JP2575663B2 - Online moisture analyzer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for accurately and efficiently analyzing water in a liquid or gas in a production apparatus online, and particularly to an online system using a Karl Fischer reagent. Water analyzer.

Online analysis of liquid or gaseous moisture in production equipment is important for managing processes in chemical equipment, such as saving energy in distillation equipment, and managing product quality.

(Prior art) Moisture analysis methods used for moisture management in processes include physical methods such as drying, distillation, and electrical resistance, and chemical methods such as gas generation, hydrolysis, and electrolytic adsorption. Or near-infrared method, gas chromatography method, and the like.

The Karl Fischer method is a water content determination method that can accurately measure a small amount of water compared to these methods.
It is used as a standard method for analyzing moisture in STM, DIN, etc.

The Karl Fischer analyzer collects a fixed amount of a sample in a titration bottle, and uses it for Karl Fischer reagent (KF).
This is a device for titration with a reagent), and electrically detects the titration end point. That is, when a minute current is passed between the bipolar platinum electrodes immersed in the sample solution, and the sample solution is titrated with the KF reagent, iodide is generated by the reaction between the KF reagent and water while the sample contains moisture, causing polarization. Although the electrode does not flow, iodine is released as the water is depleted, and a current suddenly flows. This change in the current is detected to determine the end point of the titration.

As described above, the Karl Fischer method is suitable for measuring a very small amount of water, but the method of collecting a sample for analysis is one of the important factors, and various methods have been proposed (for example, Japanese Utility Model Application Laid-Open No. 60-79135). public relations). In the case of analyzing multiple samples simultaneously, if a manual analysis method, visual observation, etc. are included, errors due to human factors are likely to occur, so automation using a computer has been attempted (for example, see Japanese Patent Application Laid-Open No. No.-87350).

However, these conventional techniques are designed to minimize errors based on human factors (individual differences, sensory judgments, skill levels, etc.) in individual analysis techniques (eg, sampling, titration, etc.). It is not related to the improvement of analytical technology from the viewpoint of continuous process management. In other words, the technology disclosed in the related art only automatically performs analysis in a range required at that time, and furthermore, there is no connection between the analytes at each time, and there is no continuity. Each analytical value has nothing to predict the next analytical value, and cannot be said to be a management analytical technique in a so-called continuous process.

The near-infrared method is used as an apparatus for analyzing moisture online for such continuous process management, but the measurement range of this method is 100 to 20000 ppm, which is necessary for management in the distillation equipment of a chemical plant. It cannot be used for analysis that requires accuracy of about several ppm. On the other hand, the Karl Fischer method is suitable for a field requiring an accuracy of about several ppm, but has not yet been completed as an on-line moisture analyzer for continuous process management as described above. The reason for this is that, conventionally, a method was used in which analysis was performed under predetermined conditions without predicting fluctuations in water in the process.
There are many failures in terms of the amount of sample collected, and despite the fact that it is an expensive KF reagent, the number of analyzes must be increased inevitably, or the analysis has been attempted with a large amount of sample to ensure certainty. Conceivable.

(Problems to be Solved by the Invention) Accordingly, an object of the present invention is to provide an apparatus which can effectively use a KF reagent in continuously measuring the water content in a liquid or a gas in a production apparatus by the Karl Fischer method. It is in.

(Means for Solving the Problems) The present inventor has conducted various studies on a method for effectively performing moisture analysis in a liquid or gas sample using a KF reagent in a manufacturing apparatus, and as a result, has used a computer. Analyze past analytical values, compare the analytical values with the appropriate analytical capacity range of the Karl Fischer analyzer, predict the appropriate amount of liquid or gas sample, the amount of KF reagent added, etc. We succeeded in performing high-precision water analysis automatically and on-line directly from the manufacturing equipment, and completed the present invention.

 That is, the gist of the present invention is as follows.

