JPH0545138B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and an apparatus used in a chip cooking process and operation management of a recovery boiler, etc.
In particular, the present invention relates to a method and apparatus for estimating the concentration of organic components in black liquor, which continuously estimates the concentration of organic components in order to effectively utilize black liquor, which is the waste liquid of the chip cooking process for producing paper pulp.

[Conventional technology]

In the chip-cooking process, pulp is produced using chips, chemicals, steam, etc. At this time, dilute black liquor is discharged as waste liquid from the chip-cooking process, so this dilute black liquor is concentrated in a concentrator to produce a thick black liquor. After turning it into a liquid, it is injected into a recovery boiler. The recovery boiler suspends and dries the concentrated black liquor to form a charbet, and by burning this charbet, steam, dust mainly composed of sodium sulfate, raw materials for chips cooking chemicals, etc. are recovered from the recovery boiler, and the steam is For example, it is used to drive various drive devices in plants, in-house power generation, and even in the chip cooking process, etc. On the other hand, the collected dust is mixed with the concentrated black liquor, and the drug raw material is used as a drug in the chip cooking process. .

By the way, the black liquor discharged from the chip cooking process is composed of organic components, inorganic components, and water. Of these, the organic components are composed of lignin and hydroxyl acids, while the inorganic components are It is composed of sodium carbonate, sodium sulfate, sodium sulfide, etc.

In particular, the concentration of organic components in the black liquor is an extremely important source of information for the operational management of recovery boilers and chip cooking processes. When the properties of black liquor change due to adjustments to the formulation, amount, cooking time, etc. of the chemicals to be added, the properties of the black liquor will fluctuate as a result of these changes. It has a property that fluctuates depending on the amount of mixed dust. For this reason, the most reliable and accurate method for measuring the concentration of organic components in black liquor is the direct measurement method, in which the black liquor discharged from the chip cooking process is collected and analyzed over several days. However, as mentioned above, it is extremely difficult to immediately and continuously measure the organic component concentration, which changes from moment to moment. On the other hand, it is important from the standpoint of operational management of the chip cooking process and recovery boiler to know the concentration of organic components in black liquor immediately and continuously even if it sacrifices some measurement accuracy.

Therefore, conventional methods have been used to continuously estimate the concentration of organic components in black liquor, but the measurement principle is to estimate the concentration of organic components in black liquor using two or more different densitometers. (PULP & PAPER
CANADA VOL, 75, NO, 12, 1974 P83), a specific example of which is a method of estimating the concentration of organic components using a photorefraction type densitometer and a gamma ray type densitometer.

[Problem that the invention seeks to solve]

However, this method for estimating the concentration of organic components in black liquor is
This is a common method for estimating the component concentration of a solution containing two components (Industrial Measurement Handbook Coronasha P789), and it attempts to utilize the difference in optical refractive index between substances and the difference in density between substances. However, no results have yet been obtained that accurately estimate the concentration of black liquor. On the other hand, a photorefraction type densitometer
It is assumed that the ratio of the inorganic component A3-a and the organic component A2-a in the dissolved solid component A7 in the solution A5 shown in FIG. It is used as a device for estimating the concentration of solid content A8 in black liquor A1, that is, the solid content concentration, from the change in the optical refractive index of dissolved A1.
It has generally been said from experience that the photorefraction type densitometer used as a device for estimating the solid content concentration has a high detection sensitivity for organic components in black liquor; however, according to experiments conducted by the inventors, It has been confirmed that when attempting to estimate the concentration of organic components using only a formula concentration meter, the difference between the estimated value and the analyzed value varies by approximately 2.4% of the estimated value in terms of standard deviation.

Therefore, the first invention was made by focusing on the above-mentioned points, and is capable of estimating the organic component concentration of black liquor immediately and continuously, and which is sufficiently durable for use in operational management, combustion control, etc. An object of the present invention is to provide a method for estimating the concentration of organic components in black liquor that can estimate the concentration of organic components with high accuracy.

Further, the object of the second invention is to provide a black liquor organic component concentration measuring device that can continuously and highly accurately measure the organic component concentration with a simple configuration and can sufficiently contribute to operational management, combustion control, etc. Our goal is to provide the following.

