Isokinetic Sampling and Analysis of Halogens and Halogen Acids
by Ion Chromatography
This method describes the collection of inorganic anions (halogens and halogen acids) in stack gas emission samples from hazardous waste incinerators and municipal waste combustors. The collected samples are analyzed using Method 9056. This method collects the emission sample isokinetically and is therefore particularly suited for sampling at sources, such as those controlled by wet scrubbers, emitting acid particulate matter (e.g., HCl dissolved in water droplets). It is noted that this method is not to be used for demonstrating compliance with HCl emission standards less than 20ppm.
The method was written for the collection and analysis of HCl and Cl2 but has the potential for collection of all halogens and halogen acids, but has not yet been fully evaluated for that use. This method is similar to EPA Methods 26 and 26A.
Samples are collected isokinetically using a modified Method 5 train consisting of a Teflon mat or quartz filter and a series of impingers. The 1st impinger (also called the Knockout iminger) is filled with 50mL of 0.05M H2SO4, 2nd and 3rd impingers are filled with 100mL 0.05M H2SO4 solution. The 4th and 5th impingers are filled with 100mL of 0.1M NaOH. The 6th impinger is filled with 200-300g of silica gel.
After collection, the contents of all impingers are measured to later assist with the determination of stack moisture. The contents of the silica gel impinger are weighed for weight gain to also use in the determination of stack moistures. This method also allows for the determination of particulate matter (PM). If PM is being determined the filter and front half rinse must be collected. The filter is folded such that the particulate is on the inside on the filter and placed in a petri dish. The front half of the train (probe, nozzle and front half of the filter holder) is rinsed with acetone. This is collected and analyzed for PM.
The contents of the Knockout impinger and two H2SO4 impingers are combined into one container along with the water rinses of the impingers. The contents of the two NaOH impingers are combined into one container along with the water rinses of the impingers. Each fraction of the train is analyzed separately. Typically, the halogen acids (HCl, HBr, HF) are determined from the H2SO4 impingers and the halogens (Br2, Cl2) from the NaOH impingers.