11/4/2011

Revised draft mercury section of the Ferroalloys preamble

1. Mercury Emissions The raw materials used to produce ferroalloys contain various amounts of mercury, which is emitted during the smelting process. These mercury emissions are derived primarily from the manganese ore although there may be trace amounts in the coke or coal used in the smelting process. While some of the mercury that is in particulate or oxidized forms is captured by the particulate control devices, the more volatile ele mental mercury is largely emitted to the atmospher e . We found that mercury emissions are emitted from the furnaces as measured during the ICR test program (estimated to be 540 pounds per year (lb/yr) at one plant and 140 lb/yr at the other plant)

. Pursuant to CAA section 112(d)(2) and 112(d)(3), we are proposing to revise the 1999 NESHAP to include emission limits for mercury. As discussed above, the MACT floor limit is calculated based on the average performance of the units in each category plus an amount to account for these units’ variability. To account for variability in the operation and emissions, the stack test data were used to calculate the average emissions and the 99 percent upper predictive limit (UPL) to derive the MACT floor limit. For more i nformation on how we calculated the MACTfloors and other emission limits, see the Ferroalloys Production

MACT Floor Analysis document, which is available in the docket. Using this method, the MACT floor (or 99 percent UPL) for exhaust mercury concentratio ns from existing furnaces is 80 μg/dscm at 2 percent carbon dioxide (CO 2 ). This MACT floor limit is higher than the actual emissions measured during the ICR performance tests at each plant. Therefore, we anticipate that both of the existing sources would b e able to meet this limit without installing additional controls. With regard to new sources, as described above, the MACT floor for new sources cannot be less stringent than the emissions performance that is achieved in practice by the best

controlled si milar source. A variability analysis similar to that used for existing sources was then performed to calculate a 99 percent UPL using the three run test data from the top

source. For this source category, we calculate that the UPL MACT floor limit for new sources is 16 μg/dscm at 2 percent CO 2 . This limit is based on the performance of the best performing source. The next step in establishing MACT standards is the beyond the floor analysis. In this step, we investigat e other mechanisms for further reducing HAP emissions that are more stringent than the MACT floor level of control in order to “require the maximum degree of reduction in emissions” of HAP. In setting such standards , section 112(d)(2) requires theAgency to consider the cost of achieving the additional emission

reduction s , any non - air quality health and environmental impacts, and energy requirements. Historically, these factors have included factors such as solid waste impacts of a control, effects of emis sions on bodies of water, as well as the energy impacts. As described below, we considered beyond

- the

- floor control options to further reduce emissions of mercury. Because of our limited data set, we considered setting a MACT limit for existing sources ba sed on the performance of the best performing source ( i.e. , based upon the test data used to calculate the MACT floor for new sources) such that the MACT limit for existing sources would be the same as the UPL MACT limit for new sources ( i.e. , 16 μg/dscm). Under this option, the best performing source would need no additional controls to meet the limit, since their current performance defines the new source limit. With regard to the other facility in the source category, as described below, we believe this limit could be achieved by the addition of an activated carbon injection system, which is a proven technology for mercury control. Compliance would be demonstrated by periodic performance testing and continuous parameter monitoring. In evaluating a beyond the floor option, we evaluate, among other things, the costs of achieving additional emissionreductions beyond the floor level of control. No facilities in

the source category use add

- on control devices or work practices to limit mercury emissions beyond what is achieved as co

- control of the emissions with the particulate matter control device. However, we identified both carbon bed technology and activated carbon injection as commercially available mercury emission reduction techniques. Carbon bed techno logy (which is one of the primary control devices used at Industrial Gold Production facilities in the U.S. to minimize mercury emissions, as described in the proposed rule for that category 1 ) does not appear to be a viable technology to control the large volumes of airflow generated by the electric arc furnaces in the Ferroalloys Production source category. The carbon bed technology is applicable to gas streams with low volumes of airflow, and is characterized with relatively high pressure drops. According ly this technology is not used in industries with high volumes of airflow, such as industrial boilers and power plants. In contrast, activated carbon in jection has been used to control mercury emissions at various types of facilities that have large volume s of airflow including some coal

- fired power plants, waste incinerators and cement kilns. Based on available information, activated carbon in jection appears to be a

1 National Emission Standards for Hazardous Air Pollutants: Gold Mine Ore Processing and Production Area Source Category . Proposed Rule (75 FR 22470);technologically feasible control for mercury for these larger

volume combustion sources. M e rcury reductions of up to 90 or 9 5 percent have been reported at these other sources and should also be achievable at ferroalloys production facilities. Based on data and information on these mercury controls for other combustion sources (such as utility b oilers, incinerators and cement kilns), and based on our experience with these controls,

w e conclude that activated carbon injection is a viable control technology for the Ferroalloys Production source category
. Activated carbon injection can be installed upstream or downstream of an existing particulate matter control device. In cases where a source is concerned about potential impacts of waste carbon on the source’s waste stream and resulting disposal options or the ability to sell or reuse baghouse dust , the source can install the activated carbon injection downstream of the particulate matter control device with a separate polishing baghouse to collect the carbon. In other cases, the source can install the activated carbon injection upstream of the part iculate matter control device and use the existing particulate control device to remove the carbon from the airstream. We reviewed facility specific control options that included putting the mercury controls downstream of the existing furnace baghouse to a void the potential issues with sale or reuse ofbaghouse dust associated with upstream controls. Under this

