Laboratory gasification of five Canadian coals

Results of a gasification study of five Canadian coals in a 100g laboratory fixed-bed gasifier are reported. The coals were three bituminous coals (Byron Creek, Prince and Devco) and two lignites (Coronach and Bienfait). When gasified in an equal mixture of nitrogen and oxygen at 850 °C, the lignites reacted more rapidly and produced more liquid and gaseous products than the bituminous coals, whereas the bituminous coals produced more methane but less carbon monoxide. Overall rates for both the gasification and combustion processes were 3.20, 2.80, 1.84, 1.70 and 1.25 wt% carbon conversion per min for Coronach, Bienfait, Prince, Byron Creek and Devco coals, respectively.     

Oxygen-steam gasification of coals in a spouted bed

A bituminous and a sub-bituminous coal from Western Canada have been gasified in oxygen-steam and air-steam mixtures in a 0.30-m diameter, 50 kg coal/h continuous spouted bed reactor. Results are presented to show the effects of the blast composition and reactor temperature on gas heating value and carbon conversion. Operation in the ash agglomeration mode is illustrated, and the role of K₂CO₃ as catalyst explored. Results from a wide range of experimental gasification conditions are compared with predictions of an equilibrium model.     

灰融聚流化床粉煤气化技术及后续配套工艺

介绍了灰融聚流化床粉煤气化技术的技术原理、流程、技术指标以及选择该技术进行气头改造的主要优势和后续配套工艺。     

Reactivities of 34 coals under steam gasification

The reactivities of 34 coal chars of varying rank with H₂O have been determined to examine the effect of coal rank on the gasification rate of coal char. The reactivities of chars derived from caking coals and anthracites (carbon content > 78 wt%, daf) were very small compared with those from non-caking (lower-rank) coals. The reactivities of low-rank chars do not correlate with the carbon content of the parent coals. To clarify which factor is more important in determining the reactivity, the evolution of CO and CO₂ from char, the moisture content of char and the amount of exchangeable cations were determined for these low-rank coals or their chars. These values were considered to represent the amount of active carbon sties, the porosity and the catalysis by inherent mineral matters, respectively. It was concluded that the amount of surface active sites and/or the amount of exchangeable Ca and Na control the reactivity of low-rank chars in H₂O.     

Low temperature gasification of brown coals catalysed by nickel

Nickel catalyst exhibited an extremely high activity in the gasification of some low rank coals at a temperature as low as 750 K. Approximately 85% of Yallourn coal was converted within 30 min in steam at 773 K. A high nickel loading, > 4 wt% was necessary. It seems essential for coal high in oxygen and low in sulphur to be gasified in this manner. Oxygen-containing functional groups on the coal surface seemed to play an important role in keeping the nickel catalyst in a finely dispersed state. Hydrogen sulphide was strongly adsorbed on the nickel catalyst and retarded this reaction. Hydrogen and carbon dioxide were the main products of low-temperature steam gasification. Similar low-temperature gasification reactions were also observed in hydrogen and in carbon dioxide.     

现代煤气化技术及其煤种的适应性分析

结合国内外煤气化技术发展现状与趋势,讨论了煤质特性对气化过程的影响及其在不同气化炉型中的适应性。分析表明,煤种的多样性及气化工艺的选择促进了煤气化技术的快速发展,气流床和流化床代替固定床是煤气化技术发展的必然所趋。在充分认识各类煤气化技术优缺点的基础上,应发挥优势,针对煤种选用炉型,开发具有单炉生产能力高、煤种适应性强、气体成分可调等优势的加压气化技术以及可有效利用煤气高温显热的两段或多段式气化技术。     

不同沉积环境下煤的热解与气化特性

采用煤热解.气化连续方法,在TG-DTA/DSC热分析仪器上对煤化程度接近但沉积环境不同的5种煤的热解与气化特性进行研究,运用Coats-Redfem积分法求解煤热解动力学参数.研究结果表明:5种煤的热解机制是相似的,反应级数n=3;还原程度较弱的SH与SF煤,热解表观活化能在43-54 kJ/mol,而还原程度较强的...     

