man in blue with helmet

Edition 04/16

Article and compact news

Our AERZEN customer journal "AERZEN" will provide you with detailed information at regular intervals about our company, our products and application solutions.


Iron smelting below the smelting point

Direct reduction with AERZEN positive displacement blowers - the gas is what matters!

Steel without coke - is it possible? Current developments in iron smelting and steel production are heading in exactly this direction. Instead of reducing the iron oxide in the ore with coke to elementary iron, steelworkers are more and more often going another way. Instead of coke, reduction gas is used, mostly generated from natural gas. In many plants all over the world, positive displacement blowers made by AERZEN are taking over the gas supply of the reduction towers.

Iron smelting below the smelting point
In the steel industry, AERZEN positive displacement blowers are in operation all over the world, for example in the production of reduction gas.

It was only this autumn that the world’s biggest direct reduction plant was commissioned in Texas. Iron sponge is the substance generated from direct reduction - also called the Midrex-procedure. While the generation of raw iron is usually connected with fiery images, direct reduction plants go quite another way as far as process technology is concerned. First of all, this technology has been designed for smaller lots and smaller dimensioned plants, which can be started up and shutdown more flexibly compared with traditional blast furnaces. There is another difference between direct reduction and “steel making”: the independence from coke - and thus from coal. The background: as reducing agent no fixed carbon as bulk material is used - instead, there is a gas mixture consisting of carbon monoxide and hydrogen. Accordingly, the material flow for the combustible material differs: conveyor belts and screw conveyors in traditional steel mills; blowers and compressors in direct reduction plants. In this field of application, AERZEN has a market presence all over the world, mainly with its positive displacement blowers.
Before natural gas can be used to reduce the positively charged iron ions in the iron oxide to molecular iron, methane has to be treated in a so-called reformer. For the chemical steam reformation, natural gas with water and oxygen injection is modified into carbon monoxide and hydrogen in an endothermic reaction and using heat. Both gases are perfectly suitable for dissolving out the oxygen retained in the iron oxide. The reaction products are iron, water and carbon dioxide.

In direct reduction processes, briquettes of sponge iron are being made.

Iron sponge briquettes with high purity

Large multi-stage blowers made by AERZEN convey the initial gases with a volume flow of up to 300,000 cubic metres per hour into the reformers. From there, the separated gas is channelled in the counterflow into the shaft furnace also by means of positive displacement blowers. Reduction of iron ore to iron sponge begins. This is then cooled down immediately, to prevent the hot material, which has a temperature of approaching 1,000 degrees C, from oxidising immediately in the air. Furthermore, it is processed mechanically, in a hot state, into briquettes or pellets. The intermediate product, on the way to becoming high-grade steel, now has the quality of raw iron and can be processed accordingly in the steel works.Different process, different requirements, depending on the location: Midrex plants are suitable for smaller locations, and their requirements for raw materials are different. In its heyday, the Ruhr area benefited from access to coal as an energy source and redox agent for its ironworks, but for the Midrex process the key element is access to cheap natural gas. Therefore, it is hardly surprising that the currently biggest direct reduction furnace was commissioned in 2016 in the U.S.A. The capacity of the plant in Texas is two million tons of iron sponge, processed into briquettes while hot.

Durable and reliable

In view of the importance of gas availability in such plants, demands for durability and operational reliability of the blowers are high. For conveying and compression of process gases, AERZEN developed positive displacement blowers series GR and GQ. In sizes 12 to 21, type GR covers intake volume flows from 100 to 50,000 cubic metres per hour. Type GQ, with sizes between 17 and 22, covers the volume range between 1,500 and 100,000 cubic metres per hour. Both performance classes convey the gas based on the positive displacement principle.
“Our machines are among the biggest available in the market,” explains Pierre Noack, Head of Process Gas Division at AERZEN. Their size, in connection with a high performance density, offers the advantage that fewer machines need to be installed to handle the required gas volume. Thus, Midrex-plants can be specified more easily and commissioned faster. Another advantage is availability. In engineering, and the evaluation of the most suitable technology, calculations of the medium default probability play an increasingly important role - particularly for plants which work continuously. If bigger compressors are used, fewer of them are required, which means that less piping needs to be built, fewer connections need to be installed, and less sensor technology and actuator technology needs to be integrated into the overall control system. Against this background, higher acquisition costs may play a subordinate role - in the evaluation of the technical components, it is MTBF figures, average maintenance intervals and lifecycle costs which play the key role. “Our packaged units still have a longer service life,” says Noack, and he mentions “very satisfied customers.”

Water injection for maximum washing effect

Their long working life and operational reliability result primarily from the fact that the oil-free conveying process gas blowers have been designed as robust high performance machines. Types GR and GQ are able to withstand contaminations in gas very well, and are also highly resistant to iron dust. In addition, water can be injected into the packages. This detail has a significant impact, particularly in the conveying of aggressive process gases. With the specific injection of water, both gas and blower package can be cooled very efficiently. Another advantage is the washing effect of the water. During operation, this prevents positive displacement blowers from sustaining damage from the deposits of highly viscous residues of process gases. The two-lobe design of the machine allows an additional self-cleaning effect.
This may not be important when conveying pure natural gas into a reformer, but it is a significant aspect when primary energy sources are blended with other gases. Here, coke oven gas is first on the list. The by-product of the pyrolysis of coal and coke contains, depending on the quality of the coal, about 55% hydrogen, 25% methane, 10% nitrogen and 5% carbon monoxide. Except for nitrogen, the mixture is excellent for reducing iron ore. However, the coke oven gas also contains minor components, including tar, hydrogen sulphide, ammonia, benzene, as well as aromatic compounds, such as naphthalene. In general, in Midrex processes, it is worthwhile to use the volatile components of coal for direct reduction of iron ore, as its share of coal is 25% of the initial weight. One tonne of coal produces 280 cubic metres of pure gas from coking plant and approximately 55 kg of sticky coal tar.

