Gasification in a bubbling fluidized bed reactor was introduced as sustainable technology to treat waste such as tires. However, uncertainty arises when defining the most sustainable gasification process conditions. In this paper, eight experimental conditions were analyzed. The experiments were carried out at 700 and 850 & DEG;C with different equivalence ratios (ER) while using air as a gasifying agent. At 850 & DEG;C the effect of steam addition was also studied. A Life Cycle Assessment (LCA) was assessed to the product gas and its energy content by the following environmental impacts: Climate Change (CC), Ozone Depletion (OD), and Particulate Matter (PM). LCA methodology revealed that optimal gasification conditions provide 74, 69 and 66% environmental impact reductions in CC, PM, and OD, respectively by comparing the best and the worst-case scenarios. The combination of high temperature, low ER, and steam addition offered the most environmentally sustainable process, achieving 8.3.10-2 kg CO2 eq/MJ in CC, 1.3.10-8 kg CFC-11eq/MJ in OD and 4.9.10-5 kg PM2.5eq/MJ in PM. Despite the great savings in environmental impacts, additional efforts are still needed to reduce the energy consumption of the preheating system to ensure the product gas is levelled to conventional natural gas.

Waste tyres gasification in a bubbling fluidised bed reactor is evaluated by means of a complete characterisation of the product gas. The experiments are carried out at two temperatures, 700 and 850 degrees C, and various equiva-lence ratios (ER) while using air as a gasifying. Additionally, the effect of steam is also studied at 850 degrees C. High temperature and low ER increase the production of H2, CH4, and C2H4. Steam addition mainly affects H2 and CO production. Low carbon conversion (CC) into gas and cold gas efficiency (CGE) are obtained, increasing with temperature and ER. The lower heating value (LHV) of the gas decreases with the ER because of the higher partial combustion rates. LHV values range between 12 MJ/Nm3 with steam addition at ER = 0.13 and 850 degrees C to 5.3 MJ/Nm3 at ER = 0.33 and 700 degrees C using air only. Along with a major permanent gas (CO2, CO, H2, CH4, and C2Hn), up to 25 short-chain hydrocarbons (non-aromatic hydrocarbons ranging from C3 to C6+) and two light aromatics are present in the product gas. Among short-chain hydrocarbons, C3 and C4 compounds are present in the highest yields. All these minor hydrocarbon species (i.e., C3 to C6+), not usually reported in biomass or waste gasification studies, yield up to 13 %vol. on a N2-free basis. Their contribution to the gasification performance is important because they account for half of the energy content in the product gas. Therefore, it is important to consider them in the gasification process, not only for energy purposes but also for the chemical industry.

To demonstrate the benefits of upgrading biomass, six samples of unique materials were combusted under pulverized fuel conditions aiming at the demonstration of complete coal replacement. These fuels were: sugarcane bagasse (SCB) (raw and steam exploded); sugarcane trash (SCT) (steam exploded and washed + steam exploded); empty fruit bunch (steam exploded and washed + steam exploded). The study shows that volatiles dominate the NOX formation, thus with a proper air staging all upgraded biofuels can be used to reduce directly NOX formation, when replacing coal. Washing reduces slagging issues by removing most of K, however, in the case of the sugarcane based biofuels, Fe still plays a crucial role in the melting/slag behavior. The combustion of raw bagasse and steam exploded bagasse formed relatively low amounts of aerosols, nevertheless enriched in NaCl and KCl, which poses a potential operational/corrosion risk when deposited on heat-exchanger surfaces. For SCT and EFB, washing is essential to reduce the aerosol formation, e.g. for EFB the submicron-particle mass was reduced by more than 90% and the fouling decreased proportionally by a factor of 10. Without washing unacceptably high slagging, fouling and corrosion potentials were observed with the steam exploded EFB. (c) 2022 Published by Elsevier Ltd.

