Characteristics of penicillin bacterial residue

A hybrid selective noncatalytic reduction/selective catalytic reduction (SNCR/SCR) system that uses two types of technology, low-temperature SCR process and SNCR process, was designed to develop nitrogen oxide (NO_x) reduction technology. SCR was conducted with space velocity (SV) = 2400 hr^?1 and hybrid SNCR/SCR with SV = 6000 hr^?1, since the study focused on reducing the amount of catalyst and both achieved 98% NO_x reduction efficiency. Characteristics of NO_x reduction by NH₃ were studied for low-temperature SCR system at 150 °C using Mn-V₂O₅/TiO₂ catalyst. Mn-added V₂O₅/TiO₂ catalyst was produced, and selective catalyst reduction of NO_x by NH₃ was experimented. NO_x reduction rate according to added Mn content in Mn-V₂O₅/TiO₂ catalyst was studied with varying conditions of reaction temperature, normalized stoichiometric ratio (NSR), SV, and O₂ concentration. In the catalyst experiment according to V₂O₅ concentration, 1 wt.% V₂O₅ catalyst showed the highest NO_x reduction rate: 98% reduction at temperature window of 200~250 °C. As a promoter of the V₂O₅ catalyst, 5 wt.% Mn was added, and the catalyst showed 47~90% higher efficiency even with low temperatures, 100~200 °C. Mn-V₂O₅/TiO₂ catalyst, prepared by adding 5 wt.% Mn in V₂O₅/TiO₂ catalyst, showed increments of catalyst activation at 150 °C as well as NO_x reduction. Mn-V₂O₅/TiO₂ catalyst showed 8% higher rate for NO_x reduction compared with V₂O₅/TiO₂ catalyst in 150 °C SCR. Thus, (5 wt.%)Mn-(1 wt.%)V₂O₅/TiO₂ catalyst was applied in SCR of hybrid SNCR/SCR system of low temperature at 150 °C. Low-temperature SCR hybrid SNCR/SCR (150 °C) system and hybrid SNCR/SCR (350 °C) showed 91~95% total reduction rate with conditions of SV = 2400~6000 hr^?1 SCR and 850~1050 °C SNCR, NSR = 1.5~2.0, and 5% O₂. Hybrid SNCR/SCR (150 °C) system proved to be more effective than the hybrid SNCR/SCR (350 °C) system at low temperature.

Implications:?NO_x control is very important, since they are the part of greenhouse gases as well as the cause of acid rain and ozone hole. A technology, so-called hybrid SNCR/SCR process, was tested using Mn-V₂O₅/TiO₂ monolithic catalyst for NO_x reduction, and the method is promising. The results of this study would provide some ideas to parties such as policy makers, environmental engineers, and so on.     

Manganese-cerium oxide (MnOx-CeO2) catalysts supported by titanium-bearing blast furnace slag for selective catalytic reduction of nitric oxide with ammonia at low temperature

A series of manganese-cerium oxide (MnO_x-CeO₂) catalysts supported by Ti-bearing blast furnace slag were prepared by wet impregnation and used for low-temperature selective catalytic reduction (SCR) of NO with NH₃. The slag-based catalyst exhibited high nitrogen oxide removal (deNO_x) activity and wide effective temperature range. Under the condition of NO = 500 ppm, NH₃ = 500 ppm, O₂ = 7–8 vol%, and total flow rate = 1600 mL/min, the Mn-Ce/Slag catalyst exhibited a NO conversion higher than 95% in the range of 180–260 °C. The activity of Mn/Slag catalysts was greatly enhanced with the addition of CeO₂. The results indicated that Ti-bearing blast furnace slag had suitable phase composition as good support of SCR catalyst.

Implications: Ti-bearing blast furnace slag is a kind of industrial waste in China. Much slag was underused and piling up, which could cause many environmental issues, such as enormous waste of titanium and groundwater and soil contamination by heavy metals in leachates. The utilization of slag as the support of SCR catalyst will not only make use of solid waste but also cut down the NO_x emitted from power plant.     

