Mika Järvinen

A study on Supercritical Water Gasification of black liquor conducted in Stainless Steel and Nickel-Chromium-Molybdenum reactors.

BACKGROUND This study presents supercritical water gasification (SCWG) as an alternative treatment process for black liquor: investigating the impacts of black liquor constituents, temperature and catalyst. The preliminary experiments include SCWG of sucrose and isoeugenol in stainless steel reactor, as model compounds of sugars and lignin. Then, the experiments of SCWG of black liquor are performed in stainless steel and INCONEL 625 reactors. RESULTS The results illustrated the impacts of temperature, black liquor constituents and nickel catalyst on the SCWG process. Temperature and the INCONEL reactor promoted gasification efficiency and hot gas efficiency: over 80% hot gas efficiency was reached for black liquor in the INCONEL reactor at 700 °C. Experiments on model compounds have shown that sugars generate more carbon dioxide, while lignin generates more methane. Hydrogen fraction and yield increased with temperature; nevertheless, black liquor generated hydrogen-rich gas. The INCONEL reactor increased hot gas efficiency despite no significant impact on carbon gasification efficiency: hydrogen is promoted dramatically. In addition, temperature and the INCONEL catalyst reduce tar and char formation as well. CONCLUSIONS Supercritical water gasification (SCWG) is potentially a suitable treatment for black liquor: it has no evaporation requirement and high hot gas efficiency. This process can be a solution for non-wood mills and can increase the product spectrum of Kraft mills by operating as a parallel treatment. On the other hand, sulphur balance is to be investigated for integration with Kraft mills together with a detailed feasibility study.

Effective Thermal Conductivity and Internal Thermal Radiation in Burning Black Liquor Particles

The effective thermal conductivity of burning black liquor particles is studied. It is one of the most important parameters affecting the rate of particle heating and, consequently, processes controlled by heat transfer rate, such as the devolatilization studied here. A numerical combustion simulation sensitivity analysis, combined with experimental verification, showed that in order to have reasonable agreement between experimental and modeