油棕废弃物及生物质三组分的热解动力学研究

主要利用热重分析仪(TG)对油棕废弃物和生物质的三组分(半纤维素,纤维素和木质素)的热解特性进行了系统研究,对比分析了热解特性,计算了其热解动力学参数,并研究了升温速率对生物质热解特性的影响。研究发现半纤维素和纤维素易于热降解而木质素难于热解;油棕废弃物的热解可以化分为:干燥、半纤维素热解、纤维素热解和木质素热解4个阶段;生物质的热解反应主要是一级反应,油棕废弃物的活化能很低,约为60kJ/kg;升温速率对生物质影响很大,随升温速率加快,生物质热解温度升高,热解速率降低。     

生物质废弃物在回转窑内热解研究--Ⅰ.热解条件对热解产物分布的影响

研究了生物质类废弃物在回转窑内的热解特性,讨论了物料种类,热解终温,加热方式,给料粒径和含水率对热解产物分布的影响。物料挥发份和热解终温高,加热快,粒径小,有利于燃气产率的提高以及炭产率的降低,而水分的提高会提高焦油的产率并降低炭的产率。同时,还研究了回转窑内的温升特性和热解气体的瞬态析出特性。     

生物质废弃物热解特性的热重分析研究

采用热重分析方法,以氮气为载气,在室温和973K之间,以三种升温速率(10,20,30K/min)对三种生物质废弃物试样(稻秆、稻壳和白松木屑)进行热解实验。确定了起始分解温度D。采用了生物质整体热解分区、生物质化学组分热解分区、活化热解与消极热解分区等三种热解分区方法进行分析。由于三种试样化学成分的差别导致热解特性的差异。得到了三种试样热解动力学参数。     

高含灰量海藻热解产物及热解特性研究

对高含灰海藻进行水洗和酸洗预处理,比较了预处理前后海藻的基本特性及在700℃时管式炉热解产物成份,并进行了动力学特性分析。结果表明:高含灰海藻酸处理后,含灰量由34.9%降为12.4%,有机挥发份从56%升为64%,热值由8.89MJ/kg上升为17.65MJ/kg;高含灰量对海藻热解有明显影响作用,处理前海藻有机物有两次降解峰,而水洗和酸洗后海藻在500℃以下几乎降解完全;海藻在700℃时,热解产气率(87mL/g)低,焦油含量少(15%),经水洗和酸洗后的原料产气率高(195mL/kg),焦油得率36%;通过建立热解动力学模型,得到了原料的活化能E和频率因子。     

沼渣热解动力学、热力学分析及热解产物特性研究

采用热重分析（TG）分析沼渣的热解特性,研究沼渣的热解动力学并计算指前因子A、焓变ΔH、吉布斯自由能ΔG、熵变ΔS等热力学参数。进一步考察温度对沼渣热解产物分布与性质的影响。其热解过程可分为3个失重阶段,其中第2阶段为主要失重阶段,采用Flynn-Wall-Ozawa（FWO）法、Friedman法和Kissinger-Akahira-Sunose（KAS）法计算的平均活化能分别为410.00、471.32和420.01 kJ/mol,热力学参数计算结果表明沼渣热解过程具有稳定的能量输出。沼渣热解油的产率随温度上升先增加后降低。气体产物的高位热值（HHV）从400 ℃时的6.82 MJ/Nm³增加到700 ℃时的8.54 MJ/Nm³。红外光谱（FTIR）、拉曼（Raman）光谱表明热解温度升高生物炭结构的有序性增加。     

