3500t/d Rubber Additives RD Wastewater Triple-Effect Evaporation Crystallization System + Mother Liquor Treatment System

I.Project Overview

This system is supporting equipment for a newly built 30,000-ton/year RD (2,2,4-trimethyl-1,2-dihydroquinoline) production line of a rubber additives group. The designed processing capacity is 3500 t/d (145 t/h). It adopts an integrated process of "triple-effect forced circulation + DTB fractional crystallization + mother liquor enrichment and incineration," with steam consumption ≤0.25 t/t water, Na₂SO₄ purity ≥99%, RD residue calorific value recovery, and zero wastewater discharge, making it the world's largest zero-discharge RD wastewater treatment plant.

II.Influent Characteristics

RD synthesis uses catalytic condensation of aniline and pyruvate. The centrifuged mother liquor contains: Na₂SO₄ 180-220 g/L, RD residue 15000 mg/L, COD 80000 mg/L, color 20000 times, temperature 95℃, pH 3-4, and contains trace amounts of aniline, acetone, and fluoride ions. High COD, high color, easy foaming, easy polymerization; traditional single-effect evaporator steam consumption is 0.45t/t water, and the equipment coking cycle is <48h.

III.Process Route

1.Pretreatment: Cooling and oil removal → Neutralization (NaOH + CO₂, pH 6.5) → High-density precipitation (MgO + PAC, F⁻≤10mg/L, SiO₂≤30mg/L) → Tubular microfiltration (SDI≤3)

2.Triple-effect forced circulation evaporation: Co-current operation, vacuum gradient -70→-82→-90kPa, evaporation temperature 85→73→60℃, heat transfer temperature difference between effects ≥10℃, forced circulation flow rate 3.8m/s, forced scale prevention; the first effect falls the film to bear 70% of the load, and the second and third effects use pure forced circulation to prevent coking.

3.DTB Fractional Crystallization: Seed crystals are introduced when the triple-effect discharge density is 1.28 t/m³. Anhydrous Na₂SO₄ precipitates on the low-temperature side (55℃). After centrifugation, the dry basis purity is ≥99%, and the whiteness is ≥88. The RD-rich mother liquor is returned to the second-effect evaporator for concentration to 65% (solids content), and then pumped into the mother liquor treatment system.

4.Mother Liquor Treatment System: Rich mother liquor → Evaporator (vacuum degree -0.095MPa, dry solids ≥85%) → Mother liquor dryer (steam 0.4MPa, product water content ≤3%) → RTO incineration (1100℃, residence time 2s). The RD residue calorific value is 28 MJ/t, and the recovered steam is 2.2 t/h. The system produces no waste residue.

IV. Core Equipment Parameters

1.Total Evaporation: 145t/h (3500t/d)

2.Steam Consumption per Unit: 0.25t/t water (triple-effect); MVR interface reserved, ≤0.08t/t water after upgrade

3.Heat Transfer Area: 850m² for the first effect, 750m² for the second effect, and 650m² for the third effect, totaling 2250m², with a 20% design margin

4.DTB Crystallizer: Two units, Φ3200×6500mm, material 2507 + rubber lining, crystal slurry density 25-35%

5.Mother Liquor Scraped Evaporator: Heat transfer area 120m², evaporation intensity 180kg/m²·h, motor power 45kW

6.Centrifugal Dryer: Separation factor 1600, processing capacity 15t/h, packaging capacity 5t/h

V. Performance and Advantages

1.Low Energy Consumption: Triple-effect + mother liquor heat pump, steam cost reduced by 44% compared to single-effect.

2.Resource Utilization: The external sales price of Na₂SO₄ has increased from RMB 200/t to RMB 650/t; RD residue calorific value recovery results in annual coal savings of 11,000 tons.

3.Stable Operation: Forced circulation + online CIP, annual operating time ≥8000h, equipment availability >98%.

4.Space Saving: Modular steel structure frame, double-layer layout, occupying only 1200m², 30% less than traditional four-effect systems.

5.Intelligent Control: Automatic control system, multi-variable prediction of evaporation rate, density, and vacuum degree, fluctuation ±2%; remote monitoring software with fault SMS push notifications.

VI.Operational Data (Performance Evaluation)

1.Water Production Rate: ≥85%, Condensate TDS≤120mg/L, COD≤50mg/L, Color≤10 times, reused as boiler feedwater.

2.Miscellaneous Salt Production: Na₂SO₄ 420t/d, Moisture Content≤0.3%, Whiteness≥88, Cl⁻≤0.1%, meeting the requirements for ion-exchange membrane caustic soda feedstock.

3. Mother Liquor Treatment: Dry solids 25t/d, Calorific Value 28MJ/t, RTO incineration recovery steam 2.2t/h, no waste liquid discharge from the system.

4. Energy Consumption Indicators: Live steam 0.25t/t water, Electricity consumption 22kWh/t water, Cooling water 2.0t/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 120 million yuan; the annual revenue from Na₂SO₄ resource utilization is 270 million yuan. Carbon reduction of 0.30tCO₂ per ton of water, resulting in a total annual emission reduction of 310,000 tons.

VIII.Service and Support

1.Turnkey solution including process package, design, manufacturing, installation, commissioning, and operation and maintenance.

2.48-hour response time.

3.An MVR compressor can be connected via a bypass to the live steam inlet, allowing for seamless connection within 72 hours of downtime, reducing steam consumption to 0.08t/t water in one step.