Upgrading an old standard or building a new one?

Our HP-A system features several advantages over earlier atmospheric chlorine dioxide processes, removing the need for sodium dioxide and improving the sodium chlorate yield. Thanks to equipment similarities, HP-A is frequently used to upgrade older atmospheric installations.

Our HP-A system features several advantages over earlier atmospheric chlorine dioxide processes, removing the need for sodium dioxide and improving the sodium chlorate yield. Thanks to equipment similarities, HP-A is frequently used to upgrade older atmospheric installations.

Chemistry
Our patented HP-A process produces chlorine dioxide (ClO2) by reducing sodium chlorate (NaClO3) with hydrogen peroxide (H2O2) in a sulfuric acid (H2SO4) solution, according to the following equation:
2 NaClO3 + H2O2 + 2 H2SO4 → 2 ClO2 + 2 NaHSO4 + 2 H2O + O2. Byproducts of this reaction are oxygen (O2) and spent acid containing sodium sulfate (NaHSO4): oxygen is released to the atmosphere and the acidic sodium sulfate is reused in other plant processes. Using hydrogen peroxide as a reducing agent brings a number of advantages, including higher capacity for existing generators, a less dangerous reducing agent and purer chlorine dioxide.

HP-A process overview

  1. In the HP-A process, reactants (sodium chlorate, hydrogen peroxide and sulfuric acid) are fed to a reactor system, consisting of the primary and secondary generators, and a stripper unit:
  2. Heat used to balance the reaction derives from the dilution of the sulfuric acid.
  3. Large quantities of air are introduced into the generator for mixing and keeping the ClO2 concentration (in the gas phase) within the safe operating range.
  4. Gas is transferred to the absorption tower where chlorine dioxide gas is absorbed, then transferred to storage tanks.
  5. Liquor from the primary generator overflows into the secondary generator where the ClO2 reduction process repeats.
  6. Liquor from the second generator overflows to a stripper and remaining ClO2 is removed before the spent acid solution is discharged from the system.
  7. Tail gas from the absorption tower is further scrubbed to avoid emissions.
  8. An emergency stop interlock system is in place that will shutdown the process should pressure, temperature or flow parameters operate out of range.

HP-A Benefits
The HP-A process is an ideal choice for pulp mills that want to:

  • Upgrade existing atmospheric installations
  • Increased sodium chlorate yield
  • Chlorine-free chlorine dioxide
  • Easy to operate

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