Power Generation Gas Research Articles

Comprehensive economic analysis and multi-objective optimization of an integrated gasification power generation cycle

A novel power generation plant was devised based on the biomass integrated fired combined cycle as the central unit and supercritical CO2 cycle, regenerative organic Rankine cycle, and steam Rankine cycle as the waste heat recovery subsystems. Exergoeconomic and economic criteria were defined to evaluate the feasibility of the system for investment and construction. Thus, net present value, payback period, and sum unit cost of products were considered as the system’s evaluation criteria from the economic viewpoint. The system was firstly analyzed by developing a precise model in the Engineering Equation Solver. Then, optimal conditions were obtained by coupling the outputs of modeling procedure with artificial neural network, multi-objective particle swarm optimization, and the technique for order of preference by similarity to ideal solution (TOPSIS) approaches. It was concluded that the system has an exergy efficiency of 42.7 % with a power generation capacity of 7.768MW, a total cost rate of 34.79 $/GJ, and a total profit and payback period of 23.3 $M and 5.7 years. For the optimization results in the ε-NPV-SUCP scenario, the optimum values of 58.99 %, 30.6 $M, 35.61 $/GJ were obtained for exergy efficiency, NPV, and SUCP, respectively.

Reducing the efficiency penalty of carbon dioxide capture and compression process in a natural gas combined cycle power plant by process modification and liquefied natural gas cold energy integration

Natural gas power plants integrated with a carbon capture process, have recently attracted a lot of attention due to their capability of synergizing with renewable technologies and decarbonization of the power industry. The natural gas plant is fueled by liquefied natural gas at extremely low temperatures and is subsequently regasified. During regasification, a substantial amount of cold energy is available which is conventionally wasted. Furthermore, the integration of the carbon capture process poses a significant energy penalty on the system. This study, therefore, investigated the optimal utilization of the cold energy of the liquefied natural gas and the configuration of the post-combustion carbon dioxide capture process for the natural gas plant. Firstly, the carbon dioxide capture process was modified to reduce its thermal energy requirement. Secondly, the application of liquefied natural gas as a heat sink for the organic Rankine cycle was investigated. Subsequently, an alternative application of liquefied natural gas cold energy in the carbon dioxide compression process was evaluated. The results show that the modified carbon dioxide capture process reduces the thermal energy requirement by 12.8% and improves the efficiency of the power plant by 0.6%. The optimized organic Rankine cycle generates 4.9 MW electrical power using cold energy. In comparison, the intensified compression process integrated with liquefied natural gas regasification reduces the compression power by 7.15 MW, outperforming the application of liquefied natural gas in power generation. Thus, the optimal utilization of liquefied natural gas cold energy is in the carbon dioxide compression process as it improves the net efficiency and reduces the footprint of the liquefied natural gas cold energy utilization process. The modified carbon dioxide capture process and intensified carbon dioxide compression process using liquefied natural gas cold energy can enhance power generation by 13 MW and reduce the efficiency penalty from 6.1% to 4.8%.

Emission Mitigation and Energy Security Trade-Off: Role of Natural Gas in the Indian Power Sector

India’s Nationally Determined Contributions (NDC) aim to increase the share of non-fossil fuel, especially renewables, in power generation. But at the same time, it mentions that coal is likely to dominate the power generation in the short and medium term to meet the increase in demand and support the intermittency of renewable energy-based power generation. Thus, additional efforts to transform the thermal power generation to a more efficient and less emitting one in the near term by increasing the use of natural gas (a fossil fuel with a lower emission factor than coal) may be planned towards achieving India’s additional mitigation commitments. The paper presents the implications of a proposed increase in the share of natural gas in thermal power generation of India by looking into the trade-off between emission mitigation and energy security. Along with a Reference Scenario, three alternative emission scenarios are proposed to understand the likely impacts of increased penetration of natural gas in power generation on India’s projected emission profile up to 2050. Results suggest that higher mitigation potential can be achieved through fuel-switch in thermal generation and technological up-gradation to enhance energy use efficiency. The energy security due to the increased share of natural gas imports can be dealt with by diversifying import sources. Shifts can achieve this in the emphasis on long-term contracts.

