Raw Natural Gas Research Articles

Comparative Hydrogen Production Routes via Steam Methane Reforming and Chemical Looping Reforming of Natural Gas as Feedstock

Hydrogen production is essential in the transition to sustainable energy. This study examines two hydrogen production routes, steam methane reforming (SMR) and chemical looping reforming (CLR), both using raw natural gas as feedstock. SMR, the most commonly used industrial process, involves reacting methane with steam to produce hydrogen, carbon monoxide, and carbon dioxide. In contrast, CLR uses a metal oxide as an oxygen carrier to facilitate hydrogen production without generating additional carbon dioxide. Simulations conducted using Aspen HYSYS analyzed each method’s performance and energy consumption. The results show that SMR achieved 99.98% hydrogen purity, whereas CLR produced 99.97% purity. An energy analysis revealed that CLR requires 31% less energy than SMR, likely due to the absence of low- and high-temperature water–gas shift units. Overall, the findings suggest that CLR offers substantial advantages over SMR, including lower energy consumption and the production of cleaner hydrogen, free from carbon dioxide generated during the water–gas shift process.

Forecasting China’s CO2 emissions and identifying key drivers: an application of the improved RFAGM model and LMDI decomposition methods

ABSTRACT China, the world’s largest CO2 emitter, has pledged to reduce its carbon intensity by 18% by 2025, which requires accurate forecasting of its emissions and their drivers. However, existing gray models have limitations in dealing with fluctuating data or long-time series data, and they often suffer from overfitting and poor generalization ability. Moreover, there is a lack of research and judgment on the future changes of emission drivers. To address these issues, this study proposes a fractional order gray adaptive rolling model (RFAGM(1,1)) that optimizes the background generation and incorporates the rolling mechanism. We apply RFAGM(1,1) to forecast China’s emissions, GDP, population, and consumption of raw coal, crude oil, and natural gas from 2020 to 2025. Our results show that RFAGM(1,1) achieves significantly higher accuracy than standard gray models, except for population. The projections indicate that China will meet the 18% carbon intensity reduction target by 2025. Furthermore, the LMDI decomposition reveals that economic growth and population changes have positive cumulative impacts on emission growth (245.68% and 11.95%, respectively), while energy intensity and structural changes have negative cumulative impacts (−151.60% and −6.02%, respectively). The improved forecast enables the evaluation of climate policies, while the factor analysis provides valuable insights for developing evidence-based strategies to achieve China’s carbon peaking and neutrality goals by 2030/2060.

Impact of raw liquid natural gas composition on combustion properties and emission characteristic

Impact of raw liquid natural gas composition on combustion properties and emission characteristic

Application of the sustainable system-of-systems approach and econometric analysis to address China’s decarbonisation problem

The Sustainable system-of-systems (SSoS) approach, complemented with econometric analysis was used to address China’s decarbonisation problem, i.e. selecting fossil fuel consumption sources to be reduced in various regions to meet CO2 reduction targets with minimal effect on population and economic growth. In the SSoS, the micro-level system is represented by residents’ health expenditure, the meso-level system by industry’s CO2 emissions intensity, and the macro-level system by the government’s achievement of economic growth. Regional panel data from 2009 to 2019 were used in an econometric analysis conducted using structural equation modelling. The results show that health expenditure was affected by CO2 emissions from the consumption of raw coal and natural gas. To support economic growth, the government should reduce raw coal consumption. For CO2 emissions reduction, industry in the eastern region should reduce raw coal consumption. The key advantage is SSoS with econometrics offers a way to reach a common goal among stakeholders. Practitioner summary: This research shows that the use of the SSoS approach, complemented with an econometric analysis of key social, economic, and natural capital data, can address a complex decarbonisation problem facing a nation (China, in the present case) while considering the goals of all stakeholders (the government, industrial communities, and residential communities). Abbreviations: CEADs: Carbon Emissions Accounts and Datasets for Emerging Countries; CEIC: CEIC Global Database; GRPS: World Economic Forum’s Global Risks Perception Survey; HFE: human factors/ergonomics; ML-SEM: maximum likelihood estimation method; NDRC: National Development and Reform Commission of China; SEM: structural equation modelling; SSoS: Sustainable system-of-systems; TBL: triple bottom line

