Optimisation of data analysis method for a fluidized bed combustion test rig

Nowadays the used fuel variety in power boilers is widening and new boiler constructions and running models have to be developed. This research and development is done in small pilot plants where more faster analyse about the boiler mass and heat balance is needed to be able to find and do the right decisions already during the test run. The barrier on determining boiler balance during test runs is the long process of chemical analyses of collected input and outputmatter samples. The present work is concentrating on finding a way to determinethe boiler balance without chemical analyses and optimise the test rig to get the best possible accuracy for heat and mass balance of the boiler. The purpose of this work was to create an automatic boiler balance calculation method for 4 MW CFB/BFB pilot boiler of Kvaerner Pulping Oy located in Messukylä in Tampere. The calculation was created in the data management computer of pilot plants automation system. The calculation is made in Microsoft Excel environment, which gives a good base and functions for handling large databases and calculations without any delicate programming. The automation system in pilot plant was reconstructed und updated by Metso Automation Oy during year 2001 and the new system MetsoDNA has good data management properties, which is necessary for big calculations as boiler balance calculation. Two possible methods for calculating boiler balance during test run were found. Either the fuel flow is determined, which is usedto calculate the boiler's mass balance, or the unburned carbon loss is estimated and the mass balance of the boiler is calculated on the basis of boiler's heat balance. Both of the methods have their own weaknesses, so they were constructed parallel in the calculation and the decision of the used method was left to user. User also needs to define the used fuels and some solid mass flowsthat aren't measured automatically by the automation system. With sensitivity analysis was found that the most essential values for accurate boiler balance determination are flue gas oxygen content, the boiler's measured heat output and lower heating value of the fuel. The theoretical part of this work concentrates in the error management of these measurements and analyses and on measurement accuracy and boiler balance calculation in theory. The empirical part of this work concentrates on the creation of the balance calculation for the boiler in issue and on describing the work environment.

