CEY Issue 3 Instruction Manual

PLUG FLOW REACTORInstruction Manual CEY ISSUE 3 December 2010 Table of Contents Copyright and Trademarks ...................................................................................... 1 Use with CEX Service Unit.......................................................................................... 2 General Overview ....................................................................................................... 3 Equipment Diagrams................................................................................................... 5 Important Safety Information....................................................................................... 6 Introduction.............................................................................................................. 6 Electrical Safety....................................................................................................... 6 Wet Environment ..................................................................................................... 6 Heavy Equipment .................................................................................................... 6 Chemical Safety ...................................................................................................... 7 Water Borne Hazards .............................................................................................. 7 Description .................................................................................................................. 9 Overview.................................................................................................................. 9 Flow of Material ..................................................................................................... 10 Installation ................................................................................................................. 14 Advisory................................................................................................................. 14 Installation Process ............................................................................................... 14 Operation .................................................................................................................. 18 Operating the Software.......................................................................................... 18 Operating the Equipment....................................................................................... 29 Equipment Specifications.......................................................................................... 34 Overall Dimensions ............................................................................................... 34 Connection to Drain............................................................................................... 34 Ventilation.............................................................................................................. 34 Environmental Conditions...................................................................................... 34 Routine Maintenance ................................................................................................ 36 Responsibility ........................................................................................................ 36 General.................................................................................................................. 36 RCD Test............................................................................................................... 36 ii Table of Contents Temperature sensors Calibration .......................................................................... 36 Conductivity probe calibration ............................................................................... 37 Low conductivity Calibration (0-5 mS/cm) ............................................................. 37 Pipe work and connections.................................................................................... 38 Column packing..................................................................................................... 40 Static Premixer Packing ........................................................................................ 43 CEXC sensors fitting ............................................................................................. 44 Laboratory Teaching Exercises................................................................................. 46 Index to Exercises ................................................................................................. 46 Nomenclature ........................................................................................................ 46 Common Theory.................................................................................................... 47 Exercise A - Flow pattern characterisation - Step change ........................................ 49 Exercise B - Flow pattern characterisation - Pulse change....................................... 60 Exercise C - Conversion experiment......................................................................... 69 Contact Details for Further Information ..................................................................... 79 iii This document must not be used for any purpose other than that for which it is supplied and its contents must not be reproduced. All rights reserved.Disclaimer This document and all the information contained within it is proprietary to Armfield Limited. translated or disclosed to any third party.co. without the prior written permission of Armfield Limited. Should you have any queries or comments. adapted. please contact the Armfield Customer Support helpdesk (Monday to Friday: 0800 – 1800 GMT). in whole or in part. Contact details are as follows: United Kingdom International (0) 1425 478781 (calls charged at local rate) +44 (0) 1425 478781 (international rates apply) Email: support@armfield. Brands and product names mentioned in this manual may be trademarks or registered trademarks of their respective companies and are hereby acknowledged. modified. published.uk Fax: +44 (0) 1425 470916 Copyright and Trademarks Copyright © 2009 Armfield Limited. Any technical documentation made available by Armfield Limited is the copyright work of Armfield Limited and wholly owned by Armfield Limited. 1 . Please contact Armfield if a copy of this instruction manual is required. Contact details are included later in this document. An alternative instruction manual is available from Armfield that describes the use of the CEY in conjunction with the CEX Service Unit. 2 .Use with CEX Service Unit This instruction manual describes the use of the CEY Plug Flow Reactor in conjunction with the CEXC Computer Controlled Service Unit. CET MkII – Tubular Reactor. Reactions are monitored by conductivity probe as the conductivity of the solution changes with conversion of the reactants to product. Tubular reactors are often used when continuous operation is required but without back-mixing of products and reactants. the new CEB MkIII – Transparent Batch Reactor and CEZ – Laminar flow reactor.General Overview This instruction manual should be used in conjunction with the manual supplied with the CEXC Computer Controlled Chemical Reactor Service Unit. 3 . In addition. the feed enters at one end of a cylindrical tube and the product stream leaves at the other end. In a tubular reactor. This Manual provides the necessary information for operating the equipment in conjunction with the CEXC Computer Controlled Chemical Reactor Service Unit. and for performing a range of Teaching Exercises designed to demonstrate the basic principles of Chemical Reactors theory and use. the others being CEM MkII . Hence the properties of the flowing stream will vary from one point to another in both radial and axial directions. The long tube and the lack of provision for stirring prevent complete mixing of the fluid in the tube. all the experiments are followed visually by means of the reactor transparency and the use of colour indicators in all the experiments.Continuous Stirred Tank Reactor. It is one of five reactor types which are interchangeable on the Computer Controlled Reactor Service Unit (CEXC). The Armfield CEY-Plug Flow Reactor is an example of an ideal tubular reactor specially designed to allow detailed study of this important process. Armfield Instruction Manual CEY Plug Flow Reactor 4 . Equipment Diagrams Figure 1: Front View of Plug Flow Reactor Unit Figure 2: Top View of Plug Flow Reactor Unit 5 . Supervision of users should be provided whenever appropriate.Important Safety Information Introduction All practical work areas and laboratories should be covered by local safety regulations which must be followed at all times.  Electrical devices in the vicinity of the equipment must be suitable for use in wet environments or be properly protected from wetting. Wet Environment The equipment requires a header tank containing water. Electrical Safety The equipment described in this Instruction Manual operates from a mains voltage electrical supply. The equipment must not be operated with any of the panels removed. It must be connected to a supply of the same frequency and voltage as marked on the equipment or the mains lead. If requested then Armfield can supply a typical set of standard laboratory safety rules. and that the apparatus is operated in accordance with those regulations. check that the RCD is operating correctly by pressing the TEST button. but these are guidelines only and should be modified as required. as described in the Installation section of the manual. mishandled or badly maintained. Heavy Equipment This apparatus is heavy.  All users should be made aware that they may be splashed while operating the equipment. the RCD will switch off the electrical supply and reduce the severity of any electric shock received by an operator to a level which. Failure to trip means that the operator is not protected and the equipment must be checked and repaired by a competent electrician before it is used. As with any piece of sophisticated equipment. consult a qualified electrician or contact Armfield. The circuit breaker MUST trip when the button is pressed.  