Heat Recovery Concepts from AERZEN

Sustainability and efficiency are indispensable in the industry. Today, they undoubtedly number among the most important challenges facing system manufacturers and operators. By its very nature, however, the generation of process air requires a relatively high amount of energy. A large quantity of heat energy, known as process heat, is released in the process. It arises not only in the generated airflow, but also under the acoustic hood due to heat loss from the motor, silencer and compressor. In the past, it frequently went unused.

As a manufacturer of high-performance compressors, AERZEN has long developed innovative solutions for putting this heat energy to practical use. As a result, the company offers plant operators cutting-edge compressed air technology and right-sized systems for heat recovery from a single source

The potential savings that could result from installing a heat recovery system are immense: up to 85 percent of the heat energy can easily be used for other operations, such as water heating, drying processes or preheating burner air. Energy losses, such as those caused by venting the heated air outside, are avoided. Heat recovery therefore means targeted, resource-saving energy conservation.

The investment costs for a heat recovery system are relatively low and are quickly compensated for by the energy savings. Older plants as well can be retrofitted and optimised without spending a lot of time and money. AERZEN is happy to help you implement individual solutions. Heat recovery can be implemented for a broad range of processes and uses:

  • Supplying central heating systems
  • Warm-air heating
  • Sludge drying
  • Warm air for processing tasks (e.g. drying processes in production)
  • Producing hot water for showers and washrooms
  • Heating service water for cafeterias
  • Constructing thermal brakes
  • Heating swimming pools.

The goal of every plant designer is to reduce costs by making the most efficient use possible of the energy introduced into a process. In the area of compressed air production, heat recovery is a simple way of meeting this challenge. To understand why a working compressor generates heat energy and how that energy can be used, it is useful to look at the operating principle of an air compressor:

Operating principle of compressors: Heat sources and options for recovering heat

The large quantity of waste heat produced when compressed air is generated says nothing about the efficiency of the machine. It is a by-product that necessarily arises when generating process air. Plant operators have long not been aware of the massive energy potential contained therein. As a rule, the heat is generated in two different ways: on the one hand, from compression of the medium by the assembly and on the other, by the waste heat (cooling air) from the motor, stage and silencer and the exhaust air from the oil cooler.


Machines such as screw compressors and positive displacement blowers compress the sucked-in surrounding air by means of screws or rotary pistons. This form of air compression is a thermodynamic process that heats the sucked-in medium, for example, air or gas. From a physical standpoint, the process converts electrical energy into heat energy. When compressors are used, the process gas may reach temperatures as high as 280°C.

The logical approach to recovering heat from process air is to use heat exchangers; when heat exchangers are integrated into the airflow, a medium such as water can flow through them and be heated to a preset temperature, simultaneously removing heat from the airflow. The heated water can be reused as process or service water or fed into the central heating system. AERZEN offers precisely designed heat exchangers for this purpose, that convert the maximum amount of transferable heat with minimal pressure loss.

Cooling air (heat radiation)

Additional heat energy is created under the acoustic hood of the assembly by the radiation of the motor, oil cooler, compressor stage, rotary piston stage, piping and silencer. This strongly heated cooling air can be put to practical use as well. The heat can be consolidated in the exhaust air ducts integrated in the assembly and transported as heating air to adjoining rooms or workshops. A temperature-controlled outlet can regulate the airflow, so that a uniform ambient temperature is achieved. If no heating is required in summer, for example, the excess heat can be conducted outside.

Heat recovery in wastewater treatment

Wastewater treatment is a core sector of Aerzener Maschinenfabrik. The family-owned company is a global player in this area and is continuously developing resource-saving and environmentally friendly all-in-one solutions for customers all around the world. This includes not only the selection of ‘custom-fit’, optimal machine technology, but also concepts for recovering heat. In wastewater treatment plants, the assemblies are normally used to aerate the aeration tanks. In the process, an airflow with a pressure of approx. 1 bar is generated by AERZEN positive displacement blowers, turbo blowers and compressors working jointly or as individual assemblies. The airflow is pumped into the aeration tanks (the ‘biology’ of the plant). The oxygen contained in the air plays a decisive role in an important step in the process: biological sewage treatment.

