Feed thermal condition diagram

To complete the construction of the Y-X diagram from simulation results, the feed line must be drawn. The intersection with the diagonal of a straight line drawn through the feed composition determines one point on the q-line. One other point is determined by the feed equilibrium vapor and liquid compositions at the feed tray conditions. If the feed is a saturated liquid, the equilibrium liquid composition is the same as the feed composition, and the equilibrium vapor composition is the bubble point composition on the equilibrium curve. In this case the q-line is vertical. For a saturated vapor feed, the equilibrium vapor composition is the same as the feed composition, the equilibrium liquid composition is the dew point composition, and the q-line is horizontal. For a mixed-phase feed, the c/ line slope is determined by the feed thermal condition (Section 5.2.2). Note that, for a multi-component mixture, the feed equilibrium vapor and liquid compositions from the simulation output may not lie exactly on the equilibrium curve because of the discrepancies resulting from lumping the light components in one pseudocomponent. 

A binary stream at the rate of 1000 kmol/h containing 35% mole of component 1 (the lighter component) is to be separated in a distillation column to produce 95% component 1 in the distillate and 90% component 2 in the bottoms. The column will have a partial reboiler and a partial condenser, and will operate at 1 atm. It is proposed to utilize an existing hot process stream in the plant as a heat source for the reboiler, which limits the reboiler duty to 58 x 10 kJ/h. Using either the Y-X diagram or the H-X diagram, determine the number of theoretical trays required, the optimum feed location, the product rates, and the condenser duty. Assume feed thermal conditions that result in a saturated liquid at the feed tray pressure. Use thermodynamic data from Problem 6.1. 

Figure 13.7. Features of McCabe-Thiele diagrams for constant molal overflow, (a) Operating line equations and construction and minimum reflux construction, (b) Orientations of -lines, with slope = ql q — 1), for various thermal conditions of the feed, (c) Minimum trays, total reflux, (d) Operating trays and reflux, (e) Minimum reflux determined by point of contact nearest xD.

The binary model, conveniently represented on the Y-X or H-X diagrams, demonstrates the effect on column performance of the reflux ratio, product rate, number of trays, feed location, and thermal conditions. In the cases that follow in this section, the feed is assumed of fixed flow rate and composition. The effect of column pressure, which influences column performance through its effect on the equilibrium curve, is not considered here and is held constant. 

A distillation column with an attached side stripper is used to separate a feed stream F into products A, B, and C, as shown in the diagram. The main column has a total condenser and a partial reboiler, and the side stripper has a partial reboiler. The columns are existing units with fixed number of trays and feed and draw locations. The external feed, a product of an upstream unit, is of fixed flow rate, composition, and thermal conditions. The pressure in the columns is determined independently and is not available as a variable. Using basic modules representation, determine the degrees of freedom of this system. What variables would you specify to define the performance of these columns ... 

There is a relationship between the intersection point of the two operating lines and feed conditions. As shown in Figure 2.7, a straight line can be draw from the location of the feed composition z on the 45° line to this intersection point. As we will proof below, the slope of this line is only a function of the thermal condition of the feed, which is defined in the parameter q. The slope is —q/ l — q). This makes the construction of the McCabe-Thiele diagram very simple. 

A thermal plasma system has been developed for the decomposition of methane. A schematic diagram of the experimental apparatus is shown in Fig. 1. The system consists primarily of D.C. plasma torch, plasma reactor and filter assembly. Plasma was discharged between a tungsten cathode and a copper anode using N2 gas. All the experiments were carried out at atmospheric pressure at 6 kW input electric power and N2 flow rate of 10 to 12 1/min. The feed gas (CH4) flow rates were varied from 3 to 15 1/min depending on the operating conditions, shown in Table. 1. 

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