Influence of capillary threshold pressure and injection well location on the dynamic CO2 and H2 storage capacity for the deep geological structure

The subject of this study is the analysis of influence of capillary threshold pressure and injection well location on the dynamic CO₂ and H₂ storage capacity for the Lower Jurassic reservoir of the Sierpc structure from central Poland. The results of injection modeling allowed us to compare the amount of CO₂ and H₂ that the considered structure can store safely over a given time interval. The modeling was performed using a single well for 30 different locations, considering that the minimum capillary pressure of the cap rock and the fracturing pressure should not be exceeded for each gas separately.Other values of capillary threshold pressure for CO₂ and H₂ significantly affect the amount of a given gas that can be injected into the reservoir. The structure under consideration can store approximately 1 Mt CO₂ in 31 years, while in the case of H₂ it is slightly above 4000 tons. The determined CO₂ storage capacity is limited; the structure seems to be more prospective for underground H₂ storage. The CO₂ and H₂ dynamic storage capacity maps are an important element of the analysis of the use of gas storage structures. A much higher fingering effect was observed for H₂ than for CO₂, which may affect the withdrawal of hydrogen. It is recommended to determine the optimum storage depth, particularly for hydrogen. The presented results, important for the assessment of the capacity of geological structures, also relate to the safety of use of CO₂ and H₂ underground storage space.     

Co-optimization of CO2 sequestration and enhanced oil recovery in extra-low permeability reservoir in Shanbei

This article put forward a theoretical system, which is used to analyze co-optimization of CO₂ sequestration and enhanced oil recovery by using the methods or theories including the design of experiments, numerical simulation, net present value, and the response surface methods. A CO₂ flooding operation in an immiscible water-alternating-gas process of Shanbei extra-low permeability reservoir was estimated preliminarily by using the methods proposed in this article. The result shows that optimized values obtained from predicted values were in good agreement with the values obtained from the simulation model and it is possible to optimize a coupled CO₂ sequestration and enhanced oil recovery project.     

Carbon resistance of xNi/HTASAO5 catalyst for the production of H2 via CO2 reforming of methane

xNi/HTASAO5 catalysts (x = 2.5, 3.3, 4.4, 5.8, 8.2) were prepared for CO₂ reforming of methane. No crystalline nickel species formed on the catalysts with lower nickel content (≤4.4%), and large Ni⁰ crystallite formed on 5.8% (10 nm) and 8.2 wt%Ni/HTASAO5 (17 nm), whereas the surface concentration of Ce³⁺ decreased with Ni loading. The initial conversion of CH₄ increased from 29.5% to 46.9% with Ni loading. The xNi/HTASAO5 (x ≤ 4.4%) performed stably in the reaction due to the presence of dispersed Ni species and high surface Ce³⁺ content without coke formation, however, 5.8% and 8.2 wt%Ni/HTASAO5 exhibited decreased activity with time on stream, because of the formation of large Ni particles with lower surface Ce³⁺, leading to carbon accumulation. Thus, CH₄ conversion stabilized at about 43% and no carbon formed on 4.4 wt%Ni/HTASAO5 with optimum Ni loading.     

Integration of methane cracking and direct carbon fuel cell with CO2 capture for hydrogen carrier production

Hydrogen fuel production from methane cracking is a sustainable process compared to the ones currently in practice due to zero greenhouse gas emissions. Also, carbon black that is co-produced is valuable and can be marketed to other industries. As this is a high-temperature process, using solar energy can further improve its sustainability. An integrated solar methane cracking system is proposed where hydrogen and carbon products are sent to fuel cells to generate electricity. The CO₂ exhaust stream from the carbon fuel cell is captured and reacted with hydrogen in the CO₂ hydrogenation unit to produce liquid fuels – Methanol and dimethyl ether. The process is simulated in Aspen Plus®, and its energy and exergy efficiencies are evaluated by carrying out a detailed thermodynamic analysis. In addition, a sensitivity analysis is performed on various input parameters of the system. The overall energy efficiency of 41.9% and exergy efficiency of 52.3% were found.     