The liquid in the production apparatus of the first invention is directly supplied from the apparatus.
An analyzer for automatically measuring moisture using a Karl Fischer reagent as a sample for analysis introduced into a titration bottle, comprising: (a) a Karl Fischer automatic moisture meter and an airtight titration bottle; and (b) a titration bottle. (C) a device for automatically measuring and injecting airtightness of a sample for analysis based on a setting value of a controller described later, (d) a device for discharging a titrated and analyzed liquid, and (E) a controller; (f) the controller, (i) a control unit for storing a past moisture analysis value in a computer, and predicting a next analysis value from the moisture analysis value, and (ii) a timer. Control unit for automatic setting and instruction of analysis time, (iii) based on the appropriate analytical capacity range of Karl Fischer automatic moisture meter and the predicted moisture analysis value, Control unit for setting a proper amount of air tightness automatic weighing and infusion 析用 sample, and (iv) online moisture analyzer having a control unit for outputting the analysis result of water analysis.

(2nd invention) An analyzer for introducing a gas in a manufacturing apparatus directly into the titration bottle as an analysis sample from the apparatus and automatically measuring the water content using a Karl Fischer reagent. Automatic Fisher moisture meter and airtight titration bottle, (b) Automatic airtightness metering and injection device of water-soluble solvent to titration bottle, (c) Automatic airtightness introduction of sample for analysis based on set value of controller described later (D) a gas meter for automatically measuring the amount of gas sample after water absorption in the sample for analysis, and (e) a controller. (F) The controller (i) transmits the past water analysis value to a computer. A control unit for recording and predicting the next analysis value from the moisture analysis value; (ii) a control unit for automatically setting and instructing an analysis time by a timer; Control unit for setting the appropriate amount of automatic introduction of airtightness of the sample for analysis based on the appropriate analysis capacity range of the automatic moisture analyzer and the predicted moisture analysis value. (Iv) Measurement with the automatic Karl Fischer moisture analyzer An online moisture analyzer equipped with a control unit for calculating moisture analysis from the measured moisture amount and the gas sample amount measured by the gas meter, and (v) a control unit for outputting the moisture analysis value as an analysis result. .

 Hereinafter, the contents of the present invention will be described in detail.

In the moisture analyzer according to the present invention, the starting point of the operation of the apparatus is to know the expected value of the analysis of the liquid or gas-containing moisture in the manufacturing apparatus. The analysis expected value is, in addition to the analysis value expected from the various process control values input to the computer, the previous or previous continuous (preferably about 10) moisture analysis values are stored in the computer, It is an analysis expected value obtained by calculation. Computer calculates this analysis expectation value,
Compare with the range of the appropriate analysis capacity of the Karl Fischer analyzer to be used, and if it is outside this range, in order to increase or decrease the sample collection amount so as to obtain an analysis result that falls within the range, the liquid or liquid to be measured is Activate the gas supply.

Here, the range of the appropriate analysis capacity of the Karl Fischer analyzer is a range mainly determined by the volume of the titration bottle attached to the analyzer, and at the time when the water-soluble solvent injected into the titration bottle is dehydrated, Of course, this refers to the case where the volume of the titration bottle has a sufficient margin to the volume of the liquid inside at the end of the moisture analysis.If the volume is outside this range, for example, the volume of the bottle for titration is too small, Is not preferable because there is a possibility of overflow.

A method of measuring the water content in the water-soluble solvent after temporarily transferring the water content in the liquid or gas to the water-soluble solvent is adopted. Therefore, a water-soluble solvent is first injected into the titration bottle of the Karl Fischer analyzer in an airtight state. This injection amount is an amount calculated based on the expected analysis value calculated by the computer.

After the injection of the water-soluble solvent, the water content is removed by the KF reagent added by the operation of the automatic operation device of the Karl Fischer moisture meter at the instruction of the computer.

Subsequently, the computer operates the airtight automatic weighing device and the airtight automatic transfer device of the liquid or gas in consideration of the analysis expected value, and a predetermined amount of the liquid or gas is contained in the anhydrous water-soluble solvent. Injected or introduced. The water in the liquid or gas migrates into an anhydrous, water-soluble solvent, which is titrated by a Karl Fischer analyzer based on instructions from a computer.

