Material selection establishing operational requirements

This standard was and still is widely used by operators, either in the oil and gas production fields or refineries. Most SRV manufacturers have established a standard Bill of Materials that complies with the minimum requirements of NACE MR0175, taking into account certain specific valve material selections based on their hardness and under the condition of the following operating conditions ... 

In order to minimize the required reactor volume for a given type of reactor and level of conversion, one must always operate with the reactor at a temperature where the rate is a maximum. For irreversible reactions the reaction rate always increases with increasing temperature, so the highest rate occurs at the highest permissible tepiperature. This temperature may be selected on the basis of constraints established by the materials of construction, phase changes, or side reactions that become important at high temperatures. For reversible reactions that are endothermic the same considerations apply, since both the reaction rate and the equilibrium yield increase with increasing temperature. 

The most convenient and economic techniques of choice for the rapid analysis of starting materials and for the assessment of purity of a crude reaction product are t.l.c. and g.l.c. These techniques may also be used to monitor the progress of a reaction for which optimum conditions are uncertain, as may be the case when an established published procedure is used as the basis for carrying out other preparations of a similar nature. In these cases the reaction is monitored by the periodic removal from the reaction mixture of test portions for suitable chromatographic study. Clearly the chromatographic behaviour of starting materials and, if possible, expected products, needs to be established prior to the commencement of the reaction. For t.l.c. this would include solvent and thin layer selection, a detection method, and an appraisal of sensitivity of detection with respect to the concentration of components in the reaction medium. For g.l.c. preliminary experiments would be required to select a suitable column and the appropriate operating conditions. 

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