Upgrading fast pyrolysis liquids:blends of biodiesel and pyrolysis oil

Fast pyrolysis liquid or bio-oil has been used in engines with limited success. It requires a pilot fuel and/or an additive for successful combustion and there are problems with materials and liquid properties. It is immiscible with all conventional hydrocarbon fuels. Biodiesel, a product of esterification of vegetable oil with an alcohol, is widely used as a renewable liquid fuel as an additive to diesel at up to 20%. There are however limits to its use in conventional engines due to poor low temperature performance and variability in quality from a variety of vegetable oil qualities and variety of esterification processes. Within the European Project Bioliquids-CHP - a joint project between the European Commission and Russia - a study was undertaken to develop small scale CHP units based on engines and microturbines fuelled with bioliquids from fast pyrolysis and methyl esters of vegetable oil. Blends of bio-oil and biodiesel were evaluated and tested to overcome some of the disadvantages of using either fuel by itself. An alcohol was used as the co-solvent in the form of ethanol, 1-butanol or 2-propanol. Visual inspection of the blend homogeneity after 48 h was used as an indicator of the product stability and the results were plotted in a three phase chart for each alcohol used. An accelerated stability test was performed on selected samples in order to predict its long term stability. We concluded that the type and quantity of alcohol is critical for the blend formation and stability. Using 1-butanol gave the widest selection of stable blends, followed by blends with 2-propanol and finally ethanol, thus 1-butanol blends accepted the largest proportion of bio-oil in the mixture. © 2013 Elsevier Ltd. All rights reserved.

The effect of lignin and inorganic species in biomass on pyrolysis oil yields, quality and stability

This paper investigates four reference fuels and three low lignin Lolium Festuca grasses which were subjected to pyrolysis to produce pyrolysis oils. The oils were analysed to determine their quality and stability, enabling the identification of feedstock traits which affect oil stability. Two washed feedstocks were also subjected to pyrolysis to investigate whether washing can enhance pyrolysis oil quality. It was found that the mineral matter had the dominate effect on pyrolysis in compared to lignin content, in terms of pyrolysis yields for organics, char and gases. However the higher molecular weight compounds present in the pyrolysis oil are due to the lignin derived compounds as determined by results of GPC and liquid-GC/MS. The light organic fraction also increased in yield, but reduced in water content as metals increased at the expense of the lignin content. It was found that the fresh oil and aged oil had different compound intensities/concentrations, which is due to a large number of reactions occurring when the oil is aged day by day. These findings agree with previous reports which suggest that a large amount of re-polymerisation occurs as levoglucosan yields increase during the aging progress, while hydroxyacetaldehyde decrease. In summary the paper reports a window for producing a more stable pyrolysis oil by the use of energy crops, and also show that washing of biomass can improve oil quality and stability for high ash feedstocks, but less so for the energy crops.

Experimental investigation of performance, emission and combustion characteristics of an indirect injection multi-cylinder CI engine fuelled by blends of de-inking sludge pyrolysis oil with biodiesel

De-inking sludge can be converted into useful forms of energy to provide economic and environmental benefits. In this study, pyrolysis oil produced from de-inking sludge through an intermediate pyrolysis technique was blended with biodiesel derived from waste cooking oil, and tested in a multi-cylinder indirect injection type CI engine. The physical and chemical properties of pyrolysis oil and its blends (20 and 30 vol.%) were measured and compared with those of fossil diesel and pure biodiesel (B100). Full engine power was achieved with both blends, and very little difference in engine performance and emission results were observed between 20% and 30% blends. At full engine load, the brake specific fuel consumption on a volume basis was around 6% higher for the blends when compared to fossil diesel. The brake thermal efficiencies were about 3-6% lower than biodiesel and were similar to fossil diesel. Exhaust gas emissions of the blends contained 4% higher CO2 and 6-12% lower NOx, as compared to fossil diesel. At full load, CO emissions of the blends were decreased by 5-10 times. The cylinder gas pressure diagram showed stable engine operation with the 20% blend, but indicated minor knocking with 30% blend. Peak cylinder pressure of the 30% blend was about 5-6% higher compared to fossil diesel. At full load, the peak burn rate of combustion from the 30% blend was about 26% and 12% higher than fossil diesel and biodiesel respectively. In comparison to fossil diesel the combustion duration was decreased for both blends; for 30% blend at full load, the duration was almost 12% lower. The study concludes that up to 20% blend of de-inking sludge pyrolysis oil with biodiesel can be used in an indirect injection CI engine without adding any ignition additives or surfactants.

