Evaporative systems

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

Cooling loads can be transferred from process heat exchangers to a wastewater-evaporation system, thus reducing cooling-water requirements and total wastewater volume. 

One physical method that has attracted some commercial interest is evaporation several evaporative plants were installed in Japan in the early 1970s, nearly all followed by incinerators for the sludge produced (60). They are, however, expensive in both capital and operating costs. The most recent evaporation systems use a process known as vapor recompression, which has the claimed advantage of much lower operating costs than the eadier evaporative processes used in the wool industry. Capital costs of these processes are still high. 

Evaporation. In most chemical industry evaporation systems, the objective is product recovery, although occasionally the objective is concentration of an organic waste from an aqueous solution, to facihtate incineration. Similar equipment is used extensively for desalination of salt or brackish water (see also Water, supply and desalination). 

The reconcentration of dilute (50—60%) sulfuric acid is one of the more costly operations in the manufacture of ethanol by this process. An acid reboiler, followed by a two-stage vacuum evaporation system, raises acid concentration to about 90%. The 90% acid is then brought to 96—98% strength by fortification with 103% oleum (fuming sulfuric acid). 

Do not add a packed column to a thin film evaporator system, because complications arise. 

Rare earth sulfides, selenides, and tellurides show semiconducting properties and have potential for application in thermoelectric generation. Thin film chalcogenides of various rare earths have been prepared by multisource evaporator systems [233]. 

Solvent evaporation system (rotary evaporator, water-bath and vacuum line)... 

A typical evaporative recovery system consists of an evaporator, a feed pump, and a heat exchanger. Plating solution or rinsewater containing dilute plating chemicals is circulated through the evaporator. The water evaporates and concentrates the plating chemicals for reuse. In open evaporator systems, the water evaporates and mixes with air and is released to the atmosphere. It may be necessary to vent the contaminated airstream to a ventilation/scrubber treatment system prior to release. In enclosed evaporators the water is condensed from the air and can be reused in rinses, which further increases savings. Water reuse is preferred whenever possible. 

As with all process equipment, the design size of an evaporator system is dependent upon volumetric flow, specifically the rinsewater flow rate required and the volume of process solution dragout. When operated properly, a commercial evaporator can attain a 99% material recovery rate. 

Option 3 All of Option 2 plus ultrafiltration and carbon adsorption for oily waste, zero discharge of any processes using either cadmium or lead by using an evaporative system. 

Many caustic evaporator suppliers have schemes to separate the two types of caustic whilst making 50% solutions of both. A particularly good option is to install an extra first-effect evaporator for the membrane caustic soda and split the steam usage between the diaphragm first-effect and the new membrane first-effect, then recombine the steam again to feed to the rest of the diaphragm cell evaporator system. 

Sodium sulfite scrubbing can be configured as a regenerative process if the regeneration is performed thermally in an evaporator system. Thermal regeneration removes gaseous sulfur dioxide with the sodium bisulfite being converted back to sodium sulfite. The sulfur dioxide is then reduced to elemental sulfur or converted to sulfuric acid. 

Fig. 21. Reordered occurrence matrix for the triple effect evaporator system illustrated in Fig. 20.

In selecting a compressor for this type of operation, the main difficulty is the very large volume of vapour to be handled. Rotary compressors of the Rootes type, described in Volume 1, Chapter 8, are suitable for small and medium size units, though these have not often been applied to large installations. Mechanical compressors have been used extensively in evaporation systems for the purification of sea water. 

While refrigeration technologies can provide a near-constant GT inlet air temperature, and thus a nearly constant GT power output, refrigeration TIC systems are significantly more expensive than evaporative systems. However, the incremental net power output from the refrigeration system, when measured on a unit cost basis ( per kWe),... 

Hopper ML, Griffitt KR. 1987. Evaluation of an automated gel permeation cleanup and evaporation systems from determining pesticide residues in fatty samples. J Assoc Off Anal Chem 70 724-726. 

Carver-Greenfield multistage, oil dehydration, steam evaporator system (fermentation waste) ... 

Both concentrated and dilute waste were sent to a pair of John Zink thermal oxidizers equipped with adjustable venturi scrubbers for removal of particulates prior to stack discharge. Water process waste originating primarily from fermentation sectors was sent to the Carver-Greenfield evaporation system. The evaporator utilized a multistep oil dehydration process and was equipped with a centrifuge, waste heat boiler, and a venturi scrubber. The Clinton Laboratory reported an overall BOD and COD reduction of 90 and 99%, respectively, depending upon the configuration used. 

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