Measured in terms of the total energy costs for a wastewater treatment plant, airflow generation naturally accounts for the largest percentage. The potential for savings in this area is therefore especially high. The possibilities are vast: just one compressor with a rating of 22 kW can meet the heating needs of a single-family home.

Aerzener Maschinenfabrik’s many success stories show how the energy balance of a wastewater treatment plant can be markedly improved by implementing heat recovery solutions and choosing the optimal machine technology for each application. You can find several examples here:

Another example of highly efficient heat recovery implemented in cooperation with AERZEN can be found at the Essen-Kupferdreh wastewater treatment plant. The plant uses four positive displacement blowers to supply air to the aeration tanks. Thanks to the installation of a tube bundle heat exchanger, the plant now makes practical and efficient use of the waste heat from the blowers. The converted energy from the component now supplies heat energy to the heating system and the buffer tank for warm water. The resulting savings are colossal: heat recovery alone enables the plant in Essen-Kupferdreh to save more than 30,000 euros each year.

At the Wertach wastewater treatment plant in Bavaria, it was possible to forgo the installation of a new burner for heating boiler water, thanks to the use of a heat exchanger. In Wertach, two Delta blowers with fixed speeds are used for the basic workload. When the requirements are higher, for example, during the season when hikers and skiers visit in large numbers, a third blower with a variable speed is activated.

The warm, 68°C air generated by the compression process is cooled to under 30°C by an air-water plate heat exchanger. The resulting delta of almost 40°C can thus be used to store the boiler water of the heating system. The heat exchanger integrated in the system is equipped with flow-optimised profiles and causes almost no pressure loss in the process air flow.

If no heating is needed (e.g. in summer), it is easily switched off. A mechanical valve in the piping enables some or all of the air to be routed directly to the aeration tanks instead of through the heat exchanger, thus making demand-driven control and heat recovery possible at all times. In Wertach, heat recovery made it possible to save approx. 1,850 litres of fuel oil per year. You can find more information on the subject in the article entitled ‘Efficient heating with lost heat’ in our customer magazine.

To conform with strict environmental requirements at the Filderstadt-Bonlanden wastewater treatment plant, which was built in the 1960s in the German state of Baden-Württemberg, four Delta Hybrid rotary lobe compressors were equipped with a heat recovery system as part of a modernisation and renovation project in cooperation with AERZEN.

The combination of assemblies provides 100% oil- and absorbent-free compressed air for the aeration of the aeration tanks in a highly energy-efficient manner. The oil and absorbent-free operation means not only savings on service and maintenance, but also improved process reliability for the plant. Once the modernisation measures were complete, the system began circulating the machine-warmed ambient air via an extraction system and using it to heat other engineering rooms.

But the biggest savings were achieved by fitting a tube bundle heat exchanger into the main pipeline of the system. In the heat exchanger, heat is removed from the process air flow and used to heat water. As a result, water heating costs could be eliminated altogether. You can learn more about heat recovery in Filderstadt-Bonlanden from our customer magazine in an article entitled ‘Every kilowatt put to optimal use’.

Heat recovery in pneumatic conveying

Pneumatic conveying involves the transport of bulk goods such as flour, powder, sand or cement with the help of air. It is used in many industries, such as food processing, bulk goods, chemicals and materials. To create the required airflow, AERZEN compressors, blowers and rotary lobe compressors are often used. Very high outlet air temperatures can be achieved in the process.

The ambient air, which usually has a temperature of approx. 20°C, is sucked in and can reach temperatures of up to 280°C due to the compression process, for example, in an application involving screw compressors. To prevent the transported bulk goods from being damaged by the high temperatures, the process air often has to be cooled back down. The heat can be removed from the compressed air with the help of a heat exchanger and used for heating, water heating or process heat. Depending on the design, the pressure loss caused by the installation of a heat exchanger is 1-3% in relation to the absolute intake pressure in the aftercooler. The resulting increase in the drive output of the motor is nominal compared to the amount of energy saved by the heat exchanger.

When does it pay to recover heat?

Several factors should be considered before deciding to procure a heat recovery solution.

