Continuous on-line monitoring

There are cases in which monitoring a flowing medium is needed. This maybe required for the investigation of a reaction in an industrial flow system, for example. Ideally, the rate of flow should be known precisely then a number of observation chambers placed at known distances along the flow system allow measurements to be made at calculable reaction times. The observation chambers may consist of a sampling device with a septum or, more simply, a device to measure some physical property in situ. However, continuous monitoring in flow systems is a specialised topic usually requiring dedicated experimental set-ups and will not be covered here. 

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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],... 

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,... 

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. 

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. 

Modern ozone systems are completely automated. An ozone monitor provides continuous on-line monitoring of the ozone concentration in the gaseous effluent from the contactor. If the concentration of ozone exceeds a preset level (usually 0.05 ppm), the voltage or frequency of the ozone generator is reduced. 

In order to provide a more representative picture, sampling and analytical procedures such as automatic sequential sampling to provide composite samples over a period of time (usually 24 hours), continuous on-line monitoring, frequent sampling, or in-field measurement must be used. The first two involve the use of expensive equipment that requires a power supply, and needs to be deployed in a secure site, and the third would be expensive because of transport and labour costs. The last one can be considered as emerging techniques and represents a very useful alternative to current practice. Field techniques (both sampling and measurement methods) can be cost effective, and can provide a rapid representative overview of the parameter of interest. 

The Joint Service Agent Water Monitor (JSAWM) is a funded Department of Defense program that is intended to identify, mature and develop the technology needed for specific and sensitive detection of chemical warfare agents (CWA) in source, treated, stored and distributed water supplies. According to the JSAWM criteria, a successful detection system will function in heterogeneous liquid environments, have less than a 10 minute response time with low false alarms, work in both continuous (on-line monitoring) and batch modes, be portable, small, easy to operate, and have very low power requirements. ... 

J.M.L. Fernandez, M.D. Luque de Castro, M. Valcarcel, Automatic continuous on-line monitoring of salicylic acid and acetylsalicylic acid in pharmaceuticals, J. Automat. Chem. 12 (1990) 263. 

In order to fully describe the state of a bioprocess at all times, whether for research or control purposes, one would want continuous, on-line monitoring of all possible parameters. Unfortunately, real on-line sensors are only available for a relatively small number of measurements most of these probes are recent developments. 

Over the past several years Radiological Effluent Technical Specifications (RETS) have been implemented at nuclear power facilities in the United States. These RETS control the evaluation and release of radioactive material to the off-site environs. Radiological measurements of these releases are conducted using gamma spectroscopy, liquid scintillation, gross counting techniques and continuous on-line monitoring. 

Because of its importance, continuous on-line monitoring of emulsion polymerization reactors continues to be an area of considerable investment in terms of research and development. It is evident that to better understand the nucleation mechanisms, and to develop better control strategies,... 

Dincer AK, Kalyanpur M, Skea W. Ryan M, Kierstead T. Continuous on line monitoring of fermantation processes. E)ev fnd Microbiol 1984 25 603. 

Guo, X. and Mitra, S. Development of pulse introduction membrane extraction for analysis of volatile organic compounds in individual aqueous samples, and for continuous on-line monitoring. Journal of Chromatography A 1998,826 (1), 39-47. 

Klinkenberg, H.,Van Borm,W., and Kip, B. J. (1997).The continuous on-line monitoring of the trace elemental composition of industrial ethene gas by means of inductively coupled plasma mass spectrometry. Spectrochim. Acta, Part B 52(11), 1695. 

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