Analysis and simulation of the process of medicobiological waste treatment in a plasma chamber incinerator

Analysis of the composition and the degree of toxicity of medicobiological wastes has been performed with the use of the results of investigations made in different countries. It has been shown that such wastes are highly hazardous to ecology and a universal technology of their management is needed. We have developed and tested a plasma chamber incinerator for plasmothermal treatment of medicobiological waste. To optimize the operating conditions of the facility and prevent chemical and thermal pollution of the environment, we have constructed a model of thermal calculation of the plasma chamber incinerator. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 12–16, July–August, 2006.     

Effect of DC steam plasma on gasifying carbonized waste

A feasibility study has been conducted to determine whether steam plasma can be used for the treatment of carbonized wastes, such as the carbide of the hazardous waste. The gasification which was often called “water gas reaction” was studied to reduce the volume and weight of wastes and to produce the combustible gas like hydrogen from them by using steam plasma. In this study, the thermal plasma generated by DC plasma was used as a heat source, where steam was added to react with carbon. Graphite was used as a test piece instead of carbonized wastes. The weight of the test piece was measured before and after treatment to decide the weight reduction during the experiment. The gas produced in the reaction was analyzed. The result indicated that it is possible to reduce the weight of graphite and to produce the combustible gas from graphite by using the DC steam plasma.     

Thermal plasma processing of materials: A review

The use of thermal plasma in materials processing industries is becoming an increasingly active and attractive field for the development of new technology. The potential applications of thermal plasma processing technology cover a wide range of activities, such as: the extraction of metals, the refining/alloying of metals/alloys, the synthesis of fine ceramic powders, spray coatings, and the consolidation and destruction of hazardous wastes. A review of thermal plasma applications in materials processing is presented.     

Thermal treatment of toxic metals of industrial hazardous wastes with fly ash and clay

Waste generated from galvanizing and metal finishing processes is considered to be a hazardous due to the presence of toxic metals like Pb, Cu, Cr, Zn, etc. Thermal treatment of such types of wastes in the presence of clay and fly ash can immobilizes their toxic metals to a maximum level. After treatment solidified mass can be utilized in construction or disposed off through land fillings without susceptibility of re-mobilization of toxic metals. In the present investigation locally available clay and fly ash of particular thermal power plant were used as additives for thermal treatment of both of the wastes in their different proportions at 850, 900 and 950 degrees C. Observed results indicated that heating temperature to be a key factor in the immobilization of toxic metals of the waste. It was noticed that the leachability of metals of the waste reduces to a negligible level after heating at 950 degrees C. Thermally treated solidified specimen of 10% waste and remaining clay have shown comparatively a higher compressive strength than clay fired bricks used in building construction. Though, thermally heated specimens made of galvanizing waste have shown much better strength than specimen made of metal finishing waste. The lechability of toxic metals like Cr, Cu, Pb and Zn became far below from their regulatory threshold after heating at 950 degrees C. Addition of fly ash did not show any improvement either in engineering property or in leachability of metals from the solidified mass. X-ray diffraction (XRD) analysis of the solidified product confirmed the presence of mixed phases of oxides of metals.     

Sources, characteristics and treatment and disposal of industrial wastes containing hexachlorobenzene

Hexachlorobenzene (HCB) is a hazardous component of certain industrial wastes. The hazardous characteristics of HCB stem from its toxicity, potential for bioaccumulation and environmental persistence. A study was conducted to identify the sources and characteristics of manufacturing wastes containing hexachlorobenzene and to review and document methods currently used for treatment and disposal of HCB wastes.The chlorinated solvents and pesticide industries were found to account for nearly all HCB wastes produced (4,305 tons per year) by the 14 industries reviewed as sources of HCB wastes.Waste storage methods which are used prior to ultimate disposal include storage of solid waste cubes under plastic cover and use of water-covered lagoons. Methods for transportation of HCB wastes include use of forklift, truck, pipeline, heated tank trucks and rail. Ultimate waste disposal methods include land disposal, incineration (with or without by-product recovery), resource recovery, discharge to municipal sewage treatment plants, and emission to the atmosphere. The majority of the HCB waste handled by the industrial facilities reviewed is currently disposed of in two industrial landfills using a soil cover of 4 to 6 ft. with a polyethylene film placed at approximately the mid-depth of the soil cover. Incineration at a sufficiently elevated temperature can effectively destroy HCB; HCl can be recovered as a by-product.Very limited actual disposal cost data are available on existing facilities handling HCB wastes.     

