高硫煤热解脱硫技术研究现状

归纳了煤中硫赋存形态,阐述了热解脱硫研究的意义;根据热解过程脱硫方式,将热解脱硫分为不同气氛下热解脱硫和添加物共热解脱硫。不同气氛下热解脱硫方面,分析了惰性、氧化性、还原性3种气氛下热解脱硫效果,结果表明,还原性气氛下脱硫效果最佳,且被脱除的硫多以H2S形态逸出;炼焦煤热解形成焦炭,还原性氢仅与表面含硫化合物反应,脱硫效果有限,因此难以工业化应用。添加物共热解脱硫方面,分析了有机和无机添加物共热解的脱硫效果,结果表明,某些有机和无机添加物与煤共热解时具有脱硫效果,但对于脱除哪类形态硫及各形态硫脱除机理研究甚少;最后提出了热解脱硫技术研究的可能性方向。     

煤在还原性气氛下热解硫的析出机理研究进展

对煤在还原性气氛下热解硫的析出机理的研究进行综述,着重介绍了在氢气气氛下、焦炉气气氛下的脱硫机理及脱硫效果;并指出煤在甲烷气氛下热解,甲烷对脱硫存在促进作用。比较几种还原性气氛下煤热解的脱硫优缺点,指出甲烷对促进煤热解脱硫具有重要的研究价值和实际应用前景。     

煤在不同气氛下热解脱硫研究进展

对迄今为止有关不同气氛下煤热解脱硫的研究进行综述，着重介绍了在氧化性气氛，还原性气氛和惰性气氛下的脱硫机理，脱硫效果及影响因素；并对不同气氛下的煤热解脱硫行为进行比较，指出了煤热解脱硫存在的问题及今后的研究方向。     

高硫煤与生物质共热解脱有机硫研究

选取渭北石炭纪高有机硫煤与小麦秸秆进行共热解实验,采用正交实验考察了热解温度、升温速率、停留时间和煤与生物秸秆的混合比以及煤与生物秸秆成型压力等对热解脱有机硫及有机硫脱除规律的影响.结合FTIR和SEM分析了共热解半焦的结构特征、孔隙结构与发育情况,并讨论了低温溶剂萃取精制对煤与生物质共热解脱硫效果的影响.结果表明,热解温度对脱硫率的影响最显著.共热解制备较高脱硫率半焦所适宜的最佳水平为850℃,15℃/min,5min,1∶4和2MPa.共热解半焦孔结构发育整齐规则,孔壁薄,孔径较大,有利于热解过程中硫的析出与扩散.低温溶剂萃取提高了共热解脱硫率,尤其是热水精制煤与生物秸秆共热解脱硫率约为39%.     

还原性气氛下煤中硫热解迁移规律(Ⅰ)H2和N2气氛下煤中硫热解释出规律的比较

对煤中硫在还原性气氛下热解的迁移规律进行了实验研究.以一种中硫煤为研究对象,在一套常压固定床反应器上进行程序升温实验,热解产物在高温下与净化的空气混合后并充分燃烧,经由溶液吸收进行电解滴定,得到实验过程煤中硫的连续释出规律曲线.实验结果表明,煤中硫在H2气氛下的释出比例比在N2气氛下的释出比例要高,H2气氛下的释出比例为71.9%,N2气氛下的释出比例为32.8%.引起两者释出比例差异的主要原因是:在高于500℃的高温条件下,H2能够与煤(煤半焦)中的硫进行反应,而在N3气氛下煤(煤半焦)中的硫却不能随温度的升高而进一步释出.     

氢气氛下半焦有机硫的脱除动力学

研究了半焦颗粒在氢气氛下有机硫脱除的本征动力学行为.实验采用微分反应器,研究结果表明,半焦颗粒的脱硫与气氛、温度和半焦硫含量有关.通过比较粒子反应模型和随机孔模型,粒子反应模型仅适合于处理半焦颗粒氢气气氛脱硫的初始阶段,而随机孔模型符合整个脱硫过程.实验和理论分析揭示了脱硫过程中煤中有机硫形态的转化.     

