Corrosion probe exposures were conducted in the Harrisburg, Pennsylvania, incinerator to determine the effects of burning low-chloride sewage sludge with municipal refuse. Probes having controlled temperature gradients were used to measure corrosion rates for exposure times up to 816 hours. The effects of exposure time, metal temperature, and gas temperature were studied. The results demonstrated that the addition of the sludge reduced the initial corrosion rates of carbon and low-alloy steels to about half that from refuse alone. Little effect was observed on the rates for Types 310 and 347 stainless steels. An aluminized coating on steel resisted corrosion effectively and offers promise as a cost-effective substitute for expensive alloys. In the range 500–900° F the corrosion rates of carbon steel and T22 increased with temperature while those for the stainless steels decreased. Reducing the flue gas temperature from 1500° F to 1100° F reduced corrosion rates significantly and made them less dependent on metal temperature. The addition of low-chloride sludge to refuse is recommended as a corrosion prevention measure and a waste disposal technique.

The utilization of shredded and magnetically separated municipal refuse to supplement high-sulfur coal as fuel in a stoker-fired boiler was investigated, using the facilities of the Columbus, Ohio, Municipal Electric Plant. Corrosion probe exposures were used to show the effectiveness of cofiring with high-sulfur coal to reduce chloride corrosion of boiler tube metals by refuse. Reduced emissions of SO2 from the high-sulfur coal also resulted from dilution of the coal with refuse and by action of alkaline components of the refuse. It was demonstrated that 700 hr corrosion rates with refuse and high-sulfur coal were 5–10 times less than those with bulk refuse burning, and approximated those from coal alone. In some runs sulfur dioxide emissions were reduced by about ten percent more than the refuse dilution factor. The cofiring with refuse had no significant effect on grate ash composition, but the ash fusion temperature was lowered about 100°F.

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The utilization of municipal refuse as a supplementary fuel in a coal-fired power-generating plant has been investigated. The preparation of the solid waste consisted of shredding, ferrous metal separation, and air classification. Probes inserted in the superheater section of the stoker-fired boiler were used to collect deposits and to measure the extent of corrosion. The corrosion rates found for refuse–coal mixtures containing up to 42 weight percent refuse approximated those found with the coals and were about an order of magnitude less than those found with refuse alone. The flue gas temperatures were found to be important factors in corrosion. Sulfur oxide emissions of the high-sulfur coal were reduced both by dilution with the refuse and by the action of the alkaline components of the refuse.