滴管炉内不同煤阶煤焦水蒸气气化反应特性

在滴管炉内对煤焦与水蒸气气化反应进行了实验研究,考察了煤阶、气化温度、水蒸气与进料煤焦质量比(气焦比)对气化气体产物释放特性以及煤焦转化率的影响。实验温度为1100、1200、1300和1400℃,气焦比分别为0.4:1、0.6:1和1:1。研究发现:滴管炉内不同煤焦的水蒸气气化气体产物以H2含量最高,CH4含量最低。不同煤阶热解焦、气化温度以及气焦比的变化影响滴管炉内水蒸气气化产物气体组成和转化率的高低。随气化温度的升高,神府煤焦和北宿煤焦气化气体产物中H2和CO产率不断增大,H2/CO的比值则逐渐减小,碳转化率有不断增加的趋势。在气化温度大于1200℃的条件下,当气焦比从0.4:1增至0.6:1,神府煤焦和北宿煤焦的碳转化率变化幅度不大(5%以内);当气焦比从0.6:1增至1:1,北宿煤焦的碳转化率略微降低,而神府煤焦的碳转化率增幅则在15%以上。     

生物质与煤共气化特性研究

在热天平装置中研究了生物质焦、煤焦以及生物质焦与煤焦混合物的水蒸气气化特性.采用程序升温热重法对生物质焦(稻秆焦、高粱秆焦和玉米秆焦)、神木煤焦以及生物质焦与煤焦混合物进行了水蒸气气化实验.结果表明,生物质焦和煤焦在一定温度下的气化速率为:高粱焦＞稻秆焦＞玉米焦＞神木煤焦.并对三种生物质焦、煤焦、生物焦和煤焦混合物的水蒸气气化反应进行了动力学分析,分析认为,连续反应模型可以在一定程度上反应焦样的水蒸气气化反应动力学.     

滴管炉内不同煤阶煤焦水蒸气气化反应特性

在滴管炉内对煤焦与水蒸气气化反应进行了实验研究,考察了煤阶、气化温度、水蒸气与进料煤焦质量比（气焦比）对气化气体产物释放特性以及煤焦转化率的影响。实验温度为1100、1200、1300和1400℃,气焦比分别为0.4：1、0.6：1和1：1。研究发现：滴管炉内不同煤焦的水蒸气气化气体产物以H₂含量最高,CH₄含量最低。不同煤阶热解焦、气化温度以及气焦比的变化影响滴管炉内水蒸气气化产物气体组成和转化率的高低。随气化温度的升高,神府煤焦和北宿煤焦气化气体产物中H₂和CO产率不断增大,H₂/CO的比值则逐渐减小,碳转化率有不断增加的趋势。在气化温度大于1200℃的条件下,当气焦比从0.4：1增至0.6：1,神府煤焦和北宿煤焦的碳转化率变化幅度不大（5%以内）;当气焦比从0.6：1增至1：1,北宿煤焦的碳转化率略微降低,而神府煤焦的碳转化率增幅则在15%以上。     

加压下煤焦与水蒸气的催化气化动力学研究

以K2CO3为催化剂,利用自行设计的加压固定床反应器进行了神木煤焦-水蒸气催化气化反应动力学研究,并采用n级速率方程和Langmuir-Hinshelwood速率方程考察了水蒸气分压的影响.系统压力为3.5 MPa,气化反应温度分别为600℃,650℃和700℃,其中600℃下水蒸气分压分别为1.24 MPa,1.83 MPa和2.88 MPa;650℃和700℃下的水蒸气分压分别为1.24 MPa,1.83 MPa和2.34 MPa.研究发现,随气化温度的提高和水蒸气分压的增加,煤焦的水蒸气气化反应活性明显提高.采用n级速率方程得到煤焦与水蒸气的反应级数为0.732,活化能为102.63 kJ/mol;采用L-H方程得到活化能为109.23 kJ/mol,其速率方程可以更精确地描述反应气体压力对气化反应的影响.     

