Synthesis once-through

This takes place in the liquid phase, around 145 to 175 0. between 0.8 and 1.10 Pa absolute, in the presence of a soluble cobalt salt (naphthenate or ocxoate), as shown in Section 10.1.6.1 concerning phenol synthesis. Once-through conversion is 4 to 6 per cent and the total yield of a cyciohexanol/cydohexanone mixture, adipic add and its esters is about 80 molar per cent (Stamicdrbon process). 

Coproduction of electricity along with synthesis gas conversion offers the potential for significant cost savings. The once-through liquid-phase methanol technology was developed specifically for this... 

The ammonia synthesis takes place in two steps at different pressures (see Figure 6.15). In the first step, makeup gas is compressed to about 110 bar in a two-stage, intercooled compressor. The makeup gas is then fed to a three-bed, intercooled, once-through converter to produce about one-third of the ammonia. About 85% of the ammonia product is separated from the gas, which is then compressed to the standard pressure of up to 210 bar for the second-stage ammonia synthesis loop215,218. 

Application Production of ammonia from natural gas, LNG, LPG or naphtha. The process uses conventional steam reforming synthesis gas generation in the front-end, while the synthesis section comprises a once-through section followed by a synthesis loop. It is thus optimized with respect to enable ammonia plants to produce very large capacities with proven equipment. The first plant based on this process will be the SAFCO IV ammonia plant in Al-Jubail, Saudi Arabia, which is currently under construction. This concept provides the basis for even larger plants (4,000-5,000 mtpd). 

The ammonia synthesis loop consists of two stages. Makeup gas is compressed in a two-stage inter-cooled compressor, which is the low-pressure casing of the syngas compressor. Discharge pressure of this compressor is about 110 bar. An indirectly cooled once-through converter at this location produces one third of the total ammonia. Effluent from this converter is cooled and the major part of the ammonia produced is separated from the gas. 

Liquid ammonia is separated by condensation from the once through section, and the synthesis loop and is either subcooled and routed to storage, or conveyed at moderate temperature to subsequent consumers. 

Figure 2 shows the initial methanol synthesis activities of M-1, M-2, P-1 and P-2 catalysts at 483 523K in once-through reaction using the microreactor. The methanol yield is defined by the following equation to evaluate the methanol synthesis activity of each catalyst ... 

Udhe GmbH Ammonia—Dual pressure process Natural gas, LPG, naphtha Process uses conventional steam reforming synthesis gas generation in the front-end, while the synthesis section comprises a once-through section followed by a synthesis loop 2 NA... 

Cyclohexanone oxime is produced by the reaction of cyclohexanone with a hydroxylamine derivative. Several commercial processes are available for this step, and they differ mainly in the manufacture of the hydroxylamine derivative. At the beginning of the 1990s, a once-through synthesis of cyclohexanone oxime was claimed by EniChem (224,299). 

In addition to a small quantity of dissolved gas, mainly carbon dioxide, the raw methanol depending upon the CO2 content of the synthesis gas contains between 3.5 and 12 wt. % water as well as a number of impurities varying with the selectivity of the catalyst used and the CO content of the reactw feed gas. Crude methanol produced from synthesis gas with low CH4 content recovered from coal generally contains up to 3 500ppm byproduct in the case of a process operating with a gas loop. Byproduct formation rises to ten times this value in once through processes. Table 3.7 shows a typical crude methanol composition as can be expected on a catalyst with good selectivity and a CO partial pressure of about 6 bar in the reactor feed gas. 

Because of the problems associated with current CPL production, the focus of EniChem work has been the development of an "once-through synthesis of cyclohexanone oxime that would satisfy the following requirements 1) introduction... 

Methanol can be produced as co-product in the ammonia synthesis [239] [406]. The CO and CO2 for the methanol synthesis is obtained by a partial bypass of the shift converters and the CO2 wash. The methanol synthesis takes place in an adiabatic reactor or a simple once-through boiling water reactor and the unconverted S5mgas is passed through a methanator back to the ammonia synthesis loop. 

The combined methanol/dimethylether synthesis pushes the equilibrium to higher once-through conversion as illustrated in Table 2.15. 

Table 2.15 IGCC and once-through synthesis. (Shell gasifier) [418].

Hydrogen Enrichment of Synthesis Gas for Once-Through Methanol Production. Palo Alto, California Electric Power Research Institute, April 1987. AP-5123. 

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