In the production process of the pharmaceutical industry, dust pollution not only affects the quality of drugs and threatens the health of operators, but also may cause safety risks (such as dust explosions). Therefore, efficient dust removal is one of the core links for the compliance and safety of pharmaceutical production. Medium-efficiency bag filters, as key equipment in dust removal systems, are widely used in pharmaceutical dust control scenarios due to their stable filtration efficiency and strong adaptability. This article will conduct a detailed analysis from four dimensions: application scenarios, core technical features, key points for selection, and optimization directions.
I. Core application Scenarios of Medium-Efficiency Bag Filters in the Pharmaceutical Industry
The sources of dust in the pharmaceutical industry are diverse (such as raw material crushing, mixing, granulation, tablet pressing, coating, etc.), and the properties of the dust vary greatly (such as organic dust, inorganic dust, bacteria-containing dust, etc.). Medium-efficiency bag filters are mainly used in the “pretreatment + intermediate purification” stage, connecting primary filtration and high-efficiency filtration (HEPA). The specific application scenarios are as follows:
Dust removal in the production process of solid dosage forms
Solid dosage forms (such as tablets, capsules, and granules) are the areas where dust is most concentrated in the pharmaceutical industry. The application of medium-efficiency bag filters runs through key processes:
Crushing/sieving process: When raw materials (such as Chinese medicinal materials and chemical raw materials) are crushed, a large amount of fine dust is produced. Medium-efficiency bag filters can be connected to local dust collection hoods to capture dust with a particle size of ≥1μm, preventing the dust from spreading into the workshop environment and reducing raw material waste at the same time.
Mixing/granulation process: When the mixer and granulator are in operation, the powder is prone to escape due to stirring and air flow disturbance. The medium-efficiency bag filter can filter wet dust containing binders through the “negative pressure suction” method (moisture-resistant filter materials should be selected), preventing the dust from clogging the subsequent high-efficiency filters.
Tablet pressing/coating process: The high-speed operation of the tablet press die will produce powder debris. During the liquid spraying and drying process in the coating pot, fine particles will be generated. Medium-efficiency bag filters can intercept such dust, ensuring the accuracy of tablet pressing and the uniformity of coating, while reducing the frequency of equipment maintenance.
2. Tail gas treatment from the production of active pharmaceutical ingredients
After the synthesis of chemical active pharmaceutical ingredients, they need to go through processes such as drying and crushing. The tail gas may contain trace amounts of active pharmaceutical ingredient dust (such as dust from antibiotics and hormones). If directly discharged, it will cause environmental pollution and pose occupational exposure risks. Medium-efficiency bag filters can be used as pretreatment equipment for exhaust gas. They can first remove most of the dust (filtration efficiency ≥85%, in accordance with ASHRAE 52.2 standard), and then be combined with activated carbon adsorption or high-efficiency filtration. Meet the requirement of “particulate matter emission concentration ≤10mg/m³” stipulated in the “Emission Standard of Air Pollutants for Pharmaceutical Industry” (GB 37823-2019).
3. Return air purification in clean workshops
Pharmaceutical clean workshops (such as D-class and C-class clean areas) need to maintain a stable air flow organization. If dust is carried in the return air system, it will increase the load on high-efficiency filters and shorten their service life. Medium-efficiency bag filters can be installed in the return air duct to intercept the fine dust that settles in the workshop (such as fiber dust generated by personnel movement and dust from equipment wear), reducing the dust concentration in the clean area and ensuring the long-term efficient operation of HEPA filters.
4. Special dust control scenarios
For pharmaceutical dust with high moisture content (such as dust after spray drying) or slight corrosiveness (such as certain inorganic acid salt dust), medium-efficiency bag filters can prevent dust from adhering to the filter bags or corroding the equipment by customizing filter materials (such as polyester anti-sticking filter materials, polypropylene corrosion-resistant filter materials). At the same time, it should meet the pharmaceutical compliance requirements of “no secondary pollution” (such as avoiding the shedding of filter material fibers and mixing them into drugs).
