Efficient Incineration Research Articles

Energy recovery of solid waste disposal in Russia, State of the Art and operation experience

For Russia, there is no alternative way of a civilized solution to the problem of municipal solid wastes (MSW): through combustion (energy utilization) to complex processing. The government of the Russian Federation in 2017 adopted some decisions aimed at thermal processing of MSW. The order defines the construction of renewable energy facilities on the basis of MSW with a total electric capacity of 280 MW in Moscow region and one object with an electric capacity of 55 MW in the Republic of Tatarstan. In Russia, only three plants where the energy potential of MSW is converted into electricity were built. The results of the operation experience of fluidized bed furnaces for MSW incineration at Rudnevo plant in Russia are done. The main problems were connected with ash properties, deposit formation, and corrosion of superheater tubes. Also, the data of mathematical modeling of dynamic behavior near gas burners, chemical composition and material balance of solids, and the influence of secondary air injection on NOx formation are given. A special test rig was designed for the investigation of the corrosion mechanism. Also, the main corrosion factors (temperature of the tube surface, rates of O2, HCl, SO2, and H2O in flue gas, contains chloride and alkali metals in deposits) were found during the tests. Experience of energy recovery from waste incineration of pulp and paper mill plants is presented. Considerable attention is paid to improving the efficiency of waste incineration and bed particle agglomeration. Special experiments were carried out to optimize the bed drain flow rate. The influence of secondary air supply improvement on mixing with the main flow and boiler efficiency is given. Semi-empirical three-zone method of engineering heat calculations for fluidized bed furnaces of biomass boilers was proposed to predict both the value of outlet furnace temperature and the value of fluidized bed temperature. The method based on empirical values and relationships of the share of heat release in fluidized bed zone.

ELECTROCHEMICAL INCINERATION OF SHORT-CHAIN CARBOXYLIC ACIDS WITH NB-SUPPORTED BORON DOPED DIAMOND ANODE: SUPPORTING ELECTROLYTE EFFECT INTO THE ELECTROGENERATED OXIDANT SPECIES (HYDROXYL RADICALS, HYDROGEN PEROXIDE AND PERSULFATE)

This work describes the electrochemical oxidation study of three short chain carboxylic acids (acetic, oxalic and formic 0.18 mol L-1) using different electrolysis conditions (electrolyte composition and current density) in an electrochemical reactor fitted with niobiumsupported/BDD electrode (Nb/BBD) as anode and titanium plate as cathode. The experiments were focused to elucidate if the oxidation of these carboxylic acids involved a direct or a mediated oxidation pathway, as well as their electrochemical incineration efficiency using this electrochemical reactor. The amount of oxidizing species (hydroxyl radicals, hydrogen peroxide, and persulfate) produced at Nb/BDD electrode was spectroscopically determined. The electrochemical kinetics study in H2SO4 and HClO4 solutions, as well as the chemical oxygen demand and total organic carbon analysis for each one of the carboxylic acids studied in both media, gave us information to propose a degradation mechanism for the electrochemical degradation of the carboxylic acids in each electrolytic media. The degradation in H2SO4 is promoted by the persulfate production, whereas in HClO4 by •OH.

The practical use of module D in a building case study: assumptions, limitations and methodological issues

According to the EN 15804 and EN 15978, a material or building life cycle consists of three major life cycle stages or so-called modules: Production and Construction (module A), Use (module B) and End-of-life (module C). Potential benefits and loads occurring beyond the building’s life cycle as a result of recycling, reuse or energy recovery can be declared in an additional module D. As part of the upcoming amendment of the EN 15804 a formula was developed to facilitate the calculation of module D. This paper provides a critical discussion on the practical use of module D. First of all, the development of the formula revealed specific methodological issues, such as the unequal approach to closed and open loop recycling. Secondly, the consideration of module D in a Belgian building LCA case study provided insights in the different methodological choices, interpretations, and assumptions related to the calculation of module D. This concerns for example the calculation of net output flows of secondary materials, modelling of avoided primary production, definition of the point of functional equivalence, efficiency of incineration, etc. Aspects that are not clearly specified in the standard and therefore can be open to interpretation are illustrated with concrete examples from the building case study. Where possible, recommendations for a harmonized approach are made. In any way, the results from the case study analysis reveal that the methodological choices can have a significant effect on the results and that module D results should therefore be considered with care.

