IWS = Ionizing Wet Scrubber
DS = Dry Scrubber
FF = Fabric Filter (Baghouse)
SD = Spray Dryer (Wet/Dry Scrubber)
1 Interpolation of thermal input is not allowed. If a BIF fires between 2 ranges, the APCS temperature under the higher thermal input shall be used. Example: For a BIF firing 10-100 MMBtu/hr, Mercury is considered very volatile at APCS temperatures above 260 F and volatile at APCS temperatures of 260 F and below.
- See PDF for table 
1 Interpolation of thermal input is not allowed. If a BIF fires between two ranges, the APCS temperature under the higher thermal input shall be used. Example: For a BIF firing 10-100 MMBtu/hr, Mercury is considered very volatile at APCS temperatures above 260 F and volatile at APCS temperatures of 260 F and below.
A waste is considered chlorinated if chlorine is present in concentrations greater than 0.1% by weight. In the EPA guidance document “Guidance for Metals and Hydrogen Chloride Controls for Hazardous Waste Incinerators, Volume IV of the Hazardous Waste Incineration Guidance Series,"(1) one percent is used for the chlorinated/nonchlorinated cutoff. However, best engineering judgement, based on examination of pilot-scale data reported by Carroll et al. (2) on the effects of waste chlorine content on metals emissions, suggests that the one percent cutoff may not be sufficiently conservative.
Tables 8.1-2 and 8.1-3 were compiled based on equilibrium calculations. Metals are classified as very volatile at all temperatures above the temperature at which the vapor pressure of the metal is greater than 10% of the vapor pressure that results in emissions exceeding the most conservative risk-based emissions limits.
8.2 APCS RE Default Values for HCl and Cl2
Default assumptions for APCS RE for HCl in BIFs are shown in Table 8.2-1. This table is identical to the column for other BIFs except that cement kilns have a minimum HCl removal efficiency of 83%. Because of the alkaline nature of the raw materials in cement kilns, most of the chlorine is converted to chloride salts. Thus, the minimum APCS RE for HCl for cement kilns is independent of the APCS train.
Removal efficiency of Cl2 for most types of APCS is generally minimal. Therefore, the default assumption for APCS RE for Cl2 for all APCSs is 0%. This is applicable to all BIFs, including cement kilns.
8.3 APCS RE Default Values for Ash
Default assumptions for APCS RE for PM are also shown in Table 8.1-4. These figures are conservative estimates of PM removal efficiencies for different types of APCSs. They are identical to the figures in the Nonvolatile APCS RE column for hazardous metals presented in Table 8.1-1 because the same collection mechanisms and collection efficiencies that apply to nonvolatile metals also apply to PM.
-
See PDF for table
WS = Wet Scrubber including: Sieve Tray Tower, Packed Tower, Bubble Cap Tower
PS = Proprietary Wet Scrubber Design (A number of proprietary wet scrubbers have come on the market in recent years that are highly efficient on both particulates and corrosive gases. Two such units are offered by Calvert Environmental Equipment Co. and by Hydro-Sonic Systems, Inc.).
VS-20 = Venturi Scrubber, ca. 20-30 in W.G. Ä p
VS-60 = Venturi Scrubber, ca. >60 in W.G. Ä p
ESP-l = Electrostatic Precipitator; 1 stage
ESP-2 = Electrostatic Precipitator; 2 stage
ESP-4 = Electrostatic Precipitator; 4 stage
IWS = Ionizing Wet Scrubber
DS = Dry Scrubber
FF = Fabric Filter (Baghouse)
SD = Spray Dryer (Wet/Dry Scrubber)
8.4 References
1. U.S. Environmental Protection Agency. “Guidance on Metals and Hydrogen Chloride Controls for Hazardous Waste Incinerators," Office of Solid Waste, Washington, DC, August 1989.
2. Carroll, G.J., R.C. Thurnau, R.E. Maurnighan, L.R. Waterland, J.W. Lee, and D.J. Fournier. The Partitioning of Metals in Rotary Kiln Incineration. Proceedings of the Third International Conference on New Frontiers for Hazardous Waste Management. NTIS Document No. EPA/600/9-89/072, p. 555 (1989).
Section 9.0—Procedures for Determining
Default Values
for Partitioning of
Metals, Ash,
and Total Chloride/Chlorine
Pollutant partitioning factor estimates can come from 2 sources: default assumptions or engineering judgement. The department's default assumptions are discussed below for metals, HCl2, Cl, and PM. The default assumptions are used to conservatively predict the partitioning factor for several types of BIFs. Engineering judgement-based partitioning factor estimates are discussed in section 9.4.
9.1 Partitioning Default Value for Metals
To be conservative, the department is assuming that 100% of each metal in each feed stream is partitioned to the combustion gas. Owners/operators may use this default value or a supportable, site-specific value developed following the general guidelines provided in section 9.4.
9.2 Special Procedures for Chlorine, HCl, and Cl2
The department has established the special procedures presented below for chlorine because the emission limits are based on the pollutants HCl and Cl2 formed from chlorine fed to the combustor. Therefore, the owner/operator shall estimate the controlled emission rate of both HCl and Cl2 and show that they do not exceed allowable levels.
1. The default partitioning value for the fraction of chlorine in the total feed streams that is partitioned to combustion gas is 100%. Owners/operators may use this default value or a supportable, site-specific value developed following the general guidelines provided in section 9.4.
2. To determine the partitioning of chlorine in the combustion gas to HCl versus Cl2, either use the default values below or use supportable site-specific values developed following the general guidelines provided in section 9.4.
• For BIFs excluding halogen acid furnaces (HAFs), with a total feed stream chlorine/hydrogen ratio =0.95, the default partitioning factor is 20% Cl2, 80% HCl.
• For HAFs and for BIFs with a total feed stream chlorine/hydrogen ratio >0.95, the default partitioning factor is 100% Cl2.
3. To determine the uncontrolled (i.e., prior to acid gas APCS) emission rate of HCl and Cl2, multiply the feed rate of chlorine times the partitioning factor for each pollutant. Then, for HCl, convert the chlorine emission rate to HCl by multiplying it by the ratio of the molecular weight of HCl to the molecular weight of Cl (i.e., 36.5/35.5). No conversion is needed for Cl2.
9.3 Special Procedures for Ash
This section: (1) Explains why ash feed rate limits are not applicable to cement and light-weight aggregate kilns; (2) presents the default partitioning values for ash; and (3) explains how to convert the 0.08 gr/dscf, corrected to 7% O2, PM emission limit to a PM emission rate.
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):
