i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
Available online at www.sciencedirect.com
ScienceDirect
journal homepage: www.elsevier.com/locate/he
Thermochemical cooling for large thermal load
applications
Richard Scenna*, Michael Seibert, Michael Abraham, Terry DuBois
US Army, Combat Capabilities Development Command, C5ISR Center, UK
highlights
Cooling using endothermic steam reforming technology.
System was able to absorb up to 3411 kJ/kg of heat at peak performance.
Lower temperature conversion promoted greater heat absorption.
Higher temperatures promoted methane formation which suppressed heat absorption.
article info
abstract
Article history:
The requirement to reject heat within a small envelope has stunted the development and
Received 22 November 2022
deployment of high heat flux applications. Thermochemical cooling is a new innovative
Received in revised form
approach, inspired by engine cooling in aircraft. In aircraft, sensible heat is often rejected
4 January 2023
to the fuel, without altering its chemical composition, and dissipated through the wings.
Accepted 6 January 2023
However, sensible heat absorption is limited to 431 kJ/kg for JP8. Using endothermic re-
Available online 31 January 2023
actions, JP8 can absorb as much as 11,688 kJ/kg of heat when converted to hydrogen,
carbon monoxide, and other gases. A common refrigerant, such as R134A has an enthalpy
Keywords:
of vaporization of 209 kJ/kg. However, after evaluating multiple fuels and reforming liter-
Thermochemical
ature, it was determined that optimum lower temperature performance could be achieved
Cooling
with a methanol water mixture. This endothermic reaction is a strong candidate for heat
Reforming
absorption. Preliminary test data demonstrated heat absorption as low as 300 C, with peak
Catalyst
absorption at 400 C. At its peak (R ¼ 400 C), the reactor is capable of absorbing 3411 kJ/kg.
Future efforts will evaluate the use of JP8, which has a larger endothermic reaction
potential.
Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.
Introduction
As electric loads increase, the need for lighter weight
advanced cooling systems increases. Typically, heat has been
rejected to air through either a heat sink or a condenser. These
systems tend to be large and heavy. A typical refrigerant
(R134A) has an enthalpy of vaporization of 209 kJ/kg.
Alternatively, jet aircraft engines use the fuel as a coolant,
absorbing sensible heat and rejecting the heat to the air
through the wings [1]. If JP8 was heated up to the vaporization
point, it could absorb up to 431k J/kg. However, in practice the
heat absorption is much lower (<20 kJ/kg), to avoid carbon
formation and fouling downstream components the temperature increase is limited to less than 10 C [1,2].
* Corresponding author.
E-mail address: Richard.M.Scenna.civ@army.mil (R. Scenna).
https://doi.org/10.1016/j.ijhydene.2023.01.075
0360-3199/Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.
16224
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
Thermochemical cooling is an approach that uses endothermic reactions of the fuel to absorb heat, eliminating the
need for an air side heat exchanger or condenser. Rather than
reject heat to air through a large condenser, heat is rejected to
the fuel through endothermic reactions such as cracking or
steam reforming. This work was also motivated by steam
reforming reactors, which required large burners to provide
heat for the endothermic steam reforming reactions. While
steam reforming and thermochemical cooling share similar
characteristics and goals, they are not the same. In a reformer
the goal is to produce high yields of hydrogen and minimize
the carbon monoxide formation. However, in thermochemical
cooling, the goal is to produce species that absorb heat and
maximize the endothermic reactions. The results of this
process is syngas and lighter weight hydrocarbons.
