Solid Waste & Recycling

Feature

Power to Burn

Fairfield, New Jersey-based Covanta Energy currently owns and/or operates more than fifty waste-to-energy (WTE) plants in North America, Europe and Asia. It's the top operator of large-scale municipal waste WTE facilities in the United States...


Fairfield, New Jersey-based Covanta Energy currently owns and/or operates more than fifty waste-to-energy (WTE) plants in North America, Europe and Asia. It’s the top operator of large-scale municipal waste WTE facilities in the United States and recently acquired the North American assets of Montenay, including the WTE in Burnaby, BC. In addition to waste incinerators, the company has eight renewable biomass (wood) facilities in the US, five renewable biogas (landfill) facilities in the US, and four hydroelectric facilities in the US and Central America.

The company is actively pursuing opportunities to build more facilities or operate existing ones around the world, in places as diverse as Trezzo, Italy and Bangladesh.

Covanta says its facilities are fully compliant with emissions regulations 99.9 per cent of the time, operating 60 to 80 per cent below permit limits.

The company was chosen in a competitive bid process to construct the WTE plant planned for Durham Region, just east of Toronto, Ontario. The mass burn moving grate technology in similar facilities have achieved nearly 100 per cent compliance and will feature state of the art air pollution control equipment and continuous emissions monitoring (CEM). Covanta says that WTE is preferable to landfill disposal and protects communities from the price uncertainty associated with export to distant landfills. Other benefits extolled by Covanta include:

• Project will create $500 million+ of economic activity

• Create 800 to 1,000 jobs during construction and high-paid permanent jobs

• Competitively priced “renewable” energy and potential anchor for district heating steam loop or energy park

Covanta will design, build and operate the 140,000 tonnes/year facility in Clarington using Martin GmbH combustion technology. The plant will generate 20 megawatts (gross) of energy — enough to power 11,000 to 14,500 homes. In addition to reducing waste volume by 90 per cent while generating power, the technology will allow diversion and recycling of thousands of tons of metals over the life of the project.

Niagara Falls plant tour

In order to get a feeling for what such a facility might look like, in April I toured Covanta’s plant in Niagara Falls, New York. The Niagara plant is a commercial facility and — at 821,000 permitted tons per year — is much larger than the plant proposed for Durham.

Originally a first-generation RDF plant, the facility was converted to mass burn in 1996 and has the two largest waste-fired combustion units in North America. The main difference between the proposed Durham plant and the Niagara Falls plant is that the latter uses DBA roller grate technology and not the Martin GmbH system. (Company officials say their performance of both systems is excellent.)

The plant is ISO 14001 registered and is an OSHA VPP STAR Facility. It operates with a Title V permit and is MACT Compliant.

Key to the commercial success of the plant is cogeneration. Two 25 megawatt turbines generate electricity, and the plant sells steam to five industrial customers. Essentially, a plant like the Niagara Falls one is a power generation facility that unlike, say, a coal-fired plant, gets paid a tip fee for its raw fuel (instead of having to pay for the fuel).

As one would expect, waste is received under signed contract that specifies what may be delivered to the plant. Waste loads are checked for radioactivity, weighed at a scale house, and deposited on the tipping floor where random inspections are conducted on about 10 per cent of the material for unacceptable waste. Any special wastes detected are separated for special handling and the remainder is blended in a pit via two enormous claws operated from a control booth, then automatically fed into the combustion unit by a large hydraulic ram at the bottom of the feed hopper. The pit allows storage for up to four days of solid waste, and the area is maintained under negative draft to minimize odors. (Waste in the feed chute also provides an air seal for the boiler.)

Waste is spread evenly across the first roller grates where combustion begins. There are six roller grates at a 20 per cent incline. Computers control the speed at which the grate turns and the amount of air supplied to the boiler. The fire on the grates is self sustaining and will reach temperatures of 2,500 degrees.

Ash remaining from the combustion process drops into the water-filled ash extractor, pushed out onto a conveyor and sent for special processing. About ten per cent of the original waste volume remains (20 per cent by mass), typically containing 2.5 per cent ferrous and 0.25 per cent non-ferrous metals that are extracted and recycled.

Steam for the plant’s five industrial customers has been recorded as being 99.9 per cent available over the last 15 years. About 10 per cent of power production is utilized in-house and the remainder is sold to local utilities.

Like all such modern facilities, the plant has pollution control equipment that includes: computer controls for efficient combustion; scrubber for acid gas control; active carbon injection for mercury control; urea injection system for NOx control; and, baghouse for particulate capture. In addition to the continuous emissions monitoring system, a NYDEC monitor is onsite, and stack tests are conducted annually for trace elements and equipment accuracy.

I asked company officials how they feel about the proposed WTE plant for Durham Region being so much smaller, given that economies of scale contribute greatly to the profitability of the large Niagara Falls plant. They answered that, from a purely commercial point of view, they’d like to build a larger plant, but value the opportunity to showcase their technology in Ontario with a view to gaining public acceptance and building other plants in the future.

Guy Crittenden is editor of this magazine. Contact Guy at gcrittenden@solidwastemag.com


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