Huttunen-Saarivirta E.,Tampere University of Technology |
Kinnunen H.,Valmet Power Oy |
Tuiremo J.,Valmet Power Oy |
Uusitalo M.,Valmet Power Oy |
Antonov M.,Tallinn University of Technology
Wear | Year: 2014
Erosive wear of four boilers steels: 16Mo3, P265GH, P91 and 304L, was examined using a four-channel centrifugal erosion tester, two types of sands and one type of ash as the erodant, the particle velocities of 10 and 20ms-1 and the impact angles of 30°, 45° and 90°. The erodants varied in terms of abrasivity, which may be explained by their different composition, shape and size. Concerning the sands, abrasivity and erosivity went hand in hand, with impacts by angular and only silicon- and oxygen-containing Sand 1 causing essentially more material losses than those by Sand 2. Furthermore, because steady-state erosive wear was reached in the tests conducted with the sands, correlation between the extent of erosion and particle velocity could be established, enabling the deduction of the wear coefficient K and exponent n. Among the studied boiler steels, wear coefficient K was the highest for the grade P265GH, suggesting the greatest efficiency of material removal by the particle impacts. When the ash was used as an erodant, steady-state erosion was not reached and abrasivity and erosivity of the particles did not exhibit clear correlation. These results are presented and discussed in this paper. © 2014 Elsevier B.V.
Kuuluvainen H.,Tampere University of Technology |
Karjalainen P.,Tampere University of Technology |
Bajamundi C.J.E.,University of Jyväskylä |
Bajamundi C.J.E.,VTT Technical Research Center of Finland |
And 5 more authors.
Fuel | Year: 2014
Increased use of biomass and waste fuels, and the consequent corrosion problem have led to an increased need to study and monitor the combustion processes. This study presents an extensive physical characterization of aerosol particles measured from a bubbling fluidized bed boiler with different fuel mixtures and optional ferric sulfate feeding. The fuel mixtures included bark, sludge, peat and solid recovered fuel. Previously, the characterization of the particles analyzed from a fluidized bed reactor has mainly focused on chemical off-line analysis of collected impactor samples, large coarse mode particles or laboratory-scale reactors. In this study, the focus is in the particle size range from 3 to 500 nm, where mobility size distributions, effective density, morphology and electric net charge of particles were measured and analyzed. In the boiler, the particle size distribution in the measurement range was unimodal. Gas phase species formed a second smaller particle mode in the dilution. The number concentration of the smaller mode, peaking around 20 nm, was mostly dominating but variations were seen with respect to measurement location, fuel mixture and additive feeding. The effective density of these particles was approximately 1.4 g/cm3. The larger mode, peaking around 80 nm, was found to be more stable and the effective density of these particles decreased as a function of particle size, being 3-4 g/cm3at the maximum. The results of this work suggest that the cores of these particles already exist in the boiler and partly consist of heavier lead and zinc compounds. The ferric sulfate feeding decreased the number and mass concentration of the smaller mode particles, which are formed in the sampling and dilution processes mainly from the gas phase alkali chlorides. These condensable species were also linked to the negative net charge of particles. This study deepens the understanding of the combustion process and the sampling of aerosol particles with an aspect of on-line monitoring. © 2014 Elsevier Ltd. All rights reserved.
Valmet Power Oy and Teknologian Tutkimuskeskus Vtt | Date: 2013-07-05
The invention relates to a method and apparatus for producing a pyrolysis product, in which raw material are fed to the pyrolysis reactor and gaseous pyrolysis product fractions and by-product fractions are formed from raw material by pyrolysis in a pyrolysis reactor. According to the invention the method comprising steps: combusting at least one by-product fraction from the pyrolysis reactor in at least two combustors, and recovering energy formed in the combustor.
Valimaki E.J.,Valmet Power Oy |
Siren K.B.,Oy Sirra Ab
J-FOR | Year: 2013
A new process concept for removal of potassium, chlorine, and sulphur and simultaneous recovery of sodium has been developed. The concept consists of simplified stripping of hydrogen sulphide from green liquor (GLSS), purging of sulphur in elemental form by a liquid redox process, and crystallization of ESP dust together with stripped green liquor. The process enables simultaneous removal of the elements investigated, with smaller sodium losses than in earlier ESP dust-based processes. The element balances can be controlled independently of each other. The process has been tested in a pilot plant.
Leppanen A.,Tampere University of Technology |
Tran H.,University of Toronto |
Taipale R.,VTT Technical Research Center of Finland |
Valimaki E.,Valmet Power Oy |
Oksanen A.,Tampere University of Technology
Fuel | Year: 2014
In kraft pulp mills, black liquor is concentrated and burned in recovery boilers to produce steam and power and to recover pulping chemicals. Black liquor contains a large amount of alkali compounds, which form ash with low melting temperatures upon combustion. This causes many problems in recovery boiler operation, including fouling of the heat transfer surfaces, plugging of the flue gas passages, reduction of the heat transfer rate, and corrosion of the superheater tubes. This paper presents a model for simulating fine fume particles formed as a result of condensation of alkali compound vapors in the recovery boiler. The modeling method combines CFD modeling, equilibrium chemistry, and fine particle dynamics in a way that enables simulation of a full scale three-dimensional boiler environment. The model has been partially validated with measurements performed in an operating recovery boiler. The modeling results, particularly for the fume particle composition, agree well with the actual measurements. © 2014 Elsevier Ltd. All rights reserved.
Vaha-Savo N.,Åbo Akademi University |
Demartini N.,Åbo Akademi University |
Ziesig R.,Innventia Ab |
Tomani P.,Innventia Ab |
And 3 more authors.
