Internal Burning Research Articles

1974 ADVERSE EVENTS RESULTING FROM LASERS USED IN UROLOGY

You have accessJournal of UrologyBenign Prostatic Hyperplasia: Surgical Therapy and New Technology (I)1 Apr 20131974 ADVERSE EVENTS RESULTING FROM LASERS USED IN UROLOGY Abdulaziz Althunayan, Mohamed Elkoushy, Mostafa Elhilali, and Sero Andonian Abdulaziz AlthunayanAbdulaziz Althunayan Montreal, Canada More articles by this author , Mohamed ElkoushyMohamed Elkoushy Montreal, Canada More articles by this author , Mostafa ElhilaliMostafa Elhilali Montreal, Canada More articles by this author , and Sero AndonianSero Andonian Montreal, Canada More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.2393AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Endourologic procedures such as prostate tissue ablation and lithotripsy use different types of lasers with different wavelengths such as Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG), Holmium: YAG (Ho:YAG) and Potassium Titanyl Phosphate (KTP) lasers with the following wavelengths 1064 nm, 2100 nm, and 532 nm, respectively. Currently, there is no data regarding adverse events (AEs) to patients or operators resulting from the use of these lasers. Therefore, the aim of the present study was to collate world reports of such AEs. METHODS The Manufacturer and User Facility Device Experience (MAUDE) database of the United States Food and Drug Administration (FDA) was searched using the term “Laser for gastro-urology use”. In addition, the Rockwell Laser Industries (RLI) Laser Accident Database was searched for the following types of lasers: Nd:YAG, Ho:YAG, and KTP. RESULTS Both databases were last accessed on October 1, 2012. Overall, there were 394 AEs (160 in FDA MAUDE database from 1992 to 2012 and 234 in RLI database from 1970 to 2005). Most of the AEs were related to generator failure or fiber tip breaking, especially with smaller laser fibers. While there were 20 AEs harming medical operators, 126 AEs resulted in harm for non-medical operators using Nd:YAG and KTP. Interestingly, all 131 AEs resulting in eye injuries were associated with the use of Nd:YAG and KTP lasers as a result of improper eye protection; none were reported with Ho:YAG. Most of the reported eye injuries resulted from non-medical laser uses. These eye injuries were serious ranging from mild corneal abrasions to total vision loss. Overall, there were 36 (9%) AEs resulting in patient harm including 7 (1.7%) mortalities; 3 deaths from ureteral perforation and retroperitoneal bleeding using the Ho:YAG laser (Between 2003 - 2005) and 4 deaths from air embolisms using the Nd:YAG laser (between 1987 - 1990). Two other patients with air embolisms from Nd:YAG laser survived. Other reported patient injuries included bladder or ureteral perforation resulting in urinary diversion in a patient, minor skin burns, internal burns, and bleeding. CONCLUSIONS Most of the AEs reported relate to equipment failure. There were no eye injuries reported with the use of Ho:YAG lasers. Caution must be exercised when using lasers in urology including wearing appropriate eye protection when using Nd:YAG and KTP lasers. AEs reported in FDA MAUDE (1992-2012) and RLI (1970-2005) databases Laser type Ho: YAG Ho: YAG Nd: YAG Nd: YAG KTP KTP Database FDA RLI FDA RLI FDA RLI No. of AEs 87 53 48 161 25 20 Generator or Fiber Failure 72 (83%) 48 (90%) 26 (54%) 30 (19%) 16 (64%) 0 Harm to operator (medical) 9 (10%) 2 (3.7%) 0 4 (2.5%) 5 (20%) 0 Harm to operator (non-medical) 0 0 0 109 (68%) 0 17 (85%) Eye injury 0 0 0 113 (70%) 1 (4.0%) 17 (85%) Harm to patient 6 (6.8%) 3 (5.6%) 2 (4.2%) 18 (11%) 4 (16%) 3 (15%) Death 3 (3.4%) 0 0 4 (2.5%) 0 0 © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e810 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Abdulaziz Althunayan Montreal, Canada More articles by this author Mohamed Elkoushy Montreal, Canada More articles by this author Mostafa Elhilali Montreal, Canada More articles by this author Sero Andonian Montreal, Canada More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Characterizing char particle fragmentation during pulverized coal combustion

