Cold Model Investigation Research Articles

Cold model investigation of mixing-separation time distribution in a multi-element process coupled cyclone reactor for ionic liquid-catalyzed isobutane/butene alkylation.

The residence time distributions of a dispersed phase in a multi-element process coupled cyclone reactor for ionic liquid-catalyzed isobutane/butene alkylation were numerically studied with a CFD method. The Eulerian–Eulerian multiphase flow model and Reynolds stress model were applied to simulate the flow field distribution in the cyclone reactor. The time in which the dispersed phase flows from the inlet slot to the overflow outlet tube is defined as the mean mixing-separation time between two phases in the cyclone reactor. The effects of the structural parameter of the slot on the mean mixing-separation time were investigated in this work. The results show that the residence time distributions are unimodal except for the condition that the number of slots is 1. Besides, it is concluded that the velocity of dispersed phase flow into the reaction chamber and the relative velocity between two phases in the cyclone reactor are the main influence factors. Based on the results, a prediction model to explain the relationship between the mean mixing-separation time and the velocity of two phases was established.

Cold-model investigation of effects of operating parameters and overflow outlet diameter on separation with a liquid–liquid cyclone reactor for isobutane alkylation catalyzed by ionic liquid

A liquid–liquid cyclone reactor (LLCR) was designed to enhance mixing and accelerate separation between reaction products and catalysts during isobutane alkylation catalyzed by ionic liquid. The LLCR was designed on the basis of the axial-flow hydrocyclone. The effect of total inlet flow (Qt), feed ratio (rf), overflow ratio (ro) and overflow outlet diameter (Do) on the performance of LLCR (pressure drop, ΔP, and recovery, R) was investigated. The LLCR’s performance indices underflow pressure drop (ΔPu), overflow pressure drop, (ΔPo), glycerin water solution recovery (Rg), kerosene recovery (Rk), reduced efficiency were determined. The results were used to establish an empirical models predicting LLCR efficiencies from total inlet flow, feed ratio, overflow ratio and overflow outlet diameter. Besides, an optimal overflow ratio, ror, was proposed to realize the optimization of two-phase recovery, which is linear with the expression of feed ratio. The results show that the range of the empirical coefficients (k) in the expression of ror is 1.02–1.14.

A novel liquid-liquid cyclone reactor for ionic liquid catalyzed isobutane alkylation: Cold model investigation of the dispersed phase droplet size distribution

A novel liquid-liquid cyclone reactor for ionic liquid catalyzed isobutane alkylation: Cold model investigation of the dispersed phase droplet size distribution

The Penetration Behavior of an Annular Gas–Solid Jet Impinging on a Liquid Bath: The Effects of the Density and Size of Solid Particles

Top-blow injection of a gas–solid jet through a circular lance is used in the Mitsubishi Continuous Smelting Process. One problem associated with this injection is the severe erosion of the hearth refractory below the lances. A new configuration of the lance to form an annular gas–solid jet rather than the circular jet was designed in this laboratory. With this new configuration, the solid particles fed through the center tube leave the lance at a much lower velocity than the gas, and the penetration behavior of the jet is significantly different from that with a circular lance where the solid particles leave the lance at the same high velocity as the gas. In previous cold-model investigations in this laboratory, the effects of the gas velocity, particle feed rate, lance height of the annular lance, and the cross-sectional area of the gas jet were studied and compared with the circular lance. This study examined the effect of the density and size of the solid particles on the penetration behavior of the annular gas–solid jet, which yielded some unexpected results. The variation in the penetration depth with the density of the solid particles at the same mass feed rate was opposite for the circular lance and the annular lance. In the case of the circular lance, the penetration depth became shallower as the density of the solid particles increased; on the contrary, for the annular lance, the penetration depth became deeper with the increasing density of particles. However, at the same volumetric feed rate of the particles, the density effect was small for the circular lance, but for the annular lance, the jets with higher density particles penetrated more deeply. The variation in the penetration depth with the particle diameter was also different for the circular and the annular lances. With the circular lance, the penetration depth became deeper as the particle size decreased for all the feed rates, but with the annular lance, the effect of the particle size was small. The overall results including the previous work indicated that the penetration behavior of an annular jet is much less sensitive to the variations in operating variables than that of a circular jet. Correlation equations for the penetration depth that show good agreements with the measured values have been developed.

Penetration behaviour of an annular gas–solid jet impinging on a liquid bath: effect of the annular cross‐sectional area

Top blow injection of a gas–solid jet through a circular lance is used in the Mitsubishi continuous smelting process. One of the problems associated with such injection is the severe erosion of the hearth refractory below the lances. A new configuration of the lance to form an annular gas–solid jet rather than the circular jet was designed in this laboratory. With this new configuration, solid particles, fed through the centre tube, leave the lance at a much lower velocity than the gas, and the penetration behaviour of jet is significantly different than that of circular lance where the solid particles leave the lance at the same high velocity as the gas. In an earlier cold model investigation, the effects of gas velocity, solid feedrate and lance height of the annular lance were studied and compared to the circular lance. This paper reports on experimental work that includes the effects of the size of the annular lance, which greatly expands the applicable range of the developed correlation. It has been shown that the variation in penetration depth with the annular jet cross‐sectional area depends strongly on the mass loading of the solid particles. A correlation equation for the penetration depth that shows a good agreement with the measured values has been developed.

