Zengyi Ma

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. First, selecting the input variables of the model by analyzing the operational mechanism of circulating fluidized bed incinerators, and the corresponding heating value was classified into one of nine fuzzy expressions according to expert advice. Development of prediction models by employing four different nonlinear models was undertaken, including a multilayer perceptron neural network, a support vector machine, an adaptive neuro-fuzzy inference system, and a random forest; a series of optimization schemes were implemented simultaneously in order to improve the performance of each model. Finally, a comprehensive comparison study was carried out to evaluate the performance of the models. Results indicate that the adaptive neuro-fuzzy inference system model outperforms the other three models, with the random forest model performing second-best, and the multilayer perceptron model performing at the worst level. A model with sufficient accuracy would contribute adequately to the control of circulating fluidized bed incinerator operation and provide reliable heating value signals for an automatic combustion control system.

Thermal treatment of Indonesian lignite washery tailing

Kinetic analysis of Indonesian lignite washery tailings (LWT) was studied in this paper. Two methods were compared to evaluate the activation energy E of LWT, i.e., iso-conversional methods and model-based method. The Flynn–Wall–Ozawa method and the Kissinger–Akahira–Sunose method were chosen to represent the iso-conversional method. The Coats–Redfern method was chosen as the model-based method. Furthermore, a complementary method of iso-conversional and model-based was also used to determine the kinetic mechanism of LWT. The results provide useful information for designing a combustion or pyrolytic system using LWT as feedstock.

Industrial hazardous waste treatment featuring a rotary kiln and grate furnace incinerator: a case study in China

As one of the fastest developing countries, China is facing severe problems concerning hazardous waste treatment and disposal. This paper presents a new incineration technology and demonstration project in eastern China. The incineration system includes a rotary kiln, a grate furnace for burning out the kiln residue and a flue gas post-combustion chamber. Flue gas treatment and emission control is based on: a quench tower, followed by dry hydrated lime and activated carbon injection, a dual bag filter system, and a wet scrubber. It demonstrated that this incineration technology can effectively dispose of industrial hazardous waste with variable and complex characteristics. Gas emissions meet the demands of the Chinese Environmental Protection Association standard.

Thermal treatment of Indonesian lignite washery tailing: Part 1. Experimental

Thermal treatment of Indonesian lignite washery tailings (LWT) was investigated in this study using TG–FTIR at different heating rates of 5, 15, 25, 35, and 45xa0°Cxa0min−1. After a first drying stage, two main pyrolysis stages appeared, i.e., stage II (300–600xa0°C) and stage III (700–800xa0°C), corresponding, respectively, to low-temperature evolution of volatile matter and further carbonization of fixed carbon. The gaseous products of LWT during pyrolysis and combustion are not as complex as those of other waste materials such as hazardous waste and sewage sludge. Little or no acid and ketone compounds were observed. The heating rate had an obvious effect on the gas evolution of pyrolysis and combustion. The results provide useful information for designing a combustion or pyrolytic system using LWT as feedstock.

Characterization and migration of oil and solids in oily sludge during centrifugation

ABSTRACT The migration behaviors of oil, water and solids in sludge during centrifugation were elaborated. Size distribution, surface topography and lypohydrophilic properties were studied in detail. The average size of solids was 61u2005μm in original sludge, 31u2005μm in upper layer and 235u2005μm in bottom layer. The result shows that solvent is essential to separate oil phase into molecular light and weight fractions during centrifugation. With solvent/oil ratio increases from 1:2, 1:1, 2:1 to 5:1, molecular weight in upper layer decreases from 1044, 1043, 1020 to 846 combined with that in bottom layer increases. A model was proposed to calculate the oil residue content in solid phases after sedimentation. The findings of this paper provide information for optimizing the oil recovery and clean treatment.

Vitrification of MSWI Fly Ash Using Thermal Plasma Technology

In China, municipal solid waste incinerator (MSWI) fly ash is classified as hazardous waste owing to its high concentration of leachable heavy metals and the presence of chlorinated organic compounds, such as dioxins and furans. In this study, the vitrification process based on thermal plasma technology has been employed to convert toxic incinerator fly ashes into harmless stable products. The toxicity characteristic leaching procedure (TCLP) test has been performed to evaluate the chemical resistance of the vitrified slag. The amount of heavy metals leached is much lower compared with the regulatory limit, which reveals that the contaminants are sufficiently immobilized in the silicate matrix and the produced slag satisfies the environmental standards. The microstructure, crystalline phase, as well as the density and porosity of the glass slag are also investigated. Such vitrified product with good quality has great potential to be used as a viable alternative for construction applications. These promising results indicate that thermal plasma vitrification process is very effective and reliable for stabilization, detoxification and recycling of MSWI fly ashes.

3‐D turbulent Premixed Flamelet Stretch Visualization Based On High Speed Stereoscopic Image

According to flamelet model hypothesis, the turbulent premixed flame was assumed to be consisting with series of laminar flamelet with deferent scales and structures. Due to the complexity in turbulent flow mechanism and chemical kinetics, the most prevalent numeric simulation techniques only available with simplified cases. For deep understanding of the model and premixed combustion process, high performance 3‐D visualization diagnostic method should be developed. In this paper, a modified stereoscopic technique based on high speed images was provided for flamelet stretch characters measurement. The stereoscopic flame images were captured simultaneously with one high resolution CCD chip which was formerly calibrated, and a novel algorithm was developed for flamelet matching and the 3‐D flame front stretch rate and stretch speed were discussed. Comparing with normal multi‐camera 3‐D visualization systems, the method provided shows great advantages and potential for flame visualization, such as simple stru...