Axial Mixer Research Articles

The 3-D optimization of an axial mixer propeller through high fidelity simulations

Homogeneous mixing is an important process quality indicator in biogas fermenters for introducing fresh organic feed material to certain bacteria groups such as methanogenic bacteria for anaerobic digestion. Energy consumption for mixing processes is one of the highest operational costs in biogas plants. Thus, it is crucial to carefully consider the energy expenditure per generated thrust (the first performance metric of an axial mixer) for a biogas mixer, since biogas plants are considered as a net carbon zero energy plant. There are several different types of mixers. Axial mixers both high speed and low speed together with paddle mixers are most common among various types of mixers used in fermenter tanks. In this study it is planned to improve conventional axial biogas mixer efficiency using computer aided engineering tools for design and optimization. This goal will be achieved by using a parametric design strategy for blade geometry together with the open source CFD analysis suite OpenFOAM for measuring performance metrics (i.e. power, torque, and thrust). The most efficient design will be chosen from a set of design candidates residing inside a reasonably large parametric state space, via maximizing the thrust to power ratio.

CFD geometrical optimization to improve mixing performance of axial mixer

Although various axial static mixers have been proposed, their commercialization have been hindered by their high pressure drop characteristic and the limited operating conditions where a wide frequency range of input disturbances cannot be filtered. The static “Time-Difference-Type Mixer (TDM)” is a new practical axial mixer that effectively reduces the intermittent variation of the mixture concentration. In the present study, the TDM was modified to decrease the pressure drop and smoothen the outlet concentration profile. The geometry of the element tip was modified based on the results of CFD simulation that were successfully validated by the corresponding experiments, with the purpose of reducing the flow resistance. A decrease in the pressure drop of nearly 40% was thus achieved. The concentration profile at the outlet was also substantially smoothened using an arrangement of the branch paths of the mixer that reduced the differences among the arrival times of the mixture through increased upstream spacing of the branch paths. The performance of the TDM was sufficiently optimized to make it commercially viable.

Treatment of an Iron-rich ARD Using Waste Carbonate Rock: Bench-Scale Reactor Test Results

The treatment of acid rock drainage (ARD) places extraordinary financial burdens on governments and companies worldwide, and an improved efficiency in treatment by as little as 1% can save many millions of dollars in rehabilitation. We investigated a system for treating Fe-rich ARD using a three-stage reactor design. In the first reaction cell, Fe-rich ARD was partially neutralised using rapid periodic carbonate resuspension with a rotating axial mixer. This was followed by an air-sparged oxidation chamber and then a second reaction cell, with more carbonate periodically resuspended until a pH of 6.3 was reached, which was followed by a settlement chamber. This reactor design has a high capacity for neutralisation, with an efficiency of ≈70% of acidity neutralised by the acid neutralising capacity (g of CaCO3 equivalent) added to the reactor. Axial mixers were tested because of their low-energy requirements and their high reliability. The intermediate chamber effectively removes Fe by oxidising Fe(II) to Fe(III). Given the amount of acidity neutralised, the sludge volume produced was low compared to other technologies, providing further potential savings in sludge handling. Waste carbonate rock proved to be an effective neutralising agent, even though it was about 60% dolomite and 40% magnesite, with minor calcite, and despite the fact that magnesite has substantially slower dissolution kinetics compared to the more dominant dolomite. The mixed waste carbonates were capable of raising the pH sufficiently to reduce the heavy metal loadings in Fe-rich ARD by more than two orders of magnitude. The final settlement stage of the process was shown to be essential for metal precipitation, for the carry-over of fine carbonates, and CO2 loss. This was associated with a rise in pH, from 6.3 to 7.5. In addition, residual slow-reacting magnesite from the mixed carbonate remains in the sludge from the first reactor and provides acid buffering capacity within the sludge, which is commonly lacking in the ARD neutralisation sludge of other systems.