Spatio-temporal graph convolutional networks driven by data-physical fusion for parameter prediction of natural gas dehydration system

Triethylene glycol dehydration unit is a piece of essential device for removing moisture from raw natural gas during natural gas production. However, the existing station equipment management systems are mostly collection-oriented with little analysis, lack the effective methods of parameter prediction and fault warning, and the strong coupling between the monitoring parameters is a problem should be study. To solve these problems, this paper analyzes the time dependence and spatial correlation of these parameters. Also, a spatio-temporal graph convolutional networks prediction model driven by data-physical fusion (SG-STGCN) is proposed for constructing the graph structure. Firstly, the signed directed graph model is established based on the physical process, and the weight of each edge is obtained by using the grey relational analysis (GRA). Secondly, by stacking spatio-temporal convolutional modules, the temporal and spatial dependencies over a long range of time are captured to realize multivariate parameter prediction. Then, the real-time monitoring data of a dehydration station are used for analysis. The experimental results showed that the proposed method can achieves the best predict result compared with other methods, and can be used in the fault early warning to maintain high reliability of equipment. Finally, the SG-STGCN has been integrated and tested successfully on the real-time monitoring platform of a dehydration unit.

High sour natural gas dehydration treatment through low temperature technique: Process simulation, modeling and optimization

Among the various fossil fuels, natural gas is a clean fuel because it has a less adverse impact on the environment compared to other energy sources. Natural gas emits less hazardous gases and less CO2 upon burning. Water, CO2, N2, H2S, and other contaminants could be present in raw natural gas, depending on its geographic location. The main issue among these contaminants is CO2, which decreases the calorific value of natural gas and corrodes pipes and process equipment. Absorption, adsorption, membrane separation, and cryogenic separation are the four main CO2 separation technologies. Cryogenic technologies for natural gas purification are environmentally friendly because they involve physical separation, and no harmful chemicals are required. Although cryogenic is an attractive alternative, it has some process limitations. The water must be removed before cryogenic separation because it can create piping blockage due to ice formation. The main goal is to remove water from natural gas at optimized conditions. The absorption technique employing triethylene glycol (TEG) as a solvent is the most widely used technology for dehydrating natural gas. Water extracts from natural gas as it passes over TEG, which acts as a dehydrating agent. The harmful effects of TEG on the environment are this technology's principal drawback. The current work investigates the dehydration of natural gas utilizing a low-temperature packed bed which could be an attractive alternative due to the absence of harmful chemicals. A thorough simulation analysis was carried out to learn more about the impact of the process parameter on the separation. The results showed that the pressure increase from 1 to 5 bar resulted in water removal from 25.4 to 83.7%. The optimum temperature and pressure for maximal water removal from natural gas were also determined. The maximum water was removed at 34 bar and −7.3 °C.

CO2 removal in humid environment by ion‐exchange membranes

AbstractMany CO2 sorbents have performance degradation issues in humid environment. The recently developed moisture swing sorbent, initially used for CO2 capture from ambient air, faces the same problem of high moisture sensitivity in the adsorption environment with very dilute CO2 concentration (i.e., air). However, the performance of the sorbent, especially its moisture sensitivity, at relative high concentrations of CO2, is still unknown. In this work, the adsorption performance of a resin‐based ion‐exchange membrane loaded with CO32− (a typical moisture swing sorbent) was investigated in a series of isothermal equilibrium experiments at varying CO2 concentrations and relative humidity. The results showed that the moisture sensitivity of the adsorption capacity of the ion‐exchange membrane decreased with the initial CO2 concentration, especially when the initial CO2 concentration was above 4%. The competition mechanism of H2O and CO2 molecules in the membrane material was analyzed by the modified dynamic adsorption model. The present work indicates that the resin‐based ion‐exchange membrane could be used for carbon dioxide removal in a lot humid environments with relatively high CO2 concentration, such as fruit and vegetable storage room, raw natural gas, and flue gas.

