Commercial Mixer Research Articles

Combining a Commercial Mixer with a Wall-Tube Electrode Allows the Arbitrary Control of Concentrations in Protein Film Electrochemistry.

Protein film electrochemistry is a technique in which an enzyme is immobilized on an electrode in a configuration that allows following the changes in turnover frequency as a response to changes in the experimental conditions. Insights into the reactivity of the enzyme can be obtained by quantitatively modeling such responses. As a consequence, the more the technique allows flexibility in changing conditions, the more useful it becomes. The most commonly used setup, based on the rotating disc electrode, allows easy stepwise increases in the concentration of nongaseous substrates, or exposure to constant concentration of dissolved gas, but does not permit to easily decrease the concentration of nongaseous substrates, or to change the concentration of dissolved gas in a stepwise fashion. To overcome the limitation by mass transport of the substrate toward the electrode when working with fast enzymes, we have designed another kind of electrochemical cell based on the wall-tube electrode (WTE). We demonstrate here that by using a system combining two syringe pumps, a commercial mixer, and the WTE, it is possible to change the concentration of species in a stepwise fashion in all directions, opening new possibilities to study redox enzymes. As a proof of concept, this device was applied to the study of the electrochemical response of the cytochrome c nitrite reductase of Desulfovibrio desulfuricans.

Design improvement of compressed natural gas (CNG)-Air mixer for diesel dual-fuel engines using computational fluid dynamics

This project carried out a computational fluid dynamics (CFD) analysis using ANSYS Fluent 14.5 software to design a compressed natural gas (CNG)-air mixer for CNG-diesel dual fuel engine. This study aimed to examine the performance of existing secondary fuel premixing controller (SFPMC) commercial mixer and modify its design in terms of air fuel ratio (AFR) and CNG-air mixture homogeneity (CAMH). The design modification of the mixer involved changing the surface of control valve shaft, gas manifold, position and directions of the CNG outlet holes. Results from simulation indicated that the original mixer was unable to control AFR since it changed from 8 at the engine speed of 1000 rpm to 176.39 at the engine speed of 3600 rpm when gas inlet pressure is fixed. However, AFR for the optimized mixer is between 17.21 and 17.4, a range close to stoichiometric AFR with various engine speeds and specific locations of the control valve. In terms of CNG-air mixture homogeneity, the uniformity index (UI) of methane mass fraction (MCh4) at the outlet of the original mixer is between 0.555 when engine speed is 1000 rpm and 0.578 when engine speed is 3600 rpm. However UI of MCh4 at the outlet of optimized mixer is between 0.995 when engine speed is 1000 rpm and 0.961 when engine speed is 3600 rpm. That means the CNG and air are homogeneously mixed at the outlet of optimized mixer in comparison with the original mixer. In summary, changing the surface of control valve shaft from cylindrical to conical shape lead to gradually opening the gas way and allow to rising the gas flow rate with increasing of air mass flow rate due to growing of engine speed, so the AFR is controlled in comparison with the origin mixer. Besides, changing the asymmetrically distributed seven gas injection holes near the mixer outlet to equal distribution 10 gas injection holes far from the mixer outlet perpendicularly to the air flow stream resulted in excellent homogeneity of the air and gas mixture in the optimized mixer.

Transitory powder flow dynamics during emptying of a continuous mixer

This article investigates the emptying process of a continuous powder mixer, from both experimental and modelling points of view. The apparatus used in this work is a pilot scale commercial mixer Gericke GCM500, for which a specific experimental protocol has been developed to determine the hold up in the mixer and the real outflow. We demonstrate that the dynamics of the process is governed by the rotational speed of the stirrer, as it fixes characteristic values of the hold-up weight, such as a threshold hold-up weight. This is integrated into a Markov chain matrix representation that can predict the evolution of the hold-up weight, as well as that of the outflow rate during emptying the mixer. Depending on the advancement of the process, the Markov chain must be considered as non-homogeneous. The comparison of model results with experimental data not used in the estimation procedure of the parameters contributes to validating the viability of this model. In particular, we report results obtained when emptying the mixer at variable rotational speed, through step changes.

