Results from process scale

Ideally, a mathematical model would link yields and/or product properties with process variables in terms of fundamental process phenomena only. All model parameters would be taken from existing theories and there would be no need for adjusting parameters. Such models would be the most powerful at extrapolating results from small scale to a full process scale. The models with which we deal in practice do never reflect all the microscopic details of all phenomena composing the process. Therefore, experimental correlations for model parameters are used and/or parameters are evaluated by fitting the calculated process performance to that observed. 

This section discusses how the interpretation, evaluation, and correlation of test results from bench-scale equipment can be integrated into an approach to inherent process safety involving reactive systems. 

Kaptijn J P (1997) The Ecoclear Process. Results from Full-Scale Installations, Ozone Science Engineering 19 297-305. 

Based on the results from laboratory-scale equipment and the first production plants, the basic economics of the process were calculated. The processing costs are between 0.15 and 0.60 Euro/kg (composition of costs investment 20%, personell 37%, and operating 43%) and vary depending on the substances to be micronized, the scale of the equipment, etc. 

Process validation is documented evidence which provides a high degree of assurance that a specific process will consistently produce a product meeting its pre-deter-mined specifications and quality attributes [48]. For cell culture-derived biopharmaceuticals, important quality attributes to establish include structural integrity and potency of the API and freedom from impurities. Thus, the demonstration of removal of cell culture and process impurities is a key part of process validation. Often, due to practical considerations, some studies are performed at small scale. In these cases, periodic concurrent monitoring of impurities during large-scale production can confirm the results from small-scale studies. 

Construction of a scale model must be accompanied with an analysis to determine test conditions that ensure the test results from the scale model are representative of the processes in the prototype. In combustion applications, although most of the processes are inherently at elevated temperatures, physical modeling is usually carried out under isothermal conditions. Isothermal physical modeling technique is based on the principle of relaxation. Under this principle, the variables that are important for the phenomena under study are stressed. The variables that are stressed are duplicated as necessary to obtain a representative result. No scale physical model can be an exact model of the reality unless an exact full-scale prototype is made. However, by using accurate correlations the modeling work can provide a good qualitative understanding of the fluid dynamics in the prototype. This chapter attempts to answer the question How does one ensure that the scale model test results are representative of the actual processes in the prototype ... 

Edmonson, J.N. (1992). Consolidatedproposalsfordetermin-ing basic level 1 accident initiation frequencies for storage and process buildings using the results from the scaling analysis studies. Technical report, MOD. 

Volumetric Sweep Efficiency. As discussed in Chap. 4, reduction of the mobility ratio in a displacement process results in an improvement of volumetric sweep efficiency. However, calculation of sweep from the empirical correlations presented in Chap. 4 is probably not justified in a WAG process because of the complex nature of the flow in the region behind the oil bank. In application, the process usually is modeled with computer-based mathematical models, 165,166 Limited results from properly scaled physical models have also been reported. 

Another example is the purification of a P-lactam antibiotic, where process-scale reversed-phase separations began to be used around 1983 when suitable, high pressure process-scale equipment became available. A reversed-phase microparticulate (55—105 p.m particle size) C g siUca column, with a mobile phase of aqueous methanol having 0.1 Af ammonium phosphate at pH 5.3, was able to fractionate out impurities not readily removed by hquid—hquid extraction (37). Optimization of the separation resulted in recovery of product at 93% purity and 95% yield. This type of separation differs markedly from protein purification in feed concentration ( i 50 200 g/L for cefonicid vs 1 to 10 g/L for protein), molecular weight of impurities (<5000 compared to 10,000—100,000 for proteins), and throughputs ( i l-2 mg/(g stationary phasemin) compared to 0.01—0.1 mg/(gmin) for proteins). 

The propylene-based process developed by Sohio was able to displace all other commercial production technologies because of its substantial advantage in overall production costs, primarily due to lower raw material costs. Raw material costs less by-product credits account for about 60% of the total acrylonitrile production cost for a world-scale plant. The process has remained economically advantaged over other process technologies since the first commercial plant in 1960 because of the higher acrylonitrile yields resulting from the introduction of improved commercial catalysts. Reported per-pass conversions of propylene to acrylonitrile have increased from about 65% to over 80% (28,68—70). 

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. 

Disadvantages of these continuous countercurrent systems are associated primarily with the complexity of the equipment required and with the attrition resulting from the transpoiT of the ion exchanger. An effective alternative for intermediate scale processes is the use of merry-go-round systems and SMB units employing only packed-beds with no movement of the ion-exchanger. 

Staff profile page - the Engineering Faculty at Loughborough. .. Broad Interests and Expertise. Compressible cake filtration Selection, scale-up and process simulation of solid/liquid separation equipment Washing and. .. http //WWW. Iboro. ac. uk/departments/eng/research/staff/html/tarleton. html [More Results From www.lboro.ac.uk]... 

In many cases, two identical reaction systems (e.g., a pilot plant scale and a full-scale commercial plant) exhibit different performances. This difference in performance may result from different flow patterns in the reactors, kinetics of the process, catalyst performance, and other extraneous factors. 

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