喷动载流床中温度对霍林河褐煤快速热解产物的影响

在喷动载流床反应器内对霍林河褐煤的快速热解进行了研究,并对该煤的热解机理进行了初步分析。考察了在500～850℃范围内温度对热解产品产率分布及气体和液体产品具体组成的影响。分别利用气相色谱和色质联用仪来分析气体和液体产物的组成。实验结果表明,气体总产率及CO、H2和C1～5烃类的产率随热解温度的提高而增大;在热解温度为650℃时,液体产率最高,在煤粉粒径为0.125～0.18mm,液体产品的总产率可达23%,其中正己烷可溶物的产率可达30%以上,沸点340℃前馏分也达30%以上。液体产品中酚类产品较多;温度对液体产品的组成有极大的影响。     

流化床低温热解耦合输送床气化方案初探

针对煤制油项目中存在的煤炭资源利用效率低、吨油耗煤量高的问题,提出了流化床低温热解耦合输送床气化的原料煤利用方案(设想),并系统地阐述了该方案的原则流程、工艺特点和潜在的问题。该方案较好地整合了流化床低温热解技术和输送床气化技术的优点,可同时实现原料煤的高焦油收率、高合成气产率和高能量利用率,但仍存在潜在技术问题。     

热解温度对型煤半焦气化反应活性的影响

热解温度是影响煤焦气化反应活性的重要因素.以型煤和相似粒度的原煤为样品在不同热解温度下制备煤焦,研究了热解温度对煤焦/CO2反应活性的影响,并对型煤半焦与原煤半焦的气化性能进行比较.结果表明,褐煤中低温热解所得半焦在1000℃以上时具有较高的气化反应活性;在相同热解温度下,型煤半焦的反应活性稍高于原煤半焦;热解温度为650℃～750℃时半焦的反应活性最高.     

生物质气流床气化前的处理工艺

针对生物质气化过程面临的问题,利用慢速热解方法作为生物质气流床气化的前处理工艺并考察其可行性. 分析讨论了热解后半焦的化学组成和输送特性,并使用ASPEN PLUS模拟软件计算比较了原料与半焦的气化结果. 结果表明,半焦的能量密度随热解温度的升高而升高;热解温度在300~400℃之间,半焦的质量产率和能量产率对于气化工艺比较有利;热解后半焦的内摩擦角、休止角明显降低,堆积密度明显提高. 使用ASPEN PLUS模拟软件进行计算比较,热解温度为400℃时的气化效果最理想.     

温度梯度与产物流动对先锋褐煤热解产物分布的影响

通过两段固定床反应器分离了煤热解和二次反应过程,模拟了传统外热式固定床反应器和外热式内构件固定床反应器内挥发性热解产物流动与固相反应颗粒间的相互作用,研究了不同温度的半焦对先锋褐煤热解产物分布和品质的影响。结果表明：当半焦的温度在500～900℃时,焦油发生剧烈的二次反应,热解气收率增加,焦油收率大幅下降,H/C同时大量降低且均低于空白样,油品质下降;在100～400℃半焦作用下,焦油发生轻微的二次反应,热解气收率略微增加,焦油收率缓慢下降,但H/C均高于空白样,油品质提升。该结果验证内构件外热式固定床反应器热解产生的焦油具有更高的收率及品质。     

热解温度对半焦生成及其元素组成的影响

利用固定床反应器对3种煤样进行了Ar气气氛高温热解研究,考察了热解温度对半焦产率和其中C,H和O元素含量的影响．研究发现,挥发分主要释放温度范围集中在400℃～700℃;半焦的H／C和O／C原子比都是随温度的升高而减小,O／C原子比在300℃～600℃降低幅度很大,H／C原子比在300℃～900℃降幅较大,当热解温度达到900℃后,不同变质程度煤的半焦H／C和O／C趋于一致．热解过程中半焦的H／C和O／C变化关系与vanKrevelen图上典型煤阶的H／C和O／C关系类似．     

淖毛湖煤加氢热解产物特性及半焦气化反应性

在加压固定床反应器中进行淖毛湖煤在常压和1.5 MPa氢气和氮气中的热解试验,利用多种表征方法对比研究了氢气和氮气下的热解产物产率和组成及半焦结构的变化,并利用热重分析研究热解半焦的CO₂气化反应性。结果表明：与常压N₂中热解相比,煤在加压的H₂中热解可有效提高热解气体中CH₄和C₂～C₃的产率,在800℃热解CH₄和C₂～C₃的体积产率分别由53.5和16.6 mL/g增至345.6和20.8 mL/g。焦油和轻质焦油产率也有效提升,在600℃下,与常压N₂中热解相比,1.5 MPa H₂中煤热解的焦油产率由19.3%升至22.8%,焦油中脂肪烃含量由35.5%降至14.8%,单环芳烃含量由8.3%增至28.9%,轻质焦油质量分数和产率分别升至95.0%和21.8%。半焦的N₂吸附和拉曼光谱分析结果表明,煤在加压H_...     

