Rinnakkaispolttolaitoksen ympäristöntarkkailusuunnitelma

Diplomityössä päivitetään voimalaitoksen ympäristöntarkkailusuunnitelma vastaamaan uudistuneen ympäristöluvan ja lainsäädännön edellytyksiä. Työssä tutkitaan leijupetikatti-loiden tulipesän lämpötiloja, savukaasun viipymäaikoja tulipesässä, leijukerroskattiloiden päästöjä, päästöjen jatkuvatoimista mittaamista sekä päästöjen seurantaa ja raportointia. Tulipesän lämpötiloja mitattiin kupla- ja kiertoleijukattiloilla. Tuloksien perusteella havait-tiin kiertoleijukattilan tulipesän alaosan lämpötilojen olevan lähes riippumaton pedin lämpötilasta ja höyrykuormasta. Tulipesän yläosassa lämpötilat nousevat höyrykuorman kasvaessa, mutta pedin lämpötilalla ei havaittu vaikutusta tulipesän yläosassakaan. Molemmilla kattiloilla havaittiin voimakas vaakatasoinen lämpötilaprofiili. Kuplaleijukattilalla sekä höyrykuorma että pedin lämpötila vaikuttivat tulipesän lämpötilaan. Savukaasun teoreettiset viipymäajat laskettiin kiertoleijukattilalle. Laskelmien ja mittauksien perusteella havaittiin kattilalla mahdollisuus saavuttaa savukaasun kahden sekunnin viipymäaika 850 ºC lämpötilassa. Kattilan käyttäytymisen aukottomaksi selvittämiseksi kaikilla polttoaineseoksilla ja höyrykuormilla tarvitaan lisää toimenpiteitä kattilalla ja lisää tulipesän lämpötilamittauksia. Leijukerroskattiloiden päästöjen syntymistä ja hallintaa tutkittiin teoreettisesti kirjallisuustutkimuksena. Tutkittuihin päästöihin kuuluivat typen oksidit, rikkidioksidi, hiukkaset, hiilimonoksidi, orgaaninen kokonaishiili, suolahappo, fluorivety, raskasmetallit sekä dioksiinit ja furaanit. Jatkuvatoimisten päästömittausmittauslaitteiden toimintaperiaatteita selvitettiin kirjalli-suustutkimuksena. Samoin selvitettiin jatkuvatoimisten päästömittauslaitteiden virhelähtei-tä. Päästömittauslaitteille laadittiin pitkän ja lyhyen ajan laadunvarmistussuunnitelma. Ha-vaittiin, että nykyiset jatkuvatoimiset päästömittauslaitteet eivät täytä kaikkia uusia laatu-kriteereitä. Päästöjen jatkuvatoimiseen seuraamiseen työssä suunniteltiin uusi valvomonäyttö. Uuden näytön avulla tehostetaan päästöjen valvontaa. Päästöjen raportointiin työssä suunniteltiin vuorokausiraportti. Raporttiin kerätään jatkuva-toimisten päästömittauslaitteiden puolen tunnin keskiarvot. Raportin tarkastaa, allekirjoittaa ja arkistoi vuorossa oleva operaattori.

