A precise measurement and automatic correction system for the liquid level of the washing oil regenerator of the coking crude benzene unit

Abstract

The present invention provides a precise measurement and automatic correction system for the liquid level of the oil washing regenerator of the coking crude benzene unit, including a liquid level transmitter and a liquid level switch; the differential pressure transmitter and the liquid level switch are both connected to the DCS system. The liquid level transmitter is installed at the bottom of the oil washing regenerator, and is used to measure the liquid level of the regenerator in real time; the liquid level switch is installed on the upper part of the oil washing regenerator, and the height difference from the position of the liquid level transmitter is H; when the DCS detects that the liquid level switch is ON, it triggers the density correction calculation, compares the liquid level height h measured by the liquid level transmitter with the height H of the liquid level transmitter, and uses the height H as the correction value to calculate the new liquid density value ρ1; the new liquid density value ρ1 is brought into the next round of liquid level calculation of the liquid level transmitter. Whenever the regenerator liquid level reaches the height position of the liquid level switch, the DCS system uses the height difference H to correct the measured value of the liquid level transmitter once, so as to achieve precise measurement of the liquid level.

Description

Technical Field

[0001] The invention relates to the technical field of coking and coal chemical industry, and in particular to an automatic correction system for accurately measuring the liquid level of a washing oil regenerator of a coking crude benzene unit. Background Art

[0002] In the field of coking, the recovery of benzene from coke oven gas mainly adopts the oil-rich debenzenization process. In order to maintain the quality of the circulating wash oil, a part of the circulating oil is led out and sent to the regenerator for regeneration. Here, the wash oil is heated with indirect steam and blown with superheated steam. The oil, gas and water gas mixture blown out from the top of the regenerator is sent back to the crude benzene tower. The high-boiling polymer at the bottom of the regenerator is the residual oil, which is intermittently or continuously discharged to the residual oil tank. The operation of the wash oil regenerator has a great influence on the consumption of wash oil, and the wash oil consumption is the most important indicator of the operation of the debenzenization section. In order to better operate the wash oil regenerator, the accuracy of the liquid level measurement becomes very important.

[0003] Usually, the liquid level is measured with a double flange level transmitter. This method requires knowing the density of the medium in the regenerator in advance. The medium of the oil wash regenerator is a mixture. The density often changes with the composition of the wash oil, the working conditions of the crude benzene tower and the working conditions of the regenerator, resulting in a large range of density fluctuations. According to the conventional calculation method, there is an essential error in the liquid level measurement, which affects the measurement accuracy of the regenerator liquid level. Many sites often require maintenance personnel to measure the density offline to achieve liquid level correction calculations, which affects the operating accuracy of the oil wash regenerator and makes it difficult to achieve accurate control of the liquid level. In practice, circulating oil wash flow control is basically used. Summary of the invention

[0004] In order to solve the technical problems raised by the background technology, the present invention provides a precise measurement and automatic correction system for the liquid level of a coking crude benzene unit washing oil regenerator. Whenever the regenerator liquid level reaches the height position of the liquid level switch, the DCS system uses the height difference H to correct the measured value of the liquid level transmitter to achieve precise measurement of the liquid level.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A coking crude benzene unit washing oil regenerator liquid level accurate measurement automatic correction system comprises a liquid level transmitter and a liquid level switch; the differential pressure transmitter and the liquid level switch are both connected to a DCS system.

[0007] The liquid level transmitter is installed at the bottom of the oil washing regenerator and is used to measure the liquid level of the regenerator in real time;

[0008] The liquid level switch is installed on the upper part of the oil washing regenerator, and the height difference from the position of the liquid level transmitter is H; when the regenerator liquid level reaches the height position of the liquid level switch, the DCS system uses the height difference H to calibrate the measured value of the liquid level transmitter.

[0009] Furthermore, the liquid level switch is a high temperature contact type liquid level switch instrument or a non-contact type material level switch instrument.

[0010] Furthermore, the high temperature contact type liquid level switch instrument is selected to be one of a float level switch, a resistance level switch and a capacitive switch.

[0011] Furthermore, the non-contact material level switch instrument is selected to be a non-contact sonar material level switch.

[0012] Furthermore, the liquid level transmitter is a double flange liquid level transmitter, and a pressure transmitter is used at its interface to measure the liquid level. The liquid level of the storage tank is calculated by measuring the pressure online, and the measurement signal is sent to the DCS system in real time.

