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Dow Mitsui Chlor-Alkali Plant, United States of America

Key Data

On 1 July 2010, Mitsui and The Dow Chemical Company (Dow) signed a definitive agreement to establish a new chlor-alkali plant in Freeport, Texas, US. The plant will co-produce and market caustic soda and chlorine, known as chlor-alkali (C/A). It will have annual production capacity of 880,000mt of caustic soda and 816,000mt of chlorine. Caustic soda or sodium hydroxide (NaOH) and chlorine are used as feedstock in various industrial and chemical processes and products.

In January 2011, Samsung Engineering was awarded a $411m lump-sum turn-key contract for engineering, procurement and construction (EPC) of the project. Construction of the C/A plant will begin in 2011. The plant will be mechanically complete by January 2013.

Operations are scheduled to start in mid 2013. The project is expected to generate about 500 jobs during construction and will provide long-term, full-time employment for 50 people.

Owners and financing for the chlor-alkali plant

The JV deal became conditional in December 2010. Dow and Mitsui each own a 50% stake in the plant. In December 2010, Dow-Mitsui Chlor-Alkali, a joint venture company, was formed to construct, own and operate the world-class membrane chlor-alkali facility on the US Gulf Coast.

"The Dow Mitsui chlor-alkali plant will produce caustic soda and chlorine."

The total investment in the project is estimated to be $411m, with Mitsui investing about 50% of the total cost.

Dow had previously announced that it would build its own plant - Chlorine No. 7. The project was, however, held back, because of the economic downturn, resulting in the formation of the Dow-Mitsui JV for the chlor-alkali facility. The new C/A plant will be located in Dow's integrated manufacturing complex at Freeport, Texas.

Membrane technology

The C/A plant will be based on the modern and efficient membrane technology of Dow. The company will also maintain the facility under the JV contract. Dow's membrane technology will produce these products through electrolysis of brine, water saturated with sodium chloride (NaCl or salt).

Electrolyte process

Brine (aqueous sodium chloride) will be used as a raw material and electrolysed in a membrane cell. After this electrolytic process, the brine will be decomposed to chlorine in the anode compartment, and to sodium hydroxide solution and elemental hydrogen in the cathode compartment. The electrolysis will co-produce nearly 100% of caustic soda and about 95% of chlorine. To illustrate, 1.1lb of sodium hydroxide will co-produce 1lb of chlorine. This ratio is called an electrochemical unit (ECU).

During membrane cell technology, the anode and cathode compartments (electrodes) are separated by a membrane. The highly selective membrane will allow only the sodium ions to migrate from the anode chamber to the cathode chamber.

"The Dow Mitsui chlor-alkali plant is expected to generate 500 jobs during construction."

The brine will not be able to pass through the membrane and is saturated at the anode compartment of the cell. The chlorine gas will be liberated at the anode. The cell effluent will be aqueous caustic soda which will have substantially less sodium chloride. The chlorine produced at the plant will be converted to ethylene dichloride (EDC) using Dow's tolling conversion arrangement.

Caustic soda is used in several industries, including textiles, pulp and paper products, bleach, soaps, detergents, alumina production, petroleum refining and other chemical processing.

Chlorine is used as an oxidant for bleaching, disinfectant and purification, agrochemicals, solvents, pharmaceuticals, plastics and polymers, and as a chemical reagent.

Mitsui is one of the largest marketers of chlorine derivatives in the world and the new plant will increase its supply. The company opened a new chlor-alkali division in April 2009 to consolidate its related businesses, including alkali products, EDC, salt, polyvinyl chloride resin, vinyl chloride monomer and polyurethanes. The Mitsui and Dow strategic partnership will offer the advantages of integration and supply to downstream businesses. The membrane chlor-alkali plant will supply the increasing feedstock demand for caustic soda and competitively produce chlorine.

Diagram showing the process of chlor-alkali membrane technology.
The caustic soda (sodium hydroxide) is used for several industrial purposes.
The C/A plant will be established at Dow's integrated manufacturing complex in Freeport, Texas.
Chlorine from the plant will be converted to ethylene dichloride (EDC).