Stoker-fired Boilers Research Articles

Corrosion and Deposits from Combustion of Solid Waste—Part VI: Processed Refuse as a Supplementary Fuel in a Stoker-Fired Boiler

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.

Solid Waste as Refuse-Derived Fuel

Europe and the Far East have been using refuse-to-energy plants to power turbine generators in the production of electricity. If the U.S. would convert the total municipal refuse to energy at normal efficiency, 6% of the total U.S. electric production could be produced. Pelletized solid waste (refuse-derived fuel (RDF)) can be mixed with coal and burned in existing industrial spreader stoker-fired boilers. An RDF-to-coal volume ratio of 11 : 1 corresponding to a weight ratio of 40 : 60 and an energy ratio fo 23 : 77 was burned in a completely unmodified steam plant without unusual variations in equipment operation for a 24-h period. In addition, there was significant reduction in both SO/sub 2/ and HC emissions compared to low-sulfur coal. Difficulties were experienced with an RDF-to-coal volume ratio of 2 : 1. Control data were established for comparative purposes by burning coal for a 24-h period.

Corrosion and Deposits From Combustion of Solid Waste—Part V: Firing of Refuse With High-Sulfur Coal

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.

Corrosion and Deposits From Combustion of Solid Waste—Part IV: Combined Firing of Refuse and Coal

Combined firing of processed municipal refuse with coal has been investigated in a stoker-fired boiler. The refuse preparation consisted of shredding, magnetic separation of metals, and air classification. The nature of the deposits and the extent of corrosion of simulated boiler tube surfaces was determined by inserting probes into the boiler. For amounts of refuse up to 35 percent on a heating value basis, the corrosion rate of carbon steels was reduced substantially below that found from previous measurements for refuse alone, and below that calculated on the basis of dilution by the coal. The temperature of the boiler flue gases also was found to be an important factor in corrosion. The emissions of sulfur oxides from high sulfur coal were reduced by the action of the alkaline components of the refuse.

Coal needed for each ton used in a boiler plant

As Thai's energy security heavily relies on imported crude oil products, the Thai government has promoted the use of alternative energy sources as a substitute for fossil fuel through the Renewable Energy Development Plan. According to this plan, 3,630 MW of electricity should be derived from biomass or agricultural residue in 2021. Although some agricultural residue has been commercially used as fuel in biomass power plants, corn residue is still leftover and has a high energy potential in some regions, e.g. in the northern part of Thailand. This study focuses on the supply chain management in using corn residue as an alternative energy source for power production in Nakorn Sawan and Petchchaboon Provinces. In 2011, almost two million tons of corn residue were generated; about 200,000 tons of which were corncob (HHV of 15-16 MJ/kg) and the rest was corn trash/skin and stems (HHV of 13-15 MJ/kg). Because of the uniform and compact shape of corncobs, they can be completely utilized as fuel in a conventional stoker-fired boiler for heat production. In contrast, corn trash/skin and stems are leftover in the field or burnt on the field without any energy recovery because they are bulky and non-uniform fuel, with high moisture content, which leads to difficulty in collection and transportation, as well as for thermal conversion. According to the results of this study, a processing unit is necessary to improve the properties of corn trash/skin and stems to be used as solid fuel. This processing unit can be established as a centralized plant or on the field where the residue is generated. Regarding the economic analysis, the overall cost of bio-pellet from corn trash/skin/stems is estimated to be 49.4-56.8 US$ per ton, depending on the pelletizing capacity. The bio-pellets from corn residue can easily be transported to be used as feedstock for heating or power generation by direct combustion, co-firing, or gasification technology.

Combined Firing of Coal and Natural Gas on Stoker-Fired Units

Abstract For reasons of economy, increased capacity, and the possibility of improving operation when only inferior coals were available, the Kansas City Power & Light Company, in 1937, installed natural-gas burners in three of the chain-grate stoker-fired boilers at its Grand Avenue Station, to supplement coal firing. Later, additional boilers were equipped, the last two installations being made in 1941. Over the period of operation, the average use of gas at this station has represented 25 to 30 per cent of the fuel requirements. The reasons leading to the adoption of this combined firing system are outlined in the paper, as well as the details of the installations and the operating results achieved.

Power Stations and Air Pollution

DURING the past two years, public attention in Great Britain has been focused on the question of air pollution due to the operation of super-power electric stations. In his recent presidential address to the Junior Institution of Engineers, Dr. S. L. Pearce, engineer-in-chief of the London Power Company, discusses this problem and others of great importance at the present time owing to the practice of concentrating more and more power in single generating stations. Efficient measures are available for preventing the pollution of the atmosphere by the smoke and ash from chimney-stacks when stoker-fired boilers are used, but when pulverised fuel is adopted the problem becomes more difficult, owing to the fineness of the dust content of the ash. The recent controversy about the new Battersea power station had reference to the much more difficult problem of arresting the possible damage to buildings and vegetation, and the alleged danger to life, due to the sulphur oxides contained in the products of combustion issuing from the chimneys.

Evolution of the Slag-Tap Furnace at the Charles R. Huntley Station of the Buffalo General Electric Co.

Abstract The handling of low-fusion-ash coals at high ratings and with high efficiencies is one of the stiffest problems ever presented to a furnace designer. This paper tells how in their attempt to design a furnace that would burn any coal offered on the Buffalo market the engineers developed the slag-tap furnace for burning powdered coal, after ten years’ experience in driving stoker-fired boilers at 300 to 400 per cent of rating. Because of the greater freedom in selecting coals for a powdered-coal-fired furnace and on account of the greater capacities that could be obtained from the boilers by that method of firing, also because boilers so fired could be made to respond more readily to sudden changes in load incident to peak-load standby plant operation than by any other method of coal firing, powdered-coal firing was chosen for the 60,000-kw. 1926 extension to Charles R. Huntley Station. To obtain data for designing the furnaces under four cross-drum boilers which were purchased to deliver 200,000 lb. of steam per hour, an experimental furnace was installed under one of them. Maximum ratings were in mind and 275,000 lb. per hr. evaporation was obtained. The paper shows how these experiments, on a furnace designed to remove the ash in the dry form, led to the development of the slag-tap furnaces for the 1926 extension and again for the 1928 extension, where the ratings were increased still further. The performance of the slag-tap furnace has exceeded the expectation of its designers. Some of its advantages from both the design and operating standpoint are here enumerated: It requires a minimum of building volume It will burn efficiently and at high ratings an unusually wide variety of coals It produces quick ignition of the fuel It prevents infiltration of air into the bottom of the furnace It requires a minimum of ash-handling labor, and The ash handling is remarkably free from dust and dirt.