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The requirement for pulp mill bleaching chemicals with reduced dioxin emissions led to the rapid growth of chlorine dioxide generators in the late 1990's. The production of chlorine dioxide typically requires the use of sodium chlorate, an acid, and a reducing agent. Waste Water Treatment facilities are also becoming more interested in chlorine dioxide for sanitation purposes. These smaller system use sodium chlorite and hydrochloric acid. Universal Dynamics is well experienced in any of these system and has serviced the needs of chlorine dioxide producing pulp mill customers with the following types of activities:

• Plant Design
  1. Process design of components and material of construction
     • Mechanical
     • Electrical
     • Instrumentation
  2. Vendor selection and expediting
  3. Project management
  4. Startup and Commissioning support
  5. Utility and peripheral system design
• Operation
  1. Process Hazard Analyses
  2. Safety and Risk Audits
  3. Incident Investigation
  4. Commissioning, Operating, and Maintenance Manual creation
  5. Operator Training
• Modification
  1. Debottlenecking
  2. Plant Expansion

Traditional Chlorine Dioxide Generator Systems

Traditional chlorine dioxide generators feature a reactor vessel where the three major chemicals are combined and the explosive ClO2 gas is produced, an absorber system to absorb the gas into a water solution for application onto the pulp, a series of scrubbers for environmental control, and a method for recycle of the sodium sesquisulfate that is frequently produced as a byproduct.

The safe operation of these systems depend upon avoiding ClO2 explosions (known in the trade as "puffs" or "decompositions"), maintaining the environmental compliance ,and insuring that the materials of construction are adequate to contain the aggressive corrosivity of the reactants.

Integrated Chlorine Dioxide Systems

Integrated chlorine dioxide systems link together the various components necessary for ClO2 production and generally require only the purchase of electricity, salt, and chlorine or hydrochloric acid. These components include:

• An Electrolytic Cell line to produce sodium chlorate, which in turn requires detailed knowledge of:
  • Electrolytic cell design.
  • DC rectification, DC bus work, cathodic protection systems, and Electrical Harmonics filtering and correction.
  • The careful selection of the material of construction
• A hydrochloric acid synthesis plant to generate the acid by the combustion of hydrogen and chlorine.
• The usual chlorine dioxide generating, absorbing, and scrubbing systems.

Integrated generator systems are far more complex than the standalone systems and require a great depth of knowledge in the design, operation, and modification of the plant. Universal Dynamics engineers have published two papers on Integrated Chlorine Dioxide Systems in Canada and the UK. These papers are available upon request.

Sodium Chlorite Based Chlorine Dioxide Systems

The production of chlorine dioxide via the reaction of sodium chlorite and hydrochloric acid is adaptable to small skid-mounted package units that have applicability for water treatment systems and to supplement the more traditional larger pulp mill generators. This is a small, but growing market. Universal Dynamics engineers have the knowledge to assist customers implement systems using sodium chlorite for water disinfection.