Effect of NOx Control Processes on Mercury Speciation in Utility Flue Gas

Abstract

The speciation of Hg in coal-fired flue gas can be important in determining the ultimate Hg emissions as well as potential control options for the utility. The effects of NO_x control processes, such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR), on Hg speciation are not well understood but may impact emissions of Hg. EPRI has investigated the reactions of Hg in flue gas at conditions expected for some NO_x control processes. This paper describes the methodology used to investigate these reactions in actual flue gas at several power plants. Results have indicated that some commercial SCR catalysts are capable of oxidizing elemental Hg in flue gas obtained from the inlets of SCR or air heater units. Results are affected by various flue gas and operating parameters. The effect of flue gas composition, including the presence of NH₃, has been evaluated. The influence of NH₃ on fly ash Hg reactions also is being investigated.     

Selective Reduction of Nitrogen Oxides In Combustion Flue Gases

The body of Information presented in this paper is directed to those Individuals concerned with the removal of NO_x in combustion flue gases. A catalytic process for the selective reduction of nitrogen oxides by ammonia has been investigated. Efforts were made toward the development of catalysts resistant to SO_x poisoning. Nitrogen oxides were reduced over various metal oxide catalysts in the presence or absence of SO_x(SO₂ and SO₃). Catalysts consisting of oxides of base metals (for example, Fe₂O₃) were easily poisoned by SO₃, forming sulfates of the base metals. A series of catalysts which are not susceptible to the SO_x poisoning has been developed. The catalysts possess a high activity and selectivity over a wide range of temperatures, 250—450°C. The catalysts were tested in a pilot plant which treated a flue gas containing 110-150 ppm NO_x, 660-750 ppm SO₂, and 40-90 ppm SO₃. The pilot plant was operated at 350°C and at a space velocity of 10,000 h^-1. The removal of nitrogen oxides was more than 90% for several months.

A mechanism of the NO-NH₃ reaction has also been investigated. It is found that NO reacts with NH₃ at a 1:1 mole ratio in the presence of oxygen and the reaction is completely inhibited by the absence of oxygen. The experimental data show that the NO-NH₃ reaction in the presence of oxygen is represented byNO + NH₃ + 1/4 O₂ = N₂ + 3/2 H₂O.     

Nitrogen Oxides Emission Control Options for Coal-Fired Electric Utility Boilers

Abstract

Recent regulations have required reductions in emissions of nitrogen oxides (NO_x) from electric utility boilers. To comply with these regulatory requirements, it is increasingly important to implement state-of-the-art NO_x control technologies on coal-fired utility boilers. This paper reviews NO_x control options for these boilers. It discusses the established commercial primary and secondary control technologies and examines what is being done to use them more effectively. Furthermore, the paper discusses recent developments in NO_x controls. The popular primary control technologies in use in the United States are low-NO_x burners and overfire air. Data reflect that average NO_x reductions for specific primary controls have ranged from 35% to 63% from 1995 emissions levels. The secondary NO_x control technologies applied on U.S. coal-fired utility boilers include reburning, selective noncatalytic reduction (SNCR), and selective catalytic reduction (SCR). Thirty-six U.S. coal-fired utility boilers have installed SNCR, and reported NO_x reductions achieved at these applications ranged from 15% to 66%. Recently, SCR has been installed at >150 U.S. coal-fired utility boilers. Data on the performance of 20 SCR systems operating in the United States with low-NO_x emissions reflect that in 2003, these units achieved NO_x emission rates between 0.04 and 0.07 lb/10⁶ Btu.     

Investigation of Selective Catalytic Reduction Impact on Mercury Speciation under Simulated NOx Emission Control Conditions

Abstract

Selective catalytic reduction (SCR) technology increasingly is being applied for controlling emissions of nitrogen oxides (NO_x) from coal-fired boilers. Some recent field and pilot studies suggest that the operation of SCR could affect the chemical form of mercury (Hg) in coal combustion flue gases. The speciation of Hg is an important factor influencing the control and environmental fate of Hg emissions from coal combustion. The vanadium and titanium oxides, used commonly in the vanadia-titania SCR catalyst for catalytic NO_x reduction, promote the formation of oxidized mercury (Hg²⁺).

The work reported in this paper focuses on the impact of SCR on elemental mercury (Hg⁰) oxidation. Bench-scale experiments were conducted to investigate Hg⁰ oxidation in the presence of simulated coal combustion flue gases and under SCR reaction conditions. Flue gas mixtures with different concentrations of hydrogen chloride (HCl) and sulfur dioxide (SO₂) for simulating the combustion of bituminous coals and subbituminous coals were tested in these experiments. The effects of HCl and SO₂ in the flue gases on Hg⁰ oxidation under SCR reaction conditions were studied. It was observed that HCl is the most critical flue gas component that causes conversion of Hg⁰ to Hg²⁺ under SCR reaction conditions. The importance of HCl for Hg⁰ oxidation found in the present study provides the scientific basis for the apparent coal-type dependence observed for Hg⁰ oxidation occurring across the SCR reactors in the field.     

