Abstract: This paper starts with the characteristics of several medicinal finished crystal filtration centrifuges at home and abroad. It is applicable to the rate, adaptability and economy of filter cake filtration fixed layer type and side filter type centrifuges. In contrast, it provides useful opinions and ideas for the development, development and selection of medicinal crystal filtration centrifuges.
The realization of liquid-liquid, liquid-solid, liquid-liquid/solid separation equipment in the centrifugal force field has been more than one hundred years old. The development of the nuclear industry has succeeded in the production of gas-gas separation equipment, using the centrifugal force field to realize the substance. The phase separation equipment has many branches. The solid phase material is filtered from the suspension as a branch of the liquid-solid centrifuge. In the 19th century, various crystal filtration centrifuges appeared. According to the size of the separated particles, the centrifuge discharge method can be divided into: (1) filter cake filtration, filter cake into a fixed layer intermittent discharge centrifuge (hereinafter referred to as filter cake filtration fixed layer centrifuge), such as three-legged artificial Unloading, hanging bag unloading centrifuge, scraper unloading centrifuge, turning bag centrifuge, etc.; (2) filter cake filtration, filter cake into moving layer continuous discharge centrifuge, such as horizontal pulsation unloading, screw unloading Material, unloading, vibration discharge, centrifugal force discharge centrifuge, etc. In the pharmaceutical industry crystal (or amorphous solid phase) filtration, filter cake filtration fixed layer centrifuge is widely used. These models have appeared in the general equipment, and can be used in chemical, light industry, food, pharmaceutical and other production. In the 1990s, centrifugal filters for pharmaceutical production were introduced abroad. They were retrofitted on the basis of general-purpose models and were used in GMP applications such as the HZ-ph series of KraussMaffei, the HSZ-ph series of Ferrum, and Heinkel. HF series, Okawara's CRF series, and different forms of pharmaceutical centrifugal filters produced by companies such as Fima; Comi/Condor.
1 Theoretical basis of filter cake filtration under pressure state At present, the separation operation of medicinal centrifugal filter introduced by foreign countries and domestic technology introduction or imitation is carried out by filter cake filtration method. Its design is based on the filter theory of pressure state filter cake. Filter cake filtration rate equation under pressure (the liquid phase flow in the filter cake layer is stagnant <1m/s=:..................(1) where: V- escapes liquid phase after filtering θ time ;A-filtration area; θ-filtration time; filter cake resistance of Rc-unit filtration area; filter medium resistance of Rm-unit filtration area; -filtration pressure; μ-liquid phase viscosity;
In the 1950s, JAStorrow et al. established a centrifuge filter cake filtration rate equation based on the basic equations of pressure filtration: (2) where: Ïc-liquid phase density; ω-angular velocity; k-filter cake Intrinsic permeability; h-rotor effective length H.Grace gives the rate equation based on factors such as filter cake specific resistance, void ratio, etc.: (3)
Where: α-filter cake specific resistance; total mass of solid phase particles in W-filter cake; W=Ï€hÏs(1-ε)(r32-r22); Ïs-solid phase density; ε-void ratio formula (2) (3) It is still one of the basic equations of the filter theory of filter cake filtration fixed layer centrifuge.
2 Foreign filter cake filtration fixed layer centrifuge features Foreign introduction of filter cake filtration fixed layer centrifuge The reason why there are different models, mainly depends on the discharge method: (1) manual discharge, suspension, three-legged, etc. Such centrifuges have been widely used in pharmaceutical production, and some of them have been replaced by automatic unloading machines with industrial development; (2) automatic unloading, recommended filter cake for drug crystallization filtration, fixed layer centrifuge representative machine There are horizontal scraper discharge centrifuge, bag centrifuge and centrifugal discharge and fluidized bed drying integrated gas discharge centrifuge. Briefly introduce their characteristics:
2.1 scraper discharge centrifuge blade scraper discharge centrifuge, using the inner wide scraper to rotate the solid phase in a certain angle, the medicinal scraper centrifuge is fully enclosed structure, with automatic control system, residual filter cake removal device as shown in Figure 5. The automatic in-place cleaning and in-situ sterilizing device shown in Figure 6 can be installed through the wall as required (the process operation part and the drive part are isolated and installed to achieve contamination-free and aseptic operation).
