Steam Methane Reforming Process Research Articles

Feedback control of an experimental electrically-heated steam methane reformer

Steam methane reforming (SMR) is the most common industrial process to produce hydrogen (H2) from methane and water vapor. The SMR reactions are overall highly endothermic and traditionally, fossil fuels are burned to provide the necessary heat of reaction. However, it was found that electrifying the tubular SMR reactors using renewable electrons instead of conventional heating gives the opportunity of producing H2 with lower carbon emissions, lower reactor volumes, and higher carbon conversion. While current studies in this new technology focus on improving the catalysts or heating sources, a more efficient process control scheme can also significantly contribute to the understanding of potential challenges and opportunities of combining renewables and natural gas in the production of H2 at industrial scales. In order to further develop the electrically-heated SMR process and the associated control strategies, we have constructed an experimental Joule-heated SMR system at UCLA. The system contains a tubular reactor with a washcoated Ni/ZrO2 catalyst, two thermocouples connected to the top and bottom of the reactor, a power supply for providing electrical heating, and an on-line gas chromatograph (GC) for measuring outlet gas concentrations. The synthesis procedure of the catalyst, SMR data collection, and thermal considerations for catalyst degradation are described in this paper and are all accounted for experimentally when using a proportional integral (PI) controller to gradually increase the reactor temperature without harming the catalyst. Advanced control strategies, such as model predictive control (MPC), require a process model that uses measurement feedback to make predictions of the process time-evolution in order to optimize the control actions in real-time. We have previously developed a lumped-parameter modeling strategy for the SMR process. The MPC objective is to control the H2 production rate by manipulating the current flowing through the outer reactor shell. However, to use this model in an MPC, feedback values for all state variables should be provided by the sensors. In our experimental system, the on-line GC only gives discrete measurements with a long sampling period. To this end, the process model is incorporated into an extended Luenberger observer (ELO) that uses the reactor temperature and GC measurements to provide estimates of all the variables needed by the MPC. The ELO-based MPC system is then experimentally implemented on the process and it is demonstrated to be more efficient in terms of speed of the closed-loop response than the PI controller using delayed, measurement feedback by the GC.

Reservoir Simulations of Hydrogen Generation from Natural Gas with CO2 EOR: A Case Study

This paper addresses the problem of hydrogen generation from hydrocarbon gases using Steam Methane Reforming (SMR) with byproduct CO2 injected into and stored in a partially depleted oil reservoir. It focuses on the reservoir aspects of the problem using numerical simulation of the processes. To this aim, a numerical model of a real oil reservoir was constructed and calibrated based on its 30-year production history. An algorithm was developed to quantify the CO2 amount from the SMR process as well as from the produced fluids, and optionally, from external sources. Multiple simulation forecasts were performed for oil and gas production from the reservoir, hydrogen generation, and concomitant injection of the byproduct CO2 back to the same reservoir. EOR from miscible oil displacement was found to occur in the reservoir. Various scenarios of the forecasts confirmed the effectiveness of the adopted strategy for the same source of hydrocarbons and CO2 sink. Detailed simulation results are discussed, and both the advantages and drawbacks of the proposed approach for blue hydrogen generation are concluded. In particular, the question of reservoir fluid balance was emphasized, and its consequences were presented. The presented technology, using CO2 from hydrogen production and other sources to increase oil production, also has a significant impact on the protection of the natural environment via the elimination of CO2 emission to the atmosphere with concomitant production of H2.

Techno-economic analysis of blue ammonia synthesis using cryogenic CO2 capture Process-A Danish case investigation

