Operating curve, absorber

Once the design recovery for an absorber has been established, the operating curve can be constructed by first locating the point X9, y2 ou the diagram. The intersection of the horizontal hue corresponding to the inlet gas composition yi with the equilibrium curve y° = F x)... 

FIG. 14-6 Relationship between equilibrium curve and operating curve in a packed absorber computation of interfacial compositions. 

The recovery of the key component is specified to calculate the exit composition of the gas stream for absorbers or the exit composition of the hquid stream for strippers from Equation 6.21.2A or 6.21.2S. For both cases, it is assumed that the operating line intersects the equilibrium cinve at one end and not at some intermediate point between the ends of the operating line. This is the case for dilute solutions when both the operating and equilibrium lines are linear. Separation of dilute solutions occurs frequently when purifying waste streams. Because both the equilibrium and operating curves are linear for dilute solutions, the equation derived by Kremser [59] can be used to calculate the number of equilibrium stages. 

When metals are rolled or forged, or drawn to wire, or when polymers are injection-moulded or pressed or drawn, energy is absorbed. The work done on a material to change its shape permanently is called the plastic work- its value, per unit volume, is the area of the cross-hatched region shown in Fig. 8.9 it may easily be found (if the stress-strain curve is known) for any amount of permanent plastic deformation, e. Plastic work is important in metal- and polymer-forming operations because it determines the forces that the rolls, or press, or moulding machine must exert on the material. 

The use of an integral video screen in instruments presents very great advantages, both in the ease of operation and in the ability to develop and understand analytical methods. Complete analytical records can be stored in the instrument and a visual display of good calibration curves can be stored in memory and recalled at will. It is most useful to have a graphical display of atomisation peaks when using a furnace where a distinction can be made of the total absorbance peak and that due to the analyte absorbance. 

There are several modes of operation of an nmr spectrometer. First and most common, we hold v constant and vary (or sweep ) // . Close to u - yH, energy is absorbed by the nuclei and the current flow from the transmitter increases until v is exactly equal to yH. Further increase of // makes v < y//(l and the current flow decreases. The form of the energy-absorption curve as a function of H0 when Hn is changed very slowly is shown in Figure 9-25a. The peak is centered on the point where v = yH. When // is changed more rapidly, transient effects are observed on the peak, which are a consequence of the fact that the nuclei do not revert instantly from the — V2 to +V2 state. The resulting... 

If the solute-rich gas entering the bottom of an absorber tower is cold, the liquid phase may be cooled somewhat by transfer of sensible heat to the gas. A much stronger cooling effect can occur when the solute is volatile and the entering gas is not saturated with respect to the solvent. It is possible to experience a condition in which solvent is being evaporated near the bottom of the tower and condensed near the top. Under these conditions a pinch point may develop in which the operating and equilibrium curves approach each other at a point inside tne tower. 

Often, slightly different coordinates are used for y-x plotting. Instead of plotting y against x , one can plot y against x in this case, the operating line will be curved. At other times, y can be expressed in terms of moles of solute per mole of gas leaving the absorber. The construction described above is similar in all these cases. 

When the operating line and the equilibrium curve intersect, an infinite number of stages is required to achieve the separation (Fig. 11). The intersection point is called the pinch point and may occur at the bottom (Fig. 11a), at the top (Fig. lib), or at a tangent point (Fig. lie). The solvent rate leading to this intersection is the minimum solvent flow required to absorb the specified amount of solute. 

Procedure Concomitantly determine the absorbance of each Standard Preparation and of the Sample Preparation at 422.7 nm, with a suitable atomic absorption spectrophotometer, following the operating parameters as recommended by the manufacturer of the instrument. Plot the absorbance of the Standard Preparations versus concentration of calcium, in micrograms per milliliter, and from the curve so obtained determine the concentration, C, in micrograms per milliliter, of calcium in the Sample Preparation. Calculate the quantity, in milligrams, of calcium in the sample taken by the formula... 

Subsequent to optimisation of the heating programme, the instrument should be calibrated with aqueous standards. When a linear and reproducible calibration curve is obtained, a series of standard additions on the samples should be performed in order to elucidate whether a matrix interference is operating. This is evident when the analyte absorbance is enhanced or depressed in the sample matrix compared to the pure standard. Often however, interference is indicated by the shape of the analyte absorbance peak differing in the sample relative to that in the standard or when the analyte absorbance in the sample is irreproducible or spurious. 

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