Comparative Analysis of Carbon Capture and Storage Finance Gaps and the Social Cost of Carbon

This paper evaluates how changes in economic market and policy conditions, including the establishment of a per-unit tax on unabated emissions of carbon dioxide (CO2) set equal to estimates of the social cost of carbon (SCC), influence the economics of carbon capture and storage (CCS) for two hypothetical power generation facilities located in the United States. Data are provided from modified versions of models and resources created and managed by the National Energy Technology Laboratory. Changes in economic market and policy conditions are evaluated over a series of scenarios in which differences in the levelized cost of electricity (LCOE) provide estimates of the financial gap necessary to overcome for CCS to be considered the cost-minimizing choice for each power generation facility type considered. Results suggest that for the coal and natural gas power generation facilities considered, a per-unit tax set equal to an SCC exceeding $123 per metric ton of CO2 (/tCO2) emitted (2018 dollars) and $167/tCO2 emitted, respectively, in combination with current Section 45Q tax credits, yields investment in CCS as the cost-minimizing choice; SCC values as low as $58/tCO2 and $98/tCO2 can make CCS the cost-minimizing choice with additional support policies (e.g., free transportation and storage options).

A “full spectrum-domain-time” coalbed gas utilization model and its application in mining area

Coalbed gas (CBG) has been widely used as an important energy source. However, its utilization and allocation system is imperfect in mining areas. During the utilization process, a large amount of CBG is discharged into the air, causing environmental pollution. In this study, we proposed a “full spectrum-domain-time” CBG utilization model. In this model, by combining high methane concentration gas power generation, low methane concentration gas purification, and ultra-low methane concentration gas thermal storage and oxidation utilization, we were able to utilize CBG with full-spectrum of methane concentrations. In addition, by establishing CBG transportation and storage system in mining area, we were able to realize CBG supply in the entire network domain. Furthermore, based on the time series prediction algorithm, the CBG demand of different mining areas is predicted and regulatorily met by real time allocation. Through these three steps, an efficient “full spectrum-domain-time” CBG utilization system was formed and practically applied in Yangquan mining area. The application results showed that under the comprehensive control of “full spectrum-domain-time” CBG utilization model, CBG with methane concentration ≥0.2% could be used in the mining area and its utilization rate increased year by year, reaching the highest of 77.15%. Overall, our study provided a reference for the efficient CBG utilization in the mining area.

Risk hedging for gas power generation considering power-to-gas energy storage in three different electricity markets

The increasing penetration of intermittent renewable energy has introduced great risks to energy systems and markets. As a result, extensive research on energy storage systems (ESS) has been undertaken to address the risks caused by renewable energy. Among different types of ESSs, the power-to-gas (P2G) storage devices are of great potential. Thus, P2G has been used in this paper as a storage device to provide gas fuel for gas power generators. The aim of this paper is to investigate a portfolio strategy for gas generators to earn profits and hedge risks in three different electricity markets, namely, the spot, the ancillary, and the financial markets. The presented approach is to apply energy storage and financial derivatives to hedge the market risks of gas generators, including short put option and short call option, and the option value deduction process is also involved. Simulations are carried out based on the real historical data from 2016 to 2018 in Australian electricity markets. Three cases are presented, namely, the traditional model, the individual market case, and the proposed portfolio model. Based on the comparison of the three cases, simulation results show that the proposed portfolio model will help gas generators to earn a return of 1.0429 and hedge risks down to 0.0018. It has been found that the returns of the proposed model from 2016 to 2018 are 26.3% higher, whereas the risks are 88.1% lower on average comparing with the traditional model and the individual market case.

