JP2000146835A - Alkali concentration analyzing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali concentration analyzing device improved in pulp quality and reduced in measurement man-hours. SOLUTION: This alkali concentration analyzing device is applied to a chemical recovery cycle in which black liquor produced in a chip dissolving process in a pulp manufacturing plant is incinerated by an incineration means 7, green liquor is produced by a green liquor producing means 8 from smelted substance produced by the incineration means 7, sodium carbonate in the green liquor is converted into caustic soda by a causticizing means 11, and white liquor obtained by the causticizing is inputted into a dissolving means 1 used in the dissolving process, and the alkali concentrations of a plurality of kinds of liquids including the while liquor are continuously analyzed of using a near-infrared spectroscopic analyzer. When an alkaline liquid is analyzed by the near-infrared spectroscopic analyzer, a sample liquid is heated to a fixed temperature and then analyzed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously measuring the alkalinity of a white liquor or a green liquor in a chemical recovery cycle in a pulp manufacturing plant, thereby enabling the alkalinity concentration to be controlled, and improving and measuring pulp quality. The present invention relates to an alkali concentration analyzer that reduces man-hours.

[0002]

FIG. 8 shows a general flow chart of a chemical recovery cycle in a pulp manufacturing plant. In the figure, chips and white liquor are put into a dissolving means (separate kettle) 1 to digest the chips. When the cooking is completed, the cooking pulp and the cooking waste liquid are discharged from the continuous kettle 1.

The pulp and waste liquid mixture is supplied to a blow tank 2
To the pulp washing means 3 through which the pulp is purified and the black liquor is recovered. The black liquor collected by the washing means 3 is sent to the diluted black liquor tank 4. The black liquor contains organic substances eluted from the chip in the white liquor added first.

A part of the black liquor is returned to the continuous kettle 1 and used for diluting the caustic soda liquor. Most of the black liquor is concentrated by an evaporator (dryer) 5 and sent to a dark black liquor tank 6. Is done. The black liquor contains organic components, Na ₂ CO ₃ , Na ₂ S,
It contains alkali components such as Na ₂ SO ₄ and NaOH.

Next, the concentrated black liquor is burned in the recovery boiler 7 for the purpose of recovering soda, reducing Na ₂ SO ₄ to Na ₂ S, and recovering organic substances eluted by digestion as a heat source. The recovery boiler 7 performs oxidation, trial, reduction, and the like. The inorganic substance is taken out as a smelt from the bottom of the recovery boiler 7 in a molten state.

[0006] The smelt taken out of the recovery boiler 7 is sent to a desolver 8 where it is dissolved with a weak liquid and sent to a green liquor clarifier 9 where impurities are removed and clarified.
The clarified green liquor is stored in the green liquor tank 10.
The components of this green liquor are sodium carbonate and sodium sulfide.

The green liquor is subjected to a causticizing treatment by causticizing means 11. Causticization is performed using quicklime to produce the caustic soda required for cooking. The liquor produced by causticization is called white liquor. Since this white liquor contains insoluble calcium carbonate (CaCO ₃ ), calcium carbonate is separated and clarified by the white liquor clarifier 12. The clarified white liquor is stored in the white liquor tank 13. NaOH, Na ₂ CO ₃ , Na
Components such as ₂ S and Na ₂ SO ₄ are contained.

[0008]

By the way, as described above, the dissolving means 1 contains chips and white liquor (caustic soda liquid).
When charging the liquor, the alkali amount ratio of the white liquor and the green liquor is an important management item. Therefore, conventionally, an operator in charge collects a white liquor once or twice a day, transports it to a laboratory and analyzes it by a titration method or the like, and based on the value, determines the amount of CaO input in the causticizing means. By controlling, the alkali amount ratio of the white liquor and the green liquor was adjusted.

However, the white liquor and the green liquor have a high concentration of Na.
It is a dangerous object of a highly alkaline solution containing OH and the like, and there is a problem that the operator is also at risk when collecting the sample or performing a manual analysis. In addition, since the monitoring of the sample is not continuous, there is a problem that detailed control of the grain cannot be performed.

