Numerical Study on Flow and Heat Transfer Characteristics of Trapezoidal Printed Circuit Heat Exchanger.

Printed circuit heat exchanger (PCHE) is a promising regenerative device in the sCO power cycle, with the advantages of a large specific surface area and compact structure. Its tiny and complex flow channel structure brings enhanced heat transfer performance, while increasing pressure drop losses. It is, thus, important to balance heat transfer and flow resistance performances with the consideration of sCO as the working agent.

United Conversion Process Coupling CO Mineralization with Thermochemical Hydrogen Production.

In this work, to achieve both clean energy production and carbon emission reduction, a united conversion to couple CO mineralization with thermochemical hydrogen production is proposed. Natural magnesium silicate minerals are used to fix CO in the form of carbonate minerals, whereas HO is dissociated to produce H in the thermochemical cycle. The integration provides a new solution to the challenges of the high energy consumption and poor economic value of conventional CO mineralization processes, and the technical feasibility has been proven.

Improving microwave-assisted hydrothermal degradation of PCDD/Fs in fly ash with added NaHPO and water-washing pretreatment.

In this work, microwave-assisted hydrothermal process is applied to the PCDD/F degradation of municipal solid waste incineration (MSWI) fly ash. The effects of water-washing pretreatment and the NaHPO reagent on the degradation efficiency of PCDD/Fs are investigated. The PCDD/F content in MSWI fly ash is detected by high-resolution gas chromatography-mass spectrometry (HRGC/MS).

Environmental performance evolution of municipal solid waste management by life cycle assessment in Hangzhou, China.

There is a significant increase in the volume of Municipal Solid Waste (MSW) that is being generated across the world. Faced with this challenge and the associated environmental issues, MSW management (MSWM) in Hangzhou, China has made various positive changes in order to adapt. During the last 10 years, MSW source-separated collection was launched, which was accompanied by estimations of a new waste-to-energy (incineration) plant and food waste separate treatment methods.

Emission characteristics and vapour/particulate phase distributions of PCDD/F in a hazardous waste incinerator under transient conditions.

Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) emission characteristics and vapour/particulate phase partitions under three continued operation conditions, i.e. shut-down, start-up and after start-up, were investigated by sampling stack gas.

Life cycle assessment of pyrolysis, gasification and incineration waste-to-energy technologies: Theoretical analysis and case study of commercial plants.

Municipal solid waste (MSW) pyrolysis and gasification are in development, stimulated by a more sustainable waste-to-energy (WtE) option. Since comprehensive comparisons of the existing WtE technologies are fairly rare, this study aims to conduct a life cycle assessment (LCA) using two sets of data: theoretical analysis, and case studies of large-scale commercial plants. Seven systems involving thermal conversion (pyrolysis, gasification, incineration) and energy utilization (steam cycle, gas turbine/combined cycle, internal combustion engine) are modeled.

Waste-to-energy: A review of life cycle assessment and its extension methods.

This article proposes a comprehensive review of evaluation tools based on life cycle thinking, as applied to waste-to-energy. Habitually, life cycle assessment is adopted to assess environmental burdens associated with waste-to-energy initiatives. Based on this framework, several extension methods have been developed to focus on specific aspects: Exergetic life cycle assessment for reducing resource depletion, life cycle costing for evaluating its economic burden, and social life cycle assessment for recording its social impacts.

PCDD/F formation during thermal desorption of chlorobenzene contaminated soil.

Unintentional formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) is observed and investigated during the thermal desorption in an airflow of a sandy soil, doped artificially with either 1,2-dichlorobenzene (1,2-DiCBz) or hexachlorobenzene (HCBz) using a lab-scale experimental set-up. At all temperatures investigated (200, 250, 300, 350 and 400 °C), this thermal treatment creates significant amounts of PCDD, PCDF and polychlorinated biphenyls (PCB), starting from 1,2-DiCBz. The highest yield of PCDD/F formed from 1,2-DiCBz occurs at 250 °C, with a total (gas + residual soil) output of 117 and 166 pg/g PCDD and PCDF, respectively.

