| 1. |
- Arpadjan, S., et al.
(författare)
-
Field sampling, speciation and determination of dissolved iron (II) and iron (III) in waters
- 2012
-
Ingår i: Bulgarian Chemical Communications. - 0861-9808. ; 44:4, s. 299-306
-
Tidskriftsartikel (refereegranskat)abstract
- A simple and rapid field sampling procedure was developed for the speciation of dissolved Fe(II) and Fe(III) in waters. The determination of iron species was possible by selective batch solid phase extraction of Fe(III) using chelating resin Chelex-100 in H+ form, sample acidity range of pH 1.5-2.5, elution with 0.03 mol L-1 NH4-EDTA, and detection of Fe(III) by flame or electrothermal atomic absorption spectrometry (ETAAS). The concentration of Fe(II) was determined in the solution above the resin by direct ETAAS or after adsorption on Chelex-100 in NH4+ form without the need for preoxidation of Fe(II) to Fe(III). Water samples were collected in situ and filtered by passing them through a syringe filter (0.45 mu m). The batch procedure was performed at the field and then, the tubes containing the resins with the loaded analytes were returned to the laboratory where the iron species were eluted and determined. Field sampling prevents changes in the oxidation state of iron. The effect of humic acid was also investigated. The results obtained indicated that the method was not affected by the presence of up to 0.01% humic acid. The limit of detection (3s) was 0.8 mu g L-1 Fe (ETAAS detection). The relative standard deviation (n=10) ranged from 2% at the 1 mg L-1 Fe up to 20% at the 1 mu g L-1 Fe(III) level. Recoveries of spiked Fe(II) and Fe(III) in river, lake, tap and groundwater samples ranged from 93 to 105%.
|
|
| 2. |
- Arpadjan, S., et al.
(författare)
-
Speciation analysis of thallium in water samples after separation/ preconcentration with the EmporeTM chelating disk
- 2011
-
Ingår i: International Journal of Environmental Analytical Chemistry. - : Informa UK Limited. - 0306-7319 .- 1029-0397. ; 91:11, s. 1088-1099
-
Tidskriftsartikel (refereegranskat)abstract
- A simple, reliable and novel solid phase extraction procedure using the Empore chelating disk has been developed for determination of Tl(I) and Tl(III) in environmental water samples by electrothermal atomic absorption spectrometry (ETAAS). The influence of humic acids on separation/preconcentration of thallium species with the Empore chelating disk is investigated. The preconcentration factor and detection limit are 500 and 5 ng L-1, respectively. The recoveries are in the range 93-103% for mineral, pond, sea, snowmelt, waste waters at 28-500 ng L-1 Tl and in the range 82-112% for river waters at 18-28 ng L-1 Tl.
|
|
| 3. |
- Knutsson, Jesper, 1973, et al.
(författare)
-
Evaluation of a passive sampler for the speciation of metals in urban runoff water
- 2013
-
Ingår i: Environmental Sciences: Processes and Impacts. - : Royal Society of Chemistry (RSC). - 2050-7895 .- 2050-7887. ; 15:12, s. 2233-2239
-
Tidskriftsartikel (refereegranskat)abstract
- Metals in urban runoff water need to be monitored in order to estimate fluxes and assess their impact on the aquatic environment. Passive sampling is a useful and reliable emerging tool for measuring time averaged concentrations of metals in water bodies. This paper describes the deployment of a passive sampler to measure Cu, Ni and Zn in an urban runoff water treatment facility. The concentrations derived from the passive samplers are compared to concentrations obtained from an automated water sampler which provides pooled spot water samples and to model predictions from the visualMINTEQ computer speciation code. Results show that visualMINTEQ predictions partly describe the metal speciation in non-equilibrium systems. In addition we conclude that passive samplers are useful for monitoring and characterization of metal speciation under chemodynamic conditions. © 2013 The Royal Society of Chemistry.
|
|
| 4. |
- Knutsson, Jesper, 1973, et al.
