污泥对高灰熔融温度煤灰熔融特性调控机制

李 萌1,陈雪莉1,李风海2,许建良1,刘 霞1

(1.华东理工大学 含碳废弃物资源化零碳利用教育部工程研究中心,上海 200237;2.菏泽学院 化学化工学院,山东 菏泽 274015)

摘 要：我国高灰熔融温度煤储量巨大,灰中硅铝含量高,而部分污泥中碱性氧化物含量高,将其与高灰熔融温度煤共气化为高灰熔融温度煤灰熔融特性的调控提供了可能。研究了城市污泥(CS)和制药污泥(ZY)对高灰熔融温度焦作煤(JZ)灰熔融特性的影响。结果表明:向JZ灰中添加CS灰和ZY灰均可降低其灰熔融温度,添加ZY灰对JZ灰熔融温度降低效果更明显;CS灰和ZY灰的添加比例分别为15%和10%时,2种混合灰的流动温度降至1 380 ℃以下,满足气流床气化液态排渣要求。CS灰CaO含量高,ZY灰Fe2O3含量高,随污泥灰添加,CS灰中CaO与Al2O3和SiO2反应生成的钙长石增多,其与石英发生共熔导致液相含量增加降低了灰熔融温度;弱还原气氛下JZ-ZY灰中Fe3 被还原为Fe2 ,并使生成的铁尖晶石等铁系矿物质增多,低熔点铁尖晶石在低温下熔融及铁系矿物质与其他物质发生的低温共熔降低了JZ灰熔融温度。污泥灰添加比例相同时,与JZ-CS灰相比,JZ-ZY灰中理论固相含量更低;晶相衍射峰强度和数量更低;1 500 ℃时,ZY灰占比25%的混合灰达到全液相状态,而CS灰占比25%的混合灰中仍有部分莫来石。摩尔离子势α与2种混合灰的特征温度均呈线性正相关。JZ-ZY灰的α降幅更大,因此JZ-ZY灰熔融温度降低更明显。

关键词：高灰熔融温度煤;污泥;灰熔融特性;流动温度;调节机制

0 引 言

我国富煤、贫油、少气的资源禀赋决定了煤炭在我国能源消耗结构中将长期占据主导地位[1-2]。气化是煤炭清洁高效利用的有效方式[3-4]。气流床气化因煤种适应性广、热效率高和产品纯度高等优点成为煤气化技术的首选[5-6]。气流床气化通常采用液态排渣,灰渣的流动性是影响气化炉能否稳定运行的关键[7-8]。灰渣流动性通常由2个关键参数决定:煤灰黏度和灰熔融温度[9-12]。气流床气化炉的操作温度一般要求高于煤灰流动温度(TF)50～100 ℃,以保证气化炉顺利排渣。但在实际工业过程中,对煤灰TF有一定限制(TF<1 380 ℃),煤灰黏度宜控制在2.5～25.0 Pa·s[13]。由于煤灰黏度测量周期长且成本较高,有研究者提出通过研究和测量灰熔融温度预测灰分排渣行为[14-15]。我国高灰熔融温度煤储量丰富(>57%),单独直接用于气流床气化难以满足液态排渣要求[16]。煤灰熔融温度与煤灰化学组成关系密切[17-18]。已有研究主要采取3种方法改善煤灰熔融特性,包括向煤中添加助熔剂、配煤及煤与生物质共气化[19-20]。

