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The agitator tank is a type of reaction vessel widely used in various industries, such as chemical engineering. In this study, the structure of the three-layer blade agitator was optimized by controlling variables, and the changes in the fluid area and the suction rate of the self-suction blade during the agitation process were investigated. Using the numerical simulation analysis method, the rotation direction of the blades, the total height of the blades, and the position of the self-suction blade were changed as three factors. The FLUENT software was used to conduct simulation analysis on the agitators with different structures to obtain visualized data. The orthogonal experimental variance analysis was performed on the obtained data to determine the magnitude of the influence of each factor on the suction rate of the self-suction blade. The study found that among the three factors in this experiment, the position of the self-suction blade had the greatest impact on the suction rate, followed by the total height of the blades, and finally the rotation direction of the blades.

The exploitation of deep and ultra-deep oil and gas reservoirs has problems such as complex pressure system, narrow safety density window and high overflow risk. High-precision overflow monitoring methods help improve drilling efficiency. In this paper, high-frequency radar is proposed as a tool for monitoring the mud level of the tank, which is not affected by steam and can monitor the mud level with high precision. In view of the monitoring position, the numerical simulation method is used to calculate the surface of the mud tank, the actual size of the mud tank is scaled in equal proportions, the size of the agitator, the stirring speed and the inlet and outlet flow are numerically calculated, and the fluctuation characteristics and influencing factors of the dynamic mud surface are analyzed, and a reasonable monitoring position is analyzed. It is found that the mud surface in the center of the agitator decreases, the mud surface near the wall of the mud tank rises, The mud surface fluctuation is mainly affected by the stirring speed, the impeller diameter, and the mud height, and is less affected by inlet and outlet flow rates. Moreover, the lower the mud height, the greater the impact of the agitator; the higher the stirring speed the more intense the mud surface fluctuation; the larger the impeller diameter, the more intense the mud surface fluctuation. it was found that the mud surface near the wall between the two agitators is relatively stable, where is less affected by agitators and the mud height. It is recommended to place it at this position when using high-frequency radar for monitoring, aiming to improve the accuracy of-frequency radar mud surface monitoring.

Good solid-liquid mixing homogeneity and liquid level stability are necessary conditions for the preparation of high-quality composite materials. In this study, two rotor-stator agitators were utilized, including the cross-structure rotor-stator (CSRS) agitator and the half-cross structure rotor-stator (HCSRS) agitator. The performances of the two types of rotor-stator agitators and the conventional A200 (an axial-flow agitator) and Rushton (a radial-flow agitator) in the solid-liquid mixing operations were compared through CFD modeling, including the homogeneity, power consumption and liquid level stability. The Eulerian–Eulerian multi-fluid model coupling with the RNG k–ε turbulence model were used to simulate the granular flow and the turbulence effects. When the optimum solid-liquid mixing homogeneity was achieved in both conventional agitators, further increasing stirring speed would worsen the homogeneity significantly, while the two rotor-stator agitators still achieving good mixing homogeneity at the stirring speed of 600 rpm. The CSRS agitator attained the minimum standard deviation of particle concentration σ of 0.15, which was 42% smaller than that achieved by the A200 agitators. Moreover, the average liquid level velocity corresponding to the minimum σ obtained by the CSRS agitator was 0.31 m/s, which was less than half of those of the other three mixers.

The goal of this work was to evaluate the efficiency of two different agitation systems by measuring the nutrient distribution in a digester fed with renewable energy crops and animal manure. The study was carried out at the practical research biogas plant of Hohenheim University. A unique probe sampling system has been developed that allows probe sampling from the top of the concrete roof into different parts and heights of the digester. The samples were then analyzed in the laboratory for natural fatty acids concentrations. Three different agitation setups were chosen for evaluation at continuous stirring and feeding procedures. The results showed that the analysis approach for agitator optimization through direct measurement of the nutrients distribution in the digester is promising. The type of the agitators and the agitation regime showed significant differences on local concentrations of organic acids, which are not correlated to the dry matter content. Simultaneous measurements on electric energy consumption of the different agitator types verify that by using the slow-moving incline agitator with large propeller diameters in favor of the fast-moving submersible mixer with smaller propeller diameters, the savings potential rises up to 70% by maintaining the mixing quality.

