Design and application of a novel coal-fired drum boiler using saline water in heavy oil recovery

In this paper, the design and operation of a novel coal-fired circulating fluidized bed (CFB) drum boiler that can generate superheated steam using saline water were introduced. The natural circulation water dynamics with a drum was adopted instead of the traditional once-through steam generator (OTSG) design, so that superheated steam can be generated for the better performance of the steam assisted gravity drainage (SAGD) technology in heavy oil recovery. The optimized staged evaporation method was proposed to further decrease the salinity of water in the clean water section of the boiler. The evaporating pipes of the salted water section were rearranged in the back pass of the boiler, where the heat load is low, to further improve the heat transfer safety. A CFB combustion technology was used for coal firing to achieve a uniform heat transfer condition with low heat flux. Pollutant control technologies were adopted to reduce pollutant emissions. Based on the field test, the recommended water standard for the coal-fired CFB drum boilers was determined. With the present technology, the treated recovery wastewater can be reused in steam-injection boilers to generate superheated steam. The engineering applications show that the boiler efficiency is higher than 90%, the blowdown rate is limited within 5.5%, and the superheat of steam can reach up to 30 K. Besides, the heavy oil recovery efficiency is significantly improved. Moreover, the pollutant emissions of SO₂, NO_x and dust are controlled within the ranges of 20–90 mg/(N·m³), 30–90 mg/(N·m³) and 2–10 mg/(N·m³) respectively.     

浅析两个节能技术改造项目效果和效益

为了减少热电厂的热损失,提高能源利用率，提出了锅炉加续排污容蒸汽和汽轮机汽封漏汽冷凝水技术改造和回收利用方法，通过效益和效果分析，节能和环保显著。     

基于节能的工业锅炉的最优排污控制

提出了一种节能的排污控制方法。首先根据蒸汽流量,按一定比例平滑调节排污流量,实施按需排污,同时,按电导率组建闭环控制回路,克服底部排污及给水盐浓度变化等干扰。将以上两种控制原则结合组成复合控制系统,可把锅水盐浓度持续控制在允许值的上限,使排污量降到最低,获得最大的节能減排效果。     

Effect of Two-Phase Natural Circulation Distortion on Tube Failure in Steam Boilers

Two different cases of evaporator tube ruptures in power station boilers due to natural circulation distortion are presented. The first case discussed concerns a 110-MW, unit boiler with bottom evaporation tubing inclined at 15° to the horizontal. At the high heat fluxes present in the furnace, subcooled boiling occurs in inclined tubes. For these inclinations an insufficient flow rate causes local heat transfer deficiencies due to vapor-water separation. The introduction of internally finned tubes eliminates local heat transfer deficiencies and prevents further tube failures. The second case is that of circulation interruption due to blowdown during start-up. The water level in the drum of this second 110-MW, unit boiler was controlled by inlet header blowdown during start-up. Thus, natural circulation was interrupted, causing local overheating of evaporator tubing. The event was identified by an increase of the tube rupture frequency. After changing the blowdown procedure, the interruptions of natural circulation were avoided and the tube failure frequency decreased substantially.     

电站锅炉省煤器出口水温升高对过热器吸热的影响

讨论了某台200 MW燃煤自然循环锅炉省煤器改造后出口水温升高而造成的屏式过热器超温,根据锅炉锅筒欠焓计算与水冷壁产汽量计算,并结合炉膛换热及出口烟温计算,分析了省煤器出口水温与屏式过热器吸热量之间的内在联系。现行锅炉热力计算方法未考虑省煤器出口水温与炉膛内蒸发受热面产汽量的依赖关系,不能体现省煤器出口水温较大幅度变化对炉膛吸热量的影响。     

一台DZL6.0-1.25蒸汽锅炉水冷壁管爆管事故的分析与改进

从对一台ＤＺＬ６．０－１.２５蒸汽锅炉近前炉门附近两侧炉膛水冷壁管多次发生局部爆管事故的调查出发,对该锅炉侧集箱排污系统存在的设计缺陷进行了流动分析、计算。计算表明,排污时前段集箱内流速过低是造成该段集箱区水渣大量沉积致使该区水冷壁管因水渣堵塞而引发局部爆管的根本原因。对侧集箱不同部位增开排污口方案进行的计算表明,在集箱前端增开排污口可有效地改善排污时该处集箱内水的流动性,从而消除泥渣沉积隐患。改造方案实施后,经多年的锅炉安全运行实践也证明了该方案的有效性。     

汽包锅炉获得清洁蒸汽的方法

实践证明,从锅炉出来的蒸汽总是含有少量杂质,这些杂质会沉积在蒸汽通过的各个部位,影响发电机组的安全、经济运行,所以,如何获得清洁的蒸汽对发电厂来说很重要。讨论了汽包锅炉获得清洁蒸汽的方法。     

