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The artificial island project of the Hongkong-Zhuhai-Macao Bridge is situated in a location prone to year-round exposure to extreme weather events such as tropical cyclones and typhoons, often accompanied by prolonged heavy rainfall when typhoons pass through. To mitigate operational risks of the tunnel under such extreme and adverse conditions, a local physical model test was conducted to verify the water interception capacity of the transverse ditch grate on the open section of the artificial island. The influence of grid angle, opening ratio, road slope, scale effects, and the number of transverse ditch on the water interception capacity of the grate were studied. The results indicate that the water interception capacity of the grate in the design with a 0° grid angle surpasses that of the 90° grid angle. Simultaneously, the arrangement of two transverse ditches demonstrates a significant water interception effect. The findings of this research are of great significance for the accuracy of the design and layout of the transverse ditch grates on the artificial island, the elimination of drainage hazards, risk prevention, and ensuring operational safety. [ABSTRACT FROM AUTHOR]

Few studies focused on the emission of polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/F) from different kinds of waste incinerators. This study was conducted in a full-scale MSW incineration plant to investigate the influence of different incinerator types on PCDD/F. Experimental results indicated that the 2,3,7,8-PCDD/F concentration in the inlet gas of the air pollution control system (APCS) in the studied fluidized bed was higher (2.03 ng I-TEQ/Nm3) than that of the grate (0.77 ng I-TEQ/Nm3). But gas in the outlet of APCS from both incinerators had an approximate concentration, lower than the Chinese emission limit of 0.1 ng I-TEQ/Nm3. Similar distribution patterns were observed for 2,3,7,8-PCDD/Fs, as well as 136 PCDD/F congeners. Specifically, OCDD and 1,2,3,4,6,7,8-HpCDD were major isomer constituents for 2,3,7,8-PCDD/F isomers. In terms of formation pathways, a similar formation mechanism was observed based on fingerprint characteristics of 136 PCDD/F congeners. De novo synthesis was the dominating formation pathway for both incinerators. Meanwhile, DD/DF chlorination was another contributor to PCDD/F formation, which in the fluidized bed was higher. In addition, little correlation (0.009 < R2 < 0.533) between conventional pollutants (HCl, CO, PM) and PCDD/Fs was found, suggesting little high-temperature synthesis observed and verifying the dominance of de novo synthesis. [ABSTRACT FROM AUTHOR]

This paper presents the results of the theoretical studies of the process of wear of the technological surfaces of saw gin grates. Mathematical expressions are obtained, with the help of which it is possible to determine the theoretical statistical characteristics of the raw roller and it is indicated that the wear of the grate, in the process of operation from the impact of the raw roller, occurs as a result of the abrasive deposited on it. A rod model of the process of interaction between a raw roller and a grate has also been studied, on the basis of which it is possible to determine the depth of abrasive penetration in the contact surface of the working zone of the grate. The possibility of reducing the wear of grates by increasing the area of their technological surfaces and reducing, due to this, the probability of abrasive grains getting into the same place, is substantiated. A grate with a new convex shape of the technological surface is proposed. Calculations have determined that in this case the service life of the grate increases up to 50%.

We present the results from a chemical analysis of dust samples collected in a sinter shop. Grates with dust suction in the immediate vicinity of the hot grate are proposed for dust reduction in industrial premises. The work performed in this paper supports improvement of screen reliability, reduces the negative pressure differential, and ultimately reduces energy costs by preventing the channel openings from becoming clogged with falling chunks of the material being transported. A calculation was performed to obtain the grate area and linear dimensions required to meet performance specifications, and strength calculations were performed to determine the cross-sections of the grates and the assemblies used to attach the grates to the beams. [ABSTRACT FROM AUTHOR]