Design of CO2 absorption plant for recovery of CO2 from flue gases of gas turbine

The ongoing human-induced emission of carbon dioxide (CO₂) threatens to change the earth's climate. A major factor in global warming is CO₂ emission from thermal power plants, which burn fossil fuels. One possible way of decreasing CO₂ emissions is to apply CO₂ removal, which involves recovering of CO₂ from energy conversion processes. This study is focused on recovery of CO₂ from gas turbine exhaust of Sarkhun gas refinery power station. The purpose of this study is to recover the CO₂ with minimum energy requirement. Many of CO₂ recovery processes from flue gases have been studied. Among all CO₂ recovery processes which were studied, absorption process was selected as the optimum one, due to low CO₂ concentration in flue gas. The design parameters considered in this regard, are: selection of suitable solvent, solvent concentration, solvent circulation rate, reboiler and condenser duty and number of stages in absorber and stripper columns. In the design of this unit, amine solvent such as, diethanolamine (DEA), diglycolamine (DGA), methyldiethanolamine (MDEA), and monoethanolamine (MEA) were considered and the effect of main parameters on the absorption and stripping columns is presented. Some results with simultaneous changing of the design variables have been obtained. The results show that DGA is the best solvent with minimum energy requirement for recovery of CO₂ from flue gases at atmospheric pressure.     

Assessment of key parameters in tannery sludge management: A prerequisite for energy recovery

Environmental regulations are getting more restricted related to landfilling of biodegradable waste. The solution to these problems is using the biodegradable portion of sludge waste for agricultural or thermal utilization. This paper is based on the physico-chemical analysis of different proportions of sludge with coal and rice husk for co-combustion to optimize the parameters like sulfur, ash, and gross heating value (GHV). A significant increase in GHV of secondary sludge with different combinations of coal and rice husk was observed as compared to primary sludge combinations representing 13.55–21.80 Mj/kg and 11.52–19.12 Mj/kg, respectively. The combination RSSC-1 (50% sludge and 50% coal) is highly significant with p < 0.01 and can be utilized as fuel because of the high GHV and low sulfur content. This study concludes that co-combustion of sludge in an eco-friendly manner, using modified thermal methods, may turn into a valuable fuel like traditional biomass.     

Nickelcobalt catalyst supported on TiO2-coated SiO2 spheres for CO2 methanation in a fluidized bed

Carbon dioxide (CO₂) methanation, which is the reduction of carbon dioxide to methane by hydrogen generated from renewable energy, is a promising process for carbon recycling. Towards large-scale implementation, (i) fluidized beds, which have excellent heat transfer, are promising to perform the highly exothermic reaction; and (ii) catalysts suitable for long-term use in fluidized beds are needed. In this study, a novel NiCo bimetal catalyst supported on TiO₂-coated SiO₂ spheres (NiCo/TiO₂@SiO₂) was rationally designed and evaluated for CO₂ methanation in fluidized bed reactor. The results demonstrate that NiCo/TiO₂@SiO₂ exhibited high CO₂ conversion with CH₄ selectivity of greater than 95%. Moreover, the superior performance was sustained for more than 100 h in the fluidized bed reactor, affirming the long-term stability of the catalyst. Comprehensive characterizations were conducted to understand the relationship between structure and performance. This study is expected to be valuable for the potential implementation of the CO₂ methanation process in fluidized beds.     

Analysis of a 2-D model of a packed bed reactor for methanol production by means of CO2 hydrogenation

In recent years, methanol received the attention of many researchers as a building block of the circular economy, because of its diversified applications in different areas. Generally, methanol is produced by syngas, however recent studies are dealing with its production via carbon dioxide hydrogenation. With the aim to predict conversions, efficiencies as well as concentration, pressure and temperature profiles inside the packed bed methanol reactor, mathematical models are developed in one- (1-D) and two- (2-D) dimensions. However, a deep study about a 2-D mathematical model and conditions where its use is advisable to get reliable predictions is missing in the literature. In this research, a two dimensional model for methanol reactor via carbon dioxide hydrogenation is suggested, comparing a structured catalytic packing with a more common packed bed of catalyst pellets, which differ mainly for the respective thermal conductivity. The system of partial differential equations is solved in MATLAB® and the same operating conditions set in a previous work about a one dimensional model are considered. Results show that the 2-D model is useful for both reactor typologies under the examined operating conditions, although definitely more important for the non-structured reactor, where higher temperature and concentration differences on tube cross sections are calculated because of a stronger resistance to radial heat transfer. In addition, a higher efficiency is predicted for a structured reactor in terms of carbon dioxide selectivity to methanol and methanol yield, then a lower recycle flow rate is required in this case. A sensitivity analysis is also developed for the two reactor typologies, changing feed inlet temperature, wall heat transfer coefficient and tube diameter. Conditions are investigated, for which 2-D model results tend to corresponding outputs of a 1-D model.     

