Slide 1

Oxygen Analyzer

ZirconiaOxygen analyzer

Concentration cell system

A solid electrolyte like zirconia exhibits conductivity of oxygen ions at high temperature. As shown in the figure below, when porous platinum electrodes are attached to both sides of the zirconia element to be heated up and gases of different partial oxygen concentrations are brought into contact with the respective surfaces of the zirconia, the device acts as an oxygen concentration cell. This phenomenon causes an electromotive force to be generated between both electrodes according to Nernsts equation

The principle of the zirconia oxygen analyzer is as follows:

Zirconia is one of the few compounds that actually become conductive at high temperatures & more conductive as its temperature increases

Zirconia starts out with a very high resistance at room temperature greater then one trillion ohms / cm , Having less then 1000 ohms / cm resistance at 1000 degrees Celsius & become a very good conductor

Heating the element allows different partial oxygen concentrations of the gasses to come into contact with the opposite side of the zirconias creating an oxygen concentration cell.

These ions travel through the zirconias element to the other electrode. At that point, the Nernst expression applied to calculate the force by measuring the electromotive force generated between the two electrodes.

Reference gas on one side and sample gas on the other sideOxygen ions move from the side with the highest concentration of oxygen to that with the lowest concentration. The movement of ions generates an EMF (Electro Motive Force) which can be measured to determine the oxygen content.

the EMF varies depending on the temperature of the zirconia sensor and the oxygen concentration of the reference gas (PR), in the actual device.

the zirconia sensor is placed in a constant temperature oven

air is generally used as the reference gasLimitationsFlammable gases cannot be usedSensor degradation occurs if corrosive gas (fluorine-based gases, chlorine-based gases, sulfate-based gases)is measured

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System ConfigurationThis system is for monitoring and controlling oxygen concentration in the combustion gases of a large-size boiler or heating furnace. Clean (dry) air (21% O2) is used as the reference gas and the span gas for calibration. Zero gas is fed in from a cylinder during calibration.

System ConfigurationThis example, represents typical applications in large boilers and heatingfurnaces, where there is a need to monitor and control oxygen concentration. Thereference gas and calibration-time span gas are (clean, dry) instrument air. Zero gas is supplied from a gas cylinderSystem uses auto calibration unit, with auto-switching of the calibration gas.

Calibration

The converter is calibrated in such a way that the actual zero and span gases are measured and those measured values are used to agree with the oxygen concentrations in the respective gases.There are three types of calibration procedures available:

(1) Manual calibration conducting zero and span calibrations, or either of these calibrations in turn.(2) Semi-automatic calibration which uses the touchpanel or a contact input signal and conducts calibration operations based on a preset calibration time and stable time.(3) Automatic calibration conducted at preset intervals.

Calibration Setting ProceduresSelect Points (calibration procedure) in the Calibration setup display to display the Span Zero, Span, Zero selection display. In this display, select Span Zero.

Calibration Gas Concentration Setting

(1) Zero-gas concentration

If zero-gas concentration is selected, the Numeric-data Entry display then appears.Use this display to enter an oxygen concentration value for the zero-gas calibration; if the oxygen concentration is 0.98 vol%O2, enter 00098.

(2) Span-gas concentration

With Span gas conc selected in the Calibration setup display, display the Numeric-data Entry display and enter an oxygen concentration value for the span-gas calibration; If instrument air is used, enter 02100 for a 21 vol% O2 value.

Manual Calibration

Preliminary

Before performing manual calibration, Setting Unit zero-gas flow valve is fully closed. Open the zero-gas cylinder pressure regulator so that the secondary pressure equals measured gas plus approx. 50 kPa (or measured gas pressure plus approx. 150 kPa when a chack valve is used, maximum pressure rating is 300 kPa)..

Thermox Ametek WDG-IV

The same main principle for YokoJawa oxygen Analyzer using Zirconium Oxide material

Thermox Ametek WDG-IV

Sensor operation:

A sample is drawn from the process stream by means of an air-operated aspirator and is immediately returned to the process. A portion of this gas rises past the oxygen measuring cell.

Assemble sensors parts

400-AT-001

Thermox Series 2000 WDG-IV

Manual Calibrate/Manual VerifyTo perform a manual calibration or verification, follow these steps:1. Enter the calibration gas values to match the span and zero calibration gases you intend to use to calibrate or verify your system2. Select Initiate Cal or Initiate Verify from the Calibrate key menu, depending on whether you want to perform a calibration or verification.3. Select Manual Calibrate or Manual Verify. You are then prompted to apply the 02 span gas to the calibration gas inlet port on the sensor (tubing must be free of oil and dirt):

4. Press the Enter key once you have applied this calibration gas. The span display then appears (display line 2 will only appear if you have the combustibles option; display line 3 will only appear if you have the combined combustibles and methane option):

5. Press the Enter key once the 02 reading on the far left of the first display line stabilizes. The reading on the far right of the first display line shows the setpoint value you entered using the Cal Gas Values menu option. This setpoint value should match the cal gas cylinder for the 02 span gas.If your 0, reading on the far left of the display has stabilized, yet is not near the setpoint value on the right of the display, you should check the cal gas value you entered and ensure that this value matches the cal gas cylinder for the gas you applied to the cal gas inlet port of the sensor.You are then prompted to apply the 02 zero gas to the calibration inlet port of the sensor:

6. Press the Enter key once you have applied this cal gas. The zero gas display then appears (display line 2 will only appear if you have the combustibles option; display line 3 will only appear if you have the combined combustibles and methane option):7. Press the Enter key once the zero gas reading(s) on the left of the display have stabilized. If you don't have the combustibles option, you only need to wait until the 02 zero gas value stabilizes. The reading on the far right of the first display line shows the setpoint value you entered for the 02 zero gas using the Cal Gas Values menu option. This 02 zero gas setpoint value should match the cal gas cylinder for the 02 zero gas.