The thermochemical cooling potential depends highly on
the fuel and the catalyst selected. The reforming of methanol
to hydrogen and carbon monoxide can yield upwards of
1241.5e1648.5 kJ/kg of heat absorbed through the endothermic reactions alone. In addition, depending on steam to
carbon ratio, as much as 1636e1789 kJ/kg of heat can be
absorbed through vaporization. Using endothermic reactions,
JP8 can absorb as much as 11,688 kJ/kg of heat when converted
to hydrogen, carbon monoxide, and other gases. While JP8
provides a greater potential, it is significantly harder to reform. JP8 reforms at higher temperatures; in the range of
600e900 C. This is supported by Hou et al. [3] who evaluated
RP3 aviation kerosene under supercritical conditions with the
intention of heat absorption in hypersonic flight. They determined ideal heat transfer conditions occurred between 700
and 750 C, which is suitable for hypersonic flight but not the
lower temperature heat rejection. Where methanol reforming
has been demonstrated at much lower temperatures of
200e400 C [4e7]. The initial work focused on methanol, with
future efforts directed towards exploring JP8.
The hydrogen and lighter weight hydrocarbons produced
in the thermochemical cooling process can be fed back to the
prime power producer for supplemental energy or exhausted
out. However, it has been shown in other works that the co
combustion of hydrogen with heavy hydrocarbon fuels can be
strongly beneficial for the combustion process [8e12].
Another similar process is thermochemical recuperation.
As in a traditional recuperator, the thermochemical recuperator recovers heat from exhaust and reintroducing it to the
combustion process, as chemical energy instead of sensible
heat. This could be used in thermal protection of furnaces and
gas turbines to moderate temperature [13,14]. While very
similar in approach, thermochemical cooling and thermochemical recuperation do differ in their goals. In thermochemical cooling, the primary focus is on heat removal and
not on the recovery. Where in thermochemical recuperation
the primary focus is on recovering and reusing the recovered
heat. Thermochemical cooling favors lower temperature
chemistry. Thermochemical recuperation operates with a
higher temperature heat source and favors higher temperature chemistry.
Common fuels in thermochemical recuperation are methanol, ethanol, and methane. Some thermochemical recuperation approaches also include a fuel synthesis component as in
the work done by Tola and Lonis [15]. Multiple other authors
have approached this from a theoretical perspective, Lasala
et al. [16], Orrego et al. [17].
Pashchenko [18,19] used a combination of thermodynamic
modeling and experimental data to evaluate methanol,
ethanol, and methane as potential candidates for thermochemical recuperation. He recommended methanol over the
other fuels at temperatures less than 600K. Methanol activity
was demonstrated as low as 300K but at pressures of 5 bar.
However, methanol showed the greatest recuperation at the
600K.
Tola and Lonis [15] used equilibrium analysis to study
methanol at low temperature (200e300 C) and molar steam to
carbon ratio of 1e3. Increasing steam to carbon ratios significantly improved low fuel conversion. Tola also mentioned
that above 250 C methanol equilibrium was generally a good
prediction for catalytic reactions.
In thermochemical cooling it is desirable to promote the
endothermic reactions of the reverse water gas shift, methanol cracking, and methanol steam reforming (Eqns. (1)e(3))
and suppress the exothermic methanation and the forward
water gas shift reactions (Eqns. (4)e(6)). With the goal of promoting both hydrogen and carbon monoxide and suppressing
the formation carbon dioxide and methane. A similar
conclusion was also drawn by Watanabe and Nakagaki for
thermochemical recuperation [20].
Promote
CH3 OH0H2 þ CO
DH ¼ 90:1 kJ
(1)
CH3 OH þ H2 O0H2 þ CO2
DH ¼ 49:1 kJ
(2)
CO2 þ H2 0H2 O þ CO
DH ¼ 41 kJ
(3)
CO þ H2 O0H2 þ CO2
DH ¼ 41 kJ
(4)
3H2 þ CO0CH4 þ H2 O
DH ¼ 206 kJ
(5)
4H2 þ CO2 0CH4 þ 2H2 O
DH ¼ 164 kJ
(6)
Suppress
Experimental setup
The experimental setup is shown in Figs. 1 and 2. Methanol
and water were premixed and stored in a tank on a scale.
