Characterization of bio-oils from the fast pyrolysis of white oak and sweetgum

Conversion of lignocellulosic biomass into bio-oil through fast pyrolysis process is considered one of the promising routes to supplement conventional fossil oil. Future bio-refineries require production large amounts of bio-oil from several biomass types. Characterization of the produced bio-oils is important to determine their suitability as bio-refinery feedstock. In this study, bio-oils were produced from white oak and sweetgum woods in an auger reactor at 450°C. The yields of char, liquid, and gas were calculated. The physical characterization of bio-oils was performed based on the investigation of different properties, such as pH, density, viscosity, water content, acid value, and molecular weight distribution of bio-oil components. The chemical compositions of the bio-oils were also investigated by gas chromatography/mass spectrometry and Fourier transform infra-red analyses. The physicochemical properties of the produced bio-oils were comparable to those obtained from similar woody biomass and the oils were suitable for fuel production.     

Production of a hydrogen-rich gas from fast pyrolysis bio-oils: Comparison between homogeneous and catalytic steam reforming routes

The aim of the present work is to produce hydrogen from biomass through bio-oil. Two possible upgrading routes are compared: catalytic and non-catalytic steam reforming of bio-oils. The main originality of the paper is to cover all the steps involved in both routes: the fast pyrolysis step to produce the bio-oils, the water extraction for obtaining the bio-oil aqueous fractions and the final steam reforming of the liquids. Two reactors were used in the first pyrolysis step to produce bio-oils from the same wood feedstock: a fluidized bed and a spouted bed. The mass balances and the compositions of both batches of bio-oils and aqueous fractions were in good agreement between both processes. Carboxylic acids, alcohols, aldehydes, ketones, furans, sugars and aromatics were the main compounds detected and quantified. In the steam reforming experiments, catalytic and non-catalytic processes were tested and compared to produce a hydrogen-rich gas from the bio-oils and the aqueous fractions. Moreover, two different catalytic reactors were tested in the catalytic process (a fixed and a fluidized bed). Under the experimental conditions tested, the H₂ yields were as follows: catalytic steam reforming of the aqueous fractions in fixed bed (0.17 g H₂/g organics) > non-catalytic steam reforming of the bio-oils (0.14 g H₂/g organics) > non-catalytic steam reforming of the aqueous fractions (0.13 g H₂/g organics) > catalytic steam reforming of the aqueous fractions in fluidized bed (0.07 g H₂/g organics). These different H₂ yields are a consequence of the different temperatures used in the reforming processes (650 °C and 1400 °C for the catalytic and the non-catalytic, respectively) as well as the high spatial velocity employed in the catalytic tests, which was not sufficiently low to reach equilibrium in the fluidized bed reactor.     

Thermal plasma spraying for SOFCs: Applications, potential advantages, and challenges

In this article, the applications, potential advantages, and challenges of thermal plasma spray (PS) processing for nanopowder production and cell fabrication of solid oxide fuel cells (SOFCs) are reviewed. PS processing creates sufficiently high temperatures to melt all materials fed into the plasma. The heated material can either be quenched into oxide powders or deposited as coatings. This technique has been applied to directly deposit functional layers as well as nanopowder for SOFCs application. In particularly, low melting point and highly active electrodes can be directly fabricated on zirconia-based electrolytes. This is a simple processing technique that does not require the use of organic solvents, offering the opportunity for flexible adjustment of process parameters, and significant time saving in production of the cell and cost reduction compared with tape casting, screen printing and sintering processing steps. Most importantly, PS processing shows strong potential to enable the deposition of metal-supported SOFCs through the integrated fabrication of membrane-electrode assemblies (MEA) on porous metallic substrates with consecutive deposition steps. On the other hand, the application of PS processing to produce SOFCs faces some challenges, such as insufficient porosity of the electrodes, the difficulty of obtaining a thin (<10 μm) and dense electrolyte layer. Fed with H₂ as the fuel gas and oxygen as the oxidant gas, the plasma sprayed cell reached high power densities of 770 mW cm⁻² at 900 °C and 430 mW cm⁻² at 800 °C at a cell voltage of 0.7 V.     

生物油燃烧技术研究进展

生物油可以在锅炉中单独燃烧或者与化石燃料混合燃烧用于供热和发电,可以与乙醇、甲醇和柴油等混合燃烧以驱动柴油机发电,也可以直接应用于燃气轮机中.文章分析了由于生物油燃料特性的限制而引起的燃烧应用问题和相应的解决方法.分析表明,生物油与化石燃料在锅炉和燃气轮机中混合燃烧最具有大规模应用的可能性,在柴油机中燃烧是最有开发前景的应用技术.     