[0010] The present invention has been made to solve such problems, and by continuously measuring the components of white liquor and green liquor using a near-infrared spectroscopic analyzer, it is possible to improve pulp quality. An object of the present invention is to provide an alkali concentration analyzer that reduces the number of measurement steps.

[0011]

According to a first aspect of the present invention, there is provided a combustion apparatus for burning black liquor generated in a chip melting step of a pulp manufacturing plant. A green liquor generating means for generating green liquor from smelt generated by the combustion means, a causticizing means for converting sodium carbonate in the green liquor into caustic soda, and the causticized white liquor is used in the dissolving step. Applied to a chemical recovery cycle so as to be put into the dissolving means, an alkali concentration analyzer for continuously analyzing the alkali concentration of a plurality of liquids including the white liquor using a near infrared spectrometer,
In analyzing the alkaline liquid with the near-infrared spectrometer, the sample liquid is heated to a predetermined temperature and then analyzed.

According to a second aspect of the present invention, in the alkali concentration analyzer according to the first aspect, the temperature of the sample solution is 65-65.
It is characterized by being controlled to about 70 ° C. According to a third aspect of the present invention, in the alkali concentration analyzer according to the first aspect, a dilution means for continuously diluting the sample liquid is provided when the near-infrared spectrometer is calibrated.

According to a fourth aspect of the present invention, in the alkali concentration analyzer according to the first aspect, the flow rate of the sample liquid is controlled by a head difference between tanks. According to a fifth aspect, in the alkali concentration analyzer according to the first aspect, the flow rate of the sample solution is set to 200 cc / min.
It is characterized by having a degree. According to a sixth aspect of the present invention, in the alkali concentration analyzer according to the first aspect, a chemical solution washing means for washing a window of a detector constituting the near-infrared spectrometer with a chemical solution every predetermined time is provided. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing one example of an embodiment of the present invention. In this embodiment, the chemical recovery cycle shown in FIG. 8 is omitted.
It is assumed that the sample from Sample No. 3 has been sampled and introduced into the sample inlet 21 of the sampling device 20.

In FIG. 1, a sample introduced from a sample inlet 21 is supplied to a sample liquid tank 2 via a valve V1.
2 flows into. The sample that has flowed in reaches the upper part of the hollow liquid level holding member 22a arranged in the liquid tank 22. After that, it falls inside the liquid level holding member 22a and is collected from the sample collection line 24 via the pipe P1.

On the other hand, the sample is introduced from a pipe P2 connected in the middle of the sample liquid tank 22 to a thermostat 25 via a valve V2. The thermostatic chamber 25 includes a container 26 and a temperature setting device 2.
7, a level setter 28, a heater (not shown), and the like.
The cleaning water is filled to a predetermined level via the valve V3, and is heated to about 65 to 70 ° C. by the heater and the temperature setting device 27.

The sample is heated to, for example, about 65 ° C. at the time of actual measurement. This temperature is set at the upper limit of the temperature of the sample which rises when the sampling device 20 is exposed to the atmosphere in the middle of summer, and is set to this temperature. By doing so, the temperature of the sample can be kept constant throughout the year, and stable measurement can be performed.

The sample heated in the thermostat 25 is connected to a pipe P
The light is guided to a detector 31 constituting a near infrared spectrometer by 4. Although not shown in the figure, the detector 31 is provided with a transparent member through which the sample flows, and emits light from one end of a first optical fiber provided on one side of the transparent member, and on the opposite side. The light is received by the provided second optical fiber.

The light emitted from the first optical fiber passes through the sample, so that a specific wavelength is absorbed by the amount of alkali contained in the measurement component. The sample passing through the detector 31 flows into the overflow tank 32, and overflows from the tip of the liquid level holding member 22b arranged in this tank.
The liquid level holding member 22a of the sample liquid tank 22 and the liquid level h of the liquid level holding member 22b and the inner diameter of the transparent member are adjusted so that the flow rate is about 200 cc / min.

