Improved Robust Adaptive Control of a Fluidized Bed Combustor for Sewage Sludge

This paper presents a robust model reference adaptive control scheme to deal with un-certain time delay in the dynamical model of a ?uidized bed combustor for sewage sludge. Thetheoretical analysis and simulation results show that the proposed scheme can guarantee not onlystability and robustness, but also the adaptive decoupling performance of the system.

Incineration of Municipal Sewage Sludge in a Fluidized Bed Reactor

In the present study reduction of nitrogen oxides using reburning technology, during combustion of sewage sludge (fuel I) and the mixture of sewage sludge, wasted bleaching earth and CaO (fuel II), was carried out. The experimental works were conducted in a laboratory-scale fluidized bed reactor (power up to 10 kW) with application of two types of beds: chemically inert bed (sand) and chemically active bed (CaO). The second combustion (reburning) zone in the reactor was formed by dosing into an area above the bed, additional gaseous fuel (propane). Obtained reduction in emissions of nitrogen oxides in both types of beds was at a level 70% - 79%. Additionally bed of CaO has the desulfurizing effect and also reduces the CO concentration in the exhaust fumes. A significant drawback of active bed is the adverse effect on increase of the primary NO which enters the second combustion zone. The result of this fact is higher NOx emission during combustion of the same fuel in bed of CaO in comparison to the combustion of this fuel in the sand bed, when the same maximum degree of reduction of NOx will be obtained for both types of beds.

Simulation of gas-solid flow characteristics of the circulating fluidized bed boiler under pure-oxygen combustion conditions

Under the pressure of carbon neutrality,many carbon capture,utilization and storage technologies have witnessed rapid development in the recent years,including oxy-fuel combustion(OFC)technology.However,the conventional OFC technology usually depends on the flue gas recirculation system,which faces significant investment,high energy consumption,and potential low-temperature corrosion problem.Considering these deficiencies,the direct utilization of pure oxygen to achieve particle fluidization and fuel combustion may reduce the overall energy consumption and CO_(2)-capture costs.In this paper,the fundamental structure of a self-designed 130 t·h^(-1) pure-oxygen combustion circulating fluidized bed(CFB)boiler was provided,and the computational particle fluid dynamics method was used to analyze the gas-solid flow characteristics of this new-concept boiler under different working conditions.The results indicate that through the careful selection of design or operational parameters,such as average bed-material size and fluidization velocity,the pure-oxygen combustion CFB system can maintain the ideal fluidization state,namely significant internal and external particle circulation.Besides,the contraction section of the boiler leads to the particle backflow in the lower furnace,resulting in the particle suspension concentration near the wall region being higher than that in the center region.Conversely,the upper furnace still retains the classic core-annulus flow structure.In addition to increasing solid circulation rate by reducing the average bed-material size,altering primary gas ratio and bed inventory can also exert varying degrees of influence on the gas-solid flow characteristics of the pure-oxygen combustion CFB boiler.

Experimental study on combustion characteristics of municipal solid waste

As incineration provides a relatively safe means of disposal, significant reduction of weight and volume, and energy recovery from the waste, it was adopted by many countries. For the experimental investigation on the combustion characteristics of municipal solid waste(MSW), a lab scale fluidized bed facility was constructed. Many kinds of combustion runs were conducted in this fluidized bed combustion facility. The examined parameters were bed temperature(773 to 1143K), form of fuels (scrap or whole), moisture of fuels and so on. Concentration of CO 2,CO,SO 2, O 2 and NOx in the flue gas were monitored and recorded every 5 seconds. The temperatures along the reactor are recorded every 10 seconds. Experimental results were given and analyzed.

