Tower dimensions

The propylene fractionator operates at a pressure of 1.8 to 2.0 MPa with more than 160 trays required for a high purity propylene product. Often a two-tower design is employed when polymer grade (99.5%+) is required. A pasteurization section may also be used when high purity is required. The bottoms product contains mainly propane that can be recycled to the cracking heaters or used as fuel. Typical tower dimensions and internals for a 450,000 t/yr ethylene plant with naphtha feed are summarized in Table 7. 

Overview One of the most important considerations involved in designing gas-absorption towers is to determine whether or not temperatures will vaiy along the length of the tower because of heat effects, since the sohibility of the solute gas normally depends strongly upon the temperature. When heat effects can be neglected, computation of the tower dimensions and required flows is relatively straight-... 

Mechanical-draft cooling towers are normally supplied with either central baffles or inlet louvers. This depends on the tower dimensions. On these towers the wind or spray blowout is generally confined to relatively small singlecell units where an inlet may be provided on all four faces. In this case the major remedy is to provide internal diagonal baffles to prevent crossflow of air through the air inlets. 

Recirculation, Fogging These are major problems. Design accommodation, restrictions on tower dimensions, orientation with prevailing winds, and added capacity for recirculation can boost tower cost. Because of its elevated discharge, the natural-draft tower rarely has the trouble with recirculation and fogging. 

The two principal tower dimensions to be determined are the cross-sectional area and the free-fall height. Restraints which must be considered in sizing the cross-sectional area include ... 

Overall Tower Dimension, L x W, ft. Height-Basin Curb to Fan Deck, ft. 

If, on the other hand, the equilibrium solute concentration C is very low, leading to a correspondingly low value for Cj in equation (10.1), the energy and capital costs associated with the recompressor can become major factors in determining the separation cost. This will be seen to be the case, for example, in the hypothetical process for extracting crushed rape seed with subcritical carbon dioxide which is considered in section 10.6. It would also be true of the extraction of caffeine from coffee beans if pressure reduction was used to recover the caffeine. In cases such as these the most economic flow conditions and tower dimensions will be such that Ct is quite close to the equilibrium value C. ... 

The installed capital costs for stainless steel and mild steel compressors were estimated from equations (10.5a) and (10.5b) (with W given by equation 10.13) and are given in Table 10.5. Installed costs of the extraction towers and separator unit were estimated from equations (10.6) and (10.9) or, outside the range of these equations, from the original graphs in reference [14]. Before tower cost can be estimated, tower dimensions are required. 

Selection of optimum tower dimensions. The following procedure was used to calculate the optimum tower dimensions and solvent superficial velocity. At each of a set of values of Us... 

The above procedure was repeated for annual production rates A of 5000, 5000/3 and 75 tonnes/annum, the values of Us, hr and d giving the lowest h selected in each case. Results are summarised in Table 10.3. It may be seen from this table that at the two lower production rates capital costs show shallow minima at superficial velocities close to 1.1 cm s This velocity with the corresponding tower dimensions was selected as the optimum for these production rates, consistent with the chosen value (8 hours) for At2. 

The IFP process may be combined with a Claus unit in a variety of ways as shown in Tables 9-28 and 9-29. Since operation of the proce.ss is based on physical solubility (i.e., partial pressure) of hydrogen sulfide and sulfur dioxide in the solvent, the solvent flow rates and tower dimensions are essentially the same for a relatively wide range of hydrogen sulfide and sulfur dioxide concentrations in the feed gas. This enables the process to compensate for Claus plant upsets. 

Ambient Vibration Testing of Cultural Heritage Structures, Fig. 1 (a) View of the bell tower of C eia Collegiata (Arcisate, Varese) (b) crack patterns on the fronts of the tower (dimensions in m)... 

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