MATS Performance Testing of ACI and DSI Systems: Guidelines and Lessons

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1 MATS Performance Testing of ACI and DSI Systems: Guidelines and Lessons Paper # 117 Presented at the Power Plant Pollutant Control MEGA Symposium August 19-21, 2014 Baltimore, MD Constance Senior, 1 Cameron Martin, 1 Travis Starns, 1 Paul Farber 2 ; 1 ADA-ES, Inc., Highlands Ranch, CO, 2 P. Farber & Associates, LLC, Willowbrook, IL ABSTRACT Emissions control systems being installed at power plants are guaranteed by their suppliers, not only for levels of emissions but also for such items as the consumption of reagents/adsorbents and power and for the system reliability. These guarantees sometimes have make-right or liquidated damages associated with them. Consequently there are incentives for all parties to ensure that the performance testing is carried out properly and the data analyzed in an agreed upon manner. ADA-ES, working with P. Farber & Associates, LLC, developed a guidance document for performance testing of the activated carbon injection systems, which they are supplying to multiple utilities throughout the US. This guidance document reviews the purpose of the performance testing, equipment associated with the emissions, system tuning and pretesting, achieving steady state test conditions, recommended emissions test and sampling procedures, and data to be collected during the tests. This paper will review areas that should be understood when planning, participating in, and evaluating performance and availability tests. Areas discussed will include; Purpose of a performance test Choosing a qualified test contractor How the system equipment/operation can affect the performance test Baseline testing Test conditions and steady-state operation Test data and samples Execution of the performance test Analysis of performance test data ADA-ES, Inc

2 INTRODUCTION A contract for the fabrication, installation, and commissioning of an activated carbon injection (ACI) and/or dry sorbent injection (DSI) system will invariably include provisions for testing/confirming the powdered activated carbon (PAC) or sorbent injection rate into the gas stream, as well as the pollutant removal and/or emission rate. Many of these contractual obligations/guarantees will have make-right or liquidated damages if guarantees are not met. Accordingly, it is important that performance testing is performed using protocols that acquire the proper data in the form of samples, measurements, and recorded information to evaluate the test results in relation to any performance guarantees or requirements. Since test conditions are almost never identical to the design conditions and design information that the client will have presented when contracting for an injection system, it is important that critical limits, such as a maximum air preheater (APH) outlet temperature or maximum SO3 concentration, be a part of the system contract. Testing of the ACI or DSI injection system consists of more than just the performance testing itself and includes the measures that should be taken to maximize the validity of the tests and the data and samples obtained during the testing. This also includes measurements taken prior to the performance testing to alert the Contractor to conditions that may be outside of Contract boundaries and cause for the guarantees to be voided. It is in the best interests of not only the system supplier but the Owner and/or the Engineering Contractor that the process and operating conditions be as close to Contract-agreed values as possible. This will result in a performance test that requires only minor corrections and minimum disagreements on results. Additionally, the baseline testing can identify factors (such as a very high APH exit temperature or a baghouse with leaking bags) that may prevent a successful performance test. These factors should be brought to the attention of the Owner and/or Engineering Contractor as soon as discovered so that the situation may be corrected. Additionally, the baseline tests, like the performance tests, will involve flue gas testing and sample and data acquisition. This flue gas testing should use established US EPA test methods agreed to by both the Contractor and the client. All of these criteria are necessary to ensure that performance testing for ACI and DSI systems is done in a manner that is agreeable to both the equipment supplier and the client. It is critical to have agreement on the methods to be used for analysis of the data and test results acquired during the performance testing to minimize any disagreement of the results of the performance testing. PROJECT APPROACH A contract for the fabrication, installation, and commissioning of an activated carbon injection (ACI) or dry sorbent injection (DSI) system will invariably include provisions for testing/confirming the sorbent injection rate into the gas stream, as well as the targeted pollutant removal and/or emission rate. Many of these contractual obligations/guarantees will have make-right or liquidated damages if guarantees are not met. Accordingly, it is important that performance testing is performed using protocols that acquire the proper data in the form of ADA-ES, Inc

