JPH0275911A - Liquid level detector for sealed vessel - Google Patents

Abstract

PURPOSE:To accurately detect the liquid level in a sealed vessel by providing a differential pressure gage for detecting the differential pressure between the gas pressure of the upper section inside the vessel and the gas pressure inside a pressure detecting tube. CONSTITUTION:A reaction liquid sent from a reaction system operated under a high-temperature and high-pressure condition is injected into a sealed vessel 3 through a ball valve 11 and liquid pipe 1. As the level of the reacted liquid rises in the vessel 3, the pressure inside the vessel 3 rises. When the liquid level becomes higher than the opening 4 of a pressure detecting tube 5, an enclosed state is formed in the tube 5 by the liquid getting into the tube 5 and the gas inside the tube 5 is compressed in accordance with the volume of the liquid getting into the tube 5. As a result, the gas pressure inside the tube 5 becomes higher than the gas pressure inside the vessel 3. The differential pressure is outputted from a differential pressure gage 8 and converted into a liquid level by means of a converter 9 and the liquid level is indicated in a level indicator 10. Thus the liquid level in the vessel 3 can be measured accurately.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to detecting the liquid level in a container used in various reaction systems operated at high temperature and high pressure, or detecting liquid level flowing out from the reaction system. A liquid in a closed container that can be suitably used to receive a reaction liquid into a measuring container while maintaining a high temperature and high pressure state, and to detect the liquid level in the measuring container when transferring it to the next process. This invention relates to a surface detection device.

<Conventional technology> Conventionally, devices for detecting the liquid level in a closed container under high temperature and high pressure conditions include devices that directly measure the static head difference of the liquid and devices that blow gas into the bottom of a closed system to measure the current blowing pressure. Therefore, a method that uses so-called liquid pressure, such as a device (gas barge method) that indirectly measures the hydrostatic head difference, is generally used.

Alternatively, instead of continuous liquid level measurement, if it is sufficient to detect the liquid level above or below a certain height, the difference in temperature on the side of the container due to the temperature of the liquid may be used. It is also possible to adopt a device that indirectly detects the liquid level by detecting it with a thermometer, or a device that uses electrodes. However, when using a thermometer as the detection end, there must be a large temperature difference between the liquid temperature inside the container and the surrounding temperature (for example, the vapor temperature of the liquid), and the response must be There is also the problem of slowness, which severely limits its use.

In the case of electrodes, first of all, there is a restriction that the liquid inside must be conductive, and even if the liquid is conductive, if adhesive substances are mixed in, the tip of the electrode There is a high possibility of malfunction due to steam condensation, etc. Therefore, at present, the method based on detecting the pressure of the liquid described above is often applied to measuring the level of liquid flowing into a closed container in a high temperature and high pressure state. However, with the method of directly measuring the difference in hydrostatic head of the liquid level, if the liquid contains solids, especially precipitated solids, the solids may enter the tube communicating with the liquid side of the differential pressure gauge. Not only will this build up and prevent accurate pressure from being transmitted to the differential pressure gauge, but there is also the risk of a blockage. In addition, when the fluid to be measured is a highly corrosive liquid, a silicone liquid or the like is sealed in the capillary to transmit pressure to the diaphragm, but even in this case, the blockage problem is not solved. Furthermore, due to the mounting of the diaphragm, there is a drawback that the entire detection device becomes large. Therefore, technically it is desirable to measure the liquid level using a gas purge method, but this method requires a dedicated gas supply device in addition to a purge pipe and pressure gauge, making the entire detection device complex and expensive. There is a problem. In particular, when the system pressure is 10 kg/cd or higher, this device is subject to high-pressure gas equipment and is difficult to handle. Furthermore, this device is essentially unusable if gas (or liquid) is not mixed into the liquid.

<Problems to be Solved by the Present Invention> The present invention solves the above-mentioned problems in the conventional device for detecting the liquid level in a closed container under high temperature and high pressure conditions, and has a simple structure.
It is an object of the present invention to provide a liquid level detection device that can accurately detect the liquid level.

