Recapture of Energy and Metals From MSW and ASR

CarbonTech, LLC is the business vehicle to commercialize the licensed CATO Research Corporation process (US Patent No. 7,425,315) to generate an energy rich source of carbon from wastes such as municipal solid waste (MSW) and automobile shredder residue (ASR). With a focus on renewable energy technology, CarbonTech is in a unique position to reduce waste to landfills by 90%, generate a coal equivalent source of sustainable fuel to help reduce our dependence on fossil fuels, and recover metals for scrap recycling purposes.

Supplemental Pit Fire Control Deluge System: Spokane Regional Waste to Energy Facility

After sixteen years of operation, it became apparent that the pit fire protection system installed during construction of the Spokane Regional Waste to Energy (WTE) Facility (1989–1991) was inadequate. A risk analysis was performed by Creighton Engineering Inc., a fire protection consulting firm, hired by the Spokane Regional Solid Waste System (Regional System) and Wheelabrator Spokane Inc. With input from Spokane County Fire District 10 and the City of Spokane Fire Department, a replacement supplemental fire protection system was designed and ultimately installed. This paper will describe the problems with the once state of the art fire system and the planning, design and installation of the new system.

Elements of a Successful Waste-to-Energy Boiler Upgrade

Great River Energy operates a waste-to-energy plant in Elk River, Minnesota. The plant burns 850 tons per day of refuse derived fuel (RDF) in three boilers, and its three steam turbines can produce 32 MW of electricity. In the largest of the three units, the No. 3 Boiler, steam generation was restricted by carbon monoxide (CO) and nitrogen oxides (NOx) emission limits. The plant had an interest in improving the combustion performance of the unit, thereby allowing higher average RDF firing rates while staying within emissions compliance. The project was initiated by an engineering site visit and evaluation. The boiler had a history of unstable burning on the stoker grate, which required periodic natural gas co-firing to reduce CO levels. As an outcome to the evaluation, it was decided to install a new overfire air (OFA) system to improve burnout of combustible gases above the grate. Current and new OFA arrangements were evaluated via Computational Fluid Dynamics (CFD) modeling. The results illustrated the limitations of the original OFA system (comprised of multiple rows of small OFA ports on the front and rear furnace walls), which generated inadequate mixing of air and combustible gases in the middle of the boiler. The modeling illustrated the advantages of large and fewer OFA nozzles placed on the side walls in an interlaced pattern, a configuration that has given excellent performance on over 45 biomass-fired boilers of similar design upgraded by Jansen Combustion and Boiler Technologies, Inc. (JANSEN). Installation of the new OFA system was completed in April of 2008. Subsequent testing of the No. 3 Boiler showed that it could reliably meet the state emission levels for CO and NOx (200 ppm and 250 ppm, respectively, corrected to 7% dry flue gas oxygen) while generating 24% more steam than a representative five month period prior to the upgrade. This paper describes the elements that led to a successful project, including: data collection, engineering analyses, CFD modeling, system design, equipment supply, installation, operator training, and startup assistance.

SYNCOM-Plus: An Optimized Residue Treatment Process

In a large-scale pilot plant, studies on wet-mechanical treatment of bottom ash using the SYNCOM-Plus process were carried out by MARTIN GmbH in the SYNCOM waste-to-energy plant in Arnoldstein, Austria (approx. 11000 kg/h waste throughput). Granulate of > 2 mm and fine fraction of < 5 mm were produced by dry screening, washing and wet screening. Additionally, sludge was separated from the wash water. The fine fraction and sludge as well as the boiler ash were recirculated into the furnace. In conclusion, the SYNCOM-Plus process meets all requirements which need to be complied with in an optimized and effluent-free commercial residue treatment process for the recovery of industrial products. This paper documents successful continuous operation of the SYNCOM-Plus process in direct connection with bottom ash discharge as well as the effects on combustion, flue gas composition and residue qualities.

