Air Oxygen Research Articles

Photonitration of pyrene adsorbed on silica gel with NO2

To examine the heterogeneous photonitration of pyrene with NO2 (approximately 0.2 ppm) on a heavy-traffic road, we studied the photonitration of pyrene adsorbed (pyreneads) on silica gel, which was used as SiO2 in particulate matter (PM), with NO2 (10.2, 2.0, and 0.20 ppm) under the atmospheric concentration ratio of pyreneads to NO2 and compared the results with those obtained in the dark. The effects of irradiation, wavelength, and oxygen concentration in a NO2 diluent on the photonitration were examined using a fluidized-bed column irradiated with simulated or real sunlight. Under the UV-light absorption of pyrene, the concentration of pyrene decreased exponentially in accordance with a pseudo-first-order reaction, while in the dark, it decreased sigmoidally in accordance with a H+-autocatalyzed reaction. The distribution and the yields of formed nitration products and their photooxidation products were affected by the light intensity, concentrations of NO2, and oxygen in the NO2 diluent. In the photonitration experiments using a high-pressure mercury lamp, formed 1-nitropyrene and minor dinitropyrenes were decreased by the transformation into their photooxidation products. Under 8-h exposure of pyrene to 10.2-ppm NO2, the yield of 1-nitropyrene was 42% in N2 and 28% in air. The oxygen inhibitory effect can be explained by the energy transfer from 1pyrene* to oxygen. Radical cation intermediate (pyrene•+-NO2−) was proposed for 1-nitropyrene formation. Under 24-h exposure of pyrene to 2.0-ppm NO2, the yields of 1-nitropyrene and the photooxidation products were 21.6% and 8.0%, respectively, in N2 and 4.9% and 3.8%, respectively, in air. Under 24-h exposure of pyrene to 0.20-ppm NO2, which is two times the 1-h NO2 standard in the USA and China, the yields of 1-nitropyrene and the photooxidation products were 2.3% and 3.4%, respectively, in N2 and 2.1% and 0.9%, respectively, in air. The significant decrease in the yields of 1-nitropyrene and the photooxidation products under the concentration of 0.20-ppm NO2 can be explained by their easy photodecomposition with the increase in the photolysis of pyrene. Under the concentration of 0.20-ppm NO2 in air, which is approximately the concentration on heavy-traffic roads, the decay rate of pyrene by the photonitration was increased by own photolysis, although the photonitration was inhibited by oxygen in air.

An online physical simulation method for enhanced oil recovery by air injection in shale oil

In order to understand the mechanism of air flooding shale oil, an online physical simulation method for enhanced shale oil recovery by air injection was established by integrating CT scanning and nuclear magnetic resonance (NMR). The development effect of shale oil by air flooding under different depletion pressures, the micro-production characteristics of pore throats with different sizes and the mechanism of shale oil recovery by air flooding were analyzed. The effects of air oxygen content, permeability, gas injection pressure, and fractures on the air flooding effect in shale and crude oil production in pores with different sizes were analyzed. The recovery of shale oil can be greatly improved by injecting air into the depleted shale reservoir, but the oil displacement efficiency and the production degree of different levels of pore throats vary with the injection timing. The higher the air oxygen content and the stronger the low-temperature oxidation, the higher the production degree of pores with different sizes and the higher the shale oil recovery. The higher the permeability and the better the pore throat connectivity, the stronger the fluid flow capacity and the higher the shale oil recovery. As the injection pressure increases, the lower limit of the production degree of pore throats decreases, but gas channeling may occur to cause a premature breakthrough; as a result, the recovery increases and then decreases. Fractures can effectively increase the contact area between gas and crude oil, and increase the air sweep coefficient and matrix oil drainage area by supplying oil to fractures through the matrix, which means that a proper fracturing before air injection can help to improve the oil displacement effect under a reasonable production pressure difference.

