JP3330816B2 - Atomic absorption photometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic absorption spectrophotometer for atomizing a measurement sample and atomizing the sample in a frame, and measuring the absorbance of the atomized sample.

[0002]

2. Description of the Related Art Flame atomic absorption spectrometry is one of the elemental analysis methods for measuring a metal element in a solution sample by atomizing a measurement sample, atomizing the sample in a flame, and measuring the absorbance. The photometer is a measuring device for performing the analysis method. This atomic absorption spectrophotometer has an excellent feature that the measurement can be performed easily and with high sensitivity because the analysis time is relatively short and the influence of the solvent is small. Also, there are about 50 types of measurable elements, which are used in a wide range of fields, such as measurement of impurities in steel and environmental samples. In recent years, regulation values in the field of environmental analysis have become stricter, and the role of the atomic absorption spectrometer has been increasing even in consideration of this.

When an atomic absorption photometer is actually used, acetylene gas or hydrogen gas is used as a fuel gas in order to increase the flame temperature. Since the optimum conditions of the flame vary depending on the element to be measured, it is necessary to change the flow rate of the fuel gas for the flame for each measurement sample.

Heretofore, such flow rate adjustment has been performed by providing a variable needle valve in the flow path of the fuel gas and controlling the feed rate of the fuel gas by a stepping motor. That is, in the control unit for controlling the fuel, the flow rate is obtained from the relationship between the gas pressure on the variable needle valve and the clearance area of the needle of the variable needle valve. Also, separately from the above, a frame sensor is provided in the vicinity of a burner for generating a flame, and whether or not fuel gas is flowing is confirmed by detecting whether or not the flame is actually ignited by the above-mentioned frame sensor. Was.

[0005] A flame ignition sequence by a conventional atomic absorption spectrophotometer including such a fuel gas flow rate adjustment and confirmation method will be described with reference to FIG. However, such a sequence is usually set as a program in a control unit for controlling fuel. When the ignition sequence starts, it is confirmed whether or not water for cooling the burner is flowing as shown in step S401. If water is flowing, the process proceeds to the next step S402, and if water is not flowing, an error ends. Next, in step S402, it is checked whether the air pressure for the frame is normal (sufficient). If the air pressure is normal, the process proceeds to the next step S403. If the air pressure is not normal (insufficient), an error is ended. Next, in step S403,
Check that the fuel gas pressure is sufficient. If the gas pressure is sufficient, the process proceeds to the next step S404. If the gas pressure is insufficient, the process ends with an error.

In step S404, a fuel gas flow rate is set. Actually, a pulse is sent to the above-mentioned pulse motor for adjusting the flow rate so that the fuel gas flow rate becomes an appropriate flow rate to be ignited. Next, in step S405, a pilot valve is opened to ignite the pilot flame, and in the next step S4
At 06, the burner valve is opened and the flame is ignited to the burner. Then, wait for the frame to stabilize, and step S40
At 7, the ignition of the flame is confirmed by the aforementioned flame sensor. At this time, when it is confirmed that the flame is ignited, the process proceeds to the next sequence, that is, measurement, and the like, and when it is determined that the flame is not ignited, an error ends.

[0007]

In the prior art as described above, the flow rate of the fuel gas is indirectly determined from the relationship between the variable needle valve and the stepping motor. It was not known whether it was flowing or if the required flow rate of fuel gas was actually flowing. As described above, since the actual flow rate of the fuel gas was not observed, if there was an abnormality in the variable needle valve or the stepping motor,
The ignition or measurement may be performed at a flow rate different from the set flow rate. Further, although the ignition of the flame is confirmed by the flame sensor, the method of confirming the ignition is not sufficient because it is also indirect as in the above.

[0008] An object of the present invention is to provide an atomic absorption spectrophotometer capable of surely knowing the actual flow rate of fuel gas and controlling the fuel gas safely and accurately.

