Development of a mercury transformation model in coal combustion flue gas.
نویسندگان
چکیده
A bench-scale entrained-flow reactor was used to extract flue gas produced by burning a subbituminous Belle Ayr coal in a 580-MJ/h combustion system. The reactor was operated at 400 degrees, 275 degrees, and 150 degrees C with a flow rate corresponding to residence times of 0-7 s. Transformations of elemental mercury (Hg0) and total gas mercury (Hg(gas)) in the reactor were evaluated as functions of temperature and residence time. The most significant mercury transformations (Hg0 to Hg(p) and Hg0 to Hg2+) occurred at 150 degrees C, while virtually no obvious mercury transformations were observed at 275 degrees and 400 degrees C. Approximately 30% of total mercury has been oxidized at temperatures higher than 400 degrees C. A mass transfer-capacity limit model was developed to quantify in-flight mercury sorption on fly ash in flue gas at different temperatures. A more sophisticated model was developed to demonstrate not only the temperature and residence time effects but also to consider the effective surface area of fly ash and dependence of mercury vapor concentration on mercury transformations in flue gas. The reaction orders were 0.02 and 0.55 for Hg0 and Hg(gas), respectively. Only a few percent of the total surface area of the fly ash, in the range of 1%-3%, can effectively adsorb mercury vapor.
منابع مشابه
Catm Annual Report Listing of Catm Projects
Project Description The EERC is performing fundamental research to understand mechanisms responsible for conversion of mercury to other chemical species within combustion and gasification flue gas. This research is imperative for development and validation of improved mercury emission measurement, monitoring, and control. Several tasks are devoted to understanding mercury transformations. Unbur...
متن کاملAtomistic-Level Models
Understanding the speciation of mercury throughout the coal-combustion process is crucial to the design of efficient and effective mercury removal technologies. Mercury oxidation takes place through combined homogeneous (i.e., strictly in the gas phase) and heterogeneous (i.e., gas–surface interactions) pathways. Both bench-scale combustion experiments [1] and quantumchemistry-based theoretical...
متن کاملHomogeneous oxidation of mercury during combustion: A comparison between combustion in air and oxy-combustion
Since oxy-combustion is a relatively new technology, many problems associated with the behavior of coal in this novel combustion process still need to be solved. In particular, there is a lack of knowledge regarding the behavior of toxic trace elements, and there is a need to determine whether trace element distribution among the by-products and emissions to the environment, is comparable with ...
متن کاملInvestigation of selective catalytic reduction impact on mercury speciation under simulated NOx emission control conditions.
Selective catalytic reduction (SCR) technology increasingly is being applied for controlling emissions of nitrogen oxides (NOx) from coal-fired boilers. Some recent field and pilot studies suggest that the operation of SCR could affect the chemical form of mercury (Hg) in coal combustion flue gases. The speciation of Hg is an important factor influencing the control and environmental fate of Hg...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Environmental science & technology
دوره 38 21 شماره
صفحات -
تاریخ انتشار 2004