Production Rate Optimisation

For smaller scale purifications, where the major cost contributions tend to be the fixed charges of labour and equipment, the simple cost considerations suggest that the production rate should be maximised. Several papers have appeared on this sub- 

Since the optima in chromatography are generally broad, this approach, while not giving an optimum column, would give one which approaches it. The error in this procedure is greatest for separations which need high efficiency. As noted above, the 

2 The Practical Application of Theory in Preparative Liquid Chromatography 

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An example of an application of CAO is its use in optimising the distribution of gas in a gas lift system (Fig. 11.3). Each well will have a particular optimum gas-liquid ratio (GLR), which would maximise the oil production from that well. A CAO system may be used to determine the optimum distribution of a fixed amount of compressed gas between the gas lifted wells, with the objective of maximising the overall oil production from the field. Measurement of the production rate of each well and its producing GOR (using the test separator) provides a CAO system with the information to calculate the optimum gas lift gas required by each well, and then distributes the available gas lift gas (a limited resource) between the producing wells. 

An even more powerful option is the use of micro flow reactors, which can potentially be automated to provide a complete series of optimisations [49]. For example, a glycosylation reaction was monitored over a series of reaction temperamres. Although the optimum reaction temperature for maximum yield was determined to be — 60°C, it was noted that by increasing the temperature of the reaction to — 35°C the yield only dropped shghtly but the reaction rate increased considerably. It was therefore possible to achieve a ten-fold increase in production rate. The complete optimisation took one afternoon and consumed 2 mg of starting material. 

Expressions for the entropy production rate can serve as meaningful object functions in optimisations. NET offers an insight into the nature of the solution by characterising the system s H, [Pg.10]

As only milligram or grams of product were to be purified in the above examples, relatively little effort was made to optimise the chromatographic system and quite simple concepts were applied. This is completely different to processes with production rates of 100 kg a-1 or higher. 

If production rate and hydrogen/toluene ratio at the reactor inlet (yns/yta) are set, Eqs. 13.30 to 13.34 have two degrees of freedom. Hence, two design variables must be specified, but not any combination is feasible. Douglas (1988) considers reactor conversion and purge composition as design variables and optimises the economic potential. We use his results (X = 0.78, Y p - 0.424) as a starting point. 

Up to this point, the basic regulatory plant-wide control approach has been established on the VCM production processes. The recycle HCl flow is to be maximised to increase the product production rate. However, this target may conflict with other environmental and operational objectives as covered in the optimisation section of the overall framework. Economical, environmental and operational objeetives may play an important role in the optimisation of several controller setpoints as shown earlier. Moreover, the production rate can be maximised through the pyrolysis temperature controller where a trade-off rises due to the coke formation and the increase in the by-products rates. Therefore, a number of specified objectives, constraints and external factors, such as raw materials and energy costs and the products... 

In case of the Sedimentation Tanks a very long average renewal time (T ) is observed as the water production rate is considerably lower than the design value (two Tanks can provide the max water capacity) and consequently the Operator does not endeavour to optimise the cleaning period. 

If a separation is to be performed at large scale, it is usually necessary to carry out at least some level of optimisation. This may be simply to limit the time and cost of isolating a compound for further study, or may be to minimise the costs of production. It is important to remember that the reason for optimisation often influences the conditions chosen. This is because selection of conditions to give, for example, the maximum production rate (in kg h ) may not result in product which is isolat-... 

Once the competitive isotherms for solutes are known, the theories of chromatography now allow the rapid optimisation of production rate and, through computer simulations, also allow the rapid prediction of preparative chromatograms under any desired conditions. These facilitate the full optimisation of a production scale method. 

A semi-continuous reactor is used to carry out the following parallel reaction, where P is valuable product and Q is unwanted waste. The problem is to optimise the feed strategy to the reactor such that the maximum favourable reaction selectivity is obtained, for similar systems but of differing kinetic rate characteristics. 

A typical example of HPLC method development and validation was provided by Boneschans et al. [9]. They developed an HPLC method for piroxicam benzoate and its major hydrolytic degradation products, piroxicam and benzoic acid. The authors utilised a robust stationary phase (Phenomenex Luna, Cig), with an optimised mobile phase comprising of acetonitrile/water/acetic acid (45/7/8 v/v), and a flow rate of 1.5 ml/min. The operating pH of the mobile phase (pH 2.45) was selected on the basis that it is ca. 2 pH units from the pKa of the drug, and hence reasonably insensitive to changes in mobile-phase preparation. The injection volume was 20 pi with a detection wavelength of 254 nm. They utihsed... 

Shear enhancement effects in foam formation can be understood through the modified cavity model. Shear force behaves as catalyst to reduce energy barrier to allow a quik path from stable gas cavity to unstable bubble phase. It can be concluded that both shear rate and viscosity contribute to foam nucleation in the continuous foam extrusion process. Therefore, proper die opening and process conditions will help to optimise the foam product. 11 refs. 

The maximum conversion of reactants which can be achieved in an isothermal batch reactor is determined by the position of thermodynamic equilibrium. If this conversion is regarded as unsatisfactory, the use of a simple batch reactor may be abandoned in favour of a reactor which permits removal of products from the reaction mixture. Alternatively, the reactor temperature may be changed to obtain a more favourable equilibrium however, this may result in an unacceptable reduction in the net reaction rate. Such conflicts are often resolved by the use of optimisation procedures (see Sect. 8). 

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