1 American Forest & Paper Associati on and American Wood Council Position Paper on Changes Needed to the Boiler MACT and GACT Startup and Shutdown Provisions (July 2014)

Executive Summary

AF&PA and AWC strongly agr ee with EPA that work practices are the correct compliance mechanism for startup and shutdow n periods in the area and major source boiler rules. The work practice standards that EPA originally proposed for periods of startup and shutdown required an owner/operator to minimize periods of startup and shutdown following unit-specific procedures. However, the curr ent definitions of startup and shutdown and the required work practices must be adjusted in order for facilities to be able to safely comply with the Boiler MA CT and GACT rules. The following points summarize why changes are necessary.

• The appropriate procedures for start up and shutdown vary by unit design, pollution control type, fuel firing mechanism , and integration with plant processes.

EPA should not set a “one size fits all” work practice standard to cover the diverse population of units included in the industrial, commercial and institutional (ICI) boiler and process heater source ca tegory. Such an approach would result in definitions of startup and shutdown that are overly long for some units and too

short for others.

• Work practice standards generic enough to encompass all ICI units and address the safety and other operati onal concerns put forwar d by owners and operators may not amount to anything more than gener al duty requirements in the end. By contrast, facilities currently have unit-spec ific protocols for startup and shutdown that take into account the boiler design, type of fuel fired, how the fuel is fired, the pollution control equipment in place and its operational cons traints, and other operational factors, such as the requi rements for heating up ancillary equipment and ductwork. These unit-specific protocols focus on both safety and

environmental considerations.

• The requirement to engage control devic es by the end of a defined startup period, rather than when the minimum operating temperature or gas flow requirements of the control device are met, can lead to damaged control equipment, particularly when the end of star tup is defined in a generic manner that may not be appropriate to a particular installation.

• Startup procedures ensure that equipment is brought up to normal operating conditions in a safe manner. Startup ends when the boiler/proc ess heater and its controls are fully functional.

• There is an energy efficiency incentive to minimize the time spent in startup. When units are starting up, the processes being served cannot operate optimally. Therefore, boilers and pr ocess heaters are started up as expeditiously as possible. Similarly, in creasing boiler load during startup is dependent upon the process start-up/operational st atus as well, limiting the speed of startup in many

circumstances. This means that the dur ation of boiler startup is dependent upon startup of other process com ponents which are site-specific.2 • The act of supplying even minimal quantitie s of steam or heat “for any purpose” should not define the end of startup. EPA has acknowledged in the preamble to

the current rule that “ these boilers and process heaters should be considered to be operating normally at all times during which steam of the proper pressure, temperature, and flow rate is being provided to a common header system or energy user(s) for use as either process steam, heat, or for the cogeneration of electricity [78 FR 7146]. And yet, EPA has prom ulgated a definition that, by not stipulating that the steam supplied be of the proper te mperature, pressure, and flow, would have startup end befor e normal operation is achieved.

• Because there is such diversity in t he designs and operating modes of the boilers and process heaters being regulated by the major and area source rules, there is not a single load threshold or time peri od that would represent the functional end of startup for all units (we understand that CIBO has submitted some information based on a member survey that shows st artup times by unit and unit type vary greatly). If EPA incorporat es a “load plus time” or “maximum total startup time” type of threshold into the MACT and GACT rules to define the end of startup, the time should vary by unit design and a mechanism should also be provided by which a facility may establish unit-specif ic startup criteria and document those criteria in the site-specific monitoring plan.

• A “load plus time” threshol d to delineate periods of st artup from normal operation does not address boilers that operate in st andby mode for long periods of time. For these types of units, a maximum start up time (unit-specific and included in the site-specific monitoring plan or va rying by unit type/design) is more appropriate.

• Under the current rule, units equipped with control devices that are not specifically identified in Table 3 to Subpart DDDDD of Part 63 as exempt must engage the controls when coal, biomass, or re sidual oil is first introduced into the boiler or process heater. ESPs must be included in the list of exempted air pollution control devices because an ESP cannot be safely engaged until a certain flue gas temperature and/or oxygen level is reached. Table 3 of Subpart

DDDDD must be amended to include ESPs am ong the listed controls that must be started as expeditiously as possible during startup.

• Under the current rule, boilers and process heaters must use one or a

combination of listed clean f uels when starting up. The list of clean fuels should be expanded. For example, gaseous fuels meeting the “other gas 1” classification, biodiesel, dr y (<20% moisture) biomass, and fuels that meet the TSM, HCl, and Hg emissions limits through fuel analysis are fuels that should be permissible for use as clean startup fuels.

• The shutdown definition curr ently states that shutdown begins when fuel is no longer being fired. The definition should be revised to accommodate units firing solid fuels on a grate or in a fluidized bed combustor where the residual material in the unit keeps burning after fuel feed to the unit is stopped. EPA has already indicated in guidance that they consider f uel “being fired” to mean that fuel is being fed. EPA should make this clear in the rule.

• EPA has indicated through guidance that if a shutdown is not completed to the point of both no fuel being fired and no steam or heat being supplied, then a3 shutdown has not occurred and therefore a startup cannot occur. This does not

accommodate situations where solid fuel feed is lost where the feed can be restored before a complete shutdown takes place. The rule must take these periods into account so operators can have certainty in designing monitoring and recordkeeping systems and in determining compliance when these events occur.

The shutdown definition s hould therefore be modified to say that shutdown ends

EITHER when no steam or heat is being supplied and no fuel is being combusted in the boiler or process heater OR when st artup is initiated by reintroducing fuel to the boiler or process heater after no fuel has been fed for at least 1 hour,

whichever comes first.

The following sections and the atta ched table provide more detail.

Background

In the recent Part 63 major and area s ource boiler/process heater rules, EPA established standards that apply at all times, including periods of startup and shutdown when work practice standards are to be followed. EPA correctly acknowledged the infeasibility of dem onstrating compliance with numeric standards during the transient, non-steady state periods of startup and s hutdown. Industry strongly agrees with EPA that work practices are the correct approac h for applying a standard to industrial boilers and process heaters during star tup and shutdown periods.

The work practice standards that EPA originally proposed for periods of startup and shutdown required an ow ner/operator to “ minimize periods of startup and shutdown following the manufacturer’s re commended procedures, if avail able. If manufacturer’s recommended procedures are not avail able, sources must follow recommended procedures for a unit of similar desi gn for which manufacturer’s recommended procedures are available .” [76 FR 15642].

The work practice standards were subseque ntly revised in order to require “ more than a general duty to reduce emissions ” [76 FR 80615]. Definitions of startup and shutdown were proposed in order to clar ify which periods of operation are subject to work practice

standards and when numeric standar ds would apply. The problem since has been to arrive at definitions that encompass all units included in the diverse ICI Boiler and Process Heater category.

EPA has already acknowledged that there ar e design differences amongst boilers and process heaters by establishing subcategories with different requirements. EPA should continue to acknowledge the differences amongst units by explicitly allowing facilities to establish and comply with unit-specific star tup and shutdown practices as an alternative to generic work practices. Work practi ce standards generic enough to encompass all ICI units are not likely to amount to anythi ng more than general duty requirements. By contrast, facilities currently have unit-specif ic protocols for star tup and shutdown that take into account the boiler design, type of fuel fired, how the fuel is fired, the pollution control equipment in place and its operational constraints, and other operati onal factors, such as the requirements for heating up anc illary equipment and ductwork. These unitspecific protocols focus on safely starting up the unit while minimizing emissions. EPA should allow facilities to comply with unit-specif ic startup criteria th at are documented in an enforceable site-specific plan (e.g., the site -specific monitoring plan already required by the rule).4 The requirement for control devices to be fully engaged by the end of startup can lead to damaged control equipment, particularly w hen the end of startup is defined in a generic manner that may not be appropriate to a particular installation. Startups of many types of control equi pment are dependent on a variet y of physical conditions, including minimum temperature and flow require ments. Thus, start up times are specific to the installation. Establishing the end of startup based on an across-the-board load threshold, load plus time threshold, or total time threshold could force many operators to choose between noncompliance and risking c ontrol equipment damage and increased emissions, because such operators will be unable to start the emissions control equipment safely by the end of “startup” as EPA may define it. For instance, ESPs are typically not energized until the exhaust (and ESP internal equipment) is above the appropriate moisture dew point. If an ESP is energized when moisture levels are high, there is a high potential for fouling of the ESP plates which will reduce collection efficiency. Excess sparking, which can also occur due to fouling, can cause a fire or explosion.

EPA should not set a work practice standard t hat is fundamentally in compatible with the operation of certain units. It is technologically impossi ble for some units, even top performers, to start their emissions control equipment any sooner in the startup process without risking equipment damage and creating environmental concerns. EPA should

likewise not define the end of st artup as the shortest time any particular unit in a design subcategory can reach stable operation because that unit will not be representative of the design and operation of all t he units in that subcategory.

Facilities cannot be rushed to complete startup and shutdown periods and compromise the safety of personnel and equipment. It is critical that t he startup and shutdown definitions and the associated work practices be structured to allow safe operation, and

it is critical that facilities understand and have a clear path to compliance with the requirements.

Revision to the Definition of Startup

EPA has revised the startup and shutdown de finitions from those proposed in December 2011, where startup and shutdow n periods were based on load, agreeing with commenters that,

“...load conditions separating periods of startup and shutdown from periods of normal operation can be unit-specif ic and therefore pr esupposing certain

load conditions in the def initions of periods of startup and shutdown is not appropriate” [78 FR 7146].