小型CO_2热泵系统用气体冷却器仿真研究

CO_2气体冷却器的结构和换热效果对CO_2跨临界循环影响较大.为设计出高效的气体冷却器,有必要对其性能进行模拟和优化.采用有限单元法建立了小型CO_2热泵热水器中气体冷却器稳态分布参数模型,分别对其CO_2侧和水侧的流动与换热进行了数值仿真,运用该模型分别针对CO_2侧进口压力对气体冷却器设计管长和CO_2换热性能的影响进行了分析.结果表明,CO_2侧进口压力在8~12 MPa时,从8 MPa开始每递增1 MPa,换热系数峰值比压力增加1 MPa前的依次递减约57.14%、33.33%、25.00%、9.83%,设计管长比压力增加1 MPa前的依次递减约55.60%、18.75%、11.33%、9.09%.综合考虑管道耗材与CO_2换热能力,针对小型CO_2热泵系统,气体冷却器CO_2侧进口压力取8.5~10 MPa较合理.研究可为气体冷却器设计提供理论指导.     

Effects of geochemical reactions on injectivity of CO2 in deep saline formations

CO₂ geological storage into deep saline aquifers is one of the most promising methods for reducing anthropogenic CO₂ emissions into the atmosphere. During the CO₂ geological storage, many factors may affect the final success of actual storage projects, including storability, injectivity, and seal security. In order to investigate the impact of the desiccation phenomenon on the physical and chemical behaviors around the injection well, a series of numerical simulations were performed. Simulation results demonstrated that the geochemical reactions play an important role in the CO₂ injection stage, especially the dissolution of easily soluble minerals, such as carbonates and sulfate.     

Evaluation of CO2 enhanced oil recovery and sequestration potential in low permeability reservoirs,Yanchang Oilfield,China

Sequestrating CO₂ in reservoirs can substantially enhance oil recovery and effectively reduce greenhouse gas emission. To evaluate the potential of CO₂ enhanced oil recovery (EOR) and sequestration for Yanchang Oilfield in China, a screening standard which was suitable for CO₂-EOR and sequestration in Yanchang Oilfield was proposed based on its characteristics of strong heterogeneity, high water content and severe fluid channeling after water flooding. In addition, an efficient calculation method – stream tube simulation method was presented to figure out CO₂ sequestration coefficient and oil recovery factor. After screening and evaluating, it turned out that 148 out of 176 blocks in 22 oilfields were suitable for CO₂-EOR and sequestration. CO₂ flooding after water flooding can produce 180.21 × 10⁶ t more crude oil and sequestrate 223.38 × 10⁶ t CO₂. The average incremental oil recovery rate of miscible reservoirs was 12.49% and the average CO₂ sequestration coefficient was 0.27 t/t while the two values were 6.83% and 0.18 t/t for immiscible reservoirs. There are comparatively more reservoirs that are suitable for CO₂-EOR and sequestration in Yanchang Oilfield than normal, which can obviously enhance oil recovery and means a great potential for CO₂ sequestration. CO₂-EOR and sequestration in Yanchang Oilfield has a bright application prospect.     

CO2 electrolysis in a reversible molten carbonate fuel cell: Online chromatographic detection of CO

CO₂ plays a major role in the molten carbonate fuel cell (MCFC) and its reverse process, the molten carbonate electrolysis cell (MCEC), because of the capability of the mentioned electrolyte to capture big amounts of this greenhouse gas. In particular, the co-electrolysis process together with water, would ideally yield syngas (H₂ + CO). The reduction of CO₂ in such a case has been scarcely investigated in MCEC conditions. The present study is mainly focused on the online detection by Gas Chromatography (GC) of CO₂ electrolysis product. Both thermodynamic predictions, including the chemical reactivity of CO and CH₄, and experimental results on MCFC/MCEC performance and GC detection, allowed to prove that CO is produced electrochemically with a ratio depending on the electrolysis potential, deducing also the potentials that should be avoided to inhibit the formation of carbon. This first insight will be essential for analyzing the medium and long-term performance of MCECs.     

