Probes and probe technologies
Volume II, Edition 3
Probe designs are unique to the source of emissions. What probe you use is dependent on the sample conditions so it is critical to choose the right probe for the right application. By choosing the right probe, you will see low maintenance, appropriate sampling and accurate emissions reporting. Here are 5 tips and tricks for probe selection:
Know when to use an inertial filter probe
An inertial probe is recommended for sampling locations that have high ash content. The inertial filter utilizes the particulate in the sample to scour any excessive build-up of ash on the filter element. Typically these sample locations are upstream of particulate control devices such as an ESP or bag-house. For sampling systems that are used for process control, an inertial probe is recommended as the probe may be utilized both up and downstream of control devices. In certain cases where excessive carbon is making it through the particulate control devices, an inertial probe may have a lower potential for a mercury measurement bias due to a lower amount of carbon build up on the inertial filter as compared to a non-inertial probe.
Use a non-inertial probe for compliance monitoring
Non-inertial mercury probes are the most common type of probe used for compliance monitoring. In general, these probes offer easier access to the filter element for cleaning and replacement. The probe design is compact, light weight, and designed for ease of serviceability and manufacturability.
Solutions for direct extractive techniques
Direct extractives are often used in gas-fired systems, natural gas applications or where required by local regulations. There are two probe options depending on whether the sample line is hot and wet (hot-wet) or cold and dry (cold-dry). For cold-dry applications, we recommend the Thermo Scientific™ Model PRO3000 Full Extractive Probe which extracts the sample through a heated probe barrel and filters out sub-micron particles using the heated filter. The Thermo Scientific™ Omni FTIR Multi-gas CEMS uses the hot-wet extractive measurement technique and can be used in various applications including coal-fired power plants, cement kilns, waste incinerators and industrial processes with multiple effluents.
Wet dilution has its benefits
The use of dilution extractive sampling systems for Continuous Emission Monitoring Systems (CEMs) became prevalent as a result of Title 40 of the Code of Federal Regulations Part 75 (40 CFR 75) known as the Acid Rain Program and facilities continue to find many benefits associated with running dilution extractive systems. A diluted gas is less harsh on instruments than a concentrated gas and this results in prolonged instrument life and more equipment uptime. For SO2 applications, the wet dilution method eliminates the risk of SO2 loss in the chiller and lowers the risk of measurement error or bias on a full extractive system. An additional benefit to using wet basis dilution is that the calculation of mass emission rates (for example lb/hr) is simplified. For wet dilution applications we recommend Thermo Scientific™ EPM.300 Series Diluting Stack Sampler and Thermo Scientific™ PRO2001WHP Dilution Extractive Probe.
Unique requirements for pulp and paper
US EPA regulations for the pulp and paper sector require the control of particulate matter and total reduced sulfur (TRS) compounds from sources at kraft pulp mills. These applications call for oxygen-corrected values and the Thermo Scientific™ Model PRO902C Low Flow Dilution Probe was specifically designed for use in harsh, dirty environments such as those found in pulp and paper mills. This probe chills the sample stream via a thermoelectric cooler to remove the moisture in the sample. Once the sample has been conditioned, dry air dilution lowers the sample dew point to -40C. The probe properly operates at lower temperatures and a heated sample line is never required.roper installation is critical to ensuring accurate monitoring and trouble-free umbilical life. During initial installation, be sure to run the line continuously with no loops and always in a downward position to ensure maximum flow. Avoid hot pipes and support the line on the stack with a cable tray. Trimming the line can often be avoided on site if an accurate measurement is taken at time of proposal. When the line needs to be shortened, refer to the detailed instructions supplied by the umbilical line OEM to mitigate the risk of voiding the warranty.