The latent heat recovery from boiler exhaust flue gas using shell and corrugated tube heat exchanger: A numerical study

The excessively increasing environmental concerns along with reducing fossil fuel resources introduce the trend of increasing the efficiency of boiler via implementing waste heat recovery. In the present study, the potential of latent heat recovery is investigated in the middle‐size boiler exhaust flue gas using the shell and corrugated tube heat exchanger. The main purpose of the present study is efficiency growth in flue gases using latent heat recovery of the steam energy. The heat recovery analysis is evaluated by a validated computational fluid dynamics model by a commercial software. For this study, the effect of different tube arrangements, number of tubes, and flow direction in the shell on heat transfer and pressure drop were investigated. The results showed that in‐line arrangement of the tubes in the shell presents better thermal performance and also high pressure drop among the other arrangements. As a result, by considering the thermal performance and pressure drop, radial arrangement shows higher performance. According to the obtained results from Section 2 of the present study, by considering the radial arrangement of tubes in the shell, as the number of tube rises, the thermal performance declines.     

Heat recovery from hot solid particles in a shallow fluidized bed

A heat exchanger with a shallow gas–solid fluidized bed was experimentally studied in order to analyze energy recovery from solid particles leaving a combustion process. The experiments were carried out with and without vertical baffles in a fluidized bed with immersed horizontal tubes filled with water, in a counter flow arrangement. Two particle diameters (254 and 385 μm), two solid flow rates (50 and 80 kg/h) and two gas flow rates (46 and 50 kg/h) were tested. The bed temperature along the equipment length, the mass flow rate and the inlet and outlet temperatures of solid particles, air and water were measured in order to obtain the bed-tube heat transfer coefficient and the heat exchanger effectiveness. An increment of about 55% in the heat transfer coefficient and higher values of the heat exchanger effectiveness, in experiments with the presence of baffles, was verified. The experimental results also showed that the suspension-wall heat transfer coefficient increased considerably with the solid flow rate and also when the particle diameter decreased.     

火电厂节能环保供热装置的设计及应用

排烟热损失是锅炉各项热损失中最大的一项,它直接影响锅炉效率及发电煤耗.一般情况下,排烟温度每升高10℃,煤耗将增加2 g/(kW·h)左右.因此,降低排烟温度、回收烟气热量对于节能降耗、提高经济效益具有重要的实际意义.对火电厂节能环保供热装置的设计及应用进行了探讨.该设备采用烟气余热回收技术,将高温排烟热量传递给空气,...     

某余热锅炉爆管原因分析和改造

水循环回路的合理布置和设计对余热锅炉的安全运行具有重要意义。循环回路结构复杂容易导致并联管内的流量分配较大的不均匀性。偏差管内的流量较小 ,循环倍率较小 ,容易发生水循环停滞。当余热锅炉的热负荷很低时 ,循环流速较小 ,自然循环发生停滞 ,容易导致余热锅炉发生爆管。水循环的脉动会使并联管内循环流速和管壁温度发生脉动 ,余热锅炉的安全性下降。消除并联管内的流量分配不均匀和水循环脉动 ,合理运行 ,能够提高自然循环的可靠性 ,对余热锅炉的安全运行是有利的     

某小型燃煤工业锅炉的节能改造分析

通过对某锅炉的运行现状分析,发现存在运行热效率低、锅炉出力低、排烟温度高、炉渣含碳量高等问题,采取余热利用、锅炉风室改造、水处理设备改造及加强管理人员和锅炉操作人员培训等措施,锅炉热效率提高了11.41％,吨汽耗煤量降低了9.90％,锅炉出力提高了8.63％.     

有机热载体炉烟气余热回收技术浅析

长期以来,有机热载体炉排烟温度偏高,造成大量的能源浪费,严重影响了锅炉运行的经济性。为减少热能损失,对烟气余热回收技术的可行性方案、工程应用实例进行了阐述;并指出通过锅炉烟气余热利用技术回收排烟中的显热和潜热,可以大大提高有机热载体炉的热效率,实现节能降耗。     