Syttyminen ja palamisen eteneminen partikkelikerroksessa

Syttymistä ja palamisen etenemistä partikkelikerroksessa tutkitaan paloturvallisuuden parantamista sekä kiinteitä polttoaineita käyttävien polttolaitteiden toiminnan tuntemista ja kehittämistä varten. Tässä tutkimuksessa on tavoitteena kerätä yhteen syttymiseen ja liekkirintaman etenemiseen liittyviä kokeellisia ja teoreettisia tutkimustuloksia, jotka auttavat kiinteäkerrospoltto- ja -kaasutus-laitteiden kehittämisessä ja suunnittelussa. Työ on esitutkimus sitä seuraavalle kokeelliselle ja teoreettiselle osalle. Käsittelyssä keskitytään erityisesti puuperäisiin polttoaineisiin. Hiilidioksidipäästöjen vähentämistavoitteet sekä kiinteiden jätteiden energiakäytön lisääminen ja kaatopaikalle viennin vähentäminen aiheuttavat lähitulevaisuudessa kerrospolton lisääntymistä. Kuljetusmatkojen optimoinnin takia joudutaan rakentamaan melko pieniä polttolaitoksia, joissa kerrospolttotekniikka on edullisin vaihtoehto. Syttymispisteellä tarkoitetaan Semenovin määritelmän mukaan tilaa ja ajankohtaa, jolloin polttoaineen ja hapen reaktioissa muodostuva nettoenergia aikayksikössä on yhtäsuuri kuin ympäristöön siirtyvä nettoenergiavirta. Itsesyttyminen tarkoittaa syttymistä ympäristön lämpötilan tai paineen suurenemisen seurauksena. Pakotettu syttyminen tapahtuu, kun syttymispisteen läheisyydessä on esimerkiksi liekki tai hehkuva kiinteä kappale, joka aiheuttaa paikallisen syttymisen ja syttymisrintaman leviämisen muualle polttoaineeseen. Kokeellinen tutkimus on osoittanut tärkeimmiksi syttymiseen ja syttymisrintaman etenemiseen vaikuttaviksi tekijöiksi polttoaineen kosteuden, haihtuvien aineiden pitoisuuden ja lämpöarvon, partikkelikerroksen huokoisuuden, partikkelien koon ja muodon, polttoaineen pinnalle tulevan säteilylämpövirran tiheyden, kaasun virtausnopeuden kerroksessa, hapen osuuden ympäristössä sekä palamisilman esilämmityksen. Kosteuden lisääntyminen suurentaa syttymisenergiaa ja -lämpötilaa sekä pidentää syttymisaikaa. Mitä enemmän polttoaine sisältää haihtuvia aineita sitä pienemmässä lämpötilassa se syttyy. Syttyminen ja syttymisrintaman eteneminen ovat sitä nopeampia mitä suurempi on polttoaineen lämpöarvo. Kerroksen huokoisuuden kasvun on havaittu suurentavan palamisen etenemisnopeutta. Pienet partikkelit syttyvät yleensä nopeammin ja pienemmässä lämpötilassa kuin suuret. Syttymisrintaman eteneminen nopeutuu partikkelien pinta-ala - tilavuussuhteen kasvaessa. Säteilylämpövirran tiheys on useissa polttosovellutuksissa merkittävin lämmönsiirtotekijä, jonka kasvu luonnollisesti nopeuttaa syttymistä. Ilman ja palamiskaasujen virtausnopeus kerroksessa vaikuttaa konvektiiviseen lämmönsiirtoon ja hapen pitoisuuteen syttymisvyöhykkeellä. Ilmavirtaus voi jäähdyttää ja kuumankaasun virtaus lämmittää kerrosta. Hapen osuuden kasvaminen nopeuttaa syttymistä ja liekkirintaman etenemistä kunnes saavutetaan tila, jota suuremmilla virtauksilla ilma jäähdyttää ja laimentaa reaktiovyöhykettä. Palamisilman esilämmitys nopeuttaa syttymisrintaman etenemistä. Syttymistä ja liekkirintaman etenemistä kuvataan yleensä empiirisillä tai säilyvyysyhtälöihin perustuvilla malleilla. Empiiriset mallit perustuvat mittaustuloksista tehtyihin korrelaatioihin sekä joihinkin tunnettuihin fysikaalisiin lainalaisuuksiin. Säilyvyysyhtälöihin perustuvissa malleissa systeemille määritetään massan, energian, liikemäärän ja alkuaineiden säilymisyhtälöt, joiden nopeutta kuvaavien siirtoyhtälöiden muodostamiseen käytetään teoreettisella ja kokeellisella tutkimuksella saatuja yhtälöitä. Nämä mallinnusluokat ovat osittain päällekkäisiä. Pintojen syttymistä kuvataan usein säilyvyysyhtälöihin perustuvilla malleilla. Partikkelikerrosten mallinnuksessa tukeudutaan enimmäkseen empiirisiin yhtälöihin. Partikkelikerroksia kuvaavista malleista Xien ja Liangin hiilipartikkelikerroksen syttymiseen liittyvä tutkimus ja Gortin puun ja jätteen polttoon liittyvä reaktiorintaman etenemistutkimus ovat lähimpänä säilyvyysyhtälöihin perustuvaa mallintamista. Kaikissa malleissa joudutaan kuitenkin yksinkertaistamaan todellista tapausta esimerkiksi vähentämällä dimensioita, reaktioita ja yhdisteitä sekä eliminoimalla vähemmän merkittävät siirtomekanismit. Suoraan kerrospolttoa ja -kaasutusta palvelevia syttymisen ja palamisen etenemisen tutkimuksia on vähän. Muita tarkoituksia varten tehtyjen tutkimusten polttoaineet, kerrokset ja ympäristöolosuhteet poikkeavat yleensä selvästi polttolaitteiden vastaavista olosuhteista. Erikokoisten polttoainepartikkelien ja ominaisuuksiltaan erilaisten polttoaineiden seospolttoa ei ole tutkittu juuri ollenkaan. Polttoainepartikkelien muodon vaikutuksesta on vain vähän tutkimusta.Ilman kanavoitumisen vaikutuksista ei löytynyt tutkimuksia.

Energiantuotanto kuivalla puupolttoaineella

Diplomityössä esitetään taustatietona puupolttoaineen ominaisuuksien vaikutusta energiantuotantolaitoksen mitoitukseen ja käyttöön. Työssä esitellään ensimmäisessä vaiheessa tehty laskentamalli, jolla on tehty 20 MW laitoksen mitoitus kolmelle eri polttoaineen kosteudelle. Mitoitustulosten perusteella määritellään jokaiselle laitokselle energiantuotantohinta, joita vertaillaan. Vertailun avulla saadaan tieto siitä, onko uusi laitos syytä mitoittaa kuivatulle puupolttoaineelle investointisäästöjen vuoksi. Työssä tarkastellaan myös risutukkien ominaisuuksia, hyödyntämismahdollisuuksia sekä niiden varastokuivatuksen taloudellisuutta.

