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.

The post Can’t Even Make Sense of CEMS? appeared first on Air Tox.

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.

The post Implementing CEMS Alarms: Nuisance or Necessary? 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

The post The Guide to CEMS Acronyms appeared first on Air Tox.