Solid Combustion Products Research Articles

Biomass as a renewable energy source

Conventional energy sources such as fossil fuels, oil, coal and natural gas methane are non-renewable energy sources that were once considered primary energy sources and are depleted due to intensive use which has led to the escalation of the global energy crisis. In addition, the use of fossil fuels has a significant disadvantage in terms of the emission of toxic and harmful gases into the atmosphere that pollute the environment. An alternative to the use of fossil fuels is to obtain energy by processing biomass obtained in the process of photosynthesis and used as a raw material for bioenergy production. Biomass refers to non-fossilized biological material obtained from living or until recently living organisms and biodegradable organic or carbon-based material originating from plants, animals, plant materials and microorganisms. Bioenergy can be defined as a source of energy obtained from organic matter or biomass that is explicitly used for energy purposes. Bioenergy is the largest renewable energy source in the world, which still has a large share in the supply of renewable energy sources and accounts for 70% of the total supply of renewable energy sources. Today, bioenergy is the only form of energy that meets the criteria of a closed system, in terms of the creation of carbon dioxide and solid material products of combustion. Most of the carbon released in the form of carbon dioxide is absorbed by the next generation of plants through photosynthesis or through minerals from the soil. Therefore, biomass is becoming one of the key energy resources in the fight against global warming and depletion of fossil fuel reserves. It should be noted that the primary advantage of biomass as an energy source is not in its significant potential, but in renewability. Renewability is the essential advantage that biomass has over conventional, fossil fuels that are nonrenewable and therefore cannot be the basis for long-term planning of sustainable growth that implies rational use of energy. Biomass is not a source of energy in transition, as it is often presented, but a resource that is becoming increasingly important as a modern energy source. Therefore, this chapter provides a detailed overview of biomass as the world’s largest source of renewable energy, including definitions of biomass, a history of biomass use, and current bioenergy production from biomass. Data on theclassification/categorization of biomass and the main methods for the production of bioenergy from biomass, as well as the advantages and disadvantages of using biomass for bioenergy production, are presented. Emphasis is placed on the impact of biomass on the environment and biodiversity, as well as the most significant current challenges in the use of biomass for bioenergy production, including moisture content and density of biomass, its complexity and diversity, selection of optimal pre-treatment methods and biomass processing conditions and lack of biomass data, as well as challenges to the economic sustainability of bioenergy production from biomass and other environmental, economic and social challenges.

Historical overview and current status of the production and use of biomass

It is known that the combustion of fossil fuels is the main artificial source of CO2 emissions into the atmosphere and that it leads to environmental pollution, as well as global climate changes, i.e. the “greenhouse” effect. For these reasons, instead of fossil fuels used in various branches of energy and process technology, we shouldswitch to alternative energy sources that would significantly reduce the emission of CO2 and other greenhouse gases. Biomass is plant material obtained by the reaction of carbon dioxide from air, water and sunlight, the process of photosynthesis, in order to produce carbohydrates. In adecayprocess of organic matter from plant residues, carbon is returned to the atmosphere in a form of carbon dioxide and/or methane. In the atmosphere, during the oxidation process, carbon dioxide is formed from methane again, which completes the carbon cycle in nature. Today, biofuel is the only fuel that meets the criteria of a closed system in terms of the creation of carbon dioxide and solid material combustion products. Most of the carbon released in a form of carbon dioxide is absorbed by the next generation of plants through photosynthesis or through minerals from the soil. Thus, biomass is becoming one of the key energy resources in the fight against global warming and depletion of fossil fuel reserves. Additionally, replacing fossil fuels with biomass has a beneficial impact on reducing the emission of sulfur dioxide, which causesacid rainformation. It should be noted that the primary advantage of biomass as an energy source is not in its significant potential, but in its renewability. Renewability is the essential advantage of biomass over conventional, fossil fuels that are nonrenewable and therefore cannot be the basis for long-term planning of sustainable growth that implies the rational use of energy. In the field of energetics, the European Union (EU) is aimed at reducing CO2 emissions in order to achieve sustainable development, as well as reducing dependence on imported fuels and changes in pricesof energy-generating products (oil, gas, etc.). One way to reduce CO2 emissions is to increase the share of renewable sources in total energy production. The goal of the EU countries is to achieve 20% energy savings, 20% production of energy from renewable sources, 20% reduction of CO2 emissions ("20-20-20-targets") (Directive 2009/28/EC). In order to maintain energy stability and approach closer to the EU, Bosnia and Herzegovina, as well as the Republic ofSrpska, have signed a number of laws and regulations on the use of renewable energy sources. This paper provides review data on biomass potentials (wood and agricultural) in Bosnia and Herzegovina and in the neighbouring countries. Special emphasis is on agricultural biomass. Data on physical and chemical properties of agricultural biomass as an energy fuel are presented. Thermochemical procedures of biomass processing are provided, such as: pyrolysis, gasification and combustion and the possibility of using energy from these processes. Apparatus and furnaces of the considered processes used in industrial practice are presented. An overview of pollutant emissions from the biomass combustion process is also given.

