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Why Use Conductivity Measurement For The Concentration of Acid or Base Solutions?

Why Use Conductivity Measurement For The Concentration of Acid or Base Solutions?

2020-11-20

There are numerous industrial applications where measurements and/or control of a specific chemical strength of the process is critical for optimizing the production of the end product. These specific concentrations are obtained by mixing a full strength solution with water to achieve the desired percent concentration. such as in Refining, Food, and beverage, Power, Oil and Gas, Pulp and Paper, Chemical, etc.


Acid and Base Concentration

The desired chemical concentration is achieved using a two-stage mixing procedure. During the first stage, the flow ratio control unit on the missing tank is set to provide (x) gallon per minute of the full strength solution and (y) gallons per minute of water. These values are adjusted to produce a concentration value which is slightly weaker than the desired value. This ratio control must include alarm capabilities to indicate “low flow” conditions for both the full strength solution and the water in order to prevent wasted chemicals or hazardous situations.

At the second stage, a conductivity sensor and analyzer function as a “trim control”. This combination adds small amounts of full-strength solution to the mixing tank to produce the exact concentration desired. For example, to produce a 4% caustic solution from a large bulk caustic supply at 50%, the flow ratio controller is adjusted to make a 3% solution and the conductivity information is used to add additional caustic to achieve the 4% concentration. Conductivity is a very reliable index of the concentration for most acid and base (caustic) solutions. below shows the correlation between conductivity and concentration for four common solutions.

conductivity

For most solutions, there is a peak conductivity value. Before this peak value is reached, conductivity correlates positively with concentration; after the peak, it correlates negatively. So, if the concentration range passes through the peak for that chemical the conductivity value (except the peak value) represents two different concentration values. Therefore, it is mandatory that any application near the peak of a particular solution be carefully controlled.

SJG-2083C Acid and Alkali Concentration Meter
Chemical NameChemical EquationConcentration Range
Nitric AcidHN030~25.00% 
Sulfuric AcidH2SO40~25.00%;92~100.00%; 
Hydrochloric AcidHCL0~20.00%;25~40.00%; 
Sodium HydroxideNaOH0~15.00%;25~40.00%; 
Potassium HydroxideKOH0~30.00%; 
Sodium ChlorideNaCL0~20.00%; 


Mainly Application of SJG-2083C Acid and Alkali Concentration Meter

You will find these applications in many industries. Demineralized water systems use caustic and acid solutions to regenerate the resin beds. The vegetable processing industry uses caustic solutions as a cleaning agent. Acid and caustic solutions are used in Clean-In-Place (CIP) systems to remove residue from process equipment without dismantling the systems. Solutions of acid and caustic are used to neutralize waste streams before discharge to municipal systems. Anywhere you find these acid and caustic solutions, you will find someone who is interested in their concentrations. Inductive Conductivity provides a reliable, maintenance-free method to monitor, control, and transmit this value.


inductive conductivity sensor                
Inductive conductivity sensor

with PTFE flange installation for Acid or alkali concentration measurement

acid and base concentration                
Acid and base concentration

with pipe installation, usually the thread is 3/4NPT

toroidal conductivity sensor                
Toroidal conductivity sensor

with flow-cell to measure acid or alkali concentration.

Summary by BOQU Instrument

Conductivity measurement is a reliable indicator of the concentration of most acid or base solutions. In determining the proper loop components for a particular application, the material of construction will be of primary concern. A chemical resistance chart should be consulted, or an application data sheet completed and sent to the factory in order to insure an installation that will be suited for the intended application. if need knows more info, please contact michael@shboqu.com.

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