A 2t/h triple-effect evaporator for the pharmaceutical industry to process sodium chloride.

I. Project Overview 

Sodium chloride, as a commonly used raw material salt, excipient, or reaction byproduct in pharmaceutical production, is widely present in wastewater from processes such as active pharmaceutical ingredient (API) synthesis, formulation production, and traditional Chinese medicine extraction and concentration. The recovery of sodium chloride from pharmaceutical wastewater not only involves resource reuse but also directly relates to environmental compliance and production cost control.

This project is a supporting facility for a chemical API manufacturer, designed to process "2 t/h of sodium chloride-containing pharmaceutical wastewater evaporation and concentration." The raw material comes from high-salt wastewater from the API synthesis process. The system is required to meet relevant regulatory requirements, the equipment materials must comply with pharmaceutical industry hygiene standards, the system must operate for no less than 7200 hours per year, and the condensate must meet reuse or discharge standards.

II. Process Background and Challenges Analysis

2.1 Material Characteristics

Pharmaceutical saline wastewater has the following characteristics:

Complex Composition: In addition to sodium chloride, it may contain small amounts of residual organic solvents, intermediates, catalysts, and trace heavy metals. It is necessary to prevent the decomposition or coking of organic matter at high temperatures.

High Heat Sensitivity: Some organic components are easily decomposed, discolored, or produce odors at high temperatures. Evaporation temperature must be strictly controlled.

High Hygiene Requirements: The pharmaceutical industry has clear requirements for equipment cleanliness, material traceability, and surface roughness.

Batch Variation: The concentration and composition of the wastewater vary between different production batches. The system needs to have a certain degree of operational flexibility.

2.2 Technical Challenges

1. Organic Matter and Coking Control: Trace amounts of organic matter easily coke on high-temperature heat exchange surfaces, affecting heat transfer efficiency and product quality.

2. Low-Temperature Evaporation Requirements: To retain the activity of the drug solution or prevent the decomposition of organic matter, evaporation must be completed at a lower temperature.

3. Hygienic Design: The equipment must meet the cleanliness validation requirements of the pharmaceutical industry, with no dead corners and easy cleaning.

4. Condensate Quality: Evaporation condensate must meet reuse or discharge standards and must not contain organic residues.

III. Solution and Process Route

Considering the characteristics of pharmaceutical wastewater and GMP requirements, this project adopts a "triple-effect falling film evaporation + forced circulation crystallization" process. The core process is as follows:

3.1 Pretreatment and Preheating: After the incoming liquid is precision filtered to remove suspended solids, it is preheated in multiple stages using system condensate and secondary steam waste heat, gradually increasing the temperature to the first-effect evaporation temperature.

3.2 Triple-Effect Falling Film Evaporation The preheated solution enters the triple-effect falling film evaporation system:

First Effect: Heated by external steam, the solution forms a uniform liquid film within the falling film tubes for rapid evaporation. Operating temperature is controlled between 85℃ and 95℃.

Second Effect: Utilizes the secondary steam generated in the first effect as a heat source. Operating temperature is between 65℃ and 75℃.

Third Effect: Utilizes the secondary steam from the second effect as a heat source. Operating temperature is between 45℃ and 55℃.

The triple-effect series design allows for cascaded utilization of heat energy, significantly reducing external steam consumption.

3.3 Forced Circulation Concentration and Crystallization The high-concentration sodium chloride solution, concentrated by the triple-effect evaporation, enters a forced circulation evaporator for further concentration. Once supersaturated, sodium chloride crystals precipitate. The crystal slurry is thickened in a thickener and separated by centrifugation. The wet salt enters the drying section, while the mother liquor is returned to the system for circulation or sent to the mother liquor treatment unit.

3.4 Condensate Recovery and Vacuum System The condensate generated by each effect is collected and treated uniformly to meet reuse or discharge standards; the system uses a vacuum pump set to maintain triple-effect negative pressure operation to ensure low-temperature evaporation.

IV. Key Equipment and Technical Parameters

1. Design Processing Capacity: 2t/h (evaporation water volume)

2. Feed Source: High-salt wastewater from pharmaceutical raw material synthesis

3. Evaporation Process: Triple-effect falling film evaporation + forced circulation concentration

4. First-effect temperature: 85℃～95℃

5. Second-effect temperature: 65℃～75℃

6. Third-effect temperature: 45℃～55℃

7. Main Material: 316L stainless steel (sanitary grade)

8. Surface Roughness: Ra≤0.8μm (flow surface)

9. Steam consumption per ton of water evaporated: Approximately 0.3-0.4 tons (fresh steam)

10. Designed annual operating time: ≥7200 hours

11. Automation control: PLC full-process automatic monitoring, online detection of temperature/pressure/liquid level

V. Project Highlights

5.1 Low-temperature stepped evaporation: Triple-effect falling film evaporation achieves low-temperature operation through vacuum control. The temperature decreases progressively from the first to the third effect, effectively avoiding high-temperature decomposition or coking of organic components, ensuring condensate quality, and simultaneously achieving stepped utilization of thermal energy.

5.2 Sanitary design: All flow-through components are made of 316L stainless steel with a surface roughness Ra≤0.8μm and a dead-angle-free design; Pipe connections use sanitary clamps or welding, supporting CIP (clean-in-place); Materials have complete traceability documentation, meeting the quality management requirements of the pharmaceutical industry.

5.3 High-efficiency heat transfer in falling film evaporation: The solution in the falling film evaporator is uniformly distributed in a thin film state on the inner wall of the heat exchange tubes, resulting in a high heat transfer coefficient, fast evaporation rate, and short residence time, making it particularly suitable for processing heat-sensitive materials. 5.4 Energy Saving and Consumption Reduction The triple-effect series design reduces steam consumption to about one-third of that of single-effect evaporation. The fresh steam consumption per ton of water evaporated is approximately 0.3–0.4 tons, which is relatively optimal in the pharmaceutical industry, balancing low-temperature operation with economic efficiency.

5.5 Automation and Cleaner Production The PLC control system enables automatic feeding, concentration control, automatic discharge, and fault interlock protection. Condensate, after passing testing, is reused in production or discharged in compliance with standards, reducing wastewater discharge. The system operates in a closed loop, effectively controlling the emission of volatile organic compounds.

VI. Operational Results

1. Evaporation Capacity: Stably reaches the design load of 2t/h;

2. Steam Consumption: Steam consumption per ton of water evaporated is controlled within 0.3-0.4t, meeting the expected energy efficiency of triple-effect evaporation;

3. Continuous Operation Cycle: Stable single-cycle operation with regular CIP cleaning;

4. Condensate Quality: Condensate COD and conductivity meet reuse or discharge standards;

5. Equipment Hygiene: Sanitary design facilitates cleaning verification and meets GMP requirements;

6. Automation Level: Stable system operation with minimal manual intervention and convenient maintenance.

High-salinity wastewater treatment in the pharmaceutical industry requires meeting environmental protection requirements while protecting heat-sensitive materials and adhering to sanitary production standards. This project utilizes a triple-effect falling film evaporation process, employing low-temperature stepped evaporation, sanitary material selection, and automated control to provide pharmaceutical companies with a stable and reliable sodium chloride concentration solution. Our company, with solid engineering experience and a deep understanding of pharmaceutical industry standards, helps clients achieve a coordinated balance between wastewater reduction, resource recovery, and cleaner production.