我国每年污泥产量约20亿t,工业污泥和城市污泥是我国污泥主要来源[21]。污泥产量巨大,直接排放会危害环境和人类健康[22]。填埋、土壤利用和焚烧是常见污泥处理方法,但易受空间和环境压力限制,且焚烧运行成本非常昂贵。制药污泥的焚烧运行成本占总成本的25%～65%[23-24]。 《中华人民共和国水污染防治法》强调了污泥处理政策由“重水轻泥”转变为“泥水并重”,污泥资源化利用和后续合理处置受到广泛关注。水热碳化后,部分污水污泥热值为12～20 MJ/kg,与褐煤热值(11.7～15.8 MJ/kg)相似[25-27]。污泥中含大量能量,而传统处理方式受多方面限制,因此将污泥进行热利用并回收能量是目前国内外资源化利用污泥的重要方式和研究热点[28-29]。由于部分污泥热值较低,有时需添加辅助燃料(如煤),污泥与煤在流化床中共烧可有效改善污泥燃烧性能,去除烟气中污染物(如NOx)和二噁英且有助于灰中重金属凝固[30-34]。气化是一种清洁、高效和大规模利用污水污泥的有前景的热利用方法[35-36]。为提高污泥气化产品质量并减少污染物、灰分和重金属含量,通常将污泥与煤共气化,多用于中试规模工厂[37]。相比煤单独气化,污水污泥与煤共气化CO2排放更少[38],具有污染物少、成本低和热效率高等优点。学者发现将污泥与煤混合热利用能改变煤灰熔融特性。FOLGUERAS等[39]将不同污泥加入高碱含量褐煤中,发现褐煤灰熔融温度降低,降低程度与污泥添加量有关。混合灰碱酸比(B/A)为0.7～2.0时,混合灰熔融温度最低。孙保民等[40]将城市污泥加入高钠煤中研究混合灰熔融特性,发现城市污泥中的磷会与其他物质反应,形成具有高熔点(MP)的含磷矿物,增加其灰熔融温度。

已有学者研究了低硅铝含量的城市污泥和褐煤混合物在共气化过程中的灰熔融特性[27],但鲜见城市污泥与高灰熔融温度、高硅铝含量高阶煤混合灰在共气化系统中的灰熔融特性研究。制药污泥单独热解[41]及制药污泥与其他固体燃料共热解研究较多[42],但制药污泥气化,特别是与高硅铝煤共气化研究很少。因此,笔者以高硅铝含量、高灰熔融温度焦作煤(JZ)为原料,将其煤灰分别与城市污泥(CS)灰和制药污泥(ZY)灰混合,研究混合灰的灰熔融特性,以期为煤与污泥气流床协同气化提供理论指导。

1 试 验

1.1 试验原料

CS和ZY来自山东省菏泽市污水处理厂。高灰熔融温度JZ煤来自河南焦作。3种样品被粉碎成粒径小于200 μm的颗粒,其工业分析和元素分析见表1。由表1可知,污泥灰分和挥发分较高,而固定碳含量远低于煤。

表1 污泥和煤的工业分析和原料分析

Table 1 Proximate and ultimate analyses of coal and sludge

注：a为差减法所得;b为总含量。

1.2 混合灰的制备

3种样品灰均按照GB/T 1574—2001《煤灰成分分析方法》制备。将CS灰和ZY灰分别与JZ灰混合,2种混合灰中污泥灰质量分数分别为5%、10%、15%、20%和25%,对混合灰进行灰熔融温度测定和后续分析。

1.3 灰熔融特征温度的测定

按照GB/T 30726—2014《固体生物质燃料灰熔融性测定方法》,在还原性气氛(φ(CO2)∶φ(CO)=2∶3)下,采用ALHR-2 AFT分析仪测定了混合灰的熔融温度。升温过程如下:先将灰锥以20 ℃/min升温速率加热至900 ℃,以5 ℃/min速率继续加热。升温过程中根据灰锥形状变化记录4个特征温度。

1.4 高温渣样的制备

采用高温卧式管式炉制备高温渣样。操作步骤为:先将填充约2.0 g混合灰的坩埚置于刚玉舟内,将刚玉舟推入卧式管式炉加热区位置,拧上法兰;打开CO2和CO阀门,通过调节气体流量控制器控制混合气气体组成为φ(CO2)∶φ(CO)=2∶3,使整个管式炉始终处于弱还原性气氛中,打开排气口使混合气排出管式炉防止憋压,将管式炉以20 ℃/min升温速率加热至900 ℃,以5 ℃/min升温速率继续加热至目标温度;最后关闭气体阀门,打开法兰迅速拉出刚玉舟放入液氮中激冷。

1.5 灰化学组成分析

采用X射线荧光光谱仪(XR-1800,日本岛津)分析样品灰化学组成。测量操作条件为50 kV和40 mA。

1.6 矿物质组成分析

采用X射线衍射仪(D/max rB,Rigaku,日本)分析制取的渣样矿物质组成,操作条件为:40 kV和100 mA,Kα1=0.154 08 nm。扫描范围2θ为10°～80°,步长为0.01°,扫描速度为5(°)/min。

