JPH08126836A - Liquid level control mechanism - Google Patents

Abstract

PURPOSE: To provide a liquid level control mechanism having a simple constitution and capable of controlling a liquid level in a short time. CONSTITUTION: This liquid level control mechanism is the one for controlling the level of liquid housed in a tank, which is provided with an insoluble gas holding part 60 having a communicative port 76 communicating with the inside of the tank in the lower part thereof and for hosing liquid flowing in and out through the communicative port 76 in the lower part and for housing insoluble gas above the liquid, a level gage 62 for detecting the liquid level in the tank, inflow means 64, 66, 68 for force feeding gas into the holding part, outflow means 70, 72 for causing gas to flow out to the outside from the gas holding part, and a control means 74 for controlling the inflow means and the outflow means based on a detected value of the level gage. The gas is caused to flow into or out of the gas holding part 60 to lower or raise the liquid level in the lower part of the gas holding part, thereby the liquid level in the tank is lowered or raised. At this time, based on the detected value of the level gage, the inflow or outflow quantity of the gas flowing into or out of the gas holding part is controlled by the control means 74 so that the liquid level in the tank may attain a prescribed liquid level position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a liquid surface of a liquid contained in a container, particularly a liquid surface of a liquid contained in a large container, for example, a liquid surface contained in a large container having a diameter of 10 to 50 m. Regarding the liquid level adjusting mechanism for adjusting, more specifically, the liquid level adjusting mechanism having a simple and economical structure and capable of adjusting the liquid level in a short time, especially the liquid level of the jet bubbling reaction tank The present invention relates to a liquid level adjusting mechanism suitable for adjusting.

[0002]

2. Description of the Related Art In a factory such as a chemical factory or a petrochemical factory, various liquids are contained in a container, and for various reasons, the setting position of the liquid level of the liquid contained in the container is changed and the liquid is stored for a short time. It is often necessary to adjust the liquid level at that position. The necessity of such rapid liquid level adjustment will be described by taking a jet bubbling reaction tank as an example. A jet bubbling reaction tank (hereinafter simply referred to as a reaction tank) is a compact, exhaust gas treatment device used to remove environmental pollutants such as SO ₂ , HF, Hcl, NH ₃ and dust contained in exhaust gas. It is a reaction tank with low operating cost.

As shown in FIG. 4, the reaction tank 12 is a vertical container, which is provided in the lower part of the container with an absorbing liquid storage portion 14 and on the absorbing liquid storage portion 14 for reacting exhaust gas containing sulfurous acid gas. Exhaust gas inlet chamber 16 to be introduced inside, and exhaust gas inlet chamber 16
An exhaust gas dispersion pipe 20 for introducing exhaust gas into the absorption liquid is provided, and an exhaust gas outlet chamber 22 provided on the exhaust gas inlet chamber 16 for discharging the treated exhaust gas to the outside of the system. The exhaust gas dispersion pipe 20 has an upper end connected to the lower partition wall of the exhaust gas inlet chamber 16, a lower part arranged substantially vertically so as to be immersed in the absorption liquid, and a large number of through holes 18 in the lower part. The exhaust gas outlet chamber 22 communicates with the space above the liquid surface of the absorbing liquid via a communication pipe 24 that penetrates the exhaust gas inlet chamber 16. The absorption liquid storage unit 14 stores an SO ₂ fixing agent, for example, an absorption liquid in which limestone is dissolved or suspended.

Exhaust gas containing SO ₂ is sent from the exhaust gas source to the exhaust gas inlet chamber 14 through the exhaust gas introduction duct 26, and further below the liquid surface of the absorption liquid stored in the absorption liquid storage portion 14 by the exhaust gas dispersion pipe 20. And is jetted out from the through-hole 18 in a jet form to bubble while bubbling into the absorbing liquid. As a result, a so-called jet bubbling layer A is generated below the liquid surface. Subsequently, the exhaust gas rises from the absorbing liquid, enters the exhaust gas outlet chamber 22 via the communication pipe 24, and is further discharged from the exhaust duct 28 to the outside of the system. SO ₂ in the exhaust gas is
At the same time as reacting with the SO ₂ fixing agent in the absorbing solution to form a sulfite, at the same time, it is oxidized by an oxygen-containing gas blown from an oxygen-containing gas introducing pipe 30 arranged at the bottom of the reaction tank, for example, air to be a sulfate, and Hydrate and crystallize. Although not shown, the absorbing solution containing the crystallized sulfate, for example, gypsum in a concentrated manner, is sent to a centrifugal separator by a pump through an absorbing solution discharge pipe to separate gypsum. In FIG. 4, 32 is a stirring blade for stirring the absorbing liquid, and 34 is a transparent liquid level gauge.