To begin with, the structural conditions should be checked. It is important that the waste heat source and the heat sink be positioned close together. If they are too far apart, the plans should factor in energy losses due to transport and higher costs for piping. If it takes a lot of effort to transport or store the heat, higher investment costs have to be reckoned with. Furthermore, there must be a Δ T of at least 5-10 k between the plant’s waste heat source and heat sink in order for a heat recovery installation to pay off.

In general, it could be said that heat recovery is especially beneficial when used with large assemblies and constantly running production processes. But a heat recovery system can also pay off in cases where the waste heat is lower but the workload higher. In principle, heat recovery is more profitable the more continuously the assemblies remain in operation.


The large amount of energy required to generate compressed air can be recovered and used in various ways. With AERZEN technologies and expertise, new projects in the areas of wastewater treatment and pneumatic conveying can be designed to make use of heat energy for heating rooms, halls or water (process or service water) or for steps in the production process. Many different applications are possible.

Existing plants can also be modernised using simple means that increase their efficiency. In this field, AERZEN offers its customers a broad portfolio of services, for example, a 24-hour telephone information service, a machine diagnosis and the AERaudit, in which service employees develop a plan for modernising a plant.

And with the help of AERZEN’s Room Ventilation Calculator, engineers and wastewater treatment plant owners can find a suitably designed heat exchanger for their plant themselves.

Information & documents

You have questions? LET'S TALK

Find your regional contact and get personal advice.

Aerzener Maschinenfabrik GmbH (Headquarter)

Reherweg 28

31855 Aerzen

Phone: +49 5154 81-0

Fax: +49 5154 81-9191

Emmerthaler Apparatebau GmbH

Langes Feld 4

31860 Emmerthal

Phone: +49 5155 622-0

Fax: +49 5155 622-11

Aerzen Turbo Europe GmbH

Freibusch 2-4

31789 Hameln

Phone: +49 5151 92384 0

Aerzen Digital Systems GmbH

Hefehof 8

31785 Hameln

Phone: +49 5151 40302660

AERZEN Deutschland GmbH & Co. KG (Sales)

Reherweg 28

31855 Aerzen

Phone: +49 5154 81 4000

Aerzen do Brasil Ltda

Rua Dionysio Rito, n° 300, Distrito Industrial III, L14 Q D

13213-189 Jundiaí

Phone: +55 11 4612-2021

Fax: +55 11 4612 0232


Pezinská 18

901 01 Malacky

Phone: +421 34772 5531

Fax: +421 34772 5529

- Sales Office South West

Brückenstraße 2a

66740 Saarlouis-Fraulautern

Phone: +49 6831 76828 0

Fax: +49 5154 81 716410

Aerzen Argentina SRL

Domingo de Acassuso 4743

B1605BFO Munro, Buenos Aires

Phone: +54 11 47622351


Zone Industrielle 10, Avenue Léon Harmel

92168 Antony Cedex

Phone: +33 1 46741300

Fax: +33 1 46660061


A.De. Coninckstraat 11

3070 Kortenberg

Phone: +32 2 757 22 78

Fax: +32 2 7572283


Gewerbepark Morgenstern Im Alexander 4

8500 Frauenfeld

Phone: +41 52725-0060

Fax: +41 527250066

AERZEN Nederland B.V.

Bedrijventerrein Nieuwgraaf Fotograaf 3

6921 RR Duiven

Phone: +31 26 3197530


Typograaf 5

6921 VB Duiven

Phone: +31 88 9100050

ASP AERZEN Special Products B.V.

Bedrijventerrein Nieuwgraaf Fotograaf 3

6921 RL Duiven

Phone: +31 26 4463432

Fax: +31 26 4463049


Teollisuustie 15

FI-02880 Veikkola

Phone: +358 9 8194720

Aerzen Colombia S.A.S.

Centro Empresarial Metropolitano, Bodega 27, Módulo 2 (Autopista a Medellín, km 3,4) Cota, Cundinamarca,

Código Postal 250017 Código

Phone: +57 601 841 5730

Fax: +57 601 841 5730

Aerzen Austria Handelsges.m.b.H.