[0013] The automatic correction method of the automatic correction system for accurate measurement of the liquid level of the washing oil regenerator of the coking crude benzene unit comprises the following steps:

[0014] Step 1: DCS collects the detection value of the liquid level transmitter in real time, and calculates the liquid level height h according to the set initial density value ρ0;

[0015] Step 2: When the DCS detects that the liquid level switch is ON, it triggers the density correction calculation, compares the liquid level height h measured by the liquid level transmitter with the height H of the liquid level transmitter, uses the height H as the correction value, and calculates the new liquid density value ρ1;

[0016] Step 3: Bring the new liquid density value ρ1 into the next round of liquid level calculation of the liquid level transmitter;

[0017] Step 4: Every time the regenerator liquid level reaches the height position of the liquid level switch, the DCS system calibrates the measured value of the liquid level transmitter.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) The automatic correction system for accurate measurement of the liquid level of the coking crude benzene unit washing oil regenerator of the present invention, whenever the liquid level of the regenerator reaches the height position of the liquid level switch, the DCS system uses the height difference H to calibrate the measured value of the liquid level transmitter, thereby realizing accurate measurement of the liquid level;

[0020] 2) The present invention utilizes the existing DCS control system, and the compiled calculation function realizes the online correction calculation of the medium density, which can realize accurate liquid level measurement. High temperature resistant liquid level switch or non-contact sonar liquid level switch is selected, which has long service life, high detection accuracy and small instrument investment. The non-contact liquid level switch can be used to implement the system without stopping production. Since the continuous liquid level measurement of the regenerator can realize accurate measurement, the regenerator regulation means are added to realize accurate control of the regenerator liquid level. The technology of the present invention can be operated automatically or manually intervened, with multiple operation modes to improve the adaptability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an instrument structure diagram of a coking crude benzene unit washing oil regenerator liquid level accurate measurement automatic correction system of the present invention;

[0022] Figure 2 The present invention is a control flow chart of a system for accurately measuring and automatically correcting the liquid level of a washing oil regenerator in a coking crude benzene unit. DETAILED DESCRIPTION

[0023] The specific implementation modes provided by the present invention are described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, a coking crude benzene unit washing oil regenerator liquid level accurate measurement automatic correction system includes a liquid level transmitter LT44302 and a liquid level switch LS44301; the differential pressure transmitter LT44302 and the liquid level switch LS44301 are connected to the DCS system. The ○ in the figure represents a field instrument, It represents the signal entering DCS, and LY represents liquid level compensation.

[0025] The liquid level transmitter LT44302 is installed at the bottom of the oil washing regenerator to measure the liquid level of the regenerator in real time. The liquid level transmitter is a double flange liquid level transmitter, and a pressure transmitter is used at its interface to measure the liquid level. The liquid level of the storage tank is calculated by online pressure measurement, and the measurement signal is sent to the DCS system in real time.

[0026] The liquid level switch LS44301 is installed on the upper part of the oil washing regenerator, and the height difference from the position of the liquid level transmitter LT44302 is H; when the regenerator liquid level reaches the height position of the liquid level switch, the DCS system uses the height difference H to calibrate the measured value of the liquid level transmitter.

[0027] The liquid level switch LS44301 is a high-temperature contact liquid level switch instrument or a non-contact material level switch instrument. The high-temperature type has a temperature resistance of 200°C to 350°C. The high-temperature contact liquid level switch instrument is selected as one of a float level switch, a resistance level switch and a capacitive switch. The non-contact material level switch instrument is selected as a non-contact sonar level switch. The contact switch is used in new projects or shutdown and renovation projects. When the production is not stopped, the non-contact material level switch instrument is preferred.

[0028] The position of the upper liquid level switch LS44301 should be higher than the center line of the lower flange hole set at the bottom, and should not exceed the upper limit alarm value given in the design. The height difference between the installation position of the liquid level switch and the center line of the lower flange hole for liquid level measurement should be adjusted according to actual conditions.

[0029] The measurement of the liquid level transmitter LT44302 uses the pressure-density-height formula P=ρgh. When the liquid density is known, the liquid level height h is calculated by reverse calculation from the pressure P. This method requires the density ρ of the medium in the regenerator to be known in advance. The medium of the oil wash regenerator is a mixture, and the density often changes with the composition of the wash oil, the working conditions of the crude benzene tower and the working conditions of the regenerator, resulting in a large range of density fluctuations. According to the conventional calculation method, there is an essential error in the liquid level measurement, which affects the measurement accuracy of the regenerator liquid level. Many sites often require maintenance personnel to measure the density offline to realize the liquid level correction calculation, which affects the operating accuracy of the oil wash regenerator.

[0030] like Figure 2 As shown, in the present invention, the automatic correction method of the automatic correction system for accurate measurement of the liquid level of the washing oil regenerator of the coking crude benzene unit comprises the following steps:

[0031] Step 1: DCS collects the detection value of the liquid level transmitter in real time, and calculates the liquid level height h according to the set initial density value ρ0 using the pressure-density-height formula P=ρgh;

[0032] Step 2: When the DCS detects that the liquid level switch is ON, it triggers the density correction calculation, compares the liquid level height h measured by the liquid level transmitter with the height H of the liquid level transmitter, takes the height H as the correction value, and calculates the new liquid density value ρ1 by P=ρgH;

[0033] Step 3: Bring the new liquid density value ρ1 into the next round of liquid level calculation of the liquid level transmitter;

[0034] Step 4: Every time the regenerator liquid level reaches the height position of the liquid level switch, the DCS system calibrates the measured value of the liquid level transmitter.

