WtE Plants Research Articles

Waste-to-energy and waste-to-hydrogen with CCS: Methodological assessment of pathways to carbon-negative waste treatment from an LCA perspective

A growing global population and rising living standards are producing ever greater quantities of waste, while at the same time driving ever-larger demand for energy, especially electricity, or new emerging markets, such as hydrogen in more industrialised countries. A key solution to these challenges of waste disposal, rising energy and hydrogen demand is BECCS (Bioenergy with Carbon Capture and Storage); the generation of bioenergy – in the form of electricity (WtE) or hydrogen (WtH2), as well as heat – from the thermochemical processing of waste. The addition of carbon capture and storage (CCS) to WtE or WtH2 has the potential to make waste a zero or even negative emissions energy source, thus contributing to the removal of greenhouse gases from the atmosphere. This work undertakes a pre-screening of different BECCS configurations based on state of the art technologies and then performed an assessment of representative cases in UK for WtE and WtH2, necessary to understand if novel waste thermal treatment processes may become potential alternatives or improvements to current WtE plants when retrofitted with CCS. A systematic and comprehensive examination of different key Life Cycle Assessment methodological aspects reveals the importance of the functional unit and allocation approach in determining the preferred pathway in a specific context.

Waste Management in European Countries: Indicators, Clustering, and Socioeconomic Implications

Abstract. The work is aimed at analyzing approaches to waste management and dividing them into clusters. The objectives of the study were to determine indicators related to waste management and to investigate their relationship; analyze the main groups of waste management solutions used by European countries and identify waste management clusters according to the most important parameters. The work hypothesized that there are several common groups of decisions regarding waste management (recycling, incineration or disposal is preferred). Correlation, dispersion and cluster analysis (hierarchical and k-means) were performed. It was proved that there are a strong direct link between incineration and current health expenditure per capita, waste thermally treated in WtE plants and WtE plants, waste thermally treated in WtE plants and GDP, WtE plants amount and GDP. There is a strong inverse link between recycling and landfilling, incineration and landfilling, landfilling and current health expenditure per capita. At the same time, there are weak direct links between research indicators and life expectancy at birth, government expenditure on education. Three clusters were identified regarding waste management. Cluster 1 (Czech Republic, Hungary, Lithuania, Poland, Portugal, Slovakia, Spain, Estonia): recycling and landfilling are the main methods of waste management, with their help, about 80% is destroyed, an average of four WtE plants operate, and up to one t of waste is processed. Current health expenditure per capita exceeds GDP by 4.5 times. Cluster 2 (France, Germany, Italy, UK): they recycle about half of the waste, and the rest are incinerated or landfilled in certain proportions. On average, 76 WtE plants work in the countries and about 15 tons of waste are processed. Current health expenditure per capita exceeds GDP by 1.5 times. Cluster 3 (Austria, Belgium, Denmark, Finland, Ireland, Luxembourg, Netherlands, Norway, Sweden, Switzerland): with the help of recycling and incineration, almost all waste is removed, and up to 2% remains for landfill (except Ireland - 23%). On average, 16 WtE plants work in the countries and 3 tons of waste are processed. Current health expenditure per capita is the largest and exceeds GDP by 13.5 times. The results of this study can be used by government officials to develop recommendations for improving the waste management system in their country and by scientists for further research.

The evaluation of energy consumption in transportation and processing of municipal waste for recovery in a waste-to-energy plant: a case study of Poland.

