生物质固体成型燃料抗结渣研究进展

生物质固体成型燃料具有易储存、运输及使用方便、清洁环保、燃烧效率高等优点,是开发利用生物质能的主要方向之一.但秸秆类生物质原料中无机元素(包括K,Na,Cl,S,Ca.Si,P等)含量较高,导致了生物质固体成型燃料在热化学转化利用过程中出现结渣现象,不仅对燃烧设备的热性能造成影响,而且危及燃烧设备安全,成为阻碍生物质同体成型燃料推广应用的主要因素.文章分析了秸秆类生物质燃料的结渣机理,介绍了国内外生物质燃料抗结渣特性的研究现状,探讨了原料预处理、添加剂和颗粒密度对燃料抗结渣特性的影响,最后分析了目前生物质抗结渣研究中存在的问题,并提出了未来的研究方向.     

硅和硅铝化合物对生物质结渣影响的机理研究

生物质由于含有较多碱金属,燃烧会导致设备结渣。文章研究了硅和硅铝化合物对生物质结渣影响的机理,结果表明,硅和硅铝化合物会使生物质燃烧时可溶性K倾向于转变为不可溶性的硅酸盐和硅铝酸盐,而该过程反应与纯生物质燃烧过程反应相同。在流化床炉温(815℃)附近时,硅化合物容易使灰中生成低熔点的K的硅酸盐,低温熔融结渣可能性增大,选择其作为结渣抑制剂需要慎重。在层燃炉炉温(1 000℃)附近时,硅铝化合物既可减轻碱金属结渣又使灰不易结渣聚团,是层燃炉优良的结渣抑制剂。     

循环流化床燃烧生物质的结渣问题研究

在0.2 MW循环流化床上进行实验,以棉杆为燃料,分别采用石英砂和高铝矾土颗粒作为床料,长时间稳定运行.对运行过程中的床料、结渣块取样进行XRF以及SEM分析,分析生物质循环流化床运行中产生结渣的原因.研究结果表明,床料和结渣块中富集了大量的碱金属,并且随着运行时间的延长,富集的含量越来越高.生物质灰中的碱金属和床料中的SiO2反应生成低共熔点的硅酸盐化合物是引起结渣的主要原因.     

低温热解生物质与煤共燃的结渣、积灰和磨损特性分析

利用灰分的结渣性指数t2、B／A、S／A、G，积灰沾污特性指数比和磨损指数‰对低温热解生物质单燃和与煤共燃时的结渣、积灰和磨损特性进行了研究和分析。认为：(1)低温热解生物质(锯屑、谷壳和花生壳)都不适合在电厂锅炉中直接燃烧。(2)热解生物质与煤共燃时的结渣、积灰和磨损特性取决于热解生物质灰分含量、灰成分，煤的灰分含量、灰成分以及混合比例等因素。(3)三种熬解生物质与煤共燃能够改善它们的结渣、积灰沾污和磨损性能，但又增加了煤的结渣、积灰沾污和磨损性。(4)热解生物质灰分含量越低。煤的灰分含量越高，煤的结渣、积灰沾污性能越好，越有利于提高混燃比例。(5)三种热解生物质中，热解锯屑与煤可混性最好。其他两种则相对较差。     

生物质与煤掺烧对锅炉结渣特性影响的实验研究

采用CAF digital imaging灰熔点测试仪和飞利浦分析仪器分别对稻草、木屑、谷壳等常见的生物质灰及其与煤掺烧后灰的熔融特性和灰成分进行了检测,通过软化温度DT,灰分的酸碱比(B/A)、硅铝比(SiO2/Al2O3)、硅比(G)、铁钙比(Fe2O3/CaO)等判别指数对单一生物质与煤掺烧的结渣特性进行了研究和分析.结果表明:稻草和谷壳与煤粉掺烧,灰熔点降低,引起结渣.但是掺烧木屑则不会出现灰熔点降低而导致结渣的问题.     

固体碱催化剂在麻疯树油合成生物柴油中的应用

简述了生物柴油作为燃料的优越性,讨论了以固体碱作催化剂、以麻疯树油为原料合成生物柴油的工艺条件.试验研究了该反应的最佳反应条件:固体碱催化剂的用量为麻疯树油质量的1%,油醇物质的量比为1:6,反应温度为70℃.     