Molar steam to carbon ratios (S/C) were varied between 1.25
and 2.25. A steam to carbon ratio of one was originally
explored, but a pressure build up was noted during operation,
indicative of carbon formation. Reactant mass flowrate were
calculated based on the weight change of the scale over time.
A peristaltic pump was used to meter the fluid from the tank
into the vaporizer. The flow rates were set at a constant 1.00
mlpm. This results in space velocities of 2559.3 hr1 to 2873.85
hr1.
The vaporizer consisted of coiled tubing (OD ¼ 0.25) around
a pipe, which was then wrapped in heat tape and insulation,
which was maintained at 300 C. A thermocouple was placed
in between the vaporizer and the reactor to monitor reactant
temperature. The line and reactor were wrapped in heat tape
to minimize heat loss.
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
16225
Fig. 1 e Experimental setup.
Fig. 2 e Reactor design.
The reactor was constructed of ¾” tube, 7 inches in length,
with a ¼” diameter cartridge heater mounted inside (300W)
with a thermocouple. The gap between the heater and the
tube wall was filled with 18.4g of catalyst. The catalyst was
OD ¼ 3 mm alumina sphere wash coated with rhodium, with a
catalyst loading of 5% weight. The catalyst was kept in place
with glass wool. The cartridge heater was temperature
controlled to the desired set point (300 Ce500 C). After the
reactor, a tracer gas (nitrogen) was introduced into the reformate stream at a flow rate of 1 slpm. This allowed for determination of the reformate flow rate and improved safety by
reducing carbon monoxide concentrations through dilution. A
static mixer (koflo) was placed downstream of the reactor to
insure uniform distribution of the nitrogen within the
reformate.
A sample stream was taken off the exhaust (40 mlpm) and
cooled in a micro-condenser before being analyzed by a four
channel Agilent Gas Chromatograph (Micro 3000) capable of
measuring both fixed gases and hydrocarbons ranging from
methane up to hexane with a relative uncertainty of 1.02% of
the detected value within calibration limits. A multi-point
calibration was used incorporating an upper and lower
bound using primary standards have a reported accuracy of
0.02%. The exhaust stream was sampled every 3 min. Total
molar flowrates were calculated using a molar nitrogen balance. The condenser removed liquid water and methanol.
Therefore, methanol and water molar flow rates were estimated using a molar carbon, hydrogen, and oxygen balance
(Eqns. (7) and (8)).
NCH3 OH out ¼ NCH3 OH in NCO þ NCO2 þ NCH4
þ 2 NC2 H2 þ NC2 H4 þ NC2 H6 þ 3NC3 H8
(7)
2NH2 o in 2NH2 þ 4NCH4 þ2NC2 H2 þ4NC2 H4 þ6NC2 H6 þ8NC3 H8
NH2 O out ¼
2
(8a)
The gas chromatograph was calibrated to primary standards, each containing 10e14 hydrocarbons each. Heat absorption was measured from the enthalpy difference of the
reactant and products. A thermocouple was placed right
before the entrance and exhaust of the reactor.
Analytics
Thermodynamic modeling using an equilibrium code was
conducted to estimate operating conditions during the
experiment, presented in Fig. 3 [21]. The NASA Chemical
Equilibrium Application (CEA) software was used to determine
equilibrium conditions. Methanol water mixtures were evaluated at steam to carbon ratios of 1.25e2.25, similar to what
was evaluated in the experimental work. The model was
evaluated at temperatures ranging from 300 to 500 C and at a
constant pressure of 1 atm.
Equilibrium predicted that higher temperatures favored
higher hydrogen concentrations. Modeling indicated that the
reformate would favor carbon dioxide over carbon monoxide
at lower temperatures (300e500 C). This indicated that the
16226
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
Fig. 3 e Equilibrium calculations of dry reformate composition at reactor temperatures between 300 and 500 C and steam to
carbon ratios of 1.25e2.25.
direct steam reforming conversion (Eqn. (2)) would be more
active than the methanol cracking reaction (Eqn. (1)) or a very
active forward water gas shift reaction (Eqn. (4)). Significant
methane concentrations were predicted indicating possible
activity in the methanation reactions.
