HWF NOTES ©
by David Constans
During the summer of 1992, 33 cement kiln BIF compliance tests were conducted. Eighteen of these tests report the stack emissions for ten metals, including barium and silver. However because of barium and silver's low toxicity, their physical and chemical characteristics when introduced into a cement clinkering kiln, and the particulate emission limit, their presence in the feed to cement kilns (as raw material or as a component of the fuel) appears to have minimal impact on human health based on the health based criteria set out in the BIF regulation.
This document will demonstrate that stack emissions testing and process feed rate controls for these two metals are unnecessary; that the particulate emission limit is a sufficient safeguard to protect the human health and environment.
Background Information on Ba and Ag
Neither of these metals is as toxic as the other non-carcinogenic metals. Instances of poisoning by these metals are very rare. The Reference Air Concentrations (RAC) for barium and silver are 50 ug/m3 and 3 ug/m3 respectively. These values are more than one order of magnitude higher than those of the metals; antimony, lead, mercury and thallium.
Barium and silver are refractory metals; that is they tend to remain in the clinker or the dust and exit the system with this material rather than out the stack. This is illustrated by the high system removal efficiencies for these metals. See table 1.
Barium and Silver System Removal Efficiencies For Five Kilns Taken From BIF COC Tests
|Barium SREs||Silver SREs|
(1) Some silver concentrations in the various input and output streams were below the analytical detection limit. The manner in which minimum and maximum SREs are calculated produces wide ranges in these instances.
Explanation of Tables 2 and 3
Table 2 is based on data extracted from the Commercial BIF Compliance Test Results. This table documents allowable and actual emission rates for barium, and compares these values against allowable particulate emission rates. Table 3 is identical data for silver. The following is an explanation of the columns in the tables.
Column 1 - This is the company/plant/kiln for which the compliance test was conducted.
Column 2 - This is the actual average metal emission value for barium (Table 1) or silver (Table 2) in grams per second. This is the average of the three or more runs conducted during the compliance test. Some facilities did not report emission data for Tier IA metals.
Column 3 - This is the calculated maximum allowable emission rate of barium (Table 1) or silver (Table 2) for that kiln stack based on that stack's physical characteristics and the RAC (from Part 266 Appendix IV) for the metal.
Column 4 - The values in this column are the calculated maximum allowable particulate emission rates for that kiln (based on 0.08 grains per dry standard cubic foot) expressed in grams per second. (National Cement's BIF Compliance Test Report did not supply a stack volumetric flow rate for the particulate emissions tests. Consequently, it was not possible to calculate a maximum allowable particulate emission rate expressed in grams/second.)
Column 5 - The values in this column represent the required purity of the metal at the maximum allowable particulate emission rate (based on 0.08 grains per dry standard cubic foot) that would equal the maximum allowable metal emission value. That is, if the stack were to emit the maximum allowable amount of barium or silver, what percent of the maximum allowable particulate emitted must be this metal?
The actual metal emission rates in Column 2 are included to show that barium and silver emission rates are several orders of magnitude lower than the maximum allowable metal emission rates.
It becomes immediately obvious that the maximum allowable particulate emission rate (0.08 grains/dscf) limits barium emission much more than the maximum allowable metals emission limit. The emitted particulate would have to consist of barium at purities in excess of 100% in all cases. This is clearly an impossibility. A lower particulate emission rate is unnecessary to restrict barium emissions to a safe health based level.
Similarly, to exceed the maximum allowable emission rate for silver, the emitted particulate would have to consist of silver at purities (in one instance) of 28% silver, up to several thousand percent in other kilns. Even the value of 28% would be considered extremely high grade silver bearing ore when it is understood that there are normally only a few ounces of silver in a ton of ore mined from a successful silver mine. Additionally, since silver is a refractory metal (as is barium) the kiln dust would have even higher concentrations of silver. Whatever material was the source of this high silver content would be removed from the kiln's feed and it's silver recovered.
