Reforming, autothermal

CRG catalyst is used in the reforming stage with a non-alkalized version of the 

Alwin Mittasch, Early Studies of Multicomponent Catalysts, Advances in Catalysis, Vol. 2, Academic Press, N. Y., 1950, p. 81. 

Industrial Catalysis, Ernest Benn, London, 1928, p. 327 Partington, J. Soc. Chem. Ind. 40 (1921) 99R. 

Brief History of ammonia production. Nitrogen, No. 100, British Sulphur Publishing (March-April 1976), p. 49. 

Lewis B. Nelson, History of the US fertilizer industry, Termessee Valley Authority, 1990, p. 227. 

Autothermal reformers combine some of the best features of steam reforming and partial oxidation systems. A hydrocarbon feedstock (methane or a liquid fuel) is reacted with both steam and air (or oxygen) to produce a hydrogen-rich gas, i.e.. 

The reaction takes place at high temperature (950-1100 °C) and at pressures up to 10 MPa. During this process, both the steam reforming and partial oxidation reactions run concurrently. With the right mixture of input fuel, air/oxygen and steam, the latter process supplies all the heat required to drive the former. 

Two-step reforming features are a combination of tubular reforming (primary reformer) and oxygen-fired secondary (autothermal) reforming. In this concept the tubular reformer is operating at less severe operation, i.e. lower outlet temperatures (refer to Section 2.6.2). 

The ATR technology was pioneered by SB A and BASF in the 1930s [413], by Topsoe and SBA in the 1950s [331], and later Topsoe alone [107] [111] developed the technology at first for ammonia plants and later for large-scale gas-to-liquid plants. Today, ATR is a cost-effective technology for the synthesis gas section for a variety of applications [187]. 

The feedstocks are hydrocarbons, steam, and either oxygen or air (or a mixture thereof). Optionally, carbon dioxide may be added to the hydrocarbon stream (refer to Section 2.4.2). The mixture of hydrocarbon and steam is preheated and mixed with oxygen in the burner. An adiabatic prereformer may be advantageous to eliminate thermal cracking of higher hydrocarbons in the preheater. 

A turbulent diffusion flame ensuring intensive mixing is essential to avoid soot formation. The burner is designed to avoid excessive metal temperatures in order to ensure long lifetime [109]. 

Typically, the molar ratio of oxygen (as O2) to carbon in the hydrocarbon feed stream is 0.5—0.6 with oxygen as the oxidant [111] and the temperature of the flame core may be higher dian 2000°C. Hence, the design of the combustion zone is made to minimise transfer of heat from the flame to the burner [107]. 

An alternative approach to CPO and CSR is ATR, which results from a combination of these two techniques. 

Typically, ATR reactions are considered to be thermally self-sustaining and therefore do not produce or consume external thermal energy. In fact, since ATR consists of the combination of an exothermic reaction (CPO) which produces heat, with an endothermic reaction (CSR) where heat must be externally generated to the reformer, the balance of the specific heat for each reaction becomes a very distinctive characteristic of this process. This makes the whole process relatively more energy efficient since the heat produced from CPO can transfer directly to be used by CSR. However, other exothermic reactions may simultaneously occur, such as WGS and methanation reactions. 

The composition of the gas produced is determined by the thermodynamic equilibrium of these reactions at the exit temperature, which is given by the adiabatic heat balance based on the composition and flow of the feed, steam and oxygen added to the reactor. 

A typical ATR reactor consists of a burner, a combustion chamber and a refractory-lined pressure vessel where the catalyst or catalysts are placed. The key elements in the reactor are the burner and the catalyst. Different geometries for ATR reactors have been proposed, considering, for instance, fixed beds or fluidized beds. 

The severe operating conditions in ATR necessitate catalysts with good mechanical properties and which are stable at the high temperatures of the reaction (650-900 ° C) and at the high steam partial pressure applied. 

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Hydrogen production by methanol autothermal reforming with high conductivity honeycomb supports... 

Schematic diagram of the reactor for ATR of hydrocarbons. 1 = Autothermal reformer, 2 = burner section, 3 = combustion chamber, 4 = catalyst, and 5 = heater.

Schematics of the reformer section of combined reforming of NG. 1 = Fired tubular reformer, 2 = furnace, and 3 = autothermal reformer.

N2-H2 mixture (with small amounts of Ar and CH4) [33]. The amount of air added to the secondary reformer is adjusted to give the desirable H2/N2 ratio (which is close to 3 for the NH3 synthesis). The secondary reformer is similar to the autothermal reformer described in the previous section. The pressure at the outlet of the secondary reformer is in the range 2.5-3.5 MPa. The outlet temperatures from the primary and secondary reformers are 750-850°C and 950-1050°C, respectively. 

Liu, D. et al., Characterization of kilowatt-scale autothermal reformer for production of hydrogen from heavy hydrocarbons, Int. ]. Hydrogen Energ., 29,1035, 2004. 

Cavallaro, S. Freni, S., Syngas and electricity production by an integrated autothermal reforming molten carbonate fuel cell system. Journal of Power Sources 1998, 76,190-196. 

ATR(l) [Autothermal reforming] A process for making CO-enriched syngas. It combines partial oxidation with adiabatic steam-reforming. Developed in the late 1950s for ammonia and methanol synthesis. Further developed in the 1990s by Haldor Topsoe. 

CAR [Combined autothermal reforming] A "reforming process for making "syngas from light hydrocarbons, in which the heat is provided by partial oxidation in a section of the reactor. Developed by Uhde and commercialized at an oil refinery at Strazske, Slovakia, in 1991. 

Oxidative Steam Reforming (OSR) / Autothermal Reforming of Ethanol... 

OSR) rather than autothermal reforming.23-26 The OSR concept has been reported for the first time in the reforming of methanol for H2 production27,28 and this methodology has been widely employed by others for the reforming of methanol and... 

Oxidative steam reforming/autothermal reforming of ethanol... 

Fig. 11 Free energy changes in the oxidative steam reforming/autothermal reforming of ethanol, acetaldehyde and methane.

Kinetics. Being a relatively new approach for the production of H2 from ethanol, work on the kinetics of the OSR/autothermal reforming of ethanol has been very limited in the literature. Kinetic studies would be very helpful to understand the rate determining step and activation energies of this complex reaction. 

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