At 400 C equilibrium calculations predicted a transition
point, where carbon monoxide began to rise, while carbon
dioxide concentrations decreased. The increase in carbon
monoxide could indicate activity in the reverse water gas shift
reaction or that the methanol cracking reaction was active.
Equilibrium calculations indicated higher reactor temperatures would be better for promoting heat absorption. Equilibrium modeling did not predict any formation of elemental
carbon at reactor temperatures between 300 and 500 C and
steam to carbon ratios of 1.25e2.25.
Equilibrium modeling predicted that increasing the steam
to carbon ratio would have a much smaller impact on reformate concentrations than reactor temperature. At higher
reactor temperatures of 400e500 C, increasing the steam to
carbon ratio promoted a small decrease in carbon monoxide
concentrations and a small increase in hydrogen and carbon
dioxide concentrations, which is indicative of the forward
water gas shift reaction. At a reactor temperature of 500 C,
and at steam to carbon ratio of 1.25, reformate concentrations
consisted of 49.7% hydrogen, 3.4% carbon monoxide, and
22.5% carbon dioxide. Increasing steam to carbon ratio to 1.75
shifted the reformate concentrations to 54.0% hydrogen, 3.1%
carbon monoxide, and 22.7% carbon dioxide. Increasing the
steam to carbon ratio to 2.25 caused reformate concentrations
to shift toward 57.3% hydrogen, 2.8% carbon monoxide, and
22.9% carbon dioxide. At lower temperatures of 300 C this
was not observed, indicating limiting activity in the forward
water gas shift as carbon monoxide and carbon dioxide concentrations appeared relatively constant in Fig. 3.
Increasing steam to carbon ratios decreased methane formation. This was expected as a higher oxidizer content would
promote greater oxidation of the carbon content, limiting the
formation of methane. For example, at 500 C increasing
steam to carbon ratios decreased methane content from 24.4%
at S/C ¼ 1.25, to 20.3% at S/C ¼ 1.75, to 17.0% at S/C ¼ 2.25.
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
Results
Reformate concentrations
Reactor temperature had a strong impact on dry gas concentrations. Fig. 4 shows the normalized dry reformate concentrations derived through gas chromatography. As nitrogen
was introduced in the exhaust line after the reactor to determine reformate volumetric flow rate, nitrogen quantities were
removed, and the reformate concentrations were normalized.
Hydrogen and carbon monoxide concentrations were at
their highest for reactor temperatures of 300e400 C. In this
range methane and carbon dioxide were at their lowest.
Increasing reactor temperature beyond 400 C reduced the
hydrogen and carbon monoxide concentrations, while promoting greater methane and carbon dioxide formation. At
16227
reactor temperatures of 400e500 C, higher steam to carbon
ratios favored greater concentrations of hydrogen and
reduced concentrations of methane.
Trace amounts of hydrocarbons beyond methane were
detected. Propane tended to decrease with increasing the
reactor temperature. Higher steam to carbon ratios also
appeared to suppress propane formation. Interestingly,
ethane tended to appear in greater concentrations at higher
temperatures of 450 C than at lower temperatures. No
ethylene was detected, which is a carbon precursor.
Equilibrium modeling predicted the exact opposite of the
experimental results. Equilibrium predicted greater methane
formation at lower temperatures and greater concentrations
of hydrogen only occurring at higher temperatures. In addition, equilibrium predicted carbon dioxide formation
exceeding that of carbon monoxide formation.
Fig. 4 e Dry gas concentration measured at reactor temperatures between 300 and 500 C and steam to carbon ratios of
1.25e2.25.