Ii. Core technical Characteristics and Pharmaceutical Compatibility of Medium-Efficiency Bag Filters
The requirements for dust removal equipment in the pharmaceutical industry are not limited to “high efficiency”, but also need to meet special demands such as GMP compliance, low maintenance costs, and no cross-contamination. The technical design of medium-efficiency bag filters should revolve around these demands, and the core technical features are as follows:
1. Filtration efficiency and classification: Adapted to the particle size distribution of pharmaceutical dust
Pharmaceutical dust is mostly fine particles (with particle sizes concentrated between 0.5 and 10μm). The efficiency classification of medium-efficiency bag filters needs to precisely match this characteristic. Currently, the mainstream in the industry follows the ASHRAE 52.2 standard. Common compatible grades and application scenarios are as follows:
| ASHRAE 52.2 grade |
Filtration efficiency for dust ranging from 0.3 to 1.0μm |
Suitable scenarios for the pharmaceutical industry | Core advantage |
| MERV 7 | 50%-65% | Dust removal in the raw material storage room and return air in the non-clean area | Low cost, suitable for pre-treatment of coarse dust |
| MERV 8 | 65%-75% |
Primary filtration in the crushing/sieving process |
Balancing efficiency and wind resistance, it is suitable for scenarios with high air volume |
| MERV 9 | 75%-85% | Dust removal for granulation/tablet pressing process and return air for D-class clean area | Efficiently intercept fine dust and reduce the load on HEPA |
| MERV 10 | 85%-95% | Pre-treatment of tail gas from the drying of active pharmaceutical ingredients and return air in the C-level clean area | Near-high efficiency filtration, suitable for scenarios with high cleanliness requirements |
Note: In the pharmaceutical industry, processes that come into direct contact with drugs (such as sterile preparations) usually require the addition of HEPA after medium-efficiency filters. The efficiency of medium-efficiency filters should be ≥MERV 9 to prevent fine dust from penetrating into the clean area.
2. Filter material selection: Balance compliance and dust compatibility
Filter material is the core of medium-efficiency bag filters. Its material and structure directly affect the filtration efficiency, service life and compliance. The comparison of commonly used filter materials and their characteristics in the pharmaceutical industry is as follows:
| Filter material material | Temperature resistance range | Corrosion resistance | Anti-sticking/anti-shedding performance | GMP compliance | Adapt to dust types |
| Polyester (PET) | -20℃-130℃ | Resistant to weak acids and alkalis | It can be used as an anti-stick coating (such as PTFE coating) | Compliant with FDA 21 CFR Part 177.1520 | Organic raw material medicine dust, traditional Chinese medicine powder |
| Polypropylene (PP) | -30℃-90℃ |
Resistant to strong acids and alkalis |
It has anti-sticking properties by itself and no fiber shedding | Food-grade certification is available, with no additives precipitated | Inorganic acid salt dust, moist dust |
| Glass fiber | -100℃-260℃ | Resistant to strong corrosion | It has good rigidity and is not prone to deformation | It is necessary to detect the amount of fiber shedding and adapt to high-temperature scenarios | Dust from high-temperature drying processes (such as melt granulation) |
Key requirements: Pharmaceutical filter materials must pass the tests of “no biological activity” and “no volatile harmful substances” to prevent the migration of filter material components from contaminating the drugs. At the same time, it should have the feature of “easy to clean”. In some scenarios, washable filter materials (such as polyester-coated filter materials) can be selected to reduce the replacement cost.
3. Structural design: Meets the requirements of low pollution and easy maintenance in the pharmaceutical industry
The structural design of medium-efficiency bag filters needs to avoid problems such as “dust accumulation dead corners” and “disassembly and assembly pollution”. The core structural optimization includes:
3. Structural design: Meets the requirements of low pollution and easy maintenance in the pharmaceutical industry
The structural design of medium-efficiency bag filters needs to avoid problems such as “dust accumulation dead corners” and “disassembly and assembly pollution”. The core structural optimization includes:
Bag structure: It adopts a “multi-bag parallel” design, increasing the filtration area (usually the filtration area of a single filter is 5-20 square meters), reducing the filtration rate (controlled at 1-2m/min), and minimizing dust penetration. The opening of the filter bag is sealed with an “elastic clamp” to prevent air leakage (air leakage rate ≤0.5%, in compliance with ISO 14644-3 requirements).
Frame material: 304 stainless steel or food-grade ABS plastic is selected to prevent metal rust and the generation of impurities. The surface of the frame undergoes “passivation treatment” to reduce dust adsorption.
Disassembly and assembly design: It adopts a “drawer type” or “quick-release type” structure. When replacing the filter bags, there is no need to disassemble the entire equipment, reducing the risk of operators coming into contact with dust. Some high-end models are equipped with “filter bag damage alarm devices” (such as differential pressure sensors) to monitor the status of the filter bags in real time and prevent dust leakage caused by filter bag damage.