Lannoitetehtaan typenoksidipäästöjen hallintamahdollisuudet

Työssä tarkasteltiin lannoitetehtaan typenoksidipäästöjen hallintamahdollisuuksia Kemira GrowHow Oy:n Uudenkaupungin tehtailla. Työn tavoitteena oli lannoitetehtaalta muodostuvien typen oksidien syntymekanismien etsiminen. Lisäksi työssä etsittiin sellaisia keinoja, joilla typenoksidipäästöjä voitaisiin hallita. Tutkimusosassa tehtiin mittauksia kannettavalla FT-IR kaasuanalysaattorilla teoreettisen tarkastelun tueksi sekä prosessikohtaisten päästöjen selvittämiseksi. Prosessista tehtyjen mittausten lisäksi työssä on hyödynnetty lannoitetehtaan piippuun asennettua kiinteää FT-IR analysaattoria. Prosessikohtaiset mittaukset rajattiin lannoite 2-tehtaaseen. Mittauksia suoritettiin kuudesta prosessin pisteestä. Hallintamahdollisuuksien selvittämiseksi tehtiin tutkimuksia tietyillä raaka-aineiden syötöillä. Päästöjen prosessikohtaista arvioimista varten suoritettiin myös pitot-mittauksia kaasumäärien selvittämiseksi. Mittauksissa havaittiin, että typenoksidipäästöt riippuvat valmistettavasta lajikkeesta. Suurimmaksi typenoksidipäästöjen lähteeksi osoittautuivat reaktorit, joiden osuus oli jopa 95 % typenoksidipäästöistä. Tärkein oli biotiittireaktori, jonka osuus typenoksidipäästöistä oli noin 60-90 %. Lajikkeilla, joilla ei käytetä biotiittireaktoria, osoittautui suurimmaksi typenoksidipäästöjen lähteeksi ammonointireaktorit. Hallintamahdollisuuksia pyrittiin etsimään reaktoreilta. Suurimmaksi typen oksidien hallintamahdollisuudeksi osoittautui ureafosfaatin syöttö liuotus- ja biotiittireaktoreille. Tutkimuksissa havaittiin myös laimean rikkihapon käyttämisen, väkevän sijasta, auttavan hallitsemaan typenoksidipäästöjä.

Compositional influence on the electrical performance of zinc indium tin oxide transparent thin-film transistors

In this work, zinc indium tin oxide layers with different compositions are used as the active layer of thin film transistors. This multicomponent transparent conductive oxide is gaining great interest due to its reduced content of the scarce indium element. Experimental data indicate that the incorporation of zinc promotes the creation of oxygen vacancies. In thin-film transistors this effect leads to a higher threshold voltage values. The field-effect mobility is also strongly degraded, probably due to coulomb scattering by ionized defects. A post deposition annealing in air reduces the density of oxygen vacancies and improves the fieldeffect mobility by orders of magnitude. Finally, the electrical characteristics of the fabricated thin-film transistors have been analyzed to estimate the density of states in the gap of the active layers. These measurements reveal a clear peak located at 0.3 eV from the conduction band edge that could be attributed to oxygen vacancies.

Structural and optical properties of high quality zinc-blende/wurtzite GaAs nanowire heterostructures

The structural and optical properties of three different kinds of GaAs nanowires with 100% zinc-blende structure and with an average of 30% and 70% wurtzite are presented. A variety of shorter and longer segments of zinc-blende or wurtzite crystal phases are observed by transmission electron microscopy in the nanowires. Sharp photoluminescence lines are observed with emission energies tuned from 1.515 eV down to 1.43 eV when the percentage of wurtzite is increased. The downward shift of the emission peaks can be understood by carrier confinement at the interfaces, in quantum wells and in random short period superlattices existent in these nanowires, assuming a staggered band offset between wurtzite and zinc-blende GaAs. The latter is confirmed also by time-resolved measurements. The extremely local nature of these optical transitions is evidenced also by cathodoluminescence measurements. Raman spectroscopy on single wires shows different strain conditions, depending on the wurtzite content which affects also the band alignments. Finally, the occurrence of the two crystallographic phases is discussed in thermodynamic terms.

MgO/Ag(001) interface structure and STM images from first principles

The interface of MgO/Ag(001) has been studied with density functional theory applied to slabs. We have found that regular MgO films show a small adhesion to the silver substrate, the binding can be increased in off-stoichiometric regimes, either by the presence of O vacancies at the oxide film or by a small excess of O atoms at the interface between the ceramic to the metal. By means of theoretical methods, the scanning tunneling microscopy signatures of these films is also analyzed in some detail. For defect free deposits containing 1 or 2 ML and at low voltages, tunnelling takes place from the surface Ag substrate, and at large positive voltages Mg atoms are imaged. If defects, oxygen vacancies, are present on the surface of the oxide they introduce much easier channels for tunnelling resulting in big protrusions and controlling the shape of the image, the extra O stored at the interface can also be detected for very thin films.

