HPD® Evaporation and Crystallization

Innovative Process Solutions

Dominion Salt - Mount Maunganui, NZ

Multiple-effect Salt Crystallizer Expansion

Project Background

Dominion Salt HPD multi-effect salt crystallization system

Dominion Salt's Sodium Chloride Purification Plant in Mount Maunganui, New Zealand began operation in 1973.

Demand for Dominion Salt's high-purity, sodium chloride products for their rapidly growing markets was pushing production at full capacity around the clock, only stopping for planned maintenance shutdowns.

A driving factor for this increased production is the growing demand for pure, pharmaceutical-grade salt in the Pacific Rim, Southeast Asia, and South America.

The applications for this salt include saline drips for injection, haemodialysis, eyewashes, and contact lens solutions.

The Client's Need

Production of pharmaceutical salt requires certifications according to strict manufacturing processes and quality guidelines to European, British and United States Pharmacopoeia.

The capacity of Dominion Salt's existing HPD® vacuum evaporation system used to produce purified salt was reaching its limit. This system was originally installed in 1972 by Veolia Water Technologies and was rated at approximately five tonnes per hour of production. In order for Dominion Salt to expand the overall production of their certified pharmaceutical salt production while maintaining supply to their other core markets, a capacity expansion would be required.

Expansion & Process Integration

Multiple-effect HPD® salt crystallizer

New salt crystallization equipment integrated at Dominion Salt as part of the Vacuum Salt plant expansion

Upon deciding that a capacity expansion was necessary to satisfy customer demand, Dominion Salt once again contracted Veolia to upgrade the salt plant. Dominion Salt would increase capacity from 5.2 tonnes per hour to 9.6 tonnes per hour production using the latest available HPD® salt crystallization technology.

The process and design objectives for the new crystallization system included:

  • Reliable production of high-quality salt using the existing system to the extent possible
  • Integration of a new salt crystallization section of the plant while maintaining integrity of the established, certified, pharmaceutical grade production processes
  • Increase total salt production without increasing steam consumption

A difficult aspect of the new crystallization equipment design was the integration of the expanded system with the original plant. The certified process for producing pharmaceutical salt must be strictly maintained while increasing total capacity.

Another challenging element of the project was the limitation of steam consumption. Due to constraints of steam generation on site, the increased plant capacity had to rely on existing steam volumes.