Emission characteristics for co-combustion of leather wastes,sewage sludge,and coal in a laboratory-scale entrained flow tube furnace

Four different mixed fuels consisted of leather waste, coal, and sewage sludge were combusted in a lab-scale entrained flow fluidized bed furnace. The influence of blending ratio on emission characteristics of SO₂, NO_x, HCl, particulate matter (PM), heavy metals, and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was studied. Results showed that the mixing of coal with sewage sludge had a complex effect on the emission characteristics. On the one hand, with more sewage sludge blending in the mixed fuel, the acid gas pollutant (SO₂, NO_x) decreased a lot, and the recovery of volatile heavy metals (Cd, Pb) increased at the same time. Furthermore, the leaching toxicity of Cr in the fly ash and bottom ash went down below the national standard with the adding of sewage sludge. On the other hand, the mixing of sewage sludge which consisted of more ash content resulted in the increase of the PM emission. Moreover, the high content of Cu and chlorine in the sewage sludge can promote the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) when the fuel 3 and 4 were combusted. Most importantly, the concentration of toxic PCDD/Fs in the flue gas produced from fuel 3 and fuel 4 was successfully controlled down below 0.20 ng I-TEQ/Nm³ by the active carbon.

     

Kinetics and mechanisms of interaction of simazine with humic acids

Abstract

The adsorption of simazine on two fractions of hu‐mic acids of different molecular size was investigated at a pH range of 2.5 to 6.2. The amounts of the herbicide adsorbed decreased with increasing pH for both of the two humic acids fractions used and no adsorption was observed at pH 5.5. The adsorption capacity of fraction I (M_v >100,000) exceeded that of fraction IV (M_v < 4,000) over the entire pH region used. No appreciable changes in the adsorbed amounts were observed after 24 hours.

Continuous flow dialysis techniques were used to determine the extent of binding between simazine and dissolved humic acids. It was observed that 50% and 60% of simazine added were thus removed from the dialysis bags containing humic acids fractions I and IV,respectively. Higher amounts of simazine were adsorbed by the high molecular weight humic fraction. The adsorption processes involve ionic bonds between simazine and humic acids. In addition it is likely that hydrogen bonds and physical forces are also involved in the adsorption of simazine by humic acids.     

Kinetic study of heterogeneous ozonolysis of alachlor, trifluralin and terbuthylazine adsorbed on silica particles under atmospheric conditions

To better understand the atmospheric behaviour of pesticides, heterogeneous ozonolysis of three herbicides (alachlor, terbuthylazine and trifluralin) adsorbed on silica particles were performed in a flow reactor. The experimental setup used in this study and previously validated (Pflieger et al., 2009) has been specially developed to investigate extremely slow reactivity. The pesticides were adsorbed on particles using a gas/solid adsorption equilibrium, in order to simulate atmospheric conditions. After exposure to ozone concentrations ranging from 5 to 41 ppm during 90 min to 6 h, the kinetics were calculated by comparing the initial and the remaining amounts of pesticides adsorbed on silica particles. This work offers the first results of heterogeneous ozonolysis of alachlor and trifluralin adsorbed on mineral particles. Although alachlor and terbuthylazine were expected to react with ozone, no degradation was observed which leads to a lifetime higher than 8 months towards ozonolysis (for 40 ppb of O₃). A significant degradation of trifluralin adsorbed on silica particles by heterogeneous ozonolysis was observed. The experimental data could be fit by both the Langmuir–Rideal and the Langmuir–Hinshelwood models resulting in atmospheric lifetimes (towards heterogeneous ozonolysis) of 40 and 32 days respectively (for 40 ppb of O₃). These results are discussed and compared to other studies.     

