Fast pyrolysis utilizes biomass to produce a product that is used both as an energy source and a feedstock for chemical production. Considerable efforts have been made to convert wood biomass to liquid fuels and chemicals since the oil crisis in mid-1970s. This review focuses on the recent developments in the wood pyrolysis and reports the characteristics of the resulting bio-oils, which are the main products of fast wood pyrolysis. Virtually any form of biomass can be considered for fast pyrolysis. Most work has been performed on wood, because of its consistency and comparability between tests. However, nearly 100 types of biomass have been tested, ranging from agricultural wastes such as straw, olive pits, and nut shells to energy crops such as miscanthus and sorghum. Forestry wastes such as bark and thinnings and other solid wastes, including sewage sludge and leather wastes, have also been studied. In this review, the main (although not exclusive) emphasis has been given to wood. The literature on woo...

Pyrolysis of Wood/Biomass for Bio-oil: A Critical Review

Agricultural activities and soils release greenhouse gases, and additional emissions occur in the conversion of land from other uses. Unlike natural lands, active management offers the possibility to increase terrestrial stores of carbon in various forms in soil. The potential to sequester carbon as thermally stabilized (charred) biomass using existing organic resource is estimated to be at least 1 Gt yr − 1 and “biochar,” defined by its useful application to soil, is expected to provide a benefit from enduring physical and chemical properties. Studies of charcoal tend to suggest stability in the order of 1000 years in the natural environment, and various analytical techniques inform quantification and an understanding of turnover processes. Other types of biochar, such as those produced under zero-oxygen conditions have been studied less, but costs associated with logistics and opportunity costs from diversion from energy or an active form in soil demand certainty and predictability of the agronomic return, especially until eligibility for carbon credits has been established. The mechanisms of biochar function in soil, which appear to be sensitive to the conditions prevailing during its formation or manufacture, are also affected by the material from which it is produced. Proposed mechanisms and some experimental evidence point to added environmental function in the mitigation of diffuse pollution and emissions of trace gases from soil; precluding the possibility of contaminants accumulating in soil from the incorporation of biochar is important to ensure safety and regulatory compliance.

A review of biochar and its use and function in soil

Fast pyrolysis for production of liquids has developed considerably since the first experiments in the late 1970s. Many reactors and processes have been investigated and developed to the point where fast pyrolysis is now an accepted feasible and viable route to renewable liquid fuels, chemicals and derived products. It is also now clear that liquid products offer significant advantages in storage and transport over gas and heat. These advantages have caused greater attention to be paid to fast pyrolysis, leading to significant advances in process development. The technology of fast pyrolysis for liquids is noteworthy for the wide range of reactor configurations that have been developed to meet the stringent requirements for high yields of useful liquids, for use as a fuel in boilers, engines and turbines and as a source of chemical commodities. This review summarizes the key features of fast pyrolysis and the resultant liquid product and describes the major reaction systems and processes that have been developed over the last 20 years.

http://ehsan13967.persiangig.com/document/pyrolysis5.pdf

Fast pyrolysis processes for biomass

As the oil reserves are depleting the need of an alternative fuel source is becoming increasingly apparent. One prospective method for producing fuels in the future is conversion of biomass into bio-oil and then upgrading the bio-oil over a catalyst, this method is the focus of this review article. Bio-oil production can be facilitated through flash pyrolysis, which has been identified as one of the most feasible routes. The bio-oil has a high oxygen content and therefore low stability over time and a low heating value. Upgrading is desirable to remove the oxygen and in this way make it resemble crude oil. Two general routes for bio-oil upgrading have been considered: hydrodeoxygenation (HDO) and zeolite cracking. HDO is a high pressure operation where hydrogen is used to exclude oxygen from the bio-oil, giving a high grade oil product equivalent to crude oil. Catalysts for the reaction are traditional hydrodesulphurization (HDS) catalysts, such as Co–MoS2/Al2O3, or metal catalysts, as for example Pd/C. However, catalyst lifetimes of much more than 200 h have not been achieved with any current catalyst due to carbon deposition. Zeolite cracking is an alternative path, where zeolites, e.g. HZSM-5, are used as catalysts for the deoxygenation reaction. In these systems hydrogen is not a requirement, so operation is performed at atmospheric pressure. However, extensive carbon deposition results in very short catalyst lifetimes. Furthermore a general restriction in the hydrogen content of the bio-oil results in a low H/C ratio of the oil product as no additional hydrogen is supplied. Overall, oil from zeolite cracking is of a low grade, with heating values approximately 25% lower than that of crude oil. Of the two mentioned routes, HDO appears to have the best potential, as zeolite cracking cannot produce fuels of acceptable grade for the current infrastructure. HDO is evaluated as being a path to fuels in a grade and at a price equivalent to present fossil fuels, but several tasks still have to be addressed within this process. Catalyst development, understanding of the carbon forming mechanisms, understanding of the kinetics, elucidation of sulphur as a source of deactivation, evaluation of the requirement for high pressure, and sustainable sources for hydrogen are all areas which have to be elucidated before commercialisation of the process.