CO2 Methanation: Solvent-Free Synthesis of Nickel-Containing Catalysts from Complexes with Ethylenediamine.

CO2 methanation was studied in the presence of nickel catalysts obtained by the solid-state combustion method. Complexes with a varying number of ethylenediamine molecules in the coordination sphere of nickel were chosen as the precursors of the active component of the catalysts. Their synthesis was carried out without the use of solvents, which made it possible to avoid the stages of their separation from the solution and the utilization of waste liquids. The composition and structure of the synthesized complexes were confirmed by elemental analysis, IR spectroscopy, powder XRD and XPS methods. It was determined that their thermal decomposition in the combustion wave proceeds in multiple stages with the formation of NiO and Ni(OH)2, which are reduced to Ni0. Higher ethylenediamine content in the complex leads to a higher content of metal in the solid products of combustion. However, different ratios of oxidized and reduced forms of nickel do not affect the initial activation temperature of nickel catalysts in the presence of CO2. It was noted that, after activation, the sample obtained from [Ni(C2H8N2)2](NO3)2 exhibited the highest activity in CO2 methanation. Thus, this complex is a promising precursor for CO2 methanation catalysts, and its synthesis requires only a small amount of ethylenediamine.

Differentiation of Rare Earth Elements in Coal Combustion Products from the Handan Power Plant, Hebei Province, China

As a potential source of REY (rare earth elements and yttrium), coal and its products have attracted much attention. In this paper, we aimed to study the enrichment and differentiation of rare earth elements in fly ash with different particle sizes and promote the full recovery and utilization of rare earth elements in fly ash. Our objective was to focus on the REY concentration in feed coal and its combustion products from the Handan Power Plant. We particularly focused on the distribution of REY in relation to different particle sizes, as well as on the state of occurrence (affinity), by applying stepwise chemical extraction and performing examinations using inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that the REY content is affected by the mineral composition of coal ash, and REY is more easily enriched in slag and fine ash than coarse ash. In general, the REY content decreased with the decrease in particle size in coarse ash, whereas the REY content increased with the decrease in particle size in fine ash. It was found that the concentration distribution of REY in solid combustion products is as follows: light REY (LREY) > medium REY (MREY) > heavy REY (HREY). This indicates that the enrichment of REY in solid coal products decreases with the increase in atomic number. The results also show that the occurrence state of REY in raw coal and coal ash undergoes no obvious change (residue state > organic/sulfide-bound state > iron–manganese-oxide-bound state > carbonate-bound state > exchangeable state).