A particle population balance model was developed to predict the oxidation characteristics of an ensemble of char particles exposed to an environment in which their overall burning rates are controlled by the combined effects of oxygen diffusion through particle pores and chemical reactions (the zone II burning regime). The model allows for changes in particle size due to burning at the external surface, changes in particle apparent density due to internal burning at pore walls, and changes in the sizes and apparent densities of particles due to percolation type fragmentation. In percolation type fragmentation, fragments of all sizes less than that of the fragmenting particle are produced. The model follows the conversion of particles burning in a gaseous environment of specified temperature and oxygen content. The extent of conversion and particle size, apparent density, and temperature distributions are predicted in time.Experiments were performed in an entrained flow reactor to obtain the size and apparent density data needed to adjust model parameters. Pulverized Wyodak coal particles were injected into the reactor and char samples were extracted at selected residence times. The particle size distributions and apparent densities were measured for each sample extracted. The intrinsic chemical reactivity of the char to oxygen was also measured in experiments performed in a thermogravimetric analyzer. Data were used to adjust rate coefficients in a six-step reaction mechanism used to describe the oxidation process.Calculations made allowing for fragmentation with variations in the apparent densities of fragments yield the type of size, apparent density, and temperature distributions observed experimentally. These distributions broaden with increased char conversion in a manner that can only be predicted when fragmentation is accounted for with variations in fragment apparent density as well as size. The model also yields the type of ash size distributions observed experimentally.

Burnout of soot particles in a two-stage burner with a JP-8 surrogate fuel

This work focuses on the understanding of the oxidation of soot particles which were the result of using a JP-8 surrogate fuel in a two-stage burner. The two-stage system consists of an initial premixed burner where soot was generated with an air/fuel mixture, specifically a JP-8 surrogate (m-xylene and n-dodecane), under a variety of conditions. Downstream, the soot-laden combustion gases were passed through a second, flat-flame burner where soot was burned out under fuel-lean or slightly fuel-rich conditions. Soot oxidation in the secondary burner was determined by investigating particle size distribution (PSD), flame temperature, gas-phase composition, soot surface area, and soot morphology and nanostructure as a function of the height above the second burner (HAB). Measurements of soot size distribution and number concentration as a function of the HAB under fuel lean (Φoverall=0.8) and slightly rich (Φoverall=1.14) conditions showed a decrease in particle mean diameter and a significant increase in number concentration in the region where O2 concentration decreased. In this region, the effectiveness factor for O2 was found to be 1, indicating the potential for internal oxygen diffusion and burning. This caused both the breakup of the bridges cementing primary particles and the rupture of the primary particles. Higher in the burner, where modeling suggested the presence of OH*, soot oxidation was attributed to OH* mechanisms which are faster as compared to O2 oxidation.

Suicide bombing: how to prevent death in civilians? – Authors' reply

www.thelancet.com Vol 379 January 14, 2012 e9 Submissions should be made via our electronic submission system at http://ees.elsevier.com/ thelancet/ police stations, mosques, and markets. To establish the feasibility and effi cacy of such an intervention would require investigation. It is essential to point out that, to whatever degree civilian-administered tourniquets might improve immediate rates of survival from extremity wounds caused by suicide bombs, a tourniquet is a temporary measure that does not replace the adequate health care required by victims for their continued survival. If a civilian-applied tourniquet is required temporarily to stanch severe bleeding from an extremity, to survive in the long term, that civilian will require eff ective emergency and surgical treatment to the limb once arriving at hospital. Moreover, a study of victims of civilian suicide bombs arriving at hospitals in Israel suggests that substantial proportions of victims arrive not only with extremity injuries (44%), but also with internal injuries (32%), head injuries (22%), chest injuries (21%), abdominal injuries (16%), and burns (17%). Survival of these wounds would not be aff ected by tourniquets. 30% had three or more body regions injured, 29% had severe-to-critical injuries, 52% required surgery, and 27% required intensive care—all indicators of the need for high-quality, complex treatment of injuries caused by suicide bombs in civilians, as in soldiers. Although all forms of prevention and intervention should be considered, what is known so far suggests that the provision of adequate medical treatment and facilities is one necessary component for improved survival from suicide bombs, for both military and civilian victims.