煤焦水蒸气气化特性及动力学研究

运用等温热重法，对三种不同的煤焦，在反应温度900℃～1200℃之间进行水蒸气气化实验。分别考察了常压下反应温度、水蒸气分压和煤种对反应的影响；并且对不同煤焦的反应进行动力学计算，求取动力学参数，研究发现，煤焦水蒸气的反应与煤焦—CO2的反应相比速率要快得多，并且随反应温度升高，反应速率急剧增大。     

典型高灰熔融性煤焦水蒸气气化特性研究

为解决我国高灰熔融性煤的利用难题,采用等温热重法,研究了典型贵州高灰熔融性煤焦在不同气化温度及不同水蒸气含量下的气化特性,并采用混合反应模型对试验数据进行处理,求取动力学参数。结果表明,在不同水蒸气含量下,随着气化反应温度的升高,典型贵州煤焦的反应性提高,气化反应速率的峰值增大,气化反应时间缩短;气化剂中水蒸气含量越多,煤焦反应性越好,气化反应速率的峰值越大,但当水蒸气含量大于30%后差别不明显;典型贵州煤焦与水蒸气反应的反应级数为0.912 9~1.620 9,活化能为149.34~165.12 k J/mol。     

煤焦在气化合成气中高温气化反应特性

在固定床管式炉反应器中进行了煤焦在H_2O、CO_2、H_2和CO混合气氛中气化特性的实验研究,考察了反应温度、原料气组成和加煤量对产物气组成以及碳转化率的影响。实验结果表明,在各实验条件下,合成气与煤焦反应后CO流量均增加最多,H_2少量增加。煤焦与CO_2的反应受到明显抑制。混合气体通过与煤焦反应可以提高有效气(CO+H_2)的含量,实验条件下反应出口气体中有效气浓度比反应结束时最多提高3.3个百分点。反应速率受气化剂之间的竞争和气化产物的抑制作用较为明显,在1100℃和1300℃时,煤焦在相同气化剂流量的合成气中的最高反应速率分别只有在纯气化剂(水蒸气或CO_2)中最高反应速率的49%和69%。受到多种气体组分之间的相互影响,气体在孔道里的扩散和吸附对反应影响更加显著,随机孔模型可以较好地拟合此类反应,而不考虑孔结构的均相模型和缩芯模型拟合度较差。     

一种褐煤热解煤焦的CO2气化反应特性

针对褐煤的热解-部分气化-残炭燃烧梯级利用工艺,以宁夏石沟驿褐煤为原料,采用水平管式炉在700℃～950℃温度范围内分别制备快速和慢速热解煤焦,考察了煤焦微晶结构和比表面积随制焦条件的变化.利用热重-质谱联用技术研究煤焦CO2气化反应特性,并采用不同评价指标对煤焦气化活性进行了表征.结果表明:气化温度每升高50℃,煤焦CO2气化反应速率增加50％以上;热解温度升高,虽然煤焦微晶结构的有序化程度加深,比表面积减小,但煤焦CO2气化反应活性主要受气化温度影响;快速热解煤焦的CO2气化反应活性高于慢速热解煤焦,二者的差异随着气化温度升高而增大;表征煤焦CO2气化活性的平均比气化速率和反应性指数存在线性关系.     

基于铁基载氧体煤焦化学链气化性能研究

用溶胶-凝胶法制备铁基载氧体,以500℃热解得到的半焦为固体原料,利用固定床反应器对制备的铁基载氧体煤焦化学链气化性能进行研究。实验结果表明:当氧碳比为1∶1,水蒸气流量为0.03 mL/min,气化温度为900℃时,煤焦化学链气化反应获得较高的碳转化率和合成气选择性,分别为93.42%和85.48%;水蒸气及载氧体的增多,可以提高煤焦的碳转化率,但同时会消耗合成气,导致合成气选择性降低;气化温度的提高能够促进煤焦气化反应的进行,提高CO和H_2的产率,但高温下载氧体易出现烧结问题。此外,煤焦、载氧体与水蒸气三者间的相互作用会随着煤焦气化反应的进行而有所变化。     

