Using Molten Carbonate Fuel Cell Systems for CO2 With a Natural Gas Combined Cycle Operating at Part Load

Author(s):  
Robert Flores ◽  
Jack Brouwer

Abstract Traditional carbon capture technology has been shown to effectively capture emissions, but at a cost of reducing power plant output. Molten carbonate fuel cell technology (MCFC) has the potential to be able to concentrate plant carbon emissions into a gas stream that is suitable for storage while boosting total plant power output. When considering this type of technology, the original purpose and function of the power plant must be considered. In particular, gas turbines (GT) based natural gas combined cycle (NGCC), which are capable of dynamic load following operation, are likely to need to maintain operational flexibility. This work explores the retrofit of an existing GT with MCFC technology for carbon capture when the plant is operated at part load. Physical models for major plant components are built and used to select optimal operating set points such that operating cost is minimized. Special attention is given to ensuring feasible operation across all engine components. The results show MCFC operational parameters that minimize change in fuel cell operating conditions when the gas turbine is operated at part load.

2022 ◽  
Vol 14 (1) ◽  
pp. 533
Author(s):  
Alberto Fichera ◽  
Samiran Samanta ◽  
Rosaria Volpe

This study aims to propose the repowering of an existing Italian natural-gas fired combined cycle power plant through the integration of Molten Carbonate Fuel Cells (MCFC) downstream of the gas turbine for CO2 capture and to pursuit an exergetic analysis of the two schemes. The flue gases of the turbine are used to feed the cathode of the MCFC, where CO2 is captured and transported to the anode while generating electric power. The retrofitted plant produces 787.454 MW, in particular, 435.29 MW from the gas turbine, 248.9 MW from the steam cycle, and 135.283 MW from the MCFC. Around 42.4% of the exergy destruction has been obtained, the majority belonging to the combustion chamber and, in minor percentages, to the gas turbine and the MCFC. The overall net plant efficiency and net exergy efficiency are estimated to be around 55.34 and 53.34%, respectively. Finally, the specific CO2 emission is around 66.67 kg/MWh, with around 2 million tons of carbon dioxide sequestrated.


2020 ◽  
Vol 167 (6) ◽  
pp. 064505 ◽  
Author(s):  
Jonathan Rosen ◽  
Timothy Geary ◽  
Abdelkader Hilmi ◽  
Rodrigo Blanco-Gutierrez ◽  
Chao-Yi Yuh ◽  
...  

Author(s):  
Georgia C. Karvountzi ◽  
Paul F. Duby

The goal of this study is to define the operating envelope of a 20MW molten carbonate fuel cell (MCFC)-gas turbine hybrid system, under part load conditions. The first part of the paper reviews our baseline fuel cell hybrid system model that predicts overall system LHV efficiency around 69% at full load. The second part of the paper consider several strategies: 1/ run fuel cell at full load and bypass gas turbine; 2 /run fuel cell at full load and gas turbine at part load; 3/ run fuel cell at OCV and gas turbine at full load; 4/ run fuel cell at part load and gas turbine at full load; and 5/run both fuel cell and gas turbine at part load. The best system part-load performance was achieved when the fuel cell operates at part load while the gas turbine is at full load. The highest operational flexibility is achieved when we part load both the fuel cell and the gas turbine. Depending on system targets and deliverables such as fuel cell voltage and fuel utilization or gas turbine firing temperature some of these modes may not be economical. A comparison with the performance of a conventional combined cycle 20MW power plant under part load was performed. The MCFC hybrid system showed better efficiency and better cost of electricity (COE) under part load operation than the gas turbine combined cycle part loaded.


Author(s):  
Mehdi Mehrpooya ◽  
Parimah Bahramian ◽  
Fathollah Pourfayaz ◽  
Hadi Katooli ◽  
Mostafa Delpisheh

Abstract The production of liquefied natural gas (LNG) is a high energy-consuming process. The study of ways to reduce energy consumption and consequently to reduce operational costs is imperative. Toward this purpose, this study proposes a hybrid system adopting a mixed refrigerant for the liquefaction of natural gas that is precooled with an ammonia/water absorption refrigeration (AR) cycle utilizing the exhaust heat of a molten carbonate fuel cell, 700°C and 2.74 bar, coupled with a gas turbine and a bottoming Brayton super-critical carbon dioxide cycle. The inauguration of the ammonia/water AR cycle to the LNG process increases the cooling load of the cycle by 10%, providing a 28.3-MW cooling load duty while having a 0.45 coefficient of performance. Employing the hybrid system reduces energy consumption, attaining 85% overall thermal efficiency, 53% electrical efficiency and 35% fuel cell efficiency. The hybrid system produces 6300 kg.mol.h−1 of LNG and 146.55 MW of electrical power. Thereafter, exergy and sensitivity analyses are implemented and, accordingly, the fuel cell had an 83% share of the exergy destruction and the whole system obtained a 95% exergy efficiency.


Author(s):  
Ji Ho Ahn ◽  
Tong Seop Kim

Owing to the increasing consumption of fossil fuels and emission of greenhouse gases, interests in highly efficient and low carbon emitting power systems are growing fast. Several research groups have been suggesting advanced systems based on fuel cells and have also been applying carbon capture and storage technology to satisfy the demand for clean energy. In this study, the performance of a hybrid system, which is a combination of a molten carbonate fuel cell (MCFC) with oxy-combustion carbon capture and an indirectly fired micro gas turbine (MGT) was predicted. A 2.5MW MCFC system that is used in commercial applications was used as the reference system so that the results of the study could be applicable to practical situations. The ambient pressure type hybrid system was modeled by referring to the design parameters of an MGT that is currently being developed. A semi-closed type design characterized by flow recirculation was adopted for this hybrid system. A part of the recirculating gas is converted into liquefied carbon dioxide and captured for storage at the carbon separation unit. Almost 100% carbon dioxide capture is possible with this system. In these systems, the output power of the fuel cell is larger than in the normal hybrid system without carbon capture because the partial pressure of carbon dioxide increases. The increased cell power partially compensates for the power loss due to the carbon capture and MGT power reduction. The dependence of net system efficiency of the oxy-hybrid on compressor pressure ratio is marginal, especially beyond an optimal value.


Energy ◽  
2016 ◽  
Vol 117 ◽  
pp. 578-589 ◽  
Author(s):  
Liqiang Duan ◽  
Kun Xia ◽  
Tao Feng ◽  
Shilun Jia ◽  
Jing Bian

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