By the way, the desulfurization rate of the reaction tank is determined by the P of the absorption liquid.
As long as other conditions such as H and exhaust gas flow rate are constant, as shown in FIG. 5, it depends on the immersion depth of the exhaust gas dispersion pipe. Here, the immersion liquid depth LS of the exhaust gas dispersion pipe refers to the exhaust gas dispersion pipe 20 as shown in FIG.
It is displayed by the distance from the upper end of the through hole 18 provided in the lower part of the tank to the liquid surface of the absorbing liquid.
As shown in (b), it is displayed by the distance between the liquid level of the transparent liquid level gauge 34 and the upper end of the through hole. 6 (a) and 6 (b),
FIG. 5 is an enlarged view of “B” in FIG. 4, respectively. Conventionally, in order to maintain the desulfurization rate at a constant value, the immersion depth is constant, and therefore
The liquid level of the absorbing liquid was controlled at a fixed position.

However, in the operation of the reaction tank in which the immersion depth is kept constant and the desulfurization rate is kept constant, when the SO ₂ concentration in the exhaust gas at the reaction tank inlet is small, the SO ₂ in the exhaust gas at the outlet of the reaction tank is reduced.
_{2 The} concentration is a very small value, which is much lower than the allowable value. Conversely, if the SO ₂ concentration in the exhaust gas at the reaction tank inlet is high,
The SO ₂ concentration in the exhaust gas at the outlet of the reaction tank may be higher than the allowable value. This causes environmental problems when the SO ₂ concentration at the reaction tank inlet is high, and becomes uneconomical in terms of pollution prevention economy when the SO ₂ concentration at the reaction tank inlet is low.

Therefore, it is required to change the desulfurization rate according to the change in the SO ₂ concentration of the exhaust gas to keep the SO ₂ concentration of the outlet constant. To change the desulfurization rate, as can be seen from FIG. 5, it is necessary to change the immersion liquid depth and hence the position of the liquid surface according to the variation of the SO ₂ concentration at the inlet of the exhaust gas.
That is, when the SO ₂ gas concentration at the inlet is low, the depth of the immersion liquid is made shallow, and therefore the liquid surface is lowered to reduce the desulfurization rate,
_{2 When the} gas concentration is high, the depth of immersion is deepened, and therefore the liquid surface is raised to increase the desulfurization rate. Moreover, it is necessary to adjust the immersion liquid depth, that is, the position of the liquid surface in a short time according to the fluctuation of the SO ₂ concentration in the exhaust gas.

[0008]

By the way, the reaction tank 12
Is basically the absorption liquid supply / discharge mechanism as shown in FIG.
As shown in FIG. 4, the absorption liquid storage tank 40, the supply pump 42, the discharge pump 44, the liquid level gauge 46, the control device 48, the flow control valve 5
0 and 52 are provided to control the position of the liquid surface in the reaction tank 12, discharge the waste absorption liquid from the reaction tank 12, and supply a new absorption liquid instead of the absorption liquid from the absorption liquid storage tank 40. When it is necessary to adjust the liquid level of the reaction tank 12 as described above, the conventional liquid level adjusting mechanism reacts when the liquid level is raised by the cooperation of the controller 48 and the flow rate adjusting valves 50 and 52. The operation of increasing the flow rate of the absorbing solution fed into the tank 12 and decreasing the flow rate of the absorbing solution flowing out of the reaction tank 12 is performed. When lowering the liquid level, the reverse operation is performed.

