Absorption and Stripping Model

The purpose of the absorption and stripping model is to illustrate to apprentice technicians how distillation columns can be used to separate a specific component and feed it back into the system. The principles of distillation can be used in a varaiety of ways. The basic components of the absorption and stripping model include  

Distillation column used for absorption Distillation column used for stripping Two heat exchangers for cooling Two heat exchangers for heating Stirred reactor Four pumps 

Modern process control instrumentation Vapor recovery system and flare Separator 

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Troubleshooting models are literal, physical demonstrations of the equipment and systems presently being taught in community colleges and universities. Some of these models are the reaction model, the absorption and stripping model, the separation model, and the distillation model. These models are completely outfitted with alarms, analyzers, interlocks, permissives, video trends, recorders, and control instrumentation. Process problems can be simulated using these models. 

Pump and tank model Compressor model Heat exchanger model Cooling-tower model Steam-generation model Furnace model Distillation model Reaction model Separation model Absorption and stripping model Combination of the preceding models... 

The four models used to teach process troubleshooting are the distillation model, the reaction and separation model, the absorption and stripping model, and the combination model. Each model has a complete set of process control instrumentation and equipment arrangements. Various troubleshooting methodologies are applied to these four models. A complete range of troubleshooting scenarios has been developed and is typically included with these models. 

Although the rate model can be applied to any separation, it has become most popular in absorption and stripping. Reported case studies demonstrated that, in at least some situations, a rate model can more closely approxi-... 

CHEMCALC 11. AMSIM Amine Gas Tiealing Pbnt Simulator Gulf Publishing Company, Book Division P.O. Box 2608 Houston, TX 77252 (713) 520-4444 Models processes for absorption and stripping of H2S and CO2 in a gas stream. For hydrocarbon gases, also calculates hydrocarbons absoibed and stripped. 

Other multistage vapor-liquid separations such as absorption and stripping can be modeled using variations of the rigorous distillation models, as can multistage liquid-liquid extraction. 

The McCabe-Thiele analysis can be used to model physical absorption and stripping processes that use equilibrium stages. 

A comprehensive treatment of the thermodynamics of acid gas absorption by reactive solvents is presented by Astarila ei a ,23 These authors discuss the ihenretical approach to modeling such systems and provide equilibrium data on a number of commercially important solutes and solvents. Figures 6.1-4 and 6.1-5 show comparative equilibrium curves for CO in four different alkaline solvents ai coudilions representing absorption and stripping, respectively. 

We will use the correlation of Bolles and Fair (1982), for which HTUs are defined in the same way as here. The Bolles-Fair correlation is based on the previous correlation of Cornell et al., (1960a, b) and a data bank of 545 observations and includes distillation, absorption, and stripping. This model and variations on it remain in common use fWang et al.. 2Q05V... 

Troubleshooting models—tools used to teach troubleshooting techniques. Basic models include distillation, reaction, and absorption and stripping, or combinations of these three. 

Chemical engineers have used the concept of vapor-liquid equilibrium for much of their treatment of separation processes such as distillation, absorption, and stripping. In this chapter, we examine the dynamic modeling and numerical solution of typical vapor-liquid equilibrium systems. 

Vapor-liquid mass-transfer operations, such as absorption, stripping and distillation, are carried out in packed and plate columns. The key difference is that counterflowing vapor and liquid are contacted continuously with packings, and discretely with plates. The equilibrium and operating lines of packed and plate columns are identical under the same operating conditions—feed and product flowrates and compositions, temperature and pressure. Models for the design and analysis of packed columns are based on their close analogy to plate devices. 

EPAR ATION and purification processes account for a large portion of the design, equipment, and operating costs of a chemical plant. Further, whether or not a mixture forms an azeotrope or two liquid phases may determine the process flowsheet for the separations section of a chemical plant. Most separation processes are contact operations such as distillation, gas absorption, gas stripping, and the like, the design of which requires the use of accurate vapor-liquid equilibrium data and correlating models or, in the absence of experimental data, of accurate predictive methods. Phase behavior, especially vapor-Uquid equilibria, is important in the design, development, and operation of chemical processes. 

In certain systems, phase separation is enhanced by introducing an additional feed to the separation device such as in absorption or stripping and in azeotropic and extractive distillation. Although these processes are usually multistage, their characteristics are discussed in this section using the single-stage model. 

The graphical method assumes an idealized absorption/stripping model that is defined in terms of essentially three components or groups of components a liquid, a gas, and a distributed component or solute. The liquid is assumed not to vaporize (i.e., it has a very low A -value), and the gas is assumed not to dissolve in the liquid (i.e., it has a very high A -value). The distributed component is the key component to be absorbed by the liquid or stripped by the gas. It distributes itself between the two phases to satisfy vapor-liquid equilibrium criteria (Chapter 1). 

Another simplification in the idealized model is the exclusion of energy balances and the heat of absorption or stripping. The tray temperatures must be assumed or determined independently. An isothermal column may be assumed with the implication that heat sources or sinks are available for maintaining a constant temperature. 

Earlier chapters use simplified and binary models to analyze in a very informative manner some fundamentals such as the effect of reflux ratio and feed tray location, and to delineate the differences between absorption/stripping and distillation. Following chapters concentrate on specific areas such as complex distillation, with detailed analyses of various features such as pumparounds and side-strippers, and when they should be used. Also discussed are azeotropic, extractive, and three-phase distillation operations, multi-component liquid-liquid and supercritical extraction, and reactive multistage separation. The applications are clearly explained with many practical examples. 

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