钙基脱硫剂热力学分析及机理研究

在分析钙基脱硫反应体系的基础上,从热力学角度研究了钙基脱硫剂在不同温度、不同O2/CO2气氛下的脱硫效果及原因。结果表明:钙基脱硫反应为一复杂体系,CO2,SO2,O2和SO3浓度由3个独立反应相互影响。在O2/CO2气氛下脱硫效果明显好于无限制气氛。SO2分压减少是双重作用的结果:一方面由于煤燃烧的不充分,使得煤中的固态硫没有及时转变为气态硫;另一方面固态硫本身的析硫反应也不完全。     

活性炭脱除煤气中H_2S的气氛影响及动力学研究

用活性炭对模拟煤气中的H2S进行催化氧化脱除,考察了反应温度、氧硫比以及煤气气氛组成对活性炭催化氧化脱除H2S行为的影响.结果表明,最佳催化脱硫温度约为180℃,氧硫比为1∶2.煤气气氛中,CO,CO2和H2含量的增加降低了活性炭的硫容,而水蒸气含量的提高则有利于脱硫反应的进行,提高了反应的脱硫效率和活性炭的硫容.对其动力学行为进行研究,结果表明,脱硫反应过程属于表面反应控制过程,给出了脱硫反应动力学方程及动力学参数.     

过热蒸汽下煤系黄铁矿磁性强化研究

对西山煤电集团煤样进行热处理实验研究,在高温水蒸气气氛下、热解温度在400～700℃之间,利用自制热解装置热解预处理煤样,预处理后的煤样用自制PM—C30型圆筒磁滤器磁选脱硫研究,主要研究热解温度对煤粉磁选脱硫效果的影响。发现提高热解温度对磁选脱硫效果有利,在500℃时脱硫效果最好,此时的脱硫率为56．86％,与原煤脱硫率相比提高了40．49％;对于西山煤来说,热解一磁选脱硫技术能够有效脱除无机硫,但是对有机硫脱除效果不佳。     

兖州煤热解预脱硫行为(Ⅰ)热解过程中硫的迁移

煤在一定条件下通过热解或部分气化产生可直接用于燃烧的低硫半焦,这一煤燃前预脱硫技术是实现煤炭高效、低污染利用的理想途径之一.在固定床反应器上对兖州煤进行了热解脱硫的研究,在TPD-FPD在线分析装置上分析了兖州煤中硫在热解过程中向气相转移的主要动态特征.结果表明：700℃前,兖州煤中硫向气相的转移出现在两个显著的温度范围,分别在470℃和560℃左右.通过SEM-EDX和XPS光谱分析技术对兖州原煤及其热解半焦中硫的形态及形貌进行了剖析,发现兖州原煤中黄铁矿主要与其他矿物伴生存在,而有机硫的分布极不均匀且以大量噻吩类硫形态存在,并且热解过程中其他形态的硫还向噻吩类硫转移,这就给实现兖州煤的低温高效率脱硫造成了困难.     

高硫煤泥燃烧过程中的汞排放特性

通过固定床程序升温汞脱附试验系统对所选高硫煤泥中汞排放特性进行在线监测,并利用热重分析仪对煤泥热解和燃烧特性进行研究,结合试验所得热解和燃烧特性参数,采用分布活化能模型,进行动力学分析。结果表明：煤泥的热解和燃烧过程可分为3个阶段,非等温条件下,随着升温速率增加,热解过程在高温区发生,最大失重率提升,对应峰值温度偏移,产生热滞后,利于挥发分析出;在煤泥热解过程中少量氧气的参与,抑制挥发分的析出,在7% O₂条件下综合热解特性参数值D最大。热解性能随CO₂浓度升高而得到改善;煤泥燃烧性能随升温速率的增加而得到加强,其活化能随转化率变化呈现“U”型趋势分布;煤泥中无机汞化合物主要为HgCl₂、α-HgS、HgSO₄以及硅铝酸盐类结合汞,总汞释放主要范围对应200~600℃;煤泥中汞释放量随O₂浓度增大,CO₂气氛条件下,随着CO₂浓度增加,总汞释放量逐渐增大。     