Copyright of Eastern-European Journal of Enterprise Technologies is the property of PC TECHNOLOGY CENTER and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The data on the state-of-the-art of the thermal processing of municipal solid waste (MSW) in the United States, China, Europe, and other countries are presented. The analysis of technologies for MSW incineration in layered furnaces using fire-grates and fluidized-bed furnaces, as well as using gasification and pyrolysis, is performed. It is shown that the best technology for the energy-producing MSW utilization consists in MSW incineration in layered furnaces with the use of mechanical shearing fire-grates. It is noted that, since all the enterprises for the energy-producing MSW utilization (in fact, these are TPPs, whose main fuel is municipal solid waste) are currently equipped with multistage gas purification facilities, the problems of their environmentally safe operation are completely solved. Therefore, research is mainly aimed at improving the energy efficiency of these enterprises, including through the integration of the units for MSW incineration into the thermal circuit of a TPP operating based on fossil fuel. Examples are given of foreign operating installations for the energy-producing MSW utilization with an electrical efficiency of 27–31% as well as those operating in a heating cycle with a high energy efficiency. The state-of-the-art of MSW thermal processing and the prospects for the implementation of modern technologies for the energy-producing MSW utilization in Russia are presented. Despite the fact that there is no sufficient experience in this field in Russia (only three plants have been constructed in Moscow, whose installed electric operating capacity does not exceed 12 MW), it is planned to construct four relatively large thermal power plants in Moscow oblast with an electric operating capacity of 70 MW each, in order to incinerate 700 000 t of solid waste per year. A TPP with the energy-producing utilization of 360 000 t of MSW per year with an installed electric operating capacity of 24 MW is the most promising for Russia. Such a TPP could already be in demand in more than two dozen large Russian cities. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We propose an engineering solution of a screen with elevated efficiency of separation of clay rock masses. The most rational design of undriven bar screens (namely, cantilever and spring-loaded screens) is determined. We present a mathematical model and a procedure for the evaluation of the parameters of screens. It is shown that, in the case of selection of the proper parameters for the grates of the screening surface, the screens can be used for the purposes of screening of clay rock masses. [ABSTRACT FROM AUTHOR]

Most of the rural people of Nepal use fuelwood for cooking and space heating in residential sector. Government of Nepal has announced to make Nepal as a smokeless country by replacing traditional cookstoves. Two pot mud improved cookstove is one of the most promoted cookstoves in the context of Nepal. There is a need to study the effects of different parameters on mud improved cookstove for its better performance. The objective of this work is to study the effect of variation of different parameters on two pot mud ICS and identify parameters for its better performance. Power test of cookstove, specially focusing on thermal efficiency, has been performed by changing different parameters. Effect of varying fuel feeding rate, chimney height, opening area of air fuel inlet, inlet area of interconnecting tunnel, combustion chamber height, grate height and insulating material on thermal efficiency have been studied individually. Then cookstove has been developed by different best combinations such as a) geometrical parameters b) use of grate and insulations in best geometrical parameters and formation of channel on the opening. Thermal efficiency of modified cookstove increased from 18% to 25.6%; i.e. the increment of 7.60%. Economic analysis of different thermal efficiencies cookstove has been performed. [ABSTRACT FROM AUTHOR]

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nowadays computer simulations have been shown to be powerful tools to understand the performance of systems where we have mathematical models that can capture the physics of the problem. In this paper we attempt to simulate the behavior of the particles that move inside a largescale mine mill, specifically through the grates and the discharge ducts of the material, when small changes are made in the geometry of the grates. Basically, the continuity, energy and momentum conservation equations are the ones that can solve the behavior of the material in that zone. The discrete element method is used to carry out the simulation, under the hypothesis that the restitution coefficient can substitute for the presence of the fluid inside the mill, and that by changing the angle of inclination of the grate slots the performance can improve the classification that they make and in the total discharge flow. A corollary of this study is that the pulp-lifters have a greater impact than the grates in improving the discharge flow. It was possible to quantify phenomena like flow-back and carry-over, effects that are not evaluable experimentally, in this way showing the usefulness of this simulation. The application of the DOE method has allowed to back up statistically the results and indicate that the slot angle increases the mill’s outlet flow. [ABSTRACT FROM AUTHOR]