There are deficiencies: due to the unloading method, the solid phase crystal form is destroyed during the scraping and discharging, and it is difficult to completely discharge the fine particle solid phase in the centrifugal force field to form a hard filter cake, especially deposition. A layer of filter cake on both ends of the rotor.
2.2 The bag-turning centrifuge is a bag-turning centrifuge. The working part is composed of a perforated rotor and an inner rotor with a reversible filter bag. When the material is unloaded, the inner rotor pushes out the filter cake and simultaneously flips the filter bag to complete the removal of the filter cake. Shown. Its characteristics: completely discharge, does not destroy the solid crystal form, can achieve pressure filtration (≤6ban) when adding airtight device between the feed pipe and the rotor, and the external thermal cycle system can realize the solid phase drying in the rotor. However, there is a fatigue of the filter medium (filter bag) due to repeated overturning, which affects the service life and causes solid phase contamination. In addition, the pushing stroke is twice the effective length of the rotor, the structure is slightly large and the low-speed unloading is used to solve the problem of equipment stability.
2.3 Gas discharge centrifugal filter The centrifugal filter and the fluidized bed drying are integrated into a gas discharge centrifugal filter. This type of machine is dried in the machine, which reduces the turnover of the solution, but the suspension to be filtered. The nature requirements have certain limitations. Since today's drying equipment has been greatly developed and improved in terms of cleanliness, high efficiency, energy saving, etc., the economics (including equipment cost and use cost) of using a filter drying machine and selecting a filter and drying split modular device are to be discussed. Another note: it has its superiority under certain conditions.
Characteristics and Analysis of 3 Side Filter Centrifugal Filters At the end of the 20th century, China developed a bypass filter centrifugal filter (hereinafter referred to as PL centrifuge) for the filtration of raw material crystallization (including amorphous solid phase). It is intended to replace the three-legged centrifuge, the upper suspension centrifuge, etc., which were widely used in the pharmaceutical industry at the time, to realize automatic operation.
3.1 Working principle of the side filter centrifugal filter The working principle of the PL centrifuge: after the suspension enters the rotor, the solid phase sedimentation is completed simultaneously in the centrifugal force field, and the liquid phase does not pass through the filter cake and escapes directly from the side filter medium to realize liquid/solid separation. After the solid phase is dried in the rotor, it is pushed out by the pushing device in the turning state as shown in Fig. 9.
3.2 Filtering rate of the side filter centrifugal filter and the two-factor analysis of the material adaptability The working principle of the PL centrifuge determines the filtration rate and the adaptability of the PL centrifuge. These two main indexes are superior to the filter cake filtration fixed layer. Centrifuge, the analysis of these two indicators are as follows:
3.2.1 The filtration rate is compared with the filter cake filtration fixed layer centrifuge, and the L centrifuge is set as a one-time feed, and the rate equation of the PL centrifuge filtration is given according to the pressure state in the centrifugal force field: p4): Z-filter medium (r5-r2) h area, the ratio of the two, when η = 1, the two rates are equal, the above formula becomes: 5) When the filter medium is cotton or nylon cloth, Rm=10- 9m-1, because the Rm value is small for the simplified comparison, the Rm term is omitted, and the above formula is written as:........................(6)
When the actual amount of filter media area of ​​the PL centrifuge is Z1:
Z1=Z, the speed of the PL centrifuge and the filter cake filtration fixed layer centrifuge are equal;
Z1>Z, PL centrifuge rate is greater than filter cake filtration fixed layer centrifuge speed;
Z1 < Z, the PL centrifuge rate is less than the filter cake filtration fixed layer centrifuge rate.
The Z1 value is determined according to factors such as structural tolerance.
The Z1p value of the produced PL centrifuge, the calculated Zp value and the η value are as shown in Table 1, Z1 which is not designed and designed, and the calculated Z value and η value are shown in Table 2. It can be seen from the η value in the table that under the one-time feeding condition, the rate of the PL centrifuge escaping the liquid phase is more than 120% in the filter cake filtration fixed layer centrifuge rate, and the η value is higher under the continuous feeding condition. Practice has proved that PL650 is as high as 200%.
