KR20010102600A - Development og UV-Absosrption Type In-Line Ozone Concentration Measuring Eguiment - Google Patents

Abstract

The present invention is an In-Line type ozone concentration measuring device, UV light source and detection unit ultra-short amplification circuit, Analog-Digital converter, Processor and Digital circuit, power supply circuit and temperature control circuit and UV absorbing cell according to the ozone measurement range of 10ppm or more UV absorption net type In-Line ozone concentration measuring device that can apply length 0.1-10.0cm selectively.

Description

Development og UV-Absosrption Type In-Line Ozone Concentration Measuring Eguiment

The present invention is a UV absorption type ozone concentration measuring device which can measure the ozone concentration generated in the ozone generator and the high concentration ozone usage put into industrial wastewater treatment, domestic wastewater treatment, and high water treatment process in real time. In-Line Ozone Concentration Measurement Device with Amalog-digital Transducer, Prosessor and Digital Circuit, Power Supply Circuit and Temperature Control Circuit, and having the structure to selectively apply the cell length of UV absorber according to ozone measurement purpose will be.

Recently, ozone has been applied to various industrial wastewater treatment, domestic wastewater treatment, and high-purity water treatment in Korea. In order to measure the high concentration of ozone concentration generated when wastewater treatment equipment using ozone is introduced, It is recognized that the development of UV absorption type In-Ling ozone measuring device is essential.

However, up to now, the total amount of domestic ozone measuring instruments depend on imports, which is causing difficulties in the development of ozone processing technology.

Therefore, the present invention has developed a measuring instrument that can measure the concentration of ozone generated in a high concentration ozone in real time in the field, and localize such equipment, such as livestock wastewater treatment, landfill leachate treatment, dyeing wastewater treatment, plating wastewater treatment, freshwater lake It is expected to be applied to the treatment of incoming pollutants, and by supplying the optimum amount of ozone to the appropriate place, it can reduce the operating cost of companies caused by excessive operation of the ozone generator, and by developing ozone measuring equipment with international competitiveness It contributes to industrial development.

1 is a standard system of UV absorption ozone concentration meter

2 is a multi-reflective UV absorbance meter

3 is Spectal response (R1228)

4 is a Sensor Premp lifier cricuit

5 is A / D Conveter

6 is a processor block diagram

7 Power & Temp Control Criuit

8 is a processor circuit

9 is a preamp circuit

10 is a Program Flow Chart

end. Optical Properties of Ozone (OPTICAL PROPERT IES)

Ozone's optical properties play an important role in industrial applications and in natural phenomena.

Ozone has to be treated as the most essential characteristic of the limitation of space.

The refractive index K of gaseous ozone at vacuum of 273 K in absolute temperature is n = 1.0533, 1.020 and 1.0502 at wavelengths of 480,546 and 671 nm, respectively, and n = 1.2236 at wavelengths of 535,589 (line D) and 670.5 nm in liquid state, respectively. , 1.2226 and 1.2213.

Ozone in the GAS state absorbs light such as infrared rays and ultraviolet radiation. Band absorption begins at a wavelength of 14.2 µm and remains up to 220 nm.

Absorption is particularly strong in the ultraviolet region and peaks around 260 nm as stated.

This represents a minimum approaching 200 nm. However, absorption increases slightly until it reaches the detection limit of 120 nm (see Table 1-1 below).

Table 1-1 (absorption coefficient of ozone between 100 and 220 nm)

The total amount of ozone contained in the ozone layer in the global atmosphere is about 3 mm thick under standard temperature and pressure conditions. This layer absorbs all of the ultraviolet radiation emitted by the sun, especially in the width of 200 nm-290 nm, and also absorbs the infrared radiation of the Earth's surface in the wavelength range of 9-10 µm. This has a major effect on the absorption of ultraviolet radiation at higher temperatures above 40-60 km above the Earth's surface in the equator.

Absorption in the infrared region can be obtained by Lambert-Beer law.

I = I ₀ e ^-kcl

For air ozone, the coefficients K are 3.0, 3.0 and 0.2 at wavelengths of 4.75, 9.65 and 14.1 μm, respectively, where the index C represents the number of molecules to absorb and l represents the path length per cm. The absorption coefficient is mainly dependent on the pressure, especially at wavelengths near 9.6 µm (see table below).

Table 1-2 (absorption coefficient of ozone in various wavelength regions)

Absorption Spectrum is typically divided into three categories. Hartley band at 200-300nm wavelength, Huggins band at 300-350nm wavelength and Chappuis band at 400-750nm wavelength (see Figure 1-2).

