Showing papers on "Charring published in 2008"

Mid-infrared diffuse reflectance spectroscopic examination of charred pine wood, bark, cellulose, and lignin: implications for the quantitative determination of charcoal in soils

Abstract: Fires in terrestrial ecosystems produce large amounts of charcoal that persist in the environment and represent a substantial pool of sequestered carbon in soil. The objective of this research was to investigate the effect of charring on mid-infrared spectra of materials likely to be present in forest fires in order to determine the feasibility of determining charred organic matter in soils. Four materials (cellulose, lignin, pine bark, and pine wood) and char from these materials, created by charring for various durations (1 to 168 h) and at various temperatures (200 to 450 degrees C), were studied. Mid-infrared spectra and measures of acidity (total acids, carboxylic acids, lactones, and phenols as determined by titration) were determined for 56 different samples (not all samples were charred at all temperatures/durations). Results showed spectral changes that varied with the material, temperature, and duration of charring. Despite the wide range of spectral changes seen with the differing materials and length/temperature of charring, partial least squares calibrations for total acids, carboxylic acids, lactones, and phenols were successfully created (coefficient of determination and root mean squared deviation of 0.970 and 0.380; 0.933 and 0.227; 0.976 and 0.120; and 0.982 and 0.101 meq/g, respectively), indicating that there is a sufficient commonality in the changes to develop calibrations without the need for unique calibrations for each specific material or condition of char formation.

In-depth temperature profiles in pyrolyzing wood

Abstract: The move towards performance-based design of the fire resistance of structures requires more accurate design methods. An important variable in the fire performance of timber structures is the in-depth temperature distribution, as wood is weakened by an increase of temperature, caused by exposure to high heat fluxes. New construction techniques of timber structures use new types of metallic connectors that have poor fire performance, and present evidence of low temperature failure. The temperature distribution is also an important variable in the performance of these connections. Thus, a proper prediction of temperature profiles in wood structural elements has become an essential part of timber structural design. Current design methods use empirically determined equations for the temperature distribution of the uncharred section of the wood member, but these assume constant charring rates (i.e. steady-state conditions), do not account for changes in the heating conditions, and were obtained under poorly defined boundary conditions in fire resistance furnaces. Another approach consists of calculating the temperature profiles by modelling wood pyrolysis. The energy conservation equation for the timber element is solved numerically, and several models have been created in the past. However, there has been no clear indication whether each term included in the different models adds enough accuracy to justify the increased computational cost to solve a more complicated model. Finally, comparisons of predicted and measured results show good initial agreement, but greater inaccuracy as the pyrolysis process progresses and the temperatures rise. As part of this research project, a series of experimental in-depth temperature measurements were done in wood samples exposed to various intensities of radiant heat fluxes, with clearly defined boundary conditions that allow a proper input for pyrolysis models. The imposed heat fluxes range from 10 kWċm−2, which generates an almost inert behaviour, to 60 kWċm−2, where spontaneous flaming is almost immediately observed. Mass loss measurements for all

An s- and p-containing flame retardant for polypropylene

Abstract: A novel charring agent, bis(1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane) phenylphosphine sulfide (BCPPS), has been synthesized, and it is combined with ammonium polyphosphate (APP) and melamine phosphate (MP) to impart flame retardance and dripping resistance for polypropylene (PP). The fire performance of the treated PP is investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter, and the thermal stability and thermal oxidative stability of the composites are studied using thermogravimetric analysis (TG). It has been found that the treated PP with the optimal flame retardant formulation of APP:MP:BCPPS = 12:6:12 (weight ratio, formulation 10) gives an LOI of 31.3 and UL-94 V-0 rating. The results from cone calorimeter indicate that both the heat release rate (HRR) and the total heat evolved (THE) of IFR-PP (formulation 10) decrease significantly compared with those of neat PP. The TG result shows that the IFR-PP (formulation 10) has a high yield of residual char at high temperature. FTIR is used to investigate the residue of the treated PP that degrades at 400°C for different time. The compact outer surface and the shaggy inner surface can be observed from the SEM graph of the residual chars after LOI test, which form a much better barrier for the transfer of heat and fuel during combustion and show good flame retardancy. Moreover, the treated PP and its residue are investigated by XPS analysis.