High energy consumption in fluidized bed dryers (FBDs) remains a critical challenge for tea processing, largely due to poor fluidization quality of sticky, irregular, and non-uniform tea particles. To address this issue, this study investigated the potential of horizontal-axis rotary agitators to improve the hydrodynamics of a gas-solid FBD and reduce energy losses. Computational fluid dynamics (CFD) simulations were performed using the two-fluid model combined with the kinetic theory of granular flow (TFM-KTGF), focusing on key parameters including pressure drop, standard deviation of pressure drop, solid volume fraction distribution, and granular temperature. Some configurations were analyzed: a bed without an agitator, and beds equipped with rotary agitators of varying blade numbers (three and five) and diameters (200 mm and 300 mm) at different rotational speeds. The results demonstrated that introducing a horizontal-axis rotary agitator significantly improves fluidization. The largest rotary domain (five blades, 300 mm diameter) achieved the lowest pressure drop of 315,135 Pa at 6.28 rad/s, while also promoting more uniform solid distribution and increasing granular temperature up to 2.5 × 10⁻ 3  J/kg. The agitator enhanced particle circulation, expanded lean regions within the bed, and reduced dense packing, leading to improved gas-solid contact and reduced resistance to airflow. Furthermore, increasing the agitator speed decreased pressure drop and its standard deviation, while increasing the granular temperature, confirming the beneficial effect of enhanced stirring energy. This study highlights the effectiveness of horizontal-axis rotary agitators in enhancing the hydrodynamic performance of FBDs, offering a promising approach to improve energy efficiency and drying uniformity in tea production. The insights presented here can guide future design and optimization of industrial-scale dryers handling cohesive, irregular particles.

No matter the scale, stirred tank bioreactors are the most commonly used systems in biotechnological production processes. Single-use and reusable systems are supplied by several manufacturers. The type, size, and number of impellers used in these systems have a significant influence on the characteristics and designs of bioreactors. Depending on the desired application, classic shaft-driven systems, bearing-mounted drives, or stirring elements that levitate freely in the vessel may be employed. In systems with drive shafts, process hygiene requirements also affect the type of seal used. For sensitive processes with high hygienic requirements, magnetic-driven stirring systems, which have been the focus of much research in recent years, are recommended. This review provides the reader with an overview of the most common agitation and seal types implemented in stirred bioreactor systems, highlights their advantages and disadvantages, and explains their possible fields of application. Special attention is paid to the development of magnetically driven agitators, which are widely used in reusable systems and are also becoming more and more important in their single-use counterparts.Key Points• Basic design of the most frequently used bioreactor type: the stirred tank bioreactor• Differences in most common seal types in stirred systems and fields of application• Comprehensive overview of commercially available bioreactor seal types• Increased use of magnetically driven agitation systems in single-use bioreactors

Grinding is a unit of operation of a pure mechanical process. An attritor is a grinder able to be used for fine or selective grinding. However, few studies have reported on the optimum design for the attritor. The attritor’s grinding characteristics and grinding effect depend not only on the operating conditions, but also on the geometry of the agitator. Therefore, we investigated the effect of the agitator shape on the grinding efficiency from the viewpoint of experiments, kinetic analysis, and discrete element method (DEM) simulations. We conducted grinding experiments with two different agitators. One was Agitator A, a traditional design with two pairs of 90° staggered mixing arms at the middle and bottom of the mixing shaft. The other was Agitator B, with a lower mixing arm inclined by 10° along the horizontal direction. We found that the grinding rate constant of Agitator B was approximately 40% greater than that of Agitator A. Although the size distribution of the particles was relatively dispersed after grinding with Agitator B, the distribution was concentrated mainly within two ranges (<0.5 mm and 2–4 mm) with Agitator A. These results and an elemental analysis of each size fraction suggested that the dominating grinding mode in Agitator A was surface grinding, whereas in Agitator B, it was bulk grinding. In terms of the influence of the agitator shape, the DEM simulation results showed that the kinetic energy of the grinding media in Agitator B was 0.0046 J/s, i.e., larger than the 0.0035 J/s obtained for Agitator A. A collision energy analysis showed that the dominating collision was between the media and wall in the tangential direction for both models. The collision energy of the media in Agitator B was larger than that of that in Agitator A. The results from the DEM simulation can help us evaluate the experimental results and infer the reasons why the grinding rate constant in Agitator B is larger than that in Agitator A.

