Fermin Viteri

Adapting Gas Turbines to Zero Emission Oxy-Fuel Power Plants

Future power plants will require some type of carbon capture and storage (CCS) system to mitigate carbon dioxide (CO2 ) emissions. The most promising technologies for CCS are: oxy-fuel (O-F) combustion, pre-combustion capture, and post-combustion capture. This paper discusses the recent work conducted by Siemens Power Generation, Florida Turbine Technologies, Inc. (FTT) and Clean Energy Systems, Inc. (CES) in adapting high temperature gas turbines to use CES’s drive gases in high-efficiency O-F zero emission power plants (ZEPPs). CES’s O-F cycle features high-pressure combustion of fuel with oxygen (O2 ) in the presence of recycled coolant (water, steam or CO2 ) to produce drive gases composed predominantly of steam and CO2 . This cycle provides the unique capability to capture nearly pure CO2 and trace by-products by simple condensation of the steam. An attractive O-F power cycle uses high, intermediate and low pressure turbines (HPT, IPT and LPT, respectively). The HPT may be based on either current commercial or advanced steam turbine technology. Low pressure steam turbine technology is readily applicable to the LPT. To achieve high efficiencies, an IPT is necessary and efficiency increases with inlet temperature. The high-temperature IPT’s necessitate advanced turbine materials and cooling technology. O-F plants have an abundance of water, cool steam ∼200°C (400°F) and CO2 that can be used as cooling fluids within the combustor and IPT systems. For the “First Generation” ZEPP, a General Electric J79 turbine, minus the compressor, to be driven directly by CES’s 170 MWt high-pressure oxy-fuel combustor (gas generator), has been adapted. A modest inlet gas temperature of 760°C (1400°F) was selected to eliminate the need for turbine cooling. The J79 turbine operating on natural gas delivers 32 MWe and incorporates a single-stage free-turbine that generates an additional 11 MWe . When an HPT and an LPT are added, the net output power (accounting for losses) becomes 60 MWe at 30% efficiency based on lower heating value (LHV), including the parasitic loads for O2 separation and compression and for CO2 capture and compression to 151.5 bar (2200 psia). For an inlet temperature of 927°C (1700°F), the nominal value, the net output power is 70 MWe at 34% efficiency (LHV). FTT and CES are evaluating a “Second Generation” IPT with a gas inlet temperature of 1260°C (2300°F). Predicted performance values for these plants incorporating the HPT, IPT and the LPT are: output power of approximately 100–200 MWe with an efficiency of 40 to 45%. The “Third Generation” IPT for 2015+ power plants will be based on the development of very high temperature turbines having an inlet temperature goal of 1760°C (3200°F). Recent DOE/CES studies project such plants will have LHV efficiencies in the 50% range for natural gas and HHV efficiencies near 40% for gasified coal.Copyright

An Overview of Turbine and Combustor Development for Coal-Based Oxy-Syngas Systems

Coal combustion technology is required that is capable of: (1) co-producing electricity and hydrogen from coal while; (2) achieving high efficiency, low capital cost, low operating cost, and near-zero atmospheric emissions; and (3) producing a sequestration-ready carbon dioxide stream. Clean Energy Systems, Inc. (CES) and Siemens Power Generation, Inc., are developing this technology that would lead to a 300 to 600 MW, design for a zero emissions coal syngas plant, targeted for the year 2015, CES and Siemens received awards on September 30, 2005 from the U.S. Department of Energy’s; Office of Fossil Energy Turbine Technology R&D Program. These awards are designed to advance turbines and turbine subsystems for integrated gasification combined cycle (IGCC) power plants. Studies have shown [1–4] that replacing air with nearly pure oxygen and steam in a turbine’s combustion chamber is a promising approach to designing coal based power plants with high efficiency and near-zero emissions. Siemens will combine current steam and gas turbine technologies to design an optimized turbine that uses oxygen with coal derived hydrogen fuels in the combustion process under a DOE Turbine Development Project [5]. CES will develop and demonstrate a new combustor technology powered by coal syngas and oxygen under a DOE Combustor Development Project [6]. The proposed programs build upon twelve years of prior technical work and government-sponsored research to develop and demonstrate zero-emission fossil fuel power generation. The planned system studies build upon previous work conducted by private, public, and foreign organizations, including CES [7–9], DOE’s National Energy Technology Laboratory (NETL) [10–12], Air Liquide (AL) [1,13], Lawrence Livermore National Laboratory (LLNL) [2], Fern Engineering, Inc. [14], and Japanese investigators [15, 16]. Other pertinent data related to coal gasification, advanced air separation unit (ASU), plant integration and plant systems optimization, etc., can be found in references [17–23].Copyright

Oxy-Fuel Gas Turbine, Gas Generator and Reheat Combustor Technology Development and Demonstration

