333128 A Novel Power Cycle Integrated With Post Combustion CO2 Capture Process Using LNG Cryogenic Exergy
Recent climate change and related disasters have attracted worldwide attention and brought efforts to reduce greenhouse gases especially for CO2. Among the various sources of the CO2 emission, power plants combusting fossil fuel such as coal, oil and gas contribute to the CO2 emission the most 1. Several techniques to remove CO2 from the power plant flue gas have been proposed, and amine based CO2 absorbing systems are considered the one of the most suitable options because it has been demonstrated as the most mature and less expensive technology 2. However, the large energy consumption and corresponding electricity cost increment have been pointed out as the obstacle of the commercialization. The estimated cost of CO2 capture increases the cost of electricity production by 40–85% for a supercritical pulverized coal power plant. 3 In this study, a novel pulverized coal (PC) power plant integrated with CO2 Rankine cycle utilizing Liquefied Natural Gas (LNG) cryogenic exergy has been proposed. By utilizing the latent heat of low quality steam which originally wasted in the steam condenser, this process is able to extract additional power from the CO2 Rankine cycle.
Figure. 1 Process Flow Diagram of Novel Power Generation Cycle
Figure 1 gives a principal process scheme of the novel power generating process proposed in this study. The four main parts of the process are the steam cycle, CO2 capture process, gas conditioning process and CO2 Rankine cycle integrated with LNG gasification process. Flue gas pathway is similar to the conventional power plant with post combustion CO2 capture process. The CO2 generated from the PC power plant is delivered to the Rankine cycle through CO2 capture and gas conditioning process. Steam pathway is, however, somewhat different from the conventional cycle. Both the steam condensate and low pressure steam are utilized for the CO2 Rankine cycle superheating. The steam condensate (C-1) from the Feed Water Heater (FWH) (23) is directed to preheater and the low pressure steam (S-1) id introduced to CO2 super heater (41) in CO2 Rankine cycle. In this process, Cryogenic Exergy of LNG is utilized for CO2 condensation integrating it with LNG gasification process. In addition, the steam from the low pressure turbine, in contrast to the conventional steam cycle, is condensed in the CO2 super heater in the CO2 Rankine cycle. In this manner, the latent heat of the steam which is originally wasted in conventional steam cycle can be utilized for CO2 super heating and the amount of power generation of entire plant is eventually increased. Total Energy production of the steam cycle and CO2 Rankine cycle without integration is turns out to be 70.75 MWe. On the other hand, total energy generation in the novel process is increased to 80MWe by utilizing the wasted low pressure steam. It is about 20 % increment of the total power production. The exergy efficiency of the CO2 Rankine cycle increases from 0.34% to 40% by integrating steam cycle with CO2 Rankine cycle. Using the integrated power cycle, the fuel cost for the power production can be lowered to only 61% of the conventional steam cycle from 12.8 Euro/MW to 7.81 Euro/MW.
This research was supported by a grant from the LNG Plant R&D Center funded by the Ministry of Land, Transportation and Maritime Affairs (MLTM) of the Korean government.
See more of this Group/Topical: Computing and Systems Technology Division