Mass-Burn Refuse-to-Energy Technology: A United States Case Study A l f r e d B. D e l B e l l o *

Signal Environmental Systems Inc. Liberty Lane, Hampton, New Hampshire, 03842, U S A

Summary

solicited proposals for experimental waste-to-energy technologies. Unfortunately, Baltimore paid a price for being a pioneer - the pyrolysis technology that was chosen failed, and the plant was closed in 1980. Characteristically, this City, which has seen a dramatic revival from an aging urban area to a vibrant metropolitan center, did not give up. The Northeast Maryland Waste Disposal Authority was formed when a detailed project concept was developed. After a competitive procurement and negotiation process the City chose Signal Environmental Systems (SES) and a proven mass burn refuse-to-energy technology. Unlike similar plants which have taken ten years or more to develop, the Baltimore project was implemented quickly. Starting in September 1980, the Waste Disposal Authority completed all preliminary development activities in twenty months. Following the demolition of the existing pyrolysis plant, construction of the SES facility began in May of 1983. After a three month testing period, start-up operations began in January, 1985. The SES refuse-to-energy facility currently serves One of the most serious environmental challenges the City and County of Baltimore by disposing of up facing Americans today is the problem of solid waste to 2250 tons (2290 tonnes) of solid waste each day and disposal. Each person in USA produces four pounds generating electricity, which is sold to Baltimore Gas (1.8 kg) of refuse each day and nationally 630 000 tons and Electric, and steam, which is sold to a Baltimore (640 000 tonnes) are generated. Landfill sites across Steam Co. downtown district heating and cooling the nation are rapidly reaching capacity and most loop. The facility is a successful example of the pollute the air and ground water. With 4 billion cubic public/private partnership arrangement which SES feet (0.11 billion cubic meters) of space used every pioneered in USA in 1975 with the development of its year for discarding of waste, the United States can no Saugus, Massachusetts refuse-to-energy facility (Fig. longer environmentally or economically afford to 1). The Baltimore facility was financed by a combicontinue landfilling. nation of $63 million in Signal equity and $191 million in tax exempt industrial revenue bonds. SES owns and operates the facility, and is responsible for Waste Disposal in Baltimore operation, maintenance, and debt repayment. The Twelve years ago, the City of Baltmore, Maryland City is not at risk for any aspect of the plant's realized the severity of its solid waste disposal operation and financing, thus preventing a duplicaproblem. Eager to take a leadership role, the City tion of the situation faced with the failed pyrolysis *Alfred B. DelBellowas at one time LieutenantGovernorof New plant. In return, Baltimore City and County pays a York and County Executiveof New York's Westchester County. service or tip fee per ton of refuse processed. The technology employed at the SES-Baltimore As President and ChiefExecutiveOfficerof Signal Environmental Systems Inc., he describesa refuse-to-energyfacilityestablishedby facility is a modification of the Von Roll mass-burn Signal in Baltimore, Maryland. Signal Environmental Systems are system, developed in Switzerland and used successcurrently the largest provider of resource recoveryplants in the USA, other contributorsare CombustionEngineering, American fully in Europe for nearly four decades. After Ref-Fuel and Ogden; with Foster Wheeler, Btount, and Dravo, spending millions of dollars at the SES-Saugus plant being other significant participants. for the adaptation of European technology to the

As landfill sites reach capacity and are under environmental regulations to close, communities across America face solid waste disposal crises. The City of Baltimore, Maryland, after initially choosing an experimental technology which failed, turned to a proven mass-burn resource recovery system for solid waste disposal Through a process called privatization, the City shielded itself from financial risk associated with the operation of the plant. Signal Environmental Systems owns and operates the refuseto-energy facility, which features a mass-burn technology developed in Switzerland by Von Roll, Inc., and charges the C~ty a service fee per ton of refuse processed. The success of the partnership between the public and private sectors for the provision of efficient and reliable solid waste disposal in the City and County of Baltimore can serve as a model for developing and implementing technologies to meet the many other challenges facing the country and the world as a whole.

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• ~ ! ~¸! ~ y' l ~ i

Fig. 1. The Saugus, Massachusetts, USA, refuse-to-energy facility.

electric power generation • to utility steam piped to turbine generator

ced fan refuse fuel pit

transfer conveyor

Fig. 2. Simplified diagram of the mass-burn technology system used at 272

stack

the Baltimore

refuse-to-energy

plant.

