| 1. |
- Abdelaziz, Omar, et al.
(författare)
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A conceptual framework for an integrated lignin biorefinery-petroleum refinery
- 2019
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Ingår i: ECOS 2019 - Proceedings of the 32nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9788361506515 ; , s. 4027-4037
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Konferensbidrag (refereegranskat)abstract
- Co-feeding of renewable feedstocks in general, and lignin streams in particular, in petroleum refineries is an attractive means of increasing the proportion of renewable fuel. Four separate units in an integrated refinery can be envisioned using lignin as a feedstock: the hydrotreater, the fluidised catalytic cracker, the hydrocracker and the slurry hydrotreater. A conceptual process design study, including cost assessments, is presented on the possibility of co-feeding lignin in one of these stages in a conventional crude oil refinery. The addition of lignin to an existing diesel hydrotreating unit is investigated in a refinery environment. Rigorous process simulation models were developed for such an integrated lignin-petroleum refinery based on real data. The lignin product shows good potential of ending up in the gasoline pool with about one third having a boiling point within the gasoline range, one third in the diesel range and the final third ending up in the LPG and kerosene pools. The total production cost of gasoline from lignin is estimated to be 0.82 €/L. If all or most tax reductions on fuels from sustainable sources could be utilised, lignin would be a viable resource for the production of biomass-based gasoline.
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| 2. |
- Abdelaziz, Omar, et al.
(författare)
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Continuous catalytic depolymerisation and conversion of industrial kraft lignin into low-molecular-weight aromatics
- 2018
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6823 .- 2190-6815. ; 8:2, s. 455-470
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Tidskriftsartikel (refereegranskat)abstract
- Base-catalysed depolymerisation of lignin using sodium hydroxide has been shown to be an effective approach towards exploiting industrial (technical) lignins within the pulp and paper industry. In the present work, a pine kraft lignin (Indulin AT) which is precipitated from black liquor of linerboard-grade pulp was depolymerised via base catalysis to produce low-molecular-mass aromatics without any organic solvent/capping agent in a continuous-flow reactor setup for the first time. The catalytic conversion of lignin was performed/screened at temperatures varying from 170 to 250 °C, using NaOH/lignin weight ratio ≈ 1 with 5 wt% lignin solids loadings for residence times of 1, 2 and 4 min, respectively, with comprehensive characterisation of substrate and produced reaction mixtures. The products were characterised using size exclusion chromatography (SEC), nuclear magnetic resonance spectroscopy (NMR) and supercritical fluid chromatography-diode array detector-tandem mass spectrometry (SFC-MS). The optimum operating conditions for such depolymerisation appeared to be at 240 °C and 30 h−1, yielding the highest concentration of low-molecular-weight phenolics below the coking point. It was also found that the depolymerised lignin products exhibited better chemical stability during long-term storage at lower temperatures (~ 4 °C).
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| 3. |
- Abdelaziz, Omar Y., et al.
(författare)
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Membrane filtration of alkali-depolymerised kraft lignin for biological conversion
- 2019
-
Ingår i: Bioresource Technology Reports. - : Elsevier BV. - 2589-014X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have investigated the possibility of membrane filtration as a means for obtaining a fraction containing mainly low-molecular-weight (LMW) compounds from depolymerised lignin (DL) for subsequent microbial conversion. A DL stream from continuous-mode alkali depolymerisation of a softwood kraft lignin produced at a temperature of 220 °C and a residence time of 2 min, using a NaOH/lignin weight ratio of 1 with 5 wt% lignin loading was fractionated using a polymeric membrane with a molecular weight cut-off of 500–700 Da. The permeate (DLP) volume recovery of LMW phenolics (250–450 Da) was 70% after filtration for 3.7 h. The DLP was used as a carbon source for growth of three bacterial strains; Pseudomonas fluorescens, P. putida EM42 and Rhodococcus opacus, and good growth was obtained by the first two microorganisms. This proof-of-concept study demonstrates a novel strategy for technical lignin valorisation by combining depolymerisation, nanofiltration and bioconversion.