Soodakattilan energiatehokkuuden ja -taseen laskenta

Tämä diplomityö on tehty UPM-Kymmene Oy:n Tervasaaren tehtaalle. Työn tavoitteena oli määrittää soodakattilan energiatase. Määritellyn taseen avulla voitiin tutkia kattilan energiatehokkuutta. Soodakattilan savukaasupuolen ja vesihöyrypiirin energiataseet mallinnettiin taulukkolaskentaohjelmaan. Lähtöarvojen selvittämiseksi suoritettiin yksi mittausjakso. Laskettujen savukaasupuolen ja vesihöyrypiirin tasetulosten ero oli vain 0,4 % hyödyksi saatavien lämpöenergioiden suhteen. Savukaasupuolen energiataseessa käytettiin polttoaineiden tehollisia lämpöarvoja. Lisäksi lipeän määritettyä tehollista lämpöarvoa korjattiin erillisellä kertoimella. Kattilan energiatehokkuuden tarkasteluun valittiin muuttujiksi poltettavan lipeän laatu ja lipeän kuiva-aine sekä nuohoushöyrymäärä ja ilmakerroin. Lasketuista tuloksista voitiin havaita, että siirryttäessä nykyisestä polttolipeän poltosta pelkään sulfaattipohjaisen lipeän polttoon, saavutetaan säästöjä 2,33…3,10 milj.€/a. Myös nuohoushöyrymäärän ja ilmakertoimen muutoksilla todettiin saavutettavan säästöjä.

Pyrolyysiöljyn tuottaminen kiertoleijukattilaan liitetyllä prosessilla

Pyrolyysiöljy on biomassasta nopealla hapettomalla lämpökäsittelyprosessilla saatavaa nestemäistä polttoainetta. Kasvavien uusiutuvan energian käyttötavoitteiden myötä pyrolyysiöljystä on tullut kiinnostava vaihtoehto fossiilisille polttoöljyille. Suurimmat käytön haasteet ovat alhainen lämpöarvo, korkeat kiintoainepitoisuudet ja happamuus fossiilisiin polttoöljyihin verrattuna sekä eri raaka-aineista syntyvät ominaisuuksiltaan erilaiset pyrolyysiöljyt. Pyrolyysiöljyn kaupallinen tuotanto on vasta käynnistymässä eikä sen laadulle ole olemassa standardeja, joten eri valmistajien tuotteet voivat poiketa toisistaan huomattavastikin. Suomessa on Valtion teknillisen tutkimuskeskuksen (VTT) toimesta kehitetty Integrated Thermal Process (ITP)-konsepti, jossa pyrolyysiöljyn tuotantoprosessi on liitetty kiertoleijukattilaprosessiin. Prosessien yhdistämisellä voidaan parantaa kokonaishyötysuhdetta sekä hyödyntää laitosten yhteistä käyttöä ja polttoaineen hankintaa. Pyrolyysiprosessin tarvitsema lämpöenergia otetaan petihiekan välityksellä kattilasta, jossa poltetaan myös prosessissa syntyvät oheistuotteet. Tässä diplomityössä tutkittiin pyrolyysiprosessin vaikutusta voimalaitoksen toimintaan ja luotiin malli voimalaitoksen energiataseessa tapahtuvien muutosten arviointiin. Malli laskee sekä pyrolysaattorin että raaka-aineen käsittelyn vaikutukset voimalaitoksen sähkön- ja lämmöntuotantoon. Lisäksi mallin avulla voidaan arvioida pyrolysaattorin aiheuttama raaka-aineen tarve sekä voimalaitoksen lisäpolttoaineen tarve. Työssä tarkasteltiin myös pyrolyysiöljyn ominaisuuksia ja käyttökohteita, sekä tarvittavia muutoksia olemassa olevaan voimalaitokseen. Lisäksi arvioitiin tuotannon kannattavuutta. Mallia sovellettiin esimerkkivoimalaitokseen, jossa on harkittu pyrolyysiöljyn tuotannon aloittamista. Laskelmien perusteella pyrolyysiöljyn tuotannolla on sähkön- ja lämmöntuotantoa alentava sekä polttoaineen tarvetta korottava vaikutus. Pyrolyysiprosessin lisääminen nostaa voimalaitoksen kokonaishyötysuhdetta. Suotuisissa olosuhteissa öljytuotanto ITP-konseptilla näyttäisi olevan taloudellisesti kannattavaa.