Cold Model Investigations of Melting of Ice in a Gas-Stirred Vessel

The melting of steel scrap in high temperature liquid iron melt is investigated by conducting cold model experiments of the melting of ice sample of different geometries and sizes in an argon-stirred vessel containing water. The melting process of ice samples is observed using a high-speed camera. Design of experiments is based on similarity criteria. The relationships between non-dimensional groups related to heat transfer (Nu, Re, Pr, and Gr) are derived for different experimental conditions. The results are compared with those reported in the literature. The heat transfer coefficient is estimated as a function of mixing power and is found to be in good agreement with the calculated values obtained by using reported relationships in literature.

Hydrodynamics of a dual fluidized bed gasifier

The hydrodynamics of a circulating fluidized bed gasification system with dual fluidized bed concept has been studied through a cold model investigation. The article focuses on the axial voidage, the pressure drops across various components and the solid circulation under different operating conditions. The control of solids circulation between the dual fluidized beds has been done through an L-valve system. A mathematical model of hydrodynamic behavior of the system has been presented. It is observed from the investigated operating parameters that the aeration flow, the secondary air flow and particle diameter have the strongest influence on system pressure drop and solid circulation.

Bottom blowing investigations on a cold model reactor to optimise mixing behaviour in metallurgical processes

Cold model investigations for discontinuous operating, metallurgical reactors are conducted with bottom blowing. Parameters are the bottom blowing rate, the h/d‐ratio and different bottom nozzle configurations, like a centric single nozzle, nozzle rings and screen bottoms. The main influence on the mixture behaviour is given by the h/d‐ratio. Furthermore, the mixing times are improved with increase of bottom blowing rate, nozzle diameter and eccentricity of the nozzle positions.

Cold model investigations of fluid flows and mixing within top and combined blowing in metallurgical processes

Cold model investigations were performed during top and combined blowing in metallurgical processes. The investigations include 2‐ and 3‐phase systems with gas, water and oil phase. The results of top blowing tests can be used to arrange and optimise the fluid flow. Further, conclusions can be drawn for the spraying and emulsification process, if the slag thickness is known. Under combined blowing conditions a small amount of stirring gas injected from the bottom has a great influence on mixing. According to the slag thickness, in combination with the power of the top blowing momentum, the fluid flow is dominated by top or bottom blowing. If bottom blowing is added as a stirring mechanism, a better mixing can not be guaranteed by this means. The bottom blowing conditions have to be adapted to the top blowing conditions and to the reactor geometry.

Cold Model Investigations of Fluid Flow and Mixing Characteristics by Bottom-blowing in Discontinuous Metallurgical Reactors.

Cold model investigations were performed in two and three phase systems, including water-, slag- and gas-phase. The following nozzle-arrangements were chosen: single central nozzle, centric row, eccentric row and eccentric triangle. The investigations show an intensive vortex formation in the bath as a result of a coupled variation of parameters like blowing rate and existence of a slag simulation phase. A clear-cut vortex is evident at an undercritical blowing rate. The buoyant free jets do not describe a stable path to the bath surface. Two liquid zones with two mutually distinct directions of circulation are present. In the case of the eccentric arrangements of the nozzles, a vortex occurs in the smaller partial zone; however, this vortex is not always stable. In the larger partial zone, a stable vortex with circular motion occurs. The tests with eccentric arrangements yield the best mixing results as a whole. The flow conditions in the bath at a supercritical volume flow rate effect the phenomenon of sloshing, that is an oscillating motion of the bath. The critical flow rate depends on the arrangement of the nozzles. The inception of sloshing occurs at a relatively low blowing rate with the use of a single central nozzle. Turbulent regions are observed in the bath here. In the case of eccentric nozzle arrangements, sloshing occurs only at higher blowing rates.

Cold model investigations into the effects of bottom blowing in metallurgical reactors

Cold model investigations were performed into bottom blowing involving two-phase and three-phase systems. The investigations - performed with interrelated variation of the test parameters: bottom nozzle arrangement, number of nozzles, eccentricity of the nozzles, blowing rate, geometry of the model reactor and addition of a slag simulation phase - reveal a series of specific vortex patterns in the bath. The most favourable overall degree of mixing is achieved with an eccentric triangular arrangement of the bottom nozzles. Increasing the number of nozzles on the one hand, and spacing the bottom nozzles further apart on the other, improves the flow conditions and thus the degree of mixing in the bath. Upwards of a certain critical blowing rate, sloshing occurs at the bath surface. This sloshing limit increases with increasing eccentricity of the bottom nozzles. The presence of slag reduces the mixing times while at the same time increasing the torus angular frequencies.

An ice-water model study on formation of blowhole-free skin with reference to solidification of steel

A cold model investigation on the formation of blowhole-free initial skin was undertaken in the laboratory by freezing water containing dissolved carbon dioxide. Plane front unidirectional solidification was simulated. Experiments were conducted in a stagnant bath to study the effect of CO2 concentration in water and the rate of solidification on blowhole-free skin thickness. Some experiments were also conducted with artificial gas bubbling. Initially, the variation of thickness of ice with time deviated from the parabolic rate law of solidification. The thickness of blowhole-free skin decreased with increasing concentration of dissolved CO2 and solidification rate. Mild stirring increased the thickness of blowhole-free skin. Differential equations, along with requisite initial and boundary conditions, were solved by a numerical analysis technique to compute the concentration of CO2 in water at the moving ice-water interface. This revealed that very small supersaturations were required to form blowholes although the experiments were conducted under very clean and controlled conditions. Implications of some of the findings in connection with solidification of steel are indicated.