Solid biofuels are currently used in increasing volumes to replace fossil equivalents. Next to the traditional wood-derived fuels, the advancement of biomass upgrading technologies like steam explosion (SE), followed by pelleting, further broadens the variety of materials on the market. This thermochemical and mechanical upgrading improves greatly the general properties of such fuels (homogeneity, energy density, water resistance, biological decomposition, grindability, pneumatic transport, etc.) and at the same time offers the possibility for co-production of green chemicals/biorefinery processing. However, these alternative SE-material pellets have different properties from the fossil counterparts with regard to dust formation, dielectric, ignitability, and explosive characteristics, hence posing an increased risk of fire and explosion in handling, transport, and storage of the biosolid fuels. These divergent properties need to be properly addressed before their large implementation in the industry. To shed more light on the variability of such material properties, several batches of SE pellets varying in bulk density and subjected to different handling and storage conditions were evaluated. This was done using a number of standardized equipment and following industrial standard measurement methodologies to compare steam-exploded material with standard white wood pellets and reference coals. The main body of the work focused on the explosivity of dust generated in the handling of the pellets, studied using a Hartmann tube, coupled with a high-speed camera to evaluate the sensitivity [minimum ignition energy (MIE) and minimum explosive concentration (MEC)] and the severity maximum flame front velocity (FFVmax) of explosions of the generated SE-pellet dust. Thermogravimetric analyses (TGA) was used to measure and compare the ignitability of dust layers of SE-pellet dust vs coal and as a function of co-mixture. Finally, the SE-pellet self-heating behavior was addressed using the standard "basket method" and compared with that of a commercial coal sample. The results show that the SE pellets produce very low levels of dust even after extensive weathering, hence limiting the explosion potential. The MIE and MEC of SE-pellet dusts exhibited similar values compared to those of the parent raw biomass material; however, the FFVmax revealed lower values when compared to that of the parent raw biomass. Also, the self-heating propensity is very low as the pellets are basically immune to biological degradation, while the spontaneous ignition temperature is high and in the range of nonhazardous bulk materials.

In this document, the process design for production of CAPCOM pellets is described. First, the operation units required to the process are identified and disposed in a logical order (Chapter 2). Second, the mass and energy balances are prepared (Chapter 3). Then the equipment is sized (Chapter 4).

A techno-economic assessment on upgrading routes involving washing and torrefaction is presented for roadside grass, straw and miscanthus. Washing followed by torrefaction (prewash) and torrefaction followed by washing (postwash) is compared for straw. Mass and energy balances were calculated, based on previous experimental test results. Calculated internal rates of return, total annuities and payback times and a sensitivity analysis identified the most critical input parameters for profitability as being the cost of biomass, CAPEX, consumables and sludge disposal. Application of upgraded roadside grass in small-scale installations has technical limitations, but large-scale industrial applications seem feasible in the Netherlands. For the roadside grass, a negative gate fee of 25 €/t and a biocoal market price of 4.8 €/GJ lead to an IRR of 15.6% at an optimum plant size of 100–150 kt/a dry input. Postwash appears the most profitable option in the case of predried biomass (straw and miscanthus). However, straw upgrading is not profitable unless a gate fee can be charged as well. This could be the case for residual straws from rice and sugar cane crops in countries like Brazil, Thailand and Indonesia, upgrading the material locally and exporting it. For rice straw, a gate fee of 15 €/t and a price of 6.2 €/GJ for the produced biocoal lead to an IRR of 11.6% for large-scale industrial applications. The upgraded miscanthus with production costs of 7.7 €/GJ, can compete with wood pellets in terms of fuel properties and prices only for smaller-scale installations.

Different streams of low-grade biomass of different origins (road side grass, miscanthus, wheat straw and spruce bark) were upgraded to reasonable quality commodity fuels by significantly reducing the alkali and chlorine content, through washing with water in a first step and torrefaction in a second. The aim was to produce a cleaner fuel with a higher energy content for further densification. The final goal was to demonstrate the improvements attained by the upgrading process during combustion using the lab-scale combustion simulator facility of ECN part of TNO. Analyses of the original, washed and washed/torrefied samples showed that approximately 90% of Cl and up to 60-80% of K can be removed by this upgrading route; during the torrefaction step Cl and S are removed from the solids; during torrefaction K and Na are not significantly altered; the pre-wash step is crucial for the removal of K. Si and Ca remain largely in the solid fraction; post-wash seems to be a viable route to upgrade dry-type of biomasses; "straw" like material requires more time for washing than "grass" type. The combustion results showed that: NOx emissions are generally decreased after upgrading; High temperature chlorine corrosion can be effectively mitigated; Fine particulate matter (submicron/aerosols) formation is strongly reduced, effectively reducing the risk of alkali induced fouling. However, slagging tests revealed that pre-washing and torrefaction has minor impact on the slagging propensity of the fuel. Only, slightly reduced slagging is observable and therefore the use of mineral combustion additives, or smart blending with other fuels in order to further mitigate the slagging risks is strongly recommended.