1.7 热力学平衡计算

基于吉布斯能量最小化理论,利用FactSage软件模拟了混合灰中无机物转化行为。通过Equilib模块获得理论矿物组成和液相组成。此外,选择phase diagram模块获得了JZ-CS混合灰的SiO2-Al2O3-CaO三元相图。

1.8 红外光谱(FT-IR)分析

采用衰减全反射红外光谱法(BRUKER D2,德国)研究1 600～400 cm-1熔渣样品晶体结构信息。红外光谱表征的操作条件为25 ℃。

2 结果与讨论

2.1 样品灰熔融特性分析

3种试验样品的灰熔融温度和化学组成见表2。JZ煤灰的4种特征温度均高于1 500 ℃;2种污泥的灰熔融温度值均较低,ZY灰的4种特征温度均高于CS灰。CS和ZY灰的理论矿物质组成如图1所示。由表2和图1(a)可知,CS灰中主要碱性氧化物为CaO,Ca2 可破坏硅酸盐网络结构,减少高聚物数量[43-45]。Ca2 在升温过程中参与钙长石和单斜辉石生成反应,随后钙长石和单斜辉石在低温下熔融,导致CS灰具有较低的灰熔融温度。由表2和图1(b)可知,ZY灰中主要碱性氧化物为Fe2O3,且灰中SiO2(2.00%)和Al2O3(1.13%)较低,其B/A远高于CS灰。在弱还原性气氛下,大部分Fe2O3被还原成FeO。升温过程中,只有小部分FeO参与到结晶反应中生成少量铁尖晶石并在低温下熔融,还有大量剩余高熔点Fe2O3(熔点1 560 ℃)和FeO(熔点1 420 ℃)未参与结晶反应而以氧化单体形式存在于灰渣中,在较高温度下才能熔融。因此,ZY灰的灰熔融温度高于CS灰。

图1 CS和ZY灰的理论矿物质组成
Fig.1 Compositions of theoretical mineral of CS and ZY ashes

表2 煤灰和污泥灰的熔融温度和化学组成

Table 2 Ash fusion temperature and compositions of
coal and sludge ashes

注：TD为变形温度;TS为软化温度;TH为半球温度;TF为流动温度;碱酸比B/A=(w(Fe2O3) w(CaO) w(MgO) w(Na2O) w(K2O) w(SO3))/(w(SiO2) w(Al2O3) w(TiO2))。

2.2 污泥对煤灰熔融特性的影响

2种污泥对JZ灰熔融温度的影响如图2所示。2种污泥可明显降低JZ煤灰的熔融温度;随污泥灰加入,2种混合灰的熔融温度呈非线性变化,且JZ-ZY混合灰的熔融温度降幅明显大于JZ-CS混合灰。CS灰和ZY灰的添加量分别为15%和10%时,2种混合灰的TF降至1 380 ℃以下,满足气流床气化液态排渣要求。因此,可推测ZY灰对高灰熔融温度JZ的灰熔融特性具有更好调控作用。由表1可知,污泥灰的灰分远高于煤,而ZY灰分低于CS,灰分过高会加大能耗和氧耗。因此,从调控效果和经济性角度考虑,ZY更适合作为调节高灰熔融温度JZ灰熔融特性添加剂。

图2 添加不同比例污泥灰的混合灰熔融温度变化
Fig.2 Ash fusion temperature variations in mixed ashes with
different sludge ash mass ratios

2.3 混合灰的理论矿物质组成模拟

利用Factsage软件模拟了特定压力和气氛下不同灰的理论矿物质和液相组成变化。不同混合比例JZ-CS混合灰在加热过程中矿物和液相组成变化如图3、4所示。由图3可知,随着CS灰添加比例增加,液相含量增加。由图4可知,900 ℃时液相主要成分为磷、硅和钙;随温度升高,液相中这3种元素消失,固相开始析出。随CS灰添加比例增加,钙长石(CaAl2Si2O8)增加,莫来石(Al6Si2O13)含量逐渐降低;石英(SiO2)、硫化亚铁(FeS)、长石类矿物质和磷酸铝(AlPO4)在1 100～1 200 ℃开始熔化,随温度升高,这些矿物质在较窄温度范围内快速熔化;约1 300 ℃时,大多数石英、硫化亚铁、长石类矿物质和磷酸铝熔融到液相中,从而降低了煤灰熔融温度。