[Means for solving problems]

In order to achieve the above object, a first invention provides a method for estimating the concentration of organic components of black liquor discharged from a chip cooking process in which chips are digested using chips and a chemical. The refractive index of the solution and the temperature of the black liquor are detected, and based on these refractive indexes and temperatures, the concentration of each organic component for the black liquor properties obtained based on the chip material type and the chemical added to the chip cooking process is determined. Estimate
This is a method for estimating the organic component concentration of black liquor, in which an organic component concentration corresponding to the black liquor properties is selected from these organic component concentrations.

On the other hand, a second invention is a device for estimating the concentration of organic components of black liquor discharged from a chip cooking process in which chips are digested using chips and chemicals, and a concentration meter that detects the refractive index of the black liquor solution. a thermometer that detects the temperature of the black liquor; a black liquor property setting unit that outputs a black liquor property signal determined based on the chip material type and the chemical that are input into the chip cooking process; The concentration of each organic component for the black liquor properties obtained based on the chip material type and the chemical is estimated based on the refractive index and temperature detected by the meter and the thermometer, and the black liquor property signal is calculated from these organic component concentrations. This is an organic component concentration estimating device for black liquor, comprising an organic component concentration estimating means for selecting an organic component concentration based on the organic component concentration.

[Function] Therefore, the first invention uses the above-described means so that the solid content dissolved in the black liquor changes greatly depending on the temperature, and accordingly, the refraction of the black liquor solution changes. Although the ratio varies greatly, if the concentration of each organic component is estimated for the black liquor properties based on the refractive index and temperature of the black liquor, and the organic component concentration corresponding to the black liquor properties is selected from these organic component concentrations. , it is possible to measure not only the black liquor solution, but also the concentration of organic components contained in the solid content of black liquor depending on the black liquor properties, making it possible to estimate with high accuracy, and thus to improve operational management and combustion even in immediate continuous operation. It is possible to estimate the concentration of organic components that is sufficient for use in management, etc.

In addition, in the second invention, the black liquor solution and the organic component concentration of the solids in the black liquor can be detected with high sensitivity by a simple configuration of just providing a concentration meter and a thermometer in the black liquor supply line. By estimating the concentration of each organic component for the black liquor properties using the output of the densitometer and thermometer, and selecting the organic component concentration corresponding to the black liquor properties from these organic component concentrations, the optimum concentration can be determined according to temperature changes. The concentration of organic components can be estimated continuously and with high precision, and thus it is possible to adequately deal with operational management, combustion control, etc.

〔Example〕

Below, in describing the embodiments of the first and second inventions, first, the principles of these inventions will be briefly described. Generally, black liquor has a composition as shown in FIG. That is, black liquor A1 is roughly composed of organic component A2, inorganic component A3, and water A4, and most of the organic component A2 and inorganic component A3 are in solution A5 with water A4. , the portion other than this solution A5 is the undissolved component A6. and,
Solution solid component A7 and non-solution component A6 in solution A5
The sum of these is considered to be the solid content A8.

Therefore, the refractive index N of the solution is determined by the water A4 in the solution A5 and the organic component A2-a in the solution solid component A7.
and each concentration of inorganic component A3-a,
At a constant temperature, it can be approximately expressed as a weighted sum of refractive indexes depending on the concentrations of each component.

N=x1・N1+x2・N2+x3・N3+
NO...(1) However, N: refractive index of black liquor solution, N1: average refractive index of organic component A2-a in the dissolved solid component, x1:
Concentration of similar organic component A2-a, N2: Average refractive index of inorganic component A3-a in the dissolved solid component, x2:
Concentration of similar inorganic component A3-a, N3: refractive index of water, x3: concentration of water, NO: constant. In the above equation, the sensitivity of N1 is larger than N2 and N3,
Since the correlation between the organic component concentration x1 in the solution and the refractive index N is relatively strong, if the undissolved component A6 is small, the black liquid, which is the concentration of the organic component A2 in the black liquor A1, will change from the organic component concentration X1 in the solution. The organic components of the liquid can be estimated. However, as shown in FIG. 2, when the temperature changes, the solubility of the solid content A8 changes significantly, the refractive index changes accordingly, and the organic component concentration changes greatly. For example, if inorganic components only contain non-dissolved components, inorganic component dissolved component A
As the concentration of 3-a increases, the proportion of inorganic components in the refractive index increases, and the refractive index appears as a low value even if the concentration of organic components in black liquor is the same.