Gas treatment is not necessary

Positive displacement blowers made by AERZEN are always capable of conveying fail-safe the indicated contaminations. Thus, users of Midrex plants do not need separate gas treatment. This would be necessary if turbo compressors were used instead of positive displacement blowers. However, due to the high rotation speeds, this technology does not tolerate any foreign particles, no matter how small, in the gas flow. Thanks to the different operating principles of forced displacement, positive displacement blowers operate at considerable lower surface speeds. Just to recap: The working principle of positive displacement blowers allows maximum tip speeds which are 7 - 10 times lower than the tip speeds of turbo compressors. Thus, the injection of water leads to low erosion of the positive displacement blowers, whereas turbo compressors are not equipped with continuous water injection.

Easy modernisation with Positive Displacement Blowers

In order to apply major industrial blower solutions in other application fields of raw iron production, Pierre Noack explains that “our machines have a broadband design.”  During operation, when the capabilities of the displacement machines are not being fully utilised, either calculated theoretically or facturing in optimum characteristic curves, they nevertheless work quite efficiently due to the speed control of frequency converters. In comparison with centrifugal compressors, which have a relatively small control range at constant back pressure, positive displacement blowers adapt perfectly to changing working conditions. Their speed variance creates flexibility. It makes a difference that AERZEN positive displacement blowers can operate in highly variable modes. Existing plants can be retrofitted easily, and modernised, thanks to these machines.

Compact news

Five years of AERZEN Turbo

Aerzen Turbo in Korea had a double anniversary this year, marking: five years in existence and five years of production – definitely a cause for  celebration. At the beginning of December, all employees, as well as Vice President Asia Pacific - Chuck Lim, Product Manager Turbo - Steffen Helmert, Vice President Marketing & Product Management/Director Turbo Business - Stephan Brand, as well as H.J. Lee and C.Y. Kim of the local representative HC Corporation, were invited to a joint Company Dinner. As part of the celebrations, other anniversaries were honoured: 17 of the 58 employees of Aerzen Turbo have been present since the day the company opened.
Aerzen Turbo has been producing the core components of AERZEN Turbo Blowers – Turbo stage, frequency converter and control unit, as well as complete packaged units. Turnover has increased to more than EUR 8 million over the last five years.

Application managers for Europe, Middle East and Africa

In January 2016, Markus Leidinger took over the new function of Application Manager Wastewater Treatment Plant for the Europe, Middle East and Africa regions. He had previously worked for nine years as a sales engineer in our sales office South-West. In his role he gained a considerable amount of practical experience, particularly as far as applications around sewage treatment plant technology are concerned.

First internal system audit completed

Since the beginning of 2016 AERZEN has achieved the certifications according to DIN EN ISO 9001 (quality management), 14001 (environment management) and 50001 (energy management), as well as according to OHSAS 18001 (occupational and health protection management system). These certifications are completed by DIN EN ISO 80079-34 (quality management for machines for ATEX-applications), NSQ-100 (quality management for machines for nuclear-applications) and the MID 2014/32/EU module D (quality management for the production of rotary piston gas meters). In September 2016, the quality assurance department has now carried out the first internal system audit for the integrated management system in Aerzen. Successful: All departments fulfil the management requirements.

Meeting of the Customs and Import expert forum

The Customs and Import expert forum of the IHK Hanover held a meeting at Aerzener Maschinenfabrik GmbH on 23rd November 2016. After a company presentation, which included a tour of the company premises, the around 40 participants concentrated on the first item on the agenda, the intensification of air safety rules by the Federal Aviation Authority. An exchange of information and opinions on other current topics followed. Topics included the list of goods for external trade statistics with changes for year 2017, the new preferential agreement of the EU with the Ivory Coast and the southern African states, the survey of the IHK Stuttgart regarding supplier’s declarations, and the EU-customs tariff 2017.
Further meetings have already been scheduled for 2017 – these will be on 15th February/21st June at Johnson Controls Autobatterie, Hanover, and on 21st September/29th November at Lenze Operations GmbH, Aerzen.

AERZEN Style icon

While shopping in Hamburg one of our colleagues discovered an AERZEN product in an unusual place: in the entrance area of the Stilwerk Design centre, in the middle of a café, an old AERZEN blower was exhibited. The GLa 14.18 blower, manufactured in the 1960s, had been running in a malt factory where it had been used in a silo plant.

New manager of Process Gas Division Hungary

On 1st September 2016, Dr. Imre Pesthy took over the management of Process Gas Division Hungary from Rolf Heinemeyer. Dr. Pesthy has been awarded a post-graduate degree in metallurgical process engineering, special field metallurgy and welding technology, and completed his Master’s degree in business management. He has long-term experience with leading positions in small and larger production segments of international companies. Besides supporting PGD Hungary further, Rolf Heinemeyer will focus in future on PGD business at AERZEN.