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The Solid Waste Authority (SWA) of Palm Beach County (Florida) Palm Beach Renewable Energy Facility 1 (PBREF 1) originally went online in 1989. Babcock & Wilcox Power Generation Group Inc. (B&W PGG), Barberton, Ohio, in a joint venture with San Francisco-based Bechtel Corp., engineered and constructed the municipal solid waste (MSW) facility. It included two 324,000-pound-per-hour steam capacity boilers, a 62-megawatt (MW) turbine/generator, scrubbers, electrostatic precipitators and MSW processing and recycling systems. The design capacity is 2,000 tons per day of MSW, though the facility has consistently surpassed this.

PBREF 1 is a refuse-derived fuel (RDF) energy-from-waste facility designed to reduce the volume of waste sent to the landfill in Palm Beach County, Fla., while generating electricity and recovering metals from the waste stream. The facility successfully provides a 60 percent reduction by weight in the quantity of waste landfilled while supplying enough energy to power approximately 30,000 homes.

The plant has air pollution control equipment consisting of two spray dryer absorbers, two pulse jet fabric filter houses and nitrogen oxides (NOx) controls that ensure compliance with all environmental regulations.

The site consists of a landfill, a vegetation processing facility, a compost facility, one material recycling facility, household hazardous waste collection facilities and a network of six transfer stations. The SWA owns the facility, which Palm Beach Resource Recovery Corp. (PBRRC), a subsidiary of B&W PGG, operates.

As part of an agreement renewing B&W PGG’s operations and management contract through 2029, each party was to undertake major renovations to extend the facility’s life for an additional 20 years. PBRRC would be responsible for the fuel preparation equipment. SWA agreed to replace the two boilers and air pollution control equipment, replace the distributed control system, and upgrade a number of auxiliary systems.

Engineering and construction firm KBR was selected to install the boilers and design, supply and construct the balance of the renovations. B&W PGG, the original equipment manufacturer, refurbished the two boilers at the facility by designing, supplying and fabricating select boiler components. SWA’s consulting engineer, Malcolm Pirnie (an ARCADIS company), established the minimum technical requirements for the refurbishment and provided program management and project oversight.

The project kicked off in January 2009 with the start of detailed engineering and achieved substantial completion in April 2011. The total installed cost was $181 million.

Working with the SWA, the team developed the “minimum technical requirements” that formed the basis of design for the project.

The existing boilers were refurbished. Existing dry scrubbers, duct-work and ID fans were removed and replaced with new equipment. The precipitators were removed and replaced with more modern, lower-energy-consumption fabric filters designed to meet more stringent emission limits. Upgrades to the electrical and control systems included a new plant-wide distributed control system (DCS).

One key criterion for the SWA that presented numerous challenges to the team was that the work be performed on one unit while the second remained operational during demolition and construction.

The refurbishment of each unit occurred over a five-month period, with additional time for each unit’s startup and optimization.

The project team used a critical path method, construction-driven schedule for the engineering design, construction planning and management of the work.

The critical path ran through the boiler deliveries and installations to achieve substantial completion, with engineering and procurement-related activities included. The project construction schedule was planned to support both the preoutage phase and the outage phase. Construction commenced in April 2010.

Key to Success
Having five separate entities (in this case, the owner, operator, owner’s engineer, equipment supplier and contractor), each with a vested interest in the success of a project, can at times be challenging.

While experienced, high-performance project teams recognize that their success is intricately tied to the success or failure of their partners, establishing a cooperative and collaborative approach is often easier said than done. It takes commitment from all parties involved.

One key component to the success of this project was that the line management of each organization established an expectation that there would be a collaborative, consensus-building approach. Key issues were discussed openly and decisions were reached collaboratively. This approach set a positive tone that was prevalent throughout all phases of the project.

During construction activities, each party placed key personnel on site to assist in monitoring the project’s progress and in facilitating cost-effective resolutions to problems encountered in the field, whether the problems were related to design, fabrication or construction.

B&W PGG refurbished the two existing Stirling® power boilers by designing, supplying and fabricating critical boiler components, including Inconel® 625 weld overlay furnace panels, new air swept spouts, attemperators, superheaters, generating banks, economizers, tubular air heaters, combustion systems and steam drum internals.