The present invention has been realized based on the above principle, and the method for estimating the organic component concentration of black liquor, which is the first invention, will be specifically described below. First of all,
In the chip cooking process, pulp is produced by adding chemicals and steam to the wood chips that are put into the digester. At this time, dilute black liquor is discharged from the digester as waste liquid, which is concentrated in a concentrator. The concentrated black liquor is further mixed with Glauber's salt and the recovered dust recovered from the recovery boiler to obtain a mixed black liquor. After adjusting this mixed black liquor to an appropriate temperature, it is injected into a recovery boiler as an injection black liquor, and steam, dust, drug raw materials, etc. are recovered from the recovery boiler.

Incidentally, in the above configuration, the organic component concentration of the black liquor is usually estimated as a function of the refractive index N of the black liquor solution. However, when the temperature changes, the solubility of the solid content changes significantly, and the refractive index changes accordingly, resulting in a change in the estimated organic component concentration. Figure 2 shows the relationship between the concentration measured by a photorefraction densitometer (estimated solid content concentration) and the organic component concentration with respect to temperature changes.As is clear from this figure, even at the same concentration, there is a slight The concentration of organic components changes greatly with changes in temperature.

Therefore, in the first invention, the estimated solid content concentration is detected using, for example, a light refraction means for the injection black liquor solution supplied to the recovery boiler, and the temperature of the black liquor is also detected. Then, by adding a correction value as a function of temperature to this estimated solid content concentration value, the organic component concentration is estimated. Therefore, the influence of temperature changes can be removed, and the organic component concentration can be estimated with high accuracy.
In addition, the relationship between the refractive index of the black liquor solution and the concentration of organic components in the black liquor varies depending on the properties of the black liquor, so the solubility changes and the refractive index changes. Accurate organic component concentration can be estimated by obtaining a plurality of organic component concentrations based on the obtained black liquor properties and estimating and outputting one of these organic component concentrations according to the black liquor properties.

Therefore, according to the configuration of the embodiment of the present invention, not only the refractive index of the black liquor solution but also the temperature of the black liquor is detected, and the estimated solid content concentration is corrected according to the detected temperature to determine the organic component concentration. Since an estimation method is used to estimate the organic component concentration, even if the organic component concentration is estimated continuously immediately, the organic component concentration can be estimated with sufficient accuracy for use in operational management, combustion control, etc.

Normally, the set value of the jet black liquor temperature is manipulated in order to optimize the jet black liquor droplet diameter that is fed into the recovery boiler. In other black liquor lines, no operation is performed to control the black liquor temperature to a predetermined value. Conventionally, the organic component concentration of black liquor in such conditions has been estimated using only a photorefraction densitometer, or a photorefraction densitometer and a densitometer, but for the reasons mentioned above, it has not been possible to estimate with sufficient accuracy. Can not.

In the present invention, not only the refractive index of black liquor but also
It is possible to estimate the organic component concentration with higher accuracy by taking into account the effects of temperature, black liquor properties, etc. Incidentally, Figure 2 shows the relationship between the black liquor organic component concentration obtained by sample analysis of the jetted black liquor, the black liquor temperature at the time of sampling, and the concentration (estimated solid content concentration) measured by a photorefraction type densitometer. However, as is clear from this figure, even if the concentration measured by the densitometer is the same, the temperature of the black liquor varies between ±
If the temperature differs by about 2°C, the organic component concentration will change by about ±2% of the concentration estimated by the densitometer alone. In the present invention, since the above-described temperature fluctuations are captured and corrected, the organic component concentration can be estimated with high accuracy.

Note that the present invention is not limited to the above embodiments, and can be implemented with various modifications. In other words, changes in the amount of inorganic components in black liquor do not appear as changes in the refractive index when it is saturated as a solution, causing errors in estimating the concentration of organic components in black liquor, but changes in the amount of inorganic components in black liquor do not appear as changes in black liquor density. I get caught. Therefore, if the density of the black liquor is detected and corrected by incorporating it into the estimation function, the organic component concentration can be estimated with higher accuracy.