As a result, the January 31 and Februar y 1, 2013 rules defi ne startup as:

“ either the first-ever firing of fuel in a boiler or process heater for the purpose of supplying steam or heat for heating and/or produci ng electricity, or for any other purpose, or the firing of fuel in a boiler after a shutdown event for any purpose. Startup ends when any of the steam or heat from the boiler or process heater is supplied for heating, and/or producing electricity, or for any other purpose .” [40 CFR §63.7575 and §63.11237]

The phrase “supplying... for any other purpose” is too restrictive because it implies that even using the heat that is generated when fuel is first co mbusted to safely pre-heat and protect important process equipment during the normal st artup cycle will trigger the end of the regulatory “startup, ” even though functiona lly startup has clearly not ended.5 All boilers must gradually heat up to pr event damage to the boiler pressure parts and refractory, and the period of ti me that is required varies depending upon boiler design. Some processes are designed such that downstream equipment re ceives heat and/or steam when fuel is being burned dur ing startup of the boilers or process heaters. For example, steam generated during st artup that is not yet of t he proper quality to be fed to a steam turbine or the designated process may be used to heat trace or preheat piping runs. Preheating is necessary to avoid the excessive thermal stresses that result in stress corrosion cracking. Stress corrosi on cracking drastically reduces equipment longevity and negatively impacts the ability to operat e safely. Yet, if the act of supplying low grade steam during startup for heat tracing or preheating was to define the end of startup, then the lo w grade startup steam would mo st likely be vented until the necessary steam pressure and steam temp erature are reached fo r process use or electrical generation, and electrical heat t apes or another energy source would be used to warm piping, increasing energy use unnecessarily.

EPA has acknowledged in the preambl e to the current rule that “ these boilers and process heaters should be consid ered to be operating normally at all times during which steam of the proper pressure, temperature, and flow rate is being provided to a common header system or energy user(s) for use as either process steam, heat, or for the cogeneration of electricity [78 FR 7146]. And yet, EPA has promulgated a definition that, by not stipulating that the steam supplied be of the proper temperature, pressure, and flow, would have startup end before norma l operation is achieved. The act of supplying even minimal quantities of steam or heat “for an y purpose” should not define

the end of st artup.

Above all, the boiler/process heater operator’s primary concer n during startup is safety. The startup procedures must ensure that the equipment is br ought up to normal operating conditions in a safe manner. Startup functionally ends when the boiler/process heater and its c ontrols are up to the prop er operating temperature and pressure, and are fully functional. The proc edures and the time necessary to complete a startup are site specific, and vary by boiler fuel, design, and control technique. They also depend on variables such as how long the unit has been shut down and can be affected by unexpected equipment problems during startup of the boiler or the process it supports, ambient conditions, natural fuel va riability, and required testing of new or replacement equipment or components during star tup. Therefore, t he definition of the end of startup should be revised to indicate that it occurs when safe, stable operating conditions are reached, after emissions controls are proper ly operating.

Safe, stable operating conditions should be defined on a unit-specific basis, as the various designs and operational modes of the myriad boilers and process heaters subject to the rules make establishing a st andard threshold for all units impossible. Conversations with both operators and vendors have confirmed that a one size fits all approach is not workable for all situations . We understand EPA’s desire for a “bright

line” that defines the end of startup, but not all situat ions can be accommodated with this approach. Therefore, if EPA adds a lo ad and/or time type of threshold to the startup definition, facilities with units that cannot safely or practically accommodate that common threshold must have the option to im plement a site-specific plan that, takes into account their specific operational and safe ty constraints, and provides criteria for the end of startup on a unit- specific basis.

The following types of concepts could be incor porated into the site-specific monitoring plan to define the end of a startup period:6 • The unit is firing its primary fuel for a period of time adequate to provide stable and non-interrupted fuel flow, stable and controlled air flows, and adequate operating temperatures to allow proper fuel drying and air preheat as applicable.

• Emissions controls are in service with operating parameters such as flow rates and temperatures being controlled and stable.

• The unit is supplying steam to a common header system or energy user(s) at normal operating conditions including pr essure and temperature, and is above the minimum operational stable output flow rate, as applicable to the unit.

• For stoker units, when t he grate reaches an adequate leve l of coverage with solid fuel based on visual observation and stability of air, fuel, and steam flow rates.

Boiler and process heater operat ors have a financial incentiv e to minimize the time spent in startup. When units are starting up, they are not oper ating in the most efficient mode and the process being served cannot operat e optimally. Therefore, boilers and process heaters are started up as expeditiously as possible, but safety concerns cannot be ignored, and proper procedures must be followed. In order to be practically implementable, the startup def initions in the Boiler MACT and Boiler GACT rules and the startup work practices in the Boiler MACT rule must ta ke these facts into account

and must be revised to accommodate the technical issues discussed here.

Reconsideration of Startup and Shutdo wn Definitions in the MATS Rule

Industry is following with keen interest EPA’s curr ent reconsideration of the definitions of startup and shutdown under the Mercury and Ai r Toxics Standards (MATS). While EPA has recognized in the MATS rule the operational constraints of certain pollution control equipment during startup, cert ain controls will not be fully functional and reducing HAP emissions when EPA currently defines “start up” as ending in the MATS rule. Many concepts raised by MATS commenters apply to uni ts covered under the Industrial Boiler

MACT and GACT rules. In fact, the comments on the need fo r unit-specific definitions and work practices are even more pertinent to the industrial boiler rules since the designs of industrial, commercial, and inst itutional boilers and process heaters vary more widely than the designs of utility boilers.