Radiative properties of micron-sized Al/air premixed flames described by an effective medium core-shell formulation

The goal of this article is to contribute to the knowledge of the phenomenology of the poorly understood micron-sized Al/air flames, with the intention of assessing the viability of an energy carrier based on aluminum powders. To this end, the combustion efficiency, temperature, radiative profile, and solid combustion products of a flame prototype have been studied in depth. These fundamental parameters are required to explore the possibilities of recovering the energy released by these flames. In addition, a theoretical model has been established to analyze the radiative properties of the flame, derived for an optically thin collection of independent burning Al particles, each modeled by a core-shell geometry. The structure of the shell, made up of a cloud of alumina nanoparticles, has been modeled with an effective medium following the Maxwell-Garnett relation. This approach can reproduce the experimental results and is thus suggested as a starting point for modeling experiments characterized by strong emission by the nanoparticle cloud.

Analysis of solid combustion products to establish a theoretical model of the causes of thermal runaway of ternary lithium-ion battery overcharge and heating

It is difficult to determine whether ternary lithium-ion batteries (t-LIBs) were the “source” of the actual fire scene because of the little available direct evidence left after thermal runaway combustion of lithium-ion batteries (LIBs) and the lack of relevant analytical methods for t-LIBs after complete combustion. As a result, a large number of fires involving t-LIBs are controversially identified as the cause every year. In this paper, we conducted experiments on the two most common thermal runaway types of t-LIBs to investigate the correlation model between their combustion products and thermal runaway types. In the case of overcharge, the combustion products (black powder) of t-LIBs contain aluminum elements, which may be due to the thermal reaction of aluminum. In contrast, in the case of heating, the combustion products of t-LIBs have almost no detectable elemental aluminum. The reason may be due to the ability of the electrode material to continuously decompose and precipitate a large amount of metal oxides under the overcharge condition, which constitutes the condition for the occurrence of the aluminum thermal reaction, making the presence of Al2O3 in the combustion products. However, the lack of continuous current action under the heating condition prevents the generation of the aluminum thermal reaction.

Исследование и разработка компонентов газогенераторных составов на основе нитрата натрия для повышения безопасности при разрушении искусственных объектов

In the process of extraction of the piece stone and in the destruction of concrete and brick buildings in dense urban areas, the issue of safety and efficiency of work is very important. For reducing the percussive action during blasting operations, various methods and means are used. Currently, when extracting block stone, the substances are used that can create pressure in the hole due to the combustion reaction in the deflagration mode. The article is devoted to the research and development of gas-generating compositions based on the sodium nitrate to improve safety during the destruction of artificial objects. Sodium nitrate was chosen as an oxidizer, this is primarily due to the low cost of sodium nitrate, low sensitivity to mechanical and detonation effects, and a significantly lower content of harmful compounds in the combustion products compared to analogues. Magnesium and carbon (from a gas mask and walnut) were used as fuel. Tests for the flammability of mixtures and thermodynamic calculations of combustion parameters were carried out to determine the optimal ratio of the initial components. It was established that a sufficiently high efficiency and uniformity of combustion are observed at a ratio of the initial components of 60 % — NaNO3, 20 % — Mg, 20 % — C. X-ray phase analysis of solid combustion products was carried out. It is shown that the main products are magnesium oxide and sodium carbonate. Field experiments on the destruction of concrete blocks were carried out. The performed studies and field tests showed high efficiency and safety of the use of the developed gas generator composition for the destruction of artificial objects, which can be used for the directed destruction of artificial objects or rocks of medium strength with a coefficient of 8 on the scale of the professor MM. Protodyakonov. The destruction of the concrete block occurred without the scattering of individual stone fragments, the formation and propagation of a shock air wave.

Some Aspects of the Burning Process of Antimony and Potassium Manganate(VII) Compositions.

Antimony and potassium manganate(VII) compositions are widely used in time delay elements of detonators. Despite the existing literature on such systems, there is no complete information on the burning process of Sb/KMnO4 compositions in closed systems. There are also no data on the heat of their combustion in conditions of increased pressure without the access of oxygen from the air and on the composition of solid combustion products. These issues are the subject of the presented work.

