Waiver for Cement and Light-Weight Aggregate Kilns. For cement kilns and light-weight aggregate kilns, raw material feed streams contain the vast majority of the ash input, and a significant amount of the ash in the feed stream is entrained into the kiln exhaust gas. For these devices, the ash content of the hazardous waste stream is expected to have a negligible effect on total ash emissions. For this reason, there is no ash feed rate compliance limit for cement kilns or light-weight aggregate kilns. Nonetheless, cement kilns and light-weight aggregate kilns are required to initially certify that PM emissions are not likely to exceed the PM limit, and subsequently, certify through compliance testing that the PM limit is not exceeded.
Default Partitioning Value for Ash. The default assumption for partitioning of ash depends on the feed stream firing system. There are 2 methods by which materials may be fired into BIFs: Suspension-firing and bed-firing.
The suspension category includes atomized and lanced pumpable liquids and suspension-fired pulverized solids. The default partitioning assumption for materials fired by these systems is that 100% of the ash partitions to the combustion gas.
The bed-fired category consists principally of stoker boilers and raw materials (and in some cases containerized hazardous waste) fed into cement and light-weight aggregate kilns. The default partitioning assumption for materials fired on a bed is that 5% of the ash partitions to the combustion gas.
Converting the PM Concentration-Based Standard to a PM Mass Emission Rate. The emission limit for BIFs is 0.08 gr/dscf, corrected to 7% O2, unless a more stringent standard applies [for example, a New Source Performance Standard (NSPS) or a State standard implemented under the State Implementation Plan (SIP)]. To convert the 0.08 gr/dscf standard to a PM mass emission rate:
1. Determine the flue gas O2 concentration (% by volume, dry) and flue gas flow rate (dry standard cubic feet per minute); and
2. Calculate the allowable PM mass emission rate by multiplying the concentration- based PM emission standard times the flue gas flow rate times a dilution correction factor equal to [(21-O2 concentration from step 1)/(21-7)].
9.4 Use of Engineering Judgement To Estimate
Partitioning and APCS RE Values
Engineering judgement may be used in place of the department's conservative default assumptions to estimate partitioning and APCS RE values if the engineering judgement is defensible and properly documented. To properly document engineering judgement, the owner/operator shall keep a written record of all assumptions and calculations necessary to justify the APCS RE used. The owner/operator shall provide this record to the department upon request and shall be prepared to defend the assumptions and calculations used.
If the engineering judgement is based on emissions testing, the testing will often document the emission rate of a pollutant relative to the feed rate of that pollutant rather than the partitioning factor or APCS RE.
Examples of situations where the use of engineering judgement may be supportable to estimate a partitioning factor, APCS RE, or SRE include:
• Using emissions testing data from the facility to support an SRE, even though the testing may not meet full QA/QC procedures (e.g., triplicate test runs). The closer the test results conform with full QA/QC procedures and the closer the operating conditions during the test conform with the established operating conditions for the facility, the more supportable the engineering judgement will be.
• Applying emissions testing data documenting an SRE for one metal, including nonhazardous surrogate metals to another less volatile metal.
• Applying emissions testing data documenting an SRE from one facility to a similar facility.
• Using APCS vendor guarantees of removal efficiency.
9.5 Restrictions on Use of Test Data
The measurement of an SRE or an APCS RE may be limited by the detection limits of the measurement technique. If the emission of a pollutant is undetectable, then the calculation of SRE or APCS RE should be based on the lower limit of detectability. An SRE or APCS RE of 100% is not acceptable.
Further, mass balance data of facility inputs, emissions, and products/residues may not be used to support a partitioning factor, given the inherent uncertainties of such procedures. Partitioning factors other than the default values may be supported based on engineering judgement, considering, for example, process chemistry. Emissions test data may be used to support an engineering judgement-based SRE, which includes both partitioning and APCS RE.
9.5 References
1. Barton, R.G., W.D. Clark, and W.R. Seeker. (1990) “Fate of Metals in Waste Combustion Systems". Combustion Science and Technology. 74, 1-6, p. 327
Section 10.0—Alternative Methodology for Implementing Metals Controls
10.1 Applicability
This method for controlling metals emissions applies to cement kilns and other industrial furnaces operating under interim license that recycle emission control residue back into the furnace.
10.2 Introduction
Under this method, cement kilns and other industrial furnaces that recycle emission control residue back into the furnace shall comply with a kiln dust concentration limit (i.e., a collected particulate matter (PM) limit) for each metal, as well as limits on the maximum feedrates of each of the metals in: (1) pumpable hazardous waste; and (2) all hazardous waste.
The following subsections describe how this method for controlling metals emissions is to be implemented:
• Subsection 10.3 discusses the basis of the method and the assumptions upon which it is founded;
• Subsection 10.4 provides an overview of the implementation of the method;
• Subsection 10.5 is a step-by-step procedure for implementation of the method;
• Subsection 10.6 describes the compliance procedures for this method; and
• Appendix A describes the statistical calculations and tests to be used in the method.
10.3 Basis
The viability of this method depends on 3 fundamental assumptions:
(1) Variations in the ratio of the metal concentration in the emitted particulate to the metal concentration in the collected kiln dust (referred to as the enrichment factor or EF) for any given metal at any given facility will fall within a normal distribution that can be experimentally determined.
(2) The metal concentrations in the collected kiln dust can be accurately and representatively measured.
(3) The facility will remain in compliance with the applicable particulate matter (PM) emission standard.
Given these assumptions. metal emissions can be related to the measured concentrations in the collected kiln dust by the following equation:
Where:
ME is the metal emitted;
PME is the particulate matter emitted;
DMC is the metal concentration in the collected kiln dust; and
EF is the enrichment factor, which is the ratio of the metal concentration in the emitted particulate matter to the metal concentration in the collected kiln dust.