16228
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
Reformate yields
Reformate yields were calculated using a molar nitrogen balance, shown in Fig. 5. At reactor temperatures of 300e400 C,
hydrogen, carbon monoxide, and water rapidly increased with
increasing reactor temperature. In this region, both methane
and carbon dioxide increased, but at a much slower rate than
compared to hydrogen and carbon monoxide. As seen in the
reformate concentration at reactor temperatures of
300e400 C, variations in steam to carbon ratios did not have a
significant effect on reformate yields. Methanol and water
yields were determined through a molar carbon and hydrogen
balance Eqns. (7) and (8).
As reactor temperatures exceeded 400 C, there was a rapid
decrease in carbon monoxide and hydrogen yields, along with
a rapid increase in carbon dioxide and methane yields. Water
yields increased with reactor temperature up to reactor temperatures of 450 C, after which water yields decreased.
At reactor temperatures of 450e500 C, higher steam to
carbon ratios promoted greater yields of hydrogen and
reduced yields of methane. As steam to carbon ratios
increased from 1.25 to 2.25, there didn't appear to be
discernible effect on carbon monoxide or carbon dioxide
yields. Higher steam to carbon ratios yielded a higher water
content in the reformate stream. However, at temperatures of
400e500 C, there was a net increase in water beyond what
was in the reactant mixture for all steam to carbon ratios
evaluated, indicating net water production.
Conversion and heat absorption
Conversion, as defined by the ratio of the one minus the moles
of methanol in reformate divided by the original methanol in
the reactants, was determined to be strongly dependent on
reactor temperature. Higher reactor temperatures promoted
greater kinetic activity and greater conversion. Contrary to
Fig. 5 e Reformate yields at reactor temperatures between 300 and 500 C and steam to carbon ratios of 1.25e2.25.
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
literature equilibrium was found to be a poor indicator of the
experimental results under these conditions. Approximately
95% or greater fuel conversion was achieved at temperatures
of 450 C or greater. Increased steam content provided a slight
increase in conversion. This was similar to what was predicted by equilibrium calculations.
hconv ¼ 1 Methanol in Reformate
Methanol in Reactents
(8b)
Reactor temperature also had a significant impact on heat
absorption. Heat absorption is presented on a mass basis (heat
absorbed/mass flow rate of reactants), similar to the heat of
vaporization. Heat absorption primarily occurs through two
mechanisms: 1) the enthalpy of evaporation and 2) the
endothermic reactions associated with steam reforming and
cracking. The increase in sensible heating does contribute to
the added heat absorbed but to a lesser extent than the
endothermic reactions or enthalpy of vaporization. Net Heat
Absorbed (NHA) was calculated through the enthalpy difference of the products at reactor temperature to the reactants at
room temperature Eqn. (9). Water and methanol molar flow
rates were calculated through molar balance of hydrogen and
carbon (Eqns. (7) and (8)), as the condenser would remove
them from the sample.
Hproducts Hreactents ¼ NHA
(9)
At lower reactor temperatures of 300 C presented with
limited conversion and heat absorption. At reactor temperatures of 300 C, net heat absorption was 2600 kJ/kg. Predominately all of the heat absorbed was from the sensible and
latent heat associated with heating the methanol and vaporizing it. The heat of reaction in this region was only ~350 kJ/kg.
At lower reactor temperatures of 300e400 C, variations in
steam to carbon ratio did not affect heat absorption noticeably. However as reactor temperature increased beyond
300 C, higher temperatures promoted greater conversion.
This also increased heat absorption by endothermic reactions
and the net heat absorption. At its peak heat absorption
(R ¼ 400 C), the reactor demonstrated a net heat absorption of
3411 kJ/kg (Heat of Reaction, Sensible and Evaporation), while
enthalpy of evaporation for the mixture was 1636 kJ/kg. Heat
of Reaction was endothermic in this region, absorbing up to
971 kJ/kg. In comparison, common refrigerants R134A has an
enthalpy of vaporization of 209 kJ/kg.