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| 4. |
- Ekbom, Tomas, et al.
(författare)
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Methanol production from steel-work off-gases and biomass based synthesis gas
- 2012
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Ingår i: International Conference on Applied Energy, ICAE 2012.
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Konferensbidrag (refereegranskat)abstract
- The main objective has been to describe different cases of the methanol production from steel-work off gases (Coke oven gas and Basic oxygen furnace gas) and biomass based synthesis gas. The SSAB steel mill in the town of Luleå, Sweden has been used as a basis to analyze four different methanol production cases.The studied biomass gasification technology is based on a fluidized bed gasifier unit, where the production capacity is determined from case to case coupled to the heat production required to satisfy the local district heating demand. Critical factors are the integration of the gases with availability to the synthesis unit, to balance the steam system of the biorefinery and to meet the district heat demand of Luleå.For each case, the annual production potential of methanol, the overall production efficiencies and the effects on the total steel plant have been estimated.
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| 5. |
- Kristensen, Tove, et al.
(författare)
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Parametric Analysis and Optimization of Vanillin Hydrodeoxygenation Over a Sulfided Ni-Mo/δ-Al2O3 Catalyst Under Continuous-Flow Conditions
- 2023
-
Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 66:17-18, s. 1341-1352
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental understanding of the process parameters affecting the catalytic hydrodeoxygenation (HDO) of bio-oils is of significance for enabling further progression and improvement of industrial biofuel upgrading methods. Herein, a novel demonstration and evaluation of the effect of temperature, pressure, and weight hourly space velocity in the continuous HDO of vanillin to cresol over a Ni-Mo/δ-Al2O3 catalyst are presented. Response surface methodology was used as a statistical experimental design method, and the application of central composite design enabled the generation of a statistically significant simulation model and a true optimization parametric study. The distribution of Ni and Mo on δ-Al2O3 was confirmed using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). No gradients with EDX mapping could be identified, and the elemental analysis showed well-dispersion of the metals. The mesoporous character of the catalyst-support system was unraveled using N2 physisorption. Experiments were conducted within the parametric range of 250–350 °C, 3–9 bar, and 15–35 h−1. Both temperature and pressure were found to have statistically significant linear and quadratic effects on the selectivity for cresol. The parametric interaction of temperature with pressure and space velocity also had a significant effect on the resulting response. The optimal temperature range becomes more critical at lower space velocities. Optimal selectivity for cresol was established at 314 °C, 5 bar, and 35 h−1. The fitting quality of the generated regression model was statistically confirmed and experimentally validated to describe the specified HDO process within the 95% two-sided confidence interval.
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| 6. |
- Li, Kena, et al.
(författare)
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Membrane separation of the base-catalyzed depolymerization of black liquor retentate for low-molecular-mass compound production
- 2019
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Ingår i: Membranes. - : MDPI AG. - 2077-0375. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- One way of valorizing the lignin waste stream from the pulp and paper industries is depolymerizing it into low-molecular-mass compounds (LMMC). However, a common problem in the depolymerization of Kraft lignin is the low yields of small aromatic molecules obtained. In the present work, the combination of the repeated depolymerization of lignin and the separation of LMMC from depolymerized lignin to upgrade them into value-added chemicals was studied. In so doing, we investigated the possibility of depolymerizing black liquor retentate (BLR). The base-catalyzed depolymerization of BLR was performed using a continuous flow reactor at 170–210 °C, with a 2 min residence time. The results obtained indicate that BLR can be depolymerized effectively under the experimental conditions. Depolymerized lignin LMMC can be successfully separated by a GR95PP membrane, and thus be protected from repolymerization. Through combining membrane filtration with base-catalyzed depolymerization, more than half of the lignin could be depolymerized into LMMC. Around 46 mg/g of lignin monomers (guaiacol, vanillin, acetovanillone, and acetosyringone), which can potentially be upgraded to high-valued chemicals, were produced. On the basis of our results, we suggest use of a recycling Kraft lignin depolymerization and filtration process for maximizing the production of LMMC under mild alkaline conditions.
