Can’t Even Make Sense of CEMS?
CEMS is a term that is used quite often when referring to air quality management. If you are new to the industry, or are now being subjected to CEMS regulations, this small but complex area of air emissions can seem overwhelming. Air Tox is available to assist in removing the shroud of mystery surrounding CEMS and help you understand the basics of what a CEMS is, how it works, and the different types and applications of CEM systems.
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 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.