Future fossil-fueled power generation systems will require carbon capture and sequestration to comply with government green house gas regulations. The three prime candidate technologies that capture carbon dioxide (CO2 ) are pre-combustion, post-combustion and oxy-fuel combustion techniques. Clean Energy Systems, Inc. (CES) has recently demonstrated oxy-fuel technology applicable to gas turbines, gas generators, and reheat combustors at their 50MWth research test facility located near Bakersfield, California. CES, in conjunction with Siemens Energy, Inc. and Florida Turbine Technologies, Inc. (FTT) have been working to develop and demonstrate turbomachinery systems that accommodate the inherent characteristics of oxy-fuel (O-F) working fluids. The team adopted an aggressive, but economical development approach to advance turbine technology towards early product realization; goals include incremental advances in power plant output and efficiency while minimizing capital costs and cost of electricity [1]. Proof-of-concept testing was completed via a 20MWth oxy-fuel combustor at CES’s Kimberlina prototype power plant. Operability and performance limits were explored by burning a variety of fuels, including natural gas and (simulated) synthesis gas, over a wide range of conditions to generate a steam/CO2 working fluid that was used to drive a turbo-generator. Successful demonstration led to the development of first generation zero-emission power plants (ZEPP). Fabrication and preliminary testing of 1st generation ZEPP equipment has been completed at Kimberlina power plant (KPP) including two main system components, a large combustor (170MWth ) and a modified aeroderivative turbine (GE J79 turbine). Also, a reheat combustion system is being designed to improve plant efficiency. This will incorporate the combustion cans from the J79 engine, modified to accept the system’s steam/CO2 working fluid. A single-can reheat combustor has been designed and tested to verify the viability and performance of an O-F reheater can. After several successful tests of the 1st generation equipment, development started on 2nd generation power plant systems. In this program, a Siemens SGT-900 gas turbine engine will be modified and utilized in a 200MWe power plant. Like the 1st generation system, the expander section of the engine will be used as an advanced intermediate pressure turbine and the can-annular combustor will be modified into a O-F reheat combustor. Design studies are being performed to define the modifications necessary to adapt the hardware to the thermal and structural demands of a steam/CO2 drive gas including testing to characterize the materials behavior when exposed to the deleterious working environment. The results and challenges of 1st and 2nd generation oxy-fuel power plant system development are presented.Copyright

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

In Aug 2004 the Zero Emission Norwegian Gas (ZENG) project team completed Phase-1: Concept and Feasibility Study for a 40 MW Pilot & Demonstration (PD thermodynamic efficiency, power plant investment, operations and maintenance cost. However, they do represent important considerations towards “total” optimization when designing the PD and identification of further opportunities for extended technology migration from gas turbine environment that could also permit raised turbine inlet temperatures (TIT).Copyright

Application of Existing Turbomachinery for Zero Emissions Oxy-Fuel Power Systems

Future fossil-fuel-based power generation systems must include decarbonizing technologies to capture and store (CCS) carbon dioxide (CO2 ). Oxy-fuel (O-F) combustion-based power systems are uniquely capable of capturing almost all CO2 . In the O-F power plant cycle, fuel and nearly pure oxygen, delivered from an air separation unit (ASU), are burned to form a working fluid composed primarily of steam and CO2 . Clean Energy Systems (CES), Siemens Energy, Inc. and Florida Turbine Technologies, Inc. (FIT) are jointly developing turbomachinery systems driven by O-F working fluids and have adopted a stepped development approach to advance the technology toward product realization through an initial proof-of-concept phase and subsequent development of 1st and 2nd generation power plant systems. Specific goals and objectives target incremental advancements of power plant efficiency and output while reducing capital costs and cost of electricity. In the initial proof-of-concept phase, bench-level research was performed on a primary combustion system. A 20MWth development gas generator was used to explore operability and performance limits while operating on a variety of fuels over a wide range of conditions. Further, the working fluid produced by this combustor was used to drive an existing turbine/generator set at CES’ Kimberlina prototype power plant located near Bakersfield, California. This paper summarizes the recent follow-on work to develop and demonstrate 1st and 2nd generation O-F power plant systems. Successful completion of the proof-of-concept phase led to the development of the 1st generation power plant system. Specific equipment required for this operation included a larger 170MWth combustor, which was constructed to produce additional power in this phase. An existing General Electric GE-J79 turbine was modified to extract power from this unit. All equipment required for this system has been assembled at CES’ Kimberlina power plant. In addition, a reheat combustion system is being developed to enhance the 1st generation power plant cycle. In a logical next step, a larger power output, increased-efficiency 2nd generation power plant system was defined. For this application, the Siemens SGT-900 gas turbine was selected as the basis for the Intermediate Pressure Turbine. Conceptual design studies were performed to identify the modifications needed in order to adapt the hardware to accept O-F drive gases. Specific challenges related to the mechanical design configuration, and thermal/structural behaviors of the system are delineated. Testing is being performed to characterize the behavior of materials when exposed to the steam/CO2 working fluid environment. Necessary development of long-lead items required for this system is also described.Copyright