The apparatus should be placed in a location that is sufficiently strong to support its weight. If in doubt. To give increased operator protection. will not cause injury to that person. If through misuse or accident the equipment becomes electrically dangerous. under normal circumstances. the unit incorporates a Residual Current Device (RCD). At least once each month. Your CEY Plug Flow Reactor Unit has been designed to be safe in use when installed. and should wear appropriate clothing and non-slip footwear. operated and maintained in accordance with the instructions in this manual. alternatively called an Earth Leakage Circuit Breaker.  ‘Wet Floor’ warnings should be displayed where appropriate. It is the responsibility of the owner to ensure that all users are made aware of relevant local regulations. as an integral part of this equipment. dangers exist if the equipment is misused. During use it is possible that there will be some spillage and splashing. 6 . For example. Water Borne Hazards The equipment described in this instruction manual involves the use of water. but it serves as a useful example of the need for cleanliness.  It is the user’s responsibility to handle chemicals safely.  Prepare chemicals and operate the equipment in well ventilated areas.  Follow local regulations regarding chemical storage and disposal. which under certain conditions can create a health hazard due to infection by harmful micro-organisms. and all should be made aware of safe lifting techniques to avoid strained backs. the water must be changed regularly. 7 . Be careful with possible ignition sources. Any water containing this bacterium which is sprayed or splashed creating air-borne droplets can produce a form of pneumonia called Legionnaires Disease which is potentially fatal. health and safety and other issues. two or more people may be required for safety. Chemical Safety Details of the chemicals intended for use with this equipment are given in the Operation section.  Ethyl acetate is highly inflammable.  Extreme care should be taken whilst handling either acetic acid or acetic anhydride. Avoid breathing the ethyl acetate vapours. Where manual lifting is necessary. rust. Specific Safety Guidelines:  Indigo Carmine is dangerous and so should be used with the necessary safety procedures. such as electric current.Important Safety Information  Use lifting tackle. algae or sludge in water and will breed rapidly if the temperature of water is between 20 and 45°C. Legionella is not the only harmful micro-organism which can infect water. the microscopic bacterium called Legionella pneumophila will feed on any scale. Both chemicals are highly corrosive and care should be taken to avoid contact or inhalation of vapour. Under the COSHH regulations. very hot surfaces or flames. to install the equipment <give specific instructions>. where possible. and similar injuries. When handling use of rubber gloves and protection glasses are strongly recommended.  Only use chemicals specified in the equipment manuals and in the concentrations recommended. crushed toes. ie. the following precautions must be observed:  Any water contained within the product must not be allowed to stagnate. Chemicals purchased by the user are normally supplied with a COSHH data sheet which provides information on safe handling. It is important that these guidelines are adhered to.  Safety shoes and/or gloves should be worn when appropriate. Further details on preventing infection are contained in the publication “The Control of Legionellosis including Legionnaires Disease” . the equipment must be cleaned regularly. sludge.  A scheme should be prepared for preventing or controlling the risk incorporating all of the actions listed above. 8 . Note that other hazards may exist in the handling of biocides used to disinfect the water. scale or algae on which micro-organisms can feed must be removed regularly.Armfield Instruction Manual  Any rust.e. i. If this is not practicable then the water should be disinfected if it is safe and appropriate to do so.  Where practicable the water should be maintained at a temperature below 20°C.Health and Safety Series booklet HS (G) 70. 2 mm in diameter to thoroughly mix the reactants before they enter the reactor. The plug flow reactor is an acrylic column with a total volume of 1 L. Sockets on the rear of the service unit provide connections for the conductivity probe and thermocouple plugs. The CEY should be located close to the CEXC unit to allow connection to the instrumentation. To avoid movement of the glass beads there are four meshes. PTFE pipe. It is packed with glass beads of 1. It is packed with 3 mm glass beads to give plug flow with axial dispersion and improve flow distribution.Description Where necessary. 9 . Overview The reactor column is mounted on a stand to allow careful vertical alignment of the reactor. The reactor is supplied with a Feed assembly. refer to the drawings in the Equipment Diagrams section. An additional temperature sensor T2 is supplied with the CEXC and can be monitored. silicone pipe with smaller diameter and two barbed connectors. which are located at the ends of the reactor column and the static premixer. The 6 port valve allows injection of a determined volume of liquid for tracer experiments. The temperature value is displayed on the mimic screen of the CEXC software. It is not necessary to use the Hot Water Circulator. The conductivity probe supplied with the CEXC unit is also fitted into this sensor block allowing the conductivity to be monitored at the exit of the reactor. At the bottom of the reactor a static premixer with a total volume of 1. which is made up of a 6 port injection valve.6 ml is located. The temperature of materials exiting the column is measured by temperature sensor (T1) which is fitted into the sensor block and is located at the top of the stand. See Figure 3.Armfield Instruction Manual Figure 1: CEY reactor Flow of Material Reactants are pumped from the reagent bottles to the reactor passing through the 6 port injection valve. 10 . At the exit of the reactor the stream enters the sensor block where conductivity and temperature values are monitored and then drained. See Figure 2. Description Figure 2: Flow of material circuit It is recommended to place the Plug flow reactor close to CEXC plinth in order to simplify the sensor connections and shorten the reactants path. 11 . Changing the position of the valve links the alternate port pair together (Figure 4. When the injection valve is in the load position (Figure 4. This is achieved by using a tracer solution loop of defined lengths (230 cm for a volume of 10 ml). Carrier liquid (water) is directed to the reactor. The function of the valve is to inject the tracer solution (colourful solution) in a defined volume ratio.2).Armfield Instruction Manual Figure 3: Flow Exit Reactor Injection valve operation The injection valve has 6 ports and two positions.1) the tracer solution loop is filled. 12 . When the injection valve is switched to the injection position (Figure 4. Tracer solution passes out of the injection valve and it is recirculated. In one position adjacent ports are linked together inside the valve so that there are 3 pairs of linked ports.2) the carrier liquid (water) picks up the volume of the tracer solution (dye) contained in the loop and passes it to the reactor. 2: Injection valve positions Figure 5: Injection Flow Assembly (FIA) 13 .Description Figure 4.1 and 4. If connections to the 6 port valve are necessary see below: 14 . Installation Process Locate the CEXC unit in the desired location. Locate the CEY reactor unit close to the CEXC unit. Position the reagent bottles in the channel through the unit.Installation Advisory Before operating the equipment. Position the valve on the left hand side of the base. Tubing on the left side of each feed pump is fitted into the bottles as shown. on a steady workbench. it must be unpacked. Mount the 6 port injection valve assembly on to the CEXC using the two locating studs and the black thumbnuts. Change the silicone tubing on both sides of the CEXC peristaltic pumps for the new Silicone tubing (smaller diameter). Safe use of the equipment depends on following the correct installation procedure. assembled and installed as described in the steps that follow. Tubing on the right side is connected to the corresponding ports of the valve through the barbed connector supplied. enter valve. Fit the CEXC temperature sensor into the other gland on the sensor block (top channel of the sensor).reactor. Check that the two solutions follow two different circuits: Circuit 1(for water): Bottle 1. Fit the CEXC conductivity sensor into the gland in the sensor block of the reactor unit (bottom channel of the sensor block). Sensors should be inserted as described in CEXC sensors fitting. Circuit 2(Tracer): Bottle 2-enter valve – enter Loop (exit valve) – Exit Loop (enter valve) – Exit valve. 15 .exit valve.Installation Note: Changing the length of the Loop changes the volume of tracer injected into the column. Ensure that the circuit breakers and RCD are switched to ON (up). Note: this unit must be earthed.. The installation program should auto run. Check that the voltage specified on the equipment matches the supply voltage. Insert the CEY software CD-ROM into the CD-R drive of a suitable PC. Switch on the apparatus. Connect CEXC to a PC using the USB cable supplied.Armfield Instruction Manual Connect the conductivity probe and temperature sensor (T1) plugs to the sockets at the rear of the service unit.. If it does not.’ from your Start menu. select ‘Run. type run d:\setup where d is the letter of your CD-ROM drive. 16 . The on/off switch for the apparatus is located on the orange panel on the front of the plinth. Connect the power socket at the rear of the plinth to a suitable mains electricity supply. Refer to the Operation section for further information.Installation Follow the instructions on screen. 