CN101162200A - System using chemiluminescence method to execute nitrous oxides analysis - Google Patents
System using chemiluminescence method to execute nitrous oxides analysis Download PDFInfo
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- CN101162200A CN101162200A CNA2007100112401A CN200710011240A CN101162200A CN 101162200 A CN101162200 A CN 101162200A CN A2007100112401 A CNA2007100112401 A CN A2007100112401A CN 200710011240 A CN200710011240 A CN 200710011240A CN 101162200 A CN101162200 A CN 101162200A
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Abstract
The invention relates to a gas analysis system and belongs to the nitrogen oxide analysis field. The system detects the concentration of nitric oxide in the atmosphere by using the power of light generated in the gaseous phase reaction between O3 and nitric oxide (NO) gas. The method is called as a chemiluminescence method. The system is used to measure the concentration of NO, NO2 and the concentration NOX in the atmosphere continuously, reacts rapidly when the concentrations of NO, NO2 and NOX change and can measures stably for a long time; the system can be applied in many conditions of different temperatures and humidity without any impact on the measurement precision. All operation control can be accomplished on an operation panel. The concentration of gas is displayed on the LCD display screen on the operation panel. In addition to the display screen on the operation panel, terminals are also provided to provide measurement output signals. A filter and a sampling instrument are arranged at accessible positions and the whole system is reliable in design and convenient to maintain.
Description
Technical field
Native system relates to a kind of gas analysis system, particularly a kind of with chemoluminescence method to the NO in the surrounding air, NO
2, NO
XThe system that composition is analyzed.
Background technology
Along with the deterioration of environmental aspect and the people raising to environmental consciousness, supervision is had higher requirement to environment.As the important means of environment supervision, environment supervision instrument more and more is subjected to the attention of government and enterprise.China has issued " ambient air quality " and " discharge standard of air pollutants " already, sets up more than 6000 of ambient air quality monitoring stations.But the monitoring of the ambient air quality of China is in spot sampling, lab analysis stage basically, and sampling instrument is based on manual and semi-automatic.Owing to lack the air quality monitoring instrument of continuous automatic on-line, influence and restricted Environmental Protection in China and enforce the law and environmental quality supervision and management level.The monitoring technology of development independent intellectual property right forms the environment supervision instrument industry, takes short views, and foreign exchange is saved in alternative import, satisfies the active demand of current China to the air quality monitoring instrument, drives the development of other association area; In the long term, can break the monopolization of developed country, improve the competitive power of China in the international big market of environment supervision instrument, improve environmental monitoring ability and environment supervision law enforcement modernization level, development Environmental Protection in China cause in this technical field.
Summary of the invention
At the deficiencies in the prior art, the purpose of this invention is to provide a kind of system with chemiluminescence method to execute nitrous oxides analysis.The present invention is the continuous automatic on-line monitoring system of a kind of chemoluminescence method oxides of nitrogen, combines multi-disciplinary state-of-the-art technologies such as optics, chemistry, machinery, control automatically, electronic technology, new material and computer software.Its control technology, NO
2Aspects such as the unique design of-NO transformation technology, reaction chamber, self-diagnostic function and remote control network are in international most advanced level.
Existing analytic system electrical structure complexity, fault are difficult for analyzing, and the performance of ventilating difference causes the photomultiplier job insecurity, the local communication mode is the RS-232 bus, be the bus of using the earliest in the environmental monitoring system, its communication protocol is fairly simple, and is cheap.RS-232 has its limitation, is in particular in that transfer rate is lower, and transmitting range is shorter, and antijamming capability is relatively poor, and the most important thing is that it only is suitable for point-to-point connected mode, thereby has deficiencies such as communication reliability is poor, extendability is weak.
Native system adopts local ENTERNET network, and transmission speed is fast, is beneficial to communication between instrument; Support PSTN and GPRS communication, can be equipped with simultaneously.Electrical module integrated level height, interchangeability is good, and quantity is few, and anti-interference is good.Circuit signal control is digital regulated with the adjusting employing, has avoided regulating the complicated processes of actual potential device, and instrument software adopts embedded Linux, good stability, and processing power is strong, and the instrument reaction velocity is fast.
Optical table to system improves, and adopts two cooling pieces that cryogenic temperature is provided, and helps guaranteeing the constant low temperature degree environment of PMT need of work; Improved the converter structure of system, controlled internal temperature effectively and outwards dispersed, working long hours to make the nitrogen-oxide analyzer, temperature in chassis change.
