Example volume stream measurement

The volume stream measurement benchmark could also be mapped onto the board. Mutually exclusive operations are available in this example and were exploited by the scheduler. 

Fig. 1.19. A gas buret For the measurement or delivery of gases. When the elbow (on left) is attached to the top of the buret, gas is collected and its volume is measured after equalizing the mercury levels. For example, a hydrolysis flask similar to the reaction flask in Fig. 1.18 may be attached to this elbow. When the stopcock assembly is used (at the right), the buret can be filled with gas and a measured volume of this gas can be injected into a stream of flowing inert gas. 

Cells of the second type were initially developed by Tinker and Morris at Monsanto [4] and subsequently by Penninger [5]. In these systems, the reaction solution is circulated from the autoclave through an external IR cell of relatively small volume. This arrangement means that the cell can be isolated from the main reaction vessel relatively easily (for example in the event of window failure) thus protecting the spectrometer. Cells of this sort can, in principle, be fitted to plants or pilot plants to monitor liquid streams. However, the circulation of solution from the main reaction vessel through an external cell introduces some potential problems. A pressure drop in the circulation system can lead to release of dissolved gas, which may accumulate between the cell windows and interfere with the spectroscopic measurement. A change in pressure may also influence the catalyst specia-tion, such that the observed spectra may not be truly representative of the bulk reaction solution. 

Total oxygen demand (TOD) tells us how much 02 is required for complete combustion of pollutants in a waste stream. A volume of N2 containing a known quantity of 02 is mixed with the sample and complete combustion is carried out. The remaining 02 is measured by a potentiometric sensor (Box 17-1). Different species in the waste stream consume different amounts of O,. For example, urea consumes five times as much 02 as formic acid does. Species such as NH3 and H2S also contribute to TOD. 

FIGURE 1-2 An example of a control volume that is useful for analyzing chemical behavior in a lake because it facilitates the measurement or estimation of chemical inputs and outputs. Chemicals may enter the control volume via the inflowing stream and the industrial discharge pipe and may leave the control volume across the air-water interface and sediment-water interface as well as via the outflowing stream. 

The aerodynamic diameter dj, is the diameter of spheres of unit density po, which reach the same velocity as nonspherical particles of density p in the air stream Cd Re) is calculated for calibration particles of diameter dp, and Cd(i e, cp) is calculated for particles with diameter dv and sphericity 9. Sphericity is defined as the ratio of the surface area of a sphere with equivalent volume to the actual surface area of the particle determined, for example, by means of specific surface area measurements (24). The aerodynamic shape factor X is defined as the ratio of the drag force on a particle to the drag force on the particle volume-equivalent sphere at the same velocity. For the Stokesian flow regime and spherical particles (9 = 1, X drag... 

More recently, flow titrations have been implemented in multi-commuted flow systems. With these systems, the exact amounts of the solutions involved can be modified in real time according to a concentration-oriented feedback mechanism. The flow titration really mimics a true titration because an analytical curve is not needed. A flow system exploiting a binary search to define the end point of an acid—base titration [324] is a good example of this approach. Stream directing solenoid valves were used to modify the sample and titrant volumes after every measurement via a feedback mechanism. Samples with concentrations within a range of two orders of magnitude could be titrated without modifying the flow manifold. 

The simplest way of measuring the dispersion coefficient is to inject a well-defined volume of a dye solution into a colorless carrier stream and to monitor the absorbance of the dispersed dye zone continuously by a colorimeter. To obtain the value, the height (i.e., absorbance) of the recorded peak is measured and compared with the distance between the baseline and the signal obtained when the cell has been filled with the undiluted dye. Provided that the Lambert-Beer law is obeyed, the ratio of respective absorbances yields a value that describes the FIA manifold, detector, and method of detection. (An exercise dealing with dispersion measurements is given in Chapter 6, while examples of FIA systems using limited, medium, or large dispersion are described in detail in Chapter 4.)... 

Process analysis is defined simply as a measurement taken, and a result generated in time for the data to be used to impact on the process. This means process analysis is not exclusive to techniques that require that a sample is taken. In 1987, Callis [1] defined five categories of process analysis, defined as off-line, at-line, on-line, in-line and non-invasive, as is shown in Fig. 9.1. The simplest and the most widespread example of process analysis is when samples are taken from the process stream and analysed off-line in a remote laboratory. This process is slow, samples are taken with low frequency, and there are often substantial delays between sample submission and analysis. However, the off-line method does allow for analysis by expert analysts using many of the techniques described in previous chapters of this volume. 

The concentration of a component in a mixture may be expressed in different forms. For example, mass and mole fractions express the concentration of a component as a portion of the total stream. Molar concentration is another popular measure of concentration, and it will be used extensively in this book. To calculate the molar concentration of species i in solution, c, we divide the number of moles of component i in the mixture, by the total volume of solution, V ... 

The tracer can be introduced into the reactor in the form of step or pulse. For simplicity, we will use the example of a tank reactor with a volume V and a flow of an inert liquid (water) vq- At a given instant, a chemical dye is introduced into a stream in the step-form with a concentration Co, and the concentration C is measured at the outlet of the reactor from the instant t = 0. Thus, from the mass balance presented in Figure 24.4, we have ... 

Frequently, waste streams can be eliminated or reduced by process modifications or improvements. A notable example of this is the use of save-rinse and spray-rinse tanks in plating lines. This measure brings about a substantial reduction in waste volume and frequently a net reduction in metal dragout. 

Note 2—Water should not be used as either a heating or cooling medium since aniline is hygroscopic and moist aniline will give erroneous test results. For example, the aniline point of the n-heptane reagent as measured with aniline containing 0.1 volume % water is approximately O.S C (0.9 F) higher than that measured with dry aniline. If the aniline point is below the dew point of the atmosphere, pass a slow stream of dry inert gas into the aniline point tube to blanket the aniline-sample mixture. 

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