Modelling pyrolysis with dynamic heating

In literature, the reaction kinetic of pyrolysis process is often determined and modelled under constant heating rates. In reality, the heating rate of an industrial pyrolysis process is difficult or often not necessary to be kept constant. The variation of heating rate at different reaction stages, termed “dynamic heating”, governs the pyrolysis performance such as production rate, energy consumption, product quality, etc. In this work, pyrolysis progress with dynamic heating is being studied. The rate and reaction heat of tyre pyrolysis at different heating rates are obtained experimentally. A transient model considering the effect of dynamic heating was then developed and compared with the conventional static heating model. Results show that a higher heating rate favours the production of volatiles and shifts the overall pyrolysis heat flow to more endothermic. The significance of the dynamic heating model was observed for processes with large feed size and/or with high heating rate.     

低碳供热技术节能指标与经济效益综合分析

基于能源资源与环境保护的迫切需求,结合北方采暖问题面临的严峻形势,当前需进一步探索可持续发展的清洁采暖技术。清洁采暖技术及采暖热源的选择,也应适时地根据资源情况、环境保护、能源效率及费用等综合因素进行考量,经技术经济分析比较后确定。故以北方地区某采暖工程为例,基于电能供热、天然气供热、热泵供热等新型清洁能源供热方式,本文介绍了各分布式集中供热技术原理,分析了各清洁采暖技术各自的优劣势对比,采用具体算例并结合成本、使用寿命及一次能源消耗等评价指标对供暖区域的技术方案进行经济性与节能性综合分析,发展低碳经济促进可持续发展,以期为北方地区供热方式的选择提供一定的参考依据。     

微波加热用透波材料的研究进展

微波加热技术因其绿色环保、体积加热、选择性加热等优势,已被广泛应用于化工强化、金属冶炼、陶瓷烧结、食品加工等众多领域,但微波在反应器内普遍存在透波效果差、微波利用率低等问题。随着微波加热技术的不断发展,微波加热设备中透波材料的选用越来越受到大家的关注。本文主要针对透波材料在微波加热领域中的应用现状进行综述,对透波材料的种类进行简要介绍,分别从微波加热用容器和保温材料两方面进行论述。详细介绍了氧化物、氮化物、硅酸盐、磷酸盐等高温透波材料及聚四氟乙烯、玻纤增强树脂基、环氧树脂等中、低温透波材料的研究进展,并具体论述了目前微波加热常用纤维棉、纤维毯和纤维板等各种陶瓷纤维制品的介电特性和透波性能,最后指出了目前微波加热用透波材料普遍存在的问题,并对透波材料的应用和发展作出了展望。     

Mould tool heating - the oven-free alternative

The curing of larger composite parts such as wind turbine blades in ovens or autoclaves is becoming a difficult proposition and for these components heating the mould becomes a more cost-effective and faster option. George Marsh reports on recent developments in on-mould and in-mould heating.     

Research on a New Variotherm Injection Molding Technology and its Application on the Molding of a Large LCD Panel

The polymer injection products produced by using the current injection molding method usually have many defects, such as short shot, jetting, sink mark, flow mark, weld mark, and floating fibers. These defects have to be eliminated by using post-processing processes such as spraying and coating, which will cause environment pollution and waste in time, materials, energy and labor. These problems can be solved effectively by using a new injection method, named as variotherm injection molding or rapid heat cycle molding (RHCM). In this paper, a new type of dynamic mold temperature control system using steam as heating medium and cooling water as coolant was developed for variotherm injection molding. The injection mold is heated to a temperature higher than the glass transition temperature of the resin, and keeps this temperature in the polymer melt filling stage. To evaluate the efficiency of steam heating and coolant cooling, the mold surface temperature response during the heating stage and the polymer melt temperature response during the cooling stage were investigated by numerical thermal analysis. During heating, the mold surface temperature can be raised up rapidly with an average heating speed of 5.4°C/s and finally reaches an equilibrium temperature after an effective heating time of 40 s. It takes about 34.5 s to cool down the shaped polymer melt to the ejection temperature for demolding. The effect of main parameters such as mold structure, material of mold insert on heating/cooling efficiency and surface temperature uniformity were also discussed based on simulation results. Finally, a variotherm injection production line for 46-inch LCD panel was constructed. The test production results demonstrate that the mold temperature control system developed in this study can dynamically and efficiently control mold surface temperature without increasing molding cycle time. With this new variotherm injection molding technology, the defects on LCD panel surface occurring in conventional injection molding process, such as short shot, jetting, sink mark, flow mark, weld mark, and floating fibers were eliminated effectively. The surface gloss of the panel was improved and the secondary operations, such as sanding and coating, are not needed anymore.     

