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Technologiebeitrag Prozessgas

Gas compression in the process gas and refrigeration industry

Custom-made designs for optimum transport and compression in the process gas and refrigeration industry can only be achieved if the requirements of each individual case correspond one hundred percent with the selected machine design. Before making a purchase decision, therefore, it is basically necessary to always consider the respective individual prevailing circumstances in detail from two perspectives: From the perspective of the future plant operator the current process requirements are crucial. And from the point of view of the equipment supplier these requirements must be correspondingly realised by the selection of the optimum machine design. However, a manufacturer can only fulfil these conditions if it has the necessary specialist knowledge and the corresponding range of machinery. Aerzen Maschinenfabrik has been manufacturing positive displacement blowers since 1868 and screw compressors since 1943. Aerzen has also been supplying blowers and compressors for gas compression in the process gas and refrigeration industry for over 60 years. Over this period, Aerzen has become a globally successful supplier of equipment to this specialist sector with impressive credentials in many industries, including the chemical and petrochemical industries, the steel and soda industries as well as for biomethane gas production. At Aerzen the primary focus is: "On the detailed analysis of the current situation at the customer before any other considerations. The essential criteria include the composition of the gas to be compressed, the inlet pressure and temperature, the required outlet pressure and temperature, the ambient temperature, the expected flow rates and the quantities of cooling water available for cooling. These and other parameters are essential prerequisites for a customised quotation, which also takes account of particular requirements such as special motors, frequency inverters and sound insulation measures etc." Equipment for the compression of gases must meet very specific and demanding requirements in all applications. It must not only be characterised by a very high technical gas-tightness due to the partially flammable or toxic gases. It must also meet the relevant operational guidelines demanded by the customer (e.g. ATEX regulations and Ex certifications). In addition, the materials to be used depend on the substance being pumped and the existing on-site process requirements. Depending on the type of machine, therefore, nodular cast iron, cast steel or stainless steel components will be used. 

Three compressor systems for customised solutions

Even though the company is a significant global player, the manageable size of the company and its great flexibility as a manufacturer provide distinct advantages in making an informed and targeted decision. For a custom made gas compression solution for the process gas and refrigeration industry, Aerzen offers a wide range of oil-free air rotary displacement blowers as well as screw compressors with oil injection and oil-free compression in the following ranges: 

Rotary displacement blowers, oil-free compression

GR Series
Pressure differences up to 1,5 bar
Intake volume flows from 100 to 50,000 m³/h
GQ Series

Pressure differences up to 1,5 bar
Intake volume flows from 15,000 to 100,000 m³/h

Screw compressor

Oil Injected compression
VMY 36 Series (refrigeration and process gas)
Single step pressure difference up to approx. 20 bar,
Intake volume flows from 500 to 8,900 m³/h
VMY 56 Series (refrigeration and process gas)
Pressure difference up to 25 bar;
Intake volume flows approx. 300 to 2,700 m³/h

Oil-free compression
VR Series
Pressure difference up to 52 bar
Intake volume flows approx. 650 to 120,000 m³/h

Following careful preparation in the quotation, engineering and project phases as well as in the short commission period, despite its complexity, the customer therefore always receives a very customised, sophisticated and robust solution. Aerzen gas compressors offer the operator a high standard of quality using state-of-the-art technology, high-energy efficiency and long service life, sometimes exceeding more than 30 years. 

GR Series rotary displacement blowers

The double-leaf, oil-free compression GR series includes process gas compressors for pressure differences up to 1,500 mbar and air intake flow rates of 100-50,000 m³/h. The systems, which operate on the positive displacement principle, can automatically adapt to changing operating conditions. They are used, for example, as coke oven and blast furnace gas blowers in the steel industry, and for the compression of H2-, CH-, CO mixed gas, water vapour and specific critical or toxic gases. Depending on the process requirement, Aerzen can use different materials such as nodular cast iron, cast steel or cast stainless steel for these oil-free compression systems, including the rotors and individual seal variants for the conveying chamber. The oil and conveyor chambers here are completely separated by neutral chambers. Due to their particularly rugged design the systems are resistant to impurities in the gas such as dust, tar and dirt particles or liquid fractions. Water or solvents, as well as cleaning or cooling agents, can be injected for cleaning and cooling. 

