Atmospheric pressure regenerator

For the case shown in Figure 11-32, it is assumed that a natural gas stream is saturated with water at SOO psia and 90°F and that it is desired to dehydrate this gas to a water content of 10 Ib/MMscf (dew point 28°F). With triethylene glycol a concentration of 98.5% can readily be attained with simple atmospheric pressure regeneration. The dew-point chart. Figure 11-15, shows an equilibrium dew point of about I5°F for this glycol concentration, equivalent to a 13°F approach at the top of the column. 

In general, where a simple triethylene glycol unit (atmospheric-pressure regeneration) is applicable, it is more economical from both an initial and operating-cost standpoint than a typical di7-desiccani. system. A comparison of approximate equipment costs for natural-gas dehy-... 

The regeneration of molecular sieve beds in FEP systems is accomplished by flowing heated nitrogen through the bed, in the reverse direction to adsorption, at approximately atmospheric pressure. Regeneration temperatures are modest, 90° to I00°C (194° to 2I2°F), but an amount of nitrogen equal to about 20 to 30% of the inlet air is required. The bed is cooled with low temperature nitrogen before it is ready for the adsorption step. 

In addition to the Hquid-phase -butyl nitrite (BN) process, UBE Industries has estabHshed an industrial gas-phase process using methyl nitrite (50—52). The oudine of the process is described in Eigure 4 (52). This gas-phase process is operated under lower reaction pressure (at atmospheric pressure up to 490 kPa = 71 psi) and is more economical than the Hquid-phase process because of the foUowing reasons owing to the low pressure operation, the consumption of electricity is largely reduced (—60%) dimethyl oxalate (DMO) formation and the methyl nitrite (MN) regeneration reaction are mn... 

W ste Hea.t Boilers. In a conventional FCCU flue gas system, the regenerator combustion gases pass through two stages of cyclonic separators, a sHde valve, orifice chamber, waste heat boiler, and electrostatic precipitator. The sHde valve and orifice chamber act in combination to reduce the flue gas to essentially atmospheric pressure. 

The connection box cooler receives regenerator flue gas after it has been reduced to essentially atmospheric pressure. This arrangement is not limited to the production of saturated steam. Any number of coils can be installed in the box, and normally both steam-generating and superheater coils are present. The tube temperatures within the box must be maintained above the SO dew point of 150—175°C to prevent sulfuric acid corrosion (63). 

In most units, the flue gas pressure is reduced to atmospheric pressure across an orifice chamber. The orifice chamber is a vessel containing a series of perforated plates designed to maintain a given back-pressure upstream of the regenerator pressure control valve. 

In this process, propane, and a small amount of hydrogen to control coking, are fed to either a fixed bed or moving bed reactor at 950—1300° F and near atmospheric pressure. Once again the catalyst, this time platinum on activated alumina impregnated with 20% chromium, promotes the reaction. In either design, the catalyst has to be regenerated continuously to maintain its activity. 

In view of these considerations, a large amount of effort is reported in the scientific press on the development of a process to produce benzene from n-hexane by combined cyclization and dehydrogenation. w-Hexane has a low Research octane number of only 24.8 and can be separated in fair purities from virgin naphthas by simple distillation. Recently, an announcement was made of a process in the laboratory stage for aromatiza-tion of n-hexane (16). The process utilizes a chromia-alumina catalyst at 900° F., atmospheric pressure, and a liquid space velocity of about one volume of liquid per volume of catalyst per hour. The liquid product contains about 36% benzene with 64% of hexane plus olefin. The catalyst was shown to be regenerable with a mixture of air and nitrogen. The tests were made on a unit of the fixed-bed type, but it was indicated that the fluid technique probably could be used. If commercial application of this or similar processes can be achieved economically, it could be of immense help in relieving the benzene short-age. 

Regeneration via Fluid-Bed Combustion. Table V gives the conditions of runs presented here—essentially atmospheric pressure, superficial residence time of 1 sec, excess air (115% of stoichiometric), silica bed solids. Temperatures of 983° and 1038°C were investigated. No... 

Existing physical absorption AGR processes are relatively energy inefficient for application in coal gasification they use substantial amounts of steam or stripping gas to regenerate lean solvent and power to pump lean solvent into the AGR absorber. In the treatment of crude gas with substantial carbon dioxide content, work available by expansion of separated carbon dioxide from its partial pressure in the crude gas, typically 100-300 psia, to atmospheric pressure, is not recovered. In theory, an AGR process could recover and utilize this potential energy. 

Heck demonstrated Eq. (89) for a number of acylcobalt carbonyls, preparing them from the corresponding alkyl halide and sodium cobalt carbonylate. In the presence of bases, cobalt hydrocarbonyl regenerated cobalt carbonylate ion and a catalytic reaction resulted at atmospheric pressure and at temperatures from 0° to 100° C. Thus the following reaction was reported in 56% yield at 50° C ... 

Today s coke plant gas purification processes are mostly carried out under atmospheric pressure, employing a circulated ammonia-based absorbent. The consumption of the external solvent is reduced via the use of ammonia available in the coke gas (138). An example of innovative purification processes is the ammonia hydrogen sulfide circulation scrubbing (ASCS) (Figure 17), in which the ammonia contained in the raw gas dissolves in the NH3 absorber and then the absorbent saturated with the ammonia passes through the H2S absorber to selectively absorb the H2S and HCN components from the coke gas. The next step is the thermal regeneration of the absorbent with the steam in a two-step desorption plant, whereas a part of the deaciditied water is fed back into the H2S absorber (25). 

Cracking of n-heptane was carried out on catalysts USY-1 and U1F-25 in a continuous flow, fixed bed reactor (15), at 450 aC and atmospheric pressure. In all experiments, 0.223 g of zeolite catalyst, and 8.625 g of n-heptane were used. With each catalyst the reaction was performed at 75, 150 and 375 seconds of time on stream. The catalyst was regenerated "in situ" after each experiment by passing flow of air at 5209C during 4 hours, and liquids were analyzed by GC by means of a Porapak-Q silica and a S-30 columns respectively. 

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