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Top Projects Feature Fuel, Operating Flexibility

Issue 12 and Volume 102.

Top Projects Feature Fuel, Operating Flexibility

By Douglas J. Smith, Senior Editor

Power Engineering magazine`s independent panel of judges has selected three projects to receive “Project of the Year” awards for 1998. The projects are:

Sweeny Cogeneration Project, Old Ocean, Texas

Sonoco No. 9 Boiler Project, Hartsville, South Carolina

Suralaya Steam Power Plant Units 5, 6 and 7, Java, Indonesia.

The awards, presented to the projects` owners by Power Engineering`s editors during the keynote session of POWER-GEN International `98, go to the owners and the major vendors who participated in the winning projects.

First Merchant Plant

Sweeny cogeneration plant in Texas is reported to be the first cogeneration facility in the United States that has been developed from the beginning as a merchant plant. The project, a 325 MW simple-cycle cogeneration plant, provides steam and electricity to the Phillips 66 Sweeny Refinery and Petrochemical Complex. As a merchant plant, it exports 240 MW of electricity to the Electric Reliability Council of Texas. The plant, located approximately 60 miles southwest of Houston, went into commercial operation on February 1, 1998.

According to the owners, Sweeny Cogeneration Limited Partners, the plant`s creative design includes:

An integrated water treatment plant,

Integrated gas compressors for fuel processing and

Dry Low NOx burners.

The Sweeny plant has three parallel 501D5A Siemens Westinghouse combustion turbines which exhaust into three Nooter Eriksen heat recovery steam generators (HRSGs). Each HRSG has an integral deaerator. Process steam supplied from the HRSGs is used in the Phillips Sweeny refinery and petrochemical complex. Should there be insufficient steam from the HRSGs, backup boilers, previously used for supplying process steam to the facility, are utilized.

Residue gas produced by the refinery and petrochemical plant is used by the cogeneration plant and the HRSG duct burners. According to the plant`s owners the residual gas has a hydrogen content of 10 to 20 percent but, on occasions, can reach 70 to 80 percent. Plant designers installed an on-line fuel blending system that monitors the refinery gas hydrogen content and blends in natural gas in amounts adequate to control fuel gas hydrogen content within acceptable limits. The residual gas supplies over 50 percent of the cogeneration plant`s fuel requirements.

In order to increase the pressure of residual gas to that required by the combustion turbines, four Dresser Rand gas compressors were installed. To minimize flashback and dynamic pressure fluctuations of the volatile and high flame temperature of the hydrogen rich residual gas, special consideration in the design of the combustors and the combustion turbine Dry Low NOx burner controls were required.

A new Ecodyne demineralized water treatment system, in tandem with an existing softener, supplies cooling water for the Sweeny refinery and petrochemical complex. After being used for cooling, the water is routed back to the cogeneration plant where it becomes the primary makeup for the HRSGs. Condensate from the Sweeny complex is also used for makeup water.

To minimize obstacles above and below ground, the cogeneration plant was constructed on a greenfield site. Unfortunately this was not possible for the equipment and piping connecting the refinery and petrochemical complex to the cogeneration plant. However, costs were minimized by having the engineering contractor review the site location of the equipment and pipe racks prior to any procurement and construction contracts being issued. This phase of the project included all of the piping for the steam, fuel gas, condensate, treated water, demineralized water, fire protection water, wastewater and potable water connecting the cogeneration plant to the Sweeny refinery and petrochemical complex.

Multi-Fuels at Sonoco

According to Paul Terpolilli, senior project manager at Foster Wheeler Energy Corp., the Sonoco No. 9 boiler project is the first application of Foster Wheeler`s “Compact Circulating Fluidized Bed (CFB) boiler.” The CFB boiler has been installed at Sonoco`s Hartsville, South Carolina mill. Foster Wheeler engineers say the benefits of the new design include fuel flexibility, low emissions, high availability, reduced space requirements, and reduced weight and capital cost.

Sonoco, headquartered in Hartsville, S.C., owns and operates 27 paper mills. The mills produce more than a million tons of recovered paper annually. However, to remain competitive, there is a need to reduce operating expenses and the costs for disposing of waste products. As a result Sonoco made the decision to upgrade the power plant at its Hartsville paper mill.

The Sonoco project team identified these main objectives for the Hartsville No. 9 boiler project:

Cost reduction for steam generation, purchased power and landfill,

Fuel flexibility,

Improved stoker ash utilization,

High efficiency and availability,

Reduced space requirements and

Low capital costs.

After evaluating many different technology options and vendors, Sonoco`s project team selected Foster Wheeler`s Compact CFB boiler as the best technology to meet the company`s requirements. In addition, the plant`s No. 4 steam turbine generator was upgraded, and a new intermediate pressure steam line and a dry ash handling system were installed. The existing steam turbine was modified and the intermediate extraction steam pressure was increased to 175 psi. Other modifications included replacing the old generator and installing a state-of-the-art control system.