Investigation into the performance and emissions of a stationary diesel engine fuelled by sewage sludge intermediate pyrolysis oil and biodiesel blends

This paper studies the characteristics of blends of biodiesel and a new type of SSPO (sewage sludge derived intermediate pyrolysis oil) in various ratios, and evaluates the application of such blends in an unmodified Lister diesel engine. The engine performance and exhaust emissions were investigated and compared to those of diesel and biodiesel. The engine injectors were inspected and tested after the experiment. The SSPO-biodiesel blends were found to have comparable heating values to biodiesel, but relatively high acidity and carbon residue. The diesel engine has operated with a 30/70 SSPO-biodiesel blend and a 50/50 blend for up to 10h and there was no apparent deterioration in operation observed. It is concluded that with 30% SSPO, the engine gives better overall performance and fuel consumption than with 50% SSPO. The exhaust temperatures of 30% SSPO and 50% SSPO are similar, but 30% SSPO gives relatively lower NO emission than 50% SSPO. The CO and smoke emissions are lower with 50% SSPO than with 30% SSPO. The injectors of the engine operated with SSPO blends were found to have heavy carbon deposition and noticeably reduced opening pressure, which may lead to deteriorated engine performance and exhaust emissions in extended operation. © 2013 Elsevier Ltd.

Combustion of fuel blends containing digestate pyrolysis oil in a multi-cylinder compression ignition engine

Digestate from the anaerobic digestion conversion process is widely used as a farm land fertiliser. This study proposes an alternative use as a source of energy. Dried digestate was pyrolysed and the resulting oil was blended with waste cooking oil and butanol (10, 20 and 30 vol.%). The physical and chemical properties of the pyrolysis oil blends were measured and compared with pure fossil diesel and waste cooking oil. The blends were tested in a multi-cylinder indirect injection compression ignition engine.Engine combustion, exhaust gas emissions and performance parameters were measured and compared with pure fossil diesel operation. The ASTM copper corrosion values for 20% and 30% pyrolysis blends were 2c, compared to 1b for fossil diesel. The kinematic viscosities of the blends at 40 C were 5–7 times higher than that of fossil diesel. Digested pyrolysis oil blends produced lower in-cylinder peak pressures than fossil diesel and waste cooking oil operation. The maximum heat release rates of the blends were approximately 8% higher than with fossil diesel. The ignition delay periods of the blends were higher; pyrolysis oil blends started to combust late and once combustion started burnt quicker than fossil diesel. The total burning duration of the 20% and 30% blends were decreased by 12% and 3% compared to fossil diesel. At full engine load, the brake thermal efficiencies of the blends were decreased by about 3–7% when compared to fossil diesel. The pyrolysis blends gave lower smoke levels; at full engine load, smoke level of the 20% blend was 44% lower than fossil diesel. In comparison to fossil diesel and at full load, the brake specific fuel consumption (wt.) of the 30% and 20% blends were approximately 32% and 15% higher. At full engine load, the CO emission of the 20% and 30% blends were decreased by 39% and 66% with respect to the fossil diesel. Blends CO2 emissions were similar to that of fossil diesel; at full engine load, 30% blend produced approximately 5% higher CO2 emission than fossil diesel. The study concludes that on the basis of short term engine experiment up to 30% blend of pyrolysis oil from digestate of arable crops can be used in a compression ignition engine.

Novel method for the determination of water content and higher heating value of pyrolysis oil

This research provides a novel approach for the determination of water content and higher heating value of pyrolysis oil. Pyrolysis oil from Napier grass was used in this study. Water content was determined with pH adjustment using a Karl Fischer titration unit. An equation for actual water in the oil was developed and used, and the results were compared with the traditional Karl Fischer method. The oil was found to have between 42 and 64% moisture under the same pyrolysis condition depending on the properties of the Napier grass prior to the pyrolysis. The higher heating value of the pyrolysis oil was determined using an oil-diesel mixture, and 20 to 25 wt% of the oil in the mixture gave optimum and stable results. A new model was developed for evaluation of higher heating value of dry pyrolysis oil. The dry oil has higher heating values in the range between 19 and 26 MJ/kg. The developed protocols and equations may serve as a reliable alternative means for establishing the actual water content and the higher heating value of pyrolysis oil.