Abstract Although several works on rice husk gasification have been reported, none of those works investigated and discussed the propagation front. In present work, rice husk gasification is conducted in a small-scale throat-less downdraft gasifier. The aim of the work is to investigate the effect of tuyer distance above the grate on the propagation front and performance of the gasifier. Rice husk gasification is performed at an equivalence ratio of 0.20 with variations in tuyer position above the grate of 120 mm, 190 mm, 260 mm, 330 mm, and 400 mm. The result shows that tuyer distance above the grate affects the propagation rate and the performance of the gasifier. The flame and bed propagation rates are nearly similar for the tuyer 400 mm above the grate. Meanwhile, a volume fraction of combustible gases CO, H 2 , and CH 4 improve as tuyer distance above the grate increases. Maximum values of 15.18% CO, 6.99% H 2 , and 0.99% CH 4 are obtained for the tuyer 400 mm above the grate. Maximum HHV of 3.21 MJ/Nm3 and thermal efficiency of 76.90% are also achieved for the tuyer 400 mm above the grate. Highlights • Rice husk gasification in small-scale downdraft gasifier with equivalence ratio of 0.2 • Investigation effect of tuyer distance above the grate on propagation and performance. • Tuyer distance above grate are 120 mm, 190 mm, 260 mm, 330 mm, and 400 mm. • Flame and bed propagation rates are nearly similar at tuyer 400 mm. • Maximum HHV and thermal efficiency are achieved at tuyer 400 mm above the grate. [ABSTRACT FROM AUTHOR]

A three-dimensional (3-D) finite-difference-time-domain (FDTD) analysis was used to simulate a silicon photonic waveguide. We have calculated power and transmission of the graphene used as single or multilayers to study the light transmission behavior. A new technique has been developed to define the straight silicon waveguide integrated with grate graphene layer. The waveguide has a variable grate spacing to be filled by the graphene layer. The number of graphene atomic layers varies between 100 and 1000 (or 380 nm and 3800 nm), the transmitted power obtained varies as ∼30% and ∼80%. The ∼99%, blocking of the light was occurred in 10,000 (or 38,000 nm) atomic layers of the graphene grate. [ABSTRACT FROM AUTHOR]

A grate-firing boiler was developed for wood pellet fuel, and its combustion and heat transfer characteristics were tested. The first prototype revealed problems with fuel delivery and residence time. To solve these problems, we quadrupled the number of grates and developed the second prototype with a baffle; however, the volume significantly increased in the second prototype. By examining the space usage in the second prototype, we designed the third prototype with inclined grates, which reduced the number of grates by 25 % and reduced the volume by 20 %. The experimental results show that the third prototype had similar combustion performance to the second prototype with the reduced volume. Furthermore, some grates remained unused in the combustion, and a recirculation flow appeared in the CFD results, which suggests the possibility of additional design improvements. [ABSTRACT FROM AUTHOR]

Electricity production from biomass has the potential to significantly contribute to the power mix in Portugal with lesser environmental impact than non-renewable resources. This study focuses on electricity production from the combustion of residual forest biomass from eucalypt logging activities in Portugal using life cycle assessment. In Portugal, several power plants fuelled by residual forest biomass have been commissioned in the last few years. Most of the installations use fluidised bed furnaces, and the others use grate furnaces. This study aims to compare the environmental impacts associated with these two alternative combustion technologies. System boundaries include the stages of forest management, collection processing and transportation and energy conversion. The default impact assessment method used is that suggested in the International Reference Life Cycle Data System. In a sensitivity analysis, calculations are performed using the ReCiPe method. For all of the impact categories analysed, the fluidised bed presents the smallest environmental impact. Even when the grate furnace efficiency increases and the fluidised bed efficiency decreases in the sensitivity analysis, the fluidised bed has lower impacts than the grate technology and can be the best alternative in the implementation of new power plants. [ABSTRACT FROM AUTHOR]

Paddy drying plays an important role in reducing postharvest losses in rice. This process usually involves using a dryer that requires either fossil fuels or renewable energy to heat the drying air, which removes water from the paddy. This research looked into developing a downdraft rice husk furnace used for paddy drying that resulted in an improved air-cooled grate with optimal operation. This optimal operation was used to generate sufficient heat to increase the drying air temperature by 10–15 °C at an air flow rate of 3.5 m 3 s −1 , attaining an efficiency of 80%. At optimal combustion, the carbon monoxide (CO) concentration generated in the drying air ranged from 25 to 42 ppm. The furnace's improved air-cooled grate solved the problem of pipe bending or melting during operation. The pipes in the grate reached a maximum temperature of 650 °C and did not bend or melt during operation. In addition to this, using a grate with the rotatable pipes, which allows for easy changing of the surface area that is directly in contact with the firing zone, can prolong it's the grate's lifespan, thus reducing maintenance costs. The ultimate result is a more efficient renewable energy solution for paddy drying. [ABSTRACT FROM AUTHOR]

