Evaporative concentration

Liquid Effluents. Recycling of acid, soda, and zinc have long been necessary economically, and the acid—soda reaction product, sodium sulfate, is extracted and sold into other sectors of the chemical industry. Acid recovery usually involves the degassing, filtering, and evaporative concentration of the spent acid leaving the spinning machines. Excess sodium sulfate is removed by crystallization and then dehydrated before sale. Traces of zinc that escape recovery are removable from the main Hquid effluent stream to the extent that practically all the zinc can now be retained in the process. 

Other Effects Stream concentration can have important effects on corrosion rates. Unfortunately, corrosion rates are seldom linear with concentration over wide ranges. In equipment such as distillation columns, reactors, and evaporators, concentration can change continuously, makiug prediction of corrosion rates rather difficult. Concentration is important during plant shutdown presence of moisture that collects during cooling can turn innocuous chemicals into dangerous corrosives. 

Evaporation. Evaporative concentration can produce concentrations of 100,000 times or more in certain circumstances. Heat transfer surfaces, liquid and vapor interfaces, and regions where wetting and drying conditions occur are areas subject to evaporative concentration (see Case Histories 9.1, 9.4, and 9.6). 

Eindampfer, m. evaporator, concentrator. Eindampf-gerat, n. evaporator, -schale, /. 

Specimens immersed for 54 d in evaporator concentrating caustic soda from 50 to 60 / under 88 kN/m vacuum. 

Figure 8.6 Apparatus used for saeple preparation involving solvent extraction. A, heavier-than-water continuous liquid-liquid extractor B, pressurized Soxhlet extractor for use with supercritical fluids C, Kudema-Danlsh evaporative concentrator 0, autonated evaporative concentrator.

Water Extract with methylene chloride, filter through anhydrous sodium sulfate, evaporate, concentrate GC/MS No data No data Calgon 1977... 

A two-stage evaporative concentration under vacuum, with a limited residence-time in the evaporator to limit biuret formation, produces a urea stream containing about 0.5 per cent water which can be sprayed into a prilling tower. 

Effect of Evaporative Concentration of Hexane Solutions of Compound 118... 

Table I. Recovery of Compound 118 after Evaporative Concentration of Hexane...

To 100-gram batches of 1-day-old samples of cow s urine were added 0.05, 0.1, and 0.5 mg. of Compound 118 in acetone to give 0.5, 1.0, and 5.0 p.p.m., respectively. The urines were then extracted with two 50-ml. batches of hexane. Occasional emulsions were broken by centrifuging. The hexane extracts were dried with anhydrous sodium sulfate, filtered, evaporatively concentrated, and analyzed for Compound 118 as described under Procedure. The results of these analyses are shown in Table IV. Similar experiments with human urine gave slightly better recoveries. 

Formulators can use the tendency of creams, gels, and other systems to evaporatively concentrate to advantage. Solvents are chosen and blended so that the drug remains soluble in the formed film long after application is made. This can be accomplished by replacing a fraction of the water or other highly volatile solvent found in these systems with solvents of far lower volatility. As previously pointed out, 5-15% propylene glycol is found in many topical corticosteroid creams and lotions just for this reason. 

Evaporative crystallization is not preferred if the product needs to be of high purity. In addition to evaporation concentrating the solute, it also concentrates impurities. Such impurities might form crystals to contaminate the product or might be present in the residual liquid occluded within the solid product. 

Aqueous chloric acid solutions decompose explosively if evaporative concentration is carried too far. 

Evaporation concentrates the dissolved constituents of seawater. Because the assumed inflow is twice the assumed outflow, conservative properties—properties that are not affected by precipitation, dissolution, or exchange with the atmosphere—are concentrated by a factor of 2. This increase in concentration changes the balance between the dissolved car-... 

The results are shown in Figures 6-5 and 6-6. Figure 6-5 depicts how the system evolves from its initial conditions to a repeatable oscillation about annual average conditions. This evolution is clearest for the calcium ion concentration, which rises toward twice the seawater value. Calcium does not quite reach twice the seawater value because it is removed from the system by the precipitation of calcium carbonate. The rise in calcium is a consequence of the evaporative concentration of the water s dissolved constituents. 

The evaporative concentration increases the water s ionic strength, which affects the activity coefficients and thus the carbonate solubility and dissociation constants (Butler, 1982). I ignore this effect here, but it should be included in a more realistic simulation. 

The radiocarbon ratio also evolves very rapidly from its initial value of -50 to an average value of about -8 per mil. This evolution is not a consequence of evaporative concentration but, instead, of an approach to equilibrium with atmospheric carbon dioxide. Average surface seawater contains significantly less radiocarbon than does the atmosphere because its isotopic composition is affected by exchange with the deep ocean as... 

A second and critical factor is the loss of C02 from the fluid to the atmosphere. Evaporation concentrates C02(aq), driving C02(g) to exsolve,... 

A triple-effect backward-feed evaporator concentrates 5 kg/s of liquor from 10 per cent to 50 per cent solids. Steam is available at 375 kN/m2 and the condenser operates at 13.5 kN/m2. What is the area required in each effect, assumed identical, and the economy of the unit ... 

A triple-effect evaporator concentrates a liquid with no appreciable elevation of boiling point. If the temperature of the steam to the first effect is 395 K, and vacuum is applied to the third effect so that the boiling point is 325 K, what are the approximate boiling points in the three effects The overall heat transfer coefficients may be taken as 3.1, 2.3, 1.3 kW/m2 K in the three effects, respectively. 

The wet oxidation of membrane and evaporation concentrates was effective in reducing 50% of the COD at 150°C and enhancing the biodegradability of wastewater. 

Figure 3.5 Controlled evaporation of crystallization drops in microbatch, (a) Trials incubated under a thin layer of oil that allows concentration via evaporation, thus leading to nudeation. (b) Arrest of evaporation/concentration by addition of oil to produce a thicker layer above the trials. Modified from Chayen and Saridakis (2002), Acta Cryst. D 58, 921-927, with permission from the lUCr.

Polyethylene is an organic polymer with an amorphous crystalline structure, formed by the polymerization of ethylene gas. A low-density polyethylene with a processing temperature of 130 to 150°C has been evaluated in bench-scale and full-scale tests as a final waste form for evaporator concentrates, sludges, blowdown solutions, incinerator ash, and ion exchange resins. 

Resin Elution Concentration. The first three ethyl ether elutions were combined into a 500-mL glass bottle with a Teflon cap liner. The bottles and all the laboratory glassware used in the sample analysis were cleaned with 6.0 N HC1, acetone, and hexane and then baked at 200 °C to remove the solvent. The combined elutions were brought to the laboratory for evaporative concentration and analysis. 

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