Fine ash formation during combustion of pulverised coal-coal property impacts

In many countries, legislation has been enacted to set guidelines for ambient concentrations and to limit the emission of fine particulates with an aerodynamic diameter less than 10 μm (PM₁₀) and less than 2.5 μm (PM_2.5). Ash particles are formed during the combustion of coal in pf boilers and fine ash particulates may potentially pass collection devices. The ash size fractions of legislative interest formed during coal combustion are the result of several ash formation mechanisms; however, the contribution of each of the mechanisms to the fine ash remains unclear. This study provides insight into the mechanisms and coal characteristics responsible for the formation of fine ash. Five well characterized Australian bituminous coals have been burned in a laminar flow drop tube furnace in two oxygen environments to determine the amount and composition of the fine ash (PM₁₀, PM_2.5 and PM₁) formed. Coal characteristics have been identified that correlate with the formation of fine ash during coal combustion. The results indicate that coal selection based on (1) char characterization and (2) ash fusion temperature could play an important role in the minimization of the fine ash formed. The implications of these findings for coal selection for use in pf-fired boilers are discussed.     

Characterization of Fine Particulate Emissions from Casting Processes

Fine particle (PM_2.5) emission rates and compositions from gray iron metal casting foundry were characterized for No-Bake molds poured at the Research Foundry located at Technikon, LLC (McClellan, CA). For each mold, PM_2.5 was collected for chemical analysis, and particle size distributions were measured by an Electrical Low Pressure Impactor (ELPI) to understand PM emissions during different part of the casting process. Molds prepared with phenolic urethane binders were poured with Class 30 gray cast iron at 1,427–1,480°C. PM_2.5 was collected from the pouring, cooling, and shakeout processes for each mold. Most of the PM_2.5 mass emitted from these processes was composed of carbonaceous compounds, including 37–67% organic carbon (OC) and 17–30% elemental carbon (EC). Oxides of aluminum (Al), silicon (Si), calcium (Ca), and iron (Fe) constituted 8–20% of PM_2.5 mass, and trace elements (e.g., K, Ti, Mn, Cu, Zn, and Pb) contributed 3–6%. Chemical abundances in PM were different between pouring and shakeout for each discrete mold. PM_2.5 mass emissions from pouring were 15–25% of the total from each discrete mold. Ultrafine particles (< 0.1 μm) contributed less than 1% of PM_2.5 mass, but nearly all of the particle numbers. Different mechanisms for pouring and shakeout result in variations in chemical abundances and particle size distributions. The highest PM_2.5 mass and number concentrations were observed when shakeout started. PM_2.5 size distributions in mass concentration during shakeout contained particles in the tail of coarse particles (1.6–2.5 μm) and a vapor condensation mode (0.65–1.6 μm). Flame conditions, vaporization, thermal decomposition of organic materials, and the variability of mold breakup during shakeout affect PM emission rates. A detailed chemical speciation for size-segregated PM samples at different process points needs to be conducted at full-scale foundries to obtain emission factors and source profiles applicable to emission inventories, source receptor modeling, and implementation of emission standards.     

Morphology and chemistry of fine particles emitted from a Canadian coal-fired power plant

Particles emitted from coal-fired power plants burning subbituminous coal from Alberta, Canada were examined for total particulates (PM) and size fractions PM_>10, PM₁₀, and PM_2.5. The sampling was carried out following EPA Method 201A. Three tests were performed at each station. The emitted particles were examined using SEM/EDX and gravimetric method for the determination of their sizes. The elemental composition of particles was determined using INAA and ICP-MS.The particles emitted from the stack are classified based on their morphologies and chemistries to the following: unburnt carbon, feed-coal minerals such as quartz, and by-products of the dissociation, fractionation, and contamination by minerals in coal.The emitted particles are mostly spherical and their matrices are composed of aluminosilicate minerals containing calcium. The PM_>10 fraction contains small plerospheres, fragments of char, and angular quartz and feldspar particles. The PM₁₀ fraction contains solid spheres and cenospheres, gypsum needles, and particles of char. The PM_2.5 particle size fraction is mostly composed of solid spherical aluminosilicates with some surface enrichment of elements such as Ba, Ca, and Fe.The composition of emitted particles is ferrocalsialic. Most elements in the particle size fractions are Class I or II, such as Al, Ca, and Fe. Cd, Cu, Mo, and Ti were only detected in PM_2.5 fraction.     