Experimental Study on the Effect of Bed Material Amount and Fuel Particle Size on Load Change of Circulating Fluidized Bed

The large-scale integration of new energy generation has put forward higher requirements for the peak-shaving capability of thermal power.The circulating fluidized bed(CFB)depends on the advantages of a wide load adjustment range and low cost of pollutant control to become a good peak shaving power supply.However,the large delay and inertia caused by its unique combustion mode make it very difficult to change the load quickly.To further understand the factors that affect the load change of CFB,and explore the method of increasing CFB load change rate,the load change experiment on the combustion side was carried out in the 0.1 MW CFB experiment platform.The influence law of bed material amount and fuel particle size on load change of CFB combustion side was revealed for the first time.The results indicated that the increase of bed material amount was beneficial to improve the load change rate on the combustion side of CFB and reduce the carbon content of fly ash,but had no obvious effect on NO_(x)emission.When the bed height at rest increased from 200 mm to 400 mm,the load change rate of the CFB combustion side load from 50%to 75%increased from 0.78%/min to 1.14%/min,and the carbon content of fly ash at 75%load decreased from 26.6%to 24.9%.In addition,the reduction of fuel particle size positively improved the load change rate on the combustion side of the CFB and reduced NO_(x)emission but had a negative effect on reducing the carbon content of fly ash.When the fuel particle size decreased from 0-1 mm to 0-0.12 mm,the load change rate of CFB combustion side load from 50%to 75%increased from 0.78%/min to 1.09%/min,and the NO_(x)emission and carbon content of fly ash at 75%load decreased from 349.5 mg/m^(3)to 194.1 mg/m^(3)and increased from 26.6%to 31.8%,respectively.

Experimental Studies on Combustion Characteristics of Mixed Municipal Solid Waste

In our country, municipal solid wastes (MSW) are always burnt in their original forms and only a few pretreatments are taken. Therefore it is vital to study the combustion characteristics of mixed waste. In this paper, thermogravimetric analysis and a lab scale fluidized bed facility were used as experimental means. The data in two different experimental systems were introduced and compared. It took MSW 3-3.5 min to burn out in FB, but in thermogravimetric analyzer, the time is 20-25 min. It can be concluded that, in general, the behavior of a mixture of waste in TGA can be expressed by simple combination of individual components of the waste mixtures. Only minor deviations from the rule were observed. Yet, in Fluidized Bed, it was found that, for some mixtures, there was interference among the components during fluidized bed combustion.

燃煤循环流化床锅炉掺烧污泥应用研究进展

利用循环流化床锅炉合理处置产量大且含有有害物质的污泥,可使其烟气中污染物排放浓度达标,因而燃煤循环流化床锅炉掺烧污泥具有广阔的应用前景。从污泥的掺烧现状、掺烧机理、燃烧工况、存在问题以及优化方案等方面对燃煤循环流化床锅炉掺烧污泥进行综述研究。煤炭与污泥混燃可实现燃料特性互补,消除单一燃料的负面特性。结合国内外燃煤循环流化床锅炉掺烧污泥相关工艺,指出现阶段我国污泥掺烧对燃烧效率、锅炉运行以及烟气污染物排放的影响,并提出优化工况的具体措施。综合认为,燃煤循环流化床锅炉掺烧污泥可实现污泥的减量化、无害化、资源化处置,需从污泥预处理、锅炉系统优化、数值模拟等多角度出发,进行系统优化设计和改造,以确保混合燃料在炉内高效燃烧、达标排放。

污泥与煤流化床混燃特性

污泥与煤混燃能够有效改善燃料的着火和燃烧特性,实现污泥的无害化与资源化利用。市政污水在消毒和脱水过程中引入的氯元素会增加市政污泥中氯的质量分数,进而对锅炉换热面和环保设备产生不利影响。利用热重-傅里叶红外分析仪和鼓泡流化床反应器,考察了不同操作条件对燃料着火、氯元素析出、灰粒径和元素分布的影响规律。结果表明,污泥中的挥发分较高,在其微商热重曲线中有3个失重峰,且最大失重峰出现在挥发分析出和燃烧阶段。随着污泥掺烧比例增加,燃料的着火温度和燃尽温度降低;烟气中CO、NO和SO_(2)的体积分数随着污泥掺烧比例的增加而增加,污泥中较高的挥发分促进了CO的生成,同时减弱了密相区的还原性气氛,不利于NO的还原;燃烧过程中,无论是热重还是流化床实验均表明燃料中85%以上的氯元素都以HCl形式析出,且灰对HCl的自捕集作用较弱,燃料中绝大多数氯元素最终都以气态HCl形式进行排放;飞灰的平均粒径随着污泥掺烧比例的增加而减小;随着污泥掺烧比例的增加,飞灰中钾、磷和铁的质量分数显著上升,尤其是磷元素的增幅最为明显。