EFFECTS OF SELENIUM AND MERCURY ON THE ENZYMATIC ACTIVITIES AND LIPID PEROXIDATION IN BRAIN,LIVER, AND BLOOD OF RATS

Recent studies have reported on the toxicity and related oxidative stress of selenium and mercury. The present study compares the effects of Se as sodium selenite (Na₂SeO₃) and Hg as mercuric chloride (HgCl₂) separately and in combination. Rats received repeated oral doses of Se (0.5 μmol/ml), Hg (0.5 μmol/ml), or Se in combination with Hg (0.5 μmol/ml of each) for 5 consecutive days. Rat serum, brain and liver samples were collected for biochemical assays. The following biochemical alterations occurred in response to Hg treatment: protein content (brain and liver), acetylcholinesterase (AChE) (brain and serum), acid and alkaline (AcP and AlP) phosphatases (plasma and liver) and glutathione S-transferase (GST) (plasma and liver) activities were significantly (P<0.05) decreased, while lactate dehydrogenase (LDH) (plasma, brain and liver), aspartate and alanine aminotransferase (AST, ALT) (serum and liver) activities were significantly increased. Thiobarbituric acid reactive substances (TBARS) was significantly increased in brain and liver. Effect of Se alone included decreased AcP, AlP and GST (serum and liver) activities. However, LDH (serum, brain and liver) and AST (liver) and TBARS (brain and liver) increased. Selenium in combination with Hg partially or totally alleviated the toxic effects of Hg on different studied enzymes. It is concluded that Se could be able to antagonize the toxic effects of mercury.     

Lead adsorption to metal oxides and organic material of freshwater surface coatings determined using a novel selective extraction method

Surface coatings were collected in three lakes and a river in China to study the role of the components of natural surface coatings in controlling Pb adsorption. Chemical reagents, 0.02 mol/l NH2OH HCl+0.01 mol/l HNO3, 0.4 mol/l Na2S2O4 and 10% oxalic acid, were employed to extract one or more components from surface coatings, and then Pb adsorption to extracted and unextracted surface coatings was carried out. The observed Pb adsorption to extracted and Unextracted surface coatings were analyzed using the nonlinear least squares fitting (NLSF) to estimate the relative contribution of components to the total Pb adsorption. The amounts of Pb absorption to components described by estimated gamma(max) ranged from 0.1126 to 0.7291 (mol Pb/mol Mn) for Mn, 0.0528 to 0.1927 (mol Pb/mol Fe) for Fe and 0.0196 to 0.1020 (mol Pb/kg COD) for organic material, respectively. In all waters studied, metal oxides contributed most to Pb adsorption with a lesser role indicated for organic material.     

Adsorption of air pollutants on the grain surface of Japanese cedar pollen

The contaminants adsorbed on the surface of pollen may affect the development of hay fever, because the patients of the fever are larger in areas with much air pollution than in nonpolluted areas and the fine particles and gases are susceptible to deposit on the nasal cavities and eyes by their transfer on the pollen. Since Japanese cedar pollinosis is the most common hay fever in Japan, we analyzed the air pollutants adsorbed on the surface of dispersed Japanese cedar pollen in the urban and mountainous districts. Fine anthropogenic particles were significantly adsorbed and many elements were concentrated on the surface of the pollen in the urban site of Yokohama, while they were not concentrated on the surface of the pollen collected at a mountainous site. The acid gases are also adsorbed and acidify the surface, and their amounts increase with their concentrations in the ambient air. The high adsorption of nitric acid on the pollen determined by an exposure experiment of nitric acid gas suggests that nitric acid is dissolved in the inner part of the pollen. The adsorption amounts of the gases on the pollen were especially greater than those on other natural particles, humic acid and yellow sand.     

Removal of PCDD/F from Incinerator Flue Gases by Entrained-Phase Adsorption

Abstract

The emission abatement of polychlorinated dioxins and furans (PCDD/F) issued from municipal solid waste incineration is growing in importance because of more stringent emission standards and general concern about their toxic characteristics. These substances cannot be separated by conventional gas cleanup processes but are successfully removed through adsorption onto carbonaceous materials. The simplest technique is the entrained-phase injection of pulverized adsorbents in the flue gas, followed by fabric filter separation. The various related techniques are briefly reviewed here. Operating conditions and results obtained from Flemish MSWIs are given. The results illustrate the excellent overall removal efficiency. Furans are adsorbed to a slightly higher extent than dioxins.

