The removal of lignin in a Kraft pulp mill, with the aim to utilize the lignin as more value added green product than just firing lignin in black liquor, is possible with a LignoBoost plant. The LignoBoost plant uses sulfuric acid in the process and this results in an increased net input of sulfur to the pulp mills recovery cycle. The sodium/sulfur balance in a Kraft pulp mill is an important factor to be able to run a mill optimal. The increased input of sulfur into the mill when implementing a LignoBoost plant is therefore an issue to address. A too high sulfur/sodium ratio in the Kraft pulp mill is often solved by purging electrostatic precipitator dust from the recovery boiler. The major component of the ESP dust is sodium sulfate. When purging ESP dust from the recovery boiler the mill loose sodium and the need of sodium make-up increases. A large extent of the ESP dust that is not purged is returned to the recovery cycle of the mill via the evaporation plant. If the recycled sodium sulfate could be split and returned to the recovery cycle as one controlled sodium- and one controlled sulfur component or at least split into two flows where sulfur is enriched in one flow and sodium in the other flow, the sodium/sulfur balance would be easier controlled. In this master thesis the split of sodium and sulfur in sodium sulfate is addressed. The aim is to study opportunities to: • Enrich sodium and sulfur in two flows from the dissolved ESP dust, which is normally recycled to the evaporation plant. • Produce one sulfur component and one sodium component that can be utilized in the Kraft pulp mill, especially in an integrated LignoBoost process. • Accomplish this by using an electrochemical split of the sodium sulfate from the ESP dust to generate sodium hydroxide and sulfuric acid.   To be able to produce one sulfur component and one sodium component from the dissolved ESP dust an electrodialysis with or without bipolar membranes is the method to use decided after contact with Eka Chemicals research and development department and literature studies. An electrodialysis cell produces sodium hydroxide and sulfuric acid, from the sodium sulfate solution, that can be used in the Kraft pulp mill. The difficulty by using an electrochemical cell with ion selective membranes is the need of a pure feed to the cell. If a high content of contaminations, such as multivalent ions, is present in the feed solution to the cell scaling can be formed. Scaling leads to shorter membrane life that result in higher operational cost for the cell stack. Due to the multivalent ions in the electrostatic dust a pre-treatment such as carbonate- and hydroxide precipitation removal of the ions is suggested, which results in a decrease of the multivalent ions in the feed solution.   In previous work concerning electrochemical split of sodium sulfate the lack of utilization for the produced acid became negative in an economical point of view. The need of sulfuric acid to the LignoBoost plant is an advantage for the economical study. In this master thesis is:   • An economical case study for the implementation of an electrochemical cell, electrodialysis with or without a bipolar membrane, in a Kraft pulp mill performed. • A sensitivity analysis performed and evaluated in the aim of addressing the change in payback time due to alternating: Sodium price Membrane life Utilization of the acid produced from the electrochemical cell. The economical case study concerns a Kraft pulp mill with a LignoBoost plant. Utilization of the acid to the LignoBoost- and tall oil plant is varied, as is the membrane life for the cell stack. The membrane life is varied due to the difficulty of predicting the ESP-feed solutions affect on the membranes. The feed solution has to be tested in a cell to decide the real life for the membrane in this case.   The electrodialysis cell with bipolar membranes indicates promising economical gain for future implementation in a mill with LignoBoost lignin removal compared to the electrodialysis cell that indicates no economical gain for future implementation in a mill. For a mill with both a LignoBoost plant and a tall oil plant, i.e. optimized utilization of acid from the electrodialysis with bipolar membrane, and a five years membrane life in the cell, a payback of one and a half year can be reached. The same case but for an electrodialysis results in nine and a half payback years. The sensitivity analysis show that compared to the electrodialysis with bipolar membrane, the electrodialysis cell is more vulnerable to changes for the acid utilization, sodium hydroxide price and membrane life. The BME cell is most affected by changes in the sodium hydroxide price and the ED cell affects most by changes in the membrane life.

