Effect of catalysts in the quality of syngas and by-products obtained by co-gasification of coal and wastes. 1. Tars and nitrogen compounds abatement

The aim of this work is to analyse the possibility of using co-gasification technology to process coal mixed with wastes to take profit of its energy content and at the same time to minimize the environmental impact associated with the use of wastes and to diminish the costs of flue gas treatment. The addition to coal of different types of materials, like: pine based waste, petcoke and polyethylene (PE), was not found to give rise to any operational problems, regarding both the feeding system and gasification process and led to higher energy conversions, however, the gas presented higher tars and hydrocarbons content. Several catalysts were tested, such as, dolomite, olivine, nickel and magnesium oxides, zinc oxides and cobalt and molybdenum oxides. Catalyst action was analysed in tars release and also in ammonia compounds reduction. The presence of catalysts allowed increasing hydrogen release, whilst there was a decrease in hydrocarbons and tars contents. A nickel-magnesium oxide was the catalyst that led to the highest reduction in hydrocarbons and tars. This catalyst also led to the lowest NH₃ content in the fuel gas produced, due to the catalyst efficiency in NH₃ destruction.     

Design of data feature-driven 1D/2D convolutional neural networks classifier for recycling black plastic wastes through laser spectroscopy

In this study, two types of convolutional neural network (CNN) classifiers are designed to handle the problem of classifying black plastic wastes. In particular, the black plastic wastes have the property of absorbing laser light coming from spectrometer. Therefore, the classification of black plastic wastes remains still a challenging problem compared to classifying other colored plastic wastes using existing spectroscopy (i.e., NIR). When it comes the classification problem of black plastic wastes, effective classification techniques by the laser spectroscopy of Fourier Transform-Infrared Radiation (FT-IR) with Attenuated Total Reflectance (ATR) and Raman to analyze the classification problem of black plastic wastes are introduced. Due to the strong ability of extracting spatial features and remarkable performance in image classification, 1D and 2D CNN through data features are designed as classifiers. The technique of chemical peak points selection is considered to reduce data redundancy. Furthermore, through the selection of data features based on the extracted 1D data with peak points is introduced. Experimental results demonstrate that 2DCNN classifier designed with the help of 2D data feature selection as well as 1DCNN classifier shows the best performance compared with other reported methods for classifying black plastic wastes.     

Valorisation of alumino-silicate stone muds: From wastes to source materials for innovative alkali-activated materials

Impressive amounts of wastes are produced yearly by extraction and transformation of natural stones. This work addresses the finest fraction of these wastes, named stone muds, and particularly those with a siliceous composition. The disposal in dump of these muds implies high costs, whereas their surface landing poses serious challenges, since they can damage the environment, create necrotic conditions for flora and fauna, and endanger human health. Therefore, the reemployment of these wastes is today an urgent need. In this work, a mud (QM) composed by quartz, feldspars, biotite and dolomite, is used for producing dense and foamed alkali-activated materials through an innovative and simple process, in which a mixture of mud and alkaline solution (plus foaming agent, when needed) is produced, cast in moulds and cured at 80 °C for 48 h. Another mineral powder (SRM), having a similar composition but carbonates-free, was also used, to prove the key role of alumino-silicates in producing dense alkali-activated materials, with excellent mechanical properties. Also, the foamed samples showed good mechanical properties, plus low thermal conductivity. These results demonstrate that alumino-silicate wastes could serve as source materials for producing materials suitable to be used for dense and cellular building elements, providing an effective alternative to mud disposal and related issues.     

Ultrasound-assisted Acid red dye removal using leather fibre wastes as matrix: ‘intra wastes interaction’ approach

It is desirable to make effective use of solid wastes, as well as waste liquors, of the dye house generated from leather processing. The present study deals with the adsorption of Acid red 26 (Xylidine ponceau) dye using leather fibre waste (buffing dust) as substrate matrix by the means of ultrasound, magnetic stirring and conventional heating. The research examined the effect of various process parameters: ultrasonic power, concentration of dye, temperature and time. The dye uptake data have been fitted with Freundlich and Langmuir isotherms, indicating a useful dye adsorption process. A mechanism for dye adsorption in leather fibres has also been proposed. This study shows that it is possible to remove dyes from dye house effluent streams using leather waste fibres of buffing dust by means of ultrasound. Two different toxic wastes produced by the same industry can be effectively contained. This ‘Intra wastes interaction’ approach could reduce the burden of discarding wastes of other materials in the leather industry.     

