Stage operations

Physicochemical relationships are such that soHd potassium chloride can be converted to soHd potassium nitrate ia a one-stage operation of the simplest kiad. The conversion takes place ia a stirred reaction system (Fig. 10). The overall separation is analogous to a rectification and stripping operation ia a distillation process. 

Melt Crystallization. Crystallization (qv) from a melt is inherently more attractive than distillation because the heat of fusion is much lower than that of evaporation. It also benefits from lower operating temperature. In addition, organic crystals are virtually insoluble in each other so that a pure product is possible in a one-stage operation. 

Electrodialysis. Electro dialysis processes transfer ions of dissolved salts across membranes, leaving purified water behind. Ion movement is induced by direct current electrical fields. A negative electrode (cathode) attracts cations, and a positive electrode (anode) attracts anions. Systems are compartmentalized in stacks by alternating cation and anion transfer membranes. Alternating compartments carry concentrated brine and purified permeate. Typically, 40—60% of dissolved ions are removed or rejected. Further improvement in water quaUty is obtained by staging (operation of stacks in series). ED processes do not remove particulate contaminants or weakly ionized contaminants, such as siUca. 

As it is desirable that the separative capacity of the stage be independent of the concentration of the material with which it is operating, the terms in the equation involving the concentration are set equal to a constant, taken for convenience to be unity, and the separative capacity of a single stage operating with a cut of one-half is seen to be ... 

A Back-Pressure Efficiency Factor. Because a gaseous diffusion stage operates with a low-side pressure p which is not negligible with respect to there is also some tendency for the lighter component to effuse preferentiahy back through the barrier. To a first approximation the back-pressure efficiency factor is equal to (1 — r), where ris the pressure ratiopjpj. 

The main power source is a 2,200 kW rated motor, which drives two high-speed pinions through integral gears. The first stage of the compressor operates at 17,900 rpm, while the second and third stages operate at 21,800 rpm. The unit is controlled by a local control system, but operators can also monitor the operating parameters from the plant control room. 

For nontransformer-isolated switehing power supply topologies, the output reetifier is eonneeted direetly to the power switeh and the output stage operates in the half-wave mode. In transformer-isolated topologies, the output stage ean... 

This is satisfactory for single-stage operation if temperature does not limit. 

In the two-stage operation, the feed is hydrodesulfurized in the first reactor with partial hydrocracking. Reactor effluent goes to a high-pressure separator to separate the hydrogen-rich gas, which is recycled and mixed with the fresh feed. The liquid portion from the separator is fractionated, and the bottoms of the fractionator are sent to the second stage reactor. 

Carbon Dioxide Removal. Aside from contained carbon dioxide which is removed from syngas when absorbing hydrogen sulfide, the total carbon dioxide produced in the methanation system is removed by conventional absorption in a single-stage operation in which the volume of gas to be treated is minimum and the partial pressure of the carbon dioxide is maximum. 

Wang KK, Lee M (1999) The principle of a three-staged operation in the surgery of acne scars. J Am Acad Dermatol 40 95-97... 

The experimental results are summarized in Table 2. CO2 permeance (Rco2), selectivity (oicx)2/N2) and CO2 recovery (Y) increased with decreasing CO2 mole fraction in feed gas. CO2 in the feed gas was successfully concentrated to 97-99 % by the single-stage operation. CO2... 

Figure 10.4 Equilibrium countercurrent stage operation for stripping.

Natural gas (CH4) is transported through a 6 in. ID pipeline at a rate of 10,000 scfm. The compressor stations are 150 mi apart, and the compressor suction pressure is to be maintained at lOpsig above that at which choked flow would occur in the pipeline. The compressors are each two stage, operate adiabatically with interstage cooling to 70°F, and have an efficiency of 60%. If the pipeline temperature is 70°F, calculate ... 

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