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ABSTRACT This study deals with the operating behavior, the liquid disintegration, and the aerosol collection efficiency of a venturi scrubber working in self-priming mode. In the case of a forced feed venturi scrubber, the scrubbing liquid is injected into the throat by means of a pump. The liquid load is adjustable independently from the gas flow rate. In contrast, the venturi scrubber analyzed in the present investigation works in a self-priming mode. The washing liquid is introduced due to a pressure difference between the inside and the outside of the venturi throat. This pressure difference is composed of the hydrostatic pressure of the liquid and the static pressure of the flowing gas. The atomization process of the injected liquid is equivalent to the observations made with forced feed venturi scrubbers. However, the jet penetration is most sensitive to the operating conditions of the scrubber. The cleaning efficiency of a venturi scrubber as well as the overall pressure loss grow with an increasin...

Abstract This study deals with behaviour and washing efficiency of a venturi scrubber in self-priming operation. Usually the washing liquid is injected into the throat by means of a pump, in such a way that the amount of liquid added per cubic metre of gas is adjustable independent from the gas flow rate. In contrast to this kind of design, the venturi scrubber used works via a self-priming operation, i.e. the washing liquid is injected by means of a pressure difference between the inside and outside of the venturi throat as a result of the hydrostatic pressure of the liquid and the static pressure of the flowing gas. As is well known from the literature, the cleaning efficiency of a venturi scrubber improves with the amount of liquid added per volume of gas and with increasing gas velocity in the throat. However, high gas velocities and high charges of washing liquid cause a large pressure drop. Hence, the separation efficiency and energy consumption of the scrubber have to be optimized. It is shown that the separation efficiency could be improved by a multistage injection of the washing liquid. Due to the self-priming operation, the separation efficiency remains at a high level even if the gas velocity decreases, and thus requires no regulation from the outside. Liquid separation after the venturi scrubber is realized by an immersion tube in combination with swirl promotors in the diffuser section of the scrubber which increase the rotation of the gas—liquid flow. Thereby, droplets are pushed aside to the diffuser walls and are deposited.

Abstract Pyrolysis of waste plastics to recycle valuable hydrocarbons represents an attractive technology for reducing waste and providing feedstocks for petrochemical products and fuels. Via the simultaneous processing of heavy petroleum residue fractions, synergies can be harnessed by converting bottom-of-the-barrel refining products into lighter fractions with higher value while improving processability of plastic waste materials. To investigate the effect of reactor pressure, a continuous laboratory co-pyrolysis plant was operated. The setup consisted of two consecutive tubular zones to convert a mixture of LDPE and a heavy petroleum residue to a final temperature of 450 °C at different pressures between 2 and 10 bar. The products were evaluated regarding obtained mass yields and their boiling range. Gaseous and liquid products increased with enhanced pressure, resulting in nearly tripled gas and light liquid formation, whereas more unconverted feed was consumed. Because the reactor pressure also affects the residence time by suppressing evaporation, which subsequently varies between 360 and 440 s, further investigations considering the dependence of product yields on the residence time over a range of 280 to 480 s were necessary. The comparison resulted in the conclusion that the enhancing effect of increased reactor pressure is not only caused by a retention time elongation in the hot reactor zone. Other physical effects also play a role, such as promoted heat transmission and a direct intervention of reactor pressure with the chemical reactions. In the tested range, an enhancing effect of higher reactor pressures on the cracking of the reaction mixture was observed. These novel experimental results indicate, that conversion toward lighter cracking products can be increased by pressure adjustments and highlights that the pressure should be included in process optimizations.

Biomass (especially algae) is a renewable energy source that can be a great alternative to fossil fuels. Wet algal biomass converts into products such as solid, aqueous, and gaseous phases as well as biocrude in hydrothermal liquefaction (HTL). The aim of this work was to provide detailed exergy analyses of the production of biocrude from Nannochloropsis sp. by HTL. Physical and chemical exergy of the HTL products, exergy losses, exergy efficiency, and exergy distribution of the HTL process were determined in this research. The highest exergy loss and the lowest efficiency values obtained for the heat exchanger were 65,856.83 MJ/hr and 66.64%, respectively, which was mainly caused by the irreversibility of the heat transfer process. Moreover, the HTL reactor had high efficiency (99.9%) due to the complex reactions that occurred at high temperature and pressure. Also, the optimum operating conditions of the reactor were obtained at 350 °C and 20 MPa by using sensitivity analysis. The high overall exergy efficiency of the process (94.93%) indicated that HTL was the most effective process for the conversion of algae. In addition, the exergy recovery values of the overall exergy input values in the HTL process for biocrude, as well as the aqueous, solid, and gas phases, were nearly 74.88%, 18.42%, 0.86%, and 0.76%, respectively. Exergy assessment provides beneficial information for improving the thermodynamic performance of the HTL system.

