Application scenarios of MVR evaporation crystallization equipment in fine chemical plants

The main battleground for MVR evaporation crystallization equipment in fine chemical plants can be summarized as the recovery of "three high" wastewaters—high salinity, high COD, and high value-added products. Leveraging the low-temperature, energy-saving, and fully enclosed advantages of mechanical vapor recompression (MVR), enterprises can simultaneously achieve "zero wastewater discharge" and "recovery of valuable components."

1. Zero Discharge of High-Salt Organic Wastewater: Fine chemical processes often use hydrochloric acid, sulfuric acid, or caustic soda as reaction/neutralization media, resulting in end-of-pipe wastewater with salt concentrations frequently reaching 8%–20%, and often containing unreacted raw materials and byproduct solvents. Traditional multi-effect evaporation systems are difficult to maintain long-term stability due to high steam consumption and operating costs. MVR evaporation crystallization systems reduce steam consumption to 10–25 kg per ton of water, power consumption to ≤120 kWh, TDS from 30000 mg/L to below 80 mg/L, salt recovery rate ≥98%, impurity salt rate <5%, and continuous operation cycle exceeding 365 days.

2. Concentration and Crystallization of Dyes, Pigments, and Intermediates: Dye salting-out processes generate mother liquor containing 10%–25% NaCl or Na₂SO₄, and 2%–5% dye intermediates. MVR low-temperature (50–75℃) evaporation avoids the decomposition of heat-sensitive intermediates. Simultaneously, using an OSLO/DTB crystallizer to control supersaturation within ±0.5% yields crystals with an average particle size of 0.6–1.2 mm, resulting in dye loss of <0.3% after centrifugation. Currently, several dye industrial parks in China use this process, achieving 100% condensate reuse and reducing energy consumption per ton of product by 45%.

3. Salt Separation and Purification of Pesticide Technicals and Intermediates: For wastewater containing mixed NaCl/Na₂SO₄ salts, such as bifenthrin and carbendazim, the MVR + freeze crystallization + nanofiltration "thermal salt separation" combination preferentially precipitates NaCl (purity ≥99.5%) at 80–100℃ and Na₂SO₄ (purity ≥99.2%) at 30–50℃. Glauber's salt is then further recovered via a freeze crystallizer (-5℃). Zhejiang Xinhecheng applied this route, achieving a NaCl recovery rate of ≥90% and a Na₂SO₄ recovery rate of ≥85%, saving 500,000 kWh of electricity annually.

4. Resin Washing Liquid and Organic Solvent Recovery 

The high-salt washing liquid after resin synthesis has a COD as high as 30,000 mg/L and TDS ≥8%. First, 70% of the organic matter is removed by resin adsorption, then it undergoes MVR evaporation and crystallization. The effluent COD ≤500 mg/L and can be reused for rinsing; the crystallized NaCl content is ≥98.5%, with a white appearance and no odor, meeting the industrial salt standard GB/T5462–2015, achieving "salt can be sold externally, and water can be reused."

5. Metal Salt Recovery for Electronic/Electroplating Fine Chemicals: In the production of electroplating-grade NiSO₄ and CuSO₄, the MVR forced circulation crystallizer can evaporate at 45–60℃ under vacuum of 0.5–0.8 bar, avoiding high-temperature hydrolysis of metal salts. Simultaneously, utilizing 2205 duplex steel or titanium heat exchangers, it can withstand Cl⁻>10000mg/L, achieving a salt recovery rate>95% and crystal impurities ≤0.1%, meeting battery-grade raw material requirements.

6. Bio-based Fine Chemical Concentration (Amino Acids, Fragrances): Amino acid fermentation broth has low solid content and high heat sensitivity; traditional single-effect evaporation easily leads to browning. The MVR falling film + forced circulation two-stage evaporation first reduces the moisture content to 70% at 50℃, then switches to the forced circulation crystallizer, maintaining a crystal slurry density of 25%–30%, increasing amino acid yield by 12%, reducing color by 80%, and achieving a steam compressor efficiency ≥80%, resulting in a 45% reduction in energy consumption per ton of product (equivalent to standard coal equivalent).

In conclusion, MVR evaporation crystallization equipment, with its characteristics of "low temperature, energy saving, fully enclosed operation, and high salt recovery," has become the preferred technology for zero discharge of high-salt wastewater in fine chemical industries, recovery of valuable salts, and concentration and crystallization of heat-sensitive materials. With the maturation of technologies such as AI prediction, corrosion-resistant new materials, and high-value salt separation, its application scenarios will further extend to high-end fields such as high-COD complex wastewater, electronic chemicals, and bio-based materials.