High-pressure disintegration

Meuser, F., Wittig, J., and Huster, H. 1989. Effects of high pressure disintegration of steeped maize grits on the release of starch granules from the protein matrix. Starch/Stdrke 41, 225-232. 

The latest technological developments in wheat starch production are the high-pressure disintegration (HD)53,94-97 and the Tricanter 97 processes. The HD process, which is based on a highly sheared batter and on centrifugal forces for separation, was jointly developed by the Technical University of Berlin and Westfalia Separator. 

Figure 10.2 Flow diagram of the high-pressure disintegration (HD) process. (Adapted from reference 53)...

The disintegration of the degermed grains may be improved by a high-pressure disintegration technique, which is multivalent in its application in starch manufacture. 

Application of the high-pressure disintegration technique shows the same advantages and leads to larger amounts of opened cells (less bound starch in the pulp). 

Plain-orifice atomizers are widely used for injecting liquids into a flow stream of air or gas. The injection may occur in a co-flow, a contra-flow, or a cross-flow stream. The best known application of plain-orifice atomizers is perhaps diesel injectors. This type of injectors is designed to provide a pulsed or intermittent supply of fuel to the combustion zone for each power stroke of the piston. As the air in the combustion zone is compressed by the piston to a high pressure, a very high pressure (83-103 MPa) is required to allow the fuel to penetrate into the combustion zone and disintegrate into a well-atomized spray. 

We have seen earlier in this chapter how the self-assembly of casein systems is sensitively affected by temperature. Another thermodynamic variable that can affect protein-protein interactions in aqueous media is the hydrostatic pressure. Static high-pressure treatment causes the disintegration of casein micelles due to the dismption of internal hydro-phobic interactions and the dissociation of colloidal calcium phosphate. This phenomenon has been used to modify the gelation ability of casein without acidification as a consequence of exposure of hydrophobic parts of the casein molecules into the aqueous medium from the interior of the native casein micelles (Dickinson, 2006). High-pressure treatment leads to a reduction in the casein concentration required for gelation under neutral conditions, especially in the presence of cosolutes such as sucrose (Abbasi and Dickinson, 2001, 2002, 2004 Keenan et al., 2001). 

Loss prevention of polyethylene plants is outlined in Chapter 7.2. The major hazard that can occur is the runaway of the high-pressure reactor and decomposition of ethylene besides fire and disintegration of high-pressure separators, pipes, and compressors. The critical conditions for runaway and ethylene decomposition during homo- and copolymerization are revealed together with the influence of decomposition sensitizers. Relief devices and venting systems are described. 

The major hazard that can occur in the high-pressure polyethylene process is a runaway of the reactor and decomposition of ethylene as well as fires, explosion, and disintegration of high-pressure parts. Although the last incidents are well understood, the reasons for runaway and ethylene decomposition have been evaluated only recently. Experience over twenty years has shown that decomposition mostly takes place in the reactor and in the high-pressure separator, but decompositions have also been reported from ethylene-feed and product lines. 

Typically at this plant, substitution of a gasket is authorized only after calculations ensure the substitution is acceptable. No calculations or authorizations were found. The substitution of a CAF gasket was probably intended as a one-time substitute and it was replaced in kind on each turnaround that followed. The 1/8-inch CAF gasket was theoretically acceptable in this service, but conditions would have required a full pressure test to ensure that the 24 bolts had sealed the gasket properly. Unfortunately, the risk of the gasket disintegrating under a high pressure leak was not appreciated. 

This difference in density values should be ascribed to the physical properties of crystals, At low pressures the crystals of the red form, due to their shape, can be packed more easily in a given space. At high pressures a lower mechanical strength of the yellow crystals plays a part, viz, being disintegrated they more readily fill up the space. 

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