Covanta Bristol

The Facility is located on an 18-acre site in the City of Bristol, Connecticut, and began commercial operation in May, 1988.  The Facility is a solid waste disposal and electric generating facility constructed, owned, operated, maintained and managed by the Covanta Bristol, Inc. (CBI). It processes approximately 600 tons per day of solid waste into 16.3 megawatts of renewable energy.  

The Facility receives Municipal Solid Waste (MSW) delivered by the BRRFOC member communities, and processes MSW to produces electricity.  Covanta is required to operate the Facility in accordance with Connecticut air, water, and solid waste permits which establish stringent standards designed to minimize emissions and impacts on the environment.  The technology used by the Facility is a process generally known as “mass burning,” in which solid waste is burned with little or no precombustion processing.  Mass burn technology has been used successfully in Europe since the early 1900’s and in the United States for over 30 years.

The principal components of the Facility are the waste storage area, the waste charging system, the proprietary grate system, the boilers, the dry-flue gas scrubbers, the baghouse type fabric filters, and the turbine generator.  Auxiliary equipment is provided at a level of redundancy consistent with practices common within the power-generating industry.

The Facility uses technology developed and owned by Martin GmbH fur Umwelt-und Energietechnik of Munich, Germany (“Martin”).  In excess of 150 Martin facilities are in operation worldwide, including 16 in the United States.  Martin has more than thirty (30) years of experience in the design, engineering, construction and operation of systems for solid waste combustion and energy generation.  Today there are more than 150 plants with Martin GmbH combustion units in operation, including 20 Covanta facilities.

Operations

After incoming trucks are weighed, MSW is delivered to a storage pit capable of holding up to 4,000 tons of unprocessed waste.  From the pit, the waste is lifted by one of two overhead cranes and placed into one of two combustion unit charging hoppers.  Combustion takes place in two waterwall furnaces, which operate independently.  Each has a design capacity of 325 tons of MSW per day, and has separate combustion controls and air pollution control equipment; only the tipping floor, chimney and stack are shared.  The furnaces produce steam which is used to generate electricity for sale to Connecticut Light & Power (CL&P).  The Facility has a committed capacity of 13.2 MW. 

Solid waste is gravity fed from the charging hopper down the feed chute and then moved onto the furnace grates by a hydraulically operated feeder ram.  To seal the feed chute and maintain control of the furnace draft, the hopper is kept filled with MSW.

The waste moves into the furnace down an inclined grate, where reverse-reciprocating grate bars mix the burning waste, which assures thorough “burnout” (complete combustion with minimal unburned carbon).  Forced draft combustion air is supplied to the underside of the grate bars (underfire air).  Close control of air volume and distribution promotes uniform combustion.  The uniform air distribution also cools the grate bars to prolong grate bar life.  Additional combustion air is introduced above the grate bars at the front and rear walls of the furnaces (overfire air).  The resulting intense flame turbulence eliminates virtually all volatile organic substances in the gases exiting the furnace, and ensures combustion efficiencies of well over 99%.

As the hot gases move through the boiler sections of each furnace, water in the boiler tubes is heated, generating high-pressure steam, which is directed to a turbine generator to produce electricity.  Exhaust steam from the turbine generator is condensed in a water-cooled condenser.  The electricity produced flows to electrical switchgear, and then over an interconnection line into the Connecticut Light & Power (CL&P) distribution system.  Electricity for in-plant use is generated primarily by the Facility.  The Facility ties directly into the CL&P electrical grid at the existing Forestville, Connecticut substation approximately 3⁄4 miles away. 

Air Pollution Control Systems

After leaving the steam generators, the combustion gases pass through dry-flue gas scrubbers and baghouse type fabric filters for removal of SO₂, other acid gases and particulates prior to discharge through the stack.  Advanced pollution control systems include a dry scrubber and baghouse, equipped with activated carbon injection for capturing metals and organic material present in the flue gas at very low concentrations.  A total of 10 baghouse compartments contain over 1,000 special fabric filters which remove acid gas and particulates at efficiencies of over 99%.

The Clean Air Act regulations known as Maximum Achievable Control Technology (MACT) standards, promulgated by the Environmental Protection Agency in 1995 and made effective in December 2000, resulted in the installation of a state-of-the-art mercury control system, as well as an upgrade of the plant’s continuous emissions monitoring system. The MACT standards represent some of the most stringent environmental regulations in the world. Testing is performed annually and supervised by the Connecticut Department of Environmental Protection. [BRRFOC to add link to emissions testing results]

Ash Handling

Bottom ash and grate siftings are discharged into a water-quenched ash-removal system.  This ash is then moved through equipment designed to extract ferrous materials.  After ferrous recovery the ash is deposited in a storage bunker prior to final disposal at a licensed sanitary landfill.  This ash removal system is designed to handle any size material that can be delivered through the feed chute and across the grates.  Ash from the air pollution control equipment is conveyed to the ash-removal system and disposed of with the bottom ash.

Highlights

• November 2006 – Solid Waste, Air Permits reissued by CTDEP
• July 2006 – OSHA VPP Award
• September 2005 – Covanta acquires American Ref-Fuel Company and 6 new waste-to-energy facilities, including the Connecticut Preston plant
• June 2004 – record production:  highest throughput since operations commenced (206,700tons) and highest electrical generation (137,000 MWh)