Saying goodbye to the "foggy" weather, the importance of measuring oxygen in coal-fired boilers in gas-fired boilers
In the winter of 2012, the most common vocabulary appeared on the land of China was “fog and hazeâ€. The direct cause of this hazy weather is the emission of large amounts of fumes from northern coal-fired heating boilers. Since coal-fired heating boilers have old air leakage phenomena and no subsequent dust removal equipment, a large amount of sulfur-containing dust particles are discharged into the atmosphere along with the flue gas, causing environmental pollution and damaging the human respiratory system. Due to the cold weather in the north, a large amount of acidic dust cannot diffuse into the upper air, so they gather together in the low pressure layer to form a cloudy haze of air.
With the application of various new technologies, a large number of old coal-fired heating boilers are being transformed into gas-fired gas-fired boilers. As gas-fired boilers are dominated by automatic control, the control of oxygen content in combustion is more stringent, and the level of oxygen directly affects the amount of gas used. Therefore, for heating companies, the control of aerobic content is direct and economic. Benefit related. However, due to the incorrect selection of the oxygen sensor installation position during the transformation process, the measured oxygen amount will fluctuate and the probe lifetime will be very short. The amount of oxygen measured by the coal-fired boiler is the amount of excess oxygen after combustion of the coal, so the probe can be installed on the flue gas flue. Gas boilers have different components of flue gas due to different combustion methods. If the probe is installed on a flue in the traditional way, the actual oxygen content after combustion cannot be measured correctly. Reason The composition of natural gas is methane (CH4), the combustion process:
2CH4 (Ignition) +4O2 (Combustion) → CO (Referred to Combustion) + CO2+4H2O+O2 (Faintly Free Molecule)
Cause Analysis:
1) Since methane produces a large amount of moisture after combustion, it is filled with water vapor in the flue, which causes condensation in the non-heating section of the probe. The dew will flow along the probe protection tube to the head. Because the probe oxygen measurement site is heated to about 800 °C, when the water droplets into the high-temperature head, it will form an instant vacuum in the head, when the water evaporates, then return to normal measurement. This is the phenomenon of fluctuations in the amount of oxygen seen on the scene. The following figure shows the internal condensation of the probe installed in the flue position.
Dew is in the red circle.
Then use an experimental picture to illustrate:
The oxygen content in the air.
When the probe is inserted into the water
The oxygen amount changes dramatically.
The oxygen level dropped sharply.
2) As the probe repeats the process of evaporation and drying of moisture, the oxygen meter will continue to see fluctuations in the amount of oxygen up and down. At the same time, CO2+4H2O+O2 (weakly free molecules) is present in the flue gas pipeline. At this time when the flue gas temperature is around 100°C, the flue is full of water vapor. A part of the oxygen is dissolved in water, so the oxygen measured at this time will be very weak. The oxygen content is about O2% (10-5~10-8). Therefore, it is a wrong choice to install the zirconia probe on the low-temperature flue in this case. This will not only fail to achieve the purpose of oxygen measurement, but also damage the oxygen probe.
For example, in a bathhouse filled with water mist, people may feel that breathing is very difficult. This is because the dissolved oxygen in the air can not reach 20.6% oxygen content and only 16% to 18% oxygen content. So people will feel difficulty in breathing.
Solution and installation location:
1) For the measurement of residual oxygen in a heating furnace using natural gas as fuel, the oxygen probe should be installed in the furnace or the gas outlet of the furnace gas. Because the temperature is high at that time, the water vapor is a state of gasification, and the residual oxygen involved in the combustion is involved. It is at the critical point of dissociation. At this time, the residual oxygen content can be measured to achieve the purpose of oxygen measurement, instead of being installed in the flue of the low-temperature steam state.
2) For the selection of water vapor residual oxygen measuring instruments, the Australian NOVATECH 1635 Moisture Oxygen Analyzer should be used. The purpose is to be able to measure two parameters, one can measure the water content in the flue gas, and one can measure the residual oxygen in the water vapor.
3) With the country's strict control over coal-fired boilers and the increase in the monitoring of flue gas emissions, a large number of coal-fired boilers need to be converted into gas-fired boilers, so more and more attention will be paid to oxygen measurement and monitoring. The zirconia oxygen measuring probe installation cannot be understood and used in the traditional concept, and the oxygen measurement link must be applied with a high-tech method.
Chengdu Lihao Technology Co., Ltd. has transformed many old coal-fired heating boilers into gas-fired gas-fired boilers to provide moisture-resistant, high-precision, easy-to-maintain, long-life zirconia oxygen analyzer solutions. In use, it fully meets increasingly stringent emission requirements and is well received by users.
We hope to do our part to make the city's sky bid farewell to the “fog and hazeâ€.
*. PTC heating,overheat protection, work quiet.
*. Large hot air outlet, instant get warm and hot.
*. One key and Two gear heating air optional.
*. Novel and beautiful design, easy to operate.
*. Work quietly and safe, natural warm breeze.
*. Voltage: 110V/220V; Noise<50db.
*. No radiation. high effective bring warm air.
*. Overheating protection , anti falling design.
*. Power off if falling down, very safe.
*. ABS &PP Fire-proof material, Durable 300℃
*. Good for desk in office/home/study
*. Warm up around air quickly and warm hands
Fan Heater,Handy Heater,Portable Heater,Wall Fan Heater
Shenzhen Ewong Technology CO.LTD , https://www.dgewongtech.com