Waste-to-energy plant reduces waste ash.
Construction is proceeding at a fast pace toward completion of the nation’s most advanced waste-to-energy plant in the village of Robbins, Ill., a southside suburb of Chicago.
This $400 million project has been developed as a public/private venture capitalized in part by the village issuing $320 million worth of tax-exempt resource recovery revenue bonds.
The facility’s design/build program has been led by a subsidiary of Foster Wheeler Power Systems, which will also lease and run the facility through an operating entity known as Robbins Resource Recovery Partners, LP.
The Pangere Corp., a Butler Builder in Gary, Ind., is serving as one of the project’s prime contractors.
The plant’s fuel will derive from the municipal waste of 12 Chicago subsurbs that would otherwise confront higher transportation and disposal costs due to nearly exhausted landfills now serving their areas.
The plant can process up to 550,000 tons of solid waste annually, 25 percent of which will be recovered as recyclables, and produce 50,000. kilowatts of electricity for sale to the area’s electric utility.
The plant buildings combine conventional steel and custom pre-engineered metal building structural framing with a metal roof and metal wall panel cladding.
This integration of conventional steel construction and pre-engineered systems has become increasingly common in heavy industrial-type projects where economy and speed of erection are program criteria.
Midway through the preliminary development stage, it became evident that the plant’s importance could extend well beyond the immediate interests of the village.
A state-funded study concluded in July 1990 that a serious shortfall in landfill capacity could affect dozens of other southside communities by the year 2000. The project offered an alternative method of disposal, according to the South Suburban Mayors & Managers Association.
The waste-processing and boiler technologies for the project is expected to have some unique performance characteristics absent in earlier generation waste-to-energy facilities. Pollutant emissions will be low, especially carbon monoxide and nitrogen oxide. The amount of residual ash will also be held to a minimum.
The plant will also possess a high-energy conversion efficiency. Moreover, the operating systems incorporate rate a level of redundancy that will facilitate maintenance and thereby ensure uninterrupted operation.
Trucks will deliver the waste to a tipping building that can store 3,000 tons of refuse, or nearly two days’ worth of normal deliveries. After the loads are dumped onto the tipping floor, plant personnel will inspect it and segregate unsuitable material such as large appliances.
The acceptable waste will then be pushed onto in-feed conveyors past a picking station to remove non-processible items located just ahead of the primary trommel. Using this as the first step rather than a shredder or flail mill will improve material recovery by separating glass, ferrous and aluminum cans more efficiently.
Maintenance reductions and lower power consumption are also expected by removing abrasive materials prior to shredding and from reduced loading on the shredder.
The primary trommel will open trash bags, break glass and separate any material under six inches. Material removed from the primary trommel then will be carried to a two-stage, secondary trommel screen for separation of glass and organics, aluminum-rich materials and burnable matter.
Glass will be conveyed to a further recovery system and the eventual, organic-free material sold for use in glasphalt. Organic material will be diverted to yet another point and processed off site into marketable compost.
The balance, processed into refused derived fuel, will be conveyed to a 198-foot-by-254-foot-by-61-foot storage building large enough to hold a three-day supply of boiler fuel.
The two “circulating fluid-bed boilers” are the first of their type burning refuse-derived fuel in the United States, and each is designed to burn 600 tons per day.
Unlike conventional combustors, the type used at the plant do not burn the refuse fuel on a grate or hearth. Instead, the waste is burned while caught up in a hot, churning suspension of material, entrained in a substantial upward flow of gas.
This “fluidized bed” consists of the refuse-derived fuel mixed with super-heated particulate matter comprised of an inert bed material, i.e., screened bed ash and sand.
The entrained solids in the flue gas will be recirculated through the fuel bed to increase boiler efficiency and burnout rate.
Facility air emissions will be controlled not only by the more efficient combustion of the boilers but by a selective non-catalytic reduction system, a semi-dry flue-gas scrubber and fabric-filter baghouse system. The plant’s environmental impact on air quality should be minimal and well within permissible limits.
The plant responds to a number of interrelated issues, any one of which has compromised predecessor facilities to some extent.
First, waste-to-energy facilities that recover materials for recycling are viewed more favorably by an environmentally minded public. Elimination of separating recyclables at curbside reduces overall waste-handling costs for municipalities.
The project’s improved economics derive from increases in the amount of electricity generated and reductions in the amount of waste ash.