NGCC Plants

This setup of GT, HRSG, steam turbines, and generators is called a combined cycle (CC). This type of power plant is being installed in increasing numbers around the world where there is an access to substantial quantities of natural gas. This type of power plant produces high power outputs with high efficiencies and low 

2 Integration of Hz/Syngas Production Technologies in NGCC Plants 

The combustion of natural gas accounts for approximately 21% of the U.S. emission of C02. The majority of NGCC plants are not equipped with the C02 capture capability. Researchers in both academia and industry recognize the importance of controlling the C02 emissions and are working on developing technologies to effectively capture and sequestrate C02. 

There are three main ways to capture C02 in the NGCC process post-combustion C02 capture, oxyfuel combustion, and precombustion C02 capture. 

One advantage of the post-combustion C02 capture route is that it does not require any modifications to existing combustion methods, which means current power plants can be retrofitted with this process. In fact, this method has been demonstrated at some small-scale power plants.14 

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The capture and sequestration of C02 reduces the efficiency and increases the capital cost of the NGCC plant significantly.6 Typically, -20% of the net power of the NGCC plant is lost in order to separate and sequestrate 90% of C02 emissions as shown in Figure 11.6. The addition of C02 capture units also results in -90% increase in the capital cost of the NGCC plant and -61% increase in the cost of... 

The principle of post-combustion capture is shown in Figure 11.9. The exhaust gas from the NGCC plant is sent to the C02 capture unit, which typically utilizes chemical solvents such as amines or alcohols.7"13 Chemical absorption of C02 using solvent is preferred because of the low concentration of C02 ( 5%) and low pressure in the flue gas. The solvent loaded with C02 is regenerated typically in a reboiler using low-quality steam. The C02 released from the solvent can be sent to a sequestration plant. 

For the power production scenario, the hydrogen is co-fired in a turbine at a natural gas combined-cycle (NGCC) plant. Two options were examined ... 

For the ZEPP system presented in Fig. 2.7 the allowable installed costs for the capture plant have been estimated to be in between 80 and 120M for a 1.4GWthermai input natural gas combined cycle (NGCC) plant. To meet the cost targets, an ITM based ZEPP power plant should have an electric efficiency of at least 52%. Capture ratios (carbon captured/carbon fed to the process) of 100% result in plant efficiencies lower than 50%. Capture ratios of the order of 85% are accompanied with plant efficiencies of about 52%. The allowable installed costs window is satisfied when the oxygen flux is at least 20 ml/cm min and the costs of the ITM tubes should be less than 1,500 /m. This clearly sets the targets for materials and turbine development in order for the system to be economically viable within the capture cost boundary conditions. 

NGCC plant with a slight energy efhdency decrease and an average CO2 emission abatement. 

The integration of MC membranes and fuel cells within NG combined cycle (NGCC) plants can outperform conventional amine absorption NGCC retrofitting strategies for post-combustion CO2 capture [66]. Furthermore, DPMs based on MCs impregnated in porous MIEC materials such as perovskites can be used... 

The NGCC plant consists of a single train of an advanced gas turbine. Like in some lEA studies, the calculations have been based on a Siemens 94.3A (turbine inlet temperature 1300°C and pressure ratio of 15-16) with a triple pressure reheat steam cycle (106 bar/30 bar/4.5 bar) (Fig. C-14). Due to the low partial pressure in the gas turbine exhaust gas, a CO2 removal process based on chemical absorption, using a solvent such as MEA (MonoEthanol Amine), will be required. The assiuned CO2 removal efficiency is 85 percent. Regeneration of the solvent is performed by reboiling and stripping. Low-pressure steam for the regeneration is extracted from the steam cycle. 

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