Thermal Processing of Wastes in a Shaft Incinerator with a Plasma Blast and a Combustible Filtering Material: Analysis of the Energy Consumption and Variants

As a continuation of previous publications, the authors report results of analytical substantiation and evaluation of energy consumption for different versions of thermal processing, incineration, and evaporation of a wide range of toxic and radioactive wastes in a shaft incinerator with plasma air blast beneath a layer of a charge of filtering and combustible material such as wood sawdust, which absorbs up to 98–99% of the aerosols of waste gases and fixes the aerosols in the ash. The volume and specific energy consumption of the plasma blast and also conditions and possibilities for eliminating it due to the intrinsic heat release of the wastes and wood sawdust by means of this method are determined. The expediency of incineration and vitrification of the ash residue of radioactive wastes separately in a smallvolume melting crucible is shown, which allows a no less than twofold decrease in the total energy consumption as compared to the combined version of such processing.     

Treatment and disposal of hazardous wastes in Western Europe

In western Europe, as in other industrialised areas, there has been growing concern about the disposal of wastes of a hazardous or toxic nature. The increasing quantities and complexities of wastes from industrial processes, and the greater awareness of potential risks to health of present and future generations arising from indiscriminate or inadequate methods of disposal, are causing governments to undertake an intensive examination of the whole field of waste management.Reliable data on the types and quantities of hazardous wastes are very difficult to acquire and information available is generally based on estimates.Legislative and administrative measures are being proposed and developed, which will provide a framework for better control and improved standards for the handling, treatment and disposal of toxic and other hazardous wastes.In planning disposal systems, more attention will be given to methods of recovering and recycling materials which are becoming scarce or expensive. As stricter environmental controls raise disposal costs, there will be more incentive on industry to recycle wastes, where practicable.     

Breakthrough Technologies for the Biorefining of Organic Solid and Liquid Wastes

Organic solid and liquid wastes contain large amounts of energy, nutrients, and water, and should not be perceived as merely waste. Recycling, composting, and combustion of non-recyclables have been practiced for decades to capture the energy and values from municipal solid wastes. Treatment and disposal have been the primary management strategy for wastewater. As new technologies are emerging, alternative options for the utilization of both solid wastes and wastewater have become available. Considering the complexity of the chemical, physical, and biological properties of these wastes, multiple technologies may be required to maximize the energy and value recovery from the wastes. For this purpose, biorefining tends to be an appropriate approach to completely utilize the energy and value available in wastes. Research has demonstrated that non-recyclable waste materials and bio-solids can be converted into usable heat, electricity, fuel, and chemicals through a variety of processes, and the liquid waste streams have the potential to support crop and algae growth and provide other energy recovery and food production options. In this paper, we propose new biorefining schemes aimed at organic solid and liquid wastes from municipal sources, food and biological processing plants, and animal production facilities. Four new breakthrough technologies—namely, vacuum-assisted thermophilic anaerobic digestion, extended aquaponics, oily wastes to biodiesel via glycerolysis, and microwave-assisted thermochemical conversion—can be incorporated into the biorefining schemes, thereby enabling the complete utilization of those wastes for the production of chemicals, fertilizer, energy (biogas, syngas, biodiesel, and bio-oil), foods, and feeds, and resulting in clean water and a significant reduction in pollutant emissions.     

