Municipal Solid Waste Incineration Systems Research Articles

Exhaust steam utilization in waste-to-energy strategies: From district heating to desalination

This study undertakes a comprehensive comparative analysis of different Municipal Solid Waste incineration systems, specifically targeting their energy recovery efficiencies, while also presenting a pioneering exploration of exhaust steam applications in such systems for desalination. The systems evaluated encompass electricity-only generation, air-cooled condensing steam, water-cooled condensing steam, and exhaust steam utilization for both District Heating (DH) scenarios (I, II, III) and Desalination. An energy balance model is employed to simulate and quantify the energy flows and efficiencies within these systems. The results show a wide variance in energy recovery efficiency, ranging from 11.2% for electricity-only to 66.8% for use of exhaust steam in Desalination. Notably, the DH (I) system, which incorporates heat recovery for district heating, showed a significantly higher energy recovery efficiency (57.5%) than the electricity generation-focused systems. The enhanced DH systems (II and III), which integrate condensing and two-stage extraction mechanisms, further improve energy recovery to 59.4% and 58.3% respectively. A sensitivity analysis, accounting for advancements in district heating systems, revealed a potential efficiency increase of up to 5%. The site assessment underscores the Persian Gulf, East Asia, Island Nations, and the European Mediterranean as prime candidates for WtE-desalination cogeneration, while Australia, South & Southeast Asia, the United States, and the Non-European Mediterranean demonstrate notable potential, each presenting unique attributes and challenges that influence their suitability. The efficiency and appropriateness of these systems are strongly influenced by specific external factors such as waste composition, local demand for energy and water, and geographical location.

Suppression on PCDD/Fs formation by a novel inhibition system consisting of phosphorous-based compounds coupled with a chlorine-deactivation material

The SN-containing inhibitors are effective for suppressing the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the post-combustion zone of municipal solid waste incineration systems, but the industrial application of the SN-containing inhibitors is restricted by the high cost and the generation of corrosive by-products (e.g., SOx). To develop cost-effective and environmentally friendly inhibitors, a new inhibition system consisting of P-based compounds (i.e., NH4H2PO4 (ADP) and KH2PO4 (PDP)) and a chlorine-deactivation material (CaO) was proposed in this study. Also, the performance of this inhibition system in terms of suppressing PCDD/Fs formation was evaluated in an experimental system which simulated PCDD/Fs generation in the post-combustion zone. Generally, the formation of PCDD/Fs was effectively suppressed by over 95 % by the mixed inhibitors (ADP/CaO and PDP/CaO) and the individual inhibitor of ADP. Based on the observation on PCDD/F-fingerprints and the chemical speciation of Cl and Cu, the mechanisms of inhibitors were identified as: (i) passivating metal catalyst by converting the speciation of Cu from chlorides and Cu2+ with high reactivities to phosphates, oxides, and Cu+ with low reactivities, and (ii) deactivating Cl by CaO to prevent the formation of organic Cl which was critical for PCDD/Fs formation. In addition, both mechanisms were supported by (i) the better performance of inhibitors on suppressing the PCDD/F-congeners formed via de novo pathway than congeners synthesized from chlorophenols and (ii) lower degrees of chlorination of PCDD/Fs for reaction systems with CaO involved than other systems.

Life Cycle Assessment of Advanced Circulating Fluidized Bed Municipal Solid Waste Incineration System from an Environmental and Exergetic Perspective.

The production of clean and efficient energy from municipal solid waste (MSW) is extremely urgent matter due to an increasing energy demand and environmental concerns. In this study, a high steam parameter (520 °C, 7.9 MPa) circulating fluidized bed (CFB) MSW incineration system, equipped with a mechanical, biological treatment and external heat exchanger systems, was introduced and a comparative study with a typical mechanical grate (450 °C, 5.3 MPa) incineration system and conventional CFB (485 °C, 5.3 MPa) incineration system was carried out from a life-cycle, environmental and exergetic perspective which could assess different energy and material outputs based on real operating data. Moreover, the potential system optimization of this advanced CFB system was proposed. The results showed that the advanced CFB system was more environmentally friendly and resource-efficient than conventional MSW incineration systems. The recovery of material should be given priority over energy recovery. According to the assessment of the environment, and energy and material recovery, a process improvement with an incinerated refuse-derived fuel and a semi-compost produced by MBT as a soil conditioner was highly recommended.

