On-line Gas Analysis Research Articles

Gas Transport in Mixed Matrix Membranes: Two Methods for Time Lag Determination

The most widely used method to measure the transport properties of dense polymeric membranes is the time lag method in a constant volume/pressure increase instrument. Although simple and quick, this method provides only relatively superficial, averaged data of the permeability, diffusivity, and solubility of gas or vapor species in the membrane. The present manuscript discusses a more sophisticated computational method to determine the transport properties on the basis of a fit of the entire permeation curve, including the transient period. The traditional tangent method and the fitting procedure were compared for the transport of six light gases (H2, He, O2, N2, CH4, and CO2) and ethane and ethylene in mixed matrix membranes (MMM) based on Pebax®1657 and the metal–organic framework (MOF) CuII2(S,S)-hismox·5H2O. Deviations of the experimental data from the theoretical curve could be attributed to the particular MOF structure, with cavities of different sizes. The fitting procedure revealed two different effective diffusion coefficients for the same gas in the case of methane and ethylene, due to the unusual void morphology in the MOFs. The method was furthermore applied to mixed gas permeation in an innovative constant-pressure/variable-volume setup with continuous analysis of the permeate composition by an on-line mass-spectrometric residual gas analyzer. This method can provide the diffusion coefficient of individual gas species in a mixture, during mixed gas permeation experiments. Such information was previously inaccessible, and it will greatly enhance insight into the mixed gas transport in polymeric or mixed matrix membranes.

RF-ICP Thermal Plasma for Thermoplastic Waste Pyrolysis Process with High Conversion Yield and Tar Elimination

This paper demonstrates an RF thermal plasma pyrolysis reaction apparatus that achieves 89 wt.% reaction conversion yield with no tar content. The demonstrated experimental apparatus consists of a 1100 W RFVII Inc. (104 Church St, Newfield, NJ 08344, United States) @ 13.56 MHz RF thermal plasma generator, a Navio matching network, intelligent feedback controller, and an 8-turn copper RF-ICP torch embedded in a 12 L thermochemical reactor. The intelligent feedback controller optimizes the thermal performance based on feedback signals from three online gas analyzers: CO, CO2 and NOx. The feedback controller output signal controls the RF thermal plasma torch current that provides real-time temperature control. The proposed reaction system achieves precise temperature profiles for both pyrolysis and gasification as well as increases end-product yield and eliminates undesired products such as tar and char. The identified hydrocarbon liquid mixture is 90 wt.% gasoline and 10 wt.%. diesel. The 8-turn RF-ICP thermal plasma torch has an average heating rate of +35 °C/min and a maximum operating temperature of 2000 °C and is able to sustain stable flame for more than 30 min. The reaction operating parameters are (550–990 °C τ = 30 min for pyrolysis and (1300 °C τ = 1 sec) for the gasification process. The identified hydrocarbon liquid products are 90 wt.% of a n-butyl-benzene (C6H5C4H9) and oluene (C7H8) mixture with less than 10 wt.% decane diesel fuel (C10 H22). Comsol simulation is used to assess the RF-ICP thermal plasma torch’s thermal performance.

A comparative study on the air, the oxygen-enriched air and the oxy-fuel combustion of lignites in CFB

This paper deals with the comparative combustion processes of two lignites in the air, the oxygen-enriched air and the oxy-fuel-environments. Combustion experiments were conducted in a 30 kWth circulating fluidized bed (CFB) combustor. The air combustion and the oxygen-enriched air combustion were conducted with different excess air ratios and excess oxygen percentages, respectively. Emissions of major pollutants such as CO, CO2, NOx and SO2 were measured during experiments via on-line gas analysis systems. Similarly, temperatures along the combustor axis were measured at various positions. The oxy-fuel combustion experiments were done with O2/RFG mixture. In all environments the lignites sustained stable and steady combustion processes in the temperature range of 700–950 °C under the conditions applied. Emissions of both NOx and SO2 appeared to be considerably affected by combustion atmospheres. In the oxygen-enriched combustion both the NOx and SO2 emissions were higher than that in the air combustion and increased with increase in the O2 concentration in the feed gas. In comparison to the air and the oxygen-enriched air combustion processes, however, the NOx emissions were considerably depressed in the oxy-fuel combustion. In the oxyfuel combustion processes, CO2 concentrations of up to 96% in the flue gases were reached on dry basis.

