How to improve the efficiency of coal-fired boilers to achieve economic operation?

In the adjustment of boiler operation, on the basis of ensuring safe operation, economic operation must also be achieved to improve boiler efficiency. In general boiler units, the efficiency can basically reach more than 92%, and the total loss is less than 8%. The loss is: exhaust heat loss, generally 5-6%, followed by mechanical incomplete combustion heat loss is less than 1-1.5 %, heat loss and ash slag physical heat loss are about 1%. (Physical heat loss for high ash coal ash residue will be greater).

From the point of view of quantification of indicators, the key to improving boiler efficiency is to reduce smoke loss and heat loss due to incomplete combustion of machinery. Pay attention to the flue gas temperature changes. Excessive flue gas temperature will affect the efficiency of the boiler. Too low temperature may cause low-temperature corrosion of the air preheater. Therefore, it is necessary to strengthen the adjustment according to the load changes during operation. When the coal quality changes a lot and the fuel volume increases significantly, adjust the total air volume and the primary and secondary air temperature in time to be higher than the temperature under the design coal.

(1) Control the total air volume of the boiler

The use of boiler air volume not only affects the efficiency of the boiler, but also the excessive air volume will increase the unit consumption of the blower and induced draft fan, increase the power consumption rate of the plant, and affect the increase of coal consumption in power supply. To maintain the proper air volume, the oxygen value can be observed, which is generally about 3-4%. For different coal types, when the carbon content of fly ash does not increase, low-oxygen combustion can be considered to achieve the purpose of reducing smoke loss. But according to the slagging characteristics of the coal burned by the boiler, pay attention to keep the temperature of the flue gas at the boiler outlet lower than the softening temperature of the ash to reduce the degree of slagging. For the coals that are easy to slag, the oxygen content can be appropriately kept higher. Avoid reducing atmosphere and reduce slagging.

(2) Reduce the exhaust temperature

1. Control the boiler flame center position, and adjust the flame center to move down when the superheated steam temperature and the reheated steam temperature are not low, by adjusting the air distribution of the burners in the upper, middle and lower layers.
2. It is necessary to increase the temperature of the air entering the preheater as much as possible, generally not less than 20 ℃ (in the winter heater), in order to facilitate enhanced combustion. Especially in the low-load stage, there is often a situation where the boiler oxygen content is too high, which is not only unfavorable to combustion, but also increases the unit consumption of the fan.
3. Boiler soot blower is running normally, blowing in time to ensure clean heating surface.
4. To prevent the air preheater from clogging, it can be judged from the pressure difference between the inlet and the outlet. When the pressure difference increases, it may be clogged and need to be blown up in time.