Concentration of liquid

Catalytic reduction, 8,11,15 Concentration of liquids, 4, 54 Condensation of low boiling liquids 1, 76... 

Evaporation is the oldest process for the concentration of liquid foods. Temperatures are higher compared to those of the more modern membrane filtration or freeze concentration processes. Tocopherols, carotenes, ascorbic acid, flavonoids and other phenolic antioxidants are partially destroyed by heating. Therefore, it is necessary to minimise the time needed for evaporation, and heating to the evaporation temperature should be carried out very rapidly. The temperature may be decreased if the pressure is reduced. The process is then more expensive, but losses of antioxidants become substantially lower. 

Isothermal operation Tabs calculated for the assumed liquid concentration at the outlet and current gas con centration concentration of liquid updated and calculations repeated iterative procedure... 

On Friday, February 19, a 1.5-inch feed line to the heater column was replaced with a 2-inch line, which delayed startup until later in the morning. The concentration of liquid solution in the charge tank at that time was about 57% hydroxylamine. It steadily increased throughout the day. Between 7 00 and 7 15 p.m., the concentration of liquid solution in the charge tank was recorded as 86% hydroxylamine. 

The problem of selecting the most appropriate operation will be further complicated by such factors as the concentration of liquid solution at which crystals start to form. Thus, in the separation of a mixture of ortho-, meta-, and para-mononitrotoluenes, the decision must be made as to whether it is better to carry out the separation by distillation followed by crystallisation, or in the reverse order. The same kind of consideration will arise when concentrating a solution of a solid then it must be decided whether to stop the evaporation process when a certain concentration of solid has been reached and then to proceed with filtration followed by drying, or whether to continue to concentration by evaporation to such an extent that the filtration stage can be omitted before moving on to drying. 

EXAMPLE 24.2 TOWERS FOR HIGH CONCENTRATION OF LIQUID -------------- REACTANT... 

Mass transfer controlled by diffusion in the gas phase (ammonia in water) has been studied by Anderson et al. (A5) for horizontal annular flow. In spite of the obvious analogy of this case with countercurrent wetted-wall towers, gas velocities in the cocurrent case exceed these used in any reported wetted-wall-tower investigations. In cocurrent annular flow, smooth liquid films free of ripples are not attainable, and entrainment and deposition of liquid droplets presents an additional transfer mechanism. By measuring solute concentrations of liquid in the film and in entrained drops, as well as flow rates, and by assuming absorption equilibrium between droplets and gas, Anderson et al. were able to separate the two contributing mechanisms of transfer. The agreement of their entrainment values (based on the assumption of transfer equilibrium in the droplets) with those of Wicks and Dukler (W2) was taken as supporting evidence for this supposition. 

In die above equations, the liquid and solid concentrations of liquid reactant are time-dependent (note subscript t). 

Many biological systems exhibit [he properties of liquid crystals. Considerable concentrations of liquid crystalline compounds have been lound in many parts of the hody, often as sterol or lipid derivatives A liquid crystal... 

On the other hand, the solubility in water is enormously greater (7.70 g per liter of solution at 20° and 1 atm.), while the vapor pressure rises much more rapidly than the concentration. Roscoe and Dittmar s results (1859) for water and HCl at 20° give these values ofp, the pressure of the gas in mm, and c, the concentration of liquid in grams/liter, with those ofc/p, which would be constant if Henry s law held ... 

A theoretical plate is defined as the degree of separation attained for an infinitesmal vaporization at equilibrium (i.e., the concentration of liquid in a theoretical plate is that of the first bit of vapor to be formed from the liquid in the previous one). Using this definition, approximately how many theoretical plates would be required to achieve a separation into a vapor with xB = 0.1 and a liquid with xB = 0.9 for the system described by the boiling-point diagram in Fig. 9. 

Converting from mole fraction to concentration units by multiplying by the molar concentration of liquid water, the 02 concentration is ... 

However, since the concentration of liquid water is constant and so large relative to the concentration of ions, it can be omitted from the equilibrium expression. At 25°C, the equilibrium expression can be rewritten as Equation 14.1 ... 

This equilibrium is known as a heterogeneous equilibrium, which is to say that it consists of substances that are in different states (phases). If you recall from Chapter 13, the equilibrium constant expressions for such equilibria do not contain the concentrations of liquids or solids. The equilibrium expression for this reaction will describe the degree to which the solid dissolves in solution, which is another way to say the degree to which it is soluble. And since the solid is not shown in the equilibrium expression, the equilibrium constant will express the product of the concentrations of the dissolved solute ions. For this reason, the equilibrium constant is referred to as the solubility-product constant. For this equilibrium, the solubility-product constant, Ksp is ... 

CB = concentration of liquid reactant B in the liquid phase at position z in the reactor, mole cm 3. 

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