Baimahu Lab's Homegrown Bipolar Membrane Electrodialysis Unit Passes 72-Hour Continuous Operation Test

The fully homegrown bipolar membrane electrodialysis (BMED) unit independently developed by the energy, chemical and environmental team at Baimahu Laboratory has successfully passed a 72-hour continuous full-load stability test. The unit produced

• sulphuric acid at 10% concentration, and
• caustic soda at 8% concentration,

both at purity above 99%, with specific energy consumption as low as 1,217 kWh per tonne of salt — performance the team says ranks among the best in China.

Chemical production generates large volumes of saline wastewater, which damages soil and water and threatens ecological safety if discharged directly. A BMED unit uses specialised functional membranes and an electric field to "split" the saline stream, yielding industrial-grade acid and alkali and recovering salt resources that would otherwise be discarded. It is therefore a key equipment class for industrial wastewater valorisation and green chemical manufacturing.

During development, the structure and materials of the unit's core internals were closely guarded trade secrets with no off-the-shelf products available, so the team started from scratch. The membrane stack — assembled from tens or even hundreds of special functional membranes and spacers — is the "heart" of the equipment. Its internal flow channels resemble a city's road network: poor design leads to uneven flow distribution, local crystallisation and blockage, excessive pressure drop and heating, and in turn seal failure, liquid cross-flow, spacer deformation and even membrane burn-out.

Building on years of accumulated know-how and two years of dedicated development, the team delivered two key advances:

• a proprietary shaped-channel distribution plate ensuring uniform distribution of multi-media flows, overcoming high circulation pressure drop and avoiding cross-flow, salt crystallisation blockage and membrane overheating, while cutting circulation energy use;
• a selected suspended special rubber spacer that prevents seal failure caused by deformation of sealing materials, significantly improving the safety and reliability of the homegrown BMED system.

The team also built a dedicated BMED performance testing platform, established a material performance evaluation standard system, iteratively developed an engineering design model for domestic BMED stacks adapted to multiple complex operating conditions, and completed assembly of two BMED stacks with different structures.

Passing the 72-hour continuous full-load test marks Baimahu Laboratory's full command of independent BMED stack development — from critical core components through whole-unit assembly to full-process system design — placing it among the research institutions capable of high-end BMED stack manufacturing. The team will continue optimising performance and accelerating commercial deployment.