Subject: characteristics of hearth fuel chambers and fireboxes with a grate, used in household furnaces, are considered. In hearth furnaces, the firewood is burned more cleanly with less carbon monoxide at the outlet. The disadvantage of such fireboxes is a longer process of coal burnout than in grate-fired furnaces. In furnaces with a grate, the burnout time of coals is less, which makes it possible to finish the combustion process more quickly and close the outlet latch. This increases the efficiency of the furnace but to further reduce the time of burning out the coals they have to be raked and burned on the grate. This complicates the process of operating the furnace itself. The proposed design of the compound firebox allows us to improve characteristics of both the firebox itself and the entire furnace. Research objectives: creation and study of a compound firebox that increases the efficiency of the furnace and simplifies the furnace maintenance process with the values of carbon monoxide at the outlet comparable to hearth furnaces. Materials and methods: a detailed analysis of hearth fuel chambers ECO+ was carried out according to the amount of carbon monoxide at the outlet. The results of the analysis are used for comparison with compound fuel chamber. The structure of the compound firebox was chosen based on the results of preliminary tests of several fuel chambers proposed and tested by the author in the furnace PDKSh-2.0. A peculiarity of the structure of the compound firebox is the absence of a grate and the presence of a narrow slit in the lower part of the firebox through which the incoming air enters the firewood. Between the walls of the firebox and firewood, skids are installed, forming an air gap, through which the inlet air is uniformly supplied to the entire firewood supply. With gradual combustion of firewood and formation of coal, the firewood descends to the bottom of the firebox, where they intensively burn out in the maximum air flow. Compound firebox consists of several parts, it is made of steel with a thickness of 4.0 mm and installed into the furnace fire through the fuel entry door. In studying the combustion of firewood process, a gas analyzer and an anemometer are used. Results: the results of the test of the compound firebox showed that the combustion of firewood in it is more even and takes more time. The time of burnout of coals was reduced by 40...50 %. The actual value of the furnace efficiency is increased by 2...3 %, and the СО emissions are comparable with the ECO+ furnaces. Conclusions: compound firebox without a grate can be recommended for use in household furnaces for various purposes. [ABSTRACT FROM AUTHOR]

For improving the load-following capacity of existing grate boiler units, a model predictive control concept based on the combustion power soft-sensor is developed. Because the combustion power estimation has a very quick response to the primary air flow input, the load-following speed of the boiler control system will be improved considerably. The proposed model predictive control strategy is tested with the BioPower 5 combined heat and power plant data and the results are presented, analyzed, and discussed. [ABSTRACT FROM AUTHOR]

Copyright of Eastern-European Journal of Enterprise Technologies is the property of PC TECHNOLOGY CENTER and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pulverized coal combustion was adopted at the end of the grate to provide sufficiently high preheating temperature in the grate when hematite was roasted to produce hematite pellets. Unfortunately, serious deposit which stuck to the walls at the end of the grate was found after using pulverized coal combustion. In the present study, chemical analysis methods were used to detect the chemical compositions of the preheated pellet powder, deposit sample and coal ash. In addition, the major phases and microstructure of the deposit sample were determined using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis, respectively. Furthermore, a thermodynamic software (FactSage 7.0) was adopted to analyze the deposit formation process. The chemical and mineralogical analyses indicated that the deposits contained high amounts of iron, particularly of silicate, aluminum, calcium and magnesium and, to lesser extent, of alkali metals. The deposit formation process in the grate was found to be caused by the mixing of hematite pellet fines and unburnt carbon from the coal ash. The hematite was reduced to wustite by the presence of residual carbon, which generated low melting phases forming sticky deposits on the grate walls. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop a numerical model of combustion in the furnace of a WR-40 boiler equipped with a FJBS (furnace jet boiler system). Based on previous calculations [1] and measurements [2], appropriate competent sub-numerical models were developed to match a temperature value and composition of the flue gas obtained with measurements taken at the real working boiler. The FJBS System has eight in-furnace jet-pump ventilators that uses gas propulsion (compressed air). Its task is to mix the flue-gas and any substrates of combustion at vortex, fire it up, and alignment align the temperature field. Numerical modelling results for the combustion chamber of the WR-40 boiler was shown. The concentration of O 2 , CO, CO 2 in the flue gas, the temperature of flue gas for the whole combustion chamber, the change of the mass fraction of H 2 O in the coal, and the change in the mass of coal particles along the grate were measured to demonstrate that the processes taking place during combustion of fuel on the grate was included in the numerical model (i.e., drying, degassing, the burning of carbon particles, and the burning of volatiles). Numerical calculations confirm measurement results qualitatively rather than quantitatively. Generally, the CFD (Computational Fluid Dynamics) modelling confirmed the conclusions from measurements. Obtaining reliable temperatures at the furnace chamber outlet using numerical modelling is possible based on the 0-dimensional model of the boiler. In order to get reliable results from numerical modelling, it is necessary to validate the model with real measurement data. The results obtained by numerical simulation show that the FJBS system aligns the field temperature and concentration and decreases CO in flue gas. [ABSTRACT FROM AUTHOR]

