FI85337C - DOPPROERSYSTEM. - Google Patents

Description

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UPPOPUTKIKKO

The present invention relates to a submersible evaporator, and in particular to a submersible evaporator in which the lower part of the submersible tube has been replaced by a submersible tube formed of several tubes according to the invention. The immersion tube according to the invention has the particular advantage that it provides vibration-free and efficient evaporation, and is thus suitable for the evaporation and crystallization of metal sulphate solutions and the like.

A submersible evaporator is a device in which hot flue gases are conducted below the surface of the substance to be evaporated.

In direct immersion evaporation, bubbles of hot gases discharged from the immersion tube are passed through the liquid. In this way, it is possible to achieve a very efficient heat and mass transfer from the gases to the liquid to be treated. Since heat exchangers are not required, material issues do not present difficulties. As a result, direct submersible evaporators are used especially in metallurgical and chemical processes where corrosive conditions cause material difficulties, such as heating and evaporation of strongly acidic solutions.

In immersion evaporators, the immersion tube is usually arranged in an upright position, because then the smallest possible amount of material is in direct contact with the liquid to be treated.

Numerous different submersible evaporators are already known. In these, the aim has generally been to provide as many as 2,853,337 small-sized devices in order to reduce investment costs. However, reducing the size of the device causes a decrease in the volume above the gas discharge point, and even small variations in the gas supply cause large pressure fluctuations in the immersion pipe.

Vibrations in the submersible pipe, as well as liquid droplets that may splash in it, strain the spaces and structures before the submersible pipe in general.

U.S. Patent No. 4,278,494 describes an immersion evaporator in which hot gases are fed into a liquid through a single rather large pipe. Here, preparations have been made for strong vibrations and splashing, e.g. placing the combustion chamber in a horizontal position and utilizing bellows to dampen the propagation of the vibration.

When it comes to the large capacity of the evaporating liquid and thus the larger pipe size, the vibration inevitably intensifies because the bubble size increases and the reduction of the bubble size cannot be thought of in a known way, i.e. by increasing the velocity due to too high and strong penetration of the gas jet.

U.S. Pat. No. 2,867,972 discloses an immersion evaporator apparatus in which an attempt is made to eliminate permanent vibration by notching the end of the immersion tube in a serrated manner. The idea is that the hot fuel gas discharged from the immersion tube would discharge to the side of the notch and thus soften the flow. According to the publication, the notch dampens vibration and enhances heat transfer. It should be noted, however, that at all times the main direction (impulse) of the gas is straight down the higher the velocity and the amount of gas.

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Naturally, some of the gas is discharged laterally from the notches. It is therefore quite clear that the situation is improving. However, it must be remembered all the time that the gas forms a "whole" bubble, which bounces to the surface and causes vibration, albeit less than in the previous case.

DE application publication 34 47 060 is also known, in which the dripping and thus the cooling of the liquid takes place by evaporation. The very shallow immersion depth described in the publication can be used because the equipment operates mainly by suction. The publication describes discrete tubes which are mainly in an oblique position and would require a large opening for lifting, which in many cases is disadvantageous.

The object of the present invention is to introduce a hot gas into the solution in such a way that even large amounts of gas do not form large bubbles or that the gas does not have a too long penetration distance, and thus strong vibrations. The lower end of the immersion tube according to the invention is thus formed of a plurality of straight-down tubes, the advantage being a symmetrical discharge of gas into solution. The essential features of the invention appear from the appended claims.

In the device according to our invention, the hot gases are led directly downwards or, if necessary, turned vertically downwards towards the solution. Shortly before the solution penetrates, the gas stream is divided into several tubular vertical channels. The middle of the channels are directly cross-sectioned at the discharge ends and the outer ones are bevelled.

In the conventional case where the gas is discharged into solution through one large immersion tube, it is difficult 4 85337 to use a sufficiently high gas velocity so that the vibration does not become too strong. The penetration of a gas jet into a solution is known to depend on the Ar number (modified Freude number). It can be proved computationally that the immersion tube according to the invention provides the necessary heat transfer at a lower immersion depth than with a normal single-aperture immersion tube. In this case, a higher gas velocity can be used in the discharge openings, because the distance from the bottom of the evaporator increases and because the extent of the gas jet is otherwise shortened due to the reduction in the size of the pipe. The increase in velocity in the pipeline, in turn, ensures the maximum flow resistance at the point of discharge, whereby possible vibrations do not pass through or reach at most damped.

