Innovation in Global Power - Parsons Brinckerhoff

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Renewables – The Risks, Concerns and Potential Converting Landfill Gas to High-Btu Fuel By Roger J. Lemos, Boston, Massachusetts, 1-617-960-4898, lemos@pbworld.com Landfill gases can no longer be released into the atmosphere in the USA. PB helped to design two of the largest and most sophisticated plants that clean these gases and convert them to a high-quality fuel suitable for use in homes, industry and energy generation. These facilities run unattended 24 hours/day. Acronyms/Abbreviations Btu: British thermal unit kJ/Nm 3 : kiloJoule per normal cubic meter Mmscfd: Million standard cubic feet per day Nm 3 /day: Normal cubic meters per day Figure 1: Greentree Landfill Gas Facility. The building housing the gas cleanup equipment is flanked by the SulfaTreat TM removal tanks on the left and the electrical switchgear building on the right. Figure 2: Interior of Greentree’s gas processing facility. The gas compressors raise the gas pressure to 200 psig before it reaches the Air Liquide membrane separation equipment. http://www.pbworld.com/news_events/publications/network/ PB teamed with EMCOR Energy and Technology of Connecticut, the construction contractor, to engineer, procure, and construct (EPC) two high-Btu landfill gas projects for Beacon Energy of McLean,Virginia—the Greentree Landfill Gas Project and the Imperial Landfill Gas Project. Our role was to engineer and design a gas processing facility that would take raw landfill gas from a landfill and clean it through a process of compression, filtering, moisture removal, and membrane separation so that it would meet the gas quality requirements of the interstate gas transmission system. The product gas is transported via pipeline to the interstate gas pipeline system and then sold as green energy. These two projects are among the largest and most technologically sophisticated projects of their kind ever undertaken. The Greentree Landfill Gas Project (Figures 1 and 2) has the capacity to produce 5.38 mmscfd (144,453 Nm 3 /day) of high Btu product gas, and the Imperial Landfill Gas Project has the capacity to produce 2.69 mmscfd (72,226 Nm 3 /day) of the same. PB was responsible for: • Architectural, civil, structural, mechanical, electrical, and controls system design • Startup and performance testing of each facility to ensure that the projects met the production and quality requirements of the contract. Background and Overview of the Projects The decomposition of waste in a landfill produces methane gas and carbon dioxide that, if not controlled, are released to the atmosphere. US Environmental Protection Agency (EPA) regulations require these landfill gases be captured and thermally destroyed to reduce the greenhouse gas emissions. All landfills are required to have top and bottom liners and gas collection systems to capture the landfill gas. Thermal oxidizers (known as flares) are then used to destroy the methane gas. The EPA has a program called Landfill Methane Outreach Program that encourages the beneficial and productive use of the methane produced by landfills as a fuel source. The composition of landfill gas is typically about 50 to 55 percent methane and 30 percent carbon dioxide. Water vapor, oxygen, nitrogen, hydrogen sulfide and some trace elements make up the remainder of the gas composition. The Btu content of landfill gas is low, but sufficient to produce heat in a boiler or electricity in a reciprocating gas engine. High-Btu landfill gas projects can raise the Btu value of the landfill gas considerably, however, and remove harmful contaminants. The high-Btu projects we designed increase the methane content to about 95 percent by removing other elements of the landfill gas by the following methods: •Carbon dioxide and oxygen: a membrane separation technology provided by Air Liquide •Water vapor: a series of knock-out tanks, demisters and coalescing filters •Hydrogen sulfide: a chemical absorption process. The resultant product, or residue gas, has a Btu value of more than 960 Btu/cubic foot (37,684 kJ/Nm 3 ). It meets all the requirements for pipeline quality gas that is used in homes, industry, and energy generation. PB Network #68 / August 2008 54
Renewables – The Risks, Concerns and Potential Project Challenges Met on Time We started working with the project developer, Beacon Energy, in September of 2004 to meet the first challenge of this project, which was to get project financing. It was at this early stage that we elected to team up with EMCOR Energy and Technology. Working with these two firms, we reviewed the feasibility of both projects, evaluated technical alternatives, visited the project sites, and developed preliminary engineering solutions that would meet the technical and commercial requirements. These efforts were successfully culminated when in July of 2006 the project received $60 million in non-recourse financing from John Hancock Financial Services, Inc. A key factor in obtaining the non-recourse financing was the guarantees of schedule, cost, and performance in the EPC contract between Beacon Energy and EMCOR. Engineering and design of the two projects started in July of 2006 with the execution of the EPC contract. The challenges that faced PB during engineering and design included: • Specification and procurement of the gas blowers, compressors, Air Liquide membrane units, hydrogen sulfide removal system, electrical switchgear, and plant control systems • Coordination of the plant design with the upgrade of the landfill gas collection system, modification to the landfill gas flares, pipeline to interstate gas pipeline system, and utility electrical interconnection • Site civil grading and drainage • Building and equipment foundations • Mechanical piping systems • Electrical power and control systems • Plant control system. Construction of the Greentree Gas Processing Facility started in October of 2006 and was completed in August of 2007; and construction of the Imperial Gas Processing Facility started in November of 2006 and was completed in September of 2007. The aggressive construction schedule could not have been achieved without the cooperation of the members of PB’s civil engineering group and power hydro structural group, who were responsible for the site civil, grading and drainage, building foundation, and equipment foundation design. Project Successes Upon the completion of construction, PB conducted the performance testing to ensure that each facility was in compliance with the performance requirements in the http://www.pbworld.com/news_events/publications/network/ contract. They were, and both projects have been operating continuously since turnover to the client. They had many notable commercial, technical, and environmental accomplishments, including those that follow. Most Notable Commercial Accomplishment. These are the only landfill gas projects that have qualified for long-term non-recourse project financing. Project financing was difficult to obtain due to the size and complexity of the projects and the fact that unproven new technology would be used to process the landfill gas. Major Technical Accomplishment. The engineering and design of the landfill gas processing equipment and control systems was the major technical accomplishment. The membrane separation technology used to separate the methane gas from the landfill gas had never been used before at the scale of the Imperial and Greentree Projects. PB and EMCOR had to perform extensive engineering and design to integrate the gas collection, compression, moisture removal, hydrogen sulfide removal, and gas separation technologies into a seamless process that could run unattended 24 hours a day. A complete and fully automated plant control system had to be developed to allow the plant to be operated safely. Most Impressive Environmental Benefit. Harmful greenhouse gases were eliminated from the environment and converted into green energy, thereby also reducing dependency on foreign sources of energy. A quantification of environmental benefits, using the EPA’s Landfill Gas Energy (LFGE) Benefits Calculator, yields annual benefits equivalent to any one of the following, based on 15,000 standard cubic feet/minute (402 Nm 3 /min) of landfill gas being processed: • Reducing CO2 emissions by more than 200,000 tons/year • Removing emissions equivalent to more than 340,000 vehicles • Planting the equivalent of more than 490,000 acres of forest • Displacing the use of 4.0 million barrels of oil • Producing enough energy to heat approximately 112,000 homes. The significant technical and environmental accomplishments were recognized when the EPA’s Landfill Methane Outreach Program (LMOP) awarded the Greentree Project the 2007 EPA Project of the Year Award. Related Web Sites: • www.epa.gov/landfill Roger Lemos is a vice president with the PB Power group in Boston. Since starting with PB in 1994, Roger has worked on power projects throughout the USA ranging from 4 to 640 megawatts. 55 PB Network #68 / August 2008
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