吹灰对锅炉对流受热面传热熵产影响的试验研究

建立了锅炉对流受热面传热熵产的计算模型,并给出了传热熵产生数的计算公式.对1台600 MW机组燃煤锅炉进行了不同吹灰模式的试验.结合采集的实时数据,利用建立的传热熵产模型计算了各对流受热面吹灰前后的传热熵产,得出了吹灰对各受热面传热熵产的影响曲线,分析了该锅炉各吹灰模式的利弊,提出了吹灰模式优化的建议.     

600 MW机组锅炉对流受热面污染状况实验与吹灰优化

锅炉受热面积灰污染导致锅炉运行的经济性和安全性下降。在邹电600MW机组锅炉上进行了不同吹灰间隔与吹灰强度等条件下的对流受热面吹灰实验,利用开发的基于锅炉运行热力参数的在线计算系统对实验过程中各对流受热面污染状况进行了实时监测。根据实验结果和实时监测结果建立了优化吹灰模型,开发了在线吹灰优化系统。所开发吹灰优化系统数月运行结果表明,在采用优化吹灰模型提示的吹灰方式后,锅炉日平均排烟温度比未优化前下降约6°C,锅炉效率提高0.3%以上,经济效益显著。图4表1参7     

基于增量分布的燃煤电厂锅炉受热面吹灰优化研究

针对目前锅炉受热面吹灰方式不合理的情况,权衡吹灰带来的锅炉效率的提高和蒸汽损耗,在确保锅炉安全运行的前提下,建立了吹灰优化模型。以某300 MW燃煤电厂机组锅炉省煤器为研究对象,采用集散控制系统(DCS)的数据和基本热力学计算数据实时计算受热面污染率。通过分析相同工况下多组污染率得到同一测点不同时刻的增量分布,根据其分布曲线求取数学期望,根据已知的初始清洁状态,预测未来时刻的受热面清洁状态,以单位时间内换热量最大为目标,对吹灰周期进行了优化。结果表明:与传统吹灰方式相比,采用优化后的吹灰周期指导吹灰,既提高了传热效率,又可减少不必要的蒸汽浪费。     

锅炉各受热面吹灰作用的对比研究

为优化运行性能，通过清洁因子变化对锅炉主要运行参数影响的性能计算，得到了锅炉不同部位受热面的吹灰作用种类和大小，可作为现场指导吹灰优化运行的依据。不同部位受热面的吹灰作用因受热面位置、受热面种类和大小的不同而异，其重要性也不同。位于烟气流程起始点和蒸汽流程终点的受热面是吹灰优化运行的重点。图13表3参3     

燃煤锅炉受热面灰污监测与吹灰优化

提出了一种锅炉受热面灰污监测与吹灰优化方法。该方法利用神经网络建立锅炉清洁受热面换热模型,在此基础上运用非线性动态规划技术进行受热面吹灰周期的优化。在扬子石化公司热电厂#8锅炉上进行了现场测试,结果表明所提出的方法是有效的。     

锅炉对流受热面灰污监测研究

为了提高电站锅炉对流受热面灰污监测的准确性,更好地进行吹灰优化,提出了基于最小二乘支持向量机的锅炉对流受热面灰污监测方法。以天津北疆电厂1 000 MW机组锅炉为例,建立监测模型,分析了模型建立过程中输入参数的选择、数据的采集与筛选、数据的预处理、核函数的选择等。结果表明:此模型监测结果与电厂的实际吹灰操作一致,能够较准确地实现电站锅炉受热面的灰污监测,为电厂进一步地吹灰优化打下了良好的基础。     

基于改进粒子滤波算法预测健康状态的锅炉吹灰优化

为了对锅炉受热面沉积的灰污进行及时、准确地清扫,制定合理的吹灰优化策略。采用清洁因子来评估受热面的健康状况,并根据实时监测数据结合改进粒子滤波;采用滚筒式预测单次积灰过程内清洁因子未来的变化趋势,并验证了该预测方法的准确度。同时,提出一种基于单位时间传热量损耗最低的吹灰优化模型,吹灰优化计算中采用相同工况下多组清洁因子数据进行拟合。以某300 MW燃煤锅炉为例,验证了所提优化模型的可行性。     

