WASTE/ENERGY: Power Plants Convert Tires To Energy

Thomas Edison had no idea just how many sources could be used to generate electricity.

The vast quantities of worn-out tires discarded every year represent a tremendous amount of available energy. This potential is wasted when the tires are landfilled, taking up valuable space and posing environmental concerns.

As an alternative, converting tires to electricity has greatly in-creased in recent years, and is likely to continue (see chart on page 17). This includes tire-fueled power plants in Connecticut, Florida and Illinois.

A tire-to-energy power plant in Sterling, Conn., went on-line in 1991. The 30-megawatt Exeter fa-cility is fueled by whole tires. The plant consumes 23,000 tires per day, or 288 tons, in twin boilers that supply steam to a 30-mega-watt turbine generator. The 40-megawatt Ridge Generation Station in Polk County, Fla., burns both shredded tires and wood waste.

By 1996, a third facility is ex-pected to open in Ford Heights, Ill., about 30 miles south of Chicago. Most tire-to-energy facilities mix the shredded tires with coal, oil, wood or other fuels before burning them. However, the Ford Heights facility will use a tire-fired boiler without any additional fuel. The steam produced will drive a double, uncontrolled extraction, condensing steam turbine which is mated to a synchronous generator. At an optimum, the boiler will burn just over 16,500 pounds per hour of shredded tires with a higher heating value of 14,500 BTUs-per-pound. Among commonly used fu-els, only oil has a higher energy value.

Estimates show that the $105 million Ford Heights waste tire-to-energy project will produce 19.9 megawatts of electrical power, most of which will be sold to Common-wealth Edison in Chicago. This quantity of energy could serve a-bout 16,500 U.S. households; a small portion of the electricity generated will power the plant itself.

In the process, the facility will consume 65,000 tons of tires an-nually. This equates to 6.5 million passenger car tires, about 30 percent of the scrap tires discarded in the Chicago area.

In addition to the electrical energy, incinerated tire scraps will produce byproducts that can be re-used by other industries. These non-hazardous materials include steel, zinc oxide and gypsum.

The Ford Heights facility should be complete within two years. It is a joint venture between Houston Industries Energy Inc. and Chew-ton Glen Energy Inc., San Antonio. The Illinois facility will use combustion boiler equipment similar to that at the Exeter and Ridge Gen-eration Station facilities.