Stabilized processing time

The as-spun acrylic fibers must be thermally stabilized in order to preserve the molecular structure generated as the fibers are drawn. This is typically performed in air at temperatures between 200 and 400°C [8]. Control of the heating rate is essential, since the stabilization reactions are highly exothermic. Therefore, the time required to adequately stabilize PAN fibers can be several hours, but will depend on the size of the fibers, as well as on the composition of the oxidizing atmosphere. Their are numerous reactions that occur during this stabilization process, including oxidation, nitrile cyclization, and saturated carbon bond dehydration [7]. A summary of several fimctional groups which appear in stabilized PAN fiber can be seen in Fig. 3. 

Often, the immobilized product has a structural strength sufficient to prevent fracturing over time. Solidification accomplishes the objective by changing a non-solid waste material into a solid, monolithic structure that ideally will not permit liquids to percolate into or leach materials out of the mass. Stabilization, on the other hand, binds the hazardous constituents into an insoluble matrix or changes the hazardous constituent to an insoluble form. Other objectives of solidiflcation/stabilization processes are to improve handling of the waste and pri uce a stable solid (no free liquid) for subsequent use as a construction material or for landfilling. 

Create stability and minimize variance Eliminate complexity and reduce processing time Benchmark current performance Focus attention on quality... 

Chapter 2 is employed to provide a general introduction to signal and process dynamics, including the concept of process time constants, process control, process optimisation and parameter identification. Other important aspects of dynamic simulation involve the numerical methods of solution and the resulting stability of solution both of which are dealt with from the viewpoint of the simulator, as compared to that of the mathematician. 

The few examples where SILP catalysis has been tested so far showed highly encouraging results. It is very likely that other applications where ionic catalyst solutions were tested in liquid-liquid biphasic reactions could be reinvestigated under SILP conditions. If very high catalyst stability over time can be realised or simple catalyst regeneration protocols can be developed than SILP catalysis can be expected to make its way into industrial processes. 

The hydration state of risedronate sodium was monitored continuously in a fluidized bed dryer and correlated to data on the physical stability of tablets made from the monitored material [275]. The final granulation moisture was found to affect the solid-state form, which in turn dictated the drug s physical stability over time. The process of freeze-drying mannitol was monitored continuously with in-line Raman and at-line NIR spectroscopies [276]. The thin polymer solvent coatings, such as poly(vinyl acetate) with toluene, methanol, benzene, and combinations of the solvents, were monitored as they dried to generate concentra-tion/time profiles [277]. 

The glass coating process requires high gas flows for the sputter processes as well as low hydrocarbon concentration. The only vacuum pump which satisfies these requirements as well as high pumping speed stability over time are turbo-molecular pumps which are used almost exclusively. 

The estimated operating costs were 6510/m of treated waste. This estimate inclnded binder costs of 85 cents per pound the labor costs eqnivalent to 4 fnll-time technicians at 70 per honr and the cost of the 55-gal barrels at 100 per barrel nsed to mix, cnre, store, and dispose of the waste. The operating costs of the baseline cement stabilization process are lower at 4300/m of treated waste (D20934H, p. 15). 

The introduction of autoclaves, which considerably reduced the time required for boiling, brought about a marked improvement in commercial methods of stabilization. The high installation costs for the high pressure system are fully compensated by the very much shorter stabilization process. 

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