Throughout the Pulp & Paper industry, chlorine dioxide (ClO2) is used in the pulp-bleaching process. ClO2 generators chemically convert sodium chlorate to chlorine dioxide and sodium sulfate in a strong solution of sulfuric acid. The acid is continuously purged from the generator in order to prevent the accumulation of sodium sulfate.

Separation of ClO2 generator’s waste streams allows for the recycling of the sulfuric acid. Without splitting the streams, the effluent has a very high acid content which consumes alkalinity in the Kraft liquor. In order to counter the acid level, large quantities of caustic soda is consumed.

The Eco-Tec Generator Acid Purification (GAP™) System is designed to separate the sulfuric acid from the sodium sulfate by employing the use of the Eco-Tec Acid Purification Unit APU® System known worldwide as the standard for separating salts from mineral acids in metal processing industries. The resin used in the APU® system absorbs the acid while allowing the salt solution to pass through.

Process Description of GAP™


  • Easy to install and operate.
  • Significantly less floor and head space.
  • Will not affect mill ClO2 supply in any way.
  • Cost Saving for caustic soda and sulfuric acid.
  • GAP™ system required no shut down for installation.
  • Uses Eco-Tec’s highly efficient Recoflo® ion exchange process.
  • System can recover the capital investment in less than two years.
  • Reduced operating and installation costs, reduced shipping costs.
  • High efficiency of separation/removal and very low salt cake loss.
  • Pre-assembled, skid-mounted, standard Eco-Tec materials/instructions.
  • Complete system design – Eco-Tec systems are highly automated and can often be used to service multiple lines.
  • Factory assembled modules and testing in Eco-Tec’s ISO registered facility assures fast start-up and reliable operation.
  • Proven, quality, corrosion resistant components and materials selected for long service life in a pulp and paper processing facility.
  • Technical service – Eco-Tec provides start-up supervision, customer training, and access to the ECO-SERV program that includes performance monitoring and 24 hour telephone service.