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Baltimore plant has the capacity to generate 60 megawatts of electricity. The energy output at the facility is two-fold. Electricity is sold to the Baltimore Gas and Electric Company, and steam is sold to Baltimore Steam Company. The steam, 350000 pounds/hour (158 750 kg/hour), supplies a downtown heating loop which services commercial and municipal buildings including: schools, hospitals, public housing developments; and small retail stores. Signal Environmental Systems has found that it is more efficient to extract steam from the production lines for multiple purposes than to use all of it to generate electricity. Preventing Air Pollution Fig. 3. A refuse-to-energyplant built at Peekskill, New York, to meet Westchester County's solid waste disposal problems. The Air quality is maintained by electrostatic precipiunit generates enough electricity fo 40000 homes. tators (ESPs) on each boiler. These units, designed by the Signal Air Pollution Control Division, are American refuse stream, Signal has developed a oversized, each containing four fields. Gases are technology that has proven environmentally sound pulled through the boilers and electrostatic precipitators by induced draft fans. These ESPs are designed and reliable through experience. The mass-burn technology in use today at the to keep particulate emissions below 0.019 gr/dscf at Baltimore refuse-to-energy plant is relatively simple 12 percent CO2 and assure that the SES-Baltimore (Fig. 2). Incoming garbage trucks are weighed on an plant meets stringent federal, state, and local parelectronically controlled scale to determine tonnage. ticulate emissions standards. Natural gas is used as an The trucks dump the refuse into an enclosed receiving auxiliary fuel to start combustion and to maintain pit. Without pre-sorti.ng or processing, the waste is environmental efficiency by preheating the electrothen transferred by overhead cranes (3.5 tons per static precipitators. The results of this air pollution load) into the feed hopper of each furnace. The plant control is readily seen when viewing the stack as the has three process lines, each of which can handle 750 plant is running at full capacity - visible emissions are nearly non-existent (Fig. 4). tons (760 tonnes) of refuse a day. The residue left from the combustion process is Once in the furnace, waste is moved on reciprocating Von Roll grates. These advanced 'R-type' moved from the furnace on a conveyor. Passing under grates are in use elsewhere at the SES Westchester large electromagnets, ferrous metals are removed for County, New York plant (Fig. 3). Featuring a sale to the scrap industry. The sterile residue is then 'stepless' combustion surface and improved metal- collected in an ash receiving area before it is lurgy, these grates provide greater transverse recipro- transported in covered trucks to the residue landfill. The mass burn process reduces the volume of cation and improved air distribution. Refuse is combusted in the furnace at temperatures incoming waste 95 percent. The entire refuse-to-energy process is monitored in in excess of 2500°F (1370°C). High burning temperatures act as a protection measure against the the plant's computerized control room. Detailed emission of toxic substances. In addition, primary air is introduced from beneath the grates, and secondary air is drawn in above the grates, fueling complete and efficient combustion. The air drawn from the tipping area creates a negative pressure, thus preventing the escape of dust while minimizing odors outside the facility. Waterwall boilers are used to produce superheated steam. This steam can then be used to drive a turbine and produce electricity. Specially designed boilers achieve the resource recovery industry's highest steam temperatures and pressures, enabling the facility to achieve higher energy conversion efficiency and generate more electricity. At design capacity, these boilers produce 167700 pounds of steam-perhour at 830°F (76 050 kg at 443°C) and 900 psig from the combustion of 31 tons of refuse-per-hour. The Fig. 4. The Baltimore, Maryland, USA, refuse-to-energyfacility.

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Fig. 5. This refuse-to-energy plant at North Andover, Massachusetts, serves 750000 people in the N.E. of the State.

information on temperature, emissions, combustion conditions, electricity and steam output is continuously available. The integrated design at the Baltimore plant represents 'state-of-the-art' refuse-to-energy technology in the United States. Its advanced yet flexible design allows complete combustion of the heterogeneous fuel it receives. Since refuse is a diverse resource, equipment is designed to work across a broad range of materials. At the same time, mass burning is simple and direct, eliminating the complex handling and separating stages of less successful technologies.

Currently, there are 67 operating resource recovery facilities of various sizes and technologies in the United States, and many more under construction, in negotiations, or in preliminary stages of the development process. As more and more landfills are forced to close, the pressure to build resourcerecovery facilities increases. It is projected that 60 large-scale (1500-3000 tons per day) and 100 medium-sized (200-1500 tons per day) facilities will be developed in USA over the next five years. Mass burn technology, as proven by successful and continuous operation over the past ten years, offers America's most environmentally sound answer to the solid waste disposal problem. Communities across the nation are increasingly turning to this technology as an alternative to landfilling. And through the privatization of refuse-to-energy facilities, municipalities meet their waste disposal needs by financing through a combination of tax-exempt bonds and private equity - thereby leaving their credit rating unaffected and avoiding financial risk for construction and operation. The partnership forged by the nation's private and public sectors has served to pool resources and develop a successful solution to the solid waste disposal problem. It is an arrangement that can serve as a model for developing and implementing technologies to solve the many other environmental challenges facing USA, and the world as a whole.

Other Refuse-to-Energy Plants Signal Environmental Systems operates four plants in addition to the Baltimore facility. These plants, located in Saugus, Massachusetts (1500 tons per day); North Andover, Massachusetts (1500 tons per day) (Fig. 5); Westchester County, New York (2250 tons per day); and St. Petersburg, Florida (2000 tons per day - being expanded to 3000 tons per day) (Fig. 6) each employ proprietary mass-burn technology. Together the five SES refuse-to-energy facilities process three million tons of solid waste each year and generate enough energy to power 250 000 homes and businesses. By December, 1986, they will have processed 10 million tons of solid waste and generated the energy equivalent of more than 8 million barrels of oil.

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Fig. 6. Serving a million people in PineUas County this refuse-toenergy plant at St. Petersburg, Florida, provides sufficient electricity for 56 000 homes.

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