Process development of laser machining of carbon fibre reinforced plastic composites

Abstract: The growing use of carbon fibre reinforced plastic (CFRP) composites as high performance material in aerospace and automotive industry has prompted studies in developing technologies for machining of composites in recent years. Use of lasers for cutting and drilling of composites is attractive due to its flexibility and free from tool wear. However, the large differences in material properties of the carbon fibre and the epoxy resin present serious challenges to the laser-based process. The issues related to heat affected zone (HAZ) causing charring and potential delamination have been the major obstacles for its industry applications. This paper studies the process in machining CFRP using a 10W diode pumped solid state (DPSS) Q-switched UV laser operation at the wavelength of 355 nm. HAZ, charring, material removal efficiency, and microstructure were investigated. Finite Element analysis on heat transfer phenomena in a 3D composite mesh at similar process conditions is also presented.The growing use of carbon fibre reinforced plastic (CFRP) composites as high performance material in aerospace and automotive industry has prompted studies in developing technologies for machining of composites in recent years. Use of lasers for cutting and drilling of composites is attractive due to its flexibility and free from tool wear. However, the large differences in material properties of the carbon fibre and the epoxy resin present serious challenges to the laser-based process. The issues related to heat affected zone (HAZ) causing charring and potential delamination have been the major obstacles for its industry applications. This paper studies the process in machining CFRP using a 10W diode pumped solid state (DPSS) Q-switched UV laser operation at the wavelength of 355 nm. HAZ, charring, material removal efficiency, and microstructure were investigated. Finite Element analysis on heat transfer phenomena in a 3D composite mesh at similar process conditions is also presented.

Effects of Charring Agents on the Thermal and Flammability Properties of Intumescent Flame-Retardant HDPE-based Clay Nanocomposites

Abstract: Intumescent flame-retardant (IFR) high-density polyethylene, poly[ethylene-co-(vinyl acetate)], and organically-modified clay nanocomposites consisting of ammonium polyphosphate (APP) and other charring agents, as well as the nanocomposites pentaerythritol (PER), polyamide-6 (PA), and PA/OMT were investigated. Their thermal and flammability properties have been characterized by thermogravimetric analyses, cone calorimetry, a limiting oxygen index, and the UL-94 test. Results show that the PER-contained sample exhibits different thermal and flammability behaviors from the samples containing polymer charring agents. The difference is postulated to be responsible for the formation of various intumescent structures and their changes in response to heightened temperatures.

Method for preparing active carbon

Abstract: This invention discloses a method for preparing activated carbon. It contains procedures of: A, preparation of raw material: cutting ginkgo tree wood into chips; B, Charring: dry distillation charring of said chips in a charring installation with heating temperature of 500-550deg.C, after that keeping the temperature for 40min. Then lowering the temperature to room temperature; C, breaking and sieving: the chips such charred are then broken, and then being sieved and classified into various sized granules; D, activating: said granules are then heated, under steam protective atmosphere (supply volume being 100-140ml) at temperature 800-850deg.C for 40-60min; E, aftertreatment: removing the dust and drying them, so obtaining the inventive product. The activated carbon has excellent porous structure, higher activity yield, greater specific surface area and strong decolorization. It can absorb benzene, formaldehyde, ammonia, trichloromethane and heavy metals such as lead and cadmium.

