【作者】 李海峰；

【导师】 苏胜； 向军；

【作者基本信息】 华中科技大学 ， 热能工程， 2020， 博士

【摘要】 煤气化技术是煤炭高效利用的重要技术之一。煤气化过程中产生一定浓度H₂S会对下游设备产生腐蚀,并带来严重的环境污染等问题。对煤气化气中的H₂S进行高效脱除,是实现煤炭高效清洁利用的关键问题之一。目前,中高温干法脱硫方法因其系统效率高、成本低等诸多优点,是煤气净化技术中的研究热点,其主要采用高温脱硫剂实现对煤气中H₂S的脱除。然而,目前对不同制备条件及活性组分的脱硫剂研究尚不完善,脱硫剂在脱硫-再生过程中脱硫性能稳定性及物理化学结构变化尚缺乏深入系统研究,从而无法从机理层面对脱硫剂的脱硫及再生过程进行阐释。从脱硫剂制备条件、活性组分、脱硫及再生前后物理化学结构变化以及反应动力学等多种角度对脱硫剂开展系统深入研究,对进一步提升高温脱硫剂性能及深入揭示高温H₂S脱除反应机理,具有重要的理论与实际意义。鉴于Mn活性组分在H₂S脱除方面的良好表现,首先制备了Mn_xO_y/Al₂O₃高温脱硫剂,系统性研究了焙烧温度、焙烧时间及焙烧气氛等制备条件对其脱硫性能影响,深入分析了Mn_xO_y/Al₂O₃脱硫剂物理化学结构特性对其脱硫性能的影响机理。结果表明:焙烧温度及焙烧时间对新鲜脱硫剂的穿透硫容影响较小,但H₂和N₂气氛下焙烧制备的脱硫剂穿透硫容高于空气下焙烧制备的脱硫剂穿透硫容。脱硫-再生循环过程中,脱硫剂中Al₂O₃晶型结构会发生转变,Al₂O₃与Mn Al₂O₄之间的相互转化以及孔结构的坍塌等因素导致部分Mn_xO_y会被Al₂O₃包裹,脱硫剂活性组分减少,循环脱硫-再生反应过程中脱硫剂的穿透硫容降低。实验结果表明,900^oC焙烧温度及焙烧时间≥6 h所制备的脱硫剂物理化学结构相对稳定,在循环脱硫-再生反应过程中穿透硫容的降低幅度较小。为了提高循环脱硫-再生反应过程中脱硫剂脱硫性能的稳定性,研究采用La改性Mn_xO_y/Al₂O₃脱硫剂,并结合脱硫-再生循环反应过程中脱硫剂的性能及其物化结构变化的相关分析,揭示了La改性对脱硫剂脱硫性能的影响机理。研究结果表明:La改性负载方法及制备条件对改性脱硫剂的脱硫性能存在一定影响。相比于La与Mn氧化物同时浸渍及La负载于Mn_xO_y/Al₂O₃所制备的脱硫剂,La改性Al₂O₃后负载Mn_xO_y所制备Mn_xO_y/Al₂O₃-La的穿透硫容的降低幅度较小。随着La负载量增大,Mn_xO_y/Al₂O₃-La新鲜脱硫剂的穿透硫容虽有所减小,但脱硫-再生循环反应过程中脱硫剂穿透硫容降低的幅度也有所减小。当La改性脱硫剂在制备过程中生成La Al O₃时,La Al O₃可以提高脱硫-再生循环过程中脱硫剂的热稳定性,抑制Al₂O₃包裹活性组分,从而减小脱硫剂穿透硫容的降低幅度。为了进一步改善脱硫剂脱硫性能,研究了采用Ce不同负载方法改性Mn_xO_y/Al₂O₃-La脱硫剂。研究发现,Ce改性可以降低Mn离子结合能,提高脱硫剂对H₂S的吸附力,改善了循环过程中再生脱硫剂的H₂S脱除率,但Ce负载顺序对脱硫剂脱硫性能及其稳定性存在较大影响。Ce负载于Mn_xO_y/Al₂O₃-La表面,会堵塞脱硫剂部分孔道,所制备的脱硫剂穿透硫容较低,在脱硫-再生循环反应过程中孔结构的稳定性较差,其穿透硫容降低幅度也较大。Ce与Mn同时负载制备Ce-Mn_xO_y/Al₂O₃-La脱硫剂中,Ce⁴⁺会促进Mn基电子密度增大,有助于H₂S吸附,其穿透硫容较高;同时,在脱硫-再生循环反应过程中Ce-Mn_xO_y/Al₂O₃-La脱硫剂的物理化学结构稳定性较好,其穿透硫容降低的幅度也较小。为了揭示各种关键因素对脱硫剂性能影响,系统研究了反应温度、空速以及气体组分对Ce-Mn_xO_y/Al₂O₃-La等脱硫剂的影响机制。煤气化气中H₂和CO浓度对脱硫剂穿透硫容的影响较小。CO₂和H₂O不利于脱硫剂的脱硫反应。相比于Mn_xO_y/Al₂O₃-900脱硫剂,Ce-Mn_xO_y/Al₂O₃-La脱硫剂适用的H₂S浓度范围较大。当反应温度<850^oC时,两种脱硫剂的穿透硫容随着反应温度的升高而增大;但当反应温度>850^oC,Ce-Mn_xO_y/Al₂O₃-La穿透硫容随温度的变化较小,而Mn_xO_y/Al₂O₃-900穿透硫容降低。相比于Mn_xO_y/Al₂O₃-900脱硫剂,Ce-Mn_xO_y/Al₂O₃-La脱硫剂在更大的空速范围内能保持较高的脱硫性能。为了揭示Ce-Mn_xO_y/Al₂O₃-La脱硫剂的再生特性,采用不同再生气氛及反应条件,系统研究了脱硫剂再生性能及物化结构变化规律。结果表明,再生气氛的组成及浓度对脱硫剂再生性能影响较大。相比于SO₂的再生过程,采用O₂进行脱硫剂再生的反应速率较快,再生脱硫剂的穿透硫容较高。再生过程中若O₂浓度过大,脱硫剂孔结构遭到破坏,再生脱硫剂穿透硫容明显降低。当再生反应温度为850^oC时,再生脱硫剂穿透硫容较高;再生气体空速过高,再生脱硫剂的穿透硫容较低。更多还原

【Abstract】 Coal gasification technology is the one of important technologies for efficient coal utilization,but H₂S in coal gas can corrode the downstream device and cause serious environment pollution.High efficiency H₂S removal from coal gas is one of the key issues to realize high efficiency coal clean utilization.At present,the mid-and high-temperature for H₂S removal technology using solid sorbent is the research focus on coal gas purification.However,the researches on the vairous prepare conditions and active components on sorbent are imperfect,and it lack in-depth and systematic study on the durability of desulfurization performance and the evolution of chemical and physical structure of sorbent.The intensive study on the prepare conditions,active component,the evolution of chemical and physical structure during desulfurization process and reaction kinetic has important theoretical and practical significance for further improving the desulfurization