A techno-economic comparison of power production by biomass fast pyrolysis with gasification and combustion

This paper presents an assessment of the technical and economic performance of thermal processes to generate electricity from a wood chip feedstock by combustion, gasification and fast pyrolysis. The scope of the work begins with the delivery of a wood chip feedstock at a conversion plant and ends with the supply of electricity to the grid, incorporating wood chip preparation, thermal conversion, and electricity generation in dual fuel diesel engines. Net generating capacities of 1–20 MW_e are evaluated.The techno-economic assessment is achieved through the development of a suite of models that are combined to give cost and performance data for the integrated system. The models include feed pretreatment, combustion, atmospheric and pressure gasification, fast pyrolysis with pyrolysis liquid storage and transport (an optional step in de-coupled systems) and diesel engine or turbine power generation. The models calculate system efficiencies, capital costs and production costs. An identical methodology is applied in the development of all the models so that all of the results are directly comparable.The electricity production costs have been calculated for 10th plant systems, indicating the costs that are achievable in the medium term after the high initial costs associated with novel technologies have reduced. The costs converge at the larger scale with the mean electricity price paid in the EU by a large consumer, and there is therefore potential for fast pyrolysis and diesel engine systems to sell electricity directly to large consumers or for on-site generation. However, competition will be fierce at all capacities since electricity production costs vary only slightly between the four biomass to electricity systems that are evaluated.Systems de-coupling is one way that the fast pyrolysis and diesel engine system can distinguish itself from the other conversion technologies. Evaluations in this work show that situations requiring several remote generators are much better served by a large fast pyrolysis plant that supplies fuel to de-coupled diesel engines than by constructing an entire close-coupled system at each generating site. Another advantage of de-coupling is that the fast pyrolysis conversion step and the diesel engine generation step can operate independently, with intermediate storage of the fast pyrolysis liquid fuel, increasing overall reliability. Peak load or seasonal power requirements would also benefit from de-coupling since a small fast pyrolysis plant could operate continuously to produce fuel that is stored for use in the engine on demand.Current electricity production costs for a fast pyrolysis and diesel engine system are 0.091

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/kWh at 20 MW_e and 0.199

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/kWh at 1 MW_e in the base case studied here reducing to 0.073

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/kWh at 20 MW_e and to 0.146

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/kWh at 1 MW_e when learning effects are included. These systems are handicapped by the typical characteristics of a novel technology: high capital cost, high labour, and low reliability. As such the more established combustion and steam cycle produces lower cost electricity under current conditions.The fast pyrolysis and diesel engine system is a low capital cost option but it also suffers from relatively low system efficiency particularly at high capacities. This low efficiency is the result of a low conversion efficiency of feed energy into the pyrolysis liquid, because of the energy in the char by-product. A sensitivity analysis has highlighted the high impact on electricity production costs of the fast pyrolysis liquids yield. The liquids yield should be set realistically during design, and it should be maintained in practice by careful attention to plant operation and feed quality. Another problem is the high power consumption during feedstock grinding. Efficiencies may be enhanced in ablative fast pyrolysis which can tolerate a chipped feedstock. This has yet to be demonstrated at commercial scale.In summary, the fast pyrolysis and diesel engine system has great potential to generate electricity at a profit in the long term, and at a lower cost than any other biomass to electricity system at small scale. This future viability can only be achieved through the construction of early plant that could, in the short term, be more expensive than the combustion alternative. Profitability in the short term can best be achieved by exploiting niches in the market place and specific features of fast pyrolysis. These include:

• •countries or regions with fiscal incentives for renewable energy such as premium electricity prices or capital grants;
• •locations with high electricity prices so that electricity can be sold direct to large consumers or generated on-site by companies who wish to reduce their consumption from the grid;
• •waste disposal opportunities where feedstocks can attract a gate fee rather than incur a cost;
• •the ability to store fast pyrolysis liquids as a buffer against shutdowns or as a fuel for peak-load generating plant;
• •de-coupling opportunities where a large, single pyrolysis plant supplies fuel to several small and remote generators;
• •small-scale combined heat and power opportunities;
• •sales of the excess char, although a market has yet to be established for this by-product; and
• •potential co-production of speciality chemicals and fuel for power generation in fast pyrolysis systems.

