CN209570499U - On-line monitoring device for formaldehyde content in ambient air - Google Patents

Abstract

The utility model discloses a kind of on-Line Monitor Device of Formaldehyde Determination, and sampling module, reaction module, detection module, solution conveyor module, control and data acquisition circuit and display screen are placed in casing；Using glass screw pipe as gaseous formaldehyde collecting trap, 98.5% is up to the arresting efficiency of formaldehyde in air, arresting efficiency is high, small in size, structure is simple, can be outside holding chamber；By the application of the online flow cell of long light path, the sensitivity and detection for improving wet-chemical and the detection of absorption spectroscopy techniques PARA FORMALDEHYDE PRILLS(91,95) are limited；Accurate, stable measurement is ensured by multistage accurately temperature control；Solution flow velocity is accurately controlled by electromagnetic drive micro pump；Wet chemistry method and absorption spectrum detection technique of the present apparatus based on gas diffusion absorption capture realize and carry out real-time online detection to surrounding air kind content of formaldehyde, can content of formaldehyde in live on-line continuous monitoring surrounding air.

Description

On-line monitoring device for formaldehyde content in ambient air

technical field

The utility model belongs to the technical field of environmental monitoring and relates to an online monitoring technology of ambient air quality, in particular to an online monitoring device for formaldehyde content in ambient air.

Background technique

Formaldehyde (HCHO) is a highly active compound. It is not only a tracer substance in the oxidation reaction of atmospheric volatile organic compounds, but also plays an important role in the photochemical reaction of free radicals and ozone. In addition to the outdoor atmosphere, formaldehyde is often detected indoors at a concentration several times that of the outdoors. The human body is exposed to high concentrations of formaldehyde for a long time, which can irritate the eyes and respiratory tract, and then cause headaches, nausea and other symptoms. In severe cases, it can induce nasopharyngeal cancer, Cancers such as leukemia. For this reason, the U.S. Environmental Protection Agency has identified formaldehyde as a potential human carcinogen since 1991, and the International Agency for Research on Cancer (IARC) has listed formaldehyde as a human carcinogen in 2004. Therefore, accurate measurements of formaldehyde in the atmosphere will not only enable better studies of tropospheric chemistry, but are also of critical importance to public health.

At present, the common monitoring techniques for formaldehyde in ambient air include spectrometry, mass spectrometry and wet chemical method. Both spectrometry and mass spectrometry have high time resolution and high accuracy of spectrometry, but their high cost, large volume, difficult maintenance and low sensitivity also limit their application in formaldehyde determination. Wet chemical methods have become common methods for the detection of gaseous formaldehyde due to their advantages of low cost, simple operation and high sensitivity, mainly including 2,4-dinitrophenylhydrazine method (DNPH) and Hantzsch method. The DNPH method is a standard method for the determination of atmospheric formaldehyde. This method has the advantages of accurate measurement results and the ability to simultaneously determine the content of multiple carbonyl compounds in the atmosphere. However, this method is usually offline detection, which is difficult to achieve online measurement, and the time resolution is low. The formaldehyde analyzer of the German Aerolaser company is an online formaldehyde detection instrument based on the Hantzsch reaction and fluorescence method. Although it has the advantages of high sensitivity, high selectivity, and faster online detection, the method and instrument still have a baseline that is prone to drift , frequent maintenance and susceptible to vibration and other deficiencies.

In the patent "A Method for Detecting the Concentration of Formaldehyde in the Air", an absorption liquid is used to extract formaldehyde in the air, and after reacting with the acetone internal standard solution, it is detected by liquid chromatography. "Formaldehyde Detector in Air" adopts test paper reflective colorimetry to provide an analytical instrument that can quickly quantify the formaldehyde content in the air on site. Although they have achieved rapid and accurate on-site measurement, they cannot achieve online continuous monitoring of formaldehyde.

The patents "Low Power Consumption Fast Formaldehyde Detecting Equipment" and "An Anti-Interference Analytical Instrument for Detecting Trace Formaldehyde in the Air" provide a formaldehyde measuring instrument using an electrochemical sensor, but the electrochemical sensor is subject to interference from other gases, and the sensor The disadvantages are limited life, inaccurate measurement and small concentration range.