Ammonia is a vital chemical with numerous applications. Currently, the primary methods for generating the necessary reactants for ammonia production involve steam methane reforming (SMR) and cryogenic air separation unit (CASU), while the Haber-Bosch process converts these reactants into ammonia. However, the SMR process releases substantial amounts of CO2, making it imperative to employ an efficient and cost-effective CO2 capture technology to mitigate emissions. This investigation focuses on evaluating the cryogenic CO2 capture (CCC) process for blue ammonia production and provides a thorough economic analysis, estimating both the initial investment costs and operational expenses involved in producing blue ammonia. The results indicated that the CCC process can capture 90% of the CO2 content in the flue gas emitted by the SMR, incurring an energy penalty of 0.724 MJe/kgCO2 while capturing CO2 in the liquid phase with purities exceeding 99.9%. In this case, the estimated CO2 capture costs would be 18.05, 45.1, and 16.65 USD/ton in 2021, 2022, and 2023, respectively. This represents a 40% reduction compared to the CO2 capture costs associated with conventional amine-based technology. The results of this study indicate that the annual electricity costs for ammonia production increase by 38.5% and 64.2% when employing the CCC and amine-based processes, respectively. This investigation employed an isothermal reactor for ammonia synthesis, using the heat from the exothermic reaction in a water ammonia absorption refrigeration cycle (ARC) to condense and purify ammonia. The results show that the ARC system can effectively condense ammonia at −6 °C, producing a liquid ammonia stream with 99.3% purity. This leads to a 95% reduction in power consumption compared to a vapor compression refrigeration cycle (VCRC). Consequently, this method has the potential to decrease the annual operational costs for ammonia production by 2.92%, 2.69%, and 3.13% in 2021, 2022, and 2023, respectively. This study indicated that the hydrogen production unit incurs the highest initial investment costs, as well as operating costs, in the blue ammonia production process, followed by CASU and the Haber-Bosch process.

Estimation-based model predictive control of an electrically-heated steam methane reforming process

The surge in demand for hydrogen (H2) across diverse sectors, including clean energy transportation and chemical synthesis, underscores the need for a thorough investigation into H2 production dynamics and the development of effective controllers for industrial applications. This paper focuses on an electrically heated steam methane reforming (SMR) process for H2 production, offering advantages such as enhanced environmental sustainability, compactness, efficiency, and controllability compared to conventional reforming methods. Electric heating of the entire system allows for adjustments in current to control reactor temperature, thereby impacting hydrogen production rates. However, accurately modeling hydrogen production dynamics presents a formidable challenge, as complex models with high precision are computationally unsuitable for real-time control integration. Considering these factors, an accurate and efficient first-principles-based lumped-parameter model is developed to provide a dependable estimation of hydrogen production in an electrically-heated steam methane reformer. This model is validated experimentally and then utilized in a model predictive controller (MPC). To obtain the necessary state estimate information for the MPC, an extended Luenberger observer (ELO) method is employed to estimate state variables from limited, infrequent and delayed measurements of gas-phase reactor outlet stream and frequent measurements of the reactor temperature. Simulation comparisons with a proportional-integral (PI) controller reveal a much faster response in achieving the desired H2 production rate under the estimation-based MPC. Additionally, the simulations demonstrate the robustness of the controller to process variability such as a decrease in catalyst activation energy, commonly encountered in the SMR process, highlighting its effectiveness in maintaining stable operation under varying process conditions.

Technical and economic performance assessment of blue hydrogen production using new configuration through modelling and simulation

Steam methane reforming (SMR) is the dominant process for hydrogen production, which produce large amount of carbon dioxide (CO2) as a by-product. To address concerns about carbon emissions, there is an increasing focus on blue hydrogen to mitigate carbon emissions during hydrogen production. However, the commercialization of blue hydrogen production (BHP) is hindered by the challenges of high cost and energy consumption. This study proposes a new configuration to address these challenges, which is characterized by: (a) the use of piperazine (PZ) as a solvent, which has a high CO2 absorption efficiency; (b) a more efficient heat exchange configuration which recovers the waste exergy from flue gas; (c) the advanced flash stripper (AFS) was adopted to reduce the capital cost due to its simpler stripper configuration. In addition, the technical and economic performance of the proposed energy and cost-saving blue hydrogen production (ECSB) process is investigated and compared with the standard SMR process. The detailed models of the SMR process and the post-combustion carbon capture (PCC) process were developed and integrated in Aspen plus® V11. The results of the technical analysis showed that the ECSB process with 30 wt.% PZ achieves a 36.3 % reduction in energy penalty when compared to the standard process with 30 wt.% Monoethanolamine (MEA). The results of the economic analysis showed that the lowest levelized cost of blue hydrogen (LCBH) was achieved by the ECSB process with 30 wt.% PZ. Compared to the BHP process with 30 wt.% MEA, the LCBH was reduced by 19.7 %.