     

Slow, fast and flash pyrolysis of rapeseed

Pyrolysis experiments have been conducted on a sample of rapeseed to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields and their chemical compositions. The maximum oil yield of 73% was obtained at the final pyrolysis temperature of 550–600 °C, particle size range of +0.6–1.25 mm, and sweep gas flow rate of 100 cm³min⁻¹ (N₂) at flash pyrolysis conditions in tubular transport reactor. Chromatographic and spectroscopic studies on the pyrolytic oil showed that the oil obtained from rapeseed can be used as a renewable fuel and chemical feedstock.     

Effect of temperature on the fast pyrolysis of organic-acid leached pinewood; the potential of low temperature pyrolysis

In this paper, we have evaluated the potential of organic acid (mixture of acetic, formic and propionic acid) leaching of biomass and subsequent fast pyrolysis to increase the organic oil, sugars and phenols yield by varying the fluidized bed temperature between 360 °C and 580 °C (360 °C, 430 °C, 480 °C, 530 °C, and 580 °C). The pyrolysis of acid leached pinewood resulted in more organic oil and less water and residue compared to untreated pinewood over the whole temperature range. Below 500 °C the difference was most profound; for acid leached pinewood at 360 °C the organic oil was already 650 g kg⁻¹ pine with a sugar yield of 230 g kg⁻¹ pine. At this low pyrolysis temperature no bed agglomeration was observed for acid leached pine whereas at the higher temperatures tested agglomerates were found, which were identified to be clusters of fluidization sand glued together by sticky pyrolysis products (melt). Low reactor temperatures also favored the production of monomeric phenols, though their absolute yields remained low for both untreated and leached pine (maximum: 23 g kg⁻¹ pine, 80 g kg⁻¹ lignin). GPC, GC/MS and UV-fluorescence spectroscopy showed that acid leaching did not influence significantly the yield and molecular size of the aromatic fraction in the produced pyrolysis oils. Back impregnation of the removed AAEMs into leached biomass revealed that the effects of the applied acid leaching, both with respect to the product yields and bed agglomeration, can be mainly assigned to the removal of AAEMs.     

Co-production of upgraded bio-oils and H2-rich gas from microalgae via chemical looping pyrolysis

In order to produce high-quality bio-oils and syngas from biomass, a novel pyrolysis approach based on the chemical looping concept, namely chemical looping pyrolysis (CLPy), was proposed. In the current work, thermodynamic feasibility study and experimental investigations of the proposed CLPy with calcium-ferrite oxygen carriers and Nannochloropsis sp. microalgal biomass were conducted. The results suggested that the reduced calcium-ferrite oxygen carrier facilitated the denitrification, ketonization, and hydrodeoxygenation (HDO) of bio-oils during the pyrolysis stage. Since large amounts of oxygen in bio-oils were transferred to the reduced oxygen carrier, the heating value of bio-oils was remarkably increased up to 34.2 MJ/kg and 36.0 MJ/kg by employing the reduced CaFe₂O₄ and Ca₂Fe₂O₅ oxygen carrier, respectively. In addition, a high H₂ content of 50% in the pyrolysis gas was observed at the optimal pyrolysis temperature. In the gasification stage, the production of high-quality syngas was achieved. The content of H₂ accounted for up to 70% of the gasification products when taking steam as gasifying agent, while that of CO was composed of 66% without the use of a gasifying agent. Moreover, the oxygen carrier was reduced to its reduction state, available for the next loop. In summary, CLPy proposed in this work involves the continuous transference of the oxygen from bio-oils to syngas by an oxygen carrier and provides a brand-new approach for the comprehensive utilization of biomass.     

Kinetic studies of dehydration,pyrolysis and combustion of paper sludge

The reaction kinetics of drying, pyrolysis and combustion of paper sludge have been determined in a thermogravimetric analyzer (TGA). The effects of heating rate (5–30 K min⁻¹) and sample weight (10–50 mg) on drying and pyrolysis of paper sludge have been determined. The kinetic parameters of char combustion are determined at the isothermal conditions (723–1173 K). For dehydration, pyrolysis and combustion of paper sludge, temperature can be divided into drying (−470 K), pyrolysis [low (470–660 K), medium (660–855 K)] and combustion (>855 K) ranges. From the kinetic parameters (frequency factor and activation energy) of water decomposition, two major degradable compounds are found and the experimental thermogravimetric curves predicted by those parameters. For char combustion, the reaction order is found to be unity. The char combustion is well expressed by the shrinking core model with chemical reaction controlling and the activation energy is changed from 24.3 to 10.14 kJ mol⁻¹ K⁻¹ at 873 K.     

