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1.
Assessment of technologies for disposing explosive waste 总被引:7,自引:0,他引:7
The environmental impact and safety aspects are assessed for six different techniques for disposing decommissioned ammunition. These are open burning and open detonation (OD), closed detonation (CD), fluidised bed combustion (FBC), rotary kiln (RK) Incineration, and Mobile furnace (MF) Incineration. The assessment is performed in the form of a multi-criteria decision analysis (MCDA). Objectives for minimising environmental impact and risk are defined to enable selection of the "best" technology. A framework for comparing emissions of different air pollutants is proposed. Environmental impacts are described, especially air pollutants. The environmental impacts of traditional OB and OD can be drastically reduced using controlled incineration techniques in combination with high-pressure water washout. This enables the explosive contents to be separated from the casing, and simultaneously the explosive is transformed to a desensitised water-based slurry. 相似文献
2.
Incineration and gasification technologies completed with up-to-date off-gas cleaning system for meeting environmental limits 总被引:1,自引:1,他引:0
Radek Dvořák Tomas Pařízek Ladislav Bébar Petr Stehlík 《Clean Technologies and Environmental Policy》2009,11(1):95-105
It is shown how gasification can be used for processing wastes including “waste to energy” system. First, an analysis of incineration
of wastes taking into account environmental limits is performed. This analysis is aimed at a typical arrangement of a conventional
oxidizing incineration plant consisting of waste storage and feeding systems, two-stage incinerator (primary and secondary
combustion chambers), heat recovery system involving co-generation and off-gas cleaning system. It is also focused on a new
arrangement where the primary combustion chamber (rotary kiln) is substituted by gasification reactor. The proposed concept
with a fluidised bed reactor utilizes results of experimental research with various mixtures of wastes (e.g. shredded textile
and rubber) considering typical conditions of operation. Experiments provide us with various important characteristics (heat
value of produced syngas vs. temperature in the gasification reactor, temperature in the secondary combustion chamber vs.
oxygen concentration in outlet flue gas and heat value of syngas, etc.). Then it is possible to make a comparison of conventional
incineration and gasification for a concrete industrial process involving a unit for thermal treatment of hazardous industrial
waste mixed with municipal solid wastes with capacity of 10,000 t/year. The application of gasification technology brings
about the whole range of benefits like minimizing the consumption of auxiliary fuel and decreasing size of the secondary combustion
chamber and other subsystems of the incineration plants. Involving such a system with energy and investment cost reduction
into an industrial process contributes to meeting cleaner production and environmental legislation regulations. 相似文献
3.
K. Alverbro A. Bjrklund G. Finnveden E. Hochschorner J. Hgvall 《Journal of hazardous materials》2009,170(2-3):1101-1109
The Swedish Armed Forces have large stocks of ammunition that were produced at a time when decommissioning was not considered. This ammunition will eventually become obsolete and must be destroyed, preferably with minimal impact on the environment and in a safe way for personnel. The aim of this paper is to make a comparison of the environmental impacts in a life cycle perspective of three different methods of decommissioning/destruction of ammunition, and to identify the environmental advantages and disadvantages of each of these destruction methods: open detonation; static kiln incineration with air pollution control combined with metal recycling, and a combination of incineration with air pollution control, open burning, recovery of some energetic material and metal recycling. Data used are for the specific processes and from established LCA databases. Recycling the materials in the ammunition and minimising the spread of airborne pollutants during incineration were found to be the most important factors affecting the life cycle environmental performance of the compared destruction methods. Open detonation with or without metal recycling proved to be the overall worst alternative from a life cycle perspective. The results for the static kiln and combination treatment indicate that the kind of ammunition and location of the destruction plant might determine the choice of method, since the environmental impacts from these methods are of little difference in the case of this specific grenade. Different methods for destruction of ammunition have previously been discussed from a risk and safety perspective. This is however to our knowledge the first study looking specifically on environmentally aspect in a life cycle perspective. 相似文献
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Comparison of the characteristics of bottom and fly ashes generated from various incineration processes 总被引:2,自引:0,他引:2
This study analyzed and compared the characteristics of bottom and fly ashes from three municipal solid waste incinerators (MSWIs) in Taiwan. Different incineration furnaces were investigated, including: (1) fluidized bed, (2) mass-burning, and (3) mass-burning linked rotary kiln. The particle size distribution, morphology, mineralogical and chemical composition, and leaching behavior of heavy metals of ash samples were evaluated. The results revealed that three types of incineration processes have different characteristic for ashes due to transportation and mixing system inside furnace. Particle size distribution indicated that 28.5% of MSWI-B bottom ash has lower than 180 microm and 61.2% of MSWI-A fly ash has larger than the 250 microm. The leaching concentration of Pb exceeded the regulatory level set by the Taiwan EPA in fly ashes from MSWI-B and MSWI-C, and thus must be considered hazardous wastes. Specifically, the leaching concentration of heavy metals of fly ashes from MSWI-A (fluidized bed incinerator) was lower than that of the others, and was corresponded to the regulatory levels. Therefore, a fluidized bed incineration process appears a potential of handling heavy metals for ashes. The result was also provided the valuable information for incinerator design and operation. 相似文献