A System Dynamics-Based Approach to Help Understand the Role of Food and Biodegradable Waste Management in Respect of Municipal Waste Management Systems

The long-term plan of any city in Japan is to become a material recycling society. The use of all types of municipal waste is essential in maximizing the full potential of material recovery. As such, municipalities are responsible for managing their waste, including food and biodegradable waste (FBW), and this results in some complex schemes. This study uses the system dynamics approach to illustrate and investigate the benefits of separate treatment of FBW. At the same time, to understand the dynamic interactions between all aspects and elements of the current municipal solid waste management system in Oita City. The developed model includes total environmental benefit, motivation to manage waste and resources, and yield from treatment facilities. The result shows that with the introduction of an anaerobic digester (AD) plant for FBW increases the efficiency of incineration. Furthermore, the result indicates that strengthening the regulation of waste sorted and the reduction in the amount of FBW treated in incineration will improve the current system. This study concludes that any policy or regulation less than the proposed result will yield less benefit. Thus, strengthening regulation is a crucial part of the sustainability of FBW management in the long run.

Approaches to fill data gaps and evaluate process completeness in LCA—perspectives from solid waste management systems

Large data amounts are required in an LCA, but often, site-specific data are missing and less representative surrogate data must be used to fill data gaps. No standardized rules exist on how to address data gaps and process completeness. We suggest a systematic evaluation of process completeness, identification of data gaps, and application of surrogate values to fill the gaps. The study focus on foreground process data. A solid waste management (SWM) scenario was used to illustrate the suggested method. The expected input and output flows in a waste incineration model were identified based on legislation and expert judgment, after which process completeness scores were calculated and missing flows identified. To illustrate the use of different types of surrogate data to fill data gaps, data gaps were selected for 16 different parameters in five SWM processes. We compared the global warming potential (GWP) from using surrogate data, and from leaving the gap, to identify the data gaps where representative surrogate data should be used. The completeness score for the material inputs to waste incineration was 78%, and the missing flows were auxiliary fuels and precipitation chemicals. The completeness score for air emissions were between 38 and 50% with and without expert judgment. If only greenhouse gases were considered (CO2, CH4, and N2O), the completeness score would be 67%. Applying weighting factors according to the greenhouse gas contribution in the USA gave a completeness score of 94%. The system-wide data gaps, where representative surrogate data should be applied, were the CH4 release from composting; electricity generation efficiency of incineration; recovery efficiencies at a material recovery facility; and composition of the plastic, metal, and paper fractions in the household waste; in these cases, leaving the gap changed the GWP results by > 5%. Completeness evaluation should take into account the relevance and importance of flows; relevance depends on the considered life cycle impact methods and importance depends on the weighting of the different flows. The set of expected flows and evaluation of relevance and importance must be documented in a transparent manner. The choice of surrogate values to fill data gaps depends on the availability of secondary data and on whether the data gap matters, i.e., significantly affects the LCA results. The suggested method can be used to properly document the identification of missing flows and to select and apply surrogate values to fill the data gaps.

The compatibility approach for hazardous waste incineration based on grey relational analysis

Incineration compatibility plays an irreplaceable role in the incineration process of hazardous waste. This paper introduces the Grey Relational Analysis (GRA) method for the incineration compatibility to empower each hazardous waste. In order to obtain a reasonable incineration compatibility scheme, an index system was constructed from the calorific value, water content, corrosivity and toxicity which affect the incineration effect, and the method model of incineration compatibility was established by using Grey Relational Analysis, and the relevant cases were analyzed. The research results show that the incineration compatibility scheme based on the Grey Relational Analysis method ensures the stability of incineration and improves the efficiency and quality of incineration under the premise of reducing and harmless hazardous waste.

