Selecting the right gas analyzer to optimize monitoring of NOx and other emissions
Hello, everyone money's Leanne Nichols and I'm the editor in chief and Associate Publisher Hydrocarbon Processing magazine and I'd like to welcome you to another installment of hydrocarbon processing, podcast series the main column. Today we're looking at the article selecting the right gas analyzer to optimize monitoring of Knox and other emissions. This article was written by Michael Campus in Catherine Williams of Emerson automation solutions it can be accessed through the May issue of hydrocarbon processing within the process controls instrumentation in automation section. Selecting the right gas analyzer to optimize monitoring them, Knox and other emissions. Combustion processes of all types generate emissions of one kind or another for example, hydrogen carbon-based combustion processes produce water, and carbon dioxide respectively, some emissions such as sulfur dioxide produced by the combustion of SOFA. Related Fossil fuels are classified as pollutants in a regulated by environmental agencies. Pollutants can be minimized by careful combustion control or by minimizing precursors in the fuel such as choosing to burn low sulfur coal. Pollutants that cannot be reduced sufficiently to meet regulations must be captured or converted through an emissions control system before release entreated to remove their problematic components before reaching the atmosphere. Pollutants from combustion processes are regulated around the world by local environmental agencies in the US. The Environmental Protection Agency or EPA publishes and enforces regulations including forty CFR sixty of new source performance standards forty four, sixty, three national emission standards for hazardous areas. Forty. Four seventy five emissions monitoring policy manual forty, see afar ninety six, nitrogen oxide or Nox budget trading program. The European Commission were e c also has many air quality directives and standards including the industrial emissions directive cover integrated pollution prevention. And control to minimize or mitigate emissions in the atmosphere water and soil, as well as in waste from industrial and agricultural installations. These regulations become more stringent over time so producers must stay up to date. For instance, forty cf are sixty has expanded over the years and now incorporates minimum specifications for emissions, monitoring emission measurement methods, and performance specifications. While these general environmental concepts should be basic knowledge to anyone working with combustion processes in refineries and petrochemical plants more information is required to deal with specific commissions. Understanding. NOx. Emissions. One pollutant that often proves problematic is knox because it can be generated by any combustion process using any type of fuel since there are no specific precursors that can be avoided. Knox refers to a of two compounds, nitric oxide and nitrogen dioxide, which can be both become petrochemical pollutants in the atmosphere. Ultimately causing acid rain, the two compounds tend to form together but portion of the two is unimportant for the purposes of monitoring. The critical measurement is the overall total. Combustion controls such as low nox burners help minimize formation to some extent, but these may result in other undesirable side effects. Knocks can be reduced in the gas stream through chemical injection, but this requires accurate measurement. This article will consider two different approaches for continuous knocks measurement in combustion gas tree. Measuring knocks with Kim Luminescence, the first measurement method depends on a chemical effect called. Chemical Luminescence, as a result of a chemical reaction of the intermediates nitric oxide in ozone. Nitrogen Dioxide is produced in an excited energy form by emitting a photon in the excited state. The nitrogen dioxide returns it to its ground state. The light emission or Kim Luminescence can be detected in measured and based on the amount of light emitted. The number of nitric oxide molecules can be determined. None of the Knox molecules carried by combustion gas stream are expected to be in an excited state. So this condition must be induced in the sample being analyzed, which requires several sequential steps. These steps include the following details number one, all nitrogen dioxide in the sample must be converted to nitric oxide. The sample gas stream passes through a heated bed of carbon causing a reaction in turning more than ninety eight percent of nitrogen doc dioxide into nitric oxide and carbon monoxide. Nearly all Knox molecules are now nitric oxide overall total remains essentially the same. Number to a high voltage corona discharge in a low temperature co fired ceramic generator module in the analyzer creates ozone from ambient atmospheric oxygen. A pure oxygen supply is not necessary. Number three, the ozone nitric oxide are fed continuously into a chamber where they react creating nitrogen dioxide molecules approximately ten percent of these molecules emerged from the reaction in the excited state. Number Four The excited nitrogen dioxide molecules emit their Photon in the chamber and revert to the ground state. The spent reacted gases exit with the exhaust dream. In accused essence detection or CLD analyzer the chamber in which Nitric Oxide and ozone reacts is fitted with a photo diode that can be read emissions with wavelengths between five hundred nanometers in two, thousand, five, hundred nanometers. The kimmel luminescence in this chamber has its high-intensity around eleven hundred nanometers. Software analyzes the excited molecule count in extra relates to project Knox content percentages for the entire gas dream a seal. The analyzer typically requires a cold dry sample stream although some seal the analyzers can work with hot wet sample gas streams because water vapor can quench the Kim luminescence effect before it can be captured therefore causing an under reporting of the truth knocks level. Seal the analyzers have been available for many years and the technology has long been accepted as the standard reference method for Knox monitoring by the US EPA and other regulatory agencies including the European Standard Ian One, four, seven, nine to two, thousand seventeen. Over the years, the overall performance stability durability of commercial analysers have improved among the various knocks measurement technology alternatives seal the analyzers offer very wide users. ability knocks measurement ranges from zero parts per million or PPM to ten parts per million up to ten thousand PPM. They also have the lowest purchase costs in their operational costs are minimal since there are no consumables with only the converter material. Requiring, periodic replacement