[0009]

In order to achieve the above object, the present invention is configured as follows. Measurement sample and fuel gas
And a frame chamber for mixing
Burner connected to the chamber and for igniting the flame
A light source unit that emits light including a line spectrum of a measurement element, and a spray that sprays a measurement sample into the frame chamber.
Unit, a light detection unit that detects light after light emitted from the light source unit passes through the frame and is absorbed by the measurement sample, and fuel gas control that controls the flow rate and combustion of the fuel gas And an atomic absorption spectrophotometer having a portion of the fuel gas supplied to the frame chamber .
Comprising a fuel gas flow meter for measuring the flow rate, the fuel gas system
The control unit controls the ignition of the flame.
And a control sequence for monitoring the flame combustion
And a control sequence for extinguishing the frame is performed.
In each control sequence, the fuel gas flow
Using the measurement result of the meter, the predetermined gas flow rate is
It is determined whether or not it is being supplied to the frame chamber.

[0010]

(2) Preferably, in the above (1),
The fuel gas flow meter is a thermal flow meter.

(3) Preferably, in the above (1),
Control sequence for igniting the flame
Means that the flow rate of the fuel gas is zero;
Water is flowing through the air, and the air pressure and fuel gas pressure are correct.
The fuel gas flow is normal.
Set the amount and ignite, if not normal, end the process
I do. (4) Preferably, in (3) above,
The specified flow rate of the fuel gas is
The amount is the set after ignition of the flame
Comparing the flow rate with the measurement result of the fuel gas flow meter,
Then, the comparison operation is repeated a predetermined number of times at regular intervals.

Preferably, in the above (3),
The set fuel gas flow rate is suitable for the measurement of the measurement element.
The flow rate is high, and the
The control sequence is that water is flowing through the burner and
Air pressure and fuel gas pressure are normal,
That the fuel gas flow meter is lit
Is appropriate compared to the set flow rate,
If abnormal, extinguish the flame.

Preferably, in the above (3),
The control sequence for extinguishing the frame comprises:
After stopping the flow of fuel gas, measure the fuel gas flow meter
Check that the result is zero, if not
Determines that something is abnormal and issues a vengeance.

[0015]

[0016]

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the atomic absorption photometer according to the present invention will be described with reference to FIGS.

FIG. 1 is a schematic configuration diagram of an atomic absorption spectrophotometer of the present embodiment, and FIG. 2 is a functional block diagram of the atomic absorption photometer of the present embodiment. The atomic absorption spectrometer shown in FIG. 1 includes a frame chamber 1 for mixing a sample, fuel gas, and air, a burner 2 for igniting a frame 11, a nebulizer 3 for spraying the sample, and a supply pipe for sending the sample to the nebulizer 3. 4. Fuel gas supply pipe 5, air supply pipe 6, fuel gas control unit 7 for controlling the flow rate of fuel gas and air, hollow cathode lamp 8 for generating luminous flux 8a containing line spectrum of measurement element, and frame 11 The spectroscope 9 includes a spectroscope 9 for splitting the light beam 11a, a detector 10 for detecting the light beam 9a split by the spectrometer 9, and a frame sensor 12 for checking whether or not the flame 11 is ignited.

As shown in FIG. 2, the fuel gas control section 7 includes a control section 13, a mass flow meter 14 for precisely measuring the flow rate of the fuel gas, a mass flow controller 15 for precisely adjusting the flow rate of the fuel gas, The mass flow meter 14 is provided with an air flow rate setting section 16 for adjusting the flow rate of the fuel gas.
However, an air source 18 is connected to the air flow rate setting unit 16, and a main control unit 19 also serving as an input / output device is connected to the control unit 13. Note that the air flow rate setting unit 16 may be configured with the same one as the mass flow meter 14 and the mass flow controller 15. A gas pressure gauge 20 is connected to the fuel gas supply pipe 5, and an air pressure gauge 21 is connected to the air supply pipe 6, so that the measured values of the gas pressure gauge 20 and the air pressure gauge 21 are input to the control unit 13. It has become. further,
A water cooling tube 22 passes through the water cooling tube 22 for cooling the burner 2, and a flow meter 23 for measuring the flow rate of water is attached to the water cooling tube 22.
To be entered.