热解温度和反应气氛对输送床煤快速热解的影响

在连续进料量为1.2 kg·h^-1的输送床反应器中考察了热解温度和反应气氛对不连沟次烟煤快速热解的影响。N₂气氛下,随着煤热解温度升高,焦油产率先增加后减小,600℃时达到最大值10.3%;对应的半焦产率下降,气体产率以及气油比增加。高温促进了煤挥发分的释放以及挥发分在气相中的二次反应,部分产物从固相和液相产品转化为气相产品,氢气、甲烷和乙烯等气体组分的产率明显增加。700℃下,H₂气氛能够抑制挥发分二次反应的发生,起到稳定自由基和加氢的作用,显著提高焦油产率和油品品质,同时有利于甲烷的生成。CO气氛在一定程度上同时提高了轻质和重质焦油产率。CO₂和水蒸气能够促进焦油的二次反应,特别是重质焦油的裂解,具有一定的提质作用,但会导致焦油产率下降。CH₄气氛促进了重质焦油组分的生成,使得热解焦油产率提高。     

铁元素对褐煤热解及气化特性的影响

综述了铁元素对褐煤热解及气化的影响方面的研究进展,在褐煤中植入铁元素对褐煤热解和气化的半焦产物、气体产物的影响,分析了铁在褐煤热解和气化过程中的迁移和转化,并与褐煤中植入的其他金属元素产生的影响进行了简单对比。     

采用双返料器的双循环流化床冷态实验研究

在采用双返料器的双循环流化床冷态实验系统中,测定了不同工况下的双返料器进出口压差、主床和副床物料循环率.对比单返料器冷态实验结果,分析了进出口压差对主床和副床物料循环率的影响.实验结果表明:采用双返料器后,主床和副床之间的互相影响明显减小;主床和副床流化风速变化引起的压力变化集中在双返料器下部,双返料上部压差相对稳定,...     

Coal pyrolysis and gasification in a fluidized bed thermogravimetric analyzer

The kinetics and modelling of coal gasification were studied in the newly developed fluidized bed thermogravimetric analyzer. The total weight loss obtained from the fluidized bed reactor and the total gas product are in general agreement. The presented model for the micro‐fluidized bed reactor encompasses the kinetics of coal pyrolysis as well as the gasification reactions. For coal pyrolysis, the resulting activation energies for the individual gases were 34.7 to 59.8 kcal/mol. These values are 19 to 21 % lower than those found in the literature for similar coals. This decrease of the activation energies of the endothermic pyrolysis reactions is attributed to a gradient of temperature of 185 to 209 °C. The obtained activation energy for the CO shift reaction is 46.6 kcal/mol, increasing by 20 % from the one used in the literature. This increase of the activation energy of such a mildly exothermic reaction represents an equivalent of 170 °C gradient of temperature. The effects of temperature on the yield and the composition of the gas product are studied. Experimental results and equilibrium data are also compared. The model shows reasonably good agreement with the experimental results, except for the water gas shift reaction.

     

玉米秸秆循环流化床气化中试试验

玉米秸秆是农业生产过程中产生的剩余物,其热解气化是秸秆类生物质处理应用的重要选择方向。为此,采用循环流化床气化中试装置对玉米秸秆进行了气化试验,研究空气当量比ER、原料含水率对反应温度、气化燃气组分与热值、气化效率及燃气中的焦油含量等气化特性影响规律,并通过改变进料量试验得到了在不同负荷运行条件下的优化工作参数。结果表明：①随着ER的增大,循环流化床气化炉内的反应温度升高,气化燃气中的CO₂含量增加,焦油与CO含量及燃气热值降低,气化效率随ER的增大呈现先增大后减小趋势,较理想的ER为0.26,此时的气化效率达到70.2%、燃气热值为5.1MJ/m³;②原料含水率的增大降低了气化炉内的反应温度,当原料含水率在5%～15%之间逐渐增大时,燃气中的H₂含量、燃气热值及气化效率均有提升,当含水率由15%继续增大到25%过程中,燃气热值与气化效率均出现了快速下降;③根据气化炉额定进料量设计值,改变进料负荷在66%～120%范围内,调节ER在0.26～0.3时均可得到较好的运行工况,对应得到的燃气热值为4.8～5.1MJ/m³、气化效率为69%～72%。     

