Eka Engineering: The HP-A® ClO2 process
A proprietary technology which has several
advantages over earlier atmospheric chlorine
dioxide (CIO2) processes.

The chemistry
Sodium chlorate (NaCIO3) reacts in a two-stage reactor
system with a proprietary grade of hydrogen peroxide(H2O2) in sulfuric acid (H2SO4) solution to produce CIO2.
The reaction by-products are oxygen (O2) and spent acidcontaining sodium bisulfate (NaHSO4).
The HP-A® process offers the customer the opportunity
to expand ClO2 production capacity with the existinggenerator. The older atmospheric ClO2 processes use
other reducing agents as sulfur dioxide (SO2) and sodiumchloride (NaCl) form chlorine gas (Cl2) as a by-product.

Benefits
The HP-A® process is an ideal
choice for pulp mills that look forthe below specifications:
Additional capacity fromexisting units (Mathison)• Low investment cost
• Low capital conversion/ 		expansion• Easy to operate• Very low production of CI2 as aby-product•Main reaction
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 thefollowing equation:
2 NaCIO3 + 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 more user friendly reducing which produces the purest
chlorine dioxide available.

HP-A® overview
You normally need the following systems in association with the chlorine dioxide (CIO2)
equipment:• Chlorate, acid and reducing agent storage and delivery• ClO2 product storage and delivery• Chilled water supply

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 gasphase) within the safe operating range
4. Liquor from the second generator overflows to a stripper and remaining ClO2 is removed before the spent acidsolution is discharged from the system
5. Liquor from the primary generator overflows into the secondary generator where the ClO2 reduction processcontinues
6. Gas is transferred from the reactors and strippers to the absorption tower where chlorine dioxide gas is absorbed,
then transferred to storage tanks
7. Tail gas exiting the absorption tower is further scrubbed to avoid emissions
8. An emergency stop interlock system is in place that will shut down the process should pressure, temperature orflow parameters operate out of range

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