Nizich, Sharon 

From: 

Sent: 

To: 

Cc: 

Subject: 

Attachments: 

Sharon, 

HolmesAems@aol.com 

Wednesday, September 24, 2014 3:44 PM 

Nizich, Sharon 

Barnett, Keith; tharman@cement.org 

Input from PCA 

PCAinjectionSystemNotes.docx; ProposedEditControiDevice.docx; 

ProposedRevisionsforLLLHCICEMSSpan.docx 

Attached please find three documents. The first is an explanation of the proposed cut point for the use of injection 

systems during start up. The second is a suggested edit to the work practice language to implement that proposal. The 

last is a discussion of suggested edits to the span provisions for CEMS. 

Please let me know if you have any questions. 

John Holmes 

AEMS, LLC 

1 
Startup and Shutdown Considerations for Operating Hazardous Air Pollutant 

(HAP) Air Pollution Control Devices 

The points shown below provide background information about startup and shutdown for HAPs 

regulated in Title 40 Code of Federal Regulations Part 63.1346 (g)(3). 

• During startup and shutdown (SU/SD), the particulate control devices should be in 

operation. 

• Under certain conditions, the mercury (Hg) and hydrogen chloride (HCI) control devices 

should not be in operation. Activated Carbon Injection (ACI) for Hg emissions control should 

not be in operation when there are potential fire and/or explosion safety concerns. Lime 

injection for HCI emission control should not be in operation when the sorbent injection can 

cause potential damage to the unit, duct work, and the PM control equipment. 

• With EPA mandating in the current rule that control devices be activated and operating 

during SU/SD conditions, PCA believes that extending this requirement to ACI will cause 

some equipment to be at risk for explosion because: 

o Injecting activated carbon (an explosive material) into a non-inert 

atmosphere with increasing temperatures can result in an explosive 

condition; and 

o Injecting activated carbon into minimum /low gas flow conditions can 

cause the material to fall out of suspension in the gas stream which 

results in accumulations of explosive material within the equipment, and 

creates an ideal condition for an explosion to occur. 

• Activated carbon (AC) is rated as an explosive material with a Kst1 value of less than 80, 

which categorizes AC as a weak explosive material, but still capable of exploding. Some 

cement companies have designed the ACI systems similar to pulverized coal systems, with 

explosion vents to mitigate damage to the AC storage and conveying equipment, if an 

explosion would occur. 

• During normal operations, AC is injected into the gas stream prior to the particulate matter 

(PM) control device where the oxygen content is less than 12% and considered an inert or 

non.:explosive environment. 

1 Kst value is an explosive pmperty measured in the laboratory to quantify the severity of a dust 

explosion. The Kst value is calculated as the equivalent pressure in a 1 m3 sphere from the cube law (Kst 

value = cube root of volume x explosion pressure rise) 

1 
• During periods of SU/SD, the gas stream prior to the PM control device will not be inert; it 

will be above 12% oxygen because the system is being operated at reduced fuel 

combustion rates. Also, flow rates through the unit will be lower than normal and injected 

AC can fall out and accumulate in the duct work. 

• Typically, during SU, fuel feed is increased over time until normal operating temperatures 

are achieved. During that transition, air flow increases and oxygen concentrations drop. 

Based on safety concerns, it is appropriate to defer the injection of AC until adequate flow 

and temperature is achieved and oxygen levels have dropped below 12%. Wehave looked 

for a simple indicator that represents when the appropriate combination of flow, oxygen, and 

temperature is achieved. The minimal temperature necessary to achieve less than 12% 

oxygen content in the gas stream, thus making the stream inert and non-explosive, as well 

has having adequate flow through the unit is 300 degrees F at the inlet to the bag house. 

This temperature can be measured using the existing thermocouple that monitors 

temperature to control dioxin and furan (D/F) emissions. 

• With respect to lime injection systems, lime injected into large ducts with low gas flows I 

velocities will fall out of suspension and accumulate in the· ducts and bag house equipment. 

This accumulation of lime during periods when water vapor condensation is present can 

cause the lime to cake and harden, altering and restricting gas flows into and through the 

dust collector. 