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。     

Gasification rate analysis of coal char with a pressurized drop tube furnace

Two coal chars were gasified with carbon dioxide or steam using a Pressurized Drop Tube Furnace (PDTF) at high temperature and pressurized conditions to simulate the inside of an air-blown two-stage entrained flow coal gasifier. Chars were produced by rapid pyrolysis of pulverized coals using a DTF in a nitrogen gas flow at 1400°C. Gasification temperatures were from 1100 to 1500°C and pressures were from 0.2 to 2 MPa. As a result, the surface area of the gasified char increased rapidly with the progress of gasification up to about six times the size of initial surface area and peaked at about 40% of char gasification. These changes of surface area and reaction rate could be described with a random pore model and a gasification reaction rate equation was derived. Reaction order was 0.73 for gasification of the coal char with carbon dioxide and 0.86 for that with steam. Activation energy was 163 kJ/mol for gasification with carbon dioxide and 214 kJ/mol for that with steam. At high temperature as the reaction rate with carbon dioxide is about 0.03 s⁻¹, the reaction rate of the coal char was controlled by pore diffusion, while that of another coal char was controlled by surface reaction where reaction order was 0.49 and activation energy was 261 kJ/mol.     

Catalysis of coal char gasification by alkali metal salts

A study has been made of the gasification behaviour, in carbon dioxide and steam, of a number of coal chars doped with small amounts of alkali metal carbonates. For a given additive, the magnitude of the catalytic effect increased with the rank of the parent coal. A progressive loss in catalytic activity on thermal cycling during steam gasification was associated with reaction of the alkali salts with mineral matter in the chars. The kinetic data were consistent with catalytic mechanisms involving oxidation/reduction cycles on the char substrates.     

Synthesis gas and char production from Mongolian coals in the continuous devolatilization process

Devolatilization of Mongolian coal (Baganuur coal (BC), Shievee Ovoo coal (SOC), and Shievee Ovoo dried coal (SOC-D)) was investigated by using bench-sized fixed-bed and rotary kiln-type reactors. Devolatilization was assessed by comparing the coal’s type and dry basis, temperature, gaseous flux, tar formation/generation, devolatilization rate, char yield, heating value, and the components of the raw coal and char. In the fixed bed reactor, higher temperatures increased the rate of devolatilization but decreased char production. BC showed higher rates of devolatilization and char yields than SOC or SOC-D. Each coal showed inversely proportional devolatilization and char yields, though the relation was not maintained between the different coal samples because of their different contents of inherent moisture, ash, fixed carbon, and volatile matter. Higher temperatures led to the formation of less tar, though with more diverse components that had higher boiling points. The coal gas produced from all three samples contained more hydrogen and less carbon dioxide at higher temperatures. Cracking by multiple functional groups, steam gasification of char or volatiles, and reforming of light hydrocarbon gas increased with increasing temperature, resulting in more hydrogen. The water gas shift (WGS) reaction decreased with increasing temperature, reducing the concentration of carbon dioxide. BC and SOC, with retained inherent moisture, produced substantially higher amounts of hydrogen at high temperature, indicating that hydrogen production occurred under high-temperature steam. The continuous supply of steam from coal in the rotary kiln reactor allowed further exploration of coal gas production. Coal gas mainly comprising syngas was generated at 700–800 °C under a steam atmosphere, with production greatest at 800 °C. These results suggest that clean char and high value-added syngas can be produced simultaneously through the devolatilization of coal at lower temperature at atmospheric pressure than the entrained-bed type gasification temperature of 1,300–1,600 °C.     

The catalytic steam gasification of one Australian and three Japanese coals using potassium and sodium carbonates

The catalytic steam gasification of four different coals using potassium and sodium carbonates as catalysts was carried out in a semi-flow type fixed-bed reactor. The coal was gasified with or without the catalyst under a steam—argon atmosphere at a heating rate of 50°C/s at 700–800°C. The catalytic activity of carbonates for gasification was remarkable for Japanese high-volatile coals (Miike and Takashima coals), and moderate for Australian medium-volatile coal (New Lithgow coal); however, the carbonates had little effect on gasification of Japanese lignite (Taiheiyo coal). It is assumed that Miike and Takashima coals soften and melt during the heating process to make the contact between char and catalyst better. New Lithgow and Taiheiyo coals do not have this property. Gasification was promoted significantly at lower temperatures when the catalyst was used. In both catalyzed and uncatalyzed runs the main products were hydrogen and carbon dioxide; the reaction temperature did not affect the composition of the gases much. A water—gas shift reaction occurred during gasification resulting in a large amount of carbon dioxide under a large excess of steam flow.     