The Sonoco CFB boiler operates at 1,250 psig, 950 F, with 120,000 lb/hr steam flow. To maximize the efficiency of steam usage over the boiler range, the unit has been designed to work at full steam temperatures when operating at 80 percent to 100 percent load, and at a steam temperature of 905 F when operating at 35 percent load. A variety of fuels including waste paper, fiber rejects, bark, plastic, coal and stoker ash can be fired in the CFB boiler. The table shows the fuels and the percentage heat input for each fuel. Natural gas is used for start-up.

Sonoco engineers say they plan to use all of the waste materials generated on site as a source of fuel. The balance of the heat input required to meet the plant`s steam demand will come from coal and/or bark. As the paper mill is expanded, the increased waste material generated is expected to reduce the amount of coal used by the plant.

Although with the CFB a simple Selective Non-Catalytic Reduction (SNCR) system is generally sufficient to meet the NOx limits, the low NOx limits mandated by the State of South Carolina required a deNOx system to be installed in combination with the SNCR system. In the SNCR system a reagent is injected into a separate vessel to convert the NOx to elemental nitrogen and water. Sonoco elected to use urea as the reagent because it is a non-hazardous material.

SO2 emissions limits are met by injecting limestone into the lower furnace of the CFB. Regardless of the amount of coal fired, regulations mandate that 90 percent of the sulfur in the coal be removed. In Sonoco`s case the SO2 emissions limit is 5 ppm (0.03 lb/MMBtu). When this limit is reached the plant must switch from coal to another fuel, such as bark. Sonoco reports that this limitation has had no negative impact on the project`s economics.

Foster Wheeler and Sonoco both agree that the project has been a huge success. All performance tests were completely successful, the plant has achieved an availability of over 98 percent, and the emissions are well within the limits set by the State. Similarly, landfill cost have been reduced by more than $1 million, steam costs reduced by 14 percent, a 6 MW increase in in-house electrical generation has been achieved and the cost for purchased power has been reduced by 20 percent. All of this has been achieved within the first year of plant operation.

Largest PLN Project Now On-line

The Suralaya steam power plant Units 5, 6 and 7 project is reported to be the largest power project ever for Indonesia`s Perusahaan Umum Listrik Negara (PLN). The project, located on the island of Java, Indonesia, consists of three similar pulverized coal units rated at 600 MW each. These three units are in addition to four 400 MW existing coal-fired units. Low sulfur Indonesian coal for the new units is delivered to the site by ship from Sumatra.

Included in the scope of the project were the complete power generation units, precipitators, ash handling and disposal systems, coal handling equipment, water and wastewater treatment systems, desalination plant, circulating water system, a 150 kV substation and a compressed-gas insulated 500 kV substation.

According to Black & Veatch, the project was designed and constructed using their fast track, critical path method (CPM). Utilization of the fast track CPM for scheduling helped the project to be completed two months ahead of schedule and significantly under budget. The project took five years from initial signing of the first equipment contract to commercial operation of all three units in 1997. Civil and structural engineering for the project was performed in Indonesia by PLN with assistance from Black & Veatch and their associate P.T. Encona.

All of the project`s contractors were required to maximize the local content by purchasing their materials and fabricating components in Indonesia. They were also required to employ Indonesian labor. About 50 percent of the project`s budget was spent for manufacturing components outside of Indonesia. The remaining 50 percent was spent in Indonesia for manufacturing, erection and commissioning of the units.

Because the Suralaya site is located between the sea and the mountains, there was limited space for expanding the plant. To accommodate Units 5, 6 and 7 extensive rock blasting was required. In addition, the project had to be seismically designed for earthquake equivalent levels of UBC Zone 4. This was accomplished by stabilizing the soil and by installing all of the foundations on bedrock or piled to sit on rock. The foundations for the chimneys were also piled and doweled into the bedrock. In all, 37,000 steel-cased concrete piles and 4.6 million cubic feet of concrete were installed for the foundation pilings.

In order to deliver coal to the project, a new coal unloading jetty, with two 1,925 tons/hr grab type bucket unloaders, was constructed. During its construction over 10.7 million cubic feet of seabed had to be dredged, and more than 700 steel piles were driven into rock in the seabed.

Units 5, 6 and 7 were designed for island operations using a turbine bypass system. Black & Veatch says this type of operation is unique for units of their size. With this design the units are able to continue operation and quickly re-synchronize with the electric grid should there be a grid disconnect. In addition, the units can continue to operate without tripping the coal pulverizers or losing any condensate through the safety valve discharge. The turbine bypass system also helps to achieve smooth startup of the units.

In accordance with the requirements of the Indonesian government, mitigation programs were implemented to reduce air emissions and wastewater discharges from the plant. Air emissions were dispersed by installing chimneys 900 feet tall. In addition, continuous emission monitoring equipment was installed on each chimney. To track the dispersion of pollutants a monitor has been installed on an adjacent mountain.

At the request of the World Bank, the entire plant was retrofitted with a wastewater collection system. Wastewater is composed of oily water, coal and ash runoff, and chemical wastes. However, prior to being discharged into the wastewater system the chemical wastes are neutralized. After being treated in a new heavy metals reduction facility, the wastewater is finally discharged into the sea. p

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Sweeny Cogeneration Project.

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Sonoco`s Hartsville, S. C. power plant.

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PLN`s Units 5,6 and 7 in Java, Indonesia