Optimization of Thermodynamically Efficient Nominal 40 MW Zero Emission Pilot and Demonstration Power Plant in Norway

Abstract

In Aug 2004 the Zero Emission Norwegian Gas (ZENG) project team completed Phase-1: Concept and Feasibility Study for a 40 MW Pilot & Demonstration (P&D) Plant, that is proposed will be located at the Energy Park, Risavika, near Stavanger in South Norway during 2008. The power plant cycle is based upon implementation of the natural gas (NG) and oxygen fueled Gas Generator (GG) (1500°F/1500 psi) successfully demonstrated by Clean Energy Systems (CES) Inc. The GG operations was originally tested in Feb 2003 and is currently (Feb 2005) undergoing extensive commissioning at the CES 5MW Kimberlina Test Plant, near Bakersfield, California. The ZENG P&D Plant will be an important next step in an accelerating path towards demonstrating large-scale (+200 MW) commercial implementation of zero-emission power plants before the end of this decade. However, development work also entails having a detailed commercial understanding of the techno-economic potential for such power plant cycles: specifically in an environment where the future penalty for carbon dioxide (CO2) emissions remains uncertain. Work done in dialogue with suppliers during ZENG Project Phase-1 has cost-estimated all major plant components to a level commensurate with engineering pre-screening. The study has also identified several features of the proposed power plant that has enabled improvements in thermodynamic efficiency from 37% up to present level of 44–46% without compromising the criteria of implementation using “near-term” available technology. The work has investigated: i. Integration between the cryogenic air separation unit (ASU) and the power plant. ii. Use of gas turbine technology for the intermediate pressure (IP) steam turbine. iii. Optimal use of turbo-expanders and heat-exchangers to mitigate the power consumption incurred for oxygen production. iv. Improved condenser design for more efficient CO2 separation and removal. v. Sensitivity of process design criteria to “small” variations in modeling of the physical properties for CO2/steam working fluid near saturation. vi. Use of a second “conventional” pure steam Rankine bottoming cycle. In future analysis, not all these improvements need necessarily be seen to be cost-effective when taking into account total P&D program objectives; thermodynamic efficiency, power plant investment, operations and maintenance cost. However, they do represent important considerations towards “total” optimization when designing the P&D Plant. We observe that Project Phase-2: Pre-Engineering & Qualification should focus on optimization of plant size with respect to total capital investment (CAPEX); and identification of further opportunities for extended technology migration from gas turbine environment that could also permit raised turbine inlet temperatures (TIT).

Oxyfuel combustion for CO2 capture in power plants

“…Due to the low condenser pressure, the water content of approx. 40% in the CO 2 has to be reduced by intercooled compression with condensation (Hustad et al, 2005). Alternatively, a condensation at higher pressure reduces the effort for the CPU.…”

“…In the basic cycle mainly a condenser for separating the CO 2 /steam mixture. A low condenser pressure is challenging because of the higher heat transfer resistance of the mixture compared to pure steam (Hustad et al, 2005). Additionally, a preheater for the water that is injected to the combustor is needed.…”

“…This results in a net efficiency between 43 and 47% (Martinez-Frias et al, 2002;Gou et al, 2006;Kvamsdal et al, 2007;Haines et al, 2006). Hustad et al (2005) present a cycle configuration within the ZENG project that uses solely state of the art technology. The HP and IP temperature is 565 • C and 705 • C for a steam turbine and an uncooled gas turbine, respectively.…”

“…Advanced cycle design Hustad et al (2005) propose an optimized design for the application of existing equipment as mentioned above. The HP steam parameters are increased to 150 bar and 600 • C while the main feature is a comparatively high IP outlet pressure of 3 bar at 390 • C. An HRSG generates pure steam at 1.6 bar and 356 • C. This pure steam can be expanded to a lower condenser pressure of 0.03 bar.…”

“…Hustad et al (2005) use an ASU with an outlet pressure of 30 bar for the reheat combustor and an additional compressor to reach the gas generator pressure. As mentioned before the integration of the waste nitrogen stream is possible in some configurations (Marin et al, 2003;Hustad et al, 2005). The required oxygen purity is dependent on the requirements regarding the CO 2 purity.…”