Online Measurement Techniques

Sample Initial Container Weight (g) Final Container Weight (g) 

Calculating, successively, weight fractions and Stokes diameters for all the samples as done for sample 1 above. Table 2.10 can be derived. By inspecting the time column of Table 2.10, it is implied that the experiment would have taken more that 11 days (16,384 min) for completion In fact, the whole analysis was 

From the above graph, the median size at the 50% value of F is equal to 4.5 pm. 

7 Laboratory Exercise Particle Size Analysis by Different Methods 

Particle size analysis and measurement is an important operation in many industries. The stability, chemical reactivity, opacity, flowability, material strength, and some other properties of many materials are affected by the size distribution and characteristics of the particles within them. There are numerous techniques and instrumentation for all types of particle size analysis and characterization available. Some primary properties of particulate materials, mainly shape, will determine the way the particles are detected or 

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With the advancement of online measurement techniques such as focused beam reflectance measurement (FBRM) and Fourier transform infrared (FTIR), it is now possible to obtain particle size distribution and solution concentration information rapidly through these in-situ probes. In one experiment, hundreds of data points can be generated. With proper experiment design, the model-based experimental design for crystallization is capable of obtaining high-quality crystallization kinetic data with a small number of experiments. This approach can thus save significant experimental effort and time in the development of crystallization processes. 

Besides charge control, retention aid control and defoamer control based on online measuring technique are state of the art in these fast-running machines. A small range of grades allows very smooth and stable control. 

In specialty paper and tissue production, online measuring technique has often not been used in closed-loop control in the past because of many grade changes and complex process chemistry. Small production volumes and slow running machines were not supporting acceptable payback calculations for investments in measuring technology. 

In contrast to calorimetry, most of the analytical techniques that are applied to the study of kinetics, such as concentration measurements or online measurement of reaction spectra (e.g. UV-vis, near infrared, mid infrared and Raman), can be related to integral kinetic... 

In tile next section we cover the major types of measurement devices used in the process industries, principally the big five measurements temperature, flow rate, pressure, level, and composition, along with online physical property measurement techniques. Table 8-8 summarizes the different options under each of the principal measurements. 

Time-Resolved Laser-Induced Incandescence (by Prof. Alfred Leipertz et al.) introduces an online characterization technique (time-resolved laser-induced incandescence, TIRE-LII) for nano-scaled particles, including measurements of particle size and size distribution, particle mass concentration and specific surface area, with emphasis on carbonaceous particles. Measurements are based on the time-resolved thermal radiation signals from nanoparticles after they have been heated by high-energetic laser pulse up to incandescence or sublimation. The technique has been applied in in situ monitoring soot formation and oxidation in combustion, diesel raw exhaust, carbon black formation, and in metal and metal oxide process control. 

One alternative to the direct online measurement of polymer properties is to use a process model in conjunction with optimal state estimation techniques to predict the polymer properties. Indeed, several online state estimation techniques such as Kalman filters, nonlinear extended Kalman filters (EKF), and observers have been developed and applied to polymerization process systems. ° In implementing the online state estimator, several issues arise. For example, the standard filtering algorithm needs to be modified to accommodate time-delayed offline measurements (e.g., MWD, composition, conversion). The estimation update frequency needs to be optimally selected to compensate for the model inaccuracy. Table 5 shows the extended Kalman filter algorithm with delayed offline measurements. Fig. 2 illustrates the use of online state estimator... 

Instruments for online measurement of dry and wet systems is also available. Due to the diversity of measurement techniques and the varying definitions of characteristic length, different types of instruments most likely will give different PSDs, for nonspherical particles. Therefore, it should be understood that there is no absolute standard for PSD measurement. 

TSS measurement can be carried out by gravimetry after separation by filtration or centrifugation, according to standard methods [5,24], For online measurement, these techniques cannot be applied without expensive devices. This is the reason why optical methods are often used, especially in industry. Among the different systems, turbidimetry,... 

In principle, any conventional measuring device or technique can be used in process control. But laboratory instruments normally are not suited for online measurement. The instruments must be more robust and are designed for unattended operation, with minimal skill required for operation, since plant personnel are... 

Coupling of LC to NMR is relatively simple. The effluent from the column is delivered through a polyether-ether ketone (PEEK) transfer line to the NMR flow cell, which typically has a volume of 60 jA. The measurement can be carried out in one of four modes on-flow, stop-flow, time-sliced and loop collection. In the on-flow mode, the effluent from the column flows continuously through the NMR flow cell. Because of the very short time available for the measurement when peaks elute in real time, this approach is limited to major components of a mixture. In the stop flow mode, peaks detected with a UV detector are transferred to the NMR flow cell, and the run is automatically stopped. The NMR spectra can then be acquired over a period of several minutes, hours or even days. In the time-sliced mode, the elution is stopped several times during the elution of the peak of interest. This mode is usually used when two analytes are poorly resolved. In the loop collection mode, the chromatographic peaks are stored in loops for offline NMR study. This approach is therefore not a real online hyphenated technique. 

It is worth noting the emergence of several online or in-line composition measurement techniques such as ATR-FTIR and Raman spectroscopy as well as the application of GC and NMR in an online manner [133]. 

There are several commercially available online MALS detectors. Wyatt Instruments (Santa Barbara, California, U.S.A.) commercializes two MALS detectors Dawn-DSP (18 angles) and mini-Dawn (3 angles 45°, 90°, and 135°). Precision Detectors (Franklin, Massachusetts, U.S.A.) commercializes a double-angle LS 15° and 90°. SEC online measurement of (s ) could be performed by other techniques. Viscotek Co. (Houston, Texas, U.S.A.) commercializes an alternative three-detector SEC system, the SEC . The SEC system consists of (1) an online viscometer (Vise), (2) an online rightangle LS detector (RALS), and (3) a concentration detector. This three-detector SEC system also measures More exactly, is calculated,... 

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