Table 1 Sanitary products PL centrifuge Z1, Z, h value model Z1pZpη
Table 2
Model Z1pZpη
3.2.2 Adaptability of filtered solid phase particle size Due to the principle of filtration and the method of unloading, the production scale is filtered with a filter cake. The fixed layer centrifuge can filter the solid phase particle equivalent diameter without adding a filter aid. The reason is ≥ 5 μm, because the fine particle specific resistance limits the filtration operation of the thick filter cake and the difficulty of forming a hard filter cake to increase the unloading. For PL centrifuges, it is difficult to discharge unaffected by the particle size (the non-porous surface of the PL centrifuge rotor wall is smooth, and the pressure of the solid phase on the filter medium during the discharge process is negative), as long as it can be filtered. Reach 100% removal. In addition, there is no filter cake filtration in theory, and the rate is not affected by the specific resistance of the filter cake during the filtration process, so that the centrifuge of the fixed layer centrifuge PL has a large adaptability to the solid particle size.
The premise of filter-free filtration is to achieve zero leakage theoretically in the filtration process (zero solid phase content in the effluent filtrate). Under zero leakage conditions, can the solid phase particles that can be filtered by the PL centrifuge be smaller than the filter cake? Filtering the particle values ​​defined by the fixed-layer centrifuge and meeting the production scale can be a problem that determines the adaptability of the PL centrifuge.
The suspension enters the PL centrifuge rotor, and the sedimentation force Fc of the particle a in the centrifugal force field is according to the stokes law: (7) where: Ïs-solid phase density; d-particle equivalent diameter;
The driving force of the filtrate passing through the filter medium on the side of the filter plate to produce particles. Fa:........................(8)
Where: uL-liquid phase flow rate, uL=βpr; β-filter medium characteristic parameter, β=q0/p00-filter medium pressure difference q0-the rate at which water passes through the filter medium at p0 pressure difference; r- at radius r The filtration phase pressure, pr=1/2ÏLω2(r2-r02); the tangential moving velocity of the us-solid phase particles; the solid phase particles have only radial velocity in the centrifugal force field, and the tangential velocity is zero. Equation (8) is written as: ……………(8')
The critical condition that the particles d are not deposited on the surface of the filter medium in the liquid phase: (9) where: f-the coefficient of friction between the surface of the filter medium and the solid phase particles;
The amount of liquid phase passing through the filter medium in the r to r0 range: ..................... (10) where: A-r to r0 interval filter medium total area, A = (r-r0) h1Z1; h1 - filter medium The width of the surface; the percentage of solid phase volume in the Ф-suspension;
According to the relationship of equations (7), (8) and (9), equation (10) is written as:
(11) Equation (11) is the amount of liquid phase escaped from the filter medium, and the amount of feed is: (...) (12) Formula (12) V0 = f(r) Figure 11 shows: feeding by ab line, that is, the feeding amount is decreased from b to a. Under this condition, the solid phase leakage rate is zero, and the average feeding amount is large. Due to the difficulty in controlling the decreasing feeding mode, it is abandoned in the application. Actually, the de line above the ac line is used, and the V0 value is in a constant state. The ac line feed amount is expressed in formula (11) as r=r2, and the solid phase leakage is always kept at zero. The penicillin potassium salt is filtered on a PL650 centrifuge as an example: the calculated value is <3> to 3500 L/h, and the feed is calculated. The average amount of 3000 L/h did not measure solid phase leakage.
The feed according to the de line indicates that r>r2 in the formula (11), and solid phase leakage occurs. According to the position of the de line, depending on the allowable solid phase leakage and the required injection volume, an aqueous suspension of barium sulfate (d≈2μm) precipitated with cesium hydroxide aqueous solution at -20 ° C was filtered on a PL650 centrifuge. For example, according to r=r2, the V0 value is 430L/h. When the actual feed amount is 810L/h, the solid phase leakage rate is 3.08% of the total solid phase. Taking activated carbon filtration in the production of itaconic acid as an example: the calculated value of V0 is 860L/h under the condition of r=r2, the average feed amount is about 1200L/h in production application, and the solid phase leakage rate is the total amount of solid phase. 1.25%.