图3 JZ-CS混合灰的理论矿物质组成
Fig.3 Compositions of theoretical mineral of JZ-CS mixed ashes

图4 JZ-CS混合灰的液相组成
Fig.4 Compositions of theoretical mineral of JZ-CS mixed ashes

不同混合比例的JZ-ZY混合灰的矿物质和液相组成变化如图5、6所示。由图5可知,含10%、15%、20%和25% ZY灰的JZ-ZY混合灰中出现了铁尖晶石(FeAl2O4)和铁堇青石(Fe2Al4Si5O18),这可能是由于混合灰中铁含量增加所致。Fe2 与含硫物质和氧化铝反应生成硫化亚铁和铁尖晶石;在900～1 100 ℃,铁尖晶石与氧化硅和氧化铝反应生成铁堇青石;随ZY灰添加比例增加,铁尖晶石和铁堇青石含量增加,莫来石含量逐渐降低;大部分铁尖晶石在900～1 000 ℃转化为铁堇青石;随温度升高,铁堇青石在很窄温度范围内熔化成液相[13]。铁尖晶石和铁堇青石含量增加导致莫来石减少,这可能是由于FeO增加使复杂的硅酸盐结构变为更简单结构,使硅酸盐体系变得松散,导致莫来石减少。由图6可知,随ZY灰添加比例增加,灰渣中熔融到液相中FeO显著增加,这可能是ZY灰能有效降低JZ煤灰熔融温度的主要原因。整个加热过程中,未发生磷析出和含磷结晶相形成,降低了升温过程中的固体含量。此外,ZY灰添加比例为20%时,混合灰的熔融温度小于ZY灰,这是由于ZY灰的单一氧化物在一些特定温度下大于JZ-ZY混合灰固相含量(对比图1(b)与图5(d)),如1 200 ℃时,ZY灰中固相质量分数大于40%,而JZ-ZY混合灰固相质量分数约20%。比较图3、4与图5、6发现,升温过程中,相同混合比例时JZ-CS混合灰中固相和莫来石相对含量高于JZ-ZY混合灰,液相相对含量低于JZ-ZY混合灰;1 500 ℃时,ZY灰占25%的混合灰达到全液相状态,CS灰占25%的混合灰中仍有部分莫来石。

图5 JZ-ZY混合灰的理论矿物质组成
Fig.5 Compositions of theoretical mineral of JZ-ZY mixed ashes

图6 JZ-ZY混合灰的液相组成
Fig.6 Compositions of theoretical mineral of JZ-ZY mixed ashes

2.4 混合灰的SiO2-Al2O3-CaO 三元相图分析

不同污泥灰添加比例的混合灰在三元相图中的位置可揭示升温过程中矿物质组成总体变化趋势。鉴于CS灰中CaO含量高及JZ煤灰中SiO2和Al2O3含量高(表2),使用SiO2-Al2O3-CaO三元相图模拟矿物质组成和全液相温度变化进行辅助分析,如图7所示。可知不同添加比例的JZ-CS混合灰落在莫来石区域;随CS灰添加比例增加,混合灰落点呈现向钙长石区移动的趋势,全液相温度(所有结晶相熔化为液相的温度)等温线逐渐降低;JZ灰全液相温度落点接近1 750 ℃等温线,CS灰添加比例为25%的混合灰全液相温度落点在1 600～1 650 ℃等温线之间。表明随CS灰添加比例增加,混合灰完全熔融成液相的温度逐渐降低,因此灰熔融温度逐渐降低。三元相图仅将混合灰中含量较高的3种组分(SiO2、Al2O3和CaO)作为基本数据以模拟矿物质的组成和变化,但未考虑铁、钠和硫等元素,因此可能与实际结果存在一定偏差。