Coupling effects of mineral components on arsenic transformation during coal combustion

Exploring arsenic (As) transformation during coal combustion is beneficial for reducing its pollution. Herein, combustion experiments were developed at 1100–1300 °C in a fixed-bed experimental system with 25 types of coal samples. The occurrences of As in coal and combustion products were characterized. All the original forms of As in coal were found to be unstable during combustion. As retained in ash existed as water-soluble and ion-exchangeable and residual forms, but only as residual form at combustion temperature above 1200 °C. The distribution of As in gaseous and solid combustion products varied widely by coal types, which resulted from the coupling effects of multi-minerals in coal. Co-combustion experiments were conducted using As model compounds and pure minerals, by which the interaction of Ca, Fe, Si and Al minerals to retain As was elucidated. The As transformation during coal combustion was primarily attributed to the coupling action of Ca, Fe, Si and Al minerals in coal. As a result, As was retained as Ca–Si–Al–As and Fe–Si–Al–As composite salts in the ash, which have little environmental hazard. Utilizing the coupling effects of multi-minerals during combustion help reduce As pollution from coal-fired plants.

VIS camera studies of the combustion process of pyrotechnic retarders of NGP-76 underwater fifle grenades

Abstract The study presents the combustion process of the multi-segment, low-gas pyrotechnic column of the warhead retarder of the NGP-76 underwater rifle grenade, designed to combat divers with an underwater shock wave. The combustion process, i.e. process from the ignition of the first segment of the retarder to the completion of combustion of its last segment, was recorded with a VIS camera filming at 30 frames per second. The rapid, short combustion of these outermost segments containing zirconium and Pb3O4 (minium) was accompanied by a blinding plume of brightly glowing particles of zirconium dioxide and lead vapor. The combustion of the middle segments formed from the MGS-54 pyrotechnic mixture containing BaCrO4, KClO4 and Sb2S5, determining the duration of the delay, i.e. the delay produced by the retarder, was much slower and longer than that of the outermost segments. During the combustion of each MGS-54 segment, the combustion front took the form of a flat section in the initial part of the segment, i.e. in the area of higher density, while in the further part of the segment (with lower density) the shape of the front became irregular. At the MGS-54 segment boundary, the combustion front halted briefly. Behind the combustion front, a conical tail of luminous solid combustion products became clearly visible at the MGS-54 segment boundary. The gaseous combustion products of the MGS-54 segments, formed in small amounts and revealed as white plumes, were probably KCl vapor and/or sulfur dioxide. After combustion, the retarder column of the MGS-54 segments was green in color due to the presence of chromium compounds, possibly Ba(CrO2)2.

Solvent-Free Method for Nanoparticles Synthesis by Solid-State Combustion Using Tetra(Imidazole)Copper(II) Nitrate

The development of solvent-free techniques for nanoparticles synthesis is one of the challenges of Green chemistry. In this work, the principled opportunity to obtain copper-containing nanosized particles without use of any solvents was shown. The copper complexes were prepared as precursors by the melting-assisted solvent-free synthesis. The formation of tetra(imidazole)copper(II) nitrate complex was confirmed by XRD, elemental analysis, FTIR spectroscopy, and thermal analysis. It was noted that their thermal decomposition occurs in two stages: (I) the low-temperature step may be related to redox interaction between organic ligands and nitrate-anions; (II) the high-temperature step may be related to the oxidation of the products of incomplete imidazole decomposition. TEM and XRD studies of solid products of complex combustion have shown that they are oxides with particle size less than 40 nm. Thus, the combustion of [Cu(Im)4](NO3)2 complex under air can be considered as a new approach to prepare nanosized particles of copper oxides without the use of solvents.

