The combustion of fuels is at the heart of today's energy, materials, chemicals, and transportation systems. Conventional combustion processes involve the mixing of fuel and air containing approximately 79% nitrogen (N₂) and 20% oxygen (O₂). Unfortunately, the nitrogen in the air is a detriment to the combustion process because it reduces cycle efficiencies and contributes to the formation of various pollutants including nitrogen oxides (NO_x).

Clean Energy Systems (CES) has developed high-pressure, oxygen-fuel combustion technology based on mature, proven rocket technology. Integration of that enabling oxy-fuel combustion technology into conventional power generation systems makes Zero-Emissions Power Plants (ZEPPs) based on fossil fuels practical today. These ZEPPs have multiple advantages including: compact and lower cost equipment; greater cycle efficiencies with advanced turbines, complete carbon capture and sequestration of the carbon dioxide (CO₂) effluent, and zero emissions (or ultra low emissions when the exhaust is vented to the atmosphere as in a peaking power plant). The CES technology will revolutionize the power industry by eliminating the traditional power plant stack and making zero-emission power plants a standard installation. A simplified schematic of a ZEPP is shown in Figure 1

The core of CES' technology is an oxy-fuel combustor adapted from rocket propulsion technology. This combustor burns a clean gaseous and/or liquid fuel with gaseous oxygen at near-stoichiometric conditions in the presence of recycled water. The combustion products are primarily a mixture of steam and CO2 at high temperature and pressure. Acceptable fuels include natural gas, syngas from coal, refinery residues, landfill gas, bio-digester gases, and renewable fuels such as glycerin from bio-diesel production facilities.

Figure 1. The CES ZEPP Concept

The combustion products drive conventional or advanced steam turbines or modified aero-derivative gas turbines operating at high temperatures and intermediate pressures. Every component in the CES process, except for the oxy-fuel combustor/gas generator and reheater (RH), is commercially proven and is standard in power generation or other commercial application. The CES system has the following additional attributes:

• Combustion technology that can use multiple opportunity fuels
• Zero-Emission Power Plants with full CO₂ recovery
• Efficient, cost-effective technology for enhanced oil and gas recovery (EOR and EGR) and enhanced coal-bed methane (ECBM) recovery processes
• Peaking power plant technology that addresses reliability-must-run (RMR) requirements
• Capability to produce power and hydrogen for the "hydrogen economy"
• Improved efficiencies with advanced turbine designs

CES is now concentrating its efforts on commercial opportunities that utilize the oxy-fuel combustion process with existing power turbine technology. These projects typically have the potential of multiple installations that provide the investor a suitable internal rate of return (IRR) without tax credits or government funding. Near-term opportunities include:

• Producing zero emissions electric power for merchant and/or site specific loads and CO₂ for enhanced oil or gas recovery (EOR or EGR) applications.
• Providing peak electric generating service to improve grid reliability in a low cost, ultra low emissions manner.
• Utilizing nontraditional fuel sources (i.e. emulsified fuels, glycerin, etc.) in the production of heat to produce power, steam, CO₂ and hydrogen.
• Thermal energy for the desalination of water in areas requiring electricity and CO₂ for EOR.
• Capturing waste heat/cold (LNG) energy to improve process efficiencies and economics while decreasing on site emissions.
• Retrofitting existing "must run" facilities with ultra low power generation as a means to supplement and maintain existing critical generation.
• Enhancing coal bed methane recovery through CO₂ injection and the production of oil from tar sands with power, steam and hydrogen generation.

With continual unrest in energy producing areas of the world, increasing energy prices and greater awareness of the problems associated with global warming, there is a clear need to develop more efficient energy systems that make use of a wider variety of fuel sources with lower plant emissions. The CES combustion technology addresses each of these issues. By eliminating the air in the combustion process, NO_x emissions are lower then current "best available control technology" (BACT). In addition, the power plant emissions are a mixture of CO₂ and steam. By condensing the steam, the CO₂ can be used in commercial applications such as EOR or sequestered. Since the combustion process operates at high temperatures and pressures and uses water/steam as a cooling agent, many problematic fuels can be burned in a clean and efficient manner. Finally, with advanced turbines, greater efficiencies will be achieved. CES is in the forefront in each of these areas.