烟气再循环对350 MW CFB锅炉深调运行特性影响

为解决超临界CFB锅炉超低负荷时流化安全性及NO_(x)超低排放,引入烟气再循环技术,以某电厂超临界350 MW CFB锅炉为研究对象,搭建了循环半干法脱硫后烟气的再循环辅助调峰系统,基于运行实测数据,研究该锅炉在30%~60%负荷率下烟气再循环对平均床温、分离器入口温度、排烟温度、炉膛出口烟气NO_(x)、CO质量浓度、飞灰及底渣可燃物含量、汽水参数等运行参数的影响,试验结果表明:烟气再循环协同下,30%~60%负荷SNCR脱硝后NO_(x)最终排放小于50 mg/m^(3),30%负荷实现锅炉原始NO_(x)超低排放;床温降低15~22℃,炉膛出口烟温提高10~13℃,主再热汽温在558℃以上;随锅炉负荷降低,飞灰及底渣含碳量升高,CO质量浓度未见大幅增加;40%负荷炉膛二次风SNCR脱硝NO_(x)降幅约15 mg/m^(3);负荷上升/下降变化最小速率1.23%Pe;30%负荷及以上保持干态运行,水冷壁壁温最大偏差55℃,屏过及屏再最大壁温差分别55、47℃,均未出现壁温超温。

流化床锅炉协同处置农林废弃物数值模拟研究

针对某台75 t/h循环流化床锅炉进行了农林废弃物掺烧数值模拟,通过对比实验数据验证了仿真模型的正确性与可靠性,进一步深入分析了不同掺混因素与锅炉运行参数对炉内燃烧特性、出口污染物排放以及炉膛磨损的影响。结果表明:低农林废弃物掺烧比与高一次风配比有利于改善燃烧特性,而高农林废弃物掺烧比将降低出口污染物排放。

城市污泥与煤混烧过程中NO_x和N_2O的排放特性

在热输入为02MW的循环流化床试验台上进行了城市污泥与煤的混烧试验,着重研究了污泥/煤掺混质量比、空气过剩系数、二次风率等因素对NOx及N2O排放的影响.研究表明,随着污泥掺烧比例的增大,流化床密相区和稀相区的温度明显下降,烟气中NO和NO2的质量浓度均呈下降趋势,而N2O的质量浓度则明显上升;随着空气过剩系数的增加,NOx和N2O的排放质量浓度均呈增加趋势;在空气过剩系数保持不变的条件下,随着二次风率的增加,密相区的还原性气氛增强,NOx和N2O的排放质量浓度呈下降趋势.

流化床内干化污泥燃烧污染物排放特性研究

采用小型电加热流化床焚烧实验台,对干化污泥燃烧的污染物排放特性进行了研究.实验通过改变干化污泥中水的质量分数(7.3%,28.4%和41.5%),不同的炉膛温度,石灰石的添加以及污泥和煤混烧等多种工况对污染物的排放特性进行了研究.研究结果表明,当污泥含水质量分数由41.5%降为7.3%,CO和N2O的排放质量浓度分别提高了一倍和四倍;相反,丙烷、己烷和苯胺等有机污染物的排放质量浓度明显下降,NOx的排放质量浓度降低了70%;煤对污泥燃烧二恶英的排放有明显抑制作用,并且二噁英的排放质量浓度和HCl的质量浓度有很明显的关联;此外,石灰石能促进NOx生成,但抑制N2O生成,而对二恶英的排放质量浓度几乎没有影响.