The impact of water, BTEX compounds and ethylene glycol on the performance of perfluoro(butenyl vinyl ether) based membranes for CO2 capture from natural gas

Glassy perfluoropolymers offer a remarkable resistance towards many species that can alter the separation performance of conventional polymeric membranes. In this study, the performance of Cytop® and CyclAFlor™ random copolymers of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD) are studied for the first time for carbon dioxide capture in the presence of impurities that are common in raw natural gas. Water vapor sorption isotherms were S-shaped for both polymers, indicating the formation of water clusters. The water permeability decreased with vapor activity in both perfluoropolymers as the formation of these clusters decreased water diffusivity. The presence of the water clusters, however, had no impact on the performance of Cytop® and poly(50%PBVE-co-50%PDD) for CO2/CH4 separation. Typical concave sorption isotherms were obtained for toluene and xylene in poly(50%PBVE-co-50%PDD), while convex isotherms were observed in Cytop®. It was speculated that this change in isotherm shape may have been due to the small number of larger free volume elements within Cytop®, as observed in x-ray diffraction analysis. Neither toluene nor xylene had a significant impact on CO2 and CH4 permeabilities in Cytop®, while a gradual decrease in both permeabilities was noted for poly(50%PBVE-co-50%PDD) as the vapor activity increased, due to either competitive sorption or pore blocking. Finally, liquid glycol carryover caused no change on the performance of Cytop® membranes, while a slight drop in the CO2/CH4 separation factor for poly(50%PBVE-co-50%PDD) was observed.

Carbon-dioxide-to-methanol intensification with supersonic separators: Extra-carbonated natural gas purification via carbon capture and utilization

A novel carbon-capture-and-utilization route from extra-carbonated natural gas using low-cost/low-carbon chloralkali hydrogen is disclosed. Methanol and methane-rich gas are produced without direct carbon emissions and also with low indirect emissions assuming the local electricity-matrix as 87% non-emitting. Carbon dioxide removed from raw natural gas via cryogenic extractive distillation with methanol entrainer, feeds a new Carbon-Dioxide-to-Methanol hydrogenation route intensified by supersonic separators with liquid water injection for greater methanol conversion per pass in the synthesis-loop and greater methanol recovery in the separation system. Intensified Carbon-Dioxide-to-Methanol is designed economically optimizing water/methanol injection-ratios and maximum Mach numbers of supersonic separators. Extra-carbonated natural gas processing coupled to intensified Carbon-Dioxide-to-Methanol is techno-economically assessed, demonstrating that supersonic intensification entails 2% greater methanol production, 11% less power consumption and 7.5% greater net value comparatively to non-intensified counterpart. The intensified process removes 99.2% of CO2 from extra-carbonated gas and was analyzed at two methanol scales [8021.5 t/d, 1692.3 t/d] giving, respectively, [9.5, 41.5] payback-years, and [2896.4MMUSD, 41.37MMUSD] net values (60years). A critical feasibility factor is low-cost/low-carbon by-product hydrogen from chloralkali industries, for which the break-even prices were respectively evaluated for the two scales as [685USD/tH2, 358USD/tH2]. A third, better and safer, option is to couple intensified Carbon-Dioxide-to-Methanol to large-scale Carbon-Dioxide-to-Enhanced-Oil-Recovery providing hedging against insufficient offer of low-cost/low-carbon hydrogen while practically keeping the project net value (60years) despite twofold investment.

Performance analysis of natural gas sweetening unit with amine solution and blends

In this study, raw natural gas data from Uch gas field located in Dera-Bugti of Balochistan, Pakistan is simulated for performance analysis over amine absorber unit in Aspen HYSYS V9.0. The primary amine, MDEA was selected to remove bulk CO2 and reduce H2S to ppm level, where secondary amines, MEA, DEA and Sulfolane were selected to observe CO2 levels in sweet gas. The primary amine in isolation and blend with secondary amine was simulated and analysed over absorber performance. The absorber performance is reported as CO2, H2S and water content in sweet gas, hydrocarbons in rich amine and its temperature. MDEA in isolation resulted in minimum 14.13 and 12.78 mol% CO2 in sweet gas and rich amine temperature of 81.11oC and 82.13oC with 24 and 30-Trays, respectively at 2500 m3 /h of lean amine recirculation rate. Among the tested blends, MDEA/MEA, MDEA/Sulfolane showed no significant improvement on absorber performance compared to isolated MDEA. However, MDEA/DEA blends indicated that CO2 in sweet gas can be reduced to 12.07, 3.41, 1.85 mol% with rich amine temperature of 89.05, 111.72 and 124.80oC, respectively. The lowest CO2 detected of 1.85 mol% was achieved with 40 mol% MDEA and 15 mol% DEA blend at 2500 m3 /h recirculation rate and rich amine temperature of 124.80oC. The results indicated that MDEA/DEA blend has the potential to attain CO2 of less than 2 mol%. The higher rich amine temperature raise concern that can be resolved by using heat stabilized salt.

