Analyzing hydraulic head of fluid flow in underground porous medium

Hydraulic head is distributed through a medium with porous aspect. The analysis of hydraulic head from one point to another is used by the Richard's equation. This equation is equivalent to the groundwater ow equation that predicts the volumetric water contents. COMSOL 3.5 is used for computation applying Richard's equation. A rectangle of 100 meters of length and 10 meters of large (depth) with 0,1 m/s fl ux of inlet as source of our fl uid is simulated. The domain have Richards' equation model in two dimension (2D). Hydraulic head increases proportional with moisture content.

Brittleness of Paper

Brittleness is a well-known material characteristic but brittleness of paper is vaguely covered. The objective of this thesis was to characterize the phenomenon and causes around brittleness of paper and to clarify if it is a measurable property. Brittleness of paper was approached from the perspectives of paper physics and paper mills. Brittleness is a property of dry paper and it causes problems at the finishing stages of paper machine. According to paper physics, brittle materials fail in the elastic regime, while ductile materials can locally accumulate a plastic deformation prior to the fracture and they are often able to withstand higher stresses. Brittleness of paper is vastly affected by the surrounding conditions: paper as a hygroscopic material tries to get to the equilibrium. It is also affected by the quality of the pulp used. Measurement techniques can be divided into two categories: based on the viscoelastic behavior of paper and on the exposure to the mechanical stress of sort. The experimental part of the thesis was based on the trials with brittle and non-brittle mill-made LWC papers. It is divided into three parts: strength testing of the brittle and non-brittle papers, analysis of the conditions that may contribute the brittleness and the experimental methods to evaluate brittle behavior. The strength measurements confirmed the influence of the moisture content, but only tensile energy absorption and the fracture toughness measurements provided modest differences between the brittle and non-brittle papers. Versatile analysis of the possible contributing factors resulted into speculation, while the brittle papers contained higher amount of starch, triglycerides and steryl esters. The experimental research proved that the formation, the sensory impression and the variation of local strains may contain the crucial information of paper brittleness.

Puuhakkeen käsittely- ja poltto-ominaisuuksien parantaminen

Nykyaikana yhteiskunta tavoittelee uusiutuvaa ja ympäristöä säästävää energiantuotantoa. Biopolttoaineiden käyttö vähentää fossiilisten polttoaineiden osuutta energiantuotannossa. Jotta biopolttoaineilla voidaan korvata fossiilisia polttoaineita, biopolttoaineita täytyy jalostaa. Tämän diplomityön tarkoituksena on selvittää puuhakkeen jalostuksen merkitystä hakkeen käytölle ja kannattavuudelle. Hakkeen kuivaamisella ja seulonnalla voidaan parantaa hakkeen käsittely- ja poltto-ominaisuuksia. Kosteuden ja tasalaatuisuuden merkitys suurenee, kun haketta käytetään pienissä kattiloissa. Pienissä kattiloissa lämmöntuotannon hyötysuhde pienenee merkittävästi kosteuden suurentuessa. Tällöin polttoaineen kulutus ja energiantuotantokustannukset suurenevat. Suuremmissa kattiloissa hyvälaatuisella hakkeella on mahdollista korvata kalliimpia vara- ja huippukuormapolttoaineita, kuten öljyä. Tällöin fossiilisten polttoaineiden osuus pienenee. Lisäksi kuivaaminen ja seulominen ovat edullisia jalostusprosesseja esimerkiksi pelletin tuotantoon verrattuna.

Comparison of energy balances of steam explosion and torrefaction technologies

The present study introduce two pretreatment technologies which are torrefaction and steam explosion, and compare energy balance for both technologies to investigate and compare the use of these technologies to improve pelletization. In this research, torrefaction and steam explosion pretreatments were accomplished on the mixed small diameter wood (70%) with moisture content of 40 %, and logging residues (30%) with moisture content of 45 % at temperature 230 ̊C, and treatment duration 10 min. Competing methods were evaluated, and the results showed higher volumetric energy for steam explosion pellet than torrefied pellet.