For example, in the example shown in FIG. 6, when the diameter of the reaction tank 12 is 40 m, the position of the liquid surface is 10 from the current position.
When it is necessary to adjust the liquid level in 1 minute by setting it up or down by cm, it is necessary to allow the absorbing solution to flow in and out at a flow rate of about 130 m ³ / min. For this purpose, in addition to the reaction tank 12, a large absorption liquid storage tank 40 for storing 130 m ³ or more of the absorption liquid and 130 m of the absorption liquid are stored.
Large feed and discharge pumps with a flow rate of ³ / min are needed, and the pump capacity determines the time required for liquid level adjustment. Alternatively, as another method, there is a means in which a container for storing the absorption liquid of 130 m ³ or more is installed at a position higher than the reaction tank and gravity flows down.

However, any of the above-mentioned conventional liquid level adjusting mechanisms requires a large facility and a lot of site, which increases the facility cost and is economically burdensome. Therefore, the purpose of the present invention is to
An object of the present invention is to provide a liquid level adjusting mechanism having a simple structure and capable of adjusting the liquid level in a short time.

[0011]

In order to achieve the above object, a liquid level adjusting mechanism according to the present invention is a mechanism for adjusting a liquid level position of a liquid contained in a container, which is a communication port with the inside of the container. And a gas reservoir portion for accommodating a liquid that flows in and out through a communication port and an insoluble gas on the liquid, an inflow means for allowing the gas to flow into the gas reservoir portion, and a gas And an outflow means for outflowing the gas from the gas reservoir to the outside so that the gas may flow into or out of the gas reservoir to lower or raise the liquid level in the gas reservoir, thereby raising or lowering the liquid level in the container. It is characterized by having done.
The gas used in the present invention is not particularly limited as long as it is insoluble, and air or exhaust gas in the case of the above-mentioned jet bubbling reaction tank can be used. Further, the inflow means may be composed of, for example, a gas cylinder and a pipe connected to it, or may be composed of a compressor and a pipe connected to it.

A preferred embodiment of the present invention further comprises a liquid level gauge for detecting the liquid level of the liquid in the container, and a control means for controlling the inflow means and the outflow means based on the detection value of the liquid level gauge. Based on the detection value of the liquid level gauge, the inflow amount or outflow amount of the gas flowing into or out of the gas reservoir is adjusted by the control means so that the liquid level in the container reaches the set liquid level position. It is characterized by doing so.

The liquid level adjusting mechanism according to the present invention can be suitably applied as a liquid level adjusting mechanism of the absorbing liquid in the jet bubbling reaction tank, in which case the gas reservoir is formed along the peripheral wall of the jet bubbling reaction tank. A reaction tank peripheral wall provided outside, and a top plate connected to the reaction tank peripheral wall at one peripheral edge,
The whole annular container formed by the side wall hanging from the other peripheral edge of the top plate and the bottom plate connecting the lower edge of the side wall and the peripheral wall of the reaction tank, or forming a part of the annular container and facing them. It is configured by closing both end faces, the communication port is provided on the peripheral wall of the reaction tank between the top plate and the bottom plate, and the top plate is provided with an inlet for letting in gas in and an outlet for letting out gas. It features.

Further, in another liquid level adjusting mechanism according to the present invention which can be suitably applied as a liquid level adjusting mechanism of the absorbing liquid in the jet bubbling reaction tank, the gas reservoir is formed along the peripheral wall of the jet bubbling reaction tank. The reaction vessel peripheral wall is provided inside, the top plate whose one peripheral edge is connected to the reaction chamber peripheral wall, and the side wall hanging from the other peripheral edge of the top plate, the upper side formed by a closed annular body. , Or formed by partially forming the annular body and closing the opposite end surfaces thereof, and the opening of the lower edge of the side wall and the peripheral wall of the reaction tank functions as a communication port, and an inlet for introducing gas. It is characterized in that the top plate is provided with an outlet for letting it flow out.

[0015]

1 is a schematic flow sheet showing the operating principle of the liquid level adjusting mechanism according to the present invention. The liquid level adjusting mechanism according to the present invention includes a container-shaped gas reservoir 60, a liquid level gauge 62 for detecting the liquid level of the liquid in the container C, an inflow pipe 66 having an automatic control valve 64, and a connection therewith. A gas cylinder 68, an outflow means including an outflow pipe 72 having an automatic control valve 70, and a control device 74 for controlling the inflow means and the outflow means based on the detection value of the liquid level gauge 62. I have it. The lower portion of the gas reservoir 60 and the container C communicate with each other through a communication pipe 76, whereby liquids are transferred to each other. It should be noted that it is also possible to operate manually without providing the control device 74.

