JP2006234630A - Method of diagnosing abnormality - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of diagnosing abnormalities of an on-line analyzer enabling early discovery and coping abnormal indication values of the on-line analyzer. <P>SOLUTION: The variation situation of naphtha compositions is monitored by using a plurality of different on-line analyzers, and the following processes are used in a chemical process for controlling the flow rate of naphtha, according to variations in the naphtha compositions; a first process of setting a region surrounded by the upper-limit and lower-limit values for indicating the correlation between naphtha density and the content of representative constituents of naphtha; a second process of displaying the indication value of an on-line naphtha densimeter and the analysis value of a naphtha representative constituent by on-line process gas chromatography as a set of process values; a third process of monitoring a process value in the second process with the setting region of the first process as a normal value monitoring region, and issuing an alarm, when the process value is positioned outside the normal value monitoring region; a fourth process of measuring naphtha density according to the alarm; and a fifth process of determining the presence or the absence of abnormalities in the on-line naphtha densimeter, or the like, based on the measured value of the naphtha density. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an abnormality diagnosis method for an on-line analyzer. More specifically, the present invention relates to a method for diagnosing abnormality of an online analyzer that enables early detection and handling of an abnormal indication value of the online analyzer.

  In a chemical process, it is extremely important to keep track of the fluctuations of chemical substances handled. For this purpose, composition analysis and density change measurement of chemical substances are continuously performed and monitored online. However, it does not always indicate a normal value due to factors such as sensor contamination and fluctuations in sample supply conditions. In general, as a method of diagnosing process abnormality, a set of process data is collected sequentially from the target process, and in the abnormality diagnosis method for diagnosing whether or not the process data is abnormal, (a) for a set of process data, A procedure for setting a first line function by plotting a plurality of points corresponding to the other data in advance to set the upper limit of one of the data, and (b) one set of data in advance for one set of process data The procedure for setting the second line function by plotting multiple points corresponding to the other data and setting the second line function, and (c) collecting a set of data while executing data collection from the target process An abnormality diagnosing method having a procedure for outputting an abnormality for the set of data when there is no region between the first polygonal line function and the second polygonal line function is disclosed (Patent Document 1). reference). However, it is cumbersome to apply the method of collecting process data and setting the upper and lower limits with a line function to simple process data, and when monitoring processes using multiple different online analyzers In addition, a simpler abnormality diagnosis method has been demanded.

JP-A-5-288580 (pages 1 to 4)

  In such a situation, the problem to be solved by the present invention is to provide a method for diagnosing abnormality of an on-line analyzer that can quickly find an abnormality indicating value of the on-line analyzer and enable early countermeasures.

In other words, the invention according to claim 1 includes the following steps in a chemical process in which the naphtha composition fluctuation state is monitored using a plurality of different on-line analyzers and the flow rate of naphtha is controlled in accordance with the naphtha composition fluctuation. This is an abnormality diagnosis method for an online naphtha analyzer.
1st process: The process which sets the area | region enclosed by the upper limit and lower limit which show the correlation with the content of the naphtha density and the representative component of a naphtha 2nd process: The indication value and online process gas chromatography of an online naphtha density meter The process of displaying the analysis value of the naphtha representative component by the process value as a set of process values Third process: The process area of the second process is monitored using the setting area of the first process as the normal value monitoring area, and outside the normal value monitoring area Step of issuing a warning when the process value is located Step 4: Step of measuring the naphtha density in response to the step 3 warning Step 5: Online naphtha density meter or online based on the measured value of naphtha density Step of determining presence or absence of abnormality in process gas chromatography When the representative component of naphtha in the first step is normal pentane, the first step to When performing three steps by a computer, it may implement the present invention more effectively.

  According to the present invention, it is possible to provide an on-line analyzer abnormality diagnosis method that enables early detection and handling of an abnormality indicator value of an on-line analyzer.