17 . The basic operation of the CEY has been confirmed. Run the software. ensure that you have read the Important Safety Information at the beginning of this manual. If multiple experiments are available then a menu will be displayed listing the options. Some of the major features are highlighted below. If IFD:ERROR is displayed check the USB connection between 18 . but full details on the software and how to use it are provided in the presentations and Help text incorporated in the Software.Operation Where necessary. Additionally. Operating the Software Note: The diagrams in this section are included as typical examples and may not relate specifically to the individual product described in this instruction manual. Wait for the presentation screen to open fully as shown: Before proceeding to operate the software ensure that IFD: OK is displayed at the bottom of the screen. Help on Using the Software or Using the Equipment is available by clicking the appropriate topic in the Help drop-down menu from the upper toolbar when operating the software as shown: Before operating the software ensure that the equipment has been connected to the IFD5 Interface (where IFD5 is separate from the equipment) and the IFD5 has been connected to a suitable PC using a USB lead. refer to the drawings in the Equipment Diagrams section. For further information on these actions refer to the Operation manual. The Armfield Software is a powerful Educational and Data Logging tool with a wide range of features. The apparatus must be set up in accordance with the Installation section. Load the software. to assist users. To view the presentations click Next or click the required topic in the left hand pane as appropriate. so users can jump immediately to the facility they require. directly in engineering units. Mimic Diagram The Mimic Diagram is the most commonly used screen and gives a pictorial representation of the equipment. 19 . calculated variables etc. Toolbar A toolbar is displayed at the top of the screen at all times. with continuously updated display boxes for all the various sensor readings. To aid recognition. as shown: The upper menu expands as a dropdown menu when the cursor is placed over a name. The user is met by a simple presentation which gives them an overview of the capabilities of the equipment and software and explains in simple terms how to navigate around the software and summarizes the major facilities complete with direct links to detailed context sensitive ‘help’ texts. If the problem persists then check that the driver is installed correctly (refer to the Operation manual).Operation the IFD5 and the PC and confirm that the red and green LED’s are both illuminated. pop-up text names appear when the cursor is placed over the icon. Presentation Screen . the software starts with the Presentation Screen displayed. To return to the Presentation screen at any time click the View Presentation icon from the main tool bar or click Presentation from the dropdown menu as shown: For more detailed information about the presentations refer to the Help available via the upper toolbar when operating the software. Click More while displaying any of the topics to display a Help index related to that topic.Basics and Navigation As stated above. The lower row of icons (standard for all Armfield Software) allows a particular function to be selected. similar to the diagram as shown: 20 .Armfield Instruction Manual To view the Mimic Diagram click the View Diagram icon from the main tool bar or click Diagram from the View drop-down menu as shown: A Mimic diagram is displayed. 21 .Operation The details in the diagram will vary depending on the equipment chosen if multiple experiments are available. Manual data input boxes with a coloured background allow constants such as Orifice Cd and Atmospheric Pressure to be changed by over-typing the default value. Motor Speed and Discharge / Volume flowrate (from pressure drop across an orifice plate) are continuously displayed in data boxes with a white background. A box marked Motor Setting allows the speed of the motor to be varied from 0 to 100% either stepwise. which is an inherent characteristic of pressure sensors. by typing in values. Pressing the Zero button just before starting a set of readings resets the zero measurement and allows accurate pressure measurements to be taken referenced to atmospheric pressure. as shown: Clicking on the appropriate accessory or exercise will change the associated mimic diagram. The mimic diagram associated with some products includes the facility to select different experiments or different accessories. The data boxes associated with some pressure sensors include a Zero button alongside. graphs etc to suit the exercise being performed.Armfield Instruction Manual In addition to measured variables such as Temperature. The button always defaults to off at startup. 22 . It is usual to operate the equipment with the motor initially set to 100%. This action must be carried out before the motor is switched on otherwise the pressure readings will be offset. calculated data such as Motor Torque. usually on the left hand side of the screen. Pressure and Flowrate (from a direct reading flowmeter). These are automatically updated and cannot be changed by the user. if required. Clicking this button switches the power on (1) and off (0) alternately. or using the up / down arrows as appropriate. This button is used to compensate for any drift in the zero value. Control Facilities in the Mimic Diagram A Power On button allows the motor to be switched off or on as required. table. the green LED marked Watchdog Enabled will alternate On and Off. Click the the icon from the toolbar to start recording. a single set of samples is taken only when requested by the operator (useful when conditions have to be changed and the equipment allowed to stabilize at a new condition before taking a set of readings). One set of data will be recorded each time the icon from the icon is clicked. Namely. the parameters for Automatic sampling can also be set. Continuous sampling can be selected. Details on the operation of any automatic PID Control loops in the software are included later in this section. Data Logging Facilities in the Mimic Diagram There are two types of sampling available in the software. When the software and hardware are functioning correctly together. samples are taken regularly at a preset but variable interval. The type of logging can be configured by clicking Configure in the Sample dropdown menu from the upper toolbar as shown: In addition to the choice of Manual or Automatic sampling. Automatic logging is selected when transients need to be recorded so that they can be plotted against time. the time interval between samples can be set to the required number of minutes or seconds. If the Watchdog stops alternating then this indicates a loss of communication between the hardware and software that must be investigated. Manual logging is selected when obtaining performance data from a machine where conditions need to stabilize after changing appropriate settings. with no time limit or sampling for a fixed duration can be set to the required number of hours.Operation then reduce the setting as required to investigate the effect of reduced speed on performance of the equipment. In Manual logging. click icon from the toolbar to stop recording. The type of logging will default to manual or automatic logging as appropriate to the type of product being operated. minutes or seconds as shown: 23 . In Automatic logging. namely Automatic or Manual. To record a set of set of data values from each of the measurement sensors click the main toolbar. Armfield Instruction Manual Tabular Display To view the Table screen click the View Table icon click Table from the View dropdown menu as shown: from the main tool bar or The data is displayed in a tabular format, similar to the screen as shown: 24 Operation As the data is sampled, it is stored in spreadsheet format, updated each time the data is sampled. The table also contains columns for the calculated values. New sheets can be added to the spreadsheet for different data runs by clicking the icon from the main toolbar. Sheets can be renamed by double clicking on the sheet name at the bottom left corner of the screen (initially Run 1, Run 2 etc) then entering the required name. For more detailed information about Data Logging and changing the settings within the software refer to the Help available via the upper toolbar when operating the software. Graphical Display When several samples have been recorded, they can be viewed in graphical format. from the main To view the data in Graphical format click the View graph icon tool bar or click Graph from the View drop-down menu as shown: 25 Armfield Instruction Manual The results are displayed in a graphical format as shown: (The actual graph displayed will depend on the product selected and the exercise that is being conducted, the data that has been logged and the parameter(s) that has been selected). Powerful and flexible graph plotting tools are available in the software, allowing the user full choice over what is displayed, including dual y axes, points or lines, displaying data from different runs, etc. Formatting and scaling is done automatically by default, but can be changed manually if required. To change the data displayed on the Graph click Graph Data from the Format dropdown menu as shown: The available parameters (Series of data) are displayed in the left hand pane as shown: 26 Operation Two axes are available for plotting, allowing series with different scaling to be presented on the same x axis. To select a series for plotting, click the appropriate series in the left pane so that it is highlighted then click the appropriate right-facing arrow to move the series into one of the windows in the right hand pane. Multiple series with the same scaling can be plotted simultaneously by moving them all into the same window in the right pane. To remove a series from the graph, click the appropriate series in the right pane so that it is highlighted then click the appropriate left-facing arrow to move the series into the left pane. The X-Axis Content is chosen by default to suit the exercise. The content can be changed if appropriate by opening the drop down menu at the top of the window. The format of the graphs, scaling of the axes etc. can be changed if required by clicking Graph in the Format drop-down menu as shown: For more detailed information about changing these settings refer to the Help available via the upper toolbar when operating the software. PID Control Where appropriate, the software associated with some products will include a single or multiple PID control loops whereby a function on the product can be manually or 27 Alternatively.Armfield Instruction Manual automatically controlled using the PC by measuring an appropriate variable and varying a function such as a heater power or pump speed. the operator can retain manual operation and simply vary the value from 0 to 100% in the Manual Output box. If any of the PID settings need to be changed from the default values then these should be adjusted individually before clicking the Apply button. If appropriate. the PID loop can be changed to Automatic operation by clicking the Automatic button. 