生物质燃烧过程中氯及钾析出特性研究

氯和钾在燃烧过程中以气态析出,是引起生物质直燃锅炉受热面积灰及腐蚀问题的主要原因,利用马弗炉在650、700、750、800和850℃5个温度下燃烧麦秆、稻秆、玉米秆、棉花秆、油菜杆和稻壳6种生物质,分别使用离子计和原子发射光谱法测量吸收液中的氯和钾浓度,研究这6种生物质燃烧过程中氯和钾的析出特性。结果表明:不同温度下,Cl和K以气态析出的量有明显差别,保持温度低于750℃即可有效抑制两者析出进入烟气。     

酒糟与无烟煤混合燃烧的热重分析

目前，酒糟的处理方式主要局限在肥料和饲料，对无烟煤与酒糟混合燃烧研究较少。将废弃酒糟与无烟煤按不同比例进行混合燃烧，与其单独燃烧的过程进行对比，通过热重分析法、动力学理论及综合燃烧特性指数对实验结果进行研究。结果显示：酒糟、无烟煤分别单独燃烧时，只有3个燃烧过程，分别是水分的析出、挥发分的燃烧以及固定碳的燃烧；酒糟与无烟煤混合燃烧过程包括水分的析出、挥发分的燃烧以及各自固定碳的燃烧等4个阶段；酒糟与无烟煤混合物中酒糟所占比例越大，其综合燃烧特性指数也越大；增加酒糟比例能够改善无烟煤的燃烧状况，使其燃烧更加充分。根据Coats-Redfern法对二者混合燃烧反应过程的动力学特征进行研究，当反应级数n为2.2时，得到最佳拟合效果，酒糟热解活化能E为42.22 kJ/mol，指前因子A为4.51×10⁵ min^-1。     

西欧三国生物质能技术考察情况

（续上期）4、TecnogroupBeooS.P.A生物质发电装在该场为意大利TaregroUpBaD在生物质热电联产方面多种成功试验的一个。所发的电卖给国家电网，所产热回供给碾米厂（见图勺。稻壳储存在相应的料仓内（大约对机），可供2天连续运行的用量。自动传输带送稻壳至炉上进料器，一个变速系统的电机分配稻壳到炉内的炉栅上。稻壳靠重力落下，被存于底部的正在燃烧的稻壳床所点燃，整个燃烧过程分2个阶段：第1阶段在底床上燃烧，第2阶段被燃烧空气带到炉子出口时燃烧。在空气中的燃烧阶段保证了在一个合适的温度下完全燃烧，以防磨损，并保证稳定…     

稻壳流化床锅炉的设计、运行的若干问题

稻壳流化床锅炉的设计、运行的若干问题刘皓，黄琳，林志杰，刘德昌，伍蔚恒（华中理工大学）１．稻壳燃烧特点作者对稻壳的燃烧特性进行了大量的固定床、流化床燃烧及热重分析、输送特性及结焦特性等实验，研究发现，稻壳的燃烧具有以下特点：（１）极易着火。作者研究发...     

内在矿物质对煤粉燃烧过程影响的动力学研究

本文采用数学建模方法研究煤粉内在矿物质析出对其燃烧的动力学影响.在MIT Graham研究工作的基础上,借鉴内在矿物质群平衡演化析出模型,建立包含表面矿物质结构演化的焦炭燃烧动力学模型.理论分析表明,在焦炭燃烧过程中,表面矿物质层内的气体传质过程会经历由分子扩散到努森扩散的转变.与已有的焦炭燃烧灰壳模型进行对比分析,结果表明,已有灰壳模型在焦炭燃烧初期较高地估计了表面矿物质对气体传质的抑制作用.当内在矿物含量低于10%(质量分数)时,焦炭燃烧全过程中内部矿物质对气体传质的抑制作用不明显.     

稻壳在循环流化床中燃烧现象的分析

为了研究稻壳在循环流化床中的燃烧特性，在生物质循环流化床试验台上对稻壳进行了燃烧试验。通过对试验过程中各测点温度及压力变化的分析，探讨了二次风和循环回料对稻壳在循环流化床燃烧炉内燃烧过程的影响。试验结果表明：二次风可以促进挥发分在稀相区的燃烧，对提升稀相区的温度作用明显；正常循环回料使得温度沿炉膛高度均匀分布。所得结论对生物质循环流化床的试验研究及实际运行有一定的参考意义。     