Pressforming of a tray from a pulp sheet

The aim of this thesis work was to verify the possibility to produce tray packages directly from pulp sheets using press forming techniques. The different existing raw materials of pulp, various sources of molded pulp and different methods of production of molded pulp were studied. Nine different raw materials which were used for experimental work were provided by Stora Enso mills, and Stora Enso Research Centre, Imatra, Finland. The laboratory tests were carried out using LUT Adjustable packaging line at Lappeenranta University of Technology. The results prove that long virgin fibres of pine pulp seems to have better formability with high moisture content compared to others. No significant improvements were noticed with conditioned samples, never the less far studies has to be done to find optimal conditions for production. The results indicated the possibility for making pressformed tray from two different pulp qualities (Sunila pulp and Enopine). The method could prove to be beneficiary as the production line could be shortened and investment in board machines could be avoided if the trays were pressed directly from pulp sheets. Also the labour costs would be reduced. However, there is much work to be done before the quality of a tray produced out of a pulp sheet is comparable to a tray produced out of tray board.

Biomassan käsittely voimalaitoksissa

Tässä diplomityössä tutkitaan biomassan esikäsittelyä suurissa voimalaitoksissa. Työssä keskitytään puusta saataviin polttoaineisiin. Biomassan esikäsittely on tärkeä osa voimalaitoksen toimintaa. Sillä pyritään saamaan puulle halutut ominaisuudet loppukäyttöä, kuten polttoa tai kaasutusta varten. Puubiomassan tärkeimpiä ominaisuuksia ovat kosteus, palakoko ja tasalaatuisuus. Työ on jaettu neljään osaan. Ensimmäisessä osassa tutkitaan kiinteän biomassan ominaisuuksia ja ongelmia. Toisessa osassa esitellään erilaisia voimalaitoksissa käytettäviä puubiomassoja ja niiden erityisominaisuuksia ja -vaatimuksia. Kolmannessa osassa esitellään biomassan käsittelyä voimalaitoksella. Käsittely jaotellaan vastaanottoon, esikäsittelyyn, varastointiin ja käsittelylaitteistoihin. Kolmannessa osassa tutkitaan myös käsittelyn erityisvaatimuksia ja esitellään esimerkkejä biomassan kokonaiskäsittelystä laitoksella. Työn neljäs osa paneutuu biomassan käsittelyn turvallisuus- ja ympäristöasioihin. Puubiomassan esikäsittely on suunniteltava käytettävien puulaatujen ja -määrien mukaan. Biomassan kosteuden ollessa korkea, on tutkittava onko kuivurien käyttö kannattavaa ja perusteltua. Jos voimalaitokselle tuleva puu on epätasalaatuista tai sisältää epäpuhtauksia, on käytettävä erilaisia puhdistus- ja murskainlaitteistoja. Biomassan käsittelyssä syntyy melua ja päästöjä. Ympäristö- ja terveyshaittojen ehkäisemiseksi käsittelylaitteistoihin on suunniteltava tarpeelliset suojat ja varojärjestelmät.

Rankapuun ja -hakkeen laadun vaihtelu terminaalivarastoinnissa

Työssä tutkittiin polttoaineterminaalissa varastoitavan puupolttoaineen laadunmuutoksia. Tutkimuksessa tarkasteltiin hakettamattomien rankapuiden ja rankapuuhakkeen kosteuden ja lämpöarvon muutosta. Myös kuiva-ainetappiota tutkittiin aikaisempien tutkimusten perusteella. Tutkimusaineisto kerättiin Etelä-Savon Energian polttoaineterminaaleista. Kosteus-pitoisuuksia mitattiin Hydromette M2050 -pikakosteusmittarilla ja uunikuivaus-menetelmällä standardin SFS-EN 14774 mukaisesti. Tutkimuksessa huomattiin pikakosteusmittarin toimivan riittävän luotettavalla tasolla rankapuiden mittauksissa, mutta hakkeen mittauksissa mittari osoittautui toimimattomaksi. Varastointiaika ei vaikuttanut polttoaineiden lämpöarvoihin, mutta kosteuspitoisuus vaihteli suuresti. Tutkimustuloksista pääteltiin rangan kuivuvan terminaalivarastossa ja hakkeen kosteuden pysyvän vakiona. Energiasisällön puolesta rankapuuta voidaan varastoida yli 2 vuotta, mutta hakkeen varastointiaika tulisi pitää mahdollisimman lyhyenä.

