Vaporization point

The transfer of supersaturated liquor from the vaporizer (point B, Fig. 18-69) often causes salt buildup in the piping and reduction of the operating cycle in equipment of this type. The rate of buildup can be reduced by circulating a thin suspension of solids through the vaporizing chamber however, the presence of such small seed ciystals tends to rob the supersaturation developed in the vaporizer, thereby lowering the efficiency of the recirculation system. 

CVD Reactions. The rhodium halides, like those of the other platinum group metal s, are volatile with a decomposition pointtoo close to the vaporization point to make them usable for CVD transport. The metal is commonly produced by the decomposition of metallo-organic precur-... 

Stated physically, the critical condition for pyrophoricity under the proposed assumptions is that the heat release of the oxide coat formed on a nascent sphere at the ambient temperature must be sufficient to heat the metal to its vaporization point and supply enough heat to vaporize the remaining metal. In such an approach one must take into account the energy necessary to raise the metal from the ambient temperature to the vaporization temperature. If r is assumed to be the radius of the metal particle and 6 the thickness of the oxide coat [(r - <5) is the pure metal radius], then the critical heat balance for pyrophoricity contains three terms ... 

Co and Fe catalysts have also been studied for the partial oxidation of methane to synthesis gas. Their potential relies on the fact that Co and Fe have higher melting and vaporizing points than Ni. Lower performances were mostly observed, however, which is probably related to the higher activity of CoO and FC2O3 for the complete oxidation of methane [121, 132, 133]. The recognized order of reactivity for partial oxidation is in fact Ni Co > Fe. However, it was observed that the performance of Co improves when a promoter is added. An extensive study of the catalytic partial oxidation of methane over CO/AI2O3 catalysts with different metals (0.1 wt% of Ni, Pt,... 

Note Most laboratories use the freezing point method of determining osmolality. However, if the vaporization point method is used, the alcohols may be driven off and their contribution to osmolality will be lost. 

Consistent with the stable/metastable distinction, four distinct triple points are seen in Fig. 7.5 three (triangles) of stable type (a-(3-vapor point at 96°C, 0.01 Torr /3-liquid-vapor point at 120°C, 0.025 Torr and a-13-liquid point at 155°C, 1290 atm) and one (cross) of metastable type (/3-liquid-vapor point at 120°C, 0.02 Torr). 

Various comparisons have been made (4, 27, 28, 61, 74, 89, 106, 111). For a particular task of fitting data, the recognition of an actual upper size limit leads to the modified logarithmic representation of Mugele and Evans (89). However, for pure mathematical ease the Rosin-Rammler distribution employed by Probert (98) is preferable from a vaporization point of view. 

Cooling the system is continued until the temperature of Point 2, where the hydrate phase (vertical area that begins at Point 7) forms from the vapor (Point 8) and liquid (Point 6). At Point 2 three phases (Lw-H-V) coexist for two components, so Gibbs Phase Rule (F = 2 — 3+2) indicates that only the isobaric pressure of the entire diagram is necessary to obtain the temperature and the concentrations of the three phases (Fw, H, and V) in equilibrium. 

Heat is used in the laboratory for a variety of applications which include speeding up chemical reactions, evaporating solvents, facilitating crystallization, softening or melting materials, and distillation by bringing chemicals to their vapor points. 

Heat is typically used to bring a solution to its vapor point (boiling) so that it may be distilled, reduced, or purified. Although this procedure works in most cases, not all solutions can be safely heated. Some materials break down in heated conditions, and some do so violently. Fortunately, there are two alternative methods to... 

The thermal efficiency of this cycle is that of a Carnot engine, given by (5.8). As a reversible cycle, it could serve as a standard of comparison for actui steam power plants. However, severe practical difficulties attend the operatk of equipment intended to carry out steps 2 3 and 4 1. Turbines that take i saturated steam produce an exhaust with high liquid content, which causes sevel erosion problems, t Even more difficult is the design of a pump that takes in mixture of liquid and vapor (point 4) and discharges a saturated liquid (poll 1). For these reasons, an alternative model cycle is taken as the standard, at lei for fossil-fuel-buming power plants. It is called the Rankine cycle, and diSei from the cycle of Fig. 8.2 in two major respects. First, the heating step 1 2 ... 