Utility model content

In order to overcome the deficiencies of the prior art above, the utility model provides an online monitoring device for formaldehyde content in ambient air. Real-time online detection can continuously monitor the formaldehyde content in the ambient air on-site.

The principle of the utility model is: the utility model provides an ambient air formaldehyde online monitoring device utilizing the principle of wet gas diffusion capture and long optical path online flow cell technology, a sampling module, a reaction module, a detection module, a solution delivery module, control and The data acquisition circuit and display screen are placed in the casing; the electromagnetically driven micropump is used to precisely control the microsolution, reduce daily maintenance, and realize rapid, online and continuous measurement of low-concentration formaldehyde in the atmosphere. The utility model adopts a combination of wet chemical method and spectroscopic method to carry out online monitoring of ambient air formaldehyde, and provides a new measurement technology for online measurement of formaldehyde in the atmosphere. During the sampling process, the air passes through the spiral tube trap under the action of the vacuum diaphragm pump, and the absorption liquid also enters the spiral tube trap from the same end, and the absorption liquid forms a liquid film on the tube wall by the liquid tension. Due to the increase of the gas-liquid interface in the spiral tube trap, the gas components of the air diffuse and mass transfer between the interfaces, and fully contact with the absorption liquid for absorption. Then the gas-liquid separation is realized at the other end of the spiral tube trap. Using 2,4-pentanedione (acetylacetone) as the derivative solution of formaldehyde, the formaldehyde solution and acetylacetone undergo a derivatization reaction under high temperature conditions to generate a yellow compound (3,5-diacetyl-1,4-dihydrodi methylpyridine (DDL)), with the strongest absorption at a wavelength of 415 nm. The total reflection long optical path online flow cell is used to make the solution absorb reflected light multiple times in the total reflection flow cell, thereby improving the detection sensitivity and detection limit. The liquid-phase sample that has absorbed the component to be measured (formaldehyde) enters the total reflection long optical path online flow cell after derivatization reaction. Under the thickness of the absorbing layer, the concentration of the component to be measured is proportional to its absorbance. On-line monitoring of formaldehyde content in ambient air can be realized according to the absorbance.

The technical scheme provided by the utility model is:

An on-line monitoring device for formaldehyde content in ambient air comprises a casing, a sampling module, a reaction module, a detection module, a solution delivery module, a control and data acquisition circuit and a display screen. Among them, the sampling module, the reaction module, the detection module, the solution delivery module, the control and data acquisition circuit and the display screen are all placed in the casing, and the display screen is embedded in the casing.

The sampling module includes a sampling pipeline, a formaldehyde removal device, an electromagnetic three-way valve, a particle filter head, a spiral tube trap, a condensation device, a gas-liquid separation device, a drying tube, a gas flow meter and a vacuum diaphragm pump. The reaction module includes a mixing tee, a reaction kettle and a bubble removal device. The rear end of the spiral tube trap of the sampling module is connected to the second electromagnetically driven micropump of the solution delivery module, and then connected to the reaction kettle of the reaction module through the mixing tee of the reaction module; the detection module includes a microporous filter membrane, a full Reflective long pathlength online flow cell, light source, photodetector and thermostat. The reaction kettle is connected to the bubble removal device, and the bubble removal device is connected to the fourth electromagnetically driven micropump of the solution delivery module, and then connected to the microporous filter membrane, and then enters the total reflection long optical path online flow cell of the detection module; the solution delivery The module includes four solenoid-driven micropumps and two peristaltic pumps. The first electromagnetically driven micropump connects the absorption liquid with the sampling module, the second electromagnetically driven micropump connects the spiral tube trap with the mixing tee of the reaction module, and the third electromagnetically driven micropump connects the derivative liquid with the reaction module. The fourth electromagnetically driven micropump connects the air-removing device of the reaction module with the microporous filter membrane of the detection module. The first peristaltic pump is connected with the total reflection long optical path online flow cell in the detection module; the second peristaltic pump is connected with the rear end of the gas-liquid separation device in the sampling module.