The kinetics of oxidation of Diesel soots by NO 2

The kinetics of oxidation of three soots, from a Diesel engine fuelled by either Ultra-Low Sulphur Diesel (ULSD) or biodiesel, by NO 2 have been measured in a packed bed at various temperatures (300–550 °C) and [NO 2] (20–880 ppm) relevant to regenerating a Diesel Particulate Filter. Adsorbed hydrocarbons and oxygen accounted for a significant fraction (∼20% by mass) of the otherwise carbonaceous material. After pre-treatment (heating up to 550 °C in a flow of pure Ar and holding the temperature at 550 °C for 1 h) to ensure consistency between samples, they were subsequently burned at a fixed temperature in a flow of NO 2 + Ar. For this, a balance on oxygen atoms entering and leaving the packed bed showed that during oxidation in NO 2 any oxygen remaining in a soot after pre-treatment was not rapidly liberated as CO or CO 2. A mass balance on the element nitrogen demonstrated that no N 2 or N 2O was formed below 550 °C; mass balances on carbon and oxygen demonstrated that all the carbon ended up as CO or CO 2 and below 550 °C the nitrogen yielded only NO. The oxidation of soot in NO 2 was found to be first-order with respect to NO 2. Also, the soot derived from biodiesel was more reactive than soot from ULSD; nevertheless, the apparent activation energies for oxidation by NO 2 were the same (70 ± 18 kJ mol −1) for each carbon. When the distribution of diameters of the individual spherules of soot was taken into account, it was not possible to tell whether there was internal burning of porous spherules or, on the other hand, non-porous, solid spherules were burning on their exteriors.

Physiological disorders of Brassicas /Cole crops found in Swaziland: A review

Physiological disorders of Brassicas/Cole crops are abnormalities in leaf and stem morphology, colour, or both which are not caused by infectious diseases or insects. The abnormalities occur as a result of environmental stress, nutritional deficiencies or excesses on the plant. Reported causes of physiological disorders include genetic, environmental factors, nutrition, and cultural practices such as irrigation practices and tying leaves (blanching) for curd protection in cauliflower. Information was obtained through review of existing literature and informal surveys in the four agro-ecological zones of Swaziland coupled with brief interviews of key farmers and producers of Brassicas. Physiological disorders encountered in this study included premature bolting of Brassica juncea, head splitting in head forming Brassicas, failure of or multiple head formation called blindness, riciness in cauliflower, oedema, internal tip burn, black petiole, pepper spot, vein streaking necrosis and necrotic spot in cabbage. Measures to alleviate these physiological disorders of Brassicas are suggested. Key words: Physiological disorders, Brassicas/Cole crops, alleviating disorders, climate change.

Influence of Atmospheric Pressure Fluctuation on Air Leakage Rate of Airtight-wall

Aiming at strengthening the airtight-wall tightness, reducing its leakage rate, so that extinguishing the combustion in the burning area as soon as possible, this paper proposes the new ideas that the atmospheric pressure changes is important affecting factor to airtight-wall leakage rate in airtight burning area. Adopting the comprehensive research method of theoretical analysis, field measurement, and numerical calculation, this paper studies the influence law of the periodical change of the atmospheric pressure on the airtight-wall leakage rate, the results show that: the curve of underground pressure is sinusoid approximately; the atmospheric pressure changes is the main reason for the internal and external pressure difference of the airtight-wall; the gas exchange capacity of internal and external burning area is large, the gas exchange capacity of calculation example is more than 1400m3 every day. To reduce the firewall leakage rate, this paper proposes the specific solutions including building gas pressure balance room, strengthening airtight-wall tightness, and reducing the burning area volume, etc.

Prescribed Burning in State Park Properties of North Carolina and Nearby Coastal States

Prescribed burning has been used by the North Carolina Division of Parks and Recreation (DPR) since 1974 to reduce hazardous fuel loads, to restore/maintain specific habitats, and to preserve rare species populations within state parks, recreation areas, and natural areas. System-wide staff training, development of burn prescriptions, and burning procedures were mandated according to agency guidelines. During 2002–2007, prescribed burns within state park properties were conducted mostly in the coastal plain, but system-wide coverage was far less than adequate to maintain fire-dependent communities. The number of hectares treated per year as a percentage of the number needing treatment decreased yearly. In addition to weather conditions, common obstacles to achieving burning goals included conflicts with other responsibilities, lack of trained staff/dedicated funding, and increasing wildland-urban interfaces. Prescribed burning data and associated information from state parks and natural areas in Virginia, South Carolina, Georgia, and Florida indicated that interagency burning agreements, full-time burning staff, and use of contractors have improved burning results significantly in recent years. Prescribed fire councils have served as advocates for prescribed burning at state-wide levels, while prescribed burning legislation has helped to limit smoke and, in some states, fire damage liability. Suggested enhancements for the DPR prescribed burn program include: use of both internal and external burning organizations, development of cooperative agreements with analogous programs, pursuit of earmarked state funds and outside grants, expansion of staff burn training, active participation in prescribed fire advocacy groups, and site-specific public information/education to address local concerns and to promote benefits of prescribed burning.