Design and CFD Application Value Series from Raw Natural Gas Processing to Automated Utilization Need

Abstract: Fluid flow systems are common in the energy value chain and are typically complex. To assure the system's performance, understanding and control are essential. Computational fluid dynamics (CFD) is a one-of-a-kind tool that predicts fluid flow events using numerical methods. It allows you to study fluid flow patterns and access non-measurable variables. Because of the rapid advancement of computer science, CFD can currently be used to handle the bulk of industrial operations that require fluid flows. The application's scope is extensive, and the problems it can solve are diverse, spanning from process design validation and optimization to operating condition management and troubleshooting. A few experiments done by Imo State University Petroleum and Gas Lab on upstream natural gas treatment systems to downstream industrial end-use for combined heat and power plants and petrochemical furnaces will demonstrate the application of CFD in troubleshooting. Keywords: CFD, Utilization, Automated, Natural Gas

Development of Amine-Functionalized Metal-Organic Frameworks Hollow Fiber Mixed Matrix Membranes for CO2 and CH4 Separation: A Review.

CO2 separation from raw natural gas can be achieved through the use of the promising membrane-based technology. Polymeric membranes are a known method for separating CO2 but suffer from trade-offs between its permeability and selectivity. Therefore, through the use of mixed matrix membranes (MMMs) which utilizes inorganic or hybrid fillers such as metal-organic frameworks (MOFs) in polymeric matrix, the permeability and selectivity trade-off can be overcome and possibly surpass the Robeson Upper Bounds. In this study, various types of MOFs are explored in terms of its structure and properties such as thermal and chemical stability. Next, the use of amine and non-amine functionalized MOFs in MMMs development are compared in order to investigate the effects of amine functionalization on the membrane gas separation performance for flat sheet and hollow fiber configurations as reported in the literature. Moreover, the gas transport properties and various challenges faced by hollow fiber mixed matrix membranes (HFMMMs) are discussed. In addition, the utilization of amine functionalization MOF for mitigating the challenges faced is included. Finally, the future directions of amine-functionalized MOF HFMMMs are discussed for the fields of CO2 separation.

Energy sources evaluation based on multi-criteria decision support approach in China

This study aims to develop a comprehensive evaluation approach to analyze and grade the energy sources based on statistical data. A brief bibliometric analysis for energy sources evaluation shows that clean, sustainable and environment friendly of energy development is the main trend. Four kinds of energy sources including raw coal, crude oil, natural gas and electricity, are analyzed. The approach is developed based on the extended technique for order performance by similarity to ideal solution (TOPSIS) and criteria importance through inter-criteria correlation (CRITIC). The CRITIC method is utilized to assign the weights of attributes and the extended TOPSIS is applied to grade the energy sources. An example about energy sources evaluation in China is adopted. Results show that non-renewable energy sources (raw coal and crude oil), are main energy sources from 2010 to 2018. Additionally, the correlation analysis and sensitivity studies are presented to illustrate the feasibility of the developed approach. Developed approach provides a tool in energy sources analysis.

Evaluating strategies for monetizing natural gas liquids from processing plants – Liquid fuels versus petrochemicals

The processing of natural gas resources is a critical step for monetizing them. Its evaluation should deal with the volatility of prices of raw gas and natural gas liquids, the processing technology and the composition of the raw gas. This study combines different approaches – process engineering, probabilistic discounted cash flow (DCF), and market failure analysis – to evaluate the technical aspects, financial results and market barriers of natural gas processing. Two productive strategies are compared: fuels or petrochemicals. Brazil is used as a case study, since the country experienced a ramping production of associated rich gas from pre-salt basins and lacks the required gas processing capacity. Findings indicate that the processing plant designed with turboexpander was able to produce the required scale for the fuel and the petrochemical markets. The Petrochemical Strategy reached a higher average net present value (US$ 2448 millions) compared to the Fuel Strategy (US$ 2006 millions) in a 30-years DCF analysis, at a higher standard deviation, however. This highlights the importance of performing the stochastic NPV to deal with price volatilities. The Petrochemical Strategy is also challenged by market failures found in Brazil, while the Fuel Strategy has social and infrastructure advantages in a stablished domestic market.