The Electronic Structure of Co-Sputtered Zinc Indium Tin Oxide Thin Films

Zinc indium tin oxide (ZITO) transparent conductive oxide layers were deposited via radio frequency (RF) magnetron co-sputtering at room temperature. A series of samples with gradually varying zinc content was investigated. The samples were characterized with x-ray and ultraviolet photoemission spectroscopy (XPS, UPS) to determine the electronic structure of the surface. Valence and conduction bands maxima (VBM, CBM), and work function were determined. The experiments indicate that increasing Zn content results in films with a higher defect rate at the surface leading to the formation of a degenerately doped surface layer if the Zn content surpasses 50%. Furthermore, the experiments demonstrate that ZITO is susceptible to ultraviolet light induced work function reduction, similar to what was earlier observed on ITO and TiO2 films.

Kaivosteollisuudessa syntyvän kipsin hyödyntäminen

Diplomityön tarkoituksena oli tutkia ja kehittää käyttökohde kaivosteollisuudessa syntyvälle märälle kipsisivuvirralle, joka sisältää metalliepäpuhtauksina alumiinia, rautaa ja mangaania ja jonka määrä on noin 1 000 000 t/a. Kirjallisuuden pohjalta tutkittiin aluksi mahdollisuutta hyödyntää kipsiaines asfaltti- ja sementtiteollisuuden raaka-aineena. Sementin joukkoon lisätään tavallisesti noin 5 p-% kipsiä, mutta harvinaisimpiin sementtilaatuihin sitä voidaan lisätä jopa 30 p-%. Tästä huolimatta vain pieni osa tutkimuksen kohteessa syntyvästä kipsisivuvirrasta voitaisiin hyödyntää tässä sovelluksessa. Lisäksi kipsisivuvirran sisältämät epäpuhtaudet täytyisi poistaa tai saattaa inaktiiviseen muotoon. Myöskään sen kosteuspitoisuus ei saisi olla suuri. Näin ollen tämän kipsisivuvirran hyödyntäminen asfaltti- ja sementtiteollisuuden lisäaineena ei ole mahdollista Seuraavaksi harkittiin kipsin kierrättämistä, jolloin yhtenä vaihtoehtona oli hajottaa kipsi termisesti rikkioksideiksi ja valmistaa niistä rikkihappoa. Taloudellisista syistä hajoamistuotteen on oltava rikkitrioksidia, josta voitaisiin veteen imeyttämällä valmistaa rikkihappoa. Kipsin hajottaminen termovaa´alla osoitti, että kipsi vaatii noin 1400 ºC:n lämpötilan ja haihtuvat komponentit ovat H2O, SO ja SO2, muttei SO3. Alempien oksidien muuttaminen rikkihapoksi vaatisi katalyyttisen hapetuksen, mikä olisi käytännössä liian kallista. Toisena vaihtoehtona kipsin kierrättämiseksi tutkittiin sen biologista pelkistämistä rikkivedyksi ja kalsiumhydroksidilietteeksi. Laboratoriossa Ca(OH)2-lietteestä valmistettiin hiilidioksidin avulla kalsiumkarbonaattia, jolloin päästiin 90 %:n kalsiumhydroksidin konversiossa. Lisäksi alumiinihydroksidi saatiin erotettua kipsilietteestä kokeellisesti hydrosyklonin avulla. Diplomityössä päädyttiin siihen, että sulfaatin biologinen pelkistäminen ja alumiinihydroksidin mekaaninen erotus jatkuvatoimisesti on varteenotettava vaihtoehto kipsisivuvirran hyödyntämiseksi.

L-tyrosine and nitric oxide synergize to prevent cytotoxic effects of superoxide.

We found previously that the nitric oxide donor DEA/NO enhanced lipid peroxidation, DNA fragmentation, and cytotoxicity in human bronchial epithelial cells (BEAS-2B) when they were cultured in LHC-8 medium containing the superoxide-generating system hypoxanthine/xanthine oxidase (HX/XO). We have now discovered that DEA/NO's prooxidant action can be reversed by raising the L-tyrosine concentration from 30 to 400 microM. DEA/NO also protected the cells when they were cultured in Dulbecco's Modified Eagle's Medium (DMEM), whose standard concentration of L-tyrosine is 400 microM. Similar trends were seen with the colon adenoma cell line CaCo-2. Since HPLC analysis of cell-free DMEM or LHC-8 containing 400 microM L-tyrosine, DEA/NO, and HX/XO revealed no evidence of L-tyrosine nitration, our data suggest the existence of an as-yet uncharacterized mechanism by which L-tyrosine can influence the biochemical and toxicological effects of reactive nitrogen species.