Modeling char oxidation behavior under Zone II burning conditions at elevated pressures

For accurate modeling of the coal combustion process at elevated pressures, account must be made for variations in char-particle structure. As pressure is increased, particle swelling increases during the devolatilization of certain bituminous coals, yielding a variety of char-particle structures, from uniform high-density particles to thin-walled non-uniform low-density particles having large internal void volumes. Since under Zone II burning conditions the char conversion rate depends upon the accessibility of the internal surfaces, the char structure plays a key role in determining particle burnout times. In our approach to characterize the impact of char structure on particle burning rates, effectiveness factors appropriate for thin-walled cenospherical particles and thick-walled particles having a few large cavities are defined and related to the effectiveness factor for uniform high-density particles that have no large voids, only a random distribution of pores having a mean pore size in the sub-micron range. For the uniform case, the Thiele modulus approach is used to account for Zone II type burning in which internal burning is limited by the combined effects of pore diffusion and the intrinsic chemical reactivity of the carbonaceous material. In the paper, the impact of having a variety of char structures in a mix of particles burning under Zone II burning conditions is demonstrated.

Impact of exhaust gas recirculation (EGR) on the oxidative reactivity of diesel engine soot

This paper expands the consideration of the factors affecting the nanostructure and oxidative reactivity of diesel soot to include the impact of exhaust gas recirculation (EGR). Past work showed that soot derived from oxygenated fuels such as biodiesel carries some surface oxygen functionality and thereby possesses higher reactivity than soot from conventional diesel fuel. In this work, results show that EGR exerts a strong influence on the physical properties of the soot which leads to enhanced oxidation rate. HRTEM images showed a dramatic difference between the burning modes of the soot generated under 0 and 20% EGR. The soot produced under 0% EGR strictly followed an external burning mode with no evidence of internal burning. In contrast, soot generated under 20% EGR exhibited dual burning modes: slow external burning and rapid internal burning. The results demonstrate clearly that highly reactive soot can be achieved by manipulating the physical properties of the soot via EGR.

An unusual circumstance of internal chemical burn injury – A case report

Chemical burn injuries including nitric acid injuries are rarely seen in routine clinical practice. In this article, we describe a case of chemical burns due to ingestion of nitric acid in which the history was not of an accidental but of a suicidal nature. Spillage of nitric acid (vitriolage) is frequently reported especially in the third-world countries, but an ingestion injury like this is uncommon and rarely reported.

Lightning Strike – Mechanisms of Energy Transfer, Cause of Death, Types of Injury: Effects on the Nervous System

We thank Zack et al. for their comprehensive review of the mechanisms and sequelae of lightning injuries. The effects of lightning strike on the nervous system, however, require some clarification and additional information, since injuries to the nervous system are the most common and momentous cause of long-term problems in survivors (1). When the resistance of the skin is broken during lightning strike, the body is exposed to a short pulse of direct current; tissues with low electrical resistance such as the vascular and nervous system are particularly affected. Acute lesions are not always detectable, even when modern imaging techniques are used. In contrast to injuries caused by alternating current, internal burns are extremely rare (1). In principle, all parts of the nervous system can be affected - not only the cranial nerves and the peripheral nervous system (2). Apart from transient, qualitative and quantitative impairment of consciousness and the pathognomonic keraunoparalysis (lightning paralysis) - a paresis and impaired sensitivity of the extremities of unclear etiology that usually lasts less than an hour - structural lesions may be found in the CNS, e.g. the visual cortex (3) or the myelon (1, 2). The consequences of lightning injuries to the peripheral nervous system are less well documented. However, the multitude of autonomous disorders that have been described in case reports together with pathophysiological considerations of a particular vulnerability of non-myelinated nerve fibers suggests an involvement of the peripheral nervous system. The etiology of the common subacute neurological and psychiatric deficits is not clear. These range from non-specific complaints, such as chronic fatigue and disrupted sleep, to clearly defined disorders like depression, post-traumatic stress disorder and cognitive deficits, which restrict the patient’s quality of life (2, 3). The conclusion is that all survivors of lightning strikes should be given neurological-psychiatric aftercare and eventually rehabilitation. A systematic study of the neurological, neurophysiological, and neuropsychological sequelae of lightning injuries is currently being conducted at the Department of Neurology, University of Regensburg.

