Process control, monitoring using

Process control instrumentation controls the FCC unit in a safe, monitored mode with limited operator intervention. Two levels of process control are used ... 

Martin, E. B., Morris, A. J., and Zhang, J. (1996). Process performance monitoring using multivariate statistical process control. IEE Proc. Control Theory 143, 132. 

Acoustic chemometrics can be used for monitoring of both process state and product quality/quantity for better process control. Monitoring process states can provide early warnings which trigger the process operator to change relevant process parameters to prevent critical shutdown situations. 

The PCM (process control monitor) 5000 is an FTIR instrument from Analect/Applied Instrument Technologies that measures the physical and chemical properties of liquid, solid and gaseous in-process samples. The heart of the system is a rugged optical head coupled with a patented fibre optic system. The system is configured for continuous, unattended operation in harsh and hazardous environments. The PCM 5000 FTIR uses close-coupled sample cells (7000-450 cm ). The instrument is configured with a selfdiagnostic module to monitor the critical parameters of its own operation. 

FIGURE 40.17 Different parameters that are subjects of process control monitoring for SiGe. Reprinted from Maul, J.L., Chou, E-F., Lu, Y.H. (2004) Use of SIMS in SiGe process control. Applied Surface Science, 231-232,713-715. Copyright (2004), with permission from Elsevier. 

AlGhazzawi, A. and Lennox, B. Model predictive control monitoring using multivariate statistics. J. Process Control 19(2) 314-327. doi 10.1016/j.jprocont.2008.03.007, 2009. 

There are a number of mathematical tools that are used in the world of manufacturing. Statistical Process Control is used to monitor and control the process parameters that are used to manufacture parts. Tolerance Analyses are used to analyze and predict fit and function of final assemblies. Pareto Analysis techniques are used to assess the contribution of various factors in problem situations. Design of Experiments techniques are used to quantify the variables in a given process or application. 

Various tests were performed to quantify energy efficiency gains and process control improvements, using a combination of bench-top setups and production rans on a laboratory injection molding machine. A samphng of the results is presented herein. Additional lab tests are underway and envisioned, as are monitored installations on a spectrum of production machines. 

Chemical Gas Detection. Spectral identification of gases in industrial processing and atmospheric contamination is becoming an important tool for process control and monitoring of air quaUty. The present optical method uses the ftir (Fourier transform infrared) interference spectrometer having high resolution (<1 cm ) capabiUty and excellent sensitivity (few ppb) with the use of cooled MCT (mercury—cadmium—teUuride) (2) detectors. 

Fiber-Optic Probes. Fiber-optic probes provide remote sampling capabilities to Raman instmmentation, are stable, and give reproducible signals. Their historical niche has been in environmental monitoring. More recently these probes have been used in chemical process control and related areas such as incoming materials inspection. 

Statistical Process Control. A properly miming production process is characterized by the random variation of the process parameters for a series of lots or measurements. The SPG approach is a statistical technique used to monitor variation in a process. If the variation is not random, action is taken to locate and eliminate the cause of the lack of randomness, returning the process or measurement to a state of statistical control, ie, of exhibiting only random variation. 

Analysis of zinc solutions at the purification stage before electrolysis is critical and several metals present in low concentrations are monitored carefully. Methods vary from plant to plant but are highly specific and usually capable of detecting 0.1 ppm or less. Colorimetric process-control methods are used for cobalt, antimony, and germanium, turbidimetric methods for cadmium and copper. Alternatively, cadmium, cobalt, and copper are determined polarographicaHy, arsenic and antimony by a modified Gutzeit test, and nickel with a dimethylglyoxime spot test. 

The process monitors and controllers typically also have the capabiUty for data logging, analysis, and display. This capabiUty has made on-line control of pilot plants, as well as commercial-scale processes, desirable. Pilot-plant appHcations for on-line control have been described (106), and the use of such systems for both monitoring and process diagnosis has been discussed (107). A number of commercially available process control programs that mn on microprocessors have been reviewed (108). Virtually all of them incorporate graphic display as an integral part of the interactive capabiUty of the program. 

The creation and analysis of process flow sheets has become much easier because of the availabihty of automated systems to draw and revise them. The goal of the use of the flow sheet as the input for process simulation and for process control is likely to be achieved reasonably soon. The use of interactive graphic displays for process monitoring and control is pervasive today. 

Historical DataBase Subsystem We have discussed the use of on-hne databases. An historical database is built similar to an on-line database. Unlike their on-line counterparts, the information stored in a historical database is not normally accessed directly by other subsystems for process control and monitoring. Periodic reports and longterm trends are generated based on the archived data. The reports are often used for long-term planning and system performance evaluations such as statistical process (quality) control. The trends may be used to detect process drifts or to compare process variations at different times. 

The monitoring of pollutant concentration or mass flow of pollutants is of interest to both plant owners and control agencies. Industry uses such measurements to keep a record of process operations and emissions for its own use and to meet regulatory requirements. Control officials use the... 

Gas-monitoring systems are more widely used than particulate monitoring systems. They can also be used for both emission compliance monitors and process control systems. Gas monitors may be of either the in situ or... 

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