掘进巷道风流温度分布规律的数值模拟

根据紊流状态下的守恒原理 ,导出了描述掘进巷道风流紊流流动和温度分布的微分方程。通过对矿内风流流动及热力过程的理论分析及现场实测 ,系统地开展矿内风流流场和风流温度场的分布规律及其耦合作用机理的理论分析与研究 ,并利用PHOENICS程序进行数值模拟 ,初步得出了矿井掘进巷道风流温度与各种参数的变化规律。掘进巷道风流温度随风速提高呈负幂函数规律降低 ,随入风流温度升高而线性升高。     

An incident investigation on an unexpected loss of containment and damage to PHI-TEC II during acrylonitrile runaway tests

This article investigates a laboratory incident that occurred during the analysis of a thermal runaway reaction of acrylonitrile monomer. This failure, which was attributed to an human error, resulted in financial losses and corresponding unexpected results. The incident not only damaged the interior of the vessel and other instrument parts, but also exposed the researchers to considerable danger, necessitating their escape from the laboratory. The failure characteristics are discussed, and countermeasures are developed to prevent such a type of incident from reoccurring.     

Full scale treatment of ASR wastes in a modified rotary kiln

A plant, designed for the thermo-valorisation of tyres, was specifically modified in order to treat Automobile Shredder Residue (ASR). Results from two full-scale combustion experiments, carried out on large ASR feeding lots (thousands of tons) indicate the proposed technology as a potential route to help the fulfilling of impending 95% reuse and recovery target set by the End of life Vehicle (ELV) Directive (January 2015). The paper describes the main operational troubleshot occurred during the first experiment (emissions at the stack out of regulatory limits and problems of clogging on the conveyer belt) and the consequent upgrading solutions (pre-treatment, introduction of waste double low-flow screw feeder and a cyclone prior to the main fan, modification of rotatory kiln inlet) adopted to allow, during the second long-term experiment, a continuous basis operation of the plant in full compliance with the discharge limit to the atmosphere. Characterization of both ASR and combustion residues allowed to quantify a 18% of combustion residues as not dangerous waste while only the 2% as hazardous one. A pre-treatment for the reduction of fines in the ASR was recommended in order to achieve the required energy recovery efficiency.     

Thermal risk in batch reactors: Theoretical framework for runaway and accident

Thermal safety and risk of accidents are still challenging topics in the case of batch reactors carrying exothermic reactions. In the present paper, the authors develop an integrated framework focusing on defining the governing parameters for the thermal runaway and evaluating the subsequent risk of accident. A relevant set of criteria are identified in order to find the prior conditions for a thermal runaway: failure of the cooling system, critical temperature threshold, successive derivatives of the temperature (first and second namely) vs. time and no detection in due time (reaction time) of the runaway initiation. For illustrative purposes, the synthesis of peracetic acid (PAA) with hydrogen peroxide (HP) and acetic acid (AA) is considered as case study. The critical and threshold values for the runaway accident are identified for selected sets of input data. Under the conditional probability of prior cooling system failure, Monte Carlo simulations are performed in order to estimate the risk of thermal runaway accident in batch reactors. It becomes then possible to predict the ratio of reactors, within an industrial plant, potentially subject to thermal runaway accident.     

Pressure and temperature increase of LPG in a thermally coated pressure vessel exposed to fire: Experimental and model results

Damage caused by incidents with transport tanks with compressed liquified gas is amongst the most extreme that can be encountered with transport vessels. This is particularly the case with the Boiling Liquid Expanding Vapor Explosion (BLEVE), which may occur if such a tank is exposed to fire for a prolonged period. Therefore, the local Dutch LPG transport sector adopted a thermally insulating tank coating as a ‘standard outfit’ for their tank trailers, with the aim to delay a BLEVE for a sufficiently long period for emergency services to take appropriate measures and for people near the accident location to be evacuated. On a European scale however, no consensus has been reached on the cost-benefit of such measures.With the current drive towards “greener” and renewable energy sources, this issue has regained attention with alternative fuels such as LNG, CNG and Hydrogen and a need was felt for (better) theoretical models and experimental data concerning the behavior of transport tanks carrying these substances.In this paper a new tank thermal (equilibrium) model is described to predict pressure and temperature behavior of a multi layered, thermally insulated tank containing a compressed liquified gas exposed to heat. Results are compared with data of three bonfire experiments, in which 3 m³ tanks, filled for ca. 50% with LPG were exposed to fire. A good match between modelled and experimental pressure and temperature evolution in time could be obtained using a constant value for the thermal conductivity of the insulation layer. The modelling showed that the thermal insulation value is crucial for an accurate prediction of these parameters as well as the opening time for a pressure safety valve. As relevant temperatures may cover a very wide range (from cryogenic in LNG-tanks to over 1000 °C in a fire) knowledge of the thermal (and physical) behavior of the insulating layer over a large temperature range is essential.The same holds for the behavior of the PRV when subjected to fire. Extreme temperatures may also lead to deviating behavior from what is expected based on the initial settings.     

