Compressed Air Systems Used in the Food and Beverage Industry

The food and beverage industry involves all companies involved in the processing, packaging, and distribution of food ingredients, which produces a wide range of food products including fresh, prepared, and packaged foods, alcohol, and non-alcoholic beverages.

As asian country’s economy continues to grow, the output of the food and beverage industry has continued to grow at a high rate over the past few years. The growth rate of the food and beverage industry has slowed down in recent years due to the macroeconomic impact. And the phenomenon of hot and cold has also appeared in the subsectors of the food and beverage industry: for example, the growth rate of liquor products plummeted, but casual food, convenience food segments in the next few years will maintain a high rate of growth.

Overall, although asian country’s macroeconomic growth rate has slowed down, the food and beverage industry still maintains good momentum, and the growth rate in the next few years is expected to be higher than the global growth rate of more than 50%. The output value of the food and beverage industry from 2014-2018 is shown in the following figure.

1. Processes in the Food and Beverage Industry

The food and beverage industry usually requires compressed air systems, of which the following treatments are available.

• Pipeline conveying liquids: milk, soy sauce, purified water, carbonated beverages, beer and wine.
• During fermentation: stirring of the liquid; passing air to increase the oxygen content. Examples: beer, yellow wine, soy sauce and vinegar.
• Mixing/Stirring in the dosing process: A method of mixing a liquid by introducing a stream of air into the liquid. Generally we use compressed air, but sometimes also use inert gases such as carbon dioxide and nitrogen. For example: blending of soy sauce, vinegar and wine.
• Aerating in carbonated beverages: Carbon dioxide is passed through a cylinder or storage tank.
• Air Stretching: PET bottle production.
• Conveying drives: e.g. in the slaughtering industry.
• Aseptic Packaging: Prepare pressure with sterile air.
• Blowing materials and removing impurities: hair blowing in the slaughtering industry, blowing minced meat. Blowing off powder for the cookie industry and cleaning equipment. Correction in the roasting process; using air pressure to get rid of the lees in the beer filtration process.
• Extruded materials: beer industry: after cooling the wort, sterile compressed air can be used to eject the wort from the sheet cooler. Filtration in the sugar industry, extrusion of sponges, extrusion of sugar juice.
• Drive the cylinders of the filling machine to produce a linear motion.
• Inflatable Packaging: Suitable for packaging of items with lower vacuum requirement and more inflatable amount.

All of these processes use plant gas, vacuum, high or low pressure compressed air.

2. Application of Compressed Air Systems

In these processes mentioned above, some of the compressed air does not come into contact with food or beverages. This type of compressed air is mainly used in power actuation, control cylinders and other mechanical action occasions. Since compressed air does not come into direct contact with food or beverages, the quality requirements for this type of compressed air are not very high. The pressure of compressed air is generally required to be about 0.6MPa, and the amount of air used can be determined according to the size of the production scale.

The other part, is compressed air that comes into indirect contact with food or beverages. For example, cans, beverage bottles, food packaging, etc., although compressed air does not come into direct contact with food or beverages, the requirements for compressed air are just as high. The exhaust pressure of compressed air is generally about 0.5 to 0.6MPa.

Other processes where compressed air is in direct contact with food or beverages. Generally, this type of compressed air is mainly used in a series of production processes, such as mixing, fermentation, bagging, blowing, drying, hot air spraying and pneumatic exhaust of processed raw materials. Compressed air must be de-oiled, de-bacterialized and deodorized, etc. The industry usually chooses oil-free screw compressors as the air source, and the compressed air then undergoes rigorous post-treatment. In addition to sterilization filters in the post-processing equipment, it is also necessary to configure air-water separators, high-efficiency precision filters, which are used to remove dust, water and oil in the compressed air to prevent contamination and accidents.

For this reason, compressed air quality is critical for the food and beverage industry. Table 1 shows the latest international standards for compressed air quality.

2.1 Introduction and Application of Air Compressors in the Food and Beverage Industry

Conventional air compressors can be categorized into reciprocating piston compressors, screw air compressors and centrifugal machines according to their working principle.

The principle of reciprocating piston compressor: through the rotation of the motor to drive the connecting rod and piston rod, so that the piston in the cylinder do reciprocating motion, so as to realize the suction, compression and exhaust process. Reciprocating piston compressors are currently being gradually replaced by screw compressors due to defects such as high vibration and noise.

The principle of centrifugal compressor: through the centrifugal impeller rotating at high speed, the air will be thrown to the back-end diffuser, and then by the diffuser pressure expansion to realize the air compression process. Centrifugal compressors are usually suitable for larger gas consumption.

Screw air compressors are the more common compressors today. The screw air compressor is a volumetric gas compressor with a working volume that allows for rotary motion. In the compressor there is a parallel configuration of a pair of rotors that engage with each other, and the process of air intake, compression, and exhaust is realized by the rotation of the rotors and the change of the clearance. Since the compression process generates a lot of heat, it requires lubricant to be continuously sprayed in the chamber where the rotor is located so as to lubricate the rotor and cool the compressed air. With the development of technology, advanced foreign compressor manufacturers have developed screw compressors with oil-free process. Oil-free operation of screw compressors is realized throughout the process by means of a high-precision rotor manufacturing process and a highly efficient cooling process.