At reactor temperatures greater than 400 C, net heat absorption rapidly decreased from 3411 kJ/kg to 1871 kJ/kg. At
reactor temperatures of 400e500 C, it was observed that
increased steam to carbon ratios promoted greater heat absorption through chemical reactions. At 500 C a steam to
carbon ratio of 1.25 yielded a heat absorption of 1871 kJ/kg,
while the higher steam to carbon ratio of 2.25 resulted in a
heat absorption of 2544 kJ/kg. At these conditions the heat of
reaction became negative, which indicated exothermic
reactions.
Discussion
Heat absorption was strongly influenced by reactor temperature and the chemical reactions. By evaluating the chemical
16229
composition of the reformate and the reactor temperature
data, basic reactions could be inferred. Conditions that promoted the greatest heat absorption promoted the highest
hydrogen and carbon monoxide concentrations. While higher
reactor temperatures (>400 C) appeared to limit heat absorption and showed reformate concentrations consisting of
increased amounts of methane and carbon dioxide, along
with reduced amounts of hydrogen and carbon monoxide, as
shown in Figs. 7 and 4.
At reactor temperatures ranging from 300 to 400 C methanol conversion appeared to be primarily driven by the
methanol cracking reaction (Eqn. (1)), where methanol decomposes into hydrogen and carbon monoxide instead of
hydrogen and carbon dioxide as expected of methanol steam
reforming. The lack of carbon dioxide formation was indicative that methanol steam reforming reaction (Eqn. (2)). This
was further supported by variations in the steam to carbon
ratio, having a minimal impact on conversion in this region, as
seen in Fig. 6. This was desirable from a heat absorption
standpoint, as methanol cracking doubles the amount of heat
that can be absorbed compared to methanol steam reforming
(90.1 kJ/mol vs 49.1 kJ).
While the primary reaction appeared to be methanol
cracking. There appeared to be some limited activity in either
the forward water gas shift or the steam reforming reaction.
This was supported by net loss in water, as water yields were
lower than the initial products, indicating water was
consumed in reactions, as seen in Fig. 5. Fig. 4 shows limited
formation of carbon dioxide, which further supported the
theory of primarily methanol cracking.
However, as reactor temperatures increased beyond
400 C, the exothermic carbon monoxide methanation reaction appeared to become more prevalent. This was also a
highly exothermic reaction, releasing 206 kJ/mol of heat,
whereas the cracking of methanol only absorbed 90 kJ/mol.
This explained the sudden decrease in heat absorption and
the exothermic heat of reaction as seen in Fig. 7. Reformate
composition was consistent with this assertion, hydrogen and
carbon monoxide yields rapidly decreased, while methane
and water yields rapidly increased as seen in Fig. 5. In addition, at reactor temperature greater than 400 C, water yields
exceeded the water content of the reactants, which indicated
a net water production, as shown in Fig. 5. This was consistent
with methanation through carbon monoxide Eqn. (5), where
hydrogen and carbon monoxide were consumed to produce
methane and water. Given the high concentrations of carbon
dioxide and low concentrations of carbon monoxide, as seen
in Fig. 4, it appeared that the methanation route through
carbon dioxide Eqn. (6) was not as active as methanation
through carbon monoxide Eqn. (5).
Interestingly, Figs. 4 and 7 showed that higher steam to
carbon ratios appeared to suppress the methanation reaction,
as less methane was formed, and promoted greater heat absorption at reactor temperatures of 400e500 C. This was most
notable at 500 C and at a steam to carbon ratio of 1.25, where a
heat absorption of 1871 kJ/kg was achieved and concentrations of methane and hydrogen were 31.2% and 42.6%,
respectively. When the steam to carbon ratio increased to
2.25, it resulted in a heat absorption of 2544 kJ/kg, with
methane
concentrations
of
21.4%
and
hydrogen
16230
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
Fig. 6 e Methanol conversion for reactor temperatures 300e500 C and steam to carbon ratios of 1.25e2.25.