The control and data acquisition circuit includes a main circuit board with a USB port, controls the temperature of each module and the solution delivery module through the main circuit board, and collects and outputs temperature information and detection signals of each module, and the signal data is from USB port output. The temperature, flow rate, detection signal and air formaldehyde content of each module are displayed on the display screen, and the control and data acquisition circuit is connected with the display screen. The sampling module is used to sample the formaldehyde in the ambient air, and convert the formaldehyde in the air into the liquid phase sample to be tested; The derivatization reaction with 2,4-pentanedione at high temperature generates the yellow sample DDL; the detection module is used to detect the intensity of the optical signal; the intensity of the optical signal is converted and output as voltage signal data by the control and data acquisition circuit for storage, and stored in the displayed on the display. The solution delivery module is used for precise distribution of absorbing fluid, derivative fluid and components to be measured, as well as delivering cleaning solution and discharging waste fluid.

For the online monitoring device for the formaldehyde content in the above-mentioned ambient air, further:

The casing is made of aluminum, and the whole is sprayed with polytetrafluoroethylene coating to prevent acid solution corrosion. The casing is equipped with a display screen window and an operable window, wherein micropumps, peristaltic pumps, spiral tube traps and microporous filter membranes are placed in the operable windows for daily maintenance and observation of the measurement process.

In the sampling module, the sampling pipeline adopts 1/4" PTFE hard tube, uses a vacuum diaphragm pump to extract air samples, passes them into the spiral tube trap, and uses 1/16" PTFE tubes to pass into The dilute sulfuric acid solution with pH=5 in the spiral tube trap is used as the formaldehyde absorption solution. Among them, the core component of the spiral tube trap is a glass tube with an inner diameter of 2mm, which is wound into a spiral structure with a diameter of 22mm. One end (left end) is the inlet of gas and liquid, and the other end (right end) is the gas-liquid separation chamber. Clad with rigid glass tubing for structural reinforcement and to provide intercalation to the water bath. At the same time, the water bath interlayer provides a constant temperature water bath for the trap, which is stable at 20°C. The trap constant temperature unit ensures that the components to be tested are captured at a constant temperature, avoiding fluctuations in sample capture efficiency caused by temperature changes; and the defoaming function avoids the interference of air bubbles on the detection. The condensing device includes a circulating water pump, a refrigerating sheet, a small water tank, a fan, a cooling fin and a temperature sensor, and the water pump and the water tank are connected to the external condensed water of the spiral tube trap through a silicone tube.

In the reaction module, the derivatization liquid and the solution to be tested for absorbing formaldehyde enter the reaction kettle through the mixing tee (polytetrafluoro tee) at the same time, and a derivatization reaction occurs under high temperature conditions to generate a yellow substance DDL. Since the reaction is relatively slow at room temperature, the reaction kettle is specifically made of a 90cm-long tetrafluoro tube coiled on a heat-conducting metal cylinder. The built-in heating rod and temperature sensor control the temperature of the reaction kettle at 75°C to accelerate Derivatization reaction.

In the detection module, the core of the total reflection long optical path online flow cell includes modules such as a convex lens, an optical path liquid path cut-in intersection port, a total reflection quartz capillary column, an optical path liquid path cut-out bifurcation port, and a constant temperature. After passing through the lens, the light enters the optical path and the liquid path cuts into the intersection port, so that the optical path and the liquid path are mixed; in order to reduce the dead volume and speed up the measurement response time, the flow cell adopts a fully reflective quartz capillary column, and the length can be selected between 0.5 and 1.5 meters. , Different measurement ranges can be obtained by selecting capillary columns of different lengths. When the length is 1.0 meters, the detection limit is 50pptv, and the detection range is 0-80ppbv. Finally, both the optical path and the liquid path are cut out of the bifurcated port through the optical path and the liquid path to flow out. In order to avoid the large heat generation of the light source and the obvious fluctuation of the frequency spectrum with temperature, the light source adopts a stable LED cool white light source. According to the frequency band characteristics of the LED, the selected wavelength is 415nm. The air-removing device is a miniature air-removing device made of glass. Temperature not only affects the flow rate of gases and liquids, but temperature fluctuations may also cause air bubbles in the absorbing liquid to escape, which is the main cause of data failure. In addition, changes in the refractive index of the solution caused by temperature will disturb the absorption of light. In order to ensure the stability of spectral absorption and dyeing reaction, the light source and photodetector are placed in a large-capacity aluminum incubator to maintain the temperature stability of the detection unit. A heating plate and a temperature sensor are built in the incubator to ensure the accuracy of temperature control. within ±0.1 degrees.

