Biomass fuelled combined heat and power:situation in the UK and the Netherlands

Combined Heat and Power (CHP) is the simultaneous generation of usable heat and power in a single process. Despite its obvious advantages in terms of increased efficiency when compared to a single heat or power generation unit, there are a number of technical and economic reasons that have limited their selection. Biomass resources can be, and actually are used as fuel in CHP installations; however several hurdles have to be sorted beforehand, among the most important is the fact that biomass energy sources are not as energy intense as conventional CHP fuels. The ultimate outcome is a limited number of CHP units making use of biomass as fuel. Even fewer CHP units use bioliquids (e.g.: fast pyrolysis biomass liquids, biodiesel and vegetable oil). The Bioliquid-CHP project is carried out by a consortium of seven European and Russian complementary partners, funded by the EU and by the Federal Agency for Science and Innovation of the Russian Federation. The project aim is to develop microturbine and internal combustion engine adaptations in order to adjust these prime movers to bioliquids for CHP applications. This paper will show a summary of the current biomass CHP installations in the UK and the Netherlands, making reference to number of units, capacity, fuel used, the conversion technology involved and the preferred prime movers. The information will give an insight of the current market, with probable future trends and areas where growth could be expected. A similar paper describing the biomass CHP situation in Italy and Russia will be prepared in the near future.

Thermochemical characterisation of straws and high yielding perennial grasses

The research is concerned with thermochemical characterisation of straws and high yielding perennial grasses. Crops selected for this study include wheat straw (Triticum aestivum), rape straw (Brassica napus), reed canary grass (Phalaris arundinacea) and switch grass (Panicum virgatum). Thermogravimetric analysis (TGA) was used to examine the distribution of char and volatiles during pyrolysis up to 900 °C. Utilising multi-heating rate thermogravimetric data, the Friedman iso-conversional kinetic method was used to determine pyrolysis kinetic parameters. Light and medium volatile decomposition products were investigated using pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) up to 520 °C. The 22 highest yielding identifiable cellulose, hemicellulose and lignin biomass markers were semi-quantified taking into consideration peak areas from GC chromatograms. Notable differences can be seen in butanedioic acid, dimethyl ester (hemicelluloses decomposition products), 2-methoxy-4-vinylphenol (lignin marker) and levoglucosan (intermediate pyrolytic decomposition product of cellulose) content when comparing perennial grasses with straw. From results presented in this study, perennial grasses such as switch grass, have the most attractive properties for fast pyrolysis processing. This is because of the observed high volatile yield content of 82.23%, heating value of 19.64 MJ/kg and the relatively low inorganic content.

A comparison of integrated biomass to electricity systems

This thesis presents a comparison of integrated biomass to electricity systems on the basis of their efficiency, capital cost and electricity production cost. Four systems are evaluated: combustion to raise steam for a steam cycle; atmospheric gasification to produce fuel gas for a dual fuel diesel engine; pressurised gasification to produce fuel gas for a gas turbine combined cycle; and fast pyrolysis to produce pyrolysis liquid for a dual fuel diesel engine. The feedstock in all cases is wood in chipped form. This is the first time that all three thermochemical conversion technologies have been compared in a single, consistent evaluation.The systems have been modelled from the transportation of the wood chips through pretreatment, thermochemical conversion and electricity generation. Equipment requirements during pretreatment are comprehensively modelled and include reception, storage, drying and communication. The de-coupling of the fast pyrolysis system is examined, where the fast pyrolysis and engine stages are carried out at separate locations. Relationships are also included to allow learning effects to be studied. The modelling is achieved through the use of multiple spreadsheets where each spreadsheet models part of the system in isolation and the spreadsheets are combined to give the cost and performance of a whole system.The use of the models has shown that on current costs the combustion system remains the most cost-effective generating route, despite its low efficiency. The novel systems only produce lower cost electricity if learning effects are included, implying that some sort of subsidy will be required during the early development of the gasification and fast pyrolysis systems to make them competitive with the established combustion approach. The use of decoupling in fast pyrolysis systems is a useful way of reducing system costs if electricity is required at several sites because• a single pyrolysis site can be used to supply all the generators, offering economies of scale at the conversion step. Overall, costs are much higher than conventional electricity generating costs for fossil fuels, due mainly to the small scales used. Biomass to electricity opportunities remain restricted to niche markets where electricity prices are high or feed costs are very low. It is highly recommended that further work examines possibilities for combined beat and power which is suitable for small scale systems and could increase revenues that could reduce electricity prices.

