Liquid mixer principle
1. Solid Mixing Mechanism 1. The mixing process in which the convective mixed solid particles are turned inside the device and moved together with the particle group is called convection mixing. Under the action of convection, the material is turned over and displaced to achieve mixing.
2, shear mixing due to particle motion produces some smooth surface, shearing occurs between the interfaces of different components, and shear force acts on the interface, so that the process of particle breakage and mixing is shear mixing.
3. Diffusion mixing The local mixing caused by the turbulent movement of the particles resulting in the exchange of adjacent particles is called diffusion mixing. Diffusion mixing can occur when the shape, filling state, and flow rate of the particles are different. In the mixing process, the above three processes occur simultaneously, and the degree of each process varies depending on the structure of the agitator.
During solid mixing, the nature of the particles has a large effect on the uniformity of the mixture. The separation phenomenon that occurs after the solid particles are mixed and allowed to stand is called the segregation effect. Inconsistent particle size is prone to segregation effects, because small particles tend to flow down in the gap between large particles, resulting in segregation.
The shape of the particles has a large effect on the mixing effect. Common particles are cylindrical, spherical, granular, etc. It has been found that different particle shapes are likely to cause different degrees of mixing. When the other conditions are the same, the mixing effect of the cylindrical particles is good, and the spherical zui is poor.
Particle density is another important factor affecting the degree of mixing uniformity. Particles with the same particle size and the same density have a separation phenomenon during mixing due to the difference in flow velocity, and the heavy material sinks to the bottom of the device, and the light floats on the upper portion, so that the mixing effect is lowered.
The properties of the particles such as surface state, fluidity, adhesion, etc., affect the mixing uniformity to varying degrees.
Second, the liquid mixing machine common liquid mixing machinery has a batching tank, a jet mixer and the like. The compounding tank has a simple structure and is mainly composed of a cylinder body, a stirrer, a cylinder head and the like. The material is added from the top, and the uniformly mixed liquid flows out from the lower portion. Intermittent and continuous mixing operations are possible.
The jet mixer consists of main components such as a shrink nozzle, a throat, and a diffuser. The working principle is as follows: when the high-pressure liquid is fired from the compression section through the nozzle to the diffuser at high speed, a vacuum is generated at the throat, the solution to be mixed is sucked, the two solutions are mixed at the throat, and then the pump diffuser exits the tail. The tube is discharged. The high pressure liquid and the inhaled solution to be mixed produce a strong shear force in the mixing section, so that the two liquids are broken into small liquid micelles and diffused to achieve the mixing effect.
Third, the solid mixing equipment in the production of pharmaceutical preparations, often in the solid state of the bulk drugs, fillers, adjuvants, etc. after crushing and sieving and then mixing in special equipment, mixed powder can be used for tableting , capsules, granules and powders.
1. The unit operation of dividing the material particles by the sieve size according to the particle size is called screening.
After the raw materials are pulverized, the particle size of the particles is not uniform, and it is necessary to perform sieving before mixing. In the pharmaceutical production process, the tool used for screening is a standard sieve. China's drug screening is made by Taylor's standard and the Chinese Pharmacopoeia standard. The Taylor standard is the name of the screen containing the sum of a hole diameter and a wire diameter (approximation number) plus the unit mesh per inch length, such as a sieve with a single hole diameter and a single wire diameter per inch length. It is called a 100 mesh sieve. The Chinese Pharmacopoeia stipulates a total of nine sieve numbers. The inner diameter of the sieve hole of the first sieve is large, and the inner diameter of the sieve of the sieve No. 9 is small. See the appendix for details.
The pore size of the screening machine used in the pharmaceutical industry is made with reference to the Chinese Pharmacopoeia. Common screening machines are circular vibrating sieving machines and electromagnetic vibrating sieving machines. Figure 9-9 is a circular vibration machine and its structural schematic. Two unbalanced weights are mounted on the drive shaft of the motor. The upper weight causes the horizontal movement of the mesh screen, and the lower weight causes the sand net to move vertically, thereby synthesizing the three-dimensional vibration of the screen. The material falls into the center of the screen. After screening, the coarse material on the screen surface is discharged from the outlet, and the sieved material is discharged from the lower outlet. The diameter of the screen is generally 0.4 to 0.5 meters, and each can be made of one to five layers of screen.