3 samples, measurements, and recorded information to evaluate the test results in relation to any performance guarantees or requirements. Since test conditions are almost never identical to the design conditions and design information that the client will have presented when contracting for an injection system, it is important that critical limits, such as a maximum APH outlet temperature or maximum SO3 concentration, be a part of the system contract. The guidance document reviewed areas that should be understood when planning, participating in, and evaluating performance and availability tests. Areas within this document include; Purpose of a performance test Choosing a qualified test contractor How the system equipment/operation can affect the performance test Baseline testing Test conditions and steady state operation Test data and samples The performance test Itself Analysis of performance test data Purpose of the Performance Test The purpose of performance testing is to satisfy/verify guarantees that are in the Contract for this system. These would include; Guarantees Contractual requirements for powdered activated carbon (PAC) injection systems may include requirements for guarantees of equipment availability, maximum injection rates, mercury emissions, and/or mercury removal across a coal-fired boiler. Note that if a mercury removal guarantee is to be included into the contract, it is important to determine if this guarantee is to be based on the mercury stack emission, the mercury in the coal, or the mercury in the flue gas at some point in the flue gas train. Guarantees can include; Process performance guarantees Mechanical performance guarantees Availability guarantees Process Performance Guarantees Make-right Make-right guarantees are those guarantees which, if not verified during performance testing, require that the Supplier modify the system, or its operation, such that the guarantee is satisfied. Emissions guarantees are almost always make-right guarantees. Note that in order to satisfy a make-right guarantee, there is a possibility of incurring liquidated damages. For example, it may be necessary to increase a sorbent/pac injection rate in order to reduce emissions down to the make-right guarantee level. This may increase the sorbent/pac injection rate beyond its guaranteed level and incur liquidated damages. ADA-ES, Inc

4 Liquidated Damages Liquidated damages are an amount estimated to equal the extent of injury that may occur if the contract is breached. These damages are determined when a contract is drawn up, and serve as protection for both parties that have entered the contract. Liquidated damages may be set for contractual items such as PAC consumption, pressure drop, or electrical/power consumption. Liquidated damages may be incurred, for example, if it is necessary to increase a PAC/sorbent injection rate beyond the amount guaranteed in the contract. Since liquidated damages are determined to be the cost over the life of the equipment (which may be 20 or 30 years), the $/pound of PAC/hr or $/kwh of energy consumption can appear to be quite high. Consequently, guaranteed levels associated with liquidated damages in a contract should be carefully set. A consideration when negotiating liquidated damages is to include bonuses for those items covered by liquidated damages. These bonuses would use the same factors as liquidated damages but would take into account test results that show lower consumptions (reagent, PAC, power, etc.) than guaranteed amounts. Mechanical performance testing Mechanical performance testing verifies the ability of all the supplied equipment to perform its intended functions within the applicable tolerances and equipment guarantees, such that when the Equipment is shipped and correctly connected to external devices, the complete system is operable as intended. The equipment should meet all conditions of the contract with the Client and any equipment guarantees before acceptance by the Client. Mechanical performance testing also includes mechanical completion testing. The mechanical completion tests should include all tests as are reasonably necessary, customary or required by Industry Standards to determine that all equipment and systems supplied by the Contractor function properly and within the parameters described in the Contract with the Client. Mechanical completion tests can be conducted when portions of the Work, such as cleanup of debris, painting and insulation, are not yet complete; however, in no instance shall a mechanical completion test be conducted when the aforementioned exclusions could affect safety, functionality or integrity of the equipment or system being tested. The mechanical completion tests should be considered complete for a given piece of equipment or system when that equipment or system can be operated properly without endangering personnel, causing damage to equipment or damage to the transmission system. In order for the mechanical completion tests to be complete, the commissioning staff should provide mechanical completion tests documentation to the Purchaser. As the supplier completes the start-up and checkout of equipment or systems, turnover packages, which include mechanical completion tests results should be prepared by the suppliers field staff and provided to the Client for review. Turnover packages should include the necessary checkout ADA-ES, Inc

5 and operation information that the Client needs to determine successful mechanical performance testing. Process Guarantee performance testing Process guarantee performance testing demonstrates the ability of the Contractor supplied equipment to satisfy the performance guarantees of the Contract. These guarantees could, most probably, include; Pollutant emission rate PAC/sorbent maximum federate Energy (electricity) consumption Change/increase in system pressure drop Sound/noise level Measurement of the pollutant emission rate involves, in some performance testing, measuring not only the emission rate of the pollutant itself (µg/nm 3 ) but the emissions/concentrations of other flue gas components such as SO3, H2SO4, HCl, and PM, as specified in the Contract. During performance testing, data from, the plant control system/historian should be recorded by the plant for the boiler being tested and should include boiler operating data as well as any process data from the system being tested. This data, in electronic format, should be obtained at the end of each day of the performance testing. Availability Tests Availability tests demonstrate the guaranteed availability factor (AF) of the supplied equipment. The availability test should take place after the successful completion of the performance test. Since the performance test has demonstrated that the ACI or DSI system has the capability to maintain the system in compliance with the pollutant emission guarantee, the availability test should not have, as one of its criteria the requirement that the system maintains this compliance during the test. This is especially significant since, during the length of the availability test, the client will have control of the operation of the injection system. It is also important that during the availability test the use of installed spares (such as spare blowers) and normal maintenance shall be allowed. Choosing a Qualified Test Contractor One of the most important factors in a successful/proper performance test is the choice of a qualified test contractor. The best test protocol will have a better chance of success if the test contractor has a good Quality Assurance program and staff qualified to perform the emissions testing. Not only does a good performance test need a qualified test contractor but also several State regulatory agencies and the EPA are requiring certified test contractors. Through a combination of EPA impetus, and the desire by source testing companies to demonstrate that their personnel are properly qualified, the ASTM (American Society of Testing and Materials) developed ASTM D7036 [Standard Practice for Competence of Air Emission Testing Bodies]. This ASTM standard is specifically called out in 40CFR75 [Continuous Emissions Monitoring] in Section 75.21; ADA-ES, Inc