Cost and performance analysis of new wood-fuelled power plant concepts

The objective of the thesis was to analyse several process configurations for the production of electricity from biomass. Process simulation models using AspenPlus aimed at calculating the industrial performance of power plant concepts were built, tested, and used for analysis. The criteria used in analysis were performance and cost. All of the advanced systems appear to have higher efficiencies than the commercial reference, the Rankine cycle. However, advanced systems typically have a higher cost of electricity (COE) than the Rankine power plant. High efficiencies do not reduce fuel costs enough to compensate for the high capital costs of advanced concepts. The successful reduction of capital costs would appear to be the key to the introduction of the new systems. Capital costs account for a considerable, often dominant, part of the cost of electricity in these concepts. All of the systems have higher specific investment costs than the conventional industrial alternative, i.e. the Rankine power plant; Combined beat and power production (CUP) is currently the only industrial area of application in which bio-power costs can be considerably reduced to make them competitive. Based on the results of this work, AsperiPlus is an appropriate simulation platform. How-ever, the usefulness of the models could be improved if a number of unit operations were modelled in greater detail. The dryer, gasifier, fast pyrolysis, gas engine and gas turbine models could be improved.

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.

Production of renewable phenolic resins by thermochemical conversion of biomass: a review

This review covers the production and utilisation of liquids from the thermal processing of biomass and related materials to substitute for synthetic phenol and formaldehyde in phenol formaldehyde resins. These resins are primarily employed in the manufacture of wood panels such as plywood, MDF, particle-board and OSB. The most important thermal conversion methods for this purpose are fast pyrolysis and vacuum pyrolysis, pressure liquefaction and phenolysis. Many feedstocks have been tested for their suitability as sources of phenolics including hard and softwoods, bark and residual lignins. Resins have been prepared utilising either the whole liquid product, or a phenolics enriched fraction obtained after fractional condensation or further processing, such as solvent extraction. None of the phenolics production and fractionation techniques covered in this review are believed to allow substitution of 100% of the phenol content of the resin without impacting its effectiveness compared to commercial formulations based on petroleum derived phenol. This survey shows that considerable progress has been made towards reaching the goal of a price competitive renewable resin, but that further research is required to meet the twin challenges of low renewable resin cost and satisfactory quality requirements. Particular areas of concern are wood panel press times, variability of renewable resin properties, odour, lack of reactive sites compared to phenol and potential for increased emissions of volatile organic compounds.

HTHP syngas cleaning concept of two stage biomass gasification for FT synthesis

The EU intends to increase the fraction of fuels from biogenic energy sources from 2% in 2005 to 8% in 2020. This means a minimum of 30 million TOE/a of fuels from biomass. This makes technical-scale generation of syngas from high-grade biomass, e.g. straw, hay, bark, or paper/cardboard waste, and the production of synthetic fuels by Fischer-Tropsch (FT) synthesis highly attractive. The BTL concept (Biomass to Liquids) of the Karlsruhe Research Center, labeled bioliq, focuses on this challenge by locally concentrating the biomass energy content by fast pyrolysis in a coke/oil slurry followed by slurry conversion to syngas in a central entrained flow gasifier at 1200C and pressures above 4MPa. FT synthesis generates intermediate products for synthetic fuels. To prevent the sensitive catalysts from being poisoned the syngas must be free of tar and particulates. Trace concentrations of H2S, COS, CS2, HCl, NH3, and HCN must be on the order of a few ppb. Moreover, maximum conversion efficiency will be achieved by cleaning the gas above the synthesis conditions. (T>350C, P>4MPa). The concept of an innovative dry HTHP syngas cleaning process is presented. Based on HT particle filtration and suitable sorption and catalysis processes for the relevant contaminants, an overall concept will be derived, which leads to a syngas quality required for FT synthesis in only two combined stages. Results of filtration experiments on a pilot scale are presented. The influence of temperature on the separation and conversion, respectively, of particulates and gaseous contaminants is discussed on the basis of experimental results obtained on a laboratory and pilot scale. Extensive studies of this concept are performed in a scientific network comprising the Karlsruhe Research Center and five universities; funding is provided by the Helmholtz Association of National Research Centers in Germany.