Estimation of heating time in tubular supercritical water reactors

Reactor efficiency and product distribution in supercritical water (SCW) reactors is greatly influenced by the design of the heating section of these reactors. However, little experimental or theoretical work is available to estimate the rate of heat transfer in such systems. In the present study, CFD modeling of the heat transfer in tubular SCW reactors has been performed. Effects of various operating parameters; i.e. reactor temperature and pressure, flow rate, reactor diameter, and the external heating mechanism, on the heating time constant, the temperature profile along the reactor, and reactor residence time are investigated. Based on numerical simulations, a semi-theoretical model is proposed to estimate the heating time constant as a function of reactor operating conditions. Results of this study provide useful insights for designing continuous supercritical water reactors as well as for the analysis of experimental data obtained from such systems.     

Heating value of biomass and biomass pyrolysis products

Studies conducted on the heating value of various types of biomass components and their pyrolysis products such as char, liquids and gases are presented. Heating values of chars are comparable with those of lignite and coke; heating values of liquids are comparable with those of oxygenated fuels such as methanol and ethanol, which are much lower than those of petroleum fuels. Heating values of gases are comparable with those of producer gas or coal gas and are much lower than that of natural gas. It is also found that the heating values of products are functions of the initial composition of biomass; correlations are developed to express these. Also, correlations are developed which explain the influence of ash elements on heating values of the pyrolysis products and on percentage distribution of energy in the products.     

蒸气式激光清洗

介绍了蒸气式（湿式）激光清洗,对基底强吸收、基底与液膜共同吸收、液膜强吸收的3种情况给予了分析讨论。给出了实验装置示意图,还介绍了蒸气式激光清洗中的一些理论问题,如峰值温度和瞬态力的估算。最后对干式和湿式激光清洗进行了简单比较。     

Electron-Beam-Induced Loop Formation on Dislocations in Yttria-Fully-Stabilized Zirconia

The nature of the strain lobes and loops that form on edge dislocations in yttria-stabilized zirconia during exposure in an electron microscope has been investigated. By changing the operating conditions, such as acceleration voltage, cycling the beam intensity, heating or cooling the specimen prior to observation, or heat treatment prior to the deformation, it has been shown that the effects result from beam heating. During specimen heating ZrN precipitates which have a large misfit with the ZrO₂-Y₂O₃ matrix form in the compressed regions of the dislocation core.     

Heat transfer during microwave combination heating: Computational modeling and MRI experiments

Combination of heating modes such as microwaves, convection, and radiant heating can be used to realistically achieve the quality and safety needed for cooking processes and, at the same time, make the processes faster. Physics‐based computational modeling used in conjunction with MRI experimentation can be used to obtain critical understanding of combination heating. The objectives were to: (1) formulate a fully coupled electromagnetics ‐ heat transfer model, (2) use magnetic resonance imaging (MRI) experiments to determine the 3D spatial and temporal variation of temperatures and validate the numerical model, (3) use the insight gained from the model and experiments to understand the combination heating process and to optimize it. The different factors that affect heating patterns during combination heating such as the type of heating modes used, placement of sample, and microwave cycling were considered. Objective functions were defined and minimized for design and optimization. The use of such techniques can lead to greater control and automation of combination heating process benefitting the food process and product developers immensely. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Modellbasierte Untersuchung des Wärmeübergangs in einer induktiv beheizten Wirbelschicht

The aim of the presented study is to develop a new technology for a highly efficient heating of fluidized beds. The energy input in fluidized beds can be performed by convective indirect heating of the fluidizing medium, or by induction by means of electrically conductive inert particles (such as iron hollow balls), in which energy is transferred via an induction field. On the surface of these particles, the heat is released directly and without contact into the fluidized bed. The impact of parameters like bed mass, air velocity and supplied induction power on the inductive heating was systematically investigated. A simplified heat transfer model was developed. With this model a good agreement with the measured values for heating and cooling can be achieved.     