图7 JZ-CS混合灰在SiO2-Al2O3-CaO三元相图中的位置
Fig.7 Positions of JZ-CS mixtures in SiO2-Al2O3-CaO ternary
phase diagram

2.5 混合灰矿物质组成的演变

1 200 ℃时不同污泥灰添加比例的JZ-CS和JZ-ZY混合灰的XRD结果如图8所示。由图8(a)可知,添加5% CS灰的JZ-CS混合灰的矿物质主要为石英、磷酸铝、莫来石、钙长石和钠长石;随CS灰添加比例增加,钙长石衍射峰变强,莫来石和石英衍射峰强度变弱。莫来石和石英均为高熔点矿物质(莫来石熔点约1 860 ℃,石英熔点约1 723 ℃)[46],莫来石最高占据分子轨道能(HOMO)和最低占据分子轨道能(LUMO)差值很大(ΔE=6.116 eV),在较高温度下可稳定存在。Ca2 被认为是煤灰中一种受体,可进入莫来石晶格并破坏部分Al—O键,导致莫来石转变为具有较低结合键能的钙长石。因此,随CS灰添加比例增加,混合灰中钙含量增加,钙长石量逐渐增加。长石矿物可与石英形成低熔点共熔物[13],温度升高时,参与形成低共熔物的钙长石含量增加,导致结晶矿物相对含量降低。由图8(a)和热力学模拟理论矿物质组成(图3、4)可知,1 200 ℃时只有部分钙长石熔化成液态,仍可从XRD图中观察到明显钙长石的衍射峰。

图8 不同污泥灰质量比的JZ-CS和JZ-ZY混合灰的XRD图
Fig.8 XRD patterns of JZ-CS and JZ-ZY mixed ashes with
different sludge ash mass ratios

由图8(b)可知,ZY灰添加比例为5%的JZ-ZY混合灰的矿物质主要为石英、莫来石和钙长石;随ZY灰添加比例增加,一些含磷矿物质和铁尖晶石逐渐出现。模拟结果中的固相没有含磷矿物质,这可能是因为模拟软件计算处于完全平衡状态,但实际操作条件下很难实现完全平衡,因此,XRD测量结果与模拟结果之间存在一些差异。ZY灰添加比例分别为10%、15%、20%和25%的JZ-ZY混合灰中出现了低熔点铁尖晶石[13],这与图5、6模拟结果一致。但铁尖晶石的衍射峰强度始终较弱,这可能是由于1 200 ℃时低熔点的铁尖晶石已熔化成液相,其中可能还包括铁系矿物质与其他矿物质发生了低温共熔[13]。Fe2O3在弱还原气氛中还原为FeO,FeO易与CaO、SiO2和Al2O3生成低熔点共熔物,从而增加液相含量[47-48]。随ZY灰添加比例增加,混合灰中晶相衍射峰强度和数量总体明显降低,说明混合灰熔融程度随之增大。涉及到的反应如下:

2SiO2 3Al2O3Al6Si2O13,

(1)

Al2O3 2SiO2 CaOCaAl2Si2O8,

(2)

P2O5 Al2O32AlPO4,

(3)

Al2O3 6SiO2 Na2O2NaAlSi3O8,

(4)

FeO Al2O3FeAl2O4。

(5)

由图8(a)、8(b)可知,随污泥灰添加JZ-ZY混合灰中高熔点石英和莫来石衍射峰强度的降低程度及总晶相的衍射峰强度降低程度明显高于JZ-CS混合灰。污泥灰添加量为10%时,JZ-ZY混合灰的石英衍射峰强度大幅降低,而JZ-CS混合灰变化不明显。添加15%、20%和25% ZY灰的JZ-ZY混合灰中结晶相的衍射峰数量和强度明显低于相同比例下JZ-CS混合灰中结晶相的衍射峰数量和强度,这可能是由于ZY灰对JZ灰熔融温度的调节效果优于CS灰。