Study of Radiant Smoldering Ignition of Plywood Subjected to Prolonged Heating Using the Cone Calorimeter, TGA, and DSC

Abstract: Maple plywood samples were heated in an oven at 180°C to a residual weight of 70%, 50%, and 30% of the virgin weight. The virgin plywood and the thermally pretreated samples were tested in a cone calorimeter over the range of 6 to 15 kW/m 2 without the use of an ignitor. Tests were conducted until smoldering/glowing combustion was observed or for eight hours if ignition was not observed. The extent of thermal pretreatment of the plywood had no measurable effect on the minimum heat flux for smoldering ignition. At heat fluxes above the minimum for ignition, ignition times were reduced for thermally pretreated samples relative to virgin wood. This is consistent with the thermal pretreatment achieving the charring required as the first step in smoldering ignition and the reduction in thermal inertia resulting from charring. Samples of the virgin and pretreated wood were subjected to thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The chemical kinetics analysis of the virgin and pretreated samples showed no change in the chemical mechanism. The thermal pretreatment simply resulted in the samples being further along the reaction pathway at the start of the ignition test. The results are not consistent with the formation of a more reactive char species commonly referred to in the fire investigation lore as “pyrophoric carbon.”

Study on Char Structure of Intumescent Flame-Retardant Polypropylene

Abstract: The structure and properties of the char of intumescent flame retardant polypropylene (IFR-PP) have been studied by cone calorimeter, scanning electron microscope (SEM) and differential scanning calorimeter (DSC). Charring tendency analysis indicates IFR-PP is more likely to form a thick and homogenous char at low heat flux than that at higher heat fluxes. The SEM study indicates different char structures are formed at different stages. DSC analysis studies thermal stability of IFR-PP. Theoretical analysis of intuemscent charring shows when intumescent velocity increases, the heat diffusing into the underlying material will decrease if the thermal diffusivity of the material keeps constant.

Method and device for producing inside and outside thermal combined two-stage continuous activated carbon

Abstract: Disclosed is a two stage continuous activated charcoal producing device with combination of inner heat and outer heat, which comprises an organic support (13), furnace bodies (5,10) an exhaust gas processing and a sub-atmospheric pressure device (1), feeding and discharging apparatuses (3,12), a motor and the driving member (6), wherein the furnace bodies are divided into a charring furnace (5) and an activating furnace (10) which are revolving furnaces installed in inclination, a hot gas flow passage (9) and a blanking pipe (8) are arranged between the two furnaces to communicate the two furnaces, a burning chamber (11) is arranged under the activating furnace. The device produces activated charcoals with materials of sawing wood (bamboo) particles and goes through the procedures of sawdust preprocessing, motor operation, feeding and ignition, charring and activating, activated charcoal discharging and after-treatment. Producing activated charcoals with this method has the advantages of even heating, even and full reaction, difficulty of crusting on the inner wall of the furnaces and heading formation and blocking of wood particles, high products obtaining rate, good quality, remarkable energetic saving resulting from full usage of waste heat, low depletion caused by zinc chloride which can be recycled, small waste gas discharging, low manufacture cost of furnaces, which is favorable for application and the like.

Making method for large-area 3C-SiC thin film of MEMS part

Abstract: This invention relate to a preparing method for large area 3C-SiC films used in MEMS devices including the following steps: 1, taking a substrate, 2, carrying out in-situ hydrogen etch to the epitaxially growing side of the substrate, 3, epitaxially growing a charring layer on the etched side of the substrate in a low-pressure chemical vapor deposition oven to take it as a transition layer of the substrate and 3C-SiC film suitable for preparing 3C-SiC films, 4, epitaxially growing a 3C-SiC film on the charring layer, 5, finishing the process of the film.

Method of preparing micropore carbon

Abstract: The invention relates to a microporous carbon material, which can be applied to fields such as molecular absorption, pressure swing adsorption separating and barrier separation. The invention discloses a method for preparing the microporous carbon material by taking phenolic resin as raw material and molding, drying and charring. Through controlling the structure of phenolic resin, the pore structure of microporous carbon material can be controlled, so as to meet the demand of the pore structure from different application field.

