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.

Liikearvon arvonalentumistestaus IAS 36:n mukaan

The main object of this Master´s Thesis was to study the goodwill impairment testing under IAS 36. The aim was also to study the process of impairment testing in companies. The definition, treatment and impairment testing of goodwill were based on the interpretative literature of the standard, articles in trade papers and in international journals. Research methodology was descriptive, qualitative and normative. The empirical data was gathered from focused interviews of companies, consultant and auditor. In the impairment testing of goodwill under IAS 36 carrying amount of cash-generating unit is compared with unit´s recoverable amount, which is defined by either fair value less costs to sell or value in use. Value in use, which is based on unit´s net present value of the future cash flows, is clearly more generally used. The greatest black spots of testing are determination of cash-generating units and allocation of goodwill to them and determination of the discount rate. These black spots enable covering-up goodwill impairment. Companies testing processes differed, which makes comparison more difficult. The documentation of testing should also be invested more in companies.

Osavalmistuksen tuotannonohjauksen kehittäminen liikkuvia työkoneita valmistavassa yrityksessä

Tämän diplomityön tavoitteena oli kehittää erään liikkuvia työkoneita valmistavan yrityksen osavalmistuksen tuotannonohjausta. Ohjauksen kehittämisessä otettiin huomioon myös tehtaan liityntäpinnat, eli koko tilaus- toimitusketju. Tuotannonohjauksesta oli tavoitteena kehittää visuaalinen ja mahdollisimman itseohjautuva. Työssä on selvitetty osavalmistuksen nykytilanne ja ohjauksen ongelmakohdat. Kappaleiden valmistamiseen käytettävät vaiheajat tarkastettiin ja tutkittiin tehtaalla valmistettavien merkittävien osien kohdalta. Osasta tuotteista selvitettiin myös tuotteiden valmistuksen läpäisyajat konkreettisten seurantalomakkeiden avulla. Yritykselle soveltuvin ohjausmallin runko etsittiin työn tavoitteen ja toimintaympäristön kautta. Lopulta parhaaksi valitun ohjausmallin toimivuus varmistettiin tietokoneavusteisen simuloinnin avulla. Toiminnan tehostamiseksi työssä on annettu idea myös kuinka tehtaan layoutia olisi hyvä muuttaa. Ohjausmallin käytännön toteutuksesta on työssä annettu esimerkki. Esimerkissä on huomioitu millaista visuaalista ratkaisua olisi parasta käyttää ohjauksen itseohjautuvuuden lisäämiseksi. Työssä annettu myös ideoita kuinka osien varastointia ja kotiinkutsujen tekemistä olisi hyvä parantaa sekä miten saldotietoja saisi mahdollisesti helpommin ylläpidettäväksi.

Gasification of Black Liquor as a Way to Increase Power Production at Kraft Pulp Mills

The study is focused on the opportunity to improve the power performance from black liquor at Kraft pulp mills. The first part of the paper includes an overview of a traditional recovery system, its development and indication of the integral drawbacks which provoke the search for more efficient methods of black liquor treatment. The second part is devoted to the investigation of black liquor gasification as a technology able to increase electric energy generation at pulp mills. In addition, a description of two most promising gasification processes and their comparison to each other are presented. The paper is based on a literature review and interviews of specialists in this field. The findings showed that while the modern recovery system meets demands of the pulp mills, pressurized oxygen-blown black liquor gasification has good potential to be used as an alternative technology, increasing the power output from black liquor.

“Valley co-creation” – exploring the emergence of a cultural product in an entrepreneur-driven value network: Case study: Black Weekend festival

The interconnected domains are attracting interest from industries and academia, although this phenomenon, called ‘convergence’ is not new. Organizational research has indeed focused on uncovering co-creation for manufacturing and the industrial organization, with limited implications to entrepreneurship. Although convergence has been characterized as a process connecting seemingly disparate disciplines, it is argued that these studies tend to leave the creative industries unnoticed. With the art market boom and new forms of collaboration riding past the institution-focused arts marketing literature, this thesis takes a leap to uncover the processes of entrepreneurship in the emergence of a cultural product. As a symbolic work of synergism itself, the thesis combines organizational theory with literature in natural sciences and arts. Assuming nonlinearity, a framework is created for analysing aesthetic experience in an empirical event where network actors are connected to multiple contexts. As the focal case in study, the empirical analysis performed for a music festival organized in a skiing resort in the French Alps in March. The researcher attends the festival and models its cocreation process by enquiring from an artist, festival organisers, and a festival visitor. The findings contribute to fields of entrepreneurship, aesthetics and marketing mainly. It is found that the network actors engage in intimate and creative interaction where activity patterns are interrupted and cultural elements combined. This process is considered to both create and destruct value, through identity building, legitimisation, learning, and access to larger audiences, and it is considered particularly useful for domains where resources are too restrained for conventional marketing practices. This thesis uncovered the role of artists and informants and posits that particularly through experience design, this type of skilled individual be regarded more often as a research informant. Future research is encouraged to engage in convergence by experimenting with different fields and research designs, and it is suggested that future studies could arrive at different descriptive results.

