Fluidized bed incinerator for medical waste that generates no residual dioxin: a mini-review

The advantages of medical waste incineration include the sterilization of bacteria, stabilization of chemical activity, and reduction in waste volume. During the incineration of medical waste, dioxin is generated owing to the high chlorine content. Based on previous research, a conventional fluidized bed combustor with a minimum retrofit to dispose of medical waste without residual dioxins is presented in this study. Coal or pyrite was added to inhibit dioxin formation in the combustion chamber. Fly ash and activated carbon which had adsorbed dioxin were pelletized with adhesive material, and the pelletized fly ash was then recycled to the incinerator for burning. The pelletized fly ash with adhesive material was finally discharged as bottom ash. Bottom ash constitutes the net output of the entire incineration system. and its dioxin content can be neglected. An incineration system that does not produce dioxin residue was achieved; however, a better formula for the pelletized fly ash is still required.

Title page (short abstract)

1. The emission of dioxin from medical waste incinerators can’t be eliminated by disabling PVC as a raw material of medical devices.

2. Based on the knowledge shown in the previous literature, an integrated fluidized bed incineration system without dioxin residual installed in a large hospital is proposed in this study.

3. There are many ways to reduce dioxin formation during the incineration process; however, conventional methods can’t eliminate the existence of dioxin in fly ash.

4. Pelletized fly ash recycled to the incinerator for re-burning and discharged in the form of bottom ash which is considered dioxin free.

     

Biosorption performance,combustion behavior,and leaching characteristics of olive solid waste during the removal of copper and nickel from aqueous solutions

Several researchers have proved that agricultural by-products constitute good adsorbents for removing heavy metals from aqueous solution. However, few investigations have identified efficient strategies for the adsorbent′s regeneration. Hence, a global methodology for the removal of copper and nickel metals from wastewater including metal biosorption, thermal treatment and residual ash landfill is proposed. In order to validate this strategy, olive solid waste (OSW), provided by an olive oil mill from Tunisia, were used to remove copper and nickel on batch experiments. Copper and nickel were adsorbed on a monolayer of OSW surface with maximal adsorption capacity (q _max) of 3.6 and 1.7 mg g^?1, respectively. Contaminated OSW with copper and nickel were combusted at 850 °C in an electrical furnace. About 96 % of each metal was recovered in residual ashes that present a good secondary raw material for copper and nickel production. Low leaching transfers (≤4 %) were observed for copper and nickel from residual ashes leading to the possibility to be landfilled. Therefore, the suggested process can be used as an alternative to the classical technologies for effluent decontamination.     

Polychlorinated naphthalenes and other chlorinated tricyclic aromatic hydrocarbons emitted from combustion of polyvinylchloride

Chloronaphthalenes (CNs) and phenanthrenes or/and anthracenes (CP/CAs) were detected in the emissions of polyvinylchloride (PVC) combustion at 900 degrees C. The presence of metallic iron, copper, or aluminum increased the formation of highly chlorinated CNs (tri- to octachloro-homologues) in the PVC combustion process. Total levels of CNs and CP/CAs were 40-48 and 76-116 mg/kg PVC, respectively, in the emissions from combustion of PVC with metals. Monochloronaphthalenes, dichloronaphtahlenes, monochlorophenanthrenes, and monochloroanthracenes were the predominant homologues. The other CN homologues were minor combustion byproducts. Detection of CNs in the PVC combustion emissions suggests that CN formation from solid waste incineration is a source of CNs in the environment.     

Preparation of phosphides in the combustion regime

The data on interaction of some transition metals with red phosphorus in the combustion regime are presented. The phase composition was investigated as a function of such parameters of combustion as rate of combustion, initial phosphorus content, pressure of ineert gas and preheating.     