• Lime injected prior to the dust collector will result in lime coating the dust collector bags. 

When water vapor condensation is present during SU/SD conditions, the lime coating the 

bags will harden and reduce the efficiency for dust removal. This activity will also result in 

reduced bag life. 

• As with starting ACI systems, a temperature of 300 degrees For higher at the inlet to the 

PM control device is a useful indicator of when it is safe to turn on and operate a lime 

injection system without risking lime fall out and deposits in the ductwork or hard layer 

caking in the PM control device or bags. 

2 
Proposed Edit to the ~nguage in 40 CFR 63.1346 (g)(3): 

"All air pollution tontrol :devices for HAPs regulated under this Subpart rflLISt be turned on arid operating 

prior to combustion of any fueL To prevent unsafe conditions and deterioration in PM control 

performance, lime and carbon injection systems must be turned on and operating only after the 

temperature at the inlet of the downstream kiln PM control device achieves 300 degrees Fahrenheit 

(five minute average)." 
The LLL provisions for HCL CEMS span for PS-18 monitors under 63.1350(1)(1)(i) are suggested 

to be revised as follows: 

(i) You must use a span value for any HGI GEMS that represents the intended upper limit of the HGI 

concentration measurement range during normal inline raw "mill on" operation. The span value should be 

a concentration equivalent to approximately two times the emissions standard and it may be rounded YJ!. 

to the nearest multiple of 5 ppm of HGI, or may be set at a minimum of 10 ppm based on HCI CEMS 

manufacturer specifications. The HGI GEMS data recorder output range must include the full range of 

expected HGI concentration values which would include those expected during "mill off' conditions. 

Engineering judgments made and calculations used to determine the corresponding span concentration 

from the emission standard shall be documented in the site-specific monitoring plan and associated 

records. 

The change to allow the 10 ppm HCI span value are needed to prevent the requirements in the 

proposed PS18 from being overly restrictive and hence prohibiting the use of HCI CEMS to 

monitor cement kiln emissions. This is justified because the current requirements in 40 CFR 63, 

Subpart LLL (63.1350(1)(1)(i)) that would apply to HCI CEMS under PS18 and Procedure 6 

specifies that the HCI span value be established at two times the concentration equivalent 

emission limit during mill-en operations, rounded to the nearest 5 ppm. Recognizing that all 

HCI CEMS provide wet basis measurements, and the effluent oxygen concentration at the 

sampling location is often greater than 7%. The as-measured concentration equivalent to 3 ppm 

HCI @ 7% 02, dry basis is typically about 2.1-2.4 ppm (wet, actual 0 2) for contemporary cement 

kiln systems, and thus, Subpart LLL requires that the HCI CEMS span value be 5 ppm. The 

proposed PS-18 and Procedure 6 include several OA/QC requirements that become exceedingly 

difficult, if not impossible, due to the low span requirement specified in LLL. 

For greater detail on the following concerns, please refer to the detailed comments submitted 

by the PCA dated July 11, 2014 regarding proposed PS-18 and Procedure 6. Proposed PS-18 

includes specifications of multi-point linearity tests for initial certification between 0 and the 

span value and requirements for quarterly audits at 20-30% of span value (0.4-0.6 ppm) and 

these requirements poses significant risks for the CEMS operator and CEMS provider, and has 

little impact on the accuracy or reliability of 30-day rolling averages provided by the CEMS. 

Furthermore, PS-18 interference test requirements include introduction of 9 different gases at 

specified concentrations while maintaining the HCI gas concentration between 10 and 40% of 

span, or testing at the regulatory HCI standard (i.e., about 2.2 ppm for cement kilns) and it is 

proposed that the sum of the deviations for each gas injection may not exceed 3% of the HCI 

gas concentration. Instrument systems with no interference may fail the test because of the 

experimental noise at the levels of the necessary measurements. The 10-40% of span for a 

cement kiln is 0.5 -2.0 ppm HCI. The± 3% tolerance of the HCI test concentration for cement 

kiln CEMS is only 0.015-0.06 ppm HCI for the sum of interfering gas injections. The tolerance 

is unacceptable because it is beyond the measurement capability of the HCI CEMS. A 

calibration error (CE) specification of 5 percent is twice as restrictive as 5 percent of span for 

the mid level gas. For cement kilns, the span is 5 ppm, the mid-level gas is 50-60% of span, and 

the "5 percent" requirement is ±0.125 ppm as opposed to the ±0.25 ppm for the 5 percent of 

span. The 5 percent specification becomes completely unachievable at the low level required at 

