Regarding the control of pH value in the denitrification system
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The pH value of our company’s denitrification system fluctuates greatly, often ranging between 4 and 9. I wonder how everyone’s systems are performing, and what control methods are being used
Generally, there are two reasons for this situation: 1. The flow rate and pH of the brine obtained through electrolysis are unstable； 2. The acid addition flow rate is unstable; there are problems with the flow meter and the metering pump. If it is winter and the temperatures are extremely low, check again to see if the pipes might freeze.
The question is a bit vague – is it related to denitration or the effluent water?
1. If the pH value of the brackish water produced by electrolysis fluctuates too much, the denitration system simply cannot handle it! You can only drive after the brackish water has stabilized! 2. Set it to manual mode when operating! Don’t automate it for now!
Acid should be added to the denitration feed water to remove free chlorine, and alkali should be added before the effluent is discharged to keep the pH at an alkaline level. If the pH of the incoming water fluctuates greatly, the cause should be sought at the outlet of the dechlorination tower – could it be that the addition of alkali at that outlet is unstable, or that the addition of sodium sulfite is unstable?
The pH value of our company’s denitration system also fluctuates significantly, often ranging between 4 and 9. These fluctuations can be reduced by adjusting the PID parameters (increasing the integration time due to the large lag), and after the fluctuations subside, manual adjustments are made before switching to automatic mode
We keep our pH level between 4 and 6
We keep the pH level between 6 and 8. The current applied during electrolysis has a significant impact on denitration; large fluctuations in pH require manual adjustment before switching to automatic mode
Electrodechlorination stabilization is a prerequisite. The delay between the denitration acid addition point and the analysis point should ideally be within 10 seconds; a longer delay results in poor performance even when the PID settings are adjusted.
1. The alkaline addition to the brackish water produced by electrolysis needs to be stable； 2. The denitrifying hydrochloric acid must be added evenly to the mixture, and the sampling points for testing should be selected appropriately ； 3. The concentration of the acid solution should be appropriate ； (Generally 10-12%) 4. Control in two stages: the first stage is controlled at 9.5-9.8, while the second stage ensures stability ；
It is estimated that the main cause of the fluctuations mentioned by the poster is the large variations in the alkalinity level of the brackish water; therefore, analysis of this brackish water is necessary.