4/18/2021 0 Comments Disadvantages Of Hydrocracking
They are typically made of wood, sheet metal, or woven gauze.The heat causes components with lower boiling points and higher volatility to be vaporized, leaving less volatile components as liquids.Mixtures with high relative volatilities are easier to separate.This makes separations of close-boiling and azeotropic feeds difficult, so special distillation techniques have to be used to separate these mixtures.
Many variables, such as column pressure, temperature, size, and diameter are determined by the properties of the feed and the desired products. Some specialized columns perform other functions, such as reactive distillation columns, which combine reaction and separation of products into a single unit. The packing provides a large surface area for vapor-liquid contact, which increases the columns effectiveness. ![]() The packing increases the time of contact, which increases the separation efficiency. The exiting vapor contains the most volatile components, while the liquid product stream contains the least volatile components. The liquid at the bottom, which is highlighted in yellow in the animation, enters a reboiler. Two streams exit the reboiler; a vapor stream, which returns to the column, and a liquid product stream. The vapor stream flows upward through the packing, picks up the more volatile components, exits the column, and enters a condenser. After the vapor condenses, the stream enters a reflux drum, where it is split into an overhead product stream, known as the distillate, and a reflux stream that is recycled back to the column. ![]() Dumped packings have either random or geometrically structured shapes and are composed of bulk inert material, such as clay, porcelain, plastic, ceramic, metal, or graphite. Individual packings are typically 3 to 75 mm in size, and have several void spaces that provide a large surface area for liquid-vapor contact. The advantages of dumped packing include high liquid flow rate capacity, high pressure capacity, and low cost. Several examples of metal, plastic, and ceramic type packings are shown in the picture below. Ceramic packings have a higher wettability than metal packings, but they are not as strong. Plastic packings have sufficient strength but experience poor wettability at low liquid flowrates. Because they are corrosion resistant, ceramic packings are used only at elevated temperatures where plastic packing would fail. It provides long uninterrupted channels for liquid and vapor flow. Although they are more expensive than dumped packings, stacked packings result in a lower pressure drop. Stacked packing is preferred for low liquid flow rates and in low pressure situations.
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