4t/h MVR evaporator system for rubber additive sodium thiram SDD

This MVR evaporator is designed for the production process of sodium formaldehyde sulfoxylate (SDD, 40% liquid) in a rubber additives company. A single unit has an evaporation capacity of 4 t/h (96 t/d), employing a "falling film + forced circulation dual-stage MVR" process. The steam consumption per ton of water evaporated is ≤0.05 t (only supplemental steam during startup). The byproduct anhydrous Na₂SO₄ has a purity ≥99% and a whiteness ≥88, achieving zero discharge of SDD wastewater and high-value utilization of salt resources.

I.Influent Characteristics

SDD synthesis employs an alkalization route using carbon disulfide and dimethylamine. The centrifuged mother liquor contains: Na₂SO₄ 200-240 g/L, SDD residue 15000 mg/L, COD 60000-80000 mg/L, color 25000 times, temperature 80℃, pH 11-12, and trace amounts of CS₂ and dimethylamine. It is prone to foaming, polymerization, and heat sensitivity.

II.Process and System Composition

1.Pretreatment Unit

Cooling to remove CS₂ (negative pressure stripping, CS₂≤5mg/L) → Neutralization (H₂SO₄, pH 7.5) → High-density softening (MgO+PAC, F⁻≤5mg/L, Ca≤20mg/L) → Tubular microfiltration (SDI≤3) → Two-stage preheating (condensate + secondary steam)

2. MVR Dual-Stage Evaporation

Falling film stage handles 70% of the evaporation, forced circulation stage is responsible for crystal growth, evaporation temperature 62℃, compressor temperature rise 20℃, compression ratio 1.8, adiabatic efficiency ≥85%. 3. DTB Fractional Crystallization: Seed crystals are inserted at a discharge density of 1.32 t/m³. Anhydrous Na₂SO₄ precipitates on the low-temperature side (55℃). Centrifugation yields ≤3% water content and ≥88 whiteness. The SDD-rich mother liquor is returned to the forced circulation section for concentration to 60% (solids removed), pumped into the mother liquor scraper evaporator, dried to ≥85%, and then sent to the RTO for incineration. The system has no waste liquid discharge.

III.Core Equipment Parameters:

1.Total Evaporation: 4 t/h (96 t/d)

2.Steam Consumption: ≤0.05 t/t water (MVR only requires start-up steam replenishment)

3.Heat Transfer Area: Falling film section 120 m², forced circulation section 80 m², total 200 m², design margin 20%

4.Compressor: Speed-increasing box-type centrifuge, impeller diameter 1.1 m, linear velocity ≤285 m/s, magnetic levitation bearing, design life 100,000 h. Vibration value <1.0mm/s

5.DTB crystallizer: Φ1800×4000mm, material 2507 + rubber lining, slurry density 25-35%

6.Centrifugal dryer: LW530×2200-N, separation factor 1500, throughput 3t/h, product water content ≤0.3%

IV.Performance and Advantages

1.Zero steam: MVR mechanical recompression, steam cost per ton of water <10 yuan, saving 90% of steam compared to triple-effect mixers.

2.Resource utilization: Na₂SO₄ meets industrial recycling standards, increasing the external sales price from 200 yuan/t to 650 yuan/t; SDD residue calorific value recovery, saving 0.5 million tons of coal annually.

3.Stable operation: Falling film + forced circulation dual-stage flow, forced scale prevention, annual operating time ≥8000h, availability >98%. 

4.Space-saving: Modular steel structure frame, single-story layout, occupying only 180m², 40% less space than a triple-effect caustic soda system.

5.Intelligent: Automatic control system, multi-variable prediction of evaporation rate, density, and vacuum degree, fluctuation ±1%.

VI. Operational Data (Performance Evaluation)

1.Water Production Rate: ≥90%, Condensate TDS≤100mg/L, COD≤30mg/L, Color≤5 times, reused as boiler feedwater.

2.Miscellaneous Salt Production: Na₂SO₄ 2.8t/d, Moisture Content≤0.3%, Whiteness≥88, Cl⁻≤0.03%, meeting the requirements for ion-exchange membrane caustic soda feedstock.

3.Mother Liquor Treatment: Dry solids 1.5t/d, Calorific Value 22MJ/t, RTO incineration recovers steam 0.8t/h, no waste liquid discharge from the system.

4.Energy Consumption Indicators: Steam 0.05t/t water, Electricity 28kWh/t water, Cooling Water 1.5t/t water.

VII. Economic and Environmental Benefits

Based on steam price of 180 yuan/t and electricity price of 0.65 yuan/kWh, the annual savings in steam costs are approximately 4.5 million yuan; the annual revenue from Na₂SO₄ resource utilization is 3 million yuan. Carbon reduction of 0.35tCO₂ per ton of water, resulting in a total annual emission reduction of 12,000 tons.

VIII. Service and Guarantee

1.One-stop turnkey solution: water quality testing + evaporator selection and design+manufacturing+ installation + commissioning + operation and maintenance.

2.Upgrade options available: expansion of the falling film section, compressor frequency increase, evaporation capacity can be increased to 6t/h, completed within 48 hours of downtime.

Choose the "Conqinphi 4t/h MVR evaporator system with rubber additive sodium formaldehyde sulfoxylate (SDD)" to reduce high COD mother liquor consumption and make every grain of salt more valuable!