Four electromagnetically driven micro-pumps in the solution delivery module are used to accurately distribute absorption liquid, derivative liquid and components to be measured. Two peristaltic pumps are used to transport the cleaning solution and discharge the waste liquid respectively.

Utilizing the above-mentioned online monitoring device for formaldehyde content in ambient air to realize online monitoring of formaldehyde content in ambient air includes the following working steps:

1) Solution preparation, prepare dilute sulfuric acid solution as absorption solution: dilute 15mL concentrated sulfuric acid to 5L to prepare absorption solution, shake evenly; prepare by diluting 385g ammonium acetate, 12.5mL glacial acetic acid and 10mL acetylacetone to 5L with deionized water Make a derivative solution and store it in the dark, at low temperature, and let it stand for 12 hours. When working continuously without interruption, the use of the above solution can last for 6 days.

2) Measurement process: The measurement process includes the sampling process, reaction process and detection process of formaldehyde.

The sampling process includes obtaining zero air and ambient air samples;

The spiral tube trap is used as the gaseous pollutant trap, and the dilute sulfuric acid solution is used as the absorption liquid to convert the formaldehyde in the sampling sample into a liquid phase sample to be tested. During specific implementation, a glass spiral tube trap is used.

During the sampling process, zero air or ambient air passes through the spiral tube trap under the action of the vacuum diaphragm pump, and the absorption liquid also enters the spiral tube trap from the same end, and the absorption liquid forms a liquid film on the tube wall by the liquid tension. Due to the increase of the gas-liquid interface in the spiral tube trap, the gas components of the air diffuse and mass transfer between the interfaces, and fully contact with the absorption liquid for absorption. Then the gas-liquid separation is realized at the other end of the spiral tube trap. At the same time, the sampling temperature is stabilized at 20°C through a constant temperature water bath, which can effectively avoid the interference of outdoor temperature difference and ensure the stability of the capture efficiency during the sampling process. The capture efficiency of formaldehyde in the air reaches 98.5%.

Reaction process: using acetylacetone (2,4-pentanedione) as the derivative solution of formaldehyde, the formaldehyde solution (liquid phase sample to be tested) and acetylacetone undergo derivatization reaction under high temperature conditions to generate a yellow compound (3,5-dione Acetyl-1,4-dihydrolutidine (DDL)) has the strongest absorption at a wavelength of 415nm. The temperature can be adjusted during the reaction, and the initial setting is 75°C. High temperature accelerates the derivatization reaction, which can improve the stability and detection limit. At the same time, it is designed to avoid light to prevent the influence of light on the reaction stability.

Detection process: The total reflection long optical path online flow cell is used to make the solution reflect and absorb light multiple times in the total reflection flow cell, thereby improving the detection sensitivity and detection limit. During the sampling process, the liquid-phase sample that absorbs the component to be tested (formaldehyde) is derivatized in the reaction process to generate DDL, and enters the total reflection long optical path online flow cell, and the characteristic wavelength light generated by the light source is absorbed by the sample to be tested. DDL absorption, after which the optical signal intensity is detected by the photodetector from the outlet of the optical path of the total reflection long optical path online flow cell. The utility model adopts a single wavelength light source of 415nm. In addition, the defoaming function at the front end of the total reflection long optical path online flow cell avoids the interference of air bubbles on the optical detection at the rear end; at the same time, the temperature during the detection process is kept constant at 35°C to ensure the stability of the optical signal intensity detection; The best detection limit is 50pptv.