Steam reforming of polystyrene at a low temperature for high H2/CO gas with bimetallic Ni-Fe/ZrO2 catalyst

Recovery of chemicals and fuels from unrecyclable waste plastics at high temperatures (>800 °C) has received much research attention. Thermodynamic equilibrium calculation suggests that it is possible to perform the low-temperature steam reforming of polystyrene. In this study, we synthesized a Ni-Fe bimetallic catalyst for the low-temperature (500 °C) steam reforming of polystyrene. XRD characterization showed that Ni-Fe alloy was formed in the catalyst. Compared to conventional Ni catalysts, the Ni-Fe bimetallic catalysts can significantly increase the H2/CO ratio in the produced gas with high gas production yield. The online gas analysis revealed that H2, CO, and CO2 were formed in the same temperature range. H2 and CO were formed simultaneously through steam reforming reactions, and CO2 was formed through water-gas shift reaction. New morphologies of carbon deposition on the catalyst surface were found, suggesting that wax could be condensed on the catalyst surface at a low temperature.

Development of calibration device for on-line atmospheric gas analyzers

An on-line calibration device for atmospheric gas analyzers is developed by combining the dynamic gas mixtures preparation system of membrane permeation which is situated in the automated air monitoring station with a standard admixing air matrix method. The continuous, standard admixing air matrix and real-time online calibration of SO2, NO2, CO gas analyzers for automated air monitoring stations are realized with the calibration uncertainties less than 3% (k = 2). At the same time, in the calibration device, the service life of the newly invented membrane permeation system is several times longer than that of the traditional method.

Electrochemical sequential reduction and oxidation facilitates the continual ambient temperature degradation of SF6 to nontoxic gaseous compounds

An efficient process for the degradation of the potent greenhouse gas, SF6, into non-toxic gaseous products at ambient temperature is still desirable. In this study, consistently generable homogeneous low/high-valent metal ions were used to degrade SF6 to non-toxic gaseous products at ambient temperature. Two homogenous electron mediators, [Ni(I)(CN)4]3− (Ni(I) low-valent) and AgSO4 or Ag(NO3)2 (Ag(II) high-valent), were generated concurrently using a membrane-divided electrolytic cell and quantified by measuring the ORP (oxidation/reduction potential) variations along with a potentiometric titration. The variation of electrogenerated Ni(I) from 6.3 mM to 4.1 mM and Ag(II) from 4.8 mM to 4.3 mM during the removal of SF6 evidenced their concurrent generation, and SF6 removal followed a mediated electrocatalytic reduction (MER) and mediated electrocatalytic oxidation (MEO) process. FTIR online gas analyzer confirmed that using the MER process only, approximately 92% of the SF6 in a gas mixture containing 5 ppm of SF6 at a 0.2 L min−1 flow rate had decomposed to OF2 (7 ppm), SOF2 (2 ppm), and SO2 (2.9 ppm). At the same time, the MER-treated gas passed into Ag(II) generated anolyte solution resulted in the complete removal of SF6, SOF2, OF2, and SO2 by the MEO process. Also, the absence of fluoride containing gases and SO2 gas in the exit gas from the MEO process and the presence of fluoride ions in the anolyte solution demonstrates the aqueous soluble products fluoride and sulfate ions formation. The possible consistent generation of homogenous electrocatalysts and their combined use in SF6 degradation at ambient temperatures is a practical technology that can be scaled up to a more practical level.

Assessment of biomass energy potential for SRC willow woodchips in a pilot scale bubbling fluidized bed gasifier

The current study investigates the short rotation coppice (SRC) gasification in a bubbling fluidized bed gasifier (BFBG) with air as gasifying medium. The thermochemical processes during combustion were studied to get better control over the air gasification and to improve its effectiveness. The combustion process of SRC was studied by different thermo-analytical techniques. The thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) were performed to examine the thermal degradation and heat flow rates. The product gas composition (CO, CO2, CH4 and H2) produced during gasification was analyzed systematically by using an online gas analyzer and an offline GC analyzer. The influence of different equivalence ratios on product gas composition and temperature profile was investigated during SRC gasification. TG/DTG results showed degradation occur in four stages; drying, devolatilization, char combustion and ash formation. Maximum mass loss ~70% was observed in devolatilization stage and two sharp peaks at 315–500 °C in TG/DSC curves indicate the exothermic reactions. The temperature of gasifier was increased in the range of 650–850 °C along with the height of the reactor with increasing equivalent ratio (ER) from 0.25 to 0.32. The experimental results showed that with an increment in ER from 0.25 to 0.32, the average gas composition of H2, CO, CH4 decreased in the range of 9–6%, 16–12%, 4–3% and CO2 concentration increased from 17 to 19% respectively. The gasifier performance parameters showed a maximum high heating value (HHV) of 4.70 MJ/m3, Low heating value (LHV) of 4.37 MJ/m3 and cold gas efficiency (CGE) of 49.63% at 0.25 ER. The ER displayed direct effect on carbon conversion efficiency (CCE) of 95.76% at 0.32 ER and tar yield reduced from 16.78 to 7.24 g/m3 with increasing ER from 0.25 to 0.32. All parametric results confirmed the reliability of the gasification process and showed a positive impact of ER on CCE and tar yield.