28 . then clicking Apply. The PID loop can be accessed by clicking the box labelled PID or Control depending on the particular software: A PID screen is then displayed as shown: The Mode of operation always defaults to Manual control and 0% output when the software is loaded to ensure safe operation of the equipment. The circuit breakers and RCD device located at the rear of the unit should be turned on beforehand. Clicking OK closes the PID screen but leaves the loop running in the background. Clicking Calculations displays the calculations associated with the PID loop to aid understanding and optimization of the loop when changing settings as shown: Clicking Settings returns the screen to the PID settings. Operating the Equipment Switching on the Unit The unit is switched on using the switch on the front of the unit. 29 . Control variable and Control Action can be varied to suit different exercises. Both the temperature controller and conductivity display should illuminate. In some instances the Process Variable. The value in the Manual Output box can be changed as required before clicking the Apply button.Operation The controller can be restored to manual operation at any time by clicking the Manual button. Derivative Time and Cycle Time (if appropriate) can be changed by the operator as required before clicking the Apply button. For more detailed information about these advanced functions within the software refer to the Help available via the upper toolbar when operating the software. however. Advanced Features The software incorporates advanced features such as the facility to recalibrate the sensor inputs from within the software without resorting to electrical adjustments of the hardware. in most instances these boxes are locked to suit a particular exercise. Where the variables can be changed the options available can be selected via a drop-down menu. Proportional Band. Settings associated with Automatic Operation such as the Setpoint. Integral Time. Recorded results can be displayed in tabular and graph format. and the software must be installed before connecting the PC to the CEXC. Operation and setting of specific controls is also provided within the experiments described in this manual. 30 .Armfield Instruction Manual Filling the feed bottles Lift the feed bottle lids and pour solutions in from above. which allows real-time monitoring and data logging of all sensor outputs and control of the heater unit and pumps. Operation of Data Logger and Software The Tubular Reactor is controlled using the CEY software supplied. Installation of the software is described in the Installation Guide. and also in the online Help Text accessible via the software Help menu. There is an extra temperature sensor ‘T3’ and ‘Low conductivity’ plugs with outputs on the software for extra connections made by the user. Mimic Diagram and software The equipment is usually controlled from the Mimic Diagram screen in the software. This shows all the sensor outputs. and controls for the pumps. The software runs on a WindowsTM PC which connects to the CEXC using a USB interface. The software may then be run from the Start menu (Start > Programs > Armfield Chemical Reactor Software > CEY). Operation of the software is described in a walkthrough presentation within the software. Operation 31 . ensuring that the hardware shuts down safely in case of a software or communications failure. The software also automatically generates a series of ‘Watchdog’ pulses.connector is necessary.Armfield Instruction Manual Feed pump speeds are controlled using up/down arrows or typing the flow rate in a value between 0 and the maximum ml/min. However. required by the plc. Concentration values must be typed in on each experiment so that the software will carry out the subsequent calculations. When tracer experiments take place. Click on the appropriate POWER ON symbol to start up the pumps. The type of experiment performed defines the operational layout. Conductivity and temperature values will be monitored on the screen and the data logged when ‘GO’ is clicked. one solution is injected into the reactor after another. Operating Plug Flow Reactor There are two modes of operation with the CEY Plug flow reactor: tracer experiment and conversion experiment operation. 32 . When performing experiments follow the experimental layouts described in each exercise. when conversion experiment takes place two solutions are injected into the reactor at the same time so that a T. In the teaching exercises section each experiment fully describes the required connections. the experiment has to be restarted since flow distribution will be affected and so will conductivity values. However. if a bubble enters the reactor when the tracer solution has been injected. Air bubbles in the reactor column Bubbles should not be allowed to enter the reactor column since this will have a negative effect on performance. All the connections should be set so that each solution passes through the correct port of the injection valve and is delivered to the reactor or back to the vessel. If any bubbles enter the column before the tracer solution is injected.Operation Operational Layout for tracer experiments Overall Process Having reviewed the components of the CEY it is worthwhile considering the process as a whole. 33 . Care should be taken not to pump any bubbles into the column. continue flowing water into the reactor until all bubbles are gone. The feed pump delivers the feed to the injection valve assembly. a. b.Equipment Specifications Overall Dimensions Reactor Unit: Height: 1381 cm Width: 859 cm Depth: 330 cm Reactor dimensions: Reactor column: Total length: 1044 mm Internal diameter: 34 mm External diameter: 40 mm Total volume column: 0. Temperature 5 °C to 40 °C. Operation outside of these conditions may result reduced performance. Indoor use. damage to the equipment or hazard to the operator.65 mm Diameter external 20 mm Connection to Drain Water exiting the equipment should be directed to a suitable drain capable of accepting volumes of up to 90 ml/min at temperatures not greater than room temperature. The chemical solutions used in each experiment at the required concentration should be directed to a suitable drain capable of accepting volumes of up to 90 ml/min at room temperature. Altitude up to 2000 m. 34 .919 dm3 Pre mixer cylinder: Length 42 mm Diameter internal 8. Environmental Conditions This equipment has been designed for operation in the following environmental conditions. Ventilation For optimum results it is advisable to operate the reactor column in a ventilated environment at a room temperature up to 25ºC. c. Normally only nonconductive pollution occurs. f. Temporary conductivity caused by condensation is to be expected. Maximum relative humidity 80 % for temperatures up to 31 °C. decreasing linearly to 50 % relative humidity at 40 °C. g. Mains supply voltage fluctuations up to ±10 % of the nominal voltage. NOTE: The normal level of transient over-voltages is impulse withstand (overvoltage) category II of IEC 60364-4-443. Typical of an office or laboratory environment 35 .Equipment Specifications d. Transient over-voltages typically present on the MAINS supply. e. Pollution degree 2. 36 . sump tray and pipework should be washed through with water to remove chemical residues. After use the feed bottles. However. and VR5 (T3 ZERO) and VR6 (T3 SPAN) for T3 (if an extra thermocouple is used). T2 and T3 windows are displayed. and then drained. T2 and T3 should be dipped into crushed ice. If a thermocouple calibrator is not available: Temperature sensor T1. Connect CEXC service unit to a PC and start up the Armfield software. should re-calibration become necessary the appropriate calibration potentiometers can be located using the diagram given in the CEXC manual (Routine Maintenance). Set to 25ºC and adjust VR1 (T1 ZERO) and VR2 (T1 SPAN) on the PCB to give 25ºC displayed on PC. Ensure the equipment has been connected to the electrical supply and switched on for at least 20 minutes. The temperature conditioning circuit (which provides the reading from the thermocouples supplied with the CEXC service unit) is located on a printed circuit board (PCB) inside the plinth on the right-hand side. Temperature sensors Calibration The temperature sensors are calibrated before delivery and should not require recalibration. Repeat the same procedure for T2 by adjusting VR3 (T2 ZERO) and VR4 (T2 SPAN) on the PCB to give 25ºC displayed on PC. Regular maintenance of the equipment is the responsibility of the end user and must be performed by qualified personnel who understand the operation of the equipment. and then adjust the ZEROS to give 0ºC. This should only be done once the unit has fully warmed up. Start up the Armfield software for the specific reactor. then sensors should be dipped into boiling water and then adjust the SPANS to 100ºC.Routine Maintenance Responsibility To preserve the life and efficient operation of the equipment it is important that the equipment is properly maintained. Open mimic diagram screen where T1. located at the rear of the plinth. should calibration become necessary use the following procedure. reactor vessel. However. If the RCD button does not trip when the Test button is pressed then the equipment must not be used and should be checked by a competent electrician. To access the PCB remove the panel on the right hand side of the plinth by removing the four fixing screws. General The equipment should be disconnected from the electrical supply when not in use. Check accuracy at 15º and 40ºC. If a thermocouple calibrator is available: Connect Thermocouple calibrator simulator to T1 input socket. RCD Test Test the RCD by pressing the TEST button at least once a month. Connect an AC Voltmeter (Range AC mV) to pins 1 and 2 of the vacant socket and adjust potentiometer VR10 on the PCB to give a reading of 50 mV (RMS) on the Voltmeter (probe excitation voltage). 