(författare)
-
Water and energy savings from greywater reuse: a modelling scheme using disaggregated consumption data
- 2021
-
Ingår i: International Journal of Water Resources Development. - : Springer Science and Business Media LLC. - 1360-0648 .- 0790-0627 .- 2538-3604 .- 2522-0101. ; 5:1, s. 13-24
-
Tidskriftsartikel (refereegranskat)abstract
- Municipal drinking water supplies are under great stress globally, and one way to mitigate the problems is the reutilization of wastewater in various settings. In this paper, a greywater reuse scheme and the impact of system design and configuration on water and energy savings are investigated. The objective of the paper was to investigate the impact of hydraulic design and performance of a greywater treatment and reuse system on water and energy savings. A simulation model was created based on real, disaggregated water consumption data that predicts the reuse potential. Three scenarios were investigated; (1) greywater collection from the bathroom and reuse for toilet flushing, (2) greywater collection from bathroom sinks and showers, and reuse as hot water for sinks and showers, and (3) a combination of (1) and (2) where greywater collection from bathroom sinks and showers is used for toilet flushing, sinks and shower. The results indicate hot water reductions between 55.6 and 58.2%, while cold water reductions ranged from 5.8 to 30.6%. Reductions in energy for producing hot water between 43.5 and 46.8% were observed. Recommendations per connected user for hydraulic design ranged from 0.033 to 0.1 dm3 min−1, 3 dm3, and 0.7–10 dm3 for treatment capacity, collection and holding tank volume.
|
|
| 5. |
- Knutsson, Pavleta, 1980, et al.
(författare)
-
Characterization of ash component desorption on novel bed material for fluidized bed boilers
- 2018
-
Ingår i: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM. - 1314-2704. ; 18:4.1, s. 195-202
-
Konferensbidrag (refereegranskat)abstract
- The use of biomass as a renewable fuel for production of heat and electricity is regarded as a key to reduce fossil fuel dependency, and thereby to reduce net CO2 emissions. Fluidized bed (FB) technology is widely accepted as the most energy efficient process for thermal conversion of biomass. One of the often-mentioned drawbacks is the building up of agglomerates within the process because of bed material-ash interaction. To avoid unplanned operational stops due to agglomeration, bed material is continuously replenished and spent bed material is removed in the form of bottom ash. The spent bed material cannot readily be reused and is usually deposited or used as construction filler material. Sand is the primary choice for bed material but novel bed materials are being tested to improve biomass conversion. Even though agglomeration is reduced and the energy efficiency of the conversion process is improved, bottom and fly ash are still being generated and need to be managed. To conceive new management strategies there is need to improve the understanding of the composition and stability of the compounds formed from the interaction between biomass ash and the novel bed materials. In the present work four bed materials (Olivine, Ilmenite, Feldspar and Manganese ore), all minerals, have been used in a biomass fueled 10MW CFB boiler. The materials have been sampled upon similar gas composition and time exposures in order to assure similarity in bed material “activity”. Bed material characterization followed by stepwise leaching have been used to identify opportunities in terms of pretreatment prior to deposition or/and the possibilities for alternative reuse.
|
|
| 6. |
- Knutsson, Pavleta, 1980, et al.
(författare)
-
Phycoremediation of heavy metals
- 2016
-
Ingår i: Energy and Clean Technologies Conference Proceedings, Sgem 2016, Vol I. - 9786197105636 ; , s. 533-540
-
Konferensbidrag (refereegranskat)abstract
- Increasing amounts of heavy metals is a growing societal problem. By using ion exchangers, heavy metals can be captured and thereby their environmental impact can be decreased. Microalgae have been shown to adsorb metals; the algal cell wall contains functional groups, such as amino-, carboxyl-, hydroxyl- and sulphate groups, to which the various metal ions could bind [1]. This makes them suitable as a sustainable alternative for environmental remediation. Removal of pollutants with algae is called phycoremediation and is well studied for e.g. waste water [2]. Within this project, we study the potential of microalgae for remediating heavy metals in low concentration originating from leaching of combustion ashes, by measuring the metal binding capacity by three phytoplankton species: Chlorella sauna, Dunaliella sauna and Scendesmus obliquus. The heavy metals assessed are divalent ions of copper (Cu), cadmium (Cd), zinc (Zn), mercury (Hg) and lead (Pb). The effect of pH has been determined, as well as binding over time.
|
|
| 7. |
- Knutsson, Pavleta, 1980, et al.
(författare)
-
Potassium speciation and distribution for the K2CO3 additive-induced activation/deactivation of olivine during gasification of woody biomass
- 2019
-
Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 248, s. 538-544
-
Tidskriftsartikel (refereegranskat)abstract
- The GoBiGas plant, which comprises a 32-MW th dual fluidized bed gasifier, was constructed as a demonstration unit for converting biomass to biomethane via gasification. On several occasions during the commissioning of the plant, low activity of the olivine bed generated a high content of tar in the produced gas, which was deleterious to the downstream equipment. The problem was attributed to a deficiency of ash constituents, and the solution was to control activation of the bed material through the addition of K 2 CO 3 to the process. This enabled extended operational periods without tar-related issues. The achieved activity could be lost during interrupted operation at which time the activation procedure had to be repeated. In the present paper analysis of the bed material samples extracted upon activation and after loss of activity using Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM-EDS)showed similar morphologies for the ash layers formed around the olivine particles. The observed differences mainly related to the distributions of potassium (K)across the layers. Furthermore, surface analysis showed differences in K speciation within the outer regions. K solubility tests and X-ray photoelectron spectroscopy analyses indicated that K was present as an oxide/hydroxide rather than as a silicate on the surface of the active olivine. The presented results are of major relevance for the operation of dual fluidized bed gasifiers with fuels that are potassium-lean when ash components need to be supplied as additives.
|
|
| 8. |
- Knutsson, Pavleta, 1980, et al.
