Modeling of water/steam circulation in Circulating Fluidized Bed boiler

A distinctive design feature of steam boiler with natural circulation is the presence of the steam drum which plays a role of the separator of vapor from the flow of water-and-steam mixture coming into steam drum from the furnace tubes. Steam drum with unheated downcomer tubes, deducing from it, and riser (screen/furnace tubes) inside the furnace is a closed circulation loop in which movement of water (downcomer tubes) and water-and-steam mixture (riser tubes) is organized. The movement of the working fluid is appears due to occurrence of the natural pressure, determined by the difference in hydrostatic pressure and the mass of water and water-and-steam mixtures in downcomer and riser tubes and called the driving pressure of the natural circulation: S drive = H steam (ρ down + ρ mix) g where: ρ down - density of water in downcomer tubes; ρ mix - density of water in riser tubes; H steam - height of steam content section; g - acceleration of gravity. In steam boilers with natural circulation the circulation rate is usually between 10 and 30. Thus, consumption of water in the circulation circuit “circulation rate times” more than steam output of the boiler. There are two aspects of the design of natural water circulation loops. One is to ensure a sufficient mass flux of circulating water to avoid burnout of evaporator tubes. The other is to avoid tube wall temperature fluctuation and tube vibration due to oscillation of circulation velocity. The design criteria are therefore reduced, in principle, to those of critical heat flux, critical flow rate for burnout, and flow instability. In practical design, however, the circulation velocity and the void fraction at the evaporator tube outlet are used as the design criteria (Seikan I., et. al., 1999). This study has been made with assumption that the heat flux in the furnace of the boiler even all the time. The target of the study was to define the circulation rate of the boiler, thus average heat flux do not change it. I would like to acknowledge professionals from “Foster Wheeler” company for good and comfortable cooperation.

Roal Oy:n käyttöhyödykejärjestelmän arviointi, optimointi ja raportointi

Prosessiteollisuudessa tarvitaan usein erilaisia apujärjestelmiä pääprosessin tueksi. Tyypillisiä tällaisia järjestelmiä ovat jäähdytys-, höyry- ja ilmajärjestelmät. Hyödykejärjestelmien kehitys jää helposti pääprosessin varjoon, joka usein johtaa tarpeettoman suuriin hyödykekustannuksiin ja järjestelmien teknisen tilan laskuun. Työn kirjallisuusosassa käsitellään Roal Oy:n fermentointiprosessin kannalta olennaisimpia hyödykevaatimuksia, niiden laskennallista ilmaisua ja vuorovaikutuksia sekä PINCH-menetelmää lämpöenergian hyötykäyttöön. Jäähdytysjärjestelmän osalta käydään läpi merkittävimmät laitetekniset ratkaisut, jäähdytystorni ja lämpöpumppu, toimintaperiaatteineen sekä luonnonvesien käyttö jäähdytykseen. Työn soveltavassa osassa seurattiin Aspergillus, Trichoderma ja Bacillus fermentointeja, joiden pohjalta luotiin kasvatuskohtainen empiirinen malli jäähdytystarpeen arviointiin perustuen sekoitustehoon, kasvatuksen hiilidioksidituottoon ja haihtumisen vaikutukseen. Kasvatuksien aikana seurattiin myös tilavuusperusteista lämmönsiirtokerrointa. Mitattujen lämmönsiirtokertoimien perustella laskettiin ominaislämmöntuottoon perustuva maksimilämpötila käytettävälle jäähdytysvedelle ja fermentorien maksimitilavuudet tunnetuilla kasvatusparametreilla eri lämpöisille jäähdytysvesille. Soveltavassa osassa käydään myös läpi Roalin höyry- ja kuumavesikulutukset ja tärkeimmät käyttökohteet. Mittaustulosten ja mallien perusteella on tehtiin kehitysehdotukset hyödykejärjestelmän optimoimiseksi.