The article presents an efficient technology of fiber cleaning on a two-drum fiber cleaner with working bodies of a new design. The influence of the aerodynamic regime on the efficiency of the machine operation, the cleaning effect, the quality and yield of the fiber, and the degree of fibrous waste in the processing of raw cotton of hard-to-clean varieties were studied. [ABSTRACT FROM AUTHOR]

The article presents a scheme for the efficient design of the grate on the elastic supports of a fibrous material cleaner. The theoretical basis for calculating the grate parameters on an elastic support with nonlinear stiffness and random perturbation is considered. The results of tests of the recommended design of a cleaner with grates on elastic supports are given. [ABSTRACT FROM AUTHOR]

in the article the scheme of effective design of the bars on the elastic supports of the fibrous material cleaner is shown. The theoretical basis for calculating the grate parameters on an elastic support with nonlinear stiffness and random perturbation is considered. The results of testo of the recommended design of a cleaner with grates on elastic supports are given. [ABSTRACT FROM AUTHOR]

Abstract: Sulphur containing additives were used to destroy alkali chlorides in the furnace of a 100kW grate reactor during combustion of a blend containing 40±4% (based on energy content) corn stover with wood chips. Ferric sulphate spray, when added to zones where alkali chlorides have already been formed and gas temperature is <1000°C, can destroy a significant portion of alkali chlorides in the furnace even at dosage S/Cl=0.4–0.6 and prevent high temperature chlorine corrosion of superheaters. This dosage can increase SO2 emissions from about 100 (without additives) to 250–350mg/Nm3 6% O2. Additive costs can be estimated at 0.4–1€/MWh electricity with blends containing 40–100% corn stover, assuming a 30% efficiency in electricity production. Mixing ferric sulphate with fuel feed had little effectiveness compared to spraying it into the upper furnace. Elemental sulphur mixed with the fuel feed was much less effective than the ferric sulphate spray. The minimum dosage of elemental sulphur needed to prevent Cl deposition (S/Cl=3) lead to high SO2 formation (≈2000mg/Nm3 6% O2). [Copyright &y& Elsevier]

Abstract: Slurry flow, including flow through the charge in the grinding chamber, through the discharge grates, along the pulp lifters and its discharge from the mill is an important contributor to the efficiency of the grinding process within a SAG mill. Poor transport of finer ground material can adversely affect grinding leading to excess energy consumption and over-grinding of fine material. This paper uses a 1-way coupled DEM–SPH method in three dimensions to analyse the full slurry flow for a 1.8m diameter by 0.6m long AG/SAG pilot mill. This provides detailed information on the internal flow of slurry within a SAG mill, including the prediction of dry regions and of slurry pooling. The importance of the end walls in generating complex three dimensional recirculation patterns in the charge and its influence on axial flow is demonstrated. Such a full 3D analysis ensures that the slurry is presented to the grate with a realistic spatial distribution and allows prediction of the flow through the grates and then within the pulp chamber. The rate of filling of the pulp chambers, the point of initiation of flow down along the rising pulp lifters, back flow into the grinding chamber and flow onto the discharge cone are all investigated. It is shown that the end wall lifters are critical to the flow through the grate generating pumping and shadowing effects which produce strongly non-uniform flow through different grate panels. [Copyright &y& Elsevier]