Tappi Journal | Year: 2014
The growing interest in production of green chemicals and biofuels from biomass provides an incentive for pulp mills to identify new possibilities in recovering more wood components from the pulping process. One possibility is to use lignin, separated from black liquor. We undertook this work to determine the combustion properties of reduced-lignin black liquors-two kraft liquors and one soda liquor-in a laboratory-scale, single-particle furnace. The combustion times, maximum swollen volume, nitric oxide formation, cyanate formation, and sulfur release were measured for the original liquors, the filtrates, and intermediate levels of lignin reduction. Combustion experiments were conducted at 900°C in 10% oxygen. Cyanate formation experiments were carried out by pyrolyzing the droplets at 800°C in 100% nitrogen to form a char. The chars were then gasified at 800°C in a 13% carbon dioxide/87% nitrogen atmosphere to obtain the smelt. Sulfur release was studied by pyrolyzing the samples at temperatures ranging from 300°C to 900°C. Liquors with the lowest lignin content had a smaller maximum swollen volume than the original sample. The devolatilization time was not affected by the lignin removal to any great extent, but lignin removal did have a clear effect on the char burning time. The amount of formed nitric oxide (g N/kg black liquor solids) remained constant or decreased slightly with increasing lignin removal in the kraft liquor samples, while for the soda samples the amount of nitric oxide formed increased. The amount of cyanate decreased clearly when comparing the samples with lowest lignin content to the original liquor samples. The peak sulfur release occurred at 500°C for both kraft liquors. In almost all experiments, the share of sulfur released was highest for the original samples and lowest for the sample with lowest lignin content. These results provide new data on combustion properties for reduced-lignin black liquors and indicate that for lignin removal levels up to about 20%, no significant changes are expected in the combustion behavior. Application: This work will help mills identify the effect of lignin precipitation on combustion properties of black liquor.
Luomaharju T.,Valmet Power Oy |
Viljanen J.,Valmet Power Oy
CFB-11: Proceedings of the 11th International Conference on Fluidized Bed Technology | Year: 2014
Valmet Power has a long experience in fluidized bed combustion. Since 1980's both Bubbling Fluidized Bed (BFB) and Circulating Fluidized Bed (CFB) boilers have been used in combustion for various types of solid fuels, from fossil fuels to biomass and nowadays more and more for recovered fuels like demolition wood and SRF. Design features for large scale CFB boiler concept for Waste-to-Energy is presented. Main design parameters of fuel mixtures, chemical as well as physical properties are described. Fuel based challenges in boiler operation, eg. bed agglomeration, fouling, corrosion and flue gas emissions, and related process design and constructional features to tackle these challenges are discussed. Reference data for full SRF combustion is gathered from 75 MWth E.ON Händelöverket, Norrköping, Sweden and from 125 MWth Stora-Enso Langerbrugge, Belgium. This data includes typical combustion efficiency, ash and flue gas emission figures and findings related to fouling and corrosion. Availability history of the boilers show that higher than 97% reliability figures are typical for Waste-to-Energy CFB boilers. Regarding full SRF boiler concept, the design of new 155 MWth Waste-to-Energy CFB boiler for Mälarenergi, Västerås, Sweden is presented. This boiler is designed to burn household waste up to 70% and industrial waste up to 100% of heat input. Also some sludge, recovered wood, peat and biomass are part of the design fuel palette. Finally, the next generation Waste-to-Energy CFB concept of 250 MWth utilizing the latest knowledge available, eg superheating steam temperature capability up to 520°C is highlighted.
Mantyniemi J.,Valmet Power Oy
Biofuture for Mankind Conference | Year: 2014
Today there is a high demand for new technologies for converting renewable resources into sustainable results. The pulp and paper industry, along with many other utilities, have the benefit of having access to renewable raw material. Therefore they have a long history of processing biomass to sustainable products like bio-energy and pulp and paper products. This forms a good platform for developing and applying technologies to produce new, high value products. In this paper, two demonstrated bio-refinery processes, LignoBoost and Integrated Pyrolysis, are discussed.
Valmet Power Oy | Date: 2012-06-08
The method includes guiding a light beam to a first optical path, the light beam being attenuated to an attenuated light beam and detecting a first value indicative of a first intensity of the attenuated light beam. The method further includes generating a last light pulse, dissociating at least part of the gas compound molecules (optionally excited) or dissociated parts thereof (optionally excited) on the first optical path to first part atoms, molecules, ions, or radicals, and to another part using the last light pulse, the light beam being further attenuated by absorption to the first part atoms, molecules, ions, or radicals on the first optical path. The method further includes detecting a second value indicative of a second intensity of the attenuated light beam and determining, using the first and second values, the gas compound content of the gas mixture. A gas compound measuring device measures uses the method.
Valmet Power Oy | Date: 2014-11-26
A method for measuring, from a thermal device, temperature, molecular number density, and/or pressure of a gaseous compound as function of distance, the gaseous compound absorbing at least some light. The method comprises generating, for a first wavelength band and a second wavelength band, a pulse sequence comprising a light pulse or light pulses, guiding the pulse sequence into the thermal device, and measuring, as function of time, the intensity of the scattered light at the first wavelength band and at the second wavelength band. The method further comprises determining information indicative of the differential absorption between the two wavelengths bands using measured intensities and determining the temperature, the molecular number density, and/or the pressure of the gaseous compound using the information indicative of the differential absorption between the two wavelengths bands. A thermal system arranged to carry out the method.