Partial oxidation processes

The electrons undergo the equivalent of a partial oxidation process ia a dark reaction to a positive potential of +0.4 V, and Photosystem I then raises the potential of the electrons to as high as —0.7 V. Under normal photosynthesis conditions, these electrons reduce tryphosphopyridine-nucleotide (TPN) to TPNH, which reduces carbon dioxide to organic plant material. In the biophotolysis of water, these electrons are diverted from carbon dioxide to a microbial hydrogenase for reduction of protons to hydrogen ... 

The partial-oxidation process differs only in the initial stages before the water gas shift converter. Because it is a noncatalyzed process, desulfurization can be carried out further downstream. The proportions of a mixture of heavy oil or coal, etc, O2, and steam, at very high temperature, are so adjusted that the exit gases contain a substantial proportion of H2 and carbon monoxide. 

Two processes, partial oxidation and thermal decomposition, are used for the production of carbon blacks. The partial oxidation process can be represented by the foUowiag reaction ... 

Equilibiium is achieved in steam leforming equilibiium is approached for partial oxidation process. 

Of the raw material hydrogen sources—natural gas, coal, and petroleum fractions—natural gas is the most often employed in ammonia plants in the 1990s and steam reforming is by far the most often used process. Partial oxidation processes are utilized where steam-reformable feeds are not available or in special situations where local conditions exist to provide favorable economics. Table 5 fists the contribution of the various feedstocks to world ammonia... 

Coal-Based Partial Oxidation Processes Two commercially establislied processes utilising coal feeds are the Lurgi process (32) and the Koppers-Tot2ek process (33) the process schemes are shown ia Figures 6 and 7, respectively. 

Heavy Hydrocarbon-Based Partial Oxidation Processes. Two major partial oxidation processes are commercially available, the SheU process (38) and the Texaco process (39). Operating conditions in the gas generator vary from 1200°C to 1370°C and from 3100 kPa to 8270 kPa (450—1200 psig). Generally, heavy oils are the hydrocarbon feeds however, the process can also accommodate feeds from natural gas to residual oils. 

An important industrial partial oxidation process is the conversion of propylene to acrylonitrile (26) ... 

The Texaeo Gasifieation proeess is a eontinuous, entrained flow, pressurised, non-eatalytie partial oxidation process in whieh earbonaeeous solids, liquids or gases reaet with oxygen. Gasification breaks the polymer ehains and eonverts the hydroearbons to their simplest forms. A detailed description is given of the proeess and its eommereial applieation. The proeess is a eommereially... 

Describe a few partial oxidation processes that are found downstream from the refinery. 

In the case of synthesis gasoline or diesel fuel from natural gas (GTL), synthesis gas is produced by a combination of steam reforming and partial oxidation processes (combined reforming) to achieve a H2 CO ratio of generally 2.1 1. This means that the overall process energy demand can be reduced to its minimum. The individual reactions are ... 

As the name implies, partial oxidation, or POX, is the partial, or incomplete, combustion of a fuel. A sub stoichiometric amount of air, or oxygen, is used. This partial oxidation process is highly exothermic and raises the reactants to a high temperature. 

The partial oxidation of ethanol was investigated, but with less intensity than in the case of steam reforming. The reason is that the use of the pure partial oxidation process is not advised for bioethanol reforming because bioethanol is an ethanol-water mixture in which removal of all the water entails a significant cost. Therefore, for bioethanol partial oxidation, the process is combined with steam reforming in autothermal schemes with the stoichiometry shown in Equation 6.18. 

This is another partial oxidation process that is usually carried out in several reactors in series with both air and HNO3 as oxidants. The student might guess that this reaction is far from the only one, and much CO, CO2, alcohols, aldehydes, and other acids are also produced that must be separated from the TPA before it is reacted to form PET. 

The gas phase oxidation of naphthalene to phthalic anhydride over V2Os-based catalysts is one of the oldest successful partial oxidation processes and is still of industrial importance today. Common commercial catalysts are modified silica-supported V—K—S—O catalysts and catalysts similar to those used for benzene or o-xylene oxidation. Maximum phthalic anhydride yields of 80—85 mol. % (92—98 wt. %) at 350—400°C are reported. By-products are naphthoquinone (2—5%), maleic anhydride (2— 5%) and carbon oxides. 

In the past, coal or heavy hydrocarbon feedstock ammonia plants were not economically competitive with plants where the feedstocks were light hydrocarbons (natural gas to naphtha). Because of changing economics, however, plants that can handle heavy hydrocarbon feedstock are now attracting increasing attention- In addition, the continuous development and improvement of partial oxidation processes at higher pressure have allowed reductions in equipment size and cost. Therefore, the alternate feedback ammonia plants based on a partial oxidation process may become economically competitive in the near future. 

Unfortunately, the absolute value of the metal-oxygen bond energy does not unambiguously define the level of selectivity in the partial oxidation process. In addition, the specific interactions between the substance being oxidized and the catalyst surface and the character of the metal-oxygen bond are important parameters as well. 

In a catalytic partial oxidation process a CO/H2 ratio is realized of 2 1. Steam transforms this mixture into a mixture of C02 and H2. C02 removal by solvent absorption, followed by desorption and compression for storage requires 1.3GJ/ton C02. To what fraction of the exergy content of the produced H2 does this correspond And to what fraction of the exergy content of the original coal, assuming an overall efficiency from coal to H2 of 70%. 

Partial oxidation processes rank next to steam-hydrocarbon processes in the amount of hydrogen made. They can use natural gas, refinery gas, or other hydrocarbon gas mixtures as feedstocks, but their chief advantage is that they can also accept liquid hydrocarbon feedstocks such as gas oil, diesel oil, and even heavy fuel oil. All processes employ noncatalytic partial combustion of the hydrocarbon feed with oxygen in the presence of steam in a combustion chamber at flame temperatures between 1300 and 1500°C. For example, with methane as the principal component of the feedstock ... 

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