EZ-HCl™

Determination of Chlorine in Hydrochloric Acid

Chlorine levels in liquid hydrochloric acid (HCl) are precisely and safely monitored by means of AppliTek’s EZ-HCl™ process analyzer. On-line measurement of chlorine in liquid HCl guarantees the purity of the end product. An additional possible reason for the measurement is that chlorine is an indicator for the amount of excess hydrogen in the synthesis of hydrochloric acid.

With increasing concerns over safety and efficiency in the chlorine manufacturing processes, AppliTek has investigated the use of proprietary on-line analyzer systems to monitor and control the HCl synthesis. Each of these on-line analyzer systems has been selected to control a specific part of the burner, by using techniques such as multi-wavelength infrared, thermal conductivity and wet-chemical liquid analysis. 

Background

Hydrochloric acid or HCl is one of the main primary products of the chlor-alkali industry and commonly produced by the exothermic reaction of hydrogen and chlorine, fed at controlled rates inside a burner. The burner consists of two concentric tubes with chlorine flowing through the inner tube and hydrogen through the outer annulus. Above the burner, the gases are ignited to produce hydrogen chloride gas. For optimum combustion and low free chlorine content in acid, the gases are burnt with about 10% excess volume flow of hydrogen. The HCl gas flows from the combustion chamber into an integrated isothermal falling-film absorber. The gas is then absorbed by water or weak acid. The absorber is either co-current or counter-current depending on the type of synthesis unit. The hydrochloric acid is normally produced with less than 1 ppm free chlorine. By adjusting the absorption water (weak acid) supply rate, the desired hydrogen chloride (HCl) solution concentration is obtained.