Thermal stability of sewage sludge pyrolysis oil

The stability of the oil phase obtained from intermediate pyrolysis process was used for this investigation. The analysis was based on standard methods of determining kinematic viscosity, gas - chromatography / mass - spectrometry for compositional changes, FT-IR for functional group, Karl Fischer titration for water content and bomb calorimeter for higher heaating values. The methods were used to determine changes that occurred during ageing. The temperatures used for thermal testing were 60 °C and 80 °C for the periods of 72 and 168 h. Methanol and biodiesel were used as solvents for the analysis. The bio-oil samples contained 10 % methanol, 10 % Biodiesel, 20 % Biodiesel and unstabilised pyrolysis oil. The tests carried out at 80 °C showed drastic changes compared to those at 60 °C. The bio-oil samples containing 20 % biodiesel proved to be more stable than those with 10 % methanol. The unstabilised pyrolysis oil showed the greatest changes in viscosity, composition change and highest increase in water content. The measurement of kinematic viscosity and gas chromatograph mass spectrometry were found to be more reliable for predicting the ageing process.

Fast pyrolysis oil fuel blend for marine vessels

The main driver for the investigation of fast pyrolysis oil marine fuel blends is EU directive 2012/33/EU which aims to cut the sulphur content of marine fuel and thereby reduce air pollution caused by marine vessels. The aim of this study was to investigate the miscibility of 3- and 4- component blends containing pyrolysis oil, 1-butanol, biodiesel (RME) and/or marine gas oil (MGO). The ideal blend would be a stable homogenous product with a minimum amount of butanol, whilst maximising the amount of pyrolysis oil. A successful blend would have properties suitable for use in marine engines. In order to successfully utilise a marine fuel blend in commercial vessels it should meet minimum specification requirements such as a flash point ≥60°C. Blends of pyrolysis oil, RME, MGO and 1-butanol were evaluated and characterised. The mixed blends were inspected after 48 hours for homogeneity and the results plotted on a tri-plot phase diagram. Homogenous samples were tested for water content, pH, acid number, viscosity and flash point as these give indicate a blend’s suitability for engine testing. The work forms part of the ReShip Project which is funded by Norwegian industry partners and the Research Council of Norway (The ENERGIX programme).

Characteristics of the upper phase of bio-oil obtained from co-pyrolysis of sewage sludge with wood, rapeseed and straw

Sewage sludge was pyrolysed with 40% mixed wood, 40% rapeseed and 40% straw. The reason for the mixture of different biomass is to investigate the impact of co-pyrolysis on the upper phase of bio-oil in terms of changes to composition, elemental analysis, viscosity, water content, pH, higher heating value and acid number that could impact on their applications. The biomass was pyrolysed in a laboratory at 450 °C and bio-oil was collected from two cooling traps. The bio-oil obtained from co-pyrolysis of sewage sludge with wood, rapeseed and straw was analysed for composition using the gas chromatography mass spectrometry. The upper phase from the co-pyrolysis process was also characterised for ultimate analysis, higher heating values, water content, viscosity, pH and acid number. There was an increase in the amount of upper phase produced with co-pyrolysis of 40% rapeseed. It was also found that the upper phase from sewage sludge with mixed wood has the highest viscosity, acid number and lowest pH. The bio-oil containing 40% straw was found to have a pH of 6.5 with a very low acid number while the 40% rapeseed was found to have no acid number. Sewage sludge with 40% rapeseed was found to have the highest energy content of 34.8 MJ/kg, 40% straw has 32.5 MJ/kg while the 40% mixed wood pyrolysis oil has the lowest energy content of 31.3 MJ/kg. The 40% rapeseed fraction was found to have the highest water content of 8.2% compared to other fractions.