The Proposed MATS rule reconsideration st ates that some commenters on that rule have requested that the end of startup be changed to four hours after 25 percent load is first reached, or 12 hours after first electr icity generation, whichever occurs first. See 78 Fed. Reg. 38004. EPA alternatively proposes to defi ne the end of startup at coal-fired EGUs as occurring at 25 percent of nameplate capacity plus th ree hours, or the start of electricity generation plus six hours, whichever comes first. See 78 Fed. Reg. 38005

. These proposed definitions are appropriate for some EGUs, but are too restrictive for others due to site-specific factors, and it would be impossible to establish such a threshold for industrial boilers and process heaters that would accommodate all sizes and designs.

As the widely divergent comments on the MA TS rule demonstrate, finding a single appropriate definition of the end of startup that account s for all boilers in any subcategory continues to challenge EPA. The highest degree of flexibility would be provided by EPA addressing the wide variations among boilers by revising the startup

definition to allow facilities to determine the minimum stable oper ating load or other relevant operating parameter with emissions controls at a stable operating condition on a unit-specific basis and include the mi nimum stable operating load or operating7 condition and the proper procedures to follow during startup and shutdown in the sitespecific monitoring plan. Establishment of the minimum st able operating load or operating condition on a site-specific bas is is analogous to setting other boiler and control device operating param eter limits on a site-specific basis, which EPA does routinely in the Boiler MACT and GACT rules.

Minimum Stable Load, Range of Op eration, and Normal Operating Load

EPA has adopted a source-specific approach to setting lower boundaries of operation in other regulatory programs. (See 40 CFR Part 75 Appendix A, Section 6.5.2.1.) Such an approach could be used to establish and document a minimum safe, stable load for unit operation that would delineate the di fference between periods of startup and shutdown and periods of normal operation.

Under Section 6.5.2.1 of Appendix A to Part 75, the owner or oper ator of an affected source identifies the low, mid, and high load levels of each unit based on the unit’s operating history. The owner or operator is required to determine the number of operating hours at each load leve l over the previous 4 oper ating quarters and calculate the percentage of time spent at ea ch load level in each quarter.

Normal operating load, as defined in Paragraph 6.5.2.1(d) of Appendix A to Part 75, is designated by the owner or operator as the most frequently used load based on the analysis of historical load dat a. Paragraph 6.5.2.1(e) of Appendix A to Part 75 requires the owner or operator to report the upper and lower boundarie s of the range of operation for each affected unit in the required site-specific monitoring plan. The owner or operator is also required to indicate, in the monitoring plan, the load level designated as normal and the two most frequently used load levels. The monitoring plan must be updated whenever the normal load level and two most frequently used load levels are redesignated.

Similar to the Part 75 procedures, a uni t-specific minimum stable load could be determined for units subject to Subpart DDDDD. The minimum stable load would be based on an analysis of unit operating data and would delineate periods of stable operation from the transient periods associated with st artup and shutdown. The

minimum stable load for each unit would be des ignated in the site-specific monitoring plan required under §63.7505(d).

Operation of Boilers in Standby Mode

At larger facilities with multiple boilers, so me of the site boilers may be maintained in standby mode. When in standby, a boiler is in a state of operationa l readiness at a low stable load, frequently below 25%. This prac tice provides continuity because as process demands increase, or the capacity of the load-carrying boilers decreases, the standby boiler can be brought online quickly to fill steam demands. When operating in standby mode, a boiler subject to the emission limits in Tables 1 or 2 or 11 through 13 to Subpart DDDDD of Part 63 (and thus s ubject to the start up and shutdown work practice standards of Table 3), would typica lly be combusting clean-burning liquid or gaseous fuels but could be combusting soli d fuel or heavy liquid and employing

emissions controls.

When EPA proposed a definiti on of startup and shutdown incorporating a 25% load threshold, a number of commenters reques ted that EPA provide clarity on how the requirements would apply to units operating in standby mode at load levels below the8 proposed threshold. If EPA is to adopt a “load plus time” threshold to delineate between periods of startup, shutdown, and normal operation, the same lack of clarity remains.

In the December 2012 response to comment s document for the reconsidered major source Boiler MACT rule (EPA-HQ-OAR -2002-0058-3846), EPA provided the following incomplete response to comment EPA- HQ-OAR-2002-0058-3510-A1, excerpt 117.

“The EPA believes that the revised definitions adequately address units operating in standby mode and that such units should not be exempt from the startup and shutdown provisions of the final rule because??”

All other comments regarding st andby mode refer back to this incomplete response. Industry respectfully disagrees that the revised definitions adequately address units operating in standby mode. Furthermore , EPA appears to have misunderstood the

concern – it was not that standby units should be exempt ed from startup and shutdown work practices, but that t he regulations should not defi ne startup and shutdown such that units operating in standby, which only ex ceed the operating threshold intermittently and may not reach 25% load duri ng startup, are per petually in a state of startup or

shutdown.

