Autothermal Reforming
Autothermal reforming (ATR) combines the steam reforming reaction and fuel
oxidation into a single unit, the exothermic oxidation providing the heat for the
endothermic reforming process.
From: Polymer Electrolyte Membrane and Direct Methanol Fuel Cell Technology:
Fundamentals and Performance of Low Temperature Fuel Cells, 2012
Related terms:
Natural Gas, Glycerol, Hydrogen Production, Partial Oxidation, Hydrogen, Carbon
Monoxide, Syngas, Steam Reforming
View all Topics
Traditional Routes for Hydrogen Production and Carbon Conversion
Jacob J. Lamb, ... Bruno G. Pollet, in Hydrogen, Biomass and Bioenergy, 2020
Autothermal reforming
Autothermal reforming (ATR) is a combination of SR and POR (both reactions
manifest themselves in one compact reactor). The ATR reactor vessel contains a
combustion zone and a set catalyst bed among a refractory-lined pressure shell. In
ATR, H2 or H2-enriched gas is injected along with steam to produce CH4. ATR is
generally operated between temperatures of 950–1050°C, a pressure of 30–50 bar,
a steam-to-carbon molar ratio (S/C ratio) of 0.5–1.5, and an oxygen-to-carbon molar
ratio (O/C ratio) of 0.6–1.0 [71–73].
> Read full chapter
The role of the fuel in the operation,
performance and degradation of fuel
cells
D.J.L. Brett, ... I. Staffell, in Functional Materials for Sustainable Energy Applications,
2012
9.3.3 Autothermal reforming
Autothermal reforming (ATR) combines the steam reforming reaction and fuel
oxidation into a single unit, the exothermic oxidation providing the heat for the endothermic reforming process. ATR is popular for smallerscale hydrogen generation
and affords higher H2 production than POX and faster start-up and response times
than steam reforming. Independent control of the steam-to-carbon and air-to-fuel
ratios means that effective heat management can be achieved.
Early ATR systems were composed of separate, but thermally integrated, burner and
steam reformer. The challenge for single-unit ATR is that the catalyst must service (or
at least be compatible with) both the steam reforming and partial oxidation reactions
and their environment. Again, the choice of catalyst must be matched to the type of
fuel used. Lighter hydrocarbons can use copper-based catalysts with longer chain
molecules using Pt, Rh and Ru or ionconduction ceria supported non-noble metal
formulation: Fe, Co, Ni (Ghenciu, 2002). PGM cermet catalysts with bi-functional
properties have more recently been developed for ATR: the PGM services the dehydrogenation role and the oxide ion conducting properties of the ceramic component
(e.g., CeO2, ZrO2, Bi2O5) perform the selective oxidation function (Ghenciu, 2002).
> Read full chapter
FUELS – HYDROGEN STORAGE |
Chemical Carriers
T.A. Semelsberger, in Encyclopedia of Electrochemical Power Sources, 2009
Autothermal reforming
Autothermal reforming is the combination of the steam reforming reaction and
the partial oxidation reaction resulting in a net reaction enthalpy of zero. The
autothermal reforming of DME based on thermodynamics (i.e., Gibbs free energy minimization) at 187 °C is shown in eqn [V]. The advantages of autothermal
reforming as compared to steam reforming are the increased energy efficiency
and faster start-up times, faster response times to transient operation. In addition,
higher hydrogen production efficiencies can be expected as compared to partial
oxidation along with an increase in energy efficiency.
[V]
> Read full chapter
FUELS – HYDROGEN PRODUCTION
| Autothermal Reforming
S. Assabumrungrat, N. Laosiripojana, in Encyclopedia of Electrochemical Power
Sources, 2009
Concluding Remarks
Autothermal reforming, which is the combined process of steam reforming and partial oxidation, is a promising technology for low-cost and high-reliability hydrogen
production. Compared to steam reforming, it is easier to operate with a smaller
system, better temperature control, lower operational temperature, lower energy
requirements, easier start-up, and less coking. However, a major drawback of autothermal reforming is the large investment needed for an oxygen production plant,
which simply becomes cost-effective only at high production capacities. Although air
can be directly used instead of oxygen, the presence of inert nitrogen causes large
gas volume and the system, therefore, requires larger equipment.
Generally, the autothermal reforming process is operated under adiabatic conditions
and the product composition as well as the reaction temperature is governed by
various operating parameters, e.g., preheat temperature of fuel, water, and air,
pressure, fuel composition, heat loss, steam-to-carbon ratio, and air-to-carbon ratio.
