What in the world is a CEMS?

CEMS is the acronym for Continuous Emissions Monitoring Systems. Also related are COMS, which are Continuous Opacity Monitoring Systems. As stated in their name, these types of systems contain equipment that monitors emissions or opacity (opaqueness of gas) on a continuous basis. Readings from these systems are typically transferred to some sort of data acquisition and storage system that can then be used to show regulatory compliance.

How do CEMS work?

There are two common types of continuous emissions monitoring systems: extractive CEMS and dilution CEMS.

In a direct extractive system, the emissions monitor analyzes a direct sample of gaseous emissions from the stack on a dry basis. This sample is obtained from the stack or duct via a probe outfitted with a filter. It then passes through a sample line, through a sample conditioner and cooler (to remove moisture) until it finally reaches CEMS analyzer. These types of systems are best suited for processes that are not particularly wet, dirty, corrosive, or highly concentrated.

In a dilution system, the emissions monitor analyzes the gaseous sample on a wet basis that has been diluted with a known ratio of air. The gas sample is obtained and delivered to the monitor in a similar fashion as the extractive system except that the sample is diluted and delivered on a wet basis to the analyzer. The analyzer measures the sample and then outputs a corrected value based on the predetermined dilution ratio. These systems are best suited for processes that are very wet, corrosive, dirty, or highly concentrated in which a direct extractive CEMS would not be and viable solution.

In both cases, readings from the monitors are then typically transferred to a DAHS, (Data Acquisition and Handling System). The DAS provides operators with CEMS data and alarms displayed in real time. Often times, the DAHS interface allows for operation of certain functions on the CEM systems, such as calibrations, blowbacks, and other maintenance controls.

CEMS Applications

CEMS can measure a wide variety of pollutants. Most commonly monitored are nitrous oxide (NOx), sulfur dioxide (SO2), carbon monoxide (CO), and ammonia (NH3). Also typically monitored for emissions calculation purposes are oxygen (O2), carbon dioxide (CO2), moisture (H20), and velocity. Other examples of less commonly monitored pollutants are HCL, mercury, particulate matter (PM) and VOC’s.

A great number of different industries employ CEMS for regulatory purposes and process-related applications. These include but are no means limited to: power generation facilities, co-generation facilities, waste incinerators, smelters, glass manufacturers, lime manufacturers, metallic processing plants, and coating and sealant operations.

Most facilities install CEMS in compliance with regulatory requirements, but can also be used as a tool to assist with operation of the facility. Since data is presented in real time, processes can be adjusted and tweaked preventatively, before compliance violations occur and can also help the facility operate more efficiently. Additionally, since there are numerous quality assurance checks that take place on CEMS data, emissions reporting is very straightforward. Data is typically very solid and defendable if proper protocols are followed.

Air Tox has an excellent working relationship with numerous vendors of CEM equipment, and has more than 25 years of experience building custom CEM systems. Contact us for any inquiries or questions you may have regarding CEM systems today.

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Non-valid data alarms

We recommend setting up alarms for whenever data is invalid for reasons other than normal maintenance, calibrations, or process down conditions. We suggest that these alarms be split up by parameter (NOx, Opacity, etc.). In order to avoid having an alarm become a nuisance, we further suggest to implement a delay instead of having it sent out for every invalid minute. One method would be to create a rule to send the alarm for the first invalid minute, and then once every 15 minutes thereafter. Another possibility would be to only send an alarm only when 15 minutes or more of data is invalid.

Emissions Warnings

Ideally, these alarms would help control emissions before an excess emission is reached. Depending on limits and operating flexibility, the thresholds on these alarms vary. However, the alarm should be configured to provide the operators enough time to make minor adjustments to correct the emissions without disrupting the process unnecessarily. Sometimes it takes trial and error to find a good set point. For instance, 1-minute alarms are typically not very useful (unless for opacity), but a 1-hour alarm may be beneficial for controlling a 4-hour average.

