Reformate purification

K. B. V. Reddy, B. A. Wilhite, Theoretical investigatirm of a water-gas-shift catalytic membrane for diesel reformate purification, AIChE J. 59 (2013) 4334—4344. 

Hence, if the hydrogen is produced from hydrocarbon or alcohol reforming, purification is required in order to reduce the CO levels to cell requirements. The most technologically feasible purification train consists of a water gas shift reaction (WGS). The reaction... 

IdaTech LLC developed a 2-kW methanol steam reformer, which worked with a palladium membrane for reformate purification. The purified hydrogen then supplied a Ballard NEXA PEM fuel cell stack. Lbffler et al. [105] and Edlund [419] described the reformer design of Idatech (see Sections 5.2.4 and 9.4). Later, IdaTech presented a 250-W methanol fuel processor/fuel cell system known as IGen , which is shown in Figure 9.13. The system had a weight of 12 kg and a volume of about 30 L. 

Since 2004 Volkswagen has been developing a diesel fuel processor/fuel cell system with IdaTech LLC, US. The system works with a palladium membrane for reformate purification. 

Reformate purification. This is necessary because the PEFC stacks are sensitive to even trace concentrations of contaminants. Especially CO and sulfur are problematic species, and must be reduced to levels of around 10 and 1 ppm or less, respectively. Sulfur removal is, in actuality, done upstream in the process (just before or just after the reformer), but CO removal must be done just prior to stack entry. 

Duke, M., Rudolph, V., Lu, G. Q. and Dinizda Costa, J.C. (2004a) Scale-up of molecular sieve silica membranes for reformate purification. AIChE Journal, 50, 2630-2634. 

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

Steam-Reforming Natural Gas. Natural gas is the single most common raw material for the manufacture of ammonia. A typical flow sheet for a high capacity single-train ammonia plant is iadicated ia Figure 12. The important process steps are feedstock purification, primary and secondary reforming, shift conversion, carbon dioxide removal, synthesis gas purification, ammonia synthesis, and recovery. 

Feed Ga.s Purifica.tion. Because nickel-based reforming catalysts are quite sensitive to sulfur, halogen, and heavy metal poisons which may be found ia natural gas, a feedstock purification system is normally required. Sulfur compounds, ia both organic and inorganic forms, are the most common... 

Reflux overhead vapor recompression, staged crude pre-heat, mechanical vacuum pumps Fluid coking to gasification, turbine power recovery train at the FCC, hydraulic turbine power recovery, membrane hydrogen purification, unit to hydrocracker recycle loop Improved catalysts (reforming), and hydraulic turbine power recovery Process management and integration... 

Figure 4.1. A process for producing hydrogen by steam reforming of hydrocarbons (1) reforming furnace (2,3) purification section, (4) shift converter, (5) pressure swing adsorption.

CH3)2. CH.CH2.CH3 mw 72.15, colorl liq, mp -159.9°, bp 27.85°, d 0.6201 g/cc at 20/4°, RI 1.35370. Sol in ethanol, ether, hydrocarbons and oils, insol in w. First prepd by Frankland in 1850 by treating iso-amyl iodide with Zn in w at 140° (Ref 2). It was isolated by Young from American petroleum (Ref 3). Present methods of prepn include fractional distn of petroleum and subsequent purification of the crude isopentane by rectification, as well as cracking and reforming of crude oil components and natural gasolines in oil refineries (Refs 4 7)... 

Trinuclear carbonyls have been studied with the anticipation that the retention would prove to be in some way inversely related to the molecular complexity. The values obtained were surprisingly high, despite careful chemical purification, as is shown in Table 10. It was suggested that the reformation mechanism must involve exchange reactions during and after the hot zone, starting with M(CO)4, as building blocks . 

Ethanol is a nontoxic substance with relatively high H2 content, and its advantage is that it can be produced from renewable sources, for example, from various biomasses and wastes. In addition, purification of the produced reforming gas has been of interest to researchers. Hydrogen purification has been studied, for instance, with membranes [19] which can also have catalytic performances. 

Purification of the generated gas by catalytic autothermal steam reforming of a broad spectrum of hydrocarbons to generate a raw synthesis gas consisting mainly of CO and H2 as energy carriers. 

Although considerable research has been conducted with Pd-alloy foils, tubes, and thinner composite membranes, long-term durability and stability need to be further demonstrated, especially in the fuel reforming or WGS operating conditions, for acceptance of this technology in a commercial sector. Furthermore, mass-scale and cost-effective production of industrial-scale Pd-alloy thin-film composite membranes need to be demonstrated to be competitive in the hydrogen production and purification market. 

Lin, Y.M. and M.H. Rei, Separation of hydrogen from the gas mixture out of a catalytic reformer by using supported palladium membrane, Sep. Purif. Technol., 25,87-95,2001a. 

In most hydrogen plants, a pressure-swing adsorption (PSA) system is used for hydrogen purification. In these plants, a major portion of reformer fuel is PSA offgas with a hydrocarbon stream for makeup fuel. 

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