Modelling of Input Parameters for Power Generation using Regression Models

In this study, multiple linear regression models were employed in the correlation of gas supply and power generation using a gas Power Plant in Niger Delta, Nigeria as a Case study. From the analysis based on outlier detection, reliability analysis and test of homogeneity, it was observed that the independent variable data such as ambient temperature, gas pressure and compressed temperature failed normality test. Therefore, the use of any linear model for either analysis or modelling of the data was not acceptable. Data used for reliability analysis of the gas pressure and compressed temperature difference were positively correlated with power generation, having a covariance value of 0.639 and 113.148. The ambient temperature was negatively correlated with power generation, having a covariance value of 14.564. The positive value showed that both dimensions exclusively increased and decreased together with respect to the output while the negative value showed that increment in value of one variable led to decrease in the value of the other, and vice versa.

U.S. Department of Energy National Carbon Capture Center, Supporting Technology Scale-up and International Collaboration

Sponsored by the U.S. Department of Energy (DOE) and operated and managed by Southern Company, the National Carbon Capture Center (NCCC) is a cornerstone of U.S. innovation in advancing the development of technologies to reduce greenhouse gas emissions. Bridging the gap between laboratory research and large-scale demonstrations, the center works to accelerate the development of carbon capture technologies from natural gas- and coal-based power plants. The facility evaluates next-generation carbon dioxide (CO₂) reduction processes from third-party developers, focusing on the early-stage development of the most promising, cost-effective technologies for future commercial deployment. Since its creation in 2009, the NCCC has performed more than 115,000 hours of technology testing. Through pilot testing of more than 60 technologies, the center has directly participated in the reduction of the projected cost of carbon capture from fossil power generation by approximately one-third. As the demand for post-combustion CO₂ capture options grows, work in this area continues to reduce the cost of carbon capture and bring new technologies closer to the marketplace. Evaluation of developing second-generation and transformational carbon capture technologies using actual flue gas under industrial conditions provides critical information on material and process suitability for scale-up to commercial applications. The center has broadened its research scope to expand testing of carbon capture technologies for natural gas power generation in addition to its existing coal-fueled testing capability. Integration of the new natural gas flue gas equipment with the existing infrastructure will allow each carbon capture project to receive either natural gas or coal flue gas independently of other projects. In addition, current and future testing at the NCCC will support research and development (R&D) of CO2 utilization technologies that will efficiently, economically, and cleanly transform CO₂ into value-added products. As its focus broadens to negative carbon concepts, the center is also extending its research to help advance direct air capture (DAC) technologies. Because reduction of CO₂ emissions is an international issue, the NCCC provides worldwide technology development leadership – it co-founded the International Test Center Network, a global coalition focused on research, development, and deployment of carbon capture, use, and storage (CCUS). Formed in 2012 in collaboration with DOE’s Office of Fossil Energy, the ITCN facilitates knowledge-sharing among carbon capture test facilities around the world to accelerate the commercial deployment of carbon capture technologies. The ITCN now has 14 test facilities that are members. The NCCC has also been active in establishing test collaborations with international groups. The facility has successfully tested technologies from seven different countries. In addition to the important work of developing cost-effective technologies, many other aspects of successful commercial deployment must be mastered. Establishing relationships to secure funding, gaining management support, meeting test goals, and satisfying legal requirements of both the international organization and the NCCC are significant achievements and forms a strong basis for future partnerships for larger-scale development. Oil and gas companies have joined the NCCC and have a strong international presence which will support international collaboration worldwide. Unanticipated benefits to the NCCC’s international collaboration have emerged in addition to establishing relationships that could form the basis for partnerships for scale-up of technology. These benefits include (1) adding value to CCUS technologies by meeting requirements of international markets, (2) increasing the value of input into studies, roadmaps and policy development by including international perspective, (3) attenuation of inconsistent support of CCUS R&D among individual countries, and (4) encouragement of passionate participants in CCUS R&D to stay in the field by expanding interest from new, international funders. The NCCC hopes to build on the international relationships that have been established to contribute to the important step of moving from early-stage R&D projects to a commercial product. In conclusion, the NCCC has demonstrated its ability to bring on board and manage a multitude of projects to develop the most promising technologies for clean, efficient fossil-fuel energy production with ultra-low CO₂ emissions. Operations at the center have resulted in significant scale-ups, process enhancements, and technological breakthroughs. The NCCC is also providing international leadership to promote the level of readiness for carbon capture technologies. This paper will detail the center’s capabilities, role in supporting international collaboration, and future plans.