Commodity Market Structure and Risk Factor Analysis in Bulgaria

Analyzing the Bulgarian raw material, crude oil and natural gas markets is an important step in setting up an early warning system (EWS). The Comprehensive Price Index is based on the weighting of imports from the energy and non-energy sectors, including the crude oil sector. The explanatory variables that describe the crisis index are analyzed and predicted by the ordered Probit model. The EWS system developed in this study takes into account the most important measurable variables that affect the raw material market, and based on this understanding, we focus on which variables can represent risk.

Spatial and temporal characteristics of China’s water footprint of energy and its matching relationship with water resources

Energy and water resources are very important for human survival and social development. Energy and water footprint can reflect the real occupation of water resources in the process of energy production. Based on the energy and water footprint evaluation model, this paper calculates the life cycle water footprint of fossil energy and power production in 30 provinces (cities and autonomous regions) in China, studies the temporal and spatial pattern evolution characteristics of China’s raw coal, crude oil, natural gas, hydropower and thermal power from 2004 to 2016, and analyzes the spatial matching relationship between China’s energy and water footprint and water resources. The results show that: (1): during the study period, the water footprint of fossil energy increases first and then decreases with 2012 as the boundary. The rapid growth of hydropower water footprint promotes the continuous growth of power water footprint. (2): In terms of spatial pattern, the water footprint of fossil energy increases in the West and decreases in the East with the Huhuanyong line as the boundary, and the Inner Mongolia, Shanxi and Shaanxi region as the high-value concentration area; in the power water footprint, there is a significant spatial boundary between hydropower water footprint and thermal power water footprint. The rapid growth of hydropower water footprint has gradually formed a high-value concentration area of power water footprint in the Yangtze River Basin, the Pearl River Basin and the southeast coast. (3): The spatial matching degree of energy and water footprint and water resources fluctuates and declines in the pattern of high in the south and low in the north. The spatial matching degree of fossil energy and water footprint is lower than that of electric power and water resources. The energy water contradiction between raw coal production and thermal power generation is the most prominent. One third of the country has the problem of energy water mismatch. North China with high energy and water footprint has great pressure on energy water matching. The contradiction between energy production and water resources allocation still exists. Truly reflect the matching relationship between energy and water footprint and water resources, help to optimize the comprehensive management of energy and water resources, and provide a quantitative basis for maximizing the energy water synergy.

Regenerable Sorbent Pellets for the Removal of Dilute H2S from Claus Process Tail Gas

The Claus process is the most important sour gas sweetening process to recover elemental sulfur from H2S, which is present in raw natural gas and byproduct gases from crude oil refineries. However, current methods for treating the tail gas of the Claus process are expensive and often not environmentally friendly. Various sorbents have been reported for H2S capture, but few reports focus on the pellet design, formation, and testing. In this study, we developed a pelletization method to prepare sorbent pellets with high sulfur capacity and good regenerability for the removal of dilute H2S from Claus process tail gas. The sorbent pellets consisted of mixed metal oxides of Cu, Mg, and Al with fumed silica as the binder and were characterized using various techniques, including X-ray and electron diffraction, N2 sorption, and scanning and transmission electron microscopy. The H2S sorption capacity was evaluated by breakthrough experiments at 150 °C in a gas stream consisting of 100 ppm of H2S in N2. The optimized sorbent pellets gave a stable breakthrough sulfur capacity of ∼5 mmol/g over three cycles of sulfidation and regeneration. They exhibited an average radial crush strength of 154 ± 40 N.

High Yield of CO and Synchronous S Recovery from the Conversion of CO2 and H2S in Natural Gas Based on a Novel Electrochemical Reactor.