Effects of storage environment on the moisture content and microbial growth of food waste

Food waste (FW) has become a critical issue in sustainable development as the world's population has increased. Direct incineration of FW remains the primary treatment option. The moisture content of FW may affect the energy efficiency of incineration. In Taiwan, FW, which includes raw (r-FW) and post-consumer (p-FW) waste, is often stored in freezers before pretreatment. This study evaluated the effects of storage environment on the moisture content and microbial growth of FW. Storage at 263 K was associated with the largest reduction in moisture content in both r-FW and p-FW. At 263 K, the moisture content of r-FW and p-FW was lowest at 96 and 72 h, respectively. The E.coli and total bacteria counts were steady over 120 h when stored at 263 K. Storage at 253 K required the greatest electricity consumption, followed by 263 K and 258 K. Based on the reduction of moisture content and increase in energy efficiency, it is suggested that FW is placed in temporary storage at 263 K before (pre)treatment. The results of this study will help waste-to-energy plants, incinerators, and waste management enterprises to implement proper (pre)treatment of FW for sustainable waste management.

Domestic Wastewater Treatment Sludge Disposal with The Combustion Process of The Thermal Drying- incineration Efficiency Investigation of The Relationship Between Energy

Bu calismada, bir evsel atiksu aritma tesisinin ham su kirlilik yuku parametrelerine gore tesis aritma verimine bagli olarak aritma camuru termal kurutma-yakma tesisinin biyokati bertaraf verimi ve biyokatinin yakilmasi ile aciga cikacak enerji verimliligi incelemesi yapilmistir. Gaziantep Merkez Atiksu Aritma Tesisi’nde bulunan tesise giren camurun ozellikleri, aritma tesisinin verimliligi, giris parametreleri, uretilen biyokati ve buna bagli olarak aciga cikan kul miktarlari tesisin faaliyete gectigi gunden beri incelenmistir. Bu veriler isiginda tesisin ekonomik getirisi ve potansiyel enerji verimliligi incelenmistir. Camur kurutma ve yakma tesisinde ortalama %88 bertaraf verimi saglandigi gozlenmistir.

Minor actinide incineration and Th-U breeding in a small FLiNaK Molten Salt Fast Reactor

Minor actinide (MA) accumulated in spent fuel is the primary contributor to the long-term radiological hazards of high-level nuclear waste. Due to its outstanding features such as fast neutron spectrum, no fuel assembly fabrication, on-line refueling and reprocessing, Molten Salt Fast Reactor (MSFR) is regarded as one of the candidate reactors for MA incineration. In the present work, we evaluate the MA incineration capability for a 500MWth FLiNaK MSFR by considering on-line MA feeding into the fuel salt and/or 233U extraction from the fertile salt, where the initial FLiNaK fuel salt is composed of 70mol% (LiF, NaF and KF) and 30mol% (ThF4, 233UF4 and MAF3). The simulated results show that, during a 50-year operation, the MA incineration efficiency with on-line MA feeding and 233U extraction scenario is significantly higher compared with the case without either MA feeding or 233U extraction. Based on the scenario of on-line MA feeding and 233U extraction, the initial MA loading is further adjusted to keep a small excess reactivity during the whole operation. And the MA incineration amount, the depletion ratio between MA and total heavy nuclides and the MA incineration efficiency at 50-year operating time are 7301kg, 77.4% and 33.3kg/TWh, respectively, with a doubling time of 39-year for 233U breeding. We also analyze and discuss the evolutions of the fuel temperature feedback coefficient, the effective delayed neutron fraction and the intensity of spontaneous fission neutron during the whole operating time.

Global warming potential of material fractions occurring in source-separated organic household waste treated by anaerobic digestion or incineration under different framework conditions