Lung ultrasonography for detection of atelectasis in adults undergoing robot assisted laparoscopic pelvic surgeries

Introduction: Robot-assisted laparoscopic pelvic surgeries are minimally invasive techniques that require the patient to be placed in the steep Trendelenburg position. Pneumoperitoneum further increases the risk of postoperative pulmonary complications. We used lung ultrasound score (LUSS) to detect post-operative atelectasis in this subset of patients.
 Methodology: Patients aged 18 to 70 y with ASA physical status I/II undergoing robot assisted pelvic surgeries in steep Trendelenburg position were enrolled. Patients were mechanically ventilated with 50% oxygen in air with a tidal volume of 6 to 8 ml/kg in volume control mode to maintain an end tidal carbon dioxide at 35−45 mmHg with positive end-expiratory pressure (PEEP) of 5 cmH2O. Ultrasonographic assessment was done; before induction (A), after extubation (F), 12 h (G) and 24 h after surgery (H) by dividing chest into 12 regions.
 Results: A total of 1152 cine-loops acquired during the study period in 32 patients were analyzed. Incidence of postoperative atelectasis was 87.5% and each lung ultrasound examination required 12.35 ± 4.68 min. Statistically significant fall in PaO2 was recorded at extubation from baseline and intra-operative values (P < 0.0001). Statistically significant difference was established between change in baseline and post-extubation LUSS to the total volume of fluid given (P = 0.002).
 Conclusion: A high incidence (87.5%) of atelectasis in adults after robot assisted laparoscopic pelvic surgeries was detected using lung ultrasound score. Lung oxygenation decreased significantly after steep Trendelenburg position and extubation. The observed statistical difference in total IV fluids administered between patient subgroups who showed increased ultrasound signs of lung edema from the A period to the F period, although suggestive of association, is no evidence of causation.
 Abbreviations: ARISCOT- Assess Respiratory Risk in Surgical patients in Catalonia; LUS- Lung Ultrasound; LUSS- Lung Ultrasound Score; OR- Operating room; PEEP- Positive End-Expiratory Pressure
 Key words: LUSS; Lung ultrasound score; Pneumoperitoneum; Robotic Surgery; Ultrasonography
 Citation: Sethi S, Kathuria R, Samra T, Saini V, Toshkhani D, Kushal P. Lung ultrasonography for detection of atelectasis in adults undergoing robot assisted laparoscopic pelvic surgeries. Anaesth. pain intensive care 2023;27(4):573−578; DOI: 10.35975/apic.v27i4.1503
 Received: October 28, 2021; Reviewed: June 06, 2022; Accepted: September 17, 2022

NOx Emission Limits in a Fuel-Flexible and Defossilized Industry—Quo Vadis?

The reduction of CO2 emissions in hard-to-abate industries is described in several proposals on the European and National levels. In order to meet the defined goals, the utilization of sustainable, non-fossil fuels for process heat generation in industrial furnaces needs to be intensified. The focus mainly lies on hydrogen (H2) and its derivates. Furthermore, biofuels, e.g., dimethyl ether (DME), are considered. Besides possible changes in the process itself when substituting natural gas (NG) with alternative fuels, the emission of nitrogen oxides (NOx) is a major topic of interest. In current European standards and regulations, the NOx emissions are specified in mg per m3 of dry off-gas and refer to a reference oxygen concentration. Within this study, this limit specification is investigated for its suitability for the use of various fuel-oxidizer combinations in industrial combustion applications. Natural gas is used as a reference, while hydrogen and DME are considered sustainable alternatives. Air and pure oxygen (O2) are considered oxidizers. It is shown that the current specification, which is built on the use of fossil fuels, leads to non-comparable values for alternative fuels. Therefore, alternative NOx limit definitions are discussed in detail. The most suitable alternative was found to be mg per kWh. This limit specification is finally being investigated for its compliance with current regulations on various aspects of Continuous Emission Monitoring Systems.

Peculiar Properties of Template-Assisted Aniline Polymerization in a Buffer Solution Using Laccase and a Laccase-Mediator System as Compared with Chemical Polymerization.