Refuse-derived fuel (RDF) can be produced from combustible materials contained in municipal waste. This article investigates energy and material flow of waste in different scenarios for production of RDF from bulky waste, separately collected waste, and mixed municipal solid waste (MSW). We compare the proportion of energy consumption in transportation, handling waste, and processing using data from the waste collection company in South Poland. The findings show the components of the reverse supply chain consuming the highest value of energy. A model of material and energy flow has taken into consideration collection of waste and transportation by two categories of waste collection vehicles: light commercial vehicles and garbage trucks. The shipping of RDF from pre-treatment facilities uses tipper semi-trailers and walking floor trailers. The findings of the study show production of RDF from municipal solid waste consumes almost 10% of energy potential in RDF. Less energy is required for the production of RDF from bulky waste (2.2-4.8%) or separately collected waste (1.7-4.1%) depending on the efficiency of collection and selected vehicles. Transportation consumes the greatest portion of energy. For mixed municipal solid waste (MSW), it can reach 79%; for separated collection waste, 90%; and for bulky waste, up to 92% of the total energy consumed. Comparing emissions for two categories of the collection vehicles, no significant difference was found for the bulky waste collections. For mixed MSW and separately collected waste, the emissions are higher for garbage trucks. A recommendation for practitioners is optimization of routing to achieve a higher collection rate at a minimized route length. For transportation of RDF to WtE plants, vehicles with higher loading capacity are essential.

An integrated biological system for air pollution control in WtE plants and interaction between NO reduction and toluene oxidation

The abatement of NO and VOCs in the flue gas from WtE plants is of great significance for improving the atmospheric environmental quality at present. In this study, a device of absorption-bioreactor coupling biotrickling-filter (ABR-BTF) was built to realize the simultaneous removal of NO and VOCs, in which the chemical absorption-bioreactor (ABR) was used for reducing NO and the biotrickling-filter (BTF) was employed for eliminating toluene. When the simulated flue gas containing 400 mg m−3 NO and 150 mg m−3 toluene passed through the system for 30 s, the removal efficiency of NO and toluene reached 85% and 90%, respectively. In contrast with the single ABR segment, the loss rate of NO complexing absorber was reduced by 85% in ABR-BTF. Meanwhile, a variety of novel bacterial genera in the field of biological denitrification and VOCs elimination were discovered within the integrated system biome. Thereinto, Candidatus_Cloacamonas and Syntrophomonas produced the hydrogen, which could as electron donors be consumed by the dissolved oxygen species during the process of VOCs degradation, promoting the biological reduction and reducing the loss rate of complexing absorbent in the ABR portion. Meanwhile, Tisierella and Desulfitobacterium could reduce sulfite to S2−, so that part of the complexing absorbent was transformed into FeS and re-entered into the circulation system through the redox reaction with Fe(III). The integrated biological purification system can efficiently remove NO and VOCs simultaneously, and overcome the problems of insufficient microbial reduction rate for poor hydrophobic VOCs, which will provide a fundamental for the optimization and industrial application of the biological technology in WtE plants flue gas treatment.

Sustainability Assessment of the Municipal Solid Waste Management in Russia Using the Decoupling Index

The annual growth of the municipal solid waste (MSW) generated and the exhaustion of existing landfills capacity have led to the processes of reforming the waste sector in Russia. But the question remains open: what is the optimal ratio between waste management practices for building a sustainable MSW management system? The purpose of this article is to evaluate the sustainability of the MSW management system in Russia according to various scenarios of its development using the decoupling index. Based on the strategic documents, authors constructed three scenarios for the MSW industry development in Russia until 2024: scenario 1 (basic), scenario 2 (MSW utilization via recycling), scenario 3 (MSW utilization via recycling and MSW incineration at WTE plants). After that, the decoupling index for all scenarios was calculated. In general, calculations of the decoupling index for 2022-2024 showed that for all scenarios (except for scenario 3 in 2022), the industry is moving into the zone of absolute sustainability. The greatest sustainability is achieved in scenario 2 – for this scenario the absolute value of the decoupling index is maximum in 2023 and 2024, thereby confirming the role of recycling in increasing the sustainability of the MSW management system. The results can be used by decision makers when reforming the MSW management system to choose the optimal ratio between the MSW management practices and the appropriate regulatory tools.