Behavior of black liquor nitrogen in combustion : formation of cyanate

The Kraft pulping process is the dominant chemical pulping process in the world. Roughly 195 million metric tons of black liquor are produced annually as a by-product from the Kraft pulping process. Black liquor consists of spent cooking chemicals and dissolved organics from the wood and can contain up to 0.15 wt% nitrogen on dry solids basis. The cooking chemicals from black liquor are recovered in a chemical recovery cycle. Water is evaporated in the first stage of the chemical recovery cycle, so the black liquor has a dry solids content of 65-85% prior to combustion. During combustion of black liquor, a portion of the black liquor nitrogen is volatilized, finally forming N2 or NO. The rest of the nitrogen remains in the char as char nitrogen. During char conversion, fixed carbon is burned off leaving the pulping chemicals as smelt, and the char nitrogen forms mostly smelt nitrogen (cyanate, OCN-). Smelt exits the recovery boiler and is dissolved in water. The cyanate from smelt decomposes in the presence of water, forming NH3, which causes nitrogen emissions from the rest of the chemical recovery cycle. This thesis had two focuses: firstly, to determine how the nitrogen chemistry in the recovery boiler is affected by modification of black liquor; and secondly, to find out what causes cyanate formation during thermal conversion, and which parameters affect cyanate formation and decomposition during thermal conversion of black liquor. The fate of added biosludge nitrogen in chemical recovery was determined in Paper I. The added biosludge increased the nitrogen content of black liquor. At the pulp mill, the added biosludge did not increase the NO formation in the recovery boiler, but instead increased the amount of cyanate in green liquor. The increased cyanate caused more NH3 formation, which increased the NCG boiler’s NO emissions. Laboratory-scale experiments showed an increase in both NO and cyanate formation after biosludge addition. Black liquor can be modified, for example by addition of a solid biomass to increase the energy density of black liquor, or by separation of lignin from black liquor by precipitation. The precipitated lignin can be utilized in the production of green chemicals or as a fuel. In Papers II and III, laboratory-scale experiments were conducted to determine the impact of black liquor modification on NO and cyanate formation. Removal of lignin from black liquor reduced the nitrogen content of the black liquor. In most cases NO and cyanate formation decreased with increasing lignin removal; the exception was NO formation from lignin lean soda liquors. The addition of biomass to black liquor resulted in a higher nitrogen content fuel mixture, due to the higher nitrogen content of biomass compared to black liquor. More NO and cyanate were formed from the fuel mixtures than from pure black liquor. The increased amount of formed cyanate led to the hypothesis that black liquor is catalytically active and converts a portion of the nitrogen in the mixed fuel to cyanate. The mechanism behind cyanate formation during thermal conversion of black liquor was not clear before this thesis. Paper IV studies the cyanate formation of alkali metal loaded fuels during gasification in a CO2 atmosphere. The salts K2CO3, Na2CO3, and K2SO4 all promoted char nitrogen to cyanate conversion during gasification, while KCl and CaCO3 did not. It is now assumed that cyanate is formed when alkali metal carbonate or an active intermediate of alkali metal carbonate (e.g. -CO2K) reacts with the char nitrogen forming cyanate. By testing different fuels (bark, peat, and coal), each of which had a different form of organic nitrogen, it was concluded that the form of organic nitrogen in char also has an impact on cyanate formation. Cyanate can be formed during pyrolysis of black liquor, but at temperatures 900°C or above, the formed cyanate will decompose. Cyanate formation in gasifying conditions with different levels of CO2 in the atmosphere was also studied. Most of the char nitrogen was converted to cyanate during gasification at 800-900°C in 13-50% CO2 in N2, and only 5% of the initial fuel nitrogen was converted to NO during char conversion. The formed smelt cyanate was stable at 800°C 13% CO2, while it decomposed at 900°C 13% CO2. The cyanate decomposition was faster at higher temperatures and in oxygen-containing atmospheres than in an inert atmosphere. The presence of CO2 in oxygencontaining atmospheres slowed down the decomposition of cyanate. This work will provide new information on how modification of black liquor affects the nitrogen chemistry during thermal conversion of black liquor and what causes cyanate formation during thermal conversion of black liquor. The formation and decomposition of cyanate was studied in order to provide new data, which would be useful in modeling of nitrogen chemistry in the recovery boiler.