The conventional chemical polymerization of aniline has been described in multiple publications, while enzymatic polymerization has been poorly explored. A comparative study of the template-assisted enzymatic and chemical polymerization of aniline in a buffer solution of sodium dodecylbenzenesulfonate micelles was performed for the first time. The high-redox potential laccase from the fungus Trametes hirsuta was used as a catalyst and air oxygen served as an oxidant. Potentiometric and spectral methods have shown that oligomeric/polymeric products of the enzymatic polymerization of aniline are synthesized in the conducting emeraldine salt form immediately after the reaction is initiated by the enzyme. The use of the laccase-mediator system enabled a higher rate of enzymatic polymerization and a higher yield of final products. Potassium octocyanomolybdate (IV) served as a redox mediator. The products of the enzymatic polymerization of aniline were studied by the ATR-FTIR, MALDI-TOF and atomic force microscopy methods. The chemical oxidative polymerization of aniline under the same conditions resulted in forming a non-conducting dark brown product.

Spectroscopic and electrochemical analyses elucidating capacity degradation mechanism of iron-ligand complex and air in all iron aqueous redox flow batteries

Capacity degradation mechanism of all iron aqueous redox flow battery (ARFB) using iron and 2,2-bis(hydroxymethyl)-2,2′,2′'-nitrilotriethanol (Fe(BIS-TRIS)) complex as redox active material for anolyte is analyzed. The capacity degradation occurs by the contact of Fe(BIS-TRIS) and oxygen in air, while this is confirmed by spectroscopic and electrochemical ways including the use of Beer-Lambert’s law. According to the analysis, charging/discharging step of catholyte including Fe(CN)6 does not affect exposure to oxygen, whereas self-discharge occurs at the step of anolyte including Fe(BIS-TRIS) that is exposed to oxygen, promoting its performance decay. This is proved by ARFB single cell tests using the electrolytes. When the electrolytes are open to air, its capacity is considerably degraded within 20 cycles. However, when anolyte is sealed to avoid contact with air, its capacity preserves 96 % of initial value even after 100 cycles. This is because the undesirable self-discharge of Fe(BIS-TRIS) affects the degradation in performance of ARFB single cell. We elucidate effect of oxygen on performance of ARFBs using Fe(BIS-TRIS) with UV–VIS spectroscopic method.

Numerical investigation of combustion characteristics under oxygen-enriched combustion combined with flue gas recirculation in a cement rotary kiln

A new technology combining oxygen-enriched combustion with flue gas recirculation (OEC-FGR) in the cement rotary kiln is put forward, based on the technical complementarity of these strategies. The effects of the flue gas recirculation rate on the combustion characteristics and NOx formation with a primary air oxygen concentration of 27% in a cement rotary kiln of 5000 t/d capacity are numerically investigated. The introduction of recirculating flue gas has significant influences the flame size, temperature distribution, and NOx formation. As the FGR rate increases, the flame lengthens and the high-temperature region shrinks. At the same time, the position of the temperature peak is delayed and the length of the calcination section is shortened. Furthermore, NOx formation is remarkably reduced, owing to the lengthened low oxygen reduction zone and lower temperature. As the FGR rate increased from 0% to 27%, the maximum NOx concentration on the center line in the kiln and the NOx concentration at the outlet decreased by 392 ppm and 343 ppm, respectively, and both decreased the most when the FGR rate increased from 0% to 10%. Moreover, good burnout is obtained with the new combustion technology, although considerable CO is generated near the burner. Since the length of the clinker calcination zone may be adversely affected by an excessively high FGR rate, the FGR rate should be carefully determined. In this study, a better compromise between calcination performance and NOx reduction could be achieved when the FGR rate was 20% .

RATIONAL CONDITIONS OF PRODUCING THE ACTIVATED CARBON WITH WELL-DEVELOPED NANOPOROUS STRUCTURE FOR THE TREATMENT OF NATURAL AND WASTE WATERS

