赤铁矿作用下煤化学链气化过程碳氮元素转化机理

以赤铁矿为载氧体,利用流化床反应装置比较传统煤气化与化学链煤气化的不同特性,同时研究气化温度、水蒸气流量、赤铁矿/煤比(即氧/碳摩尔比)、燃料种类等反应条件对化学链气化特性的影响,并分析气化反应后载氧体基本特性的变化。结果表明,化学链气化呈现2个不同的反应阶段。在初始的挥发分析出阶段,还原性气体与载氧体、NOx的氧化还原反应对碳、氮元素的转化具有重要影响,NO和N2O均明显析出;在煤焦气化阶段,载氧体能够提高半焦反应活性、促进半焦气化和N2O生成,N2O是主要的NOx产物。赤铁矿载氧体中的Fe2O3在气化过程被还原、部分转化为Fe3O4,未发现载氧体烧结现象。     

基于CuMn2O4载氧体的生物质化学链气化热力学分析

建立了以CuMn2O4为载氧体、松木屑为燃料的生物质（B）化学链气化模型,对CuMn2O4载氧体和松木屑之间的化学链气化反应进行了热力学模拟。研究了气化过程中CuMn2O4载氧体的还原过程,考察了燃料反应器内载氧体与生物质摩尔比(n(O)/n(B))、反应温度、水蒸气与生物质摩尔比(n(H2O)/n(B))、CO2与生物质摩尔比(n(H2O)/n(B))等因素对气化反应的影响,分析了空气反应器内载氧体晶格氧的恢复过程。热力学分析表明：CuMn2O4在气化反应中可以提供晶格氧,有效促进松木屑的气化。CuMn2O4载氧体中的Cu和Mn组分在化学链气化反应中分别按照CuO→Cu2O→Cu和Mn2O3→Mn3O4→MnO的顺序逐级被还原,并且Mn2O3优先CuO被还原。以气化系统的碳转化率和合成气产量为主要评价指标,优化的反应条件为：n(O)/n(B)为0.16,反应温度为1273 K,n(H2O)/n(B)为0.40,n(CO2)/n(B)为0.20。在空气反应器内,CuMn2O4载氧体还原后失去的晶格氧经空气氧化后可以恢复到初始状态。     

基于锰矿石载氧体的宁东煤化学链燃烧特性

以煅烧后的天然锰矿石为载氧体,基于热化学分析软件(HSC Chemistry 6.0)计算,并与实验相结合,在小型鼓泡流化床上进行了宁东煤气化和燃烧特性的研究。首先将模拟计算与实验结果对比,得到宁东煤与锰矿石载氧体不同掺混比下的燃烧特性;其次,基于模拟数据和实验参数,并结合修正动力学模型,对该实验工况下燃料反应器和空气反应器(FR-AR)反应系统进行热-质平衡计算。结果表明：模拟计算煤燃烧的碳转化率和气相生成物等与实验结果一致,误差小;经1173.15 K高温煅烧的锰矿石载氧体可大幅缩短煤气化时间,并与煤合成气有良好的反应活性;FR-AR系统可以实现自热平衡。     

基于铁基载氧体的市政污泥气化特性模拟及实验研究

基于Aspen Plus软件中的模拟及流化床反应器中的部分实验,研究了铁基载氧体在市政污泥化学链气化中对碳转化效率、合成气组分、硫氮污染物排放等特性的影响。结果表明：燃料反应器中氧/碳摩尔比(n(O)/n(C))的增加提高了污泥的碳转化率,但却降低了CO、H2的浓度,碳转化率趋于平稳时明显减少了羰基硫(COS)和H2S的排放;燃料反应器中温度的提升利于合成气热值和污泥气化率的提高,降低H2S排放量的同时增加SO2的生成;随着水蒸气与污泥质量流量比的增加,H2的摩尔分数明显上升,在其质量流量比超过12时,变化不再明显;空气反应器中空气与载氧体摩尔流量比(空载比)的增加会使载氧体再生程度提高,但空载比增加到1.3时,开始有大量NOx的生成;空气反应器中反应温度的升高对载氧体的再生影响不大,但会导致热力型NOx的产生。     