Portfolio management strategy for power‐to‐gas storage‐driven natural gas power generation

Portfolio management strategy for power‐to‐gas storage‐driven natural gas power generation

Identifying environmental hotspots and improvement strategies of vanillin production with life cycle assessment

Vanillin, an important aroma chemical, can be synthesized through industrial oxidation processes and biotechnological processes. Studying the environmental impacts of synthetic vanillin production processes is fundamental to making these processes feasible and sustainable; however, few studies have focused on such analyses. This study involved performing a life cycle assessment (LCA) to evaluate multiple industrial synthesis and biosynthesis processes for producing synthetic vanillin. The results indicated that human toxicity potential (HTP) appeared to be the most affected indicator among all the impact categories considered. The dominant drivers of the HTP of the vanillin synthesis process were electricity consumption and ultrapure water consumption. Improvement strategies were then proposed to investigate the possibility of reducing the environmental burdens created by vanillin synthesis. Natural gas power generation was determined to be the best choice for replacing traditional coal-fired power generation, thus reducing the negative impacts of these processes on the environment. The best ways to reduce chemical consumption were to recover organic solvents and to replace ultrapure water with industrial or distilled water. All these improvement strategies were demonstrated to be able to effectively reduce the HTP. In addition, suggestions for evaluating scaled-up vanillin production, increasing the LCA coverage to include technological advancements in biosynthesis techniques, and introducing cost-benefit analysis into the LCA were discussed.

Evaluation of potential amounts of crop straw available for bioenergy production and bio-technology spatial distribution in China under ecological and cost constraints

A comprehensive evaluation model is built to analyze the potential of straw resources and suitability distribution of technology in China under environment and cost constraints. First, from the perspective of soil erosion prevention, soil organic carbon maintenance, and long-term crop yield, the ecological return amount of straw in different provinces is calculated using scenario design, literature review, and analytic hierarchy process. These processes, combined with technical and economic parameters of different technologies, are employed to analyze the appropriate spatial distribution of straw-fired generation (SFC), biomass gasification power generation (BGPG), cellulose ethanol technology (CEP), and biomass briquette fuel (BBF) under different policy and technological progress scenarios from the project level. The changes in planting area, crop unit yield, and wage are also considered in the evaluation; the obtained results indicate the following. First, if priority is given to agricultural ecological environment, the amount of straw available is less than that determined by the existing research, i.e., approximately 2.48 × 108, 1.55 × 108, and 8.68 × 107 t under low, medium, and high return scenarios, respectively. Second, Inner Mongolia is not suitable for planning any projects, and planned projects should compensate for the local agricultural ecological environment. Third, under the current policy and technical level scenario, resources for the BBF and CEP projects should be employed to prioritize the SFC and BGPG projects. Fourth, in combination with China’s current poverty alleviation policies, the planning of biomass energy projects in Gansu, Qinghai, Sichuan, Chongqing, and Guizhou should be prioritized because of their lower labor cost.

Research on low-carbon power planning with gas turbine units based on carbon transactions

In the context of low carbon economy, introducing carbon trading and developing low-carbon energy generation is an important means to realize low-carbon development of the power system. Because gas power generation has the advantages of high efficiency, low carbon emission and strong peak load capability, the gas generator unit is added to the planning plan and a low carbon power planning model based on carbon trading is established. The goal of the model is to minimize the cost of the system integration. The cost includes investment operation cost and carbon transaction cost. And the natural gas supply constraints and carbon trading constraints are increased in the constraint condition. Finally, the discrete bacterial colony chemotaxis algorithm is adopted to solve this model. Through the model comparison and sensitivity analysis, it is concluded that the addition of gas turbine unit and carbon trading mechanism can optimize the power supply structure, promote the construction of low carbon unit. and realize the conclusion of low carbon emission reduction of power system. And the results verify the effectiveness of the proposed power planning model.