scenario, t he activated carbon injection system would be followed by a “polishing” baghouse to capture the activated carbon for disposal. In the cas e of the existing furnace scrubber, we assumed the source could put the activated carbon injection system upstream of the scrubber, the carbon would be captured by the scrubber and the resulting sludge treated according to the existing treatment process at the plant. Based on discussion 2 with a vendor and other control technology experts, we do not believe that the resulting carbon waste in either scenario would trigger waste disposal concerns. We request comment on these assumptions. We estimate that under this beyond the floor option described above ( i.e. , a proposed limit of 16 μg/dscm), that on e facility would need to install additional controls such as activated carbon injection to meet th is limit, and that this would achieve about 420 pounds of reduction per year in mercury emissions. The capit a l costs are estimated to be $1.7 million, annual ized capital and operating costs to be $1.4 million, with an overall cost

- effectiveness of $3,300 per pound. The general range of costs for me rcury controls from other MACT rules has been about $1,250 to $55,200 per pound of mercury removed (76 FR 25075, May 3, 2011). The EPA requests information on other

2 Conversation with D. Lipscomb, Albemarle. August 22, 2011.control technologies available to Ferroalloys Production

manufacturers to reduce mercury em issions. Other controls might include process changes, substitution of materials, collection or enclosure systems, work practices, or combinations of such methods; which reduce the volume of mercury emissions from existing sources.
I t is important to note that there is no bright line for determining cost

- effectiveness. Each rulemaking is different and various factors must be considered. Nevertheless, the cost

effectiveness of mercury controls in this proposed rule for Ferroalloys Production is near the lowe r end of the range. Some of the factors we consider in determining the costs of control technologies under section 112(d)(2) include, but are not limited to the following: total capital costs; annual costs; and costs compared to total revenues ( e.g. , costs to revenue ratios). Other factors besides cost are considered into our decision. For example, whether the standards significantly impact one or more small businesses, whether the controls would significantly impact production, and whether, and to what
ext ent, the controls result in adverse impacts to other media ( e.g. , hazardous waste issues). We propose that these mercury controls are feasible for the Ferroalloys Production source category from a technical standpoint and are cost effective. We are proposi ng a MACT standard for mercury emissions of 16μ g/dscm for both existing and new sources under the authority of

sections 112(d)(2) and (d)(3). To meet this proposed limit, we have preliminarily determined that a ctiv ated c arbon i njection is feasible to implement for the Ferroalloys Production source category fro m a technical standpoint and that control costs fall within the range of other mercury controls in other MACT rules
. More information regarding how the MACT standards were calculated and the costs is provided in Ferroalloys Production MACT Floor and Cost Memos, which are available in the docket for this rulemaking. We are requesting comment on the proposed standard of 16 μg/dscm for mercury

. We also seek comments and information on our conclusion that activated carbon injection technolog y to meet th e mercury emissions limit for this source category is technically and economically feasible
. Moreover, w e seek comments on the factors related to costs and economics ( such as those described in the parag raph above ) regarding the feasibility and costs of activated carbon injection for this industry. We also seek comments on other possible controls that could be effective to reduce mercury emissions beyond the floor , including the amount and cost of the res ulting emissions reductions . Furthermore, w e seek comment on whether work practices to minimize mercury emissions, such as switching tomanganese ores with low mercury content, could be technically

and economically feasible. Moreover, we request comment on whether there is a basis to subcategorize manganese production operations for mercury. For example, is there a basis on which to subcategorize ferro manganese production and silicomanganese production processes? Although we are requesting comment on subcategorization, we do not believe that s ubcategoriz a tion would have any substantive effect on the resulting standards or the costs of controls since there would be no change in the costs and feasibility of mercury controls evaluated for these

sources. We are proposing that a ny source installing activated carbon injection would be required to continuously monitor the carbon injection rate into the airstream being controlled. W e request comment on the level of variability in the carbon injection rate that should be allowed, and what percent de crease in the rate should be considered significant.
W e also propose that sources monitor the mercury content in the manganese ore. Specifically, we propose that the determination of a significant increase in mercury content would be that the 12

- month rolling weighted average mercury concentration based on monthly sampling in the manganese ore increase s by 10 percent or more compared to the baselineweighted average mercury concentration. If that limit is

exceeded, the source would be required to readjust the carbon injection rate as specified in the source’s monitoring plan or retest within 30 days if there is not a dedicated mercury control device. If a new ore is added, sampling would be required as well.
W e request comment on this ore monitoring provision. We are especially interested in any data that would show the variability in mercury concentration between different ore samples from the same location and the variability of the types of ores used in manganese prod uction. If ore type and mercury content are demonstrated to be stable, we might consider reduc ing the frequency of sampling/calculations to quarterly or less.