Ash Particle Erosion on Steam Boiler Convective Section

In this study, equations for the calculation of erosion wear caused by ash particles on convective heat exchanger tubes of steam boilers are presented. Anew, three-dimensional test arrangement was used in the testing of the erosion wear of convective heat exchanger tubes of steam boilers. When using the sleeve-method, three different tube materials and three tube constructions could be tested. New results were obtained from the analyses. The main mechanisms of erosionwear phenomena and erosion wear as a function of collision conditions and material properties have been studied. Properties of fossil fuels have also been presented. When burning solid fuels, such as pulverized coal and peat in steam boilers, most of the ash is entrained by the flue gas in the furnace. In bubbling andcirculating fluidized bed boilers, particle concentration in the flue gas is high because of bed material entrained in the flue gas. Hard particles, such as sharp edged quartz crystals, cause erosion wear when colliding on convective heat exchanger tubes and on the rear wall of the steam boiler. The most important ways to reduce erosion wear in steam boilers is to keep the velocity of the flue gas moderate and prevent channelling of the ash flow in a certain part of the cross section of the flue gas channel, especially near the back wall. One can do this by constructing the boiler with the following components. Screen plates can beused to make the velocity and ash flow distributions more even at the cross-section of the channel. Shield plates and plate type constructions in superheaters can also be used. Erosion testing was conducted with three types of tube constructions: a one tube row, an inline tube bank with six tube rows, and a staggered tube bank with six tube rows. Three flow velocities and two particle concentrations were used in the tests, which were carried out at room temperature. Three particle materials were used: quartz, coal ash and peat ash particles. Mass loss, diameter loss and wall thickness loss measurements of the test sleeves were taken. Erosion wear as a function of flow conditions, tube material and tube construction was analyzed by single-variable linear regression analysis. In developing the erosion wear calculation equations, multi-variable linear regression analysis was used. In the staggered tube bank, erosion wear had a maximum value in a tube row 2 and a local maximum in row 5. In rows 3, 4 and 6, the erosion rate was low. On the other hand, in the in-line tube bank the minimum erosion rate occurred in tube row 2 and in further rows the erosion had an increasing value, so that in a six row tube bank, the maximum value occurred in row 6.

Aerosolianalysaattorin jatkokehitys

Kiinnostus pienhiukkasia kohtaan on kasvanut voimakkaasti, koska niiden haitallisista terveysvaikutuksista on saatu uutta tietoa. Asiasta on julkaistu lukuisia tieteellisiä tutkimuksia ja viimeisimpien tietojan mukaan kohonneilla pienhiukkaspitoisuuksilla on vaikutusta jopa sydän- ja verisuonisairauksiin. Vakavien terveysvaikutusten ja kiristyvän lainsäädännön vuoksi uusille reaaliaikaisille hiukkasmittalaitteille on kova kysyntä. Tämä työ on osa suurempaa Dekati Oy:ssä toteutettua Autotest –projektia, jossa kehitetään hiukkasmittalaitteita autoteollisuudelle. Tavoitteena työssä oli kehittää hiukkasmittalaitteeseen varaaja, jossa olisi huomattavasti pienemmät pienhiukkashäviöt kuin sähköisen alipaineimpaktorin ELPI:n varaajassa. Lainsäädäntö pohjautuu nykyään pelkästään massapitoisuuden mittaamiseen eikä reaaliaikaisesti massapitoisuutta mittaavaa laitetta ole olemassa. Tässä työssä testattiin uutta hiukkasten tiheydenmääritysmenetelmää, jonka avulla on mahdollista mitata massapitoisuutta reaaliaikaisesti. Suunniteltu varaaja on helppokäyttöinen ja varaustehokkuudeltaan odotusten mukainen, mutta pienhiukkashäviöt ovat edelleen tavoiteltua suuremmat vaikkakin pienemmät kuin ELPI:ssä. Tämä johtuu osittain tilavaraushäviöistä ja osittain koronan sähkökentän vaikutuksesta näytekanavaan. Tiheysmittauksesta saatiin lupaavia tuloksia, mutta jatkokehitystä vaaditaan häiriöiden suodattamiseksi ja kuormituskestävyyden parantamiseksi.

Paikallisilmanvaihdon toimivuus baaritiskillä työntekijöiden tupakansavualtistuksen vähentämisessä

