Energy-separating-agent

Application of an energy-separating agent involves heat transfer and/ or shaft work to or from the mixture to be separated. Alternatively, vapour may be created from a liquid phase by reducing the pressure. 

Table 1 is a compilation of the more common industrial separation operations based on inter-phase mass transfer between two phases, either created by an energy-separating agent or added as a mass-separating agent. A more comprehensive table is given by Seader and Henley.1 In the following, the operations listed in Table 1 will be outlined briefly. The first two methods, distillation and absorption, will be discussed in more detail later. 

Table 1 Common separation operations based on phase creation or addition (MSA mass-separating agent ESA energy-separating agent)...

Give examples of mass- and energy-separating agents. 

A separation involving an energy-separating agent (ESA) can involve input and removal steps, such as in distillation, where there is a reboiler for energy input and a condenser for energy removal. In other cases, such as evaporation, the vapor can be discharged without... 

While heat is the most common energy-separating agent used. Table 2.3 provides examples of separation processes using gravitational, electric and magnetic fields. 

Separation processes use mass- and/or energy-separating agents to perform the separation. Mass-separating agents can be a solid, liquid or gas. Heat is the most common... 

Energy-separating agent heat input to change the temperature of a gas/liquid system. The most common example is distillation. 

Energy-separating agent heat input to a liquid phase to change the solute solubility in that phase. An example would be evaporation to remove water from a waste stream and concentrate it prior to disposal. 

Energy-separating agent heat removal to precipitate salts from an aqueous stream. 

Mass-separating agent membrane which filters suspended solids based on size. Energy-separating agent gravity settling to separate particles by size. 

Energy-separating agent heat input into the amine solution to accelerate the rate of gas desorption which regenerates the solution. 

Mass-separating agent intra-particle diffusion in a porous sorbent. Energy-separating agent application of an electric field across a liquid phase to accelerate the charged particles relative to neutrals. 

Describe circumstances in which steam can be either an energy-separating agent or a mass-separating agent. 

Distillation uses an energy-separating agent heat. It is an equilibrium-limited separation. Vapor-liquid equilibrium (VLB) is the type of equilibrium by which distillation columns separate, and vapor pressure is the primary property difference that forms the basis for separation. 

Consider, for example, the bottom section of the distillation column shown in Fig. 17.4a. Instead of work, the energy separating agent is heat transferred to the reboiler. If the heating medium (e.g., steam) in the reboiler is at a constant temperature T the work equivalent to the reboiler duty is obtained from the reversible heat engine, shown in Fig. 17.4h. For such an engine, classical thermodynamics gives the relationship... 

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