Solidification/stabilization of arsenic containing solid wastes using portland cement, fly ash and polymeric materials

Stabilization/solidification (S/S) is used as a pre-landfill waste treatment technology that aims to make hazardous industrial wastes safe for disposal. Cement-based solidification/stabilization technology is widely used because it offer assurance of chemical stabilization of many contaminants and produce a stable form of waste. The leaching behavior of arsenic from a solidified/stabilized waste was studied to obtain information about their potential environmental risk. Activated alumina (AA) contaminated with arsenic was used as a waste, which was stabilized/solidified (S/S) using ordinary portland cement (C), fly ash (FA), calcium hydroxide (CH) and various polymeric materials such as polystyrene and polymethyl methacrylate (PMMA). Toxicity characteristics leaching procedure (TCLP) and semi-dynamic leach tests were conducted to evaluate the leaching behavior of arsenic. Formations of calcite along with precipitate formation of calcium arsenite were found to be responsible for low leaching of arsenic from the stabilized/solidified samples. Effective diffusivity of arsenic ion from the matrix and leachablity index was also estimated. Minimum leaching of the contaminant was observed in matrix having AA+C+FA+CH due to the formation of calcite.     

Advances in encapsulation technologies for the management of mercury-contaminated hazardous wastes

Although industrial and commercial uses of mercury have been curtailed in recent times, there is a demonstrated need for the development of reliable hazardous waste management techniques because of historic operations that have led to significant contamination and ongoing hazardous waste generation. This study was performed to evaluate whether the U.S. EPA could propose treatment and disposal alternatives to the current land disposal restriction (LDR) treatment standards for mercury. The focus of this article is on the current state of encapsulation technologies that can be used to immobilize elemental mercury, mercury-contaminated debris, and other mercury-contaminated wastes, soils, sediments, or sludges. The range of encapsulation materials used in bench-scale, pilot-scale, and full-scale applications for mercury-contaminated wastes are summarized. Several studies have been completed regarding the application of sulfur polymer stabilization/solidification, chemically bonded phosphate ceramic encapsulation, and polyethylene encapsulation. Other materials reported in the literature as under development for encapsulation use include asphalt, polyester resins, synthetic elastomers, polysiloxane, sol-gels, Dolocrete, and carbon/cement mixtures. The primary objective of these encapsulation methods is to physically immobilize the wastes to prevent contact with leaching agents such as water. However, when used for mercury-contaminated wastes, several of these methods require a pretreatment or stabilization step to chemically fix mercury into a highly insoluble form prior to encapsulation. Performance data is summarized from the testing and evaluation of various encapsulated, mercury-contaminated wastes. Future technology development and research needs are also discussed.     

Plasma vitrification and re-use of non-combustible fiber reinforced plastic, gill net and waste glass

Fiber reinforced plastic (FRP) composite material has widespread use in general tank, special chemical tank and body of yacht, etc. The purpose of this study is directed towards the volume reduction of non-combustible FRP by thermal plasma and recycling of vitrified slag with specific procedures. In this study, we have employed three main wastes such as, FRP, gill net and waste glass. The thermal molten process was applied to treat vitrified slag at high temperatures whereas in the post-heat treatment vitrified slags were mixed with specific additive and ground into powder form and then heat treated at high temperatures. With a two-stage heat treatment, the treated sample was generated into four crystalline phases, cristobalite, albite, anorthite and wollastonite. Fine and relatively high dense structures with desirable properties were obtained for samples treated by the two-stage heating treatment. Good physical and mechanical properties were achieved after heat treatment, and this study reveals that our results could be comparable with the commercial products.     

Non-thermal plasma for oxidation of gaseous products originating from thermal treatment of wastes

A plasma reactor generating non-equilibrium plasma in a gliding discharge was applied as one of the modules of a new laboratory device for hazardous waste destruction. The degradation process of wastes containing an organic part was carried out in two stages. The first one consisted of thermal decomposition of wastes in an inert atmosphere (pyrolysis process in argon flow—the gaseous products are formed from the organic part of wastes). In the second stage products of pyrolysis were oxidized in a gliding discharge. This work was focused on study of the parameters influencing the oxidation process of gases originating from pyrolysis and flowing into the plasma reactor. Oxygen was introduced into the plasma reactor simultaneously with the gases. We investigated two factors significantly affecting the oxidation process: (a) the oxygen concentration in the initial mixture of argon and oxygen and (b) the total flow of argon and oxygen gases. The best oxidation efficiency of the processing gases in the plasma was reached when the oxygen content did not exceed 20% and when the total flow of argon and oxygen was low enough not to cause disturbances of functioning of the plasma reactor.     

