JPH0543055B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is directed to reducing SO ₂ (sulfur dioxide) in the atmosphere.
The present invention relates to an air pollution measuring device for measuring the concentration of pollutants such as.

(Prior Art) Conventionally, various air pollution measuring devices of this type have been provided. For example, focusing on the fact that sulfuric acid is produced by a chemical reaction between SO ₂ and hydrogen peroxide, we calculated the concentration of sulfuric acid produced by aerating the sample atmosphere into an absorption liquid containing hydrogen peroxide. For example, a method based on a solution conductivity method is well known in which the concentration of SO ₂ is measured by electrically detecting a change in the conductivity of an absorption liquid corresponding to the concentration of SO ₂ .

In this measuring device, one measurement period is one hour, for example, and within this one measurement period, operations such as measuring and filling the absorption liquid, adjusting the zero point of the SO ₂ concentration, measuring the ventilation of the sample atmosphere, and discharging the absorption liquid are performed. This is done automatically and continuously according to a microcomputer program. The measurement method in this case is to measure the change in conductivity as a physical property of the absorbing liquid.
Due to the so-called batch processing method, which integrates over one measurement period while converting to the concentration of SO ₂ , the measurement data is collected at the end of each measurement period, as shown in Figure 6. Only those indicating the average concentration of were obtained.

In other words, in this Figure 6, the vertical axis shows the continuous repetition of each measurement cycle, and the SO ₂ concentration (horizontal axis) starts from 0 at the start of a certain measurement cycle (for example, from 3 o'clock to 4 o'clock). The indication increases on the time axis according to the slope according to the concentration at each point in time, and after the aeration measurement time ta, which is slightly shorter than 1 hour, has elapsed, the average concentration of SO ₂ in that measurement period is calculated. At the same time, the system returns to the start point of the next measurement cycle after the time tb required for draining, measuring, and filling the absorbent, and by repeating these steps, a so-called serrated measurement record is obtained. It's getting old.

(Problem to be Solved by the Invention) However, with this sawtooth measurement record, it is only possible to know the average concentration of SO ₂ for each cycle, and it cannot be used as an effective material for air pollution control.
If you want to know the instantaneous value of SO ₂ concentration in order to understand the trend of SO ₂ concentration which changes from moment to moment, it is extremely difficult to read this directly from the above measurement records. In other words, in this measurement record, the indicated value of SO ₂ concentration with respect to the time axis does not have a linear relationship, and for example, the instantaneous value of SO ₂ concentration at a certain time tx in Fig. 6 does not correspond to the value dx at that point. , is expressed by the slope at this point, so the true instantaneous value must be determined empirically by taking into account the average concentration of the previous measurement period (2 o'clock to 3 o'clock), the slope of the measurement record, etc. However, it required considerable care and skill.

Theoretically, this instantaneous value can be obtained by differentiating the sawtooth-shaped measurement record shown in Figure 6 with respect to time, but in reality, this results in noise due to electrical noise contained in the measurement data and fluctuations in the indication. There was a problem that the data had been expanded and the reliability was poor, making it unusable as data. Furthermore, even if an instantaneous value is obtained from data from which noise components have been removed, the circuit configuration required for this purpose becomes complicated, resulting in high costs.

Furthermore, in the method of simply differentiating the measured data,
There is a sudden change in data when switching from the end of one measurement cycle to the start of the next measurement cycle, resulting in the inconvenience of performing mathematical differentiation of singular points.

The present invention was proposed to solve the above problems, and its purpose is to accurately and quickly determine the instantaneous value of SO ₂ from a sawtooth measurement record by simple calculations. It is an object of the present invention to provide an air pollution measuring device which solves the conventional difficulty in reading instantaneous values, thereby providing convenience for measurers and observers, and which has a simple configuration and can reduce costs.