Extraction of cardanol and phenol from bio-oils obtained through vacuum pyrolysis of biomass using supercritical fluid extraction

The feasibility of extraction of phenol rich oil from the bio-oils obtained through pyrolysis of cashew nut shells and sugarcane bagasse is studied. The extraction rate of phenol rich oil using CO₂ as a supercritical fluid is discussed. Operating parameters are optimized for the maximum concentration of phenol and cardanol. Higher yield of oil (50% by weight) along with higher concentration of phenols and cardanol by present method is found encouraging. The experiments were conducted in the pressure range of 120-300 bar, the temperature range of 303-333 K and the mass flow rate range of 0.7-1.2 kg/h. The process parameters are optimized to maximize the yield of extracts and its contents of phenols and substituted phenols from sugarcane bagasse pyrolysis oil. The oil samples obtained at various operating parameters are analyzed by Gas Chromatograph-Mass Spectroscopy (GC-MS) and Fourier Transform Infra-Red Spectroscopy (FTIR).     

Stability of wood fast pyrolysis oil

This study evaluates the effects of storage conditions on physical and chemical properties of biomass fast pyrolysis oils exposed to elevated temperatures over extended periods of time. It was performed on oak pyrolysis oil generated in the NREL vortex reactor. Oil samples were stored at three temperatures: 37, 60 and 90°C in glass vessels. Properties of the oils were measured after hours of storage at 90°C, and after days or weeks at lower temperatures. Chemical changes in the oils were measured using GPC (molecular weight distribution) and FTIR spectroscopy. The oil remained a single phase throughout the studied conditions. Its pH was not affected by storage. The water content, viscosity and molecular weight of the oil increased with the time and temperature of storage. First-order reaction kinetics were successfully used to predict changes in molecular weight of the stored oil. FTIR provided evidence that etherification or esterification are mechanisms for condensation of the oil during storage.     

Spray pyrolysis of CuInS2

Spray pyrolysis is a low-cost method of depositing thin films and is economically more attractive than other methods that have been used to produce stable CuInS₂ thin films. The electrical, optical and structural properties of the films, as prepared, are presented together with their evolution and with a variation of some fabrication parameters which are the fabrication temperature T_S, and the ionic ratio R = Cu : In : S in the solution.     

Comprehensive reaction mechanism for n-butanol pyrolysis and combustion

A detailed reaction mechanism for n-butanol, consisting of 263 species and 3381 reactions, has been generated using the open-source software package, Reaction Mechanism Generator (RMG). The mechanism is tested against recently published data – jet-stirred reactor mole fraction profiles, opposed-flow diffusion flame mole fraction profiles, autoignition delay times, and doped methane diffusion flame mole fraction profiles – and newly acquired n-butanol pyrolysis experiments with very encouraging results. The chemistry of butanal is also validated against autoignition delay times obtained in shock tube experiments. A flux and sensitivity analysis for each simulated dataset is discussed and reveals important reactions where more accurate rate constant estimates were required. New rate constant expressions were computed using quantum chemistry and transition state theory calculations. Furthermore, in addition to comparing the proposed model with the eight datasets, the model is also compared with recently published n-butanol models for three of the datasets. Key differences between the proposed model and the published models are discussed.     

Liquid-based high-temperature receiver technologies for next-generation concentrating solar power: A review of challenges and potential solutions

To reduce the levelized cost of energy for concentrating solar power (CSP), the outlet temperature of the solar receiver needs to be higher than 700 °C in the next-generation CSP. Because of extensive engineering application experience, the liquid-based receiver is an attractive receiver technology for the next-generation CSP. This review is focused on four of the most promising liquid-based receivers, including chloride salts, sodium, lead-bismuth, and tin receivers. The challenges of these receivers and corresponding solutions are comprehensively reviewed and classified. It is concluded that combining salt purification and anti-corrosion receiver materials is promising to tackle the corrosion problems of chloride salts at high temperatures. In addition, reducing energy losses of the receiver from sources and during propagation is the most effective way to improve the receiver efficiency. Moreover, resolving the sodium fire risk and material compatibility issues could promote the potential application of liquid-metal receivers. Furthermore, using multiple heat transfer fluids in one system is also a promising way for the next-generation CSP. For example, the liquid sodium is used as the heat transfer fluid while the molten chloride salt is used as the storage medium. In the end, suggestions for future studies are proposed to bridge the research gaps for > 700 °C liquid-based receivers.     

