Tri-reforming Process Research Articles

Optimization of C5+ production by CO2 recycle at an integrated Tri-reforming and Fischer-Tropsch process

Integration of Tri-reforming and Fischer-Tropsch processes is a novel approach for conversion of CO2 into C5+ liquid hydrocarbon. Tri-reforming converts CO2 into syngas and does not require external heat source due to methane oxidation reaction that occurs at the beginning of reactor. Fischer-Tropsch synthesis converts produced syngas in the reformer to hydrocarbon fuels. In this research, plug reactors have been modeled in a heterogeneous and one-dimensional form, and the mass and energy equations governing them in steady state have been developed. The accuracy of models is validated with literature data. Then an optimization problem aiming at maximal C5+ production is compiled with specific limitations imposed on operating conditions. Based on the modeling results, 95 % of CO2 produced at Fischer-Tropsch and 92 % CO2 produced at Tri-reforming process is captured and injected into Tri-reforming reactor for conversion into hydrocarbon fuels. Modeling results revealed that the mole fractions of C2-C4 and C5+ at outlet of Fischer-Tropsch are 0.117 and 0.023 which could be purified in separators and used as clean energy carriers. The suggested integrated route for CO2 capture and conversion into green fuels offers both environmental and technical advantages.

CATALYTIC PROCESSING OF COAL MINE METHANE INTO HYDROGEN-CONTAINING GAS: INFLUENCE OF TRI-REFORMING PROCESS CONDITIONS

In order to develop a catalytic technology for processing coal mine methane into hydrogen-containing gas, thermodynamic analysis of methane tri-reforming (TRM) was carried out, and the influence of temperature (600-850 °C), contact time (0.04-0.15 s), linear feed rate (80-240 cm/min) and composition (CH4 / CO2 / H2O / O2 / He = 1: (0.3-0.5) : (0.2-0.5) : (0.1-0.3) : (2.9-3.2)) of the reaction mixture on the conversion of the initial reagents and target products in the TRM process in the presence of a supported Ni catalyst was studied. It has been shown that with an increase in the temperature of the TRM reaction from 600 to 800 °C the process performance improves (methane conversion: 36 → 94 %, carbon dioxide conversion: 57 → 97 %, hydrogen yield: 37→91 %, carbon monoxide yield: 44→ 94 %, molar ratio H2/CO: 1.5 → 1.7), and at a reaction temperature of 850 °C the process indicators are close to equilibrium values. It has been established that varying the O/C value and the composition of oxidants makes it possible to regulate the performance of TRM process. The optimal conditions for the TRM process were identified to achieve maximum efficiency of the catalytic processing of coal mine methane into hydrogen-containing gas: temperature - in the range of 800-850 °C, contact time - 0.15 s, linear feed rate - 160 cm/min and molar ratio of reagents in the initial feed - CH4 / CO2 / H2O / O2 = 1: 0.5 : 0.2 : 0.25.

Optimization of technological parameters of the methane tri-reforming process based on the phenomenon of conservatively perturbed equilibrium

course under the condition of the phenomenon of conservative perturbed equilibrium (CPE) are considered. It is shown that the onset of the CPE point - an extremum of the over-equilibrium concentration - occurs at a certain point in time. Therefore, one of the tasks of optimal control is to calculate the time of occurrence of this point and determine the effect of temperature and pressure on its position. The modeling of the TRM process is performed for an ideal displacement reactor. The DWSIM software product was used to model the TRM process. The kinetic equations were programmed in the form of scripts. The position of the over-equilibrium concentration point was also investigated depending on the initial composition of the mixture. According to the modeling results, it was concluded that the position of the CPE point for product H₂ is constant, and depends only on pressure and temperature and does not depend on the initial composition of the mixture. This allows us to conclude that the control can ensure that the product yield with the maximum concentration is achieved. The problem of optimizing the initial composition of the mixture for the methane tri-reforming process using CPE is formulated: the objective function and constraints are defined, and the solution method is chosen. The optimization problem is to maximize the target product of methane tri-reforming, H2. The solution to the problem is the composition of the mixture (concentrations of CH4, H2O, CO2). As for the constraints, the pressure and temperature are limited by the physicochemical properties of the process and the design features of the reactor, the elemental balance must be maintained, the key component at the input must have an equilibrium concentration at a given pressure and temperature, and the concentrations of other components must be deviated from their equilibrium values. A software implementation of the optimization problem based on the Optimization Toolbox Matlab was performed. The research results indicate an increase in the efficiency of the process (increase in the output of the target component) and the possibility of implementing optimal solutions in real time, which opens up prospects for implementation in existing control systems and development of decision-making systems.