Simulation of Solid Processes by Aspen Plus

Solid processes are used for obtaining the valuable minerals. Due to their worth, it is obligatory to perform different experiments to determine the different values of these minerals. With the passage of time, it is becoming more difficult to carry out these experiments for each mineral for different characteristics due to high labor costs and consumption of time. Therefore, scientists and engineers have tried to overcome this issue. They made different software to handle this problem. Aspen is one of those software for the calculation of different parameters. Therefore, the aim of this report was to do simulation for solid processes to observe different effect for minerals. Different solid processes like crushing, screening; filtration and crystallization were simulated by Aspen Plus. The simulation results are obtained by using this simulation software and they are described in this thesis. It was noticed that the results were acceptable for all solid processes. Therefore, this software can be used for the designing of crushers by calculating the power consumption of crushers, can design the filter and for the calculation of material balance for all processes.

Modeling and simulation of forced-air cooling of strawberries using variable convective coefficient

In the forced-air cooling process of fruits occurs, besides the convective heat transfer, the mass transfer by evaporation. The energy need in the evaporation is taken from fruit that has its temperature lowered. In this study it has been proposed the use of empirical correlations for calculating the convective heat transfer coefficient as a function of surface temperature of the strawberry during the cooling process. The aim of this variation of the convective coefficient is to compensate the effect of evaporation in the heat transfer process. Linear and exponential correlations are tested, both with two adjustable parameters. The simulations are performed using experimental conditions reported in the literature for the cooling of strawberries. The results confirm the suitability of the proposed methodology.

Evaluation of empirical methods to estimate reference evapotranspiration in Uberaba, State of Minas Gerais, Brazil

Evapotranspiration is the process of water loss of vegetated soil due to evaporation and transpiration, and it may be estimated by various empirical methods. This study had the objective to carry out the evaluation of the performance of the following methods: Blaney-Criddle, Jensen-Haise, Linacre, Solar Radiation, Hargreaves-Samani, Makkink, Thornthwaite, Camargo, Priestley-Taylor and Original Penman in the estimation of the potential evapotranspiration when compared to the Penman-Monteith standard method (FAO56) to the climatic conditions of Uberaba, state of Minas Gerais, Brazil. A set of 21 years monthly data (1990 to 2010) was used, working with the climatic elements: temperature, relative humidity, wind speed and insolation. The empirical methods to estimate reference evapotranspiration were compared with the standard method using linear regression, simple statistical analysis, Willmott agreement index (d) and performance index (c). The methods Makkink and Camargo showed the best performance, with "c" values ​​of 0.75 and 0.66, respectively. The Hargreaves-Samani method presented a better linear relation with the standard method, with a correlation coefficient (r) of 0.88.

Jatropha seed oil content and yield under different irrigation and potassium fertilization levels

The aim of this research was to evaluate the effects of different irrigation depths and potassium dosages, of Jatropha seed oil content and yield. The experimental design used was randomized blocks, in split-plots, with four replicates. The treatments were four water depths (plots) and four potassium dosages (subplots) applied through irrigation water. The water depths were applied based on the percentage of accumulated evaporation of a Class A (ECA) tank and of rainfall, as following: L0 = without irrigation, L40, L80 and L120, representing 40, 80 and 120% of the balance, respectively. The potassium dosages were K30, K60, K90 and K120 (30, 60, 90 and 120kg ha-1 of potassium, respectively). The oil extraction of samples was done through chemical extraction by organic solvent. The seeds used in this test were from the sampling of two seed productions from 2009, second year of crop production. It was possible to observe that irrigation use increased oil yield and decreased the oil content of Jatropha seed. Potassium fertilization did not influence oil content and yield. There was a relative increase of efficiency in water use producing oil until certain water depth, and after that there was a decrease.

Irrigation management in pruned coffee tree crop

It was evaluated the effect of irrigation management on the production characteristics of coffee cultivar Acaiá MG-1474, planted in spacing of 3.00 m x 0.60 m, pruned in 2004, and irrigated by drip since the planting, in 1997. The experimental designed used was of randomized blocks with five treatments and four replications. The treatments consisted of irrigation management strategies, applying or not applying controlled moisture deficit in layer of 0 to 0.4m, in dry seasons of the year: A = no irrigation (control), B = irrigation during all year considering the factor of water availability in the soil (f) equal to 0.75, C = irrigation during all year considering f = 0.25, D = irrigation during all year, but in January /February /March /July /October /November /December with f = 0.25 and April /May /June /August /September with f = 0.75, E = irrigation only during April /May /June /August /September with f = 0.25. From July /2005 to June /2007 the applied water depth was defined based on Class A pan evaporation (ECA) and the period from July/2007 to June/2008 based on readings of matric potential of soil obtained from Watermark® sensors. Each plot consisted of three rows with ten plants per row, considering as useful plot five plants of center line. The results indicated that the E irrigation management was the most suitable for technical reasons.

