JPH0698241B2 - Evaporation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an improvement in an evaporation method using a multitubular heat exchanger.

[Prior Art] FIG. 4 is a vertical sectional view showing an example of a horizontal pipe falling liquid film evaporator used in a conventional evaporation method, and FIG. 5 is a transverse sectional view of the same. In these figures, while a high-temperature fluid is caused to flow as a heating medium inside a plurality of horizontal heat transfer tubes (2a) arranged in the body (1), a spray nozzle (above the heat transfer tubes (2a) is provided. Disperse the liquid to be heated from 7),
Disperse on top of heat transfer tube (2a). The dispersed liquid flows down while forming a thin film on the outer surface of the heat transfer tube (2a), during which the liquid is heated by the heating medium in the tube and evaporated. The vaporized vapor is taken out from the vaporized vapor outlet nozzle (8) at the upper part of the cylinder. On the other hand, the liquid that has not evaporated is taken out from the non-evaporated liquid outlet nozzle (9) and sprayed again from the spray nozzle (7). (21) is a preheater for heating the liquid sprayed from the spray nozzle (7) to a saturated state. In the figure, (5) is a heated fluid inlet nozzle, (4) is a heating medium inlet / outlet nozzle,
(3) is a tube support plate, and (13a) is a liquid level.

Next, FIG. 6 shows another form used in the conventional evaporation method,
FIG. 7 is a longitudinal sectional view showing an example of an evaporator (kettle type evaporator) by pool boiling, and FIG. 7 is a transverse sectional view of the same. In the pool boiling evaporator, the liquid to be heated enters from the fluid inlet nozzle (6) to be heated provided in the lower part of the barrel (1) to form the liquid pool (13). The liquid surface (13a) is located above the heat transfer tube (2b). That is, the heat transfer tube (2b) is completely immersed in the liquid, and the liquid is heated by the heating medium through the heat transfer tube (2b) and evaporated. The vaporized gas goes out from the vaporization vapor outlet nozzle (8) through the gas-liquid separation chamber (11) formed in the upper part of the barrel (1).

[Problems to be Solved by the Invention]

In the horizontal down-flow liquid film evaporator, the amount of liquid flowing down decreases toward the lower stage of the heat transfer tube, so that the heat transfer tube in the lower stage becomes dry. If there is a dry portion, that portion does not participate in the evaporation, so the efficiency is reduced accordingly. In order to prevent this and to ensure the wetting of the heat transfer tubes in the lower stage, it is necessary to increase the amount of spray liquid, but as the amount of spray liquid increases, the amount of non-evaporated liquid in the heat transfer tubes in the lower stage increases and this liquid is circulated. Therefore, it is necessary to increase the pump capacity.

On the other hand, in the kettle type evaporator, a passage (12) for natural convection circulation of liquid and a space (11) for separating gas and liquid.
Since the space other than the heat transfer section is large, the evaporator volume becomes large and the filling amount increases. Further, at the bottom of the liquid, the boiling point rises due to the liquid pressure, so the performance deteriorates.

[Means for Solving the Problems]

In order to solve the above-mentioned conventional problems, the present inventor uses a method of causing a high-temperature fluid to flow inside a plurality of heat transfer tubes that are arranged substantially horizontally inside the body of an evaporator to evaporate a liquid outside the heat transfer tubes. , By immersing the heat transfer tube of the lower part of the heat transfer tube into the liquid to be heated introduced into the lower portion of the body of the evaporator, preheat the liquid to be heated in the heat transfer tube of the lower part,
The preheated liquid to be heated is sprayed from above the heat transfer tube,
The present invention proposes an evaporation method characterized in that the outer surface of the upper part of the heat transfer tube is made to flow down like a film.

[Action]

The liquid to be heated in the lower part of the body of the evaporator immerses the heat transfer tube in the lower part, is heated by the high temperature fluid in the heat transfer tube, and partly evaporates (pool boiling). The heated non-evaporated liquid is scattered from above the heat transfer tube and flows down while forming a thin film on the outer surface of the heat transfer tube in the upper part of the body, while receiving heat from the high temperature fluid inside the tube and evaporating (film evaporation). .

〔Example〕

FIG. 1 is a diagram showing a flow of an embodiment of the present invention, FIG. 2 is a vertical side view showing an example of an evaporator used in the method of the present invention, and FIG. 3 is a transverse sectional view of the same.

In these figures, a high-temperature fluid is made to flow as a heating medium inside a plurality of horizontal heat transfer tubes (2a), (2b) arranged in the body (1). On the other hand, the liquid of the heated fluid passes through the heated fluid inlet nozzle (5) at the upper part, and then the spray nozzle (7).
To the top row of heat transfer tubes (2a). The number and arrangement of the heated fluid inlet nozzle (5) and the spray nozzle (7) are optimally determined according to the specifications of the spray nozzle and the size and structure of the evaporator.