Thermal failure of 2/3 PCP in high temperature environment and optimization analysis of stator and rotor meshing parameters

Progressive cavity pump (PCP), which has problems such as invalid and leakage of rubber bushings, is employed in heavy oil field exploitation. In this paper, based on the thermal aging mechanical test of rubber and the fitting precision evaluation result of the constitutive model, the rubber constitutive model is optimized; the finite element model of PCP is established; the deformation law of stator bushing inner wall is quantitatively analyzed by numerical simulation method; and the phenomenon that temperature field distribution and thermal aging failure of stator rubber bushings is revealed. As results: The increase in well depth, which leads to the increase in the overall temperature of the stator bushing and the decrease of the thermal hysteresis, have greatest influence on the temperature of the stator bushing; the interference, which leads the maximum temperature increases first and then decreases, has a great impact on the thermal hysteresis; and the eccentricity have little effect on the thermal hysteresis of the stator bushing. The research results provide theoretical support to optimize stator and rotor parameter matching, recommending applicable working conditions, improving invalid of stator bushing, pump leakage and other issues.     

Experimental study on thermal runaway risk of 18650 lithium ion battery under side-heating condition

To simulate the heat transfer process between lithium-ion batteries (LIBs), an electric heater with the same size and shape as LIB in this work is used to trigger thermal runaway event. The effect of state of charge (SOC), the power of heater, the cell spacing on thermal behavior of LIB was investigated as well the amount of transferred heat between the heater and LIB was calculated. The results indicate that 50% SOC is an unstable state for LIB, that a stronger jet flame becomes more likely when the SOC of LIB is higher than 50%. Additionally, the increased spacing, lower heating power and SOC can contribute to mitigate the severity of thermal runaway behavior. Further, the dominant path of heat transfer between the heater and LIB will also vary with operating conditions. The heat conduction through air is the main heat transfer path in tests with lower heating power. However, heat radiation will replace heat conduction as the primary heat transfer mode when there is a large temperature difference between the heater and LIB in tests with higher heating power. Understanding the leading heat transfer path between LIBs can provide valuable guidelines for the safety design of lithium-ion battery modules.     

热脱附法在测定空气中苯系物上的应用

对热脱附-气相色谱测定苯系物方法中的几种常用吸附剂进行了选择比较。结果表明,在测定苯、甲苯、乙苯、二甲苯以及苯乙烯时,TenaxTA/Carbograph1TD复合型吸附剂的综合吸附效率最好。TenaxTA/Carbograph1TD复合型吸附剂的检出限、精密度、准确度和保存期都得到了良好的结果,能够满足监测分析的要求。     

生物质发电工程的环保设计

简要介绍生物质发电工程环保设计的重点,确保环保达标;并总结工程设计中遇到的常见问题,给出优化设计结果,以促进生物质发电工程的不断发展。     

电厂二氧化碳捕集分离技术研究综述

电厂二氧化碳捕集与封存是二氧化碳减排措施研究热点,也是全球二氧化碳减排的重要任务之一,可分为物理吸附/吸收、化学吸收、物理-化学吸收、膜技术及生物技术等。其中物理吸附/吸收、化学吸收为电厂二氧化碳捕集主流技术。开发具有高选择性、高效率吸收剂及捕集技术,提高能源利用效率,合理布置尾部烟气脱碳处理设施是电厂二氧化碳捕集技术面临的挑战。