The calculation value of the pressure change along the flue indicates the main technical parameters of the boiler. Model boiler pressure (MPa) Rated evaporation (tPh) Outlet steam temperature Induced draft fan, blower Main technical parameters Model number of revolutions (rPmin) Full pressure (Pa) flow (m3Ph) The actual measurement of the motor power flue system we use the standard Pitot and U-shaped differential pressure gauge for the boiler.
Flue measurement data measurement part static pressure (Pa) take three average values ​​Q dynamic pressure (Pa) take three average $Q cross-sectional area F (m2) flow rate (mPs) V = 2g $ QQ flow (m3Ph) Qy = 3600VF conversion For the standard state of flow (m3Ph) boiler body outlet hood economizer -1079 can not be measured - before the inlet horizontal flue draft fan inlet front horizontal flue -20692750.7825.27072845647 fan outlet horizontal flue +157520 The fan impeller is too close and the airflow is turbulent and cannot be used for data calculation. The furnace -6 is actually measured by the flue system read by the control room meter. The fan is not turned on during the measurement, and only the induced draft fan is opened. Data for each measurement point.
The induced draft fan mismatch is calculated from the measured data. The operating point of the induced draft fan is 2225Pa at full pressure and 70725m3Ph at flow rate. It is confirmed that the full pressure of the fan cannot meet the design requirements. According to the design requirements of the boiler plant, the total pressure of the induced draft fan should reach 2637Pa. The air leakage in the flue is greatly known. The air leakage rate from the outlet of the boiler body to the inlet of the water film precipitator is 1.7%, and the air leakage rate from the inlet of the water film deduster to the inlet of the induced draft fan is 14.6%. This is because dust removal. The flue gas value behind the device is large, and it is easy to leak into the air, resulting in a large increase in air leakage.
The air volume at the outlet of the boiler body measured by excessive excess air coefficient greatly exceeds the amount of air of the boiler under rated conditions, that is, the excess air ratio is too large. Too much excess air ratio will lower the furnace temperature and affect the combustion effect. At the same time, the increase of excess air also increases the load of the induced draft fan, which is unfavorable for the energy-saving operation of the boiler. When the negative pressure value of the furnace is small, the negative pressure of the furnace is only 6 Pa. When the blower is working, the furnace is positive. The area of ​​the slag outlet and the observation hole is too large, the sealing of the coal supply port is not strict, and the air chamber and the furnace body are leaking, which may cause this situation.
It is recommended to combine the selection of the induced draft fan with the enhanced flue seal. If it is necessary to increase the negative pressure value on the existing flue gas flow system, only the fan with larger total pressure and flow rate can be used to make the working point reach C. Point as shown. Thus, although the negative pressure value of the furnace can be increased, the excess air is further increased, the air leakage amount is larger, the furnace thermal efficiency is lowered, and the fan energy consumption is increased, which is obviously undesirable. The correct improvement method should be to strengthen the flue seal, and then use the induced draft fan with full pressure and low flow rate to make the working point reach D point, as shown.
The air duct system should be matched to operate. The air should be minimized from the unrelated parts (doors, holes, furnace walls, etc.) into the furnace, and the negative pressure value of the furnace should be increased to facilitate the use of the blower to control the combustion. The blower can be changed to frequency conversion regulation, which is conducive to energy-saving operation.
Through the aerodynamic analysis and testing of SZL10-1.25 boiler smoke and air duct system, we believe that the reasonable matching of boiler induced draft fan is the key to energy-saving operation of boiler. When selecting the induced draft fan, it is necessary not only to meet the requirements of the air volume, but also to pay attention to the requirements of the full pressure. After the induced draft fan is put into operation, the pressure distribution of the flue system should be measured, so that it can be economically operated.
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