飞灰水活化团聚脱硫技术

循征流化床飞灰中含有较高的氧化钙和未燃烧碳，介绍一种流化床飞灰水活化团聚的脱硫技术，该技术主要优点是飞灰经过水活化团聚后，飞灰团聚颗粒的脱硫活性增强，在流化床中的停留时间增加，从而显著提高了钙的利用率和降低飞灰未燃烧碳含量。     

钙硫比和烟气量对灰钙循环烟气脱硫反应器脱硫效率影响的数值模拟

利用ICEM CFD 18.0软件,基于反应动力学实验结果,对额定蒸汽量40 t/h的煤粉锅炉配套的灰钙循环烟气脱硫反应器进行数值模拟,研究钙硫比和烟气量对脱硫效率的影响,同时把模拟结果和工业试验结果进行比较验证。结果表明:不同钙硫比下,反应器内SO2浓度均随反应器高度的增加先升高再降低;烟气脱硫效率随钙硫比的增加而升高,但当钙硫摩尔比从1.0增加到1.4时,脱硫效率无明显变化;不同烟气量条件下,从反应器底部到顶部SO2浓度均逐渐降低,烟气脱硫效率受烟气量影响较小,烟气量增大,脱硫效率略微减小。建议钙硫比和烟气量最佳取值分别为1.0和30 000 m3/h～40 000 m3/h。     

以煤焦混合物为燃料的循环流化床锅炉SO2排放特性

在工业运行的410 t·h^-1循环流化床锅炉上进行烟煤、70％烟煤＋30％石油焦和50％无烟煤＋50％石油焦的燃烧试验,研究了运行参数对SO₂排放特性的影响。结果表明,3种燃料均能达到良好的燃烧效果,炉内温度场分布均匀。在相同燃烧条件下,不同燃料SO₂排放量与其中的含硫量呈正相关关系。SO₂排放量随温度的升高先减小后增大,存在最佳脱硫温度;随钙硫比的增大而减小;随过量空气系数的增大而减小;随飞灰再循环量的增大而减小。对于不同种类的石灰石,大比表面积和高比孔容积的石灰石对SO₂有较好的脱除效果。考察了燃用不同燃料的最佳温度、钙硫比和过量空气系数,阐述了飞灰再循环和石灰石微观结构在循环流化床锅炉脱硫中的机理和作用,以期对循环流化床的设计和运行工作提供指导。     

清华推出烟气脱硫新技术

清华同方股份有限公司近日推出干式循环流化床烟气脱硫技术。该技术是清华大学独立开发的自有产权技术 ,其技术特点是在锅炉尾部利用循环流化床技术进行烟气脱硫。该技术已获得国家专利。该技术以锅炉飞灰作循环物料 ,反应器内固体颗粒浓度均匀 ,固体内循环强烈 ,气固混合、接触良好 ,气固间传热、传质十分理想。向反应器内喷入消石灰浆液 ,使浆液得以附着在固体颗粒表面 ,造成气液两相间极大的反应表面积 ;固体物料被反应器外的高效旋风分离器收集 ,再回送至反应器 ,使脱硫剂反复循环 ,在反应器内的停留时间延长 ,从而提高脱硫剂的利用率 ,…     

