Continuous Stirred Tank Reactor 40L CHE57 4 ABSTRACT/SUMMARY On 29th March 2012, our group consists of four members have conducted an experiment on Continuous Stirrer Tank Reactor (CSTR) 40 L for the purpose of completing the syllabus of the Chemical Engineering Laboratory subject. In this experiment, we wanted to observe and know more details about Continuous Stirred Tank Reactor (CSTR) 40 L especially about its operation and to carry out the saponification reaction between NaOH and Et (Ac) in CSTR. This experiment was carried out to determine the effect of the residence time onto the reaction extent of conversion and also to determine the reaction rate constant. Before the experiment started, we ensured the general start up procedure was carried out properly so that the the apparatus will run without any disturbance. After the methodology of start up process was done, we began the experiment by opening valves V5 and V10 to obtain the highest possible flow rate into the reactor. For this experiment, the feed flow rates were adjusted in increasing order. For each flow rate, 50 mL sample was taken to be used in the back titration procedure. In back titration, the samples were titrated with NaOH for saponification reaction. The amounts of NaOH titrated were recorded. A few calculations had been conducted to determine the conversion, residence time and concentration of NaOH. Two graphs were plotted where the slope of conductivity v's conversion graph was defined to be -0.1233. While for the second graph, the descending order of the 50th minutes to 33.33th minutes showed that the objectives were successfully achieved. More details can be viewed in the result. 1
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Continuous Stirred Tank Reactor 40L CHE574
ABSTRACT/SUMMARY
On 29th March 2012, our group consists of four members have conducted an experiment on
Continuous Stirrer Tank Reactor (CSTR) 40 L for the purpose of completing the syllabus of
the Chemical Engineering Laboratory subject. In this experiment, we wanted to observe and
know more details about Continuous Stirred Tank Reactor (CSTR) 40 L especially about its
operation and to carry out the saponification reaction between NaOH and Et (Ac) in CSTR.
This experiment was carried out to determine the effect of the residence time onto the reaction
extent of conversion and also to determine the reaction rate constant. Before the experiment
started, we ensured the general start up procedure was carried out properly so that the the
apparatus will run without any disturbance. After the methodology of start up process was
done, we began the experiment by opening valves V5 and V10 to obtain the highest possible
flow rate into the reactor. For this experiment, the feed flow rates were adjusted in increasing
order. For each flow rate, 50 mL sample was taken to be used in the back titration procedure.
In back titration, the samples were titrated with NaOH for saponification reaction. The
amounts of NaOH titrated were recorded. A few calculations had been conducted to
determine the conversion, residence time and concentration of NaOH. Two graphs were
plotted where the slope of conductivity v's conversion graph was defined to be -0.1233. While
for the second graph, the descending order of the 50th minutes to 33.33th minutes showed that
the objectives were successfully achieved. More details can be viewed in the result.
1
Continuous Stirred Tank Reactor 40L CHE574
INTRODUCTION
In a continuous-flow stirred-tank reactor (CSTR), reactants and products are continuously
added and withdrawn. In practice, mechanical or hydraulic agitation is required to achieve
uniform composition and temperature, a choice strongly influenced by process considerations.
The CSTR is the idealized opposite of the well-stirred batch and tubular plug-flow reactors.
Analysis of selected combinations of these reactor types can be useful in quantitatively
evaluating more complex gas-, liquid-, and solid-flow behaviors.
Because the compositions of mixtures leaving a CSTR are those within the reactor, the
reaction driving forces, usually the reactant concentrations, are necessarily low. Therefore,
except for reaction orders zero- and negative, a CSTR requires the largest volume of the
reactor types to obtain desired conversions. However, the low driving force makes possible
better control of rapid exothermic and endothermic reactions. When high conversions of
reactants are needed, several CSTRs in series can be used. Equally good results can be
obtained by dividing a single vessel into compartments while minimizing back-mixing and
short-circuiting. The larger the number of CSTR stages, the closer the performance
approaches that of a tubular plug-flow reactor.
The continuous stirred tank reactor (model BP 143) unit is suitable for student experiments on
continuous chemical reactions. The unit consists of jacketed reaction fitted in the agitator and
condenser. The unit comes complete with vessels for raw materials and product, feed pumps,
and thermostat.
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Continuous Stirred Tank Reactor 40L CHE574
OBJECTIVE
To verify the conductivity values by manual determination on experiment sample
To carry out saponification reaction between NaOH and Et(Ac) in a CSTR
To determine the effect of residence time onto the reaction extent of conversion
To determine the reaction rate constant
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Continuous Stirred Tank Reactor 40L CHE574
THEORY
Rate of Equation and Rate Law
The reaction rate (rate of reaction) or speed of reaction for a reactant or product in a
particular reaction is intuitively defined as how fast or slow a reaction takes place. For
example, the oxidation of iron under the atmosphere is a slow reaction that can take many
years, but the combustion of butane in a fire is a reaction that takes place in fractions of a
second.
Consider a typical chemical reaction:
aA + bB → pP + qQ (eq 1.1)
The lowercase letters (a, b, p, and q) represent stoichiometric coefficients, while the capital
letters represent the reactants (A and B) and the products (P and Q).
According to IUPAC's Gold Book definition the reaction rate r for a chemical reaction
occurring in a closed system under constant-volume conditions, without a build-up of reaction
intermediates, is defined as:
where [X] denotes the concentration(Molarity, mol/L) of the substance X. (NOTE: Rate of a
reaction is always positive. '-' sign is present in the reactant involving terms because the
reactant concentration is decreasing.) The IUPAC recommends that the unit of time should
always be the second. In such a case the rate of reaction differs from the rate of increase of
concentration of a product P by a constant factor (the reciprocal of its stoichiometric number)
and for a reactant A by minus the reciprocal of the stoichiometric number. Reaction rate
usually has the units of mol L−1 s−1. It is important to bear in mind that the previous definition