Vapor pressure systems

A survey within the Fine Chemieal Manufaeturing Organization of ICI has shown that gassy reaetion systems predominate due to established proeesses sueh as nitrations, diazotizations, sulphonations, and many other types of reaetions [22]. Very few vapor pressure systems have been identified that also generate permanent gas (i.e., hybrid type). 

The vapor pressure systems obey the Antoine relationships ... 

Figure 12-36 shows a sketeh of the temperature profile for high vapor pressure systems. 

Figure 12-36. Vent sizing model for high vapor pressure systems due to nonequilibrium effects turnaround in temperature is assumed to coincide with the onset of complete vapor disengagement.

Determine the vent size for a vapor pressure system using the following data and physical properties. 

Vapor pressure system A vapor pressure system is one in whieh the pressure generated by the runaway reaetion is solely due to the inereasing vapor pressure of the reaetants, produets, and/or solvents as the temperature rises. 

Measurement of relative humidity depends on the system used. Systems employing vacuum are usually evacuated prior to introduction of water vapor [29]. For cases in which there is not a gas-forming reaction occurring, measurement of total pressure in the system can be used as a measure of water vapor pressure. Systems in which air is not evacuated require specific measurement of water vapor pressure. (For the latter type of system, caution should be taken to assure that the relative humidity source is in close proximity to the solid, since the diffusion of water vapor through air to the solid is required to maintain a constant relative humidity in the immediate vicinity of the solid.) A wide variety of pressure measuring instrumentation is commercially available with varying accuracy, precision, and cost. 

Crude oil vapor pressure limitations for pipeline delivery may be comparable to those for tanker loading. However, a pipeline can be specifically designed as a high vapor pressure system to handle gas liquids components mixed with the crude oil, and it is quite possible that North Sea oil pipeline systems will be developed in this manner. It is not expected to be feasible to recover NGL components separate from oil and gas on the offshore platforms and construct separate NGL pipeline systems. It also may not be possible in every field to design a separation system which meets both gas specifications and low crude oil vapor pressure specifications unless an intermediate product is also made. This will be more fully discussed later In this paper. A high vapor pressure crude system will have an NGL separation and fractionation plant at the onshore pipeline terminal. The vapor pressure limitation for onshore crude deliveries will be fixed by TVP limitations at pump station suction conditions. 

A vapor pressure system warns when the supply dewar on duty is nearly empty. 

In general, for multiple concentrations, one standard is prepared in this fashion and is then diluted by a second diluent gas stream. This requires that both the original bubbler flow and the diluent flow can be accurately measured, whereas with the single concentration provided by the vapor pressure system, the bubbler flow need not be known accurately because it does not enter into the calculations. One only has to be assured that the gas is saturated. 

The behavior of high-vapor-pressure systems, which may be either boiling or hot sparged... 

After the transfer tube has been assembled and evacuated, the vapor-pressure system is filled. Since it is important that the composition of the substance in the vapor-pressure system be identical to that flowing through the test orifice, the vapor-pressure system is filled with gas obtained by vaporizing liquid from the supply dewar. The final pressure of the vapor-pressure system is fixed because during testing the liquid-vapor interface must be in the bulb and not in the pressure line. 

Figure 11.2 Open source evaporation boats (lower) and wire coils (upper figure). Wire coils are generally made of W although other low vapor pressure systems also work. Open boats are made in a wide variety of shapes and of a wide variety of materials including Ta, W, graphite, and other materials.

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