USA As Represented by Secretary of the Navy

Michael D Seltzer

Gerhard A Meyer

Robert B Green

The disclosed invention relates to a calibration method, system and apparatus for a multimetals continuous emissions monitor system (hereinafter &ldquo;multimetals CEMS&rdquo;). More specifically, this invention relates to a calibration scheme for continuous monitoring of mercury emissions from stationary sources by plasma emission spectrometry. A source of mercury vapor, preferably a mercury permeation tube, entrains mercury vapor into a constant flow of carrier air. The carrier air mixes with a constant flow of diluent air in an aerosol mixer. The mixer is operably coupled to the analyzer. A gaseous mixture having a calibration mercury concentration flows from the mixer into the analyzer at a constant rate. A graph having coordinates of analyzer signal intensity and mercury concentration is used to plot the calibration scheme. A first signal intensity generated by the analyzer in response to the calibration mercury concentration is used for the first plot on the graph. A second signal intensity generated by the analyzer in response to a blank having zero mercury concentration is used as the second plot on the graph. A linear relationship between the analyzer signal intensity and the mercury concentration on the graph is established from the first plot and the second plot. The slope intercept and slope are used to create a mathematical relationship between the analyzer signal intensity and the mercury concentration. This enables the analyzer to be calibrated by inserting a known mercury concentration into the analyzer and adjusting the signal intensity to conform to the signal intensity calculated from the graph or mathematical relationship.

Calibration scheme for continuous monitoring of mercury emissions from stationary sources by plasma emission spectrometry

A convenient apparatus and method for inserting surrogate metal-entraining aerosols into exhaust stacks for the purpose of realistic dynamic testing of an emissions monitor. The aerosols contain elements required to be detected by the monitor. The 14 metals regulated by the EPA as hazardous air pollutants are of particular interest. The method requires less time and fewer skilled technicians than conventional testing methods. In a preferred embodiment of the present invention, a burner (e.g., propane or kerosene) is combined with a combustion chamber, a fan, an air compressor, at least one peristaltic pump, at least one surrogate reservoir, and the necessary ductwork for connection to an exhaust stack. The amount of surrogate aerosol to be introduced to the stack is adjusted at the peristaltic pump. After heating by the burner and subsequent introduction into the hot stack, the surrogate homogeneously mixes with the exhaust stream and is presented to the sensor as a dry gas component of the exhaust stream. Other applications include use as an exhaust stack simulator and as a standardized source of aerosols containing hazardous air pollutants, in particular metal-entraining aerosols.

Device and method for introducing surrogates, particularly metal surrogates, into an exhaust stream, for simulating an exhaust stream, and for establishing a standardized source

Introduction of sample stream air into argon inductively coupled plasma permits continuous monitoring of hazardous air pollutant metals in combustion flue gases. In addition to entrained particulates, various molecular components of flue gas are in the plasma. These species, and reaction products thereof, such as CN species, also undergo excitation resulting in complex emission spectra of appreciable intensity. Serious spectral interference arises for several metal elements, from molecular emission bands associated with the stable CN radical, and other poly-atomic species, such as NO. Failure to account for these interferences can significantly degrade accuracy of monitoring particularly at low metal concentrations in the flue gas. This invention corrects spectral interferences arising from airborne molecular species in the argon plasma even when the magnitudes of spectral interferences encountered during the analysis of airborne metals in flue gases, are of such considerable magnitudes that, if not directly accounted for, would otherwise compromise the quality of measurements of the airborne metals. This method measures and corrects spectral interferences attributed to CN and NO that affect on-line detection of hazardous air pollutant metals. The method incorporates conventional spectrometer hardware and existing instrument software to achieve effective real-time correction of these interferences.