生物质废弃物在回转窑内热解研究--Ⅱ.热解终温对产物性质的影响

考察了不同热解终温下木块和稻壳在回转窑内热解产物－燃气、焦油和炭的成分和性质的变化。在试验温度范围内,热解气体热值约10．0－15．9MJ／Nm^3,密度1.21-1.52Nm^3/kg,且随热解终温变化呈规律性变化,木块炭的热值为29.0-33.9MJ／kg,稻壳炭则为17.6-20.8MJ/kg,热解终温的提高使炭中挥发份的降低,灰分增多,从而导致热值的降低;炭的C含量高于原始物料的C含量,而H、O则相反;元素残留率的计算表明,热解过程中H和O元素的脱除易于C元素。热解终温对焦油中饱和烃、芳香烃成分含量的影响不大,饱和链烃成分主要集中为C14－C34正构烷烃和含末端双链烯烃的碳分子链,芳香烃主要为蒽（菲）、芘、萤蒽及各自衍生物的稠环芳烃。     

桉树类生物质热解及产物释放特性研究

采用热重红外联用方法研究不同升温速率下桉树枝和桉树皮的热解特性和热解气体产物的释放特性,对比分析两者的差异性及差异机理。结果表明:桉树枝热解过程主要分为干燥、热解和碳化3个阶段,热解速率较快,气体产物释放主要集中在热解阶段进行,主要气体产物有烷烃、醇、酚、醛、羧酸、酮等多种有机气体产物和少量CO,CO2;桉树皮热解过程分为干燥、进一步干燥、热解反应、碳化及高温持续碳化5个阶段,相比桉树枝热解速率明显较低。桉树皮热解反应阶段在450⁵50℃和650550℃和650⁸00℃两个高温区间存在较为剧烈的碳化反应过程,主要气体产物为CO2和CO。     

竹废弃物热解碳足迹分析

文章针对竹废弃物热解及热解产物资源化利用的场景,基于生命周期评价和敏感性分析方法,建立了详细的生命周期碳排放清单和核算方法,确定了热解系统中碳排放和碳减排的主要贡献源,分析了热解系统碳减排能力对多个参数的敏感性程度。结果表明：1 t竹废弃物热解的碳排放为-838.684 kg,我国竹废弃物热解的年减排量为3 830万t,年发电量为2.1×10¹⁰kW·h;整个系统中碳排放的主要贡献源为生物油和合成气的燃烧发电(34.8%),碳减排最主要的贡献源为竹炭还田(34.0%);热解系统的碳减排能力对竹废弃物占比、年采伐量和热解产物产量的敏感性程度较高,敏感性系数分别为1.297,1.000和0.702;竹炭还田带来的土壤碳汇效应具有巨大的减排潜力,综合产率为8.9%的竹炭可带来1 300万t/a的碳减排量。文章认为竹废弃物热解具有较强的碳减排能力,可以为合理利用竹废弃物生产可再生能源、积极应对气候变化,实现“双碳”目标提供一条新途径。     

松塔热解特性及热解过程气体产物分析

文章以废弃松塔为原料,采用热重分析的方法,研究了松塔热解失重规律,通过管式炉热解实验,研究了松塔热解过程中气体产物的变化规律.研究结果表明:松塔热解分为3个阶段,200～500℃是松塔热解的主反应区间,最大失重峰出现在338℃,热解反应过程存在两个较明显的DTG曲线肩峰,且这两个DTG曲线肩峰均与松塔抽提物有关;松塔热...     

酸水解木质素的结构及热解产物分析

采用木质纤维典型稀酸水解残渣为实验原料,对其理化特性进行分析.对酸水解木质素(简称AHL)进行分离提纯,通过定量31P-NMR及木质素衍生化后的还原降解(DFRC)技术研究分离得到的水解残渣木质素的官能团的含量.采用TG和DTG研究AHL的热分解特性.借助Py-GC-MS分析AHL热裂解产物的主要组成.研究结果表明,AHL的热解发生在一个宽泛的温度范围内,并且DTG曲线中可以看到两个明显的失重峰;AIL热裂解产物主要由木质素大分子β-0-4连接断裂所得产物及二次裂解产物构成.     

