Lowest Gas Velocity Research Articles

Effect of Supersonic Oxygen Lance on Post-Combustion in Converter Steelmaking Process – Experiment and Analysis with Converter Simulator

Employing post-combustion technology in the converter, using the sensible heat of the hot metal and the oxidation reaction heat as a heat source, is known to compensate for insufficient heat in the converter process. However, most studies on post-combustion have been conducted using subsonic nozzles, whereas actual converter processes use supersonic nozzles. Therefore, research on the combustion behavior of supersonic jets is needed. In this study, experiments and analyses were conducted using a converter simulator and a supersonic nozzle to investigate the effect of nozzle height on the post-combustion behavior. The reaction was set to complete combustion, with an O2gas flow rate of 150 L/min blown through the upper lance and a CO gas flow rate of 300 L/min blown at the bottom of the simulator to represent the surface of the molten metal. The combustion reaction of CO gas was calculated to be rate-controlled by reactant mixing. The nozzle heights were set to 250, 380, and 530 mm from the surface of the molten metal. Post-combustion analysis showed that the lowest gas velocity was observed under the condition of the highest nozzle height of 530 mm, and the high temperature and reaction zones were widely distributed in the lower region. Therefore, to facilitate heat compensation to the molten metal, it is necessary to control the gas velocity of the molten steelgas interface slowly.

Velocity dependence of the performance of flowing-gas K DPAL with He and He/CH4 buffer gases: 3D CFD modeling and comparison with experimental results

Accurate 3D computational fluid dynamics (CFD) modeling of flowing-gas K DPAL is presented, taking into account ionization and ion–electron recombination processes, ambipolar diffusion of K ions, and electron heating. Whereas in a static K DPAL with He buffer gas, the neutral K atoms in the lasing medium are depleted by these processes, the depletion can be mitigated by application of gas flow. The lowest gas velocity necessary for effective operation of a laser with He buffer is ∼ 500 m / s , and is much higher than previously estimated [Opt. Express 25, 30793 (2017)OPEXFF1094-408710.1364/OE.25.030793]. The predictions of the model for different H e / C H 4 mixtures are presented and verified by comparing them with experimental results obtained at the Air Force Institute of Technology [“Kinetics of higher lying potassium states after excitation of the D2 transition in the presence of helium,” dissertation (Air Force Institute of Technology, 2018)].

Study of electrostatic charging of single particles during pneumatic conveying

In this study the electrostatic charging behaviour of single particles of different sizes and materials were investigated during pneumatic conveying. The particles used included 3.18 and 0.79 mm PTFE as well as 3.18 mm Nylon particles. Particles were pneumatically conveyed in stainless steel (316 Grade) tubes with 4.57 mm inner diameter. Effects of conveying tube length, conveying gas velocity and pathway of particles (i.e. addition of 90° elbows and smooth bends) on particles charge-to-mass ratio were studied. Results showed that the smaller PTFE particles reached the saturation charge in the longest straight tube at all conveying gas velocities tested. Whereas the other two larger particles reached saturation charge only in the longest straight tube and at the lowest gas velocity. For large particles moving in straight tubes, in general, the lowest gas velocity resulted in a higher charge-to-mass ratio. The particles pathway had a large impact on their charging behaviour at high gas velocities, whereas at the lowest gas velocity, the total tube length was more influential on particles charging. Finally, the charge of the particles determined by measuring the current from the conveying line was found to be in good agreement with that measured directly by a Faraday cage.

Aerated vibrofluidization of silica nanoparticles

AbstractVigorous homogeneous fluidization of 12‐nm silica particles was easily achieved by coupling aeration with vibration. Vibration (with frequency in the range of 30 to 200 Hz, and vibrational acceleration in the range of 0 to 5 g) was found to be necessary to achieve smooth fluidization. The minimum fluidization velocity, defined as the lowest gas velocity at which the pressure drop across the bed reaches a plateau, was approximately 0.3–0.4 cm/s, and essentially independent of the vibrational acceleration. However, the bed expanded almost immediately after the air was turned on, reaching bed expansions of three times the initial bed height or higher. Thus the bed appeared to exhibit a fluidlike behavior at velocities much lower than the minimum fluidization velocity. Fluidization of nanoparticles was achieved as a result of the formation of stable, relatively large, and very porous agglomerates. Practically no bubbles or elutriation of particles was observed. A fractal analysis combined with a modified Richardson–Zaki approach is proposed for prediction of agglomerate size and voidage. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1776–1785, 2004

Baffle effects on performance of catalytic circulating fluidized bed reactor

AbstractBaffle effects on the performance of a catalytic circulating fluidized bed reactor were examined experimentally. The circulating fluidized bed reactor or riser was 102 mm in diameter and 6.32 m in height. Reaction was the catalytic decomposition of ozone using FCC particles with a mean diameter of 89 μm, impregnated with ferric oxide as catalysts. Four ring‐type baffles, mounted horizontally around the riser wall, were used in this study. Ozone concentrations were measured in both axial and radial directions under various operating conditions in a riser with and without baffles. Experimental results showed that in a riser with baffles, the ozone concentration in the radial direction was more uniform and the ozone conversion was higher than that in a riser without baffles except at the lowest gas velocity used. A mathematical model developed accounted for the gas‐phase ozone conversion under various operating conditions. The gas‐solid contact efficiency in the riser was discussed in light of the model.