Rational conditions for the activation of coal of a high stage of metamorphism (anthracite) have been determined, which allow the development of a nanoporous structure. Obtained activate carbon with nanoporous structure can be use for the treatment of natural and waste waters have been carried out. The structurally sorptive characteristics and granulometric size composition of obtained samples were determined. It was established that in order to obtain a sorbent with specified properties, it is necessary to introduce oxygen into the reacting mixture at the second stage of anthracite activation and control the activation time. The activation in the first stage was carried out with steam at a temperature of 750–800 °C, and in the second stage – with steam in the presence of air oxygen at 280–300 °C. The rational content of oxygen in the activating mixture is in the range of 2.7–4.4 %, while the specific surface area of activated carbon increases, which corresponds to nano-sized pores and, accordingly, the volume of the adsorption space of coal. The process led to the development of mesoporosity ~ 0.2–0.3 cm3/g, after which the microporous sample of activated carbon was impregnated with a surfactant solution. Thus, the rational conditions of activation are the duration of the process of 1.5 hours in the presence of 4.4 % oxygen in the activating mixture. It is shown that the largest values of the total specific surface area and the specific surface area of mesopores are achieved when using ionic surfactants with alkyl chain length n = 10–16 as modifiers. In particular, the use of sodium dodecyl sulfate СН3(СН2)11SO3Na as a modifier allows to obtain the largest value of the total surface Stot 1030 m2/g and the surface of mesopores Smе 334 m2/g. It was established that the activation of modified samples of activated carbon leads to a decrease in the size of granules.The content of fractions with a size of 1.0–2.0 mm and 0.5–1.0 mm is 80–85 %, which are rational for use for water purification from organic compounds.

Understanding alkenyl succinic anhydride (ASA) size reversion due to autooxidation

Alkenyl succinic anhydride (ASA) is a sizing agent. The wettability of paperboard decreases when ASA is applied. The efficacy of ASA in board can be reversed under certain conditions, making the paper more hydrophilic and of lesser quality/value. Although it is broadly known that ASA size reversion is due to autooxidation in the presence of oxygen in air, the environmental parameters that initiate or catalyze this reaction are not well understood. Six different experimental set ups were used to understand how temperature, daylight, fluorescent light, ultravio-let (UV) light, and darkness affect oxidation of ASA. Cobb values and pyrolysis gas chromatography-mass spectrom-etry (Py-GCMS) results show that size reversion is not a simple oxidation. The oxidation reaction was found to be significantly light dependent. Temperature variations were found to have moderate effect on the chemical stability.

Effect of Disorder in the Structure of a Ferroelectric Composite Material xPbSe·(1 – x)PbSeO3 on the Smearing of the Phase Transition

This paper analyzes the experimental and theoretical studies of the problem of a diffuse phase transition (PTC) in a composite material xPbSe⋅(1 – x)PbSeO3, in which x varies from 0 to 1. The decrease in stability in the virtual cubic phase of lead selenide (PbSe) is achieved by oxidizing it with atmospheric oxygen and forming a ferroelectric disordered monoclinic phase of lead selenite (PbSeO3). The mechanism of lead selenide oxidation by air oxygen is studied by X-ray diffractometry, optical reflection in the infrared region of the spectrum, X-ray emission analysis (the chemical shift method), nuclear magnetic resonance, studies of AC and DC conductivity, differential scanning calorimetry, and other methods. The reason for the smearing of the phase transition in the xPbSe⋅(1 – x)PbSeO3 composite, in which x varies from 0 to 1, is analyzed based on the previously obtained experimental results of its detection.

Neutral Red and Safranin Т in the Photopolymerization of Methyl Methacrylate and Other (Meth)Acrylate Monomers

Features of the polymerization of methyl methacrylate and a number of other (meth)acrylate monomers in the presence of catalytic systems based on phenazine dyes (Neutral Red and Safranin Т) under visible light irradiation are investigated. It is shown that amines of various structure as well as air oxygen affect the kinetic features of polymerization and the molecular weight characteristics of polymers. It is found that polymerization may proceed in the controlled mode up to high conversions at room temperature and a low photocatalyst concentration, among them without preliminary degassing of the reaction medium.

Increasing power output and isopropanol biodegradation by trickle-bed microbial fuel cells by optimizing air relative humidity and oxygen flux at cathode