The internal system backup is provided with files such as file, sensor calibration data file, instrument calibration file, logout, error logging, historical data and all can uploads, the instrumentation program file, file, sensor calibration data file, instrument calibration file are set all can download, but the instrument software online upgrading.The instrument operating file can write down start, and test is provided with parametric procedure.The measurement data exceptional value is accepted or rejected, and mistake is appearring in the apparatus measures value, in the calibration, pines in advance, and normal value is all underlined, helps center software and handles.
Native system is to be used for measuring continuously atmosphere NO, NO
2And NO
XConcentration.This system is at NO, NO
2And NO
XRapid reaction during concentration change.Can measure steadily in the long term simultaneously.This system can be operated in very wide environment temperature and damp condition, and does not influence measuring accuracy.On guidance panel, can finish all operation control.Be positioned at the concentration of the LCD display demonstration gas on the guidance panel.Except that the guidance panel display screen, also provide terminal that the measurement output signal is provided.
The total system reliable design maintains easily.Filtrator and sampling apparatus are installed in the position that is easy to change.
The purpose of native system provides a kind of system that oxides of nitrogen composition in the surrounding air is analyzed with chemoluminescence method.
Native system is to utilize O
3With the light intensity magnitude that the gas-phase reaction of NO is sent, detect NO concentration in the atmosphere.This method is known as chemoluminescence method.Product NO in this reaction
2Outer-shell electron be in excited state, it will get back to ground state at once, discharge the light wave of 600～2400nm simultaneously, its peak wavelength is 1200nm.The light intensity magnitude that produces in the reaction is proportional with the concentration of NO, so just can directly measure the NO concentration in the atmosphere in this way.
Measuring N O
2Method similarly, it is to use a kind of round-about way.At first with NO
2Be reduced to NO, again NO that reduction is obtained and O
3Reaction records the luminous intensity size in this reaction, just can draw NO
2The size of concentration.In the instrument of reality, sample gas at first passes through reburner, the NO in the sample gas
2Be reduced to NO, and the NO in the sample gas does not change, can record NO
XConcentration equal NO+NO
2Concentration.Part sample gas is without reactor, with O
3React, can record the concentration of NO.The NO that measures
XThe concentration concentration that deducts NO be tested NO
2Concentration.
Because the detection of chemoluminescence method is to rely on analytic system with NO
2Be transformed into NO, therefore, NO
2Quantitative yield be very important, it can not be lower than NO
2Concentration range.The transformation efficiency of system determines it is the core of calibration process thus.If being lower than 96%, the conversion efficiency of converter just should change or keep in repair.
O
3Be O by internal system
3Generator produces.Because only at NO and O
3Between chemiluminescence reaction is arranged, so the concentration of NO can be directly measured be come out, and NO
2Concentration be NO by surveying more respectively
XObtain with the difference of the total amount of NO, this comparative approach be with sample gas respectively by two gas circuits, alternating current is realized through reaction chamber.
First gas circuit (circulation) is directly gone into reaction chamber with the sample pneumatic transmission so that record NO content in the sample gas.Second circulation is gone into the catalytic reduction chamber with the sample pneumatic transmission earlier, with the NO in the sample gas
2Be reduced to NO (not influencing original NO in the sample gas), be admitted to the gas-phase reaction chamber, record the NO in the sample gas through the sample gas behind the catalytic reduction
XValue.
NO+NO
2, promptly total NO
XContent.NO
2Content just equal second the circulation NO that surveys
XDeduct the NO that first circulation is surveyed.
NO, NO
2And NO
XConcentration value will upgrade after each circulation, normal about 24 seconds of cycling time.
By reading the detailed description of native system (seeing Figure 16), the one of ordinary skilled in the art will be expressly understood other feature and advantage of native system.
Description of drawings
Fig. 1 air-channel system figure
Fig. 2 ozone generator
Fig. 3 optical table
Fig. 4 circuit block diagram
Fig. 5 CPU and power unit (CPU ﹠amp; Power)
Fig. 6 numeral I/O part (Digital I/O)
Fig. 7 simulates output (Analog out)
Fig. 8 analog input (Analog in)
Fig. 9 photomultiplier tube signal prime amplifier schematic diagram
Figure 10 drive plate high voltage control
Figure 11 drive plate signal condition
The control of Figure 12 drive plate peripheral hardware
Figure 13 reaction chamber structure figure
Figure 14 system construction drawing
Figure 15 systems function diagram
Figure 16 program control flow chart (comprise software main program framework flow process, the main control flow of task, concentration shows flow of task, panel shows task, store tasks five parts)
Embodiment
Native system (seeing Figure 14 and Figure 15) is made up of four functional subsystems: air-channel system, optical system, electronic system and computer system
One, air-channel system (as shown in Figure 1)
Analyze used gas (zero gas, gas, sample gas) and be admitted to system by dust filter.Three kinds of different gases are arranged: surrounding air (sample gas), zero gas and gas under different operator schemes.Pipeline in the system adopts Teflon, and kynar or stainless steel material can guarantee the purity of measurement gas so better.Teflon pipe also is used for being connected to guarantee its purity of gas and zero gas and system in addition.