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Harris AT See CH Liu J Dunens O MacKenzie K 《Journal of nanoscience and nanotechnology》2008,8(5):2450-2457
Carbon nanotubes (CNTs) are a form of crystalline carbon with extraordinary properties, making them valuable in a broad range of applications. However, the lack of suitable large-scale manufacturing techniques, which we define as being of the order 10000 tonnes per annum, continues to inhibit their widespread use. Of the three established synthesis methods for CNTs: (i) chemical vapour deposition (CVD), (ii) laser ablation, and (iii) arc discharge, CVD techniques show the greatest promise for economically viable, large-scale synthesis. In particular, the fluidised bed CVD (FBCVD) technique, where the CVD reaction occurs within a fluidised bed of catalyst particles, has the potential to produce high quality CNTs, inexpensively, in large quantities. In this work we report on the development of a catalytic chemical vapour deposition process, using batch fluidised bed reactors, for the synthesis of straight and spiral carbon nanotubes at pilot scale (up to 1 kg/hr). We believe this to be the first report of the synthesis of spiral carbon nanotubes using fluidised bed CCVD. Iron, nickel and cobalt transition metal catalysts supported on non-porous alumina substrates were fluidised in a mixture of nitrogen, hydrogen and ethylene at temperatures between 550 and 800 degrees C for between 15 and 90 minutes. Nanotube yield was inferred from thermogravimetric analysis and the quality and size of the CNTs from transmission electron microscopy. Conflicting information in the literature about the influence of synthesis parameters on CNT properties suggests that further investigation is necessary to understand the synthesis process at a fundamental level, i.e., independent of reactor design and operation. 相似文献
9.
《Advanced Powder Technology》2020,31(2):678-694
Soft computing data-driven modeling (DDM) techniques have attracted the attention of many researchers across the globe as they do not require deep knowledge of the complex physical process. In the present research, data-driven based models have been developed using support vector regression (SVR), multilayer perceptron neural network (MLP), radial basis function neural network (RBFNN) and general regression neural networks (GRNN) techniques for predicting the bed depth profile of solids flowing in a rotary kiln. The performances of the developed models were compared and evaluated against the experimental results in terms of statistical measures such as coefficient of determination (R2), and average absolute relative error (AARE). The obtained results and findings from this research have revealed that data-driven models can predict the bed depth profile of solids flowing in a rotary kiln quite accurately. The SVR-based model exhibited the lowest AARE value of 1.72% and highest R2 value of 0.9981 while GRNN, RBFNN, and MLP models gave corresponding values of AARE as 3.69%, 55.13%, 98.15% and those of R2 as 0.9898, 0.0052 and 0.0081, respectively. Moreover, the developed DDM-based models i.e. GRNN, RBFNN, and MLP models overcame the limitations of the existing solutions which involved iterative numerical procedure entailing high degree of computational complexity. 相似文献
10.
An approach to simulate the motion of spherical and non-spherical fuel particles in combustion chambers 总被引:6,自引:0,他引:6
The objective of this paper is to identify a numerical method to simulate motion of a packed or fluidized bed of fuel particles
in combustion chambers, such as a grate furnace and a rotary kiln. Therefore, the various numerical methods applied in the
areas of granular matter and molecular dynamics were reviewed extensively. As a result, a time driven approach was found to
be suited for the numerical simulation of particle motion in combustion chambers. Furthermore, this method can also be employed
to moving boundaries which are required for the present application e.g. travelling grate. The method works in a Lagrangian
frame of reference, which uses the position and orientation of particles as independent variables. These are obtained by time
integration of the three-dimensional dynamics equations derived from the classical Newtonian approach for each particle. This
includes the keeping track of all forces and momentums acting on each particle at every time step. Viscoelastic contact forces
include normal and tangential components with viscoelastic models for energy dissipation and friction. The particle shapes
are approximated by spheres and ellipsoids with a varying size and ratio of the semi-axis accounting for the variety of particle
geometries in a combustion chamber. For these shapes the overlap of particles during contact is expressed by a polynomial
of 4th order in the two-dimensional case and a polynomial of 6th order in the three-dimensional case. A new algorithm to detect
two-dimensional elliptical particle contact with sufficient accuracy was developed. It is based on a sequence of coordinate
transformations and has demonstrated its reliability in numerous applications. Finally, the method was applied to simulate
the motion of spherical and elliptical particles in a rectangular enclosure, on a travelling grate, and in a rotary kiln.