Influence of mineral matter on pyrolysis of palm oil wastes

The influence of mineral matter on pyrolysis of biomass (including pure biomass components, synthesized biomass, and natural biomass) was investigated using a thermogravimetric analyzer (TGA). First, the mineral matter, KCl, K₂CO₃, Na₂CO₃, CaMg(CO₃)₂, Fe₂O₃, and Al₂O₃, was mixed respectively with the three main biomass components (hemicellulose, cellulose, and lignin) at a weight ratio (C/W) of 0.1 and its pyrolysis characteristics were investigated. Most of these mineral additives, except for K₂CO₃, demonstrated negligible influence. Adding K₂CO₃ inhibited the pyrolysis of hemicellulose by lowering its mass loss rate by 0.3 wt%/°C, while it enhanced the pyrolysis of cellulose by shifting the pyrolysis to a lower temperature. With increased K₂CO₃ added, the weight loss of cellulose in the lower temperature zone (200-315 °C) increased greatly and the activation energies of hemicellulose and cellulose pyrolysis decreased notably from 204 to 42 kJ/mol. Second, studies on the synthetic biomass of hemicellulose, cellulose, lignin, and K₂CO₃ (as a representative of minerals) indicated that peaks of cellulose and hemicellulose pyrolysis became overlapped with addition of K₂CO₃ (at C/W = 0.05-0.1), due to the catalytic effect of K₂CO₃ lowering cellulose pyrolysis to a lower temperature. Finally, a local representative biomass—palm oil waste (in the forms of original material and material pretreated through water washing or K₂CO₃ addition)—was studied. Water washing shifted pyrolysis of palm oil waste to a higher temperature by 20 °C, while K₂CO₃ addition lowered the peak temperature of pyrolysis by . It was therefore concluded that the obvious catalytic effect of adding K₂CO₃ might be attributed to certain fundamental changes in terms of chemical structure of hemicellulose or decomposition steps of cellulose in the course of pyrolysis.     

Numerical analysis of emission component from incineration of palm oil wastes

In the last decade, there has been an increasing awareness of the use of by-products and wastes from palm oil mills with the dual objective of reducing their environmental impacts and enhancing the economic viability of the crop. The recycling aspects of palm oil cultivation and palm oil processing have been reviewed and have provided an indication of the present and future use of palm oil biomass current applications being mainly for organic fertilizers and fuel. In the present work, the emissions from incineration of two types of palm oil wastes (POW) fibre and shell are considered, and compared to fuel oil. The results, which indicate less pollutant emission from incineration of POW compared to that of fuel oil, have been presented graphically.     

Hydrogen-rich gas production by steam gasification of palm oil wastes over supported tri-metallic catalyst

The catalytic steam gasification of palm oil wastes for hydrogen-rich gas production was experimentally investigated in a combined fixed bed reactor using the newly developed tri-metallic catalyst. The results indicated that the supported tri-metallic catalyst had greater activity for the cracking of hydrocarbons and tar in vapor phase and higher hydrogen yield than the calcined dolomite in catalytic steam gasification of palm oil wastes. A series of experiments have been performed to explore the effects of temperature, steam to biomass ratio (S/B) and biomass particle size on gas composition, gas yield, low heating value (LHV) and hydrogen yield. The experiments demonstrated that temperature was the most important factor in this process; higher temperature contributed to higher hydrogen production and gas yield, however, it lowered gas heating value. Comparing with biomass catalytic gasification, the introduction of steam improved gas quality and yield, the optimal value of S/B was found to be 1.33 under the present operating condition. It was also shown that a smaller particle size was more favorable for gas quality and yield. However, the LHV of fuel gas decreased with the increasing S/B ratio and the decreasing biomass particle size.     

