Cost, control separation

Solvent quantity is dictated by factors such as the need for dilution to minimize unwanted side reactions, the cost of separating and recovering the solvent, and the solubility of reactants and products. While it may be economically preferable to hydrogenate liquid substrates without a solvent, control of some mass transport steps may be limited and attaining high reaction... 

Nowadays, in the pharmaceutical industry, the need to obtain accurate and rehable analytical data faster and more cost-effectively, has meant that approaches to method development are becoming simpler and more straightforward. These sinpler approaches have the benefits of more consistent methods, lower method diversity, reduced inventory costs for separations consumables and more easily transferable methods from R D laboratories to manufacturing quality control (QC) laboratories. Many pharmaceutical companies have adopted this approach. 

The three valves are all built for chlorine service. Vortex meters upstream of the control valves measure and integrate the various flows. Integration of the flow to the scrubber is the least important, but given the measurement of the flow rate, it is of little added cost. A separate meter located before division of the flow can measure the total flow, or the output of the three individual meters can be added together. The valve positioners may be calibrated for ranges of 15-20 mA (direct user), 9-15 mA (liquefiers), and 4-9 mA (scrubber). The two process valves should have linear characteristics. They should be sized for fiill plant output when 90% open. Normally allowed pressure drops are 5-15 kPa for the direct-use valve and 20-30kPa for the liquefier valve. The scrubber... 

Achieve controllable cell flocculation for easy separation after continuous growth in mixed substrates Downstream processing contributes 30—50% of PHA cost, controllable flocculation reduces cells and broth separation cost, thus leading to reduction on PHA production cost ... 

The control structure presented in Fig. 4a allows two different ways for production rate manipulation. If the reactor is large enough Da = k V IF o > 3), changes of +/- 30 % in F4 can be achieved with reasonable changes in F (Fig. 2b). Note that a large reactor is often optimal from an economic viewpoint, because it minimizes the cost of separation. 

Selectivity. Solvent selectivity is intimately linked to the purity of the recovered extract, and obtaining a purer extract can reduce the number and cost of subsequent separation and purification operations. In aqueous extractions pH gives only limited control over selectivity greater control can be exercised using organic solvents. Use of mixed solvents, for example short-chain alcohols admixed with water to give a wide range of compositions, can be beneficial in this respect (6). 

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