350 MW余热锅炉变工况运行特性分析

目的  整体煤气化联合循环（IGCC）发电技术是高效、低碳的发电技术,余热锅炉是IGCC的组件之一。文章旨在研究余热锅炉变工况运行特性以提高整体煤气化联合循环发电技术的效率。 方法  通过分析余热锅炉的工作原理及传热传质原理,使用MATLAB软件展开编程计算,探究给水温度、给水压力、液相换热系数以及气相换热系数与余热锅炉内吸热量的关系。 结果  结果发现,当液相换热系数在200～1 000 W/(m²·K)和气相换热系数在20～100 W/(m²·K)范围内时,如果给水温度从30 ℃增加到100 ℃或给水压力增加,余热锅炉的吸热量将不断减少。反之,假设给水温度在30～100 ℃范围内,当液相换热系数从200 W/(m²·K)增加到1 000 W/(m²·K)或气相换热系数从20 W/(m²·K)增加到100 W/(m²·K)时,余热锅炉的吸热量不断增加。 结论  在液相换热系数与气相换热系数不变的情况下,给水温度或给水压力增加,余热锅炉的吸热量会减少;在给水温度与给水压力不变时,液相换热系数或气相换热系数增加,余热锅炉的吸热量会增加。     

棉秆循环流化床稀相区传热系数的试验研究

在热功率0.5 MW棉秆循环流化床试验装置上对稀相区传热系数进行了测定,研究了不同参数对传热系数的影响,结果表明:环形区颗粒浓度和床温对传热系数的影响较大,且随着颗粒浓度和床温的增加而增加;一次风率和过量空气系数对不同床高的传热系数也有一定影响,传热系数随一次风率的增加而增加,但一次风率过大时,传热系数会有所下降;为了得到较高的传热系数,过量空气系数存在一个最佳值;循环倍率对传热系数的影响也很明显,在一定的范围内,传热系数随循环倍率的增加而增加;当循环倍率太大时,床温有所降低,使传热系数减小.     

CFB锅炉水冷排渣余热利用的分析与优化

1前言循环流化床锅炉技术是近年来迅速发展起来的一项高效低污染清洁技术,这项技术在电站锅炉、工业锅炉以及废弃物处理利用等领域已得到广泛应用。由于流化床锅炉通常燃用高灰份燃料,因此排渣热损失较大,若能将锅炉排渣的热量进行回收利用,则可大大提高电厂运行的经济性。冷渣     

CAPE-OPEN simulation of waste-to-energy technologies for urban cities

Uncontrolled waste disposal and unsustainable waste management not only damage the environment, but also affect human health. In most urban areas, municipal solid waste production is constantly increasing following the everlasting increase in energy consumption. Technologies aim to exploit wastes in order to recover energy, decrease the depletion rate of fossil fuels, and reduce waste disposal. In this paper, the annual amount of municipal solid waste disposed in the greater metropolitan area of Thessaloniki is taken into consideration, in order to size and model a combined heat and power facility for energy recovery. From the various waste-to-energy technologies available, a fluidised bed combustion boiler combined heat and power plant was selected and modelled through the use of COCO, a CAPE-OPEN simulation software, to estimate the amount of electrical and thermal energy that could be generated for different boiler pressures. Although average efficiency was similar in all cases, providing almost 15% of Thessaloniki’s energy needs, a great variation in the electricity to thermal energy ratio was observed.     

Research,development and industrial application of heat pipe technology in China

This paper introduces some typical cases of industrial applications, which include the equipment for the waste heat recovery and the industrial process equipment. Carbon steel–water heat pipe technology, applied to air preheater and waste heat boiler, has been successfully used in many fields, such as waste heat recovery, energy conservation and environmental protection. Liquid metal high-temperature heat pipe technology has been extensively employed in the process equipment, for example, high-temperature hot air generators and heat extractors. Heat pipe technology also finds its use in chemical reactors including ammonia converters. The success of applications is founded on the basis of fundamental research of heat pipe technology, which includes the theoretical and experimental researches on the vapor–liquid two-phase flow and heat transfer inside the heat pipe, the heat transfer limits of heat pipes, the heat transfer enhancement with heat pipes, and researches on the material compatibility and life tests of heat pipes. Hi-efficient heat pipe heat and mass transfer equipment is going to play a more and more important role in the various industrial fields.     