Efforts to date have focused on securing the intellectual property rights and on developing and demonstrating the first commercial oxy-fueled gas generators. Significant milestones have included:

• In 2000 CES successfully completed "proof of concept" testing with a 110 kW prototype (Figure 2), funded in part by an energy innovations small grant from the California Energy Commission (CEC).
• CES fabricated a 10 MW_e (20 MW_t) gas generator, funded in part by the U.S. Department of Energy (DOE) under their "Vision 21" program. The testing of this oxy-fuel combustor was successfully completed in February 2003 (Figure 3).

Figure 2. Prototype Oxy-Fuel Gas Generator

Figure 3. 20 MWt Oxy-Fuel Gas Generator

• In 2002 the California Energy Commission awarded CES a contract to design and build a demonstration plant based on CES technology and the 20 MW_t oxy-fuel gas generator. Mirant, Air Liquide, and the DOE were participants in this $8 million project.
• In August 2003, CES acquired an idle 5 MW_e biomass plant, which was re-powered as a natural gas fueled near-zero-emission power plant (Figure 4). That facility provided the site for the CEC sponsored durability and reliability demonstration of the 20 MW_t gas generator. The first synchronization to the grid occurred in February 2005. More than 300 starts and 1300 hours of operation were logged through March 2006. A report describing the reliability of the oxy-fueled combustion components and overall power plant can be found in the Final Report to the CEC.
• Subsequent oxy-fueled combustor tests have been conducted using various alternative fuels including simulated coal syngas, landfill gas, glycerin (a by-product of bio-diesel production), and MSAR™ (Multiphase Superfine Atomized Residue, Quadrise Canada Corp.) a stabilized emulsion of heavy petroleum refining residuum in water.

CES' innovation has been to apply rocket engine technology to oxy-fuel combustors/gas generators and high-temperature, high-pressure turbines from aerospace applications to power generation, much like the process by which aircraft jet engines were adapted for aero-derivative turbines in conventional power plants. CES' products consist of the intellectual property (design, manufacturing, assembly, operations, etc.) of high pressure oxy-fuel combustor/gas generator systems that can be incorporated into numerous energy production cycles to produce CO2 with zero or near zero emissions to the atmosphere.

Figure 4. Kimberlina Power Plant

Having validated the CES technology, the company is now involved in the next stage of product development by entering into various agreements for modest-sized (50 to 100 MW_e) ZEPPs based on present-day steam turbine technology. With the increased focus on greenhouse gas emissions and global warming, CES is finding a high level of interest in zero emissions power plants. These facilities represent the ultimate answer for preserving the environment: stackless power plants with all combustion exhaust gases being safely sequestered in saline aquifers or usefully employed to recover additional fossil fuels. A number of projects are currently competing to be the first global Zero Emission Power Plant and CES is providing the oxy-fuel combustor for each of them. The following is a summary of the lead projects.

CES has designed the combustor and control system for the 170 MW_t Dutch natural gas SEQ-1 Project. This Zero Emission Power Plant involves the use of a modified CES process in which oxy-fuel combustion operates at modest pressure (~34.5 bar, 500 psia) on recovered natural gas from a "depleted" gas field. The process raises steam in a compact HRSG that drives conventional steam turbines. This is a nominal 50 MW_e power plant that uses the CO₂ exhaust stream for enhanced gas recovery (EGR). Several unique factors combine to favor the commercial viability of this project: (1) the Dutch government has legislation in place that subsidizes climate-neutral sources, including zero-emissions combustion systems, in a similar fashion as wind, solar, and biomass, (2) the geology of the targeted gas field has been determined to be suitable for effective EGR, (3) the project is to be located where governmental financial stimulation of employment and business activity is available, and (4) Dutch developers, working with CES, have brought together the necessary entities to evaluate the project and achieve a consensus that the project is viable. A consortium to develop the project has been formed. The Dutch government has committed €10 million to the SEQ-1 Project.

The Zero Emissions Norwegian Gas (ZENG) ZENG Project is being jointly developed by Lyse Energi AS, Nebb Engineering AS, Procom Venture AS, and CO2-Norway. These companies have formed ZENG AS for the purpose of developing projects based on the CES process. Additional support for this project effort is provided by the Norwegian Oil and Energy Department (OED), Shell, Statoil and the U.S. DOE. An artist's rendition of the proposed facility is shown as Figure 5. The goal of this program is to develop and demonstrate "near commercial" technology for Zero-Emission Power Plants (ZEPP) using Norwegian natural gas in combination with the oxy-combustion cycle developed by CES.

