Desulfurization characteristics of slaked lime and regulation optimization of circulating fluidized bed flue gas desulfurization process--A combined experimental and numerical simulation study

Circulating fluidized bed flue gas desulfurization(CFB-FGD) process has been widely applied in recent years. However, high cost caused by the use of high-quality slaked lime and difficult operation due to the complex flow field are two issues which have received great attention. Accordingly, a laboratory-scale fluidized bed reactor was constructed to investigate the effects of physical properties and external conditions on desulfurization performance of slaked lime, and the conclusions were tried out in an industrial-scale CFB-FGD tower. After that, a numerical model of the tower was established based on computational particle fluid dynamics(CPFD) and two-film theory. After comparison and validation with actual operation data, the effects of operating parameters on gas-solid distribution and desulfurization characteristics were investigated. The results of experiments and industrial trials showed that the use of slaked lime with a calcium hydroxide content of approximately 80% and particle size greater than 40 μm could significantly reduce the cost of desulfurizer. Simulation results showed that the flow field in the desulfurization tower was skewed under the influence of circulating ash. We obtained optimal operating conditions of 7.5 kg·s^(-1)for the atomized water flow, 70 kg·s^(-1)for circulating ash flow, and 0.56 kg·s^(-1)for slaked lime flow, with desulfurization efficiency reaching 98.19% and the exit flue gas meeting the ultraclean emission and safety requirements. All parameters selected in the simulation were based on engineering examples and had certain application reference significance.

Experimental Studies on a Circulating Fluidized Bed for Flue Gas Desulfurization

The tests of flue gas desulfurization were carried out on a circulating fluidized bed reactor in which the flue gas had different velocities at different sections. The SO 2 removal efficiency could be as high as 80% when Ca/S molar ratio was 1 1 and a small amount of water was sprayed into the reactor by a two phase (gas liquid) system nozzle.

Cold-modeling study of a circulating fluidized bed reactor for flue gas desulfurization (FGD)

Short residence time of the sorbent in the gas stream and formation of a dense layer of reaction product surrounding its surface influence the sulfur removal efficiency. A practical means of improving the process performance is to employ fluidized bed reaction in replacement of entrained bed reaction on normally used in cool side desulfurizaiton. This paper describes cold modeling study of a circulating fluidized bed reactor. Several aspects of the problem are discussed: fluidization behavior of CaO, attrition of the sorbent and solids entrainment from the fluidized bed. Mechanisms and key controlling parameters are identified, and an integral model based on rate of attrition and mass balance is developed for predicting steady state mass flows and particle size distributions of the system. A process flow scheme is finally presented for conducting desulfurization tests in the second stage of the study.

Experimental and mechanism studies on simultaneous desulfurization and denitrification from flue gas using a flue gas circulating fluidized bed

The oxidizing highly reactive absorbent was prepared from fly ash,industry lime,and an oxidizing additive M.Experiments of simultaneous desulfurization and denitrification were carried out in a flue gas circulating fluidized bed(CFB).The effects of influencing factors and calcium availability were also investigated on the removal efficiencies of desulfurization and denitrification.Removal efficiencies of 95.5%for SO2 and 64.8%for NO were obtained respectively under the optimal experimental conditions. The component of the spent absorbent was analyzed with chemical analysis methods.The results in- dicated that more nitrogen species appeared in the spent absorbent except sulfur species.A scanning electron microscope(SEM)and an accessory X-ray energy spectrometer were used to observe micro-properties of the samples,including fly ash,oxidizing highly reactive absorbent and spent absorbent.The simultaneous removal mechanism of SO2 and NO based on this absorbent was pro- posed according to the experimental results.

SO_2 emission characteristics from co-firing of petroleum coke and coal in circulating fluidized bed

Combustion and sulfur retention experiments of mixed fuel of petroleum cokeand coal were conducted on a pilot-scale circulating fluidized bed (CFB) combustor with the thermalinput of 0. 6 MW. The effects of several parameters, such as the primary air percentage, excess aircoefficient, bed temperature, Ca/S molar ratio and mass ratio of petroleum coke to coal on SO_2emission were verified. Experimental results show that when the ratio of petroleum coke to coal inthe mixed fuel increases, the SO_2emission increases. The maximum SO_2 emission appears when purecoke burns. The SO_2 concentration in flue gas reduces with the increase in the primary airpercentage, excess air coefficient and Ca/S molar ratio for all kinds of fuel mixtures. Therangebetween 830 t and 850 t is the optimal temperature for sulfur retention during co-firing ofpetroleum coke and coal with the mass ratio R of 1 and 3 in CFB.