H2S and CO2 are the main impurities in raw natural gas, which needs to be purified before use. However, the comprehensive utilization of H2S and CO2 has been ignored. Herein, we proposed a fully resource-based method to convert toxic gas H2S and greenhouse gas CO2 synchronously into CO and elemental S by using a novel electrochemical reactor. The special designs include that, in the anodic chamber, H2S was oxidized rapidly to S based on the I-/I3- cyclic redox system to avoid anode passivation. On the other hand, in the cathodic chamber, CO2 was rapidly and selectively reduced to CO based on a porous carbon gas diffusion electrode (GDE) modified with polytetrafluoroethylene and cobalt phthalocyanine (CoPc). A high Faraday efficiency (>95%) toward CO was achieved due to the enhanced mass transfer of CO2 on the GDE and the presence of the selective CoPc catalyst. The maximum energy efficiency of the system was more than 72.41% with a current density of over 50 mA/cm2, which was 12.5 times higher than what was previously reported on the H2S treatment system. The yields of S and CO were 24.94 mg·cm-2·h-1 and 19.93 mL·cm-2·h-1, respectively. A model analysis determined that the operation cost of the synchronous utilization of H2S and CO2 method was slightly lower than that of the single utilization of H2S in the existing natural gas purification technology. Overall, this paper provides efficient and simultaneous conversion of H2S and CO2 into S and CO.

Hybrid modelling for combined design optimization of CO2 removal and compression in raw natural gas treatment complexes

CO2 removal in raw natural gas is required to meet the sale gas specifications. The chemical solvent absorption method is one of the most commonly used technologies. The absorption-based processes, however, require an enormous amount of energy to regenerate the solvent, and are designed to discharge the captured CO2 into the atmosphere directly. The energy efficiency and greenhouse gas emissions should be considered in the gas treatment process. In this study, a new process, combining CO2 removal and compression, is proposed for raw natural gas treatment complexes. Compared with the conventional absorption-based processes, in the new process CO2 is not stripped from rich solvent in one distillation column but through multi-stage flash separators operating under different pressures and temperatures. The CO2 removed from each stage is then compressed separately to the proper pressure for carbon transportation and storage. A mathematical model is then developed to determine the optimum process configuration and operating conditions. A surrogate-based optimization framework is presented in order to strike a good balance between computational efficiency and model accuracy. The complex units are replaced by Kriging surrogate models. Aspen HYSYS is used to generated sampling points for the construction of surrogates. A method of dimension reduction is introduced to compact the surrogate models by selecting essential variables. Finally, a hybrid optimization model comprising of the surrogate models for “complex” units and explicit models for the rest of the process is formulated. The cases show the total annual cost of the CO2 removal and compression can be reduced by 20.6%–28.8% for different sweet gas purity specifications.

Upgrading exergy utilization and sustainability via supersonic separators: Offshore processing of carbonated natural gas

Offshore processing of natural gas with 44%mol carbon dioxide at remote deep-water oil-and-gas fields is invariably characterized by low-efficiency power generation via gas-fired turbines releasing hot flue-gas and entailing high degradation of resources, high carbon emissions and low sustainability. This work demonstrates how to upgrade exergy utilization and consequently process sustainability by using supersonic separators in some gas processing steps; namely: (i) water dew-point adjustment; (ii) hydrocarbon dew-point adjustment; and (iii) carbon dioxide abatement to 20%mol. To accomplish this, the exergy performance of two supersonic separator gas processing alternatives are compared with conventional gas processing comprising triethylene-glycol absorption for water dew-point adjustment, Joule-Thomson expansion hydrocarbon dew-point adjustment and membrane-permeation carbon dioxide removal. Since exergy is measured relatively to a reference environmental reservoir, two such reference reservoirs are used: RER-1: standard atmosphere with 2%mol water containing hydrocarbons at combustion chemical equilibrium with air species; and RER-2: 1atm water-saturated raw natural gas in equilibrium with liquid water. Aspen-HYSYS simulations are used to solve mass/energy balances and thermodynamic property calculations. With RER-2 the conventional gas processing conserves 63.3% of the inlet exergy, while the two alternative supersonic separator processes attain 66.5% and 72.4% of exergy conservation, proving the associate gains of exergy efficiency and sustainability.