电磁感应加热技术在注塑机螺杆上的设计

注塑机螺杆的加热工艺不断提高,传统的电阻丝螺杆加热已成为注塑机向节能环保型机械装备发展的瓶颈,新型电磁感应加热具有节能环保、加热均匀等优点,得到重点研究和快速应用.结合注塑机快速加热的工艺特点,设计一套相应的电磁感应加热控制器,有效监控电磁感应加热的过程并不断改善加热效果.     

食品和农产品干燥的一种有效方法-红外加热法

农业和食品行业需要能源高效和环境友好的干燥技术,最近红外加热干燥的应用得到广泛研究。作为现代干燥技术的另一种选择,红外干燥具有加热均匀、干燥速率高、干燥时间短、节约能源、产品品质和安全性高等引人注目的优点。研究表明。将红外方法可以减少干燥时间并且节能。与热可以对果蔬实现同步漂烫和干燥,干燥和热风干燥相结合能够有效的减少干燥时间。所开发的红外冷冻相继干燥常规的空气干燥或冷冻干燥相比,更适合于生产高品质的酥脆果蔬片。红外加对稻谷进行同步干燥和杀虫。本文将综述红外加热技术的最新研究和进展。     

Microwave-enhanced hybridizations of biopolymers with silica: effective method for rapid preparation and homogeneous dispersion

Effective hybridization of biopolymers such as chitosan or lignin was conducted by microwave-assisted sol–gel reaction of several alkoxysilanes such as tetramethoxysilane (TMOS), methyltrimethoxysilane (MeTMOS), and 3-aminopropyltrimethoxysilane (APTMS). The hybridization proceeded rapidly and efficiently via inhibition of aggregates derived from intermolecular hydrogen bonding in the biopolymers as compared with the conventional heating as a traditional method due to activated hydroxyl groups of both the biopolymers and alkoxysilanes by microwave irradiation. The composition and the thermal properties of the polymers hybridized under microwave irradiation were almost identical to those prepared by the conventional method using TGA analysis and FT-IR spectroscopy. However, the homogeneity on the surface of the hybrid obtained under microwave irradiation was better than that under conventional heating by measuring the SEM and nitrogen adsorption porosimetry analysis.     

天然气水合物的防治方法综述

随着油气田开发的不断深入和深海油气田的不断发展,天然气水合物的生成对油气田开发和管道运输均有很大危害。介绍了天然气水合物的形成机理和基本过程,概述了四种抑制天然气水合物生成的方法,分为干燥法,如干空气干燥法;压力控制法,如逐级节流法;加热法,如水套炉加热法、热水管加热法、电磁加热法;注入化学抑制剂法,如热力学抑制剂法、动力学抑制剂法和几种新型抑制剂法,并分析了各自的适用范围和作用机理,提出了国内今后的水合物抑止技术的发展方向。     

烟草加热器具供能元器件的创新思考及展望

供能元器件作为烟草加热器具的核心部件，决定了烟草加热器具的续航时间、充放电速度、预热等待时间以及使用寿命等关键参数。本文综述了电加热型烟草制品加热器具的供能元器件发展现状，分析了2种供能元器件存在的不足与潜在的研究方向。结果显示，锂离子电池作为电加热型卷烟加热器具中普遍使用的供能元器件，具有体积能量密度高且电流放电量大的特点，但是存在充放电速度慢、循环稳定性差、成本高以及存在安全隐患等劣势；介电电容器是一种电加热型卷烟加热器具的潜在供能元器件，具有充放电速度快、循环稳定性好、可靠性高、价格低廉以及安全性能好等特点，但是其体积能量密度亟待提高。供能元器件是烟草加热器具中的关键单元，重视供能元器件的开发和研究、提高供能元器件的工作性能，对促进我国新型烟草的高质量发展以及提升消费者体验具有重要意义。     