2.6 污泥对煤渣结构的影响

添加不同污泥灰混合灰的红外光谱分析结果如图9所示。1 090 cm-1处峰值归因于不对称的Si—O—Si拉伸振动[49]。由图9(a)、9(b)可知,JZ-CS混合灰的FT-IR图中,在1 090、557和460 cm-1处推测为莫来石的振动峰,对于JZ-ZY混合灰,1 090、550和457 cm-1处推测为莫来石的振动峰[50]。添加污泥灰将增加煤灰中碱性氧化物含量,使Si—O—Si键解聚,并与碱性阳离子N2 结合形成Si—O—N2 [51]。随污泥灰含量增加,莫来石Si—O—Si 的槽逐渐变浅,表明网络结构稳定性降低,导致灰熔融温度降低[52-53]。随污泥灰含量增加,JZ-ZY混合灰Si—O—Si的槽深度相比JZ-CS混合灰明显变浅,这是ZY灰相比CS灰能更有效降低高灰熔融温度JZ煤灰熔融温度的原因[52-54]。

图9 不同污泥灰比例混合灰的FT-IR结果
Fig.9 FT-IR result of mixed ash with different sludge ash
mass ratios

2.7 摩尔离子势α与熔融温度的关系

近年来,学者对离子势和灰熔融温度的关系进行研究,发现具有高离子势元素的添加剂会提高灰熔融温度,而具有低离子势元素的添加剂会降低灰熔融温度[55],并建立了有关离子势的TF预测公式[56]。为更定量表达整个灰系统对高灰熔融温度JZ灰熔融温度的影响,引入离子势相关参数——摩尔离子势α:

(6)

式中,wi为氧化物i的质量分数;Mi为氧化物i的相对分子质量;Ii为相应氧化物i阳离子的离子势,nm-1;i为Mg2 、Fe2 、Ca2 、Ti4 、Si4 、Al3 、Fe3 、K 、Na 和P5 [56-58]。

气化炉灰渣中基本不存在硫元素,因此式(6)中也将硫元素去除。HE等[59]研究了气氛对铁的氧化价态和煤渣黏度行为的影响,通过湿化学法对气化炉弱还原气氛下灰渣中铁的氧化价态进行分析,发现大部分Fe2O3在弱还原气氛中被还原成FeO,即w(FeO)/(w(FeO) w(Fe2O3))≈0.8,并且使灰渣呈较低黏度值,换算可得FeO物质的量为Fe2O3物质的量的8.89倍。n(FeO)/n(Fe2O3)=8.89常用于热力学相图计算[60]。

不同混合灰组成及α值见表3,α与煤灰熔融温度的关系如图10所示,可知2种混合灰的4种特征温度与α呈线性正相关。表明随污泥灰添加,灰渣摩尔离子势α降低,灰熔融温度随之降低;对比JZ-CS混合灰,JZ-ZY混合灰的α值降低更快,因此灰熔融温度降低更明显。

图10 α与熔融温度的关系
Fig.10 Relationship between a and ash fusion temperature

表3 不同污泥灰比例的混合灰组成

Table 3 Ash compositions of mixed ashes with different sludge ash mass ratios

3 结 论

1)ZY灰和CS灰均能有效降低JZ灰熔融温度,使其TF满足气流床气化炉液态排渣要求。ZY灰对JZ灰熔融特性的调控效果优于CS灰。由于CS和ZY灰分远高于JZ,且ZY灰分低于CS灰,灰分越多能耗氧耗越大,从经济性和调控效果角度考虑,ZY更适合作为调控高灰熔融温度JZ灰熔融特性的添加剂。

2)CS灰中CaO含量高,随CS灰比例增大,JZ-CS混合灰中的CaO与Al2O3和SiO2反应生成的长石类矿物质增多,莫来石和石英减少。长石类矿物质易与石英形成低熔点共熔物,导致混合灰的熔融温度降低。ZY灰中Fe2O3含量高,随ZY灰比例增大,混合灰中Fe2O3在还原性气氛下被还原成FeO,使铁尖晶石等铁系矿物质增多,铁系矿物质在低温下发生熔融导致灰熔融温度降低。

3)理论矿物质演变分析中,污泥灰添加量相同时,JZ-CS混合灰中固相相对含量高于JZ-ZY混合灰,液相相对含量低于JZ-ZY混合灰;随污泥灰比例增大,JZ-ZY混合灰中高熔点矿物质(石英和莫来石)的衍射峰强度及总晶相衍射峰强度的降低程度高于JZ-CS混合灰,相同比例下JZ-ZY混合灰中晶相衍射峰强度和数量低于JZ-CS混合灰。这是添加ZY灰降低JZ灰熔融温度效果更明显的原因。