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| 7. |
- Lundgren, Joakim, et al.
(författare)
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Methanol production from steel-work off-gases and biomass based synthesis gas
- 2013
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 112, s. 431-439
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Tidskriftsartikel (refereegranskat)abstract
- Off-gases generated during steelmaking are to a large extent used as fuels in process units within the plant. The surplus gases are commonly supplied to a plant for combined heat and power production. The main objective of this study has been to techno-economically investigate the feasibility of an innovative way of producing methanol from these off-gases, thereby upgrading the economic value of the gases. Cases analyzed have included both off-gases only and mixes with synthesis gas, based on 300MWth of biomass. The SSAB steel plant in the town of Luleå, Sweden has been used as a basis. The studied biomass gasification technology is based on a fluidized-bed gasification technology, where the production capacity is determined from case to case coupled to the heat production required to satisfy the local district heating demand. Critical factors are the integration of the gases with availability to the synthesis unit, to balance the steam system of the biorefinery and to meet the district heat demand of Luleå. The annual production potential of methanol, the overall energy efficiency, the methanol production cost and the environmental effect have been assessed for each case. Depending on case, in the range of 102,000-287,000ton of methanol can be produced per year at production costs in the range of 0.80-1.1EUR per liter petrol equivalent at assumed conditions. The overall energy efficiency of the plant increases in all the cases, up to nearly 14%-units on an annual average, due to a more effective utilization of the off-gases. The main conclusion is that integrating methanol production in a steel plant can be made economically feasible and may result in environmental benefits as well as energy efficiency improvements. © 2013 Elsevier Ltd.
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| 8. |
- Majeed, Maitham H, et al.
(författare)
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Directed C-H Halogenation Reactions Catalysed by PdII Supported on Polymers under Batch and Continuous Flow Conditions
- 2019
-
Ingår i: Chemistry: A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 25:59, s. 13591-13597
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Tidskriftsartikel (refereegranskat)abstract
- A new generation of N-heterocyclic carbene palladium(II) complexes containing vinyl groups in different positions in the backbone of the N-heterocycle have been developed. The fully characterised monomers were copolymerised with divinylbenzene to fabricate robust polymer supported NHC-PdII complexes and these polymers were applied as heterogeneous catalysts in directed C-H halogenation of arenes with a pyridine-type directing group. The catalysts demonstrated medium-high catalytic activity with up to 90 % conversion and 100 % selectivity in chlorination. They are heterogeneous and recyclable (at least six times) with no significant leaching of palladium in batch mode catalysis. The best catalyst was also applied under continuous flow conditions where it disclosed an exceptional activity (90 % conversion) and 100 % selectivity for the mono-halogenated product for at least six days, with no leaching of palladium, no loss of activity and an ability to maintain the original oxidation state of PdII .
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| 9. |
- Malek, Laura, et al.
(författare)
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Catalytic Abatement of NH3 Using NOx in Reducing Environment
- 2015
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 58:14-17, s. 993-1001
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Tidskriftsartikel (refereegranskat)abstract
- Removal of ammonia from synthesis gas is an important step in gas purification to prevent poisoning of downstream catalyst or formation of nitrogen oxides on combustion. This publication proposes that ammonia can be removed by using selective catalytic abatement with NOx, not unlike the selective catalytic reduction of NOx but under reducing environment. Two different catalysts have been used for the experiments; V2O5/WO3/TiO2 and H-mordenite. The conducted experiments were performed on a model synthesis gas and served to investigate the selectivity and to some extent the longevity of these catalysts under reducing atmosphere, and also the effect of water on the catalyst performance. A number of catalyst characterisation methods have been used to obtain a better understanding of the catalyst morphology and surface. The methods that have been used are Raman spectroscopy, Brunauer–Emmett–Teller nitrogen adsorption, X-ray diffraction and temperature programmed desorption using ammonia. The initial performance with respect to conversion and selectivity is good for the vanadia-based catalyst, but it is not chemically stable. This is manifested by a change in the catalyst crystal structure suggesting an oxygen depletion of the titania support and decreased activity with time-on-stream. The mordenite catalyst is stable but the activity and selectivity, especially to avoid the formation of N2O, needs to be improved before implementation. Based on the experimental work performed, none of the catalysts in their present state are suitable for the proposed operating conditions.