导热油管内强制对流换热系数的计算

以一种常见导热油为例对有机热载体锅炉的对流受热面传热系数进行计算分析。     

超超临界塔式炉半辐射区优化吹灰的研究

基于热平衡和传热原理建立超超临界塔式锅炉半辐射、半对流高温受热面的污染监测模型。依据电厂受热面进、出口烟温测点及机组运行实时数据,通过热力计算得出受热面灰污变化规律,并分析灰污系数的影响因素。经过在国内某1 000 MW超超临界塔式炉进行大量的吹灰前后对比试验,验证了灰污监测模型的正确性和适用性。结合吹灰经验,提出了合理的吹灰方案,对于锅炉吹灰系统的优化运行具有实际指导作用。     

燃煤电站锅炉受热面灰污监测研究

锅炉受热面积灰和结渣会导致锅炉运行的安全性和经济性下降。定义了新的受热面清洁因子,考虑了锅炉各受热面清洁时与灰污平衡时工质进出口焓升的变化,该清洁因子能够更显著地反映出受热面的灰污程度。应用BP神经网络预测不同工况下锅炉各受热面的工质焓升极大值与极小值,实时计算出锅炉各受热面的灰污状况,可指导和优化锅炉吹灰操作,并以屏式过热器为例进行了验证。     

锅炉热力计算中传热系数类库的实现

通过对烟气、空气和水蒸汽的物性参数进行拟合，直接采用烟气、蒸汽侧对流传热系数公式计算对流换热系数，进一步实现锅炉对流受热面的传热系数类库编制，从而可以不再采用传统的查图求取的方法，提高计算的精度和效率。     

蒸发冷却板式换热器的传热与阻力实验研究

通过对板式换热器传热的理论分析和在干工况、喷淋工况下的实验研究,得出板式换热器在喷淋情形下空气侧喷淋水量对强化对流传热系数的影响关系,进而拟合出喷淋情形下空气侧的对流传热系数的关联式。同时为了综合考虑由于喷淋造成的换热器性能的变化,还对喷淋前后空气侧的阻力变化进行了测试分析。     

干熄焦余热锅炉散热损失的计算方法

研究锅炉散热损失对提高锅炉效率具有积极的意义,一般常规锅炉的散热损失大约占到整个锅炉热效率的0.5%～3%。由于干熄焦余热锅炉的热力工况取决于干熄焦工艺流程,其没有常规锅炉的燃烧炉膛,炉体结构以及各受热面的布置形式等与常规锅炉有较大的差异,因此,对干熄焦余热锅炉热力计算时直接引用常规锅炉的散热损失计算方法,锅炉散热损失的计算结果与实际有较大的误差,影响了余热锅炉效率的计算。根据结合干熄焦余热锅炉实际运行的特点,对干熄焦余热锅炉的散热损失计算方法进行讨论。     

燃煤锅炉中过/再热器工质温差与积灰程度关联研究

为实现对燃煤锅炉无烟温测点的对流受热面积灰程度的监测,对锅炉对流受热面的传热特性及工质吸热特性进行热平衡机理分析,在热力学基础上,用相关性分析、回归分析和灰色关联分析方法对实际生产数据进行挖掘、分析,计算了对流受热面的出入口工质温差与清洁因子的灰色关联特性,建立了利用受热面进出口温差表征积灰程度的函数模型。结果表明:负荷稳定时,锅炉燃烧释放的热量也是一定的,对流受热面单位工质吸热量能反映该对流受热面的积灰程度;受热面温差与清洁因子具有极强的关联性,受热面进出口工质温差模型能很好地反映对流受热面的积灰程度。     