Laboratory studies of the rapid pyrolysis and desulphurization of a Texas lignite

Rapid heating of Alcoa D lignite particles during ‘free-fall’ through a counterflowing pyrolysis gas is an effective method of producing a low sulphur char. For 200 μm particles with residence times of seconds in steam, the organic sulphur of the lignite is reduced from ? 1.3 wt % to ? 0.8 wt % over a temperature range ≈ 700–800 °C. Similar levels of desulphurization were achieved with particles as large as 550 μm, even with shorter residence times. Devolatilization is rapid and substantial with the production of significant quantities of olefins. Steam gasification becomes important above 700 °C for the 200 μm particles. By 820 °C, the conversion of coal to gas is twice as large with steam as for nitrogen, and by 870 °C, it is about four times larger. Chars are reactive and of high surface area. Limited testing suggests that the reduced sulphur chars can be burned directly with emissions of SO₂ below 0.5 g/10⁶J (1.2 lb/10⁶ Btu).     

Influence of woody biomass (cedar chip) addition on the emissions of PM10 from pulverised coal combustion

Co-combustion of pulverised coal with a woody biomass, cedar chip was conducted in a lab-scale drop-tube furnace (DTF) to investigate the synergetic interaction between the inorganic elements of different fuels and the emissions of sub-micron particles (particles smaller than 1.0 μm in size, PM₁) and super-micron particles (particles in the size range of 1.0-10 μm, PM₁₊) during co-firing. The mass fraction of cedar chip in fuel blend ranged from 10% to 50%. All the fuels were burnt in air at two furnace temperatures, 1200 and 1450 °C. The results indicate that, under an identical calorific input, combustion of cedar chip alone favored the emission of sub-micron PM₁, which is dominated by volatile elements including K, Ca, Fe, Na and P. A large fraction of K and Na were most probably present as gaseous vapors in the furnace. The other metals mainly condensed into nano-scale nuclei which subsequently coagulated into a variety of sizes in flue gas. Coal combustion alone favored the release of super-micron particles rich in Al and Si. Emission of PM upon co-firing was a function of both cedar chip share and furnace temperature. At a small mass fraction for cedar chip in fuel blend, e.g. 10% tested here, interaction between the inorganic elements of single fuels was insignificant at either furnace temperature. Accordingly, the quantities of PM₁ and PM₁₊ emitted from co-firing at 10% cedar chip were slightly higher than from the combustion of coal alone, due to the contribution of cedar chip. Significant interaction between the inorganic elements of single fuels was observed for co-firing of coal with >10% cedar chip at the furnace temperature of 1450 °C. As has been confirmed, adding 20-30% cedar chip to coal resulted in the shift of approximately 90% of PM₁ and 50% PM₁₊ into coarse ash particles. For the cedar chip-derived alkali vapors and nano-scale/sub-micron particles, the rates of their shift into larger particles were influenced by two competing routes, homogeneous coagulation and surface reaction with coal-derived kaolin. In contrast, the shift of super-micron particles was primarily determined by their collision probability with the coal-derived mineral grains in bulk gas. A sticky surface for particles is also essential. The shift of individual metals into coarse ash differed distinctly from one another.     

Emission of suspended PM10 from laboratory-scale coal combustion and its correlation with coal mineral properties

Four pulverized coals were subjected to combustion in a laboratory-scale drop tube furnace to investigate the emission of suspended particulate matter smaller than 10 μm (PM₁₀) and to study the correlation of PM₁₀ emission with mineral properties of the coals. Combustion conditions of 1200 °C, 2.4 s and 20% atmospheric oxygen content were used and all the carbon was consumed under given conditions. The properties of PM₁₀ were studied including its concentration, particle size distribution and elemental composition. Two typical sizes were also subjected to Computer controlled scanning electron microscopy (CCSEM) analysis for determination of chemical species within them. To investigate the influence of coal mineral properties, the metallic elements in the raw coals were divided into three parts: organically bound, included inorganic particles and excluded ones. The results indicated that during coal combustion, about 0.5-2.5 wt% of inherent minerals changed into the suspended PM₁₀. With an increase in the coal ash content, the concentration of PM₁₀ increased proportionally. The resulting PM₁₀ had a bimodal size distribution with two peaks around 2.5 and 0.06 μm, respectively. SiO₂ and Al₂O₃ dominated the large mode around 2.5 μm, which is formed by the direct transformation of inherent minerals. On the other hand, SO₃ and P₂O₅ were prevalent in the small mode around 0.06 μm, which is formed by vaporization of these two elements. For other metals found in PM₁₀, the refractory metals were enriched in the large mode, with concentrations proportional to their content in the excluded minerals in the raw coal. Volatile metals were however enriched in the small mode since, they react with gaseous SO₂ and P₂O₅ to form sulfates and phosphates in the solid phase. The study showed that experimental observations agree with thermodynamic equilibrium considerations.     

