties in the film evaporator that this be applied to a maximum steam treatment capacity can.

Many existing film evaporation arrangements are i @ re thermal Capacity limited and could work with much larger capacity if an additional one Amount of vttn thermal energy would be supplied. This can be done by applying a more or less usual Verdarnplers from the fast-acting entry-level type with forced rising film to be accomplished, which steam and condensate as transfers a mixture to the pilm vaporizer without a pump between the two Units or a single vacuum condensation system for the pre-evaporator set.

As a result, the heat leaves the pre-evaporator by itself in a uniform manner Way into the film evaporator, as shown in Figure 2, and the concentration is automatically and continuously regulated therein. Possible variations in concentration in the first unit are compensated for in the film evaporation.

The invention will now be explained in more detail with the aid of the following examples.

Example 1 A water-thin pharmaceutical material with a solids content of 5%, of which 80% is desired to be evaporated as steam under a vacuum of about 5 m H, with steam (] s heating medium at an overpressure of no more than 0.21 kg / qcm (1050 C), is treated in an inverted cone type film evaporator with a horizontal heating surface of 0.09 square meters. A one-off increase is envisaged Passed film evaporator with a heating surface of 0.4 square meters among the following Circumstances: Film evaporator only pre-evaporator + film evaporator Experinuent 1 Experiment 2 Experiment 3 Feed rate of feed (kg / h) 25.9 35.5 35.5 Feed temperature 10 10 10 from pre-evaporator - - 35 from film evaporator 32 32 32 Overpressure of the steam kg / qcm pre-evaporator - - 0.21 film evaporator 0.21 0.21 0.21 vacuum (cm Hg) bottom of the pre-evaporator 6 6 7 top of the pre-evaporator 5 5 5 film evaporator 4 4 4 steam:% of feed 80 55 80 hg / k 21.0 20.0 29.0% increase - 45.5 tendency to carry along none none none Concentrate quality: Parbe good good good After doing the edits for some time the heating surfaces of the pre-evaporator and the film evaporator were found, from which it was determined because they were still completely clean. The first column of the table shows the effect with the film evaporator without the combination with the pre-evaporator according to the invention, 80% of the steam of the feed has been evaporated. That way just might 25.9 kg / h of feed can be processed. The second column shows the processing with the same arrangement, with the feed speed of the feed up to 35.9 kg / h was increased, but only 55% of the steam evaporated became. Without a pre-evaporator, this system was therefore in his maximum thermal capacity in terms of treatment and entrainment applied to the steam.

In the third column, but with the pre-evaporator according to the invention, almost 50% more steam was evaporated without exceeding the steam utilization capacity, i.e. that at a feed rate of 5 kg / h 80 of the steam, as desired, was evaporated.

Example 2 A relatively thick candy syrup with a solids content of 73.5 0, which one wishes to thicken up to a strength content of 21% under atmospheric pressure by means of steam under an overpressure of 2.1 kg / sqcm, was also treated in the combination pre-evaporator-film evaporator, as above described with and without the pre-evaporator under the following circumstances.

Film evaporator as a pre-evaporator + film evaporator experiment 1 Experiment 2 Experiment 3 3 Feed rate of feed (kg / h) 17.5 27.1 27.1 Feed temperature 15.5 15.5 15.5 "from pre-evaporator (° C) - - 120" from film evaporator (o) 135 112 135 overpressure of the steam (kg / qcm) pre-evaporator - 2.1 film evaporator 2.1 2.1 2.1 Overpressure (kg / qcm) Bottom of the pre-evaporator 0.07 0.07 0.07 Head of the pre-evaporator. Pre-evaporator 0.035 0.035 0.035 film evaporator 0 0 0 steam% of feed 19.0 11.3 19.0 kg / h 3.4 3.1% increase - 6 tendency to carry along none none none Quality of the keen-centered Syrups solid content% 91 78 91 Color very good * very good * very good * Taste very good * very good * very good * + always the same in the feed Some time after the procedure has been carried out, the surface of the pre-evaporator has been removed and the des Film evaporator investigated. It turned out that the surfaces were still completely clean. In the last experiment, it was the capacity the arrangement about 70% larger by using the pre-evaporator, from which the partial thickened syrup and the vapors were both fed into the film evaporator. Calculations show that with an increase in vapor pressure for the two evaporators while maintaining the other circumstances the capacity of the evaporator increases to a very large extent while the device still does not work with the maximum steam treatment capacity, but is still limited by thermal capacity.