Energy and exergy optimization of food waste pretreatment and incineration.

With the aim of upgrading current food waste (FW) management strategy, a novel FW hydrothermal pretreatment and air-drying incineration system is proposed and optimized from an energy and exergy perspective. Parameters considered include the extracted steam quality, the final moisture content of dehydrated FW, and the reactor thermal efficiency. Results show that optimal working condition can be obtained when the temperature and pressure of extracted steam are 159 °C and 0.

PCDD/F emissions during startup and shutdown of a hazardous waste incinerator.

Compared with municipal solid waste incineration, studies on the PCDD/F emissions of hazardous waste incineration (HWI) under transient conditions are rather few. This study investigates the PCDD/F emission level, congener profile and removal efficiency recorded during startup and shutdown by collecting flue gas samples at the bag filter inlet and outlet and at the stack. The PCDD/F concentration measured in the stack gas during startup and shutdown were 0.

Comparison of ANN (MLP), ANFIS, SVM, and RF models for the online classification of heating value of burning municipal solid waste in circulating fluidized bed incinerators.

The heating values, particularly lower heating values of burning municipal solid waste are critically important parameters in operating circulating fluidized bed incineration systems. However, the heating values change widely and frequently, while there is no reliable real-time instrument to measure heating values in the process of incinerating municipal solid waste. A rapid, cost-effective, and comparative methodology was proposed to evaluate the heating values of burning MSW online based on prior knowledge, expert experience, and data-mining techniques.

PCDD/F formation during thermal desorption of p,p'-DDT contaminated soil.

Thermal treatment of polychlorinated biphenyls (PCB) contaminated soil was shown in earlier work to generate polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF). In this study, the PCDD/F were studied arising during the remediation of p,p'-DDT contaminated soil by thermal desorption. Three kinds of soil (sandy, clayey and lateritic soil) were tested to investigate the effect of soil texture on PCDD/F formation.

Remediation of PCB-contaminated soil using a combination of mechanochemical method and thermal desorption.

The combination of mechanochemical method and thermal desorption for remediating polychlorinated biphenyls (PCBs) in contaminated soil was tested in this study. The effects of grinding time and heating time on PCB removal efficiency were investigated. The contaminated soil, mixed with CaO powder at a weight ratio of 1:1, was first ground using a planetary ball mill.

Catalytic oxidation of 1,2-DCBz over VO/TiO-CNTs: effect of CNT diameter and surface functional groups.

A series of VO/TiO-carbon nanotube (CNT) catalysts were prepared and tested to decompose gaseous 1,2-dichlorobenzene (1,2-DCBz). Several physicochemical methods, including nitrogen adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and H temperature-programmed reduction (TPR) were employed to characterise their physicochemical properties. To better understand the effect of CNT properties on the reactivity of VO/TiO-CNT catalysts, the 1,2-DCBz residue remaining in the off-gas and on the catalyst surface were both collected and analysed.

Suppression of PCDD/Fs during thermal desorption of PCBs-contaminated soil.

Thermal treatment of polychlorinated biphenyls (PCBs) contaminated soil was shown in earlier work to generate new PCBs, as well as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). In this study, this thermal desorption was conducted with addition of three distinct inhibitors, including ammonium sulphate, urea and calcium oxide, to inhibit the formation of PCDDs and PCDFs when remediating PCBs-contaminated soil. Experiments were conducted for 40 min at 400 °C after adding 1 wt.

The effect of microbubbles on gas-liquid mass transfer coefficient and degradation rate of COD in wastewater treatment.

A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined.

Investigation of hybrid plasma-catalytic removal of acetone over CuO/γ-Al2O3 catalysts using response surface method.

In this work, plasma-catalytic removal of low concentrations of acetone over CuO/γ-Al2O3 catalysts was carried out in a cylindrical dielectric barrier discharge (DBD) reactor. The combination of plasma and the CuO/γ-Al2O3 catalysts significantly enhanced the removal efficiency of acetone compared to the plasma process using the pure γ-Al2O3 support, with the 5.0 wt% CuO/γ-Al2O3 catalyst exhibiting the best acetone removal efficiency of 67.