Next, we will discuss the third embodiment of the second invention.
This will be explained with reference to the figures. In the figure, 1 is a cooking pot which is part of the chip cooking process, to which wood chips 2, chemicals 3 and steam 4 are supplied.
Chips 2 are digested with chemicals 3 and steam 4 to produce pulp 5, and as a result, dilute black liquor 6 is discharged from the digester 1 as waste liquid. This diluted black liquor 6 is concentrated by a concentrator 7 to form a concentrated black liquor 8, which is then introduced into a mixing tank 9 at a subsequent stage. In this mixing tank 9, recovered dust 11 and Glauber's salt 12 recovered from the recovery boiler 10 are mixed with the concentrated liquid 8 of the concentrator 7, and the mixture is output as a mixed black liquor 13. 14 is a black liquor heater,
Here, the mixed black liquor 13 is adjusted to an appropriate temperature by steam 15 recovered from the recovery boiler 10, for example, and sent to the recovery boiler 10 as an injected black liquor 16, where it is injected and combusted. . This recovery boiler 10 has the function of drying and burning the injected black liquor, recovering steam 4, 15 to be supplied to the digester 1, black liquor heater 14, etc., and also recovering dust 11, drug raw materials 3, etc. There is. Further, a photorefraction type densitometer 18 and a thermometer are provided in the injection black liquor supply line 17 between the black liquor heater 14 and the recovery boiler 10 to the extent that the simultaneity of measurement is not impaired. This photorefraction type densitometer 18 obtains the estimated solid concentration value S1 which is a function of the refractive index, and there are no restrictions on the wavelength band used as long as it measures the refractive index of a black liquor solution. It is something.
Reference numeral 20 denotes an organic component concentration estimation calculation unit, to which the estimated solid content concentration value S1 is supplied from the concentration meter 18, and the temperature S2 of the black liquor is supplied from the thermometer 19. The organic component concentration estimation calculation unit 20 estimates the organic component concentration using an estimation calculation formula shown in Equation (2), which will be described later. A black liquor property setting section 21 outputs a black liquor property setting signal S4 predetermined according to the type of chips and the type of medicine 3, and is supplied to the organic component concentration estimation calculation section 20.
Therefore, this organic component concentration estimation calculation unit 20 is designed to estimate a plurality of organic component concentrations as a function of temperature and refractive index based on the black liquor property signal. In other words, when the organic component concentration calculating section 20 receives a black liquor property signal of a certain chip material from the black liquor property setting section 21, for example, it selects and outputs only the organic component concentration corresponding to that chip material. It's getting old. The estimation function is selected because the solubility and refractive index change depending on the properties of the black liquor. As a means for outputting a certain organic component concentration depending on the black liquor properties, a selection section 22 is provided at the output end of the organic component concentration estimation calculation section 20 as shown by the dotted line in the figure, and a selection section 22 is provided at the output end of the organic component concentration estimation calculation section 20. black liquor property signal S
4, one of the plurality of organic component concentrations outputted from the organic component concentration estimation calculating section 20 may be selected and output.

Next, the operation of the apparatus configured as above will be explained. In addition to chips 2, a chemical raw material 3 and steam 4 are supplied from a recovery boiler 10 to a digester 1 used for the chip cooking process.
and steam 4 to produce pulp 5, and at the same time, dilute black liquor 6 is discharged from the digester 1 as waste liquid. This diluted black liquor 6 is sent to a concentrator 7, where it is concentrated to obtain a concentrated black liquor 8, which is then introduced into a mixing tank 9. In this mixing tank 9, the dust 11 and Glauber's salt 12 from the recovery boiler 10 are mixed with the concentrated black liquor 8 from the concentrator 7 to obtain a mixed black liquor 13, which is further sent to the subsequent black liquor heater 14, where it is The temperature is adjusted to an appropriate temperature using the heat of the steam 15 and then supplied to the recovery boiler 10, where it is injected as black liquor 16 into the recovery boiler.