PCDD/F removal by carbonaceous adsorbents is thereafter modeled from first principles for the contribution of both entrained-phase (η₁) and cake filtration (η₂) to the overall efficiency (η_T). Application of the model equations and comparison of measured and predicted overall efficiencies for the Flemish municipal solid waste incinerators (MSWIs) demonstrate that the approach is meaningful and that the dominant parameters are the operating temperature, the dosage and activity of adsorbent, and the fraction of adsorbent in the filter cake. The model equations enable the MSWI operators to predict the adsorption efficiencies for any combination of operating parameters and to assess the sensitivity of the process to varying operating conditions.     

Synthesis of high-purity Na-A and Na-X zeolite from coal fly ash

Coal fly ash (CFA) was used as a raw material for the synthesis of zeolite molecular sieve. The synthesis began with the pretreatment of CFA to remove impurities (e.g., Fe₂O₃, CaO, etc.) under various acid types (HCl, H₂SO₄, and HNO₃) and acid/CFA ratios (5–25 mL_acid/g_CFA). High product purity (up to 97%) was achieved with HCl (20%wt), and acid/CFA ratio of 20 mL_HCl/g_CFA. The treated CFA was then converted to zeolite by the fusion reaction under various Si/Al molar ratios (0.54–1.84). Zeolite type A was synthesized when the Si/Al molar ratios were lower than 1, whereas sodium aluminum silicate hydrate was formed when the Si/Al molar ratio were higher than 1. The highest water adsorption performance of the zeolite product, i.e., the outlet ethanol concentration of 99.9%wt and the specific adsorption capacity of 2.31 × 10^?2 g_water/g_zeolite, was observed with the Si/Al molar ratio of 0.82. The zeolite was tested for its water adsorption capacity repeatedly 10 times without deactivation.

Implications: This work evaluated the technical feasibility in the conversion of CFA to zeolite, which would help reduce the quantity of waste needed to be landfilled. This adds value to the unwanted material by converting it into something that can be further used. The synthesized products were shown to be quite stable as water adsorbent for the dehydration of ethanol solution.     

Measurements of trace gases in the tropical tropopause layer

A unique dataset of airborne in situ observations of HCl, O₃, HNO₃, H₂O, CO, CO₂ and CH₃Cl has been made in and near the tropical tropopause layer (TTL). A total of 16 profiles across the tropopause were obtained at latitudes between 10°N and 3°S from the NASA WB-57F high-altitude aircraft flying from Costa Rica. Few in situ measurements of these gases, particularly HCl and HNO₃, have been reported for the TTL. The general features of the trace gas vertical profiles are consistent with the concept of the TTL as distinct from the lower troposphere and lower stratosphere. A combination of the tracer profiles and correlations with O₃ is used to show that a measurable amount of stratospheric air is mixed into this region. The HCl measurements offer an important constraint on stratospheric mixing into the TTL because once the contribution from halocarbon decomposition is quantified, the remaining HCl (>60% in this study) must have a stratospheric source. Stratospheric HCl in the TTL brings with it a proportional amount of stratospheric O₃. Quantifying the sources of O₃ in the TTL is important because O₃ is particularly effective as a greenhouse gas in the tropopause region.     

Adsorption behavior of α -cypermethrin on cork and activated carbon

Studies were undertaken to determine the adsorption behavior of α -cypermethrin [R)-α -cyano-3-phenoxybenzyl(1S)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate, and (S)-α-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] in solutions on granules of cork and activated carbon (GAC). The adsorption studies were carried out using a batch equilibrium technique. A gas chromatograph with an electron capture detector (GC-ECD) was used to analyze α -cypermethrin after solid phase extraction with C18 disks. Physical properties including real density, pore volume, surface area and pore diameter of cork were evaluated by mercury porosimetry. Characterization of cork particles showed variations thereby indicating the highly heterogeneous structure of the material. The average surface area of cork particles was lower than that of GAC. Kinetics adsorption studies allowed the determination of the equilibrium time—24 hours for both cork (1–2 mm and 3–4 mm) and GAC. For the studied α -cypermethrin concentration range, GAC revealed to be a better sorbent. However, adsorption parameters for equilibrium concentrations, obtained through the Langmuir and Freundlich models, showed that granulated cork 1–2 mm have the maximum amount of adsorbed α-cypermethrin (q_m) (303 μg/g); followed by GAC (186 μ g/g) and cork 3-4 mm (136 μg/g). The standard deviation (SD) values, demonstrate that Freundlich model better describes the α -cypermethrin adsorption phenomena on GAC, while α -cypermethrin adsorption on cork (1-2 mm and 3-4 mm) is better described by the Langmuir. In view of the adsorption results obtained in this study it appears that granulated cork may be a better and a cheaper alternative to GAC for removing α -cypermethrin from water.     