生物质流化床燃烧过程中的结渣特性

在生物质燃料的热化学转化技术中,生物质流化床燃烧技术具有诸多独特的优势,但在实际的流化燃烧利用过程中,经常出现床料结渣的现象.文章对这一现象进行了概述,并从生物质燃料特性、运行条件、床料类型以及覆盖层的形成等方面分析了结渣的影响因素,探讨了由床料与燃料灰之间发生反应所引起的结渣的内在机理,最后提出了相应的防止措施.     

中国南方典型农业生物质结渣特性实验研究

实验研究了广东省典型农业生物质稻杆、甘蔗渣/叶的燃烧结渣特性。采用GB/T212-2001和ASTM E1755标准进行灰化实验,采用角锥法和一步法检测生物质的熔融特性。实验结果证实ASTM的低温灰化标准更适合稻杆类高无机盐含量的生物质原料。稻杆中碱金属氧化物含量达20%以上,是导致灰渣粘结和熔融的主要因素。由于角锥法灰熔点检测法提前将部分碱金属和Cl元素转化和析出,导致检测结果远高于实际燃烧的熔融温度;相比而言,一步法更具有直观性和指导作用。通过一步法实验获得稻杆临界结渣温度为700℃ ~ 750℃,甘蔗渣为850℃ ~ 900℃,甘蔗叶为900℃ ~ 950℃。CaO和Al₂O₃添加剂对于生物质燃烧过程具有一定的抗结渣功能,CaO通过与SiO₂ (s) 反应生成高熔点的固态Ca₃Si₂O₇ (s) 和MgOCa₃O₃Si₂O₄ (s),因此能消耗物料周围的SiO₂ (s),抑制低温共融;Al₂O₃则通过生成高熔点温度的固态KAlSiO₄和固态KAlSi₂O₆,减少低温共熔现象的发生。     

钙镁负载型固体碱制备生物柴油的研究

研究了CaO-MgO/SiO2负载型固体碱催化剂的制备条件,并对其进行XRD、FT-IR、BET和CO2-TPD表征分 析,仪器分析表明CaO成功引入到载体,MgO起助催化作用增强了碱性并研究该固体碱催化剂酯交换反应催化毛豆油制备生物柴油的条件.考查反应时间、反应温度、醇油比、催化剂用量和原料中水分含量的影响.研究表明,在反应时间6h,反应温度65℃,醇油比18:1,催化剂用量3%,原料油水份含量低于1%时,生物柴油收率可达95.4%,甘油收率达96%以上.     

亚临界甲醇中固体催化剂催化酯交换反应的活性比较

对几种固体催化剂用于亚临界甲醇与大豆油的酯交换反应制备生物柴油的催化活性进行了研究。考察在不同催化剂作用下酯交换反应产物中脂肪酸甲酯（FAMEs）含量随反应时间的变化规律。结果表明。在醇油摩尔比为40，反应温度为180℃，反应压力为2～3MPa，催化剂用量为3g及反应时间为10min的条件下，K2O／γ-Al2O3催化酯交换反应的产物中FAMEs含量达90％。     

Brønsted酸性离子液体合成及催化制备生物柴油

合成4种成功能化酸性离子液体,采用红外光谱、热重分析等分析法进行表征验证,并用其催化菜籽油酯交换制备生物柴油,考察醇/油物质的量之比、反应温度、反应时间、离子液体用量和水含量对转化率的影响。结果表明,4种离子液体都有较强酸性,与浓硫酸酸性相当;带—SO₃H基团的离子液体表现出更好的催化活性,且随着烷基链的增加,催化活性提高;在（n甲醇）∶n（菜籽油）=12∶1,反应温度130 ℃,反应时间3 h,离子液体（[BSO₃HMIM][HSO₄]）用量为菜籽油质量2%（质量分数）条件下,生物柴油转化率可达99%以上。在反应体系中,水会破坏离子液体的结构并导致其失活,而升高反应温度,可缓解水对离子液体的结构破坏,在130 ℃条件下,即使水分含量为5%时,生物柴油转化率仍可保持在约85%。     

