工业热过程中无意生成持久性有机污染物的自由基转化机制

掌握无意生成持久性有机污染物(unintentionally produced persistent organic pollutants,UPOPs)的生成机制对于其在典型工业热过程中的源头控制具有重要意义,现有对二噁英等UPOPs生成机制的研究主要是基于反应后稳定化合物和目标同类物分布的检测,缺乏对自由基中间体的研究.环境持久性自由基(environmentally persistent free radicals,EPFRs)是一类新的环境污染物,其半衰期可达数月,可在环境样品以及二噁英生成过程中检出.近年来EPFRs被认为是UPOPs生成的重要自由基中间体.本文对UPOPs生成过程中前驱体种类、金属化合物、温度、反应气氛等对EPFRs生成特性的影响作用进行了综述,分析了前驱体生成UPOPs过程中同种或不同种EPFRs的转化路径.此外,基于现有UPOPs源头阻滞技术,提出了UPOPs与EPFRs协同控制的潜在方法.

工业热过程中无意产生的持久性有机污染物生成机理

持久性有机污染物(persistent organic pollutants, POPs)可在工业热过程中无意生成和被排放,而探究其生成机理是发展源头减排技术的基础.本文在梳理文献的基础上,发现二英的生成理论有了一些新的突破.关于氯酚和氯苯等前驱体在热过程中生成自由基中间体的研究,能够从分子层面上揭示二英的生成机制,丰富了POPs的生成理论体系.同时发现,碳源、氯源和催化金属的类别及含量是影响焚烧或冶金等工业热过程中典型无意POPs产生和排放的关键因素.本文也重点总结了过渡金属氯化物在POPs生成反应中起的关键作用,发现其既可作为反应的催化剂,也可作为无机氯源促使大分子碳结构的有机物发生氯化反应,经氧氯化循环促进POPs的生成.该文可为POPs的源头控制技术开发提供理论参考.

Numerical modeling dynamic process of multi-feed microwave heating of industrial solution media

The exothermic efficiency of microwave heating an electrolyte/water solution is remarkably high due to the dielectric heating by orientation polarization of water and resistance heating by the Joule process occurred simultaneously compared with pure water.A three-dimensional finite element numerical model of multi-feed microwave heating industrial liquids continuously flowing in a meter-scale circular tube is presented.The temperature field inside the applicator tube in the cavity is solved by COMSOL Multiphysics and professional programming to describe the momentum,energy and Maxwell's equations.The evaluations of the electromagnetic field,the temperature distribution and the velocity field are simulated for the fluids dynamically heated by singleand multi-feed microwave system,respectively.Both the pilot experimental investigations and numerical results of microwave with single-feed heating for fluids with different effective permittivity and flow rates show that the presented numerical modeling makes it possible to analyze dynamic process of multi-feed microwave heating the industrial liquid.The study aids in enhancing the understanding and optimizing of dynamic process in the use of multi-feed microwave heating industrial continuous flow for a variety of material properties and technical parameters.

Pyrolytic Degradation of Olive Waste Residue （OWR） by TGA： Thermal Decomposition Behavior and Kinetic Study

Olive oil is an important food industry product in Mediterranean countries. Large quantities of OWR （olive waste residue） are generated during a two- or three-phase separation process. This represents a major pollution problem for the industry and oil farms. The OWR is a source of substances of high value and can be used as a low-cost renewable energy. This work studied the behaviour of OWRs during the thermal decomposition process. The experiments of the slow pyrolysis process of three different waste olive products as olive pomace, olive tree pruning and olive kernels were performed under a nitrogen atmosphere at different heating rates, using a thermogravimetric balance. The samples were heated to a maximum temperature of 1,023 K, with four different heating rates of 2, 5, 10, 15 K/min. A comparison of different isoconversional （Flynn-Wall-Ozawa）, not-isoconversional （Kissinger） model-free and model-fitting （Freeman-Carroll） methods to calculate the activation energy and pre-exponential factor is presented. In the Kissinger method the kinetic parameters were invariant for the whole pyrolysis process. While, in the case of Freeman-Carroll, it differs with change of the heating rate. The Flynn-Wall-Ozawa technique revealed the ＂not one-step＂ mechanism of reaction that occurs during the slow pyrolysis process. The kinetic data obtained in nitrogen atmosphere may provide more useful information for engineers for a better and complete description of the pyrolysis process and can be helpful to predict the kinetic model.

The Industrial Biomass Combustor Design for Producing Heat in Dried Tuna Fish Production of Halla Food Factory

The industrial biomass combustor of Halla food factory in Thailand was designed for drying tuna fish product. The purpose of this paper needed to present the design of a factory combustor for producing heat in the drying process by thermal energy from biomass fuel combustion to reduce the investment cost. A drying chamber was made from four concrete walls in the rectangular volume of 4.7 × 4.7 × 2.5 m3 for drying tuna fishes that sliced to small pieces of around 2,680 kg fresh tuna. The hot air tube in the combustor was used for driving hot air to dry fishes in the drying chamber. Heat from acacia wood burning in the combustor with the consumption rate of 50.1 kg/h was transferred by the hot air. The design result was calculated for thermal energy and the efficiency of around 200 kW, and 32%, respectively in the case of 0.62 m3/s hot air flow rate that circulation between the combustor and the drying chamber. The experimental result shows that the moister content of 78.9%wb was decreased to around 13.8%wb in 5 days without petroleum fuel. The drying temperature was controlled at 70℃ continuously for reducing hard containing, and the closed loop tube design for the less of BaP （benzo （a） pyrene） from combustion smoking of the drying industrial process.

Solvent-free synthesis of zeolite catalysts

The most used method for preparation of zeolites is hydrothermal synthesis from silicate or aluminosilicate gels at temperatures in the range of 60-200 ℃. Excess water used in the industrial process results in several issues, including high autogeneous pressure, low efficiency, pollution, etc. To solve these problems, several strategies have been developed. This review describes the solvent-free synthesis of zeolites. The combination of solvent-free synthesis and organotemplate-free synthesis can open the pathway to a highly sustainable zeolite synthesis protocol in industry.

Combustion Irreversibilities: Numerical Simulation and Analysis

An exergy analysis was performed considering the combustion of methane and agro-industrial residues produced in Portugal (forest residues and vines pruning). Regarding that the irreversibilities of a thermodynamic process are path dependent, the combustion process was considering as resulting from different hypothetical paths each one characterized by four main sub-processes: reactant mixing, fuel oxidation, internal thermal energy exchange (heat transfer), and product mixing. The exergetic efficiency was computed using a zero dimensional model developed by using a Visual Basic home code. It was concluded that the exergy losses were mainly due to the internal thermal energy exchange sub-process. The exergy losses from this sub-process are higher when the reactants are preheated up to the ignition temperature without previous fuel oxidation. On the other hand, the global exergy destruction can be minored increasing the pressure, the reactants temperature and the oxygen content on the oxidant stream. This methodology allows the identification of the phenomena and processes that have larger exergy losses, the understanding of why these losses occur and how the exergy changes with the parameters associated to each system which is crucial to implement the syngas combustion from biomass products as a competitive technology.