Ceramic and PMMA particles differentially affect osteoblast phenotype

There is increasing evidence that wear debris particles present in periprosthetic tissues have direct effects on osteoblasts. The nature of the cell response varies with the chemistry of the particle and the number of particles. Most studies have used Ti, Ti–6Al–4V, and ultrahigh molecular weight polyethylene (UHMWPE) particles since these materials are most frequently used in implants and as a result, these particles predominate in peri-prosthetic tissues. Ceramics have also been used successfully as load-bearing surfaces in implants for years, although it is unknown how wear debris from these surfaces may contribute to aseptic bone loss. Further, particles resulting from polymethylmethacrylate (PMMA) cements used for fixation may also be involved in aseptic loosening of implants, but how these particles may affect bone formation is unknown. In the present study, we examined whether aluminum oxide (Al2O3), zirconium oxide (ZrO2), and PMMA particles exert effects on osteoblast proliferation, phenotypic expression, and local factor production, and if so, whether the effects were specific to the particle type. ZrO2 particles were produced in a custom-made axial mixer in which ZrO2 containers were filled with ZrO2 bars and 95% ethanol and then rotated continuously at room temperature. PMMA particles were prepared in a ZrO2 roller mill. Al2O3 was produced and provided by Aesculap AG. Particles were endotoxin-free with equivalent circle diameters <3μm; Al2O3 particles were significantly smaller than ZrO2 or PMMA particles. Particle suspensions were added to confluent cultures of MG63 osteoblast-like cells after diluting them 1:100, 1:10, and 1:1 with culture medium. Cells were incubated with the particles for 24h. Transmission electron microscopy showed that MG63 cells phagocytosed Al2O3 particles and exhibited ultrastructural changes consistent with cytotoxicity. This was supported by biochemical changes as well. Proliferation, alkaline phosphatase activity, and TGF-β1 levels were decreased. ZrO2 and PMMA particles increased proliferation and alkaline phosphatase specific activity. The effect of ZrO2 on alkaline phosphatase was targeted to matrix vesicles; the effect of PMMA was greater on the cells. All particles increased prostaglandin E2 production. These results show that Al2O3, ZrO2, and PMMA particles elicit direct effects on osteoblasts and that cell response depends on the particle type. None of the particles tested had the same effect as noted previously for UHMWPE: increased proliferation and decreased alkaline phosphatase. These results may indicate that the response of peri-prosthetic tissues to wear particles may be modulated by the relative contributions of the various particle types present.

ChemInform Abstract: STUDIES ON MIXING PART 37, LIQUID FLOW AT THE BOTTON OF A VESSEL WITH AN AXIAL MIXER AND RADIAL BAFFLES

Chemischer InformationsdienstVolume 4, Issue 52 Other Subjects ChemInform Abstract: STUDIES ON MIXING PART 37, LIQUID FLOW AT THE BOTTON OF A VESSEL WITH AN AXIAL MIXER AND RADIAL BAFFLES I. FORT, I. FORTSearch for more papers by this authorV. KOZA, V. KOZASearch for more papers by this authorZ. GRACKOVA, Z. GRACKOVASearch for more papers by this author I. FORT, I. FORTSearch for more papers by this authorV. KOZA, V. KOZASearch for more papers by this authorZ. GRACKOVA, Z. GRACKOVASearch for more papers by this author First published: December 25, 1973 https://doi.org/10.1002/chin.197352506AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume4, Issue52December 25, 1973 RelatedInformation

Studies on mixing. XXXVII. Liquid flow at the bottom of a vesel with an axial mixer and radial baffles

Studies on mixing. XXXVII. Liquid flow at the bottom of a vesel with an axial mixer and radial baffles

Studies on mixing. XXXV. Flow pattern in a system with axial mixer and radial baffles

Studies on mixing. XXXV. Flow pattern in a system with axial mixer and radial baffles

Studies on mixing. XXIX. Spacial distribution of mechanical energy dissipated by axial mixer in a system with radial baffles

Studies on mixing. XXIX. Spacial distribution of mechanical energy dissipated by axial mixer in a system with radial baffles

Studies on mixing. XXVII. Liquid circulation in a system with axial mixer and radial baffles

Studies on mixing. XXVII. Liquid circulation in a system with axial mixer and radial baffles

Studies on mixing. XXX. Turbulent flow in a system with axial mixer and radial baffles

Studies on mixing. XXX. Turbulent flow in a system with axial mixer and radial baffles

Study on mixing. XXVIII. Velocity field at the wall of vessel with axial mixer and radial baffles

Study on mixing. XXVIII. Velocity field at the wall of vessel with axial mixer and radial baffles