【作者】 王俊宏；

【导师】 谢克昌； 常丽萍；

【作者基本信息】 太原理工大学 ， 化学工程与技术， 2010， 博士

【摘要】 在今后相当长的一段时期内,煤炭仍将是我国的主要能源。西部开发是我国经济发展的重点,而煤炭又是西部地区的支柱产业,针对西部煤所具有的结构特征对其热化学转化特性进行研究,对于西部煤炭资源的开发利用具有重要的理论意义和现实意义。本文选取新疆哈密、宁夏灵武、神东三种西部煤作为研究对象,系统研究了这些惰质组分含量较高煤的结构特征以及热解、气化、燃烧反应性,并与强还原性的中部平朔煤进行了比较;还通过去离子水洗、单酸洗、混酸洗逐级脱除煤中的内在矿物质,考查了内在以及外加矿物质对煤热化学转化特性的影响。得到以下主要结论:1)三种西部煤具有弱还原性煤的特征,而中部平朔煤具有较强的还原性特征。弱还原性煤具有较高的惰质组分和O含量,较低的挥发份、灰分以及H/C原子比;弱还原性煤惰质组中的C含量高于镜质组,H/C以及O/C原子比低于镜质组;而强还原性煤惰质组中的C含量以及H/C原子比低于镜质组,O/C原子比高于镜质组。弱还原性煤灰分中含有较高的Fe2O3、CaO、MgO和Na2O,较低的SiO2和Al2O3;而强还原性煤中SiO2和Al2O3含量较高。西部煤大多属于不黏煤或弱黏煤,而平朔煤属于粘结性煤。随着煤中惰质组分含量的增加,芳碳率及平均缩合环数增加;惰质组中芳香微晶结构单元较大,芳香层片在空间的排列更加规整,相互定向程度也优于镜质组。随着热处理温度的升高,煤的微晶结构渐趋规整。2)提出了判断煤还原程度强弱的经验式k = I%×0.8 + O% + Rz - H%×10为定量判断煤还原程度的相对强弱提供了依据。3)煤中惰质组含量越高,其热解反应性越低。高温下弱还原性煤的二次热解反应性明显高于强还原性的平朔煤,促进了大量含氧气体的释放。弱还原性煤热解时生成的含氧气体较多,含氢气体较少,且煤中惰质组分越多,含氧气体的释放量就越多;弱还原性煤镜质组热解释放的含氧气体量也高于强还原性煤。煤热解过程中含氢以及含氧气体的释放量与煤中氢、氧元素的含量相一致。随热解温度的升高,气相产物中含氢、含氧气体的释放呈现出规律性的变化,存在一个释放温区,CO为300-900℃, CO2为200-800℃, H2为500-900℃, CH4为400-800℃, C2以上烃类气体为400-600℃.4)西部弱还原性煤焦的气化反应性高于强还原性的平朔煤焦;弱还原性煤惰质组分焦的气化反应性高于镜质组分焦,这与强还原性煤显微组分焦的气化反应性相反。煤焦的气化反应性与煤的亚显微结构密切相关,惰质组中,丝质组与半丝质组含量越高,焦的气化反应性越强;镜质组中,均质胶质体与基质胶质体含量越高,焦的气化反应性越弱。惰质组和镜质组之间存在协同作用,合适的惰质组分含量能够增加样品焦的气化反应性。与强还原性煤相比,西部煤气化反应能够生成大量的H2和CO,但CH4的生成量较少。未反应收缩核模型非常适于描述弱还原性煤焦的气化反应机理,由此得到的表观活化能基本能够反映煤焦的气化反应性。5)煤的燃烧反应性随煤中惰质组分含量的增加而增强。西部弱还原性煤的燃烧反应性高于强还原性的平朔煤。升温速率增大,煤的燃烧反应性增加;O/C质量比降低,煤的可燃性下降;实验用样量增多,最大燃烧速率温度和燃尽温度升高,最大燃烧速率下降,点火温度几乎不变;样品粒径减小,最大燃烧速率增大,但最终失重量变化不大;未反应收缩核模型也适于描述弱还原性煤的燃烧机理,由此得到的表观活化能基本能够反映煤的燃烧特性。6)硅铝酸盐阻碍煤的热解;碱土金属及过渡金属盐类促进弱还原性煤的热解,水溶性的部分盐类阻碍弱还原性煤的热解,后两类盐对强还原性平朔煤的热解作用不明显。碱土金属及过渡金属盐类促进煤热解产生含氧气体,阻碍弱还原性煤热解生成含氢气体,促进强还原性煤热解生成含氢气体;硅铝酸盐促进弱还原性煤热解生成含氧气体,阻碍生成含氢气体,而对于强还原性煤热解的作用正好相反。外加钙对煤的热解具有促进作用,主要促进煤热解生成H2、CO和CO2。外加钠对煤热解的作用与煤的种类以及钠的添加量有关。钠的加入,促进煤热解生成H2和CO2,阻碍西部煤热解生成CH4和CO,促进强还原性煤热解生成CO,对强还原性煤热解生成CH4的量影响不大。内在矿物质阻碍强还原性煤焦的气化和燃烧,而促进弱还原性煤焦的气化,对弱还原性煤燃烧的作用与煤种类有关。外加钠、钙,能够促进煤焦的气化与燃烧。由于钠的催化作用,使得弱还原性煤二次最大燃烧速率显著高于强还原性的平朔煤。更多还原