0. Note that there are two.88 mS at 25°C) and measure the temperature of the standard solution using a suitable thermometer. High conductivity Calibration (0-20 mS/cm) Fill a small beaker with a Conductivity standard solution (e. Disconnect the conductivity probe from the socket at the back of the plinth.g.1M KCI giving a conductivity of 12. Immerse the probe into the Conductivity standard solution in the beaker then adjust potentiometer VR8 to give a reading of the Standard solution in the ‘Low conductivity’ box on the software. This circuit is calibrated before despatch and should not require re-calibration. However. From the table supplied determine the actual conductivity of the solution at the measured temperature.g. should re-calibration become necessary the appropriate calibration potentiometers can be located using the diagram given in the CEXC manual (Routine Maintenance). Ensure the equipment has been connected to the electrical supply and switched on for at least 20 minutes. 0. Immerse the probe into the Conductivity standard solution in the beaker then adjust potentiometer VR7 to give a reading of the standard solution in the ‘High conductivity’ box on the software to match the conductivity. When the conditioning circuit has been re-calibrated replace the panel and re-install the probe in the appropriate reactor on the CEXC service unit. From the table supplied determine the actual conductivity of the solution at the measured temperature. Disconnect the Voltmeter then reconnect the probe to the socket having removed the probe from the appropriate reactor fitted to the CEXC. Connect the probe to the one which is going to be calibrated and read the conductivity value in the right window on the software. Conductivity probe calibration The conductivity conditioning circuit (which provides the reading from the conductivity probe supplied with the CEXC service unit) is located on a printed circuit board inside the plinth on the right-hand side. Low conductivity Calibration (0-5 mS/cm) Fill a small beaker with a Conductivity standard solution (e. 37 .01M KCI giving a conductivity of 1.41mS at 25°C) and measure the temperature of the standard solution using a suitable thermometer.Routine Maintenance When the conditioning circuit has been re-calibrated. Start up the Armfield software for the specific reactor. To access the PCB remove the panel on the right hand side of the plinth by removing the four fixing screws. replace the front panel of the electrical console and re-install the sensors in the appropriate place on the CEXC service unit. ‘High Cond’ and ‘Low Cond’ sockets. 67 10 9.22 20 11.64 18 11.Armfield Instruction Manual 12.d.d. Two basic types of connectors are used: reducing connectors for soft walled tubing connected to hard walled tubing (see below) and silicone pipe to connect barbed connector from 6-port injection valve to Teflon pipe.39 17 10.5 mm i.251 26 1.88 mS/cm at 25ºC 0.19 25 12.72 23 12.225 25 1..1 M KCl ºC mS/cm ºC mS/cm 5 8.441 Pipe work and connections The CEY pipework is mainly hard walled Teflon tubing (4 mm o.02 21 1.13 1.359 17 1.173 23 1.896 20 1.43 26 13. 38 . However for peristaltic pumps soft walled tubing is used.199 24 1. 2.91 15 10.88 19 11. This allows simple connection and disconnection as required.305 15 1.).33 21 11.48 22 12.147 22 1.332 16 1.15 16 10.413 19 1.278 10 1.386 18 1.01 M KCl ºC mS/cm ºC mS/cm 5 0.413 mS/cm at 25ºC 0.95 24 12. however there may be an instance when the user wishes to alter the arrangement. These connections are located at the inlet and outlet of the column reactor. Connection to reactor fittings Quick connectors are found in every connection between Teflon pipe and reactor unit.Routine Maintenance Connecting hard walled to soft walled tubing The CEY is supplied with all pipework and connections in place. and at the inlet and outlet of the sensor block. 39 . The barbed adaptors used on the 6-port injection valve remain connected. Pipework connections with Injection valve Any extra connection between hard walled Teflon tubing can be done using a piece of silicone tube with the same inner diameter as that provided with the equipment. and this must be done using a piece of silicone pipe (see below). The only connection that maybe required is Teflon pipe with the injection valve. 40 .Armfield Instruction Manual Column quick connectors These connectors are made up of two parts. the body. Screw cap connector until sealed Connections with quick connectors Column packing CEY column should be provided already packed. if packing or unpacking should be necessary follow the below procedure. Two steps comprise the connection. and cap which is connected to the Teflon pipe. However. which is screwed into the reactor. 1. Push cap against body until it clicks 2. See below. Empty the reactor 41 .Routine Maintenance Plug flow reactor assembly Unpacking 1. Do not unscrew the 6 screws from the top reactor 5. 8. T1 and Conductivity plugs) so that the reactor unit can be moved 3. Disconnect pipe and sensors from CEXC unit which are connected to the reactor unit (PTFE tubing. Disconnect pipe which goes from the reactor exit to sensor block 4. Disconnect CEXC unit from the electrical supply 2. Remove the lid. Keeping the lid on to avoid dropping glass beads. the mesh and the O-ring and keep them safe. Unscrew the six screws from the bottom and do not take the lid off from the column until required 6. turn the reactor around so that the bottom becomes the top of the reactor and vice versa 7. Unscrew the head screw so that the top bracket will come loose from the stand and also the top of the reactor. Turn the reactor down to its normal position 42 . Replace the mesh and o-ring 8. Turn the reactor around so that the bottom becomes the top and vice versa. Packing: 4. See Packing Column above. Unscrew the six bottom screws and remove the lid 3. fill the reactor with water blocking the other end so that it does not drain. 5.Armfield Instruction Manual Packing column Initial procedure if column is not packed 1. start the reassembly: 6. Follow the same procedure as described above until point 4 2. Replace the lid and hold it close to the reactor so as not to spill glass beads 9. Once initial procedure has been done. Then. The glass beads will gently settle. start filling in with the 3 mm glass beads. Unblock lower part of the reactor emptying the water 7. Once column is filled with water. Place it over the bottom bracket matching the holes of the reactor column and lid 11. Make sure that at the bottom of the premixer there is a small mesh 7. Fill up the premixer with water keeping the other side blocked so that it does not drain 8. Unscrew the fitting which connects the reactor column with the premixer 5. Tighten the head screw so that the top part of the reactor is fixed Static Premixer Packing Static Premixer Packing/unpacking 1.Routine Maintenance 10. Remove the premixer the reactor 3. Replace the mesh and refit the quick connector 43 . Remove the mesh 6. Remove the o-ring 4.3 mm diameter glass beads and leave sufficient room to fit the quick connector 9. Disconnect pipe connected to the premixer from the reactor column 2. Fill the premixer with 1. Tighten the six bottom screws so that the bottom part of the reactor is fixed 12. Note that CEXC is supplied with two temperature sensors. When fitting sensor use following procedure: 44  Unscrew cable gland CS  Handling the conductivity sensor carefully. Temperature sensor (T1) connection The procedure for fitting the sensor is as follows:  Unscrew gland T1  Handling carefully the temperature sensor.  Push the sensor down to the end of the channel so that the detecting part is in the flow path.  Re-tighten the gland in order to seal. and T2 is fitted in the Hot water Circulator (HWC).Armfield Instruction Manual 10. Replace the o-ring and refit the premixer into the bottom of the reactor column CEXC sensors fitting Sensor block parts and fitting It is recommended to place the CEY reactor close to CEXC plinth in order to simplify the sensor connections and shorten the reactants path. Conductivity sensor (CS) connection Be careful handling the conductivity probe since the glass part is very fragile.  Then pull the probe back a few mm to allow the flow to pass through the path. However the HWC is not required for the experiments with this reactor. pass it through the cable gland and fit it into its corresponding channel so that the two holes at the end of the . T1 is usually fitted in each reactor. pass it through the gland and fit it into its corresponding hole. ’ socket and monitor the reading on the ‘Low cond’ window. Otherwise the flow will be blocked by the conductivity probe and the conductivity values will not be accurate. connect the conductivity probe to ‘Low cond. 45 . Once the conductivity sensor is correctly positioned then retighten the gland in order to seal. For experiments described in this manual. It is IMPORTANT to fit the probe into the sensor block as described above so that the two holes of the conductivity probe will be open to the flow. high conductivity values are monitored (020mS/cm). However if other solutions are used with lower conductivity values (0-5 mS/cm).Routine Maintenance probe are positioned inline with entrance and exit of the sensor block and not towards the walls. Flow pattern characterisation . in reactor after time (mol/dm3) C0 Tracer concentration k specific rate constant L overall length of tubular reactor (cm) A cross sectional area of tubular reactor r reaction rate tR residence time (s) t elapsed time (s) T reactor temperature (K) V volume of reactor (dm3) Pe Peclet number  Tau. space time X NaOH conversion of sodium hydroxide conductivity at time t (cm2) (s) (Siemens/cm) initial conductivity 46 . in reactor at time t (mol/dm3) sodium hydroxide conc.Pulse change Exercise C . in (mol/dm3) mixed feed C NaOH (t) sodium hydroxide conc.Flow pattern characterisation .Laboratory Teaching Exercises Index to Exercises Exercise A .Step change Exercise B .Conversion experiment Nomenclature Symbol Name Unit C NaOH0 sodium hydroxide initial conc. Two experiments demonstrate the flow pattern by means of tracer techniques and the calculation of the RTD. Another experiment demonstrates the steady state conversion of a second order reaction in a tubular reactor packed with glass beads. A tubular reactor packed with glass beads has a Residence Time Distribution that is very similar to that of a plug flow reactor. DILUTION OF POTASSIUM CHLORIDE AND INDIGO CARMINE FOR USE WITH TRACER TECHNIQUES  0.01% w/w of Indigo carmine This should be made by dissolving potassium chloride as follows: Mass of Indigo Carmine = 47 .1M solution of Potassium Chloride containing 0. but with some axial dispersion. Although it may be possible to carry out demonstrations using other chemicals it is not advisable without first contacting Armfield as the materials of construction of the reactor may not be compatible.Laboratory Teaching Exercises conductivity at time sodium hydroxide conductivity Ă Arrhenius frequency factor Ea activation energy (J/mol) R gas constant (J/mol K) E(t) residence time distribution function M Initial mixing proportion = C B0 /C A0 D ax Axial dispersion Common Theory The Armfield CEY Plug flow reactor is designed to demonstrate the mechanism of chemical reactions in continuous flowing systems and also to obtain the flow pattern by using tracer experiments. For Indigo Carmine solution at determined % (w/w) respect to the potassium chloride solution. make up as follows: Then.15 gr of IC and dissolve it in distilled water up to 150 cm3 DILUTION OF ETHYL ACETATE AND SODIUM HYDROXIDE FOR USE WITH REACTION EXPERIMENT  0. 