Thermogravimetry-combustion characteristics of high-carbon fluidized-bed cyclone ashes

Thermogravimetry combustion characteristics are obtained for three samples of high-carbon cyclone ash, the samples received from an R & D fluidized bed combustion unit utilizing Ohio No. 6 bituminous coal with limestone. Non-isothermal TG combustion in air (at a programmed heating rate of 2 °C min^?1) for a cyclone ash (25.0 wt% carbon) indicates two chemically different combustibles, ≈82 wt% of higher reactivity with maximum weight-loss rate at 490 °C and 18 wt% correspondingly of lower reactivity at 645 °C. Isothermal TG combustion of the same ash at 700 °C and at 850 °C also indicates the presence of the two types of combustibles and gives an E_a of about 150 kJ mol^?1 for combustion of the lower reactivity type. Additionally, each of two other samples of cyclone ash (20.1 and 6.9 wt% carbon) contains two types of combustibles as evidenced by TG combustions. Non-isothermal TG combustion of feed coal, a single maximum weight loss at 440 °C, shows the coal has greater reactivity than each of the three ashes. A combustion chemistry explanation for two types of combustibles is suggested by the postulated reactivity order for the organic matter or maceral groups of coal, i.e., vitrinite ? exinite ? inertinite.     

Fine particle and trace element emissions from an anthracite coal-fired power plant equipped with a bag-house in China

Fine particle and trace element emissions from energy production are associated with significant adverse human health effects. In this investigation, the fine particles and trace elements emitted from the combustion of pulverized anthracite coal at a 220 MW power plant were determined experimentally in the size range from 30 nm to 10 μm with 12 channels. The particulate size distributions and morphological characteristics before and after the bag-house were evaluated. The uncontrolled and controlled emission factors of particles are compared with the calculated values from the US Environment Protection Agency, AP-42. Size-classified relative enrichment factors of As, Hg, Se, Cd, Cr, Cu, Al, V, Zn, Mn, Fe were obtained. Relative distributions of trace elements between bottom ash, fly ash and flue gas are determined by mass balance method. The bag-house collection efficiencies of particles and trace elements in the particulate phase are obtained. Finally, the controlled and uncontrolled emission factors of elements of different particulate size fractions are obtained, which will provide useful information for PM_2.5 and PM₁₀ emission inventory development, toxic and hazardous pollutant emission estimates and emission standards established for metal-based pollutants from a pulverized coal-fired boiler.     

Chemical Characteristics of Fine Particles (PM1) from Xi'an,China

Daily mass concentrations of water-soluble inorganic (WS-i) ions, organic carbon (OC), and elemental carbon (EC) were determined for fine particulate matter (PM₁, particles < 1.0 μm in diameter) collected at Xi'an, China. The annual mean PM₁ mass concentration was 127.3 ± 62.1 μg m^–3: WS-i ions accounted for ～38% of the PM₁ mass; carbonaceous aerosol was ～30%; and an unidentified fraction, probably mostly mineral dust, was ～32%. WS-i ions and carbonaceous aerosol were the dominant species in winter and autumn, whereas the unidentified fraction had stronger influences in spring and summer. Ion balance calculations indicate that PM₁ was more acidic than PM_2.5 from the same site. PM₁ mass, sulfate and nitrate concentrations followed the order winter > spring > autumn > summer, but OC and EC levels were higher in autumn than spring. Annual mean OC and EC concentrations were 21.0 ± 12.0 μg m^?3 and 5.1 ± 2.7 μg m^–3 with high OC/EC ratios, presumably reflecting emissions from coal combustion and biomass burning. Secondary organic carbon, estimated from the minimum OC/EC ratios, comprised 28.9% of the OC. Positive matrix factorization (PMF) analysis indicates that secondary aerosol and combustion emissions were the major sources for PM₁.     

