88,105 research outputs found
Centrifugal Decantation
No full textTwo liquid phases can be separated by decantation taking advantage of their different densities. When residence time should be lowered down centrifugal force instead of gravitational one can be employed. The centrifugal decanter design is based on a pressure balance and the outlet can be properly located in order to allow for a continuous operation
Lyophilization
No full textDue to the thermolability of food and pharmaceutical products the drying process cannot be performed at high temperature; lyophilization replaces then standard drying units taking advantage of sublimation instead of evaporation. Being freeze drying a batch operation, a suitable model is used to assess the operating residence time for given operating conditions. The critical importance of an optimal control system for the productivity maximization will be discussed by mean of an common industrial case study
Drying
No full textDrying is the most general expression for a set of operations aimed to remove the moisture contained in solid matrix products by mean of heat transfer. Due to the several possible configurations a wide range of models exists; they share in common heat and mass balances both in case of direct and indirect heat transfer. Internal diffusion can be either taken into account or neglected and a proper discretization should be used to model this phenomenon
Crystallization
No full textCrystallization is the non-conventional operation allowing to obtain crystals with high purity from a liquor. Taking advantage of different components solubilities, more than one pure species can be obtained from the same solution. Nucleation and growth phases can be described by dedicated models. The delta-L law derivation for the crystal growth process is explained in detail and the relationship between linear growth and growth ratio is discussed by mean of a case study
Spray Drying
No full textWhen suspensions, aerosols or slurries contain solid particles that cannot be mechanically dried a spray dryer should be employed. Widely spread in food and pharma industry, spray dryers are suitable to ensure low residence time at high temperature. The unit height is designed according to the residual moisture specification by mean of an ODEs system arising from mass and heat balances
Heat Pumps
No full textHeat pumps are widespread units employed in the daily life whether a consistent amount of energy is available at a low enthalpic level (i.e. not suitable temperature). Their particular efficiency is shown by mean of a practical example where heat balances and operating conditions are thoroughly discussed. The sizing of each unit (evaporator, condenser and compressor) follows the process design in order to provide a complete overview
Pinch Technology
No full textPinch technology is the best practice for heat exchanger networks optimization from an OPerating EXpenses point of view. Its main goal is to find a compromise between the investment required for the additional units and the external duty demand. The standard procedure is based on a preliminary thermodynamic assessment followed by the network optimization according to the feasibility of the operation. The results thus obtained allow then the decision maker to select the optimal solution according the specific needs of the case under analysis
Centrifugal Sedimentation
No full textSedimentation is a separation technology alternative to filtration for liquid-solid separation. By taking advantage of different inertial behavior the centrifugal field allows for the solid deposition on the sedimenter wall and for a continuous clarified liquid removal. A multi-layered configuration, within the feasibility limits, enhances the separation effectiveness as shown in the design problem
Cooling Towers
No full textCooling towers are the most used units designed to reduce cooling water temperature downstream the process both in once-through configurations and in those with a recycle. Their theoretical background is strictly related to the definition of humidity and wet bulb temperature. From a modeling point of view they can be solved as a standard desorption column whose specification is the outlet liquid temperature; the corresponding BVP can be smartly turned into as a standard ODE system to converge making calculations easier and allowing for the design of a packed bed unit as a case study
Multiple-Effect Evaporation
No full textMultiple-effect evaporation is the cheapest and simplest unit operation aimed to either recover the solvent from a solution or concentrate the solution itself. Several system configurations exist and the optimal one from a Net Income point of view can be selected for each specific case. By mean of a desalination case study cocurrent and countercurrent schemes are compared and advantages and disadvantages of both of them are highlighted and commented from an operability and an economic perspective
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