Improving the activity of Mn/TiO2 catalysts through control of the pH and valence state of Mn during their preparation

In this study, the authors investigated the influence of the valence state of Mn on the efficacy of selective catalytic reduction using a Mn-based catalyst. The nitrogen oxides (NO_x) conversion rate of the catalyst was found to be dependent on the type of TiO₂ support employed and on the temperature, as the catalyst showed an excellent conversion of > 80% at a space velocity of 60,000 hr^?1 when the temperature was above 200 °C. Brunauer-Emmett-Teller, X-ray diffraction, and X-ray photoelectron spectroscopy analyses confirmed that catalyst displaying the highest activity contained the Mn⁴⁺ species and that its valence state was highly dependent on the pH during the catalyst preparation.

Implications Recently, various Mn catalysts have been evaluated as selective catalyst reduction (SCR) catalysts. However, in these previous studies, only the reaction characteristics and catalytic activity on the NH₃ SCR over Mn catalysts were evaluated. There have been no studies on the effect of pH during catalyst preparation. Therefore, in this study, the effect of pH during the catalyst preparation process was examined and a new application of the Mn catalysts was proposed based on the current findings.     

A Predictive Mechanism for Mercury Oxidation on Selective Catalytic Reduction Catalysts under Coal-Derived Flue Gas

Abstract

This paper introduces a predictive mechanism for elemental mercury (Hg⁰) oxidation on selective catalytic reduction (SCR) catalysts in coal-fired utility gas cleaning systems, given the ammonia (NH₃)/nitric oxide (NO) ratio and concentrations of Hg⁰ and HCl at the monolith inlet, the monolith pitch and channel shape, and the SCR temperature and space velocity. A simple premise connects the established mechanism for catalytic NO reduction to the Hg⁰ oxidation behavior on SCRs: that hydrochloric acid (HCl) competes for surface sites with NH₃ and that Hg⁰ contacts these chlorinated sites either from the gas phase or as a weakly adsorbed species. This mechanism explicitly accounts for the inhibition of Hg⁰ oxidation by NH₃, so that the monolith sustains two chemically distinct regions. In the inlet region, strong NH₃ adsorption minimizes the coverage of chlorinated surface sites, so NO reduction inhibits Hg⁰ oxidation. But once NH₃ has been consumed, the Hg⁰ oxidation rate rapidly accelerates, even while the HCl concentration in the gas phase is uniform. Factors that shorten the length of the NO reduction region, such as smaller channel pitches and converting from square to circular channels, and factors that enhance surface chlorination, such as higher inlet HCl concentrations and lower NH₃/NO ratios, promote Hg⁰ oxidation.

This mechanism accurately interprets the reported tendencies for greater extents of Hg⁰ oxidation on honeycomb monoliths with smaller channel pitches and hotter temperatures and the tendency for lower extents of Hg⁰ oxidation for hotter temperatures on plate monoliths. The mechanism also depicts the inhibition of Hg⁰ oxidation by NH₃ for NH₃/NO ratios from zero to 0.9. Perhaps most important for practical applications, the mechanism reproduces the reported extents of Hg⁰ oxidation on a single catalyst for four coals that generated HCl concentrations from 8 to 241 ppm, which covers the entire range encountered in the U.S. utility industry. Similar performance is also demonstrated for full-scale SCRs with diverse coal types and operating conditions.     

Pilot-Scale Study of the Effect of Selective Catalytic Reduction Catalyst on Mercury Speciation in Illinois and Powder River Basin Coal Combustion Flue Gases

Abstract

A study was conducted to investigate the effect of selective catalytic reduction (SCR) catalyst on mercury (Hg) speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois Basin bituminous coals (from high to low sulfur [S] and chlorine [Cl]) and one Powder River Basin (PRB) subbituminous coal with very low S and very low Cl were tested in a pilot-scale combustor equipped with an SCR reactor for controlling nitrogen oxides (NO_x) emissions. The SCR catalyst induced high oxidation of elemental Hg (Hg⁰), decreasing the percentage of Hg⁰ at the outlet of the SCR to values <12% for the three Illinois coal tests. The PRB coal test indicated a low oxidation of Hg⁰ by the SCR catalyst, with the percentage of Hg⁰ decreasing from ～96% at the inlet of the reactor to ～80% at the outlet. The low Cl content of the PRB coal and corresponding low level of available flue gas Cl species were believed to be responsible for low SCR Hg oxidation for this coal type. The test results indicated a strong effect of coal type on the extent of Hg oxidation.     