Figure 5. 50 MWe ZENG Project Concept

ZEPPs are of particular interest in Norway because of the high tax imposed on CO₂ emissions. It is a multi-phase effort as follows: Phase 1 was a Concept and Feasibility Study and Phase 2 involved pre-engineering and qualification. Subsequent phases entail construction of a 50 MW_e demonstration power plant near Stavanger, Norway. Later, a high-efficiency 200 MW^e ZEPP will be built at a Norwegian location to be determined. The Phase 1 study was completed in July 2004 and a decision was made to initiate Project Phase-2: Pre-Engineering and Qualification in late 2005.

In California, there is growing interest in the ZEPP technology. A lead project is a proposed 50 MW_e plant that could provide CO₂ to a III WestCarb Project. WestCarb is a collaborative research project that brings together dedicated scientists and engineers from 70 public agencies, private companies, and nonprofits to identify and validate the best regional opportunities for keeping CO₂ out of the atmosphere; thereby reducing mankind's impact on the climate. In Phase III, WestCarb plans to conduct a large-volume geologic sequestration test over a 10 year period. The goal of the project is to inject 1,000,000 or more tons of CO₂ annually for approximately four years into a formation deemed to be among the best large-scale commercial storage candidates in California.

The project will be partially funded by the U.S. Department of Energy and the California Energy Commission. Their potential funding has brought together a coalition of utilities, oil/gas producers, equipment manufacturers and others interested in using CES' oxy-fueled combustion technology to build, own and operate a zero emissions commercial power plant. The proposed facility will have a 20+ year life with the CO₂ used in enhanced oil recovery processes after the projected WestCarb Phase III purchases. A combined CO₂/electric facility produces competitively priced electricity and CO₂ in addition to being the first ZEPP facility in the U.S. This facility could be in commercial operation in late 2010. CES has a potential site for the facility and identified equity and debt financing partners subject to final negotiation of contract terms and conditions.

CES is developing several additional projects using the ZEPP technology to generate a commercial source of CO₂. The largest single market for CO₂ produced in an oxy-fuel combustion process is in enhanced oil recovery (EOR) applications. EOR is the injection of fluid or gas into an oil reservoir to force more oil to the surface. Until now, EOR using CO₂ has been feasible only in limited regions since the major natural U.S. sources of CO₂ are localized. Accordingly, most CO₂ floods are in West Texas, not far from large deposits of CO₂ in New Mexico and Colorado. By linking the generation of power and CO₂ together with the CES ZEPP technology, a "triple benefit" is achieved: carbon dioxide, a major greenhouse gas, is sequestered; zero emission power is generated; and additional oil is produced from existing wells thereby lowering U.S. dependence on foreign supplies.

The potential demand for CO₂ for EOR is staggering. Based on an Advanced Resources International study, the potential demand for CO₂ could be as high as 20 billion-30 billion tons over the next several decades. This represents a 13-times increase over the daily EOR usage today. The driving force behind this increase is the fact that EOR floods may be the most cost effective method to achieve a significant increase in production from mature oil producing wells. The CES oxy-fuel gas generator could be a major factor in combining the power generation companies with the oil industry in various alliances to meet the demand for CO₂ and zero emission power plants.

With the encouragement of utility companies, CES has developed a low-emissions, sequestration-ready (LESR) power plant concept to assist them in meeting their peak power requirements. This concept involves an oxy-fuel combustor that powers a CES-modified J79 aero-derivative turbine. The CES J79 peaking power plant (Figure 6) is a simple, low-cost alternative to conventional peaker plant technologies. The main plant components are a CES oxy-fuel combustor (gas generator), CES-modified J79 gas turbine, liquid oxygen tank, vaporizer, demineralized water supply system and natural gas supply.

Figure 6. CES J79 Peaking Power Plant

The CES J79 turbine is a GE J79 turbine modified by removing the air compressor and installing a 30 MW_e generator connected to the air compressor shaft. An additional 10 MW_e is generated by a power turbine that receives the exhaust from the CES J79 main turbine.

In most installations, natural gas, provided by the local utility company at 300 to 600 psig, will be the input fuel. The J79 Peaker can be supplied with oxygen from a pipeline, by direct connection to an oxygen plant, or with liquid oxygen delivered by truck and stored in a pressurized tank. Cold air generated from vaporizing the liquid oxygen can be delivered to nearby air breathing equipment to improve its operating efficiency.

