250t/d Plate Quadruple Effect Evaporator for High-Salinity Wastewater from Rubber Additives and Sodium Sulfate

Project Background

This rubber additive manufacturer generates 250 tons of high-salt sodium sulfate wastewater daily, with a sodium sulfate content as high as 12%, COD of approximately 8000 mg/L, and a strongly alkaline pH. Previously, the traditional "dilution + biological treatment" process was used, which was not only costly but also difficult to meet environmental standards. The company faces significant environmental pressure and production bottlenecks.

Design Parameters

• Treatment Capacity: 250 tons/day

• Influent Sodium Sulfate: 12%

• Influent COD: 8000 mg/L

• Design Objectives: Sodium sulfate recovery rate ≥95%, condensate reuse rate ≥90%, achieving zero discharge

Process Flow

1. Pretreatment Stage: A combined "coagulation sedimentation + flotation" process is used to remove suspended solids and some organic matter from the wastewater, reducing the risk of scaling in the subsequent evaporator.

2. Evaporation and Crystallization Stage: A plate-type four-effect evaporator is selected, utilizing the latent heat of steam multiple times to achieve efficient concentration and crystallization of sodium sulfate.

3. Post-processing stage: Crystallized sodium sulfate is centrifuged and dried to obtain anhydrous sodium sulfate product; condensate is biochemically treated and reused in production.

Equipment Selection and Configuration

1. Plate-type four-effect evaporator: Made of 316L stainless steel, it features high heat transfer efficiency, small footprint, and easy maintenance.

2. Steam compressor: A high-efficiency centrifugal compressor is selected to ensure stable operation of the evaporator under low temperature differentials.

3. Automatic control system: A DCS distributed control system is adopted to achieve fully automated control, including real-time monitoring and adjustment of key parameters such as liquid level, temperature, pressure, and flow rate.

Auxiliary systems

1. Preheater: Utilizes secondary steam generated by the evaporator to preheat wastewater, improving system thermal efficiency.

2. Condensate tank: Collects condensate generated by the evaporator, treats it, and reuses it in production.

3. Vacuum system: Maintains the evaporator under high vacuum, lowering the boiling point and reducing energy consumption.

Treatment Results

• Sodium sulfate recovery rate: ≥95%

• Condensate reuse rate: ≥90%

• COD removal rate: ≥99%

• System operational stability: Continuous operation for 12 months without major malfunctions

Energy Consumption Indicators

• Steam consumption: 0.28 tons of steam/ton of water

• Electricity consumption: 15 kWh/ton of water

• Overall energy consumption: More than 60% lower than traditional single-effect evaporators

Economic Benefits

• Operating cost: 40% lower than traditional processes

• Investment payback period: Approximately 18 months

• By-product revenue: Annual sales revenue of anhydrous sodium sulfate is approximately 3 million RMB

Technical Advantages

1. High efficiency and energy saving: The four-effect evaporator fully utilizes the latent heat of steam, saving more than 60% energy compared to traditional single-effect evaporators.

2. Stable operation: The plate evaporator has a compact structure, high heat transfer coefficient, and strong anti-scaling ability.

3. High degree of automation: The DCS system achieves fully automated control, reducing manual intervention and operational errors.

4. Strong adaptability: The system can automatically adjust operating parameters according to wastewater quality fluctuations to ensure stable effluent compliance. 5. Resource Recycling: Achieves efficient recovery of sodium sulfate, turning waste into treasure and increasing enterprise economic benefits.

Customer Feedback: The customer stated, "Since adopting this plate-type four-effect evaporator system, our wastewater treatment costs have significantly decreased, and we have achieved the recycling and reuse of sodium sulfate, truly achieving a win-win situation for both environmental protection and economic benefits. The system has been running very stably for over a year, with almost no malfunctions, and its operation is very simple, greatly reducing our maintenance workload."

This case fully demonstrates the high efficiency, stability, and economy of plate-type four-effect evaporators in the treatment of high-salt sodium sulfate wastewater from rubber additives. Through scientific process design, reasonable equipment selection, and an intelligent control system, it not only achieves zero wastewater discharge and resource recycling but also brings significant economic and environmental benefits to enterprises, serving as a model for high-salt wastewater treatment in the rubber additives industry.