6 (f) Requirements for Air Emission Testing. On and after March 27, 2012, relative accuracy testing under 75.74(c)(2)(ii), section 6.5 of appendix A to this part, and section of appendix B to this part, and stack testing under and section 2.1 of appendix E to this part shall be performed by an Air Emission Testing Body, as defined in 72.2 of this chapter. Conformance to the requirements of ASTM D (incorporated by reference, see 75.6), referred to in section of appendix A to this part, shall apply only to these tests. Section of appendix B to this part, and section 2.1 of appendix E to this part require compliance with section of appendix A to this part. Tests and activities under this part not required to be performed by an AETB as defined in 72.2 of this chapter include daily CEMS operation, daily calibration error checks, daily flow interference checks, quarterly linearity checks, routine maintenance of CEMS, voluntary emissions testing, or emissions testing required under other regulations. CONDUCTING A SUCCESSFUL PERFORMANCE TEST How the System Equipment/Operation Can Affect the Performance Test Fuel Type The type of fuel that is being fired in a boiler will, due to its characteristics, determine critical items of flue gas concentrations and hence the ability of PAC to remove mercury from these flue gas streams. Coals in the United States (and other countries for that matter) have widely divergent properties and compositions, for example, variations in sulfur content from the low sulfur coals of the Powder River Basin to the high sulfur coals of the Illinois Basin and Gulf Coast lignite. 1 For a low sulfur coal, as is found in the Powder River Basin for example, this can result in a SO2 concentration in the flue gas of approximately 400 ppm 500 ppm and a SO3 concentration of approximately 4 ppm 5 ppm. This low concentration of SO3 has only a minor effect on the ability of PAC to remove mercury from the flue gas. On the other hand, a high sulfur coal, such as is mined in the Illinois Basin or the Gulf Coast Region, can produce a SO2 concentration of 3,000 ppm 5,000 ppm, and a concurrent SO3 concentration of 30 ppm 50 ppm, that can drastically reduce the ability of even halogenated PAC to remove mercury from the flue gas stream. Similarly, high chlorine coals when combusted will produce levels of HCl in the flue gas that will drive the speciation of mercury to high percentages of more easily collectable ionic mercury. 1 Obviously then, low chlorine containing coals will produce lower levels of HCl in the flue gas stream and will tend to have higher percentages of elemental (harder to collect) mercury. Boiler Type Just as the fuel type can affect flue gas composition and hence the effectiveness of PAC to reduce mercury emissions, the boiler type can have similar effects. Pulverized coal (PC) firing burning coal as a fine powder suspension in an open furnace is the most prevalent method in use today in the US Utility industry. Pulverized coal firing differs from the other coal combustion technologies primarily through the much smaller particle size ADA-ES, Inc

7 used and the resulting high combustion rates. Approximately 80% of the ash in the coal becomes fly ash and leaves the boiler with a very low (less than 1%) unburned carbon content. This very low carbon content in the fly ash generally results in a concurrent low native mercury removal by the ash itself in a particulate collector. The Babcock & Wilcox Company (B&W) developed the cyclone furnace concept to burn coal grades that are not well suited for pulverized coal combustion. 2 The cyclone furnace, on the other hand, fires relatively large crushed coal particles of which approximately 95% pass through a 4 mesh screen (nominal in. or 4.75 mm). Under ideal combustion conditions, the cyclone can capture approximately 70 to 75% of the original fuel ash as slag with the remainder exiting the furnace. The fly ash that exits a cyclone boiler can have up to 30% - 40% unburned carbon content. Consequently this unburned carbon aids in mercury capture and removal since, even though it is not activated carbon it still has a very high [pounds of carbon/million acf] injection ratio. Additives Fuel additives are used for mercury control by, in general, increasing the halogen content of the fuel. 3,4,5 This increase in the halogen content of the fuel results in more of the mercury in the coal to speciate to the ionic form of mercury (Hg +2 ), rather than to the elemental (Hg 0 ), more difficult to collect, form. It is important, especially if the fuel additive addition system is not under the DSI or ACI system supplier control, to determine that the addition system is not only in operation but is applying the proper/agreed upon amount of additive onto the coal. This will require measurement of the volumetric flow rate of liquid being applied to the coal and sampling (and analysis) of the fuel additive itself to determine if it contains the concentration of halogens stated by the additive supplier. Dry sorbent injection systems may also be a part of the boiler being tested for mercury removal. These additive systems may be injecting trona (sodium sesquicarbonate), SBC (sodium bicarbonate), or hydrated lime into the flue gas stream. 6 These alkaline compounds are generally injected for removal of SO3 or sulfuric acid mist (SAM) from the flue gas stream, but may also be used for the control of HCl emissions under the MATS rule. As with the additive systems adding chemicals to the coal, for mercury emissions reduction, these flue gas additive systems should also be in operation prior to the performance testing. Also, if the flue gas additive system is designed to remove SO3 or sulfuric acid mist (SAM) from the flue gas, it should be tested and shown to be effective before the performance test on the ACI addition system. It is important that not only an adequate amount of additive is being added to the flue gas to (for example) remove acid gases but that it is being distributed across the flue gas stream so that it mixes with the flue gas prior to the particulate control equipment. During testing of the ACI system, it is recommended that samples of the flue gas additive be obtained for analysis (if necessary) and that the recorded data from the plant control system historian contain the additive injection rate and the temperature of the flue gas at the point of injection. ADA-ES, Inc