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| 10. |
- Sayed, Mahmoud, et al.
(författare)
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5-Hydroxymethylfurfural from fructose : An efficient continuous process in a water-dimethyl carbonate biphasic system with high yield product recovery
- 2020
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 22:16, s. 5402-5413
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Tidskriftsartikel (refereegranskat)abstract
- Bio-based 5-hydroxymethylfurfural (5-HMF) and its derivatives have attracted enormous attention due to their valuable market potential. Production of pure 5-HMF is challenging owing to the high reactivity of its functional groups and formation of by-products. In this study, an efficient continuous process for 5-HMF production in a biphasic system and its recovery at high yield and selectivity was developed. After an initial screening of different solvents, a water/dimethyl carbonate (DMC) system was selected for acid catalyzed fructose dehydration in a continuous mode using 0.23 M HCl as a catalyst. Effects of various reaction parameters on substrate conversion, product yield and selectivity, were determined. The process using 30% (w/v) fructose in water with three times the volume of DMC at 1 min residence time in a tube reactor at 200 °C provided 96.5% fructose conversion and 87.2% 5-HMF yield with a selectivity of 85.5% and 95.8% in aqueous and organic phases, respectively. Increasing the fructose concentration in the water phase to 52% gave 96.4% conversion and 74% 5-HMF yield. Using a fructose-glucose mixture as substrate had no effect on fructose conversion but affected slightly the selectivity of 5-HMF in the aqueous phase. Recovery of 5-HMF with ≥93% purity from DMC was achieved by solvent evaporation under vacuum, and improved by prior treatment with activated carbon, especially together with Na2CO3. Evaluation of the purified 5-HMF in a reaction with pentaerythritol showed comparable performance to the commercial 5-HMF in the production of a spirocyclic diol, a monomer for the production of polyesters and polyurethane.
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| 11. |
- Selimi, Jon, et al.
(författare)
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Purification of lipid oil using ion exchange resins
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Ingår i: Biomass Conversion and Biorefinery. - 2190-6815.
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Tidskriftsartikel (refereegranskat)abstract
- Oil upgrading technologies for fuel production from second-generation feedstocks require pretreatments, such as the removal of ash metals in crude oil, to improve the catalytic performance in the process. The aim of this work was to purify lipid crude oil, derived from black soldier fly larvae (BSFL), from calcium by dry washing using ion exchange resins. Commercially available ion exchange resins suitable for organic liquids, namely GF 202 and Amberlyst 15DRY (AL 15), were selected for the purification experiments. The lipid material dissolved in nonanoic acid in different concentrations of mixtures was passed through a resin-filled plug-flow reactor at 50 °C and 75 °C with a liquid hourly space velocity (LHSV) of 4 h−1. The oil samples were analyzed for calcium using inductively coupled plasma-optical emission spectrometry, while the resin surfaces were examined by scanning electron microscopy. AL 15 showed a better overall performance and led to a case where over 99% of calcium was removed. Graphical abstract: (Figure presented.).
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| 12. |
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| 13. |
- Svensson, Helena, et al.
(författare)
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Modeling of soot formation during partial oxidation of producer gas
- 2013
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Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 106, s. 271-278
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Tidskriftsartikel (refereegranskat)abstract
- Soot formation in a reverse-flow partial-oxidation reactor for reforming of gasifier producer gas has been studied. The process was modeled using a detailed reaction mechanism to describe the kinetics of soot formation. The numerical model was validated against experimental data from the literature and showed good agreement with reported data. Nine cases with different gas compositions were simulated in order to study the effects of water, hydrogen and methane content of the gas. The CO and CO2 contents, as well as the tar content of the gas, were also varied to study their effects on soot formation. The results showed that the steam and hydrogen content of the inlet gas had less impact on the soot formation than expected, while the methane content greatly influenced the soot formation. Increasing the CO2 content of the gas reduced the amount of soot formed and gave a higher energy efficiency and methane conversion. In the case of no tar in the incoming gas the soot formation was significantly reduced. It can be concluded that removing the tar in an energy efficient way, prior to the partial oxidation reactor, will greatly reduce the amount of soot formed. Further investigation of tar reduction is needed and experimental research into this process is ongoing.