Pyrolytic oil from fluidised bed pyrolysis of oil palm shell and itscharacterisation

Biomass in the form of oil palm shellwas pyrolysed in an externally heated 5 cm diameter, 30 cm high fluidised bed pyrolysis reactorwith nitrogen as the fluidising gas and silica sand as the bed material. The pyrolysis oil wascollected in a series of condenser and ice-cooled collectors. The char was collected separatelywhile the gases were flared. The effects of process conditions, like fluidised bed reactortemperature, feed size and fluidisation gas flow rate on the product yields were studied. Theproduct yields were found to be significantly influenced by the process conditions. Thecomposition of oil was determined at fluidised bed temperature of 500°C at which the liquidproduct yield was maximum. The oil was analysed by Fourier Transform infra-red (FTIR)spectroscopy and gas chromatography/mass spectrometry (GC/MS) techniques. In addition, thephysical properties of the oil were determined. The results showed that the oil was highlyoxygenated containing a high fraction of phenol-based compounds. Detailed analysis of the oilshowed that there was no concentration of biologically active polycyclic aromatic species in theoil. A brief preliminary economic analysis is presented at the end of the paper (see Appendix). ©1999 Elsevier Science Ltd. All rights reserved.     

Optimum conditions for maximising pyrolysis liquids of oil palm empty fruit bunches

As production of palm oil is expanding, a more efficient use of oil palm biomass to obtain more energy from oil palm plantations is investigated. The work was carried out on a fluidised bed bench scale fast pyrolysis unit, with the objective of determining the important conditions and key variables which are required to maximise the liquid yield and its quality. The investigation on the impact of reactor temperature, varying residence time by changing the nitrogen flow rate and combined impact of ash content and particle size on the product yields is presented. The properties of the liquid product were analysed and compared with wood derived bio-oil and petroleum fuels. It was found that in all cases the liquid product separated into two phases presenting difficulties for fuel applications, which are critically discussed. Potential solutions are also proposed which include upgrading of the liquid for fuel applications and other useful applications.     

Biodiesel production from palm oil via heterogeneous transesterification

This paper presents the study of the transesterification of palm oil via heterogeneous process using montmorillonite KSF as heterogeneous catalyst. This study was carried out using a design of experiment (DOE), specifically response surface methodology (RSM) based on four-variable central composite design (CCD) with α (alpha) = 2. The transesterification process variables were reaction temperature, x₁ (50–190 °C), reaction period, x₂ (60–300 min), methanol/oil ratio, x₃ (4–12 mol mol^?1) and amount of catalyst, x₄ (1–5 wt%). It was found that the yield of palm oil fatty acid methyl esters (FAME) could reach up to 79.6% using the following reaction conditions: reaction temperature of 190 °C, reaction period at 180 min, ratio of methanol/oil at 8:1 mol mol^?1 and amount of catalyst at 3%.     

Life cycle assessment of two palm oil production systems

In 2009 approx. 40 Mt of palm oil were produced globally. Growing demand for palm oil is driven by an increasing human population as well as subsidies for biodiesel and is likely to increase further in coming years. The production of 1 t crude palm oil requires 5 t of fresh fruit bunches (FFB). On average processing of 1 t FFB in palm oil mills generates 0.23 t empty fruit bunches (EFB) and 0.65 t palm oil mill effluents (POME) as residues. In this study it is assumed that land use change does not occur. In order to estimate the environmental impacts of palm oil production a worst and a best case scenario are assessed and compared in the present study using 1000 kg of FFB as functional unit.The production and treatment of one t FFB causes more than 460 kg CO_2eq in the worst case scenario and 110 kg CO_2eq in the best case scenario. The significant greenhouse gas (GHG) emission reduction is achieved by co-composting residues of the palm oil mill. Thus treating those residues appropriately is paramount for reducing environmental impacts particularly global warming potential (GWP) and eutrophication potential (EP).Another important contributor to the EP but also to the human toxicity potential (HTP) is the biomass powered combined heat and power (CHP) plant of palm oil mills. Frequently CHP plants of palm oil mills operate without flue gas cleaning. The CHP plant emits heavy metals and nitrogen oxides and these account for 93% of the HTP of the advanced palm oil production system, of which heavy metal emissions to air are responsible for 79%. The exact emission reduction potential from CHP plants could not be quantified due to existing data gaps, but it is apparent that cleaning the exhaust gas would reduce eutrophication, acidification and toxicity considerably.     