流化床煤燃烧过程不同气氛下的气态氮释放特征

利用微型流化床反应装置,结合快速过程质谱仪,在850~940℃操作温度下,研究了三种不同粒度分布烟煤和无烟煤在热解、气化和燃烧反应条件下四种主要气态氮产物HCN、NH₃、NO和NO₂的释放规律。结果表明,微型流化床可以实时检测挥发分氮和焦炭氮的动态释放序和类型,热解、气化和燃烧反应气氛的改变主要影响HCN和NH₃的释放量。热解产物的气态氮主要是来自于挥发分,燃烧反应的HCN和NH₃的释放量与温度有明显关系,而气化反应的各类气态氮释放量随温度变化波动不大。煤颗粒尺寸和温度变化对烟煤和无烟煤中各类气态氮释放量产生影响比较复杂,其中NH₃的释放特性是区分挥发分N释放和半焦N释放的重要特征。     

南台子煤催化加氢热解产物分布的初步研究

以新疆伊犁南台子煤为考察对象,在常压固定床反应器上和温度500℃～700℃范围内,系统研究了以氧化铁为主催化剂和硫为助剂时,催化加氢热解过程中产物的分布.结果表明,氧化铁的加入最高可使焦油产率增加约2％,半焦产率下降约4％,水产率增加约4％,气产率略有降低.助剂硫的加入有利于与铁生成Fe1-xS,从而有利于煤的催化加氢热解.     

Sulfur distribution within coal pyrolysis products

The pyrolysis of coal leads to distribution of sulfur compounds in pyrolysis gas, char and tar generated during the process. The effect of the process parameters of autothermal coal pyrolysis in the circulating fluidized bed reactor on total sulfur distribution has been investigated. Several experimental tests were performed at the temperature of 920°C. Non-coking coal from the Wieczorek Mine (Upper Silesian Coal Basin) and brown coal from the Bełchatów Mine were examined for sulfur distribution. It was found that distribution of total sulfur in coal pyrolysis products is basically affected by coal to air ratio and addition of steam or acceptor to the pyrolysis process.     

Effectiveness of high temperature pyrolysis in sulfur removal from coal

A series of Polish hard coals of different rank that contained sulfur in the quantity from 0.37 to 4.90 wt% was investigated in this study. The coals were subjected to pyrolysis at 1000°C in an atmosphere of the gases evolved during the pyrolysis process. Results have shown a decreasing trend in the degree of sulfur removal by high temperature pyrolysis with increasing coal rank. The effectiveness of pyrolysis in sulfur removal appears to be related to the proportion of the non-thiophenic sulfur to the total organic sulfur in the coal. These are linear correlations between the total sulfur content in the coke and total, pyritic and organic sulfur contents in the initial coal.     

Desulfurization of a Turkish lignite at various gas atmospheres by pyrolysis. Effect of mineral matter

An investigation was made of the removal of pyritic and organic sulfur by pyrolysis at ambient pressure of a Turkish lignite under nitrogen and carbon dioxide atmospheres and the effect of mineral matter on the sulfur removal in pyrolysis of HCl and HCl/HF-treated coal under carbon dioxide atmosphere. Results obtained indicated that both pyritic and organic sulfur removal increased with increasing pyrolysis temperature. The pyrolysis in carbon dioxide atmosphere had more effect on the organic sulfur removal at high temperatures. As a consequence of treatment of coal with HCl, pyritic sulfur removal increased but organic sulfur removal decreased. This implies that the removal of carbonates from coal negatively affects the organic sulfur removal. The observed decrease in organic sulfur removal may be related to the decrease in pyrolytic conversion. It was observed that HCl/HF treatment has an increased effect on the pyritic removal and organic sulfur removal during pyrolysis. The increase in organic sulfur removal after HF-treatment therefore might be due to the removal of clay minerals in the raw coal structure. In addition, it may be said that the presence of silicate minerals in the coal matrix can be induced that the easily removable organic sulfur compounds are converted to thermally stable and non-removable organic sulfur compounds (thiophenic or condensed thiophenic compounds) at these temperatures. Increase in the pyritic sulfur removal of HCl-treated and HCl/HF-treated coal samples may be attributed to the fact that increase of mass and/or heat transport in comparison with untreated coal as a result of elimination of mineral matter.     