Plasma versus Thermal Effects in Flue Gas NOx Reduction Using Ammonia Radical Injection

Abstract

A plasma-assisted ammonia injection technique was previously demonstrated as having the potential to remove NO_x from combustion flue gases at SCR-comparable levels without the use of catalysts. However, these demonstrations did not prove the advantage of plasma assistance because they did not explicitly account for enhanced radical production by bulk thermal heating. An experiment using hot ammonia injection was performed to separate this thermal effect from the effect of radical production via interaction with a plasma. Under excess air conditions, results show that a thermal effect does provide improved NO_x reduction, but not to the level achieved with the use of a plasma source. However, heating the injection gases provides only a minor improvement in NO_x reduction at NH₃/NO_x ratios and temperatures typical of commercial cold SNCR applications. The plasma effect in ammonia radical injection was also found to be significant, accounting for an additional 15% to 35% of absolute NO_x reduction beyond any thermal benefit at typical excess air conditions. The ammonia radical injection technique continues to show promise as an effective NO_x reduction alternative.     

改进钒基SCR脱硝催化剂的抗碱金属中毒性能

以锐钛矿型二氧化钛和钛钨粉(5%WO3-TiO2)为载体,制备了系列钒和钨负载量不同的钒钛催化剂,考察碱金属和碱土金属(钾、钠和钙)对催化剂在氨选择性催化还原(NH3-SCR)氮氧化物反应中催化活性的影响。钾、钠和钙对钒钛催化剂的中毒影响大小顺序为钾钠钙。提高钒钛催化剂中钒的含量可显著提高催化剂的SCR活性和抗碱金属中毒性能,但高钒负载量(4.5%V2O5)造成催化剂氮气选择性明显下降,氧化亚氮生成显著增加。钨的添加有利于提高钒钛催化剂的低温活性和抗碱金属中毒性能,对氮气选择性无明显影响。     

Computational modelling of NOx removal by selective non-catalytic reduction

This paper presents the results of computational kinetic modelling of the removal of nitrogen oxides (NO_x) from flue gases by selective non-catalytic reduction (SNCR) process using urea as a reducing agent. CHEMKIN and SENKIN computer codes were used with latest reaction mechanism parameters for simulated conditions in an isothermal plug flow reactor. Flue gas initial conditions were simulated as 70 litres/min propane containing 500 ppm background NO_x. A range of molar ratios was studied at optimum temperature. Carbon monoxide and hydrogen were investigated as potential enhancers to lower the temperature window. The modelling results suggested that the optimum temperature for peak reduction was around 1075°C with optimum molar ratios of 1.5. Hydrogen was found to be an efficient enhancer. The optimum residence time was found to be about 80 milliseconds.     

燃煤烟气低温SCR脱硝中试研究

低温选择性催化还原(SCR)脱硝是国内外脱硝技术研发的热点,但目前主要集中在实验室小试范围,无法完全反映催化剂在实际烟气中的运行状况。在30 t/h循环流化床燃煤锅炉脱硫除尘装置后建设了2 000~5 000 m3/h的SCR脱硝中试装置,经系统研究发现,中试使用的蜂窝式催化剂对SO2和NO具有很强的吸附能力,且反应温度、喷氨速率和气体空速均会影响催化脱硝效率。为期5 d的连续运行实验结果表明,催化剂的脱硝效率一直稳定在30%~50%,并未发现明显的失活,这证明设计除雾除尘器、较大的混合器、混合器与反应器间较长的管路均有利于缓解催化剂因SO2、H2O和飞灰中的碱性金属导致的失活。     

Deactivation of the Vanadia Catalyst in the Selective Catalytic Reduction Process

Results are summarized of a comprehensive study of the effects on the SCR process of all major possible poisons encountered in the combustion gases from U.S. coals. A general rule evolved from this study Is that the effect of the additive on the catalyst activity Is directly related to the basicity of the additive; poisoning Is caused by the basicity. Quantitative effects are presented, while a qualitative summary is given as follows: strong poisons-alkali metal oxides; weak poisons-oxides of alkaline earth metals, arsenic, lead phosphorus and chlorides of strong alkaline metals. SO₂ is a promoter due to its acidity. HCI, although acidic, reacts with both NH₃ (forming NH₄CI) and V₂O₅ (forming VCI₂ and VCI₃) and consequently strongly deactivates the SCR reaction.

