99% Caustic Soda Flakes EPC Project

1.Chlor Alkali Plant technology Overview

Product Overview

The chlor-alkali industry is a basic chemical industry that electrolyzes saturated brine (NaCl) solutions while simultaneously producing caustic soda (sodium hydroxide), chlorine, and hydrogen. The complete sets of chlor-alkali equipment provided by our company use internationally advanced ion membrane electrolysis technology, featuring significant advantages such as low energy consumption, high product quality, and pollution-free operation, making them the mainstream technical route in the global chlor-alkali industry.

The complete unit can produce a variety of chlor-alkali products such as 15% sodium hypochlorite, 32%-50% caustic soda, tablet alkali (solid alkali), 31%-33% high-purity hydrochloric acid, liquid chlorine, and more. These products are widely used in alumina, chemical, papermaking, dyeing, water treatment, PVC production, pharmaceuticals, pesticides, and other industries.

2. System Process

2.1 Process Overview

This chlor-alkali production unit uses raw salt (NaCl) as the main raw material, employing zero-distance sub-membrane electrolyzers as the core equipment, and produces chlorine, hydrogen, and caustic soda through electrolysis of saturated brine. The entire system uses a DCS distributed control system for fully automated operation, ensuring a stable, safe, and efficient production process.

2.2 Main Process Units

The entire unit consists of the following core process units:

3. Process flow

3.1 Main Process Flow

Raw salt→Saltized salt→Primary brine purification→Secondary brine purification (chelated resin tower)→ion membrane electrolysis 

Anode chamber: Cl⁻discharge → chlorine gas (Cl₂) → cooling, drying, compression → liquid chlorine / hydrochloric acid / sodium hypochlorite

Cathode chamber: H⁺discharge → hydrogen (H₂) → scrub compression → hydrochloric acid synthesis / fuel utilization

Cathode solution: NaOH solution→32% caustic soda product→multi-effect evaporation→50% caustic soda→concentrated flake→alkali

3.2 Principles of electrolysis reactions

The ion membrane electrolysis method uses a cation exchange membrane to separate the anode chamber from the cathode chamber. The membrane has selective permeability, allowing only Na⁺to pass through, while Cl⁻and OH⁻cannot pass through.

Overall reaction equation: 2NaCl + 2H₂O→2NaOH + Cl₂↑+ H₂↑ 

Anode reaction: 2Cl⁻- 2e⁻ →Cl₂↑ 

Cathode reaction:2H₂O + 2e⁻ →H₂↑+ 2OH⁻ 

Refined brine is injected into the anode chamber, and pure water is poured into the cathode chamber. During electrolysis, Na⁺carries a small amount of water molecules through the ion membrane to migrate to the cathode chamber, where it combines with OH⁻to form a NaOH solution.

3.3 Main Product Destinations

Chlorine gas: some are dried and compressed to produce liquid chlorine products; One part is used to synthesize hydrogen chloride with hydrogen to produce 31%-33% hydrochloric acid; Tail chlorine is used to react with caustic soda to produce 15% sodium hypochlorite 

Caustic soda: can directly produce 32% ionized membrane caustic soda; Concentrated by multi-effect evaporation to 50% liquid alkali; Further concentration and tablet formation can produce flake alkali (solid base)

Hydrogen: Used for hydrochloric acid synthesis or as a clean fuel

4. Product specifications

5. Technical Advantages

5.1 Core Technical Advantages of the Ion Membrane Method

1. High product quality: Caustic soda has high purity and low salt content (50% NaOH contains only 50-60ppm of NaCl), meeting the quality requirements of high-purity caustic soda in high-end industries such as chemical fiber and pharmaceuticals.

2. Low energy consumption: The DC electricity consumption per ton of caustic soda is only approx.2000 kWh, significantly lower than the diaphragm and mercury methods.

3. No pollution: The ion membrane method does not produce mercury pollution (mercury process) or asbestos waste (membrane method), making it a green and environmentally friendly clean production technology.

4. High degree of automation: The entire device uses a DCS distributed control system, enabling full-process automatic control and stable and reliable operation.

5. High purity of chlorine and hydrogen: The product has high chlorine and hydrogen purity, which is beneficial for deep processing downstream utilization.

6. High current efficiency: current efficiency can reach 95%-96%, and the electrolyzer operates stably.

5.2 Technical Features of the Equipment

- Uses zero-pole distance sub-membrane electrolyzer technology to further reduce cell voltage and reduce energy consumption.

- The electrolyzer uses titanium anodes, carbon steel cathodes, and high-quality cation exchange membranes, offering strong corrosion resistance and long service life.

- Equipped with chlorine gas treatment and liquefaction systems to achieve efficient chlorine gas recovery and utilization.

- Utilizes multi-effect falling film evaporation technology, offering high thermal efficiency and low steam consumption.

- Key equipment materials are made of titanium, nickel, Hastelloy, and other corrosion-resistant materials to ensure long-term stable operation.

5.3 Customized Services

Customized designs can be provided according to customer production capacity requirements.

6. Model Specifications

Ion membrane electrolyzer series

Main equipment configuration (taking a 100,000-ton caustic soda unit with an annual output as an example)

7. Application Fields

8. Why choose us

Full-process solution: complete chlor-alkali equipment supply from brine refining to electrolysis, chloro-hydrogen treatment, and product refining.

Advanced technology: Adopts internationally mainstream zero-pole distance sub-membrane electrolysis technology, offering low energy consumption and high efficiency.

Customized services: We can provide customized designs based on customer production capacity requirements (10,000 tons/year ~ 1,000,000 tons/year).

High-quality materials: Key equipment uses corrosion-resistant materials such as titanium, nickel, and Hastelloy alloys to ensure long-term stable operation.

Automated control: Full-process DCS distributed control system is easy to operate, safe, and reliable.

Comprehensive after-sales service: We provide installation guidance, commissioning, training, and long-term technical support.

Note: The above equipment models and parameters are reference specifications; specific configurations can be customized according to customers' actual production capacity requirements. Welcome to call or write to us for detailed technical solutions.

CHLORY is the leading manufacturer of Chlor-Alkali plant EPC project in China with 20 years experiences.