Air must be through infiltration exsiccator in the system with the water vapor filtering after particulate filter filters the above particle of 5 μ m.This is because water vapor can quencher take place with the nitrogen dioxide molecules collision of excited state on the one hand, makes measurement result on the low side; Steam partial pressure is excessive on the other hand, then has big difference with the calibration gas condition, makes measurement result produce error.While water vapor enters ozone generator and also can cause ozone concentration to reduce.So how infiltration exsiccator filtering water vapor effect also directly influences the performance index of chemoluminescence method oxides of nitrogen system.
The infiltration exsiccator adopts sleeve type structure.Interior pipe is permeable membrane, and outer tube is a metal tube.Air passes through through interior pipe with certain flow rate under the normal temperature, and under certain suction function between inner and outer pipe, water vapor is penetrated into outer tube from inner tubal wall.Native system uses a kind of macromolecule permeable membrane, and hydrone is had higher selectivity, and gas circuit structure has been done bold improvement, and system accuracy will increase.
By the vacuum pump that is connected to pipe adapter ambient air outside continuously is extracted in the reaction chamber by dust filter, during discharging, gas is earlier through placing the outer tube of system board infiltration exsiccator, emits through the carbon filter on the external vacuum pump (be used for removing be introduced in the vacuum pump original ozone not influence the generation of ozone) again.
Surrounding air offers ozone generator as source of oxygen.Surrounding air is pumped in the system through the interior pipe of a carbon filter and infiltration exsiccator.Gas is to be introduced to ozone generator after by a wetness in the infiltration exsiccator.Moistures all in the air can permeate away by the inner tubal wall of infiltration exsiccator, at last the surrounding air of drying are sent into ozone generator.Wetly on the outer tube wall of exsiccator, these moistures are discharged with the gas of the gas of the outer tube of flowing through and vacuum pump.O in the surrounding air
2Enter O
3Generator is converted to O
3, again by entering in the reaction chamber behind the restrictor.
The gas that enters reaction chamber can be sample gas, zero gas or gas, and this will select to decide according to operator scheme.The inner air path system is by forming as the lower part:
1. sample gas, zero gas, gas triple channel solenoid valve
2. permanent exsiccator
3. humidity indicator
4. ozone generator
5. zero source of the gas
6.Teflon particulate filter
7. restrictor
8. catalytic converter (NO
2→ NO)
9. flowmeter
10. pressure transducer
Air-channel system has following several mode of operation:
● " SAMPLE " (sample gas) pattern
Under " SAMPLE " (sample gas) mode of operation, sample gas enters into dust filter (can remove diameter greater than 5 microns particle) by the Teflon pipe, and enters in the system by the pipe joint arrangement that indicates " sample gas " printed words.Normal opening through solenoid valve enters again, and is determined whether through catalyst by automatic transfer valve.
Gas enters stainless steel filter and removes the acticarbon that may be mixed in the sample gas then, and this acticarbon comes from the catalytic conversion chamber.Then sample gas enters the optical table (see figure 3) through a restrictor, reacts with ozone there.
● " ZERO " (zero gas) pattern
Under " ZERO " mode of operation, from the standard of system zero source of the gas or from the zero source of the gas of the outside solenoid valve 2 of flowing through, i.e. drift is striden the normal opening that floats valve (seeing Figure 15) and entered system by public outlet.If solenoid valve 1 (seeing Figure 15) action, air-flow can flow out through valve 1 by the identical gas circuit of top described " SAMPLE " pattern.
● " SPAN " (gas) pattern
Under " SPAN " pattern, gas source is in outside gas source or derive from the NO of system
2Gas source, the normally closed port (now opening) of the valve 2 of flowing through and a common port.Solenoid valve 1 action, air-flow are flowed out through valve 1 by the gas circuit of " SAMPLE " pattern equally.
Two, optical system
Optical system is designed to an independent assembly, the characteristics that have shock resistance, anti-vibration and not influenced by thermograde.The installation of all optical device all seals with " O " type circle.
Optical system is made up of two big parts: reaction chamber and photomultiplier transit guard system.