Assessment of an experimental method for determining the three key parameters of VOC emissions from solid materials

The VOC emission processes from a solid material can be described by three key parameters: the partition coefficient (K), the initial emittable concentration (C0) and, the diffusion coefficient (D). These emission key parameters need to be determined experimentally for a VOC-material pair. A new method from literature allows determining simultaneously the three emission key parameters. However, this method has been evaluated in a single experiment only for formaldehyde. Therefore, the purpose of this study is to assess the efficiency and the reproducibility of the experimental method from literature performing three tests in the same experimental conditions. This work permits to determine the three key parameters of eight main VOC emitted from a particleboard and to evaluate the accuracy of the experimental method. Successfully, experiments carried out using a 128 L well-mixed chamber containing a particleboard, and connected to an online gas analyzer (Selected Ion Flow Tube-Mass Spectrometry), allow the effective characterization of the source material. Results evidence that compared to other VOCs, formaldehyde shows a specific behaviour: the response of formaldehyde between airtight and ventilated regimes is highly contrasted with those of other emitted VOCs.

Acute Resveratrol Administration Increases Neural Effort but Not Whole Body Metabolism or Cognitive Performance in Healthy, Young Participants

Research into the cognitive enhancing effects of polyphenols is small but growing. Single doses of the stilbene polyphenol resveratrol can increase cerebral blood flow (CBF) but have failed to improve cognitive performance in young, healthy cohorts. As both CBF and overall energy expenditure are closely related to neural activity, this randomised, double-blind, placebo-controlled, crossover investigation, assessed the metabolic consequences of resveratrol during high cognitive demand via indirect calorimetry (ICa). Twenty-seven, self-reported healthy participants (15 male, 12 female; mean age = 22) who reported themselves free of any food intolerances and any herbal supplementation or prescription medications were recruited for the current study. Participants arrived at the testing facility at 8 a.m. on three separate occasions to complete a serial subtraction demand battery 45 min and 2 and 3 h following administration with 500 mg, 250 mg trans-resveratrol or inert placebo, while connected to an online gas analysis system. A series of within-subjects ANOVAs (with planned comparisons) revealed a significant shift towards higher carbohydrate oxidisation during cognitive demand, as indexed by a significant increase in respiratory exchange ratio (RER) at 45-min and 3-h time points, following administration of 500 mg resveratrol. Despite this, no subsequent resveratrol-related benefits to cognitive performance were observed. These results show that acute supplementation with resveratrol in young, healthy adults can modulate fuel utilization during cognitive demand, yet this does not translate into clear improvements in cognitive performance. This study adds further understanding behind the lack of cognitive effects of resveratrol in young and or healthy individuals. Future research should direct efforts towards assessing the cognitive impact of resveratrol, and other vasoactive polyphenols, in populations with age-related or dietary-induced metabolic deficits.

Advantage of Co Embedded γ-Al2O3 Catalysts Over MgO and SiO2 Solid Oxides in the Selective Production of Styrene Monomer

A series of cobalt oxide (Co3O4) loaded (5–20wt%) γ-Al2O3, MgO and SiO2 supported catalysts were prepared by wetness-impregnation method and tested for oxidative dehydrogenation (ODH) of ethylbenzene (EB) in vapor phase atmospheric pressure conditions. Among Co oxide doped catalysts, Co3O4/γ-Al2O3 (CA) has afforded a superior catalytic activity in view of desirable EB conversion and styrene (ST) yields. Thus unusual catalytic properties of 15CA catalyst were supposed to be due to adequate acidic-basic nature, thermal stability and synergistic effect of Co-Al species along with uniform distribution of active Co oxide ions. Moreover, dramatic catalytic activity of Co3O4 incorporated γ-Al2O3 catalyst can be explained on the basis of beneficial CO2 conversion subsequently production of better CO yields during the online gas analysis. All calcined catalysts have been characterized by different sophisticated techniques to elucidate the surface metal composition and influence of Co3O4 oxide species on catalytic activity presentation during the oxidative dehydrogenation of EB reaction.