A COMPARATIVE STUDY ON SAFETY, EXERGETIC, AND ENVIRONMENTAL ANALYSIS FOR BIOMETHANOL VIA BIOGAS REFORMING

The energy crisis and global warming caused by fossil fuel combustion have received increasing attention in recent years. Biomethanol is a clean and environmentally friendly energy produced by reforming biogas-derived syngas. To investigate the most suitable and efficient biomethanol production process, this paper compares the biomethanol production via three different biogas reforming processes, namely steam reforming, autothermal reforming, and tri-reforming using Aspen Plus simulator through safety index, energy and exergetic, and environmental analyses. For the process performance, the tri-reforming process achieved the highest energetic and exergetic efficiencies of 63.17% and 41.24%, respectively, due to producing the highest yield of methanol. In the environmental analysis, the steam reforming of the biogas process showed the lowest CO2 emission intensity of 3.16 ton CO2/ton methanol. The major source of CO2 emission is the combustion of biogas. The Dow Fire and Explosion Index was used for the safety aspect. The biomethanol reactor was discovered to be the most hazardous equipment.

The effect of carbon dioxide in the feed stream of tri-reforming of methane process compared to the partial oxidation of methane.

In this work, we studied the effect of CO2 in the feed stream of the TRM process performance of nickel supported on LaFeO3 perovskite for hydrogen production compared to the POM reaction. The perovskite and nickel supported on LaFeO3 were synthesized and characterized by thermogravimetric analysis (TGA/DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and programmed reduction temperature (TPR). The catalytic tests were carried out in temperatures varying from 700 to 800 °C with feed flow of 350 cm3/min and 200 cm3/min for TRM and POM, respectively. The hydrogen selectivity for the tri-reforming was 78%, while for the partial oxidation reaction, only 55% H2 at 700 °C. Results showed that the hydrogen selectivity for the Ni/LaFeO3 catalyst is significantly higher for the tri-reforming process, suggesting that CO2 enhanced the hydrogen selectivity compared to the partial oxidation of methane. Analyses by Raman spectroscopy and thermogravimetric calculations showed structural modifications of the catalysts after the reaction. The Raman spectrum showed segregated NiO and Fe3O4 and low carbon formation at 700 °C. The proposed mechanism suggests methane and oxygen adsorption, lattice oxygen and CO2 on surface active sites, and vacancies for both reactions.

Optimization and improvement of a conventional tri-reforming reactor to an energy efficient membrane reactor for hydrogen production

This study represents a numerical investigation of methane tri-reforming process with full computational fluid dynamics (CFD) in a conventional and a novel membrane fixed-bed reactor. A 2-D non-isothermal axisymmetric model is stablished to analyze the influence of relevant parameters. Three single objective optimization are conducted to maximize the H2 purity, energy efficiency and CO2 conversion, individually. The decision variables are the molar ratios of CO2/CH4, H2O/CH4 and O2/CH4 and the reactor inlet temperature. The optimization results indicate that the maximum value of energy efficiency in the conventional reactor is 73.29%. Moreover, when the H2 purity is maximum, the energy efficiency is almost 2% lower than its maximum value. Therefore, the novel membrane reactor is simulated using the first optimal conditions to achieve an energy efficient process for H2 production. A “hot-spot”, which is beneficial for the high endothermic reactions, is observed near the reactor entrance. It is proved that the hotter and greater “hot-spot” is in favor of the H2 production and energy efficiency. The counter-current configuration is more efficient due to its higher “hot-spot”. Finally, it is found that as the sweep gas velocity increases, the H2 purity and H2 recovery increase due to the “hot-spot” increment.