Polycyclic aromatic hydrocarbon (PAH) emissions from a coal-fired pilot FBC system

Due to the extensive amount of data suggesting the hazards of these compounds, 16 polycyclic aromatic hydrocarbons (PAHs) are on the Environmental Protection Agency (EPA) Priority Pollutant List. Emissions of these PAHs in the flue gas from the combustion of four coals were measured during four 1000h combustion runs using the 0.1MW heat-input (MWth) bench-scale fluidized bed combustor (FBC). An on-line sampling system was designed for the 16 PAHs, which consisted of a glass wool filter, condenser, glass fiber filter, Teflon filter, and a Tenax trap. The filters and Tenax were extracted by methylene chloride and hexane, respectively, followed by GC/MS analysis using the selective ion monitoring (SIM) mode. In this project, the effects of operating parameters, limestone addition, chlorine content in the coal, and Ca/S molar ratio on the emissions of PAHs were studied. The results indicated that the emissions of PAHs in an FBC system are primarily dependent on the combustion temperature and excess air ratio. The injection of secondary air with high velocity in the freeboard effectively reduces PAH emissions. The addition of extra limestone can promote the formation of PAHs in the FBC system. Chlorine in the coal can possibly lead to large benzene ring PAH formation during combustion. The total PAH emission increases with an increase in the sulfur content of coal. Incomplete combustion results in PAHs with four or more benzene rings. High efficiency combustion results in PAHs with two or three benzene rings.     

燃烧氧化偶联离子色谱法检测甲醇中有机氯

本文提出采用燃烧氧化偶联离子色谱法测定甲醇中有机氯含量的新方法。方法先用离子色谱法直接定量甲醇中无机氯含量,再用离子色谱法测量甲醇中所含的总氯在燃烧氧化过程生成的Cl_2、HCl、气态的无机氯化合物被I吸收生成的Cl~-来定量甲醇中总氯含量。由测得的总氯含量和无机氯含量,计算得甲醇中有机氯含量。实验结果表明该方法经济、简单、准确、灵敏。     

Theoretic model and computer simulation of separating mixture metal particles from waste printed circuit board by electrostatic separator

Traditionally, the mixture metals from waste printed circuit board (PCB) were sent to the smelt factory to refine pure copper. Some valuable metals (aluminum, zinc and tin) with low content in PCB were lost during smelt. A new method which used roll-type electrostatic separator (RES) to recovery low content metals in waste PCB was presented in this study. The theoretic model which was established from computing electric field and the analysis of forces on the particles was used to write a program by MATLAB language. The program was design to simulate the process of separating mixture metal particles. Electrical, material and mechanical factors were analyzed to optimize the operating parameters of separator. The experiment results of separating copper and aluminum particles by RES had a good agreement with computer simulation results. The model could be used to simulate separating other metal (tin, zinc, etc.) particles during the process of recycling waste PCBs by RES.     

Luminescent properties of La3PO7:Eu3+ nanoparticles

La3PO7:Eu3+ samples were prepared by combustion and annealing and characterized by X-ray diffraction and transmission electron microscopy. It was found that the average size of the particles is about 80 nm. The red emission from the 5D0 --> 7F2 transition of the Eu3+ ions under ultraviolet light excitation is much stronger than the orange emission from the 5D0 --> 7F1 transition. The emission spectra, charge transfer band, laser selective excitation spectra, and time-resolved spectra indicate that symmetry of the local environment of Eu3+ lacks an inversion center and Eu3+ ions occupy at least two types of sites in the La3PO7 crystal. The superior color chromaticity compared to other phosphates and borates doped with Eu3+ means La3PO7:Eu3+ may have potential as a luminescent material.     

直喷柴油机两种燃烧方式混合气形成的比较

利用KIVA-3V软件模拟了柴油机两种燃烧方式的混合气形成过程中的浓度场和温度场.模拟计算与实验结果表明,在常规柴油机燃烧方式中,燃油边喷边烧,混合气浓度和温度变化很大,导致预混合燃烧和扩散燃烧并存,NOx和碳烟比较高,CO和HC排放很低;利用早喷可以形成浓度场和温度场分层分布的均质混合气,实现均质充量压燃(HCCI)燃烧,碳烟和NOx很低,但CO和未燃烧的燃油排放很高.     

Cost-Minimization Model for Reducing Sulphur Dioxide Emission from Coal-Fired Generating Stations

To limit emission of sulphur dioxide, an electrical utility has several available options: (i) Burn low-sulphur coal, (ii) remove SO₂ from flue gases after combustion (Flue Gas Desulphurization or FGD), and (iii) remove sulphur from coal before combustion (Physical Coal Cleaning or PCC). Options (ii) and (iii) vary in their cleaning capabilities and scale economies. Pre-cleaning of coal followed by post-cleaning of flue gases may thus be less costly than either PCC or FGD alone to obtain a given level of sulphur removal. A mathematical programming model to determine the best combination of options is developed from empirical cost data and solved for typical conditions encountered by North American utilities. Sensitivity analyses are carried out with respect to the various operating and capital costs, as well as the maximum SO. emission level. The latter enables assessment by the regulatory authorities of proposed environmental standards. Finally, we show how the model can aid a utility in directing its R&D effort by estimating the target sulphur removal capability which should be sought for each control technique and the cost saving (ROI from R&D) if successful.     