Työssä tarkasteltiin tupakkalain vaikutuksia ravintoloiden ilmanvaihtoon ja työntekijöiden tupakansavulle altistumiseen. Lisäksi tutkittiin, mitä muita määräyksiä Suomessa ja muualla on ravintoloiden ilmanvaihdosta ja minkälaisin ilmanvaihdollisin menetelmin voidaan ravintolatyöntekijöiden altistumista tupakansavulle vähentää. Kokeellisena osana tutkittiin Halton Oy:n kehittämän baaritiskin paikallisilmanvaihtojärjestelmän suojaustehokkuutta ja toimivuutta suomalaisessa yökerhossa. Järjestelmään kuului kattoon sijoitettu kohdepuhallus ja baaripöytään sijoitettu ilmaverholaitteisto. Mittaukset suoritettiin käytännön olosuhteissa toimivassa ravintolassa. Mitattuina suureina olivat sisäilman nikotiini- ja hiukkaspitoisuus työskentelyalueella ja asiakkaiden oleskeluvyöhykkeellä. Lisäksi käytettiin merkkiainemenetelmää tupakansavun leviämisen seuraamiseen. Saavutettu suojaustehokkuus oli mittaustavasta ja tilanteesta riippuen 72-95%. Mittaukset osoittivat, että tutkitulla paikallisilmanvaihtoratkaisulla voitiin hyvin oleellisesti vähentää ympäristön tupakansavun kulkeutumista työntekijöiden hengitysvyöhykkeelle. Paikallisilmanvaihto on kuitenkin toteutettava osana koko ravintolan ilmanvaihtoa ja säädettävä oikein hyvän tuloksen saavuttamiseksi.

Influence of reactant absorption and dissolution in heterogeneous precipitation processes

In this research work, the aim was to investigate the volumetric mass transfer coefficient [kLa] of oxygen in stirred tank in the presence of solid particle experimentally. The kLa correlations as a function of propeller rotation speed and flow rate of gas feed were studied. The O2 and CO2 absorption in water and in solid-liquid suspensions and heterogeneous precipitation of MgCO3 were thoroughly examined. The absorption experiments of oxygen were conducted in various systems like pure water and in aqueous suspensions of quartz and calcium carbonate particles. Secondly, the precipitation kinetics of magnesium carbonate was also investigated. The experiments were performed to study the reactive crystallization with magnesium hydroxide slurry and carbon dioxide gas by varying the feed rates of carbon dioxide and rotation speeds of mixer. The results of absorption and precipitation are evaluated by titration, total carbon (TC analysis), and ionic chromatrography (IC). For calcium carbonate, the particle concentration was varied from 17.4 g to 2382 g with two size fractions: 5 µm and 45-63 µm sieves. The kLa and P/V values of 17.4 g CaCO3 with particle size of 5µm and 45-63 µm were 0.016 s-1 and 2400 W/m3. At 69.9 g concentration of CaCO3, the achieved kLa is 0.014 s-1 with particle size of 5 µm and 0.017 s-1 with particle size of 45 to 63 µm. Further increase in concentration of calcium carbonate, i.e. 870g and 2382g , does not affect volumetric mass transfer coeffienct of oxygen. It could be concluded from absorption results that maximum value of kLa is 0.016 s-1. Also particle size and concentration does affect the transfer rate to some extend. For precipitation experiments, the constant concentration of Mg(OH)2 was 100 g and the rotation speed varied from 560 to 750 rpm, whereas the used feed rates of CO2 were 1 and 9 L/min. At 560 rpm and feed rate of CO2 is 1 L/min, the maximum value of Mg ion and TC were 0.25 mol/litre and 0.12 mol/litre with the residence time of 40 min. When flow rate of CO2 increased to 9 L/min with same 560 rpm, the achieved value of Mg and TC were 0.3 mol/litre and 0.12 mol/L with shorter residence time of 30 min. It is concluded that feed rate of CO2 is dominant in precipitation experiments and it has a key role in dissociation and reaction of magnesium hydroxide in precipitation of magnesium carbonate.

Quantification of Proteins and Cells: Luminometric Nonspecific Particle-Based Methods

New luminometric particle-based methods were developed to quantify protein and to count cells. The developed methods rely on the interaction of the sample with nano- or microparticles and different principles of detection. In fluorescence quenching, timeresolved luminescence resonance energy transfer (TR-LRET), and two-photon excitation fluorescence (TPX) methods, the sample prevents the adsorption of labeled protein to the particles. Depending on the system, the addition of the analyte increases or decreases the luminescence. In the dissociation method, the adsorbed protein protects the Eu(III) chelate on the surface of the particles from dissociation at a low pH. The experimental setups are user-friendly and rapid and do not require hazardous test compounds and elevated temperatures. The sensitivity of the quantification of protein (from 40 to 500 pg bovine serum albumin in a sample) was 20-500-fold better than in most sensitive commercial methods. The quenching method exhibited low protein-to-protein variability and the dissociation method insensitivity to the assay contaminants commonly found in biological samples. Less than ten eukaryotic cells were detected and quantified with all the developed methods under optimized assay conditions. Furthermore, two applications, the method for detection of the aggregation of protein and the cell viability test, were developed by utilizing the TR-LRET method. The detection of the aggregation of protein was allowed at a more than 10,000 times lower concentration, 30 μg/L, compared to the known methods of UV240 absorbance and dynamic light scattering. The TR-LRET method was combined with a nucleic acid assay with cell-impermeable dye to measure the percentage of dead cells in a single tube test with cell counts below 1000 cells/tube.