No abstract

Steel production is an important source of particulate matter emission. In this study, both filterable and condensable fine particulate (PM 2.5 ) emissions from an electric arc furnace (EAF) and four integrated iron and steel plants were measured. Chemical compositions including water soluble ions and metal elements of these two types of PM 2.5 were analyzed. The results show that filterable PM 2.5 concentrations emitted from sintering, coke making, blast furnace, basic oxygen furnace (BOF) and EAF are 1.01, 0.37, 0.16, 0.15 and 0.28 mg/Nm 3 , respectively. Sintering has the highest filterable PM 2.5 emission concentrations. Condensable PM 2.5 concentrations emitted from the above processes are 65.3, 89.7, 3.84, 1.32 and 2.02 mg/Nm 3 , respectively, which are much higher than filterable PM 2.5 . K, Fe, Pb and Zn concentrations are high in filterable PM 2.5 for sintering process, which is attributed to the feedstocks of recycled materials. High sulfur content of the feedstocks results in high concentrations of SO 4 2-for all the test plants. In addition to Fe, the emissions of Pb, Zn and Sn are high for EAF, which is due to the complexity of the recycled steel feedstock for EAF. SO 4 2-is the highest emission ion for sinter process and coke making. For blast furnace, BOF and EAF, however, Na + , K + and Cl -are the predominated ions. For metal elements, concentrations of Na and K are highest for all the plants, which might be caused by their high potential of vaporization.

PM 2.5 emissions from stationary sources contain a filterable and condensable portion. In this study, USEPA Method 201A/202 are used to measure filterable and condensable PM 2.5 emissions from 5 stationary sources (power plants, boilers, brick manufacturing plant, incinerators and arc furnaces). The average filterable PM 2.5 concentrations for power plant, boiler, brick manufacturing plant, incinerator and arc furnace are 0.75, 16.9, 8.67, 0.15 and 2.12 mg/Nm 3 , respectively. The amount of PM 2.5 residue on the exit tube of cyclone and front half of the filter holder is significantly higher when the filterable PM 2.5 concentrations are low. It is necessary to collect both filter and the residue particulates to avoid underestimation of PM 2.5 emissions. The condensable PM accounts for 61.2%, 73.5%, 44.2%, 52.8% and 51.2% of total PM 2.5 for power plant, boiler, brick manufacturing plant, incinerator and arc furnace plant, respectively. The real PM 2.5 contribution to the atmosphere would be underestimated if condensable PM is not included. The condensable PM fraction increases as the exhaust temperature rises. The inorganic fraction accounts for 89.0%, 69.4%, 72.3%, 89.8% and 72.8% of condensable PM, respectively, for power plant, boiler, brick manufacturing plant, incinerator and arc furnace. The inorganic fraction is dominant in the condensable PM, which might be due to the high content of SO 4 .

This study investigated the characteristics of both filterable fine particulate matter (FPM) and condensable particulate matter (CPM) emitted from coal-fired boilers (CFBs) and oil-fired boilers (OFBs) via field sampling. FPM and CPM samples were collected using USEPA Method 201A and Method 202, respectively. Mass concentrations and chemical compositions (including water-soluble ions, metal elements and carbon contents) of collected PM2.5 samples were analyzed. The results show that PM2.5 (FPM + CPM) emission concentrations for CFBs and OFBs are 20.2 ± 10.4 and 157 ± 82.7 mg/Nm3, respectively. In terms of the emission factor, emission of FPM from OFBs is 307.4 ± 50 g/kL of oil and from CFBs is 57.1 ± 13.8 g/t of coal. Significantly higher concentrations are emitted from OFBs than from CFBs due to the reason that better control devices are installed in most CFBs. The average CPM fraction constitutes 58.7 and 54.8% of PM2.5 for CFBs and OFBs, respectively, showing that CPM from the boilers contributes a significant fraction of PM2.5 emissions. FPM sample analysis reveals that SO4 2– is the primary characteristic of water-soluble ion and occupies 64.2 and 80.6% of total water-soluble ions for CFBs and OFBs, respectively. SO4 2– is a main contributor of ions, while NO3 – follows. The species in CPM are dominated by water-soluble ions, including SO4 2–, NO3 –, and NH4 +. The results indicate that CPM is formed primarily by water-soluble ions. The results also show that organic carbon (OC) concentrations are predominant for CFBs, and elemental carbon (EC) is predominant for OFBs.

This study investigated indicatory metals in the filterable (FPM2.5) and condensable (CPM) particulate matter emitted from six different types of stationary stacks (based on fuels and raw materials, n = 33), namely, coal boiler (COL), heavy oil boiler (HOL), wood boiler (WOD), diesel boiler (DSL), natural gas boiler (NGS), and incinerator (INR). FPM2.5 and CPM samples were collected following U.S. EPA Method 201A and Method 202, respectively. The samples were analyzed for mass concentrations and metal compositions. Results showed that the concentration of CPM was higher than that of the FPM2.5 for all types of stacks except WOD. Comparability analysis of FPM2.5, CPM, and TPM2.5 (FPM2.5 + CPM) metal profiles assessed by using the coefficient of divergence (COD) showed a heterogeneous (COD = 0.32–0.99) relationship among six groups of emission stacks. However, FPM2.5, CPM, and TPM2.5 metal profiles within a group of stack revealed homogeneous (COD = 0.19) to heterogeneous (COD = 0.79) relations. Indicatory metals for COL were found to be Ca, Ba, V (FPM2.5), Se, Cd, and Co (CPM) and V, Se, and Co (TPM2.5). Similarly, indicatory metals for HOL included Ca, V, Ni (FPM2.5), V, Se, and Cd (CPM) and V, Co, and As (TPM2.5). Ca, Ni, Ba (FPM2.5), Se, V, and Cd (CPM) and V, Cd, and As (TPM2.5) were recognized as indicatory metals for WOD boilers. Similarly, K and Ca were found to be indicatory metals for DSL, NGS, and INR. The indicatory metals for different emission sources and for different particle fractions (FPM2.5 and CPM) reflect the differences in fuel types, combustion temperatures, and particle formation mechanisms. The results of the present study are expected to provide valuable information for source apportionment modeling and to better assess the contributions of the aforementioned emission sources to the ambient concentrations of PM2.5 and metal elements.