The mass flow meter 14 is a thermal type flow meter, which has a very thin bypass flow path, and surrounds two places of the bypass flow path in a solenoid shape with a heating wire to flow the fluid flowing through the bypass flow path. Heating is performed by the heating wire on the upstream side, and the flow rate of the fluid is known from the voltage value of the heating wire on the downstream side.
The mass flow controller 15 is a device having a precision needle valve for controlling the flow path cross-sectional area by precise movement of the needle and precisely setting the flow rate of the fluid. The needle valve applies a set voltage to the needle drive source. This sets the flow rate. Usually, the mass flow meter 14 and the mass flow controller 15 are used in combination.

In the operation of the atomic absorption spectrophotometer as described above, the test material is dissolved in an acidic solution such as nitric acid or hydrochloric acid to prepare a sample solution for measurement. Then, the sample solution is introduced into the nebulizer 3 from the supply pipe 4 to form a mist,
The atomized measurement sample is discharged into the frame chamber 1. The flow rate of the fuel gas supplied from the fuel gas source 17 is measured by the mass flow meter 14, the flow rate is set by the mass flow controller 15, and then supplied into the frame chamber 1 via the fuel gas supply pipe 5. Is done. Further, the air from the air / air source 18 is supplied into the frame chamber 1 via the air supply pipe 6 after the flow rate is set by the air flow rate setting unit 16. Mass flow meter 1
The flow rate of the fuel gas by the control unit 4 and the flow rate of the air by the air flow rate setting unit 16 are compared and monitored with respective flow rates preset in the control unit 13.

In the frame chamber 1, the measurement sample, fuel gas and air are mixed and sent to the burner 2. And
The mixed gas is released into the atmosphere from the elongated slit of the burner 2 and ignited by the mixed gas to form a frame 11 on the slit of the burner 2, and the elements in the measurement sample are atomized into atomic vapor. . Further, the flame sensor 12 monitors the presence or absence of ignition of the flame 11. When a light beam 8a having a line spectrum of a measurement element is passed from the hollow cathode lamp 8 to the frame 11 where the atomic vapor is present, light absorption occurs due to the atomic vapor in the frame 11. Thereafter, the light beam 11a passing through the frame 11 is split by the spectroscope 9, and the split light beam 9a is
And an atomic absorption measurement is performed. The data of the atomic absorption measurement is sent to the main controller 19 and subjected to data processing, and the analysis result is output.

Next, a flame ignition monitoring sequence according to the present embodiment will be described with reference to FIG. However, this sequence is set as a program in the control unit 13 of the fuel gas control unit 7 (the same applies to the sequences in FIGS. 4 and 5 below). First,
In step S101, it is confirmed whether or not the burner 2 is extinguished by the flame sensor 12. If it is not extinguished, that is, if it is ignited, the process jumps to the end. Proceed to sequence. If the fire has been extinguished, the process proceeds to step S102, and it is confirmed by the mass flow meter 14 that the fuel gas is not actually flowing. Here, if the fuel gas is flowing, it means that the fuel gas is flowing despite the fact that ignition is not performed, so that an error is terminated. On the other hand, if the fuel gas is not flowing, the process proceeds to the next step S103. move on. Steps S101 and S10 above
2, the frame sensor 12 and the mass flow meter 1
4, the fire extinguishing state of the burner 2 is double-checked, so that the possibility of erroneous outflow of fuel gas due to any failure can be reduced.