Ignition and combustion enhancement of composite fuel in conditions of droplets dispersion during conductive heating on steel surfaces with different roughness parameters

The ignition and combustion of single organic coal-water fuel (OCWF) droplets made of coal (30%), waste engine oil (35%), and water (35%) during conductive heating on the surfaces of the machine steel modified with abrasive materials and laser radiation were studied experimentally. The experimental conditions (material and temperature of the heating surfaces) corresponded to the operating conditions of modern furnace chambers of boilers at thermal power plants. It is found that the ignition delay and burnout times during conductive heating of OCWF droplets on steel surfaces can be controlled by changing the surface roughness parameters. On the example of 7-mg OCWF droplets with a radius of about 1.2 mm, it is shown that for processing of heating surfaces, it is necessary to use the abrasive materials with an average grit size of 100 μm to decrease the ignition and burnout times. The abrasive materials with an average grit size of more than 100 μm have an insignificant effect on the ignition delay and burnout times of OCWF droplets. However, such processing significantly increases the deposition of solid combustion products (ash deposits) with an increase in the surface roughness. Laser processing of steel surfaces is of particular interest in the implementation of passive ways of controlling the ignition and combustion characteristics of OCWF droplets. This way of changing the surface texture allows controlling the ignition delay and burnout times in a wide range of the heating source temperatures, as well as reducing the intensity of the solid product deposition on the heating surface during the OCWF combustion. The positive effect from laser processing of heating surfaces to intensify the fuel droplet combustion consists in increasing the velocity of vapor flows from combustible fuel components due to the droplet dispersion. This, in turn, intensifies the formation of a combustible vapour-gas mixture and increases the velocities of flame propagation together with the dispersion products of fuel droplets along the textured surface.

Composition of solid and gaseous primary combustion products of boron-based fuel-rich propellant

The investigation of the primary combustion products of boron-based fuel-rich propellants is conducive to understanding the mechanism of the two-stage combustion process and provides important information for the prediction and organization of secondary combustion processes. The present investigation methods include numerical simulation and experimental analysis. The former deviates considerably from the actual conditions. The latter is currently a reliable and practical method, although it is difficult to quantify when the components are complex. In this work, SEM, LPSA, XRD, XPS, IC, ICP–MS, AAS, EDS, and chemical analysis methods were employed to qualitatively and quantitatively analyze the 3 solid products (aggregations, condensed-phase products, and flocculent products) at 1, 5, and 10 bar. GC, GC–MS, and IC combined with chemical tests were adopted to investigate the gaseous products (including chlorine-containing gas) for the first time. The solid products primarily included B2O3, B(HO)3, unburned boron, KB5O8(H2O)4, KCl, C, NH4Cl, NH4Mg(H2O)6Cl3, B13C2, Fe3O4, Mo, MgO, Mg(OH)2, MoO3, C3N4, BN, MgCO3(H2O)3 (or MgCO3), MoO2, Fe4(Fe(CN)6)3, and FeB (or BFe4), and the first 7 were dominant. The reaction degree of boron was less than 50 wt% (increasing with increasing pressure), indicating the significance of the secondary combustion process. The reacted boron was likely to react with O and C but not with N. The generated B2O3 vapor easily combined with H2O to form B(HO)3 or reacted with KCl (from the thermal decomposition of KP) and H2O to produce KB5O8(H2O)4 after cooling. There was less B13C2 (its content increased with increasing pressure, resulting in increases in particle size), since it was easily oxidized to generate B2O3. NH4Cl was produced by the oxidation-reduction reaction between the NH3 and HClO4 released from large-sized AP, and some of it crystallized with MgCl2 and H2O to form NH4Mg(H2O)6Cl3. The gaseous products primarily included N2, H2, CO, CH4, CO2, C2H4, C2H2, HCl, C4H6, C3H6, Cl2, C6H6, and other hydrocarbons. N2 and H2 had the highest content. The N2 content increased with increasing pressure, while the content of the combustible gases decreased, indicating that high pressure promotes the propellant reaction. The results also show that high pressure was conducive to the low-temperature decomposition of AP (producing more HCl and Cl2) and the reaction of boron and hydrocarbons (generating more B13C2), while it had an adverse effect on the C reaction (producing less COx and mostly CO). Nevertheless, the increasing pressure had little effect on the combustion product components but did affect the content within the pressure range.