Economic assessment of clean hydrogen production from fossil fuels in the intermountain-west region, USA

The transition from fossil fuels to carbon-neutral energy sources is necessary to reduce greenhouse gas (GHG) emissions and combat climate change. Hydrogen (H2) provides a promising path to harness fossil fuels to reduce emissions in sectors such as transportation. However, regional economic analyses of various H2 production techniques are still lacking. We selected a well-known fossil fuel-exporting region, the USA's Intermountain-West (I-WEST), to analyze the carbon intensity of H2 production and demonstrate regional tradeoffs. Currently, 78 % of global H2 production comes from natural gas and coal. Therefore, we considered steam methane reforming (SMR), surface coal gasification (SCG) and underground coal gasification (UCG) as H2 production methods in this work. We developed the cost estimation frameworks of SMR, SCG and UCG with and without carbon capture, utilization and sequestration (CCUS). In addition, we identified optimal sites for H2 hubs by considering the proximity to energy sources, energy markets, storage sites and CO2 sequestration sites. We included new production tax credits (PTCs) in the cost estimation to quantify the economic benefit of CCUS. Our results suggest that the UCG has the lowest levelized cost of H2 production due to the elimination of coal production cost. H2 production using the SMR process with 99 % carbon capture is profitable when the PTCs are considered. We also analyzed carbon utilization opportunities where CO2 conversion to formic acid is a promising profitable option. This work quantifies the potential of H2 production from fossil fuels in the I-WEST region, a key parameter for designing energy transition pathways.

Generalized effectiveness factor correlations for nickel catalyst pellets under low-pressure steam methane reforming conditions

In this study, generalized correlations are proposed to predict the effectiveness factors of nickel-based catalyst pellets used in low-pressure steam methane reforming (SMR) systems suitable for small-scale fuel cell applications. Previously, the authors have shown that over 99 % of the total reaction occurs within a thin layer of 0.2 mm thickness from the surface of porous Ni catalyst pellets. Thus, by developing the correlations based on the 0.2-mm-thick active reaction thickness, the proposed effectiveness factor correlations are applicable to catalyst pellets of various shapes used in the low-pressure SMR process. The method of using these effectiveness factor correlations for analyzing fixed-bed SMR systems is also addressed, along with the method for considering the variations in the catalyst properties.

Techno-economic comparison of ammonia production processes under various carbon tax scenarios for the economic transition from grey to blue ammonia

Ammonia synthesis is a carbon-intensive process, with significant volumes of carbon dioxide produced during the preliminary production of hydrogen from a fossil fuel feedstock. Since carbon emissions vary significantly depending on the hydrogen production method, the impact of carbon capture and storage (CCS) implementation on the overall economic performance of the ammonia synthesis process differs. Therefore, it is crucial to (1) integrate cost-effective CCS into various ammonia synthesis processes and (2) conduct a comprehensive comparison of grey and blue ammonia systems together, considering the economic costs of the carbon emissions. This study aims to investigate the economic feasibility of large-scale ammonia processes under various carbon tax scenarios and suggest carbon-efficient options for the ammonia industry. Three ammonia synthesis processes are designed that differ in their hydrogen production method – steam methane reforming (SMR), autothermal reforming (ATR), and hybrid SMR-ATR – and these three options also have grey ammonia and blue ammonia production versions. The grey ammonia production systems do not include a carbon capture procedure, while the blue ammonia systems ensure that the CO2 emissions are below 0.065 t CO2/t NH3. In the present study, both the grey and blue versions of the three ammonia production processes are subjected to techno-economic evaluation under various carbon tax scenarios. For the grey ammonia systems, economic feasibility varies depending on the carbon tax scenario under consideration. Grey ATR becomes the most cost-effective option within a carbon tax of 95 $/ton to 115 $/ton. In contrast, the economic viability of the blue ammonia systems is unaffected by the carbon tax policy environment. In particular, blue ATR exhibits 6% and 14% lower levelized cost of ammonia (LCOA) compared to the blue SMR and blue Hybrid SMR-ATR, respectively. Overall, the results indicate that, below a carbon tax threshold of 62 $/ton, the SMR process without carbon capture is economically favorable. However, for carbon tax above 62 $/ton, the ATR process with carbon capture has greater economic feasibility than other options. A minimum carbon tax of 62 $/ton is required to promote the transition to blue ammonia. These findings thus provide valuable insight into the establishment of effective carbon regulations in response to the global demand to tackle the climate crisis.