Study on fractions of adsorbed Pb and Cd onto natural surface coatings

The speciation and extent of migration of adsorbed Pb and Cd in natural surface coatings (NSCs) were investigated using sequential extraction procedure to provide an understanding of distribution of the adsorbed Pb and Cd. Extractions were conducted on NSCs before and after Pb and Cd adsorption treatment under controlled laboratory conditions with initial Pb and Cd concentrations ranging from 0.2-2.5 mol/l. The Langmuir adsorption isotherms were applied to estimate equilibrium coefficients of Pb and Cd adsorption to NSCs components. The results showed that 58.50% of adsorbed Pb in average existed in tightly adsorbed form, and the remaining Pb was mostly present as solid oxides/hydroxides (34.00%) and exchangeable and soluble form (7.50%) in NSCs, respectively. Large amount of adsorbed Cd (70.51% in average) was present in exchangeable and soluble form, following a decreasing order in tightly adsorbed form (18.61%), solid oxides/hydroxides (9.87%), and easily oxidizable solids/compounds (1.01%), respectively. No Cd was found in strongly held oxides and precipitates. Compared to the distribution of adsorbed Pb in NSCs, Cd distribution showed that less migration of Cd from exchangeable and soluble form to solid oxides/hydroxides after adsorbed to NSCs, indicating fewer sites for Cd to adsorb to NSCs and less affinity of Cd to the NSCs. These percent distributions of metals provided an additional interpretation to that Pb adsorption to the NSCs greater than that of Cd, less retention of Cd than that of Pb and less roles attributed for Pb/Cd adsorption by organic materials in NSCs, which were observed based on the selective extraction techniques in the independent investigations.     

Adsorption of mercury by activated carbon prepared from dried sewage sludge in simulated flue gas

Conversion of sewage sludge to activated carbon is attractive as an alternative method to ocean dumping for the disposal of sewage sludge. Injection of activated carbon upstream of particulate matter control devices has been suggested as a method to remove elemental mercury from flue gas. Activated carbon was prepared using various activation temperatures and times and was tested for their mercury adsorption efficiency using lab-scale systems. To understand the effect of the physical property of the activated carbon, its mercury adsorption efficiency was investigated as a function of its Brunauer–Emmett–Teller (BET) surface area. Two simulated flue gas conditions, (1) without hydrogen chloride (HCl) and (2) with 20 ppm HCl, were used to investigate the effect of flue gas composition on the mercury adsorption capacity of activated carbon. Despite very low BET surface area of the prepared sewage sludge activated carbons, their mercury adsorption efficiencies were comparable under both simulated flue gas conditions to those of pinewood and coal activated carbons. After injecting HCl into the simulated flue gas, all sewage sludge activated carbons demonstrated high adsorption efficiencies, that is, more than 87%, regardless of their BET surface area.

Implications: We tested activated carbons prepared from dried sewage sludge to investigate the effect of their physical properties on their mercury adsorption efficiency. Using two simulated flue gas conditions, we conducted mercury speciation for the outlet gas. We found that the sewage sludge activated carbon had mercury adsorption efficiency comparable to pinewood and coal activated carbons, and the presence of HCl minimized the effect of physical property of the activated carbon on its mercury adsorption efficiency.     