Decatizing and charring process of cotton wood

Abstract: The invention discloses a method for steaming and charing of cottonwood. The method is characterized in that in a closed hot pressing system, high-pressure steam with the temperature more than 130 DEG C is used to make the refrigerating treatment to the cottonwood or single plates, and according to different initial moisture contents of the single plates, the pressure of the steam is controlled between 0.3 and 0.5MPa, and the steaming time is controlled within 3 hours; treated single plates are hot-pressed into multilayer veneers which are sawed into standard plates, the standard plates are put in a temperature humidity chamber for balancing, and the cottonwood after steaming and charing is obtained. The cottonwood treated by the method of the invention has the advantages of improving indexes such as dimensional stability and rotproofness, etc., making wood color deep, saturated, uniform and more beautiful, improving the decorative function of the cottonwood, widening the application of the cottonwood and breaking a new market for the high-end application of the cottonwood.

Method for preparing charcoal/charcoal heating element of high resistance and high purity

Abstract: The invention relates to a preparation method for a carbon/a carbon heating unit with high resistance and high purity; in the method, carbon cloth and short carbon fiber web fetus are adopted to be alternately laminated or wound into a cylinder to form horizontal fabric which is added with vertical fabric along the thickness direction by adopting a needling technique to prepare a prefabricated body of the heating unit with a three-direction structure; the prefabricated body is processed with furfural acetone resin or phenolic resin vacuum pressure impregnation and curing treatment, charring at normal pressure and other densification techniques until the density reaches 1.55g/cm and then high-temperature vacuum purification is carried out below 2,000 DGE C and the carbon/the carbon heating unit with high resistance and high purity can be produced after mechanical processing. The carbon/the carbon heating unit of the invention has outstanding features of high resistance and high purity and has the advantages of short production period, low production period and long service life, which is mainly applicable to a U-shaped heating unit of a polysilicon hydrogenation furnace as well as a large cylindrical heating unit of a polysilicon pulling furnace.

Catalyst for producing vinyl acetate by acetylene method as well as preparation method and use of catalyst

Abstract: The invention belongs to the field of producing vinyl acetate by an acetylene method and relates to a catalyst for producing vinyl acetate by the acetylene method as well as a preparation method and applications of the catalyst. The catalyst for producing vinyl acetate by the acetylene method takes resin-based derived carbon as a carrier; the derived carbon takes a polyvinylidene chloride microsphere prepared by a suspension polymerization method as a precursor, or directly leads the polyvinylidene chloride resin to be formed into the polyvinylidene chloride resin of the needed type by mechanical pelleting as the precursor and multi-step charring processes are carried out on the precursor; then the precursor is washed by hot acetic acid, and dried to obtain the microsphere of the derived carbon used for the catalyst carrier. The charring processes are as follows: under the protection of inert gases, the charring temperature is gradually raised to 1000 DEG C from the room temperature and then the temperature is maintained for 2 hours. Then the catalyst of the invention is obtained by loading an active component of zinc acetate which accounts for 5 to 35weight percent of the total weight of the catalyst carrier. The catalyst prepared by the method is good in mechanical intensity, is regular in structure, is easy to be filled and shows excellent catalyzing performance.

Preparation technique of carbon-based material having energy-storage property

Abstract: A process for preparing carbon material with the property of energy storage is a method of high-temperature strong base activation, which takes petroleum pitch coke as raw material and is composed of processes of crushing and grinding, screening, charring, catalyzing and activating, washing, drying and alkali recovery. The energy storage carbon material can be mass-produced and has specific surface area of 2500-4000m2g, iodine sorption value 2500-3500mg/g, methylene blue value of 600-1200mg/g, ash less than 1%, nano microporous aperture of 0.75-1.5mm and micro volume rate larger than 90-95%. The process particularly meets the absorption and storage requirements, thereby facilitating the wide and safe application of natural gas.

