Mixing point

The mix point, = 0.0673, falls on a straight line connecting x and The extract composition is then determined hy drawing a straight line from x,-throiigh Zm until the line intersects the extract line at the final extract composition, i/e = 0.084. The delta point is then found at the intersection of two lines. One line connects the feed and extract compositions x and y. The other line connects the raffinate and solvent compositions x,- and y. ... 

The volumetric flowrate into the plug flow is Uq and the feed concentration of A is C g- portion of A exiting from the reactor is fed back through a pump and mixed with the feed stream, referred to as R (i.e., the recycle ratio). The volumetric flowrate at the entrance of the reactor is u = UgCl + R). A balance at the mixing point M gives... 

When the airflow meets a surface whose temperature is lower than the dewpoint, water vapor from the air condenses on the surface of the cooling coil. If all air comes into contact with the cold surface, the state of the air after the process will be at point 3. Some air always escapes the cold surface, and therefore the state of air after contact with the coil is a mixture of saturated air (3) and escaped air (1). The mixing point (2) lies on the line connecting points 1 and 3, as shown in Example 8. The nearer point 2 is to point 3, the more effective is the cooling coil. 

When economizer vapors are mixed with the compressor vapors, the temperature from this mixing point on is lower to the next stage of compression than if the economizer had not been used. ... 

A material balance about the mixing point gives... 

The material balance around the mixing point of a loop reactor is given by Equation (4.21) for the case of constant fluid density. How would you work a recycle problem with variable density Specifically, write the variable-density counterpart of Equation (4.21) and explain how you would use it. 

The flow rate of a hot coal/oil slurry in a pipeline is measured by injecting a small side stream of cool oil and measuring the resulting temperature change downstream in the pipeline. The slurry is initially at 300°F and has a density of 1.2 g/cm3 and a specific heat of 0.7 Btu/(lbm °F). With no side stream injected, the temperature downstream of the mixing point is 298°F. With a side stream at 60°F and a flow rate of 1 lbm/s, the temperature at this point is 295°F. The side stream has a density of 0.8 g/cm3 and a cp of 0.6 Btu/(lbm °F). What is the mass flow rate of the slurry ... 

The flow behaviour of rubber on a mill is dependent on the material, nip width, roll speed and temperature, and certain combinations can give flow instabilities, the worst case from the mixing point of view being bagging , i.e., loss of adhesion of the rubber compound to the mill rolls. A decrease in nip width, an increase in speed or temperature, can overcome this problem. 

A recycle PFR, operating at steady-state for the reaction A +. . - products, is shown schematically in Figure 15.6, together with associated streams and terminology. At the split point S, the exit stream is divided into the recycle stream (flow rate RqJ and the product stream (flow rate q,), both at the exit concentration cA1. At the mixing point M, the recycle stream joins the fresh feed stream (flow rate q0, concentration cAo) to form the stream actually entering the reactor (flow rate (1 + R)q0, concentration ca o)-The inlet concentration c Ao may be related to cAo, cA1, and R by a material balance for A around M ... 

From a material balance for A around the mixing point M, the molar flow rate of A entering the reactor is... 

Assume that flow in each tank is BMF, and that the residence time in the transfer lines (pipes) between the inlet to the first tank and the mixing point M is negligible. 

The final outlet concentration is given by the balance at the mixing point... 

Within the frame of the present first series of experiments it was almost always oxygen which was injected into supercritical water-methane mixtures. There were several reasons for this first choice. One of these was the desire, to study rich flames and their possible products first. Often the water to methane mole fraction ratio was 0.7 to 0.3. But mixtures down to a methane mole fraction of 0.1 were also used. It was possible, however, to inject oxygen and methane simultaneously into the supercritical water and produce a flame. Not possible was the production of true premixed flames. After a retraction of the thin inner nozzle capillary of the burner (see Fig. 1 b) the two gases could be mixed just below the reaction cell, but the flame reaction proceeded from the nozzle tip in the cell back towards this mixing point immediately. 

Figure 4.6 — Manifold used and recording obtained with the flow-through photometric sensor for the determination of formaldehyde. PRA />-rosaniline q flow-rate P peristaltic pump M mixing point R reactor SV switching valve IV injection valve D detector W waste. (Reproduced from [89] with permission of Marcel Dekker, Inc.).

This indicates that the feed into the PFTR is therefore diluted with the product stream. A balance on the flow of A at the mixing point yields... 

If the flow rate is too low, the flame flash back and propagate back up the tube to the mixing point and extinguish, ff the flow rate is too high the flame will lift off the top of the tube and either extinguish or bum as a turbulent lifted flame. 

Students have probably noticed that is it nearly impossible to maintain a stable flame within the tube of a Bunsen burner it will either bum at the top or flash back to the mixing point. There is usually no stable steady state for a flame reaction in a straight tube. 

Flow in the tube wih be parabolic if the flow is laminar (Re<2100), and thus gases near the center of the tube may propagate downstream, while gases near the wall propagate upstream toward the mixing point. This further destabilizes a premixed flame within a tube. 

This nomenclature is shown with Example 14.3. On the triangular diagram, the proportions of feed and solvent locate the mix point... 

Either the solvent feed ratio or the compositions Ej and RN serve to locate the mix point M. 

Both maximum and minimum limits exist of the solvent/feed ratio. The maximum is the value that locates the mix point M on the binodal curve near the solvent vertex, such as point Mmla on Figure 14.7(b). When an operating line coincides with a tieline, the number of stages will be infinite and will correspond to the minimum solvent/feed ratio. The pinch point is determined by the intersection of some tieline with line RnS- Depending on whether the slopes of the tielines are negative or positive, the intersection that is closest or farthest from the solvent vertex locates the operating point for minimum solvent. Figure 14.9 shows the two... 

The mix point is located by establishing the solvent/feed ratio. 

As the solvent/feed ratio is increased, the mix point M approaches the solvent point S, and poles P and Q likewise do so. At total reflux all of the points P, Q, S, SE, and M coincide this is shown in Figure 14.7(b). 

Figure 14.9. Minimum solvent amount and maximum extract concentration. Determined by location of the intersection of extended tielines with extended line RNS. (a) When the tielines slope down to the left, the furthest intersection is the correct one. (b) When the tielines slope down to the right, the nearest intersection is the correct one. At maximum solvent amount, the mix point Mm is on the binodal curve.

---