(Means for Solving the Problems) In order to achieve the above object, the present invention detects changes in physical properties such as conductivity of an absorption liquid that has absorbed pollutants such as SO ₂ in the atmosphere within a certain measurement period. sequentially detect,
In an air pollution measurement device using a so-called sawtooth recording method, the indication changes with a slope according to the concentration of the pollutant corresponding to this change, and the average concentration of the pollutant is indicated at the end of the measurement cycle. Over a period of time, the concentration of pollutants for each unit measurement time is sampled multiple times from the sawtooth measurement record, and based on these values, the approximate value of the slope of the measurement record is calculated by the least squares method, etc., and multiplied by a predetermined constant. By sequentially repeating the steps of determining the instantaneous value of the concentration of the pollutant, continuous data of the instantaneous value is obtained.

At this time, the sampling period is updated sequentially every time the unit measurement time elapses, but the calculation steps can be simplified by using the above calculation results for the current sampling period to perform calculations for the immediately following sampling period. It is planned.

(Operation) That is, in the present invention, on a so-called sawtooth measurement record indicating the average value of the concentration of the pollutant, the instantaneous value of the concentration of the pollutant is sequentially determined from the slope of the approximate expression of this measurement record, In this calculation, the instantaneous value can be obtained in a small number of calculation steps by using the calculation results from the immediately preceding sampling period and calculating the slope for that sampling period using only the minimum number of calculations. be.

(Example) An example of the present invention will be described below with reference to the drawings.

Figure 1 shows an air pollution measuring device according to the present invention.
This figure shows a schematic configuration when applied to an SO ₂ measurement device. In the figure, 1 is a gas absorption section containing an absorption liquid 2 containing a hydrogen peroxide solution, and a sample is placed in this gas absorption section 1. Intake port 3 that takes in the atmosphere;
An intake system consisting of a filter 4 and a flow meter 5, and an exhaust system consisting of a suction pump 6 and an exhaust port 7 are attached, respectively. This exhaust system also includes a solenoid valve 8, a flow rate regulator 9, and a bypass filter 1.
0 is connected.

On the other hand, the absorption liquid 2 is supplied from below the gas absorption unit 1 to a supply tank 11, a liquid feeding pump 12, and a solenoid valve 13.
The liquid is supplied via the electromagnetic valve 14 and discharged into the drain tank 15 via the electromagnetic valve 14. In addition, inside the gas absorption part 1, 16 shows the electrode for detecting the level of the absorption liquid 2, and 17 shows the resistance for temperature compensation, respectively.

Furthermore, a pair of measurement electrodes 18, 18 are arranged in the gas absorption section 1 so as to be immersed in the absorption liquid 2, and these measurement electrodes 18, 18 are connected to an analog input interface 19. There is. This analog input interface 19 is connected to the measuring electrode 1
This is for detecting the electric conductivity of the absorbing liquid 2 between 8 and 18, that is, the value of the current that changes depending on the concentration of SO ₂ and converting it into a digital signal.

The analog input interface 19 is connected to the CPU 20 via a bus, and the CPU 20 supplies, measures, and discharges the absorption liquid 2 via the digital input/output interface 21, and also operates the suction pump 6. A ROM 24 stores a series of measurement programs, such as a program for recording the SO ₂ concentration calculated from the conductivity of the absorption liquid 2 with a recorder 23 via an analog output interface 22, A RAM 25 for storing data is connected thereto.

Furthermore, an operation display section 27 is connected to the bus via a key and display interface 26. This operation display section 27 is used to supply, measure, vent, and adjust the zero point of the absorption liquid 2 during manual operation.
It is equipped with input keys for setting each operation mode such as measurement, and a display for displaying the time and current operation mode.

Further, the input/output port 28 connected to the digital input/output interface 21 and the analog output interface 22 is for connecting input/output devices other than the recorder 23 and the operation display section 27.