Gewerbepark Tresdorf II/1

2111 Tresdorf

Phone: +43 2262 74388

Fax: +43 2262 74399


Al. Niepodleglosci 18

02-653 Warszawa

Phone: +48 22 489 55 22

Fax: +48 22 489 55 27


Alíz Utca 4

1117 Budapest

Phone: +36 1 4392200

Fax: +36 1 4391922

AERZEN CZ s.r.o.

Hraniční 1356

69141 Břeclav

Phone: +420 519 326 657

Fax: +420 519 326658


Calle Adaptación 15-17

28906 Getafe (Madrid)

Phone: +34 91 642 4450

Fax: +34 91 642 2903


Rua Alfredo Lopes Vilaverde, 15B Escritório 3

2770-009 Paço de Arcos

Phone: +351 21 468 2466

Fax: +351 21 468 2467


Aerzen House, Langston Road

IG10 3SL Loughton, Essex

Phone: +44 2085028100

Fax: +44 2085028102


61 Woodlands Industrial Park E9 E9 Premium, #07-01

757047 Singapore

Phone: +65 6254 5080

Fax: +65 6254 6935


company profile

Aerzen Taiwan Machinery

Branch office of Aerzen Asia No.170, Ln. 879, Guangfu Rd., Bade Dist.,

Taoyuan City 33457

Phone: +886 3 366 6660

Fax: +886 3 366 6536


company profile


Östra Bangatan 20

19560 Arlandastad

Phone: +46 8 59441880

Fax: +46 8 59117209

Aerzen Scandinavia Norway

Raveien 320

3184 Borre

Phone: +47 33 29 22 12

Aerzen Scandinavia Denmark

Industrivej 2

5550 Langeskov

Phone: +45 78 72 92 90


108 Independence Way

Coatesville, PA 19320

Phone: +1 610 380 0244

Fax: +1 610 380 0278


980 Rue Valois, Suite 100 Vaudreuil-Dorion

J7V 8P2 Quebec

Phone: +1 450 424 3966

Fax: +1 450 424 3985

Aerzen México S.A. de C.V.

Cerrada Uniroyal # 18-A, Col. La Michoacana

Metepec, 52166

Phone: +52 722 235 9400

Fax: +52 722 235 9401

AERZEN MAKINE San. Ve Tic. Ltd. Sti.

IMES Sanayi Sitesi, C Blok, 308. SK, No:14, Y.Dudullu

34776 Ümraniye Istanbul

Phone: +90 216 420 00 32

Fax: +90 216 420 00 79


company profile

AERZEN Machines (India) PVT. LTD.

Plot No. E-115/116, G.I.D.C , Manjusar, Tal. Savli, Dist:

Vadodara-391 775 Gujarat

Phone: +91 2667 264-817

Fax: +91 2667 264-818


company profile


Via Raffaello Sanzio, 52

20021 Bollate (MI)

Phone: +39 02 6707 5277

Fax: +39 02 6707 5003


No. 655 Yuan Dian Road, Min Hang District

Shanghai 201108

Phone: +86 21 3323 9000

Fax: +86 21 3323 9199

Aerzen Romania S.R.L.

Sat Tunari Comuna Tunari Sos. De Centura nr. 25A

RO 077180 Judet Ilfov

Phone: +40 21 243 1883

Fax: +40 21 243 1884

Aerzen ME - FZE

DSO-DDP-Office-A1-222 Dubai Silicon Oasis P.O. Box: 341445


Phone: +971 0 432 431 66

Aerzen Adria d.o.o.

Varazdinska ulica, II odvojak 3

42000 Varazdin

Phone: +385 42 370 808

Fax: +385 42 370 018

Aerzen Australia Pty Ltd

57-59 Rodeo Drive

3175 Dandenong

Phone: +61 3 97067702

Fax: +61 3 9706 8584

Aerzen Chile SPA

Limache 3363 – Bodega 13

CP: 2520642 Viña del Mar

Phone: +56 32 235 8900

Aerzen Andina Perú SAC

Carr. Panamericana Sur Km. 29.5 Almacenes F-08 y F-09 ZI Megacentro – Altura Puente Vidu

 Lurin – Lima

Phone: +51 1 434 3831


Sheraton Housing 35 el moltaka el araby, Nozha elgedida. Appt - 7, 8, 9.


