Steam distribution, selective control

T he selection of a particular method depends on the size of the installation, availability of water or steam, the degree of control required, and the methods used for conditioning and distributing the air. 

Various amines find application for pH control. The most commonly used are ammonia, morpholine, cyclohexylamine, and, more recently AMP (2-amino-2-methyl-l-propanol). The amount of each needed to produce a given pH depends upon the basicity constant, and values of this are given in Table 17.4. The volatility also influences their utility and their selection for any particular application. Like other substances, amines tend towards equilibrium concentrations in each phase of the steam/water mixture, the equilibrium being temperature dependent. Values of the distribution coefficient, Kp, are also given in Table 17.4. These factors need to be taken into account when estimating the pH attainable at any given point in a circuit so as to provide appropriate protection for each location. 

The control rods perform dual fimctions of power distribution shaping and reactivity control. Power distribution in the core is controlled during operation of the reactor by manipulation of selected patterns of rods. The rods, which enter from the bottom of the near-cylindrical reactor, are positioned in such a manner to counterbalance steam voids in the top of the core and affect significant power flattening. These groups of control elements, used for power flattening, experience a somewhat higher duty cycle and neutron exposure than the other rods. 

Selective adsorption properties are obtained from the structure, controlled distribution of pore sizes, high surface areas and chemical nature of the matrix. Applications include the recovery of a wide range of solutes from the aqueous phase, including phenol, benzene, toluene, chlorinated organics, PCBs, pesticides, antibiotics, acetone, ethanol, detergents, emulsifiers, dyes, steroids, amino acids, etc. Regeneration may be effected by a variety of methods which include steam desorption, solvent elution, pH change and chemical extraction. 

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