1. Introduction
Designing a new or renovated pharmaceutical factory is an important undertaking, encompassing pharmaceutical processes, equipment, civil engineering, HVAC, water supply and drainage, utilities, and other aspects - it is an integrated effort requiring coordination among multiple disciplines. Compared with the design of a mechanical factory, pharmaceutical factory design has many special considerations.
2. Applications and Quality Requirements for Compressed Air in Pharmaceutical Factories
2.1 Primary Applications of Compressed Air
In pharmaceutical factories, compressed air is mainly used in filling machines for liquid preparations; granulators, coating machines, capsule fillers, packaging machines, and printing machines for solid preparations; extraction tanks in extraction processes; as well as for laboratory and pilot-scale use, material conveying, drying, purging, pneumatic instruments, and automatic control systems. In many of the aforementioned applications, compressed air comes into direct contact with pharmaceutical products; therefore, strict quality requirements are imposed on compressed air in pharmaceutical factory design.
2.2 The Necessity of Compressed Air Quality Control
The quality of compressed air in pharmaceutical factories is primarily controlled in terms of its moisture content, oil content, dust particle content, and biological particle content. Additionally, the compressed air must be odorless.
Compressed air containing oil, when in direct contact with pharmaceutical products, will contaminate the drugs. Compressed air containing liquid water droplets can cause corrosion of pipelines, valves, and equipment; the water droplets and rust deposits will likewise contaminate the drugs and affect product quality.
The presence of large quantities of dust particles and microbial particles in the air is of great concern to the pharmaceutical industry. Particulate matter, especially dust, directly affects drug quality and can thereby endanger human life. Microorganisms (biological particles) pose an even greater hazard to the human body. Microorganisms, primarily referring to bacteria and fungi, not only cause pharmaceutical products to become contaminated and deteriorate, but once mistakenly administered - whether entering the body through the gastrointestinal tract or parenterally - they directly affect human health, with potentially more severe consequences. Therefore, compressed air used in pharmaceutical factories must primarily target the control of particulate matter and microorganisms. This is one of the key distinctions between pharmaceutical factories and other types of factories (such as electronics and machinery factories) that only control particulate matter.
3. Compressed Air Station Design for Pharmaceutical Factories
3.1 Determination of the Compressed Air Station Process Flow
The process flow for the compressed air station in a pharmaceutical factory is briefly outlined as follows:
Suction filter → Air compressor → Aftercooler → Air receiver tank → Pre-filter → Precision filter → Drying unit → Post-filter → Odor removal filter → Sterilizing filter → Distribution piping network
The above process flow is subject to different configurations depending on the scale of the pharmaceutical factory, the type of air compressor, and the specific quality requirements for the compressed air. During the design phase, the user's gas quality indicators and usage characteristics should be carefully studied and analyzed before a rational compressed air station process system is established.
3.2 Selection of Air Compressor Type
The commonly used air compressors fall into three categories: reciprocating (piston), screw, and centrifugal types.
Centrifugal compressors have a large single-unit capacity with an adjustment range of 70%–100%, but they are prone to surging at low air volumes, making this type unsuitable for pharmaceutical factories.
Reciprocating (piston) compressors, while lower in price, have large structural dimensions, require a robust concrete foundation, have many wearing parts, demand significant maintenance effort, produce considerable noise and vibration, and have a relatively low level of automation. For these reasons, they have been less commonly adopted in pharmaceutical factories in recent years.
Screw compressors feature compact dimensions, require only a light-duty foundation, produce no pulsating airflow, have low vibration and noise levels, require minimal maintenance, and offer a high level of automation.
3.3 Selection of Drying Units
Pharmaceutical factories have varying requirements for compressed air moisture content. For example, small-scale traditional Chinese medicine factories with a lower level of automation may only require a pressure dew point of 5°C to 10°C. In contrast, large- and medium-sized pharmaceutical factories with a higher level of automation and numerous pneumatic control instruments and devices require a pressure dew point of -20°C to -40°C.
Compressed air drying methods can generally be divided into two types: refrigerated and adsorption. When the pressure dew point requirement for the compressed air is greater than or equal to 3°C, an adsorption dryer or a combined refrigerated + adsorption drying system should be used.
Additionally, when selecting drying equipment, one should not rely solely on nameplate data; the effects of inlet compressed air temperature, pressure, and ambient temperature on dryer performance must also be taken into account.
3.4 Filter Selection
Filters should be selected and combined based on their respective functions, performance characteristics, and precision ratings. The treatment capacity should also be corrected according to the temperature and pressure of the compressed air.
3.5 Compressed Air Station System and Building Design
In the process system design and layout of the compressor station, the following issues should be considered:
A. When a refrigerated dryer is used, the pre-filter should be located upstream of the refrigerated dryer to prevent large quantities of liquid water, solid dust particles of various sizes, oil contamination, and oil vapor from entering the dryer directly, which would degrade its operating condition.
B. When an adsorption dryer is used, an oil removal filter should be installed upstream to remove oil contamination from the compressed air and prevent the desiccant from being "poisoned" and rendered ineffective. A post-filter should be arranged downstream to eliminate desiccant dust and other contaminants.
C. When a refrigerated dryer is used, the discharge temperature of the air compressor should also be noted. If the compressor discharge temperature exceeds the maximum allowable inlet temperature of the refrigerated dryer, a high-temperature model should be selected.
D. Ventilation design for the compressor station building
In the design of compressed air stations for pharmaceutical factories, we typically use air-cooled screw compressors with indoor air intake, making the ventilation measures for the station building critically important. Insufficient ventilation will cause the air compressor's flow rate to drop below its rated output. Excessively high ambient temperatures will make it difficult to start the compressor and can also lead to heat accumulation within the compressor enclosure, causing motor overheating or even burnout, thereby creating a fire hazard.
For the ventilation of the compressed air station, our standard design approach is as follows: air inlets (louvers) are installed at the lower portion of the exterior wall of the compressor room, with the number and area of louvers determined by calculation based on the station capacity. The distance between the louvers and the outdoor ground level is generally no less than 300 mm to prevent rain splash. The louver orientation should preferably face the shaded side of the building, and the inlets should not be located on the same side as the exhaust outlets to prevent short-circuiting of hot and cold air. Exhaust ducts are arranged at the cooling air discharge outlets of the air-cooled compressors to direct the cooling air outdoors. Additionally, mechanical exhaust fans are installed on the exterior wall of the compressor room for whole-room ventilation. Through these measures, the temperature in the compressor room is effectively reduced, thereby ensuring the normal operation of the air compressors and their auxiliary equipment.
Suzhou Pharma Machinery Co.,Ltd.
2026/09/21
Gino