Identification of indoor air quality events using a K-means clustering analysis of gas sensors data

Commercial miniature gas sensors, because they are smaller and cheaper than conventional instruments, can be deployed in large numbers to investigate indoor air quality, for research and operational purposes. To compensate for their limited metrological performances, it is necessary to develop relevant data treatment procedures. We applied an unsupervised classification approach based on the bisecting K-means algorithm to data acquired by online gas analyzers and by miniature sensors during a measurement campaign in a low energy school building. This procedure, applied to the analyzers measurements, was able to distinguish the ventilation status and the specific air quality events taking place in the classroom. The same procedure applied to the data from the sensors, even though they were not calibrated beforehand, was also able to identify the same events. The good agreement between the two sets of results validates the methodology and opens up new perspectives for a massive deployment of sensors inside buildings.

P2G movable modular plant operation on synthetic methane production from CO2 and hydrogen from renewables sources

Renewables are steadily growing becoming a significant part of the global energy mix, in particular in the power sector. An attractive solution could be represented by Power to Gas (PtG), an energy storage strategy. In the PtG process renewable or excess electric energy is used for water electrolysis to produce hydrogen that is then combined with CO2 and converted into methane (synthetic or substitute natural gas, SNG) through the Sabatier reaction. SNG is particularly interesting because leads to an easily transportable (in the existing infrastructures) fuel with a wide proven market for power, thermal and mobility final use applications. The key issue consist on putting together green hydrogen produced by electrolysis fed by renewables with high content CO2 gases supplied from different sources (e.g. syngas from gasification, biogas, geothermic fields, soil gas and gas wells). In this work the CO2 hydrogenation process, coupled with renewables, has been study in a modular, moveable, skidable plant, in the scale of 0.2–1 Nm3/h of produced SNG. The pilot plant is equipped with a methanation unit constituted by a multi-tubular fixed bed reactor able to work in cooled or adiabatic conditions; water produced is separated by a plate&shell condenser. Several sensors, an online gas analysis system and a data acquisition system allow monitoring continuous experimental tests. The methanation facility is able to work in the range of 1–5 bars. The paper reports the results of first experimental activities related to SNG production with Ru based supported catalyst. The experimental activity was carried out in order to check the operability of all components and to improve the knowledge on methanation process in different conditions relevant to Power-to-Gas applications. Different weighted hourly space velocity (WHSV), gas inlet composition, reagent mixture, H2/CO2 ratio, temperature and pressure conditions have been investigated. Increasing pressure drives CH4 production as CO2 conversion is kinetically boosted by raising pressure. Results show that a decreasing trend of XCO2 is observed by increasing WHSV. Results indicate high CO2 per pass conversion with CO2/H2 concentrate feed using Ru based catalyst. Finally the effect of CH4 in the feed was studied emulating two reactors in series. Biogas representative CO2/H2/CH4 mixtures were tested in order to study direct methanation as a biogas upgrading technology.

CO2 Product Quality: Assessment of the Range and Level of Impurities in the CO2 product Stream from MEA Testing at Technology Centre Mongstad (TCM)

During the recent MEA campaign at the Technology Centre Mongstad (TCM), a broad range of operational conditions have been explored for the post-combustion amine-based CO2 capture demonstration plant. This paper presents CO2 product composition data from online gas analyzers, originating from CO2 capture of two different flue gas sources available at TCM. Detailed composition data obtained by manual sampling and laboratory analysis, both internally at TCM and by Airborne Labs International Inc. is presented. Among the impurities identified and analyzed for, ammonia, formaldehyde and acetaldehyde are the compounds not commonly reported in the literature. The solvent quality, in terms of metal content and amount of degradation products, seemed to be the most influential parameter affecting the concentration of acetaldehyde and ammonia in the CO2 product gas. In addition, ammonia slip was found to be correlated with operating temperature of the overhead stripper system.

