Particularity of pharmaceutical filter centrifuge The centrifuge is widely used in the pharmaceutical industry, and it is still the main equipment for separation in the current raw material production process. Due to the different applications, processes, and physical and chemical properties of the centrifuges of pharmaceutical manufacturers, the centrifuges also have different requirements, such as anti-corrosion requirements, explosion-proof requirements, media temperature, and workshop purification level. The following discusses some special issues involved in the application of filter centrifuges in the pharmaceutical industry. 1 Sealing requirements Whether the centrifuge is used for non-sterile drugs or sterile drugs, or for pharmaceutical intermediates or finished drugs, the production process places high demands on the environment. For example, in a clean workshop, there are Corresponding cleanliness requirements, the good sealing performance of the equipment keeps the outside effectively isolated from the inside of the machine. However, the solids, liquids, and gas phases in the inner cavity of the centrifuge must not cause pollution to the workshop environment. On the contrary, the external environment must not pollute the internal materials. Therefore, the pharmaceutical factory should inform the manufacturer of the centrifuge when placing an order and put forward sealing requirements. The improved design of the sealing performance of the centrifuge, and fully reflected in the manufacture, should be considered in the following aspects: 1.1 Sealing of the cover The cover is generally flip-over type, and there should be reliable sealing measures on the interface between the cover and the case. If the seal structure or material corrosion resistance fails, it may cause leakage of liquid and gas phases, causing harm to the environment and personnel. Dovetail grooves are processed on the flange of the machine cover, and a sealing strip is installed to ensure the positioning reliability of the sealing strip. The sealing strip has a trapezoidal hollow structure to ensure its sealing performance. The sealing strip is made of silicone rubber and other materials, and the sealing strip material is determined according to the anticorrosion requirements of the materials to be processed. 1.2 Sealing of bearing The sealing of the spindle nut and bearing position, the sealing measures of the previous traditional models are relatively simple, and can only achieve relative sealing. Such as the spindle nut part, the joint surface of the spindle nut and the drum, generally no sealing ring is provided, and the liquid phase or gas phase infiltration of the centrifuge is prone to occur during the operation, which causes corrosion to the spindle cone surface and even penetrates into the bearing, causing damage to the bearing , Thereby affecting the normal use of the machine. The upper bearing cover is generally provided with a skeleton seal and other structures, but a part of the upper bearing cover to the cone surface of the drum is exposed, and the gas mist in the centrifuge internal cavity may cause corrosion on the exposed surface of the main shaft. In centrifuges used in the pharmaceutical industry, most of the separated materials contain organic solvents such as solvents or media such as acids and bases. Therefore, the sealing requirements of these parts should be fully considered when ordering equipment. In the design, the above-mentioned structural improvements should be considered, such as the tightening and sealing of the upper end of the main shaft, the use of two shaft end ring stacks, and two O-ring isolation installation methods to eliminate the possibility of liquid leakage. For the seal on the upper side of the upper bearing cover, it may be considered to change the structural type of the upper bearing cover, such as setting a labyrinth sealing device to reduce or eliminate the erosion of the main shaft by the gas mist. The exposed surface can also be coated with nickel-phosphorus alloy to eliminate or reduce the possibility of corrosion. 1.3 Sealing of the working area of ​​the transmission belt The transmission belt of the traditional centrifuge is open, only a protective cover is provided at the motor end, mainly from the perspective of safety. However, the pollution of the dust generated by friction to the environment is not controlled, and it is not feasible to use it in a clean area. Therefore, the working area of ​​the transmission belt must be sealed to prevent the leakage of friction dust. 1.4 Sealing of other parts The external pipes of the centrifuge, such as feed pipes, washing pipes, washing pipes and other pipes, generally use the flange installation method to ensure the sealing performance of the interface. For occasions with high cleanliness requirements, the interface should be selected hygienic quick-open interface device to facilitate cleaning. The more complicated sealing part is the solid phase outlet of the lower discharge centrifuge. Due to its large discharge port and the special shape of the interface, it brings great difficulty to design and manufacture. The common practice is to transfer the hopper from the outlet of the bottom of the centrifuge to a round port with a suitable diameter, connect a butterfly valve, and install a gasket on the flange mounting surface to achieve the sealing requirements. Afterwards, the outlet of the butterfly valve was connected with a flexible tube to the silo. If the main product is a separated solid phase, the requirements for the solid phase are very high. Even the liquid phase dripping from the cleaning hole of the online cleaning tube is not allowed to enter the solid phase. Therefore, the hygienic-grade quick-open interface device should be used in the design of the on-line cleaning tube, so as to remove the cleaning tube after completing a separation and thoroughly clean the tube. There are many explosion-proof requirements in the production of the pharmaceutical industry. Because the medium has organic solvents such as methanol, ethanol, toluene, etc., the safety of the centrifuge during operation has become the primary requirement for type selection. 2.1 Several elements that caused an explosion The three elements that cause an explosion are temperature, fire source, and oxygen. Among them: (1) temperature, for a specific medium, whether it is liquid phase or gas phase, the working temperature of the centrifuge should be taken into consideration when designing the process, because it is a process problem, it will not be analyzed here in detail; In the design of the centrifuge, enough safe space should be applied to the moving parts to eliminate the possible mechanical friction and impact. The machine must have measures to eliminate static electricity. At the same time, the braking device is generally used in the form of energy-consuming braking (non-contact braking, the disadvantage is that the braking time is longer than the contact type, especially when the full load is large inertia. So), mechanical friction brakes are not allowed. In addition, for the transmission belt, anti-static belt is used to eliminate or reduce the possibility of static electricity. 