Effect Distillation

Figure 14.4 Double-effect distillation. (From Smith and Linnhoff, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...

Consider special multiple-effect distillation schemes if the D/B ratio is either very high or very low, or if the relative volatihty is low. 

Seawater Distillation. The principal thermal processes used to recover drinking water from seawater include multistage flash distillation, multi-effect distillation, and vapor compression distillation. In these processes, seawater is heated, and the relatively pure distillate is collected. Scale deposits, usually calcium carbonate, magnesium hydroxide, or calcium sulfate, lessen efficiency of these units. Dispersants such as poly(maleic acid) (39,40) inhibit scale formation, or at least modify it to form an easily removed powder, thus maintaining cleaner, more efficient heat-transfer surfaces. 

For a more complete discussion of salt-effect distillation see References 75—77. 

There are a number of ways to provide the heating or cooling medium at temperatures closer to the optimum level. One is by use of double-effect distillation, which uses the overhead vapor from one column as the heat source for another column such that the second column s reboiler becomes the first column s condenser. This basically cuts the temperature differential in half, and shows up as an energy saving because external heat is suppHed to only one of the units. 

Bansal V, Ross R, Perkins JD, Pistikopoulos EN (2000) The Interactions of Design and Control Double Effect Distillation,... 

Distillation processes, 26 61-73. See also Distillation(s) freeze-desalination, 26 71 materials and scaling issues in, 26 71-73 multi-effect distillation, 26 65-67 multistage flash evaporation, 26 61-65 vapor compression distillation, 26 67 Distillation reactors, 21 332 Distillation region diagrams (DRD), 22 302, 303, 331... 

Double-cell system, in soil and ground water treatment, 25 835 Double crucible technique, 11 135-136 Double-deck kiln, 15 530 Double-drum dryers, 9 134 Double-drum separator, 15 446 Double-effect distillation, 10 153 Double end point titration method,... 

Multidentate V-heterocyclic ligands, thorium and, 24 767 Multidimensional gas chromatography, 4 617-618 6 433-434 Multidrug resistant bacteria, 18 252 Multi-effect distillation (ME), 26 65—67 Multi-effect vapor-compression submerged-tube desalination plant, 26 70 Multielevation piperacks, 19 515 Multifeed fractionation, 10 616 Multifilamentary superconductor, 23 846 Multifilament sutures, 24 218 threads for, 24 207 Multifilament yarns, 11 177-178 Multifile patent searches, 18 244 Multifunctional aliphatic epoxies, 10 376 Multifunctional coatings, 1 714-716 Multifunctional epoxy resins, 10 367-373, 418, 454... 

Salt distillation, of hafnium, 73 84 Salt domes, 22 798 Salt-dome sulfur deposits, 23 569 Salt effect distillation, 8 816—817 Salt flats, 5 786 Salt-fog unit, 78 72 Salt formation(s), 22 798 amino acids, 2 570 ammonia, 2 685—686 carboxylic acids, 5 40—41 citric acid, 6 637 cycloaliphatic amines, 2 501 fatty amines, 2 522 Salt industry... 

Desalination has been practiced for many years, although the early large-scale industrial applications were in the 1960s in the Middle-East using thermal desalination technologies such as multistage flash or multi-effect distillation. These plants used sophisticated thermal or vacuum systems to effectively distil a portion... 

Low Temperature Multi-effect Distillation (LTTIED) Combined With Power Generation (Dual-Purpose)... 

The antioxidant and acid neutralization properties of most fuel stabilizer formulations help to prevent the initial formation of most acids. Compounds such as tertiary-alkyl primary amines, as shown by the example in FIGURE 6-5, are quite effective distillate fuel additives. These oil-soluble amines can be formulated into stabilizer formulations at relatively low concentrations and can provide a significant boost in overall performance of a fuel stabilizer. 

Toon and Tolbert (1995) suggest that if Type I PSCs are primarily ternary solutions rather than crystalline NAT, the higher vapor pressure of HN03 over the solution would in effect distill nitric acid from Type I to Type II PSCs, assisting in denitrification of the stratosphere. This overcomes the problem that if Type II PSCs have nitric acid only by virtue of the initial core onto which the water vapor condenses, the amount of HN03 they could remove may not be very large. The supercooled H20-HN03 liquid layer observed by Zondlo et al. (1998) clearly may also play an important role in terms of the amount of HNO, that can exist on the surface of these PSCs. 

Forward Combustion Injection of hot air into deposit to effect distillation and thermal cracking (Pan American Petroleum)... 

A variety of desalting technologies has been developed over the last 40 years. Based on their commercial success, they can be classified into major (viz., multistage flash distillation, MSFD multiple-effect distillation, MED vapor compression, VC ED RO) and minor (i.e., freezing, membrane distillation solar humidification) processes. 

The locations of the singular points in reactive membrane separation processes depend on both the separation effects (distillation/membrane separation) and the reaction effect. Singular points can be generally obtained as steady-state solutions of Eq. (88) ... 

In alternative (a) pure products are obtained in each column. Since the relative volatility diminishes with the pressure, higher reflux is needed in the H P column. The balance of duties can be obtained by adjusting the split of the feed. Roughly speaking, by double-effect distillation the energy consumption is divided by two. In alternative (b) there is a large temperature difference between top and bottom that may be exploited by a sloppy split in the HP column with the heavy component, while in alternative (c) this is done with the light component. Alternative (c) is the best for the present case study since it allows a lower temperature of the hot utility. 

The main methods used in desalination units are reverse osmosis and multi-effect distillation. The energy consumption of a desalination plant using the technology of reverse osmosis depends on its size, the contents of sea water and the desired quality of the produced water and usually ranges between 5-7 kWh/m3 when sea water is used. When well water in coastal regions is used for desalination the energy consumption is less than half of the above. The nominal capacity of small-size desalination units for rural housings is of the order of 400 W. 

Apart from standard Quickfit equipment, labs should also have some one-piece distillation kits, which provide more effective distillation. A short-path distillation apparatus is very useful for low-hold-up, high-throughput distillations, particularly on a small scale. These can now be purchased but are very expensive. They can easily be constracted by a glassblower according to the design shown in Fig. 4.2. Note that distance B on the diagram is cmcial and corresponds to the length of a Quickfit thermometer from bulb to joint... 

Gas chromatography is a very sensitive technique requiring only very small amounts of sample (lO g). A solution of about 1% is sufficient and a few microlitres of this is injected into a heated injector block. A stream of carrier gas, usually helium, passes through the injector and sweeps the vapours produced onto the column, which is contained in an oven. The temperature of the oven can be accurately controlled and can either be kept constant or increased at a specified rate. Separation of the components in gc is not based on the principle of adsorption, as it is in liquid chromatography, but on partition. A gc column is rather like an extremely effective distillation column with the relative volatility of the components being the main factor which determines how quickly they travel through the column. 

In order to minimize decomposition and to reduce the temperature required for effective distillation at a given pressure, it is desirable to wrap the distillation assembly with asbestos or other insulating material. 

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