Carbon Monoxide
Carbon monoxide (CO) is formed in the combustion process when carbon in the fuel does not burn completely. The CO gas is odorless, colorless and highly toxic. The greatest source of CO emissions is vehicles, which accounts for approximately 60 % of total CO emission in the United States. In some cities the emissions from automobiles can even reach 95 % of the total emis- sions of CO. Other sources of CO emissions are industrial processes, such as combustion boilers and incinerators (Oland, 2002).
The control of the combustion process is therefore important in terms of boiler efficiency since incomplete combustion results in increased emissions of CO and PM, which means that energy is being wasted. In good com- bustion systems, CO should be limited to a few parts per million (ppm), normally in the range of 20-25 ppm. If CO exceeds 1000 ppm it is usually the result of air starvation or very poor fuel-air mixing and is the symptom of serious problems within the combustion process. The combustion of liquid and gaseous fuels generally generates significantly less CO emissions than the combustion of solid fuels. Therefore, combustion control is an important design and operating concern in solid fuel boilers (Oland, 2002; Mulliger & Jenkins, 2008).