This study compared the environmental profiles of anaerobic digestion (AD) and incineration, in relation to global warming potential (GWP), for treating individual material fractions that may occur in source-separated organic household waste (SSOHW). Different framework conditions representative for the European Union member countries were considered. For AD, biogas utilisation with a biogas engine was considered and two potential situations investigated – biogas combustion with (1) combined heat and power production (CHP) and (2) electricity production only. For incineration, four technology options currently available in Europe were covered: (1) an average incinerator with CHP production, (2) an average incinerator with mainly electricity production, (3) an average incinerator with mainly heat production and (4) a state-of-the art incinerator with CHP working at high energy recovery efficiencies. The study was performed using a life cycle assessment in its consequential approach. Furthermore, the role of waste-sorting guidelines (defined by the material fractions allowed for SSOHW) in relation to GWP of treating overall SSOHW with AD was investigated. A case-study of treating 1tonne of SSOHW under framework conditions in Denmark was conducted. Under the given assumptions, vegetable food waste was the only material fraction which was always better for AD compared to incineration. For animal food waste, kitchen tissue, vegetation waste and dirty paper, AD utilisation was better unless it was compared to a highly efficient incinerator. Material fractions such as moulded fibres and dirty cardboard were attractive for AD, albeit only when AD with CHP and incineration with mainly heat production were compared. Animal straw, in contrast, was always better to incinerate. Considering the total amounts of individual material fractions in waste generated within households in Denmark, food waste (both animal and vegetable derived) and kitchen tissue are the main material fractions allowing GWP mitigation with AD when it is compared to incineration. The inclusion of other material fractions in SSOHW sorting guidelines may be considered of less importance.

Current and future prospects for heat recovery from waste in European district heating systems: A literature and data review

Municipal solid waste has seen increasing annual volumes for many decades in contemporary Europe and constitutes, if not properly managed, an environmental problem due to local pollution and greenhouse gas emissions. From an energy perspective, waste is also an alternative fuel for power and heat generation; energy recovery from waste represents an effective measure to reduce landfilling and avoid disposal emissions while simultaneously reducing the equivalent demand for primary energy supply. A key factor for obtaining the full synergetic benefits of this energy recovery is the presence of local heat distribution infrastructures, without which no large-scale recovery and utilisation of excess heat is possible. In this paper, which aims to estimate municipal solid waste volumes available for heat recovery in European district heating systems in 2030, a literature and data review is performed to establish and assess current and future EU (European Union) waste generation and management. Main conclusions are that more heat can be recovered from current Waste-to-Energy facilities operating at low average heat recovery efficiencies, that efficient incineration capacity is geographically concentrated, and that waste available for heat recovery in 2030 is equally determined by total generation volumes by this year as by future EU deployment levels of district heating.

Experimental Study on Molten Salt Oxidation of High Salt Content Pharmaceutical Residue

The pharmaceutical residues from chemical synthesis pharmaceutical industry often contain some alkali salts due to the widely use of alkali salts in the manufacturing process, the waste management of such is a significant challenge. Generally, the residues are disposed by landfill and incineration. However landfill is unsustainable and the incineration's efficiency is effected by furnace slag-bonding during combustion, that affects the widely use of incineration. On the other hand, molten salt oxidation is an efficient, flameless thermal process, has the inherent capability of destroying organic constituents of wastes while retaining the inorganic constituents in the molten salt. Therefore, a new access is proposed by disposing the residues using molten salt oxidation. A high salt content pharmaceutical residue that contains 28.82wt% Na has been selected as the sample. Molten salt oxidation experiments have been conducted in a lab-scale molten salt reactor using a ternary salt (Li,Na,K)2CO3. The experimental parameters investigated here are the temperature of molten salt and the excess air factor. The concentrations of the CO, NOx and SOx in the off-gas are monitored on-line. Results show that the concentration of CO decreases with temperature increasing, especially at temperature higher than 600̊C. The SOx in the off-gas has been detected rarely, irrespective of the operating conditions. When the temperature is below 700̊C, the concentrations of NOx in the off-gas are under 200ppm, but as the temperature reached 700̊C, due to the nitrite in salt bath begins to decompose, the concentration increases dramatically, suggests the operating temperature should below 700̊C in order to suppress the emission of NOx. Compared to the temperature's role, the effect on the residue's oxidation of the excess air factor is relative small. In the drained salt no char has been found and the XRD analysis shows that the main content of the salt is still (Li,Na,K)2CO3. The results of our study show molten salt oxidation is a promising alternative technology for the disposal of high salt content pharmaceutical residues from the chemical synthesis pharmaceutical industry, and it may be also suitable for other high salt content residues from the fine chemical industry, however, more research is needed to verify this possibility.