This article examines the state of a gas suspension during vertical pneumatic transport upward. A comparison is made between pneumatic lifts with screw-type pneumatic pumps, chamber-type pneumatic pumps, and pneumatic-chamber air-lift pumps. The material is lifted in high concentrations and at low velocities in the gas mixture. Thus, the consumption of compressed gas is also low. [ABSTRACT FROM AUTHOR]

Based on the analysis of heat transfer mechanics, physical and chemical change of pellet drying and preheating process in grate, the mathematical model is established and solved by three-diagonal matrix algorithm. With Visual Basic 6.0 a simulation software is developed. The model is verified by measurements at a domestic pellet plant, and the temperature distribution of pellet bed is gained. Meanwhile, the influence of different operation parameters on the pellet thermal process is studied. The results can be taken as a basis of practical production control and the grate optimizing design. [ABSTRACT FROM AUTHOR]

The objective of this paper is to optimize the parameters of pellet drying and preheating process in grate. A mathematical model of drying and preheating is developed, and is verified by the experiments. Further, the operating parameters of wind temperature, wind speed, grate speed and bed depth etc. are investigated through the orthogonal method using the simulation results. And a relationship of drying, preheating effects and operating parameters is achieved. The results show that the optimization effect can be achieved in the given range when air velocity is about 3.0 m/s and temperature is about 300, 500, 800, and 1 100 °C in the updraft drying zone, downdraft drying zone, preheating I zone, and preheating II zone respectively. The work is help for saving energy and reducing emissions in pellet induration. [ABSTRACT FROM AUTHOR]

Solid recovered fuels (SRFs) derived from commercial/industrial and municipal solid waste-type streams containing high heat value plastics offer a number of synergies for biomass combustors. This article covers technical and operational synergies to increase biomass combustion efficiency in a grate fired system typical for waste-to-energy technology. The transfer of laboratory results to pilot scale is presented by a new approach based on experimental data in laboratory scale and a mathematical model using key combustion parameters. Agreement between the experimental data and the mathematical model is sufficient to use the model for scale up. Because of the sometimes poor biomass fuel quality in biomass combustion facilities, the following unfavorable operating conditions occur: fouling and slagging on the furnace and boiler walls. These effects lead to lower operating hours due to more frequent cleaning cycles. The low- and medium-priced biomass available from the market has very low heat values (5 GJ/t) and high alkali metal content. Biomass availability in most European Union (EU) countries lead to an increased amount of low-grade biomass fed into grate-type combustors. Efforts of the American Chemistry Council, the Institute of Technical Chemistry, and Plastics Europe have assessed the synergies through laboratory-scale experiments and have continued to demonstrate the biomass and SRF synergies on a large-scale pilot grate-type incinerator. This article points out that primary air preheat influences energy efficiency of the total process for the combustion of wet biomasses positively. Local combustion behavior of the wet biomass will depend on the degree of mixing and the moisture content. Results from this pilot scale confirm that SRF addition of 20–40 wt% lead to more homogeneous combustion behavior and an increase of energy efficiency from 2% to 3% absolutely. [ABSTRACT FROM AUTHOR]