Nanoscale Mixing of Soft Solids

Assessing the state of mixing on the molecular scale in soft solids is challenging. Concentrated solutions of micelles formed by self-assembly of polystyrene-block-poly(ethylene-alt-propylene) (PS-PEP) diblock copolymers in squalane (C(30)H(62)) adopt a body-centered cubic (bcc) lattice, with glassy PS cores. Utilizing small-angle neutron scattering (SANS) and isotopic labeling ((1)H and (2)H (D) polystyrene blocks) in a contrast-matching solvent (a mixture of squalane and perdeuterated squalane), we demonstrate quantitatively the remarkable fact that a commercial mixer can create completely random mixtures of micelles with either normal, PS(H), or deuterium-labeled, PS(D), cores on a well-defined bcc lattice. The resulting SANS intensity is quantitatively modeled by the form factor of a single spherical core. These results demonstrate both the possibility of achieving complete nanoscale mixing in a soft solid and the use of SANS to quantify the randomness.

A method for measuring the imbibation rate of powder in a liquid

Mixing of powders into liquids is a common unit operation. Mixing can be divided into several steps: imbibation of the powder into the liquid being the first. Under some circumstances, for instance, if the powder has poor wetting properties, imbibation can be the rate-determining step. In this study imbibation in a commercial mixer was studied and a method to measure powder imbibation in a model that simulates the commercial mixer was developed. The imbibation mechanism in the commercial mixer is based on a wave drawing the powder down into the liquid, and surface flow transporting it towards the wave. A wave imbibation model was constructed based on the same mechanisms, in which physical parameters such as wave height, surface velocity and surface residence time could be varied. An experimental procedure was used to determine the maximum imbibation rate. Measurements were found to have good reproducibility, with a standard error of means of 4.7% for spray-dried sodium caseinate. The maximum imbibation rates were found to be of the same magnitude in the commercial mixer and the wave imbibation model: 0.04 kg/s m in the commercial mixer and 0.06–0.16 kg/s m in the wave imbibation model for spray-dried sodium caseinate powder.

A GENERIC-TEE-PLENUM MIXING SYSTEM FOR APPLICATION TO SINGLE POINT AEROSOL SAMPLING IN STACKS AND DUCTS

The ANSI/HPS-N13.1-1999 standard is based on the concept of obtaining a single point representative sample from a location where the velocity and contaminant profiles are relatively uniform. It is difficult to predict the level of mixing in an arbitrary stack or duct without experimental data to meet the ANSI/HPS N13.1-1999 requirements. The goal of this study was to develop experimental data for a range of conditions in "S" (S-shaped configuration) duct systems with different mixing elements and "S" systems having one or two mixing elements. Results were presented in terms of the coefficients of variation (COVs) for velocity, tracer gas, and 10-mum aerodynamic diameter (AD) aerosol particle profiles at different downstream locations for each mixing element. Five mixing elements were tested, including a 90 degrees elbow, a commercial static mixer, a Small-Horizontal Generic-Tee-Plenum (SH-GTP), a Small-Vertical Generic-Tee-Plenum (SV-GTP), and a Large-Horizontal Generic-Tee-Plenum (LH-GTP) system. The COVs for velocity, gas concentration, and aerosol particles for the three GTP systems were all determined to be less than 8%. Tests with two different sizes of GTPs were conducted, and the results showed the performance of the GTPs was relatively unaffected by either size or velocity as reflected by the Reynolds number. The pressure coefficients were 0.59, 0.57, and 0.65, respectively, for the SH-GTP, SV-GTP, and LH-GTP. The pressure drop for the GTPs was approximately twice that of the round elbow, but a factor of 5 less than a Type IV Air Blender. The GTP was developed to provide a sampling location less than 4-duct diameters downstream of a mixing element with low pressure drop condition. The object of the developmental effort was to provide a system that could be employed in new stack; however, the concept of GTPs could also be retrofitted onto existing system applications as well. Results from these tests show that the system performance is well within the ANSI/HPS N13.1-1999 mixing criteria--the COVs for velocity, tracer gas, and 10-microm AD aerosol particles are less than the 20% criteria levels.

Characterization of wet powder masses using a mixer torque rheometer. 4. Effect of blade orientation

A commercial mixer torque rheometer has been used to investigate the effect of blade orientation on the two contra-rotating shafts. Experiments have been performed on a model wet mass consisting of microcrystalline cellulose and water. Blade orientation has significant effects on the measured torque responses with respect to water content as well as on the yield stresses and kinematic viscosities calculated by applying the Casson model to mean torque values obtained on testing specific premixed wet masses. It is essential that, inter alia, blade orientation be kept constant if different wet masses are to be directly compared as in batch monitoring or scale-up.

