If there is feed water to the boiler, there must be sewage. Boiler blowdown means that in order to control the water quality of boiler boiler water to meet the required standards and keep impurities in the boiler water within a certain limit, it is necessary to continuously exclude the boiler water containing salt and a large amount of alkali and the deposited slag and sewage Mud, loose sediment. The amount of boiler blowdown is directly related to the quality of the feed water. The greater the alkalinity and salt content of the feed water, the more sewage the boiler needs. Everyone can have such a recognition: for every 1% increase in the pollution rate of industrial boilers, the fuel consumption will increase by 0.3%. In this way, fuel is wasted and the energy consumption and comprehensive management level of the boiler cannot be correctly evaluated.
1. Calculation of sewage discharge rate:
Boiler discharge index is expressed by the blowdown rate, which is the percentage of waste water discharge (Q pollution) to the boiler evaporation (Q steam). It is expressed as follows: K = Q pollution / Q steam × 100%
When the water quality of the boiler is stable, it can be known from the balance of the amount of material that the amount of a certain substance brought into the furnace with the feedwater is equal to the sum of the amount of sewage discharged and the amount of saturated steam. Then (Q fouling + Q steam) × S feed = Q steam × S steam + Q pollution × S pollution
In the formula, S feed, S steam, and S pollution respectively represent the content of a substance in feed water, saturated steam, and sewage. The S value in the formula can be based on the salt content, or according to a component (such as alkalinity, chlorine, etc.). Ion) content. Then K = Q pollution / Q steam = (S to -S steam) / (S to -S steam) × 100%
2. Pay attention to the following three points when calculating the sewage discharge rate:
(1) The calculation of the sewage discharge rate can be based on the alkalinity or chloride ion (chlorine ion has a relatively fixed proportional relationship with the salt content, and usually the chloride ion is used instead of the salt content) to calculate the sewage discharge rate. Finally, the larger value is taken as the Sewage discharge rate. Generally, the sewage discharge rate of heating boilers should be controlled below 10%.
(2) For industrial steam boilers with large capacity, the steam humidity is very low due to the good effect of the steam-water separation device. In this way, the salt content in the saturated steam is much lower than the salt content in the feed water, so the salt content in the steam can be ignored in the calculation of the blowdown rate of this type of boiler, that is, K = S to / (S pollution-S Give) × 100%
(3) For most industrial steam boilers, especially those with a small drum volume, simple steam-water separation device, and saturated steam with a large amount of water, the steam humidity is usually around 3%, (and the sewage discharge rate is controlled at 5% ~ The comparison of the 10% range is not too low.) Under this condition, the salt content of steam cannot be ignored when calculating the boiler blowdown rate. Because K = (S to -S steam) / (S to -S to) = CL-to / (CL-to-CL-to)-CL-to / (CL-to-CL-to)
Here CL-steam / CL-fouling is steam humidity, CL-fouling = CL-boiler water, that is, the chloride ion content in the sewage is equal to the chloride ion content in the boiler water, where CL-feed, CL-fouling, CL-steam, CL -Boiler water indicates the content of chloride ions in feed water, sewage, saturated steam, and boiler water. It can be seen that if the salt content in the steam is ignored, the calculated blowdown rate will be too large (the difference is greater than the steam humidity).
The above is what I have shared for you about the calculation of the industrial steam boiler blowdown rate. I hope it will be helpful to everyone.
