Example 7-9 Converting Valve Capacities

The capacity of a valve as read from a manufacturer s table or chart is 45,000 cubic feet per hour of free air (14.7 psia and 60°F). What is the capacity of the valve in terms of the vapors expected lo pass through the valve under the rated conditions at the same setting If methanol is in the tank at 55°F 

The SpGr correction factor = 1.0518 (interpolated) and the temperature correction at 55°F = 1.0048 both are from Table 7-16. 

Chemical L /M Molecular Weight Heat of Vaporization Btu per Lb. at Boiling Point 

Note For data on other chemicals, see chemistry handbook. 

Applied Process Design for Chemical and Petrochemical Plants 

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This is the most common mode of addition. For safety or selectivity critical reactions, it is important to guarantee the feed rate by a control system. Here instruments such as orifice, volumetric pumps, control valves, and more sophisticated systems based on weight (of the reactor and/or of the feed tank) are commonly used. The feed rate is an essential parameter in the design of a semi-batch reactor. It may affect the chemical selectivity, and certainly affects the temperature control, the safety, and of course the economy of the process. The effect of feed rate on heat release rate and accumulation is shown in the example of an irreversible second-order reaction in Figure 7.8. The measurements made in a reaction calorimeter show the effect of three different feed rates on the heat release rate and on the accumulation of non-converted reactant computed on the basis of the thermal conversion. For such a case, the feed rate may be adapted to both safety constraints the maximum heat release rate must be lower than the cooling capacity of the industrial reactor and the maximum accumulation should remain below the maximum allowed accumulation with respect to MTSR. Thus, reaction calorimetry is a powerful tool for optimizing the feed rate for scale-up purposes [3, 11]. 

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