The "flue gas concentration evaporation drying" technology is adopted and consists of a series of sub-technologies: The application of multiple core technologies such as online TDS measurement of high-salt wastewater, magnesium resource utilization of desulfurization wastewater, double-pass loop flue gas heating spray, salt extraction from concentrated liquid, solid separation of concentrated brine, low-temperature flue gas flash evaporation, multi-fluid spray drying, and evenly distributed flue gas air curtain ensures normal operation in wastewater environments with high COD, high viscosity, and high suspended solids. It features low investment, small maintenance and low operating costs.

Zero discharge technology for desulfurization wastewater is a specialized technical system designed for highly polluted wastewater generated by flue gas desulfurization systems in thermal power plants, steel mills, etc. It achieves complete interception of wastewater pollutants and recycling of water resources through a full-process treatment of "pretreatment - concentration and reduction - solidification and separation". As a "tough nut to crack" in Industrial wastewater treatment, desulfurization wastewater contains high salt (with chloride ion concentration reaching over 20,000 mg/L), high heavy metals and high suspended solids. This technology fundamentally solves its discharge problem and is the core support for enterprises to implement environmental protection policies.

I. Core Technical Logic: Overcome pollution difficulties in stages

The technical system is centered around "reduction, harmlessness and resource utilization", achieving the goal of zero emissions through three-stage treatment. The pretreatment focuses on "pollution reduction", removing heavy metals and suspended solids to prevent clogging of subsequent equipment. The core of concentration and reduction is "water conservation", which involves reducing the volume of wastewater and increasing the concentration of pollutants through membrane or thermal methods. Solidification separation achieves "desalination", crystallizing and separating the salts in the concentrated liquid. Eventually, only solid waste residue is produced, and the water resources are fully reused. Each link is closely linked, specifically addressing the pain points of desulfurization wastewater, such as high salt content, high toxicity, and difficulty in treatment.

Ii. Mainstream Process Path: The combined application of membrane method and thermal method

The current mainstream technology mainly adopts the combined process of "pretreatment + membrane concentration + evaporation crystallization". The pretreatment process adopts the "chemical precipitation + clarification + filtration" procedure. By adding chemicals such as lime and sodium sulfide, heavy metal ions form precipitates, which are then removed through a clarification tank and a filter. The removal rate of suspended solids reaches over 95%. Membrane concentration mostly adopts disc tube reverse osmosis (DTRO), which has strong anti-pollution ability and can concentrate the volume of wastewater to 1/5-1/10 of the original water volume, retaining over 99% of salt ions. Evaporation crystallization is achieved through multi-effect evaporation (MED) or mechanical vapor recompression (MVR) technology, where the concentrated liquid is evaporated to crystallization. The separated industrial salt can be recycled and reused, and the distilled water is used as supplementary water for the circulating water.

Iii. Key Technological Breakthroughs: Addressing the Challenge of High-salt Corrosion

The strong corrosiveness of high-salt wastewater is a core technical challenge. In recent years, breakthroughs have been made in two major directions: First, material upgrading. The concentration and evaporation equipment adopts corrosion-resistant materials such as duplex steel and titanium alloy, extending the equipment's service life to more than five years. The second is process optimization. Some projects have introduced "softening + advanced oxidation" pretreatment to reduce water hardness and organic matter content, and to minimize membrane fouling and equipment scaling. After a 1 million kilowatt thermal power plant applied the optimized process, the cleaning cycle of membrane modules was extended from 15 days to 60 days, and the operational stability was significantly improved.