| 1. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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Chemical-looping combustion of solid fuels in a 100 kW dual circulating fluidized bed system using iron ore as oxygen carrier
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437 .- 2213-2929. ; 4:1, s. 1029-1039
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is an innovative carbon-capture technology with potential to drastically reduce the cost of capture. By using a circulating bed material to transfer oxygen from the combustion air to the fuel, air and fuel are never mixed and the CO2 can be obtained as a separate flue gas stream, undiluted by N2. In other words, carbon capture is inherent to the CLC process. Here, we present findings from a 100 kW chemical-looping combustor for solid fuels. The oxygen carrier used in the present tests was an iron ore from Tierga, Spain. In total, 26 h of operation using bituminous coal and wood char as fuel was achieved. The highest gas conversion with bituminous coal was 87%, and the highest gas conversion using wood char as fuel was 93%. The carbon capture efficiency with bituminous coal was 94-98%, which is lower than what has been observed with ilmenite. For the wood char, the carbon capture was even lower. The fate of nitrogen and sulfur was investigated. It was found that 84 wt% of the S-containing gas was SO2, and only 16 wt% was H2S. The nitrogen analysis indicates that the fuel-N converted to gas was distributed as 10 wt% NO, 37 wt% NH3, and 53 wt% N2. It was found that the oxygen-carrier particles retained their high reactivity throughout the operational period. Furthermore, the expected lifetime of the iron ore was found to be approximately 300 h.
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| 2. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Enhanced performance of manganese ore as oxygen carrier for chemical-looping with oxygen uncoupling (CLOU) by combination with Ca(OH)2 through spray-drying
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437 .- 2213-2929. ; 4:4, s. 3707-3717
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping with oxygen uncoupling (CLOU) is an innovative combustion technology with inherent capture of the CO2 and potential to drastically reduce the cost of capture. The process requires two interconnected reactors, between which the oxygen carrier particles are circulated while carrying oxygen from the combustion air to the fuel. In this work, the reactivity and mechanical stability of five materials were studied; three natural ores and two materials which were combinations of an ore and Ca(OH)2. The overall aim was to investigate the feasibility of making a reactive and mechanically stable material using cheap raw materials and an industrially relevant particle manufacturing process. The two combined materials behaved differently from their natural counterparts. The Brazilian ore + Ca(OH)2 showed a decrease in reactivity towards methane, but higher reactivity towards syngas in comparison to the pure ore. The South African ore + Ca(OH)2 showed a major improvement in reactivity towards both syngas and methane, which could be attributed to formation of a perovskite-structure material with significant CLOU properties. A comparison between the pure ores and the combined materials show that the addition of Ca(OH)2 had generally a beneficial impact on the mechanical stability of the oxygen carriers. As a significant change in the particle size distribution was seen for all oxygen carrier materials after repeated redox cycles with long reduction periods, the particle disintegration was likely caused by the chemical phase transformations occurring inside the particles, rather than by mechanical forces.
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| 3. |
- Ashour, Radwa M., et al.
(författare)
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Preparation and characterization of magnetic iron oxide nanoparticles functionalized by L-cysteine : Adsorption and desorption behavior for rare earth metal ions
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier. - 2213-3437. ; 4:3, s. 3114-3121
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Tidskriftsartikel (refereegranskat)abstract
- In this work, magnetic iron oxide nanoparticles functionalized with L-cysteine (Cys-Fe3O4 NPs) was synthesized and fully characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infra-red (FTIR), thermogravimetric analysis (TGA) and zeta potential measurements. The synthesized Cys-Fe(3)O(4)NPs has been evaluated as a highly adsorbent for the adsorption of a mixture of four rare earths RE3+ ions (La3+, Nd3+, Gd3+ and Y3+) from digested monazite solutions. The influence of various factors on the adsorption efficiency such as, the contact time, sample pH, temperature, and concentration of the stripping solution were investigated. The results indicate that Cys-Fe3O4 NPs achieve high removal efficiency 96.7, 99.3, 96.5 and 87% for La3+, Nd3+, Gd3+ and Y3+ ions, respectively, at pH = 6 within 15 min, and the adsorbent affinity for metal ions was found to be in order of Nd3+ > La3+ > Gd3+ > Y3+ ions. Using the Langmuir model, a maximum adsorption capacity of La3+, Nd3+, Gd3+ and Y3+ at room temperature was found to be 71.5, 145.5, 64.5 and 13.6 mg g (1), respectively. The Langmuir isotherm and pseudo-second order model fitted much better than the other isotherms and kinetic models. The obtained results for the thermodynamic parameters confirmed the spontaneous and endothermic nature of the process. Moreover, the desorption was carried out with 0.1 M nitric acid solutions. In addition, Cys-Fe3O4 NPs can be used as a highly efficient adsorbent for the adsorption of La3+, Nd3+, Gd3+ and Y3+ ions from digested monazite solutions.
