Absorption column design specification

The absorption column design represents a compromise between mass transfer factors and economic considerations. The final design specification is for a column of 1.8 m diameter, approximately 32 m high, and containing 59 sieve trays. 

Formulate a statement of the design criteria for the unit. What is the general design criteria What is the design (or the unit) intended to achieve For example, a reactor is usually required to achieve a particular conversion of reactants to products, a distillation column must provide a particular separation, an absorption column provides removal of a specific level of impurity, etc. 

This section discusses the design of a suitable absorption column for the production of nitric acid by the single-pressure process. A comprehensive design study determined the column mechanical details and physical characteristics, together with its anticipated performance. This chapter contains the operating criteria and product specifications, the solution method, and finally the results of the design calculations. Details of the design calculations and all associated data are included in Appendix G. 

Part II contains the design of a major item of equipment (in this case study, it is a sieve-tray absorption column (Chapter 9) ), including the mechanical design, fabrication, materials specification, detailed engineering drawing, HAZOP study, control scheme and associated instrumentation. In summary, as complete and professional a design as... 

Insufficient absorption or off-specification for exit scrubbed gas feed gas concentration off spec/feed gas temperature or pressure outside operating window for amine absorbers > 50 °C for H2S and < 24 °C for C02/feed gas pressure has de-creased/[solvent flowrate too low] for glycol dehydration 12.5 to 25 L TEG per kg water removed/[solvent incorrect] /incorrect feed tray location/[column operation faulty] /absorber operating conditions differ from design/[absorber malfunction]. ... 

Tray Columns. The contactor, or absorber, is typically a countercurrent column containing an integral scrubber at the bottom, a central trayed or packed absorption section, and a demister at the top. The basic design correlations for absorption columns are described in Chapter 1 and only matters specific to dehydration contactors are covered in the following paragraphs. 

While tray columns and packed columns are invariably the devices used for stripping, other devices are occasionally used for absorption or scrubbing. These are often proprietary, and the vendor does the design based on the specifications provided by the user and/or process designer. While the foregoing material is based on countercurrent contacting of gas and liquid, there may be some instances when cocurrent operation has advantages ... 

The design firm normally generates procurement specifications. These specifications will include definition of all major components such as materials of construction, agitator requirements, nozzles, etc. Major equipment for API processing is similar to fine chemical production and can include reactors, centrifuges, condensers, heat exchangers, distillation columns, extractors, absorption equipment, chromatography equipment, dryers, blenders, crystallizers, mills, etc. These components wiU normally require validation [installation... 

Both total flows Vj and Lj will be largest where Yj and Xj are largest. This is at the bottom of the column for absorption, and therefore you design the diameter at the bottom of the column. In strippers, flow rates are highest at the top of the column, so you design the diameter for the top of the column. Specific design details for absorbers and strippers are discussed by Kister et al. (2Q08) and Zenz 119971. 

Multi-functional detectors monitor the column eluent by the measurement of more than one physical or chemical property simultaneously, employing a single sensing cell. To date, three bifunctional detectors and one trifunctional detector have been described. The three bifunctional detectors have combined UV absorption and fluorescent detection, UV absorption and electrical conductivity detection and UV absorption and refractive index detection. The latter uniquely combines a bulk property detector with a solute property detector producing, at least in theory, the nearest approach to a universal detector. The trifunctional detector incorporates UV absorption, electrical conductivity and fluorescence functions. Multi-functional detection provides detector versatility and a means of confirmir solute identity. Such detectors have to be designed, so that the performance specifications are not seriously compromised, and the cell and eluent conduits do not contribute significantly to peak dispersion. 

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