Three Membrane Steps in Chlor-Alkali Brine

In the production process of chlor-alkali enterprises, the degree of fluctuation in raw salt composition, the level of refined brine quality control, the amount of sulfate accumulation and the salt loss rate of salt mud all affect production stability and overall operating costs. Jiuwu Hi-Tech has built technical capabilities covering membrane material production, process design and complete equipment manufacturing around primary brine refining, membrane desulfation, concentrated brine recovery and salt mud washing.

With an engineering track record of 185 primary brine refining projects, 380 sets of inorganic membrane filtration equipment for chlor-alkali enterprise projects and a converted capacity of about 24 million tonnes of caustic soda, Jiuwu Hi-Tech can provide customers with targeted process optimization solutions based on raw salt characteristics and site conditions.

Recently, the 43rd National Chlor-Alkali Industry Technical Exchange Conference was held in Kunming. This is an authoritative technical event with outstanding influence and high recognition in the domestic chlor-alkali field. The conference gathers leading enterprises across the industrial chain, research institutes and technical experts, and is a core platform for the concentrated display of industry technical achievements. Jiuwu Hi-Tech participated in the exchange with products including alumina ceramic membranes, silicon carbide ceramic membranes, organic tubular membranes and spiral-wound membranes, and delivered a technical presentation on "The Application of Jiuwu Membrane Technology in Chlor-Alkali Brine Systems", focusing on key processes and membrane separation technology applications in chlor-alkali production.

Around the key issues in chlor-alkali production, Jiuwu Hi-Tech highlighted three types of application solutions, and combined multiple types of membrane products to provide technical options for different production conditions. From stabilizing refined brine quality and controlling sulfate concentration to reducing salt loss, membrane separation technology is providing new process paths for chlor-alkali enterprises to optimize production operation and resource utilization.

Ceramic membrane primary brine refining: coping with raw salt fluctuation and ensuring refined brine quality

Inorganic membrane brine refining process

Core customer problems

Raw salt from different sources has different impurity composition and filtration characteristics. In particular, high-magnesium raw salt and raw salt with an inverted calcium-to-magnesium ratio tend to increase the difficulty of filtration and operation control. Enterprises must ensure refined brine quality while also taking into account equipment footprint, cleaning and maintenance, and operating costs.

Jiuwu solution

Key points of Jiuwu ceramic membrane primary brine refining process

Precision filtration with ceramic membranes, with flexible switching between cross-flow and dead-end filtration modes according to raw salt quality:

• When the impurity load is high and cake formation is likely, cross-flow filtration is used to improve membrane surface operating conditions;

• When refined salt with fewer impurities is used, it can be switched to dead-end filtration to reduce circulating pump operation;

• Combined with fully automatic acid cleaning, online turbidity monitoring, abnormal condition interlocking and DCS control, automated management of the filtration and cleaning process is achieved.

Core value

One set of equipment adapts to different raw salt conditions, optimizing the operating mode while ensuring outlet water quality.

Jiuwu Hi-Tech has accumulated 185 project references in the field of primary brine refining. Actual project data show that outlet suspended solids can be controlled below 0.5 ppm, and the total calcium and magnesium with the supporting refining process can reach below 1 ppm. At the same time, the solution has a short process flow, high equipment integration and a small footprint, which also helps new projects save space and existing plants to retrofit.

Membrane desulfation: controlling sulfate accumulation and optimizing brine circulation

Membrane desulfation process

Core customer problems

Sulfate gradually accumulates in the brine circulation system, affecting the management of brine reuse. Enterprises need to reduce the sulfate concentration in reused brine, properly handle the separated high-sulfate water, and control environmental risks in the treatment process.

Jiuwu solution

In 2008, Jiuwu Hi-Tech, together with experts from Nanjing Tech University, removed the patent restriction of a Canadian company in China through legal proceedings, reducing the investment cost of the membrane desulfation process.

The solution in this field sets up multiple free chlorine detection and interlocking points in the pretreatment stage, achieving both the goals of zero free chlorine entering the membrane and effectively extending the service life of the nanofiltration membrane. The whole unit can also be supplied as skid-mounted integration according to customer needs, shortening the on-site installation period.

Core value

Through sulfate separation and brine reuse, it can effectively help enterprises control the system sulfate load. The process requires no introduction of barium ions, avoiding the barium sulfate hazardous waste generated by the traditional barium salt precipitation route.

Jiuwu Hi-Tech has accumulated 89 project references in the field of chlor-alkali membrane desulfation. Actual project data show that the sulfate concentration of low-sulfate water can be below 1 g/L, and the sodium sulfate in high-sulfate water can be concentrated to about 80 g/L.

Concentrated brine reuse and salt mud washing: reducing salt loss and disposal burden

Membrane concentration brine reuse process

Core customer problems

The concentrate produced by primary brine membrane filtration, although low in solids content, carries a large water volume. If it enters the filter pressing stage directly, it increases the treatment load; the sodium chloride remaining in the salt mud also causes raw salt loss and increases subsequent disposal costs.

Jiuwu solution

Jiuwu Hi-Tech uses the concentrate discharge pressure of the ceramic membrane to carry out secondary concentration through a PE sintered curtain membrane, without adding an extra transfer pump. The filtered clear liquid returns to the primary brine main pipe, and the concentrated mud water then undergoes counter-current salt washing to further recover the sodium chloride in it.

Actual project data show

• The recovery rate can reach above 60%, and the discharge volume can be reduced to 1/2 to 1/3 of the original;

• The sodium chloride content in the salt mud filter cake can be controlled below 1%;

• The amount of wash water can be reduced by about half.

Application value and engineering experience

By optimizing the concentrated brine treatment and salt mud washing process, enterprises can reduce salt loss with the waste stream and lower wash water consumption and disposal burden.

Membrane product matrix: matching materials and modules to the separation task

Multiple types of membrane products displayed on site

During the conference, Jiuwu Hi-Tech displayed products including alumina ceramic membranes, silicon carbide ceramic membranes, organic tubular membranes and spiral-wound membranes, covering application needs under different separation precisions, material characteristics and operating conditions.

Relying on capabilities in membrane material R&D, module development, process design and system integration, Jiuwu Hi-Tech can provide product selection, sample testing, small-scale pilot testing, process design, complete equipment, installation and commissioning, and operator training, helping customers determine the suitable membrane products and process route starting from actual production problems.

From primary brine refining to concentrated brine reuse and membrane desulfation, Jiuwu Hi-Tech continues to promote the deep integration of membrane separation technology with chlor-alkali production scenarios. In the future, the company will continue to focus on the actual needs of chlor-alkali enterprises in stable production, cost control and resource recycling, deepen innovation in membrane materials and process technology, and help the chlor-alkali industry improve quality, increase efficiency and achieve green development with mature engineering experience and systematic solutions.