Table (1) contains the measurement results of the absorption coefficients for the three sectors. The absorption coefficient for the numerical values shown in the table is calculated by applying the following formula.

I = I ₀ e ^-kℓ

Ozone's visual spectrum shows an absorption band at 600 nm, which is blue in all three band states above, and purple-blue shades at sunset and in the crystallization of dawn.

The maximum absorption of the three sectors in the ultraviolet region is at wavelengths of 255.3, 313.5 and 343.9.

Table (1) [Aboerption coefficient (k) of ozone]

(Continued Table 1)

(Continued Table 1)

I. Measurement of ozone by direct photometer

(DRIECT PHOTOMETR IC DETERM INAT ION OF OZONE)

Iodine (I ₂₎ titration assay and direct photometric measurement is an important method in the analysis of ozone, iodine titration assay is easy way to eliminate the absolute calibration (Calibration).

Direct photometer measurement is the only measurement method based on ozone molecules in which ozone remains intact. That is, no chemicals or reactions are used in the determination of ozone.

Recently, so-called absolute photometry has been recognized as an independent process for measuring ozone as well as methods for analyzing standard ozone sources.

Prior to the introduction of this measurement method, the absorption coefficient of ozone must be determined accurately.

The measurements carried out by Demore for this purpose hint at the possibility that the pressure is independent of the absorption coefficient within the range of p.p.m.

The principle of measurement is based on the absorption band of ozone in the ultraviolet region.

Appropriate wavelengths are obtained by installing, as a light source, partial optical filters, monochromarors, and radiated light emitted from the finished spectrophotometer.

The measurement is performed by most instruments near the ozone maximum absorption at 255.3 nm.

If this is in a good environment, the exact match of the mercury's spectral line at 253.7 nm yields a stronger absorption band.

Since the absorption coefficient is directly proportional to the ozone concentration of the gas, Beer's law applies.

Beer-Lambert's law can be applied to reduction in light stress.

log I ₀ / I _c = kcℓ

I ₀ is the contrast of the original light, C is the concentration of ozone in the gas, ℓ is the path length of the light turning around the gas, and K is the absorption coefficient.

If the passage length is constant, absorption is directly proportional to the ozone concentration.

log I ₀ / I _c

If we consider the carrier, algebraic relations apply.

I ₀ / I _c

The instruments described above were developed to measure ozone concentrations in the range of 0.5-20%.

For example, ozonated oxygen flows down the ozone generator before reaction. Thus, the value of C is relatively large, and the passage length l must be small to achieve the optimum absorption range.

It should be recognized that a gas-shaped light absorptive meter is preferred to use the indicated d by calculating pure ozone at standard conditions or by making kc 1 indicating the thickness of the ozone layer reduced in cm. For that reason α is given in cm ^-1 for the absorption spectra.

In devices developed by Alway And Slomp, the current deviations generated by the measurement and associated phototubes are amplified and transmitted to a two-phase servomoter, in order to reduce this deviation in the resistors in the circuit of the relevant phototube. To slide it.

The circulation of the motor can be directly recognized by the instrument dial as ozone concentration or percent depending on the measurement method used. To facilitate the amplification, the output current of the phototube has the characteristic of alternating current, which is obtained by feeding the photoelectric tube as a voltage on both sides of the cross or by installing a circulating sector in the direction of light.

Setting of zero point (100% transmission) is effected by sample which ozone is removed.

The great advantage of this optical measurement method is that the judgment procedure does not interfere with the process.

One particular area of direct photometric judgment is the measurement of atmospheric ozone.

Other methods used here face low concentrations and therefore require longer optical path lengths by multiple arrangements of magnitude.

Long-path spectrophotometers at the Earth's surface are used to measure the absorption of general light within the ultraviolet range under two selective wavelengths.

Renzetti's instrument made this measurement possible, for example 265 and 313 nm, and considered the minimum ozone concentration at night as the end point. The ozone concentration can be calculated from the data obtained from the following formula: 2p.p.h.m.

In the formula, C represents the actual ozone concentration in pphm. C ₀ represents the minimum ozone concentration at night. I ₀ ¹ and I ₀ ² represent the intensity of light reaching the detector at the minimum concentration of ² p.phm at wavelengths of 265 and 313 nm. I1 and I2 represent the intensity of light reaching the detector during measurement at wavelengths of 256 and 313 nm. S represents the optical path length in km. α ₁ denotes the absorption coefficient at 265nm, 0.123km ^-1, pphm ^-1. α ₂ denotes the absorption coefficient at 313nm, 0.00087km ^-1, pphm ^-1.

