3t/h phosphate polyether polyol triple-effect concentrator

I. Project Background

The client's wastewater mainly originates from the production process of polyether polyols and phosphate series products, amounting to approximately 70 tons daily. This wastewater is characterized by three highs: high COD (15000~25000 mg/L), high salt content (phosphate content 5%~8%), and high viscosity (due to residual polyether polyols). Furthermore, the polyether component is significantly thermosensitive, easily decomposing and deteriorating at high temperatures, and coking and adhering to the walls. Traditional single-effect evaporation consumes enormous amounts of energy, while direct disposal incurs high hazardous waste treatment costs. The company urgently needs an evaporation and concentration solution that balances energy saving and material protection.

After technical evaluation, our company customized a 3-ton/hour phosphate-polyether polyol triple-effect evaporation and concentration system for them, achieving the dual goals of significant wastewater reduction and recovery of valuable components.

II. Process Scheme

 This system employs a triple-effect co-current vacuum evaporation process, consisting of a first-effect falling film evaporator, a second-effect forced circulation evaporator, a third-effect crystallization concentrator, and a vacuum condensation system.

The first effect uses live steam for heating, preheating the wastewater to 75-85°C under negative pressure. The polyether polyol remains stable in the low-temperature environment, resulting in significant water evaporation and the generation of secondary steam. The second effect utilizes the secondary steam from the first effect as a heat source, driving the high-viscosity liquid at high speed through a forced circulation pump, preventing phosphate deposits and scaling on the heat exchange surfaces. The third effect further utilizes waste heat to concentrate the liquid to the designed concentration. The three effects operate in series, utilizing steam heat energy in a cascade manner, reducing overall energy consumption by approximately 65% compared to single-effect evaporation.

To address the foaming and heat-sensitive characteristics of polyether polyols, the system is equipped with an automatic defoamer dosing device and a low-temperature vacuum protection system, ensuring the evaporation temperature is controlled below 110°C throughout the process, effectively preventing material deterioration and coking. The concentrated phosphate is discharged as a supersaturated slurry, while the polyether polyol is enriched in the concentrated mother liquor. Both are then separately introduced into subsequent separation and purification processes.

III. Equipment Parameters

1. Processing Capacity: 3 t/h (phosphate-polyether polyol mixed wastewater)

2. Feed COD: 15000~25000 mg/L

3. Feed Solids Content: 6%~10%

4. Discharge Concentration Ratio: 8~10 times

5. Evaporation Method: Triple-effect co-current vacuum evaporation

6. First-Effect Evaporation Temperature: ≤110℃

7. Steam Consumption: Approximately 0.38 t steam/t water

8. System Vacuum Degree: -0.08~-0.085 MPa

9. Annual Operating Time: 7200 

IV. Operational Results

After commissioning, the system has operated stably for over 20 months, demonstrating excellent performance across various indicators:

1. Concentration Efficiency: Stable processing capacity of 3 tons of wastewater per hour, with a discharge volume reduction of over 85%, significantly reducing subsequent hazardous waste disposal volume;

2. Energy Saving: The triple-effect thermal coupling design reduces steam consumption to as low as 0.38 tons/ton of water, saving over one million yuan in steam costs annually;

3. Material Protection: Polyether polyols showed no significant decomposition under low-temperature vacuum conditions, with an effective component retention rate exceeding 92%. The concentrated mother liquor can be directly reused in upstream production or sold for purification;

4. Phosphate Recovery: The phosphate concentration in the concentrated slurry is increased to over 35%, creating favorable conditions for subsequent crystallization separation or resource utilization;

5. Operational Stability: The forced circulation design effectively handles high-viscosity materials, preventing coking and blockage on the heat exchange surfaces, resulting in zero unplanned shutdowns per year.

V. Project Highlights

1. Low-Temperature Vacuum Protection for Heat-Sensitive Substances: Operating at low temperature and negative pressure throughout the process, polyether polyols do not decompose, change color, or stick to the walls, fundamentally solving the problem of evaporating heat-sensitive organic wastewater.

2. Triple-Effect Cascade Energy Saving: Utilizing the latent heat of steam three times, steam consumption is only one-third that of single-effect evaporation, resulting in significant economic benefits in the energy-intensive chemical industry.

3. High-Viscosity Anti-Clogging Design: A double-effect forced circulation evaporator combined with a high-flow axial pump achieves a feed flow rate exceeding 2.5 m/s, preventing phosphate crystal deposition and allowing for long-term continuous system operation.

4. Resource-Based Closed-Loop System: Polyether polyol concentrate mother liquor is reused for production, and phosphate enrichment liquid is subsequently used for salt extraction, achieving triple benefits of "wastewater reduction - resource recovery - cost reduction".

The successful implementation of this project verifies the technological maturity and economic viability of the triple-effect vacuum evaporation process in treating heat-sensitive, high-viscosity, and high-salt organic wastewater from chemical industries. With a processing capacity of 3 tons per hour, this solution precisely matches the continuous production needs of medium-sized chemical enterprises, addressing both environmental compliance pressures and the recovery of valuable materials, truly achieving a balance between environmental and economic benefits.

Our company specializes in the research and development of evaporation concentration and crystallization separation technologies, offering a full range of solutions including multi-effect evaporation, MVR evaporation, and falling film evaporation. We can provide customized designs for different material characteristics. We welcome inquiries from customers in the chemical, pharmaceutical, and new materials industries to jointly explore the path of wastewater resource utilization.