Internal thermal injury: A case report

Internal burns resulting from thermal injury are not well documented in the literature. Thermal burns are categorized as first, second, and third degree based on depth, however, those burns that extend into deeper tissues have not had such a clear classification. Fourth degree burns are defined as injury extending to the subcutaneous fat, muscle, or bone. Although cutaneous second and third degree burns can be mapped to yield a percentage burn, this does not adequately describe the deeper tissue damage in a given burn patient. There have been very few reports of diffuse deep tissue burns resulting from thermal injury. We will refer to this as internal thermal injury. A 47-year-old male fire fighter was involved in a training exercise and was found unresponsive. This patient had been in the basement of a facility specially designed for fire fighter training exercises where he was found unconscious with an estimated exposure time of 8 min. The patient expired in cardiac arrest within 24 h of presentation. The physiological impact of high ambient temperatures on fire fighters has been well documented in the literature. Internal thermal injury was suspected given the history. Values assessed in training buildings, such as the one in which the patient was found, showed temperatures of 50-130 degrees C on the ground and 100-190 degrees C at 1 m above the ground. Temperatures of over 278 degrees C had been recorded within training buildings. Pain threshold is reached at a skin temperature of approximately 44 degrees C, and burn injury can occur at lower temperatures, depending on time of contact. Skin temperatures of fire fighters were found to range from 39 to 45.5 degrees C and core temperatures were measured by a miniature sensor in the form of a pill and were found to rise by 0.6-1 degrees C in 1 h within a training building. Therefore, it is possible that fire fighters undergo internal thermal injury before the sensation of cutaneous burn injury may be perceived. Kevlar is a material found in fire fighting gear and has been documented to have a degradation temperature of 520 degrees C. Kevlar can withstand high environmental temperatures; however, a great number of thermal injuries are due to an overheating of the body regardless of the thermal properties of Kevlar.

Flare case histories demonstrating problems and solutions

AbstractA flare is an important safety device for control and disposal of combustible gases. They are designed in accordance with API, ASME, EPA, and other codes. However, many other details and possible oversights, not found in the recommended practices, standards, and codes, can lead to dangerous conditions—bottlenecks, equipment malfunction, overpressure, flameout, vapor clouds, liquid carryover (burning rain), internal burning, and explosions. These normally overlooked details are also covered in this article. Vents and vent stacks will also be reviewed since they are simply a flare without a flame. They also use much of the same technology as a flare, except for the pilots, ignitors, and flame retainers. Some of these unsafe conditions, their causes, and their initial warning signs are presented from actual field experience and discussed in order to educate the engineer (design, piping, process, operating), plant operators, and maintenance people. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006

PYTHONS KEEP THE PRESSURE UP

![Figure][1] Staying warm takes an awful lot of effort. Mammals, and other warm-blooded creatures, ramp up their metabolic rates to keep the internal fires burning. However, fires don't rage unless they're well stoked, so mammals have souped-up their cardiac systems and raised their systemic

Evaluation of the Ultrasonic Dissector in Thyroid Surgery. A Prospective Randomised Study

Background: The use of ultrasonic dissectors in endoscopic surgery has proved to be of value, particularly for the prevention of bleeding and the reduction of electrical internal burns. This prospective randomised study was performed in order to evaluate the efficacy, security and cost of using the ultrasonic hook in thyroid surgery. Methods: Thirty-four consecutive euthyroid patients with multinodular goitre for whom a total thyroidectomy was indicated, were randomly assigned either to group I, Ultracision® or to group II, conventional hemostasis. Pre-, peri-, and postoperative biochemical, clinical, surgical and economical variables were compared between both groups. Results: The use of the ultrasonic hook resulted in a significant reduction in operating time, blood loss, and maybe in “transitory hypoparathyroidism”; postoperative analgesic consumption was also reduced in this group. Considering the cost, the ultrasonic hook was no more expensive than conventional hemostasis, as long as a minimum of 15 patients shared the initial unit cost of the device.Conclusion: Even if the use of the ultrasonic dissector is not of major interest in terms of patient management or cost-saving in the context of total thyroidectomy, essential advantages reside in significant reductions of operating time, blood loss and organ injury, (particularly parathyroid).The reduced operating time undoubtedly represents a positive feature of the ultrasonic dissection technique.

