This paper reports the results of an investigation on SO2 formation from sulfur in fuel (Fuel-S) and SO2 capture by limestone in a bench-scale bubbling fluidized bed combustor. Conversion of fuel-S to S in ash (ash-S), S in char (Char-S) and S in volatile matter (Volatile-S) during pyrolysis and combustion was experimentally evaluated under fluidized bed combustion condition. The formation of SO2 from fuel-S in a fluidized bed consisted of sand, which was inert for SO2 capture, indicated that SO2 was formed from char-S and volatile-S and the contribution of ash-S played only minor role in SO2 formation. Under limestone feed conditions, the emission of SO2 was strongly dependent on conversion of fuel-S to char-S during pyrolysis, whereas conversion to volatile-S had little influence on SO2 emission. This implies that the sulfur in the volatile matter is oxidized at the bottom of the bed and most part of SO2 from volatile-S is captured in the dense bed. In contrast, char-S is considered to be oxidized to SO2 throughout the bed, thus the SO2 from char formed in the vicinity of the bed surface is considered to escape from the bed without being captured by limestone since the contact time is short. These results suggest that the conversion of combustible sulfur (char-S+volatile-S) to char-S is very important to predict the SO2 emission from bubbling fluidized bed combustors under limestone feed conditions.
Electricity consumption in the Internet, electronic network, in Japan was calculated with statistics for 1998. Methodologies to allocate the electricity consumption to each service provided by Internet were proposed. Then, electricity consumption and CO2 emissions associated with downloading 1 CD of music by Internet, especially, using dialup, were investigated. In addition, CO2 emissions associated with distributing 1 CD of music by ordinal compact disc were investigated and compared with those by Internet. CO2 emissions for downloading 1 CD of music by Internet were dependent on transmission speed, 0.79kg-CO2 if the communication speed is 64kbps (actual throughput: 51 kbps), and 0.16kg-CO2 if the communication speed is 1.5Mbps (actual throughput: 1.2Mbps). On the other hand, it was calculated that CO2 emissions for distributing 1 CD of music by ordinal compact disc was 0.33kg-CO2. CO2 emissions for downloading 1 CD of music by Internet will be reduced further with the increase in transmission speed.