基于Aspen Plus的0.3MWth CFB燃煤中试装置全流程模拟

循环流化床锅炉具有煤种适应性广,负荷调节能力强,污染物超低排放等优点,被广泛应用于煤的清洁燃烧。为探究循环流化床污染物生成和排放规律,以0.3 MWthCFB燃煤中试装置系统为实际模型,利用Aspen Plus对煤燃烧和污染物控制装置全流程建模。采用Gibbs最小自由能热力学分析方法对煤燃烧产物进行了分析计算,并利用软件自带的灵敏度分析工具,对不同的操作参数进行了灵敏度分析,预测了锅炉运行参数对烟气组分、选择性催化还原脱硝效率和石灰石-石膏湿法烟气脱硫效率的影响规律,获得了过量空气系数、烟气温度、氨氮比和钙硫比对NOx和SOx脱除效率以及SO3生成的影响曲线。结果表明,在循环流化床煤燃烧条件下,温度变化对NOx和SOx的生成影响显著,温度升高会促进NH3、HCN等前驱物的转化,促进燃料氮生成NOx;高温条件下,SO2生成反应的化学平衡向正方向移动,但反应速率会随温度和浓度的升高而降低,SO3则与之相反。在选择性催化还原脱硝过程中,较低温度时,脱硝率随温度升高而增加,最佳活性温度在360℃左右; SCR反应温度低于380℃时,SO3含量呈显著上升趋势,380℃出现一极大值点,而后趋于平缓并略有下降。NSR1时,脱硝率随氨氮比增加而增加,最佳氨氮比在1.05。湿法烟气脱硫过程中,增加钙硫比能明显提高脱硫效率,最佳钙硫比在1.05左右,并降低SO3排放;脱硫系统入口烟气温度升高会导致脱硫效率降低,但促进了SO3的生成。     

石灰石粒度和品质对干法脱硫效率的影响

使用Catlab反应器,采用100 m L/min的模拟烟气(二氧化碳、氧气、氮气、二氧化硫、水蒸气的体积比为15∶13.6∶61.2∶0.2∶10)连续循环30次,对4种不同品质的石灰石在4种不同粒度条件下对二氧化硫的脱除效果进行研究。结果表明,采用镁含量较低的石灰石,当脱硫反应总时间小于60 min时,单位时间的脱硫效率随石灰石粒径的减小而增大,当反应时间大于60 min以后,脱硫效率受石灰石粒径影响的趋势变缓。采用镁含量较高的石灰石,当脱硫反应总时间小于30 min时,单位时间的脱硫效率随石灰石粒径的减小而增大,当反应时间大于30 min以后,脱硫效率受石灰石粒径影响的趋势变缓。气固脱离反应过程符合固体产物层扩散控制的缩核模型,所以当石灰石中含有一定量二氧化硅时,由于二氧化硅在循环流化床锅炉工况温度下不会与其他组分发生反应,所以二氧化硅存在的位置均成为气态二氧化硫的扩散通道,从而有利于更多氧化钙参与脱硫反应。     

燃煤流化床锅炉炉内脱硫工业化技术研究

采用石灰石作为燃煤循环流化床锅炉炉内脱硫剂,当石灰石粒径为1.5~2.0 mm,流化床锅炉炉内钙硫摩尔比为2.7,床温为880℃时,尾气中的SO_2排放浓度为173 mg/m~3,无需进行锅炉尾气二次脱硫即可满足《锅炉大气污染物排放标准》要求,同时,炉内脱硫反应对锅炉效率的影响甚微,锅炉运行综合经济及环保效益最佳。     

CO2活化CaCO3作为脱硫剂的半干法烟气脱硫实验研究

CaCO3脱硫剂对SO2的化学反应活性直接影响其烟气脱硫效率和脱硫剂的利用率.提高CaCO3的脱硫反应活性,对降低烟气脱硫生产成本具有重要的意义.在高1.1 m、内径12.5 cm的流化床反应器内的半干法烟气脱硫过程中,利用CO2气体为活化介质对CaCO3脱硫剂浆液进行活化处理,并以活化后的CaCO3为脱硫剂,实验研究了CO2活化对CaCO3脱硫剂烟气脱硫效率的影响.结果表明,CO2气体对CaCO3的活化处理,增大了CaCO3在溶液中的溶解度,提高了CaCO3与SO2间反应的活性,促进了CaCO3脱硫剂烟气脱硫效率的显著提高.在实验条件下,当饱和接近度为15～18 K、钙硫比为1.2、脱硫剂粒径为64 μm时,经CO2气体活化后的CaCO3脱硫剂其脱硫效率达到92%,接近于相同条件下Ca(OH)2的脱硫效率.该研究结果为提高CaCO3脱硫剂的烟气脱硫反应活性,提供了一种新的工艺技术方法.     