Simulation-based assessment of the potential of offshore blue hydrogen production with high CO2 capture rates with optimised heat recovery

Hydrogen is a versatile component and is acknowledged to play an important role in the energy transition. However, hydrogen is predominantly produced from fossil fuels, with natural gas being the most used source. The steam-methane reforming (SMR) is the process used to produce hydrogen from natural gas. Although this process can produce hydrogen relatively cheaply, it is carbon-intensive. If carbon capture and storage (CCS) is applied to the SMR process, clean hydrogen (in this case, labelled as blue hydrogen) is produced. Nevertheless, CCS will add costs to the production process. Despite the capture costs, transport and storage contribute to the overall costs of CCS. Hydrogen could be produced offshore close to a storage site to minimise the overall costs of CCS. This work investigates the production of blue hydrogen with high capture rates (98, 99 and 99.5%). Heat recovery is optimised to provide the required energy for the SMR and capture processes. The cost estimation shows that it is possible to produce blue hydrogen at costs around 2.7 $/kgH2 and a carbon footprint below 0.2 kgCO2/kgH2.

A novel on-site SMR process integrated with a hollow fiber membrane module for efficient blue hydrogen production: Modeling, validation, and techno-economic analysis

Steam methane reforming (SMR) is widely used in the hydrogen production industry; however, a significant amount of CO2 is released during this process. Several efforts have been made to produce low-CO2 hydrogen (blue hydrogen) via SMR; however, the proposed solutions are not applicable to small-scale plants. Therefore, this study proposes an on-site SMR process combined with a hollow fiber membrane module (HFMM) for CO2 capture in small-scale plants. First, mathematical models for the on-site SMR process and HFMMs were developed, and their accuracy was validated with real-world data. Second, we designed and implemented the SMR–HFMM model based on different operating conditions and gas compositions at three potential CO2 capture locations (dry syngas, PSA tail gas, and flue gas). The CO2 capture performances at these three locations were compared using five performance indicators: stage cut, separation factor, CO2 recovery rate, permeate composition, and retentate composition. Finally, to evaluate the integrated processes for each CO2 capture location, feasible ranges of the number of HFMMs and the levelized cost of hydrogen (LCOH) were calculated. In the case of CO2 captured in dry syngas, the number of HFMMs required to achieve a CO2 purity of over 90% was calculated to be 10–25. Furthermore, despite additional HFMM installation, the LCOH was 0.8%–1.5% lower than that of the conventional on-site SMR process that is 7.07–7.13 USD/kgH2. The proposed integrated SMR–HFMM process is a potential solution to the problem of CO2 emissions in on-site SMR processes with a lower LCOH. Therefore, the findings of this study could be of significant importance in improving the environmental sustainability of hydrogen production in small-scale plants.

Techno-economic Analysis and Optimization of Intensified, Large-Scale Hydrogen Production with Membrane Reactors.

Steam methane reforming (SMR) currently supplies 76% of the world's hydrogen (H2) demand, totaling ∼70 million tonnes per year. Developments in H2 production technologies are required to meet the rising demand for cleaner, less costly H2. Therefore, palladium membrane reactors (Pd-MR) have received significant attention for their ability to increase the efficiency of traditional SMR. This study performs novel economic analyses and constrained, nonlinear optimizations on an intensified SMR process with a Pd-MR. The optimization extends beyond the membrane's operation to present process set points for both the conventional and intensified H2 processes. Despite increased compressor and membrane capital costs along with electric utility costs, the SMR-MR design offers reductions in the natural gas usage and annual costs. Economic comparisons between each plant show Pd membrane costs greater than $25 000/m2 are required to break even with the conventional design for membrane lifetimes of 1-3 years. Based on the optimized SMR-MR process, this study concludes with sensitivity analyses on the design, operational, and cost parameters for the intensified SMR-MR process. Overall, with further developments of Pd membranes for increased stability and lifetime, the proposed SMR-MR design is thus profitable and suitable for intensification of H2 production.