Irrigation with domestic treated sewage and nitrogen fertilizing in sunflower cultivation

The objective of this study was to evaluate the productive performance of sunflower plants irrigated with different levels of domestic treated sewage and groundwater well with different doses of nitrogen. It was used randomized blocks design in split-split plots with four replications. In the plots, we evaluated the effect of two types of irrigation water, in the subplots we evaluated the five irrigation levels expressed as 25, 50, 75, 100 and 125% of the Class A pan Evaporation (CAE), and in the sub subplots, we evaluated the effect of four different doses of nitrogen (25, 50, 75 and 100 kg ha-1). The irrigation of sunflower with domestic sewage produced greater yield potential of grain and oil. The use of water from treated wastewater can replace up to 50 kg N ha-1 without affecting productivity. It is recommended for the commercial production of sunflower the use of treated sewage water with irrigation depth relative to 100% of CAE (296.64 mm) and nitrogen of 25 kg ha-1.

Technology for sugarcane agroindustry waste reuse as granulated organomineral fertilizer

Aiming to evaluate the use of sugarcane industry waste such as byproducts from vinasse concentration process, it was assessed the organomineral fertilizer BIOFOM (concentrated vinasse, filter cake, boiler ash, soot from chimneys and supplemented with mineral fertilizers). The study included characterization and agronomic potential analysis of a test plant (corn), by noting the differences between mineral fertilizers and BIOFOM fertilization until 45 days after sowing. The technology traditionally used to produce BIOFOM was based on vinasse evaporation with high heat transfer coefficients. It was observed that the technology, which can be formulated according to the needs of any crop, could be used in many cases as mineral fertilizer. Therefore, the use of this organomineral fertilizer reduces waste generation of sugarcane industry.

Corrosion behaviour of boiler tube materials during combustion of fuels containing Zn and Pb

Många förbränningsanläggningar som bränner utmanande bränslen såsom restfraktioner och avfall råkar ut för problem med ökad korrosion på överhettare och/eller vattenväggar pga. komponenter i bränslena som är korrosiva. För att minimera problemen i avfallseldade pannor hålls ångparametrarna på en relativt låg nivå, vilket drastiskt minskar energiproduktionen. Beläggningarna i avfallseldade pannor består till största delen av element som är förknippade med högtemperaturkorrosion: Cl, S, alkalimetaller, främst K och Na, och tungmetaller som Pb och Zn, och det finns också indikationer av Br-förekomst. Det låga ångtrycket i avfallseldade pannor påverkar också stålrörens temperatur i pannväggarna i eldstaden. I dagens läge hålls temperaturen normalt vid 300-400 °C. Alkalikloridorsakad (KCl, NaCl) högtemperaturkorrosion har inte rapporterats vara relevant vid såpass låga temperaturer, men närvaro av Zn- och Pb-komponenter i beläggningarna har påvisats förorsaka ökad korrosion redan vid 300-400 °C. Vid förbränning kan Zn och Pb reagera med S och Cl och bilda klorider och sulfater i rökgaserna. Dessa tungmetallföreningar är speciellt problematiska pga. de bildar lågsmältande saltblandningar. Dessa lågsmältande gasformiga eller fasta föreningar följer rökgasen och kan sedan fastna eller kondensera på kallare ytor på pannväggar eller överhettare för att sedan bilda aggressiva beläggningar. Tungmetallrika (Pb, Zn) klorider och sulfater ökar risken för korrosion, och effekten förstärks ytterligare vid närvaro av smälta. Motivet med den här studien var att få en bättre insikt i högtemperaturkorrosion förorsakad av Zn och Pb, samt att undersöka och prediktera beteendet och motståndskraften hos några stålkvaliteter som används i överhettare och pannväggar i tungmetallrika förhållanden och höga materialtemperaturer. Omfattande laboratorie-, småskale- och fullskaletest utfördes. Resultaten kan direkt utnyttjas i praktiska applikationer, t.ex. vid materialval, eller vid utveckling av korrosionsmotverkande verktyg för att hitta initierande faktorer och förstå deras effekt på högtemperaturkorrosion.