Heat exchanger network design of an organic Rankine cycle integrated waste heat recovery system of a marine vessel using pinch point analysis

The coexistence of different kinds of waste heat sources on marine vessels with various temperature ranges increases the need for an optimal heat exchanger network (HEN) design for the heat collection process to reduce the unutilizable heat that needs to be discharged to overboard. The optimal HEN design has not been taken into consideration by using pinch point analysis in previous studies of marine organic Rankine cycle (ORC) systems that utilize from different kinds of waste heat sources. The objective of the study is to determine the optimal HEN design for an ORC integrated waste heat recovery system of a marine vessel by utilizing the pinch point analysis to improve the overall energy efficiency. Lubricating oil, high-temperature cooling water and scavenge air of the main engine, and the exhaust gas emitted from the boiler plant were identified as the major waste heat sources of a reference container ship. A heat collection stream, in which thermal oil is used as the heat transfer fluid that transfers the collected heat to an ORC system, was proposed. The pinch point analysis showed that the optimum waste heat recovery could be gained by separating the scavenge air cooler into three stages and the lubricating oil cooler into two stages. The results of the parametric study for the varying evaporator inlet pressure between 1000 and 3000 kPa showed that R1234ze(Z) yields the best performance among nine different organic working fluids with the thermal efficiency and exergy efficiency of 15.24% and 86.47% for the ORC system, respectively. For the proposed configuration, the unavailable waste heat that cannot be transferred to thermal oil was found as 23.71%, 16.56%, 13.17%, and 7.81% of the total waste heat produced by the heat sources, and also 8.24%, 9.80%, 11.55%, and 12.93% of the net power output produced by the main engine can be recovered for 25%, 50%, 76%, and 100% maximum continuous rating (MCR), respectively.     

Study of immersed heat exchange surface for high-efficiency heat recovery from wire-rim tires in a fluidized-bed boiler

In an internally circulating fluidized-bed (ICFE) boiler, the fluidized bed is separated by a partition into main combustion and heat recovery chambers. The flows in these chambers are generated by using silica sand as the fluidizing medium. To determine the overall heat transfer coefficient (HTC) of the boiler's panel-type immersed heat transfer tubes, combustion tests were performed with wire-rim tires. The overall (HTC) of a panel tube array was lower than that of a zigzag tube arrangement. In practice, the heat absorbed by the fins makes the coefficients of either type of tube array almost identical. The air flowrate in the circulating bed at the bottom of the heat recovery chamber can be changed to control the overall HTC to a value virtually identical with that of a zigzag tube array. The combustion of wire-rim tires leads to a buildup of wires in the zigzag array, hampering the transfer of heat. Yet, the panel-type array showed no buildup so that it was possible to maintain steady operation with this type of tube arrangement. © 1997 Scripta Technica. Inc. Heat Trans Jpn Res. 25 (2): 120–134, 1996     

工业锅炉水处理及节能监管

工业锅炉水处理不当会造成热量损失,浪费能源。为了节约能源,本文从锅炉结垢、冷凝水回收及过量排污等方面着手,对水垢形成机理及水垢形成数学模型构建进行了研究,对冷凝水排放造成的热损失及给水水质不良而过量排污导致的热损失进行了分析,总结出可以从防止结垢以提高锅炉热效率,回收凝结水以提高热利用率,减少和回收排污热以减少排污热损失等三方面提出节能措施。最后对做好水处理工作及节能监管提出了相应的对策。     

Effects of ellipsoidal and regular hexahedral particles on the performance of the waste heat recovery equipment in a methanol reforming hydrogen production system

Hydrogen production from methanol has attracted attention due to its wide range of raw material sources and mature technology. Using waste heat of industrial high temperature solid particles like blast slag and steel slag etc. To provide vaporization heat and reaction heat for the reaction between methanol and water is an emerging technology for hydrogen production from methanol, which can save additional thermal energy resources. Herein, the performances of equipment that uses the waste heat of ellipsoidal and regular hexahedral particles to provide a heat source for methanol to hydrogen were explored by the DEM-CFD method. Compared with spherical particles of the same equivalent diameter, ellipsoidal and regular hexahedral particles have poor fluidity in the stagnant area, and the empty area is enlarged and irregular in shape. The average velocity peaks of the ellipsoidal and regular hexahedron particles are larger than those of spherical particles, and the overall mean velocity fluctuation of ellipsoidal particles is similar to that of spherical particles while the regular hexahedron particles' is larger. The average temperature drop rate of the ellipsoidal and regular hexahedral particles is slower than that of spherical particles, the uniformity of temperature distribution is worse than that of spherical particles. The ellipsoidal and regular hexahedral particles’ average effective heat transfer coefficient is smaller than that of spherical particles, and the heat transfer effect is weaker than that of spherical particles. The effective heat transfer coefficient of ellipsoidal particles is 2.95 W/(m⁻²∙K⁻¹) lower than that of spherical particles and the effective heat transfer coefficient of hexahedral particles is 6.09 W/(m⁻²∙K⁻¹) lower than that of spherical particles. Therefore, compared with the spherical particles of the same equivalent diameter, ellipsoidal and regular hexahedral particles produce less hydrogen.     

