Oxygen injection nozzle

Figure 13.4 DSM transonic oxygen injection nozzle. (Courtesy DSM.)...

Besides thermal degradation of molecules, there is also degradation resulting from oxidation arising through contact between molten plastic and oxygen in the air. PA plastics are particularly sensitive to this. An air bubble may get into the HR following removal of the injection nozzle, or into the injection cylinder as a result of decompression. 

Within the frame of the present first series of experiments it was almost always oxygen which was injected into supercritical water-methane mixtures. There were several reasons for this first choice. One of these was the desire, to study rich flames and their possible products first. Often the water to methane mole fraction ratio was 0.7 to 0.3. But mixtures down to a methane mole fraction of 0.1 were also used. It was possible, however, to inject oxygen and methane simultaneously into the supercritical water and produce a flame. Not possible was the production of true premixed flames. After a retraction of the thin inner nozzle capillary of the burner (see Fig. 1 b) the two gases could be mixed just below the reaction cell, but the flame reaction proceeded from the nozzle tip in the cell back towards this mixing point immediately. 

In the 1940 s a CVD process using a flame to produce homogeneously nucleated (powder) oxides of titanium, zirconium, iron, aluminum, and silicon was reported. A mixture of metal halide vapor and oxygen is injected through the central nozzle of a burner, with fuel gas and supplemental oxygen provided through two concentric outer rings. At 950°C to 1100 C flame temperature, the metal halide vapor decomposes to form very fine oxide powders. 

Fig. 3.58 Schematic of a flame assisted spray p5oolysis (FASP) reactor consisting of a two-fluid nozzle for atomizing the liquid precursor with oxygen and a cylindrical torus (FASP) ring with boreholes to inject and combust C2H2 with the precursor solution spray. The ring was located at 1 cm above the nozzle and the spray was shielded from air entrainment by a tube. Reproduced with permission from [317], Copyright 2013, Elsevier...

Molecular iodine is injected transverse to the primary oxygen flow near the throat of a supersonic nozzle, as shown in Fig. 11. The molecular iodine is rapidly dissociated to atomic iodine by the presence of the singlet oxygen in a complex, multistep mechanism. The flow is fully dissociated as it reaches the exit plane of the nozzle and before entering the gain region. 

FIGURE 11 Supersonic mixing nozzle for a COIL where molecular iodine is injected transverse to the flow of singlet oxygen. 

The presence of ether-oxygen linkages gives the polymer chain flexibility to permit fabrication by conventional melt-processing techniques. The polymer can be injection molded, provided the cylinder and nozzle are capable of reaching 425 C. It also may be extruded. The polymer must be dried before processing. Injection molding barrel temperatures should be 270-360°C at the rear, 295-390°C in the middle, and 300-395°C at the front. 

A nozzle level only for steam injection provides the minimum fluidization (bed voidage >0.4) and permits an independent moderator supply. Further nozzle levels for the injection of steam and oxygen are situated above it [125,137]. 

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