A review of catalytic upgrading of bio-oil to engine fuels

In this review, we summarize the knowledge of the production and properties of charcoal that has been accumulated over the past 38 millenia. The manipulation of pressure, moisture content, and gas flow enables biomass carbonization with fixed-carbon yields that approachor attainthe theoretical limit after reaction times of a few tens of minutes. Much of the heat needed to carbonize the feed is released by vigorous, exothermic secondary reactions that reduce the formation of unwanted tars by augmenting the charcoal yield in a well-designed carbonizer. As a renewable fuel, charcoal has many attractive features:  it contains virtually no sulfur or mercury and is low in nitrogen and ash; it is highly reactive yet easy to store and handle. Carbonized charcoal can be a good adsorbent with a large surface area and a semimetal with an electrical resistivity comparable to that of graphite. Recent advances in knowledge about the production and properties of charcoal presage its expanded use as a renewable fuel, red...

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The Art, Science, and Technology of Charcoal Production†

This paper describes an analytical approach to determine the chemical composition of bio-oils in terms of macro-chemical families. Bio-oils from the vacuum pyrolysis of softwood bark and hardwood were first fractionated using solvent extraction. Fractions obtained were then characterized using GC-MS, thermogravimetric techniques (TG) and Gel Permeation Chromatography (GPC). Thermogravimetric and molar mass distribution curves of each fraction were interpreted in terms of macro-families applying curve-fitting procedures. The composition of the different macro-fractions obtained was in agreement using both methods. The proposed procedure enables a thorough description of bio-oil composition as a mixture of water, monolignols, polar compounds with moderate volatility, sugars, extractive-derived compounds, heavy polar and non-polar compounds, MeOH–toluene insolubles and volatile organic compounds.

Characterization of bio-oils in chemical families

Production of dl-limonene by vacuum pyrolysis of used tires

This paper completes a study the ultimate objective of which was to provide background information on biomass pyrolysis oils (bio-oils) regarding their use as a gas turbine liquid fuel. The bio-oil was obtained by vacuum pyrolysis of softwood bark residues. The stability and ageing of the bio-oil and mixtures thereof were evaluated. The samples were stored at 40, 50 and 80°C for up to 168 h and at room temperature for up to one year, period after which the phase separation time, viscosity, solid and water content and average molecular weight were measured. The results indicated that the properties of the bio-oil were significantly altered when the bio-oil was heated at 80°C, but that the variations after heating at 40 and 50°C were not critical. It was found that the molecular weight increase after heating the bio-oil for one week at 80°C was equivalent to keeping the sample for one year at room temperature. The addition of aqueous phase to the bio-oil lowered its thermal stability significantly. A rapid phase separation occurred after heating at 80°C and, therefore, the total aqueous phase concentration in the bio-oil must be limited to 15%. Ageing of the raw bio-oil at room temperature resulted in a dramatic viscosity increase during the first 65 days, period after which a plateau was reached. The addition of methanol to the bio-oil was beneficial for the bio-oil properties as well as for the stability of the bio-oil and its mixtures. Methanol dissolved some structured components of the bio-oil and thus reduced the viscosity increase rate. Moreover, the addition of methanol to the bio-oil/pyrolytic aqueous phase mixtures delayed the phase separation process.

Bio-oils obtained by vacuum pyrolysis of softwood bark as a liquid fuel for gas turbines. Part II: Stability and ageing of bio-oil and its blends with methanol and a pyrolytic aqueous phase

Vacuum pyrolysis of softwood and hardwood biomass: Comparison between product yields and bio-oil properties

The multiphase complex structure of biomass pyrolysis oils can be attributed to the presence of char particles, waxy materials, aqueous droplets, droplets of different nature, and micelles formed of heavy compounds in a matrix of hollocellulose-derived compounds and water. Bio-oil complexity is illustrated by use of two oils produced from the vacuum pyrolysis of softwood bark residues (SWBR) and hardwood rich in fibers (HWRF). The effect of waxy materials on bio-oil behavior was studied by differential scanning calorimetry (DSC), optical microscopy, and surface tension measurements as well as by steady and dynamic rheological techniques. At around 45 °C the melting of waxy materials occurs. Bio-oil cooling rate was found to have an important effect on some bio-oil rheological characteristics. This may be due to crystallization of waxy materials. Strain and frequency sweep tests proved the existence of a network (gel) structure in the bottom layer of oils derived from SWBR. This structure may be formed of ...

Hooshang Pakdel

Papers

Characterization of bio-oils in chemical families

Production of dl-limonene by vacuum pyrolysis of used tires

Bio-oils obtained by vacuum pyrolysis of softwood bark as a liquid fuel for gas turbines. Part II: Stability and ageing of bio-oil and its blends with methanol and a pyrolytic aqueous phase

Vacuum pyrolysis of softwood and hardwood biomass: Comparison between product yields and bio-oil properties

Multiphase Structure of Bio-oils