Scaleup process condition

This section focuses only on process scaleup—i.e, scaling up from one chemical system to another, and also scaling up from one set of process conditions to another using the same system. Equipment factors such as column diameter, operating regime, and tray geometry are considered separately in the following section. 

In the above procedure, errors in VLE are compensated by equivalent errors in tray efficiency. If the relative volatility calculated by the simulation is too high, fewer stages will be needed to match the measured test compositions, i.e., efficiency will be lower. Scaleup will be good as long as the VLE and efficiency errors continue to equally offset each other. This requires that process conditions (feed composition,... 

When process conditions are changed, the VLE and efficiency errors no longer offset each other equally. If the true relative volatility is higher than the simulated relative volatility, then the scaleup will be conservative. If the true volatility is lower than the simulated relative volatility, scaleup will be optimistic, and often dangerous. This is illustrated using the following example. 

However, each set of factors entering in to the rate expression is also a potential source of scaleup error. For this, and other reasons, a fundamental requirement when scaling a process is that the model and prototype be similar to each other with respect to reactor type and design. For example, a cleaning process model of a continuous-stirred tank reactor (CSTR) cannot be scaled to a prototype with a tubular reactor design. Process conditions such as fluid flow and heat and mass transfer are totally different for the two types of reactors. However, results from rate-of-reaction experiments using a batch reactor can be used to design either a CSTR or a tubular reactor based solely on a function of conversion, -r ... 

When scaling the process, the model and prototype must have Reynolds numbers in the same regime (i.e., laminar or turbulent flow) in order to achieve similar results. Ideally, the two reactors would have nearly identical or identical Reynolds numbers. In order to satisfy this requirement for scaleup, the model and prototype must be similar to each other with respect to reactor design, fluid flow, and physical dimensions. According to the principle of similarity, for every process condition and point in the model, there must be a corresponding condition and point in the prototype.This principle is applied to the scaling process by observing similar requirements for several other dimensionless ratios or variables that must be treated in a similar fashion. 

The scaleup process is not just a matter of plugging values into prescribed equations, nor can exact scaleup criteria be obtained from generalized correlations for certain types of equipment. Instead, in a good scaleup approach, all variables that describe the process are determined desired process conditions and the magnitude of the scaleup taken into account and a design selected. Scaleup designs are based almost exclusively on the principle of similarity. 

The constant may depend on process variables such as temperature, rate of agitation or circulation, presence of impurities, and other variables. If sufficient data are available, such quantities may be separated from the constant by adding more terms ia a power-law correlation. The term is specific to the Operating equipment and generally is not transferrable from one equipment scale to another. The system-specific constants i and j are obtainable from experimental data and may be used ia scaleup, although j may vary considerably with mixing conditions. Illustration of the use of data from a commercial crystallizer to obtain the kinetic parameters i, andy is available (61). 

The hydrophilic surface characteristics and the chemical nature of the polymer backbone in Toyopearl HW resins are the same as for packings in TSK-GEL PW HPLC columns. Consequently, Toyopearl HW packings are ideal scaleup resins for analytical separation methods developed with TSK-GEL HPLC columns. Eigure 4.44 shows a protein mixture first analyzed on TSK-GEL G3000 SWxl and TSK-GEL G3000 PWxl columns, then purified with the same mobile-phase conditions in a preparative Toyopearl HW-55 column. The elution profile and resolution remained similar from the analytical separation on the TSK-GEL G3000 PWxl column to the process-scale Toyopearl column. Scaleup from TSK-GEL PW columns can be direct and more predictable with Toyopearl HW resins. 

Scaleup of the fluid-bed MTO process has been successfully demonstrated in the 100 B/D plant. Results obtained in this unit are in close agreement with those obtained in the 4 B/D pilot plant under the same conditions. Total olefin yields for the 100 B/D demonstration plant were similar to those obtained in the 4 B/D unit (Fig. 6), and methanol breakthrough occurred at approximately the same propane/propene RI for both units (Fig. 

When solids are suspended in an agitated tank, there are several ways to define the condition of suspension. Different processes require different degrees of suspension, and it is important to use the appropriate definition and correlation in a design or scaleup problem. The degrees of suspension are given below in the order of increasing uniformity of suspension and increasing power input. 

All three processes considered here are exothermic. Since slurry reactors on an industrial scale are operated under close to adiabatic conditions, a major scaleup problem is that of the thermal control of such reactors. Recently, Shah and Carr (10) have described a custom made agitated adiabatic slurry reactor, which can be used to evaluate the thermal behavior of the large scale reactors. 

This may require a change in the laboratory-scale operating conditions so that the product is economically achievable in a commercial process. The intentional lessening of product goals in the laboratory or pilot plant to enable economic scaleup is called diplomatic scaleup because it may require diplomacy to convince the bench chemist and management. 

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