48 .2 M solution of 1 M Sodium Hydroxide Then. in order to obtain a solution 0.2 litres of 1M NaOH and add distilled water until 1 litre. of KCl and 0.25 M solution of Ethyl Acetate containing 0.Armfield Instruction Manual Then.1 g of IC and dissolve it in distilled water up to 1 litre  Follow the same procedure for 1 M solution: If the necessary volume is 150 cm3.18gr of KCl and 0.459 g. the indigo carmine at determined concentration C% (w/w) respect to the concentrate should be diluted as follows:  1 L of 0. weight 11. weight 7. measure 0.2 M from a 1M NaOH solution.01% w/w of IC This should be made by diluting concentrated Ethyl Acetate as follows: As explained before. Exercise A . which is obtained using tracer techniques. and a dye. The commonly used perturbations in a plug flow reactor are a Pulse change and Step change. This characterisation will be performed using a model considering a plug-flow reactor with axial dispersion and by determination of the Residence Time Distribution. RTD. therefore detectable by conductivity measurement. Tracer techniques use several perturbations in the inlet of the reactor and wait for the reactor response. In this exercise the Step change as a perturbation is studied.Step change Objective The aim of this practical exercise is to study the flow pattern characterisation of a tubular reactor packed with glass beads. The RTD curve allows us to obtain the permanence of each fraction of volume of fluid inside the reactor and also to demonstrate its behaviour. The most common perturbations used in a plug flow reactor are the named Step change and Pulse change. The perturbations use tracer solutions containing a detectable solution which can be detected and therefore followed. Method The study of the flow pattern in a reactor is usually done by using tracer techniques which consist of injecting several perturbations in the inlet reactor and waiting for its response. In this experiment the tracer solution is made up of a salt.Flow pattern characterisation . Coloured tracer solution is used in order to make the propagation of the concentration wave visible. ideal or not ideal. 49 . Step change Step input or step change consists of an instant change in concentration of the tracer from one concentration to another. This allows the full comprehension of the reactor behaviour. which allows it to be followed visually. Equipment Required Armfield service unit CEXC Armfield Plug Flow reactor unit CEY Compatible PC with Armfield software Chemicals Distilled water Potassium Chloride Indigo carmine Theory The flow characterisation of a reactor is done by the determination of the RTD. reactor response to a Step change of C(t) = C 0 [1-H(t-0)] at the inlet concentration: (3) for a plug flow reactor. by this change in concentration. one has access to the P curve which allows the determination of the RTD: 50 . experimentally. considering a semi infinite reactor. (4) C: concentration at the reactor outlet C 0 : the initial concentration (tracer concentration) Pe: Peclet number δ: Dirac delta function Then.Armfield Instruction Manual The response of the reactor is mathematically represented by the following function: C(t) = C 0 [1-H(t-0)] (1) (H) = Heaviside function The RTD equation for plug flow with axial dispersion. (2) Integration of these equations gives the curve named Danckwerts curve P(t). closed to the diffusion and in steady state conditions. Pe. Those two parameters are obtained by minimising the square of the residuals relative to the experimental curve. equation (2) can be written as (6) The axially-dispersed plug flow model has two parameters in the E(t) curve: . When the tendency is Pe = 0 the residence time distribution (RTD) is wider and the reactor behaves as stirred tank reactor. When Pe = ∞ axial dispersion does not exit and the reactor behaves as an ideal plug flow reactor. the mean residence time. the ratio between the useful reactor volume V and the feed flow rate follows: . .e. . Therefore. It is used as a correlation parameter which takes into account the axial dispersion model.Exercise A (5) For an ideal reactor in general. When Pe number decreases some axial dispersion appears. i.. This is explained in detail in the results treatment section The normalisation of the concentration C/C 0 is obtained experimentally by recording the conductivity values during experiment. Experiment set up Re-arrange the experimental assembly in accordance with the following: 51 . since conductivity of a solution varies linearly with the concentration. is equal to the space-time. and for an axially-dispersed plug flow reactor in particular. Peclet number is a parameter used to measure the behaviour of a chemical reactor. has to be connected to the right port of the injection valve. 52 . See Installation section for valve connections. IMPORTANT: It is essential when handling these chemicals to wear protective clothing.1 M Potassium Chloride containing 0. Temperature and conductivity sensors have to be correctly fitted in accordance with CEXC sensors fitting section and plugged in the right socket at the rear of the CEXC service Unit. As the experiment involves the collection and storage sensors data. Ensure pumps are calibrated and they give the right flow rate The T connector supplied with the reactor unit is used in this case.Armfield Instruction Manual Layout Step experiment Verify the directional process of the six port injection valve by following the labels. The procedure on how to make the solutions is given in the introduction of this section. the USB port located on the right hand side of the plinth must be connected to the Armfield IFD data logger. This will enable data logging of conductivity. Connect it to the entrance of the reactor. flow rates and temperature at selected time intervals over a selected period.01% of Indigo Carmine. Procedure Make up 1 litre of 0. The PTFE pipe. Ensure there is enough volume of solutions made to the correct concentrations and they are well mixed. and bottle 2 with 2 litres of water. which comes with the T connector. Refit the lids. Arrange the experimental assembly in accordance with Experiment set up above. gloves and safety spectacles. Remove the lids of the reagent bottles and carefully fill bottle 1 with the tracer solution. Results treatment  Make up a table with the values of your experiment as follows: 53 . and the end of the experiment. The reactor can be left with water in the coil ready for the next experiment. Type the flow rate in the software 50 ml/min in each window for each pump so that the total flow rate of the solution entering the reactor will be 100 ml/min. At the exit the solution is directed to the sensor block where conductivity probe is fitted and conductivity values are continuously registered. Take the feed pipe from the reagent bottle 2 and introduce it into reagent bottle 1. It is recommended to check the flow rate sometimes by measuring it at the exit of the conductivity probe. stop the experiment and the pump. Check whether the solution conductivity corresponds to its concentration and start the conductivity data acquisition. in the middle. The recorded times will allow estimation of the reactor space time and the space time in the connection tubes. Collection of data should continue until steady state conditions are reached in the reactor. Empty the reactor by means of inverting the pump tubes and connected the pumps will suck the water out from the reactor.Exercise A Set data collection of conductivity at 3 seconds on the software. Turn off the peristaltic pump and change the tubes from vessel 1 to vessel 2 with water and turn on the pump again. Flow more distilled water to clean the reactor. so that both pumps pump the same solution into the reactor. taking note of the time at which this change has been done. Start the conductivity data acquisition in the computer. Take note of the time the solution takes to reach the reactor (column) and the time taken from the exit of the reactor solution takes until detector. Rinse the feed bottles with distilled water and pump the water through the reactor to rinse out the chemicals. otherwise try to identify and solve the problem. Take note of the temperature at the exit stream at the beginning. Check if the peristaltic pumps tubes have the flexibility and position required to a keep a constant flow rate. When the conductivity logged is 0. 2. This takes approximately 30 minutes. Notes: 1. Switch on the pumps by pressing POWER ON and instigate the data logger program (or begin taking readings if computer is being used) by pressing ‘GO’.00 mS/cm2. Solution is pumped from reagent bottles to injection valve and hence to the reactor. 63 SQD Flowrate and reactor volume are parameters of the experiment. Start the spreadsheet program. The “tubes time” as explained on the experimental procedure is the time taken by the solution travelling through the connection tubes before and after reactor column until it reaches the conductivity cell. The calculations are best carried out using a spreadsheet such as EXCEL so that the results can be displayed in tabular and graphical form.00 Tubes time (s) 16. this data can be transferred onto the spreadsheet. This time must be calculated before or during the experiment at the flow rate of the experiment.76 Residence time (s) Pe tau (V/Fr) (s) 210. At this point. a set of readings of conductivity against time are stored in the computer.  