               INTEGRATED IRON AND STEEL RTR (07/10/17-DLJones)

Emission Factor Evaluation for Blast Furnace Bell Leaks: 0.6 lb PM leak/ton iron produced 
0.6 lb PM/ton iron was estimated 30,000 tpy PM for whole 1975 U.S. steel industry (EPA, 1978)

Summary of derivation: 	Calculations based on an estimate of the average size of the gap in new bells (50 um) and particle size distribution of blast furnaces gas (from Japanese blast furnaces). Assumed that all particles less than 50 um in the blast furnace gas leaving burden on its way to uptake ducts would instead leak through the bell. Calculations also utilized typical PM loading (gr/scf) of blast furnace gas obtained from U.S. industry (AIST) and total volume of gas in blast furnaces in U.S. industry in 1973 (Battelle, 1975).  EPA (1978) considered bell leaks to be a "grey area" because: (1) this estimate is based on "few available data;" (2) "some data has not been verified"; (3) "emission estimates cannot be accepted as accurate;" and (4) "needs further research." Industry (AISI) on the EPA (1978) task force said the estimates significantly overstate the case. 

Derivation of emissions estimate and citations:

 Estimate of PM loading (gr/dscf) in BF gas as it leaves burden (AIST, 1957)
 Estimate of particle size distribution of BF gas from Japanese BFs (Battelle, 1975) at 28% <= 50 um
 Assumes all particles <= 50 um (bell gap in new bells) will leak out of bell as gas exits BF
 Developed BF pressure adjustment factor to apply Japanese BF estimates to U.S.
 Estimated how often U.S. companies change bells (on average 2.5 yrs) 
 Estimate of total BF gas (ft[3]) for 1973 U.S. steel industry from study of Japanese BFs (Battelle, 1975)
 Emission factor result for 1973 U.S. steel industry was 30,000 tons per year or 0.60 lbs PM/ton iron
 EPA (1978) stated that the bell leak estimates are based on only a few data points, some data has not been verified, should not be considered accurate. But that the data indicate that there could be a problem that may have significance to air quality. 
 EPA stated that for any blast furnace, as service life on a particular bell increases, the emissions going past its seal become greater. The question posed by EPA was whether the increase in emissions are part of normal operations or abnormal. The EPA (1975) believed the emissions are normal; therefore, bell leaks constitute a "grey area" for regulatory purposes
 Industry association (AISI) that worked with EPA (in 1978) during the study said that the data significantly overstated emissions
 HAP content of BF dust: EPA (1978) states there is "considerable variation in the chemical content" of PM from blast furnaces. (pg. 75)

References: 

AIST. Association for Iron and Steel Technology. The Making, Shaping and Treating of Steel. 9[th] ed. Warrendale, PA. 1957. https://www.aist.org 

Battelle, 1975. "Potential for Energy Conservation in the Steel Industry." Battelle Columbus Laboratories, Columbus, OH.  PB-244-097, pages V-67 and V-68. 1975.

EPA, 1978. "Pollution Effects of Abnormal Operations in Iron and Steel Making-Volume III. Blast Furnace Ironmaking, Manual of Practice." EPA-600/2-78-118C. U.S. Washington, DC. 20460. June 1978