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| 14. |
- Svensson, Helena, et al.
(författare)
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Soot formation in reverse flow reforming of biomass gasification producer gas
- 2010
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Ingår i: Proceedings of 18th European biomass conference and exhibition. Lyon, France. - : ETA Renewable Energies and WIP Renewable Energies. - 8889407565 ; DVD, s. 766-770
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Konferensbidrag (refereegranskat)abstract
- The aim of this work was to determine the extent to which soot is formed and if there are any ways of reducing the formation of soot. In order to determine if soot formation will be a critical issue for the reverse flow reforming process modeling of the process was undertaken. The reformer was modeled using a detailed reaction mechanism to describe the kinetics of soot formation.The results of the simulations show that soot will be formed under the modeled conditions. Almost 10 % of the ingoing carbon will be converted to soot. It is worth noting that the tars present in the gasification producer gas account for more than 5 % of the ingoing carbon. The soot formation can be reduced with more than 20 % by using a simple thermal pre-reformer where higher hydrocarbons (C2 and higher) and some of the tars are reformed. By using a low temperature reverse flow reformer as a pre-reformer the soot formation can be reduced by nearly 30 % making it a highly effective alternative. A catalytic pre-reformer will most likely produce better results because of the lower temperature needed for reforming the higher hydrocarbons as compared to methane.
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| 15. |
- Tunå, Per, et al.
(författare)
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A new process for well-head gas upgrading
- 2013
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Ingår i: Journal of Natural Gas Science and Engineering. - : Elsevier BV. - 2212-3865 .- 1875-5100. ; 13, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- As oil-prices and environmental concerns are increasing, it is of interest to better use the well-head gas. This light fraction co-produced with petroleum is generally flared and in this paper a method for upgrading and returning the co-product to the petroleum stream is suggested. The method is based on a conversion of the gas to synthesis gas and upgrading this synthesis gas into liquid hydrocarbons. But as the placement of such systems would be remote, the design has been performed using the following criteria. First of all the system has to be robust in design and secondly it has to be self-sustaining in that no additional feedstocks or chemicals are required for its operation and thirdly, the product should be crude oil compatible. In the paper, the system has been outlined, the major unit operations designed and heat and mass balances have been determined. Six cases have been compared, differing in reforming and oxygen generation technology. The comparison has been made on both a technical and production economic premises. In each case the investment cost has been determined and from this, and the calculated produced hydrocarbons, a production cost per barrel has been determined. The production of hydrocarbons well-head gas is a viable route and the production cost for the hydrocarbons vary between $71 and $156 a barrel, with the lower cost being quite attractive with the crude prices of recent years (around $100 a barrel). The production cost is however heavily influenced by the investment cost and the fact that the stranded natural gas is considered free. The production of an alternative, upgraded fuel would be a possibility; this however warrants additional investment in both production equipment and infrastructure.