Hydrogen production via biomass gasification, and modeling by supervised machine learning algorithms

Prediction of clean hydrogen production via biomass gasification by supervised machine learning algorithms was studied. Lab-scale gasification studies were performed in a steel fixed bed updraft gasifier having a cyclone separator. Pure oxygen, and dried air with varying flow rates (0.05–0.3 L/min) were applied to produce syngas (H2, CH4, CO). Gas compositions were monitored via on-line gas analyzer. Various regression models were created by using different Machine Learning (ML) algorithms which are Linear Regression (LR), K Nearest Neighbors (KNN) Regression, Support Vector Machine Regression (SVMR) and Decision Tree Regression (DTR) algorithms to predict the value of H2 concentration based on the other parameters that are time, temperature, CO, CO2, CH4, O2 and heating value. The highest hydrogen value in syngas was found around 35% vol. after gasification experiments with higher heating value (HHV) of approximately 3400 kcal/m30.05 L/min and 0.015 L/min were the optimum flow rates for dried air and pure oxygen, respectively. In modeling section, it was observed that H2 concentrations were being reflected effectively by the concentrations estimated through the proposed model structures, and by having r2 values of 0.99 which were ascertained between actual and model results.

ENERGETIC VALORIZATION OF SAWMILL RESIDUES THROUGH SLOW PYROLISIS PROCESS

Brazil is a large producer of sawmill wastes, commonly used to supply boilers and produce energy. In order to reduce unwanted characteristics of the material, thermochemical conversions through carbonization is an alternative. The aim of this study is to characterize the energetic proprieties of raw biomass and pyrolyzed biomass of sawmill residues. In order to analyze the environmental impact in the emission of pyrolysis gases, the behavior of gases during the thermic treatment was determined. Eucalyptus sp. and Pinus sp. residues slow pyrolysis was performed in an electric kiln, whose gases were conducted through a condensable gas recovery system and an online gas analyzer. The charcoal, bio-oil and non-condensable gases yields were estimated. The wood’s and charcoal’s proximate analysis (extractives, lignin, holocellulosis, ash content), higher heating value, equilibrium moisture and density were appraised. The wood’s chemical components were esteemed. Hardwood and softwood’s charcoal presented several differences, especially in yields due to types of lignin. Hardwoods produce a higher amount of acetic acid in slow pyrolysis. This acid was converted, mainly, in carbon dioxide and e a minor extent in methane and carbon monoxide. The gas release was affected by the temperature and wood’s composition. The main gases resulting from the slow pyrolysis of wood are CO2, CO, CH4, H2. The emission of this gases to the atmosphere in addition to increasing the environmental impact caused by the industry is still a waste of energy that could be harnessed more efficiently. Pyrolysis increased the energetic characteristics of sawmill waste. However, in spite of the advantages of carbonization, ways to mitigate the emission of gases emitted in an operational scale should be evaluated.

Compatibility of NiO/CuO in Ca–Cu Chemical Looping for High‐Purity H2 Production with CO2 Capture

AbstractCa–Cu chemical looping is a novel and promising approach for converting methane into pure H2 following the principle of sorption‐enhanced reforming. Its operational efficiency is largely determined by an appropriate coexistence of Cu‐based oxygen carriers and Ni‐based catalysts. Here, NiO/CuO composites are synthesized and their catalytic activity for H2 production is measured using a fixed‐bed reactor system equipped with an online gas analyzer. It is reported that the presence of CuO can hinder the activity of Ni‐based catalysts in H2 production, and experimental results show that the negative effect of CuO is strengthened with increasing CuO content and calcination temperature during sample preparation. With the help of a series of specific test and characterization techniques, interaction rules between NiO and CuO are further investigated and understood, and based on that an action mechanism model is proposed. Furthermore, an arrangement of mixed particles that avoids the intimate contact of CuO/NiO is suggested and tested, and a superior performance is demonstrated while observing no restrictions of CuO on Ni‐based catalysts in sorption‐enhanced steam‐methane reforming under the conditions of Ca–Cu chemical looping.

Dry Reforming of Methane at High Pressure in a Fixed-Bed Reactor with Axial Temperature Profile Determination

A continuously operated flow setup with fixed-bed reactor and online gas analysis enabled kinetic investigations of catalysts for the carbon dioxide reforming of methane under industrially relevant conditions at temperatures up to 1000 °C and at pressures up to 20 bar. A coaxial reactor design consisting of an inner- and an outer highly alloyed steel tube allowed obtaining axial temperature profiles by means of a moveable thermocouple. A NiAl2O4-based catalyst was tested at 820 °C and pressures of 1, 10 or 20 bar and compared to a conventional Ni catalyst used for steam reforming of methane. A significant cold spot was detected even when using only 10 mg of catalysts diluted in 1 g of silicon carbide. The specifically designed NiAl2O4/Al2O3 dry reforming catalyst with a high dispersion of the active Ni0 phase was found to be far superior to the conventional steam reforming catalyst.