Example 8.5 One mole of water, HjO, in the solid state (ice) is heated at constant pressure (1 atm) from its initial temperature of 233 K through both its melting and vaporization points. Heating is stopped when the temperature of the vapor reaches 700... 

The reaction mixture containing 10% Fc203 plus C is introduced into the reactor at 50 C. The CI2 gas is used in 10% excess and is preheated to 200°C by the products leaving. The reactor is kept at the vaporization point of FeCb (300 C) at which the liquid FeCls is vaporized and swept out by the gases formed. 

Points 1 and 2 mean a qualitative and quantitative analysis of equilibrium vapors. Point 3 mentions some of the thermochemical properties which can be evaluated from the analytical data. 

Thermal dissociation in the solid phase takes place if the decomposition point of the product is signihcantly lower than its vaporization point. In the opposite case, thermal dissociation takes place in the gas phase. Halides usually have a significantly lower dissociation temperature than the corresponding oxides that is, dissociation in solid phase is barely possible. The extremely high electron density in a graphite tube at temperatures above 1200°C can lead to a reduction of stable metal oxides of, for instance, iron, chromium, and manganese in solid or liquid phase. This reduction is typically observed at temperatures of around 500°C lower than the dissociation point of the oxides. The last reaction is the dissociation of carbides in the gas phase ... 

This presentation is limited to two models, the Murphree plate efficiency and the modified Murphree plate efficiency, and their applications to columns in the service of separating both binary and multicomponent mixtures. For convenience of application, these efficiencies are restated in terms of the vaporization plate efficiency. Definitions of the vaporization point and plate efficiency follow immediately and the Murphree plate efficiencies are defined in a subsequent section as they arise in the development of the perfectly mixed liquid phase model. 

The definition of the vaporization point efficiency is axiomatic. For let a and b be any two nonzero numbers which are finite and positive. Then if a is unequal to b, there exists a positive number c such that a = cb. Similarly, if the fugacity of component / in the vapor phase at any point above the liquid on a plate is unequal to its fugacity f[ in the liquid, then there exists a multiplier called the vaporization point efficiency, such that... 

The vaporization plate efficiency is defined in a manner analogous to the vaporization point efficiency. Let /be the fugacity of component i in the perfectly mixed vapor phase which leaves any plate j of a distillation column and /j- be the fugacity of component i in the liquid phase leaving plate j. If/JJ is unequal to fji (where both / and / j- are nonzero, finite and positive), then there exists a positive number such that... 

THE MODIFIED MURPHREE POINT EFFICIENCY AND THE CORRESPONDING VAPORIZATION POINT EFFICIENCY... 

For each subcritical temperature T < 1, dynamic System 3 has a simple equilibrium point, i.e. dp/dA = 0 = dP/dA, at (pG(T), Pa(T)), (pd(T), Pa(T)), and (pL(T), P<7(T)). Using well-established methods of dynamic system theory—for simple equilibrium points it suffices to examine the eigenvalues of System 3—one then determines that both the saturated vapor point (po(T), Po-(T)) and the saturated liquid point (Pl(T), PV(T)) are (orbitally stable with respect to A) dicritical nodes, i.e. that each solution path p(A), P(A) approaches the equilibrium point from a definite direction and, conversely, each direction corresponds to exactly one path (see Figure 2). 

Figure 2. Universal plot of all A — Ac data (x < 10) for the substances investigated. Labels V ana L designate vapor and liquid branches, respectively. For quantum substances (a> < —0.1), only vapor points are...

Points on the s-g curve are those sets of temperatures and pressures at which solid coexists in equilibrium with vapor. Points to the left of the line lie below the sublimation temperature, and so correspond to conditions under which the solid is stable. Those points to the right of the s-g curve are points above the sublimation temperature, and so are conditions under which the gas is the stable phase. The s-g curve must intersect the others at the triple point because of the conditions expressed by Eqs. (12.13). 

Note The osmolality may be measured as falsely normal if a vaporization point osmometer is used instead of the freezing point device, because volatile alcohols will be boiled off. 

Equation 3.29 implies that, in the Xi X2 space, a CS will pinch at the equilibrium vapor point of Xa if operated at = 0. 

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