Continuous stirred tank reactor (CSTR):

Conductivity measurement

Name of student: Shwan Sarwan Sadiq

Group: B

Date of Exp. OCT 28th 2015

Submission date: NOV 11th 2015

Supervisor: ms.lameha

Chemical Engineering Department

Chemical reactors lab

3rd stage

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Table of content:

Aim of the experiment 3 Theory 4 &5 Apparatus 6&7 Methodology

8,9,10,11,12,13,14,15,16,17,18 Data sheet 19 Graphs 20 Discussion 21,22&23 References 24

Aim of the experiment:

Measurement of the conductivity for a base – water

Mixture along time at high temperature using different

Concentrations.

Theory:

CSTR:

_it’s called ‘mixed reactor ‘, ‘back mix reactor’, ‘Continuous stirred

Tank reactor CSTR ‘. It’s a reactor in which contents are

well mixed And uniform throughout. Thus, the exit stream

from the reactor has the same composition as the fluid

within the reactor. The pattern of flow is mixed flow and is

used primarily for liquid phase reactions.

More specifically, continuous stirred tanks are used for

relatively slow reactions of liquids and slurries. .

_Its normal operation is at steady state, where the conditions

in the

Reactor don't change with time and it’s assumed to be

perfectly mixed,

So the contents have relatively uniform properties such as

temperature, Density, etc.

Conductivity:

Conductivity is a measure of how well a solution conducts

electricity. To carry a current a solution must contain charged

particles, or ions. Most Conductivity measurements are made

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in aqueous solutions, and the ions responsible for the

conductivity come from electrolytes dissolved in the Water.

Salts (like sodium chloride and magnesium sulfate), acids (like

Hydrochloric acid and acetic acid), and bases (like sodium

hydroxide and Ammonia) are all electrolytes. Although water

itself is not an electrolyte, it does have a very small

conductivity, implying that at least some ions are Present.

The ions are hydrogen and hydroxide, and they originate

from the Dissociation of molecular water.

_In conductivity works, it is necessary to work with as pure

As possible solvents because any impurity affects to

Conductivity therefore, the distilled water has to be used

During the experiments rather than tap water.

Apparatus:

To study CSTR reactor, it is necessary to use a service

Module and Interface called QUSC. This unit provides the

reagents and the thermostatized water to the reactor under

study.

Base module and interface, QUSC:

QUSC. Service Unit:

_This unit is common for the Chemical Reactors, and can

work with one or several reactors.

_ Accommodation and exchange system of the reactors,

quick and easy to handle.

_It supplies all the services for the operation of each reactor

_ Anodized aluminum structure and panels of painted steel.

_ Main metallic elements in stainless steel.

_ Diagram in the front panel with similar distribution to the

elements in the real unit.

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_2 Peristaltic dosing pumps with variable speed. Flow rate

up to 3 l. /h.

(Unit standard disposition). With another disposition, they

could reach a flow rate up to 10 l./h.

_ Thermostatic bath of 6 l. capacity. Temperature control of

hot water in order to maintain the reactor temperature.

_Pump of 3 l. /min., to impel the thermostatization water

from the bath to the reactor.

_2 Tanks for the reagents, of 1 l. capacity each one, made in

Pyrex glass.

_The control of the reaction is carried out by a conductivity

sensor,

Which allows the reaction evolution parameterization in real

time.

_ Three “J” type temperature sensors, one to know the

thermostatic

bath temperature in a continuous way and two sensors

to know the

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Water temperature at the thermostatic bath water inlet and

outlet.

_ Quick connectors with shutoff valve that enable an easy

coupling of

The Service Unit to the chosen reactor.

_All elements of this unit are chemically resistant.

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Electronic Console:

Metallic box.

_ Temperature sensors connectors.

_ Digital display for temperature sensors.

_ Selector for temperature sensors.

_ Peristaltic pumps controllers and switches.

_ Water pump switch.

_ Stirrer switches.

_heating element controller.

The reagents supply circuit is constituted by a PTFE pipe of 6

mm. The reagents are introduced into two Pyrex vessels

of 1 liter each placed at the rear part. There are two

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Peristaltic pumps to move the reagents. The following valves

are located at the Module’s base:

_The 6 mm valves (1) are mounted at the peristaltic

pumps outlet and they must be connected to the reagent

inlet of the Reactor.

_The ball valves with the mark (2) are of water outlet and

inlet.

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They have a tube of 8 mm which must be connected to

the water inlet and outlet of the reactors. The

connections are Interchangeable between them.

_The temperature control system consists of a thermostatic

Bath, whose temperature is controlled by means of a PID

Control on this bath temperature. The thermostated water

System is also composed of a thermostatization water

impeller pump, with variable flow by means of the valves (2).

_The data acquisition and process control system is

Centralized in the electronic interface connected to the

different elements which constitute both the base

module and the reactor module.

Continuous Stirred Tank Reactor Module:

The body of the reactor, made in Pyrex glass, has a capacity

of 2 liters and it is specially designed to work in

continuous, although it also allows to work in discontinuous

if the reagents are introduced to the desired volume and

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the pump are stopped. There is a manual discharge valve at

the lower part for this purpose.

_During the operation in continuous, the final product outlet

is carried out by the stainless steel tube (4) which is

regulable in height, loosening the brass nut.

This allows to work with different reaction volumes.

_The stirring system (1) with speed control and indication

allows The study of the influence of both continuous and

discontinuous Agitation in the reaction kinetics.