半焦燃烧分段反应动力学参数的计算

利用TG/DSC热重分析仪对半焦在空气气氛下不同升温速率进行热重实验,运用Flynn-Wall-Ozawa方法对半焦的燃烧动力学参数进行分析研究。结果表明:通过活化能的变化趋势可以把半焦的燃烧过程分为三段:水分和挥发分的析出、挥发分的燃烧、固定碳的燃烧。对半焦燃烧过程的燃烧动力学参数进行分段拟合,可以得到每段燃烧过程的表观活化能、表观指前因子、反应级数等动力学参数以及每个阶段的转换温度点,拟合曲线与实验数据的拟合程度很好。     

生活垃圾燃烧特性的分析及在工程中的应用

从燃烧的角度，对垃圾焚烧与煤的燃烧在燃烧机理上的区别加以论述，阐明垃圾的燃烧过程主要是挥发分的析出的燃烧，是气相燃烧为主、多相燃烧为辅的非均相燃烧的混合过程，是在450℃左右低温垃圾有机挥发分析出和析出挥发分的燃烧、燃尽为主的过程，不同于煤的燃烧，以挥发分析出和燃烧为辅，而以固定碳在800℃以上燃烧为主的过程。根据垃圾燃烧特性，论述了垃圾焚烧炉在设计、建造和运行中应注意的问题。     

基于TG-DTG热分析方法的泥炭燃烧特性研究

采用热重分析技术对不同埋藏深度泥炭的燃烧特性进行研究,考察其着火、燃烧和燃尽特性,并通过反应动力学方法分析泥炭的燃烧行为。研究表明,泥炭燃烧过程近似于一般生物质,大致可分为水分析出阶段、挥发分析出燃烧阶段和固定碳燃烧阶段。利用Coats-Redfern法模拟了三个样品的反应动力学,分别用一级反应和三级反应模型得到泥炭挥发分燃烧和固定碳燃烧两个阶段的动力学参数,其中挥发分燃烧阶段反应活化能较低,大约只有固定碳燃烧时的一半,有利于其着火和燃烧。     

燃用稻壳流化床锅炉的试验研究及35t／h锅炉的设计

介绍了在小型试验台上燃用稻壳流化床锅炉的关键技术，诸如稻壳，稻壳与砂，稻壳与砂及煤等多组份物料的流化特性与混合特性，并介绍了稻壳在流化床中的着火特性和燃烧特性，得到了一系列有指导意义的结论。在此基础上，完成了３５ｔ／ｈ稻壳流化床锅炉的设计，为稻壳流化床燃烧锅炉设计和运行提供了理论依据和实际经验。     

稻壳燃烧特性与动力学模型的研究

采用热重分析仪,在空气气氛下对稻壳的燃烧热失重状况进行了研究,并分析了四种升温速率（5,10,20,50℃／min）对燃烧特性指数的影响。利用Coats-Redfern模型,Freeman—Caroll模型和Flynn—Wall-Ozawa模型分别计算了稻壳燃烧的活化能及频率因子。实验表明：随着升温速率的升高,燃烧性能得到良好改善,但反应起始温度和终止温度由于受热滞后性影响,向高温区偏移使着火温度升高。模型计算结果表明：稻壳燃烧的表观活化能较低,升温速率对活化能的影响并不明显,Coats—Redfern模型、Freeman-Caroll模型可用于估算,Flynn—Wall—Ozawa模型可作为重要数据参考。     

Greenhouse gas emission mitigation potential of rice husks for An Giang province, Vietnam

To evaluate the greenhouse gas (GHG) emission mitigation potential of rice husk utilization, a life cycle inventory analysis was conducted for 18 scenarios. The allocation of fuels, other than rice husks, was decided based on the current demand for and supply of rice husks. To prevent the bulky nature of rice husks, briquette production is also discussed. In the power generation scenarios, the differences between two capacities (5 MW and 30 MW) were analyzed. The results of analysis reveal that CH₄ and N₂O emissions from open burning contribute largely to the current GHG emissions. Therefore, ceasing open burning alone has a large GHG mitigation potential. The use of briquettes, even though GHG is emitted during the production stage, can still contribute to GHG emission mitigation as the production is more efficient than rice husk burning or dumping. In the power generation scenarios, most GHG emissions were derived from the combustion process. Therefore, gasification which has a little combustion process is the most efficient GHG mitigator. Both the replacement of grid electricity by generated electricity, and the replacement of diesel oil by pyrolyzed oil show larger GHG mitigation potentials than what could be derived from open burning cessation alone.     