4. Energy consumption and operational stability: Compatible with the continuous production requirements of the pharmaceutical industry
Pharmaceutical production mostly operates continuously for 24 hours. The energy consumption and stability of medium-efficiency bag filters are of vital importance
Frame material: 304 stainless steel or food-grade ABS plastic is selected to prevent metal rust and the generation of impurities. The surface of the frame undergoes “passivation treatment” to reduce dust adsorption.
Disassembly and assembly design: It adopts a “drawer type” or “quick-release type” structure. When replacing the filter bags, there is no need to disassemble the entire equipment, reducing the risk of operators coming into contact with dust. Some high-end models are equipped with “filter bag damage alarm devices” (such as differential pressure sensors) to monitor the status of the filter bags in real time and prevent dust leakage caused by filter bag damage.
4. Energy consumption and operational stability: Compatible with the continuous production requirements of the pharmaceutical industry
Pharmaceutical production mostly operates continuously for 24 hours. The energy consumption and stability of medium-efficiency bag filters are of vital importance
Wind resistance control: The initial wind resistance of a new filter bag is usually ≤120Pa. As dust accumulates, the wind resistance will gradually increase. When the wind resistance reaches 250-300Pa, the filter bag needs to be replaced (or cleaned). By optimizing the filter bag spacing and air flow distribution, the operating air resistance can be reduced and the energy consumption of the fan can be decreased.
Temperature and moisture resistance: For high-temperature dust in the pharmaceutical drying process (such as 100-120℃), temperature-resistant filter materials (such as glass fiber) should be selected. For wet dust (such as the tail gas from spray drying, with a relative humidity of ≥80%), anti-condensation filter materials (such as polypropylene membrane-coated filter materials) should be selected to prevent the filter bags from absorbing moisture and caking.
Iii. Key Points for Selection and Compliance of Medium-Efficiency Bag Filters
When the pharmaceutical industry selects medium-efficiency bag filters, both “technical compatibility” and “GMP compliance” must be met simultaneously. The core selection points are as follows:
Selection based on the characteristics of dust
Dust particle size and concentration: If the dust particle size is ≤1μm and the concentration is ≥50mg/m³, MERV grade 10 filter material should be selected. If the dust particle size is ≥5μm and the concentration is ≤10mg/m³, MERV grade 8 filter material can be selected to balance efficiency and cost.
Chemical properties of dust: For acidic dust (such as hydrochloride types), polypropylene filter material is preferred; for alkaline dust (such as carbonate types), polyester filter material is preferred; for solvent-containing dust (such as ethanol volatile dust), solvent-resistant filter material (such as PTFE-coated polyester) should be selected.
Dust viscosity: For high-viscosity dust (such as granulation dust containing binders), anti-sticking coating filter materials (such as PTFE-coated polyester) should be selected, and the distance between filter bags should be increased to prevent dust adhesion and filter bag clogging.
2. Selection based on working condition parameters
Processing air volume: Based on the design air volume of the dust removal equipment (for example, the air volume of a local dust removal hood is usually 1000-5000m³/h), calculate the required filtration area of the filter (filtration area = processing air volume/filtration rate, the filtration rate is usually taken as 1-2m/min) to avoid dust penetration due to excessively high filtration rate.
Operating temperature and humidity: For high-temperature conditions (> 100℃), select glass fiber filter material; for medium-temperature conditions (50-100℃), choose polyester filter material; for low-temperature and high-humidity conditions (< 50℃, RH≥80%), choose polypropylene filter material. Avoid deformation or moisture absorption of the filter material.
Installation space: When the space for the return air system in the clean workshop is limited, “compact” bag filters (such as thin structures with a depth of ≤300mm) can be selected. For outdoor exhaust gas treatment, a “vertical” structure can be selected to save floor space.
3. Key Points of GMP compliance
Material certification: Materials such as filter materials, frames, and sealants need to provide “food grade” or “pharmaceutical grade” certification (such as FDA certification, EU 10/2011 certification) to prevent the release of harmful substances.
Traceability: Each filter must be accompanied by a “Product Qualification Certificate”, which includes information such as the batch of filter material, production time, and test report, meeting the GMP requirements for “material traceability”.
Cleaning and disinfection: If the filter is installed in a clean area (such as Class C or Class B), it must have a “sterilizable” feature (for example, the frame can withstand 121℃ moist heat sterilization or VHP sterilization) to prevent the growth of microorganisms. After the filter bags are replaced, the interior of the equipment needs to be cleaned to prevent cross-contamination.
Emission compliance: In coordination with subsequent high-efficiency filtration or adsorption equipment, ensure that the particulate matter concentration in the final exhaust is ≤10mg/m³ (in compliance with GB 37823-2019), and at the same time prevent dust escape during filter bag replacement (operation must be carried out in a closed environment).
