## 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 Inputfrom PCA PCAinjectionSystemNotes.docx; ProposedEditControiDevice.docx; ProposedRevisionsforLLLHCICEMSSpan.docx

Attached please find three documents. The first is an explanation ofthe 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 ofsuspension 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 ofexploding. Some cement companies have designed the ACI systems similarto 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 ofvolume x explosion pressure rise) 

## 1

## • During periods of SU/SD, the gas stream priorto 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 lowerthan normal and injected AC can fall out and accumulate in the ductwork.
• Typically, during SU, fuel feed is increased over time until normal operating temperatures are achieved
. During that transition, airflow increases and oxygen concentrations drop. Based on safety concerns, it is appropriate to deferthe injection ofAC until adequate flow and temperature is achieved and oxygen levels have dropped below 12%. Wehave looked for a simple indicatorthat represents when the appropriate combination offlow, 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 baghouse
. 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 ofsuspension and accumulate in the·ducts and baghouse equipment. This accumulation of lime during periods when watervapor condensation is present can cause the lime to cake and harden, altering and restricting gas flows into and through the dust collector.
• Lime injected priorto 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 ofwhen 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 tothe

**~nguage** 

## in 40CFR 63.1346 (g)(3): 

## "All air pollutiontontrol :devices for HAPs regulated underthis Subpart rflLISt 

## be turned on 

## arid operating priorto combustion ofany fueL To prevent unsafe c onditions and deterioration in PM control performance, lime and carbon injection systems must be turned on and operating only afterthe temperatureatthe inletofthe 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 ofthe HGI concentration measurement range during normal inline raw "mill on" operation
.The span value should be aconcentration equivalent to approximately two times the emissions standard and it may be rounded 

### YJ!. to the nearest multiple of5 ppm of HGI, ormaybe setata minimum of 10ppm basedon HCI CEMS manufacturerspecifications. 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
. Engineeringjudgments 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 allowthe 10 ppm HCI span value are needed to prevent the requirements in the proposed PS18 from being overly restrictive and hence prohibitingthe 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 applyto HCI CEMS under PS18 and Procedure 6 specifies thatthe 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 atthe sampling location is often greaterthan 7%. The as-measured concentration equivalentto 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 thatthe 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 lowspan requirement specified in LLL. For greater detail on the following concerns, please referto the detailed comments submitted bythe PCA dated July 11, 2014 regarding proposed PS-18 and Procedure 6
. Proposed PS-18 includes specifications of multi-point linearitytests for initial certification between 0 and the span value and requirements for quarterly audits at 20-30% ofspan value (0.4-0.6 ppm) and these requirements poses significant risks forthe CEMS operator and CEMS provider, and has little impact on the accuracy or reliability of 30-day rolling averages provided bythe CEMS. Furthermore, PS-18 interference test requirements include introduction of9 different gases at specified concentrations while maintainingthe HCI gas concentration between 10 and 40% of span, ortesting atthe regulatory HCI standard (i.e., about 2.2 ppm for cement kilns) and it is proposed thatthe sum ofthe deviations for each gas injection may not exceed 3% ofthe HCI gas concentration. Instrument systems with no interference may fail thetest because ofthe experimental noise atthe levels ofthe necessary measurements. The 10-40% ofspan for a cement kiln is 0
.5 -2.0 ppm HCI. The±3% tolerance ofthe HCI test concentration for cement kiln CEMS is only 0.015-0.06 ppm HCI forthe sum of interfering gas injections
. The tolerance is unacceptable because it is beyond the measurement capability ofthe HCI CEMS. A calibration error (CE) specification of5 percent is twice as restrictive as 5 percent ofspan for the midlevel gas. For cement kilns, the span is 5 ppm, the mid-level gas is 50-60% ofspan, and the "5 percent" requirement is ±0.125 ppm as opposed to the ±0.25 ppm forthe 5 percent of span. The 5 percent specification becomes completely unachievable atthe low level required at 0-30 percent ofspan. The 7-day zero and upscale calibration drift, and the three-level 1calibration error (linearitytests) specifications are 5% ofspan, 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 offield calibration standards (use of zero, low, mid and high range) over 0-5 ppm range for cement kilns forthe calibration errortest (CE i
.e., linearitytest) and calibration drifttest (CD). It is uncertain whether gas manufacturers can even prepare these gases consideringthe subtle differences in concentrations at so many concentrations levels between zero and 5 ppm. The lll provisionsfor 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 importantthat 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) ofthis 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 ofa concentration level between 50 and 150 percent ofthe highest hourly concentration measured during the period of measurements above span, and must be introduced at the probe
. Record and report the results ofthis procedure as you would for a daily calibration
. The "above span" calibration is successful ifthe value measured by the Hg GEMS is within 20 percent ofthe certified value ofthe reference gas. Ifthe value measured by the Hg GEMS exceeds 20 percent ofthe certified value ofthe reference gas,then you must normalize the one-hour average stack gas values measured above the span during the 24-hour period preceding orfollowing 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) ofthis section using the following procedure. Any time 

### two consecutivetile 

### one-hour average measured concentration of HGI exceeds er is

**e*~ested** te e*aeed the span value for 9reaterthan t>,...e he10rs you must,

**within~** 24 hours before or afterthe '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 ofthe applicable performance specification and be ofa concentration level between 50 and .wG 

### 150 percent ofthe highest hourly concentration measured during the period of measurements above span, and must be introduced at the probe
. Record and report the results ofthis procedure as you would for a daily calibration. The 'above span' calibration is successful ifthe value measured by the HGI GEMS is within 20 percent ofthe certified value ofthe reference gas. Ifthe value measured by the HGI GEMS is not within 20 percent ofthe certified value ofthe 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 performinsthe "above spanH calibration checkwhilethe systemis mecuuring elevatedconcentrations. The languageaswrittencreatesa perverse incentivetodo itsomeothertimewhich will take a much longer period tocompletebecause ofthetimefortheHCI gas Injection to reach equilibrium andthentorecoverto

**th~** low concentli!tion afterthe 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
_