污泥流化床焚烧技术研究和环境影响分析

在分析污泥的各种处理方法如农用填埋，抛海以及回转窑焚烧等基础上，提出了采用污泥异比重流化床焚烧新技术．着重对污泥能量的利用进行分析，并对污泥在流化床内的结团与着火特性进行试验研究，对污泥焚烧后ＳＯ２、ＮＯｘ、氟、氯以及重金属排放等进行了分析和试验，表明污泥流化床焚烧在技术上可行，污染物排放能满足环保要求，不致引起二次污染。是一种颇具应用前景的污泥处理方法。

城市下水污泥和煤／LPG在循环流化床上的混烧试验研究

在高6000 mm、直径300mm的循环流化床上进行了含水率为79％的湿污泥与煤／石油液化气(LPG)的混烧试验。试验结果表明:无论用煤还是LPG作为辅助燃料,试验都能在设定的工况条件下稳定运行;向炉内加入石灰石的量达到钙硫摩尔比为3．4∶1时,二氧化硫和氯化氢的排放达标,脱硫效率和脱氯效率分别为75％和94％;在试验中, 烟气中NOx排放、烟气中汞含量和二恶英类排放都不超标;试验产生的飞灰含碳量低,飞灰中痕量元素的浸出毒性不超标;计算表明,如果利用余热干燥污泥和预热空气可有效地减少辅助燃料的消耗量。

污泥在流化床内燃烧过程及结团微观机理分析

本文利用污水污泥在小型电加热流化床内燃烧过程的电镜照片，结合污泥在深床层低风速流化床燃烧时的凝聚结团特性，燃烧时水分和挥发份析出特性等，对污泥在流化床中的燃烧过程进行微观分析。还对６种不同污泥的电镜照片进行了比较，得出的微观机理对于分析污泥流化床燃烧过程具有重要意义。

污泥与煤在循环流化床混烧过程中的汞排放特性

在密相床截面积为0.23m×0.23m、高度为7.00m的循环流化床燃烧试验装置上进行了含汞污泥与煤的混烧试验.测试并分析讨论了污泥与煤混烧过程中汞的分布,探讨了Ca/S摩尔比、脱硫剂种类、过量空气系数等运行参数以及烟气成分对汞在烟气、飞灰和炉渣中形态分布的影响规律.结果表明,大部分汞进入烟气,且元素汞是混烧烟气中的主要存在形态.钙基脱硫剂对烟气中氧化态汞有较强的吸附脱除作用,CaO对汞的脱除效果要好于CaCO3.随着烟气中SO2、NOx浓度的增大,烟气中二价汞所占份额呈上升趋势.过量空气系数对烟气和灰渣中汞的浓度和形态分布有较大的影响.

含油污泥高温燃烧利用技术研究

对胜利油田含油污泥理化性质进行了研究,提出了含油污泥高温燃烧利用技术.该技术利用特殊锅炉将水煤浆与含油污泥掺和燃烧,通过流化床处理、烟气处理系统及粉尘回收系统,实现了含油污泥无害化处理,解决了环境污染问题.实验检测结果表明:炉膛温度高达1150℃,降低了燃烧对含油污泥干度的要求;除尘效率达到99.5%以上,烟尘、烟气符合国家排放标准;节约燃煤18.6%～22.2%.该技术有很强的环境效益与经济效益.

循环流化床锅炉煤燃烧效率研究(英文)

人们已经认识到飞灰含碳量是燃煤循环流化床锅炉的重要问题 .它影响了燃烧损失和锅炉效率 .在循环流化床实验台上对六种煤的燃烧进行了研究 ,与燃用相同煤种的循环流化床锅炉的结果比较 ,并与热重分析 (TGA)数据关联 .结果表明 ,飞灰含碳量不仅受运行参数如床温、过量空气系数、配风情况、床存量及床质量的影响 ,而且受煤特性影响 ,煤本身的反应活性是最主要的 .利用热重分析 (TGA)数据可以预测该燃料在循环流化床锅炉燃烧时的飞灰含碳量 .

蒸压养护对固硫灰渣膨胀性能的影响研究

循环流化床燃煤固硫灰渣含有较高的SO3和f-CaO,常温下水化时易产生较大的体积膨胀。研究了蒸压养护和自然养护下,2种固硫灰和1种固硫渣的线性膨胀率和强度发展,并用X射线衍射和SEM分析了其水化产物,结果表明:蒸压养护对固硫灰渣的膨胀有显著的抑制作用;蒸压养护后固硫灰渣中无二水石膏、钙矾石生成,在钙组分充足时生成了托贝莫来石;蒸压养护后固硫灰渣的水化产物更加丰富、结晶更完善,从而强度更高。