АНАЛИЗ МЕТОДОВ ДИАГНОСТИКИ ОБРЫВА СТЕРЖНЯ РОТОРА АСИНХРОННОГО ДВИГАТЕЛЯ

Relevance Uninterrupted operation of industrial facilities, oil and gas sector, metallurgy, power generation and other industries directly depends on reliable operation of critical mechanisms driven by electromechanical converters, operated as a part of working complexes. Reliability of operation of such mechanisms depends on reliability of all elements that make up the technological process. Inductions motor with squirrel-cage rotor (including high-voltage motors) is one of the most common types of converters of electrical energy into mechanical energy. Its uninterrupted operation directly depends on the reliability of two main elements: stator and rotor. If the causes of induction motor failure due to stator causes (inter-turn, inter-phase and single-phase short circuits) are determined by the provided protections, the damage in the rotor circuit can be implicit and exist for a long time, violating the machine uptime. Also, most of the faults in the inductions motor, leading to an emergency shutdown of technological processes of working complexes have their own history of development. At the moment of occurrence and during the period when the defect does not affect the serviceability of the machine, but its operation becomes critically dangerous, because it is not possible to determine the presence of the defect. So, for example, the breakage of the short-circuited rotor core of a high-voltage induction motor manifests itself at the stage of exit to the air gap at the time of operation, with subsequent damage to the stator winding and the magnetic core. In this case, the existence of this defect took place within a certain period of time, sufficient for its detection by means of diagnostic devices. The article analyzes the currently developed systems for diagnosing the presence of a fault according to various parameters (temperature, noise, vibration, analysis of electrical values consumed) both in the stator and in the rotor. It is determined that the most promising and technically feasible are methods based on the analysis of stator currents. When studying the works in the direction of inductions motor diagnostics it was found that a significant proportion of failures of mechanisms operated in the working complexes due to failure of inductions motor occurs due to broken rotor bar. Aim of research Analyze the existing methods for diagnosing induction motors during operation. Research methods The article used general scientific research methods: the method of analysis of literary sources, the study and generalization of information, comparison, classification. Results The analysis of existing methods of continuous diagnostics of induction motors for internal electrical and mechanical damage is carried out. It has been determined that the most promising from the point of view of economic and technical feasibility are methods based on the analysis of currents consumed by the stator.

Surface alloying of FeCoCrNiMn particles on Inconel-718 using plasma-transferred arc technique: microstructure and wear characteristics.

Inconel-718 (IN-718) is a commonly used nickel-based superalloy in various fields, such as gas turbine and power generation applications. However, the lower wear and oxidation resistance hinder their wide usage. In this work, FeCoCrNiMn particles were mechanically ball-milled and preplaced on the IN-718 substrate. Then, the preplaced FeCoCrNiMn particles were scanned by heat source using plasma-transferred arc (PTA) technique. The effect of PTA alloying on the phase changes, microstructure, nanohardness and wear resistance has been investigated. The result showed that the PTA region contained different phases, such as FCC, BCC and intermetallic. No cracks were observed in the PTA alloyed region. Moreover, the porous free structure was viewed in the alloyed region, which revealed that the PTA alloying process was effectively used to perform the alloying process. More hard phases, such as NiFe, CoMn, Cr9Mn25Ni21, MnNi, FeCo, FeMn and MnCo, were formed on the PTA-alloyed region. The obtained wear rate of the substrate specimen at 30 N applied load is 2.45 × 10−3 mm3 m−1 and 1.79 × 10−3 mm3 m−1 for the PTA specimen. Similarly, the wear rate of the substrate specimen at 50 N is 5.38 × 10−3 mm3 m−1 and for the PTA sample, it is 2.29 × 10−3 mm3 m−1. The PTA specimen showed lower CoF than the substrate specimen due to increased surface hardness and minimum deformation of asperities. The primary wear type was mildly abrasive, accompanied by slight oxidative wear. Oxygen reacted with the surface alloying elements and formed different oxides, such as CoO, Cr2O3, MnO2, Mn2O3, Mn3O4, FeO and Fe2O3. These dense oxidation films covered the working surface and enhanced the wear resistance. The worn-out PTA surface showed that the wear scar depths were shallow and lower than the substrate, and reduced the roughness.