This equation can be rearranged to calculate a maximum allowable dust metal concentration limit (DMCL) by assuming worst-case conditions that: metal emissions are at the Tier III (or Tier II) limit (see s.
NR 666.106), and that particulate emissions are at the particulate matter limit (PML):
The enrichment factor used in the above equation shall be determined experimentally from a minimum of 10 tests in which metal concentrations are measured in kiln dust and stack samples taken simultaneously. This approach provides a range of enrichment factors that can be inserted into a statistical distribution (t-distribution) to determine EF95% and EF99% . EF95% is the value at which there is a 95% confidence level that the enrichment factor is below this value at any given time. Similarly, EF99% is the value at which there is a 99% confidence level that the enrichment factor is below this value at any given time. EF95% is used to calculate the “violation" dust metal concentration limit (DMCLv):
If the kiln dust metal concentration is just above this “violation" limit, and the PM emissions are at the PM emissions limit, there is a 5% chance that the metal emissions are above the Tier III limit. In such a case, the facility would be in violation of the metals standard.
To provide a margin of safety, a second, more conservative kiln dust metal concentration limit is also used. This “conservative" dust metal concentration limit (DMCLc) is calculated using a “safe" enrichment factor (SEF). If EF
99% is greater than two times the value of EF95% , the “safe" enrichment factor can be calculated using Equation 4a:
SEF = 2 EF95%
(4a)Q02
If EF99% is not greater than two times the value of EF95% , the “safe" enrichment factor can be calculated using Equation 4b:
SEF = EF99%
(4b)
In cases where the enrichment factor cannot be determined because the kiln dust metal concentration is nondetectable, the “safe" enrichment factor is as follows:
SEF = 100
(4c)
For all cases, the “conservative" dust metal concentration limit is calculated using the following equation:
If the kiln dust metal concentration at a facility is just above the “conservative" limit based on that “safe" enrichment factor provided in Equation 4a, and the PM emissions are at the PM emissions limit, there is a 5% chance that the metal emissions are above one-half the Tier III limit. If the kiln dust metal concentration at the facility is just above the “conservative" limit based on the “safe" enrichment factor provided in Equation 4b, and the PM emissions are at the PM emissions limit, there is a 1% chance that the metal emissions are above the Tier III limit. In either case, the facility would be unacceptably close to a violation. If this situation occurs more than 5% of the time, the facility would be required to rerun the series of 10 tests to determine the enrichment factor. To avoid this expense. the facility would be advised to reduce its metals feedrates or to take other appropriate measures to maintain its kiln dust metal concentrations in compliance with the “conservative" dust metal concentration limits.
In cases where the enrichment factor cannot be determined because the kiln dust metal concentration is nondetectable, and thus no EF95% exists, the “violation" dust metal concentration limit is set at 10 times the “conservative" limit:
DMCLv=10×DMCLc
(6)
10.4 Overview
The flowchart for implementing the method is shown in Figure 10.4-1. The general procedure is as follows:
• Follow the certification of precompliance procedures described in subsection 10.6 (to comply with s.
NR 666.103(2)).
• For each metal of concern, perform a series of tests to establish the relationship (enrichment factor) between the concentration of emitted metal and the metal concentration in the collected kiln dust.
• Use the demonstrated enrichment factor, in combination with the Tier III (or Tier II) metal emission limit and the most stringent applicable particulate emission limit, to calculate the “violation" and “conservative" dust metal concentration limits. Include this information with the certification of compliance under s.
NR 666.103(3).
• Perform daily and/or weekly monitoring of the cement kiln dust metal concentration to ensure (with appropriate QA/QC) that the metal concentration does not exceed either limit.
- If the cement kiln dust metal concentration exceeds the “conservative" limit more than 5% of the time (i.e., more than 3 failures in last 60 tests), the series of tests to determine the enrichment factor shall be repeated.
- If the cement kiln dust metal concentration exceeds the “violation" limit, a violation has occurred.
• Perform quarterly tests to verify that the enrichment factor has not increased significantly. If the enrichment factor has increased, the series of tests to determine the enrichment factor shall be repeated.
10.5 Implementation Procedures
A step-by-step description for implementing the method is provided below:
(1) Prepare initial limits and test plans.
• Determine the Tier III metal emission limit. The Tier II metal emission limit may also be used (see s.
NR 666.106).
• Determine the applicable PM emission standard. This standard is the most stringent particulate emission standard that applies to the facility. A facility may elect to restrict itself to an even more stringent self-imposed PM emission standard, particularly if the facility finds that it is easier to control particulate emissions than to reduce the kiln dust concentration of a certain metal (i.e., lead).
• Determine which metals need to be monitored (i.e., all hazardous metals for which Tier III emission limits are lower than PM emission limits—assuming PM is pure metal).
• Follow the compliance procedures described in Subsection 10.6.
• Follow appropriate guidelines for preparing test plans and waste analysis plans for the following tests:
- Compliance tests to determine limits on metal feedrates in pumpable hazardous wastes and in all hazardous wastes (as well as to determine other compliance parameters);
- Initial tests to determine enrichment factors;
- Quarterly tests to verify enrichment factors;
- Analysis of hazardous waste feedstreams; and
- Daily and/or weekly monitoring of kiln dust for continuing compliance.
(2) Conduct tests to determine the enrichment factor.
• These tests shall be conducted within a 14-day period. No more than 2 tests may be conducted in any single day. If the tests are not completed within a 14-day period, they shall be repeated.