However, the present invention is characterized in that the instantaneous value of the SO ₂ concentration is determined from the sawtooth measurement record shown in FIG. 6 by changing the microcomputer program. That is, multiple apparent SO ₂ concentration values x _i are sampled every unit measurement time t _i (for example, every 10 seconds) from the sawtooth measurement record over a certain sampling period (for example, 4 minutes), and these values are The slope obtained by the least squares method based on the value x _i is multiplied by a predetermined constant, and the value is _calculated as
This is the instantaneous value of concentration. This operation is performed in units of measurement time t _i
The instantaneous value of the SO ₂ concentration is continuously obtained by repeating each sampling period that is sequentially updated each time the period elapses.

In addition, in the sawtooth measurement record, the slope calculation described above is stopped during the time when the SO ₂ concentration is held for draining or measuring the absorbent, and the instantaneous value of the SO ₂ concentration is also held at the last calculation result. .

Furthermore, when one measurement period ends and the sawtooth measurement recording instruction returns to 0 to start a new measurement period, the previous sampling period (4 minutes)
Since the data x _i for the previous measurement period is not available, the instantaneous value is determined using the data x _i for the last sampling period in the previous measurement cycle.

Below, how to obtain this instantaneous value is shown in Figures 2 to 4.
To explain in detail with reference to the figures, first, as shown in Fig. 2, in a sawtooth measurement record with a measurement period T (1 hour), _the unit measurement time t _i ( ;10 seconds, where i=-N~
2N+1 (25) apparent SO ₂ per N)
Assuming that the measured concentration value x _i is obtained, the following approximate expression holds true during this sampling period t _s : x=at+b (1). Now, to find the slope a using the method of least squares, a=1/K _N 〓 ^i=-N x _i・i ...(2) [However, K=1/3N (N+1) (2N+1)] All you have to do is calculate. However, performing this for 2N+1 data places a heavy burden on the microcomputer that is also performing other processing, so in the present invention, by using the calculation results in the immediately preceding sampling period,
This reduces the number of calculation steps and increases the margin for other interrupt processing by the microcomputer.

That is, the total sum of x _i・i in the period from i=-N to i=N is _N 〓 ^i=-N x _i・i= _N-1 〓 ^i=-N-1 x _i・(i+1)+N ^It _{is expressed as} ⁽ _{x N + _} can be expressed as _N 〓 ^i=-N x _i = _N-1 〓 ^i=-N-1 x _i +x _N −x _-N-1 ...(4). In other words, the value of _N 〓 ^i=-N x _i・i in a certain sampling period is the value of _N-1 〓 ^i=-N-1 x _i・i in the immediately preceding sampling period,
It can be determined by slight additions and subtractions using x _i, etc., which are the sawtooth measurement data currently imported. Note that equation (4) is used to find a term corresponding to _N-1 〓 ^i=-N-1 x _i in equation (3) in the next sampling period.

In this way, equations (3) and (4) are calculated, and _N 〓 ^i=-N x _i・i
By multiplying by a constant, the instantaneous value of SO ₂ at each point in time can be obtained. Here, 2N+1 data x _i sampled from the sawtooth measurement record
is stored in the RAM 25 or the like, and is sequentially updated as shown in e of FIG. 2 by removing the oldest data and taking in the latest data every time the unit measurement time t _i elapses. The series of steps described above is shown in a flowchart as shown in FIG.

Next, when the measurement cycle T ends one hour after the start of measurement and you move on to the next measurement cycle T, the 2N value stored at the end of the previous measurement cycle is
For +1 pieces of data x _i , the final value y _N is determined by the least squares method. The method is to first find a in equation (2) by multiplying the value obtained by equation (3) by a constant 1/K, and then calculate x _i in equation (4).
From the total sum _N 〓 ^i=-N x _i and the number of data 2N+1, the average value b is determined by b=1/2N+1 _N 〓 ^i=-N x _i (5). Theoretically, since y _N is the sum of this average value b and a·N, it can be determined as follows: y _N =b+a·N (6).