The cathode air flow rate and relative humidity (RH) of a trickle-bed microbial fuel cell (TB-MFC) were optimized using the response surface methodology to obtain a high oxygen flux and a low electrical resistance at the cathode and thereby promote the oxygen reduction reaction. Under optimal air flow rate (2.20 L/min) and RH (20%) conditions, the TB-MFC system exhibited the highest oxygen flux (3.08%/cm2‧min) and the lowest resistance (5.33 Ω); its regression model had an R2 > 0.95 and the desirability coefficient was 0.78. These results demonstrate that the optimized air flow rate and RH support high oxygen flux and low resistance at the cathode. Using biochar combined with conductive carbon black (CCB) as the cathodic catalyst and optimal cathodic operating conditions, yielded a mineralization efficiency of isopropanol of 96.9% and a power density of 555 mW/m3 at an empty bed residence time and isopropanol influx concentration of 60 s and 300 ppmv, respectively. These results suggest that isopropanol can be effectively mineralized directly into CO2 and H2O by a TB-MFC, reducing the by-product accumulation, and thus increasing the power generation of the TB-MFC. Optimizing the air flow rate and RH of the biochar/CCB-based cathode in the TB-MFC increases the oxygen flux and reduces the electrical resistance of the cathode of TB-MFC, which can thus be used to treat exhaust gases that contain organics.

Physico-chemical features of tool wear of PCBN

The effects of physical and chemical interaction between a tool equipped with a superhard composite based on cubic boron nitride (SBNB) and the components of the material being processed and air oxygen were studied using the results of the study of model thermal activation and real thermal triboactivation of the tool contact areas in the cutting zone. It is shown that, depending on the thermobaric load, chemical interaction between the elements of the contacting materials and air oxygen is realized at the working areas of the tool: – the tool material is oxidized by air oxygen to form boric anhydride; – the metals that make up the processed material interact with boron nitride to form borides of the MeхB type; – the effect of contact-reactive melting is realized on the contact surfaces of the tool with the formation and melting of eutectics of the Me-MeхB type. The performance of a cutting tool equipped with a composite based on cubic boron nitride is limited by the chemical interaction of the tool material with the material being processed and air oxygen in the cutting zone. The cutting temperature corresponding to the formation of a liquid phase from the products of interaction on the working areas of the tool is an attractor for increasing the cutting speed.

Effect of daylight and air oxygen on nanozymatic activity of unmodified silver nanoparticles: Shelf-stability

In this work, unmodified silver nanoparticles were synthesized by a simple and cost-efficient method and then characterized by TEM imaging and UV-Vis. spectroscopy. Thereafter, their nanozymatic activity was investigated by catalyzing the oxidation of 3,3’,5,5’-tetramethyl-benzidine (TMB) as the standard peroxidase substrate. The results exhibited a specific activity as high as 5.4 µM min-1 for the as-prepared unmodified silver nanoparticles. Afterward, the effect of daylight and air oxygen on the peroxidase-like activity of these nanozymes was checked within 7 days. The results revealed that the activity of unmodified silver nanoparticles was approximately retained at about 75%, and 63% after 7 days exposing daylight and air oxygen, in order. The shelf-self of the as-prepared nanozymes was also investigated at 4 ℃ under dark conditions, revealed that these nanozymes saved about 96% of their initial activity after 10 days of storage at 4 ℃ under dark conditions. KEYWORDS:Unmodified silver nanoparticles; Peroxidase-like nanozymes; Air oxygen; Daylight; Shelf-stability

Effect of daylight and air oxygen on nanozymatic activity of unmodified silver nanoparticles: Shelf-stability

In this work, unmodified silver nanoparticles were synthesized by a simple and cost-efficient method and then characterized by TEM imaging and UV-Vis. spectroscopy. Thereafter, their nanozymatic activity was investigated by catalyzing the oxidation of 3,3’,5,5’-tetramethyl-benzidine (TMB) as the standard peroxidase substrate. The results exhibited a specific activity as high as 5.4 µM min-1 for the as-prepared unmodified silver nanoparticles. Afterward, the effect of daylight and air oxygen on the peroxidase-like activity of these nanozymes was checked within 7 days. The results revealed that the activity of unmodified silver nanoparticles was approximately retained at about 75%, and 63% after 7 days exposing daylight and air oxygen, in order. The shelf-self of the as-prepared nanozymes was also investigated at 4 ℃ under dark conditions, revealed that these nanozymes saved about 96% of their initial activity after 10 days of storage at 4 ℃ under dark conditions. KEYWORDS:Unmodified silver nanoparticles; Peroxidase-like nanozymes; Air oxygen; Daylight; Shelf-stability

Structure stability and optical properties of spatial confined all-inorganic perovskites nanocrystals under gamma-ray irradiation