Phone: +20 2 22698855

Fax: +20 2 22696611

Aerzen AIRGAS (PTY) Ltd.

175 Domkrag Street, Robertville Ext. 1

Roodepoort, Johannesburg

Phone: +27 0 11 474 2193

Fax: +27 0 11 474 2321


4-Jinnah Cooperative Housing Society, Block 7/8, Main Sharea Faisal

75350 Karachi


company profile


14, Grevenon Str.

11855 Athens

Phone: +30 210-3423201-3

Fax: +30 210-3459967

Aerzen Adria d.o.o.

Varazdinska ulica, II odvojak 3

42000 Varazdin

Phone: +385 42 370 808

Fax: +385 42 370 018


Patraikou 21-23, Flat 101, Palouriotisa TK 1048, P.O. Box 25283

1308 Nicosia

Phone: +357 22441222

Fax: +357 22490641

L.A Engineering & Consulting Ltd

PO Box 2907, 25 Ha‘ela Street

40500 Even Yehuda

Phone: +972 9 8996544

Fax: +972 9 8996547


Ul. Archaritza 2A

4006 Plovdiv

Phone: +359 32 966 681

Fax: +359 32 966 702

Aerzen Adria d.o.o.

Varazdinska ulica, II odvojak 3

42000 Varazdin

Phone: +385 42 370 808

Fax: +385 42 370 018

Airgas Compressors (PTY) Nigeria Limited

3, Adebukola Omolabake Street, Off Eric Omobude Street, Ifako Bus Stop, Along Oworonsoki - Ogudu Expressway


Phone: 00234 0 1 843 4234

Aerzen Thailand Co., Ltd

36/60 Village No. 5, Phlu Ta Luang, Subdistrict, Sattahip District

20180 Chonburi

Phone: +66 0 38 020 090

Fax: +66 86 664 1337


Representative office of AERZEN ASIA PTE. LTD Floor 8th, Unit 802A, Dai Minh Convention Tower, 77 Hoang Van Thai, Tan Phu Ward, District 7, Vietnam

 Ho Chi Minh City

Phone: +84 28 3535 2760

Aerzen Turbo Co, Ltd

800 Jeongjung-ri, Osong-eup, Heungdeok-gu, Cheongju-si,

Chungcheongbuk-28220 Korea

Phone: +82-43-238-6500

Fax: +82 70 4170 4567

local partner: DEWA Projekt OÜ

Väike-Ameerika 15

10129 Tallinn

Phone: +372 50 39239


Teollisuustie 15

FI-02880 Veikkola

Phone: +358 9 8194720

Aerzen Australia - New Zealand Office

Unit 17a Hobill Avenue Wiri

2104 Auckland

Aerzen Australia Pty Ltd

57-59 Rodeo Drive

3175 Dandenong

Phone: +61 3 97067702

Fax: +61 3 9706 8584


Unit 6a, Castlecomer Business Park, Kilkenny Rd, Ballyhimmin

R95 Castlecomer, Co. Kilkenny

Phone: + 353 567807085

Aerzen Korea Ltd

Hyundai Terrace Tower, E-dong #608, 7, Yeonmujang 5ga-gil, Seongdong-gu,

04782 Seoul

Phone: +82 44 277 6500

Fax: +82 2 6463 0064

Aerzen Turbo Co, Ltd

800 Jeongjung-ri, Osong-eup, Heungdeok-gu, Cheongju-si,

Chungcheongbuk-28220 Korea

Phone: +82-43-238-6500

Fax: +82 70 4170 4567

Aerzen Arabia Ltd.

Abed Al-Mis’hal Tower 9th Floor, office 907, Building 3958, District 35514 Al Jubail, Kingdom of Saudi Arabia


Phone: +966 13 362 8826

Service Centre - Aerzen Arabia Ltd.

Rezayat Group Dammam Port Area, Dammam Kingdom of Saudi Arabia


Contact us