8 Control Equipment Other emissions control equipment and systems can also affect the measured performance of both DSI and ACI systems. Some SCR systems with several layers of catalysts can convert up to 2% to 3% of the SO2 in a flue gas stream to SO3. 7 Since this phenomenon was observed, catalyst manufacturers have been working on, and have developed, low-oxidation catalysts. 8,9 These low-oxidation SCR catalysts can reduce the SO2 oxidation to less than 1% in a 3 to 4 layer SCR system but, the oxidation is not eliminated. This potentially means that for a flue gas from PRB combustion the SO3 at the APH inlet could be about 8 ppm (4 ppm from combustion and 4 ppm from SCR oxidation). More significantly, the SO3 concentration from bituminous coal combustion could be as high as 40 ppm 60 ppm (50% from combustion and 50% from SCR oxidation). This SO3 will impede the ability of PAC to remove mercury from a flue gas stream and potentially prohibit high levels of mercury emissions reduction. A high concentration of SO3 will also result in corrosion of downstream (from the SCR) ductwork and equipment in a power plant and is one of the reasons that utilities have and are installing alkaline (i.e. trona, SBC, and hydrated lime) injection systems. An electrostatic precipitator (ESP) collects particulate matter (PM) by applying an electrostatic charge onto particles via electrons from the discharge electrodes (DE). These charged particles are attracted to grounded collection electrodes (CE) where they lose their charge and the particles are retained on the CEs. The collection electrodes are periodically rapped in order to release the collected particles that fall into hoppers underneath sections of the precipitator. Once the particles have been deposited on the collection electrodes, they are essentially out of the flue gas stream. The implications of this collection of PM s, vis-à-vis ACI or DSI, is that the majority of the adsorption of mercury by the PAC or reaction of acid gases by dry sorbents takes place in the flue gas stream between the point of injection and the point/time of the collection by the ESP. A baghouse, or fabric filter, consists of arrays of cylindrical bags of a permeable fabric. These arrays are usually divided up between individual compartments where the collection of compartments makes up the baghouse. Gas passing into a compartment distributes itself among the filter bags. As the gas passes through the fabric of the filter bags, the PM is separated out (i.e. filtered) and forms a filter cake on the surface of the filter bag. The filter cake, along with the fabric of the bag, provides the filtration that results in very high PM removal efficiencies for a baghouse. PAC or alkaline sorbent injected into a flue gas stream entering a baghouse will become a part of the filter cake and, after a period of time, build up to a steady state concentration in the filter cake. Since the gas passing through a baghouse must pass through this enriched filter cake, then there is pollutant removal not only during the time-of-flight (as with an ESP) but also during the time that the gas is passing through the filter cake. Essentially then, for the same flue gas, at the same temperature, containing the same amount of mercury less PAC and/or sorbent would be theoretically needed for the same amount of pollutant removal due to the additional contact time between the flue gas and the PAC or sorbent. Note that it does take some time for this enrichment in the filter cake to build up so that a PAC or DS injection system performance test should not commence immediately after initiating injection. ADA-ES, Inc