2.2 Explosion-proof measures can be implemented When it comes to explosion-proof occasions, nitrogen protection may be considered. However, the nitrogen protection of some centrifuges is actually only a nitrogen inlet pipe and a nitrogen outlet pipe are provided on the casing. When the centrifuge is working, the inner cavity is filled. Into nitrogen. As for whether the nitrogen concentration can reach the safe range, there is no quantitative control, so the reliability of its nitrogen protection is very poor. An online oxygen detection device is added to the nitrogen protection system to detect the oxygen in the inner cavity of the centrifuge during operation, and control its oxygen content within a safe range, that is, to achieve quantitative control. Generally, when ordering, explosion-proof requirements should be put forward, and more precise manufacturing requirements should be placed on the configuration of the centrifuge, such as: configuration of explosion-proof motor, on-site explosion-proof button, anti-static belt, inverter control, explosion-proof solenoid valve, explosion-proof proximity switch, explosion-proof isolation Grid, electrostatic grounding, energy consumption braking, nitrogen protection, online detection of oxygen content, etc. However, not all occasions with explosion-proof requirements must be configured, and should be appropriately configured according to the actual process and environment. 3 Cleaning requirements In the inner cavity of the centrifuge, a plurality of cleaning heads or cleaning tubes are provided, and the centrifuge can clean the inside of the centrifuge without opening the cover or during the operation. The main points are the following parts: (1) cleaning the bottom surface of the drum and the bearing seat; (2) the surface of the liquid retaining plate and the outer surface of the drum drum; (3) the inner surface of the drum drum; (4) the inner surface of the flip cover and The surface of the feed, scraper and other devices; (5) The inner surface of the shell. 4 Anticorrosion requirements and surface treatment The pharmaceutical industry should generally choose a stainless steel structure. Although some external parts are not in direct contact with the material, it is still appropriate to choose a stainless steel material, which is more beneficial to the surface cleaning and the clean workshop environment. According to the corrosion data (chemical properties, temperature, concentration, etc.) of the separated materials, select the appropriate materials, such as 304, 321, 316L, titanium and other materials. For the pipes used, for some occasions with high cleanliness requirements, hygienic grade pipes and hygienic grade quick-opening structures should be used to eliminate possible pollution caused by pipelines. Also easy to clean. In addition, for some structural parts that are not in direct contact with the material or only support, it can also be made of stainless steel. During structural design and production, the surface is smooth and the transition is smooth, eliminating hygienic dead corners, and eliminating dead corners such as liquid accumulation and material accumulation. All stainless steel surfaces should be polished and polished to make them smooth. 5 Air source requirements Pneumatic actuating elements configured in the centrifuge, such as pneumatic scrapers, gas-assisted scrapers, gas recoil devices, etc., whose power source is gas (compressed air or compressed nitrogen), the gas source should be purified to ensure that the drugs are not Impurity contamination. If used in explosion-proof applications, the gas source should be nitrogen. 6 Requirements for cleaning of residual filter cake and regeneration of filter cloth In the centrifuges commonly used in the pharmaceutical industry, the discharge centrifuge (manual upper discharge or hanging bag discharge) is shown in Figure 1, which is one of the common models. The filter bag is raised every time it is discharged. It is said that the residual filter cake is easier to clean up, and the regeneration of the filter cloth is also more convenient, so I will not introduce it more here. Here we mainly talk about another common model, that is, the method of cleaning the residual filter cake and regenerating the filter cloth of the scraper discharge centrifuge, as shown in Figure 2. Scraper discharge centrifuge (LGZ, GK and other models), because it is an automatic scraper type centrifuge, the filter cloth is installed on the drum wall, and it is more difficult to remove and install than the upper discharge centrifuge There is a safe distance (5 ~ 10 mm) from the filter cloth to prevent the scraper from scratching the filter cloth. The existence of this residual filter cake layer is not a big problem for general chemical products. However, in the pharmaceutical industry, the presence of residual filter cake cannot meet the requirements for eliminating contamination between batches. To achieve the purpose of cleaning the residual filter cake, a gas-assisted scraper is set on the scraper, as shown in Figure 3. A gas recoil nozzle is provided on the outside of the drum filter hole. During scraping, high-pressure gas impacts the filter cloth and the residual filter cake layer from the outside to the inside through the drum filter hole, causing the filter cloth to oscillate in pulse and generate a displacement inward With a flexible thrust, the filter cloth is brought close to the blade edge to reduce the thickness of the residual filter cake layer. At the same time, the high-pressure gas sprayed by the gas recoil assisting blade blows off the residual filter cake on the filter cloth. Through this device, the residual filter cake can be effectively reduced or eliminated, and at the same time, the filter cloth can be regenerated to a certain extent. The cleaning of the residual filter cake can eliminate the residual filter during the next filtration of some materials with small particle size or high viscosity. The filtration resistance generated by the cake improves the filtration efficiency. 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The filter type centrifuge (hereinafter referred to as centrifuge) is a solid and liquid phase separation device. Because it is a forced separation under a centrifugal force field, the separation factor can reach 600 or even more than 1,000. The separation effect is good and the production capacity is large. Realize automatic control. Therefore, centrifuges are widely used in the pharmaceutical industry.
2 Explosion-proof requirements 