A chemical reactor is a pressure vessel with internals (agitator, baffles, dip pipes, spargers) and often external heat transfer surfaces (jackets, limpet coils, internal coils). Ohm Engineers builds jacketed and limpet-coil reactors at our Vadodara facility — the vessel, nozzles, and heat-transfer surfaces are fabricated to your drawing; agitator and licensor internals are supplied when specified on the order.
Batch vs Continuous (CSTR)
- Batch reactor: Suitable for multi-product plants, reactions requiring long residence time, or processes where continuous feed is impractical. Heat removal is often the limiting factor — exothermic reactions may require external circulation through a heat exchanger (external loop).
- CSTR (Continuous Stirred Tank Reactor): Suitable for single-product continuous plants with well-characterised kinetics. Residence time distribution is defined by tank volume ÷ volumetric flow rate.
- Plug flow (tubular reactor): For reactions where back-mixing must be minimised. Not discussed in detail here but relevant for fast exothermic reactions.
Jacket Types for Heat Transfer
| Jacket Type | Heat Transfer Area | Best For | Limitations |
|---|---|---|---|
| Conventional jacket (full or partial) | Low — limited by vessel surface | Moderate heat duties, low viscosity | Dead zones at jacket inlet; poor for viscous fluids |
| Limpet coil (half-pipe welded to shell) | Medium — covers most of shell | Exothermic reactions, moderate viscosity | Welding stress on shell; inspection access limited |
| Dimple jacket | Medium — uniform coverage | Food, pharma, clean services | Lower pressure rating than limpet |
| Internal coil | High — large surface in vessel | High heat duty exothermic reactions | Obstructs mixing; cleaning difficulty |
Agitator Selection Basics
Agitator type determines mixing intensity, power consumption, and heat/mass transfer at the vessel wall:
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Always specify agitator tip speed (m/s) and power per unit volume (kW/m³) rather than only motor kW — motor kW depends on fluid density and viscosity at operating conditions.
- Pitched blade turbine (PBT): General purpose, good axial flow. Suitable for most liquid-liquid and solid-liquid mixing.
- Anchor agitator: High viscosity (> 10,000 cP). Scrapes vessel wall — improves heat transfer in viscous systems.
- High-efficiency impeller (HE-3, A310): Low power number, strong axial flow. Preferred for large reactors where power cost matters.
- Gas dispersion (Rushton turbine): For gas-liquid reactions. High power draw; specify only when gas dispersion is the primary requirement.
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