Sensors and Process Control

Since emulsion polymerisation is generally a sensitive process, care must be taken to ensure the consistency of the final product from batch to batch or during a single continuous operation. Furthermore, emulsion polymers are products by process , meaning that the manner in which the polymerisation is carried out is perhaps more important than the raw materials in determining the form of the final product. For this reason, it is desirable to monitor the emulsion polymerisation process on-line (although in practice, many commercial producers measure properties after 

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Develop real-time sensors and process controls that are more reliable and robust in harsh environments. 

Fundamental knowledge of physical and chemical science Materials of construction Model validation and technology transfer End user product quality Process characterization and development Advanced sensors and process control Best practices (from other industries)... 

This chapter presented a concept drawing of a distillation process that included flow rate sensors, liquid level sensors, temperature sensors, and process control valves. The process streams were identified and labeled. The standard definition of reflux ratio was presented, and the concepts of separation power and material balance split were introduced. 

Figure 10.1 Three methods of accomplishing process control (revised and reprinted from R, P, Madding, "Infrared sensors and process control," Proc. SPIE446, Thermo-Sense VI, 1984, pp, 9-17).

The SPC system starts with the premise that the specifications for a product can be defined in terms of the product s (customer s) requirements, or that a product is or has been produced that will satisfy those needs. Generally a computer communicates with a series of process sensors and/or controllers that operate in individual data loops. 

One of the major breakthroughs in nanotechnology is the use of nanomaterials as catalysts for environmental applications [149]. Nanomaterials have been developed to improve the properties of catalysts, enhance reactivity towards pollutants, and improve their mobility in various environmental media [150]. Nanomaterials offer applications to pollution prevention through improved catalytic processes that reduce the use of toxic chemicals and eliminate wastes. Nanomaterials also offer applications in environmental remediation and, in the near future, opportunities to create better sensors for process controls. 

Miller H.H., Hirschfeld T.B., Fiber optic chemical sensors for industrial and process control, Proc. SPIE-Int. Soc. Opt. Eng. 1987 718 39. 

Applications of infrared sensors have been reported in the fields of biology/biochemistry, medical diagnostics, environmental monitoring and process control. IR sensors can measure analytes in solid, liquid or gaseous form using one of several different transducer layouts. 

The majority of currently deployed IR sensors operate in the near-IR. Although near-IR sensors suffer from limited selectivity and sensitivity due to the relatively unstructured broadband absorptions in this frequency range, the easy availability of waveguides and other instrumentation give this spectral range a significant advantage over the mid-IR. Main application areas involve substance identification and process control. 

A variety of optical oxygen sensor systems have been developed for applications such as biomedical, environmental and process control . But very few of them have been critically assessed for their suitability for food packaging applications. It has been proven that substantial development, optimization and redesign of the oxygen-sensitive materials and fabrication processes are required for the oxygen sensors to match practical requirements for these applications5. In particular, specific requirements of food applications are ... 

Displacement sensors are used in a very wide field of applications in research, development, quality inspection, automation, machinery and process control. Many physical parameters can be reduced to a displacement or change of distance, and can be measured with highest precision. Displacement sensors detect physical parameters like bending, deflection, deformation, diameter, eccentricity, elongation, gap, length, play, position, revolution, roundness, shift, stroke, thickness, tilt, tolerances, vibration, wear and width. 

The growing nse of more complex PAT (versus the historically used simple univariate sensors such as pressure, temperature, pH, etc.) within manufacturing industries is driven by the increased capabilities of these systems to provide scientihc and engineering controls. Increasingly complex chemical and physical analyses can be performed in, on, or immediately at, the process stream. Drivers to implement process analytics include the opportunity for live feedback and process control, cycle time reduction, laboratory test replacement as well as safety mitigation. All of these drivers can potentially have a very inunediate impact on the economic bottom line, since product quality and yield may be increased and labor cost reduced. 

Multiplexed diode-laser sensors were applied for measurement and control of gas temperature and species concentrations in a large-scale (50-kilowatt) forced-vortex combustor at NAWC to prove the viability of the techniques and the robustness of the equipment for realistic combustion and process-control applications [11]. The scheme employed was similar to that for measurements and control in the forced combustor and for fast extractive sampling of exhaust gases above a flat-flame burner at Stanford University (described previously). 

The current research focus within the sensor development field seems to be concentrated on miniaturization while incorporating multiple quantitative analytical capabilities. Other high-demand characteristics are shorter response time, minimal hardware requirements, multiple analyte and media capabilities, and improved sensitivity, selectivity, and specificity (Zemel 1990). Advancements and improvements for both biological and chemical threat agent sensors will have numerous other benefits to diverse applications, such as quality and process control, biomedical analysis, medical diagnostics, fragrance analysis, environmental pollution monitoring, and control forensics. 

McLean. A. (1990) Sensor aided process control in iron and steelmaking. Solid State Ionics. 40/41, 737 2. 

Array chemical sensors represent an important recent development that involves many sensor platforms. When combined with fast computational methods for pattern recognition and data analysis, these methods have substantial potential for analysis of complex mixtures and process control. 

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