The reason why the flow rate of the sample is set to about 200 cc per minute is due to the relation between the power of the heater and the response to the components of the sample. If the flow rate is large, a large heater power is required, and the flow rate is too small. And the response becomes slow.

The sample overflowing in the overflow tank 32 falls through the pipe P5 and falls into the sample collection line 2
Collected at 4. One end of an air line 33 provided above the overflow tank 32 is open to the atmosphere to stabilize the pressure in the tank and maintain the liquid level h. The sample that has entered the air line 33 is discharged from a drain line 35 via a waste liquid tray 34.

The chemical liquid tank 36 is configured to be supplied with air from an air inlet 37 at a predetermined timing via a control device (not shown). Then, in the cleaning mode, the chemical solution measured in the measuring tank 38 by the supply of air is conveyed by the pipe P6 to clean dirt attached to the inner wall of the transparent member of the detector 31 via the check valve 39. ing.

By the way, since a papermaking plant operates while keeping the alkali concentration at an optimum value, a substantially uniform sample continuously flows from the sample inlet. Therefore, only one lab value required for the calibration work after maintenance can be obtained, and in order to obtain another different point, conventionally, the lid of the sample liquid tank 22 is opened, and water, an alkali salt, or the like is charged here. Then, the component values were forcibly changed.

However, since the sample continuously flows into the sample liquid tank, it is difficult to keep the alkali concentration constant for a predetermined time even if the sample concentration is changed, and the indicated value is stable even when the calibration operation is performed. There was a problem not to do. In addition, since the sample is a strong alkaline aqueous solution having a pH of about 14, there is a problem that opening the lid while the sample is flowing is dangerous for an operator.

Therefore, in the present invention, a diluting means for continuously diluting the sample liquid is provided above the sample liquid tank 22 during the calibration operation. That is, the inlet (a) of the calibration line 40
Is connected to the washing water inlet 30 (a), and the washing water flows through the valve V4, the flow meter 41 and the valve V5. By continuously diluting a certain amount of water with such a configuration, a plurality of laboratory values can be obtained. The washing water is also supplied to the washing line 42 as necessary, and the inside of the sample liquid tank is cleaned via the valves V6 and V7.

Next, an experimental example of near-infrared causticization analysis using an infrared spectrometer will be described. Where NaOH, Na ₂ S, Na ₂ C
_Three aqueous solutions composed of different components of O ₃ were prepared. Then, several aqueous solutions having different alkali concentrations were prepared, and near-infrared spectra were measured. FIG. 2 shows a near-infrared spectrum obtained at this time.

Although it is clear from FIG. 2 that the shape of the spectrum differs depending on the difference in each alkali concentration, a clear peak cannot be separated for each alkali component in the near infrared region. The correlation between the near-infrared spectrum and the concentration of each alkali component was determined by PLS regression using this wave number region.
FIG. 3 shows the correlation of NaOH, FIG. 4 shows the correlation of Na ₂ S, and FIG. 5 shows the correlation of Na ₂ CO ₃ .

For each component, quantitative analysis was possible with a prediction error (1σ) of 1 g / l or less. FIG. 6 shows a plot of the regression coefficient at each wave number. This plot implies that the absolute value has a strong correlation with the lab value in the wave number region. From this plot, it was confirmed that each of the three components had a correlation with the laboratory value in a different wave number region. By such an analysis method, it is possible to search for the assignment of each component from the slope and apex of a large near-infrared peak.

FIG. 7 shows the output at the time of continuous measurement in the process conducted by the present applicant. In the figure, the part where the trend of the analysis value is greatly decreased is that the sample is diluted with water and the alkali concentration is forcibly reduced. It can be seen that the followability of the indicated value is good, and that the alkali concentration analysis by the near-infrared spectroscopy can be sufficiently used.

The foregoing description of the present invention has been presented by way of illustration and example only of particular preferred embodiments. Accordingly, the present invention is subject to many modifications, without departing from its essence,
It will be apparent to those skilled in the art that variations can be made. For example,
The arrangement of each device does not necessarily have to be as shown in FIG. 1, and it is sufficient that the required functions are satisfied. The scope of the present invention, which is defined by the description in the appended claims, is intended to cover alterations and modifications within the scope.