The existing BIF Compliance Test data amply demonstrates that for barium and silver, the maximum allowable particulate emission rate of 0.08 gr/dscf is sufficiently restrictive to safeguard human health based on the health based standards in the BIF Regulations. Therefore stack emissions testing and process feed rate controls for barium and silver are unnecessary, and should be deleted from Part B requirements at permitted facilities as well as future versions of the BIF regulations. No environmental or health benefit exists from current expenditures to comply with this portion of the regulations.
|Percentage of Metal in Particulate Required to Emit Metal Limit|
|Ash Grove - Chanute, KS #1||3.81E-03||2777.78||7.31||38023.06%|
|Ash Grove - Chanute, KS #2||4.38E-03||2777.78||6.91||40182.29%|
|Ash Grove - Foreman, AR #1||543.48||5.47||9927.95%|
|Ash Grove - Foreman, AR #2||543.48||4.91||11066.92%|
|Ash Grove - Foreman, AR #3||847.46||0.80||2247.97%|
|Ash Grove - Louisville, NE #1||1.14E-02||1219.51||11.07||11016.33%|
|Ash Grove - Louisville, NE #2||3.22E-02||185.19||8.24||2247.97%|
|Giant-Harleyville, SC #4||2.22E-02||480.77||4.73||10165.54%|
|Giant-Harleyville, SC #5||1.84E-02||538.79||5.10||10557.55%|
|Holnam, Holly Hill, SC #1||1.86E-03||152.16||8.88||1714.32%|
|Holnam, Holly Hill, SC #2||7.18E-04||197.47||12.97||1522.76%|
|Keystone-Bath, PA #1||5.94E-04||126.26||4.17||3031.48%|
|Keystone-Bath, PA #2||8.07E-04||434.78||12.99||3347.65%|
|Lafarge-Fredonia, KS #1||114.16||3.71||3075.38%|
|Lafarge-Fredonia, KS #2||733.14||4.80||15273.70%|
|LSI-Cape Girardeau, MO||9.40E-03||996.02||22.55||4416.24%|
|Medusa, Wampum, PA #1 & #2||1.31E-03||735.29||8.41||8745.15%|
|Medusa-Wampum, PA #3||3.42E-04||735.29||3.53||20806.98%|
|North Texas-Midlothian, TX||264.55||5.30||4989.42%|
|Texas Industries-Midlothian, TX||3.61E-03||757.58||5.18||14611.74%|
|Percentage of Metal in Particulate Required to Emit Metal Limit|
|Ash Grove - Chanute, KS #1||1.12E-04||166.67||7.31||2281.38%|
|Ash Grove - Chanute, KS #2||9.84E-05||166.67||6.91||2410.94%|
|Ash Grove - Foreman, AR #1||32.61||5.47||595.68%|
|Ash Grove - Foreman, AR #2||32.61||4.91||664.02%|
|Ash Grove - Foreman, AR #3||50.85||0.80||6357.73%|
|Ash Grove - Louisville, NE #1||1.15E-03||73.17||11.07||660.98%|
|Ash Grove - Louisville, NE #2||3.38E-04||11.11||8.24||134.88%|
|Giant-Harleyville, SC #4||1.08E-04||28.85||4.73||609.93%|
|Giant-Harleyville, SC #5||1.06E-04||32.33||5.10||633.45%|
|Holnam, Holly Hill, SC #1||2.56E-05||9.13||8.88||102.86%|
|Holnam, Holly Hill, SC #2||5.03E-05||11.85||12.97||91.37%|
|Keystone-Bath, PA #1||1.71E-05||7.58||4.17||181.89%|
|Keystone-Bath, PA #2||1.88E-05||26.09||12.99||200.86%|
|Lafarge-Fredonia, KS #1||6.85||3.71||184.52%|
|Lafarge-Fredonia, KS #2||43.99||4.80||916.42%|
|LSI-Cape Girardeau, MO||1.34E-05||59.76||22.55||264.97%|
|Medusa, Wampum, PA #1 & #2||44.12||8.41||524.71%|
|Medusa-Wampum, PA #3||44.12||3.53||1248.42%|
|North Texas-Midlothian, TX||15.87||5.30||299.37%|
|Texas Industries-Midlothian, TX||7.00E-06||45.45||5.18||876.70%|