Synthesis and anti-bacterial activity of Cu, Ag and Cu-Ag alloy nanoparticles: A green approach

Metallic and bimetallic nanoparticles of copper and silver in various proportions were prepared by microwave assisted chemical reduction in aqueous medium using the biopolymer, starch as a stabilizing agent. Ascorbic acid was used as the reducing agent. The silver and copper nanoparticles exhibited surface plasmon absorption resonance maxima (SPR) at 416 and 584 nm, respectively; while SPR for the Cu-Ag alloys appeared in between depending on the alloy composition. The SPR maxima for bimetallic nanoparticles changes linearly with increasing copper content in the alloy. Transmission electron micrograph (TEM) showed monodispersed particles in the range of 20 ± 5 nm size. Both silver and copper nanoparticles exhibited emission band at 485 and 645 nm, respectively. The starch-stabilized nanoparticles exhibited interesting antibacterial activity with both gram positive and gram negative bacteria at micromolar concentrations.     

Synthesis of CuO,Cu and CuNi alloy particles by solution combustion using carbohydrazide and N-tertiarybutoxy-carbonylpiperazine fuels

Solution combustion synthesis has been used for the preparation of finely dispersed copper oxide, copper and copper–nickel bimetallic particles. The structure and morphology of the materials are studied by XRD and SEM techniques. The fuel content in the combustion mixture is found to be a crucial factor in controlling the formation of oxide and metal particles. Starting with copper nitrate trihydrate as oxidizer (O) and carbohydrazide as fuel (F), we obtained CuO (F/O=0.75–1), mixed valence copper oxides, CuO+Cu₂O, (F/O=1.0–1.5) and metallic Cu (F/O=2). At very low fuel content (F/O=0.5), a polymeric phase of copper hydroxide nitrate is isolated from the combustion residue. We also report the use of a new organic fuel N-tertiarybutoxy-carbonylpiperazine for the preparation of Cu, Ni and CuNi bimetallic particles.     

Highly enhanced luminescence of SrB4O7:Eu phosphor prepared by the combustion method using glycine as fuel

Eu²⁺ ion doped into SrB₄O₇ matrix was prepared by combustion method heated at 900 °C in air, using urea (U) or glycine (G) as fuels in different ratios (U100, A10, A25, G10, G25, G75, and G100). In some compositions, ammonium acetate (AA) was used to reduce the exothermicity of combustion reaction. X-ray diffraction and luminescence spectroscopy were used to characterize the material. The high intense emission band at 367 nm is assigned to 4f⁶5d → 4f⁷(⁸S_7/2) transition arisen from divalent europium ion. It is observed that the interconfigurational transition is dependent on the molar ratio of glycine:urea fuels. Glycine fuel favors Eu²⁺ formation in SrB₄O₇ host lattice prepared by combustion method.     

利用BP网络建立稻壳制备高纯纳米SiO2数学模型

为降低纳米SiO2的制备成本,以稻壳为原料,经盐酸预处理、高温燃烧,成功制得了高纯纳米SiO2.通过正交实验和BP神经网络系统研究盐酸体积分数、燃烧温度和燃烧时间的变化对SiO2纯度的影响规律,并采用XRD、FT-IR、BET及FE-SEM对所得到的SiO2样品进行表征.研究表明:影响SiO2纯度的主次因素依次为燃烧温...     

Thin films of molybdenum and tungsten disulphides by metal organic chemical vapour deposition

Thin films of MoS₂ and WS₂ have been prepared on various substrates (glass, quartz, LiF, MgO, mica, molybdenum, gold, platinum, aluminium, copper, steel, graphite, MoSe₂) by metal-organic chemical vapour deposition using sulphur or hydrogen sulphide and the hexacarbonyls of the transition metals as volatile components. The deposition technique is described here. The thin layers have been examined by X-ray powder diffraction and scanning electron microscopy. Time-resolved microwave conductivity measurements were used to detect the photoactivity of these materials.     