Waste-to-Energy and recycling: The role of plant ownership and waste mobility

This paper proposes a stylized two-region model to study the joint effect of waste mobility and WtE plant’s ownership on waste disposal choices, welfare and environmental quality. The aggregate level of recycling emerging from the mobility/private ownership scenario is excessive relative to the first best. By contrast, under waste autarky, the institutional configuration of the WtE plant turns out to be neutral and the resulting level of recycling is generally suboptimal. The analysis further shows that mobility may not be Pareto improving for both regions, and that the engagement of local authorities in the decision of how much waste to incinerate has a sound economic justification, especially in the presence of old-generation WtE plants. Finally, this work provides new insights into the debate about the relationship between WtE incineration and recycling by suggesting that the two opposing views within such debate are not totally incompatible; rather they capture different dimensions of the problem. In particular, the view that WtE combustion represents an obstacle to recycling is consistent with what is found at the local level when burning waste for energy recovery becomes available. while the view that the two activities are positively correlated is more in line with the findings at the aggregate level.

EFFECTIVENESS OF INTEGRATED CARBON CAPTURE TECHNOLOGY IN WASTE TO ENERGY PLANTS AND IMPLEMENTATION PROSPECTS

The population in ASEAN is projected to increase to 722 million by 2030. This massive population increase had an impact not only on population quantity but also on the environment. This is reflected in the increasing number of pollution results such as waste products and carbon pollution. Waste to Energy Plants has been successful in converting waste to electrical energy by incineration, but there are still carbon emissions that has to be dealt with and on the other hand carbon pollution has been a major problem for ASEAN this past 10 years, with the data from Global Carbon Atlas showing 1671.7 MtCO2 are emitted from the combined 10 countries in 2019. The industry categories of petroleum refineries, chemicals and others are responsible for contributing the most greenhouse gases. Analysis from the International Energy Agency shows comparison between few of the most promising solutions for carbon emission, one of them being Carbon Capture Storage (CCS). This technology captures CO2 that has been emitted to the atmosphere. Indonesia, the biggest country in ASEAN is also the region’s most contributing country in terms of carbon emission where the CCS technology should be developed more. In this paper, the author uses a descriptive qualitative method and data reference from previous research. The results indicate that the usage of CCS is very effective to reduce the CO2 emissions emitted from Waste-to- Energy Plants with 95% accuracy. This, in effect, will ensure effective expert knowledge communication to the general public and foster social acceptance of this technology.
 
 Keywords: Carbon dioxide, Carbon Capture and Storage, WtE Plants, and Process Integration
 
 

Environmental potential assessment of MSWI bottom ash-based alkali-activated binders

Alkali-activated binders (AABs) stand out as a sustainable alternative to ordinary Portland cement (OPC) as they can be formulated using by-products or waste as raw materials. However, the presence of hazardous compounds in residues can lead to an increase in AABs' toxicity due to the highly alkaline media. Therefore, it is extremely important to evaluate their environmental risks to validate their use as building materials. This study environmentally assessed AABs prepared with two different fractions (0–30 mm and 8–30 mm) of weathered bottom ash (AA-WBA) from WtE plants. The potential leachate toxicity of AA-WBA was assessed using granular and monolithic leaching tests that simulated end-of-life and service life scenarios, respectively. Furthermore, an acute toxicity test with crustacean Daphnia magna as model organisms was conducted to determine the relationship between the leachate metal(loid) concentrations and the ecotoxicity of AA-WBA. The results showed higher metal(loid) concentrations in AA-WBA specimens prepared with the 0–30 mm fraction of WBA. The service life scenario revealed multiple metal(loid)-release mechanisms. The 48 h EC50 value (close to 10%; moderate toxicity) indicated that the use of the coarse fraction of WBA increased the immobilisation of the metal(loid)s. Finally, the correlation between the concentrations of some of the metal(loid)s and toxicity was demonstrated.

EU countries experience analysis in using various fume gas treatment systems from acid gases removing for WTE Plants

The existing method of selecting the structure of a Waste to energy plant (WTE plant) for thermal utilization of MSW in the Russian Federation is often not applicable to real objects, which leads to the need for each project to search for new methods, select the criteria for choosing the best technology.Conducting a comparative analysis of various structural schemes WTE plant, common in the EU and Japan, will help to identify their main advantages and disadvantages, determine the scope of application.This article describes the statistical indicators of the flue gas treatment system (FGT) from acid gases, which can be applied at the stage of feasibility study, development of basic engineering. When building a WTE plant in urban conditions and striving to minimize the gross emissions of acid gases into the atmosphere, a wet FGT cleaning system can be recommended, which will provide low emissions of HF, HCl, and SOx. The system with a wet reactor will reduce the gross emissions of harmful substances during the construction of WTE plant with high-capacity, and in this case it is justified.When building WTE plant with medium-capacity (up to 350 thousand tons of MSW per year), it may be recommended to use a semi-dry and dry FGT, while the highest preference should be given to the technology with a semi-dry reactor as the most promising.