A liquid level detection device for a closed container according to the present invention, which has been made to achieve the above object, detects the liquid level of a closed container having a liquid inflow pipe and a liquid outflow pipe. A pressure detection tube having an opening at one end and a closed end at the other end is inserted into or outside the container such that the opening is located below the liquid level to be detected in the container. The device is characterized in that a differential pressure gauge is installed to detect the differential pressure between the gas pressure in the upper part of the container and the gas pressure in the pressure detection tube.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram showing an example of an embodiment of the present invention,
In a closed container 3 having a liquid inflow pipe 1 and a liquid outflow pipe 2, a pressure detection pipe 5 having an opening 4 at one end and closed at the other end is set upright. Note that the position of the opening 4 of the pressure detection tube 5 is determined in advance so as to be below the liquid level to be detected in the closed container 3. Further, in FIG. 1, the pressure detection tube 5 is designed to pass through the lid plate 6 of the closed container 3, but it is completely sealed to prevent gas from flowing out from the penetration portion. - One end of the gas introduction tube 7A is communicated with the lid plate 6 of the used book closed container 3, the other end is communicated with the differential pressure gauge 8, and one end of the gas introduction tube 7B is communicated with the closed part of the pressure detection tube 5. The other end is communicated with the differential pressure gauge 8. Note that heat radiation fins or the like are attached to the gas introduction pipes 7A and 7B as necessary to prevent the differential pressure gauge 8 from being heated.

Further, 9 is a converter connected to the differential pressure gauge 8 in an instrumentation manner,
10 is a display connected to the transducer 9 in an instrumented manner, and 11 and 12 each indicate a ball valve.

<Effect> Next, an outline of the operation of the present invention will be explained.

A ball valve 11 is opened, and a reaction liquid flowing out of a reaction system operated at high temperature and high pressure flows into an empty closed container 3 through a liquid inlet pipe 1. Due to this inflow, the reaction liquid 13 accumulates in the closed container 3 as shown in FIG. 2, and as the liquid level rises, the inside of the closed container 3 becomes pressurized. However, in the state shown in FIG. 2, the liquid level in the closed container 3 has not reached the position of the opening 4 of the pressure detection tube 5, and the upper gas pressure in the closed container 3 and the gas in the pressure detection tube 5 are are equal and the differential pressure gauge 8
The output of is zero. Via the converter 9, the level indicator lO therefore indicates that the liquid level is below the liquid level to be detected.

After this, in this state, the liquid level is lower than the opening 4 of the pressure detection tube 5.
This continues until Figure 3, when it reaches the position . When the liquid level reaches the state shown in FIG. 4 above the opening 4 of the pressure detection tube 5, the pressure detection tube 5 becomes liquid-sealed with the inflowing reaction liquid 13, and the reaction liquid 13 entering the pressure detection tube 5 becomes The gas existing in the upper space of the pressure detection tube 5 is compressed according to the volume of the gas, and becomes higher than the gas pressure inside the closed container 3. This differential pressure is output from the differential pressure gauge 8, and this value is sent to the converter. 9, the liquid level is converted to a liquid level, and the level indicator 10 displays the liquid level.

Next, the principle of liquid level detection in the present invention will be explained in more detail.

After the liquid level reaches the opening 4 of the pressure detection tube 5, the - liquid flows into the closed container 3, of which Xcd reaches the pressure detection tube 5.
Assume that the vehicle ascends inside a closed container 3 other than the above. Here, the pressure of the system immediately after the liquid level reaches the opening 4 of the pressure detection tube 5 and the size of each part are as follows.

System pressure P. kg/cd Space volume between liquid inlet and sealed container 3 vlcfl! Volume of pressure detection tube 5 V (cffl Cross-sectional area of sealed container 3 5IICa (excluding pressure detection tube 5) Cross-sectional area of pressure detection tube 5 5ccrI Pressure due to pressure difference due to compression of gas and hydrostatic head difference of liquid Assuming that the differences are equal, a balanced equation is created: Differential pressure ΔP Vc (V ΔP is a hydrostatic head difference due to the difference between the liquid level in the closed container 3 and the liquid level in the pressure detection tube 5.

Below, we will show the results of calculations performed by applying actual values to the above formula. Each numerical value is as follows.

Po = 95kg/cd E = 5000cd SR = 24.92cd
v, =1.1cd 5c=0.25
5J However, the liquid is fresh water (ρ = 0.001 k+r/cd
).