In step S103, it is confirmed by the flow meter 23 whether or not the water for cooling the burner 2 is flowing through the water cooling pipe 22, and if it is flowing, the flow proceeds to the next step S104.
If it does not flow, an error ends. Step S104
Then, whether the air pressure is normal (sufficient) is checked by the air pressure gauge 21. If the air pressure is normal, the process proceeds to the next step S105, and if the air pressure is not normal (insufficient), an error ends. In step S105, whether the fuel gas pressure is normal (sufficient) is checked by the gas pressure gauge 20, and if the fuel gas pressure is normal, the next step S10
The process proceeds to step 6, and if not normal (insufficient), an error is ended.

In step S106, the mass flow controller 15 sets the flow rate of the fuel gas. At this time,
For example, the control unit 13 sets a set voltage corresponding to the ignition flow rate.
To the mass flow controller 15. Next, in step S107, a pilot flame valve (not shown) is opened to ignite the pilot flame, and in the next step S108, the burner 2 valve is opened to ignite the flame 11 in the burner 2. Thereafter, the ignition of the flame 11 is confirmed by the flame sensor 12 in step S109 until the flame 11 is stabilized. At this time, if it is determined that the flame 11 is not ignited, an error is terminated. If it is confirmed that the flame 11 is ignited, the process proceeds to the next step S110. In step S110, it is checked whether or not the flow rate of the fuel gas is the set appropriate flow rate. That is, the actual fuel gas flow rate is measured by the mass flow meter 14, and the control unit 13 compares and monitors the measured actual fuel gas flow rate with the flow rate set by the mass flow controller 15. In addition, step S110 has a micro loop that repeats the above-described comparison and monitoring operation a predetermined number of times at a fixed time interval, for example, a minute time interval of about 100 microseconds. As a result of the comparison and monitoring, if the fuel gas flow rate is different from the set flow rate, an error is terminated. If the fuel gas flow rate is appropriate, the flame ignition confirmation sequence is terminated and the process proceeds to the next sequence (for example, measurement). .

The actual fuel gas flow rate is measured by the mass flow meter 14 and compared with the control unit 13 to check and monitor the actual fuel gas flow rate within a certain period of time due to the presence of step S110. It is possible to verify whether the adjustment of the fuel gas flow rate at the time of ignition of the fuel gas is normal. In particular, in the related art, the set flow rate of the fuel gas may be different from the actual flow rate due to a failure of the stepping motor or clogging in the vicinity of the valve. Further, it is possible to prevent erroneous outflow of the fuel gas at the time of ignition and improve safety.

Next, a flame combustion monitoring sequence according to this embodiment will be described with reference to FIG. This sequence is always executed while the fuel gas is burning and the frame 11 is formed. First, in step S201, it is confirmed by the flow meter 23 whether or not the water for cooling the burner 2 is flowing through the water cooling pipe 22, and if it is flowing, the next step S2
02, if it does not flow, it is recognized as abnormal, and the flow proceeds to the frame extinguishing sequence (see FIG. 5). In step S202, whether the air pressure is normal (sufficient) is checked by the air pressure gauge 21. If the air pressure is normal, the process proceeds to the next step S203. If the air pressure is not normal (insufficient), the flow proceeds to the flame extinguishing sequence. move on. In step 203, the gas pressure gauge 2 checks whether the fuel gas pressure is normal (sufficient).
If the fuel gas pressure is normal, the process proceeds to the next step S204, and if the fuel gas pressure is not normal (insufficient), the process proceeds to the flame extinguishing sequence. In step S204, the ignition of the flame 11 is confirmed by the flame sensor 12, and when it is determined that the flame 11 is not ignited, the process proceeds to the flame extinguishing sequence. When it is confirmed that the flame 11 is ignited, Next step S205
Proceed to.

