Evaporator integration

The RO process was implemented at the Institute of Atomic Energy, Swierk. The wastes collected there, from all users of nuclear materials in Poland, have to be processed before safe disposal. Until 1990 the wastes were treated by chemical methods that sometimes did not ensure sufficient decontamination. To reach the discharge standards the system of radioactive waste treatment was modernized. A new evaporator integrated with membrane installation replaced old technology based on chemical precipitation with sorption on inorganic sorbents. Two installations, EV and 3RO, can operate simultaneously or separately. The membrane plant is applied for initial concentration of the waste before the evaporator. It may be also used for final cleaning of the distillate, depending on actual needs. The need for additional distillate purification is necessitated due to entrainment of radionuclides with droplets or with the volatile radioactive compounds, which are carried over. 

The amount of freshly distilled THF necessary to obtain a 0.1-0.5 M solution of dithiane is added. A 5% excess of BuLi in hexane (1.5-2.5 M) is added at a rate of 3-5 mL/min to the solution stirred at 40 C.. After 1.5-2.5 h at -25 to -15 °C, most dithianes are metalated quantitatively as determined by deuteration of an aliquot of the solution containing 50-100 mg of dithiane. This is done by injecting the withdrawn solution into 1-3 mL of D O in a small separatory funnel and extracting with ether, methylene chloride, or pentane the orange layer is dried for a few minutes with K2CO3 and concentrated evaporatively. Integration of the dithiane C2-proton NMR signal vs. any other well-defined and separated peak of the particular dithiane thus provides the extent of deuteration with an accuracy of 5"/ within 15 min. 

Smith, R., and Jones, P. S., The Optimal Design of Integrated Evaporation Systems, Heat Recovery Systems and CHP, 10 341, 1990. 

The concept of the appropriate placement of distillation columns was developed in the preceding chapter. The principle also clearly applies to evaporators. The heat integration characteristics of distillation columns and evaporators are very similar. Thus evaporator placement should be not across the pinch. ... 

Evolving Evaporator Design to Improve Heat Integration... 

It was noted earlier that dryers are quite difierent in character from both distillation and evaporation. However, heat is still taken in at a high temperature to be rejected in the dryer exhaust. The appropriate placement principle as applied to distillation columns and evaporators also applies to dryers. The plus/minus principle from Chap. 12 provides a general tool that can be used to understand the integration of dryers in the overall process context. If the designer has the freedom to manipulate drying temperature and gas flow rates, then these can be changed in accordance with the plus/minus principle in order to reduce overall utility costs. 

For any one ion type (e.g., Cs ), measurement of its abundance in a sample requires the sample to be evaporated over a period of time. The total yield of ions is obtained by integrating the area under the ion-yield curve (Figure 7.8c). 

Berylha ceramic parts ate frequendy used in electronic and microelectronic apphcations requiting thermal dissipation (see Ceramics as ELECTRICAL materials). Berylha substrates are commonly metallized using refractory metallizations such as molybdenum—manganese or using evaporated films of chromium, titanium, and nickel—chromium alloys. Semiconductor devices and integrated circuits (qv) can be bonded by such metallization for removal of heat. 

Some use is being made of lower grade heat sources, such as moist air from driers, and the constmction of auxiHaries, such as condensers, integral with the evaporator body. A further step is elimination of the conventional condenser—cooling tower—vacuum pump circuit by recirculating last-effect Hquor over the equivalent of a cooling tower built as an integral part of the evaporator body. 

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