The invention is further illustrated by the accompanying drawings, in which Figures 1 and 2 are schematic diagrams of prior art solutions, Figure 3 is a schematic drawing of a submerged pipe according to the invention with a closed space between the pipes, and Figure 4 is a schematic diagram of a submerged pipe with separate pipes.

Figure 1 shows a normal single orifice, flat-edged immersion tube 1 immersed in a tank 3 containing an evaporable liquid 2. The liquid is introduced into the tank through a pipe connection 4, the gases escape through 5 and the crystallized metal salt is discharged through 6 at the bottom of the tank. It is known that the gas jet 7 creates a vacuum zone around it, whereby the solution, especially at the discharge opening and in the vicinity, mixes with the gas jet. The higher the jet speed, the stronger the mixing.

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Especially in large immersion pipes, in order to reduce the penetration, the speed has to be reduced, whereby the gas bursts in large bubbles as shown in Fig. 1, swinging from one side to the other of the immersion pipe. When a large bubble bursts to the surface, the resulting pit fills with fluid from the environment, causing the surface to oscillate and splatter and thus contribute to the intensification of the vibration. It should also be noted that due to the lower speed, not much environmental liquid is absorbed into the gas, so the popping phenomenon is particularly strong due to the high lifting force.

Figure 2 shows a notched pipe 8 mentioned in the prior art. The phenomena described above in connection with Figure 1 also apply in this case. However, the situation is considerably improved compared to the case of Fig. 1, since part of the gas is discharged from the notches 9 in small gas discharges 10, thus smoothing out the surface rise somewhat. However, according to the case of Figure 1, a high buoyancy force (little liquid in the bubble) and a fluctuation from side to side for the main flow still apply. As stated above, the effect of the notch is weakened by the principle of continuity of the gas flow, i.e. the main flow is still very strong downwards.

Figure 3 shows a submersible tube 11 according to the invention, the lower part of which is formed by a plurality of downwardly directed tubes 12, the gaps of which are filled. In this case, small discrete jets 13 are initially formed, but they have some tendency to merge into one large jet because there is no liquid around the jets that they could absorb, but only below and on the side of the entire jet set. However, as stated above, several separate jets have a lower penetration into the liquid, and the advantage over the former is, however, a considerable reduction in the lifting force and thus in the surface oscillation.

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Figure 4 shows a particularly advantageous device solution for a submersible pipe according to the invention. The immersion tube 11 is immersed at its lower part in a tank 3 containing the liquid to be evaporated 2. The lower part of the immersion tube is formed by a plurality of separate, straight-down tubes 12 through which hot gases flow into the liquid to be evaporated. The immersion tube consisting of separate tubes is further surrounded by a circulation tube 14. The gas discharged from the immersion tube into the liquid is preferably controlled and limited by a tubular circulation tube surrounding the immersion tube, which at the same time provides a favorable liquid circulation. Openings 15 are placed in the liquid interface at the liquid interface, from which the gas or mixture of gas and liquid introduced through the immersion tube can be discharged into the liquid.

The tubes 12 of the outer circumference of the immersion tube are preferably chamfered at an angle of 45 ° so that the longer side of the lower end 16 of the tube is closest to the center of the tube. The gas now rises symmetrically and calm thanks to the side-rising jets. Since the gaps in the pipe are not filled, the jets are able to absorb the liquid sufficiently and thus retain their own jets, and in this case the "hydrogenated" jets rise as separate small jets due to the low lift. As a result, there are no large, oscillating bumps around the immersion tube. Thanks to the separate showers, the gas stays well inside the circulation tube.

Studies have shown that the immersion tube according to the invention has caused the vibration of the equipment to fall to one third of the vibration of the former prior art single-tube immersion evaporator.

Claims (5)

7 85337 Device for reducing the heart rate and vibration of a submersible evaporator when conducting hot gases through a submersible pipe (11) and a surrounding circulation pipe (14) to a liquid, characterized in that the lower part of the submersible evaporator submersible tube (11) is formed of a plurality of perpendicular downwards tubes (12). Device according to Claim 1, characterized in that the tubes (12) are separate. Device according to Claim 1, characterized in that the tubes on the outermost circumference of the immersion tube are chamfered so that the longer side of the tube is closest to the center. Device according to Claims 1 to 2, characterized in that the tubes on the outermost circumference are chamfered at an angle of 45 ° at their lower part. Device according to Claim 1, characterized in that the number of tubes is preferably 4 to 20. 8 85337