On-line monitoring

Sensors used for monitoring of polymerization reactors can be classified into two large categories  

Temperature, pressure, flow rates and level are measurements in the first group that are routinely performed at plant site. These measurements are well established and will not be addressed in this section, even though tracking the trajectory of these operational variables might be enough to ensure the production of the polymer of interest in some processes. On the other hand, sensors used for monitoring of trajectories of structural polymer properties are very difficult to develop, but provide much more useful information to carry on closed-loop control strategies. 

However, there are still a number of important polymer properties that can only be measured by laborious and time-consuming off-line analyses. In this category one can include the MWD (especially in dispersed systems and/or for polyolefins), branching and crosslinking density, the gel content, the PSD, among other properties. (Despite the several examples reported in the scientific literature, at present no commercial equipment can ensure the fast and robust on-hne measurement of the entire size distribution of polymer particles in industrial reactors.) 

Some of the properties that cannot be measured on-line can be inferred fi om the measurements of other variables by means of state estimation methods and software sensors 

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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],... 

Sodium and chloride may be measured using ion-selective electrodes (see Electro analytical techniques). On-line monitors exist for these ions. Sihca and phosphate may be monitored colorimetricaHy. Iron is usually monitored by analysis of filters that have had a measured amount of water flow through them. Chloride, sulfate, phosphate, and other anions may be monitored by ion chromatography using chemical suppression. On-line ion chromatography is used at many nuclear power plants. 

ON-LINE MONITORING OF HYDRODYNAMIC FLOW PROFILES IN MICROFLUIDIC CHANNELS BASED UPON MICROELECTROCHEMISTRY... 

A separate unit is used for programming and editing (e.g. a handheld programmer or a computer). For on-line editing, keyboards are used. For on-line monitoring, a PLC is interfaced with a computer and special software. 

Anon, On-Line Monitors Attack Process Corrosion , Processing, 34, 34-35, February (1986)... 

Asher, J., Conlon, T. W., Tofield, B. C. and Wilkins, N. J. M., Thin Layer Activation-A New Plant Corrosion Monitoring Technique , Proc. Conf. On-Line Surveillance and Monitoring , entitled On-Line Monitoring of Continuous Plants, Ellis Horwood, London (1983)... 

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. 

In summary, these exploratory data suggest that the chromatographic method used could be a valuable tool for study of this polymerization reaction. Reasonable data were obtained for amount and composition of the copolymer. Formation of graft polymer and/or nitrile rich polymer was detected. More detailed chromatographic study of this batch polymerization could lead to a practical on-line monitoring method... 

Electrochemical On-Line Corrosion Monitoring On-line corrosion monitoring is used to evaluate the status of equipment and piping in chemical process industries (CPI) plants. These monitoring methods are based on electrochemical techniques. To use on-line monitoring effectively, the engineer needs to understand the underlying electrochemical test methods to be employed. This section covers many of these test methods and their applications as well as a review of potential problems encountered with such test instruments and how to overcome or avoid these difficulties. 

Electrochemical Determination. An electrochemical method has been developed to allow on-line monitoring of biohlm activity in aqueous environments. 

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

Kuban P. and Karlberg B., On-line monitoring of kraft pulping liquors with a valveless flow injection-capillary electrophoresis system, Anal. Chim. Acta, 404, 19, 2000. 

Special optical fibres have been intensively investigated during recent years because of their potential wide-range use for on-line monitoring of material properties or processes in a number of areas of human activity (environment protection, food industry, medicine etc.) Their technology can be considered an integral part of the team-work on optical fibre sensors development. Despite special optical fibres represent a unique and often indispensable tool for a variety of sensor applications, special fibre production still represents only a small fraction of the market. Probably it is because of their low consumption (in comparison with standard telecommunication fibres), the need for much more advanced know-how and lower reproducibility. 

Heitzer A., Malachowsky K., Thonnard J.E., Bienkowski P.R., White D.C., Sayler G.S., Optical biosensor for environmental on-line monitoring of naphthalene and salicylate bioavailability with an immobilized bioluminescent catabolic reporter bacterium, Appl. Environ. Microbiol. 1994 60 1487-1494. 

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