At this time, a photorefraction type concentration meter 18 and a thermometer 19 are installed in the injection black liquor supply line 17, and these meters 18 and 19 measure the estimated solid content concentration S1,
The temperature S2 of the black liquor is detected and supplied to the organic component concentration calculation section 20. This organic component concentration calculation section 20
are the organic component concentrations S5-1 to S5 for the black liquor properties, which vary depending on the type of chip 2, the type of chemical 3, etc.
-n is calculated, and the corresponding organic component concentration is selected based on the black liquor property signal S4 set by the black liquor property setting section 21, and outputted as an estimated organic component concentration value S5.

As for the estimation calculation formula of the organic component concentration calculation section 20, if the temperature change range and the solid content concentration change range are relatively small, a simple calculation formula such as the following formula can be used to estimate with sufficient accuracy.

S5=α1S1+β1S2 +δ1 (when S4=1) αiS1+βiS2+δi (when S4=i) αnS1+βnS2+δn (when S4=n)...(2) Here, αi, βi, δi (i=1, 2,...n) are The fixed concentration estimated value S1 output from the constant concentration meter 18 is estimated as a function of the refractive index N of the black liquor solution shown in equation (1), so it can be expressed as S1=f(n). S2 is the temperature detected by the thermometer 19. In addition,
If the temperature change range and solid content concentration change range are large, the organic component concentration S5 can be estimated with high accuracy using a more complicated calculation formula.

Therefore, according to the configuration of the embodiment of the second invention as described above, a thermometer 19 is provided in the injection black liquor supply line 17 in addition to the photorefraction type densitometer 18, and the temperature is a function of the refractive index. The temperature of the black liquor, which is a factor in the fluctuation of the refractive index, is considered as a correction value for the estimated solid content concentration value S1, and the organic component concentration is estimated. It can be estimated. Moreover, the black liquor property setting section 21 sets the black liquor property signal in advance according to the chip material type and the type of chemical 3,
For each black liquor property signal, multiple organic component concentrations are determined as shown in equation (2), and one of the multiple organic component concentrations is selected according to the black liquor property signal to estimate the organic component concentration. Since it is configured to output as follows,
Estimation errors caused not only by temperature but also by changes in black liquor properties can be removed, organic component concentrations can be estimated with high accuracy, and chip cooking processes and recovery boilers can be appropriately managed and combustion controlled. It is something.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications. For example, the organic component concentration estimation calculation section 20 may include the black liquor property setting section 21. Moreover, if a gamma ray type density meter or a vibration type density meter 23 is installed in the injection black liquor supply line 17 in addition to the concentration meter 18 and thermometer 19 as shown by the dotted line in FIG. can be corrected to improve estimation accuracy. In other words, as mentioned above, when the black liquor is saturated as a solution, changes in the amount of inorganic components do not appear as changes in the refractive index, but as changes in the density of the black liquor. cause an error. Therefore, by detecting the density S3 of the black liquor using the densitometer 23 and correcting it using this density S3, the error can be removed and the organic component concentration can be estimated with higher accuracy. In this case, the organic component concentration may be estimated for each black liquor property signal S4=i in the above equation (2), for example, when S4=1, S5=α1S1+β1S2+γ1S3+δ1. S3 is the detection density and γ1 is a constant.

Next, FIG. 4 is a block diagram illustrating combustion control of a recovery boiler using the estimated value of the organic component concentration of the injected black liquor as one of the application examples of the method and estimation device of the present invention. That is, this device includes, in addition to the device shown in FIG. 3, a volumetric flow meter 31 for detecting the volumetric flow rate of black liquor, a combustion air flow rate calculation section 32, a lower stage air flow controller 33, a middle stage air flow controller 34, This configuration includes an upper stage air flow rate controller 35. Normally, the recovery boiler 10 is a boiler that burns the injected black liquor 16, but in order to increase the combustion efficiency of this boiler, the estimated organic component concentration S5, the black liquor detected by the volumetric flow meter 31 of the injected black liquor are Volumetric flow rate S
6. Supply the gamma ray density S3, black liquor property signal S4, etc. to the combustion air flow rate calculation section 32, and use these signals S3 to S6 to determine the required amount of combustion air to be injected into each stage of the recovery boiler 10. The air flow rate command values S7 to S9 are determined and supplied to the air flow rate controllers 33 to 35 at each stage. Then, the air flow rate command value S7 is determined by the air flow rate controllers 33 to 35 at each stage.
~S9 and the actual air flow rate S17~S19 are compared, and the lower stage of the recovery boiler 10 is adjusted so that the deviation becomes zero.
The middle stage and upper stage combustion flow rates S27 to S29 are obtained and supplied to the recovery boiler 10. Therefore, if the estimation method and estimation device of the present invention are applied to the recovery boiler 10, combustion control of the recovery boiler 10 can be performed appropriately.

