CN115031803A - Method for measuring mixed liquid interface liquid level in liquid storage container - Google Patents

Abstract

The invention discloses a method for measuring the interface liquid level of mixed liquid in a liquid storage container, which comprises the following steps: measuring the total height of the liquid level in the liquid storage container, defining the total height as H, measuring the static pressure of the total liquid level in the liquid storage container, defining the static pressure as delta P, defining the height of the interface liquid level as H, and utilizing the formula H as delta P-rho _{Lower part} gH/(ρ _{Lower part} ‑ρ _{Upper part of} ) g is calculated to obtain the height of the interface liquid level h, wherein rho _{Lower part} 、ρ _{On the upper part} The density values of the lower liquid and the upper liquid are respectively, g is the gravity acceleration, the method has the advantages that the double sensors are adopted to respectively measure the total height of the liquid level in the liquid storage container and the static pressure of the total liquid level, the interface liquid level of the mixed liquid in the liquid storage container can be quickly and accurately measured through the specific interrelation of the double sensors, the real-time monitoring in the process can be realized, and the possibility is provided for realizing the automatic control of the interface liquid level.

Description

Method for measuring interface liquid level of mixed liquid in liquid storage container

Technical Field

The invention relates to a method for measuring liquid level of liquid, in particular to a method for measuring interface liquid level of mixed liquid in a liquid storage container.

Background

The measurement of liquid level is a routine operation in chemical industry, and the existing measurement methods mainly include a differential pressure method, a floating ball method and the like. In many cases, however, it is often the case that two immiscible liquids of different densities are present in a reservoir, and the interface formed by these two liquids is called the interface. In chemical production, there are many equipments which require accurate control of interface liquid level, such as phase separator, coalescer, extraction tower, etc. However, the measurement of interface level has been a difficult point. The differential pressure method is mainly used in the situation that the total height of the liquid level is constant, and the floating ball method is difficult to use in the situation that materials are hung and the density of the materials is changed.

Disclosure of Invention

The invention aims to provide a method for measuring the liquid level of a mixed liquid interface in a liquid storage container, which can accurately measure a phase interface formed by two liquids with different densities.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method for measuring the interface liquid level of mixed liquid in a liquid storage container comprises the following specific steps: measuring the total height of the liquid level in the liquid storage container, defining the total height as H, measuring the static pressure of the total liquid level in the liquid storage container, defining the static pressure as delta P, defining the height of the interface liquid level as H, and utilizing the formula H as delta P-rho _{Lower part} gH/(ρ _{Lower part} -ρ _{On the upper part} ) g is calculated to obtain the height of the interface liquid level h, wherein rho _{Lower part} 、ρ _{Upper part of} The density values of the lower liquid and the upper liquid, respectively, and g is the gravitational acceleration.

Preferably, the total height H of the liquid level in the liquid storage container is measured by using a floating ball level meter, and the static pressure Δ P of the total liquid level in the liquid storage container is measured by using a differential pressure transmitter.

Furthermore, the floating ball liquid level meter is preferably a magnetic telescopic floating ball liquid level meter, the measurement precision can be improved, the error is less than or equal to 1mm, and the preferred type of the differential pressure transmitter is as follows: EJA-110E.

In order to ensure the measurement accuracy, the gravity acceleration g is preferably 9.7930.

Compared with the prior art, the invention has the advantages that the double sensors are adopted to respectively measure the total height of the liquid level in the liquid storage container and the static pressure of the total liquid level, the interface liquid level of the mixed liquid in the liquid storage container can be quickly and accurately measured through the specific mutual relation, the real-time monitoring in the process can be realized, and the possibility is provided for realizing the automatic control of the interface liquid level.