The Carbonation Behaviors of Limestone Particle in Oxygen-Fuel Circulating Fluidized Bed O₂/CO₂Flue Gas

Limestone powder is still applied as SO2 sorbent in emerging oxygen-fuel circulating fluidized bed boiler, but its carbonation in O2/CO2 flue gas is an unclear problem. For a better understanding of carbonation behaviors, the tube furnace heating system was built for simulating circulating fluidized bed boiler flue gas by regulating the supply of O, CO2, N2, SO2 and H2O, and Carbonation reaction was tested. Thermal gravimetric analysis and scanning electron microscopy were used. It was found that carbonation is closely related to temperature, CO2 concentration, impurities, water vapor, and cycle times;high temperature can promote carbonation process;high concentration of CO2 can inhibit the chemical reaction stage speed of carbonation process, but it has little effect on the final conversion rate;water vapor can increase the final conversion rate of carbonation;the cycle times will reduce the activity of carbonation. The presence of carbonation turns the traditional boiler flue gas indirect desulfurization model into indirect desulfurization mechanism which does not have a negative impact on SO2 removal efficiency.

Activity and characteristics of ＂Oxygen-enriched＂ highly reactive absorbent for simultaneous flue gas desulfurization and denitrification

An ＂Oxygen-enriched＂ highly reactive absor- bent was prepared by mixing fly ash, lime and a small quantity of KMnO4 for simultaneous desulfiarization and denitrification. Removal of SO2 and NO simultaneously was carried out using this absorbent in a flue gas circulating fluidized bed （CFB）. The highest simultaneous removal efficiency, 94.5% of SO2 and 64.2% of NO, was achieved under the optimal experiment conditions. Scanning Electron Microscope （SEM） and Accessory X-ray Energy Spectrometer （EDX） were used to observe the surface characteristics of fly ash, lime, ＂Oxygen-enriched＂ highly reactive absorbent and the spent absorbent. An ion chromatograph （IC） and chemical analysis methods were used to determine the contents of sulfate, sulfite, nitrate and nitrite in the spent absorbents, the results showed that sulfate and nitrite were the main products for desulfurization and denitrification respectively. The mechanism of removing SO2 and NO simultaneously was proposed based on the analysis results of SEM, EDX, IC and the chemical analysis methods.

一电厂热工控制DCS系统设计

以西山孝义金岩公司自备电厂为背景,主要结合循环流化床锅炉机组的运行特点和控制特性,对其热工系统运用集散控制方式进行控制,并采用浙大中控的WebFiled JX-300X系统对单元机组的热工控制系统做了初步的整体设计。

基于DCS的循环流化床锅炉床温模糊控制技术

循环流化床锅炉是一个具有分布参数、非线性、时变、大滞后、多变量紧密耦合的多输入多输出的变参数系统,常规控制方法难以取得理想的控制效果。该文根据循环流化床锅炉运行特性,提出基于DCS实现的循环流化床锅炉床温模糊控制技术,实践表明控制效果理想,具有良好的应用前景。

基于DCS的循环流化床锅炉节能减排自控系统研究

该文针对燃煤电厂循环流化床锅炉大气污染物排放问题,基于DCS技术和脱硝脱硫工艺,设计开发了循环流化床锅炉节能减排自控系统,实现了烟气脱硝、脱硫的全工况监测与控制。系统现场运行结果表明,系统能够较好地控制循环流化床锅炉烟气中SO2和氮氧化物排放浓度,实现节能减排目标,保证发电项目的顺利进行。

基于PLC的煤泥泵送系统纳入DCS的技术改造

以某发电有限公司300 MW联合循环流化床#2机组煤泥泵送系统中的PLC控制系统为改造对象,基于上海新华控制技术(集团)有限公司XDC800 DCS系统进行组态、调试、投运,把原有控制的煤泥泵送系统纳入到机组DCS控制系统中,实现集控室远端集中控制,使煤泥泵送系统的运行和维护变得简捷、直观、全面,是此次全厂DCS一体化技术的实施内容,对类似煤泥泵送系统的DCS化改造具有借鉴意义。

DCS在循环流化床锅炉的应用一例

介绍了DCS在循环流化床锅炉的应用一例,并讨论了它的功能。

引进 410t/h 循环流化床锅炉 DCS 控制系统

循环流化床锅炉与常规的煤粉炉有较大的差别。本文介绍了４１０ｔ／ｈ循环流化床锅炉所用ＤＣＳ控制系统网络结构。概要介绍了应用处理器、操作处理器、通讯处理器及控制处理器的功能和作用，以及控制的内容。