化学链气化过程中昭通褐煤灰对锰矿石载氧体的影响

为探究化学链气化过程中煤灰及其组分对锰矿石载氧体的影响及作用机理,制备了昭通褐煤煤灰,以煤灰中主要组分Fe₂O₃、CaO和MgO等氧化物颗粒配制单一及混合组分的模拟煤灰,在高温流化床反应器中以水蒸气为气化剂进行了系列研究。结果表明：添加5%(质量分数)褐煤煤灰后,合成气产量升高而碳转化率降低,且随着煤灰添加量的继续增多,合成气产量呈先降低后升高趋势,而碳转化率则呈现先升高后降低趋势,在煤灰添加质量分数为15%时,出现最高的碳转化率79.7%和最低的合成气产量0.702 L。Fe₂O₃组分明显提高了碳转化率和合成气产量;CaO与Mn₂O₃高温反应生成了Ca₂Mn₂O₅,提高了载氧体选择性,使得合成气产量增大;MgO显著降低了碳转化率和合成气产量。双组分及MgO-Fe₂O₃-CaO三组分模拟煤灰的研究发现,MgO对气化反应进程抑制作用强于Fe₂O₃和CaO的促进作用,相比于Fe₂O₃-MgO双组分模拟煤灰,CaO-MgO模拟煤灰对载氧体气化活性的抑制作用影响最大。     

基于铁酸钙载氧体的稻壳化学链气化反应特性

铁酸钙载氧体(CaFe2O4/Ca2Fe2O5,简称CF)具有弱氧化性,在化学链气化过程中对CO选择性高,且可以通过碳酸化反应捕集CO2,提高合成气的低位发热量。分别在热重分析仪和固定床反应器上对基于铁酸钙载氧体的稻壳（简称R）化学链气化反应特性进行研究,分析铁酸钙载氧体与CO2的碳酸化反应特性,考察铁酸钙载氧体与稻壳的质量比(mCF/mR)、反应温度和循环反应次数对稻壳化学链气化特性的影响,并采用XRD和SEM等手段对载氧体进行表征。结果表明：当反应温度为370~840 ℃时,铁酸钙载氧体与CO2发生碳酸化反应;当反应温度为800 ℃、mCF/mR =0.73时,反应器出口合成气的CO2产率较低,低位发热量最高;经过10次化学链循环气化反应,CaFe2O4循环再生能力良好,但铁酸钙载氧体的碳酸化反应性能下降。     

低阶煤固定流化床热解及半焦气化实验研究

采用固定流化床研究了三种低阶煤的常压热解及其热解半焦的气化特性,探究了样品粒度、反应温度、反应时间及流化气中O2含量对上述过程的影响,确定了循环流化床热解-气化耦合工艺适宜的反应条件。结果表明,在实验选择范围内,样品的粒度基本不会影响热解过程,在水蒸气气氛下,温度越高,热解气体产率越高,半焦产率越低;600 ℃和20 min时能获得最高的焦油产率。循环流化床热解-气化耦合工艺碳的有效利用率率高于原煤固定流化床气化工艺,同时副产煤焦油;温度越高,有效气产率和有效碳转化率越高;实验范围内,O2含量对合成气产率的影响较小,但可以调节H2和CO的相对含量;900 ℃、半焦气化15 min即可获得较理想的合成气产率及有效碳转化率。     

加压流化床反应器中煤焦化学链气化实验与数值模拟研究

采用CPFD模拟和实验相结合的方法,研究了0.1～0.5 MPa压力条件下,鄂尔多斯烟煤焦和Fe2O3/Al2O3载氧体(OC)的流动特性及气化反应行为。结果表明,颗粒体积分数是影响加压下煤气化速率和合成气品质的关键因素,当颗粒体积分数在1.0%～2.8%区间、操作压力从0.1 MPa加压至0.3 MPa时,煤焦气化速率增长2.7倍,合成气摩尔分数由72%增长至78%。操作压力及颗粒流态的改变对水煤气变换反应速率无显著影响,通过煤焦气化反应和载氧体还原反应的耦合可实现合成气组分比例的调控。XRD表征显示Fe基载氧体各还原态组分分布与模拟结果一致。操作压力升至0.3 MPa,载氧体还原反应速率的增幅减小,释氧量增大50.18%;继续升压至0.5 MPa,显著促进了载氧体还原反应速率的增加,但释氧量仅增加3.92%。     

碱金属掺杂对NiFeAlO4载氧体结构及反应特性的影响

采用溶胶-凝胶法和浸渍法制备了碱金属掺杂的尖晶石结构NiFeAlO4载氧体,考察了制备方法、碱金属种类、碱金属掺杂比例对NiFeAlO4载氧体结构、煤化学链燃烧特性和循环稳定性的影响。结果表明,溶胶 凝胶法制备的钾掺杂NiFeAlO4载氧体具有更好的反应性,当载氧体与煤质量比为20∶1时,掺杂质量分数为5% K2CO3的NiFeAlO4载氧体与煤反应的碳转化率为99%,高于NiFeAlO4载氧体与煤反应时的碳转化率（87%）。与NiFeAlO4载氧体相比,掺杂质量分数为5% K2CO3的NiFeAlO4载氧体呈现出更好的循环稳定性,主要归因于碱金属K的掺杂改善了载氧体的反应活性,对载氧体的团聚有抑制作用,且反应前后载氧体晶相结构保持不变。     