GQ Series rotary displacement blowers

For pressure differences up to 1.2 bar (to special order as single stage unit to 1.5 bar, or as two-stage unit to 3.0 bar), the similarly oil-free GQ series of rotary displacement blowers are available for air intake flow rates from 15,000 to 100,000 m³/h. For pressure differences up to 2.0 bar, for example with Midrex® processes in the steel industry, several systems are operated in parallel and as two stage systems. The GQ series systems also use the positive displacement principle. They can also adapt automatically to changing operating conditions. The GQ series machines are mainly used in the steel industry for the compression of process and cooling gas and are equipped for these purposes with special combined conveying chamber seals. As a special extreme challenge and as an example of the high level of expertise of Aerzen, the GR series are validated under KTA regulations as certified oil-free air rotary displacement blowers for the compression of water vapour in secondary circuits in nuclear power plants. These blowers represent the highest standards of manufacture, inspection procedures and test certification. The preparatory work, the preliminary tests and the procurement of raw material, on their own, can take up for such orders to three years until the start of production. All GQ systems are relatively resistant to impurities in the gas (e.g.  dust, dirt or liquid fractions). Continuous water injection can be used for cooling the gas and for cleaning the conveying chamber. 

VMY Series screw compressor with oil injection for the refrigeration industry

<font face="Arial, serif">Initially for many years and with great success, Aerzen only developed and manufactured the compressor stages for screw compressors with oil injection, which were then added and distributed by external system builders to functional refrigeration systems. Since 2012 a subsidiary specialising in refrigeration systems has taken over the sales, design engineering and packaging. Aerzen HUNGÁRIA KFT. in Esztergom, Hungary operates as a centre of excellence and offers VMY series screw compressors for refrigeration technology application worldwide. Integrated oil separation systems reduce the residual oil content of 1 to 5 mg/m³. Aerzen VMY series refrigeration systems with oil injection allow the output to be adjusted from 100 to 20%, by an integrated control of the flow rate, for particularly cost effective compression of natural gas, inert gases, ammonia, helium, hydrocarbons, hydrogen chloride, carbon dioxide, gas mixtures and process gases. The oil injection makes the compressor insensitive to fluctuating volumes, temperatures and pressures. Aerzen VMY series screw compressors are used for closed cooling circuits (ammonia, freon, helium)</font>

VMY Series screw compressors with oil injection for the compression of process gases.

Aerzen VMY series screw compressor with oil injection cooling are customised to meet the varying needs of the process gas industry. They are used for gas compression, e.g. natural gas, inert gases, hydrocarbons and other gas process mixtures. The areas of applications cover chemicals, petrochemicals and power generation equipment, etc. The oil injection makes the compressor resistant to fluctuating gas volumes, temperatures and pressures. Residual levels of 5 to 1 ppm can be achieved, through integrated oil separation, at the limit of supply.

VR series oil-free screw compressors for process gas technology

Through oil-free operation and the option of water injection, Aerzen VR series screw compressors, with upper gas inlet and lower gas outlet, can be used for gases with varying molecular weights, impurities or a tendency to polymerize and for processes which must not contain oil. The operating limits of the equipment are determined by the pressure and temperature ranges and the permissible speed of the compressor. The compressors are mechanically loaded with pressure differences up to 12 bar (high pressure range up to 25 bar) at maximum discharge temperatures of 250°C (160°C with compressor stages in stainless steel). Single and multi-stage, process gas screw compressor are available with intercooling. The compressor units operate at flow rates from 600 m³/h to 120,000 m³/h with main rotor speeds of 2000 and 20000 1/min. Aerzen oil-free process gas screw compressors have an asymmetrical 4 + 6 - rotor profile (male rotor 4 teeth, female rotor 6 teeth). This profile combination results in a relatively strong rotor core diameter for the allowable pressure drops.International regulatory requirements such as API 619,613,614,671 etc., acid gas regulations (NACE) and customer specifications can be taken into account in the compressor unit. VR series oil-free screw compressors are used in chemical and petrochemical plant, i.e. refineries, in coking plants, soda factories and steel mills for conveying flare gas, coke oven gas, lime kiln gas, mixed gases and gases with hydrogen sulphide concentrations (sour gas). Water injection is carried out in gases for reducing to acceptable operating temperatures to avoid polymerization such as butadiene concentration, which is required for the preparation of styrene-butadiene rubber. The injection of solvents for purification is also possible on a temporary basis. The cleansing effect of injection water and sealing water leakage is regarded as a particular advantage of the VR series oil-free compressor type, wherever deposits of gas impurities, such as tar, naphthalene and traces of polymerised polymer deposit on the rotors and housing walls.


There are no "off-the peg" solutions for gas compression in the process gas and refrigeration industry. Almost every application requires an individual solution, which needs to be identified in close cooperation between the supplier and the operator in the planning phase. Not only through its extensive and varied product range Aerzen offers optimal conditions for custom-made solutions for gas compression in the process gas and refrigeration industry. With its high level of expertise, Aerzen also offers customer-specific solution paths for particularly economically viable and durable designs, optimised for operational energy-efficiency of gas compression in the process gas and refrigeration industry, based on six decades of comprehensive worldwide experience acquired in diverse areas.

Author: Norbert Barlmeyer, Technical Journalist for Druckluft-Technik, Bielefeld