The calculation results are shown in FIGS. 5 and 6. As is clear from FIG. There is a linear relationship, and as shown in FIG. 6, the liquid level and the differential pressure are in a linear relationship. Therefore, by measuring the differential pressure gauge, it is possible to measure the liquid level inside the closed container 3.

Based on the principle described above, the liquid level in the closed container 3 is detected, and when the liquid level reaches a predetermined level, the ball valve 11 is closed to stop the flow of the reaction liquid 13, and then The ball valve 12 is opened, and the pressure of the compressed gas formed above the closed container 3 causes the reaction liquid 13 in the container 3 to flow.
After that, the ball valve 12 is closed, and the ball valve 11 is opened again and the same operation as described above is carried out, so that the reaction liquid 13 flowing out from the reaction system operated at high temperature and high pressure is maintained at high temperature and high pressure. The amount of liquid is sequentially measured in a sealed container 3 and transferred to the next step via a liquid outflow pipe 2.

Note that when the reaction liquid 13 flows into the closed container 3 from the liquid inflow pipe 1, the gas present in the closed container 3 is compressed according to the amount of inflow, but the pressure of the compressed gas may not become too high. In order to prevent this, a safety valve (not shown) may be provided above the closed container 3 to allow gas to leak under a certain pressure.

FIG. 7 is an explanatory diagram showing another embodiment of the present invention,
Instead of erecting the linear pressure detection tube 5 in the closed container 3, one end of the L-shaped pressure detection tube 5 is joined to the side wall of the closed container 3, and the joint is used as the opening 4, One end of the gas introduction pipe 7B is connected to the other end of the pressure detection pipe 5,
The other structure is the same as that in FIG.

Even if the comb-shaped pressure detection tube 5 shown in FIG. 7 is attached to the outside of the closed container 3, the liquid level inside the closed container 3 can be measured using the same principle as described above.

Further, although one pressure detection tube 5 shown in FIG. 1 or FIG. 7 is provided in the closed container 3, a plurality of pressure detection tubes 5 may be provided as required. Note that when a plurality of pressure detection tubes 5 are provided, a differential pressure gauge 8, a converter 9, and a display section 10 are connected to each of the plurality of pressure detection tubes 5.

<Effect> As explained above (the liquid level detection device for a closed container according to the present invention has gas inlet pipes 7A and 7B to which the differential pressure gauge 8 is connected)
Since the pressure gauge does not come into contact with the liquid to be measured at all, not only will no blockage occur, but even when used at high temperatures, the body of the differential pressure gauge can be heated simply by attaching heat radiation fins, etc. to the gas inflow pipes 7A and 7B. can be prevented,
It is possible to easily measure the level of liquid flowing into a sealed container in a high temperature and high pressure state without causing problems such as blockage troubles or troubles due to high temperatures. Moreover, in the present invention, since the detection end for differential pressure is only gas pressure, the device is simple and inexpensive. Therefore, the liquid level detection device of the present invention can be said to be a technically and economically very advantageous method.

[Brief explanation of the drawing]

1 to 7 are explanatory diagrams showing embodiments of the present invention, FIG. 1 is an explanatory diagram showing an example of embodiment B of the present invention, and FIGS. 2 to 4 are explanatory diagrams showing embodiments of the present invention. It is an explanatory diagram showing a usage state. Further, FIG. 5 is a graph showing the relationship between the amount of liquid flowing into the closed container and the differential pressure, FIG. 6 is a graph showing the relationship between the differential pressure and the liquid level, and FIG. It is an explanatory diagram showing an embodiment. 1...Liquid inflow pipe 2...Liquid outflow pipe 3...Airtight container 4...Opening 5...Pressure detection tube
8...Differential pressure gauge Fig. 2 Fig. 3 Fig. 4 Fig. 5 Liquid inflow rate of sealed container (ccλ Fig. 6 0 20 40 60 80
To. Differential pressure (mmHz)

Claims (1)

[Claims] A device for detecting a liquid level in a closed container having a liquid inflow pipe and a liquid outflow pipe, the pressure detection pipe having an opening at one end and a closed end at the other end. A sensor is installed inside or outside the container so as to be located below the liquid level to be detected, and is used to detect the differential pressure between the gas pressure in the upper part of the container and the gas pressure in the pressure detection tube. A liquid level detection device for a closed container characterized by installing a differential pressure gauge.