Calibration drift alarms

Sometimes it is not always clear just by glancing at a calibration report if there has been a failure or significant drift or perhaps daily calibration checks are not reviewed on a daily basis. In those cases, implementing an alarm for a calibration failure or major drift can be helpful as a secondary check to ensure excessive downtime is avoided due to a daily calibration failure.

Specific Malfunction Alarms

Often analyzers have numerous internal operational alarms that can be beneficial for troubleshooting and avoiding catastrophic failures. If these are brought into the data system, operators can see them and alert maintenance personnel so they can be addressed in a timely fashion. These could be such things as internal temperature, pressure, or gas flow alarms, which could indicate an obstruction or part failure. There can also be alarms on other CEM system components, such as rack, shelter, and heated sample line temperatures. Any of these alarms can provide valuable advanced warning that something is wrong on the system before excessive downtime is incurred.

Are you questioning whether your CEMS alarms are configured properly? Air Tox can assist with reviewing your current alarm configuration and advise on best practices. Contact us here.

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Emission Limits

Source: U.S. Environmental Protection Agency

 Testing

• Initial Compliance Test (by March 21 2016)
• Annual Compliance Tests, and/or use of CEMS

Continuous Compliance

• Annual pollution control device inspections (based on control device)
• Monitoring of operating parameters and limits
  • including minimum operating or afterburner temp, feed rate of sludge, moisture content of sludge, and site specific operating requirements for fugitive ash
  • other specific requirements based on control device

Record keeping and Reporting

• Increments of Progress – 1st and 2nd increment
• Initial Compliance Report
• Annual report
• Deviation report
• Qualified operators status report (if a qualified operator is not available for 2 weeks or more)

Other

• All operators must be fully trained and qualified- “An SSI unit cannot be operated unless a fully trained and qualified SSI unit operator is accessible, either at the facility or can be at the facility within 1 hour”. An annual review/refresher course is also required. This documentation must be updated annually on site.
• A site-specific monitoring plan must be submitted before March 21 for each continuous monitoring system, bag leak detection system (if applicable), and for ash-handling.

The post What you need to know about the EPA’s new Sewage Sludge Incinerator Rule appeared first on Air Tox.

A calibration becomes out of control (OOC) when the cal drift value is 4 times the drift specification limit, or when the cal drift value is over 2 times the drift specification limit for 5 days in a row. The latter situation is for Part 60 calibrations only. For a Part 75 calibration, the data becomes invalid from the time of the failed calibration to the time of the next passing calibration. For Part 60 calibrations, data is invalidated back to the last good calibration up until the next passing calibration. In short, those invalid hours can add up pretty quick, especially with multiple OOC cals.

How to avoid:

• If a cal has been drifting over 2 times the drift limit for 3 days or more, make necessary adjustments and run a calibration until drift is under 2x the limit. This avoids having 5 days in a row of drift over 2x the limit.
• Recalibrate a failed cal as quickly as possible to minimize downtime
• Schedule regular maintenance on the analyzers to minimize chances of an analyzer malfunction
• Remember to change cal gas values in the DAS system when you change out a cal gas bottle. The calibration can be manually revalidated if this is the cause of an OOC cal, but this wastes time and can cause unnecessary confusion on site.
• Call Air Tox for help with adjusting and recalibrating analyzers. We have a 24×7 emergency service that can dial into your system at any time to perform calibrations.

Poor Maintenance:

An analyzer requires regular maintenance in order for it to function properly. The lack of regular maintenance can lead to major system failures, which can take up to days to correct.

How to avoid:

• Develop and maintain a regular maintenance schedule. An effective schedule will include weekly, quarterly, semi-annually, and annual items to be checked, tested and replaced. Air Tox can advise on what specific elements should be included in this schedule, and are experts at performing maintenance services.

Missed or Failed Audit Tests:

Audit tests such as a Linearity check, Cylinder Gas Audit (CGA), and Relative Accuracy Test Audit (RATA) are required on a quarterly and annual basis. Data becomes invalid on the expiration of the grace period for these audits, or when an audit is failed.

