Energy Efficiency of a Simulated Synthetic Natural Gas Combined Cycle (SNGCC)

The objective of this investigation is to analyze the impact of the flue gas recirculation (FGR) ratio on the different energy inputs and outputs of a SNGCC power plant as well as its overall efficiency. Simulation results indicate that increasing flue gas recirculation increases the energy consumed by the recirculation compressor and the energy produced by the gas turbine. On the other hand, it decreases the production of energy of the steam turbine and the energy consumed by the pump of the steam cycle. The overall energy efficiency of the SNGCC power plant is highest (41.09%) at a value of 0.20 of the flue gas recirculation. However, the flue gas composition with a FGR ratio of 0.37 is more suitable for effective absorption of carbon dioxide by amine solutions. Based on the low heating value (LHV) of hydrogen, the corresponding overall efficiency of the power plant is 39.18% and the net power output of the plant is 1273 kW for consumption of 97.5 kg/hr. of hydrogen.

Thermodynamic analysis and combined cycle research on recoverable pressure energy in natural gas pipeline

Current research and ways of capturing mechanical energy are discussed in this paper. By the aid of the comprehensive thermodynamic analysis and Aspen simulation tool, the amount of a vailable work that can be produced from capturing the pressure energy has been calculated. Based on the comprehensive thermodynamic analysis, two systems have been proposed to capture pressure energy of natural gas to generate electricity. In this study, the expression of exergy is given which can be used in evaluating purposes. A problem with this multidisciplinary study is the complicated boundary condition. In conclusion, a technical prospect on recoverable natural gas pressure energy has been presented based on total energy system theory.

Process Simulation of a 620 Mw-Natural Gas Combined Cycle Power Plant with Optimum Flue Gas Recirculation

The main objective of this investigation is to obtain an optimum value for the flue gas recirculation ratio in a 620 MW-Natural Gas Combined Cycle (NGCC) power plant with a 100% excess air in order to have a composition of the exhaust gas suitable for an effective absorption by amine solutions. To reach this goal, the recirculated flue gas is added to the secondary air (dilution air) used for cooling the turbine. The originality of this work is that the optimum value of a Flue Gas Recirculation (FGR) ratio of 0.42 is obtained from the change of the slope related to the effects of flue gas recirculation ratio on the molar percentage of oxygen in the exhaust gas. Compared to the NGCC power plant without flue gas recirculation, the molar percentage of carbon dioxide in the flue gas increases from 5% to 9.2% and the molar percentage of oxygen decreases from 10.9% to 3.5%. Since energy efficiency is the key parameter of energy conversion systems, the impact of the flue gas recirculation on the different energy inputs and outputs and the overall efficiency of the power plant are also investigated. It is found the positive effects of the flue gas recirculation on the electricity produced by the steam turbine generator (STG) are more important than its cooling effects on the power output of the combustion turbine generator (CTG). The flue gas recirculation has no effects on the water pump of the steam cycle and the increase of energy consumed by the compressor of flue gas is compensated by the decrease of energy consumed by the compressor of fresh air. Based on the Low heating value (LHV) of the natural gas, the flue gas recirculation increases the overall efficiency of the power plant by 1.1% from 57.5% from to 58.2%.

An Improved Combined Power System Utilizing Cold Energy of LNG

In order to improve efficiency of a combined power system in which waste heat from exhaust gas could be efficiently recovered and cold energy of liquefied natural gas(LNG) could be fully utilized as well. A system simulation and thermodynamic analysis were carried out,the Kalina cycle was reorganized by changing the concentration of "basic composition",so that a better thermal matching in the heat exchanger could be obtained and the irreversibility of the system was decreased. It was found that the Kalina cycle generally used in the bottom of combined power cycle could also be used to recover the cold energy of LNG. The results show that the exergy efficiency of 42.97% is obtained. Compared with the previous system attained the exergy efficiency of 39.76%,the improved system has a better performance.

