Comparison of Supercritical Carbon Dioxide Cycles for Oxy-Combustion

Abstract

Advanced oxy-combustion coupled with supercritical carbon dioxide (sCO2) power cycles offers a path to achieve efficient power generation with integrated carbon capture for base load power generation. One commonality among high efficiency sCO2 cycles is the extensive use of recuperation within the cycle. This high degree of recuperation results in high temperatures at the thermal input device and a smaller temperature rise to the turbine inlet. When combined with typical high side pressures ranging from 150 to 300 bar, these conditions pose a non-trivial challenge for fossil fired sCO2 cycles with respect to cycle layout and thermal integration. A narrow thermal input window can be tolerated for indirect cycles such as those used for nuclear power generation and concentrating solar power plants, however, it is at odds with traditional coal or natural gas fired Rankine cycles where the working fluid has been condensed and cooled to near ambient temperatures. Coal fired sCO2 cycles using oxy-combustion have been examined by Southwest Research Institute and Thar Energy L.L.C. under DOE award DE-FE0009593. Under this project, an indirect supercritical oxy-combustion cycle was developed that provides 99% carbon capture with a 37.9% HHV plant efficiency. This cycle achieves a predicted COE of $121/MWe with no credits taken for the additional 9% of carbon capture, and represents a 21% reduction in cost as compared to supercritical steam with 90% carbon capture ($137/MWe). Direct fired sCO2 cycles for natural gas or syngas are currently being evaluated by Southwest Research Institute and Thar Energy L.L.C. under DOE award DE-FE0024041. Initial evaluations of direct fired supercritical oxy-combustion cycles indicate that plant efficiencies on the order of 51% to 54% can be achieved with direct fired natural gas oxy-combustion when paired with the recompression cycle with 1,200 °C firing temperatures at 200 bar. Direct fired natural gas or syngas sCO2 cycles still face significant technology development needs, with the pressurized oxy-combustor a significant component with a low Technology Readiness Level, (TRL) as defined by the DOE. In addition to the combustion system, significant work will be required to prepare the sCO2 turbomachinery for the turbine inlet temperatures required to achieve plant efficiencies greater than 50%.

Thermodynamics analysis of S-CO<sub>2</sub> recompression-reheating cycle for coal fired power plant

“…炉, 其热力系统采用二次再热再压缩循环, 最终得到 的系统总利用效率可达41.35%. Mcclung等人 [12] 同样 提出S-CO 2 循环与碳捕捉技术耦合的概念, 原因与 Johnson 同 Moullec 相 似 , 认 为 S-CO 2 循 环 效 率 较 高 , 与碳捕捉技术结合能够使碳捕捉技术更具竞争力, 其锅炉形式为富氧燃烧锅炉, 最终可以实现99%的 碳捕捉、 37.9%的高位发热量效率. 对于不带碳捕捉的 系统构建, Mecheri等人 [13] 在Moullec的基础上去掉了 碳捕捉部分, 单独分析了S-CO 2 循环应用于燃煤发电 的特点, 其锅炉选用π式煤粉炉, 文中以二次再热再 压 缩 循 环 为 基 础 , 得 出 了 在 汽 轮 机 入 口 参 数 为 30 MPa, 620℃时理论上系统总效率可达47.8%, 并认为 该 效 率 高 于 超 超 临 界 朗 肯 循 环 火 电 机 组 的 效 率 .…”

Performance and cost potential for direct-fired supercritical CO2 natural gas power plants

“…[5,6] SwRI evaluated alternative natural gas-fired direct sCO2 cycles with reported plant HHV thermal efficiencies ranging 46.5-51.1 percent. [7] Figure 1: Schematic of a natural gas-fueled direct-fired sCO2 power cycle…”

How to Construct a Combined S-CO2 Cycle for Coal Fired Power Plant?

“…The solutions for this problem can be divided into three categories: (1) adding flue gas cooler [21][22][23], (2) raising air temperature [18,24,25], (3) constructing combined cycle [26][27][28].…”

“…However, this scheme has lost some advantages of the S-CO 2 cycle, such as simple system and compact layout. McClung et al [27] suggest absorbing residual heat through two series recompression cycles. Both top and bottom cycles are S-CO 2 cycles.…”