Polychlorinated dibenzo- p-dioxins and furans (PCDD/Fs) emissions in flue gas from two types of municipal solid waste incinerators (MSWIs) most commonly used in China were investigated in this study. The selected incinerators include two grate-type MSWIs: MSWI-A (350 t/d) and MSWI-B (150 t/d), and two fluidized bed MSWIs: MSWI-C (400 t/d) and MSWI-D (400 t/d), which are all equipped with semi-dry lime scrubber and bag filter except MSWI-D equipped with cyclone and wet scrubber (WS) as air pollutant control device (APCD). Results indicated that the emission concentration and the international toxic equivalents (I-TEQs) of the PCDD/Fs from the stacks were in the range of 1.210∼10.273 ng/Nm3 and 0.019∼0.201 ng I-TEQ/Nm3, respectively. They were greatly lower than the emission regulation standard of PCDD/Fs in China (1.0 ng I-TEQ/Nm3). However, only the PCDD/Fs emission level from MSWI-C was below 0.1 ng I-TEQ/Nm3. Although the homologue profiles were distinct, the contributions of the 2,3,7,8-subsituted congeners to the total I-TEQ were similar among all the investigated MSWIs. Two major 2,3,7,8-substituted congeners, 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD, account for 47% and 9% (average values) of the total I-TEQ values, respectively. The correlation between PCDD/Fs levels and composition of flue gas was also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Waste to energy (WtE) plants are utilised for the production of heat and electricity. However, due to corrosion at super heater surfaces a relatively low 25% of the waste lower heating value can with the present technology be converted to electricity. High contents of Cl, Na, K, Zn, Pb and S in waste cause relatively high super heater corrosion rates. The Cl-content in waste is one of the key-factors for volatilisation of alkali and heavy metals in WtE plants. Little is known about the release of Cl, Na, K, Zn, Pb, and S along grate of waste incineration plants. The 26 t h−1 WtE plant Vestforbrænding unit 5 in Denmark was used for measurements of temperature, gas-concentration (O2/CO/CO2), and sampling of gas phase Cl, Na, K, Pb, Zn, and S. Unit 5 has 6 ports distributed along the 13 m long grate between 1.5–1.8 m above the grate. Five of these ports were used for measurements. Two aqueous absorption systems containing a solution of NH3 or a solution of H2O2/HNO3 were used to collect the gaseous samples. Tar was found to condense in the sampling system at the ports near the fuel inlet. The experiments showed the majority of Cl, Na, and K to be volatilised during the early stages of combustion. The maximum release of Cl, Na, and K was measured in port 2 as 177 ppm v , 71 ppm v , and 44 ppm v respectively. The maximum average gas temperature of 1140 was measured in port 3 compared to the temperatures at ports 2 and 4 of 816 and 551 respectively. It has been suggested to use flue gas from the area of the grate near port 3 with a high temperature, that contains relatively low amounts of corrosive elements, and lead to a separate high temperature super heater and thus increase the electrical efficiency. [Copyright &y& Elsevier]

Abstract: Through the years, Danish utilities have gained significant knowledge on how to minimize or even avoid ash deposition problems in utility boilers, firing a worldwide suite of high-volatile bituminous coals. In the early 1990s, the Danish Government decided on a 20% reduction in the CO2-emission before the year 2005, based on the 1988-level. Biomass is considered CO2-neutral due to its short time of regeneration, compared to fossil fuels. Thus, the Danish power producers are enjoined to burn 1.0Mtonnes of straw, 0.2Mtonnes of wood chips and 0.2Mtonnes of straw/wood chips (free choice) every year beyond year 2005. As a consequence of this, the CHEC Research Centre, Department of Chemical Engineering, Technical University of Denmark, being partly funded by the Danish power utilities, has during the last decade, investigated ash and deposit formation, and corrosion, in utility boilers fired with coal, petcoke, orimulsion, and different types of biomass (straw (barley, rape and wheat), wood (beech, spruce, fibreboard, bark and waste wood), shea nuts, olive stones, etc.). A number of reviews of these full-scale measuring campaigns have been provided in the open literature. Recently, a project on the formation of ash and deposits in waste incinerators has been initiated. This paper summarizes our findings, including recent activities on: (1) deposit formation during coal–wheat straw co-firing in suspension-fired boilers; (2) a pilot-scale study of ash and deposit formation in the Sandia Multi-Fuel Combustor (MFC); (3) a full-scale measuring campaign dealing with the effect of co-firing of biomass on the ash and deposit formation; (4) a full-scale measuring campaign addressing low-temperature corrosion of tubes in the air pre-heater of a straw-fired utility boiler; (5) a lab-scale study of the corrosion of superheater materials in straw-fired utility boilers, and, finally; (6) a fundamental study on ash and deposit formation in municipal solid waste incinerators. The paper provides insight into the experience gained on ash, deposit and corrosion formation in thermal fuel conversion systems fired with solid non-fossil fuels, and focuses attention on how these results fit into our current understanding of this subject. A complete and updated list of references covering our research activities within this area during the last decade is provided. In addition, a brief overview of current and future research activities is provided. [Copyright &y& Elsevier]