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.
• Simultaneous stack samples and kiln dust samples shall be taken.
- Stack sampling shall be conducted with the multiple metals train according to procedures provided in section 10.3 of this Methods Manual.
- Kiln dust sampling shall be conducted as follows:
- Follow appropriate sampling and analytical procedures such as those described in the waste analysis plan as they pertain to the condition and accessibility of the dust.
- Samples should be representative of the last ESP or Fabric Filter in the APCS series.
• The feedrates of hazardous metals in all pumpable hazardous waste streams and in all hazardous waste streams shall be monitored during these tests. It is recommended (but not required) that the feedrates of hazardous metals in all feedstreams also be monitored.
• At least 10 single (noncomposited) runs are required during the tests.
- The facility shall follow a normal schedule of kiln dust recharging for all of the tests.
- Three of the first 5 tests shall be compliance tests in conformance with s.
NR 666.103(3); i.e., they shall be used to determine maximum allowable feedrates of metals in pumpable hazardous wastes. and in all hazardous wastes, as well as to determine other compliance limits (see s.
NR 666.103(3)(a)).
- The remainder of the tests need not be conducted under full compliance test conditions; however, the facility shall operate at its compliance test production rate, and it shall burn hazardous waste during these tests such that the feedrate of each metal for pumpable and total hazardous wastes is at least 25% of the feedrate during compliance testing. If these criteria, and those discussed below, are not met for any parameter during a test, then either the test is not valid for determining enrichment factors under this method, or the compliance limits for that parameter shall be established based on these test conditions rather than on the compliance test conditions.
• Verify that compliance emission limits are not exceeded.
- Metal emissions may not exceed Tier III (or Tier II) limits.
- PM emissions may not exceed the most stringent of applicable PM standards (or an optional self-imposed particulate standard).
• The facility shall generate normal, marketable product using normal raw materials and fuels under normal operating conditions (for parameters other than those specified under this method) when these tests are conducted.
• Chromium shall be treated as a special case:
- The enrichment factor for total chromium is calculated in the same way as the enrichment factor for other metals (i.e., the enrichment factor is the ratio of the concentration of total chromium in the emitted particulate matter to the concentration of total chromium in the collected kiln dust).
- The enrichment factor for hexavalent chromium (if measured) is defined as the ratio of the concentration of hexavalent chromium in the emitted particulate matter to the concentration of total chromium in the collected kiln dust.
(3) Use the enrichment factors measured in Step 2 to determine EF95% , EF99% , and SEF.