Nopeaan pyrolyysiin perustuvan bioöljyn tuotantolaitoksen liiketoiminnallinen malli ja kannattavuuslaskenta Savonlinnan seudulla

Pyrolyysiöljy on biomassasta nopealla hapettomalla lämpökäsittelyprosessilla valmistettavaa nestemäistä polttoainetta. Kasvavien uusiutuvan energian käyttötavoitteiden myötä pyrolyysiöljystä on tullut varteenotettava vaihtoehto fossiilisille polttoöljyille. Suurimmat käytön haasteet ovat alhainen lämpöarvo, happamuus ja korkeahkot kiintoainepitoisuudet verrattuna fossiilisiin polttoöljyihin. Nämä haasteet ovat kuitenkin ratkaistavissa. Työssä tarkasteltiin bioöljyn tuotantolaitoksen liiketoiminnallista mallia ja kannattavuutta Savonlinnan seudulle sijoitettuna. Tätä varten selvitettiin alueellinen raaka-aineen saatavuus ja hinta, sekä potentiaaliset markkinat pyrolyysiöljylle. Kannattavuuslaskentaa varten luotiin exel – pohjainen laskentatyökalu, jolla laskettiin pyrolyysiöljyn tuotannon omakustannushinnat ja kannattavuudet eri laitosvaihtoehdoille. Saaduille tuloksille tehtiin herkkyysanalyysi, jolla selvitettiin merkittävimmät kannattavuuteen vaikuttavat tekijät. Laskettujen tulosten perusteella pienemmät 100 BDMTPD (Bone Dry Metric Ton per Day) tuotantolaitokset eivät ole kannattavia investointeja. Suuremmat 400 BDMTPD tuotantolaitokset ovat kannattavia, kunhan raaka-aine saadaan kohtuulliseen hintaan ja investointikustannukset pysyvät kurissa.

Waste-to-Energy Scenarios in the China Context

Waste incineration plants are increasingly established in China. A low heating value and high moisture content, due to a large proportion of biowaste in the municipal solid waste (MSW), can be regarded as typical characteristics of Chinese MSW. Two incineration technologies have been mainly established in China: stoker grate and circular fluidized bed (CFB). Both of them are designed to incinerate mixed MSW. However, there have been difficulties to reach the sufficient temperature in the combustion process due to the low heating value of the MSW. That is contributed to the usage of an auxiliary fossil fuel, which is often used during the whole incineration process. The objective of this study was to design alternative Waste-to-energy (WTE) scenarios for existing WTE plants with the aim to improve the material and energy efficiency as well as the feasibility of the plants. Moreover, the aim of this thesis was to find the key factors that affect to the feasibility of the scenarios. Five different WTE plants were selected as study targets. The necessary data for calculation was gained from literature as well as received from the operators of the target WTE plants. The created scenarios were based on mechanical-biological treatment (MBT) technologies, in which the produced solid recovered fuel (SRF) was fed as an auxiliary fuel into a WTE plant replacing the fossil fuel. The mechanically separated biowaste was treated either in an anaerobic digestion (AD) plant, a biodrying plant, a thermal drying plant, or a combined AD plant + thermal drying plant. An interactive excel spreadsheet based computation tool was designed to estimate the viability of the scenarios in different WTE cases. The key figures of the improved material and energy efficiency, such as additional electricity generated and avoided waste for landfill, were got as results. Furthermore, economic indicators such as annual profits (or costs), payback period, and internal rate of return (IRR) were gained as results. The results show that the AD scenario was the most profitable in most of the cases. The current heating value of MSW and the tipping fee for the received MSW appeared as the most important factor in terms of feasibility.

Wastewater Treatment and Deinking Sludge Utilization Possibilities for Energy and Material Recovery in the Leningrad Region

Operation of pulp and paper mills generates waste including wastewater treatment sludge and deinking sludge. Both sludge types are generated in large amounts and are mainly disposed of in landfills in the Leningrad Region resulting in environmental degradation. The thesis was aimed at seeking new sustainable ways of sludge utilization. Two paper mills operating in the Leningrad Region and landfilling their sludge were identified: “SCA Hygiene Products Russia” and “Knauf”. The former generates 150 t/day of deinking sludge, the latter – 145 t/day of secondary sludge. Chemical analyses of deinking sludge were performed to assess applicability of sludge in construction materials production processes. Higher heating value on dry basis of both sludge types was determined to evaluate energy potential of sludge generated in the Leningrad Region. Total energy output from sludge incineration was calculated. Deinking sludge could be utilized in the production process of “LSR-Cement” or “Slantsy Cement Plant Cesla” factories, and “Pobeda” and “Nikolsky” brick mills without exceeding current sludge management costs.

