The custom manufacturer of extraction tanks would like to introduce the principle of extraction and the selection of equipment.

　　Custom Manufacturer of Extraction Tanks: What is the principle behind the extraction method?

　　The principle of extraction involves adding a solvent that is immiscible with water but capable of effectively dissolving pollutants from wastewater, ensuring thorough mixing and contact between the solvent and the wastewater. Since the solubility of pollutants in the solvent is greater than their solubility in water, most of the pollutants in the wastewater are transferred into the solvent. The solvent is then separated from the wastewater, thereby achieving the goal of extracting pollutants and purifying the wastewater. The solvent used is called the extractant, the extracted pollutants are referred to as the solute, and the extractant containing the pollutants after extraction is known as the extract or phase. Wastewater treated by extraction is called the raffinate or phase.

　　The extractant used in the extraction process must exhibit excellent thermal and chemical stability. It should not only be immiscible with water but also incapable of undergoing any chemical reactions with impurities present in the wastewater, and it must not corrode equipment such as centrifugal extractors. At the same time, the extractant should be easy to recover and reuse. The extractant should possess good selectivity—that is, it should have a strong ability to separate specific pollutants from wastewater. The greater the density difference between the extractant and the wastewater, the better, as this facilitates rapid separation of the pollutant from the water after extraction. Furthermore, the surface tension of the extractant should be moderate. If the surface tension is too low, the extractant may emulsify in the wastewater, hindering phase separation. Conversely, if the surface tension is too high, although phase separation becomes easier, the dispersion will be poor, thereby impairing full contact between the two phases.

　　Custom Manufacturer of Extraction Tanks: Selecting Extraction Equipment

　　Since there are many types of extraction equipment, the following factors should generally be considered when selecting equipment:

　　① The physical properties of the system, such as density, interfacial tension, and ease of emulsification. For systems with a large density difference and low interfacial tension, equipment requiring no external energy can be selected. For systems with a small density difference and high interfacial tension, it is easy to choose equipment equipped with external energy.

　　② Determine the theoretical number of stages required to complete the given separation task. When the required number of theoretical stages is less than 2 to 3, any type of extraction equipment can meet the requirements. However, when more theoretical stages are needed—say, exceeding 4 to 5 stages—a sieve-tray column is recommended. If even more theoretical stages are required, equipment with external energy input can be selected, such as mixer-settlers, pulsed columns, or rotating-disc columns.

　　③ Regarding the residence time of the extractant, when the kinetics of the extraction process are rapid and the contact time between the extractant and the feed liquid is short, a centrifugal extractor can be used. Conversely, when the residence time is long, a mixer-settler is typically employed.

　　④ For low hourly processing capacities, packed columns and pulse columns can be used; when the processing capacity is high, mixed contactors, sieve-tray towers, and tray towers can be selected.

　　⑤ Factory conditions, such as the size of the area and the height of the workshop, the difficulty of equipment investment and maintenance, and experience in the design and operation of extraction equipment.

　　That’s all for today’s introduction to custom extraction tank manufacturers. Thank you for watching!