9 The type of FGD system will have an effect on mercury emissions 10 and also on the timing of performance testing. Dry FGD systems remove SO2 from flue gas streams through the use of hydrated lime. This hydrated lime is introduced into the flue gas stream either as a slurry or as a dry powder. Unreacted lime, reaction products, and fly ash are all entrained in the flue gas stream and are carried over into a particulate collector, almost always a pulse-jet fabric filter. In the fabric filter, these materials form the filter cake on the filter bags and additional SO2 removal takes place. At the same time, additional mercury removal (beyond that achieved in the flue gas stream prior to the baghouse) also occurs. Due to water evaporation in the dry scrubber itself, the flue gas temperature is much lower than would be seen with a baghouse treating flue gas directly from a boiler. Consequently, this lower temperature results in more mercury removal than would be seen with a fabric filter at the higher temperature. Additionally, since dry FGD systems are quite efficient at removal of SO3 there is less interference by SO3 of mercury removal by PAC. Wet FGD systems usually use either a hydrated lime or limestone slurry to remove the SO2 from the flue gas. This slurry is injected into a large reaction tank located in the bottom of the wet scrubber tower. In the reaction tank, mixers are used to mix all of the solids in the reaction tank as well as to keep the solids in suspension. Air is bubbled into the reaction tank, near to the tank s bottom, for the forced oxidation of sulfites to sulfates. Wet FGD systems differ from the dry systems not only due to the nature of the waste product (dry powder versus wet slurry) but also due to the fact that the PM in the flue gas stream is removed by a PM control device (either an ESP or baghouse) prior to the flue gas entering the wet FGD scrubber vessel. Consequently any PAC injected into the flue gas stream will, for all intents and purposes, be removed by this PM device prior to the FGD system. Wet FGD systems can be efficient at collecting ionic mercury (Hg +2 ) but are not very effective on collecting/removing elemental mercury (Hg 0 ). Some wet FGD system suppliers have given guarantees of 90% ionic mercury removal across the scrubber vessel, but, these guarantees do not take into account any re-emission that may occur. Re-emission is a physio-chemical phenomenon that reduces ionic mercury to elemental mercury [Hg +2 Hg 0 ]. This elemental mercury is then re-emitted into the flue gas stream and exits the wet scrubber vessel. Therefore, with a wet scrubber, it is not unusual for speciated mercury measurements to show more elemental mercury leaving a wet FGD system than has entered the system. Scrubber additives have been developed and tested at full-scale for the purpose of suppressing this re-emission of mercury from wet FGDs. 11 The mercury re-emission and re-emission additives are significant with regard to performance testing for several reasons. Wet scrubbers, although being fairly effective removal devices for ionic mercury, are rather ineffective when attempting to remove elemental mercury. A high re-emission level within a wet FGD system can result in a mercury emission in excess of guarantees, not related to the effectiveness of the PAC being injected into the flue gas. ADA-ES, Inc

10 The volume of the reaction tank in most wet FGD systems is quite large and can be as much as one million gallons. The addition of a re-emission agent to a wet FGD system is usually done gradually and may take several days, or even several weeks, to attain the desired concentration in the reaction tank. If a performance test is being carried out with a wet FGD system that is using a scrubber re-emission additive, then the performance test should be scheduled after the reaction tank has developed the desired/needed level of re-emission additive. It may be possible to reduce this delay time if a large batch of re-emission additive is added to the reaction tank. Performance (mercury removal/emission) guarantees may assume a certain level of mercury removal in the FGD system and consequently, a maximum level of re-emission across the scrubber vessel. Performance testing with a system that includes a wet FGD system should have the mercury level, and the mercury speciation, measured at both the inlet and the outlet (which may be in the Chimney/Stack) of the FGD system. Speciated mercury concentrations can be measured using a continuous mercury monitor (i.e. EPA Method 30A) that can report on both the total and ionic mercury or with a speciated sorbent trap (i.e.using a speciated sorbent trap with EPA Method 30B apparatus). Sampling of a wet FGD system, during a performance test, should include a sample of the scrubber blowdown stream. If necessary this stream could be analyzed for the concentration of re-emission additive should the mercury emission or the level of scrubber re-emission not be in accordance with the Contract. Test Protocols Testing of the ACI or DSI system consists of more than just the performance testing itself and includes the measures that should be taken to maximize the validity of the tests and the data and samples obtained during the testing. This also includes measurements taken prior to the performance testing to alert the supplier to conditions that may be outside of Contract boundaries and cause for the guarantees to be voided. System Tuning and Pretesting System tuning should be performed as soon as possible after mechanical completion of the system. This tuning includes; Calibration of the feeders Operation of the conveying blowers/compressors Calibration of instrumentation such as thermocouples, pressure sensors Automatic and manual switching of feeders and blowers to redundant modules where these redundant systems exist. Calibration of alarms Confirmation of connection to and proper operation of the injection system control system and the plant/ control system/dcs Note that calibration of the feeders is very important as this information will be used to verify carbon consumption requirements. Additionally, the injection rate is usually expressed as Pounds of PAC or sorbent/million actual cubic feet of flue gas at the point of injection. If a flue gas flow rate measurement is not being made at the point of injection, then it will be necessary to use an existing measurement and adjust it to conditions at the point of injection. ADA-ES, Inc

