The combustion of Orimulsion and its generation of air lpollutants

摘要

Orimulsion, a bitumen--in-water emulsified fuel produced in Venezuela, has shown increased use throughout the world as a replacement for heavy fuel oil and, more frequently during the past several years, coal. Orimulsion has relatively high levels of sulfur, nickel, and vanadium compared to many fuel oils and coals, and has been the subject of much debate regarding the environmental impacts of its use. From a combustion perspective, Orimulsion behaves similary to a heavy fuel oil. Reported experience shows that Orimulsion ignites easily in boilers, results in stable flames, and is compatible with existing ignition and flame detection systems. Results reported to date indicate that air emissions from the combustion of Orimulsion can depend upon plant--specific design and operational parameters, similar to air emissions from other fossil fuels. Standard NO_x control technologies such as LNBs and SCR have been shown to provide emissions reductions similar to those achieved when using heavy fuel oil, and Orimulsion has been used as a reburning fuel for NO_x reductions. Conventional wet limestone FGD scrubbers have been successfully applied to Orimulsion--fired units, and ESPs have been used to achieve PM emissions reductions of 90-97/100 over uncontrolled levels. HAP emissions do not appear to be significantly different than those from other fossil fuels and are primarily dependent upon the content of the trace elements in the fuel. Differences between Orimulsion and other fossil fuels from an air pollution control perspective include an increased flue gas volumetric flow rate when compared to heavy fuel oil that can impact ESP performance in retrofit situations, a less dense fly ash that could lead to potential handling problems, and SO_3 emissions as a result of high fuel sulfur and vanadium contents. Emerging issues such as the role of transition metals in health effects mechanisms associated with exposure to PM_2.5 may increase the importance of controlling transition metal emissions including vanadium from Orimulsion and other fossil fuels.