Towards sustainable Iron- and steelmaking with economic optimization

The iron and steelmaking industry is among the major contributors to the anthropogenic emissions of carbon dioxide in the world. The rising levels of CO2 in the atmosphere and the global concern about the greenhouse effect and climate change have brought about considerable investigations on how to reduce the energy intensity and CO2 emissions of this industrial sector. In this thesis the problem is tackled by mathematical modeling and optimization using three different approaches. The possibility to use biomass in the integrated steel plant, particularly as an auxiliary reductant in the blast furnace, is investigated. By pre-processing the biomass its heating value and carbon content can be increased at the same time as the oxygen content is decreased. As the compression strength of the preprocessed biomass is lower than that of coke, it is not suitable for replacing a major part of the coke in the blast furnace burden. Therefore the biomass is assumed to be injected at the tuyere level of the blast furnace. Carbon capture and storage is, nowadays, mostly associated with power plants but it can also be used to reduce the CO2 emissions of an integrated steel plant. In the case of a blast furnace, the effect of CCS can be further increased by recycling the carbon dioxide stripped top gas back into the process. However, this affects the economy of the integrated steel plant, as the amount of top gases available, e.g., for power and heat production is decreased. High quality raw materials are a prerequisite for smooth blast furnace operation. High quality coal is especially needed to produce coke with sufficient properties to ensure proper gas permeability and smooth burden descent. Lower quality coals as well as natural gas, which some countries have in great volumes, can be utilized with various direct and smelting reduction processes. The DRI produced with a direct reduction process can be utilized as a feed material for blast furnace, basic oxygen furnace or electric arc furnace. The liquid hot metal from a smelting reduction process can in turn be used in basic oxygen furnace or electric arc furnace. The unit sizes and investment costs of an alternative ironmaking process are also lower than those of a blast furnace. In this study, the economy of an integrated steel plant is investigated by simulation and optimization. The studied system consists of linearly described unit processes from coke plant to steel making units, with a more detailed thermodynamical model of the blast furnace. The results from the blast furnace operation with biomass injection revealed the importance of proper pre-processing of the raw biomass as the composition of the biomass as well as the heating value and the yield are all affected by the pyrolysis temperature. As for recycling of CO2 stripped blast furnace top gas, substantial reductions in the emission rates are achieved if the stripped CO2 can be stored. However, the optimal recycling degree together with other operation conditions is heavily dependent on the cost structure of CO2 emissions and stripping/storage. The economical feasibility related to the use of DRI in the blast furnace depends on the price ratio between the DRI pellets and the BF pellets. The high amount of energy needed in the rotary hearth furnace to reduce the iron ore leads to increased CO2 emissions.

