| 1. |
- Wallmo, Henrik, 1977, et al.
(författare)
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The influence of hemicelluloses during the precipitation of lignin in kraft black liquor
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:2, s. 165-171
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Tidskriftsartikel (refereegranskat)abstract
- Removing lignin from black liquor is one way of recovering valuable organic substances for alternative use as well as reducing the energy surplus in a modern, energy-optimised kraft pulp mill. By using the recently developed "LignoBoost" process it is possible to upgrade black liquor streams of different origin to form valuable chemicals. In this investigation a combination of membrane filtration and the LignoBoost concept was used. The primary objective of the work was to investigate whether or not the filtration properties of the black liquor were affected by its hemicellulose content. The hemicellulose content in the black liquors was lowered prior to precipitation using three different pre-treatment techniques, and the filtration properties were compared to the reference black liquors of evaporated softwood and hardwood black liquor. The pre-treatment methods used were heat-treatment, ultrafiltration and a combination of ultrafiltration and nanofiltration. It was shown that the filtration resistance was lowered considerably when the hemicellulose content in the black liquor was reduced prior to precipitation. The experiments also showed that it was possible to produce a hardwood lignin product of high purity i.e. low sodium (0.2 w-% of TIDS) and hemicellulose content (0.7 w-% of TDS)
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| 2. |
- Rudolph, Gregor, et al.
(författare)
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Investigations of alkaline and enzymatic membrane cleaning of ultrafiltration membranes fouled by thermomechanical pulping process water
- 2018
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Ingår i: Membranes. - : MDPI AG. - 2077-0375. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- The pulp and paper industry is one of the most important industrial sectors worldwide, and has considerable potential for the sustainable fractionation of lignocellulosic biomass to provide valuable compounds. Ultrafiltration (UF) is a suitable separation technique for the profitable production of hemicelluloses from process water from thermomechanical pulping (ThMP), but is limited by membrane fouling. Improvements in cleaning protocols and new alternative cleaning agents are required to ensure a long membrane lifetime, and thus a sustainable process. This study, therefore, focuses on the cleaning of polymeric UF membranes after the filtration of ThMP process water, comparing alkaline with enzymatic cleaning agents. The aim was to develop a cleaning procedure that is efficient under mild conditions, resulting in a lower environmental impact. It was not possible to restore the initial permeability of the membrane when cleaning the membrane with enzymes alone, but the permeability was restored when using a two-step cleaning process with enzymes in the first step and an alkaline cleaning agent in the second step. Scanning electron microscopy gave a deeper inside into the cleaning efficiency. Attenuated total reflectance Fourier-transform infrared spectroscopy analysis confirmed that not only polysaccharides, but also extractives are adsorbed onto the membrane surface.
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| 3. |
- Thuvander, Johan, et al.
(författare)
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Reduction of energy demand by use of air sparging during ultrafiltration of alkali-extracted wheat bran hemicelluloses
- 2018
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Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762. ; 138, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- The flux during membrane filtration can be enhanced by the use of a two-phase gas–liquid flow. This has been shown to be an energy-efficient alternative to increasing the cross-flow velocity. In this work, air sparging was used to increase the flux during ultrafiltration of alkali-extracted wheat bran hemicelluloses. Batch filtration was performed in a pilot unit with a ceramic ultrafiltration membrane with a nominal cut-off of 10 kDa. Parametric studies with and without air sparging were performed at temperatures of 30 °C, 50 °C and 80 °C and cross-flow velocities of 1, 3, 5 and 7 m/s. The limiting flux was not affected by air sparging at 30 °C, while a slight increase was observed at 50 °C and a considerable increase was obtained at 80 °C. Air sparging reduced the energy demand per m3 permeate produced during dead-end batch ultrafiltration at 80 °C and 1 m/s from 0.96 kWh/m3 to 0.51 kWh/m3.