煤粉炉和循环流化床锅炉飞灰吸附汞动力学及其吸附机制

在固定床吸附反应器内对两台300MW等级燃煤发电机组循环流化床锅炉和煤粉锅炉飞灰样品进行气相零价汞吸附实验,通过改变实验工况研究温度、入口汞浓度和入口气体流量对飞灰汞吸附能力的影响。采用颗粒内扩散模型、准一阶和准二阶动力学模型、耶洛维奇（Elovich）模型对实验数据分别进行拟合,从动力学的角度探讨两种锅炉飞灰对气相零价汞吸附的影响机制以及两种锅炉飞灰与气相零价汞之间吸附动力学行为差异。结果表明：相同工况下循环流化床锅炉飞灰汞吸附过程的穿透时间和平衡吸附量远大于煤粉锅炉飞灰。吸附温度为150℃时,两种锅炉飞灰对气相零价汞的平衡吸附量最大。由于外扩散阻力随气体入口流量的增加而减小,入口汞浓度的增加可提高传质推动力,飞灰对汞的吸附得以增强。动力学分析表明飞灰的零价汞吸附由外扩散、内扩散和表面化学吸附共同控制,其中表面化学吸附是该吸附过程中的控制步骤;准二阶动力学模型和Elovich动力学模型更适合于描述该吸附过程。相同实验条件下,循环流化床锅炉飞灰吸附过程拟合所得的颗粒内扩散系数、准一阶动力学常数和初始吸附速率均大于煤粉锅炉飞灰。     

煤粉炉和循环流化床锅炉飞灰吸附汞动力学及其吸附机制

在固定床吸附反应器内对两台300MW等级燃煤发电机组循环流化床锅炉和煤粉锅炉飞灰样品进行气相零价汞吸附实验,通过改变实验工况研究温度、入口汞浓度和入口气体流量对飞灰汞吸附能力的影响。采用颗粒内扩散模型、准一阶和准二阶动力学模型、耶洛维奇(Elovich)模型对实验数据分别进行拟合,从动力学的角度探讨两种锅炉飞灰对气相零价汞吸附的影响机制以及两种锅炉飞灰与气相零价汞之间吸附动力学行为差异。结果表明:相同工况下循环流化床锅炉飞灰汞吸附过程的穿透时间和平衡吸附量远大于煤粉锅炉飞灰。吸附温度为150℃时,两种锅炉飞灰对气相零价汞的平衡吸附量最大。由于外扩散阻力随气体入口流量的增加而减小,入口汞浓度的增加可提高传质推动力,飞灰对汞的吸附得以增强。动力学分析表明飞灰的零价汞吸附由外扩散、内扩散和表面化学吸附共同控制,其中表面化学吸附是该吸附过程中的控制步骤;准二阶动力学模型和Elovich动力学模型更适合于描述该吸附过程。相同实验条件下,循环流化床锅炉飞灰吸附过程拟合所得的颗粒内扩散系数、准一阶动力学常数和初始吸附速率均大于煤粉锅炉飞灰。     

Removal of mercury in aqueous solution by fluidized bed plant fly ash

Coal combustion in power plant produces fly ash. Fly ash may be used in water treatment to remove mercury (Hg²⁺) from water or to immobilize mercury mobile forms in silts and soils. Experiments were carried out on two kinds of fly ashes produced by two circulating fluidized bed plants with different chemical composition: silico-aluminous fly ashes and sulfo-calcic fly ashes. For the two kinds of fly ashes, adsorption equilibrium were reached in 3 days. Furthermore, removal of mercury was increased with increasing pH. Sulfo-calcic fly ashes allow us to remove mercury more efficiently and more steady. The chemical analysis of fly ash surface was carried out by electron spectroscopy. The results show that mercury is bound to ash surface thanks to several chemical reactions between mercury and various oxides (silicon, aluminium and calcium silicate) of the surface of the ashes.     