Effect of ambient conditions on dimensional stability and stiffness of commercial paperboard and paperboard trays

The objective of this study was to develop laboratory test methods for characterizing the effects of changed moisture content on paperboard trays produced by press-forming process. Influence of moisture on the properties of unconverted paperboard such as bending stiffness, bursting strength, and curling was studied. Paperboard and tray samples were tested after storing in different relative humidity conditions (35, 50, 65, 80 and 95% RH). The effect of PE and PET extrusion coatings on these properties was also studied. It was found that increase in moisture content of paperboard decreases bending and bursting strength, dimensional stability and stiffness of paperboard trays. Such physical and mechanical properties as bending stiffness and curling of paperboard seem to define the stiffness of ready-made trays and their dimensional stability. Paperboards and trays with extruded PE and PET one sided coatings demonstrated higher strength properties but at the same time had lower dimensional stability comparing to uncoated paperboards. Samples with smaller polymer coat weight had better dimensional stability than respective samples with higher coat weight. It was also found that preconditioning of paperboard in lower humidity environment before press-forming could improve dimensional stability and stiffness of ready-made tray.

The feasibility of torrefaction for the co-firing of wood in pulverised-fuel boilers

Torrefaction is the partial pyrolysis of wood characterised by thermal degradation of predominantly hemicellulose under inert atmosphere. Torrefaction can be likened to coffee roasting but with wood in place of beans. This relatively new process concept makes wood more like coal. Torrefaction has attracted interest because it potentially enables higher rates of co-firing in existing pulverised-coal power plants and hence greater net CO2 emission reductions. Academic and entrepreneurial interest in torrefaction has sky rocketed in the last decade. Research output has focused on the many aspects of torrefaction – from detailed chemical changes in feedstock to globally-optimised production and supply scenarios with which to sustain EU emission-cutting directives. However, despite its seemingly simple concept, torrefaction has retained a somewhat mysterious standing. Why hasn’t torrefied pellet production become fully commercialised? The question is one of feasibility. This thesis addresses this question. Herein, the feasibility of torrefaction in co-firing applications is approached from three directions. Firstly, the natural limitations imposed by the structure of wood are assessed. Secondly, the environmental impact of production and use of torrefied fuel is evaluated and thirdly, economic feasibility is assessed based on the state of the art of pellet making. The conclusions reached in these domains are as follows. Modification of wood’s chemical structure is limited by its naturally existing constituents. Consequently, key properties of wood with regards to its potential as a co-firing fuel have a finite range. The most ideal benefits gained from wood torrefaction cannot all be realised simultaneously in a single process or product. Although torrefaction at elevated pressure may enhance some properties of torrefied wood, high-energy torrefaction yields are achieved at the expense of other key properties such as heating value, grindability, equilibrium moisture content and the ability to pelletise torrefied wood. Moreover, pelletisation of even moderately torrefied fuels is challenging and achieving a standard level of pellet durability, as required by international standards, is not trivial. Despite a reduced moisture content, brief exposure of torrefied pellets to water from rainfall or emersion results in a high level of moisture retention. Based on the above findings, torrefied pellets are an optimised product. Assessment of energy and CO2-equivalent emission balance indicates that there is no environmental barrier to production and use of torrefied pellets in co-firing. A long product transport distance, however, is necessary in order for emission benefits to exceed those of conventional pellets. Substantial CO2 emission reductions appear possible with this fuel if laboratory milling results carry over to industrial scales for direct co-firing. From demonstrated state-of-the-art pellet properties, however, the economic feasibility of torrefied pellet production falls short of conventional pellets primarily due to the larger capital investment required for production. If the capital investment for torrefied pellet production can be reduced significantly or if the pellet-making issues can be resolved, the two production processes could be economically comparable. In this scenario, however, transatlantic shipping distances and a dry fuel are likely necessary for production to be viable. Based on demonstrated pellet properties to date, environmental aspects and production economics, it is concluded that torrefied pellets do not warrant investment at this time. However, from the presented results, the course of future research in this field is clear.

