Oxidation non-catalytic partial

Another method of production, widely used by refineries, is partial oxidation of hydrocarbons such as crude oil or natural gas. This process is widely used at European refineries to produce hydrogen additives for fuels, petrochemicals, and other hydrogen uses. The basic process is carried out at temperatures of 1200-1450°C and requires pure oxygen. The NPO process is inherently less efficient than steam reforming. 

Based on existing technology, a refinery hydrogen unit, using crude oil as a feedstock and a rated output of IOOMW-H2, has a capital cost of 50 million, or an overnight capital cost of approximately 500.5 /kW-H2 (CONCAWE 1999). Based on a thermal efficiency of 36.8%, the crude oil input for this facility is estimated at 8.6 million GJ per year, or 3.1 million GJ-H2. The O M costs are difficult to separate from that of the refinery itself. H2 im initially assumes annual O M costs for the hydrogen refinery unit are 4% of the overnight capital costs. 

While the costs for the other production facilities in H2Sim are estimates for 2020, the NPO estimates are for a facility built in 2005. H2Sim assumes no large changes in these costs (adjusted for inflation) by 2020. The real room for improvement with NPO is the overall efficiency. 

If hydrocarbons are used for the production of hydrogen, whether as a feedstock or for the production of electricity, then there will be emissions of carbon dioxide. In reality, cars using hydrogen produced via coal gasification could release higher amounts of carbon dioxide than current vehicles. As concerns about climate change propel the move to a hydrogen economy, it is important to discuss the carbon implications 

This estimate assumes a 1.4 GWt solar plant, with a 69% capacity factor and an efficiency of 45 % for the H2 thermochemical facility. 

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Non-catalytic partial oxidation (POX) of hydrocarbons from residual fuel oils to methane is commercially proven by two processes, one offered by Texaco and the other by Shell. Davy has experience with both processes. Each process has a large number of plants in operation, with feeds varying from natural gas to high sulfur residual oil. (In fact, so long as the feedstock can be pumped, it is a suitable feestock for a partial oxidation gasifier. 

A non-catalytic partial oxidation process based on the above reactions has been largely used for the past five decades for a wide variety of feedstocks, in particular heavy fractions of refinery, such as naphtha, vacuum fuel oil, asphalt residual fuel oil, or even whole cmde oil. The absence of catalysts implies that the operation of the production unit is simpler (decreased desulfurization requirement) but the working temperatures results higher than 1200°C. The high values of this parameter permit satisfactory yield to H2 and CO to be obtained without using a selective catalyst. 

A catalytic partial oxidation (CPO) reaction permits operation temperature to be lowered and meets the requirements of recently proposed decentralized applications based on small-scale reformer plants [17], better than the SR or the non-catalytic partial oxidation process. This evaluation is based on the dependence of costs associated with both SR and CPO manufacmre and management plants by... 

Without consideration of microsystems vhere exothermic processes could be coupled effectively with the SR process, the kinetics, and hence the throughput, are considerably limited by the rate at which the heat can be transferred to the catalytic bed where the endothermic reforming takes place [1]. In most industrial cases, the heat is transferred inside the reactor by non-catalytic partial oxidation (POX) (Equation 25.2) and by autothermal reforming (ATR) (Equation 25.3) in adjacent reaction chambers. 

As mentioned before, autothermal reforming can also be achieved via non-catalytic partial oxidation. As an example, the scheme presented in Figure 8 shows a partial oxidation route to produce synthesis gas. 

Gasification of Methane and oxygen to syngas, a non-catalytic partial oxidation reaction taking place at temperatures above 1300°C... 

The non-catalytic partial oxidation [486] (POX, Texaco, Shell) needs high temperature to ensure complete conversion of methane and to reduce soot formation. Some soot is normally formed and is removed in a separate soot scrubber system downstream of the partial oxidation reactor. The thermal processes typically result in a product gas with H2/C0=1.7—1.8. Gasification of heavy oil fractions, petcoke, coal and biomass may play an increasing role as these fiaetions are becoming more available and natural gas (NG) less available. 

Contrary to the catalytic steam reforming, the non-catalytic partial oxidation process is also suitable for heavier hydrocarbons such as heavy oils, pitch or coal. Usually, oxidation takes place with prue oxygen. If air is used, the effort for the separation of nitrogen from the synthesis gas would be higher than for the air separation. The reaction is strongly exothermal and is realized uncooled in the... 

Non-catalytic partial oxidation is applied indnstrially by Texaco and Shell for the conversion of heavy oils to synthesis gas. In the ease of the Shell, basic partial oxidation process, liqnid fnel is fed to a reactor together with oxygen, and steam. A partial combustion takes place in the reactor, which yields a product at around 1150°C. It is this high temperature that poses a particular problem for conventional partial oxidation. The reactor has to be made of expensive materials to withstand the high temperatures, and the... 

Process Conditions. When using oxygen for the conversion of hydrocarbons, it is possible to achieve high equilibrium temperatures. This allows the use of high pressures (40-50 bar) while still maintaining a low content of methane in the product gas. The non-catalytic partial oxidation (Texaco, Shell) requires very high temperature (ca. 1400°C) in order to cope with carbon formation. 

Briiggemann, P., Seifert, P., Meyer, B., and Miiller-Hagedorn, M. (2010) Influence of temperature and pressure on the non-catalytic partial oxidation of natural gas. 

Feng W, Knopf FC, Dooley KM. Effects of pressure, third bodies, and temperature profiling on the non-catalytic partial oxidation of methane. Energy Fuels 1994 8 815—22. 

The design of secondary reformers is discussed in [90, 92, 127]. Special designs where primary and secondary reforming or primary reforming and non-catalytic partial oxidation are combined in one unit are suggested in [128-130, 964]. 

Non-catalytic partial oxidation or gasification of hydrocarbons or solid feedstocks are alternatives to steam reforming and autothermal reforming for production of synthesis gas. 

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