Syngas production by methane tri-reforming: Effect of Ni/CeO2 synthesis method on oxygen vacancies and coke formation

The CH4 tri-reforming process can contribute to mitigating CO2 emissions and enables the formation of syngas with different H2/CO ratios. Ni catalysts supported on CeO2 were synthesized by hydrothermal and ionothermal methods and were applied in methane tri-reforming reactions with GHSV of 48,000 mL/g.h, at atmospheric pressure and temperature of 800 °C. The catalytic activity in the tri-reforming reaction was enhanced by changing the morphological properties of the catalyst by appropriate selection of the amount of ionic liquid used in the synthesis procedure. Changing the composition resulted in methane conversion increasing from 60 % to 95 % and carbon dioxide conversion increasing from 40 % to 55 %. Increased Ni dispersion was related to the oxygen vacancies on the Ni-Ce surface, which created interfacial active sites. The results of XANES combined with XPS revealed that a partial reduction of Ni species contributed to high hydrogen yields, due to the distribution of active sites over the catalyst surface. These sites remained active during 5 h, demonstrating the positive effect of the ionic liquid used in the CeO2 synthesis. In addition, post-reaction characterization results showed Ni re-oxidation on the ceria support produced without ionic liquid.

CO2 utilization for methanol production; Part I: Process design and life cycle GHG assessment of different pathways

The process design and life cycle assessment (LCA) of various methanol production processes, including the conventional natural gas reforming process and alternative CO2 utilization-based pathways, are performed in this work. Three main technologies are considered for the CO2 conversion to methanol: direct CO2 hydrogenation, dry reforming and tri-reforming of methane. For each pathway, a process simulation that includes the CO2 capture from typical flue gas of a cement kiln, the methanol synthesis and purification steps, is performed using the Aspen engineering suite. In addition, for each process, several heat integration measures are considered to maximize thermal efficiency. According to the simulation results, the thermal efficiency of the direct CO2 hydrogenation process (47.8 % LHV) is higher than the dry reforming (40.6 % LHV) while it is lower than the conventional (68.4 % LHV) and tri-reforming (57.9 % LHV) processes. The LCA results showed that the direct CO2 hydrogenation pathway is an environmentally friendly option, only when the electricity GHG intensity is lower than 0.17 kg CO2 equivalent per kWh of electricity. As a result, in the context of Canada, the CO2 hydrogenation options can be recommended only for the provinces where low-carbon electricity is available, such as Quebec, British Columbia, Manitoba and Ontario.

Thermoeconomic analysis and multi‐objective optimization of a solid‐oxide fuel cell plant coupled with methane tri‐reforming: Effects of thermochemical recuperation

An 80-kW solid-oxide fuel cell (SOFC)-based power plant coupled with methane tri-reforming is proposed and analyzed from the viewpoint of thermoeconomics. In order to integrate the SOFC power generation section with the external reformer, part of the exhaust gases from the afterburner is recycled and utilized as a reformer agent in the reactor. The main challenge in performing the economic analysis is the determination of the costs associated with the tri-reforming process, in particular the reactor cost. To accomplish this, a mathematical procedure is suggested and applied for a fixed-bed reactor based on both the chemical equilibrium and chemical kinetics describing the tri-reforming process. The effects on system performance of important design parameters, including current density, SOFC operating temperature, and exhaust gas recirculation (EGR) percentage, are investigated. The results indicate that system performance is enhanced by using lower values of current density and higher values of SOFC operating temperature. In addition, considering the thermal and environmental performance of system as criteria, the use of EGR is not recommended. However, as the EGR percentage increases, the product unit cost decreases, making EGR advantageous from an economic perspective.