Miniature-scale liquid-fuel-film combustor

A new concept is explained for the miniaturization of cylindrical direct-injection liquid-fueled combustors wherein the fuel is flowed in a wall film that reduces heat losses, optimizes vaporization rate, and inhibits quenching. A simple analysis indicates that if a combustor of this type were part of a miniature engine, power levels from 10 W to 10 kW would be achievable with combustor volumes varying from a few hundred cubic millimeters to a few cubic centimeters and fuel flow rates varying from about 1 mg/s to 1 g/s. The combustor takes advantage of the fact that a surface area advantage of film combustion over spray combustion occurs for small volumes as the surface-to-volume ratio of the combustor increases. In addition, the wall film of fuel prevents heat losses while cooling the combustor surfaces. Photographs of a laboratory demonstration of the miniature film combustor concept with methanol and hepatane fuel and a mechanically swirled airflow are presented. The methanol flame required some methane gaseous fuel for stability, but the heptane fuel burned successfully alone. The experiments demonstrated externally and internally anchored flame modes, and a transition between them. The stability of internal burning was affected by internal fluid, dynamics and film dryout.

97/03069 Radiation extinction limit of counterflow premixed lean methane-air flames

This work focuses on the understanding of the oxidation of soot particles which were the result of using a JP-8 surrogate fuel in a two-stage burner. The two-stage system consists of an initial premixed burner where soot was generated with an air/fuel mixture, specifically a JP-8 surrogate (m-xylene and n-dodecane), under a variety of conditions. Downstream, the soot-laden combustion gases were passed through a second, flat-flame burner where soot was burned out under fuel-lean or slightly fuel-rich conditions. Soot oxidation in the secondary burner was determined by investigating particle size distribution (PSD), flame temperature, gas-phase composition, soot surface area, and soot morphology and nanostructure as a function of the height above the second burner (HAB). Measurements of soot size distribution and number concentration as a function of the HAB under fuel lean (Φoverall = 0.8) and slightly rich (Φoverall = 1.14) conditions showed a decrease in particle mean diameter and a significant increase in number concentration in the region where O2 concentration decreased. In this region, the effectiveness factor for O2 was found to be 1, indicating the potential for internal oxygen diffusion and burning. This caused both the breakup of the bridges cementing primary particles and the rupture of the primary particles. Higher in the burner, where modeling suggested the presence of OH*, soot oxidation was attributed to OH* mechanisms which are faster as compared to O2 oxidation.

Distribution and burning modes of char particles during combustion

The distribution and burning modes of various types of char produced from typical Chinese coals in a one-dimensional combustibility evaluation furnace were investigated. The results suggest that the char types formed in the devolatilization zone represent the initial distribution, with no significant combustion taking place. Corpohuminite and textinite in lignite appear to have thermal behaviour similar to inertinite during pyrolysis. Highly vesiculated cenospheres are rarely developed in lignite and semianthracite, due to their poor thermoplasticity. The percentages of different char types generally decrease during combustion although the different reaction rates, further fragmentation and internal burning may also result in the reverse change in some cases. The burning modes of various char particles are associated with the changes in external morphology and internal structure, cenospheres usually burn in a constant-diameter mode, while fragments tend to burn in a constant-density mode. Solid char shows two different burning modes: constant-density and mixed modes. Solid char burning in the mixed mode is considered to be depleted more quickly than that burning in the constant-density mode.

The influence of heterogeneous kinetics and thermal radiation on the oxidation of graphite particles

Numerical integrations have been performed to study the influence of porosity and radiation on the combustion of spherical graphite particles in a quiescent atmosphere. Two sets of heterogeneous rate constants, one assuming no internal burning and another assuming partial internal burning, have been employed for this purpose. Based on the quasi-steady burning conditions, the numerical predictions have shown for nonporous particles the existence of a critical particle diameter below which strong burning conditions cannot be sustained. This critical particle diameter is found to be a strong function of the porosity. The influence of thermal radiation on the burning characteristics has also been examined and a complex interaction identified between surface kinetics, gas-phase kinetics, mass transport through the boundary layer and thermal radiation.