3) Zero calibration process: 30 minutes of zero calibration is required before step 2). When zeroing, the air first passes through the formaldehyde removal device to obtain zero air, and the optical signal intensity measured in step 2) is the optical signal intensity at the zero point.

4) Calibration process: The calibration process is required after each replacement of the solution prepared in step 1).

During the calibration process, the air first passes through the formaldehyde removal device to obtain zero gas. Then carry out step 3) to obtain the optical signal intensity of zero point; then change the absorbing liquid in step 2) into the formaldehyde standard solution of gradient concentration prepared in the laboratory, and measure the zero gas through step 2) to obtain the formaldehyde standard solution optical signal intensity .

5) formaldehyde content calculation: step 4) obtain formaldehyde standard solution optical signal intensity and zero-point optical signal intensity, now according to Lambert Beer's law, the concentration size of formaldehyde is directly proportional to absorbance, and absorbance and concentration relation are as follows:

A=Kc Formula 2

In the formula, A is the absorbance, I is the _zero -point optical signal intensity obtained in step 4), I is the optical signal intensity of the formaldehyde standard solution in the step 4), K is a coefficient, and c is the concentration of formaldehyde. According to formula 1 and formula 2, according to step 4) measured I ₀ , I, and known corresponding c (concentration of formaldehyde in the formaldehyde standard solution), the coefficient K is calculated.

Using the obtained coefficient K, the light signal intensity of an ambient air sample obtained by measuring according to step 2) can be calculated by using formula 1 and formula 2 to obtain the formaldehyde content in the sample, that is, the concentration of formaldehyde in the liquid phase.

In addition, the concentration of formaldehyde in the liquid phase needs to be converted to the concentration of formaldehyde in the gas phase, that is, the concentration of formaldehyde in the ambient air. The conversion method is as follows:

In the formula, P is the atmospheric pressure (101kPa), M _HCHO is the molar mass of formaldehyde (g/mol), R is 8.314Pa·m ³ ·mol ^-1 ·K ^-1 , T is the spiral tube trap in the sampling module The temperature (unit is K), F _l is the liquid flow rate (0.5mL/min), F _g is the gas flow rate (0.7L/min), and γ is the trapping efficiency of the spiral tube trap to air formaldehyde (the utility model is 98.5%).

Compared with the prior art, the beneficial effects of the utility model are:

The utility model provides an online monitoring device for formaldehyde content in ambient air.

Based on the wet chemical method and absorption spectrum detection technology of gas diffusion absorption and capture, real-time online detection of formaldehyde content in ambient air can be realized, and the formaldehyde content in ambient air can be continuously monitored on-site and online.

The utility model is an on-line monitoring technology of formaldehyde in ambient air combined with wet chemical method and spectroscopic method, and provides a new measurement technical means for on-line measurement of formaldehyde in the atmosphere. Compared with the prior art, the technical advantages of the utility model are mainly reflected in the following aspects:

(1) Combining chemical and optical methods, using the principle of wet gas diffusion and trapping and total reflection long optical path online flow cell technology, to achieve rapid, online and continuous measurement of low-concentration formaldehyde in the atmosphere, and the response speed is faster than chemical methods ( The response time is 3 minutes, and the data time resolution can reach the second level), the detection limit of the measurement is higher than that of the optical method, and the degree of interference is significantly lower than that of the sensor method.

(2) Using a glass spiral tube as a gaseous formaldehyde trap, the trapping efficiency for formaldehyde in the air is as high as 98.5%. It has the characteristics of high trapping efficiency, small size, simple structure, and can be placed outdoors.

(3) Through the application of long optical path online flow cell, the sensitivity and detection limit of formaldehyde detection by wet chemistry and absorption spectroscopy technology are improved by using absorption spectroscopy, which is suitable for various environments (outdoors such as urban areas and industrial areas, Indoor, etc.) online and continuous monitoring of air formaldehyde.

(4) Accurate and stable measurement is ensured through multi-level precise temperature control.