performance and intensive study on the reaction mechanism of high temperature H₂S removal from coal gas.The paper firstly prepared the Mn_xO_y/Al₂O₃ sorbent with good desulfurization performance,and then investigated the effect of calcination conditions（calcination temperature,calcination time,calcination atmosphere）on the desulfurization performance of Mn_xO_y/Al₂O_3,indicating the influence mechanism of evolution of physical and chemical structure on the desulfurization performance of Mn_xO_y/Al₂O₃.The result shows that the calcination temperature and calcination time have slight effect on breakthrough sulfur capacity（BSC）of fresh sorbent.The BSC of Mn_xO_y/Al₂O₃ calcined in H₂ and N₂ are higher than BSC of Mn_xO_y/Al₂O₃ calcined in air.The phase transformation of Al₂O₃,the mutual transformation between Al₂O₃ and Mn Al₂O₄,and the disappearance of some micropores during desulfurization-regeneration cycles could lead Mn_xO_y to be covered by Al₂O₃,which cause the loss of active component.It leads the BSC decreasing during several desulfurization-regeneration cycles.When the calcination temperature of sorbent is 900°C and the calcination time is above 6 h,the tissue structure of sorbent is more stable,which is beneficial for the BSC durability during several desulfurization-regeneration cycles.In order to improve the durability of desulfurization performance of sorbent during desulfurization-regeneration cycles,the paper studied the effect of loading sequence and prepared conditions on the variation of desulfurization performance and physical-chemical structure of Mn based sorbent modified with La during desulfurization-regeneration cycles,which can reveal the effect mechanism of La modification on the sorbent for high temperature H₂S removal.The results show that the La loading methods,La amount and preparation conditions have effect on the desulfurization performance of sorbent.Compared the sorbent with co-impregnation of Mn and La and the sorbent with La loading on the surface of Mn_xO_y/Al₂O₃,Mn_xO_y/Al₂O₃-La with Mn loading on the Al₂O₃ modified with La has better BSC durability.The extent of BSC decreasing of Mn_xO_y/Al₂O₃-La during desulfurization-regeneration cycles decreases with the increasing of La amount while the BSC of fresh sorbents decrease.The formation of La Al O₃ in sorbent modified with La can improve the thermal stability of tissue structure of sorbent,it can inhibit Mn_xO_y being covered with Al₂O₃,leading better BSC durability during desulfurization-regeneration cycles.The Ce modified the sorbent with different loading sequences,aiming to further improve the desulfurization performance of sorbent.The results show that the Ce loading can decrease the binding energy of Mn ion and improve the H₂S adsorption capability of regenerated sorbent,which can significantly increase H₂S removal efficiency of regenerated sorbent during desulfurization-regeneration cycles.The Ce loading sequence has effect on the desulfurization performance of sorbent modified with Ce.The BSC and BSC durability of Ce/Mn_xO_y/Al₂O₃-La with Ce loading