Research on the Influence of Kitchen Waste Separation on MSW Incineration

With the acceleration of urbanization and industrialization, the amount of MSW in China generated is growing fast, while the pollutants generated in the disposal process of MSW has gradually attracted people’s attention. This paper presents the generation and composition status of MSW in China, summarizing the problems during MSW incineration disposal, providing an assumption of kitchen waste separation and using heat balance calculation to analysis the impact of kitchen waste separation on MSW incineration. Results shows that after kitchen waste separated from MSW, the amount of MSW reduced obviously, moisture content dropped, calorific value improved, auxiliary fuel is not need to ensure the proper incineration process and combustion efficiency improved; meanwhile, the generation of greenhouse gases and air pollutants is reduced significantly. Overall, the separation of kitchen waste not only reduced the difficulty and handling stress of MSW incineration, but also improved the incineration efficiency, reduced the generation of pollutants during incineration process.

Waste to Energy – Energy Recovery of Green Bin Waste: Incineration/Biogas Comparison

This study presents how to determine marginal incinerator energy efficiencies. This concept should be applied in assessments of the treatment of specific waste streams to create a level playing field when comparing different technologies, for instance in life-cycle assessments. The marginal efficiencies depend on the technical level, the surrounding energy system, and the waste type/heating value. The concept of marginal efficiency is in this article applied to the treatment of green bin waste. The thermal treatment options considered are incineration and anaerobic digestion with biogas combustion in a reciprocating gas engine. The comparison is made only with regard to energy yield. The comparison is carried out for three different types of energy systems: power producing, combined heat and power, and combined heat and power with flue gas condensation. For a power-only energy system, the electrical efficiency of anaerobic digestion is found to be comparable to incineration. However, for an energy system with district heating as an option, the energy recovery of incineration is much higher than biogas. Furthermore, if the waste heat recovery technology flue gas condensation is used, the total efficiency of incineration is almost twice as high as the biogas technology, with the same boundary conditions applied. Although this study produces specific figures of energy recovery yields for a number of different scenarios for incineration and biogas production, the aim of the study is not a technology comparison as such. A proper technology comparison, including life-cycle assessments, should deal with many other issues than just energy recovery, for instance, other environmental factors, initial cost, operating and maintenance costs, and commercial aspects. However, this study does show that when undertaking such technology assessments, it is crucial to the results that: • Proper and relevant boundary conditions are applied: if district heating is possible, this changes results dramatically. Optimally, a specific site should form the basis for a comparison. • Energy recovery efficiencies must be linked to the actual waste steam considered. For green bin waste, this study has shown that margin efficiencies of up to 125 % can be achieved. This is much higher than efficiencies reported in the literature (95 %) [1•, 2•]. Therefore, one main conclusion is that efficiencies used for comparisons of technology must be waste-type (and calorific-value) specific to obtain reliable results in the comparisons.

Electrogeneration of hydrogen peroxide for electro-Fenton system by oxygen reduction using gold nanoparticle electrodeposited on graphite cathode

In this study, the electrochemical deposition of gold (Au) onto graphite has been performed under different deposition potential conditions. These Au particles electrodeposited on the graphite were used as cathode for O2 electrochemical reduction and H2O2 production in acidic solution, and the hydrogen peroxide (H2O2) electrogenerated on graphite modified by gold particles was used in electro-Fenton process. Results show firstly that the O2 cathodic reduction on gold particles electrodeposited on the graphite electrode in acidic medium with two well-defined reduction waves at −300 mV/SCE and −1,300 mV/SCE; those waves indicated reduction of two O2 electrons to H2O2. Secondly, the optimal cathodic potential condition for H2O2 generation on cathode modified was −300 mV and unmodified one was −500 mV/SCE. The electrolysis time, dissolved oxygen level, magnetic stirring, and pH were systematically studied; the hydrogen peroxide production increased with the aeration and electrolysis time and then became stationary after 2 h of electrolysis. The maximum H2O2 accumulation increased up to 60 mg/L with air compressed, at −300 mV. Optimized parameters (potential, oxygen level, and concentration of ferrous ions) were also applied to incinerate the Belgard EV2030 sodium salt of polycarboxylic acid. The incineration efficiency onto optimized parameters shows that 74% of Chemical oxygen demand was incinerated in the modified electrode that confirms the positive gold modification effect onto the performance.