(5) The flow rate of the solution is precisely controlled by the electromagnetically driven micropump, reducing routine maintenance and data loss due to aging of the peristaltic pump.

Description of drawings

Fig. 1 is the exterior view of the ambient air formaldehyde on-line monitoring device provided by the utility model embodiment;

Fig. 2 is the structural diagram of the ambient air formaldehyde on-line monitoring device provided by the utility model embodiment;

Fig. 3 is the schematic structural diagram of the spiral tube trap in the ambient air formaldehyde on-line monitoring device provided by the embodiment of the present invention;

Fig. 4 is the schematic structural view of the reactor in the ambient air formaldehyde on-line monitoring device provided by the utility model embodiment;

In Figures 1 to 4, 1—operable window; 2—display screen; 3—formaldehyde removal device; 4—electromagnetic three-way valve; 5—particulate filter head; 6—condensing device; 7—coil trap; 8—reactor; 9—bubble removal device; 10—total reflection long optical path online flow cell; 11—light source; 12—photoelectric detector; 13—incubator; 14—gas-liquid separation device; 15—drying tube; 16 —gas flowmeter; 17—vacuum diaphragm pump; 18, 19, 20, 21—respectively the first to fourth electromagnetically driven micropumps; 22, 23—first peristaltic pump, second peristaltic pump; 24—condensate water circulation pump ;25—temperature sensor; 26—heating rod; 27—heating plate; 28—tee; 29—spiral tube; 30—water bath interlayer; 31—gas-liquid separation chamber; 32—reactor shell; 33—insulation material; 34—heat conducting metal; 35—tetrafluoro tube; 36—temperature sensor; 37—heating rod.

Detailed ways

Below in conjunction with accompanying drawing, further describe the utility model through the embodiment, but do not limit the scope of the utility model in any way.

The utility model provides an online monitoring device for formaldehyde content in ambient air. Based on the wet chemical method of gas diffusion, absorption and capture and absorption spectrum detection technology, real-time online detection of formaldehyde content in ambient air can be realized, and the environment can be continuously monitored on-site. Formaldehyde content in the air. The utility model adopts the solution of the total reflection long optical path online flow cell to reflect and absorb light multiple times in the total reflection flow cell, and the online monitoring of the formaldehyde content in the ambient air can be realized according to the absorbance, and the detection sensitivity and detection limit are improved. The utility model provides an ambient air formaldehyde online monitoring device utilizing the principle of wet gas diffusion and trapping and long optical path online flow cell technology, adopts an electromagnetically driven micropump, precisely controls the microsolution, and reduces daily maintenance.

Fig. 1 is the exterior view of the ambient air formaldehyde on-line monitoring device provided by the embodiment of the present invention; Fig. 2 shows the composition and structure of the device. Use this device to monitor the formaldehyde content in the ambient air online. The specific implementation is as follows: dilute 15mL of concentrated sulfuric acid to 5L to prepare an absorption solution, and shake it evenly; Make up to 5L to prepare a derivative solution and store it in the dark, at low temperature, and let it stand for 12 hours.

When sampling, the electromagnetic three-way valve 4 is switched to the sampling mode, and the sample gas directly passes through the particulate matter filter head 5 to remove particulate matter, and under the action of the vacuum diaphragm pump 17, passes through the spiral tube trap 7 (shown in FIG. The structure of the helical tube trap), while the absorption liquid enters the helical tube under the simultaneous action of the first electromagnetically driven micropump 18 and the air flow and forms a liquid film on the tube wall, and the formaldehyde component is absorbed and transferred to the liquid phase. The trapping temperature was controlled at 20 °C by a constant temperature water bath. Before the gas flow passes through the gas flow meter 16 and the gas pump 17, it needs to pass through the gas-liquid separation device 14 and the drying pipe 15 to remove the moisture in the gas, so as to prevent the damage of the flow meter and the gas pump due to accumulation of liquid, and the waste liquid is discharged through the second peristaltic pump 23. In the liquid phase, the sample to be tested and the derivative liquid are respectively passed through the small PTFE tee under the control of the second electromagnetically driven micropump 19 and the third electromagnetically driven micropump 20 and mixed. After mixing, the sample to be tested enters the reaction kettle 8 for dyeing Reaction (Figure 4 shows the structure of the reactor in this embodiment), the reaction temperature is constant at 75°C. Before entering the detection module, the sample to be tested passes through the micro-bubble removal device 9 to avoid the influence of bubbles on the measurement. After removing air bubbles, the fourth electromagnetically driven micropump 21 pushes the sample to be tested into the total reflection long optical path online flow cell 10, and under the specific light source 11 of 415 nm, the photodetector 12 detects the optical signal intensity of the sample to be tested. The temperature of the detection module was kept constant at 35°C.

