Specifying a chemical engineering teaching laboratory in Bangladesh: the unit operations and reactor experiments that matter, chemical storage and segregation, fume extraction and exhaust treatment, and a waste route decided before the first experiment runs.
Ask a chemical engineering department where the spent solvent from the extraction experiment goes and you will get one of three answers. The good answer names a labelled container, a contractor and a logbook. The usual answer is that it accumulates in a drum behind the store. The bad answer is the sink. Which answer a department gives is a fair predictor of how the rest of the laboratory is run, because waste is the decision that gets deferred until it cannot be.
Chemical engineering is the most demanding teaching laboratory to set up properly. It combines the drainage problems of a fluids laboratory, the heat and instrumentation of a thermal laboratory, and a chemical inventory that carries real risk.
Build the equipment list around the operations a graduate must have handled physically. Simulation covers the design calculation; the laboratory covers what the calculation does not tell you, which is that packing channels, that a filter cake cracks, and that a column takes a long time to reach steady state.
| Operation | Experiment | Notes on the rig |
|---|---|---|
| Fluid flow and particles | Pressure drop through fixed and fluidised beds, minimum fluidisation velocity, bed expansion | A unit such as the EDIBON LFFC computer controlled fixed and fluidised bed unit covers this cleanly |
| Mechanical separation | Plate and frame filtration, sedimentation and settling rate, centrifugal separation | Messy; needs floor drainage and a solids disposal route |
| Size reduction | Crushing and grinding, sieve analysis and particle size distribution | Noisy and dusty; site away from analytical work |
| Mixing | Power consumption of an agitated vessel, mixing time, effect of baffles and impeller type | Modest utilities, high teaching value per taka |
| Heat transfer | Concentric tube, shell and tube and plate exchangers; parallel and counter flow | Shared with the thermal laboratory if the timetable allows |
| Evaporation | Single effect evaporation, boiling point elevation, capacity and economy | Needs a heat source and condenser cooling |
| Distillation | Batch distillation, continuous column with reflux, number of theoretical stages, effect of reflux ratio | The flagship rig; tall, needs headroom, cooling water and time |
| Absorption | Gas absorption in a packed column, mass transfer coefficient, flooding and loading | Needs a gas supply and an exhaust route |
| Liquid-liquid extraction | Extraction in a packed or agitated column, distribution coefficient, stage efficiency | Solvent inventory and a waste route are part of the purchase decision |
| Adsorption and ion exchange | Breakthrough curves, regeneration | Low hazard, good for large groups |
| Drying and humidification | Tray drying rate curves, cooling tower performance, psychrometrics | Cooling tower is best sited outdoors or at a window |
If the budget forces a choice, protect distillation, heat exchange and fluidisation. Between them they cover mass transfer, energy transfer and particle mechanics, and every one of them maps onto an industry in Bangladesh that hires these graduates: textiles and dyeing, fertiliser, cement, pharmaceuticals, sugar, edible oil and food processing.
Reaction engineering laboratories fail in a specific way. Students run a prescribed reaction, take samples at prescribed times, and produce a rate constant that the demonstrator already knew. Nothing about reactor behaviour has been learned. The fix is to build the laboratory around comparison rather than around a single reaction.
Choose reactions with mild reagents and simple analysis where the pedagogy allows it. A saponification followed by conductivity gives clean kinetics with a modest hazard profile, and it does not generate a waste stream that becomes a procurement problem. Reserve the more demanding chemistry for postgraduate work under supervision.
A teaching laboratory accumulates chemicals faster than it consumes them, because every project buys a bottle and every project ends. Within a few years there is a cupboard of unlabelled containers that nobody will take responsibility for, and disposing of it costs more than it cost to buy.
On sourcing: some reagents are readily available in Dhaka and some are not, and the ones that are not can hold up a semester. Check local availability once for every reagent your experiments depend on, and for anything that has to be imported, order a full year's requirement in one cycle rather than repeating the paperwork.
A fume cupboard is a ventilation system with a box on the front. Departments buy the box and then discover that the system was the expensive part.
Where flammable or toxic gases are used, fixed gas detection belongs in the specification alongside the extraction. A monitored point in the laboratory and one in the cylinder store, integrated so that an alarm is heard where somebody will act on it, is a modest cost against the alternative. Honeywell Midas and E3Point devices cover the usual laboratory and building applications.
Write the waste route into the experiment sheet itself, next to the method. If an experiment cannot state where its output goes, it is not ready to run.
Departments serving the food, dairy and pharmaceutical sectors increasingly want pilot-scale equipment, and it is a different proposition from bench work. A pasteurised milk, yogurt or milk powder pilot plant introduces hygienic design, cleaning in place, product contact materials, batch records and a genuine scale-up question.
The practical requirements are floor loading, headroom, a hygienic floor and drainage that copes with cleaning chemicals as well as product, a hot water or steam source, and secure storage for the cleaning agents. Decide whether the plant is a teaching asset or a small production facility, because if any product will ever leave the building the food safety obligations change entirely, and that decision belongs to the institution rather than to a keen lecturer.
A chemical engineering laboratory is judged by its drains and its store cupboard, not by its newest rig.: Vvon Technologies installation team