地沟油制备生物柴油过程中硫化物迁移及脱除研究

采用地沟油等餐饮废弃油脂转化制备生物柴油中会含有一定量的硫化物,针对上述问题,考察传统的酸碱两步法制备生物柴油过程中硫化物的迁移,并以离子液体（[Hnmp]H₂PO₄）为萃取剂和催化剂,H₂O₂为氧化剂,对粗生物柴油进行萃取氧化脱硫,并利用正交实验法对萃取氧化脱硫反应工艺进行优化。结果表明：反应过程使用的试剂和操作条件几乎不会增大生物柴油制备过程中的硫含量以及改变硫化物在反应体系中的存在形态,硫化物含量及存在形式与原料油自身所含硫化物形态有关。S元素在地沟油原料及生物柴油粗成品中的存在形式主要以噻吩、硫醇、硫醚、硫胺素、硫代葡萄糖苷等物质为主,其中噻吩类硫化物约占地沟油原料或生物柴油中总含硫质量分数的93%以上。在粗生物柴油与离子液体体积比为10∶3,粗生物柴油与H₂O₂体积比为10∶1.2,反应温度75 ℃,反应时间70 min条件下,生物柴油脱硫率达94%以上,脱硫后的生物柴油满足最新国Ⅵ柴油排放标准（GB 17930—2016）硫含量≤10 mg/kg要求。     

我国生物质能源现代化应用前景展望(四)——生物质能源转化生命周期分析

生物质种类不同,转化为运输燃料的途径也是多种多样,生命周期排放的温室气体和能耗也不相同。总结对比主要生物质转化途径的全生命周期分析(LCA)结果,有助于明确需要进一步改进的技术难题和方向。生物质转化为醇类燃料时,使用E85比使用传统汽油的碳排放明显下降,纤维素生化转化途径排放的二氧化碳当量值约为传统汽油的0.2~0.7倍,热化学途径约为传统汽油的0.6~0.9倍,玉米干法为传统汽油的0.8~1倍。油脂类生物质转化为酯类燃料时,生物柴油减排温室气体的效果,动物油脂地沟油、棕榈油豆油、椰子油菜籽油。动物油脂、地沟油生产生物柴油可减排温室气体70%~90%,以植物为原料的生物柴油可减排10%~90%。生物质转化为烃类燃料时,菜籽油基喷气燃料可减排温室气体13%~55%,F-T合成油比油脂加氢具有更好的减排效果,BTL通常可减排80%以上的温室气体,CBTL的减排效果与掺入生物质的比例有关,热解汽柴油的温室气体减排率为58%~70%。对于微藻生物燃料工艺过程,在微藻产率和含油量不太低的情况下,池子系统的温室气体排放低于石油柴油。     

Biodiesel production from mixed soybean oil and rapeseed oil

The biodiesel (fatty acid methyl esters, FAME) was prepared by transesterification of the mixed oil (soybean oil and rapeseed oil) with sodium hydroxide (NaOH) as catalyst. The effects of mole ratio of methanol to oil, reaction temperature, catalyst amount and reaction time on the yield were studied. In order to decrease the operational temperature, a co-solvent (hexane) was added into the reactants and the conversion efficiency of the reaction was improved. The optimal reaction conditions were obtained by this experiment: methanol/oil mole ratio 5.0:1, reaction temperature 55 °C, catalyst amount 0.8 wt.% and reaction time 2.0 h. Under the optimum conditions, a 94% yield of methyl esters was reached ∼94%. The structure of the biodiesel was characterized by FT-IR spectroscopy. The sulfur content of biodiesel was determined by Inductively Coupled Plasma emission spectrometer (ICP), and the satisfied result was obtained. The properties of obtained biodiesel from mixed oil are close to commercial diesel fuel and is rated as a realistic fuel as an alternative to diesel. Production of biodiesel has positive impact on the utilization of agricultural and forestry products.     

Effect of reaction parameters on the catalytic transesterification of cottonseed oil using silica sulfuric acid

Transesterification of refined cottonseed oil was studied in the presence of silica sulfuric acid as a new heterogeneous solid acid catalyst to overcome the drawbacks of homogeneous alkali and acid catalysts. The effect of various reaction parameters, such as oil to methanol ratio, reaction temperature, reaction time, and catalyst amount, was investigated. The highest methyl ester conversion was obtained at 373 K using 5% catalyst amount and 1:20 methanol ratio within 8 h. Silica sulfuric acid was found to be a promising catalyst for cleaner biodiesel production without tedious post treatments for the product purification.     

Heterogeneous catalysis for biodiesel production from Jatropha curcas oil (JCO)

This work focuses on the development of heterogeneous catalysts for biodiesel production from high free fatty acid (FFA) containing Jatropha curcas oil (JCO). Solid base and acid catalysts were prepared and tested for transesterification in a batch reactor under mild reaction conditions. Mixtures of solid base and acid catalysts were also tested for single-step simultaneous esterification and transesterification. More soap formation was found to be the main problem for calcium oxide (CaO) and lithium doped calcium oxide (Li-CaO) catalysts during the reaction of jatropha oil and methanol than for the rapeseed oil (RSO). CaO with Li doping showed increased conversion to biodiesel than bare CaO as a catalyst. La₂O₃/ZnO, La₂O₃/Al₂O₃ and La_0.1Ca_0.9MnO₃ catalysts were also tested and among them La₂O₃-ZnO showed higher activity. Mixture of solid base catalysts (CaO and Li-CaO) and solid acid catalyst (Fe₂(SO₄)₃) were found to give complete conversion to biodiesel in a single-step simultaneous esterification and transesterification process.     