An improved water electrolysis and oxy-fuel combustion coupled tri-reforming process for methanol production and CO2 valorization

CO2 containing emissions from electric power plants are major contributors to the consistent rise of atmospheric CO2 concentration. The tri-reforming process has significant relevance as it converts non-inert components (CO2, H2O, O2) of the flue gas (with co-feed as methane) to synthesis gas without the intervention of an energy intensive CO2 separation step. Subsequent synthesis gas conversion to methanol is an important consideration. The conventional process employed air-fuel combustion based power plant generated flue gas in the tri-reforming coupled methanol production process to valorize CO2. Subsequently, the oxy-fuel combustion and water electrolysis coupled tri-reforming based methanol production process was developed as an improvement over it. In this paper, further advancements have been made to this coupled process. The following contributions have been made: (i) modification of the coupled process to increase the throughput of the water electrolysis unit to provide an inlet oxygen stream to the tri-reforming process to supplement an oxygen deficient flue gas stream, (ii) analysis of the synergistic role of simultaneous oxygen and hydrogen inputs from the water electrolysis unit on the performance of the overall process, and (iii) proposition of limiting the oxygen input to the tri-reformer to thermoneutrality to avoid exothermicity related issues. The above propositions have been implemented and compared with the base case coupled process via simulation runs in Aspen Plus V11. The results demonstrated a substantial improvement in both CO2 valorization potential (by 13.40%) and profitability (by 31.59%) of the process.

Multi objective optimization of a tri-reforming process with the maximization of H2 production and minimization of CO2 emission & power loss

In this study, the process optimization of a tri-reformer reactor is conducted for the synthesis of hydrogen gas from natural gas using multi-objective optimization (MOO) approach. Specifically, four MOO problems are solved using three objective functions, namely maximization of H2, minimization of CO2, and minimization of power loss. It should be noticed that the power loss is an important economic factor due the large pressure drop and flowrates in packed bed reactors. However, it has not been used as an objective function for the optimization based design and/or operation of fixed bed reactor for reforming process to the best of authors’ knowledge. Three of the four MOO problems are 2-objective in nature with all the permutation and combination of the three objectives. The fourth MOO problem is solved considering all the three objectives, simultaneously. For all the MOO problems, feed conditions of O2, H2O, and Temperature are considered as the optimization variables. The results obtained with 3 objective functions are observed to be superior to the ones obtained from 2 objective problems.

Process simulation and economic feasibility assessment of the methanol production via tri-reforming using experimental kinetic equations

The purpose of this paper is to assess via techno-economic metrics the feasibility of a tri-reforming coupled methanol process. The simulation of the tri-reforming reactor considered empiric kinetic equations, developed by our group in previous studies. The flue gas coming from the furnace that provides the energy required by the reforming reactor was also used as feed, in order to reduce the CO2 emissions. A sensitivity analysis was carried out to determine the influence of the feed composition and temperature in the tri-reforming process results, studying H2O/CH4 and O2/CH4 ratios (0.5–1.5 and 0.35–0.40, respectively), and varying the temperature between 850 and 1050 °C. The methanol plant was also simulated, and an economical study was carried out to know if the proposed process would be economically feasible. The most relevant economic parameters (including the Net Present Value, the Internal Rate of Return, the Payback Period and the break-even) were calculated, showing a quite robust process from an economical point of view.

An oxy-fuel combustion based tri-reforming coupled methanol production process with improved hydrogen utilization

CO2 valorization has been identified as an alternative to sequestration in view of its significant economic potential. The first pre-requisite in most of the CO2 valorization processes is an energy consuming capture step, which is avoided in the tri-reforming process. However, direct utilization of flue gas also posed a problem due to the presence of non-reactive nitrogen which severely limited its process efficacy. Coupling of the conventional process with an oxygen-oxidant based power plant addressed this problem in an earlier study where coupling of water electrolysis process supported the upstream plant while furthering the CO2 valorization objective (Dwivedi et al., 2018). This paper further addresses three aspects of the proposed valorization process: (i) low in-reactor hydrogen utilization, (ii) lower profit metric, and (iii) atmospheric pressure operation (that inevitably lead to large reactor sizes) of the tri-reformer. The following contributions have therefore been made in this paper: (i) evaluation of the role of tri-reforming reactor pressure on the relative performance of the modified process over the conventional process, at higher tri-reforming reactor pressures, and (ii) improved the process efficacy in terms of in-reactor hydrogen utilization (from ≈30 % to 81.61 %) of the coupled process (by employing higher pressure in the tri-reformer and a two-staged methanol reactor setup) thereby mitigating the major drawback of lower profit metric with respect to the conventional process. Simulation runs of the modified and conventional processes have been executed in Aspen Plus V8.4 in order to establish their relative efficacy.