1. reaction chamber (seeing Figure 13)
The structure of chemoluminescence method analysis of nitrogen oxide system optics reaction chamber:
From chemoluminescence method analysis of nitrogen oxide system basic functional principle as can be seen, optical system is its core ingredient, and it is made up of reaction chamber and photomultiplier transit guard system two big parts.Because photomultiplier has been a kind of precision detection element of standard in the world; Therefore, the structure of reaction chamber can directly influence NO
XAccuracy and the measuring accuracy measured.
Reaction chamber is positioned at the rear portion of detector.Its function is to allow air sample gas mix with ozone, produces chemiluminescence reaction.Reaction chamber should have the air intake opening of an ozone, the air intake opening of a sample gas and an exhausr port.The gas of discharging should emit in the middle of reaction chamber.Above-mentioned two-way inlet air flow should enter reaction chamber from the both sides of reaction chamber.
The photon number that reaction chamber produces is directly proportional with the concentration of NO in the sample gas.Optical filter should be inserted in the centre of reaction chamber and photomultiplier, the confined reaction chamber can be provided and allow photon by entering two kinds of functions in the photomultiplier.
The factors such as distance of the material of reaction chamber, geometric configuration, sample airshed, reaction chamber and photomultiplier all can influence reaction efficiency, and the acquisition of these data all needs to carry out a large amount of tests, and are therefrom analyzed selection.Chemiluminescence reaction and temperature also have substantial connection, when temperature is high, and the luminescence efficiency height, so reaction chamber need remain under 45 ℃ the constant temperature.Simultaneously, because reaction chamber should reduce condensation wherein apart from the condenser of photomultiplier very near (working temperature of photomultiplier is 0～4 ℃).
Reaction chamber has been designed to an independently assembly, and it has shock resistance, against shock and is not subjected to the characteristics of influence of temperature change.
Light reaction chamber body adopts the stainless steel material of 1Cr18Ni9Ti, has very high anti intercrystalline corrosion ability, there is a reaction chamber that reaches the dome-type of mirror finish its inside, heating arrangement and temperature-detecting device are installed on body, make the reaction chamber uniform heating, and remain on by pick-up unit under 45 ℃ the duty; Two air intake opening places that are positioned at the sphere both sides respectively installed the very little stainless steel in root hole footpath (material is: 1Cr18Ni9Ti) wireway, directly with sample gas and O
3Mix before delivering to optical lens, produce chemiluminescence reaction; Sample gas and O
3Sample gas current limiting tube and O flow through respectively before by wireway
3Current limiting tube, assurance enters the sample gas and the O of reaction chamber
3Flow velocity and air pressure are constant, and each gas-phase reaction is all under equal conditions carried out; The light wave that the dome-type minute surface discharges gas reflects fully, reduces the loss of light wave, keeps the degree of accuracy of measuring; Emit the vent port of the gas of discharging in the middle of the reaction chamber rear portion.
Light reaction chamber pedestal adopts polyoxymethylene (POM) material, and it has good comprehensive performances and coloring, and common polyformaldehyde material is made the black polyoxymethylene, to reduce reflection of light; Polyoxymethylene has very high creep resistance and anti-relaxation ability, and hydroscopicity is little, and dimensional stability is good, and rub resistance can very well satisfy the requirement of light reaction chamber to the material technology performance index.Sealing is to adopt fluorine unpigmented rubber sealing gasket between light reaction chamber pedestal and the light reaction chamber body, and its ozone resistants, anti-marquis's property, heat impedance, the empty property learned of anti-ization and mechanicalness are all very outstanding, and be 20 years its serviceable life.
2. photomultiplier transit guard system (see figure 9)
The photomultiplier transit guard system is the whole parts in detection instrument unit.It is made up of photomultiplier, photomultiplier preamplification board, thermoelectric cooling module and drying tube, and all these is installed in the airtight case.The basic function of photomultiplier transit guard system is that the low light level signal that ozone and nitric oxide production gas phase photochemical reaction produced in the reaction chamber is changed into electric energy, and these electric energy are amplified.
Photomultiplier transit bobbin carriage and thermoelectric cooling chamber can create proper temperature environment so that the photomultiplier operate as normal.Photomultiplier is very sensitive to light, must in the dark just can tell the photon that produces in the reaction chamber.This device can provide this environment.
Thermoelectric cooling module can be created a stationary temperature, is approximately 3 ℃, and it has dual-use function.First function is that low-temperature operation helps long-term stability; Second function is to reduce dark current, to improve the sensitivity of photomultiplier.
Dark current photomultiplier under complete dark condition itself produces, and it is produced by the defective in the pipe, can be divided into three types usually; Internal driving leaks, should from the electronics heat radiation and the revival of pipe fitting.
