Contents 7 Minimum Stripping

Ethylene Stripping. The acetylene absorber bottom product is routed to the ethylene stripper, which operates at low pressure. In the bottom part of this tower the loaded solvent is stripped by heat input according to the purity specifications of the acetylene product. A lean DMF fraction is routed to the top of the upper part for selective absorption of acetylene. This feature reduces the acetylene content in the recycle gas to its minimum (typically 1%). The overhead gas fraction is recycled to the cracked gas compression of the olefin plant for the recovery of the ethylene. 

A thirty-plate bubble-cap column is to be used to remove n-pentane from a solvent oil by means of steam stripping. The inlet oil contains 6 kmol of n-pentane/100 kmol of pure oil and it is desired to reduce the solute content of 0.1 kmol/100 kmol of solvent. Assuming isothermal operation and an overall plate efficiency of 30 per cent, what is the specific steam consumption, that is kmol of steam required/kmol of solvent oil treated, and the ratio of the specific and minimum steam consumptions. How many plates would be required if this ratio is 2.0 ... 

Combustibility is also influenced by the amount of oil present the minimum reaction temperature (i.e., the minimum temperature required to cause onset of spontaneous combustion) is lowest in the region where the clay is saturated with 50-60% oil and rises (i.e., becomes less pyrophoric) as the oil content is further reduced to 40% and then to 30%. What these data suggest is that spent clay should be stripped of as much oil as possible before the resultant filter cakes are exposed to the atmosphere. The incorporation of ethoxyquin (a well-known antioxidant used to control spontaneous combustion in fish meal) into the clay/oil mass at the 100-ppm level did reduce the tendency to undergo spontaneous combustion however, whether this approach is practical and how it could be accomplished in plant operations is an open question. 

The diisocyanate and polyols can be reacted in various combinations by using diols, triols, and tetrols, or combinations of these in which the NC0 0H ratio is lower than 2. Typical idealized structures are shown in Figure 2. The adducts and polymers can be produced with a relatively low content of free unreacted disocyanate. Because of the volatility and irritant characteristics of diisocyanates such as TDI, it is Important to keep the unreacted TDI to a minimum, particularly for spray applications. A vacuum stripping step is often recommended to eliminate this hazard. 

A suspension of 6.207 kg of (5)-TH(3C.(5)-CSA (95% d.e.) in toluene (124 L), water (9.9 L), and 30% NaOH (2.5 L) was stirred at 40°C until dissolution (40 min). After cooling to room temperature, the organic layer was separated and polish filtrated. The toluene was stripped off under reduced pressure until a minimum volume. Then, EtOH (74 kg) was added to the reaction mixture and the toluene/EtOH azeotropic mixture (bp 76.7°C azeotropic composition toluene EtOH 32 68) distilled at ambient pressure until a residual toluene content of maximum 1% was achieved (gas chromatography [GC] analysis). A mass adjustment (Ig (5)-TH(3C/5 g reaction mixture) was then performed by addition of EtOH (7.2 kg), followed by the addition of L-tartaric acid (1.986 kg) dissolved in water (305 L). The mixture was then heated for 1 h at reflux and stirred for 16 h at room temperature. The crystals were filtered, rinsed twice with water (17 L), and dried at 50°C under reduced pressure for 20 h to afford 4.595 kg of (5)-TH(3C-(L)-tartrate monohydrate (yield 86%, 99% d.e.). 

In the future, it is probable that the supplier of emichment services will permit a customer to specify the assay ( U content) of the tails to which feed is to be stripped so as to minimize the combined cost to the customer of natural UF feed and separative work. F re 12.20 shows qualitatively the effect of tails composition on the contributions to product cost arising from costs for feed and for separative work in stripping and enriching sections. The amount of separative work required in the enriching section is independent of tails composition. But the cost of separative work required in the stripping sections varies from zero when = zp (no stripping) to infinity when xw = 0. Conversely, the cost of feed varies from infinity when Xftf = zp to a minimum at rcn =0, as may be seen from Eq. (12.152). There is therefore an optimum tails assay Xo between Xu = 0 and Xfy = zp, at which the sum of the cost of separative work and the cost of natural uranium feed is a minimum. 

Dissolved Gas Removal. It has been pointed out previously that it is desirable, in order to avoid erosion by liberated gas, to keep the dissolved gas content of the pile to a minimum. For very complete removal of the dissolved gas something approaching a counter-current stripping column would be necessary. However, in the present case there is reason to think that no extraordinarily... 

The wet track abrasion test is used to determine the minimum bitumen content and the mixture s resistance to stripping. The test is the same as the one used in mix design for slurry seals, briefly described in the above paragraph. 

Water Content (Water Activity). The ability of the solvent to strip off the bound water from the enzyme s surface depends not only on its polarity but also on its water content. Thus, the water content - more precisely the water activity (flw) [79] - of an organic solvent has to be adjusted to the enzyme s requirements in order to ensure optimum activity [80-82]. The minimum amount of water required to maintain enzyme activity also depends on the enzyme type Whereas lipases are able to operate at extremely low water activities of 0.0-0.2, oxidoreductases and glycosidases require aw of 0.1-0.7 and 0.5-0.8, respectively [83]. 

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