Hydrodynamic characteristics of mixing in a three-phase system (gas-liquid-solid)‎

Dissertant

Hadi, Raid Tariq

Thesis advisor

Muhammad, Thamir J.
Sulaymun, Abbas Hamid

University

University of Technology

Faculty

-

Department

Department of Chemical Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2004

English Abstract

An investigation was conducted on the critical gas velocity and applied power for complete suspension of solid particles in QVF hemispherical bottom gas spared vessel of 0.46 m inside diameter and lm height.

The operating conditions used are ; particle size (dp), of 63-90, 90-125, 125-180 and 180-250 pm, height of liquid level to vessel diameter ratio (L / D) of 0.7, 0.9, 1.1 and 1.3, weight of solids (Ws) of 0.4, 0.8, 1.2 and 1.6 kg.

Single ring sparer with size of holes (d0) equal to 1 mm, different gases (air, helium, argon and carbon dioxide), Newtonian liquids (water and kerosene) and non-Newtonian liquids four concentrations of carboxy methyl cellulose solutions).The critical gas velocity and total applied power were found to increase with increasing particle size, solid concentration and gas density and with decreasing L / D ratio and liquid viscosity.

A comparison between experimentally gas sparging and theoretically mechanical agitation shown that the first system is less efficient (larger power) in most cases.

However, sometimes, gas sparging fills a real need in applications involving aggressive gases as well as in high temperature and pressure operation.

Empirical correlation for critical gas velocity has been found as follows : VGC / VS = 12.748 (Re)-0.052 (Fr).618 (We).108 dp / L 0.100 (Δ p) / pL-2.206 pG / pL 0.005 CW / PL 0.205 Statistical analysis shows that the average absolute error and correlation coefficient are 1.42 % and 0,994, respectively.

Bubble monitoring and analyzing system (BMAS) technique consists of electro-resistivity probe, interface, visual basic program and personal computer (Pentium 3), was used in this work to measure the bubble rise velocity, bubble diameter, bubble, frequency, number of bubbles and gas hold-up.

The electro-resistivity probe consisted of two tips, which are aligned vertically and are 0.85 cm apart.

The probe detects the difference in conductivity of gas and liquid. Gas hold-up is correlated with the critical gas velocity and liquid and solid properties.

The correlation obtained gives an average absolute error and correlation coefficient of 0.95 % and 0.9778, respectively. ∈G = 1.157 (gμ4L ) / pLσL3-2.275 VGC μL / σL 0.143 pG / pL 0.179 Δp / pL-0.035 CW / (PL )-0.143 μG / μL 0.296 The average liquid circulation velocity is calculated using empirical correlation presented by Zehnder (1982).

In addition, the mixing time pulse technique) and intensity of mixing, have been measured in present study.

The optimum operating conditions are obtained by calculating the intensity of mixing for the different experimental conditions.

It was noticed that mixing intensity is maximum for particle size in the range of 180 to 250 urn, L / D = 1.1 and Ws = 1.6 kg An analytical model was derived to estimate the liquid velocity in three phase system using forces balance and L / D = 0.7-1.3, dp = 63-250 um and Ws = 0.4-1.6 kg.

The model derived is : VL= [█(2 / 3 d2b g (pL-pG) 1 / 2 db Vb2 (εs ps + 0.44pL)-4σ@1 / 2 dbps εs / εL2 (1 + 2εL @Vb / VL))] Results of comparison between the analytical correlation and two-empirical correlations presented by other investigators show that the.

average absolute error is equal to 21.4 % and 11.7 % respectively The particle settling velocity of three phase systems is estimated by a modified forces balance.

The empirical correlation obtained gives low error at particle size in the range of 125 to 250 p.m. [(dpg (PS -PL) + 2psV2br) / (3 / 4 CDPL)]

Main Subjects

Chemistry

Topics

• Fluid dynamics

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305955