Chemical changes in biomass during torrefaction

Torrefaction is moderate thermal treatment (~200-300 °C) of biomass in an inert atmosphere. The torrefied fuel offers advantages to traditional biomass, such as higher heating value, reduced hydrophilic nature, increased its resistance to biological decay, and improved grindability. These factors could, for instance, lead to better handling and storage of biomass and increased use of biomass in pulverized combustors. In this work, we look at several aspects of changes in the biomass during torrefaction. We investigate the fate of carboxylic groups during torrefaction and its dependency to equilibrium moisture content. The changes in the wood components including carbohydrates, lignin, extractable materials and ashforming matters are also studied. And at last, the effect of K on torrefaction is investigated and then modeled. In biomass, carboxylic sites are partially responsible for its hydrophilic characteristic. These sites are degraded to varying extents during torrefaction. In this work, methylene blue sorption and potentiometric titration were applied to measure the concentration of carboxylic groups in torrefied spruce wood. The results from both methods were applicable and the values agreed well. A decrease in the equilibrium moisture content at different humidity was also measured for the torrefied wood samples, which is in good agreement with the decrease in carboxylic group contents. Thus, both methods offer a means of directly measuring the decomposition of carboxylic groups in biomass during torrefaction as a valuable parameter in evaluating the extent of torrefaction. This provides new information to the chemical changes occurring during torrefaction. The effect of torrefaction temperature on the chemistry of birch wood was investigated. The samples were from a pilot plant at Energy research Center of the Netherlands (ECN). And in that way they were representative of industrially produced samples. Sugar analysis was applied to analyze the hemicellulose and cellulose content during torrefaction. The results show a significant degradation of hemicellulose already at 240 °C, while cellulose degradation becomes significant above 270 °C torrefaction. Several methods including Klason lignin method, solid state NMR and Py-GC-MS analyses were applied to measure the changes in lignin during torrefaction. The changes in the ratio of phenyl, guaiacyl and syringyl units show that lignin degrades already at 240 °C to a small extent. To investigate the changes in the extractives from acetone extraction during torrefaction, gravimetric method, HP-SEC and GC-FID followed by GC-MS analysis were performed. The content of acetone-extractable material increases already at 240 °C torrefaction through the degradation of carbohydrate and lignin. The molecular weight of the acetone-extractable material decreases with increasing the torrefaction temperature. The formation of some valuable materials like syringaresinol or vanillin is also observed which is important from biorefinery perspective. To investigate the change in the chemical association of ash-forming elements in birch wood during torrefaction, chemical fractionation was performed on the original and torrefied birch samples. These results give a first understanding of the changes in the association of ashforming elements during torrefaction. The most significant changes can be seen in the distribution of calcium, magnesium and manganese, with some change in water solubility seen in potassium. These changes may in part be due to the destruction of carboxylic groups. In addition to some changes in water and acid solubility of phosphorous, a clear decrease in the concentration of both chlorine and sulfur was observed. This would be a significant additional benefit for the combustion of torrefied biomass. Another objective of this work is studying the impact of organically bound K, Na, Ca and Mn on mass loss of biomass during torrefaction. These elements were of interest because they have been shown to be catalytically active in solid fuels during pyrolysis and/or gasification. The biomasses were first acid washed to remove the ash-forming matters and then organic sites were doped with K, Na, Ca or Mn. The results show that K and Na bound to organic sites can significantly increase the mass loss during torrefaction. It is also seen that Mn bound to organic sites increases the mass loss and Ca addition does not influence the mass loss rate on torrefaction. This increase in mass loss during torrefaction with alkali addition is unlike what has been found in the case of pyrolysis where alkali addition resulted in a reduced mass loss. These results are important for the future operation of torrefaction plants, which will likely be designed to handle various biomasses with significantly different contents of K. The results imply that shorter retention times are possible for high K-containing biomasses. The mass loss of spruce wood with different content of K was modeled using a two-step reaction model based on four kinetic rate constants. The results show that it is possible to model the mass loss of spruce wood doped with different levels of K using the same activation energies but different pre-exponential factors for the rate constants. Three of the pre-exponential factors increased linearly with increasing K content, while one of the preexponential factors decreased with increasing K content. Therefore, a new torrefaction model was formulated using the hemicellulose and cellulose content and K content. The new torrefaction model was validated against the mass loss during the torrefaction of aspen, miscanthus, straw and bark. There is good agreement between the model and the experimental data for the other biomasses, except bark. For bark, the mass loss of acetone extractable material is also needed to be taken into account. The new model can describe the kinetics of mass loss during torrefaction of different types of biomass. This is important for considering fuel flexibility in torrefaction plants.