Incineration and gasification technologies completed with up-to-date off-gas cleaning system for meeting environmental limits

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.     

Anaerobic co-digestion of hazardous tannery solid waste and primary sludge: biodegradation kinetics and metabolite analysis

Generation of solid waste is inherent to manufacture of leather from skin and hide. Solid wastes generated at various unit operations of the tanning process considerably vary in quantity and composition. Fleshing is a type of animal tissue waste generated during the preparatory leather processing stage in relatively larger quantities as compared to other types of solid waste in the tanning industry. Fleshing mainly contains fat and protein and residual chemicals such as lime and sulphide used in the ‘unhairing’ process of beam house operation. Another type of solid waste in tanning industry which requires safe disposal is the primary sludge from tannery wastewater treatment plant. This study shows that both fleshing and primary sludge contains a significant quantity of volatile solids amenable for biodegradation. Different proportions of waste fleshing and primary sludge were subjected to anaerobic digestion. The studies were carried out in a laboratory scale reactor with an aim of developing an appropriate technology for recovery of bioenergy from the waste and subsequently ensure their safe disposal. Volatile solid destruction between 41 and 52%, specific gas production between 0.419 and 0.635 l/g volatile solids feed and methane yield between 71 and 77% were achieved. Further, the biomethanation potential of animal fleshing and substrate specific kinetics of the reaction process were also examined.     

Preparation of high-purity gallium from semiconductor fabrication waste

This review summarizes the results of systematic studies aimed at developing processes for the preparation of high-purity gallium from semiconductor fabrication waste. A classification is proposed for Gacontaining waste materials according to the host and impurity compositions. We compare the efficiencies of different processes for the fine purification of crude gallium recovered from waste materials: wet-chemical processing, vacuum heat treatment, filtration, electrorefining, and directional solidification. Taking into account the behavior of impurities during the purification process and the nature of the waste materials, we have developed a multistep, environmentally safe process for preparing high-purity (99.9999%) gallium from unconventional raw materials. The product of this process compares well with gallium produced from conventional raw materials. We demonstrate that the use of semiconductor fabrication wastes as raw materials in large-scale-production of high-purity gallium and related microelectronic products is a commercially viable approach.     

Vitrified metal finishing wastes I. Composition, density and chemical durability

Durable phosphate glasses were formed by vitrifying waste filter cakes from two metal finishing operations. Some melts formed crystalline components during cooling. Compositional analysis of dried, heat treated and vitrified samples was made using energy-dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, inductively-coupled plasma spectroscopy and Leco induction furnace combustion analysis. Hydrolytic dissolution, measured by an adapted product consistency test, was reduced by up to 3 orders of magnitude upon heat treatment or vitrification, surpassing the performance of borosilicate glass in some cases. This was attributed to the high levels of iron and zinc in the wastes, which greatly improve the durability of phosphate glasses. One of the wastes arose from a metal phosphating process and was particularly suitable for vitrification due to its high P2O5 content and favourable melting behaviour. The other waste, which arose from a number of processes, was less suitable as it had a low P2O5 content and during heating it emitted harmful corrosive gases and underwent violent reactions. Substantial volume reductions were obtained by heat treatment and vitrification of both wastes. Compositions and performances of some vitrified wastes were comparable with those of glasses which are under consideration for the immobilisation of toxic and nuclear wastes.     