When marking zero, the electromagnetic three-way valve 4 cuts into the channel 3 of the formaldehyde removal device to obtain zero gas. The zero air passes through the particulate matter filter head 3 to remove particulate matter, and under the action of the vacuum diaphragm pump 17, passes through the helical tube trap 7, while the absorption liquid enters into the helical tube under the simultaneous action of the first electromagnetically driven micropump 18 and air flow. air flow through

The gas-liquid separation device 14 , the drying pipe 15 , the gas flow meter 16 and the gas pump 17 are then discharged, and the waste liquid is discharged through the second peristaltic pump 23 . The absorption liquid and the derivative liquid are mixed under the control of the second electromagnetically driven micropump 19 and the third electromagnetically driven micropump 20 respectively, and then enter the reaction vessel 8 . After passing through the micro-bubble removal device 9, it enters the detection module for zero point calibration. In the liquid phase calibration, similarly, the electromagnetic three-way valve 4 is cut into the channel 3 of the formaldehyde removal device to obtain zero gas, and a series of formaldehyde solutions with gradient concentrations are set, and enter the spiral under the simultaneous action of the first electromagnetically driven micropump 18 and the air flow. tube. The formaldehyde solution and the derivative solution enter the reaction module and the detection module sequentially through the same control and reaction steps, and finally the light absorption signal is detected. During zeroing and calibration, all controls of the reaction module, detection module and solution delivery module are the same as those during sampling.

During cleaning, the air pump 17 and the first to fourth electromagnetically driven micropumps 18 to 21 stop working, the first peristaltic pump 22 is turned on, and a potassium hydroxide solution with a mass concentration of 1 mol/L is prepared as a cleaning solution. Under the action, it enters the long optical path detection pool to clean the pipeline in the detection pool.

It should be noted that the purpose of the disclosed embodiments is to help further understand the utility model, but those skilled in the art can understand that: without departing from the spirit and scope of the utility model and the appended claims, various replacements and modifications are possible. It is possible. Therefore, the utility model should not be limited to the content disclosed in the embodiments, and the protection scope of the utility model is subject to the scope defined in the claims.

Claims (9)

1. a kind of on-Line Monitor Device of Formaldehyde Determination, including casing, sampling module, reaction module, detection mould Block, solution conveyor module, control and data acquisition circuit and display screen；Wherein, sampling module, reaction module, detection module, Solution conveyor module, control and data acquisition circuit and display screen are placed in casing, and display screen is embedded on casing；

The sampling module include sample lines, except formaldehyde plant, three-way solenoid valve, particulate matter filtering head, helix tube collecting trap, Condensing unit, gas-liquid separation device, drying tube, gas flowmeter and vacuum diaphragm pump；The helix tube collecting trap uses glass Pipe coiling thread-like structure, one end are the entrances of gas and liquid, and the other end is gas-liquid separation chamber；It is whole to use horminess glass tube Cladding with enhancing structure and provides water-bath interlayer；Water-bath interlayer provides water bath with thermostatic control for collecting trap；

The reaction module includes mixing tee, reaction kettle and air bubble eliminating device；

The detection module includes micropore filtering film, the online flow cell of total reflection long light path, light source, photodetector and constant temperature Case；

The solution conveyor module includes four electromagnetic drive micro pumps and two peristaltic pumps；