Pulverized coal combustion and entrained flow gasification are two of the main technologies worldwide that use coal as feedstock. In a coal-fired power plant the pulverized fuel is transported pneumatically with air in dilute phase to the boiler whereas in the second case the coal is ientrained into the gasifier in dense phase. Biomass could be an option for the direct replacement of coal, however several past experiences with co-firing have shown several limitations using this feedstock, among which the pneumatic conveying. Torrefaction, followed by densification, is a process that can improve the characteristics of the biomass. However, the behavior of torrefied biomass during pneumatic transport has not been investigated in much detail. The present work will show the pneumatic conveying behavior of coal, raw and torrefied biomass at dilute phase and dense phase. Complementary work on grindability and fluidization will be provided for a better insight. About 25% less gas is necessary to transport torrefied biomass in dilute phase and about 2-3 times more is transported in dense phase when compared with raw biomass. The present work pinpoints the role of particle morphology in the pneumatic transport and how milled torrefied biomass pellets resemble coal particles. There is an attempt to correlate all the results (grindability, fluidization and pneumatic transport) with the defined variable cp (flowability), a simple ratio that has the potential to give a preliminary and easy assessment of the morphological properties of a given material and its expected pneumatic behavior.

Four low-grade biomasses (road side grass, miscanthus, wheat straw and spruce bark) were subjected to washing tests with water at lab scale, with the aim to optimize the combination of washing temperature, time and liquid over solids (L/S) ratio and evaluate the efficiency of salts removal (mainly K and Cl). A quick and cheap analysis method, based on conductivity measurements of the eluates, compared with chemical analysis done both on liquids and solids, was developed to assess the removal efficiency immediately after the washing process. Lab scale torrefaction tests were performed on the washed biomasses and the option of washing afterwards (post-washing) was also investigated. Based on the lab results larger quantities of the four biomass materials were washed and torrefied at pilot scale to provide reliable data to support the upscaling of possible upgrading routes. Analyses of the original samples, washed samples and washed/torrefied samples confirmed the achieved decrease in salts content. Fuel characterization and calculated fuel indexes usually used for evaluating emissions, high temperature corrosion and ash melting tendency were used as a first indication on the achievement of enhanced performance.

A modified Hartmann tube apparatus was used to study the explosivity properties of dusts from torrefied biomass pellets. The sensitivity of the dusts to explode was assessed by determining the minimum ignition energies (MIE) and the minimum explosible concentrations (MEC). The severity of the explosion was evaluated by flame front velocity (FFV) measurements via a method developed by ECN. A comparison was made with reference materials like white wood and coal dusts.Dust from torrefied biomass pellets presented MIE and MEC values in the same range as the white wood pellets dust, but depending on the material sometimes even higher values were obtained. The severity of an explosion of torrefied biomass dust tends to be lower when compared with white wood dust explosions, especially when comparing the impact effects of moisture, particle size and temperature, as in a real case scenario. However, torrefied biomass materials still present higher explosion reactivity than coals.

This chapter describes the current practice with respect to transport, on-site handling, storage, milling and pneumatic conveying of biomass during co-firing in coal-fired power stations, and the associated design of handling and storage equipment, as well as the required hardware modifications to convert existing dedicated coal-fired power plants. Thermal biomass pre-treatment technologies, such as torrefaction and steam explosion, result in the production of high-quality solid bioenergy carriers that offer distinct advantages in comparison with conventional white wood pellets. The use of torrefied or steam-exploded biomass pellets mitigates extensive hardware modifications, and facilitates on-site fuel handling and storage in a manner that is more comparable with coal. The potential benefits will be described based on proprietary results with torrefied biomass pellets produced in the ECN pilot torrefaction plant. In conclusion, an overview of foreseen trends and directions for biomass processing and thermal pre-treatment for co-firing will be provided.

Gasification of spent lignin pellets was used to obtain a gas suitable for energy production. Spent lignin was obtained from second-generation cellulosic ethanol demo plant using wheat straw as feedstock. Gasification of lignin did not give rise to any feeding problems, thus no significant changes were needed in the existing gasification installation. The rise of temperature and steam flow rate favoured the formation of H-2, while hydrocarbons (CnHm) and tar contents decreased. The increase of equivalent ratio (ER) also decreased hydrocarbons and tar contents, but syngas higher heating value (HHV) was reduced. The use of natural minerals improved lignin gasification. The presence of dolomite led to the highest H-2 and to the lowest CnHm and tar contents. Results obtained at bench-scale were confirmed at pilot-scale, as similar trends were obtained. However, as the residence time in pilot gasifier was higher, greater gas yields with higher H-2 and CH4 concentrations were obtained, while tar contents decreased. After syngas hot cleaning and upgrading, the final syngas composition showed to be suitable for a wide range of applications (e. g. energy production and synthesis of chemicals), since it was substantially enriched in hydrogen, whereas tar and heavier gaseous hydrocarbons were completely destroyed. (C) 2014 Elsevier Ltd. All rights reserved.