According to the data in production and experiment, (1) the solid phase zero leakage can be realized by feeding under the ac line; (2) The filtration of the solid equivalent diameter of 2~5μm can be extended by increasing the feeding time (reducing the V0 value) The top phase is filled with the rotor (deposited to the position of r2) or the feed amount is increased within the allowable range of solid phase leakage. It shows that the PL series centrifuge can meet the production scale requirement of solid equivalent diameter ≥ 2μm suspension.
When the suspension with a solid diameter of ≥5μm is filtered, due to the inertia of the feed (as shown in Figure 12), the solid phase is deposited in an arc-shaped manner on the surface of the filter medium, and the utilization ratio of the filter surface is 50 to 75% of the total area ( The larger the particle, the closer it is to the lower limit), this factor should be taken into consideration when determining the amount of feed.
PL centrifuge has better filtration rate and adaptability than filter cake filtration centrifuge, and has the characteristics of complete discharge, no damage to crystal form and good sealing performance.
4 Conclusions Raw material medicine finished product filtration centrifuge In today's international market, the medicinal horizontal scraper discharge centrifuge, bag-turning centrifuge, etc. are available to meet GMP and FDA-approved models. Due to the continuous development of pharmaceutical, bioengineering, fine chemical and other industries, new models that meet the requirements will be continuously introduced in the field of centrifugal filtration. The centrifugal filtration and drying machine is a new type of machine, and it is subject to certain pharmaceutical production areas. The conditions are also limited to other models that have been modified according to the characteristics, such as three-legged scraper discharge and bag discharge centrifuge.
PL centrifuge is a self-innovated model in China. It has developed two small and medium-sized models, PL400 and PL650. Among them, PL650 has passed the ministry identification and small batch production, and it is separated from penicillin potassium salt and itaconic acid decolorization and deodorization. The liquid-solid separation applications of tea saponin extraction have achieved good results. Practice has proved that the side filtration principle is reliable, and the model manufactured according to this principle can completely replace several kinds of filter cake filtration fixed layer centrifuges recommended by foreign countries. PL centrifuges have relatively low cost of use and manufacturing costs based on the unit yield of the drug substance.
The realization of liquid-liquid, liquid-solid, liquid-liquid/solid separation equipment in the centrifugal force field has been more than one hundred years old. The development of the nuclear industry has succeeded in the production of gas-gas separation equipment, using the centrifugal force field to realize the substance. The phase separation equipment has many branches. The solid phase material is filtered from the suspension as a branch of the liquid-solid centrifuge. In the 19th century, various crystal filtration centrifuges appeared. According to the size of the separated particles, the centrifuge discharge method can be divided into: (1) filter cake filtration, filter cake into a fixed layer intermittent discharge centrifuge (hereinafter referred to as filter cake filtration fixed layer centrifuge), such as three-legged artificial Unloading, hanging bag unloading centrifuge, scraper unloading centrifuge, turning bag centrifuge, etc.; (2) filter cake filtration, filter cake into moving layer continuous discharge centrifuge, such as horizontal pulsation unloading, screw unloading Material, unloading, vibration discharge, centrifugal force discharge centrifuge, etc. In the pharmaceutical industry crystal (or amorphous solid phase) filtration, filter cake filtration fixed layer centrifuge is widely used. These models have appeared in the general equipment, and can be used in chemical, light industry, food, pharmaceutical and other production. In the 1990s, centrifugal filters for pharmaceutical production were introduced abroad. They were retrofitted on the basis of general-purpose models and were used in GMP applications such as the HZ-ph series of KraussMaffei, the HSZ-ph series of Ferrum, and Heinkel. HF series, Okawara's CRF series, and different forms of pharmaceutical centrifugal filters produced by companies such as Fima; Comi/Condor.