X-ZrO2 addition (X= Ce, La, Y and Sm) on Ni/MgAl2O4 applied to methane tri-reforming for syngas production

Nickel supported on MgAl2O4 spinel (Ni/MA) and the effects of X-ZrO2 (X = Ce, La, Sm and Y) addition to the support were studied in Methane Tri-Reforming (MTR) process. The characterization techniques employed were XRD, B.E.T., H2-TPR, H2-TPD, CO2-TPD, XPS, and in situ XANES. The presence of lanthanides and Y associated to ZrO2 modified the Ni0 dispersion and the surface basicity. These properties influence the coke formation, which increased as the metallic dispersion diminished. Ce-ZrO2 association on the spinel support led to the greatest catalytic performance, increasing reactants conversions due to its adequate base properties that allowed the adsorption of new reactants molecules due to coke elimination, associated to its smallest apparent Ni0 average size. Moreover, the Ce-Zr support favored the NiO activation, without compromising the nickel dispersion.

Modeling and Simulation of Novel Bi- and Tri-reforming Processes for the Production of Renewable Methanol

Flue gases from coal, gas, or oil-fired power plants, as well as many heavy industries, are claimed as primary sources of CO2 emissions. Although CO2 capture and storage can play a role in decreasing CO2, its cost is preventing it from the broad application. Converting flue gases into methanol offers a change to mitigate CO2 emissions and a way to produce useful chemicals. In this study, two novel technologies including bi- and tri-reforming are analyzed for methanol production from CO2. The environmental and economic results are examined as two significant factors for green design. Preliminary evaluations pointed out that the reforming-based routes can be considered as a hopeful method for CO2 treatment during the transition stage from a carbon-based- to the carbon-free program.

Process simulation of bio-dimethyl ether synthesis from tri-reforming of biogas: CO2 utilization

The main contributions of this work are to study the suitable condition of biogas tri-reforming for DME synthesis process and to design the systems of the biogas tri-reforming process coupling with the DME synthesis. The effects of operating parameters in terms of boundary of carbon formation, steam to carbon ratio, and oxygen to carbon ratio on the biogas reforming process are firstly investigated. To utilize more CO2 in the system, CO2 produced from the DME synthesis is recycled to use in the biogas tri-reforming process. The H2 and CO yields of the tri-reforming process increase with increasing the CO2 recirculation ratio while the DME yield and system efficiency decrease. The requirement of gas cleaning unit for the DME synthesis coupling with the biogas tri-reforming system is also analyzed. The results indicate that the system with CO2 removal from syngas has more impact on the DME yield than that with H2O removal. On the contrary, the total CO2 emission intensity of the system with H2O removal is lower than that with CO2 removal. When comparing all cases, the system with both H2O and CO2 removals achieves the highest DME yield and system efficiency.

Potential of tri-reforming process and membrane technology for improving ammonia production and CO2 reduction

In this work, a tri-reforming process was coupled with a membrane separation unit to enhance efficiency of ammonia (NH3) synthesis process in terms of CO2 emission, NH3 production, and NOx emission. Primary and secondary reformers were replaced by a tri-reforming process, while a Perovskite membrane was applied to separate nitrogen (N2) from oxygen (O2). A conventional NH3 synthesis process and the proposed process were simulated by Aspen-Hysys and compared in order to investigate the performance of the proposed sterategy. The simulation results indicated that when temperature increased and pressure decreased, conversion of hydrocarbons and H2/CO ratio were improved from 1.73 to 2.54, which resulted in an increase in NH3 production by 27 %, and a decrease in CO2 emission rate from 1192 kg/h to approximately 1 kg/h. The proposed sterategy was optimized in terms of different parameters e.g., temperature and pressure. Optimum reaction pressure and temperature were determined to be between 1 and 10 bar and 500–800 °C, respectively. The results of the study revealed that the proposed strategy not only removed amine and methanol sweeteners which reduce the operational costs of the process, but also decreased the NOx content from 8220 ppm to almost 10 ppm.