Rankahakkeen laadunhallinta aumavarastoinnissa

Diplomityössä selvitettiin rankahakeaumojen peittämisen vaikutuksia laatuun voimalaitoksen polttoaineena. Selvityksen kohteena olivat aumojen sisälämpötilat eri kohdissa aumoja sekä hakkeen kosteuden muutos ja kuiva-ainetappiot varastoinnin aikana. Tutkimuksen kohteena olivat Etelä-Savon Energian polttoaineterminaaliin kootut hakeaumat. Aumojen sisäistä lämpötilaa asennettiin mittaamaan yhdeksän lämpötilasensoria kuhunkin aumaan. Hakkeiden kokonaismassat tutkimuksen alussa laskettiin aumoihin purettujen kuormien massoista. Kuormista määritettiin kosteudet ja lämpöarvot standardien mukaisesti. Näytteiden käsittely tapahtui terminaalilla ja niiden kosteus selvitettiin uunikuivausmenetelmällä. Käyttöpaikalle kuljetuksen yhteydessä kuormat punnittiin ja kosteudet mitattiin uudestaan. Tutkimuksen aikana havaittiin langattomien lämpötilasensorien lukemisen hakeaumojen sisältä olevan vaikeaa. Sensorit olivat kuitenkin pääsääntöisesti säilyneet toimintakuntoisina varastoinnin aikana ja niiden sisältämät lämpötilatiedot päästiin lukemaan aumojen purkamisen jälkeen. Tutkimuksen perusteella hakeaumojen peittäminen on kannattavaa. Hake säilyi tutkimuksen ajankohtana peitetyssä aumassa kuivempana kuin peittämättömässä. Hake ei myöskään jäädy peitteen alla yhtä paljon kuin peittämättömänä, mikä parantaa hakkeen käsiteltävyyttä kuormaa tehdessä ja voimalaitoksella. Kuiva-ainetappioista ei voitu esittää luotettavia tuloksia kokeen keskeydyttyä sään takia.

Jätteiden kemiallisten ominaisuuksien spektrometriset online-mittausmenetelmät

Tässä diplomityössä käsiteltiin spektrometrisia online-mittausmenetelmiä jätteiden kemiallisten ja fysikaalisten ominaisuuksien määrittämiseksi. Tavoitteena oli selvittää, mitä ominaisuuksia menetelmillä voidaan mitata ja kuinka luotettavia tuloksia mittauksilla saadaan. Diplomityössä suoritettiin kirjallisuuskatsaus, jossa käsiteltiin kolmen spektrometrisen menetelmän soveltuvuutta reaaliaikaisiin jätemittauksiin. Työn empiirisessä osassa FPXRFanalysaattorilla mitattiin neljän eri jätenäytteen alkuainepitoisuuksia. Mittauksen tarkoituksena oli selvittää, mitä alkuaineita menetelmällä voidaan mitata. FPXRF-analysaattorilla saatuja tuloksia verrattiin ICP-MS-menetelmällä saatuihin tuloksiin regressioanalyysin avulla. Työssä todettiin, että FPXRF-analysaattori sopii parhaiten kaliumin, kalsiumin, ja raudan pitoisuuksien määrittämiseen. Lisäksi lyijyn, sinkin, kromin, kloorin, kuparin, kadmiumin, arseenin, fosforin, molybdeenin ja vanadiinin määrittäminen on mahdollista, mutta tarkan pitoisuuden saamiseksi laboratoriomenetelmien käyttö voi olla tarpeen. Tutkituista jätenäytteistä menetelmä soveltui parhaiten tuhkalle ja kompostille niiden fyysisten ominaisuuksien, kuten homogeenisuuden ja kosteuspitoisuuden takia. Biojätteelle menetelmä soveltui huonosti. FPXRF-analysaattorin luotettavuuteen vaikuttaa näytteen kosteuspitoisuus, homogeenisuus, partikkelikoko, mittaustapa ja laitteen kalibrointi. Työssä tarkastelluilla menetelmillä ei voida tällä hetkellä täysin korvata laboratorioanalyyseja. FPXRF-analysaattoria voidaan kuitenkin käyttää kvalitatiiviseen tai semikvantitatiiviseen haitta-aineiden analysointiin, millä voidaan vähentää kalliiden laboratorioanalyysien tarvetta.