Photomultiplier is made up of three basic elements of character: negative electrode, dynode and anode are formed.The light sensation negative electrode produces free electron when being subjected to illumination.Dynode is handled with special coating, helps strengthening Secondary Emission.When free electron struck it surperficial, it was launched than preceding once more electronics, also cries " electronics amplification ".Electron impact has determined magnification (gain) to the energy on dynode surface.Anode has positive electricity polarity, has the final function of collecting of free electron.
As an example of photomultiplier work,, make photon enter photomultiplier through optical filter if produced a certain amount of light in the reaction chamber.Photon bumps against on the photochromics of negative electrode and is absorbed, and produces the electronics of some then.These electronics are attracted by adjacent dynode again, because have positive potential on the dynode.Because Secondary Emission effect, the electronics of greater number can be launched out, is attracted by next dynode, and the polarity of each grade dynode all increases to some extent than the polarity of upper level, therefore when the emitting of electron stream one-level level, electron amount just increases or has amplified.
Electronics from afterbody (the tenth one-level) dynode attracted on the anode.Anode links to each other with the output plughole of photomultiplier.
Pressure correction
The measurement of native system is subjected to the influence of absolute pressure in the reaction chamber.Native system utilizes built-in computing machine and sensor to measure and proofread and correct each reading to adapt to the variation of pressure parameter.Pressure is recorded by a sensor, and this sensor is arranged near the joint the optical table outlet.
The flow control of whole gas circuit is in certain limit, the flow control of whole gas circuit is in 200cc/min (ratings) scope, and the ozone flow is controlled at 25cc/min (ratings), and stable more good more, degree of stability is less than 5%, and the flow and the pressure of gas circuit are controlled by restrictor.
The pressure transducer that is positioned at the reaction chamber gas outlet can be monitored the force value of air-flow.Vacuum transducer is installed in the joint, and it is between reaction chamber and vacuum pump.It can measure the absolute pressure in the anti-chamber, is used for the automatic pressure calibration, fault or other gas circuit problem of pump can be shown.
Pressure transducer output is connected on the other pressure transmitter circuit plate of sensor, by pressure unit output 4-20mA electric current.Transmit signals to drive plate by cable and plug.Two potentiometers are arranged on the pressure unit plate, and one is zero potentiometer, and another is to transfer the scalar potential device.Vacuum pump must be linked to each other with the output of pressure transducer during zeroing, preferably the vacuum values of Chan Shenging is 1mmHg, unless absolute demand, this value should not changed.When sensor is exposed to when outside, transfer mark work, can be arranged to force value identical with testing laboratory barometrical value.
Ozone generator (as shown in Figure 2)
Used ozone generator belongs to the gaseous emission type in the native system.Three kinds of basic elements of character are arranged, and they are internal electrodes, pyroceram shell and ozone circuit board.The silver-plated conducting film of glass shell is as the electrode of corona discharge.Gas is by the internal electrode of hollow, and space around the process is at last from terminal a discharge of narrow glass shell.When adding high pressure to internal electrode, at this moment between internal and external electrode, produce discharge, generate ozone.
NO
2-NO catalytic reaction converter
Catalyst is with NO in the air
2Change into NO.Be raised to 280 ℃ by adding the thermal control plate conversion chamber, add thermal control plate and be connected with a thermistor that is installed in the converter.
NO
2The transformation efficiency of-NO converter is analyser measuring N O
XAn important indicator of accuracy and precision.NO
2Transforming agent is housed in-NO the converter can be at high temperature with NO
2Quantitative yield is NO, and transforming agent often uses metal, carbon or both potpourris, and temperature is controlled at 200-400 ℃, and conversion ratio is generally more than 96%.
Oxides of nitrogen is one of major pollutants in the atmosphere, and NO
2Be again the principal ingredient of oxides of nitrogen, thereby the accuracy of NO2 measurement of concetration directly reflect the performance of analysis of nitrogen oxide system.
NO in the system
2-NO converter is with NO
2Quantitative yield is the reaction unit of NO, and following reaction takes place:
NO
2+M→NO+MO
M is a solid catalyst, adopts the potpourri of metal (as: molybdenum), pure carbon or metal and carbon more.Catalyzer is different not to be waited at 200～900 ℃ temperature of reaction because of selecting for use.Use metal to make catalyzer, make NO because of reacting back generation metal oxide
2Carry out slowly with the further reaction of metal, often improve by improving temperature of reaction; Use pure carbon to make catalyzer, the reaction back generates CO and CO
2Gas, and make the C surface be in fresh state always, further reaction is more easily carried out.But, use this catalyzer conversion ratio usually stable inadequately because of the difficult control of carbon treatment process.