In other setups, the difference between the incident light and the decayed light across the path length of approximately 100 m in atmospheric air is measured at 265, 280 and 313 nm, respectively.

Razumovskii has developed a laboratory spectrophotometer with an elongated type cuvette.

The instrument has an optical path length of 100 mm and a sensitivity of 10 ^-6 mol dm ^-3 .

Other systems have a sensitivity of 2x10 ^-7 mol dm ^-3 .

In another photometer, the air sample passes through one of the cells and the associated gas passes through the rest of the cell. In this case, the reference gas can be obtained after removing ozone from the gas sample through catalytic decomposition.

The concentration of ozone can be calculated by the difference in the intensity of the emitted light at 253.7 nm passing through two cells. Concentrations can be measured by this method in the range of 0 to 100 pphm (0 to 2 mg m ^-3 ).

Solar radiation is used as a source of light to measure atmospheric ozone concentrations and to investigate the vertical distribution of ozone concentrations, and absorption is measured at selected wavelengths through a predetermined path length within known methods. .

In recent years, measurements have been made by automatic photometers equipped with narrow-band filters on satellites or exploration rockets that send signals to ground stations.

Krueger has published a survey report that includes measuring the intensity of solar radiation at four selected wavelengths between 270nm and 330nm during vertical fall with a photometer mounted on a parachute descending probe. The measurement results are used to calculate ozone concentrations at different heights.

The absorption spectrum characteristic of ozone produced a clear detection result of the Earth's atmosphere by spectroscopy of the radiation emitted from the sun and stars.

U.V photometers can also be used to measure ozone in the atmosphere by absorbing light within the infrared range.

All. Calibration of Ozone and Other Methods of Measuring Ozone Concentration

(Calibration and areas in which different analytical method are used)

Although we have seen several methods used to determine ozone concentrations, with the exception of a few methods, calibration is required, or a calibration gas (O ₃ standard gas) capable of reproducing specifications containing ozone in particular.

This is particularly true for commercial equipment, and widely used equipment includes a standard ozone source.

These continuous sources of ozone are in photochemical ozone generators that operate from a variety of ultraviolet light sources and the operating parameters of the device are precisely controlled.

Naturally, these devices are considered to be one of the absolute methods, such as lodometry or absolute photometry.

Recently, the problem of standardization of ozone has emerged in the field of measurement of air ozone.

The selection of appropriate analytical methods and instruments depends on the specific case requirements and the concentration range to be measured. The measurement ranges of the main methods are listed in Table 1-3. Direct photometers and lodometry are commonly used, but lodometry is only considered one of the measurement methods. In addition, the Thermal Method is an easy way to measure the concentration of ozone in the gas range in%. But it is limited to oxygen and air.

For the measurement of atmospheric ozone concentrations, instruments are widely used chemiluminescence, and electro-measuring methods are on the decline.

For aqueous media, various color reaction methods besides redox reaction, direct electrometry and photometry will be used.

Table 1-3 (Typical measuring ranges associated with the individual groups of analytical method)

la. Measurement principle of ozone

Methods for measuring the ozone concentration include a chemiluminescence method, potassium iodide method, ultraviolet absorption method, etc. In the present invention, the device was developed using an ultraviolet absorption method that is easy to measure automatically and high accuracy. The ultraviolet absorption method can measure the concentration of a gas having a characteristic of being absorbed in the ultraviolet region by detecting absorbed energy in its own ultraviolet spectrum, and usually 254 nm of mercury or the like is used as a light source. The zero gas containing ozone and the sample gas containing ozone are alternately passed in the cell through which the gas to be measured passes, and the intensity of light passing through this is measured by a sensor with a built-in UV filter. The concentration can be measured. This law is expressed as

That is, it is defined as the ratio between the amount of ultraviolet rays detected by zero gas and the amount of ultraviolet rays absorbed by the sample gas, and it is defined at standard temperature and air pressure of 273.15。k, 1 atm, and must be converted according to the actual measurement environment and the desired unit. Substituting factor K

c = KC, C = Substituting in the above equation Are organized by

The equation for concentration c is as follows.

k can be composed of two terms: the concentration conversion term K _STP and the correction term CF _TP for temperature and pressure under standard conditions. In other words, K = (K _STP ) (CF _TP ) where K _STP is a constant that converts the measured value in the unit you want and has different values depending on conversion values such as ppm by volume, ppm by weight, percent, g / m ^3, etc. For example, it is 1000000 for ppm by volume and 2141.4 for g / m ³ .