Internal carbon loop strategy for methanol production from natural gas: Multi-objective optimization and process evaluation

In this study an internal carbon loop strategy for producing methanol from natural gas (NG) by introducing CO2 to enhance methanol productivity and minimize greenhouse gas (GHG) emissions. The overall process consists of a steam methane reforming (SMR) process (hydrogen production), methanol synthesis process (carbon utilization), crude methanol separation process, chemical absorption process (carbon capture), and CO2 compression and storage processes (carbon storage). Methanol was produced using hydrogen, carbon monoxide, and carbon dioxide as the products and by-products of the steam methane reforming process. In particular, the pressure of the compressed CO2 for storage was utilized to enhance profitability. A strategy for injecting the pressurized CO2 into the reforming reactor, methanol reactor, or splitting it between the two reactors was examined. The process variables used were the steam/natural gas ratio (1.5, 2.0, 2.5), CO2/natural gas ratio (0–0.5), natural gas flow rate (3000 kmol/h), reforming reaction pressure (5 barg), and methanol reaction pressure (80 barg). Methanol production was 2800–3000 tonMeOH/day under according to operating conditions. Carbon pricing was considered to assess the feasibility of installing and operating a carbon capture and storage (CCS) unit. The effect of the process economic and environment variables was investigated on total energy duty, levelized cost of methanol (LCOM) from a techno-economic analysis (TEA) perspective, and global warming potential (GWP) from a life cycle assessment (LCA) standpoint using local sensitivity analysis (LSA). Subsequently, multi-objective optimization (MOO) for levelized cost of methanol and global warming potential was performed to find optimal operating variables and establish various relevant scenarios. Scenario analysis reveals that implementing an internal carbon loop strategy through relatively simple retrofits can increase levelized cost of methanol by 12.8% while reducing global warming potential by 41.5%.

Oxy-fuel combustion-based blue hydrogen production with the integration of water electrolysis

Blue hydrogen is gaining attention as an intermediate step toward achieving eco-friendly green hydrogen production. However, the general blue hydrogen production requires an energy-intensive process for carbon capture and storage, resulting in low process efficiency. Additionally, the hydrogen production processes, steam methane reforming (SMR) and electrolysis, emits waste heat and byproduct oxygen, respectively. To solve these problems, this study proposes an oxy-fuel combustion-based blue hydrogen production process that integrates fossil fuel-based hydrogen production and electrolysis processes. The proposed processes are SMR + SOEC and SMR + PEMEC, whereas SMR, solid oxide electrolysis cell (SOEC), and proton exchange membrane electrolysis cell (PEMEC) are also examined for comparison. In the proposed processes, the oxygen produced by the electrolyzer is utilized for oxy-fuel combustion in the SMR process, and the resulting flue gas containing CO2 and H2O is condensed to easily separate CO2. Additionally, the waste heat from the SMR process is recovered to heat the feed water for the electrolyzer, thereby maximizing the process efficiency. Techno-economic, sensitivity, and greenhouse gas (GHG) analyses were conducted to evaluate the efficiency and feasibility of the proposed processes. The results show that SMR + SOEC demonstrated the highest thermal efficiency (85.2%) and exergy efficiency (80.5%), exceeding the efficiency of the SMR process (78.4% and 70.4% for thermal and exergy efficiencies, respectively). Furthermore, the SMR + SOEC process showed the lowest levelized cost of hydrogen of 6.21 USD/kgH2. Lastly, the SMR + SOEC demonstrated the lowest life cycle GHG emissions. In conclusion, the proposed SMR + SOEC process is expected to be a suitable technology for the transition from gray to green hydrogen.

Comparison of Derivative-Free Optimization: Energy Optimization of Steam Methane Reforming Process

In modern chemical engineering, various derivative-free optimization (DFO) studies have been conducted to identify operating conditions that maximize energy efficiency for efficient operation of processes. Although DFO algorithm selection is an essential task that leads to successful designs, it is a nonintuitive task because of the uncertain performance of the algorithms. In particular, when the system evaluation cost or computational load is high (e.g., density functional theory and computational fluid dynamics), selecting an algorithm that quickly converges to the near-global optimum at the early stage of optimization is more important. In this study, we compare the optimization performance in the early stage of 12 algorithms. The performance of deterministic global search algorithms, global model-based search algorithms, metaheuristic algorithms, and Bayesian optimization is compared by applying benchmark problems and analyzed based on the problem types and number of variables. Furthermore, we apply all algorithms to the energy process optimization that maximizes the thermal efficiency of the steam methane reforming (SMR) process for hydrogen production. In this application, we have identified a hidden constraint based on real-world operations, and we are addressing it by using a penalty function. Bayesian optimizations explore the design space most efficiently by training infeasible regions. As a result, we have observed a substantial improvement in thermal efficiency of 12.9% compared to the base case and 7% improvement when compared to the lowest performing algorithm.