Plot the dimensionless concentration curve C/C 2 along time with the experimental data Dimensionless concentration curve (column C)  54 Eliminate from column C those values relating to the connection tubes (column D) . Using the Armfield data logger.Armfield Instruction Manual Useful volume reactor (ml) 372 Flowrate (ml/s) 1. In order to obtain the integral of the equation (4).Exercise A  Plot a column with equation (2). perform as follows:  Plot the “mean point” column of E column: (Column F) 55 . although the t r and Pe are unknown and without taking into account the integration: Pe and t r numbers will be found through the model equation using the solver function. F i + 1 . set in the SQD cell of your table the function SUMXMY2 selecting column D and H. using the following excel function: SUM(F i .Armfield Instruction Manual  Plot the “accumulative sum” of the last one.…)  (Called column G) Then plot the final “model equation” (equation 4): 1-G i (called column H) In order to use the solver function. experimental and model curves. 56 . which means will sum the squares of the differences between these two columns. which means will minimize this value. go to the Solver function and in “set target cell” select SDQ cell. as well as the unknown columns. In “by changing cells” select the cells of residence time and Pe number on the table built.Exercise A  Then. 57 .  Press Solve bottom. Pe and residence time numbers will be found. in “Equal to” select “Min” with value 0. Note: The smaller value of SDQ the better match between curves and therefore between residence time distribution and space time. and compare them.Armfield Instruction Manual  Plot Experimental and Model columns. Repeat the experiment changing some variables. Normalised potassium chloride concentration at the reactor outlet along time. like flow rate and tracer concentration. Repeat the same experiment without static premixer and compare the difference. columns D and H. to understand how significantly these parameters affect the residence time distribution. 58 . Study the different Pe numbers and the curves obtained. Compare the reactor space time. As experimental errors are common. significantly affect the space time calculation? 59 . A significant difference between both values. make a sensible analysis to determine where the experimental errors affect the results more significantly. with the mean residence time. . . or the . beyond the experimental errors.Exercise A Reactor responses for the plug flow reactor with axial dispersion model Conclusion One of the possible causes of the difference between model and experimental curve can be the error on the reading of the conductivity because of dead or stagnant volumes. used in the flow rate measurement. may indicate the presence of dead volumes or stagnant regions when presence of short circuits when . For example: does 1 sec error in the reading of the time required to fill graduated cylinder. or even other anomalies. obtained from tracer experiment. Exercise B . which is obtained using tracer techniques. 60 . This characterisation will be performed using a model considering a plug-flow reactor with axial dispersion and by determination of the RTD. In this exercise the pulse change perturbation will be studied. A coloured tracer solution is used to make the propagation of the concentration wave visible. The commonly used perturbations in a plug flow reactor are a Pulse change and Step change.Flow pattern characterisation . This curve enables the permanence of each fraction of volume of fluid inside the reactor to be determined and also to show if its behaviour is ideal or non ideal and how it differs. Method The study of the flow pattern in a reactor is usually done using tracer techniques which consist of introducing several perturbations at the inlet of the reactor and monitoring the effect in the reactor. Tracer techniques use several perturbations at the inlet of the reactor and wait for the reactor answer.Pulse change Objective The aim of this practical exercise is to study the flow pattern characterisation in a tubular reactor packed with glass beads. The most common perturbations used in a plug flow reactor are a Pulse input and Step input. Equipment Required Armfield service unit CEXC Armfield Plug Flow Reactor CEY Feed assembly Optional Equipment Compatible PC with Armfield software Chemicals Distilled water Potassium Chloride Indigo Carmine Theory The flow characterisation of a reactor is done by the determination of the RTD. Exercise B Pulse input Pulse input consists of an instantaneous injection of a small quantity of tracer solution and it is mathematically represented by the following function: C(t) = C 0 [H(t-0)-H(t-Δt)] (1) H: Heaviside function Δt:duration of the perturbation And the response of the reactor is: (2) Taking into account that for a plug-flow reactor the RTD is: (3) δ(t) : Dirac delta function  : space time t r : Residence time The response of a plug flow reactor with axial dispersion to a pulse input in the inlet concentration is: (4) For a sufficiently small pulse. : 61 . Equation 5 predicts that the maximum concentration appears at t = . For finite pulses. for plug flow with axial dispersion. is simplified: (6) For infinitesimal pulses. See Injection valve operation. the maximum concentration comes out at t =  + Δt/2. equation 5 is given by: (7) Experimental set up Re-arrange the experimental assembly in accordance with the following: .Armfield Instruction Manual (5) Then. Layout Pulse experiment Verify the directional position of the six port injection valve so that water is pumped into the reactor and coloured solution (tracer) is being recirculated. Ensure pumps are calibrated and they give the right flow rate 62 . in these circumstances. equation (4). The loop will contain the coloured solution. Ensure there is sufficient volume of solutions and that they are well mixed. Thus. the data USB port on the right hand side of the service unit must be connected to the Armfield IFD data logger and the computer as detailed in the instruction leaflet supplied with the interface. Start the software using option Pulse Experiment. The solution inside the loop (tracer) will be injected into the reactor. start data acquisition by pressing ‘GO’. Type flow rates in the software for each solution and press ‘POWER ON’ to start up the pumps. IMPORTANT: It is essential when handling these chemicals to wear protective clothing. ports will be blocked. turn the handle of the valve until it clicks so it is sure that connections between ports have been done properly. flow rates and temperature values at selected time intervals over a selected period. To make sure air does not get inside the conductivity cell. and take note of the time at which this has been done. Ensure that the injection valve is in the loading position (L position).1% of Indigo Carmine. take out conductivity sensor and as the water is exiting the reactor and overflows through the cell. Procedure Make up the tracer solution with 250 cm3 of 1 M Potassium Chloride solution containing 0. Note that the flow rate of the tracer solution is not important as it will be recirculated all the time. 63 . The total time will help to obtain the space time spent in the connection tubes and to predict the reactor space time. When switching the injection valve from one position to another. Once the loop has been loaded with tracer it is RECOMMENDED to stop the pump. At the same time switch the injection valve position to injection position (I). pressure will increase and pipe will split splashing with the solution contained. Temperature and conductivity sensors have to be correctly fitted in accordance with CEXC sensors fitting section and plugged in the correct sockets at the rear of the unit. Rearrange the experimental assembly in accordance with Experimental set up above. Connect the single PTFE tube to the reactor through the quick connector. This will enable data logging of the conductivity. Pour about 250cm3 of tracer solution in bottle 1. and about 1 litre of distilled water in bottle 2. Take note of the time required for the water to reach the reactor entrance (after static premixer). gloves and safety spectacles. so if blockage occurs during switch pressure will not increase on the tracer channel. Then. the time spent in the reactor column. Otherwise. As the experiment involves the collection and the storage of sensors data. fit the sensor back into the cell and screw until sealing. and the time spent between the exit reactor and the detector.Exercise B T connector supplied with the unit is not necessary in this case since just one solution is injected into the reactor at a time. Finish the experiment when the conductivity is approximately 0.01 mS/cm. At the end. Flow distilled water through the continuous flow electrode to remove any potassium chloride residues. At this point. 64 . a set of readings of conductivity with time will be stored in the computer. Click again ‘POWER ON’ to finish the experiment.Armfield Instruction Manual Once the tracer is injected. Stop data logging. this data can be transferred onto the spreadsheet. empty and wash the reactor column with distilled water. CEY in the Pulse injection experiment Results The calculations are best carried out using a spreadsheet such as Microsoft EXCEL so that the results can be displayed in tabular and graphical form. On conclusion of the experiment using the Armfield data logger. change the valve position to loading position (L). Start the spreadsheet program.  Plot a column with the following equation: (Column D) as t r and Pe are unknown.Exercise B  Make up a table as follows: 1. those values relating to the connection tubes. Dimensionless concentration curve Eliminate from C(t) curve. it is likely that nonsensical values will appear.63 SQD  With the values of time and conductivity obtained from the experiment plot the dimensionless concentration curve along time: C/C 0 against time. (Column E) 65 .  Then plot the final “model curve” .00 Tubes time (s) 16. It will be necessary to use the solver function.76 Flowrate (ml/s) Residence time (s) Pe tau (V/Fr) (s) 210. (See Column C) The following step is to determine the Peclet number and Residence time. Armfield Instruction Manual In order to use the solver function. which will minimize this value. go to solver and in “set target cell” select SDQ cell. and also the two columns (model and equation).  