As shown in FIG. 1B, the lowest position of the liquid surface of the container C is assumed to be level 1, and the corresponding liquid surface in the gas reservoir 60 is set to level 1. At this time, the level 1 of the container C is at the same height as the level 1 of the gas reservoir 60 or at a higher position. When it is desired to raise the liquid level in the container C to level 2, the controller 74 sets the liquid level set value to level 2, and then the automatic control valve 64 is opened to collect gas from the gas cylinder 68. Introduced into part 60. As a result, a part of the liquid in the gas reservoir 60 is transferred to the container C through the communication pipe 76. Liquid level gauge 6
The detected value of 2 is always input to the control device 28, and when the detected value reaches the level 2, the automatic control valve 64 is closed and the liquid level of the gas reservoir 60 is lowered to the level 2.
Has reached. When it is desired to increase from level 1 or level 2 to level 3, the same operation as described above is performed.

On the contrary, when it is desired to lower the liquid level in the container C from level 3 to level 2 or level 1, the controller 7
In 4, the set value of the liquid level is set to level 2 or level 1, and then the automatic control valve 70 is opened to discharge the gas in the gas reservoir 60 to the outside. As a result, a part of the liquid in the container C is transferred to the gas reservoir 60 through the communication pipe 76. When the detection value of the liquid level gauge 62 reaches level 2 or level 1, the automatic control valve 70 is closed, and the liquid level of the gas reservoir 60 is lowered to the level as shown in FIG. 1 (b). Reach 2 or Level 1. In this case, the liquid is mainly transferred due to the difference in height between the liquid surface of the container C and the liquid surface of the gas reservoir 60.

As described above, by introducing the gas into the gas reservoir 60, the liquid in the gas reservoir 60 is transferred to the container C by the pressure of the gas, and the liquid in the container C is vaporized due to the difference in height of the liquid surface. The liquid is transferred to the reservoir 60 and the liquid level of the container C is adjusted to the set position. Moreover, the gas pressure required to transfer the liquid from the gas reservoir 60 to the container C is a relatively small pressure equal to the difference in height between the liquid surface of the container C and the liquid surface of the gas reservoir 60. Therefore, like the conventional liquid level adjustment mechanism,
Since it is not necessary to transfer the liquid from the storage tank with a pump, etc., and the liquid is transferred using a gas suitable for flowing in and out at a large flow rate, the pressure of the gas, regardless of the capacity of the pump, etc. The time required for liquid level adjustment can be set short by considering the dimensions of the communication port. Further, since the liquid is transferred by the pressure of the gas or the height difference of the liquid level, the liquid level can be adjusted by a simple mechanism. Further, after the liquid surface reaches the set liquid surface position, the control device can be controlled to maintain the liquid surface at that position.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. Example 1 FIG. 2 (a) is a schematic flow sheet showing an example in which the liquid level adjusting mechanism according to the present invention is applied to a jet bubbling reaction tank, and FIG. 2 (b) is an arrow XX of FIG. 2 (a). FIG. 3 is a plan view of the gas reservoir portion in FIG. 2, and both figures exclude the stirring blades and the like that are not directly related to the present invention. The same parts as those shown in FIG. 1 among the parts shown in FIGS. 2 and 3 are designated by the same reference numerals. The liquid level adjusting mechanism of this embodiment is the same as the reaction tank 1 shown in FIG.
In addition to the configuration of 2, a gas including a gas reservoir 60, a liquid level gauge 62 for detecting the liquid level of the liquid in the container, an inflow pipe 66 having an automatic control valve 64, and a gas bomber 68 connected thereto. Outflow pipe 7 having inflow means and automatic control valve 70
It comprises an outflow means consisting of 2 and a control device 74 for controlling the inflow means and the outflow means based on the detection value of the liquid level gauge 62.