Application of space-charge electrostatic precipitator for collection of oil mist from pyrolysis gases

A novel electrostatic precipitator CAROLA® is developed for collection of fine oil mists. It operates on the principle of unipolar particle charging in the corona discharge and particle precipitation under the field of space charge. The pilot precipitator was tested at different gas temperatures. It is shown that the increase of gas temperature changes the characteristics of the corona discharge and particle size distribution, especially for droplets sub-micron droplets. The CAROLA® precipitator was used for collection of oil mist from pyrolysis gases at the HALOCLEAN® plant. The flow rate of biomass in the HALOCLEAN® plant was 15-30 kg/h. The particle mass concentration in the raw gas was over 100 g/Nm. The operation voltage of the precipitator was 10-12 kV and corona current up to 0,1 mA. Single stage electrostatic precipitator ensured mass collection efficiency 97-99,5% for pyrolysis oil mist.

Comparison of the effect of pre-treatment and catalysts on liquid quality from fast pyrolysis of biomass

The overall objective of this work was to compare the effect of pre-treatment and catalysts on the quality of liquid products from fast pyrolysis of biomass. This study investigated the upgrading of bio-oil in terms of its quality as a bio-fuel and/or source of chemicals. Bio-oil used directly as a biofuel for heat or power needs to be improved particularly in terms of temperature sensitivity, oxygen content, chemical instability, solid content, and heating values. Chemicals produced from bio-oil need to be able to meet product specifications for market acceptability. There were two main objectives in this research. The first was to examine the influence of pre-treatment of biomass on the fast pyrolysis process and liquid quality. The relationship between the method of pre-treatment of biomass feedstock to fast pyrolysis oil quality was studied. The thermal decomposition behaviour of untreated and pretreated feedstocks was studied by using a TGA (thermogravimetric analysis) and a Py-GC/MS (pyroprobe-gas chromatography/mass spectrometry). Laboratory scale reactors (100g/h, 300g/h, 1kg/h) were used to process untreated and pretreated feedstocks by fast pyrolysis. The second objective was to study the influence of numerous catalysts on fast pyrolysis liquids from wheat straw. The first step applied analytical pyrolysis (Py-GC/MS) to determine which catalysts had an effect on fast pyrolysis liquid, in order to select catalysts for further laboratory fast pyrolysis. The effect of activation, temperature, and biomass pre-treatment on catalysts were also investigated. Laboratory experiments were also conducted using the existing 300g/h fluidised bed reactor system with a secondary catalytic fixed bed reactor. The screening of catalysts showed that CoMo was a highly active catalyst, which particularly reduced the higher molecular weight products of fast pyrolysis. From these screening tests, CoMo catalyst was selected for larger scale laboratory experiments. With reference to the effect of pre-treatment work on fast pyrolysis process, a significant effect occurred on the thermal decomposition of biomass, as well as the pyrolysis products composition, and the proportion of key components in bio-oil. Torrefaction proved to have a mild influence on pyrolysis products, when compared to aquathermolysis and steam pre-treatment.

Using biomass-based fuels including pyrolysis liquids for power and CHP production

The use of biomass-derived liquids (in short: bioliquids) instead of solid biomass can help overcome some of the barriers hindering a wider use of biomass in smaller-scale CHP systems. Relevant bioliquids included biodiesel, vegetable oils as well straight and upgraded pyrolysis oil. In this joint EU-Russian research project Bioliquids-CHP prime movers (engines and turbines) will be developed and modified so that these can run efficiently on bioliquids. At the same time, bioliquids will be upgraded and blended in order to facilitate their use in prime movers. Preliminary results with regard to bioliquid selection, production, and characterisation; the selection and modification of a micro gas turbine; and the development of engines and components are discussed. The research also covers NOx emission reduction and control and an assessment of the benefits and economics of bioliquids-based CHP systems in EU and Russian markets.

