Chlor-Alkali

Evaporation and Crystallization

HPD® Technology in the Chlor-alkali industry assists industry manufacturers in meeting their production requirements for processing rate and purity while achieving low operating costs with ease of operation and maintenance. These systems are utilized in brine treatment, brine evaporation, salt crystallization, sodium hydroxide concentration, and inorganic crystal production from naturally occurring and/or pre-treated brines.
 

In caustic concentration systems, HPD technology concentrates diaphragm cell caustic from a dilute solution to final product strength in multiple-effect, forced circulation crystallizers while crystallizing sodium chloride. HPD technology concentrates membrane cell caustic in multiple-effect, HPD® falling film evaporators that feature excellent turndown ability with a superior steam economy.
 

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Industrial Crystallization Expertise

Veolia is active in brine treatment, providing systems for batch or continuous brine treatment for the removal of hardness from brine entering into a salt and/or chlor-alkali brine circuit. Veolia also offers evaporation equipment to resaturate depleted brine to address concerns with the water balance in the chlor-alkali plant or. Based on vast experience in industrial crystallization, HPD® Single-stage or multiple-effect salt crystallizers produce chemical-grade salt with minimal impurities that can be utilized in the chlor-alkali brine circuit with minimal secondary treatment requirements.

Systems Designed for Efficiency & Process Goals

In the soda ash industry, Veolia supplies processes for the production of dense soda ash (DSA), light soda ash (LSA), sodium carbonate decahydrate, and sodium bicarbonate. Large, single-effect mechanical vapor recompression (MVR) HPD® crystallization systems are used where energy costs dictate.

As a single point of responsibility, Veolia Water Technologies offers comprehensive laboratory studies, chemical analysis and piloting, process design, technical and commercial development, complete project management and project execution, as well as, in-depth training with on-going service.

Veolia is committed to providing the highest quality and most efficient systems to meet the client's process and budgetary requirements.

SHINTECH, INC. - PLAQUEMINE, LOUISIANA USA

The Client's Needs

Shintech, Inc., the largest producer of polyvinyl chloride (PVC) in the United States, desired to become more vertically integrated in its production operations in addition to expanding its capacity to meet growing demand in the North American market. This vertical integration included the production of the PVC precursor vinyl chloride monomer (VCM) from a dedicated in-plant chlor-alkali facility.

In order to achieve the desired production goals, major chemical processing equipment was necessary to generate the large quantities of high-quality sodium chloride as raw material needed to support the chlor-alkali plant operations. Other process needs for the plant included concentration equipment of the by-product caustic soda.

Veolia Water Technologies was selected to provide the salt purification plant and caustic soda evaporation system for Shintech's new Plaquemine facility. This was due to Veolia's commercially demonstrated experience in this industry with the ability to manage and execute large-scale, turnkey construction projects.
 

Technology Solutions

The salt purification system, essentially the heart of the plant, consisted of a single-stage HPD® salt crystallizer fed from an upstream reactive brine pre-treatment process. Driven by mechanical vapor recompression (MVR), the system is designed with a nameplate capacity of 820,000 metric tons per year (mtpy) of high-quality sodium chloride that is utilized in the chlor-alkali plant. When completed, this system would be the largest, single-stage evaporated salt system in the world.

The companion project awarded involved a by-product of the chlor-alkali plant. An HPD evaporator system was designed to concentrate the merchant membrane cell caustic from 32 wt% to 50 wt%. This system would produce 1,520 metric tons per day (mtpd) of sodium hydroxide on a dry basis.

The concentration system was designed as a steam-driven, triple-effect, HPD falling film evaporation train and is configured to maximize steam economy. The challenge for Veolia was to design the system with a minimum turndown of 15% of design capacity required by Shintech.
 

Turnkey Project Execution

Veolia was initially awarded the salt plant as a turnkey project due to their extensive experience in design, management, and building the largest evaporated salt plants in the world. Recognizing the ability to execute complex projects, the caustic concentration system project was also awarded on a turnkey basis. This full-system supply and installation allowed Shintech to focus on other aspects of the plant.

  • The scope of both projects also included:
  • Civil works including foundations and pilings
  • Structural steel
  • Mechanical piping, valves, and insulation
  • Electrical, controls, and instrumentation
  • Startup, commissioning, and operator training support

The Results

Due to successful execution of the projects and performance of the HPD salt purification and caustic concentration systems, Shintech again selected Veolia for further expansion of the Plaquemine facility.

A nearly identical plant was constructed adjacent to the original site. Both the new salt crystallizer and caustic evaporation systems were started up in early 2011.