Air Monitoring

Real Time Measurement Of Particulate At Low Concentration From The Emission Of Stationary Source In The Steel And Power Industries Using a TEOM™ based Emissions Monitor

Oct 03 2014

Author: Edward C. Burgher, Gilles Gonnet on behalf of CEM

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Abstract
Historically, measurements of particulate matter emissions from large stationary sources to comply with regulatory standards have employed a variety of methods depending on local agency requirements. More recently, with the establishment of regulatory norms for member states of the European Union, new methods have been established to provide a common basis for evaluating emission sources. In the USA,
measurement of PM in emissions sources must be performed in accordance with U.S. EPA Method 5 or, in some cases, Method 17. As with the historical methods used in Europe and the USA, one of the newer methods, EN 13284-1 is based on filtration of particulate matter from a sample collected in-situ and isokinetically and requires the filter to be analyzed in a laboratory. The repeatability of a measurement made with any of the manual methods can be influenced adversely by factors including handling and transport of the filter, conditioning the filter before and after the sampling, and filter weighing. Also, because the measurement using the manual methods can only represent the average emission over the time period sampled, some important data like transitory concentration, stratification in the duct being sampled and the influence of the variation in parameters such as velocity,temperature and pressure on the particulate concentration is difficult or impossible to determine. Consequently, these limitations prompted customers of Rupprecht and Patashnick Company to request the company to develop a new method based on its patented Tapered Element Oscillating Microbalance (TEOM™) technology.

While this new method, named the TEOM Series 7000 Source Particulate Monitor, provides an in-situ measurement collected by filtering source gases at isokinetic sampling conditions, the filter handling and weighing processes are completely different. A filter is placed on the top of the hollow-tube, oscillating element that is housed in a temperature controlled mass transducer assembly. As a carefully controlled vacuum is applied to the opposite end of the tapered element, source gases are extracted from the stack isokinetically and passed through the filter thereby capturing any particulate matter that was entrained in the sample gases. As the filter weight increases with the accumulation of particulate matter, the frequency of oscillation decreases. The change in frequency can be determined in real-time and converted to mass. Tracking mass change with collected sample volume over time permits calculation of mass concentration measurements that can be continuously reported and/or reported as an average over a user specified time period. The method also incorporates procedures to dry the sample filter prior to and after the test in-situ and to recover any residual particulate matter left in the sample inlet during sampling thereby eliminating measurement errors introduced by filter handling, transport, etc. The ability of the Series 7000 method to measure and report data in real-time, can increase the amount of information available for characterization of process or control system variability or for calibration/correlation of indirect source measurement techniques such as triboelectric, optical or beta attenuation.

Since it is important to understand the agreement between the different methods, and characterize the performance of the new, TEOM-based method this paper reports on a series of tests comparing the TEOM Series 7000 method to NF EN 13284-1 (for low concentration emissions), and NFX 44052 (for high concentration emissions). Results of the twelve test runs performed at the steel mill indicate that the Series 7000 provides a valid measurement equivalent to the reference methods and confirms the conclusion of other laboratories like the TÜV Rheinland who evaluated the Series 7000 in 2001. The evaluation also allowed evaluation of the Series 7000
for calibrating or auditing indirect automatic measuring systems for PM. Results of the tests also found that the Series 7000 method is well suited for the calibration of continuous measuring system using light scattering, transmissiometry or beta attenuation methods. The evaluation also showed that the monitor was robust and well adapted to the industrial environment while being easy to use and reliable.

In a second series of tests, conducted at a large, coal-fired power plant located in the mid-western U.S., paired TEOM Series 7000’s were used to evaluate the systems’ capacity to make precise, real-time measurements with very short measurement time response. This precision evaluation was conducted in conjunction with assessment of stratification of a PM emissions source with respect to PM at the stack’s normal sampling locations. This series of tests found excellent agreement between in the paired Series 7000 trains and showed how the Series 7000 method can be used to rapidly provide detailed information regarding stratification in a sampling plane.
Results indicate that the sampling location would be suitable for installation of a PM AMS.

Keywords: particulate matter, source sampling, stack sampling, real-time isokinetic PM measurement

Introduction

As reported in a paper presented at CEM 2002 [Burgher, 2002], Rupprecht & Patashnick Co., Inc. developed a new instrumental method for measuring the particulate matter concentration in emission sources. This method, named the TEOM® Series 7000 Source Particulate Monitor (“TEOM SPM”), incorporates R&P’s patented TEOM technology and significantly enhances the amount of particulate matter emissions information that can be achieved from conducting an emissions testing program. For instance, when siting particulate matter continuous automatic measuring systems (“PM AMS”) it is important that the monitor is installed such that it will collect a representative sample regardless of the emission unit operating load. Secondly, as currently available PM AMS do not directly measure particulate matter mass, it is necessary to establish and verify the PM CEMS monitor accuracy over a range of operating conditions using methods such as EN-13284-1, EPA Method 5, ISO 9096 or the TEOM Series 7000.

While TEOM SPM method provides an in-situ measurement collected by filtering source gases at isokinetic sampling conditions, as does recognized reference methods, the filter handling and weighing processes are completely different. With a TEOM SPM, a filter is placed on the top of the hollow-tube, oscillating element that is housed in a temperature controlled mass transducer assembly. The mass transducer is affixed to the end of a long sample probe that allows the mass transducer to be positioned in an emission source. By applying a carefully controlled vacuum to the opposite end of the tapered element, source gases are extracted from the stack isokinetically and passed through the sample filter. The filter captures any particulate matter present in the sample gas stream. As particulate matter accumulates, the filter weight increases which results in decreasing the tapered element oscillating frequency. The change in frequency can be determined in real-time and converted to mass. The result is mass concentration measurements that can be continuously reported and/or reported as an average over a user specified time period. Sample filter conditioning prior to and after the test can also be accomplished in-situ thereby eliminating measurement errors introduced by filter handling, transport, etc. The ability of the Series 7000 method to measure and report data in real-time, can increase the amount of information available for characterization of process or control system variability or for calibration/correlation of indirect source measurement
techniques such as triboelectric, optical or beta attenuation.

Since it is important to understand the agreement between the different methods used to make source PM emissions measurements, this paper reports on a series of tests designed to evaluate the performance of the Series 7000 method in comparison to NF EN 13284-1 (for low concentration emissions) and NFX 44052 (for high concentration emissions). In the first set of tests conducted by the laboratory LECES with the support of Ecomesure, the TEOM SPM method was compared to NF EN 13284-1 and to NFX 44052 in three different sources at a steel mill. Following the methods comparison tests, the Series 7000 was then used to calibrate an opacitybased continuous emissions monitor.

It is also important that the reference method used to calibrate or audit an automatic measuring system for PM be inherently precise regardless of source conditions or test operators, etc. For example, while European standards such as EN 14181 and U.S. standards such as Performance Specification 11 (PS-11) do not explicitly include precision requirements for reference method measurements, the correlation of the automatic measurement system to the reference method can be significantly influenced by the precision of the reference method measurements. To demonstrate the precision of the TEOM Series 7000 method when used in real-world test conditions, a second series of tests, conducted in the fall of 2003, were devised testing to evaluate the precision of method in an emission source produced by a coal-fired, power plant. This series of test were also designed to investigate particulate matter emissions stratification at two sampling locations normally used for emissions permit limit compliance determinations.


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