The need to produce energy from poor quality carbonaceous materials has increased, in order to reduce European dependency on imported fuels, diversify the use of new and alternative fuels and to guarantee secure energy production routes. The valorisation of a poor quality solid residual fuel (SRF), with high content of ash and volatile matter, through its conversion into fuel gas was studied. The rise of gasification temperature and equivalent ratio (ER) led to higher gas yields and to lower undesirable gaseous components, though higher ER values led to a gas with lower energetic content. To reduce the negative effect of SRF unfavourable characteristics and to diversify the feedstocks used, SRF blended with three different types of biomass wastes: forestry pine, almond shells and olive bagasse was co-gasified. The use of biomass wastes tested was valuable for SRF gasification, as there was an increase in the overall reactivity and in H-2 production and a reduction of about 55% in tar released, without great changes in gas yield and in its HHV. The use of natural minerals mixed with silica sand was also studied with the aim of improving SRF gasification performance and fuel gas quality. The best results were obtained in presence of dolomite, as the lowest tar and H2S contents were obtained, while an increase in gas yield was observed. Co-gasification of this poor quality SRF blended with biomass wastes in presence of dolomite increased gas yield by 25% while tar contents decreased by 55%. (C) 2013 Elsevier Ltd. All rights reserved.

Fluidised bed technology is applied to both combustion and gasification processes because of its versatility. Solid particles are released in both processes but their composition may differ because of the behaviour of inorganic mineral matter under oxidizing or reducing conditions. They are controlled by using cyclones, bag filters and electrostatic precipitators. Gaseous pollutants vary with the exception of HCL which is formed in both cases. Sulphur based pollutants are easier to deal with by using sorbens during both combustion and gasification. With other gaseous pollutants, other controlling measures are required. In gasification, the presence of tars could interfere with the emission of pollutants. This chapter summarises the principal pollutants of concern and measures for control. Emission levels from both combustion and gasification processes are constantly being reviewed and made more stringent. Control techniques have to accompany these changes in the emissions permitted by legislation.

A thermodynamic model was applied to foresee the occurrence of fouling, slagging, and bed agglomeration phenomena during fluidized bed monocombustion of three different types of biomass, namely straw pellets, olive cake, and wood pellets. The cocombustion effect in reducing the occurrence of deposits and agglomerates of blends of 5, 15, and 25% (wt.) biomass with coal was also assessed. Chemical fractionation was applied to evaluate the reactive and nonreactive fraction of elements in the fuels, which was used to estimate their partition between the freeboard and bottom zone of the boiler. Qualitative and semiquantitative analytical techniques, namely, X-ray diffraction and scanning electronic microscopy energy dispersive spectroscopy were used to compare the results from the simulation with the mineralogical and morphological composition of ash and deposits formed during combustion. The thermodynamic modeling revealed to be a powerful tool in foreseeing the formation of melt and liquids salts, depending on the temperature and chemical composition of fuels. The main discrepancies observed. between the experimental and simulated data were due to particularities of the combustion process, which are not incorporated in the software, namely, kinetic limitations of the reactions, possible occurrence of secondary reactions in the ashes, and elutriation effects of ash and silica sand particles.

The behavior of Cynara cardunculus L. was studied during fluidized-bed (FB) combustion and gasification. The Cynara had a low moisture content and considerable lower heating value (LHV). Cynara presented significant quantities of S, Cl, and ash, which contained high levels of Na, K, P, Ca, and Si. The fuel N conversion to NOx was high because of the large release of NH3 and HCN during pyrolysis. The conversion of the fuel S to SO2 was low because of S retention mainly as alkali sulfates. HCl emissions were higher than the usual legal limits imposed in European Union (EU) countries, although retentions of 40-55% fuel Cl could be estimated. The co-combustion of Cynara with eucalyptus was tested with benefits regarding process conditions, pollutant emissions, and ash behavior, but still, the HCl concentration surpassed the legal limit. The tendency for bed agglomeration was also observed during the gasification of cardoon. Two strategies were carried out to minimize this adverse effect: (1) co-gasification of cardoon with eucalyptus and (2) addition of natural minerals to the gasification bed. The results of the first strategy caused a decrease in H-2 levels, while tar, hydrocarbon, and CO amounts were found to increase. On the other hand, the addition of natural minerals did not lead to any significant change in the major gas components, although some tar and hydrocarbon abatements were observed, with olivine being the most effective. Dolomite and ZnO gave rise to a greater reduction in HCl and sulfur compounds in the gas phase, respectively.