EPA’s revised definition of st artup should take these units into account by either allowing a site-specific definit ion of the startup procedures required to reach minimum stable operating load or a maximum amount of time for start up for these units.

Clean Fuels Requirement Under MACT

The current work practice standard in Boiler MACT requires facilities to either start up on clean fuels or engage control devices prior to burning fuels not listed as clean fuels (except for the listed exempt control devices, which must be engaged as expeditiously as possible). At some facilit ies, the use of clean fuels prior to engaging control devices will require installation of dedi cated burners to fire these fuels and installation of fuel delivery and or storage facilities, both of which may be impracticable to install on a sitespecific basis. In addition, operation and maintenance of burners that are infrequently used may be very problematic. For example, natural gas burners t hat are installed on biomass boilers may be prone to buildup of fly ash deposits on critical flame sensors and plugging of the burners. In addition, fuel actuator va lves can malfunction due to infrequent operation. Maintenance and in spection of these components can be problematic given the infrequency of access and the problems associated with startup on a clean fuel, especially after unplanned out ages. In some situations the periodic operation and maintenance of these systems has been so probl ematic that such burner systems have been decommissioned despite the st rong desire of the operator to have the ability to fire a backup fuel in t he event of loss of the primary fuel.

Additionally, due to the nature of the fuels, the air flow rate s, air flow distribution, and the overfired air configuration are completely different for a natural gas burner than a

stoker or fuel cell boiler bur ning biomass. Unless a boiler is designed to burn natural gas and biomass at the same time, it may be im practical to install natural gas as a startup fuel.

In addition to the operational difficulties asso ciated with use of clean fuels, it should be

noted that EPA did not consi der the added cost and burden of requiring clean fuel combustion for startup in situations wher e controls are not engaged prior to burning solid fuel or heavy liquid. First, clean fuels may not be universally available in sufficient quantities. Use of listed clean fuels to start up results in increased capital and operating9 costs for many facilities and in the increas ed use of non-renewable fossil fuels; these fuels are in many cases more expensive than a unit’s primary operating fuel and require

different infrastructure to accommodat e (which may not be available, depending on location and other factors). In many cases the boilers mu st be retrofitted with systems

to burn the alternative fuels such as natur al gas when startup may only occur a few times per year. This represents a significant expense for a very limited amount of use. Furthermore, many facilities would be requir ed to obtain permit modifications prior to making this change to their boilers.

The requirement in the March 2011 MACT ru le to establish star tup procedures that minimize emissions and to train operators made more sense from an operational safety, cost, GHG emissions, and sustain ability perspective.

Expansion of the List of Clean Fuels Under MACT

The list of clean fuels, as written, is too na rrow. The list should be expanded to include all gaseous fuels meeting the “other gas 1” classification. Biodiesel should also be added to the list, as distillate oil is sometime s a biodiesel blend. Fuels that meet the TSM, HCl, and Hg emission limits using fuel analysis should be added to the list of clean fuels. Dry biomass (<20% moisture content) should also be added to the list of clean fuels for units operating with a mechani cal collector (i.e., multiclone). Dry

biomass is included in EPA’s definition of “clean cellulosic biomass” and will burn

cleaner than other solid fuels. It is a clean fuel for startup because it exhibits low HCl, Hg, and CO emissions due to its chloride, merc ury, and moisture c ontent. Therefore it is a reasonable work practice for solid fuel boilers to burn only dry biomass as clean fuel during startup. Permitting authorities shoul d have the flexibility to approve other clean fuels that EPA may not have consider ed (e.g., other renewable fuels).

Time to Properly Engage Pollution Control Devices Under MACT

Under the current rule, certai n pollution controls do not have to be engaged immediately upon startup, but are requir ed to be engaged “as expeditiously as possible.” We recommend modifying this provision to take into account safety and protection of process equipment and pollution controls, as we ll as to recognize that some pollution controls are engaged gradually. A ccordingly, we recommend re vising the text to “as expeditiously as possible in a manner consistent with the manufacturer’s recommendations or standard industry practices” , to take into acc ount worker safety and protection of the control device and other equipment that could be impacted by improper operation or failure of the pollution control system.

Under the current rule, units equipped with an ESP must either fire “clean fuels” throughout startup or engage the ESP when feeding of coal, biomass, or residual oil into the boiler or process heater begins. Howe ver, ESPs have operating constraints that dictate that they be included in the list of ai r pollution controls that must be started as expeditiously as possible. An ESP cannot practically be engaged until the flue gas temperature exceeds the moisture and acid dew points, and the oxygen level in the device is low enough to avoid a fire or explosi on of combustible materials in the device.