This paper presents a real and application-based scenario for a dynamically driven catalytic methanation unit, using off-gases from an integrated steel mill as input. Several parameters are subject to dynamic changes during the standard production of steel, such as the available amount and composition of the accumulating process gases, the temperature and operating pressure as well as their periodicity. In addition, the available amount of hydrogen can vary depending on the available fluctuating renewable energy for the installed electrolyzer. Analysis of operating parameters and process routes in steelmaking revealed that among many theoretically possible modes of driving a dynamic methanation unit, which are defined in the literature, there is only one realistic application-based scenario. The definition of this case is supported by experiments performed with a three-stage methanation setup in lab-scale. This experimental campaign covered real cases with dynamic flow rates, adjusting the amount of blast furnace and converter gases based on high variations in the availability of hydrogen. It was possible to achieve very stable product gas compositions, even though load changes in gas input power up to 64% in the range of one to 120 min were executed. The dynamic variations did not result in any additional catalyst deactivation through the whole experimental campaign.

Abstract Storage options for increasing amounts of volatile energy supplied by renewable sources are of growing interest. One promising concept is power-to-gas, where electrical energy is transformed to gas that can be stored more easily. H 2 produced by electrolysis powered by excess energy is combined with CO 2 in a methanation to produce CH 4 . Possible CO 2 sources are numerous, but biogas is special, as it is a renewable source itself and already contains CH 4 concentrations of up to 60% v/v. Normally the CH 4 needs to be removed prior to methanation, requiring two gas upgrading steps. The newly developed process described in this paper circumvents this by directly feeding biogas to the methanation. For evaluation of this concept two process chains were realized. The classic setup consisted of a catalytic methanation and membrane based gas upgrading being fed with H 2 and CO 2 from bottles. The alternative process was coupled with a two-stage fermentation to study effects of changing biogas compositions. Both process chains have been demonstrated on a scale of about 0.5 m 3 (STP)/h. Results for both will be presented in this work and the positive implications regarding the future implementation of biogas into power-to-gas systems will be discussed.

AbstractThe present work describes the results achieved during a study aiming at the full replacement of the natural gas demand of an integrated hot metal production. This work implements a novel approach using a biomass gasification plant combined with an electrolysis unit to substitute the present natural gas demand of an integrated hot metal production. Therefore, a simulation platform, including mathematical models for all relevant process units, enabling the calculation of all relevant mass and energy balances was created. As a result, the calculations show that a natural gas demand of about 385 MW can be replaced and an additional 100 MW hydrogen-rich reducing gas can be produced by the use of 132 MW of biomass together with 571 MW electricity produced from renewable energy. The results achieved indicate that a full replacement of the natural gas demand would be possible from a technological point of view. At the same time, the technological readiness level of available electrolysis units shows that a production at such a large scale has not been demonstrated yet.

Die Umstellung der Energieversorgung auf erneuerbare Quellen (Wind, Photovoltaik) wird in Zukunft verstarkt die Volatilitat in der Stromerzeugung erhohen. Um eine ausgeglichene Leistungsbilanz im Stromnetz sicherzustellen, werden Speicher benotigt – nicht nur kurzzeitig, sondern auch saisonal. Die bidirektionale Kopplung bestehender Energieinfrastruktur mit dem Stromnetz kann hier Abhilfe schaffen, indem der Strom in Elektrolyseanlagen zur Wasserstofferzeugung genutzt wird. Der Wasserstoff kann Erdgas in der vorhandenen Infrastruktur (Gasspeicher, Pipelines) in begrenztem Umfang beigemischt werden oder in einer gaskatalytischen Reaktion, der Methanisierung, mit Kohlendioxid und/oder Kohlenmonoxid direkt zu Methan umgesetzt werden. Durch den Ruckgriff auf die Erdgasinfrastruktur wird eine Entlastung der Stromnetze erreicht und eine Speicherung der erneuerbaren Energien auch uber lange Zeitraume ermoglicht. Ein weiterer Vorteil dieser als „Power-to-Gas“ bezeichneten Technologie ist, dass das so erzeugte Methan eine Senke fur CO2-Emissionen darstellt, da damit fossile Quellen substituiert werden und so CO2 in einem geschlossenen Kreislauf gefuhrt wird.

Fluctuating energy sources require enhanced energy storage demand, in order to ensure safe energy supply. Power to gas offers a promising pathway for energy storage in existing natural gas infrastructure, if valid regulations are met. To improve interaction between energy supply and storage, a flexible power to gas process is necessary. An innovative multibed methanation concept, based on ceramic honeycomb catalysts combined with polyimide membrane gas upgrading, is presented in this study. Cordierite monoliths are coated with γ-Al2O3 and catalytically active nickel, and used in a two-stage methanation process at different operation conditions (p = 6–14 bar, GHSV = 3000–6000 h−1). To fulfill the requirements of the Austrian natural gas network, the product gas must achieve a CH4 content of ≥96 vol %. Hence, CH4 rich gas from methanation is fed to the subsequent gas upgrading unit, to separate remaining H2 and CO2. In the present study, two different membrane modules were investigated. The results of methanation and gas separation clearly indicate the high potential of the presented process. At preferred operation conditions, target concentration of 96 vol % CH4 can be achieved.