11 During the pre-test tuning of the system, information should be obtained from the plant control system that will give an indication of whether the actual plant conditions are the within the design range of the injection system. This will also be an opportunity to determine if process conditions, such as flue gas temperature at the point of injection, are within Contract parameters. Baseline Tests - Establishing Levels and Preliminary Data Baseline testing serves several purposes; 1. Establishing that the unit operations such as flue gas flow rate, SO2 and SO3 concentration levels, and air heater inlet/outlet temperatures are within the limits set forth in the guarantees. If limits that affect the guarantees are exceeded, then the unit operation will have to be adjusted to bring operations within guarantee limits. 2. Establishing that the fuel being fired is approximately the same as was in the system design information in the Contract. 3. Establishing that the mercury level in the flue gas (or the coal) does not exceed levels indicated in the Contract. 4. Establishing that related/relevant equipment such as an electrostatic precipitator (ESP), fabric filter/baghouse, and/or wet/dry FGD system is being operated in a proper manner that will not adversely affect the results of the performance tests. A Proper Manner refers to a stable operation of the boiler and its related equipment and no malfunctions that can affect the Baseline and/or performance tests. 5. Establish that the minimum sampling times as called forth in the performance test protocol will collect sufficient weight of samples (dust, HCl, etc.) to be above the Practical Quantitative Limit (as set by the Method) for that substance. If the baseline sampling shows that the sample volume was too small, then the sampling rate or total sample volume should be increased to acquire sufficient sample for an accurate analysis. 6. Establish the initial/baseline performance of the system without PAC or reagent injection. 7. It is in the best interests of not only the system supplier but the Owner and/or the Engineering Contractor that the process and operating conditions be as close to Contractagreed values as possible. This will result in a performance test that requires only minor corrections and minimum disagreements on results. Additionally, the baseline testing can identify factors (such as a very high air heater exit temperature or a baghouse with leaking bags) that may prevent a successful performance test. These factors should be brought to the attention of the Owner and/or Engineering Contractor as soon as discovered so that the situation may be corrected. Test Conditions Performance test conditions should be as close to Contract operating conditions as possible. Conditions should be verified through installed instrumentation from the plant/unit and should be available to the system supplier personnel. The test conditions are part of the data recorded during each run of the performance test, preferably in electronic (Excel, csv, or equal) form. Steady State Operations The NSPS and MACT programs require that performance tests be conducted under such conditions as based upon the representative performance of the facility. For much of the same reasons, the injection system performance test should also be conducted under conditions that ADA-ES, Inc

12 represent the normal operation of the facility. Additionally, operations during periods of startup, shutdown and malfunction do not constitute representative conditions for the purposes of a performance test. Consequently, not only should the facility be operating under normal conditions but also at the maximum design load of the facility. This operation should be a stable enough operation that the results from all of the performance test runs can be compared to each other and the conditions during a test run are steady enough that there does not have to be continuous corrections by the Test Contractor when performing the emissions tests. This steady state operation is very important since the measurement of flue gas velocity (and hence flow rate) will not have valid orifice coefficients (with the measurement probe) if the flow variation is more than ±3% at the velocities expected in both duct work and the stack. Not only should the gas flow rates be steady but also other factors, such as the air heater outlet temperature, should be stable as well. This means that normal system operation including air preheater soot blowing, ESP DE and CE rapping (where an ESP is part of the system), baghouse compartment cleaning (where a baghouse is part of the system), and wet and dry FGD system chemistry and conditions should be maintained during performance testing. Conditioning Time Each of the APCD systems needs to come to, if not a steady state, then at least a steady level of sorbent, mercury re-emission additive, or FGD process chemistry, some suggestions are as follows (Table 1) for mercury sorbent injection systems. Table 1. Conditioning times suggested before performance testing. ESP, 1 day PAC buildup on the collecting electrodes/plates could affect the electrical operation of the ESP, with a minor effect on Hg removal. Baghouse, 3-5 days Dry FGD/FF, 5-7 days Wet FGD, 1 week minimum PAC starts to accumulate on the bags, through multiple cleaning cycles. This can affect both Hg removal and pressure drop. The baghouse should be allowed to come to steady state. Recycle of the FF ash back into the dry FGD will take a few days to come to steady state. Hg sorbent will be recycled along with the lime from the dry FGD. Either with additives or sorbent injection, it may take a considerable time for the chemistry in the FGD slurry to stabilize, depending on the blowdown rate and volume of absorber tank. Performance Testing The purpose of the performance testing is to verify guarantees including pollutant emissions and/or emission reductions and PAC/sorbent consumptions as stated in the Contract. For these tests to be representative of system operation, it is important that the system tuning and baseline ADA-ES, Inc