Drawings

FIG. 1 is a schematic view of a measurement device used in an embodiment of the present invention;

FIG. 2 is a schematic view of a configuration of a panel operation screen of a control system designed by the method of the present invention;

fig. 3 is a schematic diagram illustrating an algorithm configuration of a control system designed by the method of the present invention according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

The first embodiment is as follows: a method for measuring mixed liquid interface liquid level in a liquid storage container aims at a liquid storage container 1 with two different liquids shown in figure 1, a magnetic telescopic floating ball liquid level meter 2 and a differential pressure transmitter 3 of EJA-110E of the Yoghurt corporation are installed on the liquid storage container 1 in a conventional measuring and installing mode, total height H of the liquid level in the liquid storage container 1 is obtained through measurement of the floating ball liquid level meter 2, static pressure delta P of the total liquid level in the liquid storage container 1 is obtained through measurement of the differential pressure transmitter 3, the interface liquid level height is defined as H, and the formula H is used as delta P-rho _{Lower part} gH/(ρ _{Lower part} -ρ _{On the upper part} ) g can be calculated to obtain the height of the interface liquid level h, wherein rho _{Lower part} 、ρ _{On the upper part} The density values of the lower liquid and the upper liquid are provided by the process, g is gravity acceleration, and a local value is preferred for ensuring the measurement accuracy, wherein the reference g is 9.7930.

The interfacial level h measurement formula is derived as follows:

ΔP＝ΔP _{on the upper part} +ΔP _{Lower part}

ΔP＝ρ _{On the upper part} g(H-h)+ρ _{Lower part} gh

h＝ΔP-ρ _{Lower part} gH/(ρ _{Lower part} -ρ _{On the upper part} )g。

A set of control systems can be designed using the method of the present invention as shown in fig. 2 and 3.

The interface to a control system is shown in fig. 2, where the system is not activated. The following are illustrated in the figures: and the interface liquid level of the LIT-N03 after DCS calculation, LIT-N03A is the total liquid level differential pressure measured by a differential pressure transmitter, and LIT-N03B is the total liquid level height measured by a floating ball liquid level meter.

In FIG. 3, the interface liquid level after the LIT-N03 is calculated by DCS, the LIT-N03A is the total differential pressure of the liquid level measured by a differential pressure transmitter, and the LIT-N03B is the total height of the liquid level measured by a floating ball liquid level meter. LV-N03 is a tower bottom discharge regulating valve for controlling interface liquid level, LV-N03 and LIT-N03 form a PID control loop for automatically controlling LIT-N03 interface liquid level to be kept at the set interface liquid level.

In order to verify the correctness of the method, the calculation result is compared with the liquid level (sight glass) on the spot after the normal debugging. The densities of the two liquids in the liquid storage tank are respectively the density rho of the lower liquid _{Lower part} ＝1050kg/m ³ Upper layer liquid density ρ _{Upper part of} ＝850kg/m ³ 。

Example 1: the total height of the floating ball is 1.6 meters, the total static pressure of the liquid level is 70kp, the calculation result is 6.518 meters, the field is 6.525 meters, and the absolute value of the height difference is 0.7 cm.

Example 2: the total height of the floating ball is measured to be 1.5 meters, the total static pressure of the liquid level is 68kpa, the calculation result is 5.290 meters, the field is 5.282 meters, and the absolute value of the height difference is 0.8 cm.

As can be seen from the above examples, the results obtained by using the method of the present invention and the absolute value of the height difference of the interface liquid level obtained by observing with the sight glass on site are both less than 1cm, and the requirements of the process control are completely satisfied.

Claims (5)

1. A method for measuring the interface liquid level of mixed liquid in a liquid storage container is characterized by comprising the following steps: measuring the total height of the liquid level in the liquid storage container, defining the total height as H, measuring the static pressure of the total liquid level in the liquid storage container, defining the static pressure as delta P, defining the height of the interface liquid level as H, and utilizing the formula H as delta P-rho _{Lower part} gH/(ρ _{Lower part} -ρ _{On the upper part} ) g is calculated to obtain the height of the interface liquid level h, wherein rho _{Lower part} 、ρ _{On the upper part} Density values for the lower and upper liquids, respectively, and g is the acceleration of gravity.

2. The method according to claim 1, wherein the total height H of the mixed liquid interface in the liquid storage container is measured by a float level meter, and the static pressure Δ P of the total liquid level in the liquid storage container is measured by a differential pressure transmitter.

3. The method of claim 2, wherein the float gauge is a magnetically contracted float gauge, and the differential pressure transmitter is of the type: EJA-110E.

4. A method as claimed in claim 1, wherein the gravitational acceleration g is selected to be local.

5. A method of measuring the interfacial surface level of a mixed liquid in a liquid storage container as claimed in claim 4, wherein said gravitational acceleration g has a local value of g 9.7930.

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