The temperature and pressure conversion term CF _TP can be expressed as

Therefore, the concentration conversion term and temperature pressure conversion term

You can see that the expression is completed. Finally, the equation for calculating the gas concentration using the ratio of zero gas and sample gas detected by the UV sensor can be derived as follows.

hemp. Ozone Meter System

1) Configuration of the device

The most effective method for continuously measuring ozone concentration is a light source, a photometer, and a quartz procell. The ozone concentration can be measured by configuring a measurement system. The construction of the device is generally shown in FIG. 1, a low pressure mercury lamp as a light source, and a photomul as a photometer.

When using low concentrations of ozone, double-beam spectrophotometers are ideal in terms of measurement accuracy and stability whenever possible.

2) Measurement procedure

By supplying the sample gas continuously to the quartz procells, a potential signal proportional to the ozone concentration can be obtained.

3) Precautions

(1) Since a limit is placed on the ozone concentration measurable by the spectrophotometer, it corresponds to the optical path length (the length of the quartz cell). A typical spectrophotometer has a maximum absorbance of 2 (Log [Io / i]) and a luminous intensity of about 0.001. Therefore, the relationship between ozone concentration and calorific cell length that can be measured at 253.7 nm is shown in Table 3-1. However, when the high-pressure mercury lamp is used as a light source, the measurement is performed by using light having a plurality of wavelengths, which is slightly different from the table.

In addition, one method is to use the cell of the multiple light path of FIG. 2 for low concentration ozone measurement.

(2) If the amount of light emitted from the light source is too strong, the decomposition of ozone by light cannot be ignored and measurement error occurs.

(3) When measuring the gaseous ozone concentration, if the sample gas temperature or pressure is different, the density (= ozone concentration) of the gas will fluctuate and give an error.

(4) In the measurement of liquid ozone concentration, in many cases, accurate absorbance cannot be obtained due to light absorption by soluble organics or light scattering by suspensions. As a countermeasure, the dissolved ozone may be aerated and transferred to the air, or the dissolved ozone may be completely decomposed into a catalyst and corrected by passing the sample water through the reference cell.

Ozone Concentration and Cell Length

Cell length (cm) Application concentration range (ppm) 0.1 1,500-150,000 1.0 150-15,000 10.0 15 to 1,500 100.0 1.5 to 150

4) UV light source and detector

Cell length of ozone concentration meter developed through this permanent is divided into 1) 1,000 2) 10,000 3) 20,000 4) 60,000 5) 60,000 ppm and above.The standard type of cell length 50mm is obtained according to the measured ozone concentration. Including five types of sample passage lengths, the low-pressure mercury lamp with a wavelength of 253.65nm and the UV filter with 254nm were suppressed and the quartz window was finally installed on the surface in contact with the sample gas.

In order to stabilize the output of low pressure mercury, the circuit was designed to maintain 55 ℃ by installing semiconductor temperature sensor and heater in UV Lamp Housing.

Photomultiplier Tube R1228 was installed at the end facing the UV lamp, and the built-in filter and characteristic collinearity were configured to have maximum sensitivity around 254nm.

Since the concentration value of the sample is affected by the temperature, a semiconductor sensor is installed in the sample exhaust of the fin for temperature measurement. 3 shows the response characteristics of the detection sensor.

5) Shortest amplification circuit

The output of the R1228, a UV sensor, needs to be amplified to a sufficient size because the current is output in proportion to the intensity of the light while DC bias is applied and has a very weak output. In addition, in order to amplify weak signal by increasing S / N, selection of ultra short amplification element is very important. In this development, amplification circuit is composed using OPA128 OP Amp, BURR-BROWN's electrometer element.

The force impedance was set to 500k to match the sensor and the gain was adjusted to a maximum output of 4V. In order to cut off the noise from the peripheral circuit, a shield was installed and a connector for output signal and power supply was installed. The output of the first stage amplifier is connected to the input of Multiplex for A / D conversion. The circuit is shown in FIG.

6) Analog-Digital Conversion

The detection signal amplified to the sufficient size through the ultra short amplifier must be A / D converted for digital processing. In this development, ICL7109 converter which has excellent noise characteristics and low speed conversion is used due to the characteristics of this device.

The converter is a signed 12-bit converter with Dual Slop Intergration, which can be connected to an 8-bit bus and has a very stable conversion capability.