Problems and prospects of creating an environmentally friendly WtE plant

The main stages in choosing the optimal technology for thermal treatment of MSW (municipal solid wastes) at the stage of feasibility study are discussed. The analysis of the influence of the fuel component on the structure of the WTE plant is carried out. Recommendations have been developed for choosing the optimal energy structure of a WTE plant, ash and slag management schemes, and thermal utilization technologies that are most suitable for the location of the facility. A study was conducted on the influence of the selected structure of the energy complex on the decision to choose a gas treatment system. A comparison of criteria for choosing the structure of the energy complex at the MSW in comparison with the energy thermal power plant (TPP) is made.Due to the economic and environmental problems that appear during the construction of WTE plants, when it comes to waste scheme for cities and regions, it is recommended to use a scheme with the maximum use of secondary raw materials from waste and thermal treatment only of residues that are not subject to recycling, from which the fractions containing the largest amount of pollutants (RDF fuel) are extracted. The technology using deep recovery of secondary raw materials will simplify the structure of WTE plant, reduce capital and operating costs, and most importantly reduce emissions of harmful substances into the atmosphere with flue gases, ash and slag.

The potential of sustainable municipal solid waste-to-energy management in the Palestinian Territories

Global energy demand and MSW generation are increasing as population and living quality continue to grow. Efforts are oriented towards developing and adopting sustainable solutions. Palestinian territories depend on imported energy (100% fossil fuel and 89% electricity) from Israel, and suffer from MSW accumulation environmental consequences due to improper disposal method. West Bank MSW generation rate reached 2600 ton per day (0.91 kg per capita per day) in 2019, and it increases 4% annually. Three MSW dumping sites are currently operating, namely; Zahrat Al-Finjan to serve middle and northern West Bank area (of 88% utilization rate), Al-Menia (of 9% utilization rate) to serve southern area, and one in the city of Jericho (overloaded). Palestinian government strategic plans (2017–2022) aim to reduce imported energy dependency, reduce CO2eq emissions, and adopt sustainable solutions for MSW disposal. WTE is considered a promising solution to achieve these objectives.This research investigates three WTE options for the West Bank, two of them assume producing electricity by incineration, which are building a plant in Zahrat Al-Finjan (1500 ton/day), or building a smaller plant in a transfer station (750 ton/day), the third option assumes waste-to-heat option for local industrial loads. To perform the study, all MSW, energy, and population data were collected and analyzed spatially. After that, considered options were analyzed from economic and environmental point of view, and different operational incentives were proposed to enhance its feasibility.Results show that waste to heat plant is the most feasible. Unfortunately, this option is impractical due to demand unavailability. For electric generation plants in Zahrat Al-Finjan and the transfer station, MARR and plant life time were assumed 10% and 30 years, respectively. If the proposed plants will be responsible for handling MSW collection and transferring costs, NPV for it will be 25.2 and −2.63 million U.S dollars, RoR equals to 12% and 9.7%, and SPP equals to 8.5 and 11 years, respectively. While if the Palestinian government will continue taking this burden, Zahrat Al-Finjan and transfer station WtE plants NPV will be 207 and 12.5 million U.S dollars, RoR equals to 22% and 11.3%, and SPP equals to 4.6 and 9 years, LCOE equals to 0.0486 and 0.0497 $/kWh, and annual saved CO2eq equals to 1.23 and 0.58 Mt CO2eq, respectively.

