Markus Haider

Heat exchangers and thermal energy storage concepts for the off-gas heat of steelmaking devices

The fluctuating thermal emissions of electric arc furnaces require energy storage systems to provide downstream consumers with a continuous amount of thermal energy or electricity. Heat recovery systems based on thermal energy storage are presented. A comparison of different thermal energy storage systems has been performed. For the purpose, suitable heat exchangers for the off-gas heat have been developed. Dynamic process simulations of the heat recovery plants were necessary to check the feasibility of the systems and consider the non-steady-state off-gas emissions of the steelmaking devices. The implementation of a pilot plant into an existing off-gas duct of an electric arc furnace was required to check the real behavior of the heat exchanger and determine suitable materials in view of corrosion issues. The pilot plant is presented in this paper.

An overview of state of the art and research in the fields of sensible, latent and thermo-chemical thermal energy storage

Due to the increase in volatile renewable power and heat generation (wind or solar), thermal energy storage (TES) has obtained growing importance and interest. The technology can be distinguished into three main types: sensible, latent and thermochemical storage. Apart from low and medium temperature heat applications, high temperature TES also is an attractive means to store power in the form of heat (before the thermodynamic transformation process). Thermochemical storage allows for long duration seasonal storage of energy.ZusammenfassungZufolge der Zunahme der Erzeugung von Strom und Wärme aus volatilen erneuerbaren Quellen wie Sonne oder Wind hat auch die thermische Energieerzeugung enorm an Bedeutung und Interesse gewonnen. Die Technologien werden nach dem Grundprinzip üblicherweise in sensible, latente und thermochemische Speicherung unterschieden. Abgesehen von Wärme-Anwendungen im Niedrig- und Mittel-Temperatur-Bereich, bietet die Hochtemperatur-Wärmespeicherung attraktive Lösungen auch zur Speicherung von Strom, indem die Wärme noch vor der Transformation im thermodynamischen Prozess gespeichert wird. Thermochemische Speicherung hat das Potential, längerfristig Energie zu speichern.

A Comparison between Passive Regenerative and Active Fluidized Bed Thermal Energy Storage Systems

Active Fluidized Bed Thermal Energy Storage (sandTES) offers a promising alternative to the current state of the art thermal energy storages (TES), such as active TES based on molten salt or passive TES (Regenerators) realised as a porous packing of ceramics. The characteristic of a sandTES system applying sand in an active TES using a fluidized bed heat exchanger (HEX) is explained. The exergetic performance of a sandTES is compared to a passive Regenerator.

New Design of a Bimetallic Finned Tube for the Use in Latent Heat Thermal Energy Storage Units

The use of finned tubes as enhancement method to increase the heat flow rate into a phase change material, which has in many cases a low thermal conductivity, is a common method. A highly efficient and easy-to-assemble solution for finned heat exchanger tubes is a key component for innovative thermal energy storage systems which play a key-role in electricity production and industrial heat management.In the present article the results of the investigation for different designs of bimetallic heat exchanger tubes is presented. These tube designs are developed for the use in latent heat thermal energy storage systems (LHTES) at a medium temperature range. For the use in latent heat thermal energy storage systems, the probably high pressure of the heat transfer medium and the high temperature differences between the operating temperature and the ambient temperature are challenging. Therefore, the bimetallic finned heat exchanger tube consists of a steel tube, where the heat transfer fluid flows, and an aluminum tube with longitudinal fins, which should improve the heat transfer to the phase change material. Due to different thermal expansion coefficients, displacements of the tubes are given. To guarantee a high heat transfer rate between the two connected tubes the contact between aluminum and steel plays an important role.In the present study 4 prototypes (including the new design) were designed, analyzed and compared on the connection strength. Long-term tests for simulating the application in a LHTES were done to determine the creep rupture properties of the compositions. All prototypes were tested successfully; the new design is convinced in many aspects of that challenge and is submitted to the Austrian patent office. Main advantages of the new design are the simple production and assembling compared to other analyzed prototypes. Furthermore, the new design shows the best results under the analyzed operation conditions and the layout of the geometry has a high optimization potential in terms of stresses.Copyright

Concept of a utility scale dispatch able solar thermal electricity plant with an indirect particle receiver in a single tower layout

Flexible dispatch able solar thermal electricity plants applying state of the art power cycles have the potential of playing a vital role in modern electricity systems and even participating in the ancillary market. By replacing molten salt via particles, operation temperatures can be increased and plant efficiencies of over 45 % can be reached. In this work the concept for a utility scale plant using corundum as storage/heat transfer material is thermodynamically modeled and its key performance data are cited. A novel indirect fluidized bed particle receiver concept is presented, profiting from a near black body behavior being able to heat up large particle flows by realizing temperature cycles over 500°C. Specialized fluidized bed steam-generators are applied with negligible auxiliary power demand. The performance of the key components is discussed and a rough sketch of the plant is provided.