Nylon-made 180 ml grinding vessel for laboratory-scale cell disruption

A 180 ml grinding vessel, made of Nylatron® GS Nylon adapted to a commercial mixer mill, is described for the laboratory-scale disruption of microorganisms. The new design is inert and is 1.6 times lighter than the previously aluminum 180 ml mortar, which did not permit enzyme and protein releases similar to that observed when commercial 12.5 ml stainless steel mortars were used. With this improvement, maximum enzyme and protein releases observed within 10 and 20 min, respectively, were similar to what was achieved with a commercial 12.5 ml stainless steel mortar.

Laboratory scale disruption of microorganisms with a 180 ml grinding vessel adapted to a commercial mixer mill

A 180-ml grinding vessel was adapted to a commercially available mixer mill used for small-scale cell disruption by grinding with glass beads and was compared to the currenly used 12.5 ml mortar. The disruption of the following microorganismswas monitored by estimating the protein content of the cell extract and the release of intracellular enzymes: β-galactosidase from Bifidobacterium infantis strain ATCC 27920, hydantoinase from Pseudomonas putida strain DSM 84 and maltase from commercial baker's yeast Saccharomyces cerevisiae strain Bud. Maximun enzyme release occurred within 2.5–10 min and maximum protein release by 10–30 min depending on the organism used. The 180-ml jar is proposed as an alternative to other expensive equipments used for continuous large-scale disruption.

The use of bagasse as a potting medium for ornamentals

Five ornamental species grew as well in media that included composted bagasse as those grown in peat moss or pine bark. Plants of most of the species grown in a potting mix which included fresh bagasse grew at reduced rates and the medium shrank excessively. For some species, a medium containing both bark and bagasse may increase production compared with media containing either bark or bagasse alone. Boron (0.1 g l −1) applied at fortnightly intervals reduced dry matter production in all species. Media mixed in a commercial mixer (5 m 3) had similar effects on plant dry weight to those mixed with a small mixer (0.05 m 3). African violets ( Saintpaulia sp.) grew well in a range of media, but produced greater root dry matter in a mix containing a high proportion of composed bagasse.

Physical and chemical changes of medicinals in mixtures with adsorbents in the solid state. IV. Study on reduced-pressure mixing for practical use of amorphous mixtures of flufenamic acid.

Flufenamic acid (FFA) was mixed with magnesium aluminum silicate (MAS) at a reduced pressure of about 10 to 50 mmHg employing a commercial mixer for pharmaceutical production. An amorphous state of FFA in the mixture was efficiently achieved with this equipment, and the dissolution of FFA was enhanced in comparison with that of the physical mixture. Effects of the conditions of mixing, such as pressure, temperature and rotating speed, on dissolution of FFA were determined. Through stability tests at 40 degrees C under both dry and humid conditions, no change in dissolution profiles was recognized in a 5% FFA mixture stored under any conditions. On the other hand, decreases in dissolution behavior were observed in 10% and 20% FFA mixtures when they were stored under humid conditions. These results suggested that humidity should be avoided during the storage of amorphous mixtures of FFA with MAS for production purposes.

Rubber Stocks for Improved Performance of Polyester Cord Tires

Abstract Carcass stocks were developed with acceptable properties and good adhesion to polyester tire cords after severe heat aging in laboratory tests. These stocks contained vulcanization accelerators that did not liberate amines and were based either on synthetic poly (isoprene) (IR)/butadiene/styrene (SBR) elastomer blends, as recommended in previous work, or natural rubber/SBR compounds containing an additive to inhibit the deleterious effects of amines present as impurities in NR. Standard SBR/poly (butadiene) (BR) tread stocks containing amine-free accelerators were developed to match the exceptionally long scorch time and good physical properties attained with sulfenamide accelerators normally used in such stocks. Large batches (˜400 pounds) of amine-free tread stock were processed without any scorch problems on a commercial Banbury mixer and tread extruder. With these tread stocks, containing amine-free accelerators, it is possible to build completely amine-free polyester cord tires. In a variety of wheel tests designed to assess durability under extreme conditions, 2-ply tires with cords of Dacron polyester containing amine-free tread and carcass stocks showed highly improved durability (180-440 per cent) compared to control tires made with stocks containing amines. In a wheel test simulating the running of a tire underinflated for an extended period (low pressure endurance test), tire durability increased with decreasing amine content of the rubber stocks used. In a special high temperature tire fatigue test to produce break-above-bead failures, tires combining an experimental Dacron polyester with low carboxyl content and in amine-free stocks ran 350 per cent longer than tires of standard T-68 Dacron in amine containing stocks. These tests clearly illustrated the additive benefits of combining an improved polyester with stocks having reduced amine content.