Synthesis and utilization of mesoporous alumina as a supporting material of Ce‐promoted Ni‐based catalysts in the methane reforming process

AbstractDue to the large applications of hydrogen as a feedstock of chemical industries and as an energy carrier, its production on large scales with low costs has attracted researchers. Steam reforming of methane (SRM) is the most common process for producing H2‐rich syngas over Ni/Al2O3 catalysts, which suffer from coke deposition and Ni particles agglomeration. For overcoming these issues, we have synthesized mesoporous alumina (MA) as a supporting material of Ni particles, structure, and activity, which were compared with the bulk alumina (BA) supported catalysts in the SRM process for the first time. Besides, cerium as an appropriate promoter for lowering deposited coke was added to all prepared catalysts. The reaction temperature (600–700°C), Ni loading (10–25 wt.%), and Ce loading (1–5 wt.%) were the parameters that were optimized for maximizing H2 yield and CH4 conversion. Prepared samples were characterized by various techniques before and/or after reaction. The results of TEM and XRD depicted the formation of nanocrystalline and mesoporous structure for Ni‐MA catalysts compare to Ni‐BA samples. The observations indicated that 20Ni‐3Ce/MA had the highest catalytic performance, achieving a CH4 conversion of 91.0% and H2 yield of 92.8% at 700°C.

Steam methane reforming over a preheated packed bed: Heat and mass transfer in a transient process

The primary method of large scale hydrogen production is steam methane reforming (SMR) in the packed bed reactors filled with the catalysts. In these reactors, heat is mostly supplied through the reactor wall to compensate for the endothermic effect of SMR reactions. In this paper, an alternative route of steam methane reforming process over a preheated packed bed filled with Ni-based catalyst particles was studied. Consequent packed bed heating with hot flue gas and cooling with H2O - CH4 endothermically reacting mixture was investigated. Numerical model has been developed for the cooling and heating processes and realized via Ansys Fluent. The analyses were performed for various steam-to-methane ratios and different initial temperature distributions. Results are indicating that the packed bed volume averaged temperature increases by 98 °C after 15 s of heating with flue gas. Packed bed cools down by more than 125 °C after 15 s of the SMR process. Mixture species distribution was also analysed along the reformer length. Hydrogen outlet molar fraction constantly decreases from 0.38 to 0.25 at the process beginning and end, respectively. The highest hydrogen production was observed on the half of the packed bed closer to the reformer outlet.

Production of purified H2, heat and biochar from wood: Techno-economic and life cycle assessment of small scale units

Hydrogen is forecasted to contribute to the energy transition. This study evaluates the production of purified H2, heat and biochar from woodchips. Three pyrogasification processes are compared: gasification (O2/H2O) with or without catalytic reforming and water gas-shift, autothermal pyrolysis. Techno-economic and life cycle assessments were conducted based on detailed mass and energy balances. On the economic front, the historical market prices of hydrogen, heat and biochar are not sufficient to reach profitability. The subsidies required to reach profitability and the avoided CO2 emissions from reference steam methane reforming (SMR) process were evaluated. It is estimated between 130 and 310€/tCO2 avoided which can be reduced with higher price of hydrogen. On the environmental front, the pyrogasification processes are more attractive than SMR regarding global warming, ozone depletion layer and fossil fuel consumption potentials. Meanwhile, the acidification potential and the photochemical oxidant formation are higher than SMR.