Bury,burn, or gasify: assessing municipal solid waste management options in Indian megacities by exergy analysis

With increasing consumption propelled by economic prosperity, waste generation per capita in developing countries is growing quickly. Traditional approaches of open dumping and landfilling are encountering physical constraints, particularly in megacities, and the need for alternate municipal solid waste (MSW) management strategies is urgent. Among alternatives that are commonly considered are waste-to-energy technologies including incineration and plasma gasification. Previous studies convey the benefits of such technologies, but most do not consider the waste and environmental conditions in tropical megacities such as Mumbai, India, making these studies of limited use to developing countries. This article evaluates the exergetic potential of converting MSW to useful work by thermal and biochemical conversion technologies in the Indian context, considering the facts that the scale of production, composition, climate, segregation practices, moisture content of MSW, etc. in a developing tropical country like India differ significantly from those in developed societies in temperate climate locations. Both, exergy and economic analysis find gasification to be attractive in terms of its monetary return and thermodynamic efficiency. However, this analysis also identifies major hurdles in adopting advanced waste-to-energy technologies including lack of waste segregation, high moisture content, and high capital cost of the most thermodynamically efficient technology.     

Re‐Use of Marble Stone Powders in Producing Unsaturated Polyester Composites

The main goal of this study is to evaluate the potential of waste stone powders as filler in composite materials with a matrix of unsaturated polyester. These wastes are generated in the form of stone fragments and stone‐cutting sludge. Ground marble wastes are thoroughly characterized with the aim to use them as fillers: Mineralogical and chemical composition, particle size distribution, and morphology of these waste stone powders are investigated. Unsaturated polyester resin composites with the different stone powder fillers are prepared. The influence of powder type on the composites’ mechanical properties (tensile, bending, impact, and hardness characteristics), water resistance, thermal stability as well as surface fracture morphology of composites are studied. The moduli of the composites increase by 100%, the hardness of the composites may be improved by 80% upon loading with the “waste” filler, leading to an economical material and helping to reduce waste.

     

包装废弃 PET 瓶的处理及再生资源化技术 研究进展

废弃 PET 作为生活与工业中随处可见的固体废弃物之一,因其具有 稳定的物理化学特性而难以在自然界中降解,是目前需要回收处理的重要固 体废弃物之一。概括了废弃 PET 主要有三种回收技术,即物理回收法、化学 回收法和生物回收法,并分别简述三种回收法的原理、优缺点和研究现状。 可见,回收废弃 PET 主要采用物理回收法,化学回收法作为辅助技术,生物 回收法仍处于研究阶段。化学回收法能有效实现废弃 PET 资源的高效利用, 因而我国在废弃物处理技术发展进程中的关键是通过化学回收法将废弃 PET 进行高效率降解转化,再将产物用于制备新型的高纯度化工原料,以提高废 弃 PET 的再生资源化利用率,使利用率达到 90% 以上。     

The management of arsenic wastes: problems and prospects

Arsenic has found widespread use in agriculture and industry to control a variety of insect and fungicidal pests. Most of these uses have been discontinued, but residues from such activities, together with the ongoing generation of arsenic wastes from the smelting of various ores, have left a legacy of a large number of arsenic-contaminated sites. The treatment and/or removal of arsenic is hindered by the fact that arsenic has a variety of valence states. Arsenic is most effectively removed or stabilized when it is present in the pentavalent arsenate form. For the removal of arsenic from wastewater, coagulation, normally using iron, is the preferred option. The solidification/stabilization of arsenic is not such a clear-cut process. Factors such as the waste's interaction with the additives (e.g. iron or lime), as well as any effect on the cement matrix, all impact on the efficacy of the fixation. Currently, differentiation between available solidification/stabilization processes is speculative, partly due to the large number of differing leaching tests that have been utilized. Differences in the leaching fluid, liquid-to-solid ratio, and agitation time and method all impact significantly on the arsenic leachate concentrations.This paper reviews options available for dealing with arsenic wastes, both solid and aqueous through an investigation of the methods available for the removal of arsenic from wastewater as well as possible solidification/stabilization options for a variety of waste streams.