Greenhouse gas credits from integrated waste-to-energy plant

In Europe, most of the district heat is produced from fossil energy sources such as coal or natural gas. Together with the intention to divert municipal waste from landfill, which is still the main way of treatment in approximately half of the EU countries, there is a potential for the construction of waste-to-energy plants (WtEP) that can partially replace fossil fuels. An important factor in planning the construction of new WtE plants is the assessment of the project’s economy. However, the ecological aspect of the project, namely the greenhouse-gas (GHG) savings, is becoming a topic of discussion nowadays. In terms of GHG savings, WtE plant integration into an existing district heating system (DHS) has a positive impact, but its level is often only roughly estimated. The paper presents a comprehensive mathematical optimization tool working on a daily time interval that is able to evaluate the impact of changing current technology or WtE plant construction on global warming potential. The technical parameters such as boiler output range, energy efficiency, etc. are considered. The tool also allows to put in the context the GHG savings and economic benefits of the project. These two factors are very difficult to compare. The study answers the question of how to deal with this issue and presents the possibility of comparison, which is generally transferable to any two parameters. Due to two poorly comparable criteria, the result does not include a single optimal solution, but clearly illustrates the view of the overall issue and gives a good basis for the final decision. The method used are illustrated in real-world DHS with various parameters where the relationship between GHG savings and the economic benefits of the integration of a WtE plant is evaluated. The whole problem is the task of linear integer programming and is implemented in the GAMS programming environment.

Environmental and economic assessment of sustainable municipal solid waste management strategies in Iran

Waste management in urban areas has always been a major concern for municipalities. The gigantic population growth results in massive waste production, leading to a worrying rise in the level of greenhouse gas emissions, a major global issue. The most common techniques for energy recovery from waste are WTE and landfill gas plants. In this research, four different waste management scenarios have been investigated, and the emitted GHGs are analysed using the IPCC guideline for municipal solid waste (MSW) in Tehran. Furthermore, the total cost of each scenario is calculated. Also, effect of various parameters, such as plant usage, methane recovery factor, and MSW heating value, on the emissions is evaluated. The results depict that among all the investigated alternatives, scenario 3 (in which 50 % of the waste was burned in WTE plant, 30 % landfilled, and 20 % recycled) has the least GHG emissions in the target region. For a more thorough analysis, a cost comparison between the scenarios was performed, indicating that landfilling with recovery is the most economical option. Focusing on various technical, economic, and environmental aspects of waste management, this paper provides a comprehensive framework for a combined plan of action in the waste management sector of Iran.

Long-term opportunities for electricity production through municipal solid waste incineration when internalising external costs

A further deployment of waste-to-energy incineration facilities (WtE plants) is expected in Europe in order to abate the use of landfills for municipal solid waste. Besides being a straightforward solution for this waste management purpose, WtE plants contribute to reducing the dependence on fossil fuels for electricity production. In this sense, this article follows a combined Life Cycle Assessment (LCA) and Energy Systems Modelling (ESM) approach to prospectively assess the potential role of a national power generation system as a driving force for the promotion of WtE plants when internalising external costs. Since the internalisation of external costs for sustainability-oriented, long-term energy planning typically involves a life-cycle perspective, emphasis is laid on the controversial choice of a method to allocate the life-cycle environmental burdens of WtE plants between their waste management and power generation functions. A high penetration of WtE plants (up to 10% of the total electricity production) is found only when the waste management service is assumed to bear all burdens. On the contrary, a negligible contribution of WtE plants to the prospective electricity production mix is found when the burdens are completely or partly allocated to the power generation function. Hence, under a (sensible) balanced approach of shared burdens, the power generation system is concluded not to be a driving force for the increased role of WtE plants. Furthermore, the need for policy-makers (or other relevant decision-makers) to set the allocation method in LCA of WtE plants is stressed.

