Batch Evaporation Crystallization

Teaching objectives

• Batch crystallisation of a solution by evaporation followed by cooling
• Influence of operating conditions on crystallisation
• Simple reactions at atmospheric or reduced pressure
• Reaction kinetics, and reversible and irreversible reactions
• Evaporation, and total reflux reactions
• Heat balance, mass balance and yield calculations

Equipment

• Graduated borosilicate glass feed tank of 10 litres nominal volume, with a product vacuum system for filling reagents
• Grignard type cylindrical reactor: AISI 316L stainless steel vessel with insulated double jacket for thermal oil heating, flush mounted drain valve and AISI 316L stainless steel lid
• Variable speed stirring assembly in AISI 316L stainless steel with an inclined three-bladed rotor, interchangeable, driven by an ATEX variable speed motor
• AISI 316L stainless steel cooling coil for the reaction mixture
• Borosilicate glass column head with temperature plug
• Vertical condenser with borosilicate glass body and AISI 316L stainless steel coil heat exchanger
• AISI 316L stainless steel distillate heat exchanger and graduated borosilicate glass receiver tanks
• Temperature control unit using thermal oil, with circulation pump and temperature control, and insulated flexible hoses
• AISI 316L stainless steel process pipework, reinforced PVC cooling fluid tube, and AISI 316L stainless steel vacuum piping to a common manifold
• Borosilicate glass vacuum trap and liquid-ring vacuum pump
• AISI 316L stainless steel bag filter of 20 litres capacity, working under reduced pressure
• Support framework in AISI 304L stainless steel tube with aluminium connecting nuts and adjustable feet
• Reactor vessel dismantles downwards, leaving the upper section in place

Instrumentation

• Condenser cooling water feed with variable area flowmeter, adjusting valve and flow switch that cuts the heating if cooling water is lost
• Variable area flowmeters with adjusting valves on the crystallisation reactor cooling water feed and the distillate cooler feed
• Reflux flow measured by variable area flowmeter
• Reactor and plant pressure by Bourdon type gauges
• IP55 command and control cabinet with emergency stop and operating buttons, housing a digital temperature indicator for the crystallisation reactor with a Pt100 Ohm probe, a stirrer speed controller and digital indicator, and two digital temperature indicators reading six Pt100 Ohm probes

Dimensions and weight

1750 mm x 850 mm x 3000 mm, approximately 300 kg

Services required

• 400 V / 50 Hz / 3 phase + N: 10 kW
• Cold water at 10°C / 3 bar: 2 m³/h