The larger the air volume of the boiler, the more the flue gas volume, the greater the flue gas velocity, and the higher the flue gas temperature. Fan air volume is the air volume generated by machinery, the air flow is determined by the machine, while flue gas volume is related to combustion, which is generated by fuel combustion. There is a certain relationship between the velocity of the air supply and the velocity of the flue gas, but the relationship is not very fixed, so it is not advisable to judge the velocity of the flue gas in the flue duct by the air supply volume.
The velocity of flue gas in the flue duct should be as large as possible in the design, so as to reduce the flue size. If the velocity is too small, if the flue gas contains dust, it will settle and pile up on the pipe wall, and the larger pipe diameter will also greatly increase the cost. However, the flue gas has a certain range of velocity requirements (15-18m/s), too large velocity cannot be selected, which will intensify the vibration of air duct, decline the heat exchange effect. If the velocity is high, the energy loss will be large, the pressure drop will be large, and the energy consumption of fan will be much more.
In general, the flue gas is high-temperature and dusty. If the flow rate is too fast, the flue gas and water-cooled flue will not get good heat exchange, and the dust will not settle down well, which will cause great harm to the subsequent process. In addition, the flow velocity of the original flue gas is slower than that of the net flue gas. The design flow velocity of the original flue gas is less than 15m/s, generally between 13-15m/s;
To sum up, it is necessary to measure the velocity of flue gas in the flue duct continuously. The velocity cannot be too large or too small. Then it will need to install a high temperature resistant flue gas flow velocity transmitter, also known as the air flow transmitter, or the air volume sensor. According to the measurement principle of pitot tube gas flow rate, the positive end of pitot tube is facing the air flow direction and the negative end is back-facing the air flow direction; the microprocessor continuously collects the dynamic pressure, static pressure and temperature sensor signals and automatically calculates the dynamic pressure, static pressure and temperature values, and then automatically calculates the boiler, furnace and various exhaust pipes according to the input values of parameters such as atmospheric pressure, humidity, pipeline cross-sectional area, etc Gas flow rate, actual flow rate and standard flow rate.
By installing a high temperature resistant flue gas air flow velocity sensor, the flow rate of flue gas can be monitored in real time, so that the process can run under the optimal condition. At the same time, GE-374 series flue gas flow sensor can customize 1 or 2 of upper and lower limit alarm signals. When the speed of flue gas is too low or too high, it will send out alarm switch signals, and timely inform relevant personnel to check and adjust the equipment.
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