Action of nickel catalyst during steam gasification of bituminous and brown coals

Steam gasification of a bituminous coal and a brown coal has been carried out in the presence of a nickel catalyst. The action of catalyst particles during gasification was investigated by comparing a series of scanning electron microscope (SEM) photographs taken at stages throughout the experiment. Finely dispersed catalysts with an average diameter of <10 nm were observed upon devolatilization. During the steam gasification of bituminous coal, the carbon substrate around the catalyst was gasified. At higher catalyst loadings considerable catalyst agglomeration occurred and was associated with a decrease in effectiveness of the catalyst. On the other hand, catalyst particles remaining well-dispersed in brown coal after 80 wt% char conversion maintained an extraordinarily high activity.     

Distribution of volatile sulphur containing products during fixed bed pyrolysis and gasification of coals

Three sub-bituminous and two bituminous coals from Western Canada were used to study the evolution of H₂S, COS and SO₂ during the pyrolysis and gasification processes in a fixed bed reactor. For all types of coals, most of H₂S and SO₂ were released during the devolatilization stage. COS was formed only during the gasification stage in the presence of CO₂. The mineral matter of coal may have played a role during the gasification stage. Some observations made during this latter stage in CO₂ and/or steam were interpreted in terms of the equilibrium effects.     

Electron spin resonance studies of some Canadian coals

Nine Canadian coals of different rank and composition were studied by electron spin resonance. For percentage of fixed carbon in the range of 43 to 78 wt%, the free radical g values were found to increase with decreasing carbon content, and did not level off for the low rank coals. The free radical linewidths are attributed to atomic species such as oxygen and not to protons of hydrogen.     

Formation of carbonaceous cenospheres during fluidized-bed combustion of bituminous coals

The discovery of cenospheres in fly ash from fluidized-bed combustors is reported and differences between the fluidized bed and more conventional combustors which are likely to affect cenosphere formation are indicated. Morphological studies and qualitative chemical analyses obtained by electron microscopy/energy dispersive X-ray specttometry (SEM/EDS) techniques show differences in composition between the ‘window’ areas of cenospheres and their ‘skeletons’.     

Model for drying during fluidized-bed combustion of wet low-rank coals

An unsteady state heat conduction model with a convective boundary condition is proposed for the drying of low-rank, high-porosity coals, such as lignites, during fluidized-bed combustion. The drying front is assumed to be the receding surface of a wet core. The solution technique for this moving boundary problem is based on the heat balance integral approach with immobilization of the moving boundary by a change in space variable. The governing cubic equation describing the drying curve in dimensionless form may be solved easily by the Newton—Raphson method. The model predictions are compared with experimental data for Mississippi lignite with excellent agreement. A correlation for estimation of total drying time is proposed. The temperature profiles obtained may be used for the study of the coupled drying and devolatilization in fluidized-bed combustors. The profiles could also be of importance in the study of formation of fissures/cracks in lignites subjected to intense heating conditions encountered during fluidized-bed combustion.     

Catalytic gasification of chars

The gasification of pure and cobalt-doped chars obtained by carbonization of wood sawdust is compared. The catalytic action of cobalt affects both the kinetics of char gasification and the texture of the resulting porous carbons.     

煤气化方法的比较及分析

分析比较了固定床、流化床、气流床3种气化方式中各典型工艺的工艺流程、优缺点及工业化应用。     

新河烟煤地下气化模型

为了探索烟煤地下气化过程的基本规律,为新河“煤炭地下气化发电示范工程”制定合理的工艺参数,测定了新河烟煤反应活性,并进行了富氧-水蒸气地下气化模型实验;研究了不同工艺条件下,出口煤气有效组分含量、热值的变化规律.实验结果表明,气化初期因煤层中含水,纯氧直接气化,可获得合格的煤气;在保持汽氧比在1.5∶1～2∶1之间时,新河烟煤采用富氧-水蒸气正向供风、辅助孔供风和反向供风连续气化可获得有效气体组分在70%、热值在10 MJ·m^-3左右的煤气;新河烟煤的产气率平均为1950 m³·t^-1,煤层气化率可达到74.6%.     