Potencial de usinas waste to energy no nordeste brasileiro: projeção e análise comparativa de impactos na esfera ambiental e no setor energético

A gestão dos resíduos sólidos urbanos (RSU) e a oferta de eletricidade são preocupações presentes no Brasil. Nesta conjuntura, as usinas de geração de energia a partir de resíduos sólidos (Waste To Energy -WTE) surgem como alternativa de investimento que poderia trazer benefícios tanto para a gestão dos RSU, pela mitigação de impactos ambientais, quanto para o setor elétrico brasileiro. Este trabalho tem o objetivo de analisar de forma comparativa cenários futuros na gestão de RSU no Nordeste levando em conta investimentos em usinas WTE. Para isto, foram projetados por meio de método quantitativo de modelagem - em um período de 20 anos - os impactos sobre a ocupação de espaço para gestão dos RSU, as emissões dos gases metano e carbônico, e a geração de energia na região. Os resultados destacam o potencial benéfico das usinas WTE, através do aumento considerável na geração de energia e da diminuição notável das emissões de gases de efeito estufa (GEE) e da ocupação de espaço

Theory and practice of corrosion related to ashes and deposits in a WtE boiler

Corrosion of heat-exchanging components is one of the main operational problems in Waste-to-Energy plants, limiting the electrical efficiency that can be reached. Corrosion is mainly related to the devolatilization and/or formation of chlorides, sulphates and mixtures thereof on the heat-exchanging surfaces. Theoretical considerations on this corrosion were already put forward in literature, but this paper now for the first time combines theory with a large scale sampling campaign of several Waste-to-Energy plants. Based on the outcome of elemental and mineralogical analysis, the distribution of Cl and S in ashes sampled throughout the plant during normal operation is explained. Cl concentrations are high (15–20%) in the first empty pass, decrease in the second and third empty pass, but increase again in the convective part, whereas the S concentrations show an inverse behavior, with the highest concentrations (30%) observed in the second and third empty pass. Sampling of deposits on specific places where corrosion possibly occurred, gives a better insight in the mechanisms related to corrosion phenomena in real-scale WtE plants and provides practical evidence for some phenomena that were only assumed on the basis of theory or lab scale experiments before. More specific, it confirms the role of oxygen content, temperatures in the different stages of the boiler, the presence of polysulphates, Pb and Zb, and the concentrations of HCl and SO2 in the flue gas for different types of boiler corrosion.

Energy, environmental and operation aspects of a SRF-fired fluidized bed waste-to-energy plant

A methodology based on the ISO 14031:2013 guideline has been developed and applied to a full-scale fluidized bed waste to energy plant (WtE) burning solid recovered fuel (SRF). With reference to 3years of operation, the data on energy and environmental performance, on raw materials consumptions such as sand and diesel fuel, accidental reasons of plant shutdown, have been acquired and analyzed. The obtained results have allowed to quantify the energy and environmental performance of the WtE plant under investigation by varying the amount and mixings of the inlet waste, available in form of thickened and fluff (similar to coriander) SRF. In terms of the energy performance, the fluidized bed technology applied to the SRF was able to guarantee an adequate production of electricity (satisfying the market demands), showing a relative flexibility with respect to the inlet waste. In terms of net energy production efficiency, the plant showed values in the range of 13.8–14.9% in line with similar installations. In terms of the environmental performance, the adoption of a cleaning system based on SNCR (Selective Non Catalitic Reduction)+semi-dry scrubbing+Fabric filter generated emissions usually well below the limits set by the EU Directive 2000/76/EC as well as the Italian Law 46/2014 (more restrictive) with reference to all the key parameters. In terms of the plant shutdown, the majority of problems focused on the combustion chamber and boiler due to the erosion of the refractory material of the furnace as well as to the breaking of the superheaters of the boiler. In contrast, the mechanical and electrical causes, along with those related to the control and instrumentation system, were of secondary importance. The sand bed de-fluidization was also among the leading causes of a frequent plant shutdown. In particular, results showed how although the SRF presents standard characteristics, the use of different mixtures may affect the number of plant shutdowns. The full-scale data highlighted how the lower the rate of fluff in the mixture was, the greater the number of plant shutdown due to sand bed de-fluidization was. Finally, the aspects in terms of the energy, environmental protection and raw material consumption have been discussed with reference to similar WtE plants such as Robbins (Chicago, USA), Lidköping (Sweden), Toshima (Tokyo, Japan), Madrid (Spain), Dundee (Scotland, UK) and Valene (Mantes la Jolie, France).

