Methanation Pilot Plant with a Slurry Bubble Column Reactor: Setup and First Experimental Results

As a part of various research projects, a methanation pilot plant with a slurry bubble column reactor (SBCR) was commissioned and operated. The plant has a nominal load of a 100 kW methane output (lower calorific value) with a reactor diameter of 260 mm and a reactor length of 2500 mm. First experimental data on the steady-state and dynamic operation of catalytic CO2 methanation are presented. Steady-state results from laboratory-scale studies (<1 kW methane output) published previously were confirmed qualitatively at the pilot plant eliminating wall effects unavoidable in small-scale reactors. As predicted, high H2/CO2 ratios increase CO2 conversion, but excess H2 apparently promotes decomposition of the liquid phase (dibenzyltoluene) used in the bubble column reactor. Additionally, due to the increased reactor dimensions compared to laboratory equipment, it was now possible to observe a thermal response of the SBCR under conditions of rapid gas load changes characteristic of envisaged power-to-gas applications with volatile renewable electricity. As the predicted robustness of the SBCR-concept toward a dynamic operation with fast load changes was demonstrated successfully, it offers an attractive alternative to the established fixed-bed methanation technologies with their inherent limitations on dynamic operability

Effect of gas jet angle on primary breakup and droplet size applying coaxial gas-assisted atomizers

This study investigates the influence of gas jet angle on primary jet breakup and the resulting droplet size distribution for coaxial gas-assisted atomizers. In industrial applications, the gas jet of these atomizers are typically angled towards the liquid jet, whereas in most spray investigations in literature, parallel flow configurations are used. To enable a detailed analysis of the influence of the gas jet angle, three atomizers with angles of 0°, 15° and 30° were examined. Other geometric parameters, such as liquid jet diameter, gas gap width and wall thickness were kept constant. For each atomizer, two gas velocities at constant liquid mass flow were investigated i.e., two gas-to-liquid ratios (GLRs). An additional set of experiments was performed at increased system pressure using three atomizers with identical gas jet angles, but with an adapted gas orifice area in order to keep gas velocity, GLR and momentum flow ratio constant for all pressure levels. Water and a glycerol/water-mixture were applied in order to investigate the influence of liquid viscosity. The primary breakup process was monitored by a high-speed camera, whereas the resulting droplet size was detected using a phase-Doppler anemometer. For all system pressures and liquid viscosities under investigation, a distinct influence of gas jet angle on primary breakup as well as on resulting droplet size distribution was observed for low gas velocity

Comparison of spray quality for two different flow configurations: Central liquid jet versus annular liquid sheet

The research work of the present study is focused on the detailed comparison of two external mixing twin fluid nozzle concepts: (i) a central liquid jet with annular gas stream, (ii) an annular liquid sheet with central gas jet. Both nozzle types are applied in high pressure entrained flow gasifiers (EFG), where atomization is characterized by low Gas-to-liquid ratio (GLR) and high fuel viscosity. In order to compare spray formation as well as atomization efficiency in terms of Sauter mean diameter, a nozzle with equal orifice area of the gas and liquid exit is investigated. The nozzle enables equal atomization conditions concerning GLR, liquid mass flow, velocity of liquid and gas, as well as momentum flow ratio for both nozzle configurations. 4 Newtonian liquids: water and three glycerol/water mixtures with viscosity of 1mPas, 50mPas, 100mPas and 200mPas are used for the experiments in both nozzle configurations at various GLR. For spray analysis, a high speed camera, a shadowgraphy system as well as a phase-doppler analyzer are applied. The use of three different measuring techniques allows for characterization of primary breakup as well as local drop size distribution. With the high speed camera the breakup regime morphology is detected and classified for both operating configurations. Radial measurements of the local Sauter mean diameter are conducted with the phase-doppler analyzer. Furthermore, the spray angle is detected and the integral Sauter mean diameters for all operating conditions is compared for both nozzle configurations to evaluate atomization efficiency

Towards system pressure scaling of gas assisted coaxial burner nozzles – An empirical model

The present study investigates the influence of system pressure, gas velocity, and annular gas gap width on the resulting droplet size. Three external-mixing twin-fluid atomizers are operated at a constant liquid mass flow. The nozzle geometry is kept similar, except that the annular gas gap width is changed. At every system pressure level (1 – 21 bar), three different gas velocities were investigated by changing the gas mass flow. High-speed camera images are used for observation of primary breakup and discussed with regard to local measurements of droplet size performed by a phase Doppler anemometer. The gas momentum flux as well as the gas momentum flow were applied to describe the atomization process under varying operating conditions. Finally, an empirical model is derived, enabling the system pressure scaling of external-mixing twin-fluid atomizers for the range of gas momentum flow under investigation

Energy Loss of Leading Hadrons and Direct Photon production in Evolving Quark-Gluon Plasma

We calculate the nuclear modification factor of neutral pions and the photon yield at high p_T in central Au-Au collisions at RHIC (\sqrt{s}=200 GeV) and Pb-Pb collisions at the LHC (\sqrt{s}=5500 GeV). A leading-order accurate treatment of jet energy loss in the medium has been convolved with a physical description of the initial spatial distribution of jets and a (1+1) dimensional expansion. We reproduce the nuclear modification factor of pion R_{AA} at RHIC, assuming an initial temperature T_i=370 MeV and a formation time \tau_i=0.26 fm/c, corresponding to dN/dy=1260. The resulting suppression depends on the particle rapidity density dN/dy but weakly on the initial temperature. The jet energy loss treatment is also included in the calculation of high p_T photons. Photons coming from primordial hard N-N scattering are the dominant contribution at RHIC for p_T > 5 GeV, while at the LHC, the range 8<p_T<14 GeV is dominated by jet-photon conversion in the plasma.Comment: 21 pages, 16 figures. Discussions and references added. New figure includind photon dat

Loss Comparison of Small Delta- and Star-Connected Permanent Magnet Synchronous Machines

Delta-connected stator windings are often used in mass production of small Permanent Magnet Synchronous Machines (PMSMs). In comparison to star-connected stator windings, a delta-connected winding system offers advantages for manufacturing and lowers production costs. A main disadvantage of motors with such a winding system are additional losses caused by the Zero-Sequence Current Component (ZSCC). In this paper the ZSCC and its impact on the generated losses in a delta-connected PMSM used as a traction motor for a pedal electric cycle (Pedelec) is analysed. The calculated results are compared to those of a star-connected PMSM with the same design. We will show that the amplitude of the ZSCC depends on the operating point of the machine. As a result, the copper losses in the delta-connected machine are up to 5.8 % higher than the ones in the star-connected machine. On the other hand, the iron losses are 1 % smaller in the delta-connected machine. The efficiency of the delta-connected machine is still up to 4 % smaller