A best available technology for reliable and cost-effective chlorine dioxide used in ECF pulp production.

Our large-scale, single-vessel processes (SVP) generate chlorine dioxide in a vacuum environment and produce a solid salt cake byproduct. Systems are available that use methanol and hydrogen peroxide as a reducing agent.

Benefits of the SVP-LITE process process

Reaction chemistry
Our patented SVP-LITE process generates chlorine dioxide (ClO2) by reducing sodium chlorate (NaClO3) using methanol (CH3OH or MeOH) in a sulfuric acid (H2SO4) solution, according to the following reaction:     9 NaCIO3 + 2 CH3OH + 6 H2SO4 → 9 ClO2 + 3 Na3H(SO4)2 + 0.5 CO2 + 1.5 HCOOH + 7 H2O.
The byproduct of this reaction is an acidic salt cake, sodium sesquisulfate Na3H(SO4)2, that is approximately 18 wt% sulfuric acid. By recovering the sulfuric acid from the sodium sesquisulfate salt, acid feed requirements and salt cake volume can be reduced approximately 17% and 25%, respectively. Recovering this acid is the function of the salt-cake wash (SCW).

The key feature of the SVP-LITE process is the circulation over the main reactor vessel, which is kept under vacuum:

  1. Reactants (chlorate, methanol or hydrogen peroxide and sulfuric acid) are fed to the reactor system where they react to form chlorine dioxide and a salt cake byproduct precipitates.
  2. Steam is added to the reboiler for heating the generator solution
  3. Gas leaving the generator is a mixture of chlorine dioxide and water vapor, which is absorbed into water in the absorption tower.
  4. The absorption tower tail gas is further scrubbed to avoid emissions.
  5. A side stream of the reactor solution is fed to the filter, which removes the salt cake byproduct.
  6. The reactor solution is returned to the reactor.
  7. Chlorine dioxide water from the absorption tank is transferred to storage tanks.

Benefits of SVP-LITE
The SVP-LITE process is an ideal choice for pulp mills that want to:

  • Eliminate chlorine in the chlorine dioxide water in order to produce real ECF pulp
  • Have low salt cake make-up requirements
  • Economically expand the capacity of existing SVP (R3) plants
  • Eliminate chlorine water or sodium hypochlorite use

It is possible to convert any SVP process to another with only minor equipment changes.

Chlorine dioxide technologies