Ejector internals

To obtain the design vacuum from ejectors, the design steam pressure must be maintained. Since the ejector internals are not adjustable, the steam... 

If an ejector is not overloaded at a normal gas rate, reducing the gas load will not result in greatly improved vacuum. The ejector is simply oversized at the lower charge rate and wastes steam without obtaining any appreciable benefit in lower vacuum tower pressure (see Chapter 13). To save this wasted steam, new ejector internals are needed. The internals... 

Air leaks (CO, CO2, or O2) Noncondensable hydrocarbons Worn ejector internals Low motive steam pressure of temperature Wet motive steam Fouled condenser... 

The compressor can be driven by electric motors, gas or steam turbiaes, or internal combustion (usually diesel) engines. The compressor can also be a steam-driven ejector (Fig. 7b), which improves plant reUabiUty because of its simplicity and absence of moving parts, but also reduces its efficiency because an ejector is less efficient than a mechanical compressor. In all of the therm ally driven devices, turbiaes, engines, and the ejector mentioned hereia, the exhaust heat can be used for process efficiency improvement, or for desalination by an additional distillation plant. Figure 8 shows a flow diagram of the vertical-tube vapor compression process. 

A further source of stress may arise from incorrect mould design. For example, if the ejector pins are designed in such a way to cause distortion of the mouldings, internal stresses may develop. This will happen if the mould is distorted while the centre is still molten, but cooling, since some molecules will freeze in the distorted position. On recovery by the moulding of its natural shape these molecules will be under stress. 

As a result of their form, hollow stirrers utilize the suction generated behind their edges (Bernoulli effect) to suck in gas from the head space above the liquid. As rotating ejectors , they are stirrers and gas pumps in one and are therefore particularly suitable for laboratory use (especially in high pressure autoclaves) because they achieve intensive gas/liquid contacting via internal gas recycling without a separate gas pump [58/1]. A particularly effective type of this stirrer - the pipe stirrer - is depicted in Fig. 28. 

Description Ammonia and carbon dioxide react at 155 bar to synthesize urea and carbamate. The reactor conversion rate is very high under the N/C ratio of 3.7 with a temperature of 182-185°C. Unconverted materials in synthesis solution are efficiently separated by C02 stripping. The milder operating condition and using two-phase stainless steel prevent corrosion problems. Gas from the stripper is condensed in vertical submerged carbamate condenser. Using an HP Ejector for internal synthesis recycle, major synthesis equipment is located on the ground level. 

Removal is generally performed by automatic ejectors, which are operated by the machine when the mold opens in the parting plane at the end of the injection molding cycle. These ejectors ensure, that the article is separated from the surrounding cavity in spite of imdercuts, adhesive forces, and internal stresses which tend to retain the part within the cavity. 

Many options are available besides the traditional liquid gravity spray into a vessel filled with gas. These include options where the liquid is pumped through a jet or spray nozzle. Venturi jet the liquid and gas are mixed in the venturi. Plunging jet (buss loop reactor) vertical column filled about 2/3 with liquid, no internals. Liquid is withdrawn at the bottom and liquid is pumped into a top-mounted jet that induces air and resulting mix impinges vertically under the top surface of the liquid. (This is in contrast with the jet loop, Section 6.13, where the ejector is at the bottom of the liquid column.)... 

The ejector-based reactor can be constructed in various configurations. Firstly, the jet can be either upflow or downflow, hi this book, only the downflow type is considered. In this type, the venturi loop reactor can be with or without a draft mbe. In case there is a draft tube, there is an additional internal circulation loop within the reactor. An outer circulation loop already exists because the hquid + catalyst slurry is continuously recycled by the external pump through the heat exchanger and the primary nozzle. 

Steam jet vacuum equipment is very reliable. However, unsatisfactory performance of an ejector can be caused by external or internal causes. Unsatisfactory performance can also be classified as sudden or gradual. The gradual loss of vacuum will normally suggest internal erosion or corrosion a sudden loss of vacuum will normally suggest external causes. Since it is easier to check external causes of trouble, all possible external causes should be checked first. 

SOFC systems can be designed to include a heat recovery component such as an adsorption chiller heater for CHP applications [72-76]. An example is a small (1-lOkW) methane-fueled residential CHP SOFC system that integrates CGR, AGR, and internal reforming [73]. The system consists of a fuel-cell stack, steam prereformer, various fluid delivery devices (blowers, ejectors, compressor, and water pump), heat exchangers, and catalytic combustor and power conditioning device along with a heat recovery component. Based on certain system parameters (50active area, nominal cell temperature of 800 °G, current density of 0.57 A cm , power density of0.40-0.43 Wcm , S/G ratio of 2.0, SOFC... 

The residue from an atmospheric distillation tower can be sent to a vacuum distillation tower, which recovers additional liquid at 0.7 to 1.5 psia (4.8 to 10.3 kPa). The vacuum, which is created by a vacuum pump or steam ejector, is pulled from the top of the tower. Relative to atmospheric columns, vacuum columns have larger diameters and their internals are simpler. Often, instead of trays, random packing and demister pads are used. 

After opening the mold, the molded part usually remains on the ejector half. Undercuts (lateral breakthroughs), bosses, offset or internal threads require additional moving mold parts. 

EFFECT ON POLYMER AND/OR OTHER ADDITIVES Figure 11.1 shows the effect of cetyl stearate on the reduction of the ejection force. Figure 11.2 shows the effect of an internal release agent on some mechanical properties. The combinations of ester type release agents, such as discussed in Figures 11.1 and 11.2, were patented." Silicone oil sprayed on a mold surface was found to reduce ejection force in the consecutive shots, but ejection force increased by about 20% in 10 shots following spray application. Ejector pin pressure was reduced by about 50% with the addition of 3,000 ppm of paraffin wax, or 3,000 ppm behenate with 30 ppm of stearic acid. A polymeric resin... 

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