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| 4. |
- Bajwa, Anjali, et al.
(författare)
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Removal of volatile organic compounds over bagasse ash derived activated carbons and monoliths
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437. ; 4:2, s. 1561-1573
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Tidskriftsartikel (refereegranskat)abstract
- The unburned carbon in bagasse ash was separated and used as a starting material for activated carbon and carbon monolith preparation. The separated carbon was steam activated in a rotary kiln under different conditions and compared with carbon activated in limited supply of air. The activated carbon from the rotary kiln showed surface areas ranging from 324 to 601 m(2)/g. Different phenolic resins and cellulosic binders were used to prepare the monoliths using slurry casting method. The effects of different preparation conditions on the properties of the monolith were studied. Upon monolith formation, the surface area was reduced slightly and surface areas in the range 92-479 m(2)/g were achieved. The activated carbons and monoliths were tested for static adsorption of volatile organic compounds (VOCs) using benzene, xylene, hexane and toluene as model compounds. With the activated carbons, adsorption capacities as high as 22.5, 31.1, 27.5 and 25.0 g/100 g sample were obtained for toluene, benzene, xylene and hexane, respectively. The adsorption capacities were reduced for the corresponding monoliths. The waste derived activated carbons and monoliths show promising results as adsorbents for the removal of volatile organic compounds.
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| 5. |
- Carlsson, My, et al.
(författare)
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Energy balance performance of municipal wastewater treatment systems considering sludge anaerobic biodegradability and biogas utilisation routes
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437. ; 4:4, s. 4680-4689
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Tidskriftsartikel (refereegranskat)abstract
- The energy balance of a municipal wastewater treatment (WWT) system was evaluated considering the influence of excess biological sludge anaerobic biodegradability (BDAn) and of biogas utilisation as either fuel for co-generation of heat and power (CHP) or for vehicle transport. Sludge thermal pre-treatment prior to anaerobic digestion and high-rate carbon removal were considered as modifications of a reference municipal WWT system to impact the sludge BDAn. Both thermal pre-treatment and a high-rate process with a short sludge retention time (SRT = 1-3d) led to ∼30% higher sludge BDAn than that of untreated sludge from a low-rate WWT system with long SRT ( > 8d), which enhanced methane yields and energy production correspondingly. An efficient separation (40% of CODin) of primary solids promoted biogas production by capturing a significant part of the incoming COD, and lowered aeration energy demands for carbon oxidation due to lower loads of particulate organics into the biological treatment. Thermal pre-treatment can most effectively increase the biodegradability of sludge originating from a low-rate WWT system with a long SRT. Sludge solubilization alone as an indicator of increase biodegradability by a pre-treatment is inadequate for sludge types with inherently high biodegradability. A WWT system with primary separation, sludge pre-treatment, and CHP from biogas can be a net electricity producer and self-sufficient in thermal energy, provided the thermal energy from CHP is available for the pre-treatment. With other types of energy carriers as inputs and outputs, the WWT performance also needs evaluation with respect to the energy economic and environmental value.
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| 6. |
- Ivanov, Alexander E., et al.