Thermogravimetric analysis of polystyrene: Influence of sample weight and heating rate on thermal and kinetic parameters

This article studies the influence of the heating rate and sample weight on the thermal decomposition of polystyrene (first-order kinetics). For this purpose, the kinetic parameters (i.e., frequency factor and activation energy), variables at the maximum decomposition rate (such as conversion, reaction rate, and temperature), as well as some characteristic temperatures have been determined for a series of experiments where the heating rate varies (0.5–11.5 K/min) and also, the sample weight (6.0–25.1 mg). Some mathematical equations have been developed that allow: (1) evaluation of the activation energy of thermal decomposition by different ways and comparing the results obtained; (2) relating different parameters between themselves, such as the heating rate with the temperature at the maximum decomposition rate or the frequency factor with the heating rate and sample weight. Finally, some theoretical explanations of the variation of thermal and kinetic parameters have been proposed. © 1996 John Wiley & Sons, Inc.     

微波辅射树脂催化合成L-氨基酸酯的研究

在微波辐射下,强酸性阳离子交换树脂为催化剂,一步酯化合成了8种空间位阻较高的L-氨基酸异丙酯和异丁酯,并用1HNMR和IR对其结构进行了表征。研究结果表明,微波辐射大大加速了酯化反应,所得8种酯的酯化收率均在50~70%之间。微波辐射反应所需时间大幅缩短,仅为常规加热时间的1/48~1/72,且反应物极性越大,反应时间缩短越明显。同时,就微波辐射功率、辐射时间及加热方式对酯化反应的影响进行了研究。     

Visualization study of foaming process for polyimide foams and its reinforced foams

In this article, the foaming processes of polyimide foams and its reinforced foams were observed by a self‐made visualization device at different heating rates ranging from 10°C/min to 120°C/min. Contributing factors such as chemical structure of polyimide, fillers, and heating rate were investigated to determine the effects on the inflation onset temperature and morphological change of polyimide foam precursor powders. The results showed that the powder might grow into a single bubble mesostructure at a lower heating rate or a multibubble mesostructure at a higher heating rate. Because of the filling of reinforcing fillers, the inflation morphology of reinforced polyimide foam precursor powders show a different change trend with the increase of temperature compared to the pure polyimide foam precursor powders. For all kinds of polyimide foam precursor powders investigated in this article, the inflation morphologies showed a similar variation trend with different heating rates, and the final inflation degrees were slightly different. The inflation onset temperatures of all polyimide foam precursor powders studied decreased with increasing heating rate. POLYM. COMPOS., 2010. © 2008 Society of Plastics Engineers     

新型空气-水双热源复合热泵系统性能和除霜实验

针对低温环境条件下热泵逆循环除霜存在的诸多问题,提出了一套具备预热除霜功能的新型空气-水双热源复合热泵系统（new air-water double source composite heat pump system,AWDSHPS-N）,通过阀门切换和低温水源侧水泵的启停控制可直接进入除霜模式,除霜过程中可保证制热的连续性,每次除霜时长不超过5 min。利用恒温恒湿环境仓模拟室外环境条件,可调控水温的低温水箱模拟太阳能等低温热源搭建AWDSHPS-N实验台,对不同测试工况下,单空气源制热模式（air source heating mode,ASHM）、单水源制热模式（water source heating mode,WSHM）、空气-水双热源制热模式（air-water source heating mode,AWSHM）3种制热模式将水从18℃加热至51℃的系统性能系数（coefficient of performance,COP）进行了实验,结果表明：AWSHM的COP比ASHM提高了6.1%~20.5%;当环境温度和低温水源温度均高于15℃时,系统COP高低顺序为AWSHM、ASHM和WSHM。