Susteinable steelmaking by process integration

Environmental issues, including global warming, have been serious challenges realized worldwide, and they have become particularly important for the iron and steel manufacturers during the last decades. Many sites has been shut down in developed countries due to environmental regulation and pollution prevention while a large number of production plants have been established in developing countries which has changed the economy of this business. Sustainable development is a concept, which today affects economic growth, environmental protection, and social progress in setting up the basis for future ecosystem. A sustainable headway may attempt to preserve natural resources, recycle and reuse materials, prevent pollution, enhance yield and increase profitability. To achieve these objectives numerous alternatives should be examined in the sustainable process design. Conventional engineering work cannot address all of these substitutes effectively and efficiently to find an optimal route of processing. A systematic framework is needed as a tool to guide designers to make decisions based on overall concepts of the system, identifying the key bottlenecks and opportunities, which lead to an optimal design and operation of the systems. Since the 1980s, researchers have made big efforts to develop tools for what today is referred to as Process Integration. Advanced mathematics has been used in simulation models to evaluate various available alternatives considering physical, economic and environmental constraints. Improvements on feed material and operation, competitive energy market, environmental restrictions and the role of Nordic steelworks as energy supplier (electricity and district heat) make a great motivation behind integration among industries toward more sustainable operation, which could increase the overall energy efficiency and decrease environmental impacts. In this study, through different steps a model is developed for primary steelmaking, with the Finnish steel sector as a reference, to evaluate future operation concepts of a steelmaking site regarding sustainability. The research started by potential study on increasing energy efficiency and carbon dioxide reduction due to integration of steelworks with chemical plants for possible utilization of available off-gases in the system as chemical products. These off-gases from blast furnace, basic oxygen furnace and coke oven furnace are mainly contained of carbon monoxide, carbon dioxide, hydrogen, nitrogen and partially methane (in coke oven gas) and have proportionally low heating value but are currently used as fuel within these industries. Nonlinear optimization technique is used to assess integration with methanol plant under novel blast furnace technologies and (partially) substitution of coal with other reducing agents and fuels such as heavy oil, natural gas and biomass in the system. Technical aspect of integration and its effect on blast furnace operation regardless of capital expenditure of new operational units are studied to evaluate feasibility of the idea behind the research. Later on the concept of polygeneration system added and a superstructure generated with alternative routes for off-gases pretreatment and further utilization on a polygeneration system producing electricity, district heat and methanol. (Vacuum) pressure swing adsorption, membrane technology and chemical absorption for gas separation; partial oxidation, carbon dioxide and steam methane reforming for methane gasification; gas and liquid phase methanol synthesis are the main alternative process units considered in the superstructure. Due to high degree of integration in process synthesis, and optimization techniques, equation oriented modeling is chosen as an alternative and effective strategy to previous sequential modelling for process analysis to investigate suggested superstructure. A mixed integer nonlinear programming is developed to study behavior of the integrated system under different economic and environmental scenarios. Net present value and specific carbon dioxide emission is taken to compare economic and environmental aspects of integrated system respectively for different fuel systems, alternative blast furnace reductants, implementation of new blast furnace technologies, and carbon dioxide emission penalties. Sensitivity analysis, carbon distribution and the effect of external seasonal energy demand is investigated with different optimization techniques. This tool can provide useful information concerning techno-environmental and economic aspects for decision-making and estimate optimal operational condition of current and future primary steelmaking under alternative scenarios. The results of the work have demonstrated that it is possible in the future to develop steelmaking towards more sustainable operation.

Review of water electrolysis technologies and design of renewable hydrogen production systems

An electric system based on renewable energy faces challenges concerning the storage and utilization of energy due to the intermittent and seasonal nature of renewable energy sources. Wind and solar photovoltaic power productions are variable and difficult to predict, and thus electricity storage will be needed in the case of basic power production. Hydrogen’s energetic potential lies in its ability and versatility to store chemical energy, to serve as an energy carrier and as feedstock for various industries. Hydrogen is also used e.g. in the production of biofuels. The amount of energy produced during hydrogen combustion is higher than any other fuel’s on a mass basis with a higher-heating-value of 39.4 kWh/kg. However, even though hydrogen is the most abundant element in the universe, on Earth most hydrogen exists in molecular forms such as water. Therefore, hydrogen must be produced and there are various methods to do so. Today, the majority hydrogen comes from fossil fuels, mainly from steam methane reforming, and only about 4 % of global hydrogen comes from water electrolysis. Combination of electrolytic production of hydrogen from water and supply of renewable energy is attracting more interest due to the sustainability and the increased flexibility of the resulting energy system. The preferred option for intermittent hydrogen storage is pressurization in tanks since at ambient conditions the volumetric energy density of hydrogen is low, and pressurized tanks are efficient and affordable when the cycling rate is high. Pressurized hydrogen enables energy storage in larger capacities compared to battery technologies and additionally the energy can be stored for longer periods of time, on a time scale of months. In this thesis, the thermodynamics and electrochemistry associated with water electrolysis are described. The main water electrolysis technologies are presented with state-of-the-art specifications. Finally, a Power-to-Hydrogen infrastructure design for Lappeenranta University of Technology is presented. Laboratory setup for water electrolysis is specified and factors affecting its commissioning in Finland are presented.

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.

Network Structures and Modularity among Biofuel Heating System Manufacturers

The aim of this thesis was to study network structures and modularity among biofuel heating system manufacturers in the Finnish bioenergy sector by utilizing the perspectives of numerous Finnish bioenergy specialists. The study is qualitative due to the fact that the research material was gathered with semi-structured theme interviews during May and June 2010. The research methodology used in the thesis combines conceptual and action-oriented approach. Networks, value nets, and modularity were studied from different perspectives. Three network and platform strategies were discovered and a general network structure was formed. Moreover, benefits and disadvantages of networks and modularity among biofuel heating system manufacturers were illustrated. The analysis provides a comprehensive perception of the industry. The results of the research were constructed by implementing existing theories into practice. Also future recommendations for the biofuel heating system manufacturers were given. The results can be considered to be beneficial because the number of previous studies about the subject is relatively small. The reliability of the study is eminent because the number of the interviews was inclusive.