稻壳水热炭化学结构和燃烧特性及动力学分析

以稻壳为原料,利用水热碳化技术结合元素分析和热重法,考察水热反应强度对水热炭化学结构和燃烧特性及动力学的影响。结果表明：1）随着反应强度参数（lg R₀）的增大,水热炭整体挥发分和氧元素质量分数呈减少趋势,而C元素质量分数则逐渐增加,当水热反应强度lg R₀为4.90~6.19时,参数变化尤为显著,lg R₀为6.19时,C元素和O元素的质量分数分别为50.5%和21.3%,O/C和H/C原子比分别为0.32和1.21;2）相对于原料,水热炭的燃烧损失集中在固定碳和挥发分燃烧阶段,着火和燃尽温度均有小幅上升;3）当lg R₀由3.25增至6.49时,挥发分燃烧损失减小,固定碳燃烧损失增大,着火与燃尽温度呈整体向高温区转移的趋势,综合燃烧特性指数（S_N）呈先增加后减小的趋势;4）固定碳燃烧段活化能低于挥发分燃烧段,本次采用的动力学模型分析水热炭燃烧动力学结果可靠,相关系数（R²）均在0.92以上。     

Particulate matter and gaseous emission rate from combustion of Thai lignite and agricultural residues in a fixed-bed combustor

This research has been conducted in order to obtain a database of emission rate of particulate matter and gases (CO, NO, and SO₂) from combustion of lignite and agricultural residues, such as rice husk. The experimental investigation was performed in a fixed-bed combustor. Thirteen stages–electrical low-pressure impactor was used to collect particles ranging in sizes from 40 nm to 10 μm. The results show that emission rate of total mass of particulate matter from combustion of rice husk is lower than that of lignite combustion but the total number of particles emitted is higher. This implies lower particle density from agricultural residue combustion. For co-firing lignite and rice husk, particulate matter emission is found to be higher than combustion of either lignite or rice husk and an increase in rice husk mass fraction in fuel mixture leads to an increase in particulate matter emission. From these quantitative data, it could be mentioned that the fuel characteristics influenced directly on particulate emission. For gaseous emission factors, CO and NO_x concentration decrease as SA/TA ratio increases. Meanwhile, SO₂ emission tends to increase. Both NO_x and SO₂ emissions are reduced as increased rice husk mass fraction in fuel mixture.     

Overview of combustion and gasification of rice husk in fluidized bed reactors

Rice is cultivated in more than 75 countries in the world. The rice husk is the outer cover of the rice and on average it accounts for 20% of the paddy produced, on weight basis. The worldwide annual husk output is about 80 million tonnes with an annual energy potential of 1.2 × 10⁹ GJ corresponding to a heating value of 15 MJ/kg. India alone generates about 22 million tonnes of rice husk per year. If an efficient method is available, the husk can be converted to a useful form of energy to meet the thermal and mechanical energy requirements of the rice mills themselves. This paper provides an overview of previous works on combustion and gasification of rice husk in atmospheric bubbling fluidized bed reactors and summarizes the state of the art knowledge. As the high ash content, low bulk density, poor flow characteristics and low ash melting point makes the other types of reactors like grate furnaces and downdraft gasifiers either inefficient or unsuitable for rice husk conversion to energy, the fluidized bed reactor seems to be the promising choice. The overview shows that the reported results are from only small bench or lab scale units. Although a combustion efficiency of about 80% can normally be attained; the reported values in the literature, which are more than 95%, seem to be in higher order. Combustion intensity of about 530 kg/h/m² is reported. It is also technically feasible to gasify rice husk in a fluidized bed reactor to yield combustible producer gas, even with sufficient heating value for application in internal combustion engines. A combustible gas with heating value of 4-6 MJ/Nm³ at a rate of 2.8-4.6 MW_th/m² seems to be possible. Only very little information is available on the pollutant emissions in combustion and tar emissions from gasification. The major conclusion is that the results reported in the literature are limited and vary widely, emphasizing the need for further research to establish suitable and optimum operating conditions for commercial implementations.     

Experimental study on ignition and combustion of coal-rice husk blends pellets in air and oxy-fuel conditions