Oxidative Reforming of Methane on Structured Nickel–Alumina Catalysts: a Review

A summary is given for the results of studies on the creation of modified nickel–alumina catalysts on structured supports for the oxidative conversion of methane (steam and carbon dioxide conversion, combined oxy-(carbon dioxide)-steam, and tri-reforming processes) to give synthesis gas with an H2/CO ratio that can be varied from 1.4 to 4.0. Methods for reducing the carbonization of the nickel–alumina catalysts, especially by introducing modifying additives of compounds of s- and f-elements, are considered along with an analysis of possible mechanisms for these processes. Oxides of rare earth elements (La2O3 and CeO2) are multifunctional additives that allow regulation of both the structural characteristics and catalytic properties of nickel–alumina systems. Ways to improve the catalysts for the oxidative reforming of methane are indicated.

Perspective of catalysts for (Tri) reforming of natural gas and flue gas rich in CO2

Natural gas is an attractive feedstock for the synthesis of fuels and chemicals, currently derived from petroleum. The increasing global demand for more environment friendly processes and materials is a motivation to look for natural gas chemical conversion technologies. Carbon dioxide is a gaseous compound, which is also considered to be one of the main contributor to greenhouse effects. Methane tri-reforming is an important way for CO2 utilization aiming at hydrogen and syngas production, without separation of carbon dioxide. One expects that the tri-reforming process decreases the greenhouse gas emission. The main challenges in bringing this reforming technology to practice rest in catalysts development and the understanding of the reaction mechanisms for kinetic modeling and process optimization. What can be done?The main goal of this article is to describe factors to consider in search of catalysts suitable for the reforming of flue gas rich in CO2 and related processes. First, we discussed the relevant metal oxides catalysts and the effect of the supports for methane tri-reforming as well as combined or separated reforming processes for syngas production. Secondly, we described an investigation of two different supported catalysts based on multi-wall carbon nanotubes (MWCNT) and perovskite-type oxides. Structural changes of the catalysts as observed by different characterizations techniques for both in situ and post-reaction analyses. We showed that the tri-reforming processes are promising, but it is important to find out suitable, stable catalysts. Carbon nanotubes are promising as supports because they are capable of dispersing the metal particles. However, better understanding of the surface reaction, carbon formation mechanisms and the structural modifications are essential to explain these phenomena in further improvement and search of better catalysts.

Thermodynamic analysis of a new chemical looping process for syngas production with simultaneous CO2 capture and utilization

Since typical CO2 capture technologies lack the consideration of a reliable CO2 storage method or integration with CO2 utilization, this study proposes a new chemical looping reforming process for syngas production with simultaneous CO2 capture and utilization. It integrates chemical looping, mixed reforming (i.e. CO2 reforming and partial oxidation) and calcium looping using CO2 carriers (CCs) and oxygen carriers (OCs). This novel process implements energy-efficient operation, attains flexible H2/CO ratio, and captures CO2 with immediate CO2 conversion. Through thermodynamic screening, Fe- and Cu-based metal/metal oxides and CaO and MnO are identified as the potential OCs and CCs. For process characteristics, almost full CO2 capture is achieved, CH4 conversion rate is over 92.11%, maximum CO2 utilization rate is 99.18%, H2/CO ratio is close to 2, and energy consumption is reduced by 40.74% and 68.62% compared to that of conventional mixed reforming and tri-reforming processes, respectively. Steam addition, low pressure and high temperature are benefit to enhance system performance. From experiment results, gas product distribution, solid reactivity and crystalline phases for solid demonstrate the feasibility of this novel process. More importantly, this process provides a new route to achieve integrated CO2 capture and conversion with the clean usages of carbonaceous energy sources.