Utilization of Cryogenic Exergy of LNG by MGT (Mirror Gas Turbine)

Author(s):  
Y. Tsujikawa ◽  
K. Kaneko ◽  
S. Fujii

In the course of the worldwide efforts to suppress the global warming, the saving energy becomes more important. Recently, the LNG (liquefied natural gas) terminals in our country have received more than 50 million tons of LNG per year. Therefore, the utilization of the cryogenic exergy in connection with the regasification of LNG gains more and more importance. The aim of this paper is the recovery of the energy consumed in liquefaction using the MGT (Mirror Gas Turbine), which is a kind of new combined cycle of a conventional gas turbine worked as a topping cycle and TG (inverted Brayton cycle) as a bottoming cycle. The optimum characteristics have been calculated and it is shown that this cycle is superior to the current-use gasification systems in employing seawater heats in terms of thermal efficiency and specific output. In the present cycle, the cold of LNG is used to cool the exhaust gas from a turbine of TG, and then the exergy of the liquefied natural gas is transformed to electric energy with a very high efficiency. The main feature of this new concept is the removal of an evaporation system using seawater.

1980 ◽  
Vol 102 (2) ◽  
pp. 225-230 ◽  
Author(s):  
G. Krey

In the course of the world-wide efforts to save energy, the utilization of cold in connection with the regasification of liquefied natural gas gains more and more importance. The aim is the partial recovery of the energy consumed in liquefaction. There are particular advantages when using the closed-cycle gas turbine, in which the exergy of the liquefied natural gas is transformed to electrical energy with a very high efficiency. The paper deals with the optimization, design, and operational behavior of such a plant.


Author(s):  
R. Chacartegui ◽  
D. Sa´nchez ◽  
F. Jime´nez-Espadafor ◽  
A. Mun˜oz ◽  
T. Sa´nchez

The development of high efficiency solar power plants based on gas turbine technology presents two problems, both of them directly associated with the solar power plant receiver design and the power plant size: lower turbine intake temperature and higher pressure drops in heat exchangers than in a conventional gas turbine. To partially solve these problems, different configurations of combined cycles composed of a closed cycle carbon dioxide gas turbine as topping cycle have been analyzed. The main advantage of the Brayton carbon dioxide cycle is its high net shaft work to expansion work ratio, in the range of 0.7–0.85 at supercritical compressor intake pressures, which is very close to that of the Rankine cycle. This feature will reduce the negative effects of pressure drops and will be also very interesting for cycles with moderate turbine inlet temperature (800–1000 K). Intercooling and reheat options are also considered. Furthermore, different working fluids have been analyzed for the bottoming cycle, seeking the best performance of the combined cycle in the ranges of temperatures considered.


Author(s):  
Vikram Muralidharan ◽  
Matthieu Vierling

Power generation in south Asia has witnessed a steep fall due to the shortage of natural gas supplies for power plants and poor water storage in reservoirs for low hydro power generation. Due to the current economic scenario, there is worldwide pressure to secure and make more gas and oil available to support global power needs. With constrained fuel sources and increasing environmental focus, the quest for higher efficiency would be imminent. Natural gas combined cycle plants operate at a very high efficiency, increasing the demand for gas. At the same time, countries may continue to look for alternate fuels such as coal and liquid fuels, including crude and residual oil, to increase energy stability and security. In over the past few decades, the technology for refining crude oil has gone through a significant transformation. With the advanced refining process, there are additional lighter distillates produced from crude that could significantly change the quality of residual oil used for producing heavy fuel. Using poor quality residual fuel in a gas turbine to generate power could have many challenges with regards to availability and efficiency of a gas turbine. The fuel needs to be treated prior to combustion and needs a frequent turbine cleaning to recover the lost performance due to fouling. This paper will discuss GE’s recently developed gas turbine features, including automatic water wash, smart cooldown and model based control (MBC) firing temperature control. These features could significantly increase availability and improve the average performance of heavy fuel oil (HFO). The duration of the gas turbine offline water wash sequence and the rate of output degradation due to fouling can be considerably reduced.