Steam gasification of coal char catalyzed by K2CO3 for enhanced production of hydrogen without formation of methane

Steam gasification of coal char catalyzed by potassium carbonate was investigated on a laboratory fixed-bed reactor to examine the catalytic effects not only on the reaction rate but also on the reaction selectivity, and non-catalytic gasification of coal char was performed by way of contrast. It was observed that the catalytic gasification of coal char with steam occurred significantly in a temperature range of 700-750 °C, producing a hydrogen-rich gas with slight formation of carbon monoxide and virtually no formation of methane. An oxygen transfer and intermediate hybrid mechanism of the catalytic char gasification with steam is proposed for understanding of the experimental data regarding both the kinetic behaviors and reaction selectivity. The study has highlighted the advantages of the catalytic gasification of coal char over the conventional coal gasification with respect to the reaction selectivity. The catalytic steam gasification of coal char makes it possible to eliminate or simplify the methane reforming and water-gas shift processes in the traditional gas-to-hydrogen purification system.     

煤的水蒸汽及二氧化碳高温气化活性评价

选用燃料比(固定碳/挥发份)1到8,变质程度从褐煤到无烟煤(包括粘结性的和非粘结性的)的六种煤焦为试样,在1100—1400℃下,用热重量法进行了含O_2、H_2O、CO_2气化剂的实验室气化,用修正体积反应模型式进行了数据处理和活性评价.并将高温区的结果与低温区(1000℃以下)的实验结果进行了比较.     

煤焦二氧化碳气化反应活性影响因素研究现状

煤二氧化碳气化反应是一种煤清洁利用的手段,其关键是提高反应活性。综述了原煤性质、热解过程、反应温度与压力、催化剂,以及二氧化碳气速、煤焦的粒度等因素对反应活性的影响,并对煤焦气化技术进行了展望。     

Fe/赤泥催化水蒸气气化煤焦的反应性与微结构特性

利用固定床反应器和自制Fe/赤泥（RM）、RM催化剂,进行了900℃煤焦/催化剂不同质量比的水蒸气气化实验,并采用原位红外（FTIR）、物理吸附仪（BET）、拉曼光谱（Raman）等测试手段,分析了催化气化过程中不同阶段煤焦的气化反应性、表面官能团、孔隙结构和碳微晶结构的演变规律。结果表明,Fe1/RM2催化剂可显著提高煤焦-水蒸气的气化反应性。在Fe1/RM2/煤焦-水蒸气反应过程中,煤焦表面形成-CH₂、-COOH、酚羟基等活性官能团并与Fe1/RM2活性组分相互作用,形成新的小分子基团或化合物;煤焦的比表面积先增大后减小（6.98～323.22m²/g）,平均孔径呈现相反的变化趋势（2.91～11.25nm）;碳有序化程度先降低后提高,碳转化率为36%煤焦中无定形碳的相对含量最高（0.371）。在煤焦-Fe1/RM2-水蒸气反应初期（X_C<36%）,煤焦表面活性基团增多、比表面积增大、有序化程度降低,综合提高了煤焦-水蒸气气化反应性;降低36%≤X_C≤62%阶段的碳有序化程度,对煤焦气化反应性的提高具有显著意义。     

煤焦与水蒸气加压气化反应活性的研究

采用填充床热天平反应器（ＰＢＢＲ）系统,于０．０９８ＭＰａ～２．４５ＭＰａ压力和７５０℃～１０００℃温度下进行了煤焦与水蒸气气化反应的活性研究,以基碳转化率（Ｘ）和比气化速率（Ｂ）作为反应活性的评价指标。结果表明,煤焦的Ｘ和Ｂ随着温度和压力的增加而增加;煤焦的气化反应活性顺序为：褐煤焦＞气煤焦＞贫煤焦。