Emissions Performance of a Novel Combustor Burning Shredded Wood

The Air Force Research Laboratory, Airbase Technologies Division (AFRL/RXQ) is engineering and evaluating the Transportable Waste-to-Energy System (TWES). This trailer mounted system will convert military base waste and biomass waste streams to useful heat and power. The Department of Energy (DOE) Federal Energy Management Program (FEMP) is a TWES funding partner. The first stage of the project is a suspension-type combustor (furnace). The furnace has been built and tested. A key feature of the furnace system is its unique patented combustion coil design. The design is intended to maximize ablative heat transfer by increasing particle residence time near a radiant ignition source. The innovative features of the design are targeted at ensuring that the system can be highly fuel-flexible to convert a variety of biomass and other waste streams to energy while demonstrating very low emissions. In 2008, the unit underwent two days of emissions stack testing using established Environmental Protection Agency (EPA) testing protocols. During the testing, extensive real-time data were also collected. This paper presents the data and corresponding analysis of the recent emissions testing performed while utilizing dry wood chips as a control fuel. Detailed emission comparisons are presented using publicly available information from commercial units and from a similarly sized experimental system for small biomass combustion. Key combustion efficiency factors, such as carbon monoxide emissions and nitrogen oxide emissions are presented. The authors also provide commentary on the results for next generation units and the use of this mode of energy conversion for small scale systems.

The Center for Sustainable Utilization of Resources: Quantifying Climate Change Impacts of Managing Wastes

The environmental impact and potential for utilization of the billions of tons of used products and materials discarded each year by humanity is immense. The sheer magnitude of the materials and complexity of waste management and reuse make the issue of quantifying impacts and best practices all the more difficult. In recognition of this task, the Earth Engineering Center (EEC) of Columbia University and the Environmental Engineering Group of North Carolina State University combined resources in 2008 to form a research organization that is focused on defining and promoting best practices for sustainable waste management. This is the Center for Sustainable Use of Resources (SUR; wwwSURcenter.org) and its mission is to quantify the greenhouse gas emissions and other life cycle impacts of various “waste” management practices; and use this information for advancing the best practical means for managing used materials, in the U.S. and globally. The SUR Center builds on the strengths of past research at Columbia and North Carolina State on recycling, composting, waste-to-energy, and landfilling. This paper describes some of the research work completed and underway at the Center.

Handling Oahu’s Waste Disposal

Oahu has special needs and requirements when it comes to dealing with solid waste on the island. The City and County of Honolulu has successfully addressed this problem in the past and is working on solutions for the future. Five percent of the island’s electrical power has been generated reliably from the 2000 tons per day of waste processed by their H-POWER Waste-to-Energy Facility. The facility has been processing waste for nearly twenty years and the volume of refuse going to the landfill is reduced by 90 percent. Honolulu is considering the best solutions for the island’s waste for the coming years. Waste-to-energy works in partnership with recycling to reduce the island’s increasing waste volumes. Recycling programs are in place and additional recycling measures are being considered. Landfill space is limited and questions exist regarding the ongoing use of the existing landfill and what will happen when it is closed. In an island setting, some alternatives available to other areas such as long haul to distant landfills are not available to bridge solid waste issues. Therefore practical solutions must be found and implemented in a timely manner. A number of initiatives and plans are in development. Measures are underway to prepare the H-POWER facility for future emission requirements and operation for the next twenty years. Steps have been taken toward expansion of the existing facility. Permitting and negotiations with agencies and utilities are under way. This paper will explore and expand upon these issues showing how they are interrelated to one another.

The Design and Operation of an Advanced NOx Control System on the New 636TPD MWC at the Lee County WTE Facility

In September of 2007, a new 636TPD Municipal Waste Combustor was brought on line at the Lee County WTE Facility in Fort Myers, FL operated by Covanta Energy. This unit was the first new Waste to Energy unit built in the United States in a number of years and included a lower permitted daily average NOx emissions requirement of 110ppm @ 7%O2 while maintaining ammonia slip to less than 10ppm. To meet this new stringent NOx emissions requirement, the boiler was designed with advanced combustion controls including Flue Gas Recirculation combined with a urea based Selective Non-Catalytic Reduction Process to provide a combined NOx reduction of approximately 70% while maintaining the required ammonia slip. The SNCR System provided by Fuel Tech was designed with 3 levels of seven wall injectors installed in the upper furnace. Both boiler load and Furnace Gas Temperature were used as a feed forward control with the CEM NOx signal as a feed back to automatically select the injector levels and reagent feed rates to maintain the targeted NOx while also maintaining ammonia slip control. This paper will outline the design considerations, the details of the process and the operation of the systems on this unit.