As shown in FIG. 2B, the gas reservoir 60 is formed around the peripheral wall 78 on the outside of the reaction tank 12, and is connected to the peripheral wall 78 at one peripheral edge. The top plate 80, a cylindrical side wall 82 that hangs down from the other peripheral edge of the top plate 80, and a bottom plate 84 that connects the lower end of the side wall 82 and the peripheral wall 78. An annular opening is formed above the connecting portion that connects the peripheral wall 78 and the bottom plate 84.
6 is provided to connect the gas reservoir 60 and the inside of the container C. In this embodiment, the diameter of the reaction tank 12 is 4
Assuming that the width of the top plate 80 is 2 m, the height of the side wall 82 is about 2 m, assuming that the height of the top plate 80 is 2 m and the difference in liquid level (difference between the level 1 and the level 3 of the reaction tank 12 in FIG. Good, the difference between the liquid surface of the reaction tank 12 and the liquid surface of the gas reservoir 60 (difference between level 1 and level 3 ') is about 95 cm. Therefore, the pressure required to raise the liquid level is about 115 cm in the water column.

The operation principle and effects of the liquid level adjusting mechanism of the present embodiment are the same as those of the liquid level adjusting mechanism shown in FIG. 1, and further, in the case of the present embodiment, as a wall facing the side wall 82 of the gas reservoir 60. Since the peripheral wall 78 of the reaction tank 12 is used, it is economical. In the present embodiment, the gas reservoir 60
Is formed so as to make one round along the outer circumference of the reaction tank 12, but may be provided only on a part of the outer circumference. Further, instead of the gas cylinder 68, air or exhaust gas may be sent in by a compressor, and in the case of exhaust gas having a pressure, compression by the compressor is not necessary. Furthermore, the exhaust gas at the inlet of the reaction tank 12
It is also possible to automatically set the liquid level of the absorbing liquid in the reaction tank 12 according to the relationship shown in FIG. 5 based on the measured value of the SO ₂ concentration.

Embodiment 2 FIG. 3 shows the structure of a gas reservoir of Embodiment 2 in which another liquid level adjusting mechanism according to the present invention is applied to a jet bubbling reaction tank (hereinafter simply referred to as a reaction tank). It is a schematic diagram.
As shown in FIG. 3, the gas reservoir 60 of the liquid level adjusting mechanism of the present embodiment is formed around the peripheral wall 78 inside the reaction tank 12, and is connected to the peripheral wall 78 at one peripheral edge. It is composed of an annular top plate 90 and a cylindrical side wall 92 that hangs from the other peripheral edge of the top plate 90. An annular opening between the lower edge of the side wall 92 and the peripheral wall 78 functions as a communication port 76 for communicating the gas reservoir 60 with the inside of the container C. The operation principle and effects of the liquid level adjusting mechanism of the present embodiment are the same as those of the liquid level adjusting mechanism shown in FIG. 1, and further, in the case of the present embodiment, the reaction tank 12 is a wall facing the side wall 92 of the gas reservoir 60. Since the peripheral wall 78 is used, it is economical. In the present embodiment, the gas reservoir 60 is formed so as to make one round along the inner circumference of the reaction tank 12.
It may be provided only on a part of the inner circumference. Further, as in the first embodiment, air or exhaust gas may be sent in by a compressor instead of the gas cylinder 68, and in the case of exhaust gas with pressure, compression by the compressor is not necessary. Further, the liquid level of the absorbing liquid in the reaction tank 12 can be automatically set according to the relationship shown in FIG. 5 based on the measured value of the SO ₂ concentration of the exhaust gas at the inlet of the reaction tank 12.

[0023]

According to the present invention, gas is caused to flow into or out of the gas reservoir to lower or raise the liquid level in the gas reservoir, thereby raising or lowering the liquid level in the container. Unlike the conventional liquid level adjusting mechanism, it is not necessary to transfer the liquid from the storage tank with a pump or the like, and the liquid is transferred by the pressure of gas, so that the liquid level can be adjusted with a simple mechanism in a short time. Furthermore, a liquid level gauge for detecting the liquid level of the liquid in the container, and a control means for controlling the inflow means and the outflow means on the basis of the detection value of the liquid level gauge are provided, and based on the detection value of the liquid level gauge. By controlling the inflow or outflow amount of gas flowing in or out of the gas reservoir by the control means so that the liquid level in the container reaches the set liquid level position, the liquid level can be adjusted automatically and rapidly. Can be done. Further, by forming the gas reservoir along the peripheral wall of the container, an economical liquid level adjusting mechanism can be realized.