船用增压锅炉的炉膛对流传热计算

由于增压锅炉燃烧压力的提高,强化了对流传热,如果仍按常压燃烧锅炉炉膛热力计算,忽略对流传热,将直接影响增压锅炉炉膛热力计算的准确性。文中对增压锅炉与常压燃烧锅炉炉膛特性参数进行了比较,对前苏联增压锅炉的试验数据进行了分析探讨,指出了增压锅炉炉膛对流传热的影响因素。同时提出增压锅炉炉膛传热计算应将辐射与对流传热分开计算,给出了适用于增压锅炉炉膛对流传热的计算公式,并进行了实例计算分析,与前苏联增压锅炉试验的计算数据结果相近。对于完善增压锅炉的炉膛热力计算具有一定的理论和实际指导意义。     

Modelling and experimental studies on heat transfer in the convection section of a biomass boiler

This paper describes a model of heat transfer for the convection section of a biomass boiler. The predictions obtained with the model are compared to the measurement results from two boilers, a 50 kW_th pellet boiler and a 4000 kW_th wood chips boiler. An adequate accuracy was achieved on the wood chips boiler. As for the pellet boiler, the calculated and measured heat transfer rates differed more than expected on the basis of the inaccuracies in correlation reported in the literature. The most uncertain aspect of the model was assumed to be the correlation equation of the entrance region. Hence, the model was adjusted to improve the correlation. As a result of this, a high degree of accuracy was also obtained with the pellet boiler. The next step was to analyse the effect of design and the operating parameters on the pellet boiler. Firstly, the portion of radiation was established at 3–13 per cent, and the portion of entrance region at 39–52 per cent of the entire heat transfer rate under typical operating conditions. The effect of natural convection was small. Secondly, the heat transfer rate seemed to increase when dividing the convection section into more passes, even when the heat transfer surface area remained constant. This is because the effect of the entrance region is recurrent. Thirdly, when using smaller tube diameters the heat transfer area is more energy‐efficient, even when the bulk velocity of the flow remains constant. Copyright © 2006 John Wiley & Sons, Ltd.     

蓄热式连续加热炉内流动与换热特性的数值模拟

以某公司大方坯蓄热式连续加热炉为研究对象,对该炉建立了三维物理数学模型,分别采用可实现双方程湍流模型,PDF非预混燃烧模型、离散坐标法辐射模型(DO模型),应用Fluent数值仿真软件进行了模拟研究,得到了蓄热式连续加热炉内的流场和温度场的分布规律,并对炉内对流换热系数的分布进行了详细的分析研究.结果表明:钢坯表面局部对流换热系数在各加热段内分布不均匀,这主要是由于烧嘴进口射流所引起的局部流速的差异性,从整体上来看,预热段和加热1段的对流换热系数要高于其它各段.     

Natural convection heat transfer from upward-facing plates in saline water

Saltwater or brackish water is used as a coolant in most industries. Therefore, understanding the heat transfer processes and hydrodynamics during the natural convection in saline water is crucial for enhancing the efficiency of a heat exchanger. This study elaborates on the natural convection heat transfer in saline water under atmospheric conditions. A DC power supply is used to regulate the power given to the heater in a liquid pool for thermal analysis. The pool liquid comprises solutions with varying salinity from 0%, 0.2%, 0.5%, and 2%. The effect of varying salinity on the heat transfer coefficient and the thermal aspects encountered during the desalination process is analyzed. The temperature distribution across the surface of the heater is monitored using an infrared camera. It is studied for the solution of different salinities. The heat transfer coefficient and Nusselt number are investigated during natural convection for normal water and salt solution of different concentrations. It is inferred from the study that in the regime of natural convection, there is no significant difference in the Nusselt number for normal water and saltwater for the lower value of temperature difference between the plate and pool. The heat transfer coefficient in 0.2% saline water is higher as compared to the other solutions.     

JN50-5.0/470-T生物质热分解燃料锅炉的开发与设计

文章介绍了金牛股份有限公司开发研制的JN50-5.0/470-T生物质热分解燃料锅炉设计与开发过程,着重探讨燃烧生物质热分解燃料锅炉设计和结构布置方法以及对流受热面的设计特点,为同类型的锅炉设计提供借鉴经验.     

The heat transfer coefficients of the heating surface of 300 MWe CFB boiler

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.