Application of Gas-Aerosol Adsorption Data to the Selection of Air Quality Standards

A quantitative approach is presented for selecting air quality standards which take into account pollutant gas-aerosol synergistic effects. These synergistic health effects have been postulated to be due to the adsorption or absorption of the pollutant gas by the aerosol particles. The approach presented in this paper assumes that the synergistic toxic agent is the adsorbed pollutant gas. Therefore, limiting the concentration of the adsorbed pollutant gas limits the magnitude of the synergistic effects. The concentration of the adsorbed pollutant gas is related to the concentrations of the gaseous phase pollutant gas and the atmospheric aerosol using the Langmuir adsorption isotherm. An example is presented of the selection of air quality standards for sulfur dioxide and the atmospheric aerosol using concentration data for these two pollutants along with health effect data.     

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.     

适宜处理分散性生活污水的人工湿地除磷填料的筛选及改性

为提高人工湿地除磷效能,从沸石、陶粒、萤石、膨胀蛭石、石灰石、麦饭石、火山岩、牡蛎壳、钢渣和废砖块这10种具有较高磷素饱和吸附量的填料中,筛选出钢渣、沸石和石灰石3种适宜处理分散性生活污水的人工湿地填料,并分别使用不同浓度梯度的酸(碱)、盐对3种填料进行改性,以增强其除磷能力。研究结果表明,钢渣、沸石和石灰石分别经2 mol/L AlCl3、2 mol/L NaOH及2 mol/L AlCl3、0.5 mol/L AlCl3溶液改性后,磷素吸附量达到最高值(0.272、0.0801和0.351 mg/g),而双常数方程能更好地描述优选填料对生活污水中磷的吸附动力学过程,综合考虑填料的吸附效果、成本及来源,改性石灰石是人工湿地处理分散性生活污水时较为理想的除磷填料;此外,填料经铝改后,氮磷吸附效果普遍优于其他改性条件,且Al-P有利于植物直接吸收利用,含铝废水来源广泛,故利用铝改液处理人工湿地填料具有较高的应用推广价值。     

弱碱性树脂吸附-解吸苦味酸

考察了水中苦味酸在弱碱性离子交换树脂D301R上的吸附与解吸。研究了吸附热力学、动力学特性及吸附机理。结果表明,树脂在pH=2.7～10.2时,吸附能力最好。等温平衡吸附遵循Freundlich模型。吸附过程为吸热、熵增的自发过程。吸附动力学符合Lagergren准二级速率方程,颗粒内扩散为吸附速率的主要控制步骤,吸附速率常数为7.23×10-5～1.20×10-4g/(mg.min),吸附活化能为19.4 kJ/mol。树脂上吸附的苦味酸可用HNO3+丙酮混合液定量洗脱,洗脱率达99%。静态吸附和脱附的比较结果证实了吸附过程中存在不可逆化学吸附。树脂对苦味酸的吸附主要是通过静电吸附、酸碱络合吸附、氢键吸附等协同作用来完成的。     

Relationship of Particulate Control,SO2 Removal,and Waste Management

Results with the EPRI 2.5 MW(e) Integrated Environmental Control Pilot Plant (IECPP) indicate the interrelationship of particulate penetration, SO₂ scrubber operation, waste production, and waste properties. Tests compared a fabric filter/wet scrubber and ESP/wet scrubber, the latter operated to simulate 1979 New Source Performance Standards (NSPS), 1971 NSPS, and pre-NSPS ESP units. Tests were conducted with low-sulfur coal producing a flue gas concentration of400ppm; flue gas spiking could be used to increase SO₂ to 2000 ppm. Scrubber waste was dewatered in a thickener and vacuum belt filter (to 55 percent solids content), and mixed with fly ash. The pilot SO₂ scrubber—when preceded by an ESP and forced to operate in zero-discharge—captured less SO₂ than when preceded by a fabric filter. Also, scrubber operation with the ESP produced a greater quantity of waste with difficult handling characteristics, as compared to operation with the fabric filter. These difficulties occurred with particulate penetration above 0.10 lb/MBtu, which could reduce reagent utilization to 80percent. These results are attributable to inhibited limestone dissolution due to accumulation of an aluminum/fluoride compound. For both lowsulfur and simulated high-sulfur test conditions, allowing wastewater discharge to purge aluminum/fluoride content restored performance to design levels. Particulate control efficiency also affected solid waste physical properties. The fabric filter/wet scrubber produced the lowest solid waste permeability (10^?8 cm/s). ESP operation at 1979 NSPS and pre-1971 NSPS ESPs increased solid waste permeability to 10^?7 and 10^?6 cm/s, respectively. These results are meaningful for SO₂ scrubbers both for new plants and for retrofit to units with pre-NSPS ESPs, and could become significant with the increasing trend to restricted water discharge.     

