Impingement mixing equipment

In many instances, one wishes to produce solid parts so as to maximize the toughness of the product. In some cases, the economics of the busines will not permit the high cost and process sophistication of reaction injection molding equipment. Low-pressure casting is then the process of choice. Casting machine prices are usually 20 to 50% of those of RIM machines. They are typically smaller and simpler machines. They use static or dynamic mixers rather than impingement mix heads. 

Anotlier cause of water hammer is lack of proper drainage ahead of a steam control valve. When the valve opens, a slug of condensate will enter the equipment at a high velocity, producing water hammer when it impinges on the walls. In addition to this, the mixing of the steam that follows wifli the relatively cool condensate will... 

Sizing, 451, 453, 455, 459, 462 Sonic flow, 461 Types, illustrations, 411-421 Rupture disk, liquids, 462, 466 Rupture disk/pressure-relief valves combination, 463 Safely relief valve, 400 See Relief valve Safety valve, 400, 434 Safety, vacuum, 343 Scale-up, mixing, 312, 314—316 Design procedure, 316-318 Schedules/summaries Equipment, 30, 31 Lines, 23, 24 Screen particle size, 225 Scrubber, spray, 269, 270 Impingement, 269, 272 Separator applications, liquid particles, 235 Liquid particles, 235 Separator selection, 224, 225 Comparison chart, 230 Efficiency, 231... 

Binder liquid should wet the solid particles and not the interior walls or the mixing tools of the equipment. If parts of the mixer are wetted, build-up occurs which is difficult to remove. Different spray patterns are available with commercially available single or two phase nozzles (Fig. 7.22c and 7.23) and a suitable pattern should be selected to assure that liquid impinges only on the moving powder. Since the spray pattern depends critically on the cleanliness of the orifice area, as mentioned before, nozzles must be drip free and installed such that they remain clean or are blown free by the action of atomizing gas. This is particularly important for low capacity nozzles which are often preferred because the binder liquid should be always completely ab-... 

Two-impinging-jets are also used in reaction-injection-molding processing equipment to provide good micromixing for viscous fluids [3-6]. It is one of the techniques used to reduce the timescale of micro-mixing in precipitators [6]. 

The process can be broken down into several unit operations, as shown in Fig. 6.6. A necessary condition for the success of easy mixing by impingement is that the reactants each possess low viscosity also only low pressures are needed to fill the mould and this reduces the costs of capital equipment, especially for large parts, which makes RIM economically attractive compared with a typical thermoplastic injection-moulding process. A comparison of RIM and thermoplastic injection moulding is shown in Table 6.5. 

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