Material Resources, Energy, and Nutrient Recovery from Waste: Are Waste Refineries the Solution for the Future?

Waste refineries focusing on multiple outputs of material resources, energy carriers, and nutrients may potentially provide more sustainable utilization of waste resources than traditional waste technologies. This consequential life cycle assessment (LCA) evaluated the environmental performance of a Danish waste refinery solution against state-of-the-art waste technology alternatives (incineration, mechanical-biological treatment (MBT), and landfilling). In total, 252 scenarios were evaluated, including effects from source-segregation, waste composition, and energy conversion pathway efficiencies. Overall, the waste refinery provided global warming (GW) savings comparable with efficient incineration, MBT, and bioreactor landfilling technologies. The main environmental benefits from waste refining were a potential for improved phosphorus recovery (about 85%) and increased electricity production (by 15-40% compared with incineration), albeit at the potential expense of additional toxic emissions to soil. Society's need for the outputs from waste, i.e., energy products (electricity vs transport fuels) and resources (e.g., phosphorus), and the available waste composition were found decisive for the selection of future technologies. On the basis of the results, it is recommended that a narrow focus on GW aspects should be avoided as most waste technologies may allow comparable performance. Rather, other environmental aspects such as resource recovery and toxic emissions should receive attention in the future.

Comparing technologies for municipal solid waste management using life cycle assessment methodology: a Belgian case study

The present study aims at identifying the best practice in residual municipal solid waste management using specific data from Liege, a highly industrialized and densely populated region of Belgium. We also illustrate the importance of assumptions relative to energy through sensitivity analyses and checking uncertainties regarding the results using a Monte Carlo analysis. We consider four distinct household waste management scenarios. A life cycle assessment is made for each of them using the ReCiPe method. The first scenario is sanitary landfill, which is considered as the base case. In the second scenario, the refuse-derived fuel fraction is incinerated and a sanitary landfill is used for the remaining shredded organic and inert waste only. The third scenario consists in incinerating the whole fraction of municipal solid waste. In the fourth scenario, the biodegradable fraction is collected and the remaining waste is incinerated. The extracted biodegradable fraction is then treated in an anaerobic digestion plant. The present study shows that various scenarios have significantly different environmental impact. Compared to sanitary landfill, scenario 4 has a highly reduced environmental impact in terms of climate change and particulate matter formation. An environmental gain, equal to 10, 37, or 1.3 times the impact of scenario 1 is obtained for, respectively, human toxicity, mineral depletion, and fossil fuel depletion categories. These environmental gains are due to energetic valorization via the incineration and anaerobic digestion. Considering specific categories, greenhouse gas emissions are reduced by 17 % in scenario 2 and by 46 % in scenarios 3 and 4. For the particulate matter formation category, a 71 % reduction is achieved by scenario 3. The figures are slightly modified by the Monte Carlo analysis but the ranking of the scenarios is left unchanged. The present study shows that replacing a sanitary landfill by efficient incineration significantly reduces both emissions of pollutants and energy depletion, thanks to electricity recovery.

Incineration or Autoclave? A Comparative Study in Isfahan Hospitals Waste Management System (2010)