杨树皮热解和燃烧特性研究

通过热重分析技术,对木材加工企业产生的废弃物——速生材杨树树皮的热解和燃烧过程进行试验研究,得到杨树皮的热分析曲线,分析了杨树皮热解和燃烧特性,为木材加工剩余物的能源化利用提供基础数据。     

废轮胎热解油特性及其燃烧应用

随着石油资源的日益枯竭及废轮胎数量的日益增多,利用废轮胎热解制取燃料油对缓解能源供应紧张局面,充分利用废弃资源都具有重要意义.废轮胎热解油具有热值高、灰分低、粘度低和残炭值低等优点,但也存在整体性能较柴油差的缺陷.与柴油混合作为发动机燃料使用的结果表明,废轮胎热解油可以作为重柴油使用;炉内燃烧试验表明.废轮胎热解油污染物排放量较柴油高.探索合适的废轮胎热解工艺,提高废轮胎热解油的品质,是将废轮胎热解油直接作为燃料油使用须研究的主要课题之一.     

生物质热解燃烧过程Cl析出规律研究

用化学平衡软件“Factsage”计算了稻草秸秆在200～800℃温度范围内热解条件和500 ～900℃温度范围内燃烧条件下,与Cl相关的各种无机物质的热力学平衡分布.采用管式炉反应器,研究了秸秆在热解和燃烧条件下的Cl的析出规律.理论计算结果表明,当温度低于600℃时,Cl主要以固态KCl的形式存在;在温度超过600℃,热转化中Cl的气化析出随温度升高而增加,在氧化性气氛下该趋势加剧.管式炉实验与理论计算的生物质Cl析出率随温度升高的变化趋势总体吻合,但是析出份额上有显著差异.     

Production of hydrogen by lignins fast pyrolysis

This paper reports the results of experiments performed on the flash pyrolysis of lignin samples submitted to controlled heat flux densities (short flashes of a concentrated radiation). Two types of lignins are used: Kraft and Organocell lignins. Microscopic observations of the reacted samples reveal the formation of an intermediate liquid compound that precedes the further formation of char, vapours and gases. The rates of mass loss and the production rates of the products are determined for both lignins. The results are compared to each other and to those obtained in former similar studies made with cellulose.

The analyses of the produced gases reveal high syngas and H₂ contents (respectively 87 and 50 mol%). This composition is compared to results obtained in other different thermal conditions with lignins and other types of biomasses. The possible mechanism of hydrogen formation is further discussed.     

Evolution,challenges and path forward for low temperature combustion engines

Universal concerns about degradation in ambient environment, stringent emission legislations, depletion of petroleum reserves, security of fuel supply and global warming have motivated research and development of engines operating on alternative combustion concepts, which also have capability of using renewable as well as conventional fuels. Low temperature combustion (LTC) is an advanced combustion concept for internal combustion (IC) engines, which has attracted global attention in recent years. LTC concept is different from the conventional spark ignition (SI) combustion as well as compression ignition (CI) diffusion combustion concepts. LTC technology offers prominent benefits in terms of simultaneous reduction of both oxides of nitrogen (NO_x) and particulate matter (PM), in addition to reduction in specific fuel consumption (SFC). However, controlling ignition timing and combustion rate are primary challenges to be tackled before LTC technology can be implemented in automotive engines commercially. This review covers fundamental aspects of development of LTC engines and its evolution, historical background and origin of LTC concept, encompassing LTC principle, its advantages, challenges and prospects. Detailed insights into preparation of homogeneous charge by external and internal measures for mineral diesel and gasoline like fuels are covered. Fuel requirements and fuel induction system design aspect for LTC engines are also discussed. Combustion characteristics of LTC engines including combustion chemistry, heat release rate (HRR), combustion duration, knock characteristics, high load limit, fuel conversion efficiencies and combustion instability are summarized. Emission characteristics are reviewed along with insights into PM and NO_x emissions from LTC engines. Finally, different strategies for controlling combustion rate and combustion timings for gasoline and mineral diesel like fuels are discussed, showing the way forward for this technology in future towards its commercialization.