Fig. 7 e Heat of Absorption on a mass basis through vaporization and endothermic reactions at reactor temperatures
300e500 C and steam to carbon ratios of 1.25e2.25.
concentrations of 52.2%. This may be due to the increased
oxidizer content brought by higher steam to carbon ratios.
Conclusion
Heat absorption due to thermochemical cooling was demonstrated over a broad range of reactor temperatures from 300 to
500 C. At its peak (R ¼ 400 C) the reactor was capable of
absorbing 3411 kJ/kg. In comparison, a common refrigerants
R134A has an enthalpy of vaporization of 209 kJ/kg. Future
efforts will look to evaluate JP8 with its more endothermic
reactions.
Heat absorption and the chemistry of the reactor were
strongly determined by reactor temperature, while steam to
carbon ratio only affected the reaction at higher temperatures
(>400 C). At low temperatures 300e400 C, the reactions were
dominated by methanol cracking and the reverse water gas
shift. This was associated with the high hydrogen and carbon
monoxide concentrations. Of the predicted endothermic reactions, methanol cracking resulted in the highest heat absorption, which correlated well with observed data.
Higher reactor temperatures, beyond 400 C, appeared to
promote reactions that negatively impacted the heat absorption by endothermic reactions. It was believed that higher
temperatures promoted the methanation reactions, reducing
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 8 ( 2 0 2 3 ) 1 6 2 2 3 e1 6 2 3 1
heat absorption. Higher steam content was found to decrease
methane formation. Higher steam to carbon ratios promoted
higher oxidizer content which could have reduce the formation of methane.
Optimum heat absorption conditions occurred in regions
with high carbon monoxide and hydrogen yields. Future
catalyst and rector designs should focus on promoting
methanol cracking and reverse water gas shift, while reducing
the forward water gas shift reaction and methanation
reactions.
Equilibrium modeling was not a good predictor of experimental results at conditions evaluated in this work. It was able
to predict a transition point at 400 C, but was not able to
actually accurately predict what happened. Equilibrium predicted that higher temperatures would be better for heat absorption but in fact experimental data showed that lower
temperatures were more favorable. In addition, modeling
indicating that methanol steam reforming would be the
dominant reaction. However experimentation indicated that
methanol cracking was the dominant reaction. At lower
reactor temperatures, equilibrium was able to predict that
steam to carbon ratio would have a minimal impact on the
reformate concentrations.
[5]
[6]
[7]
[8]
[9]
[10]
[11]
Declaration of competing interest
[12]
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
Acknowledgments
The authors acknowledge the support of United States Army's
U.S. Army Combat Capabilities Development Command
(CCDC) Independent Laboratory Innovative Research (ILIR)
program and Centers supplies Command, Control, Communications, Computers, Cyber, Intelligence, Surveillance and
Reconnaissance (C5ISR). The authors also gratefully
acknowledge the help and support provided by NASA CEA
code used herein.
[13]
[14]
[15]
[16]
[17]
references
[18]
[1] Grey C, Shayeson M. Aircraft fuel heat sink Utilization AF
APL. 1973.
[2] Edwards T. Cracking and deposition behavior of supercritical
hydrocarbon aviation fuels. Combust Sci Technol
2006;178(1e3):307e34.
[3] Hou Ling-yun, Zhang Ding-rui. Xiao-xiong Zhang Interaction
between thermal cracking and steam reforming reactions of
aviation kerosene. Fuel Process Technol 2017;167:655e62.
[4] Mei Deqing, Qiu Xingye, Liu Haiyu, Wu Qiong, Yu Shizheng,
Xu Liming, Zuo Tao, Wang Yancheng. Progress on methanol
reforming technologies for highly efficient hydrogen
[19]
[20]
[21]
16231
production and applications. Int J Hydrogen Energy
2022;47(84):35757e77. ISSN 0360-3199.