Reaction kinetics of the combined pyrolysis and steam-gasification of carbonaceous waste materials

Synthesis gas production by steam-gasification of carbonaceous waste materials with high volatile contents (e.g., sewage and industrial sludge, fluff, and scrap tire powder) is kinetically examined. A multiple pseudo-component first-order reaction model is formulated to describe the rates of the combined pyrolysis and gasification processes. Arrhenius-type kinetic parameters are determined by dynamic thermogravimetric experimental runs conducted in the temperature range 473-1476 K.     

Chemical Recycling and Kinetics of Aqueous Alkaline Depolymerization of Poly(Butylene Terephthalate) Waste

Depolymerization reactions of poly(butylene terephthalate) (PBT) waste in aqueous sodium hydroxide solution were carried out in a batch reactor at 80–140 °C at atmospheric pressure by varying PBT particle size in the range of 50–512.5 μm. Reaction time was also varied from 10–110 min to understand the influence of PBT particle size and reaction time on the batch reactor performance. Agitator speed, particle size of PBT and reaction time required were optimized. Disodium terephthalate (salt) and 1,4‐butanediol (BD) remain in the liquid phase. BD was recovered by the salting‐out method. Disodium terephthalate was separated by acidification to obtain solid terephthalic acid (TPA). The produced monomeric products (TPA and BD) and PBT were analyzed. The yields of TPA and BD were in agreement with PBT conversion. The depolymerization reaction rate was first order to PBT concentration as well as first order to sodium hydroxide concentration. The acid value of TPA changes with the reaction time as well as particle size of PBT. This indicates that PBT molecules get fragmented and hydrolyze simultaneously with aqueous sodium hydroxide to produce BD and disodium terephthalate. Activation energy, Arrhenius constant, equilibrium constant, Gibbs free energy, enthalpy and entropy were determined. The dependence of the hydrolysis rate constant on reaction temperature was correlated by the Arrhenius plot, which shows an activation energy of 25 kJ/mol and an Arrhenius constant of 438 L/min/cm².     

Gasification – An Opportunity to Design Environmentally Compatible Processes in the Chemical and Pulp & Paper Industry

Production wastes and residues generated in particular in the chemical and pulp & paper industries are currently incinerated or recycled. A stricter environmental legislation and the general prohibition imposed on waste incineration in some countries suggest to open new ways of waste disposal and resource recovery. This work describes how residual and waste materials can not only be disposed of but also converted into a raw gas which can be further processed to obtain valuable materials and synthesis gas in strict compliance with environmental standards by using various modifications of an entrained‐flow gasification technology.     

Operation performance of a pilot-scale gasification/melting process for liquid and slurry-type wastes

A gasification/melting facility that can operate up to 10 bar and 1,550 °C with a maximum 1 ton/day capacity was developed for liquid and slurry-type combustible wastes. The main focus of the system development was minimal use of expensive fuel for maintaining the reaction temperature by replacing it with cheap waste oil for energy input. The carbon conversion obtained was 97% while the cold gas efficiency reached 77.6% for the refined waste oil. When the feed was refined oil mixed with fly ash from a municipal waste incinerator, the carbon conversion and cold gas efficiency were 93% and 71.9%, respectively, with a slag conversion ratio of 0.93. The slag produced from fly ash exhibited environmentally acceptable heavy-metal leaching values and thus can be applicable as road material and for other purposes. The optimal O₂/feed ratio was 0.9–1.0 when only the refined waste oil was gasified, whereas the O₂/feed ratio had to be higher than 1.2 when fly ash was mixed. In addition, data showed that gasifier temperature can be estimated by on-line methane concentration measurements.     

生物样品快速灰化装置用于处理生物废物的可行性

本文研究了用生物样品快速灰化装置处理生物废物的可能性。该装置的特点是加速炭化和灰化，灰化温度为３５０－４５０℃，灰化时间为５－７ｈ，操作简便。用该装置灰化处理了兔子和白鼠尸体，处理结果表明，一炉可处理３ｋｇ动物尸体，灰样不沾容器内壁，便于收集和进行水泥固化，灰化温度不超过４５０℃，不会引起放射性核素的严重挥发损失，废物中所含放射性核素基本上保留在灰分中。     

广东省医院核医学放射性“三废”现状及有关问题初探

广东省是我国核医学较为发达的地区,在全省医疗系统中设置核医学科的医院有约５０家,拥有发射计算机断层仪４０余台,主要使用＾１３１Ｉ,＾１２５Ｉ,＾９９Ｍｏ－＾９９ｍＴｃ,＾９０Ｓｒ,＾１５３Ｓｍ等１０多种放射性同位素。本文在笔者参加广东省换（核）发《放射性药品使用许可证》工作的基础上,调查了总结了全省医院核医学科放射性药吕使用情况和放射性“三废”排放,处理的情况,并就当前各医院在放射性“三废”管理和