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| 16. |
- Tunå, Per
(författare)
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Generation of synthesis gas for fuels and chemicals production
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many scientists believe that the oil production will peak in the near future, if the peak has not already occurred. Peak oil theories and uncertain future oil deliveries have stimulated interest in alternative sources of fuel and chemicals. This interest has been enhanced by concerns about energy security and about the climate change caused by emissions of carbon dioxide. The result has been increased interest in substituting fossil fuels with renewable energy sources such as wind, solar and biomass. However, this has proved particularly difficult in the transportation sector. The most likely source of renewable hydrocarbon fuels for transportation is biomass. It comes in many forms, none of which are suitable for direct use in internal combustion engines and gas turbines. Thus the biomass has to be refined to convert its energy into a more usable form. The most versatile conversion of biomass is thermochemical conversion via gasification and downstream synthesis, which allows the production of both fuels and chemicals. In the biomass gasification process, a gasifier converts the solid biomass into a gaseous product known as producer gas. The producer gas contains the desired components carbon monoxide and hydrogen, but it also contains water, carbon dioxide, lower hydrocarbons, tars and impurities that need to be removed from the gas. Reforming the tars and hydrocarbons in producer gas is difficult because of the amount of sulphur present. This thesis investigates the use of reverse-flow reactors to reform the tars and hydrocarbons in biomass generated producer gas.. Reverse-flow reactors operate by periodically reversing the direction of flow to enable high levels of heat recovery. The high heat recovery enables non-catalytic reformers to be operated at efficiencies near that of catalytic reformers. The operation of reverse-flow reactors is investigated experimentally in a tar-cracking reactor using dolomite as bed material and also theoretically using computer models. The investigations show that reverse-flow reactors have great potential, offering a chemically robust alternative to conventional reformers when operating on sulphur-containing biomass-generated producer gas. Furthermore, operation of reverse-flow tar crackers using dolomite as bed material is an efficient and viable solution for tar removal and syngas boosting. The producer gas also contains ammonia in varying amounts depending on the gasifier’s operating parameters and feedstock. Ammonia can be a poison for catalysts and, if the producer gas is burnt, will produce elevated levels of NOX in the flue gas. The selective catalytic oxidation of ammonia in synthesis gas was thus also investigated by experiments on a model synthesis gas. This thesis also covers mass and energy balance calculations to determine the efficiency and economics of synthetic fuels and chemicals plants. Several possible plant configurations were investigated, both stand-alone and integrated. The integration of a pulp and paper mill with a fuel synthesis plant is a very likely scenario as the biomass logistics are already located on-site. Another possible integration scenario involves steel plants, where large quantities of energy-rich gases are handled as off-gases in coke production. Utilisation of this off-gas coupled with biomass gasification was also investigated. In the stand-alone plants, the difference between reverse-flow reformers and conventional non-catalytic reformers was investigated as front-ends to well-head gas upgrading to produce crude oil via the Fischer-Tropsch synthesis. Furthermore a well-to-wheel comparison of synthetic natural gas, methanol, ethanol, dimethyl ether, Fischer-Tropsch diesel and synthetic gasoline was performed. The comparison used woody biomass as feedstock and computed mass and energy balances for complete plants from gasifier to fuel as well as for lignocellulosic ethanol production by fermentation. Efficiency in regard to feedstock to travel distance (Well-to-Wheel) and the cost of transportation was also investigated. Ammonia is one of the most valuable chemicals for modern agriculture. Current production is almost entirely based on fossil fuels. Thus small-scale production of ammonia from renewable feedstocks was also investigated.
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| 17. |
- Tunå, Per, et al.
(författare)
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Modeling of Reverse Flow Partial Oxidation Process for Gasifier Product Gas Upgrading
- 2010
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Ingår i: Proceedings of the 5th International Conference on Thermal Engineering:Theory and Applications 2010. - 1894503937
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Konferensbidrag (refereegranskat)abstract
- Biomass gasification is one of the alternatives to producing liquid fuels and chemicals from biomass residues. The gas produced in gasification contains CO, H2, H2O, CO2, light hydrocarbons and tars. Depending on the gasifier type, operating conditions and fuel, the light hydrocarbons can contain as much as 50 % of the total energy contents in the gas. The gas also contains catalyst poisons such as sulfur, as H2S and COS. This paper presents simulation work of a reverse flow partial oxidation reformer that reaches efficiencies approaching conventional catalytical processes. Furthermore, different reactor designs and parameter variations such as pressure are investigated. For comparison, natural gas simulations are included which clearly show the benefits of using reverse flow operation with lean gases such as gasifier product gas.
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| 18. |
- Tunå, Per, et al.
(författare)
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Modelling of a reverse-flow partial oxidation reactor for synthesis gas production from gasifier product gas.