(författare)
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Flow permeable composites of lignin and poly(vinyl alcohol) : Towards removal of bisphenol A and erythromycin from water
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier. - 2213-3437. ; 4:2, s. 1432-1441
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Tidskriftsartikel (refereegranskat)abstract
- Monolithic composites of Polyphepan (R) or Kraft lignin embedded in a poly(vinyl alcohol) (PVA) matrix were synthesized using cryogelation technique and studied as flow permeable adsorbents for bisphenol A and erythromycin removal from water. Adsorption isotherms of bisphenol A on pristine Polyphepan provided the equilibrium dissociation constant K-L = 2.6 x 10 (6) M and the maximal binding capacity Q(max) = 20 mu mol/g; for erythromycin K-L was in the 9.6 x 10 (6) M to 5.8 x 10 (5) M range, and Q(max) was between 55 mu mol/g and 94 mu mol/g. Embedment of lignins into PVA cryogels resulted in monoliths with adequate flow permeability and the composites essentially retained the binding capacity for both bisphenol A and erythromycin. Percolation of contaminated water through the monoliths resulted in 10-fold reduction of the pollutant concentrations within 12-70 column volumes of the effluent. Due to the higher loading of lignin, the Kraft lignin-PVA composite showed higher adsorption capacity for erythromycin than Polyphepan-PVA. Stability and reversible compression of the monoliths in the flow of water were studied. Limitations are associated with leakage of soluble lignin, strongly expressed in the case of Kraft lignin-containing composites. (C) 2016 Elsevier Ltd. All rights reserved.
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| 7. |
- Mäkitalo, Maria, et al.
(författare)
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Prediction of the long-term performance of green liquor dregs as a sealing layer to prevent the formation of acid mine drainage
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437. ; 4:2, s. 2121-2127
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Tidskriftsartikel (refereegranskat)abstract
- One of the mining industry's main concerns is the management of waste rock and tailings generated by sulfide ore extraction. Upon exposure of atmospheric oxygen, iron sulfides oxidize generating acidity. Infiltrating water form a metal-rich acidic leachate called acid mine drainage (AMD), that can cause serious environmental problems. Green liquor dregs (GLD) is a material that resists the passage of oxygen and water and could thus be used to seal mine wastes, preventing their oxidation and AMD formation. To enable its use in dry mine waste covers, the long-term efficiency of such GLD sealing layers must be evaluated. In this study, fresh GLD and GLD aged for 3 to 13 years was collected from two sites and analysed to determine how aging affects its chemical and physical properties. Aged and fresh GLD were very similar with respect to all the properties important in a sealing layer. In particular, there was no evidence of calcite dissolution in aged GLD samples. Aged GLD also exhibited high water saturation (>91%) and chemical stability, both of which are important for effective long-term sealing. The shear strength of GLD deployed in the field increased over time but not sufficiently to ensure the long-term physical integrity of a pure GLD sealing layer. The development of hybrid materials with improved shear strength will therefore be necessary.
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| 8. |
- Solis, Jerry L., et al.
(författare)
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Calcium and tin oxides for heterogeneous transesterification of Babasssu oil (Attalea speciosa)
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier. - 2213-3437. ; 4:4, s. 4870-4877
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Tidskriftsartikel (refereegranskat)abstract
- Non-edible oils and waste cooking oils are alternatives to uphold a sustainable large scale production of biodiesel considering large volumes and by-products. Babassu oil (Attalea speciosa) offers a challenging case study scenario for the preparation of a heterogeneous catalytic material. This study shows the binary synthesis of calcium and stannic oxide (CaO/SnO2) catalysts for transesterification of oils with high content of free fatty acids (FFAs). The catalysts were prepared with several mass ratios of CaO:SnO2 in the proportions of 1:4, 4:1, 7:3 and 1:1. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and N2-physisorption analyses. Biodiesel production was tested using a 23 full factorial design with variables such as temperature, methanol/oil molar ratio, and catalyst weight relative to oil. Such design statistically proved that there was no significant effect over the response variable. Furthermore a Box-Behnken design surface response analysis using the same three variables with three levels was performed with MATLAB showing a non-linear relation and statistical response of the optimal conditions for biodiesel production. The optimal experimental conditions were found to be 54.1°C, agitation speed at 250rpm with 6wt.% of CaO/SnO2 (7:3 mass ratio of the binary catalyst) and 10:1 (methanol:oil) molar ratio. The catalyst has shown a high potential for conversion of Babassu oil by fine-tuning as a single step by simultaneous esterification and transesterification to biodiesel.
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