1 Theoretical basis of filter cake filtration under pressure state At present, the separation operation of medicinal centrifugal filter introduced by foreign countries and domestic technology introduction or imitation is carried out by filter cake filtration method. Its design is based on the filter theory of pressure state filter cake. Filter cake filtration rate equation under pressure (the liquid phase flow in the filter cake layer is stagnant <1m/s=:..................(1) where: V- escapes liquid phase after filtering θ time ;A-filtration area; θ-filtration time; filter cake resistance of Rc-unit filtration area; filter medium resistance of Rm-unit filtration area; -filtration pressure; μ-liquid phase viscosity;
In the 1950s, JAStorrow et al. established a centrifuge filter cake filtration rate equation based on the basic equations of pressure filtration: (2) where: Ïc-liquid phase density; ω-angular velocity; k-filter cake Intrinsic permeability; h-rotor effective length H.Grace gives the rate equation based on factors such as filter cake specific resistance, void ratio, etc.: (3)
Where: α-filter cake specific resistance; total mass of solid phase particles in W-filter cake; W=Ï€hÏs(1-ε)(r32-r22); Ïs-solid phase density; ε-void ratio formula (2) (3) It is still one of the basic equations of the filter theory of filter cake filtration fixed layer centrifuge.
2 Foreign filter cake filtration fixed layer centrifuge features Foreign introduction of filter cake filtration fixed layer centrifuge The reason why there are different models, mainly depends on the discharge method: (1) manual discharge, suspension, three-legged, etc. Such centrifuges have been widely used in pharmaceutical production, and some of them have been replaced by automatic unloading machines with industrial development; (2) automatic unloading, recommended filter cake for drug crystallization filtration, fixed layer centrifuge representative machine There are horizontal scraper discharge centrifuge, bag centrifuge and centrifugal discharge and fluidized bed drying integrated gas discharge centrifuge. Briefly introduce their characteristics:
2.1 scraper discharge centrifuge blade scraper discharge centrifuge, using the inner wide scraper to rotate the solid phase in a certain angle, the medicinal scraper centrifuge is fully enclosed structure, with automatic control system, residual filter cake removal device as shown in Figure 5. The automatic in-place cleaning and in-situ sterilizing device shown in Figure 6 can be installed through the wall as required (the process operation part and the drive part are isolated and installed to achieve contamination-free and aseptic operation).
There are deficiencies: due to the unloading method, the solid phase crystal form is destroyed during the scraping and discharging, and it is difficult to completely discharge the fine particle solid phase in the centrifugal force field to form a hard filter cake, especially deposition. A layer of filter cake on both ends of the rotor.
2.2 The bag-turning centrifuge is a bag-turning centrifuge. The working part is composed of a perforated rotor and an inner rotor with a reversible filter bag. When the material is unloaded, the inner rotor pushes out the filter cake and simultaneously flips the filter bag to complete the removal of the filter cake. Shown. Its characteristics: completely discharge, does not destroy the solid crystal form, can achieve pressure filtration (≤6ban) when adding airtight device between the feed pipe and the rotor, and the external thermal cycle system can realize the solid phase drying in the rotor. However, there is a fatigue of the filter medium (filter bag) due to repeated overturning, which affects the service life and causes solid phase contamination. In addition, the pushing stroke is twice the effective length of the rotor, the structure is slightly large and the low-speed unloading is used to solve the problem of equipment stability.
2.3 Gas discharge centrifugal filter The centrifugal filter and the fluidized bed drying are integrated into a gas discharge centrifugal filter. This type of machine is dried in the machine, which reduces the turnover of the solution, but the suspension to be filtered. The nature requirements have certain limitations. Since today's drying equipment has been greatly developed and improved in terms of cleanliness, high efficiency, energy saving, etc., the economics (including equipment cost and use cost) of using a filter drying machine and selecting a filter and drying split modular device are to be discussed. Another note: it has its superiority under certain conditions.
Characteristics and Analysis of 3 Side Filter Centrifugal Filters At the end of the 20th century, China developed a bypass filter centrifugal filter (hereinafter referred to as PL centrifuge) for the filtration of raw material crystallization (including amorphous solid phase). It is intended to replace the three-legged centrifuge, the upper suspension centrifuge, etc., which were widely used in the pharmaceutical industry at the time, to realize automatic operation.