Photofermentive production of biohydrogen from oil palm waste hydrolysate

Oil palm empty fruit bunch (OPEFB) was hydrolyzed with dilute sulfuric acid (6% v/v; 8 mL acid per g dry OPEFB) at 120 °C for 15-min to release the fermentable sugars. The hydrolysate contained xylose (23.51 g/L), acetic acid (2.44 g/L) and glucose (1.80 g/L) as the major carbon components. This hydrolysate was used as the sole carbon source for photofermentive production of hydrogen using a newly identified photosynthetic bacterium Rhodobacter sphaeroides S10. A Plackett–Burman experimental design was used to examine the influence of the following on hydrogen production: yeast extract concentration, molybdenum concentration, magnesium concentration, EDTA concentration and iron concentration. These factors influenced hydrogen production in the following decreasing order: yeast extract concentration > molybdenum concentration > magnesium concentration > EDTA concentration > iron concentration. Under the conditions used (35 °C, 14.6 W/m² illumination, initial pH of 7.0), the optimal composition of the culture medium was (per L): mixed carbon in OPEFB hydrolysate 3.87 g, K₂HPO₄ 0.9 g, KH₂PO₄ 0.6 g, CaCl₂⋅2H₂O 75 mg, l-glutamic acid 795.6 mg, FeSO₄⋅7H₂O 11 mg, Na₂MoO₂⋅2H₂O 1.45 mg, MgSO₄⋅7H₂O 2.46 g, EDTA 0.02 g, yeast extract 0.3 g). With this medium, the lag period of hydrogen production was 7.65 h, the volumetric production rate was 22.4 mL H₂/L medium per hour and the specific hydrogen production rate was 7.0 mL H₂/g (xylose + glucose + acetic acid) per hour during a 90 h batch culture of the bacterium. Under optimal conditions the conversion efficiency of the mixed carbon substrate to hydrogen was nearly 29%.     

Enhanced hydrogen production in catalytic pyrolysis of sewage sludge by red mud: Thermogravimetric kinetic analysis and pyrolysis characteristics

The catalytic mechanism of red mud (RM) on the pyrolysis of sewage sludge was investigated. The thermogravimetric data were used to study the kinetic characteristics by using a discrete distributed activation energy model (DAEM) to clarify the effects of three main components (Fe₂O₃, Al₂O₃, SiO₂) in the RM on the pyrolysis of organic matters in sewage sludge. The modeling results showed that the pyrolysis of organic matters, especially at the higher temperature stage, was promoted by Fe₂O₃ and Al₂O₃ in the RM. Adding Fe₂O₃ or the RM alone could reduce the mean activation energy of sewage sludge pyrolysis by 13.9 and 20.1 kJ mol^?1, respectively. The modeling results were validated by pyrolysis experiments of raw sludge with different additives at 600, 700, 800, and 900 °C. The experimental results showed that the addition of Al₂O₃, Fe₂O₃ or the RM could produce more gas than the addition of SiO₂, especially at high temperatures. Fe₂O₃ and Al₂O₃ acted as catalysts in the tar decomposition by in-situ catalyzing the cracking of CC and CH bonds to produce more gases. Especially, Fe₂O₃ and Al₂O₃ increased the H₂ yield from sewage sludge pyrolysis at 700, 800, and 900 °C by 268.5 and 50.7%, 111.1 and 56.0%, 10.9 and 10.3%, respectively. The char obtained from pyrolysis of sewage sludge with the RM possessed magnetic property, which has various potential applications. The research indicates that the RM is an efficient catalyst in the pyrolysis of sewage sludge.