DCS在中小型循环流化床机组自动化控制中的应用

从工程实际出发,对中小型循环流化床机组自动化控制进行了探讨。本文站在DCS控制的角度,分别从DCS控制必要性、循环流化床汽轮发电机组DCS控制等方面,就如何以科学、合理的方式,实现适合中小型循环流化床机组的DCS控制,阐述个人的一点体会。

基于TDCS9200的循环流化床锅炉控制系统设计与开发

针对循环流化床锅炉的工艺特点和控制需求，开发了基于TDCS9200-DCS系统的循环流化床锅炉控制系统。该文详细介绍了该控制系统的技术方案和系统特点。该系统实现了锅炉的自动控制，试运行结果表明，达到了规定的设计性能指标并能满足工艺要求。

循环流化床锅炉DCS控制方案

介绍了循环流化床锅炉控制系统在DCS控制系统中的组态应用。对循环流化床主要的自动控制系统进行了分析,给出了DCS控制系统的配置方案,并对其实现的主要功能进行了介绍。

霍尼韦尔PKS430 DCS系统在480t/h CFB燃烧与蒸汽自动控制中的应用研究

在循环流化床(CFB)锅炉应用越来越广泛的背景下,结合工程设计与实际调试、运行经验,采用国际知名品牌霍尼韦尔DCS控制系统实现锅炉复杂控制回路的自动控制。锅炉装置的核心作用是通过燃料燃烧产出合格蒸汽,推动下游汽轮机做功。实现锅炉负荷自动控制,需综合考虑燃烧与蒸汽综合自动控制,可极大程度提升锅炉效率。CFB锅炉燃烧与蒸汽综合控制,具体涉及锅炉负荷控制、风量控制、燃料控制等多项控制策略。其中,理解工艺过程、熟悉控制系统、清楚被控对象过程特性和深入参与现场调试工作,对获得良好的控制效果是非常重要的。结合运行经验,针对复杂控制回路研究控制策略实现控制非常有意义[1]。

Geldart C类脱硫灰颗粒在环流耦合提升管内稳定流动特性

我国CO_(2)的排放中70%来自工业领域,故工业过程的碳捕集对实现“双碳目标”十分关键。工业烟气中往往含有的硫氧化物会腐蚀设备并使后续脱碳等过程使用的催化剂中毒。因此,工业烟气的深度脱硫技术对后续的CO_(2)捕集或提纯过程至关重要。循环流化床半干法烟气脱硫因具有脱硫效率高、无污染、停留时间可控等优点受到广泛关注。循环流化床脱硫工艺中作为脱硫剂的脱硫灰颗粒为典型Geldart C类颗粒。由于C类颗粒的强黏附性,其在循环流化床操作中容易结块,从而影响装置稳定运行。为了强化脱硫灰颗粒在循环流化床内的流动稳定性,提出了环流强化的耦合提升管反应器的概念,并自行设计搭建了一套导流筒内径100 mm、高度300 mm,外筒内径160 mm、高度760 mm,输送段内径75 mm、总高度12.6 m的环流耦合提升管。在U_(g)=4 m/s、G_(s)=45 kg/(m^(2)·s),U_(g)=7 m/s、G_(s)=25 kg/(m^(2)·s)的操作条件下,考察了环流段的压力分布、标准差以及功率谱密度。当环隙区气速为0.4 m/s时,环流流动能够实现稳定、连续的密相环流流动。在C类颗粒形成稳定流动基础上,讨论了环流耦合提升管内的流动特性分布规律,包括固含率和颗粒速度。实验发现,环流流动的设计可以强化C类颗粒的流动特性,大幅提高耦合反应器内C类颗粒脱硫灰固含率,并实现了C类颗粒循环流态化装置的稳定运行。同时,这些研究结果可以为C类颗粒新型循环流态化反应器设计提供参考。

循环流化床锅炉及其DCS控制系统

针对循环流化床锅炉的运行控制特点,研究了循环流化床运行过程中床温控制、燃烧控制、风量控制以及传热控制等过程。对循环流化床锅炉工艺要求进行探究,分析了循环流化床锅炉控制特点以及难点,并对循环流化床的DSC控制系统的子控制系统进行设计。

DCS在循环硫化床锅炉安装调试中的应用

从DCS对环境的要求、接地的要求、电缆敷设的要求等方面,阐述了DCS的安装要求,对DCS调试中存在的主要问题进行了分析,并提出了一些针对性的改进措施。