Understanding the in vitro dissolution rate of glasses with respect to future clinical applications

Glass is a unique material with a long history. Several glass products are used daily in our everyday life, often unnoticed. Glass can be found not only in obvious applications such as tableware, windows, and light bulbs, but also in tennis rackets, windmill turbine blades, optical devices, and medical implants. The glasses used at present as implants are inorganic silica-based melt-derived compositions mainly for hard-tissue repair as bone graft substitute in dentistry and orthopedics. The degree of glass reactivity desired varies according to implantation situation and it is vital that the ion release from any glasses used in medical applications is controlled. Understanding the in vitro dissolution rate of glasses provides a first approximation of their behavior in vivo. Specific studies concerning dissolution properties of bioactive glasses have been relatively scarce and mostly concentrated to static condition studies. The motivation behind this work was to develop a simple and accurate method for quantifying the in vitro dissolution rate of highly different types of glass compositions with interest for future clinical applications. By combining information from various experimental conditions, a better knowledge of glass dissolution and the suitability of different glasses for different medical applications can be obtained. Thus, two traditional and one novel approach were utilized in this thesis to study glass dissolution. The chemical durability of silicate glasses was tested in water and TRIS-buffered solution at static and dynamic conditions. The traditional in vitro testing with a TRISbuffered solution under static conditions works well with bioactive or with readily dissolving glasses, and it is easy to follow the ion dissolution reactions. However, in the buffered solution no marked differences between the more durable glasses were observed. The hydrolytic resistance of the glasses was studied using the standard procedure ISO 719. The relative scale given by the standard failed to provide any relevant information when bioactive glasses were studied. However, the clear differences in the hydrolytic resistance values imply that the method could be used as a rapid test to get an overall idea of the biodegradability of glasses. The standard method combined with the ion concentration and pH measurements gives a better estimate of the hydrolytic resistance because of the high silicon amount released from a glass. A sensitive on-line analysis method utilizing inductively coupled plasma optical emission spectrometer and a flow-through micro-volume pH electrode was developed to study the initial dissolution of biocompatible glasses. This approach was found suitable for compositions within a large range of chemical durability. With this approach, the initial dissolution of all ions could be measured simultaneously and quantitatively, which gave a good overall idea of the initial dissolution rates for the individual ions and the dissolution mechanism. These types of results with glass dissolution were presented for the first time during the course of writing this thesis. Based on the initial dissolution patterns obtained with the novel approach using TRIS, the experimental glasses could be divided into four distinct categories. The initial dissolution patterns of glasses correlated well with the anticipated bioactivity. Moreover, the normalized surface-specific mass loss rates and the different in vivo models and the actual in vivo data correlated well. The results suggest that this type of approach can be used for prescreening the suitability of novel glass compositions for future clinical applications. Furthermore, the results shed light on the possible bioactivity of glasses. An additional goal in this thesis was to gain insight into the phase changes occurring during various heat treatments of glasses with three selected compositions. Engineering-type T-T-T curves for glasses 1-98 and 13-93 were stablished. The information gained is essential in manufacturing amorphous porous implants or for drawing of continuous fibers of the glasses. Although both glasses can be hot worked to amorphous products at carefully controlled conditions, 1-98 showed one magnitude greater nucleation and crystal growth rate than 13-93. Thus, 13-93 is better suited than 1-98 for working processes which require long residence times at high temperatures. It was also shown that amorphous and partially crystalline porous implants can be sintered from bioactive glass S53P4. Surface crystallization of S53P4, forming Na2O∙CaO∙2SiO2, was observed to start at 650°C. The secondary crystals of Na2Ca4(PO4)2SiO4, reported for the first time in this thesis, were detected at higher temperatures, from 850°C to 1000°C. The crystal phases formed affected the dissolution behavior of the implants in simulated body fluid. This study opens up new possibilities for using S53P4 to manufacture various structures, while tailoring their bioactivity by controlling the proportions of the different phases. The results obtained in this thesis give valuable additional information and tools to the state of the art for designing glasses with respect to future clinical applications. With the knowledge gained we can identify different dissolution patters and use this information to improve the tuning of glass compositions. In addition, the novel online analysis approach provides an excellent opportunity to further enhance our knowledge of glass behavior in simulated body conditions.