有机热载体锅炉尾部高效余热利用装置的设计与应用

有机热载体锅炉广泛应用于纺织、印染行业,由于高温定型和染整的特殊工艺以及有机热载体锅炉的构造和运行原理造成其尾部排烟温度在300℃左右,产生巨大的热能浪费。为减少热能损失,通过高温烟气的余热回收利用,提高有机热载体锅炉的综合热效率,可实现节能降耗和减排。本课题运用热管技术设计研制了结构合理、操作方便、高效的有机热载体锅炉尾部高温烟气的回收再利用装置。     

NACT滚筒冷渣机工业性能研究

报道第一台NACT(新型灰渣冷却技术)滚筒冷渣机的工业试验结果。工业测试显示,锅炉满负荷运行时NACT滚筒冷渣机的表观传热系数大于95 W/(m~2·K),几乎是现有滚筒冷渣机产品传热系数的2倍。该装置采用扬料板组织灰渣运动,设置迎合抛洒灰渣的对流受热面,将主导热阻由灰渣接触热阻转变为灰渣对流冲刷热阻,大幅度提高了总传热系数。工业测试结果显示:滚筒转速对NACT滚筒冷渣机性能影响巨大。随着滚筒转速提高,灰渣处理量直线升高,但不同转速下的排渣温度升高速率不同;滚筒转速增加,表观传热系数升高,有利于传热过程。增加滚筒对流传热份额,延长灰渣在滚筒内停留时间,是滚筒设计的关键。     

Heat Transfer and Thermodynamic Performance of LiBr/H2O Absorption Heat Transformer with Vapor Absorption Inside Vertical Spiral Tubes

In this paper, an absorption heat transformer (AHT) with falling film of aqueous LiBr solution inside vertical spiral tubes is installed and tested. The variations of coefficient of performance (COP), thermal efficiency (E_th ), and the heat transfer coefficient of the absorber at different falling film flow rates, hot water flow rates, and operating temperatures are investigated experimentally. The results demonstrated that the coefficient of performance and thermal efficiency of the system decrease with the increase in the flow rate of LiBr solution, and the influence of flow rate of hot water on COP and E_th is insignificant. The available COP in the experiments is higher than 0.4. The heat and mass transfer coefficients of the absorber increase with the increase of the flow rate of LiBr solution, up to 400W/m²/K and 0.013 kg/m²/s (temperature of waste heat is 90°C). The heat transfer coefficient of the absorber increases with the increase of the temperature of waste heat, and decreases with the increase of the cooling water temperature. Meanwhile, the computer code ABSIM (Absorption Simulation) is used to simulate the AHT systems, and the simulated results are compared with the experimental data.     

带相变蓄热小型热泵冷凝热回收性能实验研究

通过实验初步研究了采用光管螺旋相变蓄热器替代传统水蓄热器的小型家用热泵冷凝热回收系统的性能,对相变蓄热和水蓄热的冷凝热回收过程进行了对比实验,分析并得到了两类冷凝热回收系统的性能参数及综合能效系数。实验数据表明:与水蓄热系统相比,光管螺旋相变蓄热器体积减小,并且系统运行较传统水蓄热工况下更加平稳,但存在传热效果较差、热回收率低的缺点,回收率仅为15%,系统综合能效系数2.9。可知,相变蓄热器的内部结构对系统综合能效系数影响很大。     

An experimental and theoretical investigation into the heat transfer of a finned water wall tube in a circulating fluidized bed boiler

Heat transfer improvement in a water wall tube with fins was investigated in a circulating fluidized bed (CFB) boiler. Experiments were first conducted in a 6 MWth CFB boiler then a model was developed to analyse and interpolate the results. Temperatures at some discrete points within the wall cross‐section of the tube were measured by burying 0.8 mm thermocouples within a tube. Experimental data showed an increase in heat absorption up to 45 per cent. A good agreement between measured and predicted values was noted. The distribution of temperature in the metal wall and of heat flux around the outer wall of a tube with longitudinal and lateral fins was analysed by numerical solution of a two‐dimensional heat conduction equation. Effects of bed‐to‐wall heat transfer coefficient, water‐to‐tube inside heat transfer coefficient, bed temperature, water temperature and thermal conductivity of the tube material on the heat flux around the water tube are discussed. The present work also examines the influence of the length of the longitudinal fin and the water tube thickness. Heat flux was highest at the tip of the longitudinal fin. It dropped, but increased again near the root of the lateral fin. Copyright © 2000 John Wiley & Sons, Ltd.