How to Avoid:

• Make sure you are aware of your site-specific audit requirements to ensure that the grace period for completing them is not missed.
• All involved parties should be familiar with testing protocols and procedures
• Complete quarterly maintenance before an audit so that analyzers are functioning at maximum potential
• Complete a daily calibration before the start of an audit
• If your facility has a flow monitor, running a flow test to verify the accuracy of the flow curve and velocity data is recommended before a RATA.
• Air Tox is extremely competent in performing all audit tests, and has a wealth of experience troubleshooting should a test fail for any reason.

The post Simple Tips for Avoiding Downtime appeared first on Air Tox.

Ever feel like you’re reading a different language when it comes to your CEMS and COMS regulations or permit? Don’t feel uncomfortable any longer! Here is a reference guide that explains the acronyms you need to know to, well, be in the know!

BAF- Bias Adjustment Factor (determined in RATA)

BTU- British Thermal Unit

CAMD- Clean Air Markets Division

CEMS- Continuous Emissions Monitoring System

CGA- Cylinder Gas Audit (audit performed under Part 60 every quarter for CEMS)

COMS- Continuous Opacity Monitoring System

CSAPR- Cross State Air Pollution Rule

DAHS- (or DAS)- Data Acquisition (and Handling) System

DR- Designated Representative

DT- downtime

ECMPS- Emissions Collection and Monitoring Plan System

EDR- Electronic Data Report (submitted to the EPA through ECMPS)

EE- excess emission

EGU- Electrical Generating Unit

FF2L- Fuel Flow to Load

GCV- Gross Calorific Value (quantity of heat produced when fuel is combusted; the GCV will vary based on fuel type and sample)

NAAQS- National Ambient Air Quality Standards

NSPS- New Source Performance Standards

OOC- Out Of Control (refers to CEMS/COMS monitors)

Part 60- 40 CFR 60- Code of federal regulations under the Clean Air Act

Part 75- 40 CFR 75- Code of federal regulations under the Clean Air Act

PNG- Pipeline Natural Gas

PPM- Parts per million (concentration)

QAQC- Quality Assurance, Quality Control

RA- Relative Accuracy

RATA- Relative Accuracy Test Audit (yearly audit performed under Part 60/75 for CEMS)

RM- Reference Method

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Quarterly reporting under Part 75 (EDR’s) often requires more than just the standard Linearity Tests and RATA’s to maintain compliance. This blog focuses on a fairly simple but easy to overlook test: the fuel flow to load. For every quarter in which a flowmeter accuracy test is not conducted, this test must be run for quality assurance purposes. Compliance can be measured in either a fuel flow to load ratio or gross heat rate (GHR).

Once the baseline fuel flow to load ratio or GHR is established, a fuel flow to load test must be run each subsequent QA operating quarter (>168 hours). This is calculated by comparing the quarter’s FFTL ratio with the baseline ratio or the GHR to the reference GHR. The steps are as follows:

1. Calculate hourly fuel flow to load or GHR ratios:

2. Calculate percent difference from baseline ratios:

3. Calculate arithmetic average of all of the hourly percent difference (percent D_h)

The below information is also reported with the fuel flow to load test:

• Average difference between FFTL baseline or GHR ref and quarterly FFTL or GHR
• # of hours of QA-assured data
• # of hours excluded due to co-firing
• # of hours excluded due to ramping
• # of hours excluded due to low range (<25% unit load)

This is where the information is entered into ECMPS:

If you have any questions on this test, you can access the ECMPS support page under our resources. You can also Contact Us.

The post The Why’s and When’s of Fuel Flow to Load: FFTL Testing appeared first on Air Tox.

Often, QA tests that are not conducted quarterly, or even yearly, are sometimes accidentally ignored. However, their low frequency does not mean they are any less important. The fuel flow to load baseline test is one such QA activity. Since long stretches of time may elapse between tests, it is easy to forget just how this test is run. Below is a description of what a fuel flow to load baseline involves, and why it is important.

