Are there any standards for the dust content in the flue gas at the boiler outlet?
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:) Hello everyone. Our factory originally used a 20T chain grate boiler that had been in use for over a decade. This year, the boiler was upgraded to a 25T circulating fluidized bed boiler. During operation, it was observed that there was very little ash; in comparison, last year we upgraded another boiler and found a large amount of ash at the ash discharge outlet of the dust collector. My question is: 1. Is there any specific ratio for the dust content in the flue gas at the boiler outlet (before it reaches the dust collector)? 2. What causes this, and how can it be resolved? ! Looking forward to an early reply from my comrades! ! Thank you
Approximately 3. GB13223-1996 Standards for Emissions of Air Pollutants from Thermal Power Plants (applicable to coal-fired boilers and thermal power plant boilers with a capacity of 65 t/h or more). 4. GB13271-2001 Standards for Emissions of Air Pollutants from Boilers (applicable to boilers other than coal-fired power generation boilers and boilers with a capacity of more than 65 t/h)
The general technical specifications for industrial boilers specify exact requirements for the initial dust emission concentration of boilers using various combustion methods.
Refer to GB13271-2001 \"Emission Standards for Air Pollutants from Boilers\"
The reason for the large fly ash volume may be: 1. Excessive draft air flow； 2. The cyclone separator does not perform well in capturing fly ash. ……I am also thinking about other reasons.
Our factory has also just replaced the 10T chain furnace with a 15T circulating fluidized bed, but the return material system is almost useless. The boiler has insufficient output, produces a lot of fly ash, and has low thermal efficiency, which is really frustrating for us.
The “circulation” in a circulating fluidized bed refers to the unburned fuel returning to the furnace after being separated by the gas-solid separator to continue burning and thereby improve the burnout rate; therefore, the performance of the gas-solid separator has a direct impact on the efficiency of the circulating fluidized bed. I think the problems mentioned by LZ and LS are all related to issues in the design of the gas-solid separator. It’s possible to check the fly ash and calculate the burnout rate, or increase the size of the fuel particles fed into the furnace to see if that improves the situation. If that doesn’t work, then it will be necessary to redesign it.
1 When the fuel is coal with low moisture, weak caking tendency, and a high proportion of fines, fly ash loss increases, especially when ventilation is increased to boost combustion intensity. 2 The combustion method in the boiling furnace also has a significant impact on fly ash loss. 3 The height of the furnace also has an impact. If the furnace is small, the flow path of the flue gases within it and their residence time are too short; the fuel does not have enough time to burn completely before being carried away, which increases fly ash loss. (I guess the original poster’s modifications weren’t successful; the recycling rate wasn’t controlled properly.)