Tailpipe emission characteristics of PM2.5 from selected on-road China III and China IV diesel vehicles

Eighteen China III and IV diesel vehicles, including light-duty diesel trucks (LDDTs), medium-duty diesel trucks (MDDTs), heavy-duty diesel trucks (HDDTs) and buses, were tested with real-world measurements using a portable emission measurement system (PEMS). The emission factors (EFs), chemical components and surface morphology of emitted particles from these vehicles were characterized. Measured features included organic carbon (OC), elemental carbon (EC), water soluble ions (WSIs) and trace elements of PM_2.5. The modelling system MOtor Vehicle Emission Simulator (MOVES) was also employed to estimate the PM_2.5 EFs from these vehicles. Carbonaceous content made up 35.8–110.8% of PM_2.5, the largest contribution of all the determined chemical components; WSIs and elements accounted for less than 10%. The average PM_2.5 EFs of MDDTs and HDDTs were 0.389 g·km^?1 and 0.115 g·km^?1, respectively, approximately one order of magnitude higher than that of LDDTs. The PM_2.5 EFs of China III buses were much lower than those of China III MDDTs and HDDTs, indicating that the inspection maintenance program (I/M) system was carried out effectively on public diesel vehicles. Moreover, the chemical composition of 9.2–56.2% of the PM_2.5 mass emitted from China IV diesel trucks could not be identified in the present study. It was possible this unidentified mass was particle bound water, but this hypothesis should be confirmed with further measurements. The SEM images of PM_2.5 samples presented a loose floc structure. In addition, the trends of variation of estimated PM_2.5 EFs derived from the MOVES simulation were essentially consistent with those of tested values.

Copyright © 2018 American Association for Aerosol Research     

Effects of coal blending on the reduction of PM10 during high-temperature combustion 1. Mineral transformations

Two coals with comparable mineral particle distributions, but different contents of Ca were blended and combusted. Mineral transformations and their effects on particulate matter smaller than 10 μm (PM₁₀) emissions were investigated during the combustion of single and blended coals. Combustion experiments were carried out at 1450 °C in air atmosphere using a lab-scale drop tube furnace (DTF). The particle size distributions (PSD), morphologies, elemental compositions, and chemical composition of minerals in coal and PM were analyzed. The results indicate that emissions of PM smaller than 1 μm (PM₁) and particulate matter sized between 1 and 10 μm (PM_1–10) are reduced compared to their calculated linear results during combustion. The transformation of P, S, Al, and Si from submicron particles to PM larger than 1 μm (PM₁₊) reduces PM₁ emissions. The transformation of Ca, Fe, Al, and Si from PM₁₀ to particles larger than 10 μm (PM₁₀₊) reduce PM_1–10 emissions. The high concentration of Ca in coal blends enhances the liquid phase percentage produced during combustion, and as a result, improves both the adhesion of volatilized P, S, Al, and Si on the sticky surface of large particles to be transformed to PM₁₊, and the probability of collision and coalescence of particles to form larger particles of Ca–Fe–Al–Si, Ca–Al–Si, or Fe–Al–Si. Thus, as Ca, Fe, Al, and Si are transformed into PM₁₀₊. PM₁ and PM_1–10 emissions are reduced accordingly.     

Combustion Behavior of Fluorocarbon/Boron/AP Propellant at high pressure

Thermal decomposition and the burning properties of fluorocarbon/boron/AP propellant granule have been investigated. The fluoro-carbon binder (FBDR) was oxidized by the decomposition products of admixed ammonium perchlorate (AP) and its decomposition region was 150°C lowered in the slow thermolysis. The boron particles, however reacted with neither FBDR nor AP at 550°C. In the micro-motor tests, the boron particles completely burnt at a pressure range of from 30 MPa to 80 MPa in a short period of time (one millisecond) even at a low characteristic exhaust velocity. Minimum free volume, however, was needed to complete the combustion reaction in the chamber case. The characteristic exhaust velocity significantly decreased at below the characteristic chamber length of 11 cm. The boronized propellant showed low temperature sensitivity between −30°C and 60°C.     

