High-Pressure Reaction Equipment Design

The internationally accepted (SI) unit of pressure is the Pascal (Pa) and consequently for high pressure processes the megapascal. In synthetic applications it is more common to use the bar as the unit of pressure (1 MPa = 10 bar). Therefore, the unit used in this book is also the bar. Because various other units are still in use it is important to be familiar with the most important conversions. 

1 mm Hg (torr) 1.3332X10- 1.3332x10 1.3158x10 1.3595x10 1.9337X10- 1 

The literature is not entirely consistent as to the definition of high and low pressure. However, at pressures above 6000 bar the question of material choice (particularly if corrosive fluids are to be employed in the system) becomes critical and a specialized reactor design must be chosen [17,18]. As such, this discussion focuses on systems designed for use at pressures below 6000 bar. 

The numerous possible high pressure applications and their associated requirements can be satisfied by a variety of different assemblies of reaction vessels, closures, tubing, valves, pumps or compressors. First, an overview of these different components is presented, after which several complete high-pressure systems found in the literature are discussed. At this point it should be emphasized that in showing equipment from one manufacturer or another, no preference for a particular product is being expressed. Further details on equipment employed for spectroscopy at high pressure are provided in Chapter 3. 

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Fink R, Beckman EJ. High-pressure reaction equipment design. In Jessop PG,... 

The circulation flow method is applicable for the studies of almost any heterogeneous catalytic reaction. At high pressures steel equipment is used instead of glass. The first circulation flow reactor for high pressures was designed by Sidorov (6) the gas mixture is circulated in this reactor by means of steel bellows that are actuated by a rod introduced into the reactor also through bellows, without any packing. 

A second but relatively uncommon form of reaction initiation by radiation is by pulse radiolysis. The method requires very specialized equipment. A critical aspect of the method involves knowing with confidence which species have been generated by the pulse, and therefore what are the reaction consequences of its generation. A second important aspect is that in the high-pressure mode, the design of a cell must permit sufficient radiation to be incident... 

Chemical processing under "extreme conditions" of high temperatures and pressures requires more tliorough analysis and extra safeguards. As discussed in Chapter 7, e.xplosions at liigher initial temperatures and pressures are much more severe. Therefore, chemical processes under extreme conditions require specialized equipment design and fabrication. Otlier factors tlrat should be considered when evaluating a chemical process are rate and order of the reaction, stability of the reaction, and tlie healtli hazards of the raw materials used. 

Adiabatic Reaction Temperature (T ). The concept of adiabatic or theoretical reaction temperature (T j) plays an important role in the design of chemical reactors, gas furnaces, and other process equipment to handle highly exothermic reactions such as combustion. T is defined as the final temperature attained by the reaction mixture at the completion of a chemical reaction carried out under adiabatic conditions in a closed system at constant pressure. Theoretically, this is the maximum temperature achieved by the products when stoichiometric quantities of reactants are completely converted into products in an adiabatic reactor. In general, T is a function of the initial temperature (T) of the reactants and their relative amounts as well as the presence of any nonreactive (inert) materials. T is also dependent on the extent of completion of the reaction. In actual experiments, it is very unlikely that the theoretical maximum values of T can be realized, but the calculated results do provide an idealized basis for comparison of the thermal effects resulting from exothermic reactions. Lower feed temperatures (T), presence of inerts and excess reactants, and incomplete conversion tend to reduce the value of T. The term theoretical or adiabatic flame temperature (T,, ) is preferred over T in dealing exclusively with the combustion of fuels. 

With steam generated at or close to the boiler design pressure it is inevitable that some of the steam-using equipment will have to be supplied at a lower pressure. In some cases the plant items themselves have only been designed to withstand a relatively low pressure. Sometimes a reaction will only proceed when the steam is at a temperature below a certain level or an unwanted reaction will occur above a certain level. For these and similar reasons, steam often is distributed at a relatively high pressure which must then be lowered, close to the point of use. Pressure-reduction stations incorporating pressure-reducing valves are fitted to perform this function. 

This is one of the simplest applications of the flow of a compressible fluid and it can be used to illustrate many of the features of the process. In practical terms, it is highly relevant to the design of relief valves or bursting discs which are often incorporated into pressurised systems in order to protect the equipment and personnel from dangers which may arise if the equipment is subjected to pressures in excess of design values. In many cases it is necessary to vent gases evolved in a chemical reaction. 

Pressure resistant construction is characterized by a design pressure of a vessel or equipment that is higher than the pressure that can be reached in case of an explosion or runaway reaction. When decomposition of condensed materials need to be considered then it is usually very expensive to realize pressure resistant construction because of the high pressures that can be expected. 

Mod Phys 18, l (1946) (Recent work in the field of high pressure. Review of the entire field between 1930 and 1945 with 647 references) 13) Krase, Design and Construction of High Pressure Compressors and Reaction Equipment, FIAT Final Rept 611 (1945) 14) H. C. 

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