Spraying polyacrylamide solution to improve the removal of particle-phase dioxins by bag filter in a full-scale municipal solid waste incineration system

A field experiment was conducted in a modern municipal solid waste (MSW) incineration power plant to explore the feasibility of using chemical agglomeration agent anionic polyacrylamide (PAM) to reduce the atmospheric emission of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Spraying PAM solution into the cooling tower caused an obvious decrease in the volume fraction of ultrafine and fine particles with diameter of 0.3–30 μm in BF fly ash, and a significant reduction in dust content in stack gas. The increased agglomeration of particles promoted the removal of particle-phase PCDD/Fs by BF, and thus resulted in a lower atmospheric emission of PCDD/Fs. The calculated removal efficiency of PCDD/Fs by BF was almost positively proportional to the concentration of PAM solution, while inversely proportional to the average content of dusk in stack gas. Compared with the control treatment, the spraying of 0.1 g/L PAM solution enhanced the removal efficiency of total tetra-to octa-CDD/Fs (∑PCDD/Fs) from 93.8% to 97.8% by BF, and resulted in a decrease of 47.0% in the concentration of international toxicity equivalent (I-TEQ) in stack gas. During the experiment of 2 d, the spraying of PAM solution did not induce a significant change in the differential pressure of BF, and did not essentially affect the partitioning behaviors of PCDD/F homologues between flue gas and BF fly ash. In view of technical safety and low cost, PAM application is recommended for reducing the atmospheric emission of PCDD/Fs from MSW incineration system.

Environmental and energy performances of the Italian municipal solid waste incineration system in a life cycle perspective.

The environmental and energy performances of the Italian municipal solid waste incineration (MSWI) system was investigated by a life cycle assessment approach. On average the 39 MSWIs operating in Italy in 2018 treated about 6,000,000 Mg of residual municipal solid waste (RMSW) recovering on average from 448 kWh Mg-1 RMSW to 762 kWh Mg-1 RMSW of electricity and from 732 kWh Mg-1 RMSW to 1102 kWh Mg-1 RMSW of heat. The average quantity of CO2eq Mg-1 RMSW emitted ranged from about 800 up to about 1000 depending on the size and on the energy recovery scheme of the facility. Avoided impacts (i.e., negative values) were detected for the kg PM2,5eq Mg-1 RMSW and for human health (disability-adjusted life year Mg-1 RMSW). The determination of the hybrid primary energy index (MJ Mg-1 RMSW) indicated that mainly large size facilities and those operating according to a power and heat energy recovery scheme are effectively able to replace other primary energies by the exploitation of the lower heating values of the RMSW.

Formation and inhibition of Polychlorinated-ρ-dibenzodioxins and dibenzofurans from mechanical grate municipal solid waste incineration systems

This study is carried out in two full-scale (300 t/d) municipal solid waste incinerators (MSWI), focusing on the inhibition effect on polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/F) formation by the Sulfur-, Phosphorus-, and Nitrogen-containing inhibitors. The inhibition efficiencies of total PCDD/F range from 45.77 % to 58.55 %, meanwhile, from 50.1 % to 57.6 % for toxic PCDD/F. X-ray photoelectron spectroscopy results conduct the inhibition effect on the three key factors of PCDD/F formation: catalytic metal, carbon source and chlorine source. Inhibitors can increase the proportion of inorganic chlorine form at the ash surface. The changes of sulfur and phosphorus forms support the inhibition mechanisms of PCDD/F. De novo synthesis is the stable inhibition pathway in this study, meanwhile, the chlorophenols-route and dibenzodioxin and dibenzofuran chlorination also work in some tests. The results are the basics for further industrial application of PCDD/F inhibitors and benefit in controlling the PCDD/F emission from MSWI.

Reduction of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans by Chemical Inhibition and Physisorption from a Municipal Solid Waste Incineration System

This study was based on a full-scale (450 t/d) circulating fluidized bed (CFB) municipal solid waste incinerator (MSWI), focusing on the reduction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in flue gas and ash affected by S-, P-, and N-containing inhibitors and a fabric filter with active carbon injection (FF + ACI). The inhibitors injection coupled with FF + ACI effectively reduced total PCDD/F by 98.81% and toxic PCDD/F by 99.32% from flue gas, ensuring PCDD/F emissions lower than the national standard (0.1 ng I-TEQ/Nm3). The inhibitors reduced 43.51% PCDD/F in flue gas and 34.88% PCDD/F in ash, and the inhibition effect on PCDD/F formation pathways follows the order of chlorophenol (CP) route formation > de novo synthesis > dibenzo-p-dioxin and dibenzofuran (DD/F) chlorination. Sulfonating phenolic precursors is an important inhibition pathway of PCDD/F in this study. FF + ACI could effectively remove the total concentration of PCDD/F in flue gas by 97.58% and 97.92% with and without inhibitors injection, respectively, and the removal efficiencies on toxic PCDD/F are both 98.67% for two conditions. Additionally, FF + ACI had a weaker RE on congeners with two or more groups of chlorine substituents at the meta-position than those with fewer groups. The results will pave the way for further industrial optimized designs of air pollution control devices to control the PCDD/F emission from MSWI.

