Chillers

Dehydration can be performed by a number of methods cooling, absorption and adsorption. Water removal by cooling is simply a condensation process at lower temperatures the gas can hold less water vapour. This method of dehydration is often used when gas has to be cooled to recover heavy hydrocarbons. Inhibitors such as glycol may have to be injected upstream of the chillers to prevent hydrate formation. 

The Phillips process is a two-stage crystallisation process that uses a pulsed column in the second stage to purify the crystals (79,80). In the pulsed column, countercurrent contact of the high purity PX Hquid with cold crystals results in displacement of impurities. In the first stage, a rotary filter is used. In both stages, scraped surface chillers are used. This process was commercialized in 1957, but no plants in operation as of 1996 use this technology. 

A.nnual energy and fuel costs electric energy costs chiller or compressor pumps chilled water heating water condenser or tower water weE water... 

Uses. In architectural and industrial appHcations vibrational isolators are used to reduce transmission of vibration into building stmctures from rotating or reciprocating machinery, such as ventilating fans, pumps, chillers, industrial machinery, and the piping and ductwork coimected to this equipment (6). Vibration isolators also can be used to isolate vibration-sensitive equipment or noise-sensitive areas from sources of vibration. Examples are special pneumatic isolators to protect electron microscopes, and isolators used to support floating concrete floors in recording studios. 

The temperature of the anodizing solution also has an effect on the anodic film stmcture. Thus chillers are used to maintain a consistent temperature in the bath while the part is being anodized, and air agitation is continuously appHed to ensure a uniform temperature. The result is a consistent anodic film density of uniform pore size. 

Insofar as they are used to purify other products, several processes used in the refinery fall under the classification of dewaxing processes however, such processes must also be classified as wax production processes (2). Most commercial dewaxing processes utilize solvent dilution, chilling to crystallize the wax, and filtration (28). The MEK process (methyl ethyl ketone—toluene solvent) is widely used. Wax crystals are formed by chilling through the walls of scraped surface chillers, and wax is separated from the resultant wax—oil—solvent slurry by using fliUy enclosed rotary vacuum filters. 

There are two commercial solvent crystaUi2ation processes. The Emersol Process, patented in 1942 by Emery Industries, uses methanol as solvent and the Armour-Texaco Process, patented in 1948, uses acetone as solvent. The fatty acids to be separated are dissolved in the solvent and cooled, usually in a double-pipe chiller. Internal scrapers rotating at low rpm remove the crystals from the chilled surface. The slurry is then separated by means of a rotary vacuum filter. The filter cake is sprayed with cold solvent to remove free Hquid acids, and the solvents are removed by flash evaporation and steam stripping and recovered for reuse (10). 

One of the early column crystallizers was that iatroduced for the separation of xylene isomers (see Xylene and Ethylbenzene). In this unit, shown schematically ia Eigure 25, -xylene crystals are formed ia a scraped-surface chiller above the column and fed to the column. The crystals move downward counter-currenfly to impure Hquid ia the upper portion of the column and melted -xylene ia the lower part of the column. Impure Hquor is withdrawn from an appropriate poiat near the top of the column of crystals while pure product, xylene, is removed from the bottom of the column. The pulse unit drives melt up the column as reflux and iato a product receiver. 

Figure 4.29 Corroded internal surface of a copper chiller tube. The light-colored deposits are primarily iron oxides and silicates reddish material is cuprous oxide.

As part of a protective maintenance activity, the chiller was examined by eddy current. An eddy current check revealed no failures. However, when the chiller was returned to service, leakage of chill water was detected. 

Pinhole perforations were discovered in the walls of chiller condenser tubes of an air-conditioning system. Close laboratory examination of the internal surfaces of affected tubes revealed distinct patches of small pits (Fig. 12.18) and pit sites aligned along longitudinal mandrel marks and fine scratches (Fig. 12.19). In some locations, transversely oriented pit sites that were aligned with the locations of the fins on the external surface branched off the primary longitudinal pit alignment (Fig. 12.20). 

Combination of evaporative and refrigerated inlet systems—The use of evaporative coolers to assist the chiller system to attain lower temperatures of the inlet air. 

Problem A deethanizer overhead chiller experienced tubeside plugging due to freezing. 

Solution Added a small package TEG dehydrator to the stream ahead of the chiller. 

If condensing temperature is normal, 3. Process overload of chiller... 

Refrigerant circulation or kettle or Chiller 2. Expansion valve capacity. 

Air conditioning (water chillers) - HCFC-22 has been used in small chillers, and CFC-11 and -12 have been used in large chillers that employ centrifugal compressors. HFC blends are now beginning to be introduced to replace HCFC-22 in small chillers HCFC-123 and HFC-134a are the preferred replacements for large units. Chillers that have used CFC-114 can be converted to use HCFC-124 or can be replaced by HFC-134a units. 

Chiller A heat exchanger in which heat is removed from the warmer water or air. 

Cooling The removal of sensible or latent heat from a medium by means of a chiller. 

Water chiller A water-cooling device operating either by the direct expansion of a refrigerant by an absorption system or by evaporative cooling. 

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