Yun Jinwon, Van Trinh Ngoc, Yu Sangseok. Performance
improvement of methanol steam reforming system with
auxiliary heat recovery units. Int J Hydrogen Energy
2021;46(49):25284e93. ISSN 0360-3199.
Liu Yanyong. Catalytic steam reforming of methanol over
highly active catalysts derived from PdZnAl-type
hydrotalcite on mesoporous silica MCM-48. Int J Hydrogen
Energy 2022:360e3199.
Chougule Abhijeet, Sonde Ramakrishna R. Modelling and
experimental investigation of compact packed bed design of
methanol steam reformer. Int J Hydrogen Energy
2019;44(57):29937e45. ISSN 0360-3199.
Seibert Michael, Sen Nieh. Comparison of hydrogen and
hydrogen-rich reformate enrichment of JP-8 in an open
flame. Fuel 2017;ume 210:91e7. ISSN 0016-2361. https://doi.
org/10.1016/j.fuel.2017.08.056.
Seibert Michael, Sen Nieh. Simulation of dual firing of
hydrogen-rich reformate and JP-8 surrogate in a swirling
combustor. Int J Hydrogen Energy 2013;38(14):5911e7. ISSN
0360-3199. https://doi.org/10.1016/j.ijhydene.2013.02.072.
Clayton RM. Reduction of gaseous pollutant emissions from
gas turbine combustors using hydrogen-enriched jet fuel-A
Progress Report. NASA Tech Memo 1976:33e790.
Burguburu J, Cabot G, Renou B, Boukhalfa A, Cazalens M.
Comparisons of the impact of reformer gas and hydrogen
enrichment on flame stability and pollutant emissions for a
kerosene/air swirled flame with an aeronautical fuel injector.
Int J Hydrogen Energy 2011;36(11):6925e36.
Burguburu J, Cabot G, Renou B, Boukhalfa A. Effects of H2
enrichment on flame stability and pollutant emissions for a
kerosene/air swirled flame with an aeronautical fuel injector.
Proceedings of the Combustion Institute; 2011.
Pashchenko Dmitry. Natural gas reforming in
thermochemical waste-heat recuperation systems: a review.
Energy 2022;251(123854). ISSN 0360-5442.
Pashchenko Dmitry. First law energy analysis of
thermochemical waste-heat recuperation by steam methane
reforming. Energy 2018;143:478e87.
Tola Vittorio. Francesco Lonis Low CO2 emissions chemically
recuperated gas turbines fed by renewable methanol. Appl
Energy 2021;298:117146.
Lasala Silvia, Privat Romain, Herbinet Olivier,
€ l.
Arpentinier Philippe, Bonalumi Davide, Jaubert Jean-Noe
Thermo-chemical engines: unexploited high-potential
energy converters. Energy Convers Manag 2021;229:113685.
ISSN 0196-8904.
rez-Orrego Daniel, Nascimento Silva Fernanda, de
Flo
Oliveira Junior Silvio. Syngas production with thermochemically recuperated gas expansion systems: an exergy
analysis and energy integration study. Energy
2019;178:293e308. ISSN 0360-5442.
Pashchenko Dmitry. Thermochemical waste-heat
recuperation as on-board hydrogen production technology.
Int J Hydrogen Energy 2020:360e3199.
Pashchenko Dmitry. Industrial furnaces with
thermochemical waste-heat recuperation by coal
gasification. Energy 2021;221:360e5442.
Watanabe Tsunenori, Takao Nakagaki. 149 - characteristics
of a steam-reforming catalyst for a DME-fueled chemically
recuperated gas turbine. Stud Surf Sci Catal 2007;172:579e80.
0167-2991.
NASA glenn's computer code CEA (chemical equilibrium
with applications). 2021. https://www1.grc.nasa.gov/
research-and-engineering/ceaweb/.