Pulverized fuel sources

Petroleum coke (also known as pet coke) is a carbonaceous solid derived from the cracking processes of oil refineries and has been a source of relatively cheap pulverized fuel for the kiln industry. It is called green coke until it is thermally treated into crystalline or calcined pet coke used in the manufacture of electrodes for steel and aluminum extraction. Green coke comes from several sources, all from the petroleum refinery industry. Table 6.2 gives some green coke analyzed by Polak (1971) showing their sources and their elemental analyses. 

Coal accounts for 90% of the proven energy reserves in the United States, and is a source of fuel for nearly half of the nation s electricity, typically via combustion in pulverized coal (PC)-fired boilers. While the U.S. is rich in coal reserves,... 

In the case of the cement rotary kiln, the fluid flow through the kiln freeboard comes from several sources such as secondary hot combustion air, combustion and decarbonation products and inleakage air. In direct firing kilns, the pulverized solid fuel is injected through the burner pipe nozzle with the external diameter in the range of 250 to 600 mm into the kiln with an internal diameter of 2.4 to 6.2 m. 

The primary source of CO2 is the burning of fossil fuels - specifically gas, oil, and coal - so stabilization of atmospheric CO2 concentration will clearly require substantial reductions in CO2 emissions from these sources. For example, one commonly discussed scenario to stabilize at 500 ppm by the mid-twenty-first century suggests that about 640 Gt CO2 (c. 175 GtC) would need to be avoided over 50 years, with further emission reductions beyond 50 years. As references, a 1000 MW pulverized coal plant produces 6-8MtC02 c. 2MtC) per year, while an oil-fired single-cycle plant produces about two-thirds this amount and a natural gas combined cycle plant produces about half this amount. Thus the above scenario would require that the atmospheric emissions from the equivalent of 2000-4000 large power plants be avoided by approximately the year 2050. 

An interesting research proposal in the 1930 s was to develop processes and motors for the direct use of solid fuels that utilize either compacted or highly pulverized materials from renewable resources. Although commercial applications for mobile power have not been reported, turbogenerator type motors based on the expansion and compression cycles in refrigeration have been proposed to utilize solid fuels as the energy source. 

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