Online liquid alkali concentration analyzer is a key equipment used for real-time monitoring of sodium hydroxide solution concentration in industries such as chemical engineering and water treatment, which can effectively improve production efficiency and safety.
It mainly measures concentration through conductivity method or critical angle refraction principle. The conductivity method is based on the positive correlation between the number of ions generated by alkaline ionization and the concentration, and calculates the concentration by measuring the conductivity; The refractive index law utilizes the characteristic of the refractive index of a solution changing with concentration to achieve high-precision detection through optical devices.
The online liquid alkali concentration analyzer is mainly based on two core principles for measurement:
Refraction method: By utilizing the linear increase in refractive index of sodium hydroxide solution with increasing concentration, the concentration can be inferred by measuring the refractive index of the solution. The sensor is equipped with a built-in light source (usually LED monochromatic light) and a refractive prism. The light enters the contact surface between the prism and the solution at a fixed angle, with some of the light refracted into the solution and others reflected. The photodetector receives reflected light intensity, and when the concentration of the solution changes, the refractive index changes, the critical refractive angle changes accordingly, and the reflected light intensity also changes accordingly. The instrument has a built-in calibration curve that converts the reflected light intensity signal into a concentration value.
Conductivity method: Sodium hydroxide is a strong electrolyte that dissociates into Na ⁺ and OH ⁻ after dissolving in water. The conductivity of the solution increases with the increase of ion concentration (showing an approximately linear relationship in the low to medium concentration range). The concentration can be indirectly calculated by measuring the conductivity. The sensor contains a pair of electrodes (usually platinum or titanium alloy, corrosion-resistant), and a constant alternating current is applied between the electrodes. Ions move in a directional manner under the action of the electric field to form a current. The instrument measures the resistance between the electrodes (conductivity=1/resistance x electrode constant), and the magnitude of the current is positively correlated with the ion concentration.
Application scenarios
Chemical industry: In the fields of chlor alkali industry, fine chemicals, etc., real-time monitoring of liquid alkali concentration at the outlet of electrolytic cells and the inlet and outlet of evaporators is carried out to ensure the stability of the production process and product quality.
Textile printing and dyeing: In processes such as fabric desizing and boiling, the concentration of sodium hydroxide solution is controlled within an ideal range to ensure uniform quality of fabric pre-treatment.
Paper industry: Accurately controlling the concentration of alkali solution in pulp cooking, pulp bleaching and other processes to improve pulp yield and whiteness.
Electroplating industry: In alkaline electroplating processes such as galvanizing, copper plating, and nickel plating, real-time monitoring of plating solution concentration is carried out to ensure stable coating quality.
Water treatment industry: In the process of wastewater treatment, alkaline solution is added to adjust the pH value or chemical precipitation treatment is carried out to monitor the concentration and pH value changes of alkaline solution in real time, ensuring that the wastewater treatment meets the standards.