The characterisation and optimisation of modified herbaceous grasses for identifying pyrolisis-oil quality traits

The primary objective of this work is to relate the biomass fuel quality to fast pyrolysis-oil quality in order to identify key biomass traits which affect pyrolysis-oil stability. During storage the pyrolysis-oil becomes more viscous due to chemical and physical changes, as reactions and volatile losses occur due to aging. The reason for oil instability begins within the pyrolysis reactor during pyrolysis in which the biomass is rapidly heated in the absence of oxygen, producing free radical volatiles which are then quickly condensed to form the oil. The products formed do not reach thermodynamic equilibrium and in tum the products react with each other to try to achieve product stability. The first aim of this research was to develop and validate a rapid screening method for determining biomass lignin content in comparison to traditional, time consuming and hence costly wet chemical methods such as Klason. Lolium and Festuca grasses were selected to validate the screening method, as these grass genotypes exhibit a low range of Klason /Acid Digestible Fibre lignin contents. The screening methodology was based on the relationship between the lignin derived products from pyrolysis and the lignin content as determined by wet chemistry. The second aim of the research was to determine whether metals have an affect on fast pyrolysis products, and if any clear relationships can be deduced to aid research in feedstock selection for fast pyrolysis processing. It was found that alkali metals, particularly Na and K influence the rate and yield of degradation as well the char content. Pre-washing biomass with water can remove 70% of the total metals, and improve the pyrolysis product characteristics by increasing the organic yield, the temperature in which maximum liquid yield occurs and the proportion of higher molecular weight compounds within the pyrolysis-oil. The third aim identified these feedstock traits and relates them to the pyrolysis-oil quality and stability. It was found that the mineral matter was a key determinant on pyrolysis-oil yield compared to the proportion of lignin. However the higher molecular weight compounds present in the pyrolysis-oil are due to the lignin, and can cause instability within the pyrolysis-oil. The final aim was to investigate if energy crops can be enhanced by agronomical practices to produce a biomass quality which is attractive to the biomass conversion community, as well as giving a good yield to the farmers. It was found that the nitrogen/potassium chloride fertiliser treatments enhances Miscanthus qualities, by producing low ash, high volatiles yields with acceptable yields for farmers. The progress of senescence was measured in terms of biomass characteristics and fast pyrolysis product characteristics. The results obtained from this research are in strong agreement with published literature, and provides new information on quality traits for biomass which affects pyrolysis and pyrolysis-oils.

Characterisation of waste derived intermediate pyrolysis oils for use as diesel engine fuels

This paper studies the characteristics of intermediate pyrolysis oils derived from sewage sludge and de-inking sludge (a paper industry residue), with a view to their use as fuels in a diesel engine. The feedstocks were dried and pelletised, then pyrolysed in the Pyroformer intermediate pyrolysis system. The organic fraction of the oils was separated from the aqueous phase and characterised. This included elemental and compositional analysis, heating value, cetane index, density, viscosity, surface tension, flash point, total acid number, lubricity, copper corrosion, water, carbon residue and ash content. Most of these results are compared with commercial diesel and biodiesel. Both pyrolysis oils have high carbon and hydrogen contents and their higher heating values compare well with biodiesel. The water content of the pyrolysis oils is reasonable and the flash point is found to be high. Both pyrolysis oils have good lubricity, but show some corrosiveness. Cetane index is reduced, which may influence ignition. Also viscosity is increased, which may influence atomisation quality. Carbon residue and ash content are both high, indicating potential deposition problems. Compared with de-inking sludge pyrolysis oil (DSPO), sewage sludge pyrolysis oil (SSPO) has a higher heating value, but higher corrosiveness and viscosity. The conclusions are that both intermediate pyrolysis oils will be able to provide sufficient heat when used in diesel engine; however poor combustion and carbon deposition may be encountered. Blending of these pyrolysis oils with diesel or biodiesel could overcome these problems and is recommended for further investigation.

Decentralised off-grid electricity generation in India using intermediate pyrolysis of residue straws

Use of agricultural residues, like wheat or rice straw for energy generation, is the most effective measure in terms of costs and availability. The present paper focuses the need of such measure, its impact on the environment as practiced today (open burning). The application of intermediate pyrolysis technology for straw conversion in India is discussed herein. A 20 kg/h Pyroformer has been coupled to a direct quenching system without filtration. The process temperature was around 360 ?C and the yields for the product fractions, char pyrolysis oil, and non-condensable gas fractions were, 32%, 35%, and 33% respectively. The pyrolysis oil was condensed in a quenching unit using bio-diesel or diesel. The blend produced was 30 % pyrolysis liquid and 70 % bio-diesel. The engine has been tested with the pyro-oil/biooil mixture over a long term (75 hours). An overall economic analysis of the process has been carried out.