Transition mutation in codon 248 of the p53 tumor suppressor gene induced by reactive oxygen species and a nitric oxide-releasing compound.

Exposing the human bronchial epithelial cell line BEAS-2B to the nitric oxide (NO) donor sodium 1-(N,N-diethylamino)diazen-1-ium-1, 2-diolate (DEA/NO) at an initial concentration of 0.6 mM while generating superoxide ion at the rate of 1 microM/min with the hypoxanthine/xanthine oxidase (HX/XO) system induced C:G-->T:A transition mutations in codon 248 of the p53 gene. This pattern of mutagenicity was not seen by 'fish-restriction fragment length polymorphism/polymerase chain reaction' (fish-RFLP/PCR) on exposure to DEA/NO alone, however, exposure to HX/XO led to various mutations, suggesting that co-generation of NO and superoxide was responsible for inducing the observed point mutation. DEA/NO potentiated the ability of HX/XO to induce lipid peroxidation as well as DNA single- and double-strand breaks under these conditions, while 0.6 mM DEA/NO in the absence of HX/XO had no significant effect on these parameters. The results show that a point mutation seen at high frequency in certain common human tumors can be induced by simultaneous exposure to reactive oxygen species and a NO source.

Nitric oxide and ethylnitrosourea: relative mutagenicity in the p53 tumor suppressor and hypoxanthine-phosphoribosyltransferase genes.

Nitric oxide (NO) is a cellular messenger which is mutagenic in bacteria and human TK6 cells and induces deamination of 5-methylcytosine (5meC) residues in vitro. The aims of this study were: (i) to investigate whether NO induces 5meC deamination in codon 248 of the p53 gene in cultured human bronchial epithelial cells (BEAS-2B); and (ii) to compare NO mutagenicity to that of ethylnitrosourea (ENU), a strong mutagen. Two approaches were used: (i) a novel genotypic assay, using RFLP/PCR technology on purified exon VII sequence of the p53 gene; and (ii) a phenotypic (HPRT) mutation assay using 6-thioguanine selection. BEAS-2B cells were either exposed to 4 mM DEA/NO (Et2N[N2O2]Na, an agent that spontaneously releases NO into the medium) or transfected with the inducible nitric oxide synthase (iNOS) gene. The genotypic mutation assay, which has a sensitivity of 1 x 10(-6), showed that 4 mM ENU induces detectable numbers of G --> A transitions in codon 248 of p53 while 5-methylcytosine deamination was not detected in either iNOS-transfected cells or cells exposed to 4 mM DEA/NO. Moreover, ENU was dose-responsively mutagenic in the phenotypic HPRT assay, reaching mutation frequencies of 24 and 96 times that of untreated control cells at ENU concentrations of 4 and 8 mM respectively; by contrast, 4 mM DEA/NO induced no detectable mutations in this assay, nor were any observed in cells transfected with murine iNOS. We conclude that if NO is at all promutagenic in these cells, it is significantly less so than the ethylating mutagen, ENU.