[0035] The installation position of the liquid level switch LS44301 and the installation position of the double flange liquid level transmitter LT44302 are fixed, and the installation position of the liquid level switch LS4430 and the height difference H of the lower flange of the double flange liquid level transmitter LT44302 are fixed. In the DCS control system, a medium density compensation calculation module is compiled. When the start-up conditions are met, the actual density ρ of the medium in the regenerator can be calculated based on the pressure difference value P and the height difference H measured by the double flange liquid level gauge, realizing the density correction calculation of the medium in the regenerator. The DCS liquid level calculation module calculates the precise continuous liquid level of the regenerator in real time based on the measured differential pressure value and the corrected density.

[0036] At the same time, the value of the upper limit liquid level switch LS44301 introduced can also perform upper liquid level alarm and interlock, improving the situation where the washing oil regeneration efficiency is low due to the excessively high liquid level of the washing oil regenerator. In addition, since the continuous liquid level of the regenerator can be accurately measured, the control of the regenerator can be converted from the traditional feed flow control single mode to the regenerator liquid level control mode. The present invention increases the controllability of the washing oil regenerator and improves the working efficiency of the washing oil regenerator.

[0037] The condition for starting the DCS density compensation calculation module of the present invention is that when the liquid level is triggered to the upper limit, that is, when the liquid level switch LS44301 is turned from OFF to ON, the compensation calculation is performed once. During the production process, the feed amount of the regenerator can be manually controlled to increase the liquid level value to trigger the correction module calculation, or the DCS density compensation calculation can be started when the liquid level fluctuates to the upper limit as the process production proceeds without manual intervention. If the number of compensation calculations is to be increased, it can be adjusted by lowering the setting height of the upper limit liquid level switch, so that the liquid level can often trigger the upper limit of the liquid level switch when the regenerator is in normal production, thereby increasing the frequency of the DCS density compensation calculation and making the continuous liquid level measurement more accurate.

[0038] The present invention utilizes the existing DCS control system, and the compiled calculation function realizes the online correction calculation of the medium density, which can realize accurate liquid level measurement. The high temperature resistant liquid level switch or the non-contact sonar liquid level switch is selected, which has a long service life, high detection accuracy, and small instrument investment. The non-contact liquid level switch can be used to implement the system without stopping production. Since the continuous liquid level measurement of the regenerator can realize accurate measurement, the regenerator regulation means are added to realize accurate control of the regenerator liquid level. The technology of the present invention can be operated automatically or manually intervened, with multiple operation modes to improve the adaptability of the system.

[0039] Figure 1 There is also a circulating oil wash flow closed-loop control part of the oil wash regenerator (existing technology part), and the circulating oil wash flow closed-loop control part of the oil wash regenerator includes a flow sensor FT44309 and a regulating valve FRC44309, which are also connected to the DCS system.

[0040] The above embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the above embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.

Claims

1. An automatic correction method for the liquid level accurate measurement automatic correction system of the washing oil regenerator of the coking crude benzene unit, characterized in that: The correction system includes a liquid level transmitter and a liquid level switch; the liquid level transmitter and the liquid level switch are both connected to the DCS system; The liquid level transmitter is installed at the bottom of the oil washing regenerator and is used to measure the liquid level of the regenerator in real time; The liquid level switch is installed on the upper part of the oil washing regenerator, and the height difference from the position of the liquid level transmitter is H; when the liquid level of the regenerator reaches the height position of the liquid level switch, the DCS system uses the height difference H to calibrate the measured value of the liquid level transmitter; The automatic correction method comprises the following steps: Step 1: DCS collects the detection value of the liquid level transmitter in real time, and calculates the liquid level height h according to the set initial density value ρ0; Step 2: When the DCS detects that the liquid level switch is ON, it triggers the density correction calculation, compares the liquid level height h measured by the liquid level transmitter with the height H of the liquid level transmitter, uses the height H as the correction value, and calculates the new liquid density value ρ1; Step 3: Bring the new liquid density value ρ1 into the next round of liquid level calculation of the liquid level transmitter; Step 4: Every time the regenerator liquid level reaches the height position of the liquid level switch, the DCS system calibrates the measured value of the liquid level transmitter.

2. The automatic correction method of the automatic correction system for accurate measurement of the liquid level of the washing oil regenerator of the coking crude benzene unit according to claim 1 is characterized in that: The liquid level switch is a high temperature contact type liquid level switch instrument or a non-contact type material level switch instrument.

3. The automatic correction method of the automatic correction system for accurate measurement of the liquid level of the washing oil regenerator of the coking crude benzene unit according to claim 2 is characterized in that: The high temperature contact type liquid level switch instrument is selected to be one of a float level switch, a shift type level switch and a capacitive switch.

4. The automatic correction method of the automatic correction system for accurate measurement of the liquid level of the washing oil regenerator of the coking crude benzene unit according to claim 2 is characterized in that: The non-contact material level switch instrument is selected to be a non-contact sonar material level switch.

5. The automatic correction method of the automatic correction system for accurate measurement of the liquid level of the washing oil regenerator of the coking crude benzene unit according to claim 1 is characterized in that: The liquid level transmitter is a double-flange liquid level transmitter, and a pressure transmitter is used at its interface to measure the liquid level. The liquid level of the storage tank is calculated by measuring the pressure online, and the measurement signal is sent to the DCS system in real time.

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