Some manufacturers recommend that such temperatures be maintained for several hours to ensure adequate heatin g of the equipment. Prem ature starting of this equipment will lead to short-term stability problems t hat could result in unsafe conditions and longer term degradation of ESP performance due to fouling, increased chances of wire damage, or increased corrosion within t he chambers. In certain processes, the length of time spent in startup prior to engaging control devices may require several10 hours to reach the stable conditions necessa ry to avoid risks associated with explosions and fires associated with ESP sparking. Vendor s providing this equi pment incorporate these safety and operational concerns in to their standard operating procedures. 1

Commenters on the MATS reconsideration have echoed our concerns. They stated

that ESPs at coal-fired units must be de- energized at all times when the flue gas temperature may be below the acid dew point. The ESP also must be de-energized during the firing of startup fuels until coal firing results in volatile gas concentrations that are below levels that would pose an expl osive hazard in the ESP. According to commenters, one ESP manufacturer recomm ends that the ESP remain de-energized during startup until flue gas temperatures within the ESP remain above 200 degrees

Fahrenheit for two hours.

During periods of startup, combustion begi ns as fuel is introduced and an ESP cannot be engaged until its equipment has been adequately warmed up and the requisite fuel gas temperature is reached. As the contro l device is heated up, additional fuel is added until the ESP (and other equipmen t) meets its design temper ature and normal fuel firing

rates are resumed. Some ESPs have safe ty interlocks (oxygen sensors and alarms) that shut down the ESP or pr event startup of the ESP at high flue gas oxygen levels to avoid a fire or explosion in the unit. The ox ygen level in flue gas is typically high during startup, so the ESP may not engage due to these safety controls until more stable operating conditions are reached. Additionall y, some units which currently have clean fuel startup burners or igniters can not burn enough clean fuel to achieve the temperature, moisture, and/or oxygen levels necessary for safe operation of the ESP. Therefore, ESPs must be included in the list of air pollution cont rols that must be started as expeditiously as possible.

Definition of Shutdown

The shutdown definitions in the MACT and GACT rules also need to be revised. The

current definition is: ‘‘Shutdown means the cessation of operation of a boiler or process heater for any purpose. Shutdown begins eith er when none of the steam and heat from the boiler or process heater is supplied fo r heating and/or producing electricity, or for any other purpose, or at the point of no fuel being fired in the boiler or process heater,

whichever is earlier. Shutdown ends when t here is both no steam or heat being supplied and no fuel being fired in the boiler or process heater.’’

The definition is problematic fo r units firing solid fuels on a grate or in a fluidized bed

combustor where the residual material in t he unit keeps burning after fuel feed to the unit is stopped. In this case, fuel is still burni ng (which is not considered “being fired” if EPA makes a regulatory change to confirm the statement in their Boiler MACT
“Questions and Answers 2 ” document indicating that t he intended meaning of firing is feeding fuel) in the unit despite the fact that load reduction is occurring, additional fuel is not being fed, and the shutdown process has clearly begun. The shutdown definition

should be revised to state that “shutdown begins either when none of the steam and heat from the boiler or process heater is s upplied for heating and/or producing electricity or when fuel is no longer being fed to t he boiler or process heat er. Shutdown ends

when there is both no steam or heat being supplied and no fuel being combusted in the

1 See Appendix I of AF&PA’s August 23, 2010 comm ents on the June 4, 2010 proposed rule for an excerpt of an ESP operational manual.

2 http://www.epa.gov/ttn/atw/boiler/boilermactqanda.pdf , question 57.11 boiler or process heater or when startup is initiated by reintr oducing fuel to the boiler or process heater after no fuel has been fed for at least 1 hour, whichever comes first.”

Note also that the terms “supplying” and “o r for any other purpose” are too open-ended

and could be read to mean that steam and heat supplied for uses within the boiler itself will delay onset of the shutdown period. Many boilers use steam to drive rotating equipment such as feedwater pumps, prehe at feedwater, and operate de-aerators. Some of these uses, e.g., operating feedw ater pumps and preheat ing feedwater, begin in the early stages of starting a boiler and continue until the boiler is cooled down.

These terms in effect limit the use of energy during shutdow n periods for these purposes. As a result, an operator may be mo tivated to use less efficient and more expensive electrical power where feasible. E fficient and cost effective internal uses of steam and heat for operating the boiler shoul d not be discouraged by definitions that unnecessarily limit the durat ion of the startup and shut down periods and that may require costly retrofits to boilers with no commensurate env ironmental benefit.

Conclusion

As supported above and in the attached table, the startup and shutdown definitions and work practices should be revised to improv e clarity and more fu lly address industry’s operational and safety concerns. The changes should acknowledge the wide variety of boiler designs covered by these standards and the fact that a one-size-fits-all approach