Depending on design capacity, agitators consume about 5 to 20% of the total energy consumption of a wastewater treatment plant. Based on inhabitant-specific energy consumption (kWh PE120−1 a−1; PE120 is population equivalent, assuming 120 g chemical oxygen demand per PE per day), power density (W m−3) and volume-specific energy consumption (Wh m−3 d−1) as evaluation indicators, this paper provides a sound contribution to understanding energy consumption and energy optimization potentials of agitators. Basically, there are two ways to optimize agitator operation: the reduction of the power density and the reduction of the daily operating time. Energy saving options range from continuous mixing with low power densities of 1 W m−3 to mixing by means of short, intense energy pulses (impulse aeration, impulse stirring). However, the following correlation applies: the shorter the duration of energy input, the higher the power density on the respective volume-specific energy consumption isoline. Under favourable conditions with respect to tank volume, tank geometry, aeration and agitator position, mixing energy can be reduced to 24 Wh m−3 d−1 and below. Additionally, it could be verified that power density of agitators stands in inverse relation to tank volume.

Agitators are used in practically every industrial process that involves fluid handling. However, few chemical engineers understand what separates agitator gear drives -- the component that is most critical for ensuring the reliability and durability of the agitator system from standard commercial gear drives. Although most large agitator manufacturers make their own gear drives, some buy specialized '\"agitator service\" gear drives, which have larger internal shafting and more robust bearings than standard commercial gear drives. Other manufacturers still opt to use standard commercial gear drives, which require careful application. Companies in the chemical process industries have come to expect long life and high reliability from their agitators. For the most part, the major agitator manufacturers have delivered on that expectation. It is not unusual to have agitators in the field that have been running around the clock for 20 years or more without a rebuild. However, this has not always been the case.

The three-blade combined agitator consists of two propulsion blades of the same type (including planar propeller blades b, δ = 36.87°) and a curved blade (θ = 30°). Using numerical simulation methods, the power characteristics, flow field distribution, turbulence characteristics and dead zone percentage of two kinds of three-blade combined agitators (TBCAs) from laminar flow to turbulent flow in a mixing vessel were studied. Moreover, the torque measurement method was used to perform experimental verification. The results show that the predicted power curve is consistent with the experimental results. The fluid velocity near the propeller blades in the TBC-B type agitator (δ = 36.87°) is significantly high, and the maximum increase of the total velocity can reach 30.3%. The fluid flow velocity near the curved blades is increased, and the radial diffusion ability of the fluid at the bottom of the stirring vessel is enhanced. When mixing low-viscosity fluids, the TBC-B type agitator can increase the fluid velocity near the paddle area, with a maximum increase of 22.1%. The vertical combination of curved blades and planar propeller blades can effectively reduce the tangential velocity and increase the axial and radial velocities. When stirring high-viscosity fluids, the speed of the TBC-B type agitator in the near paddle area and far end of the blade is higher than that of the TBC-A type agitator. Under the same conditions, the TBC-B-type agitator exhibits superior fluid discharge performance and can be used in a wider range of viscosities. When Re = 44,910, the dead zone percentage of the TBC-A type agitator is 0.0216. The percentage of dead zones produced by the TBC-B-type agitator is smaller, and the mixing effect is superior to that of the TBC-A-type agitator.