Suggested guidelines for emergency treatment of medical waste during COVID-19: Chinese experience.

During the period of COVID-19, the medical waste disposal capacity is seriously inadequate. The main technical process of the municipal solid waste incineration system is the same as that of the medical waste incineration system. Under the conditions of optimizing the technological process, improving the supporting facilities, and controlling the co-processing ratio, the municipal solid waste incinerator (grate furnace) co-processing medical waste is feasible. Some suggested guidelines for emergency treatment of medical waste from COVID-19 have been provided by China.

Partitioning and removal behaviors of PCDD/Fs, PCBs and PCNs in a modern municipal solid waste incineration system

An extensive evaluation on a modern full-scale municipal solid waste incineration system was conducted for characterizing the distribution of highly toxic chlorinated aromatics, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs), and their corresponding mass fluxes in post combustion zone. It was found that the flue gas/fly ash partitioning behaviors of chlorinated aromatics could be essentially described by their octanol-air partition coefficients (KOA) and strongly affected by the flue gas temperature. Above 93% of chlorinated aromatics formed in boiler section was partitioned into the flue gas and transported into the subsequent flue gas cleaning system, in which above 92% of Cl3–8DDs, Cl3–7DFs, Cl5–10Bs and Cl4–8Ns in flue gas was removed by the discharge of fly ash. The results of mass flux calculation indicated that the memory effect in flue gas cleaning system remarkably elevated the emission levels of chlorinated aromatics, especially the less chlorinated ones. The memory effect should mainly result from the direct chlorination mechanism mediated by the deposited particles. In addition, activated carbon injection could cause an obvious increase in PCBs emission. The obtained results provided some important implications for further reducing the emission of highly toxic chlorinated aromatics.

Dichlorination in a circulating fluidized-bed incinerator for municipal solid waste incineration system

Cl is one of the main pollutants emitted from domestic waste incineration systems. In this study, we focused on the process of Ca dechlorination in the furnace of a circulating fluidized-bed waste incineration system. We analyzed the stability of CaCl2 and Ca in the furnace, the dechlorination process, and distribution of Cl in the incineration system. The results show that the optimal Ca/Cl molar ratio for Ca dechlorination in the circulating fluidized-bed waste incinerator is 2:1; moreover, the dechlorination product CaCl2 was found to decompose at high temperatures (> 850 °C). At temperatures > 700 °C, we measured CaCl2 decomposition rates up to 80%. Ca was added in the furnace, mainly to provide a dechlorination Ca source for the decomposition of limestone into tail flue gas. The amount of Ca2+ in the flue decreased gradually, parallelly to the temperature of the flue gas. Stable CaCl2 was formed after HCl was captured, and relatively small solid particles appeared in the ash collecting bag.

A Review on Technologies of Removal of Dioxins and Furans from Incinerator Flue Gas

The demands of our society generate wastes that tend to increase in quantity as the standard of living increases. The most effective means of dealing with the problem is to reduce the amount of wastes generated. Incineration is one of the oldest technologies to reduce the amount of generated waste. But one serious drawbacks of this process is the emission of dioxins and furans in flue gas. Dioxins and Furans are regarded as very harmful chemicals which can have serious health effect causing cancer, reducing immunity. Various techniques are available for the treatment of flue gas emission depending upon the type of feed stocks. Some popular and effective methods are using sulphur compounds namely (NH4)2SO4, pyrite (FeS2), changing the operating conditions of incinerations etc. The main aim of this paper is to suggest a cost effective, efficient and a long lasting method to treat the flue gas so that the concentration of dioxins and furans can be reduced effectively as well as to eradicate the challenges associated with the process. The present review discusses the current views on methods to minimize dioxins and benzo-furans, namely polychlorinated dibenzo-dioxins (PCDDs) and dibenzo-furans (PCDFs), formation in different types of incineration systems. Municipal solid waste incineration system, hazardous solid waste incineration system and Bio medical waste incineration system has been considered in this case. This paper briefly introduces with the formation mechanism and the various sources including the precursors of PCDD/Fs formation so that it can be controlled during the combustion and later it discusses about an effective method to reduce the formation and fight with the associated challenges. The findings of this paper will help the stakeholders in decision making process in establishing a sustainable future of waste management and will set future directions for better and innovative research addressing the problems.