Homogeneity range of copper molybdenum sulphide CuxMo6S8−y

A series of copper molybdenum sulphides Cu₂Mo₆S_8?y were prepared by direct combination of the elements at 1100 °C. X-ray examination of the resulting samples suggested that the phase boundaries of the Cu₂Mo₆S_8?y single phase region extended between values for (8?y) of 7.7 and 7.85 respectively. At low sulphur contents the phase is in equilibrium with molybdenum, and with molybdenum disulphide at the higher sulphur compositions. Optimum conditions for hot pressing the composition Cu₂Mo₆S_7.59 were also evaluated. The copper content of dense samples of this composition was subsequently varied by solid state electrochemical coulometry at 95°C to produce Cu_xMo₆S_7.59 samples having copper contents of 0.29, 1.05, 1.49, 2.61, 3.13, and 3.36. X-ray examination of these samples and inspection of other published data suggested that the phase Cu_xMo₆S_7.59 could exist over a range of copper concentrations corresponding to x values of 1.0 and 3.4.     

Evaluation of hazardous waste incineration in lime kiln: Rockwell lime company

During a one-week test burn, hazardous waste was used as supplemental fuel and co-fired with petroleum coke in a lime kiln in eastern Wisconsin. Detailed sampling and analysis was conducted on the stack gas for principal organic hazardous constituents (POHCs), particulates, particulate metals, HCl, SO₂, NO_x, CO, and THC and on process streams for metals and chlorine. POHCs were also analyzed in the waste fuel. Sampling was conducted during three baseline and five waste fuel test burn days. Results show average destruction and removal efficiences (DREs) greater than 99.99% for each POHC and little change in pollutant emissions from baseline to waste fuel test conditons. In addtion, material balance results show that 95% of chlorine enters the process from the limestone fed and the chlorine exits the kiln in the baghouse dust and lime product at 61% and 38%, respectively.     

Effects of calcium-based sorbents on PCDD/F formation from pentachlorophenol combustion process

Calcium-based sorbents are widely employed to reduce the acidic gases emission from combustion processes, and also have effects on trace organic pollutants formation and emission. Batch experiments were conducted to investigate the effects of calcium-based sorbents on pentachlorophenol (PCP) forming PCDDs/Fs during high temperature combustion processes. The results indicated that highly chlorinated PCDD/F homologues were the predominant dioxin products from PCP thermo decomposition, and only minor increasing of PCDDs happened when Ca/Cl ratio was lower than 1, while a major jump occurred when Ca/Cl ratio increased from 1 to 2. The CaO addition clearly promoted the production of all chlorinated dibenzo-p-dioxins homologue and 4-7DFs homologue. Comparison of total PCDD/F emission and its I-TEQ for three different calcium-based sorbents addition (CaO, CaCO3, basic fly ash) indicated that CaO and fly ash containing CaO had almost the same promotion effects on PCDDs/Fs originated from PCP, while CaCO3 inhibit PCDD/F formation greatly with inhibition efficiency up to 70%. Such effects may be partly proved by the observed clearly different micro-surface structures of their reaction residues. The mechanism of CaO on condensation and dechlorination reactions for PCP forming PCDDs and acid-base interaction were proposed to speculate the promotion effects of CaO, and the reaction precedence was used to speculate the inhibition effects of CaCO3 on PCDDs/Fs originated from PCP. The results of the present paper might be useful for the industrial application of calcium-based sorbents to control PCDD/F emission.     

A review of factors controlling the gas turbine hot section environment and their influence on hot salt corrosion test methods

Environmental and operational factors that influence the formation and deposition of corrosive species on hot section components in gas turbine engines are reviewed. In addition to air and fuel impurities, combustion gas chemistry, velocity, pressure and temperature are identified as key operational factors affecting the formation and deposition of Na₂SO₄ salt (the primary corrosive species) when trace amounts of sodium and sulphur are entrained into combustors. Test methods for ranking the resistance of different materials to hot salt corrosion are reviewed and compared in terms of the type of damage they produce. The methods considered range from a simple furnace or crucible test to burner rig and engine tests. It is shown that high velocity burner rigs, running at atmospheric pressure, allow all the relevant operational factors to be simulated, and they produce realistic hot corrosion damage similar to that observed on engine parts in service.