3.1 Working principle of the side filter centrifugal filter The working principle of the PL centrifuge: after the suspension enters the rotor, the solid phase sedimentation is completed simultaneously in the centrifugal force field, and the liquid phase does not pass through the filter cake and escapes directly from the side filter medium to realize liquid/solid separation. After the solid phase is dried in the rotor, it is pushed out by the pushing device in the turning state as shown in Fig. 9.
3.2 Filtering rate of the side filter centrifugal filter and the two-factor analysis of the material adaptability The working principle of the PL centrifuge determines the filtration rate and the adaptability of the PL centrifuge. These two main indexes are superior to the filter cake filtration fixed layer. Centrifuge, the analysis of these two indicators are as follows:
3.2.1 The filtration rate is compared with the filter cake filtration fixed layer centrifuge, and the L centrifuge is set as a one-time feed, and the rate equation of the PL centrifuge filtration is given according to the pressure state in the centrifugal force field: p4): Z-filter medium (r5-r2) h area, the ratio of the two, when η = 1, the two rates are equal, the above formula becomes: 5) When the filter medium is cotton or nylon cloth, Rm=10- 9m-1, because the Rm value is small for the simplified comparison, the Rm term is omitted, and the above formula is written as:........................(6)
When the actual amount of filter media area of ​​the PL centrifuge is Z1:
Z1=Z, the speed of the PL centrifuge and the filter cake filtration fixed layer centrifuge are equal;
Z1>Z, PL centrifuge rate is greater than filter cake filtration fixed layer centrifuge speed;
Z1 < Z, the PL centrifuge rate is less than the filter cake filtration fixed layer centrifuge rate.
The Z1 value is determined according to factors such as structural tolerance.
The Z1p value of the produced PL centrifuge, the calculated Zp value and the η value are as shown in Table 1, Z1 which is not designed and designed, and the calculated Z value and η value are shown in Table 2. It can be seen from the η value in the table that under the one-time feeding condition, the rate of the PL centrifuge escaping the liquid phase is more than 120% in the filter cake filtration fixed layer centrifuge rate, and the η value is higher under the continuous feeding condition. Practice has proved that PL650 is as high as 200%.
Table 1 Sanitary products PL centrifuge Z1, Z, h value model Z1pZpη
Table 2
Model Z1pZpη
3.2.2 Adaptability of filtered solid phase particle size Due to the principle of filtration and the method of unloading, the production scale is filtered with a filter cake. The fixed layer centrifuge can filter the solid phase particle equivalent diameter without adding a filter aid. The reason is ≥ 5 μm, because the fine particle specific resistance limits the filtration operation of the thick filter cake and the difficulty of forming a hard filter cake to increase the unloading. For PL centrifuges, it is difficult to discharge unaffected by the particle size (the non-porous surface of the PL centrifuge rotor wall is smooth, and the pressure of the solid phase on the filter medium during the discharge process is negative), as long as it can be filtered. Reach 100% removal. In addition, there is no filter cake filtration in theory, and the rate is not affected by the specific resistance of the filter cake during the filtration process, so that the centrifuge of the fixed layer centrifuge PL has a large adaptability to the solid particle size.
The premise of filter-free filtration is to achieve zero leakage theoretically in the filtration process (zero solid phase content in the effluent filtrate). Under zero leakage conditions, can the solid phase particles that can be filtered by the PL centrifuge be smaller than the filter cake? Filtering the particle values ​​defined by the fixed-layer centrifuge and meeting the production scale can be a problem that determines the adaptability of the PL centrifuge.