13 testing be successfully completed. It is also important that calibration of critical equipment, especially the gravimetric or volumetric feeders, be completed within one week of the start of the performance test. If there is more than one week between the calibration of the feeders and the commencement of the performance test, then the feeders should be re-calibrated as close to the beginning of the test as possible. In planning the performance test, a walkdown of sample locations (preferably with testing contractor) should be conducted to identify existing sample ports for inlet and outlet measurements. Ports should have 4-inch flanges and enough clearance to insert probes. Ports may have to be added for measurement locations specified in the Contract. If outlet measurements are not taken at the stack, but in a flue gas duct (e.g., ESP outlet) measurements of velocities at the duct location should be made to verify flow rate and uniformity (EPA Method 2 or 2F). Emissions testing at the injection system inlet, prior to the point of sorbent injection should include the measurements listed in Table 2. Table 2. Measurements taken at location upstream of sorbent injection to verify injection conditions. Emission O2/CO2 Test Method EPA Method 3A Moisture EPA Method 4 Flow Rate (if EPA Method 1 compliant ports exist) Temperature SO3, H2SO4 (if specified in Contract) EPA Method 2 or 2F EPA Method 2 or 2F Modified* EPA CTM-013 NH3 (If SCR is present) EPA CTM-027 *Sampling apparatus/method must be operated to prevent reaction between SO 3 and sorbent particles in the sampling system. Verification of inlet Hg concentration may be specified in the Contract, requiring coal sampling and/or flue gas sampling upstream of sorbent injection. For verifying mercury emissions, Method 30B (sorbent traps) or a Hg CEM should be used. Run times for Method 30B should be one to three hours, depending on the expected level of Hg in the flue gas. Spiked traps should be at a level appropriate to the flue gas concentration. If possible, analyze traps on site to provide quicker feedback. If using Hg CEM for performance test, all applicable certifications and calibrations must be current, and the averaging period (sample duration) should be agreed upon in advance. Hg emissions test runs should pass all QA/QC to be acceptable. ADA-ES, Inc

14 For alkaline sorbent injection systems, verification of performance might be for HCl emissions control, in which case either a stack test can be carried out using EPA Method 26, 26A, or 320. If no entrained water droplets exist in the exhaust gas, then EPA Method 26 or 320 or ASTM Method D (Reapproved 2010) with additional quality assurance can be used, but Method 26A should be used if entrained water droplets exist in the exhaust gas. Emissions testing at the system outlet (guarantee point) should include the measurements listed in Table 3. Outlet sample location can be the stack or the outlet of the particulate control device, depending on the Contract. If there is a guarantee related to re-emission of Hg from a wet scrubber, speciated mercury measurements (CEMS or trap) might be made at the FGD inlet. Table 3. Measurements taken at guarantee location to verify performance of the sorbent injection system. Emission O2/CO2 Test Method EPA Method 3A Moisture EPA Method 4 Flow Rate Mercury* EPA Method 2 or 2F EPA Method 30B or Hg CEMS HCl* EPA Method 26, 26A, or 320 Temperature EPA Method 2 or 2F *Depending on type of sorbent and guaranteed emission. Each performance test should consist of a minimum of three runs. An examination of the results of the three runs should show a consistency that will give confidence that their average will be valid for satisfying the performance guarantees. If one of the results of the three runs appears to be widely divergent from the results of the other two runs, then the Dixon Ratio Test can be used to determine if this result is a true outlier. It should be pointed out that elimination of one out of the three runs as invalid will mean than the performance test results are depending upon the average of the two remaining runs. The elimination of outlier results and the use of two runs to determine performance should be established as an agreed-upon approach, if possible, during Contract negotiations but certainly prior to the performance testing. Conditions for the performance guarantee emissions test should be fixed, including Load (MW, million Btu heat input/hr) as close to but not greater than design maximum Load stabilized at least two hours before the start of the performance test and held constant (±2% - 3%) during all runs of the performance test ADA-ES, Inc