Received: 16 November 2001 相似文献
11.
An experimental investigation was carried out for transition of combustion into detonation of oxygen-hydrogen and hydrogen-air
stoichiometric mixtures within a cylindrical channel with a diameter of 3 mm, which is less than the critical diameter of
the existence of stationary detonation in the hydrogen-air mixture. To realize the transition of combustion into detonation
in the channel, the combustible mixture was ignited within a precombustion chamber with a diameter of 14.5 mm which was arranged
in line with the channel on one of its faces. The expanding products of mixture combustion within the precombustion chamber
accelerate the flame front at the input of the channel, thus increasing the energy amount released during mixture combustion
within the narrow channel per unit time. As a result, the ratio of the burning energy to dissipative losses in channel walls
increases, which makes transition into detonation realizable. The use of the precombustion chamber allowed us to obtain the
transition of combustion into the detonation wave with the Chapman-Jouguet parameters at initial mixture pressures of 1 and
2 atm. The effect of the size of the turbulizing precombustion chamber on the length of the transition of combustion into
detonation is analyzed, and the average velocities of flame front propagation along the channel are determined. 相似文献
12.
Brailovsky I Kagan L Sivashinsky G 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2012,370(1960):625-646
The effects of hydraulic resistance on the burning of confined/obstacle-laden gaseous and gas-permeable solid explosives are discussed on the basis of recent research. Hydraulic resistance is found to induce a new powerful mechanism for the reaction spread (diffusion of pressure) allowing for both fast subsonic as well as supersonic propagation. Hydraulic resistance appears to be of relevance also for the multiplicity of detonation regimes as well as for the transitions from slow conductive to fast convective, choked or detonative burning. A quasi-one-dimensional Fanno-type model for premixed gas combustion in an obstructed channel open at the ignition end is discussed. It is shown that, similar to the closed-end case studied earlier, the hydraulic resistance causes a gradual precompression and preheating of the unburned gas adjacent to the advancing deflagration, which leads (after an extended induction period) to a localized autoignition that triggers an abrupt transition from deflagrative to detonative combustion. In line with the experimental observations, the ignition at the open end greatly encumbers the transition (compared with the closed-end case), and the deflagration practically does not accelerate up to the very transition point. Shchelkin's effect, that ignition at a small distance from the closed end of a tube facilitates the transition, is described. 相似文献
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K. T. Ewida H. El-Salmawy N. N. Atta M. M. Mahmoud 《Clean Technologies and Environmental Policy》2006,8(3):188-197
A technique for controlled burning of rice straw is presented. It relies on well-designed rice straw pellets to be burned in fluidized bed. The developed pellets have high burning rate, no fly ashes emissions and minimum bed fouling. The pellets are manufactured from ground rice straw in a disc pelletizer with the aid of bonding and suitable additive materials. The pellets are tested under controlled conditions in a test rig, which represents a single pellet fluidized bed. It is equipped with a nitrogen gun to eject the pellet and freeze the reaction at any predetermined time during combustion. The ejected pellets are weighed as well as elementary analyzed for both carbon and hydrogen, to calculate the burning rate as well as the combustion efficiency, respectively. The effect of several parameters has been evaluated including straw particle size, pellet size, type and concentration of bonding material as well as anti-sintering additives. Also, the pellets’ mechanical characteristics have been evaluated. It has been found that char combustion phase represents the controlling phase of the pellet combustion. The burning rate is higher as the void fraction of the pellet is higher. Starch showed better combustion and mechanical characteristics out of the five tested bonding materials. Adding kaolin to the pellets results in improving the sintering characteristics of the pellets. The experimental results were compared with two combustion models: the oxygen diffusion controlled and the kinetic-diffusion models. It has been found that oxygen diffusion controlled model more accurately simulates the combustion of the pellet during its char combustion phase. The model has been used to evaluate the effect of some operational parameters on the pellet combustion characteristics such as bed temperature, gas flow and oxygen concentration. 相似文献
15.
