Chlor-Alkali Plant in Kwinana, WA

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Chlor-alkali Plant in Kwinana

Overview

Coogee Chemicals is Australia’s second largest manufacturer of chlor-alkali products with three chlor-alkali facilities across Australia – two in the Perth region of Western Australia and one in Lytton, Queensland. The business was established to service the emerging local titanium dioxide pigment industry as dedicated suppliers of bulk chlorine and caustic soda feedstock.

Our primary raw material is solar salt harvested from an inland salt lake in the Eastern Goldfields region of Western Australia.

Secondary products include hydrochloric acid and sodium hypochlorite, and these two products, together with caustic soda are sold into the chemical, mineral processing, mining, water treatment, galvanizing and swimming pool markets.

Our History

Our first plant commenced production in 1988 supplying a new, greenfield, titanium dioxide pigment plant, located in the Kemerton Industrial Park, near Bunbury. The chlor-alkali plant uses German designed Lurgi monopolar membrane cells to produce chlorine and caustic soda by the electrolysis of pure brine, and has given very reliable service for over 20 years.

A second identical sister plant, located in the Kwinana Industrial Area, was started up in 1991 to supply feedstock for the local pigment plant. The production capacity of the Kwinana plant was recently expanded with the commissioning, in early 2010, of a second chlorine production train and an upgrade of common site infrastructure servicing both the old and new cell rooms. The new chlorine capacity at Kwinana is produced in a UK designed Ineos BiChlor membrane electrolyser. This is a "state of the art" large scale bipolar cell with significantly lower energy consumption than the older Lurgi cells.


Our Products

Chlorine gas, caustic soda, and hydrogen gas are produced simultaneously in the chlor-alkali process.

Chlorine

Chlorine is produced on demand and, after purification, is supplied directly by pipeline into the adjoining pigment plant as a pure, dry, compressed gas. At Kwinana, a second independent chlorine pipeline supplies dry compressed cell gas from the new production train.

Caustic Soda

Caustic soda is produced as a 32% solution. Some of this is supplied directly to the adjoining pigment plants. Most of the caustic soda is concentrated to 50% strength and distributed to a wide range of customers throughout Western Australia by road tanker, or by pipeline via Coogee’s Kwinana tank terminal.

Hydrogen

A small amount of the co-produced hydrogen is reacted with chlorine gas to produce high purity hydrochloric acid. The rest is burned as a fuel to generate steam for internal use.

Hydrochloric Acid

Pure 32% hydrochloric acid is used internally in the chlor-alkali process, and some is sold, in bulk, by road tanker to industrial customers.

Coogee Chemicals also markets by-product hydrochloric acid produced by the local pigment plant.

Sodium Hypochlorite

Concentrated sodium hypochlorite solution (bleach) is manufactured as a secondary product by reacting chlorine gas with caustic soda. Sodium hypochlorite is sold as a bleaching agent for water treatment and for swimming pool chlorination.


The Chlor-alkali Process

Chlorine is produced by the electrolysis of purified sodium chloride brine solution in membrane electrolysis cells. Product chlorine is purified, and then sent via a small intermediate buffer storage system into a fixed export pipeline into the pigment plant process. Chlorine is produced on demand, with production rate determined by customer requirements.

Sodium hydroxide and hydrogen are also produced as co-products of the electrolysis process.

The process uses an electrolytic cell, or electrolyser, to produce chlorine, caustic soda and hydrogen simultaneously by passing an electric current through purified salt and dilute caustic soda solutions, separated by an ion exchange membrane.

Ion exchange membrane electrolysis was first commercialised around 1980 and is the cleanest and most energy efficient process for manufacture of chlorine and caustic soda. Many different designs of membrane electrolyser have been developed by specialist technology suppliers. The original Coogee Chlor-Alkali plants use German designed, Lurgi electrolysers, typical of the "second generation" in the evolution of this technology. The new Ineos cell at Kwinana is representative of the "fifth generation" with improved energy efficiency and longer membrane life.

The electrolysers are fed with purified, near-saturated brine, and 30% caustic soda solution.

A direct electric current is passed to reduce the salt and produce chlorine gas in the electrolyser anode compartment. Sodium ions pass through the ion exchange membrane into the cathode compartment where caustic soda and hydrogen are produced at the cathodes. The two halves of the process are separated by an ion-exchange membrane that prevents re-mixing of the products and permits a 95% efficiency of power usage.

Weak brine leaves the electrolysers, and is stripped free of dissolved chlorine and returned for re-saturation with fresh salt.

This concentrated brine is purified in a three stage process by chemical precipitation, filtration, and ion exchange.

Chlorine gas from the cells contains about 2% oxygen and is saturated with water vapour.

The wet impure chlorine gas is cooled, dried, compressed, and liquefied by chilling to below -34°C. The oxygen impurity in the chlorine is eliminated at the liquefaction step, and is passed to atmosphere via the chlorine absorption and scrubbing system.

Liquid chlorine is drained by gravity into one of three 25 tonne capacity storage tanks filled in rotation. The plant operating licences limit the maximum inventory of liquid chlorine permitted on site to 50 tonnes. When a storage tank is selected for export the liquid chlorine is forced by nitrogen pressure through a steam-heated vaporiser into the export gas pipeline.

At our Kwinana plant chlorine produced in the new cell room is supplied directly to the customer as dry compressed cell gas, with no intermediate liquefaction or storage steps.

Caustic soda solution leaves the electrolysers at about 32% strength. Part of this is bled off and concentrated for sale in a steam heated evaporator, and the rest is diluted with water and recycled to the electrolysis cells.

The company prides itself on long term relationships built with its many customers, large and small, on the foundation of excellent service and the highest commitment to safety and quality.

Gordon Martin