USSR (Union of Soviet Socialist Republics) KURINNYI uses vitreous carbon to make catalyzer, and temperature of reaction is 150～600 ℃; ANON uses a kind of mixed catalyst, and transformation efficiency only is 88 ± 6%; People such as MATTHEWS use a kind of stainless steel to make catalyzer, and temperature of reaction is 920 ℃.In recent years, nitrogen-oxide analyzer, produced in USA adopts a kind of super material with carbon element to make catalyzer more, and temperature of reaction is about in the of 300 ℃, and conversion ratio is generally more than 96%.
We select a kind of special process for use, the charing that activated charcoal carries out in no oxygen medium about 1000 ℃ is handled, obtain elementary glass carbon product, through 2000 ℃～3000 ℃ pyroprocessing, prepare the higher glass charcoal of purity again, handle vitreous carbon and make carrier, this vitreous carbon purity is up to 99.99%, respectively add 0.05 ‰ metal and metal carbide therein and make active component, can reduce by 30～50 ℃ of temperature of reaction, transformation efficiency improves more than 2%.
Vitreous carbon purity can not brought impurity to catalytic reaction up to 99.99%; Acid and alkali resistance is good, and chemical property is stable; Specific surface area is big, can guarantee that gas-solid reaction carries out fully.In addition, also have hardness height, intensity big, be difficult for and advantage such as motlten metal adhesion.The use of metal and metal oxide can guarantee good reaction selectivity, NH
3Be converted into NO hardly, and temperature of reaction is low, long service life, performance are better than other like products.
The temperature of reaction chamber can be controlled automatically, is controlled to be example with reaction chamber temperature, has adopted multi-point temp sampling multi-point temp controlling schemes.In this product, because optical system and reaction chamber and be stored in the optical table, photomultiplier requires to be installed in the cold trap with the thermoelectric cooling module cooling on the one hand, and temperature is controlled at below 4 ℃, to guarantee to have lower dark current; Require reaction chamber temperature to reach 45 ℃ on the one hand, so that NO and O
3Fully reaction is to generate excited state NO
2Therefore, this product is realized not only photomultiplier cooling but also function that reaction chamber is heated by a temperature controller that is called " cooling/heating panel ".Entire circuit has comprised two closed temperature control loops (seeing Figure 11), has used width modulation temperature control principle, has very high temperature control precision; Temperature to refrigeratory and well heater detects in real time simultaneously, so that understand the ruuning situation of optical table.
Pressure sensor assembly
The pressure transducer that is positioned at the reaction chamber gas outlet can be monitored the force value of air-flow.Vacuum transducer is installed in the joint, and it is between reaction chamber and vacuum pump.It can measure the absolute pressure in the anti-chamber, is used for the automatic pressure calibration, fault or other gas circuit problem of pump can be shown.
Pressure transducer output is connected on the other pressure transmitter circuit plate of sensor, by pressure unit output 4-20mA electric current.Transmit signals to drive plate by cable and plug.Two potentiometers are arranged on the pressure unit plate, and one is zero potentiometer, and another is to transfer the scalar potential device.Vacuum pump must be linked to each other with the output of pressure transducer during zeroing, preferably the vacuum values of Chan Shenging is 1mmHg, unless absolute demand, this value should not changed.When sensor is exposed to when outside, transfer mark work, can be arranged to force value identical with testing laboratory barometrical value.
Three, electronic system
Electronic system is made up of CPU board (see figure 5), performance element and drive plate, the electronic system major function is to provide required computer system for photomultiplier work, the control data of receiving computer, and control each peripheral hardware (well heater, refrigerator in view of the above, solenoid valve etc.) work, and the required high pressure of control photomultiplier, intrasystem each road signal is nursed one's health the signal (temperature of each sensor in the acquisition system, pressure, flow etc.) send to the output of analog quantity.
Electronic system is introduced (Fig. 4)
The menu of electronic system is seen Fig. 4.Comprise the description of circuit board, the description and the function control of electronic package below.
The primary power (see figure 5)
Stabilized voltage supply can provide instrument work required various DC voltage.Comprise:
*± 15vdc gives amplifier
*+ 13.5vdc is to ozone generator and be used for the reaction chamber temperature adjusting
*± 15vdc provides and stablizes adjustable high pressure to photomultiplier
*+ 12vdc (non-adjustable) is used for the photomultiplier temperature regulation circuit, and provides power supply for computer system
*+ 5vdc is used for digital function
*+ 24vdc is used for solenoid control
CPU board (see Fig. 5, Fig. 6, Fig. 7, Fig. 8)
CPU board is based on the system of the 8 8-digit microcontroller 87C552 formation of Philips; use special monitoring chip to provide protection for it; reset circuit wherein can make system's reliable reset when powering on/off; reset under the situation that watchdog circuit makes system crash being subjected to strong the interference, thereby guarantee the system stability reliability service.System has 16 tunnel 16 A/D input channels, and 4 tunnel 14 D/A output channels, the input of 8 road digital quantities, 16 road digital quantity fan-out capabilities.