Press Solve button Pe and residence time numbers will be found. . 66  Then. And in “by changing cells” select the cells of residence time and Pe number on the table. set in the SQD cell the function SUMXMY2 selecting column C and E. This will sum the squares of the differences between these two columns. to minimise the difference. in “Equal to” select “Min” with value 0. along time. and compare them Normalised potassium chloride concentration at the reactor outlet. flow rate. This will help to understand the concepts explained on this section. Repeat the experiment changing some variables. tracer concentration or amount tracer injected. 67 . Study Peclet number and compare the different curves obtained.Exercise B  Then plot C (t) column (C) and model equation column (H). may indicate the presence of dead volumes or stagnant regions. a significant difference between both values. this is a sign of stagnant regions and when t r > . Comparing the reactor space time. . When t r < . t r . 68 . and the mean residence time. make a sensible analysis to determine which experimental errors affect the results most significantly. For example: does a sec error in the reading of the time that water takes to reach entrance reactor significantly affect the space time calculation? One of the possible causes of the difference between the model and the experimental curve can be the error on the reading of the conductivity because of stagnant volumes. this can be a sign of short circuits.Armfield Instruction Manual Conclusions As experimental errors are common. M = C B0 /C A0 ≥ 1.Exercise C . x A is the conversion of the limiting reactant A. in a tubular reactor packed with glass beads. for a second order reaction between sodium hydroxide and ethyl acetate. k is the reaction kinetic constant.Conversion experiment Objective The specific goal of this practical work is the determination of the steady state conversion. C A0 is the concentration of species A at the reactor inlet. Method The steady state conversion of the packed flow reactor is usually done by a reaction in a steady state condition. it will be a study of a second order reaction at 25ºC considering that the model of this reactor is Plug flow axially dispersed since this was demonstrated in the previous experiment. If we assume that the flow pattern in the reactor is described by the plug axially dispersed model. Previous expression can be written in dimensionless form: 69 . In the present work we intend to determine the steady state conversion in the same tubular reactor. B being the second reactant. at room temperature. the steady state conversion for a second order reaction should be obtained from the reactor steady state mass balance: The steady state conversion for a second order reaction should be obtained from the reactor steady state mass balance: (1) where u es the superficial velocity. z is the axial coordinate. In this case. Equipment Required Armfield service unit CEXC Armfield Plug Flow Reactor CEY Feed assembly Optional Equipment Compatible PC with Armfield software Chemicals Sodium hydroxide Ethyl Acetate Indigo Carmine Distilled water Theory In the previous experiments the flow pattern in the tubular reactor packed with glass beads was characterised. and D ax is the axial dispersion. Armfield Instruction Manual (2) where z* = zL and L is the length of the reactor. Once k 0 and Ea are known obtain the kinetic constant at the temperature of the experiment through: 70 . an analytical solution exists for the steady (7) for M >1. the steady state conversion can be determined by. (6) For an ideal plug flow reactor state conversion: . yields: (5) Finally. and for M=1: (8) The kinetic constant and activation energy are data which can be obtained with a batch reactor at different temperatures. Introducing now the dimensionless Peclet number. and the space time  = L/u: (3) Once the residence time distribution is known. Pe = uL/D ax . (4) replacing the C NaOH (t)/C NaOH0 for a second order reaction. use Figure C2 data as necessary: Figure C1: Conversion of the NaOH at different temperatures Figure C2: Linearization of NaOH conversion 71 .Exercise C If this information can not be obtained. 125 and at these different temperatures: K (17ºC) = 6. Then connect PTFE tubing to the injection valve as detailed in the Installation section. Fit the T-connector into the reactor inlet. flow rates and temperature at selected time intervals over a selected period.Armfield Instruction Manual being Ea (kJ/mol) = 29. are injected into the reactor. the data output port on the right hand side of the service unit must be connected to Armfield IFD data logger and the computer as detailed in the instruction leaflet supplied with the interface. See Injection valve operation as necessary. sodium hydroxide and ethyl acetate with indigo carmine.00E-05 m3mol-1s-1 K (27ºC) = 9. for a C A0 = 0. This will enable data logging of the conductivity.4 (11) k 0 (m3/mol s) = 12.1. Temperature and conductivity sensors have to be correctly fitted in accordance with CEXC sensors fitting section and plugged into the correct socket of the control console. 72 . As the experiment involves the collection and the storage of the conductivity data.40E-05 m3mol-1s-1 K (22ºC) = 8.60E-05 m3mol-1s-1 Experiment set up Re-arrange the experimental assembly in accordance with Figure C3. Verify the directional process of the six port injection valve so that solutions.5 m = slope M = C B0 /C A0 For example. C B0 = 0. IMPORTANT: It is essential when handling these chemicals to wear protective clothing.01% w/w indigo carmine).01% w/w. Set data collection at 3 seconds on the software. in the middle and at the end of the experiment.Exercise C Figure C3: Layout Conversion experiment Procedure Make up 1 L of sodium hydroxide of approximately 0. Bottles should be closed to protect from air. Empty the reactor by disconnecting tubes from the bottom and put a flask underneath to collect the solution inside.25 M with Indigo Carmine at 0. gloves and safety spectacles. and try to relate it with the pH of the medium and with the sodium hydroxide conversion. drain the remainder into a flask and fill reagent vessels with distilled water. Start the data acquisition by pressing ‘GO’. Set same flow rates as used in the pattern characterisation experiment (Exercise A and B). It is recommended to check flow rate and temperature at the beginning. and wait until the continuous flow reactor reaches the steady state. The reactor inlet should be yellowish. 0. When solutions are almost finished. and connect the corresponding tubes in each vessel.2 M but of rigorous titre and 1 L of ethyl acetate 0. This should take about 5 minutes. 73 .25M ethyl acetate (with 0. Fill one bottle with 0. stop data logging and turn off the peristaltic pumps. whereas the outlet nearly dark blue. by filling the right value in the software. Pay attention to the colour change between reactor inlet and outlet.2M NaOH and the other one with the other solution. Check that the conductivity values have reached the values corresponding to distilled water. k.1 M (K 0 ). K∞: Pour 100 cm3ml of the sodium hydroxide prepared into a flask and add 100 ml of distilled water mix it and take note of the conductivity value which corresponds to the sodium hydroxide 0.76 M 1. 74 . Kinetic constant.01% w/w IC) and start the magnetic stirrer. Take note of the conductivity when reaction is complete.  Make up a table as follows: V ml Pe [NaOH] 0. Measure again 100 cm3 ml of the prepared sodium hydroxide solution and pour it into a flask or glass reactor.25 M k K0 mS/cm2 K final mS/cm2 Q 1.1) K0: conductivity of NaOH K∞: Final conductivity Obtention of K 0 . IMPORTANT: It is necessary to take into account the following considerations: C NaOH0 : Concentration of NaOH in the mixture (in this case 0.25 [NaOH] 0 0.25 M ethyl acetate solution (with 0. Colour changes go from dark green to light and later on to blue at the end of the reaction. Add 100 cm3 of the prepared 0.2/2 = 0.1 ml/sec Peclet number and space time should be obtained from the last experiment. depends on the temperature. Results The calculations are best carried out using a spreadsheet such as Microsoft EXCEL so that the results can be displayed in tabular and graphical form. the flow rate should be the same in both experiments. therefore obtain that value at the temperature of the experiment. See kinetics data above as necessary. Therefore. K∞.Armfield Instruction Manual Then.2 M Tau [EtAC] 0. reconnect the tubes and start pumping distilled water into the reactor and sensor block to eliminate the residues of the experiment. The operating conditions are presented in the following table: 75 . apply the following equations: K 0 = 0.195[1+0.070[1+0.0184(T-294)] C NaOH 0 T ( ºK ) C NaOH 0 ( mol/cm3) K∞ = 0. continue as follows:  Plot the following equation (column D) to obtain C NaOH : (12)  Plot conversion column (column E) (13)  Plot same columns for Ethyl acetate (column F and G): (14) (15) The following experimental results do not intend to be real.0284(T-294)] C NaOH 0 T ( ºK ) C NaOH 0 ( mol/cm3) For C NaOH 0 < C EtAc 0 since NaOH is limiting reagent Once parameters are obtained. they are a demonstration of the data required and mathematical treatment must be done.Exercise C If those values can not be obtained by experimental method. plot the mean point of this column : .Armfield Instruction Manual Figure C4: Steady state conversions along time. Tau numbers from tracer experiment. using Pe. Operation temperature = 20 ºC Now. 76  Plot equation (6) without apply the integration. obtain the steady state conversion from the model equation and compare with the experimental value. (Column H)  Then. different temperature. 77 .Exercise C  Finally. Compare and analyse what happens and why. and different Ethyl acetate concentrations. Perform the steady state conversion experiment at different flow rate. plot the SUM of the last column so that the integration is complete. Armfield Instruction Manual Perform the experiment without pre mixer and it will observe a segregation phenomenon. 78 . uk Web: http://www.armfield.co.uk [email protected] Details for Further Information Main Office: Armfield Limited Bridge House West Street Ringwood Hampshire England BH24 1DY Tel: +44 (0)1425 478781 Fax: +44 (0)1425 470916 Email: sales@armfield. 436 West Commodore Blvd (#2) Jackson. NJ 08527 Tel: (732) 928 3332 Fax: (732) 928 3542 Email: [email protected] 79 .uk US Office: Armfield Inc.co.