Continuous on-line

A new acoustic emission system (AEBIL Acoustic Emission Binary Localizer) meeting the requirements for continuous on-line structural surveillance of critical conponents of operating plants Is described in the paper. The system is specifically designed to identify and locate structurally significant, spatially concentrated, AE sources in the presence of a high rate of spatially diffuse AE events. The system performance and reliability has been extensively demonstrated in In-plant applications. 

The results of over 1 year of continuous, on-line acoustic emission (AE) structural surveillance of high temperature / high pressure steam headers, gained on 2 M-scale 600MW supercritical multifuel ENEL power units in normal operation, are presented in the paper. The influence of background noise, the correlation between plant operating conditions (steady load, load variations, startup / shutdown transients) and AE activity and the diagnostic evaluation of recorded AE events are also discussed. 

Assessing the effectiveness and reliability of Acoustic Emission (AE) in continuous, on-line monitoring of the structural integrity of critical thermal power plant components, such as steam headers and steamline sections, is the main objective of the work reported in this paper. This is part of the work carried within the BRITE - EURAM 6056 "SIMON" Project from 10.1993 to 9.1997 with the support of the EU Commission. The "SIMON" Project Consortium included CISE [I, coordinator], MITSUI BABCOCK ENERGY [UK] HERIOT WATT University [UK], PROET / EDP[P]andENEL[I],... 

This header has undergone repair after through-thickness cracking of an assembly weld after 108.000 hours of service, it is presently in operation and periodically submitted to ultrasonic inspection during planned maintenance shutdown. Continuous on-line AE monitoring of the integrity of critical welds is expected to contribute supporting continued and safe operation of the header until its replacement, platmed to take place in 1999. 

Check for plant integrity/flammable leaks periodically or continuously on-line, as appropriate Install appropriate fire/smoke detection, audible alarms Provide adequate fire suppression systems Deal with mishaps such as spillage immediately... 

Improvements in the monitoring and operation of incinerators could minimize the accidental release of hazardons efflnents. In particular, fast-acting, continuous, on-line monitors are needed to detect excursions in operating conditions that could lead to toxic emissions. 

Mizrotsky, N. and Grushka, E., Use of system peaks in liquid chromatography for continuous on-line monitoring of chemical reactions, Anal. Chem., 67,1737,... 

Grandics, R, Szathmary, S., Szathmary, Z., and O Neill, T., Integration of cell culture with continuous, on-line sterile downstream processing, Ann. N. Y. Acad. Sci., 646, 322, 1991. 

Applications ICP-MS has become the technique of choice for the determination of elements in a wide range of liquid samples at concentrations in the ng L 1 to [igL-1 range. Typical applications of ICP-MS are multi-element analysis of liquids (even with high solid contents) element speciation by hyphenation to chromatographic techniques continuous on-line gas analysis multi-element trace analysis of polymers and trace analysis in high-purity materials. ICP-MS is routinely used for quality control purposes. 

Other techniques used for organotin speciation comprise GC-FAAS, GC-GFAAS, GC-ICP-MS, HPLC-FAAS, HPLC-GFAAS, HPLC-DCP (after continuous on-line hydride generation), HPLC-ICP-AES, HPLC-ICP-MS, etc. [555], Whereas ICP-AES does not provide an adequate response for ng levels of tin, ICP-MS can detect sub-ng to pg levels. GC-ICP-ToFMS... 

It is desirable that the process variable to be monitored be measured directly often, however, this is impractical and some dependent variable, that is easier to measure, is monitored in its place. For example, in the control of distillation columns the continuous, on-line, analysis of the overhead product is desirable but difficult and expensive to achieve reliably, so temperature is often monitored as an indication of composition. The temperature instrument may form part of a control loop controlling, say, reflux flow with the composition of the overheads checked frequently by sampling and laboratory analysis. 

We all agree that the continuous on-line/in situ detection of pollutants in water and wastewater should be the best practice for true quality monitoring. This is particularly relevant for the monitoring of emerging pollutants if we consider that for the other types of pollutants, there already exist some suitable systems. The main topic of this chapter is to show that there are some available devices for the on-line monitoring of emerging pollutants or, at least, some interesting developments. But first, it is indispensable to outline several important points in order to be sure that all potential users or developers of on-line/in situ measurement systems do know the main limits and constraints of the exercise. 