Bio-fuel composition and method for manufacture of bio-fuel composition

The invention relates to a liquid bio-fuel mixture, and uses thereof in the generation of electrical power, mechanical power and/or heat. The liquid bio-fuel mixture is macroscopically single phase, and comprises a liquid condensate product of biomass fast pyrolysis, a bio-diesel component and an ethanol component.

Techno-economic assessment and uncertainty analysis of thermochemical processes for second generation biofuels

Biomass-To-Liquid (BTL) is one of the most promising low carbon processes available to support the expanding transportation sector. This multi-step process produces hydrocarbon fuels from biomass, the so-called “second generation biofuels” that, unlike first generation biofuels, have the ability to make use of a wider range of biomass feedstock than just plant oils and sugar/starch components. A BTL process based on gasification has yet to be commercialized. This work focuses on the techno-economic feasibility of nine BTL plants. The scope was limited to hydrocarbon products as these can be readily incorporated and integrated into conventional markets and supply chains. The evaluated BTL systems were based on pressurised oxygen gasification of wood biomass or bio-oil and they were characterised by different fuel synthesis processes including: Fischer-Tropsch synthesis, the Methanol to Gasoline (MTG) process and the Topsoe Integrated Gasoline (TIGAS) synthesis. This was the first time that these three fuel synthesis technologies were compared in a single, consistent evaluation. The selected process concepts were modelled using the process simulation software IPSEpro to determine mass balances, energy balances and product distributions. For each BTL concept, a cost model was developed in MS Excel to estimate capital, operating and production costs. An uncertainty analysis based on the Monte Carlo statistical method, was also carried out to examine how the uncertainty in the input parameters of the cost model could affect the output (i.e. production cost) of the model. This was the first time that an uncertainty analysis was included in a published techno-economic assessment study of BTL systems. It was found that bio-oil gasification cannot currently compete with solid biomass gasification due to the lower efficiencies and higher costs associated with the additional thermal conversion step of fast pyrolysis. Fischer-Tropsch synthesis was the most promising fuel synthesis technology for commercial production of liquid hydrocarbon fuels since it achieved higher efficiencies and lower costs than TIGAS and MTG. None of the BTL systems were competitive with conventional fossil fuel plants. However, if government tax take was reduced by approximately 33% or a subsidy of £55/t dry biomass was available, transport biofuels could be competitive with conventional fuels. Large scale biofuel production may be possible in the long term through subsidies, fuels price rises and legislation.

In situ catalytic upgrading of bio-oil using supported molybdenum carbide

The aim of this work is to improve some of the less desirable properties of bio-oil via the catalytic fast pyrolysis of sugarcane bagasse using a novel supported molybdenum carbide (20 wt.% MoC/AlO ) catalyst. Proximate and elemental analysis of the bagasse were carried out to determine the moisture, ash, carbon, hydrogen, nitrogen and oxygen content. The ground pellets were classified in sieves to a size range of 0.25-1 mm and were pyrolysed in a 300 g h fluidised bed reactor at 500 C. MoC/AlO replaced the sand in the fluidised bed reactor in different proportions (0 wt.%, 12 wt.%, 25 wt.% and 50 wt.%) to investigate the effect of this catalyst on the pyrolysis products. Bio-oil yield results showed that ground sugarcane bagasse pellets gave high organic yields in the bio-oil of 60.5 wt.% on dry feed with a total liquid yield of 73.1 wt.% on dry feed without catalyst. Increasing the catalyst proportions in the fluidised bed reduced bio-oil yields, significantly reduced sugars (as a-levoglucosan) concentration and increased furanics and phenolics concentration in the bio-oil. It was observed that the higher the concentration of the 20 wt.% MoC/AlO catalyst in the fluidised bed the lower the viscosity of the bio-oil. © 2013 Elsevier B.V. All rights reserved.