System analysis of central receiver concepts with high temperature thermal energy storages: Receiver technologies and storage cycles

Reducing the levelized cost of electricity for solar thermal electricity (STE) plants is the most important challenge of this technology. A bottleneck at state of the art STE plants is the heat storage medium (HSM) with its temperature limits. To replace the commonly used molten salt, particles like quartz sand or corundum, enabling temperatures up to 1000 °C, are proposed as new HSM. The temperature raise leads to economical challenges, which have to be analyzed more in detail. In this work two STE plant concepts based on particles as HSM are introduced and discussed to outline advantages and issues concerning this technology.Reducing the levelized cost of electricity for solar thermal electricity (STE) plants is the most important challenge of this technology. A bottleneck at state of the art STE plants is the heat storage medium (HSM) with its temperature limits. To replace the commonly used molten salt, particles like quartz sand or corundum, enabling temperatures up to 1000 °C, are proposed as new HSM. The temperature raise leads to economical challenges, which have to be analyzed more in detail. In this work two STE plant concepts based on particles as HSM are introduced and discussed to outline advantages and issues concerning this technology.

Wärmerückgewinnung am Elektrolichtbogenofen und erste Erkenntnisse einer Versuchsanlage zur Materialuntersuchung

ZusammenfassungDieser Beitrag behandelt die Wärmerückgewinnung aus dem Heißgas des Elektrolichtbogenofens und erste Erkenntnisse einer Versuchsanlage zur Materialuntersuchung. Eine Versuchsanlage mit Salzschmelze als Wärmeträger wurde in das bestehende Abgassystem eines deutschen Elektrostahlwerks implementiert. Ziel dieser Anlage ist die Evaluierung des Einflusses von Korrosion und Staubablagerung auf die Rohrmaterialien des Wärmetauschers im Abgassystem. Erste experimentelle sowie numerische Erkenntnisse aus dieser Versuchsanlage werden kurz präsentiert.AbstractThis paper deals with electric arc furnace off-gas heat recovery and first experiences with a testing plant. The testing plant based on molten salt as heat transfer fluid was installed inside the existing off-gas system of a German mini mill. The aim of the testing plant is to evaluate tube materials and to measure the influence of hot corrosion and dust deposit. First experimental results are presented. Apart from experimental measurements, numerical simulations were performed and are briefly presented.

Numerical Modelling of the Moving Bed Inside the COREX® Melter-Gasifier

The COREX®-process is the first commercially operating smelting reduction process for the production of pig iron. For this reason, it can be seen as an alternative to the common industrial iron-making route via the blast furnace. For both, the COREX® melter-gasifier (MG) and the blast furnace, good gas-solid contact is essential for the stable and efficient operation of the process. Due to the very harsh conditions inside the MG, the possibilities for measurement of process conditions are very limited. Thus, detailed numerical models are required to gain additional understanding of the physical and chemical processes occurring within the MG.ZusammenfassungDas COREX®-Verfahren der Firma SIEMENS VAI gehört zur Gruppe der Schmelzreduktionsverfahren und war das erste Alternativverfahren zur Herstellung von flüssigem Roheisen, das neben dem Hochofenverfahren im industriellen Maßstab umgesetzt wurde. Da die Prozessbedingungen maßgeblich durch die Umwandlungen der Feststoffe innerhalb des Festbettes des Einschmelzvergasers bestimmt werden, ist ein guter Kontakt der Feststoffe mit der sie umgebenden Gasphase von größter Wichtigkeit für die Gewährleistung von effizienten und stabilen Prozessbedingungen. Da die einzelnen Vorgänge innerhalb des Einschmelzvergasers nur sehr schwer mittels Messungen quantifiziert werden können, liefern numerische Modelle zusätzliche Informationen, die zum besseren Verständnis dieser Prozesse und deren Optimierung beitragen können.

Konzentrierende Solartechnik für Kraft-, Wärme- und Kältekopplung

SummaryDue to Kyoto targets and rising energy prices solar energy is one of the renewable energy sources which encounter high growth rates. Currently, several new power plants of concentrated solar power (CSP) technology are under construction in Spain, the USA and North of Africa. The possible use of CSP technology for combined heat-power-cooling supply has also emerged especially in Mediterranean countries to satisfy the need of energy for air conditioning, space heating and domestic hot water with additional possibility of generating electricity with proper plant configurations. This article presents possible technologies and plant configurations for combined heat-power-cooling supply and gives a technical overview of the most important components.ZusammenfassungDie Solartechnik nimmt infolge der CO2-Problematik und gestiegener Energiekosten aktuell einen starken Aufschwung. Zurzeit findet in Spanien, den USA und auch Nordafrika eine neue Errichtungswelle an Solarkraftwerken statt. Aber nicht nur die zentrale, sondern auch die dezentrale Energieversorgung durch konzentrierende Solarenergiesysteme erfreut sich vor allem in den mediterranen Ländern steigender Beliebtheit. Durch geeignete Anlagenkonfiguration kann der Kältebedarf für Klimatisierungsaufgaben, der Wärmebedarf und zu einem gewissen Teil auch die Erzeugung elektrischer Energie in solchen dezentralen Anlagen gedeckt werden. Der Artikel gibt einen Überblick über mögliche Anlagenkonfigurationen auf Basis der Prozesse ORC, Kalina, Absorptionskälte, Stirling und CPV/T.