[Brief description of drawings]

FIG. 1 (a) and FIG. 1 (b) are schematic flow sheets for explaining the operation principle of a liquid level adjusting mechanism according to the present invention.

FIG. 2 (a) is a schematic flow sheet showing an example in which the liquid level adjusting mechanism according to the present invention is applied to a jet bubbling reaction tank, and FIG. 2 (b) is an arrow XX of FIG. 2 (a). FIG. 3 is a plan view of a gas reservoir in FIG.

FIG. 3 is a schematic view showing an example in which another liquid level adjusting mechanism according to the present invention is applied to a jet bubbling reaction tank.

FIG. 4 is a schematic diagram showing the configuration of a jet bubbling reaction tank.

FIG. 5 is a graph showing the relationship between immersion liquid depth and desulfurization rate.

6 (a) and 6 (b) are diagrams for explaining the immersion liquid depth.

FIG. 7: Supplying an absorption liquid to a jet bubbling reaction tank,
Alternatively, it is a schematic flow sheet of the discharging mechanism.

[Explanation of symbols]

 12 Jet bubbling reaction tank 14 Absorbing liquid storage part 16 Exhaust gas inlet chamber 18 Through hole 20 Exhaust gas dispersion pipe 22 Exhaust gas outlet chamber 24 Communication pipe 26 Exhaust gas introduction duct 28 Exhaust duct 30 Oxygen-containing gas introduction pipe 32 Stirring blade 34 Perspective liquid level meter 40 Absorbing liquid storage tank 42 Supply pump 44 Discharging pump 46 Liquid level gauge 48 Control device 50, 52 Flow rate control valve 60 Gas reservoir 62 Liquid level gauge 64, 70 Automatic control valve 66 Inflow pipe 68 Gas cylinder 70 Automatic control valve 72 Outflow pipe 74 Control device 76 Communication pipe 78 Peripheral wall of jet bubbling reaction tank 80, 90 Top plate 82, 92 Side wall 84 Bottom plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G05D 9/12 A

Claims (4)

[Claims] 1. A mechanism for adjusting the liquid surface position of a liquid contained in a container, the liquid communication device having a communication port with the inside of the container at a lower part, and a liquid which flows in and out through the communication port and is not dissolved on the liquid. Gas reservoirs each containing a volatile gas, inflow means for inflowing the gas into the gas reservoir, and outflow means for outflowing the gas from the gas reservoir to the outside. Alternatively, the liquid level adjusting mechanism is characterized in that the liquid level in the gas reservoir is lowered or raised by causing it to flow out, and thereby the liquid level in the container is raised and lowered. 2. A liquid level gauge further comprising: a liquid level gauge for detecting the liquid level of the liquid in the container; and a control means for controlling the inflow means and the outflow means based on the detection value of the liquid level gauge. Based on the detected value, the inflow amount or outflow amount of the gas flowing into or out of the gas reservoir is adjusted by the control means so that the liquid level in the container reaches the set liquid level position. The liquid level adjusting mechanism according to claim 1. 3. The container is a jet bubbling reaction tank, and the gas reservoir is provided outside along the peripheral wall of the jet bubbling reaction tank, and the peripheral wall of the reaction tank and the peripheral wall of the reaction tank at one peripheral edge. Of the top plate connected to the bottom plate, the side wall hanging from the other peripheral edge of the top plate, and the bottom plate connecting the lower edge of the side wall and the peripheral wall of the reaction vessel, or the whole of the ring container. The communication port is formed on the peripheral wall of the reaction tank between the top plate and the bottom plate, and has an inlet for letting in gas in and an outlet for letting out gas. The liquid level adjusting mechanism according to claim 1 or 2, which is provided on the plate. 4. The container is a jet bubbling reaction tank, and the gas reservoir is provided inside the jet bubbling reaction tank along the peripheral wall thereof, and the reaction tank peripheral wall and one peripheral edge are the reaction tank peripheral wall. The top plate connected to the top plate and the side wall hanging from the other peripheral edge of the top plate are formed by the whole closed annular body or by forming a part of the annular body and closing the opposite end surfaces thereof. The opening of the lower edge of the side wall and the peripheral wall of the reaction vessel functions as a communication port, and the top plate is provided with an inlet for letting in gas in and an outlet for letting out gas. Item 3. The liquid level adjusting mechanism according to item 1 or 2.