15 Fuel being fired should be as close to process design as practical and should not change over the course of the performance tests Performance test run not overlapping the scheduled daily calibration of installed CEMS Air Preheater outlet temperature at or below maximum temperature in Contract. Flue gas flow rate (acfm) at injection point at or below maximum specified in Contract. SO3 concentration at the ACI injection location, if specified in Contract The downstream equipment can include an ESP, a baghouse, and/or a flue gas desulfurization system During the emissions performance guarantee test, samples are collected to verify the conditions of the test, subject to any conditions around the guarantees as specified in the Contract (Table 4). Table 4. Samples collected during the performance test. Sample Coal Fuel Additive Wet FGD Scrubber Blowdown Sorbent Analyses or Reason for Sample Ultimate Analysis Proximate Analysis Mercury Concentration Chlorine Concentration To be analyzed if there are issues with mercury emissions reduction and speciation of mercury to ionic form To be analyzed if there are questions on mercury re-emission levels in the Wet FGD system and it is necessary to analyze for the concentration of re-emission additive Sample held in the event that there are issues regarding the sorbent Observation/Participation in performance tests The primary issue with respect to observing stack tests to determine and demonstrate performance is whether the system supplier should have an observer present for all performance tests, and if not, how often should the supplier be present to observe the tests. There may be no Contractual requirement that staff from the supplier be present to observe all performance tests. However, whenever possible, trained staff from the supplier should observe the tests to ensure that the Contract testing requirements are being met; the site-specific test plan is being followed; and the results are being accurately and completely recorded and documented in the test report Availability Testing After successful conclusion of the performance test, the availability test can begin and should cover a continuous period of hours or days as specified by the Contract. Throughout the availability test period, the vendor-supplied equipment should be operated by the Owner s staff in accordance with training and the Operating and Maintenance manuals supplied by the vendor. During the availability test, unit outage and derate data for the station are collected and an ADA-ES, Inc

16 Equivalent Availability Factor calculated in accordance with NERC GADS procedures. Outages or derates caused by the vendor-supplied equipment or systems would be recorded and used in computing the Equivalent Availability Factor during the availability test. Outages or derates caused by the errors of the Owner s operating personnel or any other cause not attributable to the vendor s equipment or the work, should not be included in calculating the Equivalent Availability Factor. SUMMARY Carrying out a successful performance test of ACI or DSI systems for MATS control requires careful planning and execution to be successful. Testing will include levels of emissions but also for the consumption of reagents/adsorbents and power and the system reliability. It is recommended that many of the aspects covered in this paper such as test methods and locations, duration and number of performance tests, and the protocols and procedures of the performance and availability testing be agreed to as early in the project as possible. These agreements will ensure that performance and availability testing for ACI and DSI systems is done in a manner that is agreeable to both the equipment supplier and the client and minimize any disagreement of the results of that testing. REFERENCES 1. Kolker, A.; Senior, C.L.; Quick, J.C. Mercury in coal and the impact of coal quality on mercury emissions from combustion systems. Applied Geochemistry, 2006, 21, Stultz, S.C. and Kitto, J.B., eds. Steam Its Generation and Use, 40th edition, The Babcock and Wilcox Company, Barberton, OH, Richardson, C.F.; Dombrowski, K.; Chang, R. Mercury Control Evaluation of Halogen Injection into Coal-fired Furnaces. Presented at Electric Utilities Environmental Conference, Tucson, AZ, January 23-25, Berry, M.; Dombrowski, K.; Richardson, C.; Chang, R.; Borders, E.; Vosteen, B. Mercury Control Evaluation of Calcium Bromide Injection into a PRB-fired Furnace with an SCR. Presented at Air Quality VI, Arlington, VA, September 24-27, Shaw, B.I.T. EMO TM. Presented at Electric Utilities Environmental Conference, Phoenix, AZ, January 30-February 1, Arambasick, K.; Dombrowski, K.; Blythe, G.; Chang, R.; Dene, C. Survey of Power Plants Using Dry Sorbent Injection for Acid Gas Control. Presented at Power Plant Air Pollution Mega Symposium, Baltimore, MD, August 20-23, Duellman, D.M.; Erickson, C.A. Operating Experience with SCRs and High Sulfur Coals and SO3 Plumes. Presented at Institute of Clear Air Companies (ICAC) NOx Forum, February, Haldor Topsøe. DNX - Topsøe SCR DeNOx Catalysts Oxidation of SO2 into SO3. ( 0files/Scr_denox/Topsoe_scr_oxidation.ashx. Accessed ) 9. Jin, P; Favale, A.; Gretta, W.J.; Wu, S.; Nagai, Y.; Kato, Y.; Morita, I. Mercury Oxidation SCR Catalyst for Power Plants Firing Low-Chlorine Coals. Presented at Presented at Air Quality VII, Arlington, VA, October 26-29, ADA-ES, Inc

17 10. Senior, C.L.; Sjostrom, S. Behavior of Mercury and Selenium in Coal-Fired Boilers and Air Pollution Control Devices: A Review of Recent Full-Scale Data. Presented at Air & Waste Management Association 104th Annual Conference and Exhibition, Orlando, FL, June 21-24, Institute of Clean Air Companies. Improving Capture of Mercury Efficiency of WFGDs by Reducing Mercury Reemissions. June ( _Reemission_Paper_v23_Fi.pdf. Accessed ) KEYWORDS MATS, Performance testing, ACI, DSI, Guarantees, Liquidated damages, availability testing ADA-ES, Inc