Probing the structure stability and optical properties of halide perovskites under radiation is of great significance to extend their applications in aerospace and radiation detection. However, the intrinsic radiation stability of perovskites still remains controversial due to the interferences of environmental factors such as moisture and oxygen in air. In this work, we reported CsPbBr3 perovskite nanocrystals (CsPbBr3 NCs) that encapsulated in amorphous glass to isolate moisture and oxygen in air, based on which the gamma-ray irradiation effect of these spatial confined CsPbBr3 NCs was investigated in detail. The results demonstrated that CsPbBr3 NCs display excellent structural stability accompanied with increased particle size and enhanced photoluminescence after an accumulated dose of 240 krad (Si). This improvement originates form the defect passivation on the perovskite surface under gamma-ray irradiation, which suppresses the nonradiative recombination substantially. Meanwhile, the decomposition of CsPbBr3 NCs occurred at the dose of 360 krad (Si) and even higher, along with a deteriorated optical performance. This work provided an ideal platform to understand the intrinsic stability of halide perovskites upon radiation conditions.

The effect of teak plantation growth on air temperature and oxygen level in green open spaces of the Research and Innovation Department of Perhutani Forestry Institute (PeFI)

Urban land utilization for urban facilities construction continues to grow and impact the urban heat island making the city uncomfortable. Green open space (GOS) is a space within a city with its function in ecological, social, economic, and architectural functions. The purpose of the research was to determine the characteristics of GOS and the effect of teak plantation growth on air temperature and oxygen (O2) levels. The research was conducted from May to November 2021 using an observational design with a purposive sampling technique, considering the variations in measured variables: number of trees, daily climate, micro-climate difference, O2 level, and wind speed. The research analysis used a descriptive study approach relevant to the observed conditions. The teak arboretum and teak hedge orchard were the GOS at the Perhutani Forestry Institute (PeFI). Arboretum had a lower temperature and higher humidity than teak hedge orchard, making the arboretum in the cool-climate category with an ideal temperature of 26.9° C and dry humidity category. This means that the PeFi office was categorized as comfortable. The oxygen levels in PeFI were between 20.9 to 21.1%, meaning that the oxygen in the PeFI environment is highly available with the presence of GOS from the observed sites.

Efficacy of preoxygenation administration in volunteers, in extending the end-expiration breath-hold duration for application to abdominal radiotherapy

End expiration breath hold (EEBH) is the preferred motion management method for abdominal Stereotactic Ablative Body Radiotherapy (SABR) treatments. However, multiple short EEBHs are required to complete a single treatment session. The study aimed to determine the efficacy of preoxygenation with hyperventilation in extending an EEBH duration.We randomised 10 healthy participants into two arms, each included breathing room air and oxygen at a rate of 10 L per minute (l/min) without hyperventilation for four minutes, and normally for four minutes and with hyperventilation for one minute at a rate of 20 breaths/minute for hyperventilation. The type of gas was blinded from the participants for each test. EEBH durations were then recorded, as well as systolic blood pressure, SpO2 and heart rate. A discomfort rating was also recorded after each breath hold.A significant increase in duration of almost 50% was observed between normal breathing of room air and breathing oxygen normally followed by hyperventilation. Vital signs remained consistent between the 4 tests. The tests were well tolerated with 75% of participants recording none or minimal discomfort.Preoxygenation with hyperventilation could be used to increase the EEBH duration for abdominal SABR patients which would assist in the accuracy of these treatments and possibly resulting in a reduction of overall treatment times.