The suspension enters the PL centrifuge rotor, and the sedimentation force Fc of the particle a in the centrifugal force field is according to the stokes law: (7) where: Ïs-solid phase density; d-particle equivalent diameter;
The driving force of the filtrate passing through the filter medium on the side of the filter plate to produce particles. Fa:........................(8)
Where: uL-liquid phase flow rate, uL=βpr; β-filter medium characteristic parameter, β=q0/p00-filter medium pressure difference q0-the rate at which water passes through the filter medium at p0 pressure difference; r- at radius r The filtration phase pressure, pr=1/2ÏLω2(r2-r02); the tangential moving velocity of the us-solid phase particles; the solid phase particles have only radial velocity in the centrifugal force field, and the tangential velocity is zero. Equation (8) is written as: ……………(8')
The critical condition that the particles d are not deposited on the surface of the filter medium in the liquid phase: (9) where: f-the coefficient of friction between the surface of the filter medium and the solid phase particles;
The amount of liquid phase passing through the filter medium in the r to r0 range: ..................... (10) where: A-r to r0 interval filter medium total area, A = (r-r0) h1Z1; h1 - filter medium The width of the surface; the percentage of solid phase volume in the Ф-suspension;
According to the relationship of equations (7), (8) and (9), equation (10) is written as:
(11) Equation (11) is the amount of liquid phase escaped from the filter medium, and the amount of feed is: (...) (12) Formula (12) V0 = f(r) Figure 11 shows: feeding by ab line, that is, the feeding amount is decreased from b to a. Under this condition, the solid phase leakage rate is zero, and the average feeding amount is large. Due to the difficulty in controlling the decreasing feeding mode, it is abandoned in the application. Actually, the de line above the ac line is used, and the V0 value is in a constant state. The ac line feed amount is expressed in formula (11) as r=r2, and the solid phase leakage is always kept at zero. The penicillin potassium salt is filtered on a PL650 centrifuge as an example: the calculated value is <3> to 3500 L/h, and the feed is calculated. The average amount of 3000 L/h did not measure solid phase leakage.
The feed according to the de line indicates that r>r2 in the formula (11), and solid phase leakage occurs. According to the position of the de line, depending on the allowable solid phase leakage and the required injection volume, an aqueous suspension of barium sulfate (d≈2μm) precipitated with cesium hydroxide aqueous solution at -20 ° C was filtered on a PL650 centrifuge. For example, according to r=r2, the V0 value is 430L/h. When the actual feed amount is 810L/h, the solid phase leakage rate is 3.08% of the total solid phase. Taking activated carbon filtration in the production of itaconic acid as an example: the calculated value of V0 is 860L/h under the condition of r=r2, the average feed amount is about 1200L/h in production application, and the solid phase leakage rate is the total amount of solid phase. 1.25%.
According to the data in production and experiment, (1) the solid phase zero leakage can be realized by feeding under the ac line; (2) The filtration of the solid equivalent diameter of 2~5μm can be extended by increasing the feeding time (reducing the V0 value) The top phase is filled with the rotor (deposited to the position of r2) or the feed amount is increased within the allowable range of solid phase leakage. It shows that the PL series centrifuge can meet the production scale requirement of solid equivalent diameter ≥ 2μm suspension.
When the suspension with a solid diameter of ≥5μm is filtered, due to the inertia of the feed (as shown in Figure 12), the solid phase is deposited in an arc-shaped manner on the surface of the filter medium, and the utilization ratio of the filter surface is 50 to 75% of the total area ( The larger the particle, the closer it is to the lower limit), this factor should be taken into consideration when determining the amount of feed.
PL centrifuge has better filtration rate and adaptability than filter cake filtration centrifuge, and has the characteristics of complete discharge, no damage to crystal form and good sealing performance.
4 Conclusions Raw material medicine finished product filtration centrifuge In today's international market, the medicinal horizontal scraper discharge centrifuge, bag-turning centrifuge, etc. are available to meet GMP and FDA-approved models. Due to the continuous development of pharmaceutical, bioengineering, fine chemical and other industries, new models that meet the requirements will be continuously introduced in the field of centrifugal filtration. The centrifugal filtration and drying machine is a new type of machine, and it is subject to certain pharmaceutical production areas. The conditions are also limited to other models that have been modified according to the characteristics, such as three-legged scraper discharge and bag discharge centrifuge.
PL centrifuge is a self-innovated model in China. It has developed two small and medium-sized models, PL400 and PL650. Among them, PL650 has passed the ministry identification and small batch production, and it is separated from penicillin potassium salt and itaconic acid decolorization and deodorization. The liquid-solid separation applications of tea saponin extraction have achieved good results. Practice has proved that the side filtration principle is reliable, and the model manufactured according to this principle can completely replace several kinds of filter cake filtration fixed layer centrifuges recommended by foreign countries. PL centrifuges have relatively low cost of use and manufacturing costs based on the unit yield of the drug substance.
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