Oxidation and waste-to-energy output of aluminium waste packaging during incineration: A laboratory study

This work reports the oxidation behaviour and waste-to-energy output of different semi-rigid and flexible aluminium packagings when incinerated at 850°C in an air atmosphere enriched with 6% oxygen, in the laboratory setting. The physical properties of the different packagings were determined, including their metallic aluminium contents. The ash contents of their combustion products were determined according to standard BS ISO 1171:2010. The net calorific value, the required energy, and the calorific gain associated with each packaging type were determined following standard BS EN 13431:2004. Packagings with an aluminium lamina thickness of >50μm did not fully oxidise. During incineration, the weight-for-weight waste-to-energy output of the packagings with thick aluminium lamina was lower than that of packagings with thin lamina. The calorific gain depended on the degree of oxidation of the metallic aluminium, but was greater than zero for all the packagings studied. Waste aluminium may therefore be said to act as an energy source in municipal solid waste incineration systems.

Combustion Air Pre-heating from Ash Sensible Heat in Municipal Waste Incineration Systems

Heat recovery from bottom ash is more important in municipal waste combustion systems than in any other solid fuel combustion since almost 50% of it comprises of non-combustibles. In this study, an ash cooling system using air as the cooling medium has been modeled for pre-heating the combustion air. Air cooling has several advantages over water cooling methods. The study involves modeling using Gambit tool and is solved with the fluent solver. Municipal solid waste incineration systems have the advantage of being located near the waste collection area apart from the high volume reduction ratio. Improvements in the emission control systems and combustion technology can make incineration a highly feasible disposal method. Low furnace temperature due to heat losses through fuel moisture loss and ash sensible heat loss has been a disadvantage with these systems. In this study, a small percentage of the combustion air is pre-heated in a non-contact type heat exchanger and its effect on the available energy of combustion gases at the evaporator outlet is studied. The study is performed for two different waste samples. Results indicate significant increase in available energy at the evaporator outlet and better relative performance for the lower grade fuel. A comparison is made with similar methods reported in the literature along with a brief discussion on the methodologies adopted. The results confirm the importance of installing ash sensible heat recovery mechanism for waste incineration systems as well as the feasibility of the air based method.

Dioxin characterisation, formation and minimisation during municipal solid waste (MSW) incineration: review

The present review discusses the current views on methods to minimise dioxins, namely polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs), formation in MSW incineration systems. The structure of this group of compounds is discussed initially and then the toxic equivalence scale is presented for the most common isomers and congeners in the dioxin family. The current status on dioxin limits imposed in various countries and by various organisations is presented. A detailed analysis of the theories leading to dioxin formation in MSW incineration is given, since, this has been one of the most controversial areas of dioxin chemistry for the past 20 years. Three dioxin formation theories were considered possible for a long time; (i) from PCDD/PCDFs originally present in the furnace feedstock; (ii) from precursor compounds (foundation formatting molecules which could react rapidly with other groups in the system to form dioxins) in the MSW feed; (iii) from de novo synthesis of smaller, relatively innocuous chemical molecules combining together to form the dioxins. Methods (ii) and (iii) are based on heterogeneously catalysed reactions. Some researchers are considering possible homogeneous thermal reaction formation of dioxin. This review demonstrates that with the advanced modern MSW combustion systems, option (i) is a most unlikely route and also methods (ii) and (iii) are quite feasible. Based on thermodynamic and kinetic data in the literature, the rate and extent of the formation of dioxins and their precursors by certain mechanisms can definitely be contributing to routes (ii) and (iii). Since even the most advanced MSW combustion systems do not produce complete combustion, predominantly because of inadequate feed preparation and turbulence, some de novo synthesis of precursors can also take place. These ‘de novo precursors’ could be carried through the combustion unit adsorbed or absorbed on particulate material such as soot and dust, but also these precursors could be formed during the cooling process by heterogeneous catalytic reactions and go on to form dioxins. The maximum rate of formation of PCDD/PCDFs from both sources lies in the temperature range 300–400 °C. This knowledge of formation rates and mechanisms provides the basis of designing combustion systems. A two stage approach is adopted; firstly, system design to achieve complete combustion and minimise formation; secondly, end-of-pipe treatment systems to remove dioxins. In the first case, combustion temperature should be above 1000 °C, combustion residence time should be greater than 1 s, combustion chamber turbulence should be represented by a Reynolds number greater than 50,000, good MSW feed preparation and controlled feed rate are also critical. In the second category, very rapid gas cooling from 400 to 250 °C should be achieved, semi-dry lime scrubbing and bag filtration coupled with activated carbon injection adsorption as end-of-pipe treatments can all play a role in prevention or minimisation of dioxins in the final flue gas emission to the atmosphere.