on Mn_xO_y/Al₂O₃-4.83La-9 are worse than that of Mn_xO_y/Al₂O₃-4.83La-9,because that the Ce oxides agglomerate on the surface of Ce/Mn_xO_y/Al₂O₃-La would lead the pore blocking.So,the BSC of Ce/Mn_xO_y/Al₂O₃-La is low.The stability of pore structure is poor,which leads less BSC durability of Ce/Mn_xO_y/Al₂O₃-La during desulfurization-regeneration cycles.The Ce⁴⁺in the Ce-Mn_xO_y/Al₂O₃-La with co-impregnation of Mn and Ce based oxides can improve the electron cloud density of Mn ion,which is beneficial for H₂S adsorption,so Ce-Mn_xO_y/Al₂O₃-La has higher BSC than other sorbents.The physico-chemical structure of Ce-Mn_xO_y/Al₂O₃-La is much stable,which leading better BSC durability during desulfurization-regeneration cycles.The paper studied the effect of the reaction temperature,space velocity and gas component in desulfurization process on the desulfurization performance of sorbent to reveal the effect of critical factor on the desulfurization performance of sorbent.H₂ and CO in coal gas almost has no effect on the desulfurization performance of Mn_xO_y/Al₂O₃-900and Ce-Mn_xO_y/Al₂O₃-La.The desulfurization performance of Ce-Mn_xO_y/Al₂O₃-La has slight differences with the various H₂S concentrations,and higher H₂S concentration is harmful for the desulfurization performance of Mn_xO_y/Al₂O₃-4.83La-9.The existence of H₂O or CO₂ is adverse for H₂S removal efficiency and BSC of Mn_xO_y/Al₂O₃-900 and Ce-Mn_xO_y/Al₂O₃-La,but H₂S removal efficiency of Ce-Mn_xO_y/Al₂O₃-La is higher than that of Mn_xO_y/Al₂O₃-900.The BSC of Mn_xO_y/Al₂O₃-900 and Ce-Mn_xO_y/Al₂O₃-La increase with the rising of reaction temperature when the reaction temperature is lower than 850°C.However,when the reaction temperature is above 850°C,the BSC of Mn_xO_y/Al₂O₃-900decreases,while the BSC of Ce-Mn_xO_y/Al₂O₃-La slightly changes with the rising of reaction temperature.The lower weight hourly space velocity（WHSV）has little effect on the BSC of sorbent,but the BSC of Mn_xO_y/Al₂O₃-900 and Ce-Mn_xO_y/Al₂O₃-La decrease with higher WHSV,the extent of BSC decreasing of Mn_xO_y/Al₂O₃-900 is higher than that of Ce-Mn_xO_y/Al₂O₃-La,indicating that Ce-Mn_xO_y/Al₂O₃-La can be applied for high temperature H₂S removal with larger WHSV range.In order to reveal the regeneration characterization of sorbent,the paper systematic analyzed the evolution law of physicochemical structure and regeneration capacity in regeneration process according to the study on the various regeneration atmosphere and regeneration conditions.The results show that the reaction rat with O₂ regeneration is higher than that of regeneration process using SO₂,and the BSC of regenerated sorbent with O₂ regeneration is higher than that of sorbent with SO₂regeneration.The pore structure of regenerated sorbent is destroyed seriously in the regeneration process with excessively high O₂ concentration,leading the lower BSC of regenerated sorbent.The BSC of regenerated sorbent is highest when the regeneration temperature is 850°C.Too high WHSV in regeneration process is unfavorable for the BSC of regenerated sorbent.更多还原