Chemical Analysis of the Cause of Thermal Runaway of Lithium-Ion Iron Phosphate Batteries

Due to the lack of effective methods to determine the cause of thermal runaway of lithium-ion batteries (LIBs), many fires are wrongly classified as LIBs fires. In this paper, we conducted different types of LIBs experiments to study the stage of thermal runaway and the distribution of combustion products. Through experiments analysis, we discovered for the first time the characteristic elements associated with the cause of thermal runaway of LIBs in the solid combustion products. Under overcharge conditions, the aluminum element was detected for the combustion products. The main reason is that a large amount of metal oxides precipitated from electrode materials react with aluminum foil at high temperatures to form alumina (Al2O3). However, under heating conditions, the aluminum element was not detected because of the lack of sufficient conditions for thermite reactions. The conclusion was verified by multiple sets of repeated experiments.

Behavior of thallium in pulverized coal utility boiler installations in Southwest China

ABSTRACT Thallium (Tl) is a toxic element that exists in coal at trace level. Coal-fired power plants (CFPPs) consume large amounts of coal and can potentially release this element into surrounding environment. However, knowledge of fates of Tl inside CFPPs and associated atmospheric emissions is still very limited. In this study, five CFPPs with pulverized coal boilers (PC) in Guizhou province, southwest China, were selected for investigation. All input and output solid materials and the stack flue gas samples were collected simultaneously. Tl concentrations in feed coal (0.10–0.34 mg·kg−1) of the five CFPPS were only a third to one half of the national average value. Tl concentrations were obviously higher in fly ash (0.39–1.13 mg·kg−1) than in bottom ash (0.09–0.25 mg·kg−1), indicating notable redistribution of Tl during coal combustion. Tl concentrations were low in limestone (0.01–0.02 mg·kg−1), flue gas desulfurization gypsum (0.01–0.03 mg·kg−1), and the stack flue gas (0.006–0.011 μg·Nm−3). Most Tl inside these CFPPs was captured by electrostatic precipitator or electrostatic precipitator-fabric filter (ESP/ESP-FF) fly ash (88.66%–97.44%), followed by bottom ash (2.13%–10.73%), gypsum (<3.89%), and stack emissions (0.01%–0.05%). Atmospheric emission factors of Tl from different CFPPs are in the range of 0.04–0.09 mg Tl·t−1 coal, 0.02–0.04 μg·(kW·h)−1, or 0.002–0.004 g Tl·TJ−1. Using these emission factors, a total of 3.96 ± 1.32 kg (range: 2.64–5.94 kg) Tl is estimated to be released into the atmosphere annually from CFPPs in Guizhou in 2017. To avoid the cross-media contamination from the combustion products, careful treatment of the captured fly ash, bottom ash, and gypsum is needed, considering that a large amount of Tl (average: 728 kg·yr−1; range: 664–792 kg·yr−1) is retained in these solid combustion products and the possibility of formation of more toxic Tl3+ during the combustion process. Implications: Thallium (Tl) is a rare but toxic element. Identifying and quantifying its source are high priorities for controling its contamination. Coal-fired power plants (CFPPs) were thought an important source of Tl, but few field studies had been conducted for this area. In this article, we investigated the fate of Tl in five pulverized coal utility power plants in Guizhou province, Southwest China, and found the Tl concentration in stack gas is in low levels of 0.006–0.011 μg·Nm−3, and less than 0.05% of total input of Tl is escaped into the ambient atmosphere. The majority of Tl (88.7%–97.4% of the total output) is detained by the ESP/ESP-FF fly ashes. Compared to the little amount (~4 kg·yr−1) of Tl that discharged into the atmosphere from Guizhuo’s CFPPs in 2017, more Tl (over 700 kg) ends up in the solid coal combustion products each year, which makes the need of careful disposal of this solid combustion waste to prevent the mobilization of Tl into the environment.