Adsorption of polychlorinated dibenzo-p-dioxins/dibenzofurans on activated carbon from hexane.

Activated carbon is widely used to abate dioxins and dioxin-like compounds from flue gas. Comparing commercial samples regarding their potential to adsorb dioxins may proceed by using test columns, yet it takes many measurements to characterise the retention and breakthrough of dioxins. In this study, commercial activated carbon samples are evaluated during tests to remove trace amounts of dioxins dissolved in n-hexane.

Thermal desorption of PCB-contaminated soil with sodium hydroxide.

The thermal desorption was combined with sodium hydroxide to remediate polychlorinated biphenyl (PCB)-contaminated soil. The experiments were conducted at different temperatures ranging from 300 to 600 °C with three NaOH contents of 0.1, 0.

Thermal desorption of PCBs from contaminated soil with copper dichloride.

Copper dichloride is an important catalyst both in the dechlorination of chlorinated aromatic compounds and the formation of PCDD/Fs. The effect of copper dichloride on polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) was studied in treated soil and off gas after thermal desorption of PCB-contaminated soil at 300, 400, 500, 600 °C. The presence of copper dichloride clearly enhances thermal desorption by promoting PCBs removal, destruction, and dechlorination.

Removal efficiencies for 136 tetra- through octa-chlorinated dibenzo-p-dioxins and dibenzofuran congeners with activated carbons.

In this study, the removal efficiency of 136 tetra- to octa-chlorinated dibenzo-p-dioxin (CDD)/furan (F) congeners from a nitrogen + oxygen carrier gas was studied using a laboratory-scale, fixed bed adsorption system. Two kinds of activated carbon with dissimilar pore structures were used as adsorbents. The total concentration of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) in the source gas was 541 ng/Nm(3) and that of the 17 toxic 2,3,7,8-substituted PCDD/Fs 96.

Effect of oxygen content on the thermal desorption of polychlorinated biphenyl-contaminated soil.

Oxygen plays an important role during the thermal treatment of soil, contaminated with polychlorinated biphenyls (PCBs), due to the potential oxidation of PCBs to form polychlorinated dibenzofurans (PCDFs). The effect of oxygen content (0, 5, 21 and 100%) in carrier gases on PCBs and PCDD/Fs was studied both in soil and gas after thermal desorption of PCBs contaminated soil at 500 °C. All 209 congeners of PCBs and 136 congeners of PCDD/Fs (P = 4 to 8) were analysed.

Comparison of adsorption behavior of PCDD/Fs on carbon nanotubes and activated carbons in a bench-scale dioxin generating system.

Porous carbon-based materials are commonly used to remove various organic and inorganic pollutants from gaseous and liquid effluents and products. In this study, the adsorption of dioxins on both activated carbons and multi-walled carbon nanotube was internally compared, via series of bench scale experiments. A laboratory-scale dioxin generator was applied to generate PCDD/Fs with constant concentration (8.

A review on black carbon emissions, worldwide and in China.

Black carbon (BC) produced from open burning (OB) and controlled combustion (CC) is a range of carbonaceous products of incomplete combustion of biomass and fossil fuel, and is deemed as one of the major contributors to impact global environment and human health. BC has a strong relationship with POPs, in waste combustion, BC promotes the formation of POPs, and then the transport of POPs in the environment is highly influenced by BC. However less is known about BC formation, measurement and emissions estimation especially in developing countries such as China.

Comparison of municipal solid waste treatment technologies from a life cycle perspective in China.

China has endured the increasing generation of municipal solid waste; hence, environmental analysis of current waste management systems is of crucial importance. This article presents a comprehensive life cycle assessment of three waste treatment technologies practiced in Hangzhou, China: landfill with and without energy recovery, and incineration with waste-to-energy. Adopting region-specific data, the study covers various environmental impacts, such as global warming, acidification, nutrient enrichment, photochemical ozone formation, human toxicity and ecotoxicity.