The Armfield CEXC family is a range of chemical reactors specifically developed for the teaching and demonstration of chemical reactor capabilities to chemical engineering students. Real chemical reactions take place within the reactors, and Armfield have developed a number of representative reactions which are easy and safe for students to use in the laboratory environment. This range of small-scale chemical reactors comprises five units, which represent the types of reactors found in the industry. Three of the reactors mount on a common bench top service unit (CEXC) whilst the other two are free-standing. PC based educational software is included along with the necessary interface device to provide computer control, automatic logging of data and analysis of results. Reactors comprise: Plug Flow, Laminar Flow, Stirred Tank, Tubular and Batch reactors.
The CEXC Chemical Reactors Teaching Unit provides the services required to run the various reactor types. It includes a hot water re-circulator used to control the temperature of the reactions, glass feed vessels for the reactants, two peristaltic pumps to pump the reagents to the reactors, computer software for data logging, sensors and instrumentation.
The CEXC is fully computer controlled, and supplied with software to allow the user to vary the feed pump speeds and flow rates, to vary the heater power in the hot water, to implement a PID control loop ensuring stable temperatures, switch on and off the hot water pump, and to control the speed of the stirrers used on some of the reactors.
Instrumentation for temperature and conductivity measurements is also supplied and these values are displayed on the computer screen. Two ‘K’ type thermocouples are included, one for the hot water and one for the reactor contents.
Note: An input for a third user supplied sensor is also provided for project work.
A dual-range conductivity sensor allows for a wide range of operation. Armfield have developed an algorithm for the saponification reaction (ethyl acetate and sodium hydroxide) linking the degree of conversion of the reactants to the electrical conductivity, thus allowing the progress of the reaction to be monitored using the software.
The service unit includes a mounting position for the reactor being used. It is possible to change reactors quickly and easily without the use of tools. All fittings on the CEXC and the reactors are of the quick-release type. The CEM-MkII, CET-MkII and CEB-MkIII reactors are completely contained on the CEXC base unit. The CEY and CEZ also include floor standing columns for positioning next to the CEXC base unit.
The CEXC provides a locating position for two standard 2.5-litre chemical storage bottles for the reagents within the plinth. This provides safety in use, and the bottles can be quickly capped and removed as necessary for safe handling. Two 2.5-litre bottles are also provided with the equipment. Alternatively, for longer experiments, larger feed vessels could be located either on the floor or on the bench next to the equipment.
The CEXC requires a computer (not supplied by Armfield), running Windows XP or above, with a spare USB port.
The CEB Transparent Batch Reactor is a double-skinned glass vessel with a one-litre internal working volume, fitted with a variable-speed agitator.
Hot water from the CEXC or cold water from the CW17 can be circulated through the jacket for temperature control purposes, maintaining the reactor contents at constant temperature.
Glands in the clear acrylic lid allow the CEXC conductivity and temperature probes to be fitted to facilitate monitoring of the reactions in progress such as the important saponification reaction. Isothermal and adiabatic operation reactions may be demonstrated. (Note, the isothermal reaction requires the Armfield CW17 accessory if experiments at low temperature are to be studied or if the ambient temperature is high).
For adiabatic operation, the use of dyes enables the chemical reaction rates to be monitored visually by the change in colour at different degrees of conversion.
Key Features
The continuous stirred tank reactor is probably the most common type of reactor found in industry. The Armfield CEM-MkII is a small-scale demonstration version for educational use. It is extremely flexible in use and can be used for both continuous and batch reactions.
The volume of the reactor is adjustable between 0.4 and 1.5 litres using an adjustable standpipe, allowing different hold-up volumes and residence times to be investigated. The temperature probe and conductivity probe (supplied with the CEXC) can be positioned in the reactor vessel.
A stainless steel coil is used for temperature control of the reactor from the hot water supply on the CEXC (or cold water from such as the Armfield CW17 Chilled Water Circulating Unit).
A variable-speed mixer/agitator is included (controlled by the CEXC) together with baffles to improve the mixing.
CEM-MkII uses the saponification reaction and uses conductivity to measure the progress of the reaction. It also uses a step input change experiment to obtain the residence time distribution.
Key Features
The Armfield Tubular Reactor is in the form of a tube wrapped in a spiral around an acrylic former, which is enclosed in a transparent tank. Water at a controlled temperature (from the CEXC) is circulated within the tank, this maintains the reactants at constant temperatures.
The reagents are piped separately to the reactor through quick-release fittings mounted on the lid and are preheated in stainless steel coils in the water tank, before being mixed and fed into the reactor coil.
Mounting positions are provided for the CEXC water temperature sensor (in the water tank) and the conductivity probe (at the reactor output).
CET-MkII uses the saponification reaction and uses conductivity to measure the progress of the reaction.
Key Features
The CEY Plug Flow Reactor demonstrates step and pulse changes for plug flow characterisation and steady-state conversion for a second order reaction. It is a tubular packed column reactor made of clear acrylic and mounted on a steel frame. A static premixer at the bottom of the column provides premixing of the reagents entering the reactor and improves the flow distribution.
A clear acrylic sensor block is mounted on the floor standing frame and houses the CEXC conductivity and temperature sensors. The reagents are fed to the reactor by the CEXC feed pumps, using PTFE tubing. A six-port injection valve fitted to the CEXC Reactor Service Unit is used to provide the step or pulse input changes of the reagents.
Tracer experiments and conversion experiments may be demonstrated and followed visually. Conductivity data logging allows the student to apply the flow pattern characterisation theory and compare it with the experimental results.
Key Features
The Armfield Laminar Flow Reactor is a tubular reactor made of clear acrylic and mounted on a floor standing steel frame, with two diffusers packed with glass beads located at the ends. A static premixer at the bottom of the column provides premixing of the reagents entering the reactor and improves the flow distribution.
It includes two reagent vessels fitted with heat exchangers, mounted in the CEXC plinth. The heat exchangers are used to cool down the reagents before performing the experiment. A cold water jacket keeps the reactor contents at constant temperature in order to maintain the laminar characteristic. A thermostatically controlled supply of chilled water is required for this, such as the Armfield CW17.
A clear acrylic sensor block is mounted on the frame for the CEXC conductivity and temperature sensors. The reagents are fed to the reactor by the CEXC peristaltic pumps, using PTFE tubing. Pulsation dampers are used to ensure a smooth flow.
Tracer experiments and conversion experiments may be demonstrated and followed visually. Conductivity data logging allows the student to apply the flow pattern characterisation theory and compare it with the experimental results.
Key Features
The Armfield Industrial Division designs and manufactures research & development systems, primarily for the food, beverage, dairy, edible oil and pharmaceutical industries. Used by many of the world's leading corporations, Armfield systems enable researchers and product developers to replicate full-scale industrial manufacturing processes on a miniature-scale in the laboratory.