Techno-economic evaluation of buffered accelerated weathering of limestone as a CO2 capture and storage option

Carbon dioxide storage technologies are needed not only to store the carbon captured in the emissions of hard-to-abate sectors but also for some carbon dioxide removal technologies requiring a final and permanent storage of CO2. The pace and scale of geological CO2 storage deployment have fallen short of expectations, and there is a growing interest in ocean-based CO2 storage options. As complementary to geological storage, buffered accelerated weathering of limestone (BAWL) has been proposed to produce a buffered ionic solution at seawater pH, derived from the reaction in seawater between a CO2 stream and a micron-sized powder of calcium carbonate (CaCO3), within a long tubular reactor. The addition of calcium hydroxide to buffer the unreacted CO2 before the discharge in seawater is also envisaged. BAWL avoids the risks of CO2 degassing back into the atmosphere and does not induce seawater acidification. This work presents a mass and energy balance and preliminary cost analysis of the technology for different configurations of discharge depth (100, 500, 3,000 m), pipeline length (10, 25, 100 km) and diameter of CaCO3 particles (1, 2, 10 µm) fed in the tubular reactor. The total energy consumption to capture and store 1 t of CO2 generated by a steam-methane reforming (SMR) process ranges from 1.3 to 2.2 MWh. The CO2 released from the CaCO3 calcination to produce the buffering solution leads to a total CO2 storage requirement 43–85% higher than the CO2 derived by SMR. The total cost to capture and store 1 t of CO2 from SMR is estimated in the range 142–189 €.

Optimization of hydrogen production by steam methane reforming over Y-promoted Ni/Al2O3 catalyst using response surface methodology

Hydrogen production from CH4 greenhouse gas through steam methane reforming (SMR) is an essential and perfect process. In this study, Y-promoted Ni-based catalysts supported on Al2O3 were utilized in this process. The response surface method (RSM) based on optimum custom design was used to investigate the synthetic parameters for Ni-based catalyst and the operating conditions of the SMR process. Independent parameters such as reaction temperature (600, 650, and 700 °C), steam to CH4 (S/C) molar ratio (1.5, 2.5, and 3.5), Ni loading (5, 15, and 25 wt%), Y loading (0, 1.5, and 3.0 wt%), and type of support (hollow or bulk alumina) were chosen for evaluation and optimization of CH4 conversion and H2 yield utilizing RSM. The design expert software recommended two optimized catalysts for bulk and hollow structures; the best choice was 16.2 Ni-2.7Y/HS-Al at 690 °C and 3.4 S/C molar ratio for achieving the maximum CH4 conversion of 93.8% and H2 yield of 97.4%. The stability test was performed to compare the activity of optimized catalysts at their optimal temperature and S/C ratio experimentally, before and after which the synthesized catalysts were characterized via XRD, TPR, FESEM, EDX, N2 adsorption/desorption, and TPO techniques.

Synthesis, characterization, and application of bio-templated Ni–Ce/Al2O3 catalyst for clean H2 production in the steam reforming of methane process

A mesoporous γ-alumina was successfully synthesized through an environmentally-friendly method using Fig leaves as a bio-template for the first time in this research. After confirming the formation of porous Al2O3 structure with different characterization techniques, it was used as a supporting material of Ni–Ce particles to effectively enhance the conversion of steam reforming of methane (SRM) process. For this purpose, we optimized Ni content, Ce content, and SRM temperature using bulk and porous structure of Ni–Ce/Al2O3 catalysts. The results of field emission scanning electron microscopy (FESEM), temperature-programmed desorption (H2-TPD), and N2 adsorption/desorption showed the formation of more dispersed Ni particles with smaller sizes on the mesoporous alumina (MAl), especially when they were promoted with CeO2. Besides the efficient influence of CeO2 on Ni particle dispersion, it was enhanced the Ni–Al interaction, increased the activity of the catalysts, and decreased the coke deposition on the catalysts during the SRM process. As a result, 20Ni-3.0Ce/MAl catalyst depicted the highest H2 yield of 96.02% and CH4 conversion of 90.20%, and the lowest produced CO2 to consumed CH4 of 0.52% at 700 °C SRM reaction. This is while the bulky catalyst with equal Ni and Ce contents had 86.09, 92.30, and 0.56 CH4 conversion, H2 yield, and CO2/CH4 molar ratio, respectively at this temperature. Besides, 20Ni-3.0Ce/MAl depicted the highest stability during 12 h continuous SRM reaction at 700 °C with the lowest reduction amounts of 3.97% and 5.12% for CH4 conversion and H2 yield, respectively.