Effects of Dilution Sampling on Fine Particle Emissions from Pulverized Coal Combustion

A dilution sampler was used to examine the effects of dilution ratio and residence time on fine-particle emissions from a pilot-scale pulverized coal combustor. Measurements include the particle size distribution from 0.003 to 2.5 μm, PM_2.5 mass, and PM_2.5 composition (OC/EC, major ions, and elemental). Heated filter samples were also collected simultaneously at stack temperatures in order to compare the dilution sampler measurements with standard stack sampling methodologies. Measurements were made both before and after the bag house, the particle control device used on the coal combustor, and while firing three different coal types and one coal–biomass blend. The PM_2.5 mass emission rates measured using the dilution sampler agreed to within experimental uncertainty with those measured with the hot-filter sampler. Relative to the heated filter sample, dilution did increase the PM_2.5 mass fraction of selenium for all fuels tested, as well as ammonium and sulfate for selected fuels. However, the additional particulate mass created by gas-to-particle conversion of these species is within the uncertainty of the gravimetric analysis used to determine the overall mass emission rate. The enrichment of PM_2.5 selenium caused by dilution did not vary with dilution ratio and residence time. The enrichment of PM_2.5 sulfate and ammonium varied with fuel composition and dilution ratio but not residence time. For example, ammonium was only enriched in diluted acidic aerosol samples. A comparison of the PM_2.5 emission profiles for each of the fuels tested underscores how differences in PM_2.5 composition are related to the fuel ash composition. When sampling after the bag house, the particle size distribution and total particle number emission rate did not depend on residence time and dilution ratio because of the much lower particle number concentrations in diluted sample and the absence of nucleation. These results provide new insight into the effects of dilution sampling on measurements of fine particle emissions, providing important data for the ongoing effort of the EPA and ASTM to define a standardized dilution sampling methodology for characterizing emissions from stationary combustion sources.     

Plerosphere and its role in reduction of emitted fine fly ash particles from pulverized coal-fired power plants

Fine particles (PM_2.5) emitted from the stacks of the coal-fired power plants are of environmental concern since they can easily enter the human respiratory track. The detailed study of the fly ash particles using scanning electron microscope/electron dispersive spectrometry (SEM/EDX) show that fine solid spherical particles (microspheres) are contained by the large cenosphere particles (>50 μm) during the combustion process. The resulting macro particles are known as “plerosphere”, which are typically impregnated by the fine microspheres. The coal-fired power plants’ particle control devices such as the electrostatic precipitators (ESP) and baghouse filters tend to capture the large plerospheres, more efficiently. Therefore, the result of this study suggests that the containment of the microspheres by plerospheres during the coal combustion process can effectively reduce the amount of fine particles and associated elements released into atmosphere.     

煤粉O2/CO2燃烧时PM2.5及其Fe、S的生成特性

沉降炉实验研究了煤粉O2/CO2燃烧时PM2.5的生成特性和主要成灰元素中危害较大的Fe、S元素生成特性.实验用DT烟煤、NMG褐煤和XLT褐煤,实验温度1300℃,在O2/CO2=1:9,1:4,3:7和O2/N2=1:4气氛下燃烧.低压撞击器(DLPI)按不同粒径大小从0.03～9.8μm共分为13级,分别收集燃烧...     

Microstructural and optical properties of the ZnS ceramics sintered by vacuum hot-pressing using hydrothermally synthesized ZnS powders

ZnS nanopowders annealed at low temperatures (≤550?°C) have a pure cubic structure, while a small amount of hexagonal phase formed in specimens annealed at temperatures ≥700?°C. The particle sizes of the ZnS nanopowders increased with the annealing temperature. ZnS ceramics that were sintered using ZnS nanopowders annealed at low temperatures (≤550?°C) exhibited low transmittance, because of their porous microstructure. ZnS ceramics that were synthesized using ZnS powders annealed at high temperatures (≥800?°C) containing large agglomerated particles, also exhibited low transmittance, due to the presence of a liquid phase. A carbonate absorption band was found from the ZnS ceramics with small grains, because carbon ions diffused from the graphite mold into the ZnS ceramics during sintering, probably through the grain boundaries, and formed carbonates. A ZnS ceramic that was sintered at 1020?°C using the nanopowders annealed at 750?°C exhibited dense microstructure, with a large transmittance, 68%, in the wavelength range 6.0–12?μm.     

Coal combustion characteristics in a pressurized fluidized bed

The characteristics of emission and heat transfer coefficient in a pressurized fluidized bed combustor are investigated. The pressure of the combustor is fixed at 6 atm. and the combustion temperatures are set to 850, 900, and 950 °C. The gas velocities are 0.9, 1.1, and 1.3 m/s and the excess air ratios are 5, 10, and 20%. The desulfurization experiment is performed with limestone and dolomite and Ca/S mole ratios are 1,2, and 4. The coal used in the experiment is Cumnock coal from Australia. All experiments are executed at 2 m bed height. In this study, the combustion efficiency is higher than 99.8% through the experiments. The heat transfer coefficient affected by gas velocity, bed temperature and coal feed rate is between 550-800 W/m² °C, which is higher than those of AFBC and CFBC. CO concentration with increasing freeboard temperature decreases from 100 ppm to 20 ppm. NO_x concentration in flue gas is in the range of 5-130 ppm and increases with increasing excess air ratio. N₂O concentration in flue gas decreases from 90 to 10 ppm when the bed temperature increases from 850 to 950 °C.     