Liquid transportation and distribution during (re)wetting : impact on coated papers in printing

In many industrial applications, such as the printing and coatings industry, wetting of porous materials by liquids includes not only imbibition and permeation into the bulk but also surface spreading and evaporation. By understanding these phenomena, valuable information can be obtained for improved process control, runnability and printability, in which liquid penetration and subsequent drying play important quality and economic roles. Knowledge of the position of the wetting front and the distribution/degree of pore filling within the structure is crucial in describing the transport phenomena involved. Although exemplifying paper as a porous medium in this work, the generalisation to dynamic liquid transfer onto a surface, including permeation and imbibition into porous media, is of importance to many industrial and naturally occurring environmental processes. This thesis explains the phenomena in the field of heatset web offset printing but the content and the analyses are applicable in many other printing methods and also other technologies where water/moisture monitoring is crucial in order to have a stable process and achieve high quality end products. The use of near-infrared technology to study the water and moisture response of porous pigmented structures is presented. The use of sensitive surface chemical and structural analysis, as well as the internal structure investigation of a porous structure, to inspect liquid wetting and distribution, complements the information obtained by spectroscopic techniques. Strong emphasis has been put on the scale of measurement, to filter irrelevant information and to understand the relationship between interactions involved. The near-infrared spectroscopic technique, presented here, samples directly the changes in signal absorbance and its variation in the process at multiple locations in a print production line. The in-line non-contact measurements are facilitated by using several diffuse reflectance probes, giving the absolute water/moisture content from a defined position in the dynamic process in real-time. The nearinfrared measurement data illustrate the changes in moisture content as the paper is passing through the printing nips and dryer, respectively, and the analysis of the mechanisms involved highlight the roles of the contacting surfaces and the relative liquid carrier properties of both non-image and printed image areas. The thesis includes laboratory studies on wetting of porous media in the form of coated paper and compressed pigment tablets by mono-, dual-, and multi-component liquids, and paper water/moisture content analysis in both offline and online conditions, thus also enabling direct sampling of temporal water/moisture profiles from multiple locations. One main focus in this thesis was to establish a measurement system which is able to monitor rapid changes in moisture content of paper. The study suggests that near-infrared diffuse reflectance spectroscopy can be used as a moisture sensitive system and to provide accurate online qualitative indicators, but, also, when accurately calibrated, can provide quantification of water/moisture levels, its distribution and dynamic liquid transfer. Due to the high sensitivity, samples can be measured with excellent reproducibility and good signal to noise ratio. Another focus of this thesis was on the evolution of the moisture content, i.e. changes in moisture content referred to (re)wetting, and liquid distribution during printing of coated paper. The study confirmed different wetting phases together with the factors affecting each phase both for a single droplet and a liquid film applied on a porous substrate. For a single droplet, initial capillary driven imbibition is followed by equilibrium pore filling and liquid retreat by evaporation. In the case of a liquid film applied on paper, the controlling factors defining the transportation were concluded to be the applied liquid volume in relation to surface roughness, capillarity and permeability of the coating giving the liquid uptake capacity. The printing trials confirmed moisture gradients in the printed sheet depending on process parameters such as speed, fountain solution dosage and drying conditions as well as the printed layout itself. Uneven moisture distribution in the printed sheet was identified to be one of the sources for waving appearance and the magnitude of waving was influenced by the drying conditions.