[0031]

As described above, according to the present invention,
When analyzing an alkaline solution with a near-infrared spectrometer, the sample solution was heated to a predetermined temperature and then analyzed, and the temperature of the sample solution was controlled at about 65 to 70 ° C., which affected the temperature of the external environment. Measurement can be performed stably.

In the calibration of the near-infrared spectrometer, a dilution means for continuously diluting the sample liquid is provided.
It is possible to obtain a plurality of laboratory values while maintaining safety. Further, since the flow rate of the sample liquid is controlled by the head difference of the tank, the configuration can be simplified. In addition, since the flow rate of the sample liquid is set to about 200 cc / min, desired responsiveness can be secured without increasing the power consumption of the heater. Further, since the chemical cleaning means for cleaning the window of the detector with the chemical at predetermined time intervals is provided, it is possible to improve the reliability of the measurement.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an embodiment of an alkali concentration analyzer of the present invention.

FIG. 2 is a diagram showing a near-infrared spectrum of an aqueous alkaline solution.

FIG. 3 is a diagram showing a correlation between a conventional analysis value of NaOH and a near-infrared analysis value.

FIG. 4 is a diagram showing a correlation between a conventional analysis value of Na2S and a near-infrared analysis value.

FIG. 5 is a diagram showing a correlation between a conventional analysis value of Na2CO3 and a near-infrared analysis value.

FIG. 6 is a diagram showing the assigned wave numbers of each calibration curve.

FIG. 7 is a diagram showing the results of continuous measurement of each alkali component.

FIG. 8 is a diagram showing a general flow of a chemical recovery cycle in a pulp manufacturing plant.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 dissolving means 3 pulp washing means 5 drying means (evaporator) 7 burning means (recovery boiler) 8 green liquor generating means (desolver) 11 causticizing means 12 separating means (white liquor clarifier) 13 white liquor tank 20 sampling device 21 sample Inlet 22 Sample liquid tanks 22a, 22b Liquid level holding member 24 Sample collection line 25 Constant temperature bath 26 Container 27 Temperature setting unit 28 Level setting unit 31 Detector 32 Overflow tank 33 Air line 34 Waste liquid tray 35 Drain line 36 Chemical liquid tank 37 Air Inlet 38 Measuring tank 39 Check valve 40 Calibration line 41 Flow meter 42 Wash line P1-P6 Pipe V1-V7 Valve

Claims (6)

[Claims] 1. A burning means for burning black liquor generated in a chip melting step of a pulp manufacturing plant, a green liquor generating means for producing green liquor from smelt generated by the burning means, and a sodium carbonate in the green liquor. A causticizing means for converting the caustic soda into caustic soda and a chemical recovery cycle in which the causticized white liquor is applied to the dissolving means used in the dissolving step, wherein the alkalis of a plurality of liquids including the white liquor are An alkali concentration analyzer for continuously analyzing the concentration using a near-infrared spectrometer.When analyzing the alkali solution with the near-infrared spectrometer, the alkali solution is analyzed after heating the sample solution to a predetermined temperature. An alkali concentration analyzer characterized by the following. 2. The alkali concentration analyzer according to claim 1, wherein the temperature of the sample solution is controlled at about 65 to 70 ° C. 3. The alkali concentration analyzer according to claim 1, wherein a dilution means for continuously diluting the sample liquid is provided when calibrating the near infrared spectrometer. 4. The alkali concentration analyzer according to claim 1, wherein the flow rate of the sample liquid is controlled by the head difference of the tank. 5. The alkali concentration analyzer according to claim 1, wherein the flow rate of the sample liquid is set to about 200 cc / min. 6. The alkali concentration analyzer according to claim 1, further comprising a chemical cleaning means for cleaning a window of a detector constituting the near-infrared spectrometer with a chemical at predetermined time intervals.