Adding salt and acid to adjust pH, issues with the interlock system of the pH meter
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Salt and acid dosing is used to adjust the pH; what about interlocks related to the pH meter? Can a interlock be set up for the pH value? Should it be linked to the salt and acid dosing pumps, or to the valve at the pump outlet?
Interlocking is definitely possible: it can be applied to both pumps and valves; however, the most common approach is to use the pH value to control the opening degree of the valves； If it is a variable-frequency pump, the pump frequency can be controlled using the pH value ； Of course, other interconnections can also be set up: for example, the valve can be switched on or off, or the pump can be started or stopped when PH reaches a certain value – it depends on the choices made in your process design ；
Reliance on pH detection for interlocking. Personally, I feel there is a lag issue. Because from the perspective of chemical reactions, there is a process of neutralization and dissolution. From an instrumentation perspective: pH is not very reliable, as the coating on the surface of the electrode sensing element tends to get dirty, which results in lag. Well, if both of the above conditions are met. When used for interlocking, it becomes unreliable. Because it lacks timeliness!
What you say makes sense. I recalled a case from the past where the pH lag time was around 2 hours; in that solution, a micro circulatory pump was used for flushing in order to address the issue of contamination on the pH meter. However, the control of that pump wasn’t very precise, and the lag time was also long, so it didn’t have an impact on the manufacturing process.
Online pH analysis should be a well-developed technology with high reliability. pH meters require regular maintenance.
This post was last edited by qugd on 2016-4-9 at 19:39. For acid-base neutralization reactions, the reaction rate is quite fast; it is therefore no problem to use pH monitoring to control the reaction process through interlock mechanisms. However, for specific operating conditions, it is necessary to properly select the configuration of the pH meter as well as the appropriate installation method, based on those conditions, requirements, and the desired detection accuracy; proper maintenance is also required. Furthermore, the uniformity of the reaction system also affects the accuracy of pH measurement and the speed of response, factors that must also be taken into account during control. As for the installation location of pH, it depends on the actual conditions of the device, but it is best to reflect the actual neutralization situation of the system as closely as possible.