对置式水煤浆气化炉内燃烧气化过程的数值模拟

以某煤处理量600 t/d对置式四喷嘴气化炉为研究对象,采用非均匀结构化网格,通过Fluent软件对其炉膛内水煤浆燃烧气化过程进行数值仿真。模拟计算了炉内温度场和气化产物浓度分布,并讨论了水煤浆浓度、喷射角度以及氧煤比等工艺参数对炉内气化燃烧过程的影响。结果表明,随喷射角度的增大和水煤浆浓度的升高,有效合成气含量有所增大;随氧煤比增大,有效合成气含量升高,并在氧煤比为1.3时达到最大值。     

Aspen Plus simulation of steam-gasification of different crude oils: A detailed comparison

The gasification process is being developed to obtain environmentally clean and efficient syngas from solid (coal, biomass, and municipal solid waste) or liquid (heavy oil and waste lubricant oil) fuels for power generation. An Aspen Plus model of crude oil gasification in presence of steam as a gasifying agent that can predict syngas yield, tar concentration, and performance parameters was developed. Effects of some critical parameters such as gasification temperature, steam-fuel-ratio on hydrogen yield, tar content, and char conversion of three different crude oils were explored. Results showed that the hydrogen yield increases by increasing steam/fuel ratio from 0.5 to 0.7 (wt/wt), and then reduces smoothly due to the endothermic behavior of methane reforming reaction, which releases three hydrogen moles. It also found that as the temperature increases within the range, hydrogen yield increases dramatically, which can be explained according to the Le Chatelier's principle on the endothermic reforming reactions of methane and tar cracking. Modeling results validated against the experimental measurements and found to be in a good agreement.     

EFFECT OF SOLVOLYTIC EXTRACTION AND PYROLYSIS PRETREATMENTS ON THE TOEMPRATURE STEAM GASIFICATION REACTTVITY OF COAL AND REDUCTION OF TAR FORMATION IN PRODUCT GASES

Pre-extraction of Talcher coal ( a bituminous coal) in anthracene oil was found to be a beneficial treatment for enhancing the reactivity for steam gasification of coal. Similarly, anthracene oil followed by liquid paraffin extraction of coal was also found to be a-better pretreatment for the steam gasification of coal. Anthracene oil extraction at 270°Cand steaming of coal at 650°C had almost equal effect on steam gasification of coal. Pyrolysis in steam of pre-extracted coals was found to further enhance the reactivity of coal for steam gasification. The studies were further confirmed by carrying out thermogravimetric analysis of pretreated coals in steam atmosphere. Degree of cross-linking in pretreated coals was studied by measurement of swelling of coal in quinoline. The formation of tar in gaseous product was reduced as a result of pre-extraction and steam pyrolysis of coal prior to their gasification in steam.     

富甲烷气自热转化催化剂及工艺条件研究

在固定床反应器中,对适合富甲烷气自热转化要求的Ni/α-Al2O3催化剂进行了一系列的工艺条件试验,考察了温度、压力、空速、水碳比和氧碳比对甲烷转化率、氢收率和CO选择性的影响,并进行了120h的寿命试验。结果显示,在甲烷空速GHSV=2000h-1,nH2O/nCH4=1.0,nO2/nCH4=0.6,P=0.5MPa,T=1073K的条件下,甲烷转化率、氢收率和CO选择性分别一直保持在96.7%、70.8%和62.4%左右,以上结果表明该催化剂具有很好的稳定性和较高的活性。     

EFFECT OF SOLVOLYTIC EXTRACTION AND PYROLYSIS PRETREATMENTS ON THE TOEMPRATURE STEAM GASIFICATION REACTTVITY OF COAL AND REDUCTION OF TAR FORMATION IN PRODUCT GASES

ABSTRACT

Pre-extraction of Talcher coal ( a bituminous coal) in anthracene oil was found to be a beneficial treatment for enhancing the reactivity for steam gasification of coal. Similarly, anthracene oil followed by liquid paraffin extraction of coal was also found to be a-better pretreatment for the steam gasification of coal. Anthracene oil extraction at 270°Cand steaming of coal at 650°C had almost equal effect on steam gasification of coal. Pyrolysis in steam of pre-extracted coals was found to further enhance the reactivity of coal for steam gasification. The studies were further confirmed by carrying out thermogravimetric analysis of pretreated coals in steam atmosphere. Degree of cross-linking in pretreated coals was studied by measurement of swelling of coal in quinoline. The formation of tar in gaseous product was reduced as a result of pre-extraction and steam pyrolysis of coal prior to their gasification in steam.