CFD simulation of CO2 removal from hydrogen rich stream in a microchannel

The main object of this research is to perform computational fluid dynamics simulation of CO₂ capturing from hydrogen-rich streams by aqueous DEA solution in a T-Junction microchannel contactor with 250 μm diameter and 5 mm length at dynamic conditions. To develop a comprehensive mathematical framework to simulate the flow hydrodynamics and mass transfer characteristics of system, the continuity and Navier-Stokes equations, two phase transport, and reaction rate model are coupled in COMSOL Multiphysics software. The developed model is solved and the effects of gas and liquid velocities as well as amine concentration on the CO₂ absorption rate, hydrogen purification fraction, and flow hydrodynamic are investigated. The absorption process consists of CO₂ diffusion from bubble bulk toward the bubble boundary, CO₂ solubility in the liquid boundary, diffusion from the boundary into the liquid bulk, and reaction with the amine molecules. The results show that when the gas and liquid streams are mixed in the junction point to form a bubble, the gas cross-section area becomes narrow, and the fluid velocity increases due to the applied force on the bubble by the liquid layers. It appears that increasing the DEA concentration in the inlet from 5% to 20% increases hydrogen purification fraction from 42.3 to 66.4%, and up to 96.7% hydrogen purity is achieved by 20% aqueous solution of DEA.     

Utilization of CO2 for syngas production by CH4 partial oxidation using a catalytic membrane reactor

In this research, a synthetic flue gas mixture with added methane was used as the feed gas in the process of dry reforming with partial oxidation of methane using a laboratory scale catalytic membrane reactor to produce hydrogen and carbon monoxide that can present the starting point for methanol or ammonia synthesis and Fischer-Tropsch reactions. 0.5% wt% Rh catalyst was deposited on a γ-alumina support using rhodium (III) chloride precursor and incorporated into a shell and tube membrane reactor to measure the yield of synthesis gas (CO and H₂) and conversion of CH₄, O₂ and CO₂ respectively. These measurements were used to determine the reaction order and rate of CO₂. The conversion of CO₂ and CH₄ were determined at different gas hourly space velocities. The reaction order was determined to be a first-order with respect to CO₂. The rate of reaction for CO₂ was found to follow an Arrhenius equation having an activation energy of 49.88 × 10⁻¹ kJ mol⁻¹. Experiments were conducted at 2.5, 5 and 8 ml h⁻¹ g⁻¹ gas hourly space velocities and it was observed that increasing the hourly gas velocities resulted in a higher CO₂ and CH₄ conversions while O₂ conversion remained fairly constant. CO₂ had a high conversion rate of 96% at 8 ml h⁻¹ g⁻¹. The synthesized catalytic membrane was characterized by Scanning Electron Microscopy (SEM) and the Energy Dispersive X-ray Analysis (EDXA) respectively. The micrographs showed the Rh particles deposited on the alumina support. Single gas permeation of CH₄, CO₂ and H₂ through the alumina support showed that the permeance of H₂ increased as the pressure was increased to 1 × 10⁵ Pa. The order of gas permeance was H₂ (2.00 g/mol) > CH₄ (16.04 g/mol) > N₂ (28.01 g/mol) > O₂ (32 g/mol) > CO₂ (44.00 g/mol) which is indicative of Knudsen flow mechanism. The novelty of the work lies in the combination of exothermic partial oxidation and endothermic CO₂ and steam reforming in a single step in the membrane reactor to achieve near thermoneutrality while simultaneously consuming almost all the greenhouse gases in the feed gas stream.     

Numerical experiments in the simulation of enhanced oil recovery from a porous formation

A numerical reservoir simulation model for the study of enhanced oil recovery (EOR) from a porous formation has been presented. The resistance to oil movement arises from viscous forces in the fluid phase as well as surface tension. Viscous forces can be lowered by hot water injection into the formation or by raising the formation temperature. These methods have been numerically analyzed in the present study. The role of the operating parameters such as the injection pressure and temperature on oil recovery has been reported. Displacement of oil by water is clearly brought out by the saturation and the temperature profiles.The numerical solution of the EOR problem experiences growth of errors during long time integration, particularly on large regions. Possible reasons are scatter in the constitutive relationship data, inexact outflow boundary condition and round-off errors in the calculation of the matrix inverse. The nature of these errors has been addressed in the present work. To solve the computationally intensive field-scale problems, two domain decomposition algorithms namely, Schwarz's and Uzawa's algorithms have been evaluated.Results show that oil recovery can be improved when the formation temperature is higher, or the injection temperature and pressure are raised. Adverse results can however be obtained when the injection temperature exceeds a critical value. Optimum conditions prevail when the speed of the oil–water interface is matched with that of the thermal front. As a computational tool, the domain decomposition algorithms are conditionally seen to improve the numerical performance of the oil recovery codes.     