Therefore, the process can be divided into oil compressors and oil-free compressors. Reciprocating piston compressors, centrifugal compressors and oil-free screw compressors are oil-free compressors.

As mentioned above, compressors in the food industry are often used in processes that directly or indirectly come into contact with food, such as material and liquid transportation, batching and mixing, or filling and blowing. Therefore it is often recommended in the food and beverage industry to use compressors with oil-free processes to reduce the risk of contamination of food and beverages being contacted by compressed air. In the production process of food and beverage in foreign countries, oil-free compressors have been widely used, but in China, the application of oil-free compressors in the food industry is still in the stage of promotion and popularization. Many food and beverage manufacturers for cost considerations, choose the oil-injected screw compressors to configure the production equipment for air post-treatment, which will invariably increase the risk of contamination of the end product due to air post-treatment failure.

2.2 Introduction and Application of Reprocessing in the Food and Beverage Industry

Large quantities of oil-water mixtures in compressed air can cause great harm to equipment and industrial air. Solid particles contained in the atmosphere itself enter the pipeline through the suction filter of the compressor. At the same time the relative humidity in the atmosphere is also generally high, the air is compressed and becomes saturated, and as the compressed air cools, the temperature decreases and the water vapor is converted to liquid water, at the same time, the compressed air produced in oil-injected compressors contains a certain amount of oil. Therefore, the wet saturated air after compression and condensation will be entrapped with a large number of liquid oil-water mixtures, which is the root cause of corrosion and rust of the equipment piping, pneumatic components and valves. Even if you choose an oil-free compressor, you can only make the compressed air free of oil, but you can’t realize that the compressed air is free of water and particulate impurities.

Compressed air is used in the food and beverage industry for filling, conveying powdered materials, fermentation and mixing, so once compressed air contains oil or other impurities it can cause contamination. In the food and beverage industry all of these contaminations can pose health risks to the end consumer and can cause substantial losses to the business. Therefore, when selecting a compressor, it is necessary to add post-processing purification equipment or dryers to filter water, oil and particles in the compressed air.

Normally compressed air in the food and beverage industry has to be classified as Class 2 or higher. After-treatment equipment is equipped with air-water separators and high-precision filters to remove particles, water and oil from the compressed air. Some process applications with direct food contact also require sterilization filters to ensure safety in the food production process.

2.3 Piping System

To ensure that high-quality compressed air can be successfully delivered to the air-using equipment or air-using terminals, in addition to the selection of the appropriate compressor and after-treatment, another important aspect is the piping system for delivering the compressed air. The piping material must be stable, non-toxic and non-hazardous, and not introduce solid impurities or other contaminants into the compressed air. For those pipelines that are in direct contact with food and beverage, the material required is sanitary stainless steel, but the cost of sanitary stainless steel is also relatively high.

Unlike conventional lines, Ingersoll Rand’s super lines are pressed from a high-performance aluminum alloy. After anodic oxidation treatment, the material performance is stable, the inner wall is smooth, and the life span is long. Not only can it ensure the quality of the compressed air delivered, but also the compression loss is extremely small, which saves energy for the user and reduces the operation cost. It is an ideal choice for most process applications. In contrast, stainless steel piping often requires fire welding during installation. Superpipe, on the other hand, has a simple and unique structure and is easy to install, which greatly improves installation speed. Comparison between super piping and traditional piping is shown in Table 2.

​

3 Examples of Applications

Budweiser, born in 1876 in the United States, has been in the development of more than 100 years with its pure taste and excellent quality to win the favor of consumers around the world, and become the world’s best-selling beer, so for a long time it has been known as the “King of Beer”. Also in China Budweiser has become the most recognizable and largest selling foreign brand of beer. Budweiser has invested in factories in Wuhan, Jinan, Foshan and Tangshan, and Ingersoll Rand has been a partner in selecting high-quality air compressors and systems for several Budweiser factories.

The application of compressed air in the making of Budweiser is divided into two main parts, one of which is not in direct contact with the ingredients, for example, it is used for instrumentation, equipment power gas and blowing lees after beer saccharification; the other part is required to be in contact with the raw material and is used for wort oxygenation and yeast expansion. After fully understanding the customer’s process and air consumption, Ingersoll Rand considers the investment cost and provides a comprehensive system solution for the customer, offering different air compressors for different air consumption requirements. The whole system of the air compressor consists of micro-oil screw, frequency conversion screw, oil-free screw air compressor, “wet” storage tank, pre-filter, dryer, post-filter and “dry” storage tank, as well as a set of control system and super pipeline, which not only saves initial investment and operating costs for the Budweiser Beer Festival, but also ensures the quality of the gas used.

4 Concluding Remarks

Because food hygiene is directly related to the safety of people’s lives, so for the food and beverage industry, the treatment of compressed air must be careful and we must protect the compressed air after-treatment equipment and piping system. If the compressed air used for food manufacturing and packaging is contaminated with bacteria, oil, etc., it will pose a health hazard to the end consumer and cause a lot of damage to the business. In the pre-investment and practical application, enterprises must understand the production process and gas quality requirements with targeted and rationalized selection of air compressors, reprocessing and piping systems, which not only makes the investment most economical for the company, but also ensures food hygiene and safety in terms of compressed air.