LIVE Digital Twin for Smart Maintenance in Structural Systems

Abstract Instabilities and failure in many industrial structures can be too costly. That includes the pipeline structures for oil and gas industries or power generation plans and infrastructural transit systems. Prognostics and health management, along with Preventive, predictive, and prescriptive maintenance, are alternative options to avoid the failure in these systems by smart and on-time maintenance. However, although it is possible to collect data dynamically from these systems through their service periods, in many cases, a trustworthy and reliable knowledge base to allow making the right decisions is not always available. This paper presents the concept of LIVE Digital Twin that relies on four phases of Learn, Identify, Verify, Extend employing various Computer-Aided Engineering (CAE) simulation strategies during the life span of the structure parallel to its design, performance, inspection, and maintenance. The architecture of LIVE Digital Twin is presented, and the details are described along with some practical case studies in Light Rail Transit (LRT) and pipeline systems in oil and gas industries. The presented concept and architecture of LIVE Digital Twin can be employed and implemented for various other applications and non-structural systems.

Natural Gas Power Generation to Promote the Construction of Ecological City

As an unsustainable resource, it is of great significance to explore more efficient and low-carbon ways of using energy. With the fast development of China’s economy, most cities are faced with the pressure of ecological environment to varying degrees. The construction of ecological city is not only the need of ecological protection and improvement of natural environment, but also the requirement of urban development. Compared with coal-fired power generation, natural gas power generation has advantages in terms of environmental pollution, energy utilization efficiency and resource occupancy, and is one of the ideal energy sources for eco-city construction. However, at present, there are constraints such as lack of subsidy policy, high fuel price, dependence on import of equipment and high cost of construction and maintenance. In the long run, the development of gas-fired power generation industry should be actively and prudently promoted from the aspects of strengthening the construction of supporting facilities and the guarantee of gas source, perfecting the mechanism of electricity price, and increasing the localization rate of key equipment, so as to achieve the goal of optimizing industrial structure, saving energy and reducing emissions, and facilitating the construction of China’s ecological city.

Simulation and economic evaluation of heat and power generation from flare gases in a combined cycle power plant

In recent decades, the release of flare gases from different units of chemical industries into the atmosphere has become a substantial environmental problem all around the world. Therefore, recovery or use of flare gases has become much more critical. Combined heat and power generation from flare gases is one of the most economical methods for recovering flare gases. Two power generator gas cycle power plant or a combined cycle power plant can be used to generate heat and power. In this research, simulation and economic evaluation of heat and power generation from flare gases in a gas cycle power plant and combined cycle power plant using PRO/II v.10 software. Finally, by changing the effective operating parameters such as air to treated flare gas ratio, the outlet pressure of compressors, outlet pressure of steam and gas turbine, outlet pressure of pumps and adiabatic efficiency steam and gas turbine, heat and power generation and total capital and operating cost were investigated and analyzed. The results of simulation and sensitivity analysis showed that the use of flare gas with a mass flow rate of 9700 kg/h (mole fraction of CH4: 0. 84) could be used to construct a combined cycle power plant with a capacity of 115 MW with an investment cost of 100 M$. This value of energy surpasses the need for an average community with 85000 families, and the excess can be sold to the national grid.

Cost-benefit comparison of carbon capture, utilization, and storage retrofitted to different thermal power plants in China based on real options approach