The fuel flow to load baseline is a necessary because it is a precursor for running quarterly QA tests on the fuel flowmeter. It establishes a “baseline” ratio for fuel flow or heat input to unit load, to which each subsequent quarter compares to. It must be calculated for each flowmeter device whenever it is installed or re-installed. A baseline test is good for 20 calendar quarters, or 5 years. After that, it must be re-established. Data collection begins immediately after the meter has passed its initial QA certification (flowmeter accuracy test and transmitter/transducer/PEI (primary element inspection), if necessary). The baseline needs at least 168 hours of data, and must be completed within four calendar quarters.

The information collected for the baseline includes:

• # of hours excluded due to co-firing
• # of hours excluded due to ramping
• # of hours excluded due to low range (<25% unit load)

If choosing to report fuel flow to load ratio (FFTL):

• Average fuel flow rate
• Average load
• Average flow to load ratio (using equation D-1b in App. D 2.1.7.1)

If choosing to report gross heat rate to load ratio (GHR):

• Average hourly heat input rate
• Baseline gross heat input (using equation D-1c in App. D 2.1.7.1)

Here is where all this information goes in ECMPS:

If you have any questions on this test, there is an ECMPS support page on our Resources page that provides additional information.

You can also Contact Us.

The post The Why’s and When’s of Fuel Flow to Load: Establishing a Baseline appeared first on Air Tox.

1. DO YOUR DUSTING…Dust can get into mechanical parts and fans causing things to work harder or overheat. Change dust filters and use low-pressure compressed air to clean dust from analyzers, heat exchangers and air intakes.
2. TURN DOWN THE HEAT…Heat is probably the biggest enemy to CEMS equipment. Check the temperature in the area where the CEMS equipment resides and make sure it remains between 68-72 degrees F.  Clean the filters in your A/C, fans and vents.  As noted above, remove any dust from heat exchangers.  If your A/C dies, a simple fix is to slide the analyzer out of the rack and remove the cover until the A/C is repaired.  This will prevent heat from being trapped inside and keep it cooler.
3. MAKE SURE YOU FLUSH…Soot and salts can build up in your sample line and compromise your sample, or cause inaccurate emissions readings. Make sure you flush your sample lines on a regular basis.  Some facilities can get away with an annual flush while others require flushing either quarterly or monthly.

Following these few simple tips can help increase the life expectancy of your equipment and provide you with more stable and accurate CEMS data.  Air Tox provides regular preventative maintenance services to many of our customers that include these items.  If you want to learn what service Air Tox can provide for you, please Contact Us.

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So, how to make the best of the day, keep warm and execute a successful test program in these challenging environmental conditions?  In addition to the warm weather gear, standard safety and PPE for climbing and testing on a stack platform, you might consider toting these amenities to your testing location to help brave the elements and enjoy a wintry day, all while effectively completing those long dioxin test runs before that winter sun sets.

• Bring a small sturdy fabric shelter to cover instrumentation and provide protection against wind, sleet and snow. You can also make a shelter with a tarp and rope, using your scouting skills to secure it to the stack railing and to other strong points.
• Bring a small collapsible table to set up instrumentation and for performing post-weights of desiccant. The table can also be used for balancing your lunch while performing sample train leak checks.
• Bring a portable propane heater that can safely be used to pump warm air into your shelter. Check propane cylinder and connections for good seals.  Make sure you have good ventilation when using the heater near the shelter.  Be sure the heater has enough clearance so nearby items don’t get burned or melted.
• Warm and gripp-y work gloves for loosening those tough impinger screws after a test run (or in between leak checks as needed) in the cold weather.
• Drink lots of water and eat high-energy snacks. Enough said. But it is really important to maintain good nutrition to fuel yourself for working outdoors for several hours at a time. Watch for signs of dehydration and over-exposure to the cold.

Got any other stories or tips of your own for surviving winter stack testing?  Feel free to share with us! Contact Us.

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