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This study examined the fluidization phenomenon using vertical vibration for fine powder in a mechanical vertical vibration for fluidized bed reactor. The fine powder used belongs to the Geldart group C with a mean powder size of 2.25 µm. It was verified that channeling and agglomeration phenomena appeared with a fluidization method without vibration of fine powders belonging to the group C. To keep fluidization phenomenon of the agglomerating fine powder superior, a smooth fluidization condition was made by giving vertical vibration function and removing cohesion between particles. To verify the smooth fluidization condition of the fine powder, changes in the bed height to diameter (H/D) ratio of the fluidized bed reactor, pressure drop due to changes of vibration frequency with superficial gas velocity, minimum fluidization velocity, and changing characteristics of bed expansion ratio were investigated experimentally. This study examined pressure drops from H/D variable of values 1 and 2, minimum fluidization velocity, and bed expansion ratios at 0 to 60 Hz of vibration frequency. There is a trend that as vibration frequency increases, the pressure drop is stabilized, minimum fluidization velocity decreases, and the bed expansion ratio increases.

The objective of this study is to eliminate the tackiness of sticky paint particles occurring in paint booths using calcium hydroxide. It ultimately aims to identify the optimal filtration velocity to determine the optimal operation condition for particle collection in the filter. As the filtration velocity increased further in the range of 0.2–0.5 m/min, the pressure drop increased rapidly, while the cleaning efficiency, overall collection efficiency, and fractional collection efficiency tended to decrease. The filtration velocity for optimal filtration condition was identified to be 0.2 m/min.

In this study, four different HVAC filters were tested to evaluate the filter layer structure effect on the Most Penetrating Particle Size. Each filter consisted of two melt-blown (MB) layers and a thermal bond (TB) layer. The MB layers were constructed with fibers with diameters of 2 μm and 5 μm diameter while the TB layer exhibited a fiber diameter of 37 μm. The positions of the three layers (MB2, MB5, and TB) were varied along the air flow direction, and four different filters were considered as follows: Filter A (MB2 → TB → MB5), Filter B (MB5 → TB → MB2), Filter C (TB → MB2 → MB5), and Filter D (TB → MB5 → MB2). When particle loading was absent (clean filter), pressure drops and collection efficiencies were almost identical for the filters, thereby indicating that the filtration performance did not significantly change with the filter layer arrangement. However, particle loading test results showed that pressure drop and most penetrating particle size (MPPS) trends depended on the location of the MB2 layer. For Filter D, the pressure drop and the decreasing rate of the MPPS were the lowest. The pressure drop increased from 3.5 to 9.4 mmH2O and the MPPS decreased from 270 to 160 nm, when the particle loading increased from 0 to 1.55 g/m2.

We evaluated the optimal conditions for fluidization of nickel oxide (NiO) and its reduction into high-purity Ni during hydrogen reduction in a laboratory-scale fluidized bed reactor. A comparative study was performed through structural shape analysis using scanning electron microscopy (SEM); variance in pressure drop, minimum fluidization velocity, terminal velocity, reduction rate, and mass loss were assessed at temperatures ranging from 400 to 600 °C and at 20, 40, and 60 min in reaction time. We estimated the sample weight with most active fluidization to be 200 g based on the bed diameter of the fluidized bed reactor and height of the stocked material. The optimal conditions for NiO hydrogen reduction were found to be height of sample H to the internal fluidized bed reactor diameter D was H/D=1, reaction temperature of 550 °C, reaction time of 60 min, superficial gas velocity of 0.011 m/s, and pressure drop of 77 Pa during fluidization. We determined the best operating conditions for the NiO hydrogen reduction process based on these findings.

An electret filter composed of electrically charged fibers exhibits high efficiency, while maintaining a low pressure drop. Therefore, the electret filter is used in heating, ventilation, and air-conditioning (HVAC) systems. However, charges on the fiber can be shielded or neutralized by collected dust particles, degrading the collection efficiency of the electret filter. Alternatively, non-electret (mechanical) filters can also be used in HVAC systems. In this study, an external electric field of 5 kV/cm was applied to a non-electret filter module used in HVAC systems to investigate the effect of dust loading on filtration performance. The pressure drop with dust loading less increased in the presence of the electric field than in the absence of the electric field, resulting in a higher dust holding capacity of the filter module. The electric field significantly affected not only the pressure drop but also the collection efficiency. The initial collection efficiency of the filter module was increased by the electric field. In addition, the electric field continuously increased the collection efficiency of the HVAC filter module under dust loading.

Geldart groups A (NiO – 1300 μm, green), B (MoO3 - 480 μm, white), and C (NiO – 30 μm, gray color and MoS2 – 25 μm, black) particles were used in a transparent, acrylic fluidized bed reactor. The experiment was carried out for four cases by setting the position of the particles injected in the reactor as a variable. For these cases, Geldart group C particles (which are typically difficult to fluidize) were included. When easily fluidizable particles were placed at the bottom of the fluidized bed reactor, particle circulation and bubbling occurred. Channeling occurred when there were particles that were difficult to fluidize. Homogeneous fluidization was possible with vibration when channeling occurred. With the increasing vibration frequency, the pressure drop increased, and the minimum fluidization velocity decreased. The occurrence of channeling via vibration resulted in a high mixing index and variations in the pressure drop.

This research has examined fluidization and product characteristics through hydrogen reduction for nickel oxide (NiO) of contained in the Geldart group C assisted by vertical vibration in a fluidized bed reactor. It has confirmed that as vibration frequency and reaction temperature increase, the pressure drop trend becomes stable and minimum fluidization velocity reduces. As the gas–solid reaction increased with the increase in reaction temperature, oxygen contained in NiO was removed with a fast reaction time and therefore, the mass loss drastically decreased. When reaction temperature increased, the reacted fraction quickly increased because of the short reaction time. In the case of fluidization that was not under vibration, SEM and TEM analysis of the products showed agglomeration and chemical bonding. However, with a vibration, no agglomeration occurred, and a porous surface appeared. For fluidization under vibration, energy-dispersive X-ray spectroscopy and mapping analysis of products showed that the oxygen content and distribution decreased, and a small amount of oxygen remained surrounding the product surface. Agglomeration occurred again at higher values, with a superficial gas velocity of 0.45 m/s and vibration frequency of 60 Hz. It has also confirmed that the vertical vibration relieves the forces between fine cohesive particles to eliminate agglomeration and give them an active fluidization state.

We fabricated and compared two high-temperature and high-pressure dust collector models: the conventional direct inlet model, where a round gas inlet pipe is connected to the bottom of the collector at a right angle; and the inertial inlet model, where a rectangular gas inlet pipe is tangentially connected. Their effects on the filtration performance of a ceramic candle filter were tested at 800 °C and 3 atm and compared. The inertial inlet model showed a slower increase in pressure drop as the filtering process progressed owing to the reduced dust load on the filter. The average cleaning interval was 4–7 times longer than that of the direct inlet model. The residual pressure drop increased in direct proportion to the filtration velocity and was about twice that of the inertial inlet model. The inertial inlet maintained a higher cleaning efficiency during operation than the direct inlet. The overall collection efficiency was over 99.999% with the inertial inlet model, allowing for slight variations according to the filtration velocity, and that of the direct inlet method was over 99.9% under the same conditions.