Mechanism design

The reactor products are so hot or corrosive that if passed directly to a heat exchanger, special materials-of-construction or an expensive mechanical design would be required. 

Mechanical Considerations. The mechanical design of a fan and the various forces that fan parts must withstand are discussed ia Reference 14. The forces result from a combination of fluid, iaertial, and vibrational effects. 

Figure 13 shows two pipe distributors, one in a branched and one in a ring configuration. These distributors minimize weeping, have good turndown, may requite the lowest pressure drop, and avoid the need for a plenum chamber. They are also well suited to multiple-level fluid injection. The disadvantages of these distributors are that there are defluidized soHds beneath the distributor and the mechanical design is more complex. 

Mechanical Design Data, Teflon Fluorocarbon Kesins, bulletin, E.I. du Pont de Nemours Co., Inc. Wilmington, Del. Sept. 1964. 

Gas-Heated Reforming. Gas-heated reforming is an extension of the combined reforming concept where the primary reformer is replaced by a heat-transfer device in which heat for the primary reforming reaction is recovered from the secondary reformer effluent. Various mechanical designs have been proposed which are variants of a shell-and-tube heat exchanger (12,13). 

Materials and Reactions. Candle systems vary in mechanical design and shape but contain the same genetic components (Fig. 1). The candle mass contains a cone of material high in iron which initiates reaction of the soHd chlorate composite. Reaction of the cone material is started by a flash powder train fired by a spring-actuated hammer against a primer. An electrically heated wire has also been used. The candle is wrapped in insulation and held in an outer housing that is equipped with a gas exit port and rehef valve. Other elements of the assembly include gas-conditioning filters and chemicals and supports for vibration and shock resistance (4). 

Is steam superheat maintained at the maximum level permitted by mechanical design ... 

P. E. Glascow and A. A. Murica, "Process and Mechanical Design Considerations for ECC Regeneration Air Distributors," presented at Katalistiks... 

It is likely that there will always be a distinction between the way CAD/CAM is used in mechanical design and the way it is used in the chemical process industry. Most of the computations requited in mechanical design involve systems of linear or lineatizable equations, usually describing forces and positions. The calculations requited to model molecular motion or to describe the sequence of unit operations in a process flow sheet are often highly nonlinear and involve systems of mixed forms of equations. Since the natures of the computational problems are quite different, it is most likely that graphic techniques will continue to be used more to display results than to create them. 

Process simulators stop generally at the process specifications for the equipment. For the detailed mechanical design of the equipment, such as heat exchangers and distillation columns, stand-alone programs are often used. They make process calculations, size the equipment, calculate thermal and mechanical stresses, design mechanical support of the parts of the equipment, design inlet and outlet nozzles, etc. 

The mechanical design of the idler roUs is a function of the particular service under which the conveyor operates. Minimum industrial standards for roU dimensions, bearings, and appHcation criteria for different service conditions have been estabHshed (14). Idler life is deterrnined by a combination of factors such as bearings, seals, shell thickness, load density, and the operating environment. 

Single-stage or two-stage cooling is used to achieve the desired degree of cooling. These alternatives achieve the same thermal efficiency, but offer different approaches to low pressure drop operation and mechanical design. 

It is advisable in most of these cases to use accelerometers. Displacement probes will not give the high-frequency signals and velocity probes because their mechanical design is very directional and prone to deterioration. Figure 10-64 shows me signal from the various types of probes. 

Sohds in divided form, such as powders, pellets, and lumps, are heated and/or cooled in chemical processing for a variety of objectives such as solidification or fusing (Sec. 11), drying and water removal (Sec. 20), solvent recoveiy (Secs. 13 and 20), sublimation (Sec. 17), chemical reactions (Sec. 20), and oxidation. For process and mechanical-design considerations, see the referenced sections. 

The mechanical-design reqmrements are identical for all three classes of construclion. The differences between the TEMA classes are minor and were hsted by Rubin [Hydrocarbon Proce.ss., 59, 92 (June 1980)]. 

Thermal and mechanical design of heat exchangers (condensers and evaporators) is presented earlier in this section. 

The plate thickness of bubble-cap and sieve plates is generally estabhshed by mechanical design factors and has little effect on pressure drop. For a sieve plate, however, the plate is an integral component of the vapor-dispersion system, and its thickness is important. 

In any event, the users of the mixer can issue a mechanical specification aud determine the speed, diameter of an impeller, aud power with in-house expertise. Or they may issue a processes specification which describes the engineering purpose of the mixing operation and the vendor will supply a description of the mixer process performance as well as prepare a mechanical design. 

Scale-Up of Batch Mixers The prime basis of scale-up of batch mixers has been equal power per unit volume, although the most desirable practical criterion is equal blending per unit time. As size is increased, mechanical-design reqmrements may hmit the larger mixer to lower agitator speeds if so, blend times will be longer in the larger... 

FIG. 18-91 Rake-mechanism designs employed for specific duties. (EIMCO Process Equipment Co.)... 

Bowl Desilter The bowl desilter provides for separation areas vv ell bevond areas possible in bowl classifiers, in which larger sizes are limited bv mechanical design. Its use is in operations involving large flow volumes and fine separations. Rake tonnages can be great or small with a devv atering compartment to suit the conditions. 

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