Introduction:Medical wastes are among hazardous wastes and their disposal requires special methods prior to landfilling. Medical wastes are divided into infected and non-infected wastes and the infected wastes require treatment. Incineration is one of the oldest methods for treatment of medical wastes, but their usage have faced wide objections due to emission of hazardous gases such as CO2 and CO as well as Carcinogenic gases such as Dioxins and Furans which are generated as a result of incomplete combustion of compositions like PVCs. Autoclave is one the newest methods of medical wastes treatment which works based on wet disinfection.Methods:The statistical population in this descriptive, comparative study includes hospitals located in Isfahan city and the sample hospitals were selected randomly. To environmentally evaluate the Autoclave method, TST (time, steam, temperature) and Spore tests were used. Also, samples were made from incinerator’s stack gases and their analyses results were compared with WHO standards.Findings:TST and spore tests results were negative in all cases indicating the success of treatment process. The comparison of incinerator’s stack gases with WHO standards showed the high concentration of CO in some samples indicating the incomplete combustion. Also, the incineration efficiency in some cases was less than 99.5 percent, which is the efficiency criterion according to the administrative regulations of wastes management law of Iran. No needle stick was observed in Autoclave method during the compaction of bags containing wastes, and the handlers were facing no danger in this respect. The comparison of costs indicated that despite higher capital investment for purchasing autoclave, its current costs (e.g. maintenance, etc) are much less than the incineration method.Discussion:Totally, due to inappropriate operation of incinerators and lack of air pollution control devices, the use of incinerators doesn’t seem rational anymore. Yet, despite the inefficiency of autoclaves in treatment of bulky wastes such as Anatomical wastes, their usage seems logic considering the very low amounts of such wastes. Also, considering the amount of generated wastes in Isfahan hospitals, a combination of centralized and non-centralized autoclaves is recommended for treatment of infected wastes. Mobile autoclaves may also be considered according to technical and economical conditions. It must not be forgotten that the priority must be given to the establishment of waste management systems particularly to personnel training to produce less wastes and to well separate them.

Self-Sustaining Thorium Boiling Water Reactors

A thorium-fueled water-cooled reactor core design approach that features a radially uniform composition of fuel rods in stationary fuel assembly and is fuel-self-sustaining is described. This core design concept is similar to the Reduced moderation Boiling Water Reactor (RBWR) proposed by Hitachi to fit within an ABWR pressure vessel, with the following exceptions: use of thorium instead of depleted uranium for the fertile fuel; elimination of the internal blanket; and elimination of absorbers from the axial reflectors, while increasing the length of the fissile zone. The preliminary analysis indicates that it is feasible to design such cores to be fuel-self-sustaining and to have a comfortably low peak linear heat generation rate when operating at the nominal ABWR power level of nearly 4000 MWth. However, the void reactivity feedback tends to be too negative, making it difficult to have sufficient shutdown reactivity margin at cold zero power condition. An addition of a small amount of plutonium from LWR used nuclear fuel was found effective in reducing the magnitude of the negative void reactivity effect and enables attaining adequate shutdown reactivity margin; it also flattens the axial power distribution. The resulting design concept offers an efficient incineration of the LWR generated plutonium in addition to effective utilization of thorium. Additional R&D is required in order to arrive at a reliable practical and safe design.

Health-Care Waste Incineration and Related Dangers to Public Health: Case Study of the Two Teaching and Referral Hospitals in Kenya

There are practically no low cost, environmentally friendly options in practice whether incineration, autoclaving, chemical treatment or microwaving (World Health Organisation in Health-care waste management training at national level, [2006] for treatment of health-care waste. In Kenya, incineration is the most popular treatment option for hazardous health-care waste from health-care facilities. It is the choice practiced at both Kenyatta National Hospital, Nairobi and Moi Teaching and Referral Hospital, Eldoret. A study was done on the possible public health risks posed by incineration of the segregated hazardous health-care waste in one of the incinerators in each of the two hospitals. Gaseous emissions were sampled and analyzed for specific gases the equipment was designed and the incinerators Combustion efficiency (CE) established. Combustion temperatures were also recorded. A flue gas analyzer (Model-Testos-350 XL) was used to sample flue gases in an incinerator under study at Kenyatta National Hospital--Nairobi and Moi Teaching and Referral Hospital--Eldoret to assess their incineration efficiency. Flue emissions were sampled when the incinerators were fully operational. However the flue gases sampled in the study, by use of the integrated pump were, oxygen, carbon monoxide, nitrogen dioxide, nitrous oxide, sulphur dioxide and No(x). The incinerator at KNH operated at a mean stack temperature of 746 °C and achieved a CE of 48.1 %. The incinerator at MTRH operated at a mean stack temperature of 811 °C and attained a CE of 60.8 %. The two health-care waste incinerators achieved CE below the specified minimum National limit of 99 %. At the detected stack temperatures, there was a possibility that other than the emissions identified, it was possible that the two incinerators tested released dioxins, furans and antineoplastic (cytotoxic drugs) fumes should the drugs be subjected to incineration in the two units.