The conversion speed is about 30ms and the status pin indicating the conversion completion status is monitored through the processor. When the conversion is completed, data is extracted into 2 bytes of MSB and LSB.

In order to receive the detection signal, the temperature conversion signal, and the pressure value of the ultra-short amplifier, the conversion circuit is equipped with multiplex at the front end and is designed to receive and convert each input signal sequentially by the signal of the processor. The circuit designed in FIG. 5 is shown.

7) Processor and Digital Circuit

The 1Chip Processor used in the development of this instrument is Intel's 8051, a versatile and affordable processor. It uses external expansion memory, has ROM 32k and RAM 8k, and connects 8255 to expand peripheral I / O. The clock is driven at 11.0592MHZ and uses the Max1232 Reset device to detect its own PSEN line and automatically return on processor down.

This processor has 256 bytes of internal memory, so it can be executed efficiently at high speed. It also has the function to control each I / O terminal individually, so it is easy to control peripheral devices. There is a decoder to control each I / O, RAM 0000: Address, 8255 is 2000: Address, LCD is 4000: Address, A / D is 6000: Address, and D / A is 8000: Address.

LCD is used to display the results of various programs and has a display area of 40 × 2 Line. The display state indicates the measured concentration after the initialization state, and the unit representation allows the display of ppm and g / m ³ to be switched.

In order to switch between zero gas input and sample gas input, the solenoid valve control signal is generated and the internal timer function is used to obtain a certain period.

A function to calibrate with span gas is included, and the measured value is calculated and processed later. There is also a calibration function for zero gas values.

4-20mA current output is designed as a function to output the detected ozone concentration value to an external device. Data processed by the processor is displayed on the LCD and input to the Digital-Analog Converter in 8 bits. The converted analog signal is waveform-formed through LPF, and is input to the current drive circuit composed of OP Amp, and the current value is output. 6 shows a Processor circuit.

8) Power Circuit and Temperature Control

This instrument designed the power of ± 5V / 1A for driving digital circuit, ± 15V / 1A for analog circuit driving, and 12V / 5A for driving solenoid, pump and temperature control heater. A filter is installed to remove various noises and a fan is installed to prevent temperature rise inside the meter.

In order to keep the UV lamp housing temperature at 55 ℃, it uses a device with a reference voltage of 200mV inside and compares it with the output of the LM34 temperature device to form an integrating circuit to maintain a very stable temperature control.

Therefore, the present invention can solve the treatment technology depending on the import to date, and can supply the measuring instrument which can estimate the concentration of ozone generated in the high concentration ozone generator in real time in the field, and localize such equipment, It is possible to be applied to landfill leachate treatment, dyeing wastewater treatment, plating wastewater treatment, pollutant treatment flowing into freshwater lake, etc. There is an advantage that can benefit the development of a competitive and competitive measuring equipment.

Claims (6)

In-line ozone concentration measuring device has UV light source and detector ultra short amplification circuit, analog-digital converter, processor and digital circuit, power supply circuit and temperature control circuit. The cell length of UV absorber is 0.1 UV absorption network type In-Line ozone concentration measuring device that can apply -10.0cm selectively. The UV light source and the detection unit according to claim 1, a UV lamp having a maximum wavelength of 250-260 nm, a UV filter of 254 nm, a absorption sensor having a 200-300 UV absorption sensitivity and a maximum absorption sensitivity of 254 nm, and quartz on the surface in contact with the sample. UV absorption type in-line type ozone concentration measuring apparatus of claim 1, characterized in that it has a structure provided with a window. The UV absorption type in-line ozone concentration measuring apparatus according to claim 1, wherein the amplifying circuit is composed of an Eketrometer element of BURR-BROWN and an OPA128 OPAMP. In claim 1, the analog-to-digital converter is a UV absorption type in-line ozone concentration measuring apparatus of claim 1, characterized in that the ICL 7109 converter having excellent noise characteristics and capable of low-speed conversion. In claim 1, the processor and the digital circuit is UV absorption type in-line type ozone concentration measuring apparatus of the item 1, characterized in that the configuration of the conversion unit can be converted to the concentration unit ppm and g / cm ³ . The power supply circuit and temperature control circuit in the above paragraph are 5V / 1A power supply for driving digital circuits, ± 15V / 1A power supply for driving AnaLoge circuits, and 12V / 5A power supply for driving solenoids, pumps, and temperature heaters. UV absorption type In-Line ozone concentration measuring device, which has a power supply circuit with a supply structure and a specialized circuit for maintaining the housing temperature of UV lamp at 55 ℃.