Study on the structure and gasification characteristics of selected South African bituminous coals in fluidised bed gasification

The gasification characteristics of three South African bituminous coals were investigated in a bubbling fluidised bed reactor. The three coals are similar in rank, but two are inertinite-rich coals and the third has a high vitrinite content. The microstructural characteristics of the parent coals and their resultant chars were determined using XRD, FT-IR, Raman and petrographic analysis. The microstructural changes that occurred in the organic (maceral) and the inorganic (mineral) fractions of the selected coals were evaluated. The change in the carbon structure was correlated to the proportions of inertinite and vitrinite macerals in the coals. High vitrinite content resulted in an increase in the order of the disordered carbon structure after gasification and this leads to greater graphitised ordered carbon structures. While a high inertinite content resulted in low or no structural transformation of the chemical structure. The transformation of inorganic mineral constituents of the coal was correlated to the amount of inertinite present in the selected coals. Higher proportions of inertinite macerals and inertinitic chars resulted in higher proportions of melted minerals. Char samples with low proportions of organic matter resulted in higher proportion of melted minerals covering the char surface.     

煤焦气化反应过程中灰的熔融特性变化

抽样选出具有代表性的一种高灰熔点煤种和一种低灰熔点煤种,在TGA-51H型高温热天平上进行煤焦-O2、煤焦-CO2和煤焦-水蒸气气化反应实验,通过扫描电镜(SEM)考察了不同气氛下煤焦气化反应过程中高、低灰熔点煤灰的熔融变化过程,并利用EDX分析了灰的熔融机制。实验结果表明:同种煤样还原性气氛下的灰熔点比氧化性气氛下低;相同条件下灰在CO2气氛下的灰熔点比其在水蒸气气氛下低。在气化反应的过程中,由于气化反应为强吸热过程,大部分热量提供给煤炭气化反应,导致Ca与Fe元素的还原反应进行缓慢,灰熔融温度比较高。     

鹤壁烟煤地下气化模型试验研究

通过自行研制的煤炭地下气化模拟试验系统,采用富氧空气/水蒸气两阶段气化工艺,完成了鹤壁煤的地下气化模型试验。文章就试验不同阶段的煤气组成、热值变化和气化过程的稳定性特征进行分析,结果如下:鹤壁煤地下气化水煤气平均热值达11.85 MJ/m3,空气煤气热值为4—6 MJ/m3,水煤气中氢气最高体积分数超过80%,相应的煤气热值达到12.91 MJ/m3;适当增大鼓风量有利于高温温度场的快速建立与恢复,试验条件下,最佳鼓风量为20 m3/h,最佳蒸汽流量为0.26 m3/h。试验为煤炭地下气化制氢提供了有力依据。     

Coal gasification using a molten iron bath

A coal gasification process using a molten iron bath as reactor has been developed by Sumitomo Metals. Pulverized coal is blown onto this molten iron together with oxygen and steam as gasification agents. Tests using a pilot plant having a capacity of 60 t (coal) day^?1, has shown that a sulphur-free carbon monoxide and hydrogen-rich gas can be generated at high coal conversion efficiency.     

高含氯固体废弃物流化床气化的二噁英生成特性

针对固体废弃物资源化过程中普遍关心的二噁英生成问题,利用自行设计建造的流化床气化综合实验平台对高含PVC模拟垃圾进行了流化床气化实验,讨论了PVC含量、空气计量系数对二噁英生成特性的影响规律。结果显示,对于PVC含量为20%的模拟垃圾,在空气计量系数由1.2降至0.4时,单位PVC的二噁英生成量和毒性当量分别由146.53 ng·g^-1和20.71 ng I-TEQ·g^-1降至2.07 ng·g^-1和0.31 ng I-TEQ·g^-1;在空气计量系数同为0.4时,随着PVC含量由20%降至1%,单位PVC的二噁英生成量及其毒性当量由23.54 ng·g^-1和3.49 ng I-TEQ·g^-1降至2.07 ng·g^-1和0.31 ng I-TEQ·g^-1。因此,在固废处理过程中,二噁英的生成风险随着PVC含量的增加而增加,而气化和低空气计量系数有利于抑制二噁英的生成。