The PBREF 1 furnaces and combustion systems were modified to a straight-walled furnace design with a PrecisionJet® overfire air system, which has resulted in better combustion mixing and controllability as well as in lower carbon monoxide and NOx emissions.

B&W PGG essentially replaced the existing boiler equipment from the combustion air fans to the outlet of the tubular air heater, reusing only the two steam drums and two mud drums. A total of eight new natural gas auxiliary burners were provided.

SWA procured the remaining equipment for the project. KBR, acting as SWA’s agent, specified the equipment and evaluated the supplier proposals.

The flue gas from each boiler is treated by pollution control equipment. Prior to this refurbishment project, the boiler flue gas was treated by a spray dryer absorber (SDA) and precipitator, one for each boiler.

The existing SDAs were demolished and replaced with two new dual-fluid atomizer SDAs, which remove hydrogen chloride (HCl) and sulfur dioxide (SO2) from the flue gas stream. The existing lime storage and preparation systems were reused. All of the existing pumps were rebuilt, and new piping was installed to supply lime slurry to the new systems. Precipitators (one for each boiler) downstream of each SDA were demolished and replaced with a pulse jet fabric filter (baghouse) for particulate control.

Other new equipment included a powdered activated carbon (PAC) system for mercury control, a selective noncatalytic reduction (SNCR) system for each boiler to control NOx emissions, an air compressor/dryer system and a distributed control system.

Additional equipment that was replaced essentially “in kind” included the bottom-ash handling system for each boiler and the fuel-feed distribution auger conveyors.

KBR (through its BE&K subsidiary) was the prime engineer, procurement and construction (EPC) contractor with overall responsibility for the project. KBR provided project management with the KBR project manager resident at the site, coordinating construction, engineering and procurement, and interacting with the owner’s site construction manager. KBR also provided construction, construction commissioning services, construction bulk materials and managed the procurement of the balance of plant equipment.

KBR completed construction commissioning, with SWA, B&W PGG and PBRRC performing plant startup and tuning of the systems.

Challenges
Challenges for this complex refurbishment project included several technical and contractual requirements for an operating plant.

The team had five months from start of demolition to first fire of RDF for each boiler while working adjacent to an operating boiler and steam turbine generator.

To overcome the schedule challenges, KBR’s execution strategy was to perform as much prework and preassembly as possible prior to the beginning of each boiler’s outage. Preassembly activities included welding boiler water wall panels on the ground and then bringing these 10-foot-wide-by-70-foot-long panels up over the boiler house and lowering them through the roof into position at the boiler.

Each pulse jet fabric filter module arrived on site fully assembled. Lagging and insulation were installed at ground level and then the entire module was set into place. Ductwork also was preassembled, insulated and lagged at ground level and then erected.

Perhaps the biggest preassembly undertaking was the approach taken for the SDAs. Each SDA was erected and welded on the ground; piping, insulation and lagging were installed and then the entire unit was lifted into place.

DCS conversion of an operating facility with systems common to both boilers and air pollution control trains also was a challenge.

To mitigate the risks associated with the DCS conversion, KBR deployed engineers to the site to perform an extensive field survey of existing conditions. In addition, configuration was reverse-engineered from the existing system. The conversion was completed over a 12-month period.

After the testing and optimization period for Boiler 1, the DCS configuration was copied and used as the starting point for Boiler 2. This substantially decreased the time required for commissioning, startup and optimization.

As a result of the refurbishment, both boilers are meeting or exceeding their RDF throughput and steam production targets. Emissions limits also have been met for all permitted pollutants. In addition, the project team met or exceeded its schedule targets and completed the project under budget.

SWA, Malcolm Pirnie, PBRRC, B&W PGG and KBR have since agreed to team together again to design and build a new waste-to-energy power plant, located due north of PBREF 1. The new facility will include three boilers as well as air pollution control. Construction on the new facility commenced in 2012, with commercial operation slated for May 2015.

The article was submitted by The Babcock & Wilcox Co., Barberton, Ohio. More information is available at www.babcock.com.