The suitable fuel for autothermal reforming is highly flexible, such as several gaseous
hydrocarbons, e.g., methane, natural gas, LPG, as well as liquid hydrocarbons,
e.g., gasoline, diesel, alcohols, naphtha, residual oil, ethylene glycol, and glycerol.
An appropriate operation condition (e.g., catalysts, temperature, fuel/oxidant ratio,
and treatment process) is strongly dependent on the fuel quality, i.e., the number of carbons and the purity of each fuel. The use of a heavy hydrocarbon fuel
with some impurities can easily suppress the reforming performance because of
coke formation and catalyst poisoning. Although less carbon deposition is usually
observed in autothermal reforming compared to steam reforming, significant
amounts of carbon deposition are still widely reported in the autothermal reforming
of propane, butane, and gasoline even under steam-rich conditions. Sulfur, even at
small amounts, can significantly reduce the catalyst service life.
Several precious metals, e.g., rhodium, pallodium, and platinum, have been widely
applied in autothermal reforming reactions because of their high reactivity with
great resistance toward carbon formation. Rhodium seems to be the most ac-
tive metal giving the highest activity and stability toward autothermal reforming.
Platinum is also a widely used precious metal for the reaction, and several researchers have reported on the comparable reforming performance of platinum
and rhodium catalysts. Palladium is another promising metal for the autothermal
reforming of oxyhydrocarbons, e.g., methanol. Recently, several investigations have
focused on the development of other alternative reforming catalysts, e.g., bimetallic
catalysts, ceria-based catalysts, and perovskite-based catalysts, to reduce catalyst
cost. A number of publications have reported the benefits of bimetallic catalysts
in terms of stability, activity, and resistance toward poisoning. For the ceria-based
catalysts, high resistance toward carbon deposition compared to conventional metal
catalysts has been widely reported, which is mainly related to the high OSC of ceria.
Perovskite-based catalysts with substitution on A and B sites with alkali earth metals
have also been considered as a promising catalyst for the autothermal reforming
reactions.
Regarding the role of the catalyst support in the reforming reactivity, until now,
several contradictory conclusions have been reported in the literature. Some studies
have concluded that catalyst supports show no effect on the catalyst reactivity,
whereas some investigations have reported a strong impact of the supports on the
reforming performance in terms of reactivity and kinetics. Apart from the study
of the support, many studies have also focused on the improvement of catalyst
performance by the addition of a modifier or promoter. The doping of cerium
dioxide over Ni/Al2O3 can improve catalytic stability by avoiding thermal sintering of
catalyst metals and preventing the deposition of carbon species on the catalyst surface. Furthermore, alkaline earth oxides, e.g., calcium oxide (CaO) and magnesium
oxide, and rare earth oxides are also known as good modifier materials for Ni-based
catalysts to reduce the amount of carbon formation.
A typical autothermal reforming reactor usually consists of a burner, a combustion
chamber, and a refractory-lined pressure vessel where catalytic reactions take place.
Recently, research and development efforts have mostly shifted from large-scale
reformers to small- to medium-scale reformers particularly as onboard vehicular fuel
processors, and several configurations of autothermal reformers fueled by various
hydrocarbon fuels have been developed, e.g., Johnson Matthey, Epyx Corporation,
DaimlerChrysler, Analytic Power LLC, MTI, General Motors Corporation, and Fraunhofer ISE. In addition, and apart from the industrial efforts, autothermal reforming
has also drawn interest from the academic side. Various systems or techniques
have been proposed to further improve reactor performance, e.g., the coupling
of membrane technology with autothermal reforming, the use of microreactor
technology, and the operation of autothermal reforming in a periodic operation
mode.
> Read full chapter
The Fischer−Tropsch Process
James G. Speight PhD, DSc, in Gasification of Unconventional Feedstocks, 2014
2.2 Autothermal Reforming
Autothermal reforming (ATR) was developed in the 1950s and is used in commercial
applications to provide synthesis gas for ammonia and methanol synthesis (Chukwu,
2002; Krumpelt et al., 2002). In the case of ammonia production, where high H2/CO
ratios are needed, the autothermal reforming process is operated at high steam/carbon ratios. In the case of methanol synthesis, the required H2/CO ratio is provided
by manipulating the carbon dioxide recycle. In fact, development and optimization
of this technology has led to cost-effective operation at very low steam/carbon feed
ratios to produce carbon monoxide-rich synthesis gas, for example, that which is
preferred in Fischer−Tropsch synthesis.