Recovery of carboxylic acids from aqueous streams by extraction and back extraction

Separation of carboxylic acids from aqueous streams is an important part of their manufacturing process. The aqueous solutions are usually dilute containing less than 10 % acids. Separation by distillation is difficult as the boiling points of acids are only marginally higher than that of water. Because of this distillation is not only difficult but also expensive due to the evaporation of large amounts of water. Carboxylic acids have traditionally been precipitated as calcium salts. The yields of these processes are usually relatively low and the chemical costs high. Especially the decomposition of calcium salts with sulfuric acid produces large amounts of calcium sulfate sludge. Solvent extraction has been studied as an alternative method for recovery of carboxylic acids. Solvent extraction is based on mixing of two immiscible liquids and the transfer of the wanted components form one liquid to another due to equilibrium difference. In the case of carboxylic acids, the acids are transferred from aqueous phase to organic solvent due to physical and chemical interactions. The acids and the extractant form complexes which are soluble in the organic phase. The extraction efficiency is affected by many factors, for instance initial acid concentration, type and concentration of the extractant, pH, temperature and extraction time. In this paper, the effects of initial acid concentration, type of extractant and temperature on extraction efficiency were studied. As carboxylic acids are usually the products of the processes, they are wanted to be recovered. Hence the acids have to be removed from the organic phase after the extraction. The removal of acids from the organic phase also regenerates the extractant which can be then recycled in the process. The regeneration of the extractant was studied by back-extracting i.e. stripping the acids form the organic solution into diluent sodium hydroxide solution. In the solvent regeneration, the regenerability of different extractants and the effect of initial acid concentration and temperature were studied.

Vesihöyrypiirin kiertolaskenta kuplapetikattilassa

Työssä selvitetään kiertolaskennan periaatteita kuplapetikattilassa, esitetään lyhyesti kattilan toimintaperiaate ja paneudutaan alan laskentaohjelmistoihin. Luonnonkierto kattilan vesihöyrypiirissä on seurausta hydrostaattisesta paineesta, joka aiheutuu tiheyserosta nousu- ja laskuputkien välillä. Kiertolaskennassa on huomioitava kaksifaasivirtauksen ominaispiirteet. Höyry ja neste virtaavat putkistossa eri nopeuksilla, jolloin esimerkiksi painehäviön määrityksessä käytetään erilaisia korrelaatioita ja käyrästöjä. Kaksifaasivirtauksen laskennassa tarvitaan kolmea eri taseyhtälöä: energiatasetta, massatasetta ja liikemäärätasetta. Luonnonkiertokattiloissa höyrykierron suunnittelussa on kaksi pääasiallista ehtoa. Ensimmäiseksi tulee varmistaa riittävä kiertoveden massavirta, jotta vältetään höyrystinputkien puhki palaminen. Toiseksi tulee välttää höyrystinputken pinnan lämpötilavaihteluita ja värähtelyitä. Alustavassa luonnonkierron mitoituksessa turvaudutaan kokemusperäiseen tietoon. Myöhemmässä tarkemmassa mitoituksessa käytettäviä ohjelmistoja ovat NOWA sekä kaupalliset PPSD ja Apros. Laskenta lähtee liikkeelle siitä, että lasketaan ensin vesihöyrykierron massavirrat erilaisilla lämpökuormilla ja höyryntuotanto määritellään painehäviöiden perusteella. NOWA- ja PPSD- ohjelmistoilla tehtyjen esimerkkilaskelmien perusteella voidaan sanoa, että tulokset riippuvat käytetystä laskentamallista.