0-30 percent of span. The 7-day zero and upscale calibration drift, and the three-level 

1 
calibration error (linearity tests) specifications are 5% of span, or ±0.25 ppm for cement kiln 

applications. The requirements necessitate having a zero, low (may also be zero), mid and highlevel calibration standards in the 0-5 ppm level. The specifications are very strict and will likely 

cause random failures. (PS18 requires an excessive number of field calibration standards (use of 

zero, low, mid and high range) over 0-5 ppm range for cement kilns for the calibration error test 

(CE i.e., linearity test) and calibration drift test (CD). It is uncertain whether gas manufacturers 

can even prepare these gases considering the subtle differences in concentrations at so many 

concentrations levels between zero and 5 ppm. 

The lll provisions for Hg and HCI CEMS above span procedures 63.13SO(k)(Z)(ii) and 

(l)(l)(i)(B) is suggested to be revised as follows to provide consistency. It is important that 

the same complex DAS programming be used for both pollutants. Significant effort has 

already been expended in programming the promulgated requirements for Hg CEMS. 

For Hg GEMS: 63.1350(k)(2)(ii) Quality assure any data above the span value established in 

paragraph (k)(1) of this section using the following procedure. Any time two consecutive one-hour 

average measured concentration of Hg exceeds the span value you must, within 24 hours before or after, 

introduce a higher, "above span" Hg reference gas standard to the Hg GEMS. The "above span" 

reference gas must meet the requirements of PS 12A, Section 7.1, must be of a concentration level 

between 50 and 150 percent of the highest hourly concentration measured during the period of 

measurements above span, and must be introduced at the probe. Record and report the results of this 

procedure as you would for a daily calibration. The "above span" calibration is successful if the value 

measured by the Hg GEMS is within 20 percent of the certified value of the reference gas. If the value 

measured by the Hg GEMS exceeds 20 percent of the certified value of the reference gas, then you must 

normalize the one-hour average stack gas values measured above the span during the 24-hour period 

preceding or following the ' above span" calibration for reporting based on the Hg GEMS response to the 

reference gas as shown in equation 19:: ... 0nly one above span calibration is needed per 24 hour period. 

For HGI GEMS: 63.1350(1)(1)(i)(B) Quality assure any data above the span value established in 

paragraph (1 )(1 )(i) of this section using the following procedure. Any time two consecutive tile one-hour 

average measured concentration of HGI exceeds er is e*~ested te e*aeed the span value for 9reater than 

t>,...e he10rs you must, within~ 24 hours before or after the 'above span' period, introduce a higher, 

'above span' HGI reference gas standard to the HGI GEMS. The 'above span' reference gas must meet 

the requirements of the applicable performance specification and be of a concentration level between 50 

and .wG 150 percent of the highest hourly concentration measured during the period of measurements 

above span, and must be introduced at the probe. Record and report the results of this procedure as you 

would for a daily calibration. The 'above span' calibration is successful if the value measured by the HGI 

GEMS is within 20 percent of the certified value of the reference gas. If the value measured by the HGI 

GEMS is not within 20 percent of the certified value of the reference gas, then you must normalize the 

stack gas values measured above span as described in paragraph (1)(1 )(ii)(G) below.! .. ·- ·- -·· .. 

2 

Commented [lPl]: Good practice requires performins the 

"above spanH calibration check while the system is mecuuring 

elevated concentrations. The language as written creates a 

perverse incentive to do it some other time which will take a much 

longer period to complete because of the time for the HCI gas 

Injection to reach equilibrium and then to recover to th~ low 

concentli!tion after the injection. Performing a calfbration check at 

25 ppm HCI when nominal HCI concentrations are less than 0.5 ppm 

during mill on operation is a bad practice_