Photomultiplier tube signal prime amplifier (see figure 9)
By the photomultiplier of high-voltage power supply power supply, the light intensity of sending according to chemiluminescence in the reaction chamber is transformed into corresponding dc signal in proportion.This signal is imported into preamplification board.The signal of preposition amplification output is delivered on the amplifier on the drive plate plate, obtains a gain-adjusted before arriving computing machine at signal.At every turn, the logical zero gas automatic zero set (AZS) of analyser, this is that a kind of electricity is regulated the dark current that is used for compensating the photomultiplier generation.
Drive plate (see Figure 10, Figure 11, Figure 12)
The major function of drive plate is that the signal with CPU board carries out level conversion and drives corresponding peripheral hardware work, simultaneously the voltage signal of intrasystem each sensor is nursed one's health the A/D that then it is sent on the CPU board.
Four, computer system introduction
The computing machine here is the embedded industrial control board of 32 of an x86 system, and configuration 256M electric board and 16M RAM use LCD display and the membrane keyboard of 320x240, use graphical user interface, makes the instrumentation intuitive and convenient, supports multilingual demonstration.
The processing capacity of computing machine comprises math function and Presentation Function, as ratio calculated, diagnostic function as failure judge, control function.As calibration sequence control periodically automatically.The LCD screen shows and the menu control mode makes instrument have " user friendly " property.
The computer system of native system inside mainly comprises:
Computing machine plate built-in industrial control machine mainboard, the operating system system adopts LINUX operating system.
Drive plate comprises the mimic channel of system: D/A (digital-to-analog) conversion, A/D (analog/digital) conversion, multi-way switch and timer etc.Its function is that analog signal conversion is become digital signal and digital signal is changed into simulating signal, so that they can be finished the work under computer control.
Automatic remote On-line Control, monitoring and diagnosis.By the standard industry INTERNET network interface of system configuration, system can constitute master-slave mode multi-computer communication network with host computer easily.Host computer is realized Long-distance Control by send control frame to system, realizes remote monitoring and diagnosis by Frame and the status frames that receives from system.Adopt MODBUS industrial field bus agreement.
The software LINUX operating system, (seeing Figure 16) makes the operation of system more reliable and more stable.
Claims (11)
1. system with chemiluminescence method to execute nitrous oxides analysis, by air-channel system, optical system, electronic system and computer system is characterized in that, this system comprises:
Air-channel system, described air-channel system is by forming as the lower part: sample gas, zero gas, gas triple channel solenoid valve, permanent exsiccator, humidity indicator, ozone generator, zero source of the gas, particulate filter, restrictor, catalytic converter (NO
2→ NO), flowmeter, pressure transducer;
Optical system, described optical system is made up of reaction chamber and photomultiplier system;
Electronic system, described electronic system is by primary power, CPU board, performance element, the preposition amplifier section of photomultiplier transit signal, flow sensor part and drive plate are formed, the electronic system major function is to provide required system for photomultiplier, the control data of receiving computer, and control each peripheral hardware (well heater, refrigerator in view of the above, solenoid valve etc.) work, and the required high pressure of control photomultiplier, intrasystem each road signal is nursed one's health the signal (temperature of each sensor in the acquisition system, pressure, flow etc.) send to the output of system analog quantity;
Computer system, described computer system is by computing machine plate built-in industrial control machine mainboard, the mimic channel of system: D/A (digital-to-analog) conversion, A/D (analog/digital) conversion, composition such as multi-way switch and timer, the function of drive part is that analog signal conversion is become digital signal and digital signal is changed into simulating signal, so that they can be finished the work under computer control.
2. the system as claimed in claim 1 is characterized in that, the infiltration exsiccator that is used for filtering water vapor that described air-channel system uses uses has higher optionally macromolecule permeable membrane to hydrone.
3. the system as claimed in claim 1 is characterized in that, the NO of described air-channel system
2-NO converter, wherein the transforming agent that uses be the glass charcoal handled with a kind of special process, this technological process is handled for the charing of activated charcoal being carried out in no oxygen medium about 1000 ℃, obtain elementary glass carbon product, again through 2000 ℃～3000 ℃ pyroprocessing, prepare the higher glass charcoal of purity, this vitreous carbon purity is up to 99.99%, respectively adds 0.05 ‰ metal and metal carbide therein and makes active component.