Simulation of a NGCC Power Generation Plant for the Production of Electricity from CO2 Emissions Part II: SNGCC Power Plant

The objective of the first part of the investigation was to use Aspen Plus software and the Redlich-Kwong-Soave equation of state in order to simulate an adiabatic methanation reactor for the production of synthetic natural methane (SNG) using 1 kg/hr of carbon dioxide. In this paper, we define the Synthetic Natural Gas Combined Cycle (SNGCC) as a combined cycle power plant where the fuel is synthetic natural gas (SNG) produced by a methanation reactor. The feed of the methanation reactor is the recycled stream of carbon dioxide of a CO2 capture unit treating the flue gas of the SNGCC power plant. The objective of the second part of the investigation is the utilization of Aspen plus software with SRK equation of state for the simulation of the SNGCC power plant. The metallurgical limitation of the gas turbine was fixed at 1300°C in this investigation. For effective absorption by amine solutions, the molar percentage of CO2 in the flue gas should be higher than 10%. Moreover, in order to reduce technical problems linked to oxidative degradation of amine in the CO2 capture plant, the percentage of O2 in the flue gas should also be lower than 5%. To reach this goal, the primary air for combustion has 10% excess air (compared to stoichiometric air) and 37% of the flue gas leaving the SNGCC is recirculated as the secondary air for cooling the turbine. As a result, the concentration of CO2 and O2 of the flue gas entering the CO2 capture unit were respectively equal to 10.2% and 2.01%. The simulation results of the SNGCC power plant indicate that 6.6 MJ of electricity are produced for each kg of carbon dioxide recycled from the CO2 capture unit of the power plant. In other terms, the production of the 24.88 kg/hr of synthetic natural gas (SNG) consumes 62.36 kg/hr of recycled carbon dioxide and 16.4 kg/hr of hydrogen. The SNG produced by the methanation reactor of the power plant generates 114 kW of electricity. It is assumed in this paper that the hydrogen needed for the methanation of carbon dioxide is a product of a catalytic reforming plant that produces gasoline from heavy naphta fraction of an atmospheric distillation unit of crude oil.

Prime Energy Challenges for Operating Power Plants in the GCC

There is a false notion of existing available, abundant, and long lasting fuel energy in the Gulf Cooperation Council (GCC) Countries;with continual income return from its exports. This is not true as the sustainability of this income is questionable. Energy problems started to appear, and can be intensified in coming years due to continuous growth of energy demands and consumptions. The demands already consume all produced Natural Gas (NG) in all GCC, except Qatar;and the NG is the needed fuel for Electric Power (EP) production. These countries have to import NG to run their EP plants. Fuel oil production can be locally consumed within two to three decades if the current rate of consumed energy prevails. The returns from selling the oil and natural gas are the main income to most of the GCC. While NG and oil can be used in EP plants, NG is cheaper, cleaner, and has less negative effects on the environment than fuel oil. Moreover, oil has much better usage than being burned in steam generators of steam power plants or combustion chambers of gas turbines. Introducing renewable energy or nuclear energy may be a necessity for the GCC to keep the flow of their main income from exporting oil. This paper reviews the GCC productions and consumptions of the prime energy (fuel oil and NG) and their role in electric power production. The paper shows that, NG should be the only fossil fuel used to run the power plants in the GCC. It also shows that the all GCC except Qatar, have to import NG. They should diversify the prime energy used in power plants;and consider alternative energy such as nuclear and renewable energy, (solar and wind) energy.

一类煤与天然气互补利用的新型发电系统

提出一种新型发电系统,通过煤和天然气的互补利用来减少能量转化过程的不可逆损失。煤气化炉采用空气和水蒸气做氧化剂,碳转化率约为60%,未转化部分形成半焦,半焦燃烧释放的热量驱动天然气重整反应,制取合成气。煤部分气化所得气化煤气和半焦燃烧驱动天然气重整所得合成气混合,作为联合循环的燃料。结果显示,新系统的热效率为51.5%,效率为50.3%,天然气折合发电效率为61%。新系统为高效合理利用煤和天然气提供了一种新途径。