〔Effect of the invention〕

As detailed above, according to the first invention, it is possible to estimate the organic component concentration with high accuracy by eliminating error factors due to temperature, and it is also possible to eliminate estimation errors caused by changes in black liquor properties. Therefore, even if the concentration of organic components is estimated immediately and continuously, operational management,
It is possible to provide a method for estimating the concentration of organic components in black liquor that can estimate the concentration of organic components that can sufficiently withstand use such as combustion control.

Further, according to the second invention, a densitometer and a thermometer are provided to detect the refractive index of the black liquor solution and the temperature of the black liquor,
Furthermore, multiple concentrations of organic components are obtained as a function of refractive index and temperature, and one of these organic component concentrations is estimated and output. Therefore, the concentration of organic components can be estimated with a simple configuration, and black An apparatus for estimating the concentration of organic components in black liquor that can eliminate estimation errors caused by changes in liquid properties, can immediately and continuously estimate the concentration of organic components, and can appropriately perform operational management, combustion management, etc. Can be provided.

[Brief explanation of drawings]

Figures 1 to 3 are shown to explain the method and apparatus of the present invention. Figure 1 is an explanatory diagram of the principle for realizing the method and apparatus of the present invention, and Figure 2 is the black liquor temperature. 3 is a diagram showing the configuration of an embodiment of the second invention, and FIG. 4 is a diagram showing the relationship between the densitometer output and the organic component concentration with respect to changes in It is a block diagram explaining combustion control. 1... Digester, 7... Concentrator, 9... Mixing tank, 10... Recovery boiler, 14... Black liquor heater, 18... Light refraction type densitometer, 19... Thermometer, 20... Organic Component concentration estimation calculation section, 21...
Black liquor property setting section, 22... selection section, 23... gamma ray density meter.

Claims (1)

[Scope of Claims] 1. A method for estimating the concentration of organic components in black liquor discharged from a chip cooking process in which the chips are digested using chips and a chemical, comprising: the refractive index of the black liquor solution; Detect the temperature, and based on these refractive index and temperature, estimate the concentration of each organic component for the black liquor properties obtained based on the chip material type and the chemical added to the chip cooking process, and calculate the concentration of these organic components. A method for estimating the concentration of organic components in black liquor, characterized in that the concentration of organic components in the corresponding black liquor properties is selected from the following. 2. The organic component concentration of the black liquor according to claim 1, wherein the means for estimating the organic component concentration of the black liquor estimates the organic component concentration determined from the refractive index by correcting it by the temperature. Concentration estimation method. 3. In an apparatus for estimating the concentration of organic components of black liquor discharged from a chip cooking process in which the chips are digested using chips and a chemical, a densitometer that detects the refractive index of the black liquor solution;
a thermometer that detects the temperature of the black liquor; a black liquor property setting unit that outputs a black liquor property signal determined based on the chip material type and the chemical that are input into the chip cooking process; the densitometer; Based on the refractive index and temperature detected by the thermometer, the concentration of each organic component for the black liquor properties obtained based on the chip material type and the drug is estimated, and the black liquor property signal is determined from these organic component concentrations. 1. An organic component concentration estimating device for black liquor, comprising an organic component concentration estimating means for selecting an organic component concentration based on the organic component concentration. 4. Estimating the organic component concentration of black liquor according to claim 3, wherein the black liquor organic component concentration estimating means estimates the organic component concentration determined from the refractive index by correcting it based on the temperature. Device.