In step S205, it is determined in step S1 of FIG. 3 whether the flow rate of the fuel gas is a set appropriate flow rate.
Confirm with the same micro loop as in 10. That is, the actual fuel gas flow rate is measured by the mass flow meter 14,
The actual fuel gas flow rate measured by the control unit 13 is compared and monitored with the flow rate set by the mass flow controller 15, and the operation of the comparison and monitoring is repeated a predetermined number of times at regular time intervals. If the fuel gas flow rate is different from the set flow rate, the flow proceeds to the flame extinguishing sequence, and if the fuel gas flow rate is appropriate, the flow proceeds to step S206.

In step S206, the burner 2 is extinguished and the formation of the frame 11 is stopped, or an operation request such as changing the type of fuel gas is input. If there is no such request, step S201 is performed. Return to That is, steps S201 to S206 are repeated as a loop until some operation request is input. In addition, the repetition time interval of the loop from step S201 to step S206 is set to a short time, for example, about 1 second. Further, if any operation request is input in step S206, the process exits this loop and proceeds to the next sequence, that is, the requested operation.

The actual flow rate of the fuel gas is measured by the mass flow meter 14, and the control unit 13 compares and monitors the actual flow rate of the fuel gas. Can be confirmed within a certain period of time. Also,
By repeating the loop from step S201 to step S206 until any operation request during the combustion of the fuel gas is input, it is possible to always accurately check the flow rate of the fuel gas during the combustion of the fuel gas. Even if an erroneous outflow of fuel gas occurs, the abnormality is found in a short time at least as long as the repetition time of the loop (for example, at most about 2 seconds when the time interval of the loop is 1 second). be able to. Therefore, safe combustion of the fuel gas can be performed during combustion of the fuel gas.

Next, a frame extinguishing sequence according to the present embodiment will be described with reference to FIG. First, step S30
At 1, the valve of the burner 2 is closed to stop the fuel gas. Then, in step S302, it is checked whether or not the flow rate of the fuel gas is 0 by the same micro loop as in step S110 in FIG. At this time, if the fuel gas flow rate is not 0, it means that the fuel gas is flowing despite the fact that the fire is extinguished, and abnormalities such as abnormality of the fuel gas control unit 7 and gas leak are considered. As shown in S303, a warning is generated and the user is notified of that. If it is confirmed in step S302 that the fuel gas flow rate is 0, the flame extinguishing sequence ends.

In this flame extinguishing sequence, the mass flow meter 14 and the control unit 13 compare and monitor whether or not the actual fuel gas flow rate is 0, and as a result, the fuel gas flow during fire extinguishing is consequently provided. A leak test can be performed, and a self-diagnosis at the time of fire extinguishing can be performed. Therefore, frame 11
It is possible to improve the safety at the time of fire extinguishing.

According to the present embodiment as described above, the actual fuel gas flow rate is measured by the mass flow meter 14,
Since a step of comparing and monitoring is provided in the control unit 13, the actual fuel gas flow rate can be confirmed within a fixed time of the micro loop, and whether the adjustment of the fuel gas flow rate at the time of fuel gas ignition is normal or not is determined. It is possible to perform verification, check the actual fuel gas flow rate during fuel gas combustion, and perform a fuel gas leak test when extinguishing a fire. In addition, since the loop of the flame ignition monitoring sequence is repeated during the combustion of the fuel gas, even if an erroneous outflow of the fuel gas occurs, it is possible to find the abnormality at least as short as the repetition time of the loop. Therefore, the fuel gas can be accurately controlled, and erroneous outflow or leakage of the fuel gas can be prevented, thereby improving safety.

[0034]

According to the present invention, the actual fuel gas flow rate and the preset flow rate are compared and monitored at regular time intervals by the flame fuel gas monitoring means, so that the fuel gas flow rate can be reliably known. It is possible to accurately control the fuel gas and improve the safety.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an atomic absorption photometer according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of the atomic absorption photometer shown in FIG.

