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How To Cleaning A Supercritical CO2 Extraction Machine

Supercritical CO2 extraction is a widely used method for extracting valuable compounds from various materials. However, the extraction equipment requires regular cleaning to remove residual pigments and lipophilic substances that adhere to the surfaces. This article presents a comprehensive overview of the cleaning process for supercritical CO2 extraction equipment, focusing on the cleaning steps, solvent selection, and drying process.

Cleaning Process

supercritical co2 extraction pumps
the co-solvent pump of supercritical co2 extraction machine

The cleaning process involves internal circulation to clean the pipelines and extraction vessels. Prior to circulation, anhydrous ethanol is added to the solvent system through the co-solvent pump. The cleaning agent consists of a mixture of supercritical CO2 and anhydrous ethanol in a volumetric ratio of 100:2 to 100:6. The liquid CO2 is stored in a tank and pressurized above the critical pressure using a high-pressure pump. Through a heat exchanger, the liquid CO2 is heated to above the critical temperature, entering the supercritical state. In this state, CO2 carries the anhydrous ethanol, allowing it to dissolve residual pigments and lipophilic substances.

The cleaning process is performed under controlled conditions of temperature (70-80°C) and pressure (15-18 MPa). The cleaning agent, comprised of supercritical CO2 and anhydrous ethanol, is circulated through the CO2 extraction vessel, CO2 separation vessel, circulation pump, mixer, filter, and related pipelines. The recommended cleaning time is 10-20 minutes. Extended contact time improves cleaning efficiency but also increases energy consumption and labor costs.

Separation and Recovery

After completing the cleaning process, the supercritical CO2 carrying residual pigments and lipophilic substances is depressurized through a throttle valve to 2-3 MPa. The heat exchanger cools down the CO2, reducing its solubility. In the separation vessel, the remaining pigments and lipophilic substances are separated from anhydrous ethanol. The CO2 fully gasifies, while the anhydrous ethanol is retained in the separation vessel. The gaseous CO2 is then liquefied by passing through a condenser and returned to the storage tank for the next cleaning cycle. The cleaning waste liquid can be collected through the lower valve of the separation vessel.

Drying Process

To remove residual anhydrous ethanol and achieve equipment drying, a rinsing step is performed using supercritical CO2 as the rinsing agent. The rinsing process is carried out at a temperature of 40-60°C and a pressure of 18-20 MPa for 5-10 minutes. Liquid CO2 is stored in a circulation tank and pressurized above the critical pressure using a high-pressure pump. Through the heat exchanger, the liquid CO2 is heated above the critical temperature, transforming into the supercritical state. The supercritical CO2 carrying residual anhydrous ethanol is sequentially circulated through the CO2 extraction vessel, CO2 separation vessel, high-pressure pump, mixer, filter, and related pipelines. The rinsing time is typically 5-10 minutes. After rinsing, the supercritical CO2 is depressurized through a throttle valve and cooled in the heat exchanger. In the separation vessel, the anhydrous ethanol is separated, while the CO2 fully gasifies and returns to the storage tank for reuse. The separated anhydrous ethanol can be collected through the lower valve of the separation vessel.

Summary

Proper cleaning of supercritical CO2 extraction equipment is essential to ensure optimal extraction performance and maintain product quality. The described cleaning process using supercritical CO2 and anhydrous ethanol effectively removes solid pigments and lipophilic substances, while the subsequent drying process ensures the removal of residual solvents.