A summary is also given for a theoretical and experimental study of the monolithic honeycomb reactor using both undoped and poison-doped catalysts. The results showed that the reactor performance can be predicted directly from the intrinsic catalyst activity through a model.     

Size Distribution of Particles That May Contribute to Soiling of Material Surfaces

ABSTRACT

This study investigated the effect of adding vanadium (V) to natural manganese oxide (NMO) in ammonia (NH₃) selective catalytic reduction (SCR). The addition of V to NMO decreased the catalytic activity at low temperatures by blocking the active site. However, the enhancement of catalytic activity was achieved by controlling NH₃ oxidation at high temperatures. From the NH₃ temperature programmed desorption and oxygen on/off test, it was confirmed that the amount of Lewis acid site and active lattice oxygen of the catalyst affects the catalytic performance at low temperature

IMPLICATIONS Recently, NMO and manganese oxide have been reported as SCR catalysts. They usually have only reported the reaction characteristics and catalytic activity on the NH₃ SCR over NMO or manganese/metal oxide catalysts. There are no studies about the effect of addition of V to NMO. Therefore, this study investigates the catalytic activity and reaction characteristics on the NH₃ SCR over NMO and V/NMO, and a new application is proposed based on the conclusions of this study.     

Comparison of titania nanotubes and titanium dioxide as supports of low-temperature selective catalytic reduction catalysts under sulfur dioxide poisoning

A series of iron–manganese oxide catalysts supported on TiO₂ and titanium nanotubes (TNTs) were studied for low temperature selective catalytic reduction (SCR) of NO with NH₃ in the presence of SO_2. The results showed that the specific surface area and the amount of Brønsted acid sites were highly correlated. The results also demonstrated that higher Mn⁴⁺/Mn³⁺ ratios and larger specific surface areas might be the main reasons for the excellent performance of MnFe-TNTs catalyst after SO₂ poisoning. The SO₂ poisoning effect could be minimized by reducing the GHSV, increasing the reaction temperature, or increasing the [NH₃]/[NO] molar ratio. The results also indicated that the formation of ammonium sulfate had a stronger effect on the NO conversion efficiency as compared to the formation of metal sulfate. Thus operating the low temperature SCR at above 230 ^oC to avoid the formation of ammonium sulfate would be the priority choice when SO₂ poisoning is a concerned issue.?Implications: Low-temperature selective catalytic reduction (SCR) has attracted increasing attention due to that it can reduce the energy consumption for the SCR process employed in industries such as steel plants and glass manufacturing plants. However, it also suffers from the sulfur dioxide (SO₂) poisoning problem. This study investigates the possibility of using titania nanotubes (TNTs) as the support of Mn/Fe bimetal oxide catalysts for low-temperature SCR to reduce the SO₂ poisoning. The results indicated that the MnFe-TNT catalyst can tolerate SO₂ for a longer time as compared with the MnFe-TiO₂ catalyst.     

Technology Innovations and Experience Curves for Nitrogen Oxides Control Technologies

Abstract

This paper reviews the regulatory history for nitrogen oxides (NO_x) pollutant emissions from stationary sources, primarily in coal-fired power plants. Nitrogen dioxide (NO₂) is one of the six criteria pollutants regulated by the 1970 Clean Air Act where National Ambient Air Quality Standards were established to protect public health and welfare. We use patent data to show that in the cases of Japan, Germany, and the United States, innovations in NO_x control technologies did not occur until stringent government regulations were in place, thus “forcing” innovation. We also demonstrate that reductions in the capital and operation and maintenance (O&M) costs of new generations of high-efficiency NO_x control technologies, selective catalytic reduction (SCR), are consistently associated with the increasing adoption of the control technology: the so-called learning-by-doing phenomena. The results show that as cumulative world coal-fired SCR capacity doubles, capital costs decline to ~86% and O&M costs to 58% of their original values. The observed changes in SCR technology reflect the impact of technological advance as well as other factors, such as market competition and economies of scale.     

