Apparatus and materials of construction

The trend in hydrogenation practice appears to be toward the use of higher pressures, where the apparatus is smaller. Under such conditions, the reaction velocity is increased the equilibrium positions are made more favorable the reaction path is better defined, with fewer side reactions and heating and cooling and heat interchange are facilitated. The design and construction of equipment for high-pressure work are, however, somewhat more complicated than for low-pressure operations. Alloy steels are by far the most common materials of construction. 

The design and construction of small-scale pilot-plant units for processing under extreme conditions of pressure and temperature have been described. This description includes material on constructing barricades, thick-walled pressure vessels, and pumps as well as information on the selection of alloys and the effects of hydrogen on the properties of metals. 

A convenient small-scale continuous unit is shown in Fig. 10-5. The materiftl to be hydrogenated, if a liquid, is fed into the small high-pressure pump—OF, if a solid, it is dissolved in a suitable solvent. All that the pump needs to do is to put sufficient pressure on the liquid to raise it to the pressure on the reactor- Binoe liquids are relatively incompressible, the work expended in this operation is small- The material is heated near the inlet 

In the operation of large units, heating of the ingoing materials is best accomplished by heat exchange wiUi the outgoing materials and adding additional heat by means of high-pressure pipe coils. A pipe coil is the 

Vtermocotw s 9. 6raduaf9nrm9 tswvng wctfercfrspkrcecf unit No.1 is rvn whsn hy trsgenating Pumpi/nHMo.2is run whw comfiressin hydrogsn 

---