A trinomial tree model based on a real options approach was developed to evaluate the investment decisions on carbon capture, utilization, and storage (CCUS) retrofitted to the three main types of thermal power plants in China under the same power generation and CO2 emissions levels. The plant types included pulverized coal (PC), integrated gasification combined cycle (IGCC), and natural gas combined cycle (NGCC) plants. We take into account a subsidy policy consistent with the 45Q tax credit of the U.S., as well as uncertainty factors, such as carbon price, technological progress, CO2 geological storage paths, oil price, and electricity price. The results showed that the investment benefit of ordinary NGCC power plants is 93.04 million USD. This provides greater economic advantages than the other two plant types as their investment benefit is negative if the captured CO2 was used for enhanced water recovery (EWR), even if 45Q subsidies are provided. Compared with NGCC + CCUS power plants, PC + CCUS and IGCC + CCUS power plants have more advantages in terms of economic benefits and emission reduction. The 45Q subsidy policy reduced the critical carbon price, which determines the decision to invest or not, by 30.14 USD t−1 for the PC and IGCC power plants and by 15.24 USD t−1 for the NGCC power plants. Nevertheless, only when the subsidy reaches at least 71.84 USD t−1 and the period limit is canceled can all three types of power plants be motivated to invest in CCUS and used the capture CO2 for EWR. Overall, the government should focus on the application of CCUS in coal-fired power plants (in addition to developing gas power generation), especially when CO2 is used for enhanced oil recovery (EOR). The government could introduce fiscal policies, such as 45Q or stronger, to stimulate CCUS technology development in China.

Power generation from municipal solid waste landfilled in the Beijing-Tianjin-Hebei region

The present study assesses the electricity generation potential of landfill gas to energy projects in the Beijing-Tianjin-Hebei region. The study used historical data on municipal solid waste disposed of in landfills in the Beijing-Tianjin-Hebei region from 2004 to 2018. The Landfill Gas Emission Model (LandGEM) software version 3.02 was used to evaluate the methane generation potential of the municipal solid waste. An economic feasibility analysis was conducted on the landfill gas to energy projects using economic indicators such as the net present value, investment payback period, and levelized cost of energy. Also, a sensitivity analysis was performed to determine the influence of variation in the discount rate, landfill gas collection efficiency, capacity factor, and power generation efficiency on the economic viability of the project. The main findings of the study show that the total electricity generation potential from landfill methane in the region is 12,525.2 GWh. The highest total electricity generation potential is in Beijing, while the lowest is in Tianjin. It was realized from the economic analysis that the project is feasible at all the locations in the Beijing-Tianjin-Hebei region. However, the project is highly feasible in Beijing, with a more positive net present value, lower investment payback period, and lower levelized cost of energy. It was found that the investment payback period of the project in the region is 11.3 y to 14.3 y, and the levelized cost of energy is $0.1402/kWh to $0.2260/kWh. The sensitivity analysis shows that at a discount rate exceeding 15%, the project is infeasible in the Beijing municipality and Hebei province, while it is infeasible at a discount rate of more than 10% in Tianjin. This study could provide technical guidance for investment in landfill gas to energy projects in the Beijing-Tianjin-Hebei region and other parts of China.

Explosion characteristics and energy utilisation of coal mine ultra-lean methane

Reasonable recycling low concentration methane, especially the ultra-lean methane (the concentration lower than 5%), is significant to resource saving and environment protection. Nowadays, low concentration gas power generation technology is well developed. Notwithstanding this, ultra-lean methane has not been applied in large scale mainly due to the high utilisation costs. Therefore, to address this issue, we break through the empirical thinking to make ultra-lean methane combustion by blending with combustible substances other than only increasing the methane concentration. Its feasibility was analysed from theoretical analysis, especially the cost analysis. Dimethyl ether (DME) was selected as the additive from a range of combustible substances. Then experimental study on the explosion parameters of coal mine ultra-lean methane blending with DME was carried out in a standard 20-L explosion spherical vessel; the lower explosion limits (LEL) at different initial temperatures (ambient temperature, 40°C, 60°C and 80°C) were tested at methane concentration of 0.5%, 1%, 2%, 3% and 4%, respectively. The experimental results indicate that the addition of DME can significantly reduce the minimum explosion concentration of methane, and both P max and (dP/dt)max increase with an increase of DME content in the total fuel. The overall trend of P max and (dP/dt)max increases first and reaches to the maximum. In addition, both CO and CO2 in explosion tail gases are consistent with the decrease trend with increasing in gas mixture. The explosion solid product contained a large number of aromatic hydrocarbon structures, and the solid particles were mainly two types of spherical and blocky with the diameter between 30 and 50 µm. The explosion phenomenon and data provide a reference for assessing the hazards of practical energy system, and guiding the designs of fuel formula and engine safety.