The control and data acquisition circuit include the main circuit board equipped with USB port, by main circuit board to the temperature of each module Degree is controlled, is controlled solution conveyor module, and acquires and export each module temperature information and detection signal, signal number It is exported according to from USB port；

Second electromagnetic drive micro pump of the rear end connection solution conveyor module of the helix tube collecting trap of sampling module, then by anti- The reaction kettle of the mixing tee and reaction module of answering module connects；Reaction kettle is connected to air bubble eliminating device, air bubble eliminating device with it is molten 4th electromagnetic drive micro pump of liquid conveyor module connects, then accesses micropore filtering film, enters the total reflection of detection module later The online flow cell of long light path；Absorbing liquid is connected by the first electromagnetic drive micro pump with sampling module, the second electromagnetic drive micro pump Helix tube collecting trap is connected with the mixing tee of reaction module, third electromagnetic drive micro pump is by derivative liquid and reaction module Mixing tee is connected, and the 4th electromagnetic drive micro pump is by the micropore filtering film phase of the air bubble eliminating device of reaction module and detection module Even；First peristaltic pump is connected with the online flow cell of total reflection long light path in detection module；In second peristaltic pump and sampling module Gas-liquid separation device rear end be connected；The control is connected with data acquisition circuit with display screen；

Sampling module converts liquid phase sample to be tested for the formaldehyde in air for sampling to the formaldehyde in surrounding air；

Reaction module for being dyed to liquid phase sample to be tested, make the liquid phase sample to be tested containing formaldehyde under constant high temperature with 2,4- pentanedione occurs derivative reaction and generates yellow sample to be tested DDL；

Solution conveyor module conveys cleaning solution and discharge waste liquid for accurately dispensing absorbing liquid, derivative liquid and component to be measured Detection module is for detecting light signal strength；

Light signal strength is stored by control with data acquisition circuit conversion output for voltage signal data, and in display screen Upper display.

2. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the casing uses aluminium Prepared material carries out spray process using polytetrafluoro coating, to prevent acid solution corrosion.

3. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the casing sets display Shield window and can action pane；It is described to place micro pump, peristaltic pump, helix tube collecting trap and micro porous filtration in action pane Film, so as to the observation of daily maintenance and measurement process.

4. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the sampling module In, the sample lines use 1/4 " tetrafluoro hard tube；Air sample is extracted using vacuum diaphragm pump, is passed through helix tube collecting trap In；The dilution heat of sulfuric acid of helix tube collecting trap pH=5 is passed through as formaldehyde absorbent using 1/16 " four fluorine tube.

5. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the sampling module In, helix tube collecting trap uses the glass tube of internal diameter 2mm, turns to the thread-like structure that diameter is 22mm；Condensing unit includes Water circulating pump, cooling piece, small-sized water tank, fan, cooling fin and temperature sensor, and pass through silicone tube for water pump, water tank and spiral shell Coil collecting trap external condensation water phase connects.

6. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the reaction module In, derivative liquid and the solution to be measured for absorbing formaldehyde pass through mixing tee simultaneously and enter in reaction kettle, and the reaction kettle specifically uses Length is that the four fluorine tube of 90cm is coiled on heat-conducting metal cylindrical body and is made, and built-in heating rod and temperature sensor are by reaction kettle Temperature is controlled in 75 DEG C to accelerate derivative reaction.

7. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the air bubble eliminating device For miniature air bubble eliminating device, using glass material.

8. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the detection module In, the total reflection online flow cell of long light path include convex lens, the incision of optical path fluid path cross port, be totally reflected quartzy capillary column, light Road fluid path cuts out bifurcated port and thermostat module；Light enters optical path fluid path after lens and cuts the port that crosses, and makes optical path and liquid Road mixing；Flow cell is using the quartzy capillary column of total reflection；Optical path and fluid path cut out the outflow of bifurcated port through optical path fluid path；It is described Light source uses the stabilization LED cool white light source of 415nm single wavelength.

9. the on-Line Monitor Device of Formaldehyde Determination as described in claim 1, characterized in that the detection module In, light source and photodetector are placed in large capacity aluminum insulating box to keep the temperature stability of detection unit.