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_ System to heat the reaction formed by a stainless steel coil

(3) through which the water from the Service Module bath

circulates. The water inlets to the coil from the service

module will be done through the fittings of 8 mm placed

at the lower part of the reactor.

_The monitoring of the reaction is carried out using a

conductivity cell with conductivity meter, which allows

measuring the evolution of the reaction in real time.

_The thermostatic bath has been designed to keep constant

the temperature around the reactor. A volume of 9 liters has

been taken, because this volume allows the control of the

temperature of water every 0.1ºC.

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The conductivity meter or conductivity sensor:

Applies a temperature compensation factor by default to

Compensate for the change of the measurement due to

Temperature. Such factor has a factory-set value of 2%,

which

implies a correction of 2% per degree increased with respect

to the reference temperature. Depending on the practical

exercise to be performed, we may want this value be 0%, so

that it does not compensate for the temperature influence

(when we want to study ionic conductivities) or have a

specific value between 0 and 5% (when we want to

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associate conductivity and conversion of the reaction directly).

The default factor is 2%, but it can be optimized by

studying the conductivity relation of each species with

the temperature and then adjusting the compensation

factor (between 0 and 5%) that better fits each reaction

1) To compensate for the compensation factor of the

Conductivity meter, press “TEMP”. The value adjusted

At that moment will appear in the screen. Press “TEMP”

Again to exit the screen.

2) To adjust the % of the compensation factor press“TEMP”

and then the key “FACTOR ADJ” successively until obtaining

the desired value (Between 0 and 5%). Press “TEMP” again

to exit.

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Methodology:

1-dissolve 4 grams of NaOH in some distilled water .

2-fill a bottle of 800 ml of the NaOH mixture and

additional distilled water. And another bottle of water.

3-fix the bottles in their places and tide the pipes and

valves.

4-power on the Electronic Console and the heater to

increase the heat of the water in the bath and read the

first temperature reading and its conductivity.

5-open the pump and read the readings of temperature

and the conductivity for every 30 seconds.

6-after finishing readings for several times turn of the

pump and the Electronic Console then pour all the liquid

in the reactor.

Graphs:

Discussion:

Conductivity is a measure of how well a solution conducts electricity. To

carry a current a solution must contain charged particles, or ions. Most

conductivity measurements are made in aqueous solutions, and the ions

responsible for the conductivity come from electrolytes dissolved in the

water. Salts (like sodium chloride and magnesium sulfate), acids (like

hydrochloric acid and acetic acid), and bases (like sodium hydroxide and

ammonia) are all electrolytes. Although water itself is not an electrolyte, it

does have a very small conductivity, implying that at least some ions are

present. The ions are hydrogen and hydroxide, and they originate from the

dissociation of molecular water.

Salts, acids, and bases are electrolytes. They dissolve in water to form ions.

Although water is not an electrolyte, a very small concentration of

hydrogen and hydroxide ions are always present in pure water.

Increasing the temperature of an electrolyte solution always increases the

conductivity. The increase is significant, between 1.5 and 5.0% per °C. To

compensate for temperature changes, conductivity readings are commonly

corrected to the value at a reference temperature, typically 25°C. All

process conductivity sensors have integral temperature sensors that allow

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the analyzer to measure the process temperature and correct the raw

conductivity. Three temperature correction algorithms are in common use.

When we have to repeated conductivity measurement it means that there

is a mistake in increasing temperature so that and it proves that the ions

that conduct in the same temperature are equal in their conductivity

motion.

Position of conductivity cell

Make sure that all the poles of the conductivity cell are completely covered

by the sample. Always position a 2-pole cell in the center of the measuring

vessel.

Low conductivity measurements:

• use a flow-through cell, to avoid atmospheric contamination from carbon

dioxide,

• use cells with low cell constant, 1 cm-1 or lower,

• use non-platinized cells for easier cleaning and faster response,

• make sure that your instrument is able to apply an appropriate

measuring frequency

High conductivity measurements

• Use platinised cells to avoid polarisation errors, preferably 4-pole cells.

• Use cells with a high cell constant (1 cm-1) or higher if possible.

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• Do not dilute samples in order to bring them into measuring range.

Conductivity is not proportional to concentration at high levels.

• Make sure that your instrument is able to apply an appropriate measuring

frequency.

Since the accuracy of any measurement depends on proper calibration, a

fresh standard must always be used. Ideally, sample beakers and sensor

should be rinsed two to three times with the sample as the presence of

contaminants can lead to additional errors in conductivity results

When setting up a conductivity measurement system, the lab manager

must make appropriate choices relating to TC(temperature compensation),

such as o whether TC should be used, o setting the reference temperature,

o choosing a linear or nonlinear TC, and o choosing the appropriate TC

factor.

References:

1. http://www2.emersonprocess.com/siteadmincenter/

PM%20Rosemount%20Analytical%20Documents/Liq

_ADS_43-018.pdf

page 1

2. http://us.mt.com/dam/MT-

NA/pHCareCenter/Conductivity_Reduce_Common_E

rrors_WP.pdf

page 3

3. http://igz.ch/de/produkte/uebersicht.asp?action=do

wnload&fileid=8205

page 21

4. http://www.thermofisher.co.nz/Uploads/file/Environ

mental-Industrial/Environmental-Monitoring-

Safety/Water-Monitoring-Treatment/Tech-Tip-Top-

Ten-Conductivity-Mistakes-NZ.pdf

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