Regulated and unregulated emissions from modern 2010 emissions-compliant heavy-duty on-highway diesel engines

The U.S. Environmental Protection Agency (EPA) established strict regulations for highway diesel engine exhaust emissions of particulate matter (PM) and nitrogen oxides (NO_x) to aid in meeting the National Ambient Air Quality Standards. The emission standards were phased in with stringent standards for 2007 model year (MY) heavy-duty engines (HDEs), and even more stringent NO_X standards for 2010 and later model years. The Health Effects Institute, in cooperation with the Coordinating Research Council, funded by government and the private sector, designed and conducted a research program, the Advanced Collaborative Emission Study (ACES), with multiple objectives, including detailed characterization of the emissions from both 2007- and 2010-compliant engines. The results from emission testing of 2007-compliant engines have already been reported in a previous publication. This paper reports the emissions testing results for three heavy-duty 2010-compliant engines intended for on-highway use. These engines were equipped with an exhaust diesel oxidation catalyst (DOC), high-efficiency catalyzed diesel particle filter (DPF), urea-based selective catalytic reduction catalyst (SCR), and ammonia slip catalyst (AMOX), and were fueled with ultra-low-sulfur diesel fuel (~6.5 ppm sulfur). Average regulated and unregulated emissions of more than 780 chemical species were characterized in engine exhaust under transient engine operation using the Federal Test Procedure cycle and a 16-hr duty cycle representing a wide dynamic range of real-world engine operation. The 2010 engines’ regulated emissions of PM, NO_X, nonmethane hydrocarbons, and carbon monoxide were all well below the EPA 2010 emission standards. Moreover, the unregulated emissions of polycyclic aromatic hydrocarbons (PAHs), nitroPAHs, hopanes and steranes, alcohols and organic acids, alkanes, carbonyls, dioxins and furans, inorganic ions, metals and elements, elemental carbon, and particle number were substantially (90 to >99%) lower than pre-2007-technology engine emissions, and also substantially (46 to >99%) lower than the 2007-technology engine emissions characterized in the previous study.

Implications:?Heavy-duty on-highway diesel engines equipped with DOC/DPF/SCR/AMOX and fueled with ultra-low-sulfur diesel fuel produced lower emissions than the stringent 2010 emission standards established by the U.S. Environmental Protection Agency. They also resulted in significant reductions in a wide range of unregulated toxic emission compounds relative to older technology engines. The increased use of newer technology (2010+) diesel engines in the on-highway sector and the adaptation of such technology by other sectors such as nonroad, displacing older, higher emissions engines, will have a positive impact on ambient levels of PM, NOx, and volatile organic compounds, in addition to many other toxic compounds.     

Optimization of Reburning for Advanced N0x Control on Coal-fired Boilers

This paper summarizes an experimental study which was conducted to investigate the chemical constraints of the reburning process and identify reburning configurations for optimal NO_x reduction in coal-fired boilers. Tests were performed on a bench scale tunnel furnace to characterize and optimize the fuel-rich reburning zone and the fuel-lean burnout zone independently. Detailed measurements ofunburned hydrocarbons, CO, NH₃, and HCN were made at the reburning zone exit. The influence of the concentrations of reactive species was examined as were temperature effects for both the reburning and burnout zone. Results indicated that reburning zone chemistry was not rate limiting. The impacts of temperature and burnout zone oxidation were of major importance. Integration of the optimum reburning and burnout zone configurations resulted in increased NO_x reduction. Over 85 percent reduction in NO_x emissions was achieved with ammonium sulfate injection in the burnout zone under optimum reburning conditions.     

Technique for Measuring the Total Concentration of Gaseous Fixed Nitrogen Species

This paper reports the development of a rapid, continuous technique for analyzing fixed nitrogen species (NH₃, HCN, CH₃NH₂, etc.). The technique uses a platinum catalyst at low pressure in combination with a conventional chemiluminescent NO _x analyzer. Previous workers observed that conventional stainless steel catalysts, and platinum catalysts operated at atmospheric pressure, do not reliably convert NH₃ to NO. The most serious problem was the variation in the efficiency of these catalysts with operating conditions. Changes in temperature, gas composition, or X_NH3 could change the conversion efficiency from 99.9% to <30%. The new conversion technique, however, is quantitative up to several thousand ppm NH₃ in either O₂/He or O₂/CO₂/N₂.