Cold box

A cold box is often used to separate the hydrogen and carbon monoxide into a high purity CO stream and a H2-rich stream. This reduces the ratio to near zero with respect to the CO stream. The H2-rich stream may undergo further purification (typically in a PSA unit) to yield a high purity H2 stream. This increases the ratio to near infinity with respect to the H2 stream. 

Adding steam to the reactor converts CO to H2 by the water gas shift reaction. This increases the H2/CO ratio. 

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After compression and removal of impurities, the air is cooled ia heat exchangers and expanded to low pressure through a turbiae, to recover energy, or through a valve. Liquid air, which forms at about 80 K, is separated via a distillation column. The column as well as the heat exchangers and the associated piping are placed within a cold box, which is packed with iasulation to minimise heat transfer (qv) between streams and to protect the system from the ambient air external to the cold box. 

In chemical plants, turboexpanders are used to produce refrigeration for cold box installations. In all except energy recovery applications, there are gas-to-gas heat exchangers downstream of the turboexpander. Figure 6-14 recaps a process flow diagram of a natural gas processing gas plant. 

Various studies by TNO (feedstock recycling of plastics for the EU, the cold box study, and various LCAs for the Dutch packaging covenant and industrial clients)... 

Table 4. Cold box present near the 5 end of major E. coli cold shock genes...

Indicates the mapped potential putative transcription start site. The cold box Is shown In boldface. 

Repression of cspA after acclimation at low temperatures appears to be mediated by the cold box region and is a possible target site for repressor binding [138]. In addition, CspA itself negatively regulates its own gene expression through the cold box [138, 139]. 

During regeneration of an adsorber in the cold box of an air separation plant, regeneration gas exited via the adsorber drain pipe. This still contained some liquid oxygen. Very low regeneration-gas flows permitted desorption of acetylene and other hydrocarbons at above normal (ppm) concentrations, these condensed or crystallised into the liquid oxygen and the mixture finally detonated, causing... 

Monitoring the purge gas from cold boxes and double walled insulated cryogenic storage tanks. 

In the purification section of an ethane cracker, the gas can be handled in one of two ways. In order to fractionate the streams, they must be liquefied. Since they are all light gases, liquefaction can be done either by increasing the pressure in a compressor or by reducing the temperature to very low points in something called a cold box. The ethane cracker in Figure 5—2 shows the compressor option. (Even then, the streams have to be cooled to assure they liquefy.)... 

The separation section of a gas oil cracker looks like a small refinery, as you can see in Figure 5 or in Figure 5—5. In addition to the fractionators and treaters used in the purification section of the simpler ethane cracker, there are facilities to separate the heavier coproducts. In the front end of the separator facilities in Figure 5-4, the cold box option for handling the liquefaction of the gases is shown. Temperatures as low as -220°F are achieved in this super-refrigerator. At those low temperatures, Freon wont do the job. Liquid air, methane, ethylene, or ammonia are often used as the refrigerant in much the same way Freon has been used in an air conditioner. 

Filtration may be carried out in a suction funnel surrounded by a Dry Ice-ethanol cooling bath, or using a cold box maintained at -50°. 

No external work is done, and the change in internal energy of the refrigerant during a complete cycle is zero. The total heat Qa + Qc released to the atmosphere per unit of time by the absorber and the condenser equals the total heat Qg + Qc absorbed per unit of time from the heater at the generator and from the cold box at the evaporator. Thus Qe = Qa + Qc — Qg, and therefore, the coefficient of performance = Qe/Qg = [iQ + Qc)/Qs]-l-... 

Cold room (4°C) or cold box Computer (PC or Macintosh) and printer Conical centrifuge tubes, 15- and 25-ml plastic Cuvettes, plastic disposable, glass, and quartz Darkroom and developing tank, or X-Omat automatic X-ray film developer (Kodak) Desiccators (including vacuum desiccators) and desiccant Dry ice... 

To a solution of 16.3 g 2,5-dimethoxy-3,4-dimethylbenzaldehyde in 50 mL nitromethane there was added 3.0 g anhydrous ammonium acetate, and the mixture was heated on the steam bath overnight. There was then added an equal volume of MeOH, and with cooling there was obtained a fine crop of yellow crystals. These were removed by filtration, washed with MeOH, and air dried to provide 4.4 g of 2,5-dimethoxy-3,4-dimethy 1-6-nitrostyrene with a mp of 120-121 °C which was not improved by recrystallization from MeOH (50 mL/g). The mother liquors of the above filtration were diluted with H20 to the point of per-manent turbidity, then set aside in a cold box. There wasachunky, granular, tomato-red crystal deposited which weighed 2.5 g when dry. It had a mp of 118-119.5 °C, which was undepressed in mixed mp with the yellow sample. Both forms had identical NMR spectra (2.20, 2.25 CH, 3.72, 3.84 OCH, 6.80 ArH 7.76, 8.28 CH=CH, with 14 cycle splitting), infrared spectra, ultra violet spectra (max. 324 nm with shoulder at 366 nm in EtOH, two peaks at 309 and 355 nm in hexane), and microanalyses. Anal. (C HlsN04) C,H,N. 

Snohvit will also be the first major development on the Norwegian continental shelf without support from a floating unit. A sub sea production system on the seabed will feed the land-based LNG plant via a 0.68 m ID, 160 km two-phase pipeline. In addition two chemical lines, an umbilical and a separate pipeline for the transport of carbon dioxide will be included. The unprocessed well stream from Snohvit is separated and the gas is treated and cooled to a temperature below the boiling point (-162 °C) to form LNG. This operation employs a large cold box (40 m high and a footprint of 15x17 meter). 

Figure 7 The spiral-wound heat exchanger (in front) to be built for the Snohvit LNG processing plant. The cold box measures 15x17 meter (footprint) having a height of 40 meter. The Statoil/Linde heat exchanger is the same type as the heat exchanger used in the Mossel-bay LNG plant in South Africa [17]. The lower tower (right) contains a plate fin heat exchanger for pre-cooling.

A hydrogen liquefier consists of piston compressors that usually can operate at three pressure levels and a liquefier cold box. The cold box includes a... 

When the valve and associated piping are installed in a large box filled with insulation ("cold box"), this requires an unusually long extension in order to keep the packing box in a warm area. The valve illustrated in Figure 2.74 can... 

Cold-box valve with weld ends and welded bonnet. (Courtesy of Flowserve Corp.)... 

The long, extended bonnet is provided with a plug stem seal to minimize liquid "refluxing" into the bonnet and packing area, thereby minimizing the heat loss due to conduction and convection. Cold boxes are commonly used in hydrogen and in the air separation industry. Valves used in these applications feature bodies with welded extension necks and standard-length bonnets to allow in-place trim maintenance from outside the cold box. On LH2 service these valves are often provided with vacuum jackets for additional... 

A simplified flow diagram for this segment of the process is shown in Figure 4, and thermodynamic analysis in Table III. The refrigerated exchangers and cold box represent about 30% of the lost work of the process. However, the tower itself has a very high percentage of the lost work in the system. Thus the details of the tower heat and material balance were examined in search of ways to improve its efficiency. 

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