Fundamentals of coal topping gasification: Characterization of pyrolysis topping in a fluidized bed reactor

Coal topping gasification refers to a process that extracts the volatiles contained in coal into gas and tar rich in chemical structures in advance of gasification. The technology can be implemented in a reactor system coupling a fluidized bed pyrolyzer and a transport bed gasifier in which coal is first pyrolyzed in the fluidized bed before being forwarded into the transport bed for gasification. The present article is devoted to investigating the pyrolysis of lignite and bituminite in a fluidized bed reactor. The results showed that the highest tar yield appeared at 823 to 923 K for both coals. When coal ash from CFB boiler was used as the bed material, obvious decreases in the yields of tar and pyrolysis gas were observed. Pyrolysis in a reaction atmosphere simulating the pyrolysis gas composition of coal resulted in a higher production of tar. Under the conditions of using CFB boiler ash as the bed material and the simulated pyrolysis gas as the reaction atmosphere, the tar yields for pyrolytic topping in a fluidized bed reactor was about 11.4 wt.% for bituminite and 6.5 wt.% for lignite in dry ash-free coal base.     

不同热解方式下长焰煤的热解特性研究比较

为提高长焰煤热解转化率,研究其热解过程和机理,采用格金干馏设备、固定床和间歇蒸气流化床3种不同热解装置,分别进行长焰煤的低温热解实验。研究结果表明,格金干馏实验中液体产率较高;在固定床低温热解装置中,煤颗粒达到完全热解需要的时间长,热解气体产物中氢气的产率高;在间歇蒸气流化床中,煤颗粒的热解反应速度快,但受热解过程中流化气吹损的影响,半焦产率低;热解气体的组成和分布也随热解气氛而改变,在水蒸气气氛条件下,水蒸气可能参与大分子烃类物质的部分反应,热解气体中CH4和C2以上小分子烃类物质CmHn总含量降低,CO2和CO含量增高。     

煤热解过程中气态产物分布的研究

利用固定床热解装置对3种不同煤种进行了热解研究,考察了温度和煤的性质对热解气态产物以及硫元素逸出规律的影响,结果表明:除了煤的性质外,温度是影响热解产物分布的重要影响因素;同时CO和CO2的逸出量与煤中氧元素的含量有关,而生成CH4和气态烃的量与H/O原子比有很大关系;热解过程中含硫物质以H2S和少量COS的方式逸出到气相,而逸出的气态硫也与煤的含硫量有直接关系.     

Sulfur removal from original and acid treated lignites by pyrolysis

Six original, three hydrochloric acid treated and three demineralized lignite samples were pyrolysed at seven different temperatures between 350 and 950 °C for 7 min under evolved gas atmosphere. All samples and their chars were analysed quantitatively for their total sulfur content and pyritic, sulfate and organic sulfur forms. The alkaline oxide contents of original lignites and their hydrochloric acid treated counterparts were determined. The results clearly indicate that calcium and sulfurous compounds in the parent lignites undergo various chemical changes during pyrolysis. The pyrolysis temperature, types of sulfur and calcium compounds, all affect the behaviour of sulfur during pyrolysis. Higher pyrolysis temperatures favour total sulfur removal for all lignites, reaching 30-54% around 850 and 950 °C. HCl treatment and demineralization decreases calcium contents, hence, increases quantitative sulfur removal from the lignites by pyrolysis. The maximum total sulfur removal from acid treated lignites is observed as 77%. The ratios of the total sulfur to heating value decreases with increases of pyrolysis temperature up to around 600 °C for acid treated lignites and no major changes are observed at higher pyrolysis temperatures; no common behaviour is observed for original lignites.