JPS6084101A - Flow-down film type evaporation apparatus - Google Patents

Abstract

PURPOSE:To effectively suppress the generation of mist without lowering evaporation capacity, by gradually enlarging the vertical opening end parts of the gaps between the heating elements of a flow-down film type evaporation apparatus from above to below. CONSTITUTION:A flow-down film type evaporation apparatus has a heater passage and is equipped with a large number of hollow flat plate shaped heating elements 2 provided vertically in parallel at predetermined intervals and a liquid to be treated is evaporated while flowed down along the outer surface of each heating element 2. A plural number of flow amount adjusting plates 4 are respectively provided to the end parts of the heating elements 2 in the width direction thereof. Each flow adjusting plate 4 has the same length as each heating element and comprises a vertically long plate shaped body of which the width is gradually narrowed from above to below. In addition, said plate 4 is contacted with the end part of each heating element 2 at the central part in the width direction thereof and almost contacted with adjacent plates 4 at the upper end part thereof to each other.

Description

[Detailed Description of the Invention] This invention is a method for concentrating various solutions in the chemical, food, machinery, and other industries.
n, r w> −u: pse Jshiyan+y NI+−
-W In general, a falling film type evaporator, as shown in FIGS. 1 and 2, has a heating fluid passage (11) and a plurality of hollow flat heating elements (11) arranged vertically in parallel at predetermined intervals. 2).The liquid to be treated is supplied to the liquid supply device (3).
is supplied to the upper end of each heating element (2) and flows down along its outer surface, where it receives heat and is evaporated and concentrated.

While the generated steam flows horizontally through the gaps between the heating elements (2) and is discharged, it is mixed with a few droplets of the liquid to be treated (hereinafter referred to as mist), so this is separated. However, in order to effectively perform gas-liquid separation in the separator, it is not preferable that a large amount of mist be mixed with the steam.

Mist is generated as shown in the figure and mixed with steam -A-
7+t, J--1! '-/; + Z 4n or 1
Then, the liquid to be treated flows forming a laminar region, a transition region, and a Q turbulent region. Further, the period from the beginning of the flow of the liquid to be treated to a certain distance is called a run-up section. In this section, the flow is completely laminar and the heat transfer resistance is large. As the flow progresses from the laminar region to the transition region to the turbulent region, the heat transfer resistance becomes smaller and heat is transferred more efficiently. As heat transfer is carried out efficiently and evaporation progresses, the liquid film becomes thinner, the heat transfer resistance becomes smaller and the heat transfer coefficient improves, and evaporation is promoted.
On the outer surface of the heating element, the rate of evaporation of the liquid to be treated differs in the vertical direction, with more evaporation occurring near the bottom.

In FIG. 1, this situation is schematically shown, and the density of the arrow indicating evaporation gradually increases from the top to the bottom.

Because the amount of evaporated steam differs in the upper and lower directions of the heating element, the steam flows laterally within the gap between the heating elements while rising toward the upper part where the amount of evaporation is less. or be disturbed. In this way, the steam flows countercurrently to the flowing liquid to be treated, and since the flow is not uniform, steam or mist is entrained.

By the way, as a conventional evaporator for preventing the mixture of steam and mist, as disclosed in Japanese Patent Laid-Open No. 53-83977, only one side end or lower end of the heating element gap is used. The heating element is fully opened or partially opened to control the direction of the evaporative vapor generated between the heating elements, and the evaporative vapor collides with the inner wall of the housing, causing a forced direction change. There is a known method that does not separate Miss I. However, regulating the direction of steam discharge leads to an increase in steam droplets between the heating elements, which makes mist more likely to be generated from the surface of the heating elements, and at the same time increases power loss in the steam flow path. Therefore, the evaporation performance decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a falling film type evaporator that can eliminate the above-mentioned drawbacks and effectively suppress mist generation without deteriorating evaporation performance.