Engines for combined heat and power

Spark-ignited (SI) gas engines are for the use of fuel gas only and are limited to the flammable range of the gas; this means the range of a concentration of a gas or vapor that will burn after ignition. Fuel gas like syngas from gasification or biogas must meet high quality and chemical purity standards for combustion in SI gas engines. Considerable effort has been devoted to fast pyrolysis over the years and some of the product oils have been tested in diesel or dual-fuel engines since 1993. For biogas conversion, usually dual-fuel engines are used, while for synthesis gas the use of gas engines is more common. The trials using wood derived pyrolysis oil from fast pyrolysis have not yet been a success story and these approaches have usually failed due to the high corrosivity of the pyrolysis oils.

The thermal performance of the polysaccharides extracted from hardwood:cellulose and hemicellulose

The pyrolytic behaviour of individual component in biomass needs to be understood to gain insight into the mechanism of biomass pyrolysis. A comparative study on the pyrolysis of cellulose (hexose-based polysaccharides) and hemicallulose (pentose-based polysaccharides) is performed by two sets of experiments including TG analysis and Py-GC-MS/FTIR. The samples of these two polysaccharide components are thermally decomposed in TGA at the heating rate of 5 and 60 K/min to demonstrate the different characteristics of mass loss stage(s) between them. The yield of pyrolytic products is examined by a fluidized-bed fast pyrolysis unit. The experiment confirms that cellulose mainly contributes to bio-oil production (reaching the maximum of 72% at 580 °C), while hemicellulose works as an important precursor for the char production (∼25%). The compounds in the gaseous mixture (CO and CO2) and bio-oil (levoglucosan, furfural, aldehyde, acetone and acetic acid) are further characterized by GC-MS for cellulose and GC-FTIR for hemicellulose, and their formations are investigated thoroughly. © 2010 Elsevier Ltd. All rights reserved.

Avaliação do desempenho da paligorsquita modificada e do carvão da pirólise do lodo de esgoto no processo de degradação fotocatalítica do fenol

The uncontrolled disposal of wastewaters containing phenolic compounds by the industry has caused irreversible damage to the environment. Because of this, it is now mandatory to develop new methods to treat these effluents before they are disposed of. One of the most promising and low cost approaches is the degradation of phenolic compounds via photocatalysis. This work, in particular, has as the main goal, the customization of a bench scale photoreactor and the preparation of catalysts via utilization of char originated from the fast pyrolysis of sewage sludge. The experiments were carried out at constant temperature (50°C) under oxygen (410, 515, 650 and 750 ml min-1). The reaction took place in the liquid phase (3.4 liters), where the catalyst concentration was 1g L-1 and the initial concentration of phenol was 500 mg L-1 and the reaction time was set to 3 hours. A 400 W lamp was adapted to the reactor. The flow of oxygen was optimized to 650 ml min-1. The pH of the liquid and the nature of the catalyst (acidified and calcined palygorskite, palygorskite impregnated with 3.8% Fe and the pyrolysis char) were investigated. The catalytic materials were characterized by XRD, XRF, and BET. In the process of photocatalytic degradation of phenol, the results showed that the pH has a significant influence on the phenol conversion, with best results for pH equal to 5.5. The phenol conversion ranged from 51.78% for the char sewage sludge to 58.02% (for palygorskite acidified calcined). Liquid samples analyzed by liquid chromatography and the following compounds were identified: hydroquinone, catechol and maleic acid. A mechanism of the reaction was proposed, whereas the phenol is transformed into the homogeneous phase and the others react on the catalyst surface. For the latter, the Langmuir-Hinshelwood model was applied, whose mass balances led to a system of differential equations and these were solved using numerical methods in order to get estimates for the kinetic and adsorption parameters. The model was adjusted satisfactorily to the experimental results. From the proposed mechanism and the operating conditions used in this study, the most favored step, regardless of the catalyst, was the acid group (originated from quinone compounds), being transformed into CO2 and water, whose rate constant k4 presented value of 0.578 mol L-1 min-1 for acidified calcined palygorskite, 0.472 mol L-1 min-1 for Fe2O3/palygorskite and 1.276 mol L-1 min-1 for the sludge to char, the latter being the best catalyst for mineralization of acid to CO2 and water. The quinones were adsorbed to the acidic sites of the calcined palygorskite and Fe2O3/palygorskite whose adsorption constants were similar (~ 4.45 L mol-1) and higher than that of the sewage sludge char (3.77 L mol-1).