Improving Steam Boiler Operation by On-Line Monitoring of the Strength and Thermal Performance

The operation of steam boilers with high efficiency requires control of thermo-hydraulic and strength parameters in the on-line mode. During operation under transient conditions, there are significant temperature differences over the circumference of the horizontal pressure vessels. This occurrence is caused by the different values of heat transfer coefficients on the inner surface of the boiler drum in the water and steam region. Large thermal stresses can occur in partially filled horizontal vessels. This takes place in large steam generator drums, superheater headers, and steam pipelines. The paper presents a method for determination of thermo-flow parameters for steam boilers. This method allows performing the calculations of the boiler furnace chamber and heating flow rates absorbed by superheater stages. These parameters are important for monitoring the performance of the power unit and determining the degree of the furnace chamber slagging. Knowledge of these parameters allows determining the degree of the furnace chamber slagging. The calculation can be performed in online mode and use to monitoring of steam boiler. The presented method allows to the operation of steam boiler with high efficiency.     

锅炉连续排污利用对火电厂热经济性影响的机理研究

随着火电机组单机功率的增大,锅炉排污水压力提高,对蒸汽品质的要求也相应严格,锅炉排污水量和能位都在提高,锅炉排污及其利用越来越引起人们的普遍重视。但目前锅炉排污利用对全厂热经济性影响的机理尚存在不同的观点。首先对现有的几种锅炉排污及其利用对全厂经济性影响的计算方法进行了分析,指出其存在的问题。然后,以某600MW凝汽式电厂机组锅炉排污及其利用为例,对各种计算方法得到的计算结果进行分析比较,并分析了计算结果产生差异的主要原因。最后,揭示出锅炉排污及其利用对全厂热经济性影响的机理。所取得的结论为全厂节能诊断和挖掘节能潜力奠定了基础。     

Estimation of the effect of biomass moisture content on the direct combustion of sugarcane bagasse in boilers

Many of the large-scale biomass combustion systems for producing heat, hot water, or steam accept biomass fuels containing relatively large amounts of moisture. Dry biomass burns at higher temperatures and thermal efficiencies than wet biomass. Flame temperature is directly related to the amount of heat necessary to evaporate the moisture contained in the biomass, the lower the moisture content, the lower the amount of energy needed to remove the water and the higher the boiler efficiency. In this article, a simple predictive tool is developed to estimate boiler efficiency as a function of stack gas temperature and sugarcane bagasse moisture content. The method quantitatively illustrates the effect of moisture content on the performance of a thermochemical process, for the direct combustion of sugarcane bagasse in a conventional boiler. The results are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 1%. The tool developed in this study can be of immense practical value for engineers to have a quick check on biomass moisture content on the boiler performance at various conditions without opting for any experimental trials. In particular, engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.     

饱和蒸汽减温在燃机余热锅炉的应用

介绍了燃气－蒸汽联合循环电站余热锅炉过热蒸汽调温的一种方法－自身饱和蒸汽减温。对余热锅炉自身饱和蒸汽减温系统的设计进行了分析,指出了实际应用中应该注意的问题。     

Hydro-X锅炉水调节剂在供热机组中的应用与节能分析

传统锅炉防垢处理一般采用磷酸盐处理方式,通过保持炉水中的磷酸根含量,在锅炉运行条件下生成碱式磷酸钙水渣并随排污排走,其排污率高,浪费了大量热量及高品质炉水。通过采用Hydro-X锅炉水调节技术替代磷酸盐加药模式,有效抑制了汽水共沸,在保证蒸汽品质的前提下,提高了锅炉水的浓缩倍数,从而降低了锅炉的排污率,相应提高了锅炉的产汽量,达到了节能降耗的目的,在供热机组中具有推广及应用价值。     

锅炉排污余热利用方法简介

大多数工业锅炉房锅炉排污基本上是直．接排放,没有采取余热回收措施,造成锅炉排污余热资源的极大浪费。介绍一种直接利用锅炉排污余热预热锅炉送风的技术方法以及应用效果。     

300 MW机组锅炉水封水温对炉膛掉焦灭火的影响

炉膛掉焦是引起锅炉运行中灭火的主要原因。从焦块掉进水封产生的水蒸气升腾进入炉膛的角度,计算了炉膛中心温度和炉内水蒸气增量的关系。在假设焦块质量为1 t、焦块和水的换热时间为10 s、焦块和水的有效作用体积比在1～7的前提下,当水封温度从80℃降低至40℃时,结果表明,掉焦导致炉内的水蒸发率、水蒸气浓度体积比、炉内烟气温度降低量都显著减少。认为降低水封水温有助于减少掉焦时水蒸气逃逸量,从而降低掉焦时炉膛灭火的可能性。     

Prediction of silica carry-over and solubility in steam of boilers using simple correlation

