Section 10.1 Process Vessels

A flammable vapor explosion in a vessel initially at atmospheric pressure can create a pressure of 10 atmospheres (NFPA 69, 1992, Section 5-3.3.1). A weak process vessel requires substantial vent area for vapor-air explosion relief. 

For examples of the output files refer to Section 7.4 for the example of analyzing a faiill Ircc for a chemical process vessel rupture. 

Pipes or dncts connected to a vessel in which a deflagration can occnr also need deflagration protection. Snch protection can be accomplished by installing a vent on the pipe with an area eqnal to the cross-sectional area of the pipe or dnct. It shonld be located on the pipe or dnct no more than two pipe or dnct diameters from the point of connection to the process vessel or eqnipment. 

OSHA 1910.106 (based on die 1969 edidon of NFPA 30) and NFPA 30 (2000) designate where conservation vents and flame arresters may be needed on storage tanks or process vessels containing flammable or combustible liquids at atmospheric pressure. Sections (b)(2)(iv)(f) and (g) of OSHA 1910.106 state as follows ... 

Calculate section by section from the process vessel to the vacuum pump (point of low est absolute pressure). 

A shell of revolution is the form swept out by a line or curve rotated about an axis. (A solid of revolution is formed by rotating an area about an axis.) Most process vessels are made up from shells of revolution cylindrical and conical sections and hemispherical, ellipsoidal and torispherical heads Figure 13.3. 

The ASME Boiler and Pressure Vessel Code, Section VIII, is the standard resource for the design, fabrication, installation, and testing of storage tanks and process vessels rated as pressure vessels (i.e., above 15-psig design). ASME B31.3 is a basic resource for process piping systems. 

Fire protection can be provided to process vessels with either manual firefighting or fixed water spray systems. Manual firefighting with monitors and hoses can be used to protect process vessels against exposure to fire. See Chapter 7, Section 7.4.3. If water spray is used, it should be applied to all outer surfaces at a rate of 0.25 gpm/ft (10 Ipm/m ) of projected (surface) area. See Chapter 7, Section 7.4.8. Multiple nozzles are typically required. Where water spray from upper nozzles can flow down the sides of the vessel, the nozzles or... 

As far as the actual use of these expressions in their most general form, Eqs. (36) and (37), probably the only case which need be considered is that represented by the bottom sketch of Table II. Here measurements are taken only on either side of the test section. This type of measurement could be used to find the dispersion characteristics of a process vessel in a plant where no means are available for inserting a probe inside the vessel. With these equations, measurements need be taken only on either side of the text section. 

In Claude s 1 process compressed air, cooled by passage through a coil surrounded by the cold gases issuing from other parts of the apparatus, enters the lower portion of the apparatus (fig. 5) at A where it reaches the inner part of the tubular vessel B of annular cross-section this vessel is surrounded by liquid oxygen. 

In this chapter we discuss important issues as we move from laboratory to pilot plant and manufacturing. A review of batch process operation and pharmaceutical research is covered in Section 3.1.2, followed by laboratory vessels and reaction calorimetry in Section 3.1.3. In Section 3.1.4 heat transfer in process vessels is presented, including the effect of reactor type and heat transfer fluid on the vessel heat transfer capability. In Section 3.1.5 dynamic behavior based on simulation studies is discussed. 

Based on initial heat flow calorimetry studies, a process development engineer must choose the appropriate reactor vessels for pilot plant studies. A pilot plant typically has vessels that range from 80 to 5000 L, some constructed of alloy and others that are glass lined. In addition some vessels may have half-pipe coils for heat transfer, while others have jackets with agitation nozzles. A process drawing for a typical glass-lined vessel is shown in Figure 4. In Sections 3.1.4.1 and 3.1.4.2 we review fundamental heat transfer relationships in order to predict overall heat transfer coefficients. In Section 3.1.4.3 we review experimental techniques to estimate heat transfer coefficients in process vessels. 

Opening of equipment for maintenance can result in loss of product. Where possible, the liquid should be blown into the previous or next process vessel or drained back into a bucket for recovery. Any product that is recovered that is not badly contaminated can be returned to a separate storage tank upstream in the process. If a substandard or off-spec glycerine tank is provided in the refining section, it can be equipped with an easily removable cover. 

A structure must be designed to resist gross plastic deformation and collapse under all the conditions of loading. The loads to which a process vessel will be subject in service are listed in this section. They can be classified as major loads, which must always be considered in vessel design, and subsidiary loads. Formal stress analysis to determine the effect of the subsidiary loads is required only in the codes and standards where it is not possible to demonstrate the adequacy of the proposed design by other means, such as by comparison with the known behavior of existing vessels. 

The next issue is the formulation of appropriate boundary conditions. The availability of suitable boundary conditions may also affect the decision concerning the extent of the solution domain. Obviously in practice, the inlet and outlet of any vessel will be connected to the associated pipe work. It is essential to decide the extent of the solution domain in such a way that it does not affect the simulated results. Generally for high velocity inlets, conditions in the process vessel do not affect the flow characteristics of the inlet pipe, and therefore it is acceptable to set the inlet boundary conditions right at the vessel boundary. More often than not, some piping at the outlet section may have to be considered if the outlet boundary condition is to be used. Alternatively, one may use constant pressure boundary conditions. Possible boundary conditions and solution domain are shown in Fig. 6.13. Before examining the influence of the solution domain on the simulated results, it is necessary to identify an adequate number of grids to resolve all the major features of the flow. 

At each node in a process (vessel or pipe section), possible deviations in process variables (such as temperature) from the design intent are formed by combinations of variables and guide words (such as more or high ), to determine the adequacy of existing systems to prevent hazardous deviations. 

In this chapter we will apply to typical process vessels the equations for the conservation of mass and of energy that were derived in Chapter 3, Sections 3.4, 3.S and 3.6. We will begin with the simplest system, namely accumulation of liquid at a constant temperature, and build up to consider more complicated systems where both a liquid and a gas are present, and where the temperature of each phase varies. In each case a full set of equations wilt be developed, and the solution cycle will be outlined. 

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