【Abstract】 At present, the development of the west regions has been a key of China’s economic development. Coal is the pillar industry in China’s western regions’s development, so it has important theoretical significance and practical utilization value to study the structure characteristics and thermal chemical conversion properties on the coals from that region.Three coals which have high inertinite content from Xinjiang Hami, Ningxia Lingwu and Shengdong mines in China’s western regions were selected as experimental coal samples. Their structure characteristics and pyrolysis, gasification and combustion reactivities were detailedly researched and compared with that of Pingshuo coal from China’s middle region. In addition, intrinsic minerals in these coals were eliminated by deionized water, single acid and compound acid washing and the influences of these intrinsic and added minerals on the thermal chemical conversion properties of these coals were also researched. Main conclusions were obtained as follows:1) Three coals from China’s western ragions demonstrate the properties of the weak reducibility and Pingshuo coal has the strong reducibility properties. Weak reducibility coals have high inertinite and O content, low volatile, ash and H/C atomic ratio; C content in inertinite is higher and H/C and O/C atomic ratio are lower than that in vitrinite; and for strong reducibility coal, C content and H/C atomic ratio in inertinite are lower and O/C atomic ratio is higher than that in vitrinite. The ashes in the weak reducibility coals have higher Fe2O3, CaO, MgO and Na2O, lower SiO2 and Al2O3, and that the ash in strong reducibility Pingshuo coal has higher SiO2 and Al2O3. Most of the coals in china’s western belong to non-coking or weak-coking coal, and that Pingshuo coal belongs to coking coal. Aromaticity and mean ring condensation number increase with inertinite content increase in coal. The aromatic crystallite unit is bigger, aromatic layer structure is more regularity and mutual directional degree is superior in inertinite to that in vitrinite. As heating treatment temperature increase coal crystallite structure becomes gradually regularity.2) The experimental relation expression has been put forward to estimate the reducibility of coal: k = I%×0.8 + O% + Rz - H%×10 to provide a basis for quantitative analysis of the relative intensity of the coal reducibility.3) The more inertinite in coal, the weaker coal pyrolysis reactivity is. The secondary pyrolysis reactivity at higher temperature on weak reducibility coals is higher than that of strong reducibility Pingshuo coal, which leads to the more realese of containing-O gases. The more containing-O gases and the lesser containing-H gases are released during pyrolysis of weak reducibility coal and its inertinite than that of strong reducibility coal and its inertinite. The yields of containing-O gases from vitrinite pyrolysis of weak reducibility coal are higher than that from strong reducibility coal vitrinite. The yields of containing-O and containing-H gases from coal pyrolysis are also consistent with O and H content in coal. With pyrolysis temperature increasing, the yields of containing-O and containing-H gases released present a regular change trends and the optimal release temperature regions are CO 300-900℃, CO2 200-800℃, H2 500-900℃, CH4 400-800℃and C2-4 hydrocarbon 400-600℃.4) The gasification reactivity of weak reducibility coal char is higher than that of strong reducibility coal char; the gasification reactivity of weak reducibility coal inertinite char is higher than that of vitrinite char; and it is just reverse to strong reducibility coal maceral char. The gasification reactivity of coal has to do with the ultrastructures of the coal. The more fusinite and semifusinite content in inertinite, the higher coal char gasification reactivity is; and that the more telocollinite and desmocollinite content in vitrinite, the weaker coal char gasification reactivity is. There are synergy action between inertinite and vitrinite and appropriate inertinite content could lead to higher gasification reactivity of char. More H2 and CO are released from weak reducibility coal gasification, but the yield of CH4 is smaller than that from strong reducibility coal gasification. Unreacted shrinking core model is fit for the mechanism description of coal char gasification process and the gasification reactivity of char could be generally reflected by activation energy calculated from the model.5) The more inertinite content in coal, the higher coal combustion reactivity is. The combustion reactivity of weak reducibility coal is higher than that of strong reducibility coal. The combustion reaction rate increases with heating rate increasing. The ignitibility of coal decreases with O/C quality ratio decreasing. As the dosage of coal sample increases, the maximum combustion rate temperature and burnout temperature increase, the maximum combustion rate decreases, but the ignite temperature almost unchanges. As the particle size of coal sample decreases, the maximum combustion rate increases, but the last weight loss is almost unchanged. Unreacted shrinking core model is also fit for the mechanism description of coal combustion process and the combustion properties of these coals can be reflected by activation energy calculated from this model.6) Aluminosilicate restrains coal pyrolysis process. Alkaline earth salts and some transition metal salts accelerate, and some water-solubility salts restrain the pyrolysis of weak reducibility coals, but the latter two salts hardly affect the pyrolysis of strong reducibility Pingshuo coal. Alkaline earth salts and transition metal salts can accelerate the formation of containing-O gases during coal pyrolysis, hold back the release of containing-H gases during weak reducibility coal pyrolysis, but accelerate that from strong reducibility coal pyrolysis. Aluminosilicate accelerate weak reducibility coal pyrolysis to release containing-O gases, and restrain to produce containing-H gases, but it is just reverse for strong reducibility coal. Added Ca can accelerate coal pyrolysis to release more H2, CO and CO2. The effect of added Na on coal pyrolysis has connection with types of coal and Na content. It can accelerate coal pyrolysis to produce H2 and CO2, restrain weak reducibility coal pyrolysis to give birth to CH4 and CO, accelerate strong reducibility coal pyrolysis to release CO and haradly influence CH4 release.The effect of minerals on coal gasification and combustion is closely interrelated with coal characteristics. It can restrain the gasification and combustion process of strong reducibility coal char; alkaline earth salts, transition metal salts and aluminosilicate can accelerate weak reducibility coal char gasification, but the effect of minerals on the combustion of the weak reducibility coal has to do with types of coal. Added Ca and Na can promote coal char gasification and combustion. Added Na can accelerate remarkably coal combustion and result that the secondary maximum combustion rate of weak reducibility coals is significantly higher than that of the strong reducibility Pingshuo coal.更多还原