Optimization of an Externally Mixed Biogas Plant Using a Robust CFD Method

Biogas plants have to be continuously or periodically mixed to ensure the homogenization of fermenting and fresh substrate. Externally installed mixers provide easier access than submerged mixers but concerns of insufficient mixing deter many operators from using this technology. In this paper, a new approach to improve homogenization of the substrate mixture is proposed by optimizing external mixer configurations across a wide range of rheological properties. Robust optimization of a biogas reactor is coupled with CFD simulations to improve parameters for the angles of inflow and the position of the substrate outlet in a large-scale fermenter. The optimization objective is to minimize the area in the tank which is poorly mixed. We propose to define this “dead volume zone” as the region in which the velocity magnitude during mixing falls below a certain threshold. Different dry substance contents are being investigated to account for the varying rheological properties of different substrate compositions. The velocity thresholds are calculated for each dry substance content from the mixer-tank configuration of a real biogas reactor in Brandenburg, Germany (BGA Warsow GmbH & Co.KG). The robust optimization results comprising the whole range of rheological properties are compared to simulations of the original configuration and to optimization results for each individual dry substance content. The robust CFD-based optimized configurations reduce the dead volume zones significantly across all dry substance contents compared to the original configuration. The outcomes of this paper can be particularly useful for plant manufacturers and operators for optimal mixer placement in industrial size biogas fermenters.BMBF - ROENOBIO project with contract number 05M2013UTA (Germany), DFG - RTG 2126 Algorithmic Optimization (Germany

Nd:YAG laser welding experiments

Laser-beam/plume interaction experiments were conducted with a pulsed Nd:YAG laser. A high speed camera was used to study plume growth phenomena and to determine maximum plume velocities. Tests were done on four different metals: Aluminum 1100, Molybdenum, Nickel 200, and Stainless Steel 304. Previous laser welding experiments have indicated that the vapor plume ejected from the irradiated base material significantly attenuates the laser beam energy for Nickel 200 and Stainless Steel 304. To substantiate this observation, the plume was subjected to a cross flow of argon gas. Metallurgical studies showed a significant increase in weld penetration for all materials except for Aluminum. These experiments also indicated that the plume ejects normal to the base material. Thus, the specimen was tilted at different angles in an attempt to reduce laser beam attenuation. Results showed no significant increase in weld depth when the tilt angle was increased. Mass loss measurements were also performed and the experimental data were an order-of-magnitude less than those predicted by a numerical laser welding code

Ruthenium-catalyzed azide alkyne cycloaddition reaction: scope, mechanism and applications

The ruthenium-catalyzed azide alkyne cycloaddition (RuAAC) affords 1,5-disubstituted 1,2,3-triazoles in one step and complements the more established copper-catalyzed reaction providing the 1,4-isomer. The RuAAC reaction has quickly found its way into the organic chemistry toolbox and found applications in many different areas, such as medicinal chemistry, polymer synthesis, organocatalysis, supramolecular chemistry, and the construction of electronic devices. This Review discusses the mechanism, scope, and applications of the RuAAC reaction, covering the literature from the last 10 years

Strategies and performance of the CMS silicon tracker alignment during LHC Run 2

The strategies for and the performance of the CMS silicon tracking system alignment during the 2015–2018 data-taking period of the LHC are described. The alignment procedures during and after data taking are explained. Alignment scenarios are also derived for use in the simulation of the detector response. Systematic effects, related to intrinsic symmetries of the alignment task or to external constraints, are discussed and illustrated for different scenarios

Lasp-1 Regulates Podosome Function

Eukaryotic cells form a variety of adhesive structures to connect with their environment and to regulate cell motility. In contrast to classical focal adhesions, podosomes, highly dynamic structures of different cell types, are actively engaged in matrix remodelling and degradation. Podosomes are composed of an actin-rich core region surrounded by a ring-like structure containing signalling molecules, motor proteins as well as cytoskeleton-associated proteins

Observation of ttˉ\bar{t}H Production

The observation of Higgs boson production in association with a top quark-antiquark pair is reported, based on a combined analysis of proton-proton collision data at center-of-mass energies of s√=7, 8, and 13 TeV, corresponding to integrated luminosities of up to 5.1, 19.7, and 35.9fb−1, respectively. The data were collected with the CMS detector at the CERN LHC. The results of statistically independent searches for Higgs bosons produced in conjunction with a top quark-antiquark pair and decaying to pairs of W bosons, Z bosons, photons, τ leptons, or bottom quark jets are combined to maximize sensitivity. An excess of events is observed, with a significance of 5.2 standard deviations, over the expectation from the background-only hypothesis. The corresponding expected significance from the standard model for a Higgs boson mass of 125.09 GeV is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is 1.26+0.31−0.26