IGNITION OF WOODEN BIOMASS PARTICLES UNDER MICROWAVE EXPOSURE AT HIGH-TEMPERATURE RADIATION-CONVECTIVE HEATING

Link for citation: Syrodoy S.V., Malyshev D.Yu., Kostoreva Zh.A., Kostoreva A.A., Omarov A.A. Ignition of wooden biomass particles under microwave exposure at high-temperature radiation-convective heating. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.159-167. In Rus. The relevance. Despite the active development of technologies for the production of electrical energy by means of wind power generators and solar batteries, by 2100, most of the energy will still be generated at thermal power plants that burn fossil fuels. As a rule, thermal power plants use coal as fuel (about 40 %). However, it should be noted that during the combustion of coal in the furnaces of steam and hot water boilers, toxic oxides of sulfur and nitrogen are intensively formed. In this regard, many scientists of the world working in the field of energy are working to create new innovative technologies for the eco- and energy-efficient production of heat and electricity. The latter include technologies for burning woody biomass in the furnaces of steam and hot water boilers of thermal power plants. The use of woody biomass can significantly reduce the environmental impact of thermal power plants on the atmosphere. However, no technology has yet been developed to burn wood with high energy efficiency. The latter is due to the high moisture saturation of woody biomass in its initial state. The main aim: experimental determination of the main stages and identification of a complex of physicochemical processes occurring together during the ignition of woody biomass particles under microwave exposure under high-temperature radiation-convective heating. Object: dry and moisture-saturated wood of two types (pine and cedar). The relative humidity of the wood from which the particles were made (with a characteristic size of 4 mm) varied from 6 (relatively dry biomass) to 42 % (moisture-saturated wood). Method. To establish the main characteristics of wood particle ignition under microwave exposure under high-temperature radiation-convective heating, a special experimental stand was developed, representing a reaction tube with heat-insulated radio-transparent walls through which a high-temperature oxidizer (air oxygen) was blown. The wood particle was mounted on the axis of the pipe so as to fall into the focus of the emitter. All processes were recorded by a high-speed video camera. Results. The paper introduces the results of experimental studies of ignition of dry and wet particles of woody biomass in the environment of air heated to high temperatures under conditions of radiation-convective and radiation-convective microwave heating. A significant influence of the type of wood on the ignition delay times (tign) was established. Rather significant effect of heating conditions on ignition is also shown, since microwave exposure leads to an acceleration of ignition of woody biomass particles. It was shown that during the ignition of wet wood particles, the effect of exposure to microwave radiation (acceleration of ignition) is more significant compared to ignition of dry wood particles. It was also found that the moisture content (φ) of woody biomass significantly affects the ignition delay times (increase in φ leads to growth in the tign value). The regularities established in the conducted experiments illustrate the prospects of using woody biomass (including moisture-saturated) in thermal power engineering as the main fuel.

Large-Scale Experimental Simulations of In Situ Coal Gasification in Terms of Process Efficiency and Physicochemical Properties of Process By-Products

This paper presents a series of surface experiments simulating underground coal gasification (UCG). The main goal of the experiments was to investigate the influence of the gasification medium and the coal rank on the gasification process. Four multi-day trials were carried out using a laboratory gasification facility designed for the large-scale experimental simulations of UCG and located in the Experimental Mine “Barbara”, located at Mikołów, Poland. Two Polish bituminous coals were investigated: coal sourced from “Piast-Ziemowit” mine and coal sourced from “Wesoła” mine. Each of the two coals was gasified in two separate experiments using oxygen-enriched air (OEA) and pure oxygen as the respective gasifying agents. Gasification with oxygen resulted in significantly higher gas quality and higher process efficiency than gasification with OEA. Higher concentrations of hydrogen (23.2% and 25.5%) and carbon monoxide (31.8% and 33.4%) were obtained when oxygen was used as a gasifying reagent, while lower concentrations were obtained in the case of gasification with OEA (7.1% and 9.5% of hydrogen; 6.4% and 19.7% of carbon monoxide). Average gas calorific values were 7.96 MJ/Nm3 and 9.14 MJ/Nm3 for the oxygen experiments, compared to 2.25 MJ/Nm3 and 3.44 MJ/Nm3 for the OEA experiments (“Piast-Ziemowit” coal and “Wesoła” coal, respectively). The higher coalification degree of “Wesoła” coal (82.01% of carbon) compared to the “Piast-Ziemowit” coal (68.62% of carbon) definitely improves the gas quality and energy efficiency of the process. The rate of water condensate production was higher for the oxygen gasification process (5.01 kg/h and 3.63 kg/h) compared to the OEA gasification process (4.18 kg/h and 2.63 kg/h, respectively), regardless of the type of gasified coal. Additionally, the textural characteristics (porosity development) of the chars remaining after coal gasification experiments were analyzed. A noticeable development of pores larger than 0.7 nm was only observed for the less coalified “Piast-Ziemowit” coal when analyzed under the more reactive atmosphere of oxygen.