New Process for Achieving Very Low NOx

Over the last two and a half years, Covanta Energy, working with their technology partner, Martin GmbH of Germany, has developed and commercialized a new technology for reducing NOx emissions from Energy from Waste (EfW) facilities. NOx levels below 60 ppm (7% O2) have been reliably achieved, which is a reduction of 70% below the current EPA standard and typical levels of today’s EfW facilities in the United States. This technology represents a significant step forward in NOx control for the EfW industry. The technology, known as VLN™, employs a unique combustion system design, which in addition to the conventional primary and secondary air streams, also features a new internal stream of “VLN™-gas,” which is drawn from the combustor and re-injected into the furnace. The gas flow distribution between the primary and secondary air, as well as the VLN™-gas, is controlled to yield the optimal flue gas composition and furnace temperature profile to minimize NOx formation and optimize combustion. The VLN™ process is combined with conventional, aqueous ammonia SNCR technology to achieve the superior NOx performance. The SNCR control system is also integrated with the VLN™ combustion controls to maximize NOx reduction and minimize ammonia slip. A simplified version of the process, known as LN™, was also developed and demonstrated for retrofit applications. In the LN™ process, air is used instead of the internal VLN™ gas. The total air flow requirement is higher than in the VLN™ process, but unchanged compared to conventional systems, minimizing the impact on the existing boiler performance and making it ideal for retrofit applications. Covanta first demonstrated the new VLN™ and LN™ processes at their Bristol, Connecticut facility. One of Bristol’s 325 TPD units was retrofitted in April of 2006 to enable commercial scale testing of both the VLN™ and LN™ processes. Since installing and starting up the new system, Bristol has operated in both VLN™ and LN™ modes for extended periods, totaling more than one year of operation at NOx levels at or below 60 ppm (7% O2). The system is still in place today and being evaluated for permanent operation. Based on the success of the Bristol program, Covanta installed LN™ NOx control systems in a number of other existing units in 2007 and 2008 (total MSW capacity of over 5000 TPD), and is planning more installations in 2009. All of these retrofits utilize the Covanta LN™ system to minimize any impacts on existing boiler performance by maintaining existing excess air levels. Going forward, Covanta is making the LN™ technology available to its existing client base and is working with interested facilities to complete the necessary engineering and design modifications for retrofit of this innovative technology. For new grassroots facilities, Covanta is offering the VLN™ system with SNCR as its standard design for NOx control. An additional feature, particular to VLN™, is the reduced total combustion air requirement, which results in improved boiler efficiency. This translates into increased energy recovery per ton of waste processed. In addition to introducing the VLN™ and LN™ processes, this paper will provide an overview of the Bristol development and demonstration project. NOx and NH3 slip data from Bristol will be presented, illustrating the extended operating experience that has been established on the system. Other operating advantages of the new technology will also be discussed, along with lessons learned during the start-up and initial operating periods. The VLN™ technology has been demonsrated to decrease NOx emissions to levels well below any yet seen to date with SNCR alone and is comparable to SCR-catalytic systems. The result is a significant improvement in NOx control for much less upfront capital cost and lower overall operating and maintenance costs. VLN™ also also goes hand in hand with higher energy efficiency, whereas SCR systems lower energy efficiency due to an increased pressure drop and the need for flue gas reheat. The commercialization of the VLN™ and LN™ processes represents a significant step forward in the reduction of NOx emissions from EfW facilities.

Control of Fine Particulate Matter by Means of High Efficiency ePTFE Membrane Filter Laminates

The COUNCIL OF THE EUROPEAN UNION has enacted laws to improve the quality of the ambient air: The “COUNCIL DIRECTIVE 1999/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air” and the “DIRECTIVE 2008/50/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 21 May 2008 on ambient air quality and cleaner air for Europe”. The Member States had to bring into force the laws, regulations and administrative provisions necessary to comply with these Directives. These Directives are raising the expectations on the reduction of fine particulate matter on the potential emitters, mainly public traffic, industry and waste-to-energy (WtE) plants. Although there is currently no European regulation on stack emissions of fine particulate matter, local regulatory authorities have tightened the emission limits of total particulate matter. For example, quite a number of Italian WtE plants are expected to meet dust emission levels of less than 2 mg/m3. In order to assure compliance strong efforts and large investments have been made to optimize the efficiency of their APC system. Different dust filtration technologies will be compared and the filtration principles of depth filtration and surface filtration will be detailed. A comparison of an experimental study and the practical performance of the different technologies are discussed. Special focus will be given to the development and application of High Efficiency Membrane Filter Laminates for retention of fine particulate matter. These filter materials consist of micro-porous expanded PolyTetraFluoroEthylene (ePTFE) membranes laminated onto suitable backing materials, retention rates of > 99.99% of PM2.5 have been achieved. A number of large European WtE plants have already completed their APC upgrades by using the High Efficiency Membrane Filter Laminates. Some of them are on operation for a couple of years, performance reviews will be detailed.