is not workable.12July 2014Controls Scenario Potential Compliance Issue Suggested SolutionAny Startup on clean fuel,engage non-listed controlsprior to adding solid fuel.May be an issue with clean fuel availability. Mayhave CO issue with transition from gas or liquid fuelto solid fuel, may not be an issue for 30-day averagedepending on compliance margin.Expand list of clean fuels to include all Other Gas 1 fuels,biodiesel, fuels that meet the HCl, Hg, TSM limits throughfuel analysis, and other clean fuels as determined bypermitting authorities. Provide adequate length of time forstartup period to cover transition from startup fuel to solidfuel. (as defined below)Wet Startup on solid fuel Shouldn’t be an issue for operating parametermonitoring – can start wet controls prior to startup(depending on design of wet controls, may not beable to meet operating parameter limitsinstantaneously, but should be able to meet 30-dayaverage).Need to address units that share a common controldevice that startup separately.Could have issues meeting 30-day rolling CO CEMSlimit if enough time is not given for startup. Need todifferentiate between cold startup (need more time)and hot restart (need less time).Startup ends either when the boiler or process heater hascontinuously maintained a steam production rate of at least25% of maximum steam or heat output at normal operatingpressure for a certain number of continuous hours3after acold startup or a certain number of continuous hours hourafter a hot restart and when all control devices are in stableoperation or when the boiler or process heater is operatingabove an alternate minimum operationally stable outputflow rate and pressure for a minimum time, as specified ina site-specific start-up plan. This would also apply to unitssharing a common control devicethat start up at separatetimes (separate startup period occurs for each unit).For units sharing a common control device that are startingup sequentially, startup ends either when the last boiler orprocess heater to start has continuously maintained asteam production rate of at least 25% of maximum steamor heat output at normal operating pressure for a certainnumber of continuous hours aftera cold startup or a certainnumber of continuous hours after a hot restart and when allcontrol devices are in stableoperation or when the lastboiler or process heater isoperating above an alternateminimum operationally stable output flow rate and pressurefor a minimum time, as specified in a site-specific start-upplan.3The time to reach stable conditions following 25% load will varybased on design, per our discussion earlier in this document.13July 2014Controls Scenario Potential Compliance Issue Suggested SolutionDry Startup on solid fuel Can’t startup ESP until certain flue gas temperatureand oxygen level are reached. NFPA 85- Boiler andCombustion Systems Hazards Code, 2011 Edition,Section 6 Multiple Burner Boilers (firing oil, gas, orPC) requires purging of precipitators prior to initialfiring to prevent a precipitator spark from igniting anexplosive mixture of unburned fuel.Manufacturer and operating company proceduresmay include a requirement to be operating on mainburners with adequate flue gas temperature and lowenough oxygen levels prior to ESP energization tolimit potential ignition of unburned fuel by aprecipitator spark.Need time within the “startup” period for thecombustion unit firing primary fuel(s) and allexempted air pollution controls to reach stableoperating conditions relative to the start of steam orprocess heater output tothe distribution system.Need to get better definition of end of startup if heator steam is immediately supplied upon ignition offuel.Need to address units that share a common controldevice that start up separately. Could have issuesmeeting 24-hour block opacity or 30-day rolling COCEMS limit if enough time is not given for startup.Need to differentiate between cold restart (needmore time) and hot restart (need less time)ESPs must be included in the Table 3, item 5 list ofexempted air pollution controls that must be started asexpeditiously as possible.Startup ends either when the boiler or process heater hascontinuously maintained a steam production rate of at least25% of maximum steam or heat output at normal operatingpressure for a certain number of continuous hours after acold restart or a certain numberof continuous hours after ahot restart and when all control devices are in stableoperation or when the boiler or process heater is operatingabove a minimum operationally stable output flow rate andpressure for a minimum time, as specified in a site-specificstart-up plan. This would also apply to units sharing acommon control device that start up at separate times(separate startup period occurs for each unit).For units sharing a common control device that are startingup sequentially, startup ends either when the last boiler orprocess heater to start has continuously maintained asteam production rate of at least 25% of maximum steamor heat output at normal operating pressure for a certainnumber of continuous hours aftera cold startup or a certainnumber of continuous hours after a hot restart and when allcontrol devices are in stableoperation or when the lastboiler or process heater isoperating above an alternateminimum operationally stable output flow rate and pressurefor a minimum time, as specified in a site-specific start-upplan.Any Unit begins startup,reaches a certain minimumstable load, then there is anequipment problem thatresults in “failed startup.”All of the above. Need to be sure that this entire period is consideredstartup, even if you reach the minimum load threshold. If,for example, the end of startup is 25% load plus 8 hours,the unit has to be over 25% for 8 continuous hours.14July 2014Controls Scenario Potential Compliance Issue Suggested SolutionWet Lose solid fuel feed, takestime to get auxiliary fuelgoing to boiler or there is noauxiliary fuel available.Sometimes wet fuel cancause high O2 conditions,which will trip the ESP,which will trip the fuel feed.Sometimes there areproblems with theequipment used to supplythe solid fuel that causeloss of fuel feed.Losing fuel feed would trigger a shutdown – however,shutdown as EPA currently interprets