The falling film type evaporator according to the present invention includes a plurality of hollow flat heating elements each having a heating fluid passage and arranged vertically in parallel at a predetermined interval. In a falling film type evaporator, the vertical opening end of each heating element gap is gradually opened larger from top to bottom. According to the invention, the vertical opening end of each heating element gap is gradually opened larger from top to bottom, so that the flow rate of steam passing through the opening is adjusted to be throttled according to the opening area. Therefore, the flow velocity of the steam flowing laterally within the same gap becomes uniform in the vertical direction, preventing the steam from flowing in the countercurrent direction to the liquid to be treated, and preventing the steam flowing above and below. Since the flow of steam is not disturbed by the Japanese roof tiles, mist is entrained in the steam, and mist generation can be effectively suppressed.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 6. 3 to 6 correspond to the falling film type evaporator shown in FIGS. 1 and 2. In each figure, the same reference numerals are given to the same components for convenience.

In each of the embodiments shown below, flow rate adjustment plates +41 +51 (61+71
By providing this, the vertical opening ends of the gaps between the heating elements (2) gradually become larger from the top to the bottom.

FIG. 3 shows a first embodiment. A plurality of flow rate adjustment plates (4) are provided at the ends in the width direction of the heating element (2), respectively. The flow rate adjustment plate (4) is a vertically long plate-like body having the same length as the heating element (2) and whose width gradually narrows from top to bottom. (3
), and their upper ends are substantially in contact with each other.

FIG. 4 shows a second embodiment. In this embodiment, a flow rate adjustment plate (5) which is almost the same as the flow rate adjustment plate (4) of the first embodiment is used.
are located between each heating element.

FIG. 5 shows a third embodiment. In this embodiment, similar to the second embodiment, flow jaw cedar plates (6) are provided between each heating element (2). Tashi style m N! The I-straight plate (6) has a constant diameter 1□1 narrower than the gap between each heating element (2);
The upper end is located at the open end of each heating element (2), and the lower end is separated from the same end by a thin thread.

FIG. 6 shows a fourth embodiment. In this embodiment, one flow regulating plate (7) is provided so as to abut each end of each heating element (2). A large number of steam outlet ports (8) are opened in the flow ij1 adjustment plate (7).

The outflow ports (8) are arranged in vertical rows at positions corresponding to the gaps between the heating elements (2), and the area of each opening increases from top to bottom. Note that the outlet (8) may be one in which a large number of outlets each having a constant opening area are arranged so that the density gradually increases from top to bottom, instead of having a large and small opening area.

Each flow rate adjusting plate +41 +51 +6) (The opening area at each height of 7+ is such that the steam evaporated at the same position above and below the heating element (2) flows almost horizontally through the gap between each heating element (2). The heating element (2) is arranged so that when J'Jt is discharged from the same opening, the flow velocity is approximately constant at each position.
It is determined according to the amount of steam that evaporates at the same upper and lower positions. Further, the gap between each heating element (2) is determined so that when the vapor evaporated at the bottom flows in a substantially horizontal direction, the flow velocity is below an allowable flow rate at which the mist is not carried away by the flow.

Flows at a current speed. As a result, the steam does not rise and flow countercurrently to the liquid to be treated (and since the upper and lower flows are not mutually disturbed, the mist is not carried away along with the steam).

[Brief explanation of drawings]

1 and 2 show a conventional example. FIG. 1 is a vertical sectional view showing the main part, and FIG. 2 is a sectional view taken along the line nn in FIG. 1. 3 to 6 are perspective views showing each embodiment of the present invention. (1)... Heating fluid passage, (2) - Fist heating element, 1
41 f51f61 +71...Flow rate adjustment plate. That's it IL/Ily! -1 wave)

Claims (1)

[Claims] A plurality of hollow flat heating elements each having a heating fluid passage and arranged vertically in parallel at a predetermined interval are provided, and the liquid to be treated flows down along the outer surface of each heating element. In a falling film type evaporator, the width of each heating element gap gradually increases from the open end of the opening to the bottom.