Performance of limestone-based sorbent for sorption-enhanced gasification in dual interconnected fluidized bed reactors

A possibility to carry out sorption-enhanced gasification (SEG) is represented by its integration with the calcium looping concept in dual interconnected fluidized beds (DIFB). This article is focused on the sorbent CO₂ uptake performance and attrition/fragmentation tendency when operating conditions simulating those of a DIFB-SEG process are adopted. Experiments were carried out on a commercial Italian limestone in a laboratory-scale DIFB reactor. Carbonation was carried out in a range of test conditions, including variable temperature (600–700°C) and absence/presence of steam (10% by volume); CO₂ concentration was set at 10% by volume. The characterization is extended by investigating the behavior of preprocessed DIFB-SEG samples on impact fragmentation tests, conducted in an ex situ apparatus. Tests were carried out for impact velocities in the range 17–45 m/s. Results were discussed considering both the impact velocity value and the operating conditions under which the sample was preprocessed in the fluidized bed.     

Effect of ring‐type internals on solids distribution in a dual circulating fluidized bed system—cold flow model study

The redistribution of solids in a counter‐current circulating fluidized bed (CFB) by effect of ring‐type internals was investigated in a downscaled cold‐flow model. The system consists of two interconnected CFB reactors, in which the primary reactor operates like a common riser while the secondary reactor operates in counter‐current. The unit works without circulation rate control devices and the inventory splits inherently between the two reactors by pressure balance and depending on the fluidization velocities. Previous studies showed an increment in the total pressure drop in the secondary reactor as result of the internals installation. With the purpose of obtaining comparable inventory in the secondary reactor with and without rings, a device for adjustment of total inventory was designed and installed. Effects of the aperture ratio, number of rings, fluidization velocity, and particles circulation rate were studied. The results obtained approach a guideline for the detailed design of similar configurations. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3612–3623, 2013     

Nickel-catalysed gasification of brown coal in a fluidized bed reactor at atmospheric pressure

Pyrolysis and steam gasification of nickel-loaded Yallourn coal were carried out in a fluidized bed reactor at ambient pressure. The pyrolysis mode was influenced by the addition of nickel catalyst. The yield of total volatile matter decreased whereas the gas yield markedly increased, when compared with uncatalysed pyrolysis. This is considered to result from tar decomposing on the catalyst and being converted to gases and deposited carbon. For the catalysed steam gasification, ≈ 80 wt% of coal conversion was achieved at 873 K and the gas yield was twelve times as much as that for the uncatalysed reaction. The homogeneous equilibrium in the gas phase controlled the composition of the product gas. The product gas contained little tarry material and a negligible amount of hydrogen sulphide. Nickel was efficiently recovered from the residue by an ammonia-leaching method.     

褐煤及其热解产品利用现状

为了提高褐煤利用率,介绍了国内褐煤资源的储量形态、分布。分析了目前褐煤的利用途径,包括共伴生资源的利用、直接燃烧、干燥脱水与成型、气化、液化、制水煤浆与热解。并进一步分析了褐煤热解气、液、固产品的利用方向。提出了褐煤半焦利用的新方法,即利用半焦干法气化,或将半焦和热解废水等制成水煤浆,通过湿法气化制得合成气,再通过甲烷化催化剂将合成气制成甲烷,或将合成气通过费托合成制成汽油柴油。     

Phase holdup and liquid dispersion in gas-liquid-solid circulating fluidized beds

Axial and radial profiles of gas and solids holdups have been studied in agas-liquid-solid circulating fluidized bed at 140mm i.d..Experimental results indicate that the axialand radial profiles of gas and solids holdups are more uniform than those in a conventionalfluidized bed.Axial and radial liquid dispersion coefficients in the gas-liquid-solid circulating fluidizedbed are investigated for the first time.It is found that axial and radial liquid dispersioncoefficients increases with increaes in gas velocity and solids holdup.The liquid velocity has littleinfluence on the axial liquid dispersion coefficient,but would adversely affect the redial liquiddispersion coefficient.It can be concluded that the gas-liquid-solid circulating fluidized bed hasadvantages such as better interphase contact and lower liquid dispersion along the axial directionover the expanded bed.