| The
Ozone Research Center of Cuba has participated
in all Ozone World Congresses in the last 17 years
and it is a corporate member of the International
Ozone Association (IOA) since 1995.
In the 15th Ozone World Congress, held in
London on September 11th-15th,
2001, the following papers were presented:
Kinetics of Cane Sugar Liquors Decoloration by Ozone
L. A. Fernández, R. Pérez Rey, M. Rodríguez1,
E.Veliz , C. Alvarez y Ch. Baluja
Ozone Research Center
1"José A. Echevarría"
Higher Polytechnic Institute
The kinetics of color remotion by
ozone in sugar cane liquors obtained from cane sugar
refining production is presented. In our Center it
has been shown that under certain conditions ozone
is a suitable decolorizing agent for this purpose,
obtaining high decoloration degrees at laboratory,
bench and pilot plant scales.
Due to the rapidity of chemical
reaction in this complex system, the rate constant
determination is rather difficult by direct kinetics
methods. Kinetic study for this process has been developed
with the use of Danckwert's model (equation 1) based
on known chemical and mass transfer principles. A
good result of this procedure by the use of a model
reaction between ozone and unsaturated hydrocarbons
was obtained.
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(1)
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The reactions involved in the
decoloration process follow a second order kinetic.
The equation provided by Danckwert's model allows
the kinetic coefficient determination (BO3) under
steady state conditions, by trial and error method.
Colorant concentration estimation
was determinate through the relation of liquor's optical
density decrease at 420 nm and ozone consumption,
taking into account the stechiometric relations. Colorants
concentration values was about 1x10-3 mole/L.
More than 20 experiments, in a continuous
reactor have been done under different experimental
conditions. At these conditions, BO3 values
were between 105 and 107 L/mole.s,
that means, according to Danckwert's
theory, that the kinetic regime of ozone absorption
correspond to a fast second order reaction.
This work brings the possibility
to make the kinetic determination of the rate coefficients
involved in a very complicated system like ozone-cane
sugar liquors, which represents a novel use of ozone
as decolorizing agent in sugar cane industry.
Modeling
Hydrodynamics and Estimation of Design Parameters of Ozone
Bubble Column
M. Bataller, E. Veliz, D. Lodos y C. Alvarez
Ozone Research Center
The impact of reactor design becomes
of primary importance for the ozone process efficiency.
The subject of this paper is to study the hydrodynamics
of water flow, in a bubble column, in order to evaluate
and estimate design parameter values such as: superficial
liquid velocity (UL) and effective contact
time (T10),
to improve the performance of existing contactors,
which are provided with identical gas diffusion system
and to use this knowledge in new columns designs.
A tracer study, followed by mathematical
modeling, has been performed. Experimental conditions
range (liquid flowrates: 1 - 3 m3/h and gas
flowrates: 0.18 - 0.54 m3/h), covered the
operating conditions of several water treatment systems
installed at different plants in service. A two
parameters model is proposed,
which adequately describes the flow liquid pattern
observed. The model consideres the reactor as the
sum of N well-mixed reactors in series plus a well-mixed
reactor of different volume.
Experimental data is reported and
discussed in terms of hydrodynamic performance of
the column expressed as Tm/t
(mean value over hydraulic residence time) and
T10/t ratios.
It was confirmed
that the superficial liquid velocity is an important
design parameter in this sort of contactor. The best
hydraulic behavior was obtained when the UL
is 63,65 m/h, corresponding to Tm/t
of 0.96, which indicates the absence of dead zone or
short circuiting. The influence of the UL on
the mass transfer was evaluated
also; the results of diferent water treatment plants
demostrated that the residual ozone concentration
in the effluent increased about a 20 %, when the UL
values were between 60 and 70 m/h.
In the order hand,
T10/t ratio
are between 0.40 and 0.47 indicating a flow pattern of
the liquid phase different to plug flow pattern. The
effective contact time estimation permits to evaluate
the T10/t
product value and the residual ozone concentration,
which should be maintained in the reactor.
Ozone
Inactivation Kinetic of Multiple Antibiotic Resistant
Strains of Bacteria
in Water
M. S. Gutiérrez, I Lezcano, E. Sánchez,
Ch. Baluja
Ozone Research Center
One of the more important problems
in antibiotic therapy is the capability of bacteria
to develop multiple antibiotic resistance. The man
can be in contact with these microorganisms by different
ways (infected water, direct contact etc.). The oxidant
property of ozone is used in water treatment as disinfectant.
The objective of this work is to determine the ozone
inactivation kinetics of different Gram positive and
Gram negative bacterial strains from clinical isolation
that resist high concentration of chlorine and compare
them with reference strains.
The final concentration of microorganisms
employed in experiments was from 105 to
107 CFU/mL and chlorine concentration was
between 0.5 - 4 mg/L in bi-distilled water. The ozone
was bubbling in a 100 mL semi - batch reactor and its
concentration in bi-distilled water was between 0.36
- 2 mg/L. The result suggests that the concentration of
chlorine for multiple antibiotic resistant strains could
be higher than in the case of reference strains. Gram
positive strains are also more resistant to chlorine
than Gram negative ones. The ozone inactivation follows
a first order kinetic law with respect to the bacterial
concentration, and a second kinetic order for ozone
concentration. The multiple antibiotic resistant strains
are more resistant to ozone than reference strains,
but there are not statistical differences between
Gram negative and Gram positive strains of a clinical
isolation. There are not statistical differences in
ozone resistance between strains of the same species
from clinical isolates.
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