at intervals of one year to three years president models do not require a pure oxygen supply. Thus eliminating that expense some suppliers engineer the cld without an eternal vacuum pump effectively removing a source of vibration that could compromise equipment integrity and reliability or at maintenance requirement. Some emissions monitoring applications require measurement of other gas components in addition to Knox Molecules to expand the number of gases that continuous emissions monitoring system or Kim's can monitor the seal. The often needs to be packaged together with a second analyzer equipped with a non dispersive infrared or non dispersive ultraviolet spectrometer in pragmatic sensors. If the footprint in the sense of the extra analyze not concerns than a seal, the based system can still be a very economical choice. However, in other situations, another approach can be used to simplify the measurement of multiple components and to reduce the number of analyzers. Direct Absorption Spectroscopy for Knox and other pollutants. This second measurement method uses an entirely different approach. Direct absorption spectroscopy utilizes a given compounds capability to absorb specific. Of electromagnetic radiation. The absorption at a given wavelength is measured allowing an analyzer to detect and quantify the presence of various compounds of interest using this technology. A single analyze can monitor a range of pollutants in a gas stream. The telltale spectral fingerprints for many polluting flue gas components can be observed in the near Init- infrared sections of the electromagnetic spectrum. The ability to create radiation with wavelengths ranging from eight hundred nanometers to twelve thousand meters depends on mix of different types of lasers, each of which can be optimized combined to generate outputs within specific segments of that large range. One current technique is using tuneful in multiple individual cascading lasers to cover this wide wavelength band, which is not possible with a single laser. Multiple lasers working together permit measurements of a longer list of specified chemical components. QUANTUM CASCADE LASER technology offers fast high resolution spectroscopy to detect and identify a range of molecules in the mid infrared wavelength range coupled with tuna diode laser spectroscopy. To cover the near infrared ban, a single instrument can provide greater insight in monitoring both in Near and mid infrared range of spectroscopy light. Quantum cascade laser in tune will diode laser narrow line with allow scanning of individual peaks of identified components with them interference in without infiltration reference cells or chemo metric manipulations. No consumables are necessary ensuring a low life cycle costs. Quantum cascade lasers are fabricated to skin a desired wavelength spectrum using a laser chirp technique. To start the process. A quantum cascade laser is post with electrical energy in heats up as the temperature increases. The wavelength of the emitted light also increases. The duration of a chirp is about one microseconds and and in this time, it scans a spectrum of between one and three wave numbers. This act is performed with all the laser modules in sequence to cover the full range of critical frequencies to monitor each of the desired chemical components. Internal signal processing software takes the raw detector signal and converts it into a spectrum for which can calculate the concentration of each analyzing. Quantum cascade lasers can be chirp at a frequency of up to one hundred kilohertz gathering many thousands of Spectra in a few seconds advanced signal processing enables real time validation of measurements in reduces the need for calibrations. Multiple reflection cells enable absorption pass links of two meters five meters compared to two hundred millimeters for Conventional Indiana photography. This technology is capable of very high sensitivity allowing it in some situations to reach into parts per billion ranges or P. P. B. Ranges. This approach offers many advantages per Kim's in refineries and petrochemical plants. Knox's certainly a major area of concern but other pollutants may be added to the list including carbon, monoxide carbon dioxide, Ammonia Sofer dioxide, water vapor in oxygen. where it is necessary to monitor list of components in a gas stream, a particular analyze can make all the required measurements. Sophisticated models can monitor up to twelve gases so that fewer analyzers may be necessary. Naturally, not all analyzer models designed to handle all of these measurements as such capabilities are costly and few applications need that degree of flexibility more frequently three to five components might require monitoring. So a user can choose the model that can measure only the components of. To minimize in lines or cost and complexity. Cascade. Quantum cascade laser tuna -able diode laser based analyzers can take a variety of forms making them easy to install implant environments. Many are now robust enough to be mounted in the field without a traditional analyzer shelter. These fueled mounted housing minimize the distance between the analyzer in the duck sampling point reducing the lag time to capture measurement. Some housings are reading certified for hazardous areas eliminating the need for a purge shelter. Internal components are often highly modular allowing fuel replacements of major subsystems including the actual laser module thereby ensuring high availability. Some analyzers can take the sample directly from the stack and hot wet state to keep acid gases from condensing. These types of analyzers often need some internal adjustment of the reading when limitation value stated on a dry basis, but they have the advantage of not requiring gas conditioning to convert this stream too cold dry. This conditioning by necessity removes water solo components from the sample stream, which is drawback in certain applications. A hotbed shrinks also sins particulates into the analyzer, which can create deposits is not captured separately treating the sample stream beforehand to cool it and remove oyster creates a cold dry stream that is free of particular. It's providing pollute level readings as specified in regulations with adjustment required. Many tools are available to measure Knox and other pollutants from combustion processes in refineries. Petrochemical plants given the full range of options. Plant personnel can select an approach that is ideally suited for a given application. You've been listening to the latest installment of Hydrocarbon Processing podcast series the main column. Remember to subscribe to the main column podcast. You can click on these subscribe on the podcast page or you can use your smartphone by saying, hey, Google Alexa or Siri subscribing to the main column podcast.