There are basically two different types of film evaporators in terms of the internal steam flow. One works on the countercurrent principle by the vapor and the liquid are moved in opposite directions to each other. The other works according to the direct current principle, in which the vapor and the liquid are in move in the same direction.

In this second type, the vapors generally leave the assembly opposite the side of the feeder, and will be about silver all the way through the blades of the Itotor subjected to a beating effect, causing foam formation and Carrying along will be highly restricted. At the pilm evaporator of the countercurrent price the vapors leave the arrangement very close to the inlet of the feed, and it it is to be expected that with such an arrangement the phenomenon of entrainment is greater when the invention is arranged. The invention is therefore a co-current type film evaporator is preferably used. The horizontal one Pillow evaporator of the inverted cone-shaped type with tangential inlet of the pre-evaporator but is also suitable, as it allows the whole thing to be with any inner surface can provide while maintaining the agitation and turbulence of the film. this is difficult with vertical film evaporators with straight walls using the countercurrent principle, in which the ratio of the diameter to the length is within certain limits must remain in order to obtain sufficient agitation of the film. Although the Effect of the film evaporator of this kind using the invention in comparison with the co-current type film evaporator is inferior, it can be applied. the pump 3 for the pre-evaporator 4 is the material directly into the film evaporator pumps, this karin can easily be used up to its maximum capacity. In the known arrangements s he film evaporator is generally by a too little material supply underloaded.

Claims (10)

Claims 1. A method for evaporating materials by means of a Film evaporator, characterized in that the material is in a pre-evaporator (4) vorverdan, pit becomes, and this vorverdanipfte material together with his Steam is fed directly to a rotor-type film evaporator (16) in which further evaporation and separation takes place. 2. The method according to claim 1, characterized in that a pre-evaporator (4) is used with no moving parts. 3. The method according to claim 1 or claim 2, characterized in that that a film evaporator (16) of the counter current type is applied. 4. Arrangement for performing the method according to claim 1, 2 or 3, characterized in that it contains a pre-evaporator (4) which is directly is connected to a rotor-type film evaporator (16). 5. Arrangement according to claim 4, characterized in that there is a pre-evaporator (4) is of the type with no moving parts. 6. Arrangement according to claim 4, 5 or 6, characterized in that the film evaporator (16) is of the i chstr @mtyp. 7. Arrangement according to claim 4, 5 or 6, characterized in that # the connection between the pre-evaporator (4) and the film evaporator (16) only through a tube (27) is formed. 8. Arrangement according to one or more of claims 4 to 7, characterized characterized in that additional elements (3) for introducing the starting material into a pre-evaporator (4) are present, as well as elements to the partially evaporated material and introduce its vapors together in the film evaporator (16), and elements around the Separate steam from the product at the end of the film evaporator (16). 90 arrangement according to claim 8, characterized in that the elements for introducing the vapors are arranged at the beginning of the pre-evaporator (4), and the Elements for guiding the partially evaporated material to the film evaporator (16), transfer these vapors into the film evaporator (16) at the other end of the pre-evaporator (4). 10. Arrangement according to claim 8 or claim 9, characterized in that that the elements for introducing the starting material into the film evaporator is a lamp (3) included, and the elements for guiding the partially evaporated material from the pre-evaporator (4) into the film evaporator (16).