Hydrogen Production with a Microchannel Reactor by Tri-Reforming; Reaction System Comparison and Catalyst Development

In this work, Pt based mono and bimetallic catalysts were tested under conditions of tri-reforming (TR). All the catalysts contained 25% of CeO₂ and a metal loading of 2.5 or 5.0% (wt%). The bimetallic catalysts contained 2.5% Pt and 2.5% of Me, where Me?=?Ni, Co, Mo, Pd, Fe, Re, Y, Cu or Zn. For all the experiments, a synthetic biogas which consisted of 60% CH₄ and 40% CO₂ (vol.) was mixed with water, S/C?=?1.0, and oxygen, O₂/CH₄?=?0.25, and fed to a fixed bed reactor (FBR) system or a microreactor. The 2.5Pt catalyst was used in order to compare the performance of each reaction system. The tests were performed at reaction temperatures between 700 and 800?°C, and at volume hourly space velocities (VHSV) between 100 L_N/(h g_cat) and 200 L_N/(h g_cat) for the FBR system and between 1000 L_N/(h g_cat) and 2000 L_N/(h g_cat) for the microreactor, at atmospheric pressure. Then, all catalysts were deposited into microchannel reactors and tested at a constant VHSV of 2000 L_N/(h g_cat) and reaction temperatures between 700 and 800?°C. Catalysts under investigation were characterized applying the following techniques: inductively coupled plasma optical emission spectroscopy (ICP-OES), N₂ Physisorption, Temperature Programmed Reduction (TPR), CO chemisorption, Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The microreactor was identified as the most efficient and promising reaction system, and the 2.5(Pt–Pd) catalyst as the bimetallic formulation with the highest activity. Therefore its activity and stability was compared with the reference 5.0Pt catalyst at 700?°C and VHSV of 2000 L_N/(h g_cat) for more than 100 h. Although slightly lower activity was measured operating with the 2.5(Pt–Pd) catalyst, a significant reduction of the Pt content compared to the reference 5.0Pt catalyst was achieved through the incorporation of Pd.     

Combustion Aspects of Sodium Azide and its mixtures with potassium perchlorate and burning catalysts

Linear burning rate, thermal aualysis, temperature profile, flame structure and cryogenic burnability for the mixtures of sodium azide (SA) of different particle sizes (3.5 μm, 22 μm, and 67 μm), potassium perchlorate (KP) and with or without three kinds of burning catalysts (GeO₂, Er₂O₃, and Y₂O₃) have been investigated. The linear burning rates increase with the KP content up to 33Wt% for similar SA particle size. The temperature-time histories in the vicinity of burning surface were obtained with 20 μm Type K thermocouple embedded in a Strand. The burning surface temperaturres of neat SA and of the SA/KP mixtures are nearly 350°C and 350°C ∼ 550°C, respectively, while the existence of the decomposition surface at 250 °C and condensed layer was suggested with SA/KP mixtures. In visual observation for the flame structure, the front of luminous flame zone appers to be in contact with the condensed phase surface. For example, however, the temperature profile suggests that there exists finitc distance from decomposition surface to flame front in the order of 0.05 mm ∼ 0.1 mm at 1 MPa for SA/KP = 80/20. The differential thermal analysis indicates that the tested catalysts have retarding effect on SA combustion, but a positive effect on neat KP decomposition in spite of being impotent for the burning rate increase of the SA/KP mixture. It was also found that SA strands containing appropatiae fractions of KP can hurn even in liquid nitrogen.     

Coal liquefaction using iron complexes as catalysts

Hydroliquefaction of Japanese Miike and Taiheiyo coals was carried out using various iron complexes as catalysts in tetralin at 375–445 °C. Iron pentacarbonyl (Fe(CO)₅) showed the highest catalytic activity, increasing coal conversion by about 10% at 425 °C under an initial hydrogen pressure of 5 MPa. Amounts of hydrogen transferred to coal increased from 1.4–2.3 wt% of daf coal in the absence of the catalyst to 2.5–4.2 wt% of daf coal in the presence of Fe(CO)₅ at 425 °C.