The ignition and combustion characteristics of anthracite-rice husk (AC-RH) and bituminous coal-rice husk (BC-RH) pellets were investigated in a vertical heating tube furnace under different experimental condition, for gas temperature (873 K–1073 K) and under air and different oxygen concentration (21–70%) in CO₂/O₂ atmosphere. The investigation of the ignition and combustion characteristics focused on ignition mechanism, ignition delay, ignition temperature and combustion process. AC-RH pellets had two ignition mechanism in CO2/O2 atmosphere: homogeneous ignition of volatile and heterogeneous ignition of char. Heterogeneous ignition region decreased while homogeneous ignition increased as rice husk blending ratio increased in oxygen concentration-gas temperature plane. Only homogeneous ignition was observed when rice husk blending ratio was 30%. As for BC-RH pellets, only homogeneous ignition occurred in all experimental conditions. The effect of the rice husk blending on the anthracite was more pronounced than the bituminous coal for ignition mechanism. As oxygen concentration increased, a significant reduction in ignition delay and ignition temperature was observed at low rice husk blending ratio and low gas temperature. but at 1073 K, high oxidizer temperature weakened the effect of biomass blending and oxygen concentration on ignition delay and ignition temperature. Meanwhile, at 20% and 30% rice husk blending ratio, it also weakened the effect of oxygen concentration and oxidizer temperature on ignition delay and ignition temperature. In contrast, blending ratio had a more significant effect on ignition behavior. The replacement of N₂ by CO₂ at the same oxygen concentration contributed to an increase in ignition delay time and internal ignition temperature, which suppressed the ignition behavior. Different ignition mechanisms corresponded to different combustion processes.     

Effects of operating conditions and fuel properties on emission performance and combustion efficiency of a swirling fluidized-bed combustor fired with a biomass fuel

This work reports an experimental study on firing 80 kg/h rice husk in a swirling fluidized-bed combustor (SFBC) using an annular air distributor as the swirl generator. Two NO_x emission control techniques were investigated in this work: (1) air staging of the combustion process, and (2) firing rice husk as moisturized fuel. In the first test series for the air-staged combustion, CO, NO and C_xH_y emissions and combustion efficiency were determined for burning “as-received” rice husk at fixed excess air of 40%, while secondary-to-primary air ratio (SA/PA) was ranged from 0.26 to 0.75. The effects of SA/PA on CO and NO emissions from the combustor were found to be quite weak, whereas C_xH_y emissions exhibited an apparent influence of air staging. In the second test series, rice husks with the fuel-moisture content of 8.4% to 35% were fired at excess air varied from 20% to 80%, while the flow rate of secondary air was fixed. Radial and axial temperature and gas concentration (O₂, CO, NO) profiles in the reactor, as well as CO and NO emissions, are discussed for the selected operating conditions. The temperature and gas concentration profiles for variable fuel quality exhibited significant effects of both fuel-moisture and excess air. As revealed by experimental results, the emission of NO from this SFBC can be substantially reduced through moisturizing rice husk, while CO is effectively mitigated by injection of secondary air into the bed splash zone, resulting in a rather low emission of CO and high (over 99%) combustion efficiency of the combustor for the ranges of operating conditions and fuel properties.     

单元体电阻炉樟树树枝、树叶与稻壳对比燃烧及特性研究

通过将樟树树枝、树叶与稻壳在单元体炉内置于不同燃烧温度及过量空气系数下对比燃烧,研究樟树特有燃烧特性.结果显示在过量空气系数为1.2时,利于樟树树枝、树叶燃烧充分;因樟树树枝、树叶不耐热、固定碳相对煤炭含量较低,避免过高温度,燃烧温度为1 000℃时,有利于燃烧;樟树树枝最易燃尽,樟树树叶较易燃尽,稻壳最难燃烧燃尽.     

纯烧稻壳差速流化床锅炉的设计改造

文章分析了稻壳的基本特性及燃烧特性。介绍了在锅炉设计中成功采用差速流化床燃烧技术,焚烧稻壳的设计改造心得。     

FeCl3对稻壳水热炭基本元素及燃烧特性影响

以稻壳为原料,FeCl₃为催化剂,利用元素分析仪和热重法研究稻壳水热炭元素结构和燃烧特性,考察水热温度、催化剂浓度对于水热炭元素结构和燃烧特性的影响。结果表明：1)随着水热温度升高,水热炭固定碳含量和热值增大,O/C和H/C原子比逐渐降低。FeCl₃的加入进一步加深了水热炭的碳化程度,但对于碳化程度影响效果,水热温度大于FeCl₃浓度;2)未添加FeCl₃时,水热炭燃烧呈双峰,且挥发分燃烧段峰值明显高于固定碳燃烧段。水热温度上升,挥发分燃烧峰值下降,固定碳燃烧峰值增加。加入FeCl₃后,固定碳燃烧范围扩大,双峰逐渐融为单峰,整体向高温区转移;3)水热温度一定时,随着催化剂浓度增大,水热炭燃烧DTG曲线由双峰变为单峰,整体向低温区转移;4)升温速率加快,导致样品着火温度、燃尽温度提高,水热炭燃烧整体向高温区转移;5)水热温度一定时,FeCl₃加入后,着火温度和燃尽温度均小幅度提前,综合燃烧特性指数S_N呈先增大后减小的趋势。FeCl