Preventing carbon ao migration by limiting surface porosity

Abstract: In the manufacture of carbon-carbon composite brake discs, migration of anti-oxidant substances into the friction surfaces is prevented by limiting or eliminating surface porosity in the carbon-carbon composite brake materials. The method includes infusing a suitable resin into pores in surface layers of the carbon-carbon composite disc and then charring the resin-infused disc to convert the resin in the pores to pyrolytic carbon. The resin may be infused into the carbon disc by submerging the disc in a molten resin. Prior to submerging the disc in the molten resin, the disc may subjected to a vacuum to remove air from the pores. While the disc is submerged in the molten resin, the pressure in the pressurizable vessel may increased to force the molten resin into the open porosity of the disc.

Theoretical and experimental study of the thermal degradation of Eucalyptus timber

Abstract: Thermal action on timber causes it to degrade through combustion of its chemical components, which leads to the release of vapors, combustible gases and surface char. This diminishes its load capacity, due to the reduction of its cross section by charring and to changes in its mechanical properties of strength and stiffness as a function of its exposure to high temperatures. This paper reports the charring rates observed on Eucalyptus structural beams and presents a numerical and experimental study of the behavior of these beams when exposed to fire, in which the properties of strength and stiffness were evaluated as a function of rising temperatures, allowing an analysis of the effect of the section factor on the internal rise in temperature of structural Eucalyptus beams.

Wood dry charring pot

Abstract: The utility model discloses a wood charing tank which is characterized in that the wood charing tank comprises a tank body, at least one end of the tank body is provided with a movable tank cover, the inner part of the tank body is provided with a heat pipe which is provided with a heat conducting medium inlet and a heat conducting medium outlet, the tank body is provided with a vacuum pipe interface, a fan pipe inlet and an outlet. The wood charing tank has the advantages that the wood can be chared at a high temperature evenly, the wood can be also dried in vacuum, the mass production is realized, the efficiency is improved and the cost is saved.

Directly reclaiming device for tamping coke-oven high-oxygen gas and reclaiming technique

Abstract: A hyperoxic gas direct reclaimer of a tamping coke oven and a reclaiming technology are disclosed. The reclaimer comprises a coal-charging car and a charring chamber, which is characterized in that the gas collecting devices are arranged on the pusher side and the coke side on the top portion of the charring chamber (9), high-pressure ammonia injectors (6) are arranged in the gas collecting devices, and a sealing door device is installed on the front end of the coal-charging car (1). The reclaiming technology comprises opening the mouth of the charring chamber (9), starting the piston rod (12) of the coal-charging car (1) to push the sealing door (3) to seal the coal inlet (10) of the charring chamber (10), pushing briquette (2) into the charring chamber (9) from the mount of pusher side to generate partial high-negative-pressure region in the inner portion of bridge pipes (5) on the pusher side and the coke side, and plugging the mouth of the charring chamber (9) with the furnace door when the briquette totally enters into the charring chamber (9). The device overcomes the restricted aspect that raw gas which is transgressed has high oxygen content when charging coal on the side of the tamping coke oven, which can not enter into the gas collecting pipes, directly reclaim raw gas with high oxygen content which is transgresses, reduces cost and largely increases economic effects.

The Development and Characterisation of Sorbents from Irish Sphagnum Moss Peat

Abstract: A range of carbon chars was produced from sphagnum moss peat by heating in a furnace with a reduced oxygen atmosphere. A series of heating times and temperatures were selected for the preparation of the chars. Comparative porosity and surface area studies, based on nitrogen sorption isotherms and mercury porosimetry data, were carried out to characterise the chars. Further characterisation studies were conducted by electron microscopy techniques. Optimum charring conditions, yielding maximum surface area for N2 adsorption, were observed at a charring temperature of 800°C and charring time 30 minutes. Using the optimum charring conditions, a further series of chars was produced. Prior to charring the raw peat was chemically pre-treated with a range of metal salt solutions of varying percentage concentration. The resulting chars were characterised as above. The adsorptive capacity of these chars for N2 was investigated on the Sorptomatic 1900 (Fisons Instruments). The adsorption isotherms were compared to the standard isotherms of Langmuir. Adsorbate uptake was seen to vary with surface area availability, pore volume, pore type and the nature of the adsorbate.