The measured value of the water concentration of the liquid or gas is obtained from this water amount and the liquid injection amount, or the remaining gas amount of the gas that has been dehydrated by contact with the water-soluble solvent, and stored in a computer. Is used for calculating the expected value of analysis at the time of the next moisture analysis.

Embodiment 1 An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an online moisture analyzer according to the present invention. The present apparatus is largely applicable to a part of a water-soluble solvent and a gas-tight automatic metering and injecting or introducing apparatus of a liquid or a gas according to the present invention, a commercially available Karl Fischer moisture meter 1, a controller 2 incorporating a computer, and an external controller 3. Divided.

When analyzing the moisture in the liquid sample, the liquid sample is introduced by the metering pump 4 and a fixed amount of the sample is sent to the titration bottle 7 via the back pressure valve 5. While the liquid in the titration bottle is stirred by the stirrer 8, the KF reagent is injected from the KF reagent 13 by the reagent pump 15 in the Karl Fischer moisture meter and titrated. The titration bottle is provided with a platinum electrode. The end point of the titration with the KF reagent is detected thereby, and the signal of the titration end point is sent to the controller 2 via the amplifier 16. After the analysis is completed, the titrant is discharged out of the system by the air ejector 10 and then prepared for analysis.

When performing moisture in the gas sample, a water-soluble solvent is put in the titration bottle in advance, and the sample is made anhydrous by titration with a KF reagent, and then the gas sample is introduced from the gas sample intake solenoid valve 6,
The amount of the gas sample after the water absorption is measured by the gas meter 14. After introducing a certain amount of the gas sample, the electromagnetic valve 6 is closed, and the water content in the solvent is measured in the same manner as the liquid sample, and the water content in the solvent and the gas sample amount are stored in the controller 2. The concentration of water in the gas sample is calculated by a computer.

When the liquid sample is analyzed, the three-way valve 12 is switched to the dehumidifier 11 to release the sample to the atmosphere. KF reagent bottle 13
A dehumidifier 11 is also provided to release to the atmosphere.

Level sensor 9 for titration bottle 7 and KF reagent bottle 13
Is installed, and the optical sensor detects abnormal rise in the liquid level of the titration bottle and decrease in the remaining amount of the KF reagent. Further, a pressure drop of the liquid sample is detected by the pressure sensor 18, and these signals are sent to the controller 2. Each device is controlled by a controller with a built-in computer.
Necessary signals such as the stop of the drive of 13, the opening and closing of the solenoid valves 6, 17 and the drive of the stirrer 8 are sent to each device and controlled.

The computer used in the present invention is incorporated as an arithmetic unit in the controller, and performs operations necessary for the next operation.

(1) Automatic setting and instruction of analysis time by a timer.

(2) Setting of sample intake based on expected analysis values and previous analysis values.

(3) Analytical operations such as ingestion of a sample into a titration bottle, titration with a KF reagent, and discharge of a titrant (in the case of a gas sample, introduction of a solvent, measurement of a gas amount after absorbing water, etc.).

(4) Calculation of water concentration from the intake of each sample and the titer of KF reagent, instruction of analysis results, and signal output to an external controller.

(5) Countermeasures for abnormalities inside the analyzer such as abnormal rise in the liquid level of the titration bottle, lowering of the liquid level of the KF reagent bottle, pressure drop of the liquid sample, and abnormalities outside the analyzer such as a power failure.

Operations in the analyzer for this purpose include driving and stopping each pump and stirrer, opening and closing each solenoid valve and three-way valve, outputting an alarm and an external signal, and the like.

The analysis time is initially set, but a large number of measured values are stored in a computer, and if the fluctuation is small, the analysis time interval may be automatically extended. In addition, an analysis time corresponding to a multi-channel sample can be automatically selected.

As for the sample intake, an appropriate analytical value is determined so as to obtain an analytical value that is higher than the expected analytical value or the analytical value up to the previous time, and to minimize the use amount of the KF reagent. If the water content in the sample is too low to provide sufficient accuracy, automatically increase the sample intake and repeat the analysis. If the water content is too high to analyze the water content in the sample, the computer automatically reduces the sample intake and performs the analysis again through a computer. A computer with a program with a storage capacity of about 32 Kbytes is used for the computer that performs these tasks.