Modification of silica supported nickel catalysts with lanthanum for stability improvement in methane reforming with CO2

Dry reforming of methane (DRM) with excessive methane composition at CH₄/CO₂ = 1.2:1 was studied over lanthanum modified silica supported nickel catalysts (Ni-xLa-SiO₂, x: 1, 2, 4, and 6% in the target weight percent of La). The catalysts were prepared by ammonia evaporation method. Nickel phyllosilicate and La₂O₃ were the main phases in calcined catalysts. The modification of La enhanced the formation of 1:1 and Tran-2:1 nickel-phyllosilicate. There existed an optimum content of La loading at 1.50 wt% in Ni–2La–SiO₂ which resulted in its highest reduction degree (95.3%). The catalysts with appropriate amounts of La exhibited higher amount of CO₂ adsorption and created more medium and strong base centers. The sufficient number of exposed metallic nickel sites to catalyze the reforming reaction, as well as enough medium and strong basic sites in Ni–La–SiO₂ interface to accomplish the carbon removal were two important factors to attenuate catalyst deactivation. The catalyst stability evaluated at 750 °C for 10 h followed the order: Ni–2La–SiO₂ > Ni–4La–SiO₂ > Ni–1La–SiO₂ ≈ Ni–6La–SiO₂ > Ni–SiO₂. Ni–2La–SiO₂ catalyst possessed the lowest deactivation behavior, whose CH₄ conversion dropped from 60.2 to 55.9% after 30 h operation at 750 °C, indicating its high resistance against carbon deposition and sintering.     

Evaluation of effective parameters on CO2 injection process in a gas condensate reservoir: A case study

One of the key problems in gas condensate reservoirs is condensate blockage phenomena or condensate banking that reduces the condensate recovery. This phenomenon occurs when by reservoir depletion the reservoir pressure declines below the dew point pressure. One of the most important and common methods to prevent condensate blockage is gas cycling. Nowadays, regarding the value of natural gas, the use of other gases such as CO₂ as a suitable replacement has increased. The purpose of this study is to evaluate different parameters such as injection rate, injection pressure, and the number of wells in CO₂ injection process, in order to determine optimum conditions for CO₂ injection with the maximum condensate recovery and minimum economic cost. The two-parameter, Peng–Robinson equation of state (EOS) was used to match PVT experimental data. Then various scenarios of CO₂ injection with different conditions have been studied, and optimum conditions for CO₂ injection were compared with the natural depletion scenario. The results showed that the injection rate and pressure play important roles in determining the best condensate recovery.     

加热炉钢坯加热质量的数值模拟研究

处理不同入炉温度的钢坯需采用合理的加热时间和工艺,针对此问题,采用数值模拟的方法研究人炉温度分别为200,400,600,700℃的钢坯最佳加热时间和加热质量。通过利用Fluent流体计算软件建立了钢坯非稳态导热模型和氧化烧损模型,模拟结果表明：在相同的加热工艺下,钢坯人炉温度为27℃,炉内停留时间为180min时,位于预热段的第5块钢坯表面受到的辐射热流最大,达到92kW／m^2,出炉钢坯氧化率为1．419％;钢坯入炉温度为200℃时,合理的炉内停留时间为150min,出炉温度达到1183℃,出炉钢坯氧化率为1．307％。     

CO2 reforming of methane for H2 production in a membrane reactor as CO2 utilization: Computational fluid dynamics studies with a reactor geometry

Computational fluid dynamics (CFD) studies have been carried out for CO₂ reforming of methane in both a packed-bed reactor (PBR) and a membrane reactor (MR) with a heating tube as a heat source at the center of a reactor. The effect of a reactor geometry on the temperature and H₂ and CH₄ concentration profiles within a PBR and a MR have been investigated numerically by changing the distance of membranes from the center of a heating tube (D_center = radial distance between the center of the reactor and the center of the membrane) for a given heating tube temperature. The distances of the center of the membranes in a MR from the reactor center were 0.028 m, 0.03 m, 0.033 m, 0.035 m, 0.038 m, 0.04 m, 0.042 m, 0.044 m and 0.045 m. With the help of COMSOL Multiphysics® modeling software, it was possible to visualize temperature and concentration profiles both axially and radially. Interestingly, it was found that H₂ enhancement is proportional to both D_center and the magnitude of the H₂ flux. Further studies for the effect of a heating tube radius proposed an optimum radius for a maximum H₂ yield enhancement in a MR. Consequently, it turned out that CFD studies can be used as a critical guideline for an efficient reactor design focusing on a reactor geometry in a MR for given conditions.