Over the last decades, several indices based on ash chemistry and ash fusibility have been used to predict the ash behaviour during coal combustion, namely, its tendency for slagging and fouling. However, due to the physical–chemical differences between coals and biomass, in this work only the applicability of an ash fusibility index (AFI) to the combustion and co-combustion of three types of biomass (straw pellets, olive cake and wood pellets) with coals was evaluated. The AFI values were compared with the behaviour of ash during combustion in a pilot fluidized bed and a close agreement was observed between them. For a better understanding of the mechanisms associated with bed ash sintering, they were evaluated by SEM/EDS and the elements present on the melted ash were identified. Evidences of different sintering mechanisms were found out for the fruit biomass and herbaceous biomass tested, depending on the relative proportions of problematic elements. The particles deposited on a fouling probe inserted in the FBC were analyzed by XRD and the differences between the compounds identified allowed concluding that the studied biomasses present different tendencies for fouling. Identification of KCl and K2SO4 in the deposits confirmed the higher tendency for fouling of fruit biomass tested rather than wood pellets.

This paper presents the study of the combustion of char residues produced during co-gasification of coal with pine with the aim of characterizing them for their potential use for energy. These residues are generally rich in carbon with the presence of other elements, with particular concern for heavy metals and pollutant precursors, depending on the original fuel used. The evaluation of environmental toxicity of the char residues was performed through application of different leaching tests (EN12457-2, US EPA-1311 TCLP and EA NEN 7371:2004). The results showed that the residues present quite low toxicity for some of pollutants. However, depending on the fuel used, possible presence of other pollutants may bring environmental risks. The utilization of these char residues for energy was in this study evaluated, by burning them as a first step pre-treatment prior to landfilling. The thermo-gravimetric analysis and ash fusibility studies revealed an adequate thermochemical behavior, without presenting any major operational risks. Fluidized bed combustion was applied to char residues. Above 700°C, very high carbon conversion ratios were obtained and it seemed that the thermal oxidation of char residues was easier than that of the coals. It was found that the char tendency for releasing SO(2) during its oxidation was lower than for the parent coal, while for NO(X) emissions, the trend was observed to increase NO(X) formation. However, for both pollutants the same control techniques might be applied during char combustion, as for coal. Furthermore, the leachability of ashes resulting from the combustion of char residues appeared to be lower than those produced from direct coal combustion.

In the scope of the COPOWER project (SES6-CT-2004) that aimed at investigating potential synergies of co-combustion of different biofuels with coal, the study of emissions of particulate matter and PCDD/F was carried out. The biofuels tested were meat and bone meal (MBM), sewage sludge biopellets (BP), straw pellets (SP), olive bagasse (OB) and wood pellets (WP). The tests performed include co-firing of 5%, 15% and 25% by weight of biofuels with coals of different origin. Both monocombustion and co-firing were carried out to compare the results. Combustion tests were performed on a pilot fluidised bed, equipped with cyclones and air staging was used in order to achieve almost complete combustion of fuels with high volatile contents and to control gaseous emissions. Particulate matter emissions were isokinetically sampled in the stack and their particle size analysis was performed with a cascade impactor (Mark III). The results showed that most particles emitted were below 10 mu m (PM10) for all the tests, however, with the increasing share of biofuels and also during combustion of pure biofuels, especially for olive bagasse, straw and MBM, it was observed the presence of very fine particles, below about I gm. With the exception of sewage sludge, greater amounts of biofuels appeared to give rise to the decrease in particulate mean diameters and increase in PM percentages below 1 mu m. One factor that influenced the total amount of PM emitted, as well as the amount of coarser PM, was the formation of less unburned matter with the increased share of biofuels. However, the most important factor that could lead to the formation of very fine particles could be related with the presence of aerosol forming elements such as K, Na (in the case of MBM) and Cl in biofuels, which even resulted in higher PM emissions when the ash content of fuels decreased, as was the case of straw and olive bagasse.For some fuel mixtures with selected sulphur and chlorine contents, dioxin and furan emissions were also determined. It was verified a correlation between the increase of PCDD/F with the decrease of PM mean diameter. Among other factors, this correlation may be due to higher specific surface area and greater Cu concentration in the fly ashes. (C) 2009 Elsevier Ltd. All rights reserved.