(Example 2) In a methanol recovery apparatus, the moisture in the recovered methanol distilled from the distillation tower is analyzed online using the moisture analyzer according to the present invention, and the control of the amount of steam in the distillation tower reboiler is performed based on the analyzed value. Went directly.

Use a 25mL / min pulse pump for sample intake, storage capacity
While controlling with a controller equipped with a 32 KB computer, moisture analysis was performed with a Karl Fischer analyzer.

The frequency of analysis of the product methanol was initially every 15 minutes, but every 3 hours was sufficient when the operation of the rectification column was stable. Also, the sample intake was always controlled to an appropriate amount by the method of the present invention.

As a result, the amount of steam used in the reboiler was reduced by 20 T (about 5% of the used amount) per year compared with the case where the control by the online analysis was not performed.

Also, the annual usage of the KF reagent was 10 kg, which was a saving of about 70% as compared with the case where the operation according to the present invention was not performed.

(Effect of the Invention) The online moisture analyzer according to the present invention mainly has the following advantages.

(1) On-line ppm of water in liquid sample in multi-channel
Highly accurate analysis values can be obtained up to the order.

(2) It is possible to analyze moisture in a gas sample online with high precision, which could not be analyzed conventionally.

(3) In analyzing water in liquid and gas samples, KF
Low consumption of reagents and low running cost.

(4) The conventional Karl Fischer analyzer simply needs to be equipped with a solenoid valve for gas sample analysis, a gas meter, an ejector for sample discharge, each level and pressure detector, and a controller with a computer. In comparison, the analyzer is cheaper.

(5) The analysis result can be output as a signal to an external controller, and can be directly used for process control to save energy in the distillation apparatus and manage product quality.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an online moisture analyzer according to the present invention.

Claims (2)

(57) [Claims] 1. An analyzer for introducing a liquid in a production apparatus directly into the titration bottle as a sample for analysis from the apparatus and automatically measuring the water content using a Karl Fischer reagent. Automatic Fisher moisture meter and airtight titration bottle, (b) Automatic airtightness measurement and injection device of water-soluble solvent to titration bottle, (c) Automatic airtightness measurement of sample for analysis based on set value of controller described later And (d) a device for discharging the titrated and analyzed liquid, and (e) a controller. (F) The controller (i) records a past moisture analysis value in a computer, and records the moisture analysis value. Control unit for predicting the next analysis value from (ii) a control unit for automatically setting and instructing the analysis time using a timer, and (iii) the appropriateness of the Karl Fischer automatic moisture meter. A control unit for setting an appropriate amount of automatic tightness measurement and injection of the sample for analysis based on the analysis capability range and the predicted moisture analysis value, and (iv) outputting the moisture analysis value as an analysis result. Online moisture analyzer equipped with a control unit. 2. An analyzer for introducing a gas in a production apparatus directly into the titration bottle as a sample for analysis from the apparatus and automatically measuring the water content using a Karl Fischer reagent, comprising: Fisher automatic moisture meter and airtight titration bottle, (b) Automatic airtightness meter and injection device for water-soluble solvent in titration bottle, (c) Automatic airtightness introduction of sample for analysis based on set value of controller described later (D) a gas meter for automatically measuring the amount of gas sample after water absorption in the sample for analysis, and (e) a controller. (F) The controller (i) transmits the past water analysis value to a computer. A control unit for storing and predicting the next analysis value from the water analysis value; (ii) a control unit for automatically setting and instructing the analysis time by a timer; A control unit for setting the appropriate amount of automatic introduction of airtightness of the sample for analysis based on the appropriate analysis capacity range of the shear moisture analyzer and the predicted moisture analysis value. (Iv) Measurement by Karl Fischer automatic moisture meter A control unit for calculating a water analysis value from the measured water amount and a gas sample amount measured by a gas meter; and (v) an online water analysis unit having a control unit for outputting the water analysis value as an analysis result. apparatus.