4)摩尔离子势α与2种混合灰的4种特征温度均呈线性正相关。表明随污泥灰比例增加,灰渣α降低,灰的4种特征温度随之降低;对比JZ-CS混合灰,JZ-ZY混合灰α降幅更大,因此其灰熔融温度下降更明显。

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Investigationon regulation mechanism of sludge on the ash melting characteristics of coal with high ash fusion temperature (AFT)

LI Meng1,CHEN Xueli1,LI Fenghai2,XU Jianliang1,LIU Xia1

(1.Engineering Research Center of Resource Utilization of Carbon-containing Waste with Carbon Neutrality,Ministry of Education,East China University ofScience and Technology,Shanghai 200237,China;2.School of Chemistry and Chemical Engineering,Heze University,Heze 274015,China)

Abstract：The reserve of high ash fusion temperature coal in China is huge, and the content of silicon and aluminum in the ash is high, while the content of basic oxide in some sludge is high. The co-gasification of sludge and high ash fusion temperature coal provides the possibility of regulating the ash melting characteristics of high ash fusion temperature coal. In this study, the effects of municipal sludge (CS) and pharmaceutical sludge (ZY) on the ash melting characteristics of Jiaozuo coal (JZ) with high ash fusion temperature were investigated. The results show that adding CS ash and ZY ash to JZ ash can reduce ash fusion temperature of JZ and adding ZY ash has a more significant effect on reducing the ash fusion temperature of JZ. When the CS and ZY ash ratio is 15% and 10%, respectively, the flow temperature of JZ-CS and JZ-ZY mixtures are reduced to below 1 380 ℃ to meet the slag discharge requirements of entrained flow gasifier CS ash has a high CaO content, and ZY ash has a high Fe2O3 content. With the addition of CS ash, the amount of anorthite formed by reaction of CaO in CS ash with Al2O3 and SiO2 increases,and its co-melting with quartz results in the increase of liquid phase content and the decrease of ash melting temperature. Under a weak reducing atmosphere, the Fe3 in JZ-ZY ash is reduced into Fe2 , and iron-bearing minerals such as hercynite increases. Hercynite with low melting point can melt at low temperature, and iron-bearing minerals easily form low melting point eutectic with other minerals, which decreases the ash fusion temperature (AFT) of JZ. When the proportion of sludge ash added is the same, compared with JZ-CS ash, JZ-ZY ash has a lower theoretical solid content, lower intensity and quantity of crystal phase diffraction peaks. When the temperature is 1 500 ℃, the mixed ash with 25% ZY ash reaches the full liquid state, while the mixed ash with 25% CS ash still contains some mullite. Mole ionic potential α is positive linearly correlated with the characteristic temperatures of both types of mixed ash. The decrease in α value of JZ-ZY ash is greater, so the melting temperature of JZ-ZY ash decreases more significantly.

Key words：high ash fusion temperature coal;sludge;ash melting characteristic;flow temperature;regulation mechanism

收稿日期：2023-06-12;责任编辑：白娅娜

DOI：10.13226/j.issn.1006-6772.AC23061201

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基金项目：上海市2020年度“科技创新行动计划”社会发展科技攻关资助项目(20dz1203300)

作者简介：李 萌(1996—),山东菏泽人,博士研究生。E-mail:lm1723346206@163.com

通讯作者：陈雪莉(1975—),河南南阳人,教授,博士。E-mail:cxl@ecust.edu.cn

引用格式：李萌,陈雪莉,李风海,等.污泥对高灰熔融温度煤灰熔融特性调控机制[J].洁净煤技术,2023,29(7):198-208.

LI Meng,CHEN Xueli,LI Fenghai,et al.Investigationon regulation mechanism of sludge on the ash melting characteristics of coal with high ash fusion temperature (AFT)[J].Clean Coal Technology,2023,29(7):198-208.

中图分类号：TQ534

文献标志码：A

文章编号：1006-6772(2023)07-0198-11