Feed casing

Hoechst WHP Process. The Hoechst WLP process uses an electric arc-heated hydrogen plasma at 3500—4000 K it was developed to industrial scale by Farbwerke Hoechst AG (8). Naphtha, or other Hquid hydrocarbon, is injected axially into the hot plasma and 60% of the feedstock is converted to acetylene, ethylene, hydrogen, soot, and other by-products in a residence time of 2—3 milliseconds Additional ethylene may be produced by a secondary injection of naphtha (Table 7, Case A), or by means of radial injection of the naphtha feed (Case B). The oil quenching also removes soot. 

Feed Composition. Feed composition has a substantial effect on the economics of a distillation. Distillations tend to become uneconomical as the feed becomes dilute. There are two types of dilute feed cases, one in which the valuable recovered component is a low boiler and the second when it is a high boiler. When the recovered component is the low boiler, the absolute distillate rate is low but the reflux ratio and the number of plates is high. An example is the recovery of methanol from a dilute solution in water. When the valuable recovered component is a high boiler, the distillate rate, the reflux relative to the high boiler, and the number of plates all are high. An example for this case is the recovery of acetic acid from a dilute solution in water. For the general case of dilute feeds, alternative recovery methods are usually more economical than distillation. 

Turn the controller on, repeat Exercise 1 and note the differences in results compared with the constant feed case of Exercise 1. 

In order to see if the system could provide the flexibility to evaluate high modulus polymer pellets, an initial comparison of an HDPE and PS resins were evaluated. The experiments were conducted at a screw speed of 50 rpm and barrel temperatures of 24 and 35 °C for the HDPE and PS resins, respectively. The temperature of the screw was maintained at the barrel temperature. These conditions are similar to what might be observed in the feed casing and very early into Section 2. As... 

Several of the most commonly used resins were studied at a screw and barrel temperature of 35 °C. As previously discussed, this temperature condition is comparable to the conditions in the feed casing or Section 1. This is just the start of solids conveying as conveying continues into Section 2 where the inside barrel wall temperatures are considerably higher. In order to visualize the contrast between the six different polymers tested, the solids conveying rates as a function of discharge pressure for these select resins are presented in Fig. 5.14. 

Grooved bore extruders have several disadvantages [42]. These include high levels of wear in the feed casing and especially on the edges of the grooves. The wear... 

Figure 5.33 Schematic of a water cooled grooved barrel feed casing. The grooves are axial (courtesy of Jeff A. Myers of Robert Barr, Inc.)...

The iead iength was 124 mm for the main flight of the barrier section and 88.9 mm for all other sections of the screw. The main flight width and clearance were 9 and 0.09 mm, respectively, in all sections of the screw. The first 2.5 diameters of the screw were inside a water-cooled feed casing. The compression ratio was 2.7 and the compression rate was 0.0050. The specific rotational rate was calculated at 2.51 kg/(h-rpm). ... 

Flow Surging Due to High Temperatures in the Feed Casing... 

Figure 12.18 Screw speed and motor current for a large-diameter extruder with a feed casing...

Lead iength, flight width, and flight ciearance were 76.2, 6, and 0.06 mm, respectiveiy, for aii sections of the screw. The first 2.5 diameters of the screw were inside a water-cooied feed casing. 

Flow Surging Caused by a Worn Feed Casing and a New Barrel... 

Figure 12.27 The solids-conveying section of a single-screw, plasticating extruder with a worn feed casing. The schematic is not to scale, and it shows a ledge formed between the oversized (worn) feed casing and the flange of a new barrel...

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