Sensor on-line

In many cases, problems cannot be overcome by biological means. This is especially true for those related to inhibition by substrate or product. There may, however, be technical solutions to these problems. Nowadays, complicated feed strategies with different substrates can be achieved through the use of flow injection analysis, on-line sensors, mass flow meters and sophisticated computer control. Such control coupled to a fed-batch mode of operation (Figure 2.5) can often eleviate problems caused by substrate inhibition. For some processes, continuous product removal can avoid the problems associated with product inhibition the various options include ... 

The development of on-line sensors is a very costly and time-consuming process. Therefore, if one has available a dynamic model of the reactor which predicts the various polymer (or latex) properties of interest, then this can be used to guide one in the selection and development of sensors. Ideas from the optimal statistical design of experiments together with the present model expressed in the form of a Kalman filter have been successfully used (58) to select those combinations of existing or hypothetical sensors which would maximize the information that could be obtained on the states of the polymerization system. Both the type of sensors and the precisions necessary for them are easily investigated in this way. By changing the choice of the measurement matrix and... 

Since nearly all products for washing and dishwashing are complex mixtures of different ingredients, an in-situ access to the relevant data is of high interest This can be achieved by using on-line sensors in the specific applications. Washing and dishwashing machines equipped with on-line sensors will be discussed as an... 

Fig. 4.7 Typical behavior of a solid detergent product during the first 20 minutes in a commercially available washing machine. Relevant parameters (pH value, conductivity A, surface tension y, peroxide content ) were detected by on-line sensorics.

Table 7 On-line sensor/analysing equipment properties (from [11])... 

On-line sensor/analysing equipment is an automatic measuring device giving an output signal linked to the value of one determinant (or more) from a medium, continuously or at regular time intervals. The choice and implementation of an on-line sensor must take into account several items or properties related to use constraints, which are presented in Table 7 (derived from [11]). 

As seen previously for some specific applications such as wastewater treatment plants, software sensors can be envisaged to provide on-line estimation of non-measurable variables, model parameters or to overcome measurement delays [81-83]. Software sensors have been developed mainly for monitoring bioprocesses because the control system design of bioreactors is not straightforward due to [84] significant model uncertainty, lack of reliable on-line sensors, the non-linear and time-varying nature of the system or slow response of the process. 

ISO (2003) Standard 15839 Water quality on-line sensors/analysing equipment for water specifications and performance tests... 

Influent uncertainty Closely related to the preceding point is the fact that the composition of the influent is highly influenced by constraints, which may vary in a random manner depending on human industrial or environmental activities [72]. Again, without suitable on-line sensors to measure these variations, only estimates based on statistical confidence intervals may be used in some cases. 

In the following, the diagnosis method has been validated using a data set of 2 weeks, with a serie of on-line measurements every 30 minutes (see Figure 10). During this period, dynamical changes were imposed on the process through Qin, the feed flow rate, while the input concentrations i.e., CODin and Zin) were supposed to be constant. However, no on-line measurements were performed on these variables so only intervals for the values of CODin and Zin are known. Moreover, several faults occurred on different on-line sensors ... 

The potential for developing NMR as an on-line sensor of the internal quality of fruits and vegetables is discussed. The literature on the NMR of horticultural products is first surveyed for potentially useful correlations between NMR characteristics and internal quality factors in commercially important harvested products. This is followed by discussions on the cellular origins of these correlations and of the technical problems to be overcome in the development of a commercial on-line NMR sensor. 

Details are given of the development of an on-line sensor using near IR spectroscoy for monitoring carbon dioxide concentration in polymeric extrusion foaming processes. The calibration curve relating the absorbance spectrum at 2019 nm to the dissolved gas concentration was derived so as to infer dissolved carbon dioxide gas concentration... 

Dorfner, R., Ferge, T, Yeretzian, C., Kettrup, A., Zimmermann, R. (2004) Laser mass spectrometry as on-line sensor for indiKtrial process analysis Process control of coffee roasting. Anal. Chem. 76 1386-1402. 

One of the most promising applications of ultrasound in the food industry is as an on-line sensor for measuring the properties of food materials during processing. There are a number of important attributes which any on-line sensor must have. It must be capable of rapid and reliable measurements, be non-invasive and non-destructive, be robust, low cost, easily automated and hygienic [104]. Sensors based on ultrasound have all of these attributes. 

On-line Sensor R D Association (ed.), Food Industries and Sensor (in Japanese), Korin Publishers, Tokyo, 1991. 

The available data from emulsion polymerization systems have been obtained almost exclusively through manual, off-line analysis of monomer conversion, emulsifier concentration, particle size, molecular weight, etc. For batch systems this results in a large expenditure of time in order to sample with sufficient frequency to accurately observe the system kinetics. In continuous systems a large number of samples are required to observe interesting system dynamics such as multiple steady states or limit cycles. In addition, feedback control of any process variable other than temperature or pressure is impossible without specialized on-line sensors. This note describes the initial stages of development of two such sensors, (one for the monitoring of reactor conversion and the other for the continuous measurement of surface tension), and their implementation as part of a computer data acquisition system for the emulsion polymerization of methyl methacrylate. 

Using a new variable defined for the second term of Eq. 10 as a function of the on-line sensor signal of ethanol concentration, one obtains ... 

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