Characterisation of Laser Beam and Paper Material Interaction

It is known already from 1970´s that laser beam is suitable for processing paper materials. In this thesis, term paper materials mean all wood-fibre based materials, like dried pulp, copy paper, newspaper, cardboard, corrugated board, tissue paper etc. Accordingly, laser processing in this thesis means all laser treatments resulting material removal, like cutting, partial cutting, marking, creasing, perforation etc. that can be used to process paper materials. Laser technology provides many advantages for processing of paper materials: non-contact method, freedom of processing geometry, reliable technology for non-stop production etc. Especially packaging industry is very promising area for laser processing applications. However, there are only few industrial laser processing applications worldwide even in beginning of 2010´s. One reason for small-scale use of lasers in paper material manufacturing is that there is a shortage of published research and scientific articles. Another problem, restraining the use of laser for processing of paper materials, is colouration of paper material i.e. the yellowish and/or greyish colour of cut edge appearing during cutting or after cutting. These are the main reasons for selecting the topic of this thesis to concern characterization of interaction of laser beam and paper materials. This study was carried out in Laboratory of Laser Processing at Lappeenranta University of Technology (Finland). Laser equipment used in this study was TRUMPF TLF 2700 carbon dioxide laser that produces a beam with wavelength of 10.6 μm with power range of 190-2500 W (laser power on work piece). Study of laser beam and paper material interaction was carried out by treating dried kraft pulp (grammage of 67 g m-2) with different laser power levels, focal plane postion settings and interaction times. Interaction between laser beam and dried kraft pulp was detected with different monitoring devices, i.e. spectrometer, pyrometer and active illumination imaging system. This way it was possible to create an input and output parameter diagram and to study the effects of input and output parameters in this thesis. When interaction phenomena are understood also process development can be carried out and even new innovations developed. Fulfilling the lack of information on interaction phenomena can assist in the way of lasers for wider use of technology in paper making and converting industry. It was concluded in this thesis that interaction of laser beam and paper material has two mechanisms that are dependent on focal plane position range. Assumed interaction mechanism B appears in range of average focal plane position of 3.4 mm and 2.4 mm and assumed interaction mechanism A in range of average focal plane position of 0.4 mm and -0.6 mm both in used experimental set up. Focal plane position 1.4 mm represents midzone of these two mechanisms. Holes during laser beam and paper material interaction are formed gradually: first small hole is formed to interaction area in the centre of laser beam cross-section and after that, as function of interaction time, hole expands, until interaction between laser beam and dried kraft pulp is ended. By the image analysis it can be seen that in beginning of laser beam and dried kraft pulp material interaction small holes off very good quality are formed. It is obvious that black colour and heat affected zone appear as function of interaction time. This reveals that there still are different interaction phases within interaction mechanisms A and B. These interaction phases appear as function of time and also as function of peak intensity of laser beam. Limit peak intensity is the value that divides interaction mechanism A and B from one-phase interaction into dual-phase interaction. So all peak intensity values under limit peak intensity belong to MAOM (interaction mechanism A one-phase mode) or to MBOM (interaction mechanism B onephase mode) and values over that belong to MADM (interaction mechanism A dual-phase mode) or to MBDM (interaction mechanism B dual-phase mode). Decomposition process of cellulose is evolution of hydrocarbons when temperature is between 380- 500°C. This means that long cellulose molecule is split into smaller volatile hydrocarbons in this temperature range. As temperature increases, decomposition process of cellulose molecule changes. In range of 700-900°C, cellulose molecule is mainly decomposed into H2 gas; this is why this range is called evolution of hydrogen. Interaction in this range starts (as in range of MAOM and MBOM), when a small good quality hole is formed. This is due to “direct evaporation” of pulp via decomposition process of evolution of hydrogen. And this can be seen can be seen in spectrometer as high intensity peak of yellow light (in range of 588-589 nm) which refers to temperature of ~1750ºC. Pyrometer does not detect this high intensity peak since it is not able to detect physical phase change from solid kraft pulp to gaseous compounds. As interaction time between laser beam and dried kraft pulp continues, hypothesis is that three auto ignition processes occurs. Auto ignition of substance is the lowest temperature in which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark. Three auto ignition processes appears in range of MADM and MBDM, namely: 1. temperature of auto ignition of hydrogen atom (H2) is 500ºC, 2. temperature of auto ignition of carbon monoxide molecule (CO) is 609ºC and 3. temperature of auto ignition of carbon atom (C) is 700ºC. These three auto ignition processes leads to formation of plasma plume which has strong emission of radiation in range of visible light. Formation of this plasma plume can be seen as increase of intensity in wavelength range of ~475-652 nm. Pyrometer shows maximum temperature just after this ignition. This plasma plume is assumed to scatter laser beam so that it interacts with larger area of dried kraft pulp than what is actual area of beam cross-section. This assumed scattering reduces also peak intensity. So result shows that assumably scattered light with low peak intensity is interacting with large area of hole edges and due to low peak intensity this interaction happens in low temperature. So interaction between laser beam and dried kraft pulp turns from evolution of hydrogen to evolution of hydrocarbons. This leads to black colour of hole edges.