Author(s):  
Stéphanie Hoffmann ◽  
Michael Bartlett ◽  
Matthias Finkenrath ◽  
Andrei Evulet ◽  
Tord Peter Ursin

This paper presents the results of an evaluation of advanced combined cycle gas turbine plants with precombustion capture of CO2 from natural gas. In particular, the designs are carried out with the objectives of high efficiency, low capital cost, and low emissions of carbon dioxide to the atmosphere. The novel cycles introduced in this paper are comprised of a high-pressure syngas generation island, in which an air-blown partial oxidation reformer is used to generate syngas from natural gas, and a power island, in which a CO2-lean syngas is burnt in a large frame machine. In order to reduce the efficiency penalty of natural gas reforming, a significant effort is spent evaluating and optimizing alternatives to recover the heat released during the process. CO2 is removed from the shifted syngas using either CO2 absorbing solvents or a CO2 membrane. CO2 separation membranes, in particular, have the potential for considerable cost or energy savings compared with conventional solvent-based separation and benefit from the high-pressure level of the syngas generation island. A feasibility analysis and a cycle performance evaluation are carried out for large frame gas turbines such as the 9FB. Both short-term and long-term solutions have been investigated. An analysis of the cost of CO2 avoided is presented, including an evaluation of the cost of modifying the combined cycle due to CO2 separation. The paper describes a power plant reaching the performance targets of 50% net cycle efficiency and 80% CO2 capture, as well as the cost target of 30$ per ton of CO2 avoided (2006 Q1 basis). This paper indicates a development path to this power plant that minimizes technical risks by incremental implementation of new technology.


Author(s):  
Mircea Fetescu

The High Efficiency-Coal and Gas (HE-C&G) is a hybrid power plant concept integrating Conventional Steam Power Plants (CSPP) and gas turbine / combined cycle plants. The gas turbine exhaust gas energy is recovered in the HRSG providing partial condensate and feedwater preheating and generating steam corresponding to the main boiler live steam conditions (second steam source for the ST). The concept, exhibiting very high design flexibility, integrates the high performance Sequential Combustion gas turbines GT24/GT26 technology into a wide range of existing or new CSPP. Although HE-C&G refers to coal as the most abundant fossil fuel resource, oil or natural gas fired steam plants could be also designed or converted following the same principle. The HE-C&G provides very high marginal efficiencies on natural gas, up to and above 60%, very high operating and dispatching flexibility and on-line optimization of fuel and O&M costs at low capital investment. This paper emphasizes the operating flexibility and resulting benefits, recommending the HE-C&G as one of the most profitable options for generating power especially for conversion of existing CSPP with gas turbines.


Author(s):  
Stefano Mazzoni ◽  
Srithar Rajoo ◽  
Alessandro Romagnoli

The storage of the natural gas under liquid phase is widely adopted and one of the intrinsic phenomena occurring in liquefied natural gas is the so-called boil-off gas; this consists of the regasification of the natural gas due to the ambient temperature and loss of adiabacity in the storage tank. As the boil-off occurs, the so-called cold energy is released to the surrounding environment; such a cold energy could potentially be recovered for several end-uses such as cooling power generation, air separation, air conditioning, dry-ice manufacturing and conditioning of inlet air at the compressor of gas turbine engines. This paper deals with the benefit corresponding to the cooling down of the inlet air temperature to the compressor, by means of internal heat transfer recovery from the liquefied natural gas boil-off gas cold energy availability. The lower the compressor inlet temperature, the higher the gas turbine performance (power and efficiency); the exploitation of the liquefied natural gas boil-off gas cold energy also corresponds to a higher amount of air flow rate entering the cycle which plays in favour of the bottoming heat recovery steam generator and the related steam cycle. Benefit of this solution, in terms of yearly work and gain increase have been established by means of ad hoc developed component models representing heat transfer device (air/boil-off gas) and heavy duty 300 MW gas turbine. For a given ambient temperature variability over a year, the results of the analysis have proven that the increase of electricity production and efficiency due to the boil-off gas cold energy recovery has finally yield a revenue increase of 600,000€/year.