Silica content of the boiler water is critical for steam turbines and scaling of boiler heat transfer surfaces. Silica (SiO₂) can volatilize with the steam in sufficient concentrations to deposit in steam turbines leading to scale formation on boiler surfaces. In this work, a simple correlation is presented to predict silica (SiO₂) solubility in steam of boilers as a function of pressure and water silica content. The solubility of silica in steam directly depends on both the density and temperature of steam. With decreasing temperature and density, solubility of silica reduces. As the pressure affects steam density which has a strong bearing on steam temperature, it has an important effect on the solubility of silica in steam. The proposed correlation predicts the solubility of silica (SiO₂) in steam for pressure up to 22,000 kPa and boiler water silica contents up to 500 mg/kg. The predictions from the proposed correlation have been compared with reported data and found good agreement with average absolute deviation being around 4%. This simple-to-use correlation can be of immense practical value for the engineers to have a quick check on silica (SiO₂) solubility in steam of boilers as a function of pressure and water silica content at various conditions without performing any experimental measurements. In particular, personnel dealing with the utility boilers would find the proposed approach to be user friendly involving no complex expressions with transparent calculations.     

电站锅炉省煤器设计与改造对过热汽温的影响

根据锅炉蒸发受热面工质侧产汽量与过热汽温之间的内在依赖关系 ,从热量和质量平衡原理出发 ,讨论了自然循环锅炉给水温度不变而省煤器出口水温偏离设计值时对过热汽温间接的影响规律。在电站锅炉尾部受热面的改造或设计中 ,为考虑其它因素而不得不改变省煤器的吸热量时 ,建议将锅炉烟气侧热力计算与工质侧的吸热产汽量计算结合起来 ,验算省煤器出口水温的变化对炉膛蒸发受热面工作以及过热汽温的影响。     

Estimation of potential savings from reducing unburned combustible losses in coal-fired systems

A potentially significant loss emanates from the combustion of coal fuels is usually called as the unburned carbon loss. All coal-fired steam generators and coal-fired vessels inherently suffer from efficiency debit attributable to unburnt carbon. The aim of this study is to develop a simple-to-use predictive tool which is easier than existing approaches, less complicated with fewer computations and suitable for engineers to determine the approximate potential savings resulting from reducing unburned coal fuel loss. The proposed method determines the benefits of reducing the combustible losses in terms of annual fuel savings for coal-fired units as a function of percent combustibles in ash, achievable percent combustibles in ash, unit design heat output and average fuel cost. Results show that the proposed predictive tool has a very good agreement with the reported data with average absolute deviation percent being around 1.77%. The proposed method is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly for various cases. The developed tool can be of immense practical value for the utility engineers to have a quick check on the benefits of reducing the combustible losses in terms of annual fuel savings for a coal-fired unit for wide range of operating conditions without the necessity of any pilot plant set up and experimental/plant trials. In particular, practice engineers would find the methodology to be user friendly involving transparent calculations with no complex expressions for the design and operation of coal-fired systems such as furnaces and boilers.     

余热锅炉汽包壁温差控制策略

阐述燃气-蒸汽联合循环启停操作过程中汽包壁温差大的现象，从余热锅炉汽包结构特点和启停过程 传热特性入手，详 热锅炉汽包 的原因，找到热锅炉负荷 汽包 大的 影 响因素。 运 优化操作包括 热锅炉汽包 、改汽包升温升 率、加快热锅炉 ， 停 汽包上、下 大，对于优化余热锅炉启停操 制汽包上、下.差 的燃气 电厂有借鉴 。     

A model on water level dynamics in natural circulation drum-type boilers

A model for water level dynamics in the drum-riser-downcomer loop of a natural circulation drum-type boiler is presented. The model is based on basic conservation rules of mass, momentum, and energy, together with well-known constitutional equations. Steam–water mixture in a drum is divided into three sub-volumes; water, steam above and below water level, and a mass balance relation is applied to each sub-volume. The amount of steam under water level is predicted using two constitutional equations for condensation rate and rise velocity of steam. The constitutional equations entail uncertain values such as superficial velocity of water and average size of steam bubbles in a drum. The superficial velocity of water is assumed to be zero and its effect is compensated by a mechanistic model on movement of the water level. Average size of steam bubbles is assumed to be an arbitrary value and its effect on the dynamics is investigated through sensitivity analysis. The model enables one to investigate the water level dynamics for changes in steam demand and/or heating rate simply from basic design values. Simulation results are compared with those in the literature in which an empirical model for the steam bubble dynamics is employed. The presented model shows a reasonable prediction of water level for a change in steam demand.     

Generalized predictive control of steam pressure in a drum boiler

An application of generalized predictive control (GPC) to superheat steam pressure of a 200 MW drum boiler is presented. The system performance is evaluated by computer simulation, using a detailed nonlinear boiler model, and compared with that obtained using conventional PI (proportional-integral) control. Results show a significant improvement in performance over a wide range of operating conditions