Patent ID: 6350426
Filing Date: 2002-02-26
Classification: G01N

Abstract:
A process for continuous production of hydrogen fluoride comprising the following steps (1) to (5):(1) a step of reacting feed fluorspar with feed sulfuric acid, (2) a step of separating a crude product from said step (1) into (a) a low-boiling mixture composed predominantly of hydrogen fluoride and (b) a high-boiling mixture composed predominantly of unreacted sulfuric acid and containing small proportions of hydrogen fluoride and water, (3) a step of purifying and isolating hydrogen fluoride from said low-boiling mixture (a), (4) a step of adding sulfuric anhydride to said high-boiling mixture (b) in an amount substantially equivalent to the amount of water contained therein for reaction to form sulfuric acid to thereby convert substantially all the water to sulfuric acid and returning it together with unreacted sulfuric acid feed to said step (1), wherein the amount of water occurring in a high-boiling mixture (b) is determined by a method for determining the concentration of water of a ternary mixture essentially consisting of sulfuric acid, hydrogen fluoride, and water, which comprises measuring at least one set of three physical quantities (1) temperature, (2) ultrasound propagation velocity, and (3) electrical conductivity or viscosity, of said ternary mixture and converting measured values to the concentration of water with reference to separately pre-constructed calibration curves representing the relationships of concentrations of respective components of a ternary mixture of sulfuric acid, hydrogen fluoride, and water to said three physical quantities, and (5) a step of supplying a supplemental amount of sulfuric acid as to make substantially the total necessary amount of sulfuric acid available for reaction with feed fluorspar.