After calculating y _N in this way, subtract y _N from each of the 2N+1 x _i's and put them back into the original data area of the memory. As a result, as shown at f in FIG. 2, the data up to 2N+1 previous sawtooth measurement records that are 0 at the start of one measurement period are aligned. Note that the total sum of x _{i N} 〓 ^i=-N x _i is obtained by subtracting y _N from all data, so _N 〓 ^i=-N x _i −
Just calculate y _N・(2N+1) and re-enter the data area of _N 〓 ^i=-N x _i .

FIG. 4 shows the above steps, and after this series of steps is completed, the process is executed again according to the procedure shown in FIG. 3.

By sequentially determining the instantaneous value of SO ₂ concentration from the sawtooth measurement record in this way, a record like the one shown in FIG. 5 can be obtained. In this Figure 5, B
1 is a sawtooth measurement record, and A is an instantaneous value record, and this instantaneous value record allows a detailed understanding of changes in the SO ₂ concentration.

In the above embodiments, the present invention was applied to an SO ₂ measuring device based on the solution conductivity method, but the application of the present invention is not limited to this in any way; for example, when NO ₂ It can also be applied to an atmospheric nitrogen oxide measuring device, etc., in which the absorbance when color develops in the absorbing liquid is the physical property of the absorbing liquid that is directly measured.

(Effects of the Invention) As described in detail above, according to the present invention, the instantaneous value of SO ₂ concentration at each point in time can be obtained from the sawtooth record with extremely few calculation steps. Even an inexperienced or unskilled person can accurately grasp changes in SO ₂ concentration at a glance, and can use it as an effective sample for air pollution control. In particular, _SO2
In cases where highly concentrated gas exists for only a very short time, conventional sawtooth recording is less useful as it can only tell the average value for one hour, but with the present invention, SO ₂ It is possible to know the maximum value of concentration.

Furthermore, without using methods such as differentiating sawtooth data, it is possible to obtain instantaneous values using the immediately preceding data even when transitioning from the end of one measurement cycle to the start of the next measurement cycle. Continuous instantaneous value records can be obtained before and after the measurement period.

Furthermore, the measuring device according to the present invention can be configured by simply making some changes to the program of a conventional measuring device and adding one channel of output to a recorder, etc., making it an extremely low-cost product. can be provided as.

In addition, when dynamically calibrating the scale using SO ₂ standard gas, in order to obtain at least two or three average value data, which is conventionally only obtained once per measurement period (1 hour), the scale is also calibrated. Although it required 2 to 3 hours, the present invention has advantages such as being able to perform the calibration work in a short time because the instantaneous value of the SO ₂ concentration can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention;
Figure 2 is an explanatory diagram of the measurement principle, Figure 3 is a flowchart for each unit time, Figure 4 is a flowchart when a new measurement cycle starts, and Figure 5 is an instantaneous value compared to the sawtooth measurement record. FIG. 6 is an explanatory diagram of conventional sawtooth measurement recording. 1... Gas absorption section, 2... Absorption liquid, 18... Measurement electrode, 19... Analog input interface,
20...CPU, 21...Digital input/output interface, 22...Analog output interface, 23...Recorder, 24...ROM, 25...
RAM, 26...key and display interface, 27...operation display section, 28...input/output port.

Claims (1)

[Claims] 1. Changes in the physical properties of an absorbing liquid that has absorbed atmospheric pollutants within a certain measurement cycle are sequentially detected, and the change in physical properties is indicated by a slope corresponding to the concentration of the pollutants. In an air pollution measurement device using a substantially sawtooth recording method, the average concentration of the pollutant is indicated at the end of the measurement period as the pollutant changes, and a plurality of unit measurements constituting a certain sampling period are updated sequentially. Based on the sampling data of a plurality of concentrations corresponding to time, the slope of the approximate expression of the sawtooth measurement record in the sampling period immediately after the sampling period is determined, and based on this slope, the concentration of the pollutant in the sampling period is determined. An air pollution measuring device characterized by being configured to obtain an instantaneous value of concentration.