  The abnormality diagnosis method of the present invention is applied to a chemical process in which the fluctuation state of the naphtha composition is monitored using a plurality of on-line analyzers. For example, when monitoring the naphtha composition that is correlated with the naphtha density and can be measured online, such as the process gas chroma value, and the measured value of the online density meter, first, the naphtha density and the content of the representative components of the naphtha An area surrounded by an upper limit value and a lower limit value indicating the correlation with each other is set. Next, the indicated value of the online naphtha density meter and the analysis value of the naphtha representative component by online process gas chromatography are displayed as a set of process values. The set range surrounded by the upper limit value and the lower limit value indicating the correlation between the naphtha density and the content of the representative component of the naphtha is set as a normal value monitoring region. The analysis value of the representative component is monitored as a set of process values, and when the process value is located outside the normal value monitoring area, a warning is issued, and the naphtha density is measured in response to the warning, and this measured value Based on the above, determine whether there is an abnormality in the online naphtha density meter or online process gas chromatography and take appropriate action.

  In this case, by using normal pentane as the value of the naphtha representative component, a more reliable process value is obtained. In addition, a process for setting a region surrounded by an upper limit value and a lower limit value indicating the correlation between the naphtha density and the content of the representative component of the naphtha, the indication value of the online naphtha density meter and the The computer includes a step of displaying the analysis value as a set of process values, a step of monitoring the process value using the set area as a normal value monitoring area, and issuing a warning when the process value is located outside the normal value monitoring area, etc. By making it execute, the present invention can be implemented more effectively.

  The present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

Example 1
FIG. 1 is a diagram showing a correlation between naphtha density and normal pentane concentration in naphtha. The horizontal axis indicates the naphtha density and is a value measured with an on-line densitometer, and the vertical axis is the value obtained by measuring the value of normal pentane, which is a representative component of naphtha, with on-line process gas chromatography. Line 1 is a line indicating the relationship between the naphtha density and the normal pentane concentration, and is a line indicating the correlation between both determined experimentally by determining the relationship between the naphtha density and the normal pentane concentration. The range surrounded by the line 2 so as to surround the line 1 is a range in which the correlation between the two obtained experimentally is surrounded by a range corresponding to a deviation of 3% of the normal pentane concentration. If online measurements are present, that is, if one process value of the online process gas chromatography and online density meter is indicated by point 4, then the online process gas chromatography and online density meter are considered to be working properly. It's okay. When the process value is outside the range corresponding to the deviation of 3% of the normal pentane concentration as shown by point 3, a warning indicating an abnormality is issued. Here, if the range surrounded by line 2 is too wide, that is, if the deviation of the normal pentane concentration is set too large, the online analyzer will be overlooked, and conversely if the deviation is set too small, it will be online. Even if the analyzer is working normally, a warning is issued. A naphtha density is measured with a density buoy in response to a warning, and if the deviation between the measured value of the naphtha density and the measured value of the online density meter is large, it is determined that the online density meter is abnormal. When the deviation between the measured value of the naphtha density and the measured value of the online densimeter is small, it is determined that the online process gas chromatography is abnormal. In this way, the graph as shown in FIG. 1 is always displayed in the instrument room for process operation, and an abnormality in the online analyzer can be discovered at an early stage by issuing a warning when an abnormality occurs.

It is a figure which shows the correlation of the naphtha density and the normal pentane density | concentration in naphtha.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Line which shows the relationship between naphtha density and normal pentane density | concentration, 2 ... The range which shows the normal value enclosed by deviation ... 3 ... The point which shows abnormal value, 4 ... The point which shows normal value

Claims (3)

In a chemical process for monitoring the naphtha composition fluctuation state using a plurality of different online analyzers and controlling the flow rate of naphtha according to the naphtha composition fluctuations, an online analyzer comprising the following first to fifth steps: Abnormal diagnosis method.
1st process: The process which sets the area | region enclosed by the upper limit and lower limit which show the correlation with the content of the naphtha density and the representative component of a naphtha 2nd process: The indication value and online process gas chromatography of an online naphtha density meter The process of displaying the analysis values of the representative components of naphtha as a set of process values by the third process: The process area of the second process is monitored using the setting area of the first process as the normal value monitoring area, and outside the normal value monitoring area A step of issuing a warning when the process value is located in the fourth step: a step of actually measuring the naphtha density in response to the warning of the third step. Fifth step: based on the measured value of the naphtha density, an online naphtha density meter or A process to determine the presence or absence of abnormalities in online process gas chromatography The on-line analyzer abnormality diagnosis method according to claim 1, wherein the representative component of naphtha in the first step is normal pentane. The on-line analyzer abnormality diagnosis method according to claim 1, wherein the first to third steps are executed by a computer.

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