Error MessagesCell is Over TempThis error message indicates that the senSor temperature is 30 'C or moreover its correct operating temperature. The software shuts off the furnaceuntil the temperature returns to a normal operating range.If this message soon goes away, it indicates that the temperature has returnedto an acceptable range. If there is a problem with the sensor temperaturecontrol system, you will see another error message after this messageappears.Excessive Cal ErrorIf a primary calibration cannot correct the sensor temperature within thesoftware's allowable limits, this message is displayed to indicate the primarycalibration has failed. This message could indicate one of the followingproblems: Calibration gas setup problem Process pressure incorrectly entered Failed cell Leak or plug in plumbing

Span Gas Range ErrorThis error message occurs if the calibration span gas does not read within the software's allowable limits. Once this error occurs, calibration of the system is aborted.This message could indicate one of the following problems: Calibration gas setup problem Process pressure incorrectly enteredAspirator air not turned off during calibration (WDG-IV only)Failed cellCell wiring reversed (Cell + and Cell - wires)Leak in plumbingPlugged plumbingZero Gas Range ErrorThis error message occurs if the calibration zero gas does not read withinthe software's allowable limits. Once this error occurs, calibration of thesystem is aborted. This error indicates one of the following problems:Calibration gas setup problemProcess pressure incorrectly entered.Cell wiring reversed (Cell + and Cell- wires)Aspirator air not turned off during calibration (WDG-IV only)Failed cell (primary calibration should be run at this time)Leak or plug in plumbing

Temp Rise FailureThis error message indicates that the sensor has failed to increase in temperaturea minimum of 10 C in a 60-second time frame during start-up. Once the system reaches the operating set point, this message will only occur if the sensor falls below the set point by 15C and fails to recover within 60 seconds. The problems that can cause this error are as follows:AC line power problem at the sensorOpen furnaceOver-temperature protection circuit trip on the sensor boardSensor board failureLoss of furnace drive signalInterconnecting wiring problemThermocouple FailureThis error message occurs when the indicated sensor temperature falls below -70C. This error message can be the result of one of the following: Open thermocouple Faulty interconnecting wiringControl unit display module failure

T/C (Thermocouple) Circuit FailureThis message appears when the control unit recognizes a sudden drop intemperature (greater than 100C). The thermocouple circuit failure messagecan be the result of one of the following problems:Shorted thermocoupleFaulty interconnecting wiringControl unit display module failureSensor board failure

ParamagneticOxygen analyzer

Paramagnetic Analyzer

High magnetic susceptibility of oxygen as compared to other gases allows it to be attracted to a magnetic field

Magnetic susceptibility is a measure of the intensity of the magnetization of a substance when it is placed in a magnetic field

In Simple word Oxygen is attracted to a magnetic field several hundred times stronger than any other gas

Lets see the video

Paramagnetic Analyzer

In the cell, two glass spheres filled with nitrogen gas are suspended with strong metal. At first, the spheres are kept in balance in an magnetic field. When oxygen molecules having a large magnetic susceptibility flow there, the molecules are pulled toward the stronger magnetic field zone and the spheres are moved away from the zone.The resulting deviation of the spheres is detected with the light source, reflecting mirror and light receiving element, and a current is flowed through the feedback loop to control so that the spheres can return to the initial balanced state.

The current flowing through the feedback loop is proportional to oxygen concentration.

Thus, oxygen concentration is converted into an electric signal.

Tunable Diodel Laser measurement systemTunable Diode Laser (or TDL) measurements are based on absorption spectroscopy. Analyzer is a TDL system and operates by measuring the amount of laser light that is absorbed (lost) as it travels through the gas being measured.

In the simplest form a TDL analyzer consists of a laser that produces infrared light, optical lenses to focus the laser light through the gas to be measured and then on to a detector, the detector, and electronics that control the laser and translate the detector signal into a signal representing the gas concentration.

Gas molecules absorb light at specific colors, called absorption lines. This absorption follows Beers law.TDL Analyzers are effectively infrared analyzers which obey the Beer-Lambert Law.

I = I0e-E.G.Lwhere I is the radiation intensity after absorptionI0 is the initial radiation intensityE is the extinction coefficientG is the gas concentration and L is the path length of the measurement area

Advantages: Capability of measuring at very high temperature, high pressures and under difficult conditions (corrosive, aggressive, high particulate service). Most measurements are rapid (5 seconds) and interference free.

Disadvantages: Initial installation for the mounting flange is required.

Thank you for your attentionPresented by:Eng. Mohamed SarhanWaiting Your feedback