CHEE 2404 Unit Operations and Unit Process Equipment

1. CHEE 2404Unit Operations and Unit Process Equipment Dr. A. Ghanem

2. Lets look at the overall process flow of a modern oil refinery:

4. The overall process is broken down into individual subsets:

5. With their own flow arrangement:

7. We notice�.. The number of individual processes is large, each one can be broken down into a series of steps that appear in process after process The individual �steps� have common techniques and are based upon the same scientific principles

9. Fluid dynamics: a study of the behaviour of fluids In Chemical processes fluid streams flow from one process to another through pipes and ducts. Process fluids are moved by pumps and compressors Fluid flowrates must be monitored by meters and are controlled by valves.

11. Heat Transfer: process fluids may need to be heated up to a certain temperature heat from a process stream may be recovered This can be done by contacting two streams in a heat exchanger.

12. Evaporation: A special case of heat transfer, where a phase change takes place. Concentrate a solution consisting of a nonvolatile solute and a volatile solvent The volatile solute evaporates leaving a more concentrated solution.

14. Humidification: Transfer of material between a pure liquid phase and a fixed gas phase that is nearly insoluble in the liquid Example: Water vapour is added to a air, cooling tower to decrease water temperature

15. Gas absorption Also known as stripping or desorption a mass transfer operation A soluble vapour is absorbed from its mixture with an inert gas by means of a liquid in which the solute gas is more soluble. Example: the removal of CO2 and H2S from natural gas or syngas by adsorption into amines or alkaline salts

17. Leaching or Liquid extraction Solid extraction involves the dissolving of soluble matter from its mixture with an insoluble solid Liquid extraction is the separation of two miscible liquids by the use of a solvent that preferentially dissolves one of them. LE an alternative to distillation for difficult separations Example: penicillin is separated from fermentation broth by extraction with butyl acetate

20. Distillation Production of a vapour by boiling the liquid mixture to be separated and then condensing the vapours without returning any to the still. (flash distillation) Return part of the condensate to the still under conditions where it can be in contact with the vapours on their way to the condenser. (rectification) Either operation may be done in batch or continuous mode.

22. Adsorption a separation process where the fluid is contacted with small particles of a porous solid which selectively adsorbs or complexes with certain components of the feed. The solid adsorbent is usually held in a fixed bed.

24. Drying Removal of water (usually small amounts) or other liquid from a solid material to reduce the content of residual liquid to an acceptable low value Water may be removed by presses or centrifuge (mechanical) or thermally by vaporization

26. Agitation and Mixing Induced motion of a material in a container Random distribution into and through one another, of two or more initially separate phases.

28. Fluidization Particle fluid interaction When a gas or liquid is passed upward through a bed of particles, at a certain velocity the particles will become suspended in the fluid.

30. Filtration the removal of solid particles from a fluid by passing the fluid through a filtering medium on which the solids are deposited.

32. Crystallization The formation of solid particles within a homogenous phase Formation of solid particles in a vapour, solidification from a liquid melt, or crystallization from liquid solution A variety of materials are marketed in crystallized form. Many are vacuum units where adiabatic evaporative cooling induced supersaturation.

34. Centrifugation a given particle settles under gravitational force at a fixed maximum rate to increase the settling rate we replace the force of gravity by a much stronger centrifugal force. More effective than gravity separators because they will separate fine drops and particles and are much smaller in size for a given capacity. Solids removal from gas: cyclones

36. Materials handling Classification: characterization of solids by size and shape Done in a series of standard screens or woven wire test sieves arranged serially on a stack, with the smallest mesh on the bottom and the largest on top. Comminution Size reduction of solid particles For example, chunks of coke must be reduced to workable size Compression, impact, attrition (rubbing) or cutting Crushers and grinders are good examples.

37. Unit Process: Reactors While not a unit operation, reactors are essential process operations They are identified on flowsheets by the type of vessel and their flow: Batch reactor Continuous stirred tank reactor (CSTR) plug flow or tubular reactor

38. Batch reactor A tank or vessel where reactants have been placed and products are removed There is no inflow or outflow of reactants or products.

39. Continuous Stirred Tank Reactor (CSTR) Run at steady state (ie no accumulation) Very well mixed Modelled as having no spatial variations in concentration, temperature, pH or reaction rate in the vessel T an C are identical everywhere in the vessel, they are the same at the exit as in the tank.

40. Plug Flow or Tubular Reactor Consists of a cylindrical pipe Assume the flow is highly turbulent and there is no radial variation in concentration.