Coal-tired electricity

Gaglia, N., Lundqvist, R., Benfield, R. Fair, J. 1991. Design of a 470,000 lb/hr coal/tire-fired circulating fluidized bed boiler for united development group. Proceedings 1991 Conference on Waste Tires as a Utility Fuel. Electric Power Research Institute, Palo Alto, CA, EPRI GS-7538, 13/1-13/20. 

After breakage the coal is loaded directly into track-mounted mine cars or into rubber -tired electric trucks known as shuttle cars. Sometimes it is loaded directly into chain-or belt-conveyers. After the coal is loaded into shuttle cars or conveyers in the production area, it is transferred to the main haulage system, which consists either of rails or conveyers... 

Particulate emissions while burning TDF or whole tires at coal-fired electric utilities. 

In conventional mining, miners use power saws to slice a deep cut 10-12 ft (3-4 m) wide, into the bottom of a coal wall. Next, holes are drilled into the coal above this cut and fill the holes with explosives. The explosions dislodge chunks of coal from the wall. Conveyors or rubber-tired electric vehicles known as shuttle cars carry the coal chunks out of the mine. 

In 1990, a test using scrap tires (2x2 in. I DE) to generate steam for electricity was conducted at the Elexsys plant. The I DE replaced 20% of the plant s coal. Results showed that IDE is an environmentally sound fuel. Particulate emissions were reduced by the lower ash content of IDE, volatile organic compounds (VOC) were reduced because of more efficient burning of I DE compared to coal, and carbon dioxide emissions were reduced because I DE contains half the fixed carbon found in coal. Nitrogen oxide, chlorine emissions, and metals were also reduced, and ferrous metals and dioxins were nondetectable (7). 

Another furnace that does not require fuel preparation is the stoker boiler, which was used by New York State Electric Gas Corporation (NYSEG) in its TDE tests. At NYSEG, the stoker boiler, which has a 1649°C (3000°E) flame temperature (as does the cyclone boiler), has routinely blended low quaUty coal, and more recently, wood chips with its standard coal to reduce fuel costs and improve combustion efficiency. In the tire-chip tests, NYSEG burned approximately 1100 t of tire chips (smaller than 5x5 cm) mixed with coal and monitored the emissions. The company determined that the emissions were similar to those from burning coal alone. In a second test-bum of 1900 t of TDE, magnetic separation equipment removed metal from the resulting ash, so that it could be recycled as a winter traction agent for roadways. 

Clinker production requires large quantities of fuel. In the United States, coal (qv) and natural gas are the most widely used kiln fuels but fuels derived from waste materials, eg, tires, solvents, etc, are increasing in importance (53) (see Fuels fromwaste Gas,natural). In addition to the kiln fuel, electrical energy is required to power the equipment. This energy, however, amounts to only about one-ninth that of the kiln fuel. The cement industry carefully considers all measures that can reduce fuel demand. 

In 1991, Goodyear began working with Cadence Environmental Energy (Indiana) to market a whole tire feed system to supplement fuel for cement kilns. The system is used by several cement manufacturers. In 1992, Goodyear furnished tires for a Tennessee Valley Authority (TVA) test bum at a Memphis power plant. The electric utility used tire-derived fuel (TDF) to supplement coal fuel in a cyclone boiler. These tests were successful. 

Most often, boilers bum tires or TDF as a supplemental fuel for either coal, gas, refuse-derived-fuel (RDF), or wood waste. The two industries where supplemental use of TDF is most prevalent are electric utilities, where the primary fuel is most often coal, and pulp and paper mills, where the primary fuel is most often wood waste, also known as hog fuel. These industries are discussed further in Chapter 5, TDF Use in Waste Wood Boilers, and Chapter 6, Tires as Supplemental Fuel in Electric Utility Boilers. 

Most facilities that bum tires or TDF use the rubber to supplement a primary fuel such as coal, gas, or vaste wood. One company, however, the Oxford Energy Company, is operating two electric power plants using tires as the only fuel, and is planning several more. 

A novel process for toxic waste handling is suggested in U.S. 4,764,282 (to Uniroyal Goodrich Tire Company). A waste liquid is soaked up into ground tire rubber to form a stable solid that can be transported with reduced risk of spillage. The resulting product can then be incinerated in a fluidized bed combustor, similar to the fluidized bed combustors used in coal-fired power stations. Estimate the cost of waste disposal via this route, allowing for a credit for the electricity produced. How does this compare to the cost of toxic waste disposal by conventional incineration ... 

Shuttle car A rubber-tired vehicle used to haul coal from the continuous miner or loader to a belt feeder or conveyor belt. It is usually electrically powered, with the power supplied through a trailing cable. Some new models are equipped with diesel engines. 

Fuel cells do not use a solid material to store their charge. Instead, low-temperature proton exchange membrane fuel cells use gases such as hydrogen and liquid ethanol (the same form of alcohol found in vodka) or methanol as fuels. These materials are pumped over the surface of the fuel cells, and in the presence of noble-metal catalysts, the protons in these fuels are broken away from the fuel molecule and transported through the electrolyte membrane to form water and heat in the presence of air. The liberated electrons can, just as in the case of batteries, be used to drive an electric motor. Other types of fuel cells, such as molten carbonate fuel cells and solid oxide fuel cells, can use fuels such as carbon in the form of coal, soot, or old rubber tires and operate at 800 degrees Celsius with a very high efficiency. 

The environmental results from the test bum showed that no permit requirements were violated. Con aring the baseline to the 20% tire (energy basis) cofiring test showed lead emission rates were 5% lower and particulate emissions rates were 28% lower. Based on the coal bunkered e last two days of the test at the 20% cofiring rate, the sulfur dioxide emission rate was 13.7% lower than the calculated expected value. Ohio Edison obtained a modification of its operating permit to include up to 20% of total boiler heat input from tires. At this rate, over three million scrap tires could be converted to electricity each year at the Toronto facility. 

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