Chlorine dioxide generation process

In a continuous method for the production of chlorine dioxide, which comprises:

• continuously maintaining a chlorine dioxide-producing reaction medium in an enclosed upright cylindrical reaction zone having a vapor space located above the liquid level of said reaction medium in said reaction zone, the reaction medium containing an alkali metal chlorate, a reducing agent capable of reducing said alkali metal chlorate to chlorine dioxide and chlorine, and a strong mineral acid,
• continuously generating chlorine dioxide and chlorine from said reaction medium and continuously evaporating water from said reaction medium at substantially the boiling point thereof while the reaction zone is maintained under a subatmospheric pressure,
• continuously removing from said reaction zone a gaseous mixture of said generated chlorine dioxide and chlorine and evaporated water through a gaseous outlet located in communication with said vapor space in said reaction zone,
• continuously depositing in said reaction zone an alkali metal salt of the anion of said strong acid, removing from a lower portion of said reaction zone a slurry containing deposited alkali metal salt and part of said reaction medium and recovering alkali metal salt from a portion of said slurry,
• admixing alkali metal chlorate with said remainder of said slurry,
• heating recycled material substantially to an elevated temperature which is the boiling point of the reaction medium at the prevailing absolute pressure in said reaction zone,
• accelerating the heated material in admixture with alkali metal chlorate, and also reducing agent when said strong mineral acid is not also the reducing agent, to establish a back pressure exceeding the difference in saturation vapor pressure of the heated mixture and of said reaction medium,
• adding strong mineral acid to said accelerated heated mixture substantially at the maximum velocity of said mixture resulting from said acceleration to provide a feed material for said reaction zone,
• allowing gaseous material in said feed material to expand while maintaining a low rate of acceleration, and
• feeding said expanded feed mixture into said vapor space,
• the improvement which comprises effecting said feeding of expanded feed mixture into said vapor space generally tangentially of the internal wall of said reaction zone, and
• inducing said gaseous material to follow the flow path of said expanded feed mixture from inlet to said reaction zone to said reaction medium and to flow radially inwardly of the internal wall of the reaction zone prior to upward passage through said vapor space towards said gaseous outlet.