- 2015
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Ingår i: Journal of Computational Methods in Sciences and Engineering. - : IOS Press. - 1472-7978 .- 1875-8983. ; 15:3, s. 593-604
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Tidskriftsartikel (refereegranskat)abstract
- Biomass gasification followed by fuel synthesis is one of the alternatives for producing liquid fuels and chemicalsfrom biomass feedstocks. The gas produced by gasification contains CO, H2, H2O, CO2, light hydrocarbons and tars. Thelight hydrocarbons can account for as much as 50% of the total energy content of the gas, depending on the type of gasifier,operating conditions and feedstock. The gas also contains catalyst poisons such as sulphur, in the form of H2S and COS. Thispaper presents simulations of a reverse-flow partial-oxidation reformer that converts the light hydrocarbons into more synthesisgas, while achieving efficiencies approaching that of conventional catalytic processes. Variations in parameters such as pressure,amount of oxidant and steam-to-carbon ratio were also investigated. Simulations of the reforming of natural gas were includedfor comparison. The results show the benefits of using reverse-flow operation with lean gases such as gasifier product gas.
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| 19. |
- Tunå, Per, et al.
(författare)
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Regenerative reverse-flow reactor system for cracking of producer gas tars
- 2014
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 4:1, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- The gas produced in a biomass gasifier contains high amounts of tars which have to be removed prior to downstream utilization. Calcined dolomite is catalytically active for tar cracking reactions and resistant to sulfur poisoning. In this study, calcined dolomite was used as bed material in a reverse-flow reactor for cracking of tars in a model synthesis gas. 1-methylnaphthalene was used as model tar compound at a concentration of 15,000 mg/Nm3. The reactor system was operated at temperatures between 700 and 850 °C in the active zone. Total tar conversion was over 95 % for the system under reverse-flow conditions at the highest temperature. Already at the lowest temperature, up to 78 % of the 1-methylnaphthlene was converted, but mainly to other more stable tar compounds such as naphthalene and benzene, reaching a total tar conversion of only 23 %. To produce tar-free gas, higher temperatures are thus needed. The use of very high temperatures does, however, lead to a significant decrease in the specific area of the dolomite, as shown by BET surface measurements. The dolomite was further characterized with x-ray diffraction and energy dispersive spectroscopy.
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| 20. |
- Tunå, Per, et al.
(författare)
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Selective catalytic oxidation of ammonia by nitrogen oxides in a model synthesis gas
- 2013
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 105, s. 331-337
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis gas generated by the gasification of nitrogen-containing hydrocarbons will contain ammonia. This is a catalyst poison and elevated levels of nitrogen oxides (NOX) will be produced if the synthesis gas is combusted. This paper presents a study of the selective oxidation of ammonia in reducing environments. The concept is the same as in traditional selective catalytic reduction, where NOX are removed from flue gas by reaction with injected ammonia over a catalyst. Here, a new concept for the removal of ammonia is demonstrated by reaction with injected NOX over a catalyst. The experiments were carried out in a model synthesis gas consisting of CO, CO2, H-2, N-2 and NH3/NOX. The performance of two catalysts, V2O5/WO3/TiO2 and H-mordenite, were evaluated. On-site generation of NOX by nitric acid decomposition was also investigated and tested. The results show good conversion of ammonia under the conditions studied for both catalysts, and with on-site generated NOX. (C) 2012 Elsevier Ltd. All rights reserved.
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| 21. |
- Tunå, Per, et al.
(författare)
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Synergies from Combined Pulp&Paper and Fuel Production
- 2012
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 40, s. 174-180
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in Undetermined In this paper, the prospect of integrating a combined paper&pulp mill with fuel production via biomass gasification was investigated. In the study, three different types of gasifiers (circulating fluidised bed, entrained flow and indirect gasification) and three fuel processes (dimethyl ether, methanol and Fischer-Tropsch wax synthesis) were investigated using computer simulations. The paper reports differences from the stand-alone cases and the integrated cases, using the electricity equivalence efficiency as a measure. Only 6 out of the 18 integrated cases studied displayed a positive result from integration and no obvious fuel selection that stand out as the most beneficial one, however the synthesis of dimethyl ether is, in combination with all gasifiers assessed a rather good choice, with an change in efficiency from integration ranging from −1% to 4%. Dimethyl ether is not the best choice if the electrical equivalence is to be maximised however. In this case the combination of circulating fluidised bed gasification and methanol synthesis should be pursued. The production of Fischer-Tropsch wax should according to the chosen measure not be produced; however there is an added value in the production of a non-oxygenated fuel which has not been taken into account in this particular study. All cases leads to a reduction of 0.4–0.9 kg CO2 per kg of dry biomass used in the process for fuel synthesis and the possibility to export bark is a more significant factor in this respect than which type of fuel is synthesised.