Experimental and model investigation on the mass balance of a dry circulating fluidized bed for flue gas desulfurization system

A moderate temperature dry circulating fluidized bed flue gas desulfurization (CFB-FGD) process was developed using rapidly hydrated sorbent. This technique has the advantages of low cost, no water consumption, and a valuable dry product CaSO₄. To keep the system operation stable, a mass balance model, based on cell model considering flow state, particle abrasion, particle residence time, particle segregation and desulfurization processes, was built to predict the system state and optimize the operating condition. Experimental studies were conducted on a pilot-scale CFB-FGD system with rapidly hydrated sorbent made from CFB circulating ash and lime (circulating ash sorbent) or coal fly ash and lime (coal fly ash sorbent). Calculated results were compared with experimental results and the relative error was less than 10%. The results indicated that feed sorbent mass, feed sorbent size, superficial gas velocity, particle abrasion coefficient and cyclone efficiency had significant influence on the mass balance of CFB system. The circulating ash sorbent was better than the coal fly ash sorbent, for providing higher desulfurization efficiency and being better for the CFB-FGD system to achieve mass balance.     

Effect of ash compositions on air pollutant emissions during fluidized bed sludge incineration

A simulation using a thermodynamic equilibrium model was performed to predict the effect of ash compositions on the behavior of air pollutants during fluidized bed sludge incineration. To investigate emission characteristics, the incineration temperature, air-fuel ratio (λ_T) and contents of calcium and chlorine were chosen as major operating parameters. For the analyses of the desulfurization of SO_x and the pollutant emissions by the limestone addition, the Ca/S molar ratio was changed from 0.5 up to 7.0. According to the simulation, NO_x was not influenced markedly by the air-fuel ratio, though greatly influenced by operating temperature. The effect of desulfurization with limestone addition was greatly influenced by ash composition, and desulfurization occurred over the Ca/S molar ratio of 5.5. This was attributed to the fact that the reactivity of the P component in ash to the added CaO was higher than that of sulfur in fuel.     

粉煤灰负载的钙基脱硫剂的制备

针对目前干法烟气脱硫工艺吸收剡利用率低、用量大等问题,开发以粉煤灰、Ca（OH）2、活化剂为主要原材料,通过固相反应／水热化合反应过程制备粉煤灰负载的高效钙基脱硫剂,其脱硫效果采用流动床气一固催化测试装置测定,脱硫率可达93％。     

Effect of bed materials and additives on the sintering of coal ashes relevant to agglomeration in fluidized bed combustion

Agglomeration propensity of Thai low-rank coal ashes was determined by measuring the compressive strength of sintered ash pellets over the temperature range of fluidized bed combustion. Physical and chemical changes of the sintered products were ascertained from scanning electron microscope-energy dispersive X-ray detection (SEM-EDX) and X-ray diffractometry (XRD). A clear difference existed in the strength–temperature relationship between these ashes. This difference was attributed to the role and relative amounts of clays and anhydrite components that form the low temperature melting eutectics. The bed materials (sand, CaO, CaCO₃, and CaSO₄) and additives (gibbsite and andalusite) when combined with the ashes caused a strength reduction due to the inert dilution effect that prevented the interaction of anhydrite and clays. To comprehend the mechanism of sintering and bed agglomeration more clearly, modified ashes which produced extra amount of amorphous silicate materials were prepared and tested. The bed materials and additives, when sintered with these modified ashes, gave reduction of pellet strength by varying extents based on three possible mechanisms namely, a pure inert effect, an inert/reaction effect and an inert/adsorption effect, with gibbsite being the most effective. Of the four test ashes, Lanna ash was the only ash that exhibited almost no strength development under all conditions, due principally to its very low clays content and relatively stable forms of mineralogical compositions.     