Degradation of PCDD/Fs by mechanochemical treatment of fly ash from medical waste incineration 总被引:1,自引:0,他引:1
The potential of mechanochemical treatment (MC) to degrade PCDD/Fs contained in fly ash was tested via grounding with and without calcium oxide (CaO) under atmospheric pressure. Three types of fly ash collected from medical waste incineration were compared, originating either from rotary kiln fluidized bed multi-stage incinerator using activated carbon spray (FA1, FA2), or a simple stoker incinerator without activated carbon spray (FA3). In test I: CaO to FA1 mixed at ratio of 6-60% was milled at rotational speed of 350 rpm; in test II: FA2 and FA3 without CaO were milled at rotational speed of 400 rpm. The duration of the tests was 2h. The results from the present study indicate that (1) under two test conditions of with and without CaO, PCDD/Fs contained in real fly ash both can be degraded by mechanochemical treatment, (2) under condition of blending with CaO, the degradation efficiency of PCDD/Fs increased with increasing ratio of CaO, (3) the degradation efficiency of PCDD/Fs may increase with rotational speed increasing and (4) the destruction and dechlorination are major mechanism for PCDD/Fs degradation. These results show that mechanochemical treatment is a high potential technology for PCDD/Fs degradation in fly ash. 相似文献
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Various aspects of fluidized bed combustion of coal are reviewed and its applicability to Indian coals is considered. Such coals are high in ash and fluidized bed combustion presents a suitable method for burning middlings and rejects from coal washeries. Moreover, fluidized bed combustors have an added advantage of contributing to the abatement of atmospheric pollution due to sulphur and nitrogen oxides. Fluidized bed combustion has some disadvantages, but they can be overcome by modern innovations, as reported in this paper. This review also discusses mathematical modelling of fluidized bed combustion, with a comparison of some models for predicting the burn-out time. 相似文献
18.
《International Journal of Engineering Science》2006,44(15-16):1071-1081
At the CEA, the incineration of radioactive wastes is carried out thanks to the IRIS process involving a oxidizing pyrolysis step performed with a rotary kiln. If the running of the process is very satisfactory for processing waste of a given composition, it appears that the behavior of the kiln may diverge when the composition of the waste change. Through the example of wastes containing a large amount of PVC and thanks to a very simple modelling of the heating of the kiln, it has been demonstrated that the deposits are involved in overheating of the pyrolysis kiln. Fundamental investigation carried out about the thermal degradation of PVC and cellulose have shown that the formation of intermediate PVC decomposition compounds together with the residues coming from the decomposition of the cellulose could be responsible of the large amount of deposits. In order to avoid the malfunctions it has been proposed to revise the furnace operating parameters by specifying a waste feed sequence that ensure a relaxation period to the furnace. By this way, the running of the facility shows a very good stability with a very thin temperature oscillation that can easily be explained by a thermal modelling of the kiln. 相似文献
19.
Modelling of heavy metal vaporisation from a mineral matrix 总被引:1,自引:0,他引:1
This study deals with the fundamental aspects of the volatilisation of heavy metals (HM) during municipal solid waste (MSW) incineration. The thermal treatment of a model waste was theoretically and experimentally studied in a fluid-bed. A mathematical model was developed to predict the fate of metallic species according to the main phenomena controlling the process: heat and mass transfer (transport phenomena), chemical reactions involving HM, and mechanism of vapour metal species sorption inside the porous matrix. The model assumes local thermodynamic equilibrium between the vapour and the metal compound on the substrate in the pores of a particle. This approach permits to predict the extent of HM vaporisation from a mineral porous matrix when its physical properties are known. Experimental data concerning CdCl(2) release from an alumina matrix in a 850 degrees C fluidised bed are in good agreement with theoretical results. 相似文献
20.
AGNIESZKA SOBCZAK-KUPIEC ZBIGNIEW WZOREK REGINA KIJKOWSKA ZYGMUNT KOWALSKI 《Bulletin of Materials Science》2013,36(4):755-764
The paper presents in vitro (in SBF) behaviour of hydroxyapatite (HAp) obtained from pork bone sludge from meat plant via two essentially different calcination methods using a stationary, electrically heated chamber oven and enlarged laboratory scale rotary kiln designed by the authors, heated by gas combustion methods enabling application of different set of physical parameters such as temperature, holding time-differing according to type of the kiln. HAp ceramic discs, after 62-days of incubation in SBF at 37 °C, characterized by X-ray diffraction (XRD), FTIR, SEM and EDS methods, underwent changes recorded by: (i) a reduction in Ca/P molar ratio in all the investigated materials resulting from modification in phase composition and (ii) weight increase in the investigated disc-samples, resulting from a precipitation of newly formed phase as an admixture of primary HPO $_{{4}}^{{2-}}$ -free HAp. They were: secondary (with HPO $_{{4}}^{{2-}}$ incorporated) HAp and chlorapatite in all the samples, while in addition to the listed above, β -tricalcium phosphate was formed on the discs made of HAp from stationary chamber oven, but not from rotary kiln. The new phases were formed in agglomerates on the surface of the investigated ceramic discs and in their pores. The results obtained proved that calcination conditions of pork bone sludge (temperature 750–950 °C, time and type of the applied kiln) under which hydroxyapatite (HAp) powders were obtained had an impact on its different behaviour in SBF, nevertheless, indicating a potential ability of the material to form a new biologically relevant interface with hard tissue and suitability for further investigations intended for medical grafting. 相似文献