The sprayed liquid to be heated flows down while forming a thin film on the outer surface of the heat transfer tube (2a) arranged above. During that time, the heat is received from the heating medium in the pipe, and it flows down while evaporating. Therefore, the flow rate decreases as it goes to the lower row.

The heat transfer tube (2b) arranged in the lower part is immersed in the liquid of the fluid to be heated, and the non-evaporated liquid flowing down the surface of the heat transfer tube (2a) arranged in the upper part is the liquid pool (13). Collect in.
The accumulated liquid receives heat from the heat transfer tube (2b) located under the liquid surface (13a) and immersed in the liquid, and part of it evaporates by boiling. The liquid surface (13a) is controlled to a predetermined level.

Both the gas evaporated while flowing down from the surface of the upper heat transfer tube (2a) and the gas boiled and evaporated in the liquid pool (13) go out through the evaporation vapor outlet nozzle (8). An amount of liquid corresponding to the amount of the gas thus discharged is replenished by the liquid supply pump (22) from the lower heated fluid inlet nozzle (6). Further, the liquid in the lower liquid pool (13) is circulated and supplied from the non-evaporated liquid outlet nozzle (9) to the upper heated fluid inlet nozzle (5) by the circulation pump (23).

In this embodiment, since only the heat transfer tube (2a) arranged on the upper side is exposed on the liquid surface (13a), even in the lowermost stage of the exposed heat transfer tube (2a), the conventional horizontal pipe external flow Compared to the evaporation method using a liquid film evaporator, sufficient wetting can be secured with a small amount of circulating liquid. In addition, in the present embodiment, the gas-liquid separator of the conventional kettle type evaporator (reference numeral (1 in FIG. 6 and FIG. 7
Since the falling film evaporation is performed in 1)), the size of the evaporator can be made more compact than the conventional kettle type evaporator. Furthermore, if the liquid supplied is unsaturated,
After being preheated in the lower pool (13), the upper heat transfer tube (2
Since it will be sprayed on a), the efficiency of liquid film evaporation will also be improved.

〔The invention's effect〕

Evaporation method of the present invention, by having the advantages of the method by the falling liquid film evaporation and the advantages of the method by pool boiling, it is possible to reduce the amount of circulating liquid compared to the conventional method by the falling liquid film evaporator, and the preheater It can be omitted. In addition, it is a highly efficient and inexpensive evaporation method because the space can be effectively used and the size can be made compact as compared with the conventional method using a kettle type evaporator.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of an embodiment of the present invention, FIG. 2 is a vertical side view showing an example of an evaporator used in the method of the present invention, and FIG. 3 is a transverse sectional view of the same. FIG. 4 is a vertical sectional view showing an example of a horizontal pipe falling liquid film evaporator used in a conventional evaporation method, and FIG. 5 is a transverse sectional view of the same. FIG. 6 is a longitudinal sectional view showing an example of an evaporator (kettle type evaporator) by pool boiling used in a conventional evaporation method, and FIG. 7 is a transverse sectional view of the same. (1) …… Body, (2a), (2b) …… Heat transfer tube, (3) …… Tube support plate, (4) …… Heating medium inlet / outlet nozzle, (5), (6) …… Covered Heating fluid inlet nozzle, (7) ……
Spray nozzle, (8) …… Evaporation vapor outlet nozzle, (9) …… Unevaporated liquid outlet nozzle, (11) …… Gas-liquid separation chamber, (12) …… Natural convection passage, (13) …… Liquid pool , (13a) …… liquid level, (21) …… preheater, (22) …… liquid supply pump, (23) …… circulation pump.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mukuro Kakiki 5007 Itozaki-cho, Mihara-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Mihara Manufacturing Co., Ltd. References JP-A-51-143575 (JP, A) JP-A-58-36601 (JP, A) Actual development Sho-56-110881 (JP, U) Actual publication 57-881 (JP, Y2)

Claims (1)

[Claims] 1. A method for causing a high-temperature fluid to flow inside a plurality of heat transfer tubes arranged substantially horizontally inside the body of an evaporator to evaporate a liquid outside the heat transfer tubes, wherein a lower part of the heat transfer tubes is By immersing the heat transfer tube in the liquid to be heated introduced into the lower part of the body of the evaporator, the liquid to be heated is preheated by the heat transfer pipe in the lower portion, and the preheated liquid to be heated is supplied from above the heat transfer pipe. A method for vaporizing, characterized in that the outer surface of the heat transfer tube in the upper part of the heat transfer tube is sprayed down in a film shape.