User:MissAndrea/sandbox

On the "Zeotropic Mixture" Wikipedia article, I want to add a proper and concise definition of zeotropic mixture. In addition, I want to add applications of zeotropic mixtures in industry, namely, applications in power generation, distillation, and refrigeration. From multiple database searches, these three applications are major applications and much research has been done on them, so I wish to reflect this in the wikipedia article. In addition, I want to dig deeper into the terms already mentioned on the wikipedia article, including "azeotropic" and "temperature glide" and how these terms relate to the definition of zeotropic because these two terms have appeared in several keyword searches on zeotropic and seem to be important to gaining a better understanding of zeotropic mixture. MissAndrea (talk) 04:51, 23 January 2017 (UTC)

Pre-Writing for my Drafting on "Zeotropic Mixtures"

Application in Distillation

Zeotropic fluid and gaseous mixtures can be separated by distillation due to the difference in boiling points between the component mixtures. This process involves the use of vertically-arranged distillation columns. When separating zeotropic mixtures with three or greater liquid components, each distillation column removes only the lowest-boiling point component and the highest boiling point component. To separate these mixtures further, a sequence of distillation columns must be used. This multi-step distillation process is also called rectification.

In each distillation column, pure components form at the top (rectifying section) and bottom (stripping section) of the column when the starting liquid (called feed composition) is released in the middle of the column. At a certain temperature, the component with the lowest boiling point (called distillate or overhead fraction) vaporizes and collects at the top of the column, whereas the component with the highest boiling point (called bottoms or bottom fraction) collects at the bottom of the column. In a zeotropic mixture, where more than one component exists, individual components move relative to each other as vapor flows up and liquid falls down.

In a concentration profile, the position of a vapor in the distillation column is plotted against the concentration of the vapor. In the figure shown, the component with the highest boiling point (propanol) has a max concentration at the bottom of the column, where the component with the lowest boiling point (methanol) has a max concentration at the top of the column. The component with the intermediate boiling point (ethanol) has a max concentration in the middle of the distillation column, so in mixtures with greater than three component substances, more than one distillation column is needed to separate the mixtures.

When designing distillation processes for separating zeotropic mixtures, the sequencing of distillation columns is vital to saving energy and costs. In addition, other methods can be used to lower the energy or equipment costs required to distill zeotropic mixtures, including combining distillation columns (which uses as much energy as the most energy-consuming separated column), using side columns (saves energy by preventing different columns from carrying out the same separation of mixtures), combining main columns with side columns (saves equipment costs by reducing the number of heat exchangers needed), and re-using waste heat for the system. Re-using waste heat requires the amount of heat and temperature levels of the waste to match that of the heat needed. Thus, using waste heat requires changing the pressure inside evaporators and condensors of the distillation system in order to control the temperatures needed. Controlling the temperature levels in a part of a system is possible with Pinch Technology. These energy-saving techniques have a wide application in industrial distillation of zeotropic mixtures: side columns have been used to refine crude oil, and combining main and side columns is increasingly used. MissAndrea (talk) 08:23, 25 January 2017 (UTC)