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GENERATION

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1984-National-Waste-Processing-Conference-Disc-09-00011984-National-Waste-Processing-Conference-Disc-09-00021984-National-Waste-Processing-Conference-Disc-09-00031984-National-Waste-Processing-Conference-Disc-09-00041984-National-Waste-Processing-Conference-Disc-09-0005FEASIBILITY OF 100 PERCENT RDF FIRING FOR POWER GENERATION M. s. MASSOUDI Raymond Kaiser Engineers Inc. Oakland, California Discussion by R. E. Sommerlad Foster Wheeler Development Corp. Livingston, New Jersey The title of the paper purports to discuss the feasibility of 100% RDF firing for power generation. It is implied that it is possible to fire 100% RDF in a single boiler. However, for the case study cited, the author suggests a much more elaborate system for a 16 MW system. The flow sheet suggests 80% heat input from RDF and 20% from coal. He also suggests that three boilers handle the RDF. This means each boiler fues 1475 lb/hr (9 tpd) of RDF and this should reflect 80% MCR in each boiler. In other words, each of the three units would be sized for 88.5 x 106 Btu/hr and the coal fued unit would be sized for 55 x 106 Btu/hr. If this is what the author intended, it is not a very cost effective design. There are ample references to previous papers in the proceedings of this conference that describe MSW and RDF power generating schemes. There are units operating here and abroad that generate more than 16 MW with heat inputs of fossil fuel of less than 20% and in most areas this is accomplished in a single waste fued or combined fired boiler. Some plants use coal for trimming but generally trimming is accomplished with pulverized coal firing. The author states that "RDF-fued boiler volume must be up to approximately three times greater than coal-fired boiler volumes to be able to generate the same amount of steam." I disagree with this statement as written. The paper devotes more space to current status and an overview of RDF firing, which contains a great of opinion 19 and several points with which one can take issue, than it does to the topic as described in the title. The author also claims this is a cogeneration plant but shows no other energy output other than power. I would ask the author to illustrate a more detailed mass and energy balance showing the four individual boilers, their maximum capacity. I would ask the author to compare heat rate costs of the four-boiler train to a single boiler train. Discussion by Balu A. Kamat North Bergen, New Jersey This paper, though well written, is very general in nature. The author is correct in his referral to very recent and limited experience of 100% RDF fired units in the U.S. Almost all plants in the U.S. using such RDF have been plagued with various types of problems, some of serious nature, at the feed end and in the combustion chambers. The author has correctly addressed the problem of corrosion but has made no reference to erosion of tubes. The problem of corrosion of boiler walls and superheater tubes have been associated mainly with combustion temperature, proximity to radiant heat, extent of protective coatings on the wall tubes, gas velocity and retention time. Such problems need further studies and a bolder approach in new prototype plants. The author's statement regarding "first major attempt to recover energy from USA started in early 1970" probably refers to use of RDF. Tynan· Incinerator Co., in 1958, was the first to build an incinerator at Oyster Bay, New York, with an energy recovery system utilizing asteam turbine and generator using mass burning technology. (1) If the total quantity of incoming air is decided, how can the ratio of OFA to UF A be kept constant? (2) How did the author determine that the RDF fired boiler volume is approximately three times greater than the coal-fired boiler volume? SUMMARY It would be interesting, in the future, to read a "followup paper" on the actual working experiences gained from this U.S. Navy plant, now under design. Discussion by Herbert I. Hollander STV/Sanders & Thomas, Inc. Pottstown, Pennsylvania The author has provided a comprehensive discussion on the use of RDF-3 (shredded beneficiated fuel fraction derived from mixed municipal refuse) as a fuel for semisuspension firing for steam generation. The arbitrary use of the term "dedicated boiler" implies there is some other kind of deSignation. To operate any boiler, a heat source(s) must be provided and once committed to this heat source or combination sources (burning or otherwise) �hether a new unit or retrofitted, it is then "dedicated" to the use of this fuel(s) until it is committed or rededicated to some other(s). Therefore, the use of the term "dedicated" contributes to confusion rather than clarity. When reference was made that the building volume required for an RDF fired boiler can be up to three times greater than that for a coal fired unit, it would have been appropriate to mention that this would also apply to all relatively high moisture fuels such as sub-bituminous, brown coals, lignites, peats and all biomass fuels. Table 2 would be more informative if it also indicated for each plant the number of steam generators, their capacity when burning fossil fuel and the type of fossil fuel; whether the plant generates principally low pressure steam for heating and process or superheated steam for power alone or for cogeneration. In all probability, prudence prevailed and capability of full capacity with fossil fuel was incorporated in most if not all of these designs. Of the projects listed only the City of Columbus is a utility. It is acknowledged that RDF can be highly variable in moisture and bulk density. The problem is aggravated by its nonuniform compressibility, and therefore fuel feeders which are strictly volumetric cannot be considered as a 20 metering device for providing even reasonable fuel flow and unit energy input predictability.


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