The CES J79 Peaker has a capital cost approximately 50% less than a comparable combustion turbine. For example, a 50 MW_e CES Peaker is estimated to cost about $25 million. This low capital cost is achievable because the CES turbine produces up to three times as much power as the comparable air-breathing gas turbine peaker plant. This is possible because the CES oxy-fuel peaking plant does not require an air compressor that constitutes a major parasitic energy load. In addition, the CES Peaker does not require expensive air pollution control equipment.

The CES J79 Peaker can be situated where low capital costs and ultra-low NO_x (below 1 ppm) emissions have sufficient value. While the liquid oxygen cost significantly increases the variable cost of the unit, there are many applications where a power supplier would prefer to minimize the capital investment particularly where the unit is meeting a needed peaking load of 1,000 hours per year or less. In addition to the low capital cost and ultra-low emissions, the CES J79 system has following desirable attributes.

• Fast start - full load in less than 10 minutes
• Output unaffected by ambient temperature
• Three times the power output when compared to conventional gas turbines
• Easy to retrofit for full CO₂ capture
• Qualifies for DOE loan guarantee for up to 80% of the capital cost

Another opportunity for the CES technology is utilizing the proprietary oxy-fuel combustor with water emulsified and water soluble fuels (i.e. MSAR™, Orimulsion, glycerin, etc.). Applying such fuels in CES technology opens new pathways to multiple products including power, fossil fuel recovery/production, heat, nitrogen and CO₂. Due to the combustion characteristics, presence of water, and impurities, these fuels are generally unsuitable for burning in conventional combustion systems without extensive facility retrofits. As a result, the components with heating value in these fuels are often unwanted or low-value by-products but represent a significant economic opportunity when combined with an appropriate combustion technology.

The oxy-fuel combustion process can utilize the water that is inherent with these sources of energy to control flame temperature. The emulsified or water soluble fuels can be burned in the gas generator, as presently configured, by injecting the fuel into the main water injection circuit. With this approach, some gaseous fuel is still required because the main injection water does not rapidly mix with the oxygen. This causes reaction times to be longer than for gas only fuels. Tests in the 20 MW_t oxy-fuel combustor indicate that up to 50% of the total heat release can come from such fuels and 50% from a gaseous fuel (methane or syn-gas) with little modification to the current gas generator.

CES is performing oxy-fuel combustor design studies that would allow use of 100% liquid fuel by replacing the current injector with a fuel-specific injector. A fuel specific gas injector could significantly improve the economics of a project by eliminating the need for a supplemental, higher-value gaseous fuel. CES has considerable experience in developing fuel specific combustion designs and in testing the oxy-fueled burning characteristics of potential fuels at its Kimberlina test facility.

CES is in early stage discussions regarding the use of the oxy-fueled combustion technology in other applications. In many instances, it is a potential customer approaching CES regarding the application of oxy-fuel combustion technology to their particular business process. The common theme for all of these applications is the need for one of more of the following products: zero emissions power, electric generation having NO_x emissions lower than current BACT requirements, commercial CO₂ for enhanced fossil fuel recovery (EOR, EGR, or ECBM), large quantities of process heat, and a source of process nitrogen. A few of these applications are described in the following paragraphs.

The CES power system can be configured for cogeneration at desalination plants. This concept is particularly attractive in desert areas near petroleum reservoirs where electricity, water and CO₂ are required. The CES plant has an efficiency advantage over conventional cogeneration systems, not only because it produces "injection ready" CO₂ for EOR, but because it is also a net producer of water. For example, a 550 MW_e CES power plant could produce about 180 million gallons of water per year.

LNG facilities are frequently located in areas that can use CO₂. The need to gasify LNG at a receiving terminal presents a good cogeneration opportunity for conventional technology. Because the CES system can use the cryogenic LNG as a heat sink for its air separation unit, steam condenser and compressors; an overall efficiency advantage over conventional generation can be achieved. This can lead to an economical source of CO₂. These types of installations are particularly attractive in the Southeast where there is a need for CO₂ in the EOR/EGR industries, multiple pipeline corridors for delivery of the CO₂ exist and the LNG import facilities operate in a base load manner.