would not becompleted if the unit continues supplying usefulsteam until fuel feed is restored. We can’t classifythese periods as malfunctions in all cases and theseperiods are not normal operation. We need to beable to call them shutdown, or we don’t know how toset up recordkeeping because we don’t havecertainty on how to classify these periods. Operatingparameters would probably be okay on a 30-dayrolling average basis. Whether or not there was anissue meeting 30-day rolling CO CEMS limit if this isnot shutdown would depend on compliance marginand length of event.The shutdown definition should accommodate the scenariowhere fuel feed is reinitiated before the unit ceases tosupply steam. Facilities need to be able to call it ashutdown, even if fuel supply is restored. Facilities shouldnot be forced to take the boiler down fully before reinitiatinga startup – this would be uneconomical and could result inmore emissions. The end of this period is a hot restart,and then the startup work practices would apply untilcertain load and time conditions are met. Could revise endof shutdown definition: “Shutdown ends when there is bothno steam or heat being supplied and no fuel beingcombusted in the boiler or process heater or when startupis initiated by reintroducing fuel to the boiler or processheater after fuel feed has been halted.”Dry Lose solid fuel feed, takestime to get auxiliary fuelgoing to boiler or there is noauxiliary fuel available.Sometimes wet fuel cancause high O2 conditions,which will trip the ESP,which will trip the fuel feed.Sometimes there areproblems with theequipment used to supplythe solid fuel that causeloss of fuel feed.Losing fuel feed would trigger a shutdown – however,shutdown as EPA currently interprets would not becompleted if the unit continues supplying usefulsteam until fuel feed is restored.Also, NFPA 85 Boiler and Combustion SystemsHazards Code, 2011 Edition, Section 6 MultipleBurner Boilers (firing oil, gas, or PC) requires trippingof electrostatic precipitators as part of a master fueltrip (MFT) to prevent a precipitator spark from ignitingan explosive mixture of unburned fuel.We can’t classify these periods as malfunctions in allcases and these periods are not normal operation.We need to be able to call them shutdown, or wedon’t know how to set up recordkeeping because wedon’t have certainty on how to classify these periods.Could have issues meeting 24-hour block opacity or30-day rolling CO CEMS limitif this is not shutdown,depending on compliance margin, type of unit, lengthof event.Need to be able to call it a shutdown, even if we get fuelback; emissions will be greater if we have to complete ashutdown before we can start back up. The end of thisperiod is a hot restart, and then the startup work practiceswould apply until certain load and time conditions are met.Could revise end of shutdown definition: “Shutdown endswhen there is both no steam or heat being supplied and nofuel being combusted in the boiler or process heater orwhen startup is initiated by reintroducing fuel to the boileror process heater after fuel feed has been halted.”ESPs must be included in the Table 3, item 6 list ofexempted air pollution controls that are not required to beoperated during shutdown.15July 2014Controls Scenario Potential Compliance Issue Suggested SolutionAny Begin shutdown uponhalting fuel feed to theboiler. For some designs,there is still fuel burning inthe boiler.Current definition says “Shutdown begins eitherwhen none of the steam and heat from the boiler orprocess heater is supplied for heating and/orproducing electricity, or for any other purpose, or atthe point of no fuel being fired in the boiler or processheater, whichever is earlier.”This could beinterpreted that shutdown does not begin unless nofuel is burning or no steam/heat is being supplied. Insome boiler designs, fuel continues to burn after fuelfeed stops.EPA should clarify that fuel being fired in this case meansfuel being fed to the combustion unit.Wet More than one unit vents toa wet control device, oneunit shuts down, the otherunit stays operating.For some wet control designs, the pressure dropdepends on the flow through the scrubber. If onlyone unit is operating, the operating parameter limitsestablished during the performance test with bothunits in operation may not be achievable.Not sure if there is a way to address this in the rule, or ifEPA would advise facilities to submit a request for alternatemonitoring and establish different operating scenarios,such as an alternate operating limit with fewer units inoperation. This is similar to the question of whetheroperating parameters must be maintained if a unit burnsgas for an extended period of time and emissions controlsfor PM, HCl, Hg are not needed. This is probably coveredunder a request to permit alternate operating scenarios aswell.16July 2014Controls Scenario Potential Compliance Issue Suggested SolutionAny – lowload/standbyunitA unit operates for manyhours in standby mode,less than 25% load, eitherburning clean fuels orburning solid fuels withemissions controls inservice.How to define the end of startup to accommodate aunit that operates in a low-load mode after initial“ignition” (e.g., it never reaches 25% load). Facilitiesshould not have to increase load above 25% just toreach the defined end of startup.Where a 25% load+time threshold can’t be accommodatedby a standby unit, the following types of concepts could beincorporated into the permit to identify the end of startup:•The unit is firing its primary fuel for a period of timeadequate to provide stable and non-interrupted fuelflow, stable and controlled air flows, and adequateoperating temperatures to allow proper fuel dryingand air preheat as applicable.•Emissions controls are in service with operatingparameters such as flow rates and temperaturesbeing controlled and stable.•The unit is supplying steam to a common headersystem or energy user(s) at normal operatingconditions including pressure and temperature, andis above the minimum operational stable outputflow rate, as applicable to the unit.•For stoker units, when the grate reaches anadequate level of coverage with solid fuel based onvisual observation and stability of air, fuel, andsteam flow rates.