Iv. Directions of Technological Optimization and Industry Development Trends
With the increasing demand for “green production” and “intelligent compliance” in the pharmaceutical industry, the technological development of medium-efficiency bag filters is showing the following trends:
1. Filter material technology upgrade: higher efficiency and longer service life
Nano-coated filter material: By applying a nano-scale PTFE coating on the surface of polyester filter material, the dust stripping rate can be increased to over 95%, extending the service life of filter bags (from 3-6 months to 8-12 months), and reducing the frequency of cleaning at the same time.
Antibacterial filter media: For biopharmaceutical scenarios (such as vaccines and antibodies), filter media containing silver ions or antibacterial polymers are developed, which can inhibit the growth of microorganisms on the surface of filter bags (antibacterial rate ≥99%) and prevent cross-contamination.
2. Intelligent operation and monitoring
Intelligent differential pressure monitoring system: Integrating high-precision differential pressure sensors and Internet of Things (IoT) modules, it can monitor the changes in the air resistance of filter bags in real time, push “replacement reminders” through the cloud platform to avoid omissions in manual inspections, and simultaneously record operational data (such as air volume, temperature, and differential pressure) to meet GMP data traceability requirements.
Automatic dust cleaning technology: For high-concentration dust scenarios (such as raw material drug crushing), a “pulse jet + acoustic wave dust cleaning” combined system has been developed, which can automatically remove the dust adhering to the surface of the filter bags, maintain stable filtration efficiency, and reduce downtime for maintenance.
3. Low-carbon and sustainable design
Recyclable filter materials: Develop degradable polyester or recycled polypropylene filter materials. After the filter bags are scrapped, they can be recycled and reused (with a recovery rate of ≥80%), reducing the generation of solid waste.
Low-energy consumption structure: By optimizing the arrangement of filter bags and air flow channels, the resistance of the filter is reduced (the initial air resistance drops from 120Pa to below 80Pa), which can reduce the energy consumption of the fan by 15% to 20%, in line with the “dual carbon” goals of the pharmaceutical industry.
V. Summary
Medium-efficiency bag filters play a crucial role of “connecting the upper and lower levels” in efficient dust removal in the pharmaceutical industry. Their application must be closely integrated with the characteristics of process dust, GMP compliance requirements, and operational stability needs. Through reasonable selection (such as choosing MERV grades based on dust particle size and filter materials based on chemical properties) and technical optimization (such as intelligent monitoring and nano-coated filter materials), the dust removal efficiency can be effectively improved, maintenance costs can be reduced, and the quality of drugs and production safety can be guaranteed. In the future, as the pharmaceutical industry pursues “intelligence” and “low-carbonization”, medium-efficiency bag filters will develop in a more efficient, intelligent and sustainable direction, providing stronger support for the compliance and greenness of pharmaceutical production.
Temperature and moisture resistance: For high-temperature dust in the pharmaceutical drying process (such as 100-120℃), temperature-resistant filter materials (such as glass fiber) should be selected. For wet dust (such as the tail gas from spray drying, with a relative humidity of ≥80%), anti-condensation filter materials (such as polypropylene membrane-coated filter materials) should be selected to prevent the filter bags from absorbing moisture and caking.
Iii. Key Points for Selection and Compliance of Medium-Efficiency Bag Filters
When the pharmaceutical industry selects medium-efficiency bag filters, both “technical compatibility” and “GMP compliance” must be met simultaneously. The core selection points are as follows:
Selection based on the characteristics of dust
Dust particle size and concentration: If the dust particle size is ≤1μm and the concentration is ≥50mg/m³, MERV grade 10 filter material should be selected. If the dust particle size is ≥5μm and the concentration is ≤10mg/m³, MERV grade 8 filter material can be selected to balance efficiency and cost.
Chemical properties of dust: For acidic dust (such as hydrochloride types), polypropylene filter material is preferred; for alkaline dust (such as carbonate types), polyester filter material is preferred; for solvent-containing dust (such as ethanol volatile dust), solvent-resistant filter material (such as PTFE-coated polyester) should be selected.
Dust viscosity: For high-viscosity dust (such as granulation dust containing binders), anti-sticking coating filter materials (such as PTFE-coated polyester) should be selected, and the distance between filter bags should be increased to prevent dust adhesion and filter bag clogging.
2. Selection based on working condition parameters
Processing air volume: Based on the design air volume of the dust removal equipment (for example, the air volume of a local dust removal hood is usually 1000-5000m³/h), calculate the required filtration area of the filter (filtration area = processing air volume/filtration rate, the filtration rate is usually taken as 1-2m/min) to avoid dust penetration due to excessively high filtration rate.