FIG. 3 is a flowchart showing a flame ignition monitoring sequence by the atomic absorption photometer shown in FIG. 1;

FIG. 4 is a flowchart showing a flame combustion monitoring sequence by the atomic absorption photometer shown in FIG. 1;

FIG. 5 is a flowchart showing a flame extinguishing sequence by the atomic absorption photometer shown in FIG. 1;

FIG. 6 is a flowchart showing a flame ignition sequence by a conventional atomic absorption photometer.

[Explanation of symbols]

 Reference Signs List 1 frame chamber 2 burner 3 nebulizer 4 supply pipe 5 fuel gas supply pipe 6 air supply pipe 7 fuel gas control unit 8 hollow cathode lamp 8a luminous flux 9 spectrometer 10 detector 11 frame 11a luminous flux 12 frame sensor 13 control unit 14 mass flow meter 15 Mass flow controller 16 Air flow setting unit 20 Gas pressure gauge 21 Air pressure gauge 23 Flow meter

Continued on the front page (72) Inventor Takashi Kimoto 882 Ma, Hitachinaka-shi, Ibaraki Pref. Measuring Instrument Division, Hitachi, Ltd. Examiner, Munehiko Higuchi (56) References JP-A-5-126730 (JP, A) JP-A-4-336397 (JP, A) JP-A-5-20568 (JP, A) JP-A-8-42847 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) G01N 21 / 00-21/01 G01N 21/17-21/61 F23N 5/18 Practical file (PATOLIS) Patent file (PATOLIS)

Claims (6)

(57) [Claims] 1. A frame for mixing a measurement sample and a fuel gas.
Frame chamber and a frame chamber connected to the frame chamber.
A burner for igniting the flame , a light source for emitting light including a line spectrum of the element to be measured, and a flame chamber.
A spray unit for spraying a measurement sample in the server, and a light detector for detecting the light after absorbing light emitted from the light source unit by the measurement sample is passed through the frame is performed, the fuel gas in an atomic absorption spectrophotometer having a flow rate and the fuel gas control unit for controlling the combustion, the flow amount of the fuel gas supplied to the frame chamber
A fuel gas flow meter that measures the
A control sequence for monitoring the flame combustion
Control sequence and control for extinguishing the frame
Sequence, and in any control sequence
Using the measurement result of the fuel gas flow meter, a predetermined
Gas flow is being supplied to the frame chamber
An atomic absorption spectrophotometer characterized in that: 2. The atomic absorption spectrophotometer according to claim 1, wherein
The fuel gas flow meter, atomic absorption spectrophotometer, which is a thermal flow meter. 3. The atomic absorption spectrophotometer of claim 1 Symbol placement,
The control sequence for igniting the flame is
The fuel gas flow rate is zero, and water flows through the burner.
Air pressure and fuel gas pressure are normal
Check that the fuel gas flow rate is normal
An atomic absorption spectrophotometer characterized in that the ignition is performed, and the processing is terminated when it is not normal . 4. The atomic absorption spectrophotometer according to claim 3, wherein
The set fuel gas flow rate is suitable for the measurement of the measurement element.
The flow rate is low and the flame
The measured flow rate is compared with the measurement result of the fuel gas flow meter.
And the comparison operation is repeated a predetermined number of times at regular intervals.
Atomic absorption spectrophotometer, characterized in that to. 5. The atomic absorption spectrophotometer according to claim 3, wherein
The set fuel gas flow rate is suitable for the measurement of the measurement element.
The flow rate is high, and the
The control sequence is that water is flowing through the burner and
Air pressure and fuel gas pressure are normal,
That the fuel gas flow meter is lit
Is appropriate compared to the set flow rate,
An atomic absorption spectrometer characterized in that the flame is extinguished if there is an abnormality . 6. The atomic absorption spectrophotometer according to claim 3, wherein
The control sequence for extinguishing the frame comprises:
After stopping the flow of fuel gas, measure the fuel gas flow meter
Check that the result is zero, if not
Is an atom characterized by determining that something is abnormal and issuing a revenge report
Spectrophotometer.