The electromagnetic vibration sieving machine is composed of an electromagnet, a screen, a frame, a spring contactor, etc., and generates vibration by using a high frequency and a small amplitude. A sliding rail is installed in the screen, and the sliding rail is mounted on the bracket, and an electromagnetic vibration device is supported on the frame of the screen to reciprocate the screen along the sliding rail. The material is added from the high end of the screen, and the coarse material is discharged from the lower port of the screen surface, and the material is discharged from the bottom of the screen. The machine has a high vibration frequency of 3,000 to 3,600 times per minute and a small amplitude of only 0.5 to 1, which can be used for sieving of viscous medicines, and has high screening efficiency.
2. Solid particle mixing machine The solid particle mixing machine commonly used in pharmaceutical production can be divided into two types: fixed type mixer and rotary type mixer according to the movement mode. Now they are introduced as follows.
(1) Fixed Mixer 1 The slot mixer is equipped with a propeller. The drug particles can be assembled from the outward center to the kerosene to push the center drug particles to both ends to achieve uniform mixing. The tank body is rotatable about a horizontal axis to discharge the charge from the tank. The mixing time is automatically controlled and the charging volume is 80%.
2 double spiral conical mixer is installed in the mixing chamber of the double spiral conical mixer with two agitators parallel to the cone wall. The two agitators are connected at both ends of the cross arm of the transmission shaft and driven by the transmission shaft. Perform a circular motion while rotating. The mixed solid particles rise from the bottom under the rotation of the propeller, and circulate in the whole container under the action of revolution, and the mixing can be achieved in a short time (2-8 minutes).
(2) Rotary mixer 1 type mixer This machine is formed by welding two cylinders of different lengths, the angle of which is generally 80°, and each cylinder is provided with a sealing cover, which can be vacuumed. The method draws the material into the cylinder so that a sterile mixing operation can be performed. When the equipment is rotated, the material in the cylinder is continuously separated and mixed, and the mixing is achieved in a shorter time.
The rotation speed of the mixer is generally controlled at about 30% to 80% of the critical speed (8 to 20r/min), and its charging volume is 30%, which is mainly used for powder mixing.
2 Two-dimensional motion mixer drum mixer is a typical two-dimensional motion mixer. Its main structural components are the base, electric motor, mixing cylinder, transmission system and propeller blades in the cylinder. After the motor is started, the mixing cylinder rotates and oscillates, and the propeller in the cylinder acts to agitate the material in the cylinder, so that the materials are thoroughly mixed. The discharge port of the mixing drum deviates from the center line of the mixing drum, so that the machine has the characteristics of rapid mixing, large mixing amount, convenient discharging, and the like, and each batch of the solid material that can be charged is mixed.
The three-dimensional motion mixer three-dimensional motion mixer is composed of a base, a transmission system, an electrical control system, a multi-directional operating mechanism, a mixing cylinder and the like. Directly connected to the mixing cylinder in the drive system is a universal joint main drive shaft and a driven shaft. The mixing cylinder is oscillated, translated and rocked under the drive shaft, and produces a vigorous alternating pulsation. The eddy current generated during the movement of the material has a varying energy gradient, and the upper body generates accelerated flow and diffusion during the mixing process. At the same time, it avoids the phenomenon of material segregation and accumulation due to the centrifugal force of the general mixer, which broadens the scope of use of the machine and can be used for mixing various materials of different densities and different particle sizes.
The three-dimensional motion mixer has a loading coefficient of about 80%, a mixing uniformity of over 99.9%, a short mixing time, no temperature rise during mixing, and can be used for aseptic mixing because of its good sealing performance, so it is widely used in biopharmaceutical production. .