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| 4. |
-
34th EMS Summer School : Membranes in Biorefineries
- 2017
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Proceedings (redaktörskap) (refereegranskat)abstract
- The EMS Summer School “Membranes in Biorefineries” is related to Annex XVII of the Industrial Energy Related Technologies and Systems (IETS)Implementing Agreement: “Membrane Filtration for Energy-efficient Separation of Lignocellulosic Biomass Components” co-ordinated by the Department of Chemical Engineering at Lund University, Sweden.The IETS Implementing Agreement is an initiative within IEA (International Energy Agency). The mission of IETS is to foster international co-operation among OECD and non-OECD countries for accelerated research and technology development of industrial energy-related technologies and systems. In doing so, IETS seeks to enhance knowledge of cost-effective new industrial technologies and system layouts that enable increase productivity and better product quality while improving energy efficiency and sustainability.
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| 5. |
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| 6. |
- Arkell, Anders, et al.
(författare)
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Back-pulsing as an energy-saving method in the microfiltration of milk
- 2014
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 35:1, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Extended shelf-life milk can be produced by a combination of microfiltration and pasteurisation. However, due to the need for high cross-flow velocity during microfiltration, the energy consumption is high. One way of decreasing the energy demand during microfiltration is to use back-pulsing for fouling control. Microfiltration was performed in constant flux mode on skim milk to measure the fouling rate. Different frequencies and durations of back-pulsing were investigated to determine the optimal conditions. The most promising conditions were used to evaluate the degree to which the cross-flow velocity could be decreased without significantly affecting the performance of the membrane. It was found that short pulses (0.2 s) at a frequency of 1 min-1 were most efficient, and the membrane performance was only slightly affected by reducing the cross-flow velocity from 5.8 m s-1 to 4.5 m s-1 with back-pulsing. This corresponds to a reduction in the energy requirement of 50%.
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| 7. |
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| 8. |
- Arkell, Anders, et al.
(författare)
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Evaluation of membrane performance and cost estimates during recovery of sodium hydroxide in a hemicellulose extraction process by nanofiltration
- 2013
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Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 118, s. 387-393
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Tidskriftsartikel (refereegranskat)abstract
- The recovery the alkaline solvent from of a residual stream after the extraction of hemicelluloses in wheat bran was investigated. The solution was withdrawn from an ultrafiltration (UF) process in which hemicelluloses were recovered. The UF permeate, containing mainly NaOH, lignin and mono- and oligosaccharides, was treated by nanofiltration (NF). Seven NF membranes were tested in a parametric study, and the two membranes showing the best performance were further evaluated in a concentration study. The mean flux of a Koch SelRO MPF 36 and a Microdyn-Nadir NP010 membrane was about 200 l/m2 h during concentration to a volume reduction of 0.75. The retention of NaOH was <20%, while the retention of lignin and sugars was about 70% and >95%, respectively. Cost estimates for a NaOH recovery process indicated that an NF plant would have a pay-back time of less than 2 months if the plant was run continuously, and 7 months if it was used 25% of the time.
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| 9. |
- Arkell, Anders, et al.
(författare)
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Increasing flux by back-pulsing in the microfiltration of milk
- 2015
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 41, s. 23-25
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Tidskriftsartikel (refereegranskat)abstract
- Milk with extended shelf-life can be produced by microfiltration (MF) and pasteurisation in a cascade arrangement. In a previous study, we have shown that back-pulsing can be used to reduce the energy requirement in the MF of defatted milk. In this study, the influence of back-pulsing on MF was investigated at higher milk fluxes than in a prior study. The MF experiments were performed in constant-flux mode. The operational time until a certain pressure build-up was used as a measure of the performance. Fluxes between 350 and 500 L m−2 h−1 were investigated, with and without back-pulsing (frequencies ranging from 6 to 0.2 min−1). It was shown that the fouling rate was strongly dependent on the permeate flux; higher flux leading to a higher fouling rate. Improved MF performance was found using back-pulsing at a flux of 350 L m−2 h−1, while at higher fluxes, back-pulsing impaired the performance.
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| 10. |
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