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 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
- 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:
- Heat used to balance the reaction derives from the dilution of the sulfuric acid.
- 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.
- Gas is transferred to the absorption tower where chlorine dioxide gas is absorbed, then transferred to storage tanks.
- Liquor from the primary generator overflows into the secondary generator where the ClO2 reduction process repeats.
- Liquor from the second generator overflows to a stripper and remaining ClO2 is removed before the spent acid solution is discharged from the system.
- Tail gas from the absorption tower is further scrubbed to avoid emissions.
- An emergency stop interlock system is in place that will shutdown the process should pressure, temperature or flow parameters operate out of range.
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