Ação promotora do berílio em catalisadores da síntese do estireno

The catalytic dehydrogenation of ethylbenzene in presence of steam is the main commercial route to produce styrene. The industrial catalysts are potassium- and chromia-doped hematite which show low surface areas leading to bad performance and short life. In order to develop catalysts with high areas, the effect of beryllium on the textural properties and on the catalytic performance of this iron oxide was studied. The influence of the amount of the dopant, the starting material and the calcination temperature were also studied. In sample preparations, iron and beryllium salts (nitrate or sulfate) were hydrolyzed with ammonia and then calcinated. The experiments followed a factorial design with two variables in two levels (Fe/Be= 3 and 7; calcination temperature= 500 and 700ºC). Solids without any dopant were also prepared. Samples were characterized by elemental analysis, infrared spectroscopy, surface area and porosity measurements, X-ray diffraction, DSC and TG. The catalysts were tested in a microreactor at 524ºC and 1 atm, by using a mole ratio of steam/ ethylbenzene=10. The selectivity was measured by monitoring styrene, benzene and toluene formation. It was found that the effect of beryllium on the characteristics of hematite and on its catalytic performance depends on the starting material and on the amount of dopant. Surface areas increased due to the dopant as well as the nature of the precursor; samples produced by beryllium sulfate showed higher areas. Beryllium-doped solids showed a higher catalytic activity when compared to pure hematite, but no significant influence of the anion of starting material was noted. It can be concluded that beryllium acts as both textural and structural promoter. Samples with Fe/Be= 3, heated at 500ºC, lead to the highest conversion and were the most selective. However, catalysts prepared from beryllium sulfate are the most promising to ethylbenzene dehydrogenation due to their high surface area which could lead to a longer life.

Desenvolvimento e caracterização de recobrimentos de Ni-Co e de seus óxidos mistos para a produção de oxigênio por eletrólise alcalina da água

This paper describes the development and characterisation of Ni-Co coatings to be used as anodes in water electrolysis. Chemical oxidation of the surface was performed through thermal treatment at 400ºC for 10 h. The resulting surfaces were analysed by X-ray diffraction, EDX, SEM, cyclic voltammetry and constant current electrolysis. The electrochemical oxidation occurring on bare surfaces during electrolysis promotes the formation of thick oxide layers resulting in loss of activity. In oxidised surfaces the chemical Ni-Co oxide grown during the thermal treatment prevents further oxidation thus retaining their activity towards oxygen evolution. An optimum condition for the growth of mixed oxide with high activity was found for the bath containing 50 g L-1 CoSO4.

Sistema com atmosfera controlada para a caracterização de sensores a gases

This paper describes a sample holder for the electrical measurement of oxides or conducting polymers in the form of pellets or films which are used as gas sensors. The system makes it possible to control the sample temperature, the gas pressure and composition. The temperature in the sample can be changed from 25ºC to 450ºC, and the gas pressure in the chamber is controlled between 5 ¥ 10-4 and 1000 mbar. The performance of the system in resistance measurements of doped tin oxide pellets and polyaniline films deposited on platinum electrodes for methane is analyzed.

Propriedades texturais e catalíticas de óxidos de ferro contendo cromo e cobre

Chromium and copper-doped hematites were prepared with the aim of studying the synergistic effect of these dopants on the textural and on the catalytic properties of the iron oxides towards the high temperature shift reaction. It was found that the most active catalysts were those with the highest amount of copper. They had the Fe(II)/Fe(III) ratio near the stoichiometric value of magnetite, the highest surface areas under the reactional atmosphere and the greatest tendency to produce the active form; they also were poorly crystalline solids. The best performance was shown by the catalyst with Fe/Cu=10, heated at 300ºC. It can thus be concluded that copper acts both as textural and structural promoter in these catalysts.

O relevante papel do agente sililante na modificação de superfícies de polímeros

The applicability of the silylant agents of the general formula Y3Si-R-X, depends on the reactivity of Y group (halide or alcoxide) attached to silicon and the organic function X (halide, amine, thiol, cyanide, etc) in the extreme position of the chain. Both groups are linked together by an organic chain R, containing usually three methylene groups. A series of these agents can be covalently bonded to an inorganic matrix, since the available OH groups are distributed on the surface, making silica gel the most common support. However, other inorganic oxides, zeolites, lamellar inorganic phosphates and chrysotile can also have these agents anchored. Some illustration are presented for immobilized surface in the use as extractors of cations from dilute aqueous or non-aqueous solutions, catalysts agents, ionic exchanged materials, support for enzyme immobilization, chromatographic applications, use in some industrial features and in many other areas. The evolution of this exciting research field to produce new materials, for many tecnological applications, is strongly dependent on the development of a sensible systematic process for the synthesis of a series of new specific silylant agents.