The CES J79 technology can also be used in reliability-must-run (RMR) applications. In these instances, a unit is located adjacent to an existing power plant that must be operated during peak load conditions; but is limited in operations due to environmental emission constraints. The ultra low emissions of the oxy-fuel combustion process within the CES J79 system can compliment the existing unit(s) in a manner where additional power is generated within the permit limits of the facility.

Currently, natural gas from coal beds accounts for approximately 7% of total natural gas production in the United States. It is estimated that one third of the natural gas in the Rocky Mountain region is coal bed methane. Producing coal bed methane requires the production and disposal of large quantities of formation water. This has caused companies to develop an enhanced coal bed methane recovery process of injecting CO₂ into the coal beds that are too deep in the ground to be mined directly. The ZEPP technology is an excellent source for this CO₂ while providing zero emissions electric power to the grid. The CES technology may be a major factor in uniting the power generation and coal production industries in various alliances to produce CO₂, natural gas and zero emissions power.

The applications described above set the stage for the second generation (within ~5 yr) units that will be based on oxy-fueled reheaters and intermediate pressure (IP) turbines capable of handling the high temperatures and pressures drive gases from CES' oxy-fuel gas generators. CES and Siemens have a strategic relationship to develop the next generation of power turbines. Recognizing the need for this technology, the DOE has contracts with both CES and Siemens Power Generation, Inc. to develop advanced combustors and turbines capable of operating on coal syngas and similar fuels. Other project participants include ConocoPhillips, Kinder Morgan, Nexant, and Air Products. This program will enable 100% separation and capture of CO₂ with high power cycle efficiencies. The improved efficiencies may make the CES ZEPP systems the Best Available Power Generation Technology (BAPGT) for Zero Emission Systems.

The second generation ZEPPs appear most likely to find application in, at least, five areas: (1) "peaker" units as described above with greater output and cycle efficiencies and complete CO₂ recovery, (2) larger natural gas fired systems (200-400 MW_e) where the recovered CO₂ can be used beneficially such as EOR, EGR, or enhanced coal-bed methane recovery, (3) larger natural gas fired systems as described in (2) that optimize the production of electricity, heat, desalinized water and commercial CO₂, (4) customized systems operating on gasified plant, animal, or municipal waste biomass, glycerin or bio-derived gaseous fuels that represent nuisance wastes and/or present environmental problems and (5) industrial scale (~50 MWe) plants operating on syngas derived from gasification of coal. Truly commercial, large-scale (400-1000 MW_e) ZEPPs based on gasified coal or opportunity fuels such as petcoke appear feasible within 10 years. They would produce power at a cost comparable with today's very best combined cycle systems, and would be emissions free. Plants that do not have a commercial use for CO₂, will likely be equipped with a bioreactor system that converts the CO₂ into clean, renewable bio-fuels that can be marketed or used to supplement the fuel supply into the oxy-fuel combustor, or the CO₂ could be sequestered in deep saline aquifers.

The second generation equipment will also be able to address a growing need for hydrogen to meet the emerging "hydrogen economy". The CES oxy-fuel combustor can generate hydrogen as part of its combustion process by simply reducing the oxygen input and increasing the water input. The hydrogen can then be separated with existing technology and utilized in refinery processes, vehicles, fuel cells and other applications. As the hydrogen market develops, CES expects that various installations will be utilized to produce a combination of CO₂, hydrogen, heat and electricity.

The CES oxy-fuel combustion process and ZEPP technologies address many of the challenges facing the energy industry. CES' oxy-fuel power system is superior to other CO₂ capture technologies because it avoids the emission of other pollutants such as NO_x and particulates, and it has the potential to be more efficient than today's most advanced combined cycle power plants. CES has taken care to establish robust intellectual property rights to its technology and the potential for a sustainable competitive advantage in the market for climate neutral power technologies. The growing concerns about global warming and GHG emissions is creating an international market for zero emission power technologies. CES' oxy-fuel power system represents an enabling technology for a variety of applications including: enhanced oil and gas recovery, low-cost, pollution-free peak power, coal-syngas power plants, grid reliability services, coal-bed methane production, LNG-receiving terminal co-generation, desalination, hydrogen production, bio-diesel production.

CES believes that the oxy-fuel combustion process and Zero Emission Power Plant represents a practical, near term solution for tomorrow's energy requirements.