Characterization of an adsorbed humin-like substance on an allophanic soil formed via catalytic polycondensation between catechol and glycine, and its adsorption capability to pentachlorophenol

An allophanic soil (AS) catalyzed the formation of dark-colored polymers via polycondensation reactions between catechol and glycine. The organic carbon content of the AS was increased from 0.16% to 1.3%, indicating that some of the dark-colored polymers had been adsorbed to the AS. The characteristics of the dark-colored polymers adsorbed on the AS were similar to those of a humin that is not extractable with an aqueous alkaline solution. Such a humin-like substance (HuLS) was separated from the AS by treatment with a mixture of HF and HCl. The HuLS and humic acid-like substance (HaLS), comprising the acid-insoluble fraction in the reaction mixture, were characterized by elemental analysis, size exclusion chromatography, pyrolysis-GC/MS and ¹³C NMR. However, the structural features of HaLS and HuLS had many points in common. These results suggest that HuLS-AS can be regarded as an organo-clay complex formed by the strong adsorption of HaLS to the AS. The adsorption of pentachlorophenol (PCP) to AS and HuLS-AS was examined at pH 5.5. At this pH, the zeta potential of the HuLS-AS showed a negative value. It would, therefore, be expected that pentachlorophenolate anions would adsorb with difficulty to HuLS-AS because of electrostatic repulsion. Nevertheless, the adsorption coefficient for PCP to HuLS-AS, as estimated by the Freundlich isotherm, was seven times larger than that for AS. These results show that HuLS, when adsorbed on the AS surface, has the capability to enhance the adsorption of PCP.     

Laboratory testing of a continuous emissions monitor for hydrochloric acid

Continuous monitoring of exhaust flue gas has become a common practice in power plants in response to Federal Mercury and Air Toxics Standards (MATS) standards. Under the current rules, hydrochloric acid (HCl) is not continuously measured at most plants; however, MATS standards have been proposed for HCl, and tunable diode laser (TDL) absorption spectroscopy is one method that can be used to measure HCl continuously. The focus of this work is on the evaluation and verification of the operation performance of an HCL TDL over a range of real-world operating environments. The testing was conducted at the University of California at Riverside (UCR) spectroscopy evaluation laboratory. Laboratory tests were conducted at three separate temperatures, 25ºC, 100ºC, and 200ºC, and two distinct moisture levels for the enhanced temperatures, 0%, (2 tests) and 4%, over a concentration range from 0 ppmv to 25 ppmv-m at each of the elevated temperatures. The results showed good instrument accuracy as a function of changing temperature and moisture. Data analysis showed that the average percentage difference between the ammonia concentration and the calibration source was 3.33% for varying moisture from 0% to 4% and 2.69% for varying temperature from 25 to 100/200ºC. An HCl absorption line of 1.742 μm was selected for by the manufacturer for this instrument. The Hi Tran database indicated that CO₂ is probably the only major interferent, although the CO₂ absorption is very weak at that wavelength. Interference tests for NO, CO, SO₂, NH₃, and CO₂ for a range of concentrations typical of flue gasses in coal-fired power plants did not show any interference with TDL HCl measurements at 1.742 μm. For these interference tests, CO₂ was tested at a concentration of 11.9% concentration in N₂ for these tests. Average precision over the entire range for all 10 tests is 3.12%.

Implications: The focus of this study was an evaluation of the operation performance of a tunable diode laser (TDL) for the measurement of hydrochloric acid (HCl) over a range of real-world operating environments. The results showed good instrument accuracy as a function of changing temperature from 25ºC to 200ºC and moisture from 0% to 4%. Such as an instrument could be used for continuous monitoring of exhaust flue gas in power plants once the Federal Mercury and Air Toxics Standards (MATS) standards have been fully implemented.