Control process improvement

Liaison with Plant Engineering Department on Process-Control Improvement... 

These data are utilized for process control, improvement of product quality, the saving of raw material and energy, and an assurance of safety. In this section, we focus on the measurement of process variables as the basis of bioprocess control. 

Engineering—Process hazard evaluations, process control improvements, turnarounds, and startups all benefit from elective procedures that accurately describe how to operate and maintain process equipment. This book presents the basic methods for ensuring that the procedures are efiective and are reviewed for accuracy. 

The advantages are as follows improved process control, improved materials handling, potential to achieve lower levels, many configurations and can be used in treatment train. The disadvantages are laboratory scale only and the costs are unknown. 

The area of plantwide control is the active focus of research in process control. Improved methodologies and approaches to the problem should be developed in the future. The incentives are great, as are the challenges. 

Reproducibility of process control improves product quality. 

Wise, B.M. and Ricker, N.L., (1991), Recent advances in multivariate statistical process control improving robustness and sensitivity. Proceedings of IFAC ADCHEM Symposium, 125. 

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. 

Manufacturing processes have been improved by use of on-line computer control and statistical process control leading to more uniform final products. Production methods now include inverse (water-in-oil) suspension polymerization, inverse emulsion polymerization, and continuous aqueous solution polymerization on moving belts. Conventional azo, peroxy, redox, and gamma-ray initiators are used in batch and continuous processes. Recent patents describe processes for preparing transparent and stable microlatexes by inverse microemulsion polymerization. New methods have also been described for reducing residual acrylamide monomer in finished products. 

Zinc. The electrowinning of zinc on a commercial scale started in 1915. Most newer faciUties are electrolytic plants. The success of the process results from the abiUty to handle complex ores and to produce, after purification of the electrolyte, high purity zinc cathodes at an acceptable cost. Over the years, there have been only minor changes in the chemistry of the process to improve zinc recovery and solution purification. Improvements have been made in the areas of process instmmentation and control, automation, and prevention of water pollution. 

J. W. Carson and T. A. Royal, "In-Bin Blending Improves Process Control," Powder Handl Proc. (Sept. 1992). 

Additionally, attempts are being made to streamline the gravure process by improving make-ready times. Press manufacturers Cemtti and Albert-Frankenthal are working on cassette systems where jobs are prepared outside the press and subsequently loaded with virtually 2ero stop time. Computer control of press functions such as compensators, angle bars, and folders also help reduce press make-ready time. 

Quality in Japan. Japanese economic prowess has been attributed variously to such quahty improvement activities as quahty circles, statistical process control (SPG), just-in-time dehvery (JIT), and zero defects (ZD). However, the real key to success hes in the apphcation of numerous quahty improvement tools as part of a management philosophy called Kaizen, which means continuous improvement (10). 

The LIMS software is essentially a database for tracking, reporting, and archiving lab data as well as scheduling and guiding lab activities. Graphical and statistical treatment of data for improved process control (qv) as well as preparation of certificates of analysis (COA) for the customer are some of the other features of a comprehensive LIMS package (30). 

Reduced Emissions and Waste Minimization. Reducing harmful emissions and minimizing wastes within a process by inclusion of additional reaction and separation steps and catalyst modification may be substantially better than end-of-pipe cleanup or even simply improving maintenance, housekeeping, and process control practices. SO2 and NO reduction to their elemental products in fluid catalytic cracking units exemplifies the use of such a strategy (11). 

Computer Control. The use of computer systems to control the operation of submerged arc furnaces, including calcium carbide, has been successfully demonstrated in the United States (see Expert systems Process control). Operations direcdy under control are mix batching, electrode position and sHp control, carbide gas yield, power control, and cooling water systems. Improvements in energy usage, operating time, and product quaHty are obtained. 

There are important economic consequences of a process being out of control for example, product waste and customer dissatisfaction. Hence, statistical process control does provide a way to continuously monitor process performance and improve product quahty. A typic process may go out of control due to several reasons, including... 

More microprocessor-based process equipment, such as smart instruments and single-loop controllers, with digital communications capability are now becoming available and are used extensively in process plants. A fieldbus, which is a low-cost protocol, is necessary to perform efficient communication between the DCS and these devices. So-called mini-MAP architec ture was developed to satisfy process control and instrumentation requirements while incorporating existing ISA standards. It is intended to improve access time while... 

Currently, the trend in process control is away from centrahzed process control and toward an increased number of small distributed-control or PLC systems. This trend will put emphasis on the evolution of the fieldbus controller and continued growth of the PC-based controller. Also, as hardware and software improves, the functionality of the controller will increase, and the supporting hardware will be physically smaller. Hence, the traditional lines between the DCS and the PLC will become less distinct as systems will be capable of supporting either function set. 

Some tvpical examples of where the dvnarnics of the positioner are siifficientlv fast to improve process control are the following ... 

Valve Application Technology Functional requirements and the properties of the controlled fluid determine which valve and actuator types are best for a specific apphcation. If demands are modest and no unique valve features are required, the valve-design style selection may be determined solely by cost. If so, general-purpose globe or angle valves provide exceptional value, especially in sizes less than 3-inch NFS and hence are very popular. Beyond type selection, there are many other valve specifications that must be determined properly in order to ultimately yield-improved process control. 

Some plants have been using computer control for 20 years. Control systems in industrial use typically consist of individual feedback and feedforward loops. Horst and Enochs [Engineering h- Mining]., 181(6), 69-171 (1980)] reported that installation of single-variable automatic controls improved performance of 20 mineral processing plants by 2 to 10 percent. But interactions among the processes make it difficult for independent controllers to control the circuit optimally. 

Statistical Process Control (SPC) The use of statistical techniques (such as control charts) to analyze a process and take appropriate action to maintain statistical control and improve process capability. 

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