2018 ◽  
Vol 2 (1) ◽  

The major growth in the electricity production industry in the last 30 years has centered on the expansion of natural gas power plants based on gas turbine cycles. The most popular extension of the simple Brayton gas turbine has been the combined cycle power plant with the Air-Brayton cycle serving as the topping cycle and the Steam-Rankine cycle serving as the bottoming cycle for new generation of nuclear power plants that are known as GEN-IV. The Air-Brayton cycle is an open-air cycle and the Steam-Rankine cycle is a closed cycle. The air-Brayton cycle for a natural gas driven power plant must be an open cycle, where the air is drawn in from the environment and exhausted with the products of combustion to the environment. This technique is suggested as an innovative approach to GEN-IV nuclear power plants in form and type of Small Modular Reactors (SMRs). The hot exhaust from the AirBrayton cycle passes through a Heat Recovery Steam Generator (HSRG) prior to exhausting to the environment in a combined cycle. The HRSG serves the same purpose as a boiler for the conventional Steam-Rankine cycle [1].


Author(s):  
Ste´phanie Hoffmann ◽  
Michael Bartlett ◽  
Matthias Finkenrath ◽  
Andrei Evulet ◽  
Tord Peter Ursin

This paper presents the results of an evaluation of advanced combined cycle gas turbine plants with pre-combustion capture of CO2 from natural gas. In particular, the designs are carried out with the objectives of high efficiency, low capital cost and low emissions of carbon dioxide to the atmosphere. The novel cycles introduced in this paper are comprised of a high-pressure syngas generation island, in which an air-blown POX reformer is used to generate syngas from natural gas, and a power island, in which a CO2-lean syngas is burnt in a large frame machine. In order to reduce the efficiency penalty of natural gas reforming, a significant effort is spent evaluating and optimizing alternatives to recover the heat released during the process. CO2 is removed from the shifted syngas using either CO2 absorbing solvents or a CO2 membrane. CO2 separation membranes, in particular, have the potential for considerable cost or energy savings compared to conventional solvent-based separation and benefit from the high pressure level of the syngas generation island. A feasibility analysis and a cycle performance evaluation are carried out for large frame gas turbines such as the 9FB. Both short term and long term solutions have been investigated. An analysis of the cost of CO2 avoided is presented, including an evaluation of the cost of modifying the combined cycle due to CO2 separation. The paper describes a power plant reaching the performance targets of 50% net cycle efficiency and 80% CO2 capture, as well as the cost target of 30$ per ton of CO2 avoided. This paper indicates a development path to this power plant that minimizes technical risks by incremental implementation of new technology.


Author(s):  
Michel Delanaye ◽  
Andrés Giraldo ◽  
Rabia Nacereddine ◽  
Mehdi Rouabah ◽  
Valentina Fortunato ◽  
...  

The paper presents recent work in the development of a clean and efficient natural gas combustor for a micro-CHP system based on a gas turbine for the residential sector. The large scale deployment of natural gas micro-CHP systems represents a great opportunity to contribute to a reduction of CO2 emissions by a substantial increase of the efficiency of primary energy source conversion. A micro-CHP system, well designed for a residential application, which means a power of 1kWe output and high efficiency (larger than 20%), may reduce annual household emissions up to factors close to 2.5. The micro-CHP system developed in this work uses a small gas turbine and an inverted Brayton cycle which advantageously allows the use of substantially larger turbomachinery components than a conventional pressurized Brayton cycle. The paper presents a new counterflow recuperator. Its design has been thoroughly studied by advanced 3D CFD to obtain compactness and high efficiency at low cost. A new flameless combustor has been developed in order to reduce to single digits the emissions of pollutants (NOx and CO) and obtain a highly efficient and stable combustion for various gases. The design methodology based on 3D CFD modelling is presented as well as experimental results demonstrating the performance of the recuperated flameless combustor for various operationg conditions.


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