Effect of limestone on the emission of NO during petroleum coke combustion

In order to investigate the effect of limestone on NO emission during petroleum coke combustion, experiments were conducted in a horizontal fixed-bed reactor connected with an on-line FTIR gas analyzer. Calcium based materials (limestone, CaO and CaSO4) were employed as solid additives, while CO2 and SO2 were mixed with the carrier gas to research their effects on NO emission. The results showed that char-N was the most important source of NO. Char-NO, which was produced by the combustion of char-N was significantly promoted with the addition of limestone. This was mostly caused by the catalytic effect of CaO, which was produced by the decomposition of limestone. To clarify the mechanism, pyrolysis experiments were carried out, and the transformation of fuel-N to gaseous-N and char-N was investigated. The conversion ratio of fuel-N to gaseous-N was promoted to a higher value by the additives, whereas the proportion of char-N slightly decreased. However, most of fuel-N still remained in char regardless of additives. Therefore, it could be concluded that the conversion ratio of char-N to NO obviously increased due to the addition of additives and then resulted in an increase in the overall emission of NO during combustion. The nitrogen species in raw material and chars were analyzed using X-ray photoelectron spectroscopy (XPS). The results showed that the conversion route of fuel-N to char-N during pyrolysis was not obviously affected by limestone, however, it was greatly affected by CaO. More nitrogen was restrained in the form of N-X in chars produced by the co-pyrolysis of petroleum coke and CaO, due to which, the positive effect of CaO on NO emission was weaker than that of the limestone.

Optical techniques for breath analysis: from single to multi-species detection

Optical spectroscopy can be used for trace-level gas analysis in different applications, including exhaled breath research. A common approach is the targeted on-line, real-time analysis of small molecules (two to five atoms). Currently, the methodology is normally used for the detection of single analytes at trace levels, or two to three species at most at the same time. The main limitation preventing sensitive multi-species detection has been the limited fast scanning range of the lasers used as light sources. This limitation is currently being eliminated by the availability of optical frequency combs (OFC) which offer wide spectral bandwidths and the benefits of a laser-type light source. Recent advances in mid-infrared OFC technology allow measurements in the so-called molecular fingerprint region of the electromagnetic spectrum, where many molecules have strong fundamental vibrational transitions that enable sensitive detection. Several technical hurdles remain to be overcome, but if these problems can be solved laser absorption spectroscopy has the potential to challenge mass spectrometry in on-line multi-species trace gas analysis.

The Effect of a Dietary Nitrate Supplementation in the Form of a Single Shot of Beetroot Juice on Static and Dynamic Apnea Performance.

The purpose of the present study was to assess the effects of acute nitrate ([Formula: see text])-rich beetroot juice (BRJ) supplementation on peripheral oxygen saturation (SpO2), heart rate (HR), and pulmonary gas exchange during submaximal static and dynamic apnea. Nine (six males and three females) trained apneists (age: 39.6 ± 8.2years, stature: 170.4 ± 11.5cm, and body mass: 72.0 ± 11.5kg) performed three submaximal static apneas at 60%, 70%, and 80% of the participant's current reported personal best time, followed by three submaximal (∼75% or personal best distance) dynamic apneas following the consumption of either a 70-ml concentrated BRJ (7.7mmol [Formula: see text]) or a [Formula: see text]-depleted placebo (PLA; 0.1mmol [Formula: see text]) in double-blind randomized manner. HR and SpO2 were measured via fingertip pulse oximetry at the nadir, and online gas analysis was used to assess pulmonary oxygen uptake ([Formula: see text]) during recovery following breath-holds. There were no differences (p < .05) among conditions for HR (PLA = 59 ± 11bpm and BRJ = 61 ± 12bpm), SpO2 (PLA = 83% ± 14% and BRJ = 84% ±9%), or [Formula: see text] (PLA = 1.00 ± 0.22L/min and BRJ = 0.97 ± 0.27L/min). The consumption of 7.7mmol of beetroot juice supplementation prior to a series of submaximal static and dynamic apneas did not induce a significant change in SpO2, HR, and [Formula: see text] when compared with placebo. Therefore, there is no apparent physiological response that may benefit free divers as a result of the supplementation.