(författare)
-
Role of potassium in the enhancement of the catalytic activity of calcium oxide towards tar reduction
- 2018
-
Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 229, s. 88-95
-
Tidskriftsartikel (refereegranskat)abstract
- Gasification in fluidized bed systems is considered to be a highly promising alternative for the thermal conversion of biomass. A major challenge for this process is the formed tars, which represent a loss of energy from the product gas and entail additional costs for their removal. Olivine is considered to be the most effective catalytic bed material in terms of its impact on tar levels in the product gas. Additions and modifications to olivine have revealed the potential to enhance its catalytic activity. In the present study, the effect of the addition of K 2 CO 3 to the gasification process on the tar decomposition capability of olivine were evaluated. The effect of the added K 2 CO 3 on the product gas was assessed in the 30-MWth pilot gasification plant GoBiGas. Once dec reases in the tar level were detected, samples of the bed material were extracted from the system and evaluated for morphological and chemical changes related to the observed catalytic effect. SEM-EDX and XPS analyses of the surfaces of the olivine particles indicate that the additive is involved in the formation of mixed oxides of Ca and K within the outermost layer of the olivine particles. DFT modeling showed that the formation of mixed Ca and K oxides changes the oxidation potential of the surface, which may explain the increased activity of ash-coated olivine towards tar reduction.
|
|
| 9. |
- Knutsson, Pavleta, 1980, et al.
(författare)
-
Use of natural ores in thermal conversion of biomass
- 2018
-
Ingår i: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM. - 1314-2704. ; 18:4.1, s. 791-798
-
Konferensbidrag (refereegranskat)abstract
- To decrease the CO2 levels in the atmosphere without compromising with the electricity production and energy security two different issues have to be addressed – replacement of the current use of fossil fuels with CO2-neutral fuels and increase in the efficiency of the existing processes for thermal conversion. Fluidized bed (FB) thermal conversion is usually considered as the most energy efficient choice when biomass and municipal solid waste are used as fuels. The bed material that is used commonly within FB boilers is sand. With the demand to increase the efficiency of the electricity generation process, alternative bed materials have been tested. These materials are usually naturally occurring minerals containing transient oxides, most often Fe or Mn. The present paper presents three naturally occurring minerals that may be utilized as bed materials – olivine, ilmenite and manganese ore, while comparing with industrial silica sand for reference. The feasibility of their utilization as bed materials in thermal conversion of biomass on their further use is discussed.
|
|
| 10. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
-
Material balances of carbon, sulfur, nitrogen and ilmenite in a 100 kW CLC reactor system
- 2014
-
Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 27, s. 188-202
-
Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is an unmixed combustion concept where fuel and combustion air are kept separate by means of an oxygen carrier, and the CO2 capture is inherently achieved. This work presents findings from a 100 kW chemical-looping combustor, which was operated with Colombian bituminous coal for 12 h, using ilmenite as oxygen carrier. The focus of the study is on a 4.7-h experiment with stable operating conditions, during which inbound and outbound gaseous, liquid, and solid flows of carbon, sulfur, nitrogen and ilmenite were carefully monitored and analyzed. The fuel power during this experiment was 71 kW. The gas conversion reached 83%, the carbon capture efficiency was 98-99%, and the solid fuel conversion based on carbon was 65%. The carbon balance confirms that a large fraction of the fuel escapes the reactor system unconverted. It also demonstrates that essentially all in- and outbound flows of carbon have been accounted for. The sulfur balance shows that the conversion in the fuel reactor of inbound sulfur is around 72%. Furthermore, it is found that 75% of the S-containing gas is SO2, and only 25% is H2S. The nitrogen analysis indicates that 62% of the nitrogen fed with the coal is converted to gas, and that the nitrogen in this gas is distributed as 1 wt-% HCN, 11 wt-% NO, 26 wt-% NH3, with the balance probably being N-2. In addition, the present work includes a comprehensive study on the structural integrity of ilmenite in circulating fluidized beds. It is found that the expected lifetime of ilmenite is approximately 700-800 h.
|
|