In the autothermal reforming process, the organic feedstock (e.g., natural gas) and
steam (and sometimes carbon dioxide) are mixed directly with oxygen and air in the
reformer. The reformer itself comprises a refractory lined vessel which contains the
catalyst, together with an injector located at the top of the vessel. Partial oxidation
reactions occur in a region of the reactor referred to as the combustion zone. It is
the mixture from this zone which then flows through a catalyst bed where the actual
reforming reactions occur. Heat generated in the combustion zone from partial
oxidation reactions is utilized in the reforming zone, so that in the ideal case, it is
possible that the autothermal reforming process can exhibit heat balance.
When the autothermal reformer uses carbon dioxide, the H2:CO ratio produced is
1:1; when the autothermal reformer uses steam, the H2:CO ratio produced is 2.5:1.
The reactions can be described in the following equations, using CO2:
Using steam:
The reactor itself consists of three zones: (1) the burner – here the feed streams
are mixed in a turbulent diffusion flame, (2) the combustion zone – where partial
oxidation reactions produce a mixture of carbon monoxide and hydrogen, and (3)
the catalytic zone – where the gases leaving the combustion zone reaches thermodynamic equilibrium.
The following are the advantages of using the autothermal reforming process: (1)
compact in design, hence less associated footprint, (2) low investment, (3) economy
of scale, (4) flexible operation – short startup periods and fast load changes, and (5)
soot-free operation.
> Read full chapter
Hydrogen Production
Gernot Voitic, ... Viktor Hacker, in Fuel Cells and Hydrogen, 2018
10.2.3 Autothermal Reforming
ATR is a technology that combines steam reforming and the POX resulting in an
overall reaction enthalpy close to zero. The process consists of an initially POX
or CPOX zone, which supplies the process heat for the subsequent endothermic
steam reforming step. Operation conditions range between 900°C and 1500°C and
1–80 bar with a sharp temperature increase in the exothermic regions, and a steady
decrease in the subsequent endothermic section. The total heat balance and the
H2/CO ratio in the product gas are adjusted by varying values of S/C and O/C. The
ATR has a higher hydrogen yield than the POX and provides more flexibility in terms
of process conditions, start-up time, and complex feedstock utilization than the SR.
Hence, it is expected that this process will play an important role in future fuel
processing industries [6,9,10,14].
(10.4)
> Read full chapter
Fuels and fuel processing in SOFC applications
S. Sui, G.H. Xiu, in High-Temperature Solid Oxide Fuel Cells for the 21st Century,
2016
14.3.4 Autothermal reforming
ATR uses both oxygen (and sometimes carbon dioxide) and steam in a reaction with
hydrocarbon to form syngas. The reaction takes place in a single chamber where the
hydrocarbon is partially oxidised. The reaction is exothermic due to the oxidation.
ATR is a combination of endothermic SR reactions (Equations 14.3 and 14.5) and
exothermic POX reaction (Equations 14.12 and 14.13). The heat produced by the
POX is used in the SR reaction to generate syngas. It is desirable to balance the
reactions in such a way that it is essentially thermoneutral, requiring no net input
of heat. The overall reaction of ATR can be described by the following Equations
(14.16)–(14.19).
(14.16)
(14.17)
(14.18)
(14.19)
The thermoneutrality of the autothermal reactor depends on the values of n and
m. In an ideal configuration, the first portion of the reactor is filled with a POX
catalyst, followed by SR catalyst in the second part of the reactor. In this concept,
the heat generated from the exothermic POX reaction is strategically coupled with
the heat requirement of the endothermic SR reaction. With novel ATR catalysts
developed in the past decade [91,92], only small amounts of the catalyst are required
to initiate oxidation at low temperatures and to produce the heat required for the
SR reaction. Two different classes of materials have been examined: Group VIII
transition metals (e.g. platinum, rhodium or nickel) supported on an ion-conducting
oxide (e.g. ceria, gadolinium-doped ceria), and mixed non-noble metal oxides with
the ABO3 stoichiometry and the perovskite structure.
Development of a low-cost and efficient fuel cell system hinges, to a large extent,
on the development of small, compact and cost-effective reformers with reduced
start-up times. ATR is particularly attractive from these considerations [6]. The coupling of exothermic and endothermic reaction changes the dynamic behaviour of the
reactor, which can be quite complex with respect to parametric sensitivities. Heat loss
is minimised by integration of reaction and heat exchange, but making the reactor
less sensitive to perturbations remains a challenge as these disturbances influence
the catalytic activity in different zones along the axis of the reactor which, in turn,
strongly affects reactor performance. Design must therefore involve optimisation of
the operating conditions and reactor/catalyst structure [93].
