Sodium chloride single-effect evaporator

I. Product Positioning

The sodium chloride single-effect evaporator is a high-efficiency, energy-saving integrated concentration/crystallization device specifically developed for NaCl-containing solutions. It employs either a "forced circulation + mechanical vapor recompression (MVR)" or "single-effect + live steam thermal compression (TVR)" process package, producing ≤12kg of steam per ton of water and consuming ≤28kWh of electricity per ton of water. Compared to traditional triple-effect evaporators, its overall operating cost is reduced by more than 50%. It is widely used in the resource recovery of sodium chloride and the "zero discharge" of wastewater in industries such as chlor-alkali, dyes, pharmaceuticals, coal chemicals, and seawater desalination.

II. Process Principle

1. Pre-concentration: The feed liquid recovers the sensible heat of the condensate through a multi-stage plate preheater, raising the temperature to 75-85℃.

2. Forced Circulation Evaporation: An axial flow pump maintains a flow velocity of 2-4 m/s within the pipe, controlling the evaporation temperature at 75-90℃.

3. Vapor Recompression: Secondary steam (75-80℃) is adiabatically compressed to 105-110℃ by a high-speed centrifugal/Roots compressor, with a ΔT = 22-28℃ and a compression ratio of 1.6-1.8.

4. Gas-Liquid Separation: Two-stage baffle + wire mesh demister ensures mist entrainment ≤20ppm, guaranteeing zero liquid hammer in the compressor.

5. Crystallization Discharge: DTB or OSLO type crystallizer is used for staged crystal growth, achieving an average particle size of 0.3-0.6 mm. After centrifugation, the industrial salt moisture content is ≤3%, the mother liquor reflux ratio is 20-40%, and the system operates continuously and stably.

III. System Composition

1. Main Evaporator: 2205/2507 duplex steel or TiAl alloy heat exchange tubes, design pressure 0.2MPa, design temperature 150℃, heat transfer coefficient ≥4000W·m⁻²·K⁻¹.

2. MVR Compressor: Three-dimensional flow high-efficiency impeller, isentropic efficiency ≥84%, frequency conversion 30-110%, noise ≤80dB(A).

3. Forced Circulation Pump: Wear-resistant alloy coated impeller, lifespan ≥25000h, double-end face mechanical seal, flow rate 500-10000m³·h⁻¹.

4. Vacuum System: Two-stage steam injection + liquid ring pump, ultimate vacuum 5kPa(a).

5. Automation: PLC + touch screen, online monitoring of key parameters, supports 4G/5G cloud operation and maintenance, one-button start/stop, achieving "unattended operation".

IV. Technical Highlights

1. Extreme Energy Saving: Secondary steam heat recovery rate ≥92%, normal operation with "zero live steam and zero cooling water," power consumption 25-30 kWh per ton of water.

2. Anti-scaling: High-speed turbulent flow + low evaporation temperature difference (≤4℃), reducing NaCl scaling rate by 70%; built-in CIP automatic cleaning nozzle, online acid/alkali washing completed in 4 hours.

3. High Crystal Quality: DTB graded crystallization, purity ≥98.5%, whiteness ≥80, meeting industrial dry salt standards, ready for direct sale.

4. Modular Design: Skid-mounted design, only flange and cable connections required on-site, shortening construction time by 40%; supports parallel operation of multiple units from 1-150 t·h⁻¹, flexible capacity expansion.

5. Green and Low-Carbon: No waste gas, high-salt mother liquor fully recirculated, carbon emission intensity reduced by 60% compared to traditional multi-effect refrigerators.

V. Typical Applications

1. Chlor-alkali brine concentration: NaCl 120g·L⁻¹ → 280g·L⁻¹, recovery rate 95%, impurity salt rate <3%.

2. Dye/pharmaceutical high-salt wastewater: TDS 60000mg·L⁻¹ → saturated, by-product industrial salt with water content ≤3%, COD enriched liquid sent for incineration.

3. Coal chemical concentrated brine: NaCl 3% → 23%, coupled with sodium sulfate MVR fractional crystallization to achieve "zero discharge".

4. Seawater desalination concentrated brine: Extracts 98.5% NaCl, used as chlor-alkali feedstock, realizing comprehensive utilization of seawater resources.

Conqinphi provides full lifecycle services including "water quality testing + solution design + equipment manufacturing + installation and commissioning + operation and maintenance training + after-sales service"; 12-month warranty on key components such as compressors and circulating pumps; real-time fault warning from cloud-based operation and maintenance center, ensuring annual availability of the equipment ≥8400h.