Correction of spectral interferences arising from CN emission in

A plasma torch for reliable analysis of airborne particulate matter permits real-time monitoring of airborne metal pollutants in flue gases from furnaces and incinerators. The torch injects sample air into argon plasma and has an outer tube to confine plasma gas for generating a plasma fireball. An intermediate tube has an outwardly flared portion concentrically disposed within the outer tube to form an outer annulus for feeding plasma gas to the fireball. The intermediate tube also has an injector sheath tube joined at its base to the base of the flared portion and concentrically disposed within the flared portion. The injector sheath tube is parallel to the outer tube. An inner capillary injector tube injects sample air into the plasma fireball. The inner capillary injector tube is concentrically disposed within the injector sheath tube to form an inner annulus that directs annular flow of auxiliary gas to alter the surface of the central region of the plasma fireball and channels the sample air to inject it through the surface and into the plasma fireball. The annular flow of auxiliary gas assures injection of the sample air at velocities which preserve residence time of the sample air to effect efficient vaporization and excitation of the metals.

Modified plasma torch design for introducing sample air into inductively

Sampling interfaces and methods of operation thereof having increased duty cycles and pressure equalizations that improve sensing of airborne metals in air samples fed to a continuous emissions monitor. Residual pressure in one or two sample reservoirs (loops) can be automatically equalized just prior to pneumatic connection between each sample reservoir loop and plasma in a plasma torch, thus minimizing or eliminating perturbation of the plasma. Deliberate sequential activation of valves allows each sample reservoir loop to be first isolated from the vacuum pump, and then momentarily as its pressure is equalized, it remains isolated from the plasma as well. Finally, pneumatic connection is made between each sample reservoir loop and the plasma allowing the contents of each sample reservoir (now at the same pressure as the plasma) to be transported into the plasma. Sampling interface having dual elongate sample reservoirs that alternate aliquots of sample air nearly doubles the rate of measurement of air entrained metals relative to a single elongate reservoir loop arrangement. By allowing measurements to be made at more frequent intervals using more representative sampling of extracted flue gases or air, the dual loops may permit the acquisition of hazardous emissions monitoring data that is more meaningful in terms of its temporal characteristics.

Sampling interface for continuous monitoring of emissions

An isokinetic sampling system and method of operation assures the taking of more valid data over a long period by automated isokinetic sampling of flue gases in the stack for a stationary combustor. Sample air is extracted from the flue gases by a sampling probe having a sampling nozzle of a precise inner diameter, a thermocouple to measure the air temperature in the stack, and a pitot tube that gives readings representative of differential pressure across sampling nozzle. A separate transducer senses absolute pressure of the flue gases. Temperatures, absolute pressures and differential pressures of the flue gases are measured and representations of the temperatures, absolute pressures and differential pressures are fed to a micromanometer which feeds signals representative of these representations to a computer that generates responsive control signals for a mass flow controller. The mass flow controller throttles the flow of sample air through it to a correct magnitude to achieve isokinetic extraction of sample air under the existing stack conditions of temperature, pressure, and velocity at the point of extraction at the sample nozzle for the selected nozzle opening, or diameter. Stack conditions can vary over time and this automated isokinetic sampling system immediately adjusts the flow rate of mass flow controller so that isokinetic sampling continues uninterrupted and valid data can be generated by monitoring sensors.

Method and apparatus for automated isokinetic sampling of combustor flue

A portable apparatus for continuous real-time measurement of airborne met, comprising an isokinetic sampler, a sample line, a sampling interface device, a pump, and an inductively coupled plasma atomic emission spectrometry (ICP-AES). A method for measurement of airborne metals by use of such an apparatus is also described, in which the sampling interface device accommodates the high, continuous sample collection flow-rates necessary for isokinetic sampling while at the same time permits sample air to be introduced into the plasma at preferred moderate flow-rates. A method for field standardization of the ICP-AES is also described whereby a relationship between aqueous solutions of metals and their aerosol counterparts is established, thus later allowing the field use of the aqueous metal solutions to simulate a particular range of airborne metal concentrations.

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Ridgecrest, CA, United States of America

Michael D Seltzer