L. R. Middendorf, J. C. Bruce, R. C. Bruce, R. D. Eckles, D. L. Grone, S. C. Roemer, G. D. Sloniker, D. L. Steffens, S. L. Sutter, J. A. Brumbaugh and G. Patonay, Continuous, on-line DNA sequencing using a versatile infrared laser scanner/electrophoresis apparatus Electrophoresis 13, 487-494... 

The studies described above have the purpose of identifying the reacting species in a solvent extraction process and developing a quantitative model for then-interactions. The fundamental parameter measured is the distribution ratio, from which extraction curves are derived. Solvent extraction work can still be carried out with simple batchwise (or point-by-point) technique, but continuous on-line measurements give faster and more accurate results. 

Of the analytical techniques available for process analytical measmements, IR is one of the most versatile, where all physical forms of a sample may be considered - gases, liquids, solids and even mixed phase materials. A wide range of sample interfaces (sampling accessories) have been developed for infrared spectroscopy over the past 20 to 30 years and many of these can be adapted for either near-lme/at-lme production control or on-line process monitoring applications. For continuous on-line measurements applications may be limited to liquids and gases. However, for applications that have human interaction, such as near-line measurements, then all material types can be considered. For continuous measurements sample condition, as it exists within the process, may be an issue and factors such as temperature, pressure, chemical interfer-ants (such as solvents), and particulate matter may need to be addressed. In off-line applications this may be addressed by the way that the sample is handled, but for continuous on-line process applications this has to be accommodated by a sampling system. 

Brumbaugh, J.A., L.R. Middendorf, D.L. Grone, and J.L. Ruth, Continuous, on-line DNA sequencing using oligodeoxynu-cleotide primers with multiple fluorophores. Proc Natl Acad Sci USA, 1988. 85(15) 5610-14. 

The portable instrumentation and low power demands of stripping analysis satisfy many of the requirements for on-site and in situ measurements of trace metals. Stripping-based automated flow analyzers were developed for continuous on-line monitoring of trace metals since the mid-1970s [16,17]. These flow systems involve an electrochemical flow detector based on a wall-jet or thin-layer configuration along with a mercury-coated working electrode, and downstream reference and counter electrodes. 

Kinetic simulation methods are used as advisory controls in potentially thermally hazardous batch amination reactions of nitroaromatic compounds. Time—temperature process data are fed as input to a kinetic simulation computer program which calculates conversions, heat release and pressure profdes. Results are compared continuously on-line with measured batch data to detect any deviations from normal operating conditions. 

Keck FS, Kemer W, Meyerhoff C, Zier H, Pfeiffer EF. Combination of microdialysis and glucosensor permits continuous (on line) s.c. glucose monitoring in a patient operated device I. In vitro evaluation. Hormone and Metabolic Research 1991, 23, 617-618. 

MESI operation requires processing of the whole sample to be extracted and has to reach steady-state permeation, which usually takes a long time. Thus, a new technical modification of MESI, called pulse introduction (flow injection-type) membrane extraction (PIME), has been developed, in which the sample is introduced to the membrane as a pulse pushed by a stream of eluent (usually water).55 This means that attaining a steady state is no longer crucial. PIME therefore provides not only a faster response and higher sensitivity, but also allows extraction of individual samples via discrete injections in addition to continuous on-line monitoring by sequential injection of a series of samples. Guo et al.56 described a mathematical model for the PIME permeation process, which showed that (a) there was a trade-off between the sensitivity and the time lag (the time taken to complete the permeation process) and (b) a large sample volume and a low flow rate enhance the sensitivity but also increase the time lag. 

Total tin was determined by continuous on-line hydride generation followed by direct current plasma emission spectroscopy. Interfacing the hydride generation-DC plasma emission spectrometric system with high performance liquid chromatography allowed the determination of tin species. Detection limits, sensitivities and calibration plots were determined. 

Another important application is in the refining of steels when the oxygen content must be controlled at the parts per million level and monitored continuously on line and many oxygen sensors are currently used in the steel industry for this purpose. The principle of operation is as described for the lambda sensor and one form is shown schematically in Fig. 4.39. In this case the reference activity is established by a chromium metal/chromium oxide mix rather than being defined by air. 

Continuous on-line chromatography - identifying the heavy element daughters... 

---