> Read full chapter
Gasification processes for syngas and
hydrogen production
J.G. Speight, in Gasification for Synthetic Fuel Production, 2015
6.2.2 Autothermal reforming
Autothermal reforming (ATR) uses oxygen and carbon dioxide or steam in a reaction
with methane to form synthesis. The reaction takes place in a single chamber where
the methane is partially oxidized. The reaction is exothermic due to the oxidation.
The main difference between autothermal reforming and steam-methane reforming
is that steam-methane reforming does not use or require oxygen. The advantage
of autothermal reforming is that H2/CO can be varied, which is particularly useful
for producing certain second-generation biofuels such as dimethyl ether synthesis,
which requires a 1:1 H2/CO ratio.
The process was developed in the 1950s and is used in commercial applications
to provide syngas for ammonia and methanol synthesis. In the case of ammonia
production, where high H2/CO ratios are needed, the process is operated at high
steam/carbon ratios. In the case of methanol synthesis, the required H2/CO ratio
is provided by manipulating the carbon dioxide recycle. In fact, development and
optimization of this technology has led to cost-effective operation at very low
steam/carbon feed ratios to produce CO-rich syngas, for example, which is preferred
in FTS. These are the advantages of using the autothermal reactor: (1) the reactor is
compact in design and therefore has a smaller footprint; (2) it has flexibility in its
operation, with short startup periods and fast load changes; and (3) it is a soot-free
operation. In addition, the reactor offers a better economic profile.
In the process, an organic feedstock (such as natural gas) and steam (there may also
be low amounts of carbon dioxide in the feed) are mixed directly with oxygen and air
in the reformer. The reformer itself comprises a refractory-lined vessel that contains
the catalyst, together with an injector located at the top of the vessel. Partial oxidation
reactions occur in the combustion zone of the reactor and the gaseous mixture
then flows through a catalyst bed where the actual reforming reactions occur. Heat
generated in the combustion zone from partial oxidation reactions is utilized in the
reforming zone, so that in the ideal case, it is possible that the process can be in
complete heat balance.
The autothermal reforming reactor consists of three zones: (1) the burner, where
the feed streams are mixed in a turbulent diffusion flame; (2) the combustion
zone, where partial oxidation reactions produce a mixture of carbon monoxide and
hydrogen; and (3) the catalytic zone, where the gases leaving the combustion zone
attain thermodynamic equilibrium. Key elements in the reactor are the burner and
the catalyst bed – the burner provides mixing of the feed streams and the natural
gas is converted in a turbulent diffusion flame:
When carbon dioxide is present in the feed, the H2/CO ratio produced is on the order
of 1:1, but when the process employs steam, the H2/CO ratio produced is 2.5:1.
The risk of soot formation in an ATR reactor depends on a number of parameters,
including feed gas composition, temperature, pressure, and especially burner design. Soot precursors may be formed in the combustion chamber during operation,
so it is essential that the design of the burner, catalyst, and reactor is such that the
precursors are destroyed by the catalyst bed to avoid soot formation.
Many observers consider the combination of adiabatic pre-reforming and autothermal reforming at low H2O/C ratios to be the preferred layout for production of
synthesis gas for large gas-to-liquids plants.
> Read full chapter
Membrane reactors for autothermal reforming of methane, methanol, and
ethanol
A. Arratibel, ... F. Gallucci, in Membrane Reactors for Energy Applications and Basic
Chemical Production, 2015
3.6 Conclusions and future trends
ATR of methane, methanol, and ethanol can be efficiently carried out in membrane-based reactors. The hotspot formation, typical of autothermal reactions,
which is detrimental for the stability and selectivity of the membrane used in such
reactors, can be circumvented by using FBMRs.
The actual trend is thus the demonstration of this kind of reactor at scales larger
than laboratory scale. Different European projects are currently investigating such
reactors and building prototypes at different scales (see, for instance, DEMCAMER,
REFORCELL, FERRET, and FLUIDCELL projects).
Future trends will see the integration of membrane reactors with other efficient
separation systems. An example is given in this chapter, when the MR for fuel
reforming is coupled with a chemical looping system to supply the energy required
for the reforming achieving an overall eutothermal reforming with integrated CO2
capture.
> Read full chapter
ScienceDirect is Elsevier’s leading information solution for researchers.
Copyright © 2018 Elsevier B.V. or its licensors or contributors. ScienceDirect ® is a registered trademark of Elsevier B.V. Terms and conditions apply.