Avaliação do desempenho da paligorsquita modificada e do carvão da pirólise do lodo de esgoto no processo de degradação fotocatalítica do fenol

The uncontrolled disposal of wastewaters containing phenolic compounds by the industry has caused irreversible damage to the environment. Because of this, it is now mandatory to develop new methods to treat these effluents before they are disposed of. One of the most promising and low cost approaches is the degradation of phenolic compounds via photocatalysis. This work, in particular, has as the main goal, the customization of a bench scale photoreactor and the preparation of catalysts via utilization of char originated from the fast pyrolysis of sewage sludge. The experiments were carried out at constant temperature (50°C) under oxygen (410, 515, 650 and 750 ml min-1). The reaction took place in the liquid phase (3.4 liters), where the catalyst concentration was 1g L-1 and the initial concentration of phenol was 500 mg L-1 and the reaction time was set to 3 hours. A 400 W lamp was adapted to the reactor. The flow of oxygen was optimized to 650 ml min-1. The pH of the liquid and the nature of the catalyst (acidified and calcined palygorskite, palygorskite impregnated with 3.8% Fe and the pyrolysis char) were investigated. The catalytic materials were characterized by XRD, XRF, and BET. In the process of photocatalytic degradation of phenol, the results showed that the pH has a significant influence on the phenol conversion, with best results for pH equal to 5.5. The phenol conversion ranged from 51.78% for the char sewage sludge to 58.02% (for palygorskite acidified calcined). Liquid samples analyzed by liquid chromatography and the following compounds were identified: hydroquinone, catechol and maleic acid. A mechanism of the reaction was proposed, whereas the phenol is transformed into the homogeneous phase and the others react on the catalyst surface. For the latter, the Langmuir-Hinshelwood model was applied, whose mass balances led to a system of differential equations and these were solved using numerical methods in order to get estimates for the kinetic and adsorption parameters. The model was adjusted satisfactorily to the experimental results. From the proposed mechanism and the operating conditions used in this study, the most favored step, regardless of the catalyst, was the acid group (originated from quinone compounds), being transformed into CO2 and water, whose rate constant k4 presented value of 0.578 mol L-1 min-1 for acidified calcined palygorskite, 0.472 mol L-1 min-1 for Fe2O3/palygorskite and 1.276 mol L-1 min-1 for the sludge to char, the latter being the best catalyst for mineralization of acid to CO2 and water. The quinones were adsorbed to the acidic sites of the calcined palygorskite and Fe2O3/palygorskite whose adsorption constants were similar (~ 4.45 L mol-1) and higher than that of the sewage sludge char (3.77 L mol-1).

Characterization of wood biochar and evaluation of its adsorption potential for removal of sulphate from produced water in offshore oil and gas industry

This thesis analyses the potential of wood biochar as an adsorbent in removal of sulphate from produced water. In worldwide offshore oil and gas industry, a large volume of waste water is generated as produced water. Sulphur compounds present in these produced water streams can cause environmental problems, regulatory problems and operational issues. Among the various sulphur removal technologies, the adsorption technique is considered as a suitable method since the design is simple, compact, economical and robust. Biochar has been studied as an adsorbent for removal of contaminants from water in a number of studies due to its low cost, potential availability, and adsorptive characteristics. In this study, biochar produced through fast pyrolysis of bark, hardwood sawdust, and softwood sawdust were characterized through a series of tests and were analysed for adsorbent properties. Treating produced water using biochar sourced from wood waste is a two-fold solution to environmental problems as it reduces the volume of these wastes. Batch adsorption tests were carried out to obtain adsorption capacities of each biochar sample using sodium sulphate solutions. The highest sulphur adsorption capacities obtained for hardwood char, softwood char and bark char were 11.81 mg/g, 9.44 mg/g, and 7.94 mg/g respectively at 10 °C and pH=4. The adsorption process followed the second order kinetic model and the Freundlich isotherm model. Adsorption reaction was thermodynamically favourable and exothermic. The overall analysis concludes that the wood biochar is a feasible, economical, and environmental adsorbent for removal of sulphate from produced water.