NaOH (caustic soda NaOH) production – Current status, electrolysis technology & market trends

Production of NaOH plays a pivotal role in the global chlor-alkali chain. The world produces an average of 45–50 million tons of caustic soda each year, of which the US and Western Europe account for about 80% of the output; the US is the largest producer with a capacity of ~18,5 million tons/year.

Current status of NaOH production in the world

About 94% of NaOH traded internationally is in liquid form, usually at a concentration of 50% by mass. Each year ~2 million tons of caustic soda are transported by sea (for alumina refining), and ~5 million tons are transported by road.

Solid caustic soda

The price of solid caustic soda is usually higher than that of liquid caustic soda by ~100–200 USD/ton (dry basis). The market is mainly located in developing countries due to limited infrastructure for using liquid caustic soda. As the infrastructure improves (China, CIS), the demand for solid caustic soda decreases, gradually shifting to liquid caustic soda.

Global caustic soda trade is around 400.000 tonnes/year and is decreasing by ~8%/year; ~225.000 tonnes are supplied by Europe. In Asia, Indonesia is an important market for caustic soda.

Liquid caustic soda

The Australian aluminium industry is the largest customer of seaborne caustic soda, consuming ~50% of seaborne caustic soda. Australia uses about 1,2 million tonnes of NaOH each year to produce ~13 million tonnes of alumina. Other major consuming markets include Brazil, Venezuela, Surinam, Jamaica, Guinea, South Korea, Colombia, etc.

NaOH price & floor-ceiling mechanism

Caustic soda prices are affected by both the demand for NaOH and the demand for its associated product, chlorine. Unlike chlorine, caustic soda prices have a “floor” and a “ceiling” due to its replacement by soda ash (Na2CO3).

• Floor price: When the price of caustic soda is too low (for example, during the 1997 crisis, below 80 USD/ton), businesses convert NaOH into soda by carbonation (~130 USD/ton), creating a "cushion" to prevent the price of caustic soda from falling further.
• Ceiling price: When caustic soda became too expensive, some industries turned to soda ash as a partial substitute.

Because chlorine is difficult to store safely, when the demand for chlorine (PVC) decreases, businesses are forced to reduce their chlor-alkali capacity, causing the supply of caustic soda to decrease and caustic soda prices to increase. Construction cycles, import taxes, exchange rates, etc. also significantly affect the supply-demand and price of NaOH.

NaOH production & regional painting

Asia Pacific

Overall, Asia is not self-sufficient in chlorine, nor is it consuming all the caustic soda it produces domestically. High electricity prices reduce its competitive advantage in exporting caustic soda compared to the US and the Middle East; Australia remains a major 50% liquid caustic soda market due to the alumina industry.

Europe

In 2001, total chlorine production in Western Europe reached 9,26 million tons (capacity utilization rate ~85,6%). In the same year, total caustic soda production reached 9,62 million tons.

Demand & consumption trends

Total global caustic soda demand (2002 reference) ~46 million tonnes. Major consumption sectors include NaOH in water treatment, textile dyeing, pulp - paper, chemicals... Demand is forecast to increase by ~3%/year, while capacity only increases by ~1%/year, creating pressure to expand or upgrade technology.

NaOH production technology (electrolysis of table salt)

NaOH – Cl products₂ - H₂ appear simultaneously in the NaCl electrolysis tank. Three main electrolysis technologies: mercury (Hg) electrode, diaphragm and ion exchange membrane.

Mercury electrode technology

Advantages: very pure caustic soda product (Rayon grade), concentration 50–52% immediately after electrolysis. Disadvantages: strict safety-environmental management requirements due to mercury.

Converted power consumption: ~3600 kWh/ton NaOH.

Diaphragm technology

Electrolysis bath gives 12–14% NaOH and contains a lot of salt; requires 3–4 concentration steps to reach 49–52%. “Technical grade” quality, NaCl/NaClO impurities₃ higher.

Total converted consumption: ~5000 kWh/ton NaOH.

Ion exchange membrane technology

Is the main trend in NaOH production modern: lowest energy consumption, extremely low impurities. The solution leaves the tank at 33–35%, then concentrated to 50% for transport.

Converted power consumption: ~3360 kWh/ton NaOH.

Technology conversion trends in NaOH production

Many European plants still operate on Hg technology due to the age of the equipment and the large capital investment for conversion. However, increasingly stringent environmental requirements are accelerating the transition to membrane.

Comparison of three technologies in NaOH production

Technical conclusions: Membrane is optimal in terms of energy and quality; Hg gives the highest quality but is environmentally stressed; Diaphragm is suitable when low CAPEX is a priority and concentrate costs are acceptable.

To know How much is NaOH? and choose the product configuration (50% liquid caustic soda, caustic soda flakes, caustic soda granules) suitable for your process, please contact Loc Thien for detailed advice.

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