Valorization of MSW-to-Energy in Thailand: Status, Challenges and Prospects

In order to effectively plan MSW management with energy recovery activities, it is important to understand and assess the current situation and highlight issues, problems, as well as the initiatives under taken. This study aims to review and assess the overall commercial WTE plants in Thailand and compare the same with other countries based on available literature, interviews and site visits. The status, challenges and prospects of WTE technologies such as landfill gas, anaerobic digestion, incineration, gasification and RDF are discussed. The existing WTE plants treat 2.54 Mt of MSW per year (9.5 % of total 26.8 Mt generated in 2013) and generate 66 MW of electricity as well as 78.26 ktoe of heat. It is estimated that about 8.17 Mt of MSW (30.5 %) will be treated which will generate 319 MW of electricity as well as 78.26 ktoe of heat when the plants presently under construction and planning stage start operation. RDF and incineration have been identified as suitable technologies for treating MSW in Thailand. RDF technology preserves resources in MSW through recycling and energy recovery. It has high potential for co-firing with other fuels in many industries as well as using in other WTE technologies such as incineration and gasification. Incineration treats and reduces large amount of MSW with high potential to generate electricity and requires minimal pre-treatment.

Evaluation of characteristics and behavior of cold sprayed Ni–20Cr coating at elevated temperature in waste incinerator plant

Hot corrosion failure of components in power plant industry, like waste incinerators and WTE plants, is still a serious issue. The chlorine present in the plant environment acts as a catalyst and thereby, accelerates the corrosion reactions through the ‘Active oxidation’ phenomenon, which consists of chloridation, evaporation and re-oxidation. In this study, efforts were made to study the hot corrosive behavior of 80%Ni–20%Cr coating in the real service medical waste incinerator environment at 900°C. The coating was deposited on a superalloy substrate by cold spraying. The coating performance has been characterized using the combined techniques of XRD, SEM/EDX and elemental X-ray analysis. The chlorine based incinerator environment is found to be so aggressive that corrosive species are able to penetrate through the uncoated superalloy. However, the cold sprayed coating is able to protect the superalloy from the highly corrosive degrading species present in this environment.

Energy implications of mechanical and mechanical–biological treatment compared to direct waste-to-energy

Primary energy savings potential is used to compare five residual municipal solid waste treatment systems, including configurations with mechanical (MT) and mechanical–biological (MBT) pre-treatment, which produce waste-derived fuels (RDF and SRF), biogas and/or recover additional materials for recycling, alongside a system based on conventional mass burn waste-to-energy and ash treatment. To examine the magnitude of potential savings we consider two energy efficiency levels (state-of-the-art and best available technology), the inclusion/exclusion of heat recovery (CHP vs. PP) and three different background end-use energy production systems (coal condensing electricity and natural gas heat, Nordic electricity mix and natural gas heat, and coal CHP energy quality allocation).The systems achieved net primary energy savings in a range between 34 and 140MJprimary/100MJinput waste, in the different scenario settings. The energy footprint of transportation needs, pre-treatment and reprocessing of recyclable materials was 3–9.5%, 1–18% and 1–8% respectively, relative to total energy savings. Mass combustion WtE achieved the highest savings in scenarios with CHP production, nonetheless, MBT-based systems had similarly high performance if SRF streams were co-combusted with coal. When RDF and SRF was only used in dedicated WtE plants, MBT-based systems totalled lower savings due to inherent system losses and additional energy costs. In scenarios without heat recovery, the biodrying MBS-based system achieved the highest savings, on the condition of SRF co-combustion. As a sensitivity scenario, alternative utilisation of SRF in cement kilns was modelled. It supported similar or higher net savings for all pre-treatment systems compared to mass combustion WtE, except when WtE CHP was possible in the first two background energy scenarios. Recovery of plastics for recycling before energy recovery increased net energy savings in most scenario variations, over those of full stream combustion. Sensitivity to assumptions regarding virgin plastic substitution was tested and was found to mostly favour plastic recovery.