SU731983A1 - Evaporating device - Google Patents

Description

(54) STEAM DEVICE

one

The invention relates to the construction of falling film evaporators and can be applied in chemical, dairy and food industry, as well as for desalinating seawater.

Known evaporator with a falling film, containing a vertical body, heat pipes dispersed in it and separator 1.

In this apparatus, the evaporated solution is evenly distributed on the inner surface of the heating tubes and, downwardly in the form of a thin film, is partially evaporated due to the heat of steam condensing on the outer surface of the tubes.

The evaporated solution coming out of the heating pipes and the generated secondary steam get into the separator where they are separated, i.e. droplets of solution settle down to the bottom of the separator, and the secondary vapor is removed from the top of the separator.

A significant disadvantage of the known evaporator is that the thin film is evaporated. the solution flowing down from the lower ends of the heating tubes is subjected to vigorous exposure to the expanding flow

secondary steam leaving the same pipes at high speed, and crushed to form a large number of tiny droplets, it is difficult to separate x from the steam flow. As a consequence, the secondary vapor removed from the evaporator takes with it a significant amount of solution, which not only is lost irreversibly, but makes

10 also impossible the rational use of condensate secondary steam without prior treatment.

A falling film evaporator is also known. It contains a vertical casing, heating tubes and a separator placed in it, and each pipe is equipped with a device for breaking the film of an evaporated solution made in the form of a cylindrical nozzle having holes on the lateral surface with edges bent inside and forming the gutter 2.

In this device, the film is evaporated

25 of the solution coming out of the heating tubes falls on the inner surface of the pipes and the edges of the orifice are torn to pieces; at the same time. the solution falls into the gutter and flows down n: im

Claims (2)

30 to the bottom of the separator, the film of one stripped off solution, flowing from the lower ends of the heating tubes, is not exposed to the flow of secondary steam, which is discharged through the holes on the side surface of the nozzles. This top machine is closest to the invention in its technical essence and the achieved result. A disadvantage of the known apparatus is that the device for breaking the film of one stripped off solution, made in the form of nozzles using special devices connected from the end to heating pipes, actually increases the lengths of the heating pipes, i.e. increases the size and intensity of the apparatus, as well as significantly complicates the design of the evaporator. The presence of these nozzles creates significant resistance to the movement of the formed secondary vapor both when it leaves the orifices in the nozzles and when it moves in the separator under the tube sheet, where the secondary steam passes between the nozzles. An increase in resistance to the output of the secondary vapor causes an increase in the boiling point of the solution in the heating tubes reduces the temperature difference between the heating vapor and the solution and thereby reduces the capacity of the evaporator. The structural complexity, due to the presence in the apparatus of a large number of nozzles, makes it difficult to clean the inner surface of the apparatus from the deposits that form during evaporation, and makes it impossible to use it for evaporation of liquids such as milk and dairy products. Regular (after 10–20 hours of operation) thoroughly flush the evaporators. The aim of the invention is to increase the productivity of the apparatus by reducing the resistance to the output of the secondary steam. The goal is achieved by the fact that in a well-known evaporator with a falling film, sodezhagayem vertical case, heated in it heating tubes with devices for breaking a film of evaporated solvent and separator, a device for breaking a film of evaporated solution made in the form of protrusions on the inner surface of the lower ends of heating tubes , each pipe is provided with an inclined chute installed under the protrusion, the internal pipes TIopepXHOcT between the protrusion and the lower end is covered with a hydrophobic material. FIG. 1 shows the evaporator with a falling film of the proposed construction; in fig. 2 - the lower end of the heating tube with protrusions for breaking the film of the solution; in fig. 3 - the lower end of the heating tube with gutters, made in the form of an insert, placed in the heating tube. In the vertical case 1 of the evaporator, heating tubes 2 are placed with the decoupling devices 3 for creating a film of the solution to be evaporated. The housing 1 is connected to the bottom with a separator 4. The devices for breaking the film are located at the lower ends of the heating tubes 2 and are made in the form of protrusions 5 (Fig. 2) or grooves 6 (Fig. 3). The protrusions 5 and grooves b are located outside the heat transfer area or at its boundary defined by the position of the upper plane of the tube sheet 7 (Fig. 2 and 3). In order to accelerate the formation of the film of the solution being evaporated into jets, the internal surface of the heating tubes 2 between the projections 5 and the lower ends of the tubes 2 may be coated with a hydrophobic material. Evaporator works as follows. The supply through the fitting 8 to the evaporator with the help of the devices 3 is evenly distributed as a thin film on the inner surface of the heating tubes 2. Heating fitting is fed into the annular space, which condenses on the outer surface of the heating tubes 2, then the condensate that is formed is discharged through the fitting 10. Due to the heat of vapor condensation, the solution flowing in the form of a film along the inner surface of the pipes is partially evaporated. The resulting secondary vapor moves down in one direction with the film of the solution to be evaporated. At the outlet of the heating tubes 2, the film of the evaporated solution moving at high speed runs over the protrusions 5 or the edges of the grooves and breaks. From the formed sections of the film spontaneously under the action of surface tension forces (this process most intensely flows on the surface that is not wetted with a solution, i.e., hydrophobic) or by means of chutes b, jet streams are formed, and from the lower ends of the heating tubes 2 the evaporated solution flows into compact jets. At the same time, the surface of the liquid, which exposes the vapor flow from the pipes, is much less, and its flow resistance is greater than with the film run-off. As a result, the streams of the evaporated solution at the exit from the pipes are not destroyed and, moving further in the same direction with the flow of the secondary vapor, spontaneously disintegrate into large droplets, which are easily separated from the flow of the secondary vapor and do not contaminate it. The evaporated solution is collected at the bottom of the separator 4 and is removed from it through the fitting 11, the secondary vapor is discharged through the fitting 12 located in the upper part of the separator 4. Thus, devices for breaking the film of the evaporated solution and forming streams of the evaporator apparatus the protrusions and grooves on the inner surfaces of the lower ends of the heating tubes, as well as the fact that the inner surface of the heating tubes between the protrusions and the lower ends of these tubes are not wetted by the blunt solution (i.e., hydrophobic), makes it considerably clearer To increase the resistance to the output of the secondary steam from the heating pipes and to improve the performance of the evaporator, as well as to improve its operation. Claim 1, a falling film evaporator comprising a vertical -8 case, heating tubes arranged therein with devices for breaking an evaporated film of a solution and a separator, characterized in that in order to increase the productivity of the apparatus by reducing the resistance to the output of the secondary steam, The devices for breaking the film are made in the form of protrusions on the inner surface of the lower ends of the pipes, 2. A non.l device, characterized in that each pipe is provided with an inclined chute installed under the protrusion. 3. Pop. 1 device, which is also distinguished by the fact that inside the pipe surface between the protrusion and the lower end is covered with a hydrophobic material. Information sources taken into account during the examination 1. E. Senet and P. Nadoban. Evaporation processes in food production . M., Pishchev. Industry, 1969, p.120, Fig.64. 2. German patent number 728271, class, 12 a, 2, 1942 (prototype).