Vessel shapes

Event Group Number Number of Events Explosion Material Source Energy Range (J) Vessel Shape Vessel Mass (kg) Number of Fragments... 

This is valid for the same degree of gas mixture turbulence and the same ignition source and is illustrated in Figure 7-58. Influence of the vessel shape is shown in Figure 7-56. The behavior of propane is considered representative of most flammable vapors including many solvents [54]. The maximum explosion pressure does not follow the cubic law and is almost independent of the volume of a vessel greater than 1 liter. For propane, town gas, and hydrogen, the volume relationship can be expressed ... 

Figure 7-56. Influence on vessel shape on the explosion data of methane. By permission, Bartknect, W., Explosions, 2nd Ed. (1980), Springer-Verlag [54].

Heat transfer panels are generally used to fit onto a process vessel shape and to transfer heat from the panel... 

Decanters are normally designed for continuous operation, but the same design principles will apply to batch operated units. A great variety of vessel shapes is used for decanters, but for most applications a cylindrical vessel will be suitable, and will be the cheapest shape. Typical designs are shown in Figures 10.38 and 10.39. The position of the interface can be controlled, with or without the use of instruments, by use of a syphon take-off for the heavy liquid, Figure 10.38. 

While Gray Yang are not denying the usefulness of such ideas, they consider that too literal an application on the distinction can lead to difficulties. For this reason they tried to unify both theories and this problem is discussed in their paper. They also examined the effect of fuel consumption on thermal explosions, definition of critical conditions and the effects of vessel shapes. Finally, the relationship between thermal explosion criteria and flame theoty described by Belles (Ref 2), as well as detonability limits were pointed out. Comments on the paper of Gray Yang of Profs R.R. Baldwin R. Ben-Aim are given on p 1061 of Ref 3 Refs 1) N.N. Semenov, "Chemical Kinetics... 

Convection blender snbclasses primarily are distingnished by vessel shape ad impeller geometry ... 

However, it is clear that slight variations in vessel shape, etched markings, or external pressure can lead to disagreements as to which thermometer gives the true temperature. Moreover, the reference points chosen to standardize the readings between different thermometers could be subject to disagreements (see Sidebar 2.4), as could the choice of thermometric fluid (e.g., Hg vs. water, each of which has different values of aP in different temperature ranges). Under these circumstances, the choice of the true temperature scale may become subject to non-scientific influences. We therefore seek a universal standard that avoids such arbitrary choices. 

It can be seen that the violence of an explosion with propane is about 1.5 times higher than one with methane, and one with hydrogen is about 10 times higher than one with methane. The explosive behavior of propane is representative of many flammable organic vapors in air. Some important relationships among pressure, temperature, turbulence, and vessel shape are discussed below. 

Effect of vessel shape and increased initial pressure. The maximum explosion pressure in confined vessels is not significantly affected by the volume or shape of the vessel in confined explosions for vessels that approximate the cubic shape, that is, with a ratio of diameter to length (or vice versa) of about 1 1 to 1 1.5. In closed elongated vessels with central ignition, spherical ignition of the flame front will cause the flame to proceed swiftly in an axial direction. In the process, it compresses... 

Sometimes structural modifications inside the mixing vessel are used to establish desired mean flow patterns. Thus draft tubes (B8, P3) may be used to emphasize an up-and-down flow pattern, and special vessel shapes (BIO, L3, P3) may be used for specific applications. 

Most of the chain reactions show such chemical inhibition, and marked inhibition by trace impurities is excellent evidence for a chain reaction. Thus 0.01 mole per cent of O2 is capable of reducing the quantum yield of the H2 + CI2 reaction by 1000 fold.- In a similar fashion free radicals are easily adsorbed on vessel surfaces, and it is common experience to find that a change in vessel shape, in surface/volume ratio (e.g., that obtained by packing the vessel with glass), or the addition of inert gases such as... 

Figure 3.2. Influence of vessel shape and stirring on the US-assisted digestion of potassium carbonate (1 g) in dimethyiformamide in (a) a 100 mi conicai vessei without stirring (b) a 100 mi round-bottomed vessei with stirring (c) a 100 mi conicai vessei with stirring (d) a 250 mi conicai vessei with stirring. (Reproduced with permission of Oxford Chemistry Press, Ref. [2].)...

ALUEUS — is boatlike, otherwise a vessel shaped like a boat. Alueus minor is a vessel of like shape but smaller size. 

CATINUS AREXARIUS — the common sand Coppel, an earthen Vessel, shaped like a round cap, with a rim of three or four fingers broad. Made of some hard earth. 

CUCURBITA - is a Vessel shaped for the most part like an inverted cone. One form is globe-shaped at the bottom another is flat. 

CYMOLIA — White washed Ore, White Silver Litharge, Marl, or Fuller s Earth. CYNNIA, CYMIA, CARORA — A Vessel shaped like an urinal. 

PYRAMIS — Otherwise, a Conical Pan-is a metallic vessel shaped like a pyramid internally, the upper part being broad. The lower part narrows down to a point. The interior is, therefore, like an inverted Cone. The lower part is useful for reducing molten metals to a regulus. 

Imhoff cone—A vessel shaped like a cone used to measure settleable solids. 

It is, however, difficult to see how this difference from cylindrical-bed behavior can be attributed to the vessel shape. A more plausible explanation possibly lies in the small bed depths used by Goltsiker (about 8 in.) since in the absence of a substantial resistance due to the weight of the bed above the inlet region, any disturbance caused by the incoming gas w ould be easily transmitted to the bed surface. 

Between these two extremes the treatment is more complex, and it is difficult to obtain explicit expressions for k. Semenov [48] has shown that it is still possible to use eqn. (7) for spherical and cylindrical vessels with volume initiation, even though the situation is diffusion controlled, provided (i) n is replaced by h, the average concentration of chain centres, and (ii) Hq is multiplied by a small numerical coefficient jj which lies between 0.6 and unity, and depends on the vessel shape and surface, i.e. 

Simple factors such as stirring or vessel shape may influence experimental results. Certainly whether or not the system was open or closed could have a profound effect. In addition, in the case of polyamides, there is the additional possibility of catalysis. 

Convection blenders reorient groups of particles in relation to one another as the result of mechanical movement, for example, caused by a paddle or a plow. As a result, circulation patterns result in this type of blenders. Subclasses of convection blenders are typically defined by vessel shape and impeller geometry. Ribbon blenders (Fig. 30), planetary blenders (Figs. 31 and 32), orbiting screw blenders (Fig. 33) are examples of convection blenders. High shear mixers comprise another sub-class of convection blenders that will be discussed separately. 

Recommended impeller diameter-to-tank diameter D/T) ratios, for liquid-liquid operations vary from 0.25 to 0.40 for radial disk turbines, from 0.4 to 0.6 for hydrofoils and propellers, and from 0.5 to 0.8 for retreat-curve, glassed-steel impellers. Vertical placement of the impeller depends on the vessel shape and the application. For dispersion by continuous addition of a dense phase fluid into a less dense fluid, the impeller should have a relatively small impeller clearance off the reactor bottom, C, with respect to the final height of the dispersion, H, i.e., the impeller should be placed low in the vessel (C H/A to H/S). For dispersion of light liquids, it is good practice to place a single impeller between 0.20 < C/H < 0.50. 

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