No cause can be found for the surging in a 40-ton negative-pressure coal-fired heating boiler; there is a video
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The last edit to this post was made by wn4800 on 2015-11-20 at 15:28. It’s a 40-ton coal-fired heating boiler that burns normally; when the furnace door is opened, it can be seen that smoke is expelled and then drawn back in in a very regular pattern, just like a person breathing. After checking the exhaust fan, the flue ducts, the steam-water separator, the interior of the wet flue gas desulfurization tower as well as the flue ducts before and after it, and the interior of the ceramic multi-tube dust collector along with the flue ducts before and after that, no signs of smoke leakage or air leaks were found inside the boiler. The blowers and exhaust fan operate normally, without any vibrations or abnormal noises. When the boiler breathes, the water surface inside the wet flue gas desulfurization tower ripples； I can’t find the cause of the problem now, and I have no idea what to do. Videos of boiler surging, videos of the furnace door surging. These are videos I uploaded to Youku showing this phenomenon in boilers.
I’ll take care of it myself; please give me some advice, experts
Due to the lack of oxygen in the smoke, opening the furnace door to allow air in will result in localized combustion.
.....Is this surging phenomenon in the boiler caused by a lack of oxygen? Yes, this can also lead to a reducing atmosphere forming around the furnace walls due to poor mixing inside the furnace. Therefore, this phenomenon occurs when the furnace door is opened to allow firing.
If fan surge is ruled out, the possible reasons are: 1. Changes in resistance during the operation of the wet flue gas desulfurization tower, with values varying from high to low. 2. The pressure fluctuations that occur during fuel combustion are mainly due to unstable combustion; for example, the control of coal feeding and air supply is inadequate. The adjustment of coal feeding and air supply should be uniform and continuous, without any significant changes. Therefore, in the case of a layer-fired furnace, it is necessary to check the grate as well as the air chambers below it ； In the case of fluidized bed boilers or bubbling boilers, check for coking, whether the air distribution plate nozzles are blocked, and whether there is ash accumulation in the air chambers ； Finally, check the coal feeder and the coal hopper to determine whether the coal supply is smooth, and to ensure that the coal supply can be adjusted in a uniform, stable, and precise manner during operation.
Hypoxia may be the main cause; a sudden deflagration leads to positive-pressure ejection, or unstable negative pressure causes it；
I can now blow air but cannot apply any load; once a load is applied, positive pressure is generated. It seems that either the exhaust airflow is insufficient or there is some blockage somewhere... Is the boiler’s power output at 100% currently? If the power is not sufficient, it means that the original draft fan is too small. Then it needs to be solved at the root level.
Under normal conditions, the exhaust air flow is around 85% and the blast air flow is around 65%, with the boiler’s power reaching around 95%. Currently, the exhaust air flow is still at 85% but the blast air flow is only 40%, yet the boiler’s power still reaches 90%; this phenomenon occurs because the blast air flow cannot be increased.
Based on what you’ve described, it should be a combustion mixture issue. Measure the components of the flue gas; it seems that there is a significant loss due to incomplete chemical combustion. The solution is to add a perturbing secondary air flow.
This post was last edited by gjn1970 on 2015-11-27 at 14:52. There is suspicion of air leaks in the exhaust ducts at the rear, including those before and after the dust collector as well as the exhaust duct at the inlet of the induced draft fan. Could it be that the water seal used to control the overflow from the wet dust collector is not functioning properly, allowing air to leak in from time to time and causing fluctuations in the system’s negative pressure?
Personally, I think it would be useful to add pressure gauges and devices for monitoring the oxygen content in the exhaust gas, in order to ensure that the air flow rate in the system is appropriate and stable. Of course, multiple pressure gauges should be installed, with measurements taken of the negative pressure both before and after each device