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Integrated Process Design

Integrated Process Design. CHOICE OF REACTOR (III) Practical reactors Example. STIRRED TANK REACTORS. Choice of Reactor Practical reactors. Allowed reaction processes:. Liquid phase, homogeneous or heterogeneous (L+L, L+S, L+G, S+L+G). Operation modes: Batch – Semi-batch – Continuous.

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Integrated Process Design

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  1. Integrated Process Design • CHOICE OF REACTOR (III) • Practical reactors • Example

  2. STIRRED TANK REACTORS • Choice of Reactor • Practical reactors Allowed reaction processes: • Liquid phase, homogeneous or heterogeneous (L+L, L+S, L+G, S+L+G). • Operation modes: Batch – Semi-batch – Continuous Non-recommended processes: • Multiple in series and some in parallel (low selectivity). • High pressure. • Hazardous products. Temperature control: • External jacket or internal coil. • External heat exchanger. • Reflux from condenser Recommended large volume PF reactor: consider using CSTR in series.

  3. TUBULAR REACTORS FIXED-BED CATALYTIC REACTORS Not-allowed reaction processes: • Heterogeneous reactions (unless static mixers are used). • Operation modes: Batch – Semi-batch. Recommended: • Residence time controlled reactions (multiple in series and polymeric without termination stage). • Highly exothermic/endothermic reactions. • High pressure.

  4. ‘Hot spots’: undesired reactions and catalyst degradation Alternatives: • Multi-tubular. • Catalyst dilution (inert solid). Not recommended when frequent catalyst regeneration is required (alternatively a moving-bed catalytic reactor may be used).

  5. FIXED-BED NONCATALYTIC REACTORS FLUIDIZED-BED NONCATALYTIC REACTORS FLUIDIZED-BED CATALYTIC REACTORS Gas + solid reactions: • Non-stationary conditions: difficult to control. Gas + liquid reactions: • Improve contact betweenphases. Advantages: • Excellent temperature uniformity. • Continuous catalyst regeneration. Disadvantages: • Complex hydrodynamic (bubbles). • Attrition of catalyst. Intermediate performance between PF and CSTR models. Gas + solid reactions (the same characteristics as catalytic reactors)

  6. TOLUENE FLUIDIZED-BED H2 STIRRED TANK REACTOR TUBULAR REACTOR FIXED-BED CATALYTIC REACTOR FIXED-BED NONCATALYTIC REACTOR FLUIDIZED-BED CATALYTIC REACTOR FLUIDIZED-BED NONCATALYTIC REACTORS • Gas phase reaction. • Catalytic heterogeneous. • Frequent catalyst regeneration.

  7. Flow pattern: • Toluene: main reaction  PF • H2:  High concentration at the exit. • Benzene: multiple in series  PF Excess of hydrogen: • Shifts the competitive reaction to the left (higher selectivity) • Reduces coke formation. • Decreases kinetics, • Separate from CH4 to recycle. Temperature: • Main reaction: highly exothermic, irreversible  T high (control ΔT !!) • Secondary reaction: endothermic, equilibrium  T low at the exit • Inert: Control ΔT (cold-shot and mCp increase) Pressure: • Main reaction : irreversible  P maximum • Secondary reaction: equilibrium Δn=0  indifferent

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