Extraction equipment

Extraction equipment Introduction Extraction equipment, also known as extractor, a type of mass transfer equipment for the extraction operation, can make the extractant and the liquid good contact, to achieve the complete separation of the components contained in the feed liquid, there are graded contact and differential contact two types . In the extraction equipment, usually one phase is dispersed in the other phase in the state of droplets, and the state of the liquid membrane is rarely dispersed.

Extraction equipment types There are many types of extraction equipment, which are divided into three types according to the equipment structure. The mixing clarifier is composed of two parts, the mixing chamber and the clarification chamber, and it belongs to the graded contact mass transfer equipment. An agitator is installed in the mixing chamber to promote droplet breakage and uniform mixing. Some stirrers can pull the heavy phase from underneath them, thereby ensuring that heavy phases flow between stages. The fining chamber is a hollow chamber with a large horizontal sectional area, sometimes equipped with guides and screens to accelerate the agglomeration of droplets. Depending on the separation requirements, the mixer clarifier can be used in a single stage or as a cascade. When the cascade is operated countercurrently, the feed solution and the extractant are added to the stages at both ends of the cascade, and the raffinate and extract are derived at the opposite stage. The working volume of the mixing chamber can be calculated from the total flow of feed solution and extractant times the time required for the extraction process. The horizontal cross-sectional area of ​​the fining chamber can be calculated from the flow of the dispersed phase liquid divided by the agglutination delamination speed of the droplets. These operating parameters must be determined experimentally. It is generally considered that when the mixing volume per unit volume consumes the same stirring power, the level effects are approximately equal. Therefore, when the design is enlarged, the production equipment can be designed according to the measured extraction time and delamination speed. The mixer clarifier has a simple structure, a high level of efficiency, a small amplification effect, and can adapt to various production scales, but the investment and operation costs are relatively large. Column towers used in extraction towers include packed towers, sieve tray towers, turntable towers, pulsating towers, and vibration towers. The towers are upright cylinders. The light phase enters from the bottom of the tower and overflows from the top of the tower; the heavy phase is added from the top of the tower and is led out from the bottom of the tower; both are reversed in the tower. In addition to sieve tray towers, most of the extraction towers belong to differential contact mass transfer equipment. The middle part of the tower is a working section, and the two ends are separation sections, which are used for the agglomeration and delamination of the dispersed phase droplets, and the sedimentation and separation of the fine droplets entrained in the continuous phase. In the extraction towers and sieve tray towers, the liquids are dispersed and mixed by their own energy, and thus the equipment performance is low, and it is only used for the occasions where extraction is easy or the requirements are not high.

The commonly used extraction tower types of extraction towers are: 1 Rotary tower In the working section, a set of ring plates are installed at equal distances, and the working section is divided into a series of small chambers. Each center of the chamber has a rotating disk as a stirrer. These discs are mounted on the spindle in the center of the tower and are rotated by mechanical devices outside the tower. The rotary table tower has a simple structure, a large processing capacity, and a very high separation efficiency, and is widely used in the petroleum refining industry and petrochemical industry. 2) The pulsation tower is equipped with a group of sieve plates (without overflow pipes) or packing in the working section. The pulsating liquid flow generated by the pulsation device is introduced into the bottom of the tower through a pipeline, so that the liquid in the whole tower reciprocates. The pulsating flow creates high-speed relative motion between sieve plates or packings to generate turbulence, which promotes fine and uniform droplets. The pulsation tower can achieve higher separation efficiency, but the processing volume is small, and it is often used in nuclear fuel and rare element factories. 3 vibrating plate tower The sieve plates are connected in series and driven by a mechanical device installed on the top of the tower to perform reciprocating motion in the vertical direction, thereby agitating the liquid flow and acting as a stirring effect in a pulsation tower. The design of the extraction tower is mainly to determine the diameter of the tower and the height of the working section. Divide the liquid flow rate by the operating speed to obtain the tower cross section and calculate the tower diameter. Then according to the characteristics of the tower and the properties of the system and the separation requirements, the mass transfer unit height and the number of mass transfer units are determined. Finally, the height of the working section of the tower is obtained by multiplying the two. There is also a calculation of the height of the working section by the equivalent height and the theoretical progression.

Centrifugal extractor for the extraction of the special centrifuge, because it can use the centrifugal force to accelerate the sedimentation and delamination of the droplets, so it allows to aggravate the stirring to make the droplets finer, thus strengthening the extraction operation. Centrifugal extraction machines have graded contact and differential contact. The former is equipped with a stirring device in a centrifugal separator to form a single-stage or multi-stage centrifugal extractor, and there are Vesta and cylindrical centrifugal extractors. The latter drum is equipped with a multi-layer concentric cylinder, with an opening in the cylinder wall, so that the liquid has a film-like and droplet-like dispersion, such as a Pod-Bernike centrifuge. Centrifugal extractors are particularly suitable for systems where the difference in the density of the two phases is small or easy to emulsify. Because the residence time of the material in the machine is very short, it is also suitable for the extraction of substances that are chemically and physically unstable.