The LignoBoost process is a valuable supplement to the Kraft process. It can increase the pulp production rate of a Kraft mill and it enables lignin separation from black liquor with a high degree of purity. However, residual xylan in black liquor has been observed to increase filtration resistance of lignin during the LignoBoost process. In order to uncover underlying mechanisms, this thesis investigates the potential influence of xylan during lignin precipitation and filtration, which are the two main steps of the LignoBoost process. For this purpose experiments based on a model system were designed. Model liquors consisted of lignin and xylan as the only organic compounds and contained lower salt concentrations (4.2-5.9 wt%) compared to black liquor. Furthermore, reference liquors were prepared without xylan addition. Precipitation mechanisms were studied in the onset precipitation region (i.e. alkaline regime) by in-situ focused beam reflectance measurements (FBRM) during step-by-step acidic precipitation of the model liquor. It was found that the onset precipitation pH does not change with the presence of xylan as all liquors started precipitation around pH 9.15. The filtration process was investigated on model liquors that had been precipitated by fast acidification to acidic regimes (pH 6.5-2.87). The use of FBRM during acid precipitation of model liquors suggested that temperature had a significant influence on the chord length distribution (CLD) of the particles. In all filtration experiments, a decrease in CLD was observed when the temperature was changed from 80 °C to 25 °C. Moreover, this thermal instability of particles seemed to be higher when added xylan was present in the liquor. The investigation of the resulting filer cakes with HPLC showed that xylan was evenly distributed through the cake. Further findings on the influence of xylan were impeded due to variations in ionic strength in the model liquors. It was found that the effect of ionic strength on filtration properties and particle sizes overshadows the effect of xylan. Higher ionic strength was observed to yield a lower filtration resistance, a higher solidosty, larger particles and lower solid surface area, as investigated by filtration measurements, laser diffraction and BET analysis. Finally, xylan was fluorescently tagged (i.e. dyed) with Remazol Brilliant Blue R to investigate xylan position in the ligninxylan filer cake, using a confocal fluorescence microscope. However, due to the autofluorescence of lignin as well as low emission intensity of the synthesized dyed xylan, xylan could not been tracked within the lignin particle. Nevertheless, valuable insight was gained into the preparation of dyed xylan and the bond stability.

Made available in DSpace on 2015-03-26T14:01:03Z (GMT). No. of bitstreams: 1 texto completo.pdf: 684853 bytes, checksum: 5aab9bbea25fa23492af8fc69a587a05 (MD5) Previous issue date: 2010-06-10 / Efforts to develop new sources of energy from renewable resources has greatly increased. Great efforts have been made in pulp mills to incorporate in foreseeable future biorefineries operations to simultaneously achieve production of pulp and biofuels aiming total or partial substitution of fossil fuels. The objective of this study was to evaluate the feasibility of using LignoBoost technology in a modern eucalyptus pulp mill and its impact in the mill energy matrix and greenhouse gases emissions. / Tem aumentado grandemente os esforços para desenvolvimento de novas fontes de energia proveniente de recursos renováveis. Grandes esforços têm sido realizados, em fábricas de celulose, para que, num futuro próximo, possam ser incorporadas nestas empresas operações de biorefinarias, visando produção simultânea de celulose e biocombustíveis para substituição total ou parcial de combustíveis fósseis. O objetivo deste trabalho foi avaliar a viabilidade do uso da tecnologia LignoBoost em uma moderna fábrica de celulose kraft de eucalipto e seus impactos na matriz energética e na emissão de gases de efeito estufa.

Carbon fiber is a lightweight, versatile material with many current and potential applications. To be able to expand the market for carbon fiber composites in other areas than special applications the production costs must be reduced. One way of accomplishing this could be to use a less expensive raw material where lignin is a good example as it can be provided at lower cost, is renewable and abundantly available compared to commercially used raw materials today. So far, the mechanical properties of lignin-based carbon fibers are inferior relative to commercial carbon fibers. For lignin-based carbon fibers to enter the commercial market more research is necessary to gain knowledge of the conversion of lignin to carbon fiber. The LightFibre project investigates the possibilities to produce carbon fibers based on a mixture of softwood kraft lignin and cellulose. The kraft lignin is isolated from black liquor in the kraft/sulfate process with the LignoBoost process. This master thesis project was conducted within in the LightFibre project and evaluated whether metal ions generally present in kraft lignin had an influence on the final carbon fiber quality in terms of mechanical properties and morphology. The mechanical properties were determined with tensile testing, the morphology by scanning electron microscopy (SEM) and the relative abundance of studied elements with electron dispersive spectroscopy (EDS). The influence of the chosen metal ions was tested by impregnation of dry-jet wet spun prefibers based on 70 wt.% softwood kraft lignin and 30 wt.% dissolving pulp cellulose. The fibers were impregnated in room temperature with solutions containing Na2SO4, K2SO4, MgSO4, FeSO4 and Al2(SO4)3 salts where the cations were the focus in these trials. The concentrations used for impregnation were 0.2 and 1M of the cations. The obtained mechanical properties of the carbon fibers of the samples impregnated with different metal ions did not deviate significantly from the reference which had a tensile strength of 870 MPa and tensile modulus of 68 GPa. The analysis of morphology with SEM showed no defects or damage of any of the fibers. Therefore, it was concluded that the impregnated metal ions: K+, Na+, Al3+, Mg2+ and Fe2+ at the obtained levels in the fibers cause no effects on the fibers during the stabilization and carbonization that affects the mechanical performance of final carbon fiber.  The amount of potassium in one of the samples was estimated to 0.1 wt.%. From the results of this study it may be suggested that the general recommendation of <0.1 wt.% ash in lignin can be exceeded, for dry-jet wet-spun kraft lignin/cellulose-based carbon fibers.