Solid-liquid-vapor separators

System Let the system be all of the units and mixing points jointly. 

Step 7 The element balances are Ti, O, H, Cl, and also m, = W or co, = lj and the inerts balance. If 5 of these are independent, we can solve for the variables whose values are unknown. 

Steps 8 and 9 The balances are in kg. The simplest balances to start with are those involving tie components. If selected properly, the equations can be solved sequentially rather than simultaneously. 

These values can be calculated solely from the data given and the Ti balance. 

To calculate the third part of the problem, we need to involve the recycle stream in the balances. Let the system be the mixing point. No reaction occurs. The balances are in kg. 

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Simprosys 3.0 contains 20 unit operation modules and 2 utilities as displayed in Figure 60.2. The 20 unit operation modules include solid dryer, liquid dryer, burner, cyclone, air filter, bag filter, electrostatic precipitator, wet scrubber, scrubber condenser, fan/blower, compressor, steam jet ejector, pump, valve, heater, cooler, heat exchanger that can also be used as an evaporator, liquid-vapor separator. 

The presence of multiple components adds a new dimension to the phase behavior of mixtures. In the pure component, molecules are always surrounded by similar species in a mixture, they are surrounded by both like and unlike species. This gives rise to self-interactions between like molecules, and crossinteraction between unlike molecules. These interactions are much more pronounced in the liquid phase, where molecules are closely packed together. The balance of self- and cross-interactions creates phase behavior that is not seen in pure fluids. If cross-interactions are favorable, components form strong mixtures that are more difficult to separate. If cross interactions are unfavorable, the mixture is weaker and separation is easier. If they are strongly unfavorable, then components may exhibit partial miscibility. Additional variety of phase behaviors comes from the number of phases that can coexist simultaneously. With mixtures we encounter problems of vapor-liquid equilibrium (VLE), but also liquid-liquid (LLE) and liquid-liquid-vapor (LLVE) equilibrium. If a solid component is added, other combinations of equilibria are observed for example, solid-liquid, solid-liquid-vapor, etc. This enormous variety is made possible by the presence of additional components. 

Figure 25-11. Liquid-vapor separation curve in the T, v diagram. Note that solid-liquid and solid-vapor domains are not shown for clarity.

The lines separating the regions in a phase diagram are called phase boundaries. At any point on a boundary between two regions, the two neighboring phases coexist in dynamic equilibrium. If one of the phases is a vapor, the pressure corresponding to this equilibrium is just the vapor pressure of the substance. Therefore, the liquid-vapor phase boundary shows how the vapor pressure of the liquid varies with temperature. For example, the point at 80.°C and 0.47 atm in the phase diagram for water lies on the phase boundary between liquid and vapor (Fig. 8.10), and so we know that the vapor pressure of water at 80.°C is 0.47 atm. Similarly, the solid-vapor phase boundary shows how the vapor pressure of the solid varies with temperature (see Fig. 8.6). 

The selection of vapor/gas/solid-liquid separators and final control and destruction equipment can be helped by considering the advantages and disadvantages of each, as given below. 

This is the fundamental distillation equation, often referred to as the Rayleigh law when in its integrated form (Rayleigh, 1896). As far as Dt is considered to be a function of F, this equation applies to the change of any species concentration in the course of phase separation. Liquid-vapor or solid-solid fractionations are liable to the same formulation. 

Tanks are used in innumerable ways in the chemical process industry, not only to store every conceivable liquid, vapor, or solid, but also in a number of processing applications. For example, as well as reactors, tanks have served as the vessels for various unit operations such as settling, mixing, crystallization (qv), phase separation, and heat exchange. Herein the main focus is on the use of tanks as liquid storage vessels. The principles outlined, however, can generally be applied to tanks in other applications as well as to other pressure-containing equipment. 

Molten Salt Distillation. Hafnium tetrachloride is slightly more volatile than zirconium tetrachloride, but a separation process based on this volatility difference is impractical at atmospheric pressures because only solid and vapor phases exist. The triple point for these systems is at about 2.7 MPa (400 psia) and 400°C so that separation of the liquids by distillation would necessarily require a massive pressurized system (13). 

The term phase defines any homogeneous and physically distinct part of a system which is separated from other parts of the system by definite bounding surfaces. For example, ice, liquid water, and water vapor are three phases. Each is physically distinct and homogeneous, and there are definite boundaries between ice and water, between ice and water vapor, and between liquid water and water vapor. Thus, we say that we have a three-phase system solid, liquid, and gas. One particular phase need not be continuous. For instance, the ice may exist as several lumps in the water. 

In addition to handling the conventional vapor/liquid process operations, the ASPEN library of process models includes solids handling and separation units, a set of generalized reactors, improved flash and distillation unit models and process models from the FLOWTRAN simulator. The user can also include his or her own model or key elements of a model, such as the reaction kinetics, in FORTRAN code. 

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