Зеотропты қоспалар: қасиеттері мен қолданылуы

A zeotropic mixture, or non azeotropic mixture, is a mixture with liquid components that have different boiling points. For example, nitrogen, methane, ethane, propane, and isobutane constitute a zeotropic mixture. Individual substances within the mixture do not evaporate or condense at the same temperature as one substance. In other words, the mixture has a temperature glide, as the phase change occurs in a temperature range of about four to seven degrees Celsius, rather than at a constant temperature. For zeotropic mixtures, the temperatures on the bubble (boiling) curve are between the individual component's boiling temperatures. When a zeotropic mixture is boiled or condensed, the composition of the liquid and the vapor changes according to the mixtures's temperature composition diagram.]] In mixtures of substances, the bubble point is the saturated liquid temperature, whereas the saturated vapor temperature is called the dew point. Because the bubble and dew lines of a zeotropic mixture's temperature composition diagram do not intersect, a zeotropic mixture in its liquid phase has a different fraction of a component than the gas phase of the mixture.]] Azeotropic and zeotropic mixtures have different dew and bubble curves characteristics in a temperature composition graph. This is due to the constant boiling point of the azeotropic mixture.

The characteristics of pool boiling are different for zeotropic mixtures than that of pure mixtures. Zeotropic mixtures and pure liquids also have different critical heat fluxes.

The ideal case of distillation uses zeotropic mixtures. 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. 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. Research has proposed using zeotropic mixtures as substitutes to halogenated refrigerants due to the harmful effects that hydrochlorofluorocarbons (HCFC) and chlorofluorocarbons (CFC) have on the ozone layer and global warming. However, there are some technical difficulties for using zeotropic mixtures. Due to their higher boiling points, zeotropic working fluids have higher net outputs of energy at the low temperatures of the Rankine Cycle than pure substances. Cleaning processes that use zeotropic mixtures include cosolvent processes and bisolvent processes. The first fluid is a solvating agent that dissolves soil in the cleaning process. This fluid is an organic solvent with a low boiling point and a flash point greater than the system's operating temperature. After the solvent mixes with the oil, the second fluid, a hydrofluoroether rinsing agent (HFE), rinses off the solvating agent. The solvating agent can be flammable because its mixture with the HFE is nonflammable. In bisolvent cleaning processes, the rinsing agent is separated from the solvating agent. This makes the solvating and rinsing agents more effective because they are not diluted. Cosolvent systems are used for heavy oils, waxes, greases and fingerprints, and can remove heavier soils than processes that use pure or azeotropic solvents. Cosolvent systems are flexible in that different proportions of substances in the zeotropic mixture can be used to satisfy different cleaning purposes. For example, increasing the proportion of solvating agent to rinsing agent in the mixture increases the solvency, and thus is used for removing heavier soils. The operating temperature of the system depends on the boiling point of the mixture, which in turn depends on the compositions of these agents in zeotropic mixture. Since zeotropic mixtures have different boiling points, the cleaning and rinse sump have different ratios of cleaning and solvating agents. The lower boiling point solvating agent is not found in the rinse sump due to the large difference in boiling points between the agents.

Mixtures containing HFC 43 10mee can replace CFC 113 and perfluorocarbon (PFC) as solvents in cleaning systems because HFC 43 10mee does not harm the ozone layer, unlike CFC 113 and PFC. Various mixtures of HFC 43 10mee are commercially available for a variety of cleaning purposes. Examples of zeotropic solvents in cleaning processes include:
Zeotropic mixtures of HFC 43 10mee and hexamethyldisiloxane can dissolve silicones and are highly compatible with polycarbonates and polyurethane. They can be used to remove silicone lubricant from medical devices. Zeotropic mixtures of HFC 43 10mee and isopropanol can remove ions and water from materials without porous surfaces. This zeotropic mixture helps with absorption drying. Zeotropic mixtures of HFC 43 10mee, fluorosurfactant, and antistatic additives are energy effiicient and environmentally safe drying fluids that provide spot free drying.