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| 22. |
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| 23. |
- Tunå, Per, et al.
(författare)
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Techno-economic assessment of nonfossil ammonia production
- 2014
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Ingår i: Environmental Progress & Sustainable Energy. - : Wiley. - 1944-7450 .- 1944-7442. ; 33:4, s. 1290-1297
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Tidskriftsartikel (refereegranskat)abstract
- The production of nitrogen fertilizers are almost exclusively based on fossil feedstocks such as natural gas and coal. Nitrogen fertilizers are a necessity to maintain the high agricultural production that the world's population currently demands. Ammonia produced from nonfossil-based feedstocks would enable renewable production of ammonia. Renewable feedstocks are one thing, but perhaps even more important in the future are the security of supply that decentralized production enables. In this study, the techno-economic evaluation of production of ammonia from various renewable feedstocks and for several plant sizes was investigated. The feedstocks included in this study are grid-based electricity produced from wind power, biogas, and woody biomass. The feedstocks differed in exergy, and to make a fair comparison, the electric equivalence ratios method was used. The results showed that the energy consumption for biogas and electricity is the same at 42 GJ/tonne ammonia. When using the electric equivalence comparison for the same cases, the results are 26 and 42 GJ/tonne, respectively. Biomass-based production has an energy consumption of 58 GJ/tonne and 31 GJ/tonne when using the electric equivalence comparison, which should be compared with the industrial average of 37 GJ (or 21 GJ electric equivalence) per tonne of ammonia. Monte Carlo simulations were used to vary the inputs to the process to evaluate the production cost. The ammonia production cost ranged from $680 to 2300/tonne ammonia for the various cases studied
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| 24. |
- Tunå, Per, et al.
(författare)
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Woody biomass-based transportation fuels – A comparative techno-economic study
- 2014
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Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 117:Part B, s. 1020-1026
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Tidskriftsartikel (refereegranskat)abstract
- Production of synthetic vehicle fuels from biomass is a hot topic. There are several alternative fuels to consider when evaluating properties such as cost of production and energy efficiency to both product and final use in a road vehicle. Thermochemical conversion via gasification and downstream synthesis of fuels as well as biochemical conversion of woody biomass to ethanol is considered in this paper. The vehicle fuels considered in this paper include methanol, ethanol, synthetic natural gas, Fischer–Tropsch diesel, dimethyl ether and synthetic gasoline from the methanol-to-gasoline process. The aim of the study is to evaluate all the different fuels on the same basis. The production cost of the various fuels is estimated as well as the overall investment cost. Well-to-wheel energy efficiency calculations were performed to evaluate how far a vehicle can travel on the fuel produced from a specific amount of feedstock. The production cost of the fuel as a function of distance travelled is also presented. Of the fuels considered in this study, dimethyl ether manages the highest efficiency from feedstock to travelled distance and manages to do so at the lowest cost. Ethanol produced from woody biomass is the most inefficient and expensive fuel, when considering biomass harvesting and transport, the production and road use (ignoring fuel distribution), in this study due to low yields in fuel production. Total investment cost for ethanol is considerably lower at MM$ 281 compared to the thermochemical fuels that ranges from MM$ 580 to MM$ 760. The production costs of the various fuels range from $79.9/MW h for synthetic natural gas to 139.6 $/MW h for Fischer–Tropsch diesel. The production cost translates to a travel cost ranging from $4.98/100 km for dimethyl ether to $8.51/100 km for ethanol
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