Operating temperature and humidity: For high-temperature conditions (> 100℃), select glass fiber filter material; for medium-temperature conditions (50-100℃), choose polyester filter material; for low-temperature and high-humidity conditions (< 50℃, RH≥80%), choose polypropylene filter material. Avoid deformation or moisture absorption of the filter material.
Installation space: When the space for the return air system in the clean workshop is limited, “compact” bag filters (such as thin structures with a depth of ≤300mm) can be selected. For outdoor exhaust gas treatment, a “vertical” structure can be selected to save floor space.
3. Key Points of GMP compliance
Material certification: Materials such as filter materials, frames, and sealants need to provide “food grade” or “pharmaceutical grade” certification (such as FDA certification, EU 10/2011 certification) to prevent the release of harmful substances.
Traceability: Each filter must be accompanied by a “Product Qualification Certificate”, which includes information such as the batch of filter material, production time, and test report, meeting the GMP requirements for “material traceability”.
Cleaning and disinfection: If the filter is installed in a clean area (such as Class C or Class B), it must have a “sterilizable” feature (for example, the frame can withstand 121℃ moist heat sterilization or VHP sterilization) to prevent the growth of microorganisms. After the filter bags are replaced, the interior of the equipment needs to be cleaned to prevent cross-contamination.
Emission compliance: In coordination with subsequent high-efficiency filtration or adsorption equipment, ensure that the particulate matter concentration in the final exhaust is ≤10mg/m³ (in compliance with GB 37823-2019), and at the same time prevent dust escape during filter bag replacement (operation must be carried out in a closed environment).
Iv. Directions of Technological Optimization and Industry Development Trends
With the increasing demand for “green production” and “intelligent compliance” in the pharmaceutical industry, the technological development of medium-efficiency bag filters is showing the following trends:
1. Filter material technology upgrade: higher efficiency and longer service life
Nano-coated filter material: By applying a nano-scale PTFE coating on the surface of polyester filter material, the dust stripping rate can be increased to over 95%, extending the service life of filter bags (from 3-6 months to 8-12 months), and reducing the frequency of cleaning at the same time.
Antibacterial filter media: For biopharmaceutical scenarios (such as vaccines and antibodies), filter media containing silver ions or antibacterial polymers are developed, which can inhibit the growth of microorganisms on the surface of filter bags (antibacterial rate ≥99%) and prevent cross-contamination.
2. Intelligent operation and monitoring
Intelligent differential pressure monitoring system: Integrating high-precision differential pressure sensors and Internet of Things (IoT) modules, it can monitor the changes in the air resistance of filter bags in real time, push “replacement reminders” through the cloud platform to avoid omissions in manual inspections, and simultaneously record operational data (such as air volume, temperature, and differential pressure) to meet GMP data traceability requirements.
Automatic dust cleaning technology: For high-concentration dust scenarios (such as raw material drug crushing), a “pulse jet + acoustic wave dust cleaning” combined system has been developed, which can automatically remove the dust adhering to the surface of the filter bags, maintain stable filtration efficiency, and reduce downtime for maintenance.
3. Low-carbon and sustainable design
Recyclable filter materials: Develop degradable polyester or recycled polypropylene filter materials. After the filter bags are scrapped, they can be recycled and reused (with a recovery rate of ≥80%), reducing the generation of solid waste.
Low-energy consumption structure: By optimizing the arrangement of filter bags and air flow channels, the resistance of the filter is reduced (the initial air resistance drops from 120Pa to below 80Pa), which can reduce the energy consumption of the fan by 15% to 20%, in line with the “dual carbon” goals of the pharmaceutical industry.
V. Summary
Medium-efficiency bag filters play a crucial role of “connecting the upper and lower levels” in efficient dust removal in the pharmaceutical industry. Their application must be closely integrated with the characteristics of process dust, GMP compliance requirements, and operational stability needs. Through reasonable selection (such as choosing MERV grades based on dust particle size and filter materials based on chemical properties) and technical optimization (such as intelligent monitoring and nano-coated filter materials), the dust removal efficiency can be effectively improved, maintenance costs can be reduced, and the quality of drugs and production safety can be guaranteed. In the future, as the pharmaceutical industry pursues “intelligence” and “low-carbonization”, medium-efficiency bag filters will develop in a more efficient, intelligent and sustainable direction, providing stronger support for the compliance and greenness of pharmaceutical production.