粗生物柴油真空精馏脱硫研究

针对采用废油脂为原料转化制备的生物柴油会含有一定量的硫化物的问题,采用真空精馏法脱除生物柴油中的硫化物,并对硫化物附存形态进行分析。结果表明：生物柴油中硫化物主要包括低沸点的硫化氢、硫醇、硫醚、硫胺素等,以及高沸点的苯并噻吩、二苯并噻吩等。采用控制精馏脱硫塔塔顶温度150 ℃、操作绝对压力300~500 Pa、回流比1的条件下,先对生物柴油中低沸点硫化物进行脱除,再将塔顶温度升至210 ℃,将中间馏分（生物柴油）从塔顶精馏出来,高沸点重馏分（生物重油、高沸点硫化物）留在塔釜底部,两步精馏切割法能将达标的生物柴油与其他馏分分离开来,可有效降低生物柴油的硫含量,脱硫率达97%,满足最新国Ⅵ柴油排放标准（GB 17930—2016）的硫含量≤10 mg/kg要求,且硫含量达标的生物柴油得率达到85%以上。     

Preparation, characterization and application of heterogeneous solid base catalyst for biodiesel production from soybean oil

A solid base catalyst was prepared by neodymium oxide loaded with potassium hydroxide and investigated for transesterification of soybean oil with methanol to biodiesel. After loading KOH of 30 wt.% on neodymium oxide followed by calcination at 600 °C, the catalyst gave the highest basicity and the best catalytic activity for this reaction. The obtained catalyst was characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), N₂ adsorption-desorption measurements and the Hammett indicator method. The catalyst has longer lifetime and maintained sustained activity after being used for five times, and were noncorrosive and environmentally benign. The separate effects of the molar ratio of methanol to oil, reaction temperature, mass ratio of catalyst to oil and reaction time were investigated. The experimental results showed that a 14:1 M ratio of methanol to oil, addition of 6.0% catalyst, 60 °C reaction temperature and 1.5 h reaction time gave the best results and the biodiesel yield of 92.41% was achieved. The properties of obtained biodiesel are close to commercial diesel fuel and is rated as a realistic fuel as an alternative to diesel.     

Comparison and effect of Cinder supported with Manganese and Lanthanum oxide for biodiesel production

In this study, comparison and effect of Cinder supported with Lanthanum and Manganese oxide as catalyst for transesterification of triglyceride to methyl ester is proposed. The reaction mechanism along with the effects of methanol to oil molar ratio, amount of catalyst to oil, reaction temperature were also discussed. Moreover reusability of catalyst, catalyst resistance toward Free Fatty Acid and water were also discussed. The results show that yield of biodiesel produced with Mn:La:Cinder catalyst was 99% at ≥150 °C in 6 h. Cinder supported with Mn shows conversion of triglycerides from soybean oil in reaction with methanol after 6 h was over 99% at 150 °C. For both catalyst 3wt% of catalyst based on oil, 24:1 methanol/oil molar ratio was reused for 7 times with regeneration. The catalysts displayed great resistance toward 2.5% water and 1% wt fatty acids.     

Waste capiz (Amusium cristatum) shell as a new heterogeneous catalyst for biodiesel production

The waste Capiz shell was utilized as raw material for catalyst production for biodiesel preparation. During calcination process, the calcium carbonate content in the waste capiz shell was converted to CaO. This calcium oxide was used as catalyst for transesterification reaction between palm oil and methanol to produce biodiesel. The biodiesel preparation was conducted under the following conditions: the mole ration between methanol and palm oil was 8:1, stirring speed was 700 rpm, and reaction temperature was 60 °C for 4, 5, and 6 h reaction time. The amount of catalyst was varied at 1, 2, 3, 4, and 5 wt %. The maximum yield of biodiesel was 93 ± 2.2%, obtained at 6 h of reaction time and 3 wt % of amount of catalyst. In order to examine the reusability of catalyst developed from waste of capiz (Amusium cristatum) shell, three transesterification reaction cycles were also performed.