利用循环流化床灰渣制备控制性低强度材料的研究

在分析循环流化床灰渣物理、化学性质的基础上,探讨了利用流化床灰渣代替粉煤灰制备控制性低强度材料(Con-trolled low strength material,简称CLSM)的可行性。实验结果表明:(1)掺加适量流化床灰渣(40%~60%)可制备性能优良的CLSM材料,其中流化床灰渣可使CLSM浆体的泌水率降低、凝结时间大幅度缩短、贯入阻力增大;(2)流化床灰渣与粉煤灰复合掺加可产生强度的"超叠加"效应,大幅度提高CLSM硬化浆体的强度;(3)堆存过程中流化床灰渣水化生成的钙矾石和二水石膏是稳定的,不会引起CLSM硬化体的有害膨胀。     

城市污泥流化床中低温空气气化及重金属迁移特性

利用自行搭建的流化床热态实验装置，系统研究了污泥的中低温气化及重金属迁移特性。研究表明，对冷煤气效率和碳转化率影响最大的是气化温度，其次是空气当量比，而一二次风配比和流化数影响较弱。污泥中低温气化的焦油产率较之高温气化明显增加。随着二次风占比和空气当量比的提高，焦油产率单调下降。气化温度由600℃升至850℃，冷煤气效率和碳转化率均呈升高趋势；空气当量比由0.2升至0.4，冷煤气效率呈先升高后下降的趋势，在0.3时达到最大值，而碳转化率则呈单调升高趋势。随着气化温度的升高，污泥中重金属转移至产气、焦油及飞灰的迁移率升高。随着空气当量比的升高，Ni、Cu的迁移率降低，Cr升高，Cd、Zn、As和Pb等其他重金属的迁移率几乎不变。     

Characteristics and composition of fly ash from Canadian coal-fired power plants

Fly ashes were collected from the electrostatic precipitator (ESPs) and/or the baghouse of seven coal-fired power plants. The fly ashes were sampled from power plants that use pulverized subbituminous and bituminous feed coals. Fly ash from bituminous coals and limestone feed coals from fluidized-bed power plant were also sampled. The fly ashes were examined for their mineralogies and elemental compositions. The fly ashes from pulverized low sulfur coals are ferrocalsialic, those from high sulfur coals are ferrosialic and the fly ashes from the fluidized bed coals are ferrocalcic. The concentrations of As, Cd, Hg, Mo, Ni, and Pb in fly ash are related to the S content of the coal. Generally, those feed coals with a high S content contain higher concentrations of these elements. The concentrations of these elements are also greater for baghouse fly ash compared to ESP fly ash for the same station. The S content of fly ash from high S coal is 0.1% for pulverized ESP fly ash and 7% for baghouse fly ash from the fluidized bed, indicating that most of the S is captured by fly ash in the fluidized bed. The baghouse fly ash from the fluidized bed has the highest content of Cd, Hg, Mo, Pb, and Se, indicating that CaO, for the most part, captures them. Arsenic is captured by calcium-bearing minerals and hematite, and forms a stable complex of calcium or a transition metal of iron hydroxy arsenate hydrate [(M²⁺)₂Fe₃(AsO₄)₃(OH)₄·10H₂O] in the fly ash. Most elements in fly ash have enrichment indices of greater than 0.7 indicating that they are more enriched in the fly ash than in the feed coal, except for Hg in all ESP ashes. Mercury is an exception; it is more enriched in baghouse fly ash compared to ESP. Fly ash collected from a station equipped with hot side ESP has a lower concentration of Hg compared to stations equipped with cold side ESP using feed coals of similar rank and mercury content. Fly ash particles from fluidized bed coal are angular and subangular with cores of quartz and calcite. The quartz core is encased in layer(s) of calcium-rich aluminosilicates, and/or calcium/iron oxides. The calcite core is usually encased in an anhydrite shell.