Vesikäyttöisen koneen venttiilikoneiston suunnittelu

Vedellä toimivat koneet ovat nykypäivänä jo vanha keksintö. Vuosien saatossa tämä tekniikka on kehittynyt öljyllä toimiviin hydraulisiin koneisiin. Nykyisin insinöörit kuitenkin yrittävät kehittää vedestä voimanlähteen koneille muuttamalla veden kemiallisen molekyylirakenteen H20 epävakaaseen, mutta runsasenergiseen vetykaasuun H2. Perinteisen hydrauliikkasylinterin toiminta perustuu nesteen kokonpuristumattomuuteen, paineeseen sekä venttiilien oikea-aikaiseen toimintaan, jota tässä työssä sovelletaan vahvasti. Tämä hydrauliikkatekniikka on ollut olemassa jo pitkään, mutta tiedettävästi vesikäyttöiset koneet ovat olleet modernin hydrauliikkatekniikan innoittajia. Aikaisimmat sovellutukset vievät juurensa aina 1600-luvun alkupuolelle, mutta hydrauliikka nesteiden kehittyessä vesikäyttöisten koneiden suunnittelu voimansiirrosta muuttui turbiineiksi.

Catalytic direct synthesis of hydrogen peroxide in a novel microstructured reactor

The direct synthesis from hydrogen and oxygen is a green alternative for production of hydrogen peroxide. However, this process suffers from two challenges. Firstly, mixtures of hydrogen and oxygen are explosive over a wide range of concentrations (4-94% H2 in O2). Secondly, the catalytic reaction of hydrogen and oxygen involves several reaction pathways, many of them resulting in water production and therfore decreasing selectivity. The present work deals with these two challenges. The safety problem was dealed by employing a novel microstructured reactor. Selectivity of the reaction was highly improved by development a set of new catalysts. The final goal was to develop an effective and safe continuous process for direct synthesis of hydrogen peroxide from H2 and O2. Activated carbon cloth and Sibunit were examined as the catalysts’ supports. Palladium and gold monometallic and palladium-gold bimetallic catalysts were thoroughly investigated by numerous kinetic experiments performed in a tailored batch reactor and several catalyst charachterization methods. A complete set of data for direct synthesis of H2O2 and its catalytic decomposition and hydrogenation was obtained. These data were used to assess factors influencing selectivity and activity of the catalysts in direct synthesis of H2O2 as well as its decomposition and hydrogenation. A novel microstructured reactor was developed based on hydrodynamics and mass transfer studies in prototype microstractural plates. The shape and the size of the structural elements in the microreactor plate were optimized in a way to get high gas-liquid interfacial area and gas-liquid mass transfer. Finally, empirical correlations for the volumetric mass transfer coefficient were derived. A bench-scale continuous process was developed by using the novel microstructral plate reactor. A series of kinetic experiments were performed to investigate the effects of the gas and the liquid feed rates and their ratio, the amount of the catalyst, the gas feed composition and pressure on the final rate of H2O2 production and selectivity.

Extended hydrogen photoproduction by nitrogen-fixing cyanobacteria

Cyanobacteria are the only prokaryotic organisms performing oxygenic photosynthesis. They comprise a diverse and versatile group of organisms in aquatic and terrestrial environments. Increasing genomic and proteomic data launches wide possibilities for their employment in various biotechnical applications. For example, cyanobacteria can use solar energy to produce H2. There are three different enzymes that are directly involved in cyanobacterial H2 metabolism: nitrogenase (nif) which produces hydrogen as a byproduct in nitrogen fixation; bidirectional hydrogenase (hox) which functions both in uptake and in production of H2; and uptake hydrogenase (hup) which recycles the H2 produced by nitrogenase back for the utilization of the cell. Cyanobacterial strains from University of Helsinki Cyanobacteria Collection (UHCC), isolated from the Baltic Sea and Finnish lakes were screened for efficient H2 producers. Screening about 400 strains revealed several promising candidates producing similar amounts of H2 (during light) as the ΔhupL mutant of Anabaena PCC 7120, which is specifically engineered to produce higher amounts of H2 by the interruption of uptake hydrogenase. The optimal environmental conditions for H2 photoproduction were significantly different between various cyanobacterial strains. All suitable strains revealed during screening were N2-fixing, filamentous and heterocystous. The top ten H2 producers were characterized for the presence and activity of the enzymes involved in H2 metabolism. They all possess the genes encoding the conventional nitrogenase (nifHDK1). However, the high H2 photoproduction rates of these strains were shown not to be directly associated with the maximum capacities of highly active nitrogenase or bidirectional hydrogenase. Most of the good producers possessed a highly active uptake hydrogenase, which has been considered as an obstacle for efficient H2 production. Among the newly revealed best H2 producing strains, Calothrix 336/3 was chosen for further, detailed characterization. Comparative analysis of the structure of the nif and hup operons encoding the nitrogenase and uptake hydrogenase enzymes respectively showed minor differences between Calothrix 336/3 and other N2-fixing model cyanobacteria. Calothrix 336/3 is a filamentous, N2-fixing cyanobacterium with ellipsoidal, terminal heterocysts. A common feature of Calothrix 336/3 is that the cells readily adhere to substrates. To make use of this feature, and to additionally improve H2 photoproduction capacity of the Calothrix 336/3 strain, an immobilization technique was applied. The effects of immobilization within thin alginate films were evaluated by examining the photoproduction of H2 of immobilized Calothrix 336/3 in comparison to model strains, the Anabaena PCC 7120 and its ΔhupL mutant. In order to achieve optimal H2 photoproduction, cells were kept under nitrogen starved conditions (Ar atmosphere) to ensure the selective function of nitrogenase in reducing protons to H2. For extended H2 photoproduction, cells require CO2 for maintenance of photosynthetic activity and recovery cycles to fix N2. Application of regular H2 production and recovery cycles, Ar or air atmospheres respectively, resulted in prolongation of H2 photoproduction in both Calothrix 336/3 and the ΔhupL mutant of Anabaena PCC 7120. However, recovery cycles, consisting of air supplemented with CO2, induced a strong C/N unbalance in the ΔhupL mutant leading to a decrease in photosynthetic activity, although total H2 yield was still higher compared to the wild-type strain. My findings provide information about the diversity of cyanobacterial H2 capacities and mechanisms and provide knowledge of the possibilities of further enhancing cyanobacterial H2 production.

De monasteriis

Invokaatio: I.N.S.S:T.

De bibliothecariis Academiae Aboënsis 4

Arkit: 1 arkintunnukseton lehti, G2-4 H2.

De angina polyposa 4

Painovuosi nimekkeestä.

De antiquo et hodierno, regni Sveciae imperio

Variantti B.

Voces Pentateuchi Persici 2

Arkit: 1 arkintunnukseton lehti, E-H2. - S. [2] tyhjä.

Ethicae praecipua praecepta & nobiliores plerasque controversias brevibus suis cum explicationibus

Variantti B.

Ethicae praecipua praecepta & nobiliores plerasque controversias brevibus suis cum explicationibus

Variantti A.

Bibliotheca Regiae Academiae Aboensis sive elenchus: in quo ejusdem scriptorum & librorum cujuscunq[ue] facultatis, certus numerus ordine alphabetico continetur; expressis quoqu formâ, loco & tempore impressionis

Arkit: A-H2, 1 arkintunnukseton lehti (A1 verso tyhjä).