There aren't many applications in the process industry that don't use fuel to produce heat. Environmental officials will soon follow where there is combustion since large-scale fired heaters, boilers, and other activities always call for monitoring and reporting. A continuous emission monitoring system (CEMS) with one or more gas analyzers like Gem 5000 to quantify the pollutants of concern is often required to determine what is coming out of the stack.
Types of Continuous Emissions Monitoring System or CEMS
There are several techniques to carry out the essential measurements because there are so many diverse applications that may be used. There are five primary kinds of measuring methodologies since the specifications for a coal-fueled rotary kiln and a fired heater burning natural gas in support of a distillation column are very different. The most typical installations are those that burn natural gas or fuel oil. The article compares cold/dry CEMS versus hot/wet CEMS while examining the CEMS choices for refineries and chemical facilities. An emphasis is placed on how hot/wet extractive CEMS solves issues that arise as a result of flue gas composition, particularly from one key component which is water.
Flue gas is generally composed of nitrogen, leftover oxygen, different contaminants, and a significant amount of water vapour (8–20%) when it exits the stack. The gas's capacity to transport water vapour is greater than air at room temperature because it is hot, often >95°C (>200°F). Water condenses when it enters the environment because the flue gas's dew point is often lower than its departure temperature but higher than the ambient temperature.
Difficulties faced in Continuous Emissions Monitoring System
Sample conditioning techniques freeze the sample gas until the moisture condenses and can be eliminated before reaching the analyzer since some gas analyzers don't handle liquid water effectively. This cold/dry method is quite popular, but it is complicated and requires a lot of maintenance since it is difficult to handle the water and some contaminants are affected by the condensation process. If the analyzer can handle high-temperature gas, the option is to maintain the gas sample hot such that water stays as vapour.
The requirement for cold gas samples has diminished as analyzer technologies have advanced and some have shown increased tolerance to greater working temperatures. A hot/wet system, a straightforward and efficient sample approach, has been made popular by this. a single sample stream that doesn't go through a chiller and flows straight from the tap site to the analyzer. To prevent condensation, the sample stream is kept as hot as is required to keep every component above its dew point.
How to overcome difficulties?
Because there is no need to correct for changes brought on by cooling and moisture removal, keeping the sample hot provides it in its purest form to produce the most accurate readings. The first Quantum Cascade Laser (QCL) system created for process gas analysis and emissions monitoring is Emerson's Rosemount CT5100 Continuous Gas Analyzer. The CT5100 is offered in two variations: a certified system for use in hazardous locations that is enclosed in a purged and pressurised enclosure, and a non-certified system for use in non-hazardous environments. Both can accommodate up to six lasers for simultaneous measurement of many gas stream constituents. The dew point of water and the majority of acid gases are higher than the 190° C (375° F) that it can handle for gas samples. Gas chillers are no longer required, allowing for a more simpler sample handling system.
