OCR Text |
Show method 29. Volatile and semivolatile organic compounds were measured using VOST and EPA method 0010/23, respectively. Aldehydes, acid gases , total particulate '2° ' CO 2' CO , NOX ' SO 2 and total hydrocarbons were also measured following EPA reference methods described in 40CFR60 Appendix A. A carbon sorption tube, was employed as a backup for mercury ~et~rmination. In all, measurements were made for the eleven toxic metals listed in the CAAA, as well as radionuclides and other metals that were also collected in the Method 29 sampling train. In order to determine APCD effectiveness, measurements of toxic compounds were taken both upstream and downstream of the ESP. In a separate program, tests were performed on a 10 MW pilot-plant utilizing a slipstream from a coal-fired utility boiler. The pilot plant consisted of a scrubber/cyclone S02 control unit, ESP, and a small 1 MW -equivalent pulse-jet baghouse. Trace metals considered in the sampling and analysis portion of the program were As, Sb, Ba, Cd, Cr, Co, Pb, Mn, Hg, Se, and V. In these tests metals removal efficiencies were determined for three configurations of the pilot-plant APCDs. These were: • Cyclone followed by an ESP • Cyclone followed by a fabric filter • S02 absorber/cyclone followed by a fabric filter. METALS PARTITIONING MODEL A metals partitioning model has been developed by EER for the EP A[ 4,5]. The model was used . to evaluate the importance of various phenomena and parameters which may control the behavior of metals in coal-fired boilers [6]. The model consists of a group of computer submodels and analytical approaches which simulate the physical and chemical mechanisms which may influence metals behavior in combustion systems. The major components of the metals partitioning model are shown in Figure 1. This figure illustrates the relationship between the submodels and illustrates schematically how they relate to the physical and chemical processes that lead to release of toxic metals from coal ash during combustion. Combustion System Thermal Analysis The combustion system thermal analysis is established first to define the background environment for the burning coal and metals vaporization, as well as for the post-flame and the condensing metal vapors. 4 |