Important Distillation Concepts

This book has been compiled for the student, engineer, or researcher that understands the fundamental concepts of distillation, or has at least attended an introductory course on the subject. The reader should be familiar with key vapor liquid 

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This chapter has only provided a brief overview of the technology of distillation. In part, to highlight some important engineering concepts and equipment, the following summary is given. As described, refinery main fractionators are distillation towers that separate very wide boiling fractions into a series of rough... 

A hydrocarbon is a chemical compound that contains hydrocarbon and carbon. Crude oil is a mixture of hydrocarbons that vary in size and structure from simple to complex. Much modern manufacturing is based on separating the various components in crude oil by their individual boiling points. Important applied concepts of chemical processing include distillation, catalytic cracking, hydrocracking, and alkylation. 

Calculations based on Murphree efficiencies are about as far as mass transfer models can be pushed. These calculations may not always be reliable, even though they are based on a huge number of experimental results. The reason is that a single overall mass transfer coefficient may be inadequate to describe all aspects of the flow and diffusion occurring in a single stage. Still, the value of any scientific effort is the product of the importance of the problem and the quality of the solution. Distillation is very important although concepts of efficiency are certainly imperfect, they seem to me to remain valuable. 

This method is one of the most important concepts in chemical engineering and is an invaluable tool for the solution of distillation problems. The assumption of constant molar overflow is not limiting since in very few systems do the molar heats of vaporisation differ by more than 10 per cent. The method does have limitations, however, and should not be employed when the relative volatility is less than 1.3 or greater than 5, when the reflux ratio is less than 1.1 times the minimum, or when more than twenty-five theoretical trays are required(13). In these circumstances, the Ponchon-Savarit method described in Section 11.5 should be used. 

One of the most important difficulties in the use of homogeneous catalysis for technical applications is the recovery and reuse of the expensive metal catalyst. Various concepts for catalyst recychng are apphed to overcome this problem in current technical applications. A simple method is to perform the catalytic reaction in a single phase and to separate the product and the catalyst afterwards by distillation of the product, as reahzed, for... 

Was this your answer Water, H20, is a compound made of the elements hydrogen and oxygen in a 2-to-i ratio. Every H20 molecule is exactly the same as every other, and there s no such thing as an impure H20 molecule. Just about anything, including you, beach balls, rubber ducks, dust particles, and bacteria, can be found in water. When something other than water is found in water, we say that the water is impure. It is important to see that the impurities are in the water and not part o/the water, which means that it is possible to remove them by a variety of physical means, such as filtration or distillation.The answerto this Concept Check is (b). 

Martin and Synge (3) introduced the important concept of theoretical plates into chromatography. Their concept was derived from partition theory and random statistics, and was related to similar ideas developed for extraction and fractional distillation. They supposed that the column could be divided into a number of sections called theoretical plates, and that solutes (dissolved compounds) could be expected to achieve equilibrium between the two phases (mobile and stationary) that exist within each plate. The chromatographic process, like an extraction process, can be visualized to occur when mobile phase (solvent) is transferred to the next plate, where a new equilibrium is established. Theoretical plate numbers of 1000 or more are common for HPLC columns, which means that 1000 separate equilibria must be established to obtain the same degree of separation by solvent... 

In Chaps. 4 and 6 we discuss specific control issues for chemical reactors and distillation columns. We shall then have much more to say about the important concepts of dominant variables and partial control. Much of the material in those chapters centers on the control of the units individually. However, we also try to show how plantwide control considerations may sometimes alter the control strategy for the unit from what we would normally have in an isolated system. 

An important alternative is the successive reaction and product extraction procedure shown in Figure 5. First the reaction of A and B is carried out in a single polar homogeneous phase containing the catalyst. Downstream, the products are extracted with a nonpolar solvent or solvent mixture. In the third unit, the distillation, the low boiling extractant is distilled off and recycled to the extraction unit. Two examples will demonstrate the practicability of this concept. 

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