Psig

Fig. 31. Density of gaseous chlorine as a function of temperature at various pressures. To convert kPa to psig, multiply by 0.145 and subtract 14.6. (77).

Fig. 2. Typical products from hydrogenation of soybean oil. Reaction conditions are 175°C, 0.02% Ni, 113 kPa (15 psig), and 600 rpm agitation. O is oleic ...

The third type of storage for anhydrous ammonia is pressurized storage without refrigeration. This is used at small terminals, ia some transport vehicles, and ia field appHcation equipment. For safety reasons, maximum allowable storage pressure ia vessels at retail locations and ia the field has been set at 1.83 MPa (265 psig) (8). This pressure is sufficient to prevent boiling at temperatures up to 46°C. Safety pop-off valves are provided to vent ammonia should higher temperatures be encountered. 

A flow diagram of the solvent-refined coal or SRC process is shown ia Figure 12. Coal is pulverized and mixed with a solvent to form a slurry containing 25—35 wt % coal. The slurry is pressurized to ca 7 MPa (1000 psig), mixed with hydrogen, and heated to ca 425°C. The solution reactions are completed ia ca 20 min and the reaction product flashed to separate gases. The Hquid is filtered to remove the mineral residue (ash and undissolved coal) and fractionated to recover the solvent, which is recycled. 

Liquefied natural gas (LNG) natural gas that has been Hquefied by reducing its temperature to 111 K at atmospheric pressure. It remains a Hquid at 191 K and 4.64 MPa (673 psig). 

Diamine. 2,2-Dimethyl-l,3-propanediamine [7328-91-8] (5) has been prepared by amination of neopentyl glycol by treating the glycol with ammonia and hydrogen at 150—250°C at 10—31 MPa (1500—4500 psig) over a Ni catalyst. The diamine is useflil for preparation of crystalline polyureas by reaction with diisocyanates (36). 

The metals are impregnated together or separately from soluble species, eg, Na2PdCl4 and HAuCl or acetates (159), and are fixed by drying or precipitation prior to reduction. In some instances sodium or potassium acetate is added as a promoter (160). The reaction of acetic acid, ethylene, and oxygen over these catalysts at ca 180°C and 618—791 kPa (75—100 psig) results in the formation of vinyl acetate with 92—94% selectivity the only other... 

MPa (300—400 psig), using a Ni-based catalyst. Temperatures up to 1000°C and pressures up to 3.79 MPa (550 psia) are used in an autothermal-type reformer, or secondary reformer, when the hydrogen is used for ammonia, or in some cases methanol, production. 

Anhydrous HCl is stored in Hquid form under pressure at —25° C and these pressure containers are rated for 2—24 MPa (300—350 psig). The material of constmction for this purpose is carbon steel which should be ductile at very low (—87°C) temperatures. 

Plastics and Elastomers. Common plastics and elastomers (qv) show exceUent resistance to hydrochloric acid within the temperature limits of the materials. Soft natural mbber compounds have been used for many years as liners for concentrated hydrochloric acid storage tanks up to a temperature of 60°C (see Rubber, natural). SemUiard mbber is used as linings in pipe and equipment at temperatures up to 70°C and hard mbber is used for pipes up to 50°C and pressures up to 345 kPa (50 psig). When contaminants are present, synthetic elastomers such as neoprene, nitrile, butyl. 

Air is compressed to modest pressures, typically 100 to 200 kPa ( 15-30 psig) with either a centrifugal or radial compressor, and mixed with superheated vaporized butane. Static mixers are normally employed to ensure good mixing. Butane concentrations are often limited to less than 1.7 mol 1 to stay below the lower flammable limit of butane (144). Operation of the reactor at butane concentrations below the flammable limit does not eliminate the requirement for combustion venting, and consequendy most processes use mpture disks on both the inlet and exit reactor heads. A dow diagram of the Huntsman fixed-bed maleic anhydride process is shown in Figure 1. 

Fig. 23. Two types of hollow-fiber modules used for gas separation, reverse osmosis, and ultrafiltration applications, (a) Shell-side feed modules are generally used for high pressure appHcations up to - 7 MPa (1000 psig). Fouling on the feed side of the membrane can be a problem with this design, and pretreatment of the feed stream to remove particulates is required, (b) Bore-side feed modules are generally used for medium pressure feed streams up to - 1 MPa (150 psig), where good flow control to minimise fouling and concentration polarization on the feed side of the membrane is desired.

The second type of hoUow-fiber module is the bore-side feed type illustrated in Figure 23b. The fibers in this type of unit are open at both ends, and the feed fluid is usually circulated through the bore of the fibers. To minimize pressure drops inside the fibers, the fibers often have larger diameters than the very fine fibers used in the shell-side feed system and are generally made by solution spinning. These so-called capillary fibers are used in ultrafiltration, pervaporation, and in some low to medium pressure gas appHcations. Feed pressures are usually limited to less than 1 MPa (150 psig) in this type of module. 

Fig. 34. Water and salt fluxes through a high performance reverse osmosis membrane, when tested with a 3.5% NaCl feed solution. The water flux increases, whereas the salt flux is essentially independent of appHed pressure (76). To convert MPa to psig, multiply by 145.

The deviation from the perfect gas law is not great at ordinary pressures and temperatures. At the highest pressure normally encountered commercially, 41 MPa (6000 psig), the compressibiUty factor of nitrogen is 1.3629 at 25°C (12). 

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