Seeking advice on boiler water issues
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I would like some advice regarding boiler water issues. In our factory’s boilers, there are problems with alkalinity and phosphate levels; the phosphate level must be between 14 and 15 for the alkalinity to be above 0.5. If it is below 14, the alkalinity does not meet the required standards. Basically, it’s very difficult to control – either the alkalinity is too low or the phosphate level is too high. Please help by sharing your experience!
It depends on whether the boiler in question is a low-pressure boiler or a medium-pressure boiler, as mentioned by the poster. Generally speaking, medium-pressure boilers have specific requirements regarding the pH value of their make-up water, which should be between 8.8 and 9.2. Additionally, for the treatment of water in medium-pressure boilers, trisodium phosphate is used to keep its concentration within the range of 5–15 mg/l. If these two conditions are met, then the pH value, phosphate level, and alkalinity of the boiler water will all be within the standard ranges. However, it is also possible that the deoxygenation effect of the deaerator is insufficient, and since the desalinated make-up water contains carbon dioxide which enters the drum water, this carbon dioxide reacts with the boiler water to form carbonates, resulting in a low pH value in the boiler water or even an acidic condition.
Is the author referring to medium-pressure boilers? Generally, in medium-pressure boilers, phosphates are not controlled at such high levels. In our boilers, the phosphate level is kept between 2–10 Mg/L, with a pH of 9.2–9.8; the pH of the feed water is maintained between 9.0–9.6. If the situation you described occurs, I think it’s likely that the make-up water isn’t treated properly, and water with higher hardness is being used. Therefore, the phosphate level needs to be between 14–15 in order to achieve an alkalinity of over 0.5. If the boiler is large and produces a lot of steam, it’s necessary to invest in a desalination system to ensure the long-term stable operation of the boiler
We keep it at 5-20mg/l
We have 35 T/H medium-pressure boilers, with the concentration controlled at 5-20 mg/l
What potion did the OP add? If it’s Na3PO4, then the alkalinity will certainly increase, as it is itself a salt of a strong base and a weak acid! You can consider using NaH2PO4; there will be no problem! !
It is also necessary to consider factors such as conductivity, silicate content, and oxygen content. The requirements for boiler water vary depending on the pressure level of the boiler; generally, chemicals can be added before the water enters the boiler to prevent rust and scale formation