4. the system as claimed in claim 1 is characterized in that, the pressure transducer output of described air-channel system is connected on the other pressure transmitter circuit plate of sensor, by pressure unit output 4-20mA electric current.Transmit signals to drive plate by cable and plug.Two potentiometers are arranged on the pressure unit plate, and one is zero potentiometer, and another is to transfer the scalar potential device.Vacuum pump must be linked to each other with the output of pressure transducer during zeroing, preferably the vacuum values of Chan Shenging is 1mmHg, unless absolute demand, otherwise this value should not changed, when sensor is exposed to when outside, transfer mark work, can be arranged to force value identical with testing laboratory barometrical value.
5. the system as claimed in claim 1, it is characterized in that, the pipeline of described air-channel system adopts Teflon, kynar or stainless steel material, Teflon pipe also is used for being connected of gas and zero gas and system, dirt filter cleaning of ambient air outside access to plant end device, carbon filter of eliminating end device of air after detecting.
6. the system as claimed in claim 1 is characterized in that, the ozone generator in the described air-channel system, surrounding air upstream end are installed the interior pipe of a carbon filter and infiltration exsiccator, in the infiltration exsiccator wetness is installed also.
7. the system as claimed in claim 1, it is characterized in that, the light reaction chamber body of described optical system adopts stainless steel material, inside a reaction chamber that reaches the dome-type of mirror finish is arranged, heating arrangement and temperature-detecting device are installed on body, make the reaction chamber uniform heating, and remain on by pick-up unit under 45 ℃ the duty; The very little stainless steel wireway in root hole footpath has respectively been installed at two air intake opening places that are positioned at the sphere both sides, directly with sample gas and O
3Mix before delivering to optical lens, produce chemiluminescence reaction; Sample gas and O
3Sample gas current limiting tube and O flow through respectively before by wireway
3Current limiting tube, assurance enters the sample gas and the O of reaction chamber
3Flow velocity and air pressure are constant, and each gas-phase reaction is all under equal conditions carried out; The light wave that the dome-type minute surface discharges gas reflects fully, reduces the loss of light wave, keeps the degree of accuracy of measuring; Emit the vent port of the gas of discharging in the middle of the reaction chamber rear portion.
8. the system as claimed in claim 1, it is characterized in that, the light reaction chamber of described optical system, adopted multi-point temp sampling multi-point temp controlling schemes, realized not only photomultiplier cooling but also function that reaction chamber is heated by a temperature controller that is called " cooling/heating panel ".Entire circuit has comprised two closed temperature control loops, and circuit controls has been used width modulation temperature control principle, and the temperature to refrigeratory and well heater detects in real time simultaneously.
9. the system as claimed in claim 1 is characterized in that, the optical table of described optical system adopts two cooling pieces that cryogenic temperature is provided.
10. device as claimed in claim 1, it is characterized in that, described computer system is 32 embedded industrial control boards of an x86, configuration 256M electric board and 16M RAM, use 320 * 240 LCD display and membrane keyboard, use graphical user interface, support multilingual demonstration, network using ENTERNET network, the processing capacity of computing machine comprises mathematics
Function: ratio, diagnostic function, control function, the control function of calibration periodically automatically.
11. the system as claimed in claim 1 is characterized in that, this system software operating system is selected LINUX operating system for use.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2007100112401A CN101162200A (en) | 2007-05-10 | 2007-05-10 | System using chemiluminescence method to execute nitrous oxides analysis |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2007100112401A CN101162200A (en) | 2007-05-10 | 2007-05-10 | System using chemiluminescence method to execute nitrous oxides analysis |
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| Publication Number | Publication Date |
|---|---|
| CN101162200A true CN101162200A (en) | 2008-04-16 |
Family
ID=39297157
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2007100112401A Pending CN101162200A (en) | 2007-05-10 | 2007-05-10 | System using chemiluminescence method to execute nitrous oxides analysis |
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| Country | Link |
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| CN (1) | CN101162200A (en) |
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| CN102053164B (en) * | 2009-10-28 | 2013-05-22 | 中国科学院大气物理研究所 | System and method for automatically acquiring and analyzing trace gas |
| CN103558212A (en) * | 2013-11-22 | 2014-02-05 | 山东省科学院海洋仪器仪表研究所 | Nitrogen dioxide detecting device and method |
| CN103792225A (en) * | 2012-10-29 | 2014-05-14 | 科蒂亚(新乡)生物技术有限公司 | Chemiluminescence analysis instrument |
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| CN102053164B (en) * | 2009-10-28 | 2013-05-22 | 中国科学院大气物理研究所 | System and method for automatically acquiring and analyzing trace gas |
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