Thermodynamically Equilibrium Compositions of the Products Formed During the Filtration Combustion of the Metal-Containing Mixtures

Thermodynamic calculations for describing the compositions of the products formed in conditions of the filtration combustion of the metal-containing mixtures were carried out. The analysis of the equilibrium compositions of the products was carried out using the TERRA high-temperature thermochemical equilibrium calculation program. According to the results of calculations, the metals were divided into two groups. First one forms both the condensed and gaseous phases and in the second one ‒ metals that are only in the condensed phase. In case of the presence of metal compounds in the gas phase, as a rule, these are the following compounds: metals, oxides, hydroxides, hydrides, sulfides and metal sulfates. Metals of the second group cannot be subjected to mass transfer under conditions of the filtration combustion wave and will remain in solid combustion products (in ash).

Behaviors of Chromium in Coal-Fired Power Plants and Associated Atmospheric Emissions in Guizhou, Southwest China

Coal burning is a main concern for a range of atmospheric pollutants, including the environmentally sensitive element chromium (Cr). Cr migrates to the environment through stack emissions and can leach out from solid coal-burning byproducts, thereby causing adverse effects on the ecosystem. In this study, atmospheric emissions of Cr from six coal-fired power plants (CFPPs), as well as the distribution of Cr inside these CFPPs in Guizhou Province, Southwest China, were investigated. Among the six CFPPs, one was a circulating fluidized bed boiler and the others were pulverized coal boilers. The results showed that Cr in the feed fuel of these CFPPs ranged from 39.5 to 101.5 mg·kg−1 (average: 68.0 ± 24.8 mg·kg−1) and was approximately four times higher than the national and global average. Cr in the feed fuel correlated significantly with the ash yield, demonstrating that Cr in coal is closely associated with ash-forming minerals. After the coal combustion and the treatment by different air pollution control devices, most Cr (&gt;92%) in the installation was retained in the captured fly ash and bottom ash, with less as gypsum (0.69–7.94%); eventually, only 0.01–0.03% of Cr was emitted into the atmosphere with a concentration of 1.4–2.2 μg·Nm−3. The atmospheric emission factors of Cr for these utility boilers were as low as 14.86 ± 3.62 mg Cr·t−1 coal, 7.72 ± 2.53 μg Cr (kW·h)−1, and 0.70 ± 0.19 g Cr·TJ−1, respectively. About 981 kg·y−1 of Cr was discharged into the atmosphere from Guizhuo’s CFPPs in 2017, much lower than previous reported values. Most of the Cr in the CFPPs ended up in solid combustion products, identifying the need for the careful disposal of high-Cr-containing ashes (up to 500 mg·kg−1) to prevent possible mobilization into the environment.

Effect of oxygen content on the reaction course and radiation performance of Si/MTV system

Large numbers of studies show that silicon (Si) will not be oxidized into silicon fluoride (SiF4) and silicon oxide (SiO2) in the MSiTV (Magnesium Silicon Teflon Viton) system, which causes a waste of energy. The limited efforts in this paper focused on adding the oxidant barium nitrate (Ba(NO3)2) to the MSiTV pyrotechnics to study the oxidation reaction course and the effect of oxygen content on the radiation combustion performance. The infrared radiation of the agent during the combustion process is tested with a Spectraline SC7000 imaging spectrometer, and the combustion performance such as the burning area and radiation temperature is tested by the SC7000 thermal imager. The solid combustion products of the medicament are collected in a vacuum box combustion experiment and tested by infrared spectroscopy for their combustion products. Assumed that the amount of oxygen in the air participating in the reaction is constant. Then the oxygen difference theory (The calculation method is listed at the end of 3.1) can be used to calculate the hypoxia degree of the pyrotechnics and simply predict the oxidation reaction history. The experimental results show that the oxidation sequence of MSiTV compositions can be divided into 3 steps with the increase of oxidant content. The first step is to oxidize the incompletely reacted Magnesium (mg) to Magnesium Oxide (MgO). The radiation performance changes little during this process for the reaction release a lot energy and make up for the mass loss of MTV. The second step is the carbon ash oxidized to generate CO which greatly reduce the emissivity of the agent. The near-infrared radiation (NIR) spectral energies was reduced by up to 33% from 724.2 J/g*sr to 484.8 J/g*sr and the mid-infrared radiation (MIR) spectral energies reduced by up to 27% from 298.0 to 218.6 J/g*sr. The third step is the simultaneous oxidation of Si to SiO2 and Carbon monoxide (CO) to (carbon dioxide) CO2 by excess oxygen. The NIR intensity gradually decreases from 484.8 J/g*sr to 232.3 J/g*sr and the MIR spectral energies decreases from 218.6 J/g*sr to 122.3 J/g*sr for the reduction of MTV content even though the oxidation of Si released much heat. The far-infrared radiation (FIR) spectral energies of the pyrotechnics increased from 29.2 W/Sr to 59.9 W/Sr, an increase of 105% owing to the strong emissivity of Si in FIR. At this moment, the near-middle-far infrared ratio changed from 2.4: 1: 0.15 of MTV to 1.9: 1: 0.5.

Thermodynamic Estimating the Mass Transfer of Compounds of Rare Metals under Conditions of a Filtration Combustion Wave

A thermodynamic calculation of the possibility of mass transfer of metal compounds in conditions of filtration combustion of metal-containing mixtures was carried out. According to the results the metals were divided into two groups: the first group includes metals that form both condensed and gaseous phases, and the second group includes metals that are only in the condensed phase. Under conditions of filtration combustion wave due to continuous evaporation and condensation, it is possible to organize mass transfer of compounds of the first group metals in order to concentrate them in a specific zone of the reactor. Metals of the second group do not participate in mass transfer under the conditions of a filtration combustion wave and will remain in solid combustion products (in ash). Their concentration is possible only if there is a large amount of a combustible component in the initial mixture. In this case, due to the burnout of the combustible part and the preservation of metal compounds in the ash residue, their concentration will occur. Concentration of metals will allow performing their further economically justified recovery by traditional methods.

Evaluation of pressure oscillations by a laboratory motor

Aeroacoustic pressure oscillation is one of the important challenges in segmented solid rocket motors with high slenderness ratio. The reason for these oscillations can be searched in vortex shedding due to grain burning surfaces, holes and slots. In this paper, a novel sub-scaled motor was used for evaluation of aeroacoustic pressure oscillations. First, the related parameters to scale down using Buckingham’s Pi-theorem were determined and then the sub-scaled motor was designed and manufactured. After this, Strouhal number in various grain forms and vortex shedding prediction criteria have been discussed. Then, one-dimensional linear and non-linear solution approaches have been presented. To understand the motor internal flow and vortex shedding formation, steady state computational fluid dynamic performed for seven regression steps and finally, two static tests have been performed. Results show that various definitions for Strouhal number are useful only for primarily glance on vortex shedding and pressure oscillations and so CFD solution and the test program are inevitable for a correct understanding of the ballistic operational condition of the motor. Experimental results demonstrated the existence of such oscillations with frequencies nearly equal to axial modes. It seems that non-linear parameters have small effects on aeroacoustic pressure oscillation and therefore the linear solution is acceptable to obtain approximate data. Of course, it should be emphasized that linear solution represents oscillations on overall motor action time, whereas the output of non-linear solution depends on thermochemistry properties of solid propellant and combustion products. Therefore, with a non-linear solution, oscillations maybe occur in some intervals of action time. FFT (Fast Fourier Transformation) results demonstrated that although both first and second acoustic modes have been excited, the position of longitudinal oscillation has an important role on which one is dominant.