Refining and Evaporation

FIGURE 13.5 Flowchart of industrial processes to produce high-fructose maize syrups. 13.5.4 Refining and Evaporation 

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Distillation data may be expressed in two ways the percent evaporated at a given temperature (Exxx) or the temperature for a given percent evaporation (T ). Because Exxx values blend linearly, these are generally preferred by refiners and blenders. Gasoline performance specifications have been reported in both ways. ASTM specifications generally prefer the format. 

Now you can reconsider the material balance equations by adding those additional factors identified in the previous step. If necessary, estimates of unaccountable losses will have to be calculated. Note that, in the case of a relatively simple manufacturing plant, preparation of a preliminary material-balance system and its refinement (Steps 14 and 15) can usefully be combined. For more-complex P2 assessments, however, two separate steps are likely to be more appropriate. An important rule to remember is that the inputs should ideally equal the outputs - but in practice this will rarely be the case. Some judgment will be required to determine what level of accuracy is acceptable, and we should have an idea as to what the unlikely sources of errors are (e.g., evaporative losses from outside holding ponds may be a materials loss we cannot accurately account for). In the case of high concentrations of hazardous wastes, accurate measurements are needed to develop cost-effective waste-reduction options. It is possible that the material balance for a number of unit operations will need to be repeated. Again, continue to review, refine, and, where necessary, expand your database. The compilation of accurate and comprehensive data is essential for a successful P2 audit and subsequent waste-reduction action plan. Remember - you can t reduce what you don t know is therel... 

In particular, the French were trying to use the steam from sugar boilers to heat sugar juice in a vacuum and evaporate the solution at low temperatures. A vacuum lowers the atmospheric pressure on the water s surface as a result, the water molecules can escape as steam at a lower temperature. The amount of latent heat needed to turn water into steam is nearly the same whether the water is in a vacuum or at atmospheric pressure. However, in the refining process, some heat escapes into the environment. Keeping water at a lower temperature reduces the amount of this lost heat and makes for a more efficient and potentially more profitable operation. 

As this ratio (Fig. 3) tends to decrease with increasing temperature, the best separations are achieved at the lowest temperatures, which on the other hand, lead to low evaporation rates. The refining temperature is a compromise between the ratio of the vapour pressures and evaporation kinetics e.g. 1120 °C Am, and 1600 °C for Cm evaporation and 900 °C for Am and 1300 °C for Cm condensation ... 

A. Gawalowsky purified the commercial salt by boiling it with freshly precipitated lead carbonate, adding sodium hydrocarbonate to the decanted liquid, and evaporating in vacuo, when sodium hydrocarbonate crystallizes out. The mother liquid is evaporated, and the first washings rejected. The main fraction is redissolved, crystallized from water with refined wood charcoal, and filtered through platinum wool. 

Thirty minutes is sufficient for sample preparation beginning with refined vegetable oils. However, the other sample preparations take up to 120 min because of the incubation, re-extraction, and evaporation steps. Usually, a batch of samples is prepared at the same time to reduce the preparation time per sample. The running time for HPLC analysis is approximately 18 min for normal phase or 14 min for reversed phase in order to quantify all tocols. The running time for normal phase could be cut to 12 min for samples without 5-tocopherol and tocotrienol. 

Mathematical models that incorporate both flow and evaporative-loss mechanisms have been prepared (158). Non-Newtonian features have been introduced recently to refine the modeling efforts and have resulted in models with quantitative predictive abilities (159). Hence, data comparison between films spun on different spinners, with nominally identical final rotation speeds, may reveal differences in film uniformity. 

Saccharification produces a 94% dextrose liquor, which can be processed in several ways. To make a dextrose syrup, the fats and protein are removed from this liquor, as in the high fructose process. The syrup is then carbon bleached, demineralized and evaporated to 71% solids. The 94% dextrose liquid may also be further refined to 99% dextrose by adsorption-separation chromatography prior to being bleached, demineralized and evaporated. 

In the early part of the 1800s chemists in Europe took willow leaves and boiled them with different solvents to try to extract the active ingredients. In 1825 an Italian chemist filtered such a solution and evaporated away the solvent. He obtained impure crystals of a compound containing some of the active ingredient. Repeated recrystallization and refinement of his experimental technique produced a pure sample of the unknown material (Figure 1.1). 

Deegan et gave three conditions that need to be met by the droplet in order for coffee staining to occur. These conditions are that the solvent meets the substrate at a non-zero contact angle, the contact line is pinned and that the solvent is volatile. These conditions were subsequently refined to being a pinned contact line and evaporation from the edge of the droplet. ... 

Properties Pale-yellow liquid. D 0.926-0.929, saponification value 290, iodine value 10-30. Soluble in ether, chloroform, benzene, and carbon disulfide the refined jaw and head oil has uniquely low pour point and high lubricity and is highly resistant to gumming, oxidation, and evaporation. 

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