Quality control, recycling technology

In fact, achieving homogeneity with recyclates, especially mixed materials, is difficult and sometimes impossible. The technology of reprocessing recycled plastics still has a way to develop. This means that quality control for recyclates is every bit as necessary as for virgin material. 

As discussed in this book, industrial costs could be greatly reduced by introducing more effective tools. Insulation, recycling, coating technology, quality control allowed improving the industrial process. 

Several pollution control technologies at the refinery promote cross-media transport, the transfer of pollutants from one medium to another. Wastewater, for example, may contain hydrocarbons that volatilize into the air at the refinery, the wastewater treatment plant converted these waterborne hydrocarbons into 2400 tons/year of sludge, which were recycled to the coker. Cross-media transport from air to water is not significant for hydrocarbons or chemical that are only slightly soluble in water (Allen et al, 1989). Studies performed by the National Center for Intermedia Transport at the University of California, Los Angeles, for instance, showed that most hydrocarbons released into the air do not transfer rapidly into other media. Therefore, ignoring intermedia transfer when examining air quality impacts is a reasonable analytical approach. Water-soluble compounds, such as methanol and MTBE, can transfer from air into water and soil media under certain conditions (Cohen et al., 1991). 

The quality of the intermediate DCE must fulfil strict purity specifications. Low impurity levels imply high energetic consumption, but higher impurity amounts are not desired for operation. The intermediate DCE is conditioned mainly in the distillation column S2. In the bottom product the concentration of the two bad impurities E and E must not exceed an upper limit, of 100 and 600 ppm, respectively, while the concentration of the good impurity E must be kept around optimal value of 2000 ppm. Because these impurities are implied in all three reaction systems through recycles that cross in the separation system, their inventory is a plantwide control problem. The problem is constraint by technological and environmental constraints, as mentioned. 

Post-consumer plastic color-measurement technology control is used in recycling of post-consumer plastics (PCPs). As the demand increased for consistent natural and other colors of particularly recycled PET and HDPE, the need for standardization and codification of color measurement based on analytical data continued to be critical. In the past the human eye was the only means of determining color quality. Samples... 

The flow sheet of the technical process is shown in Figure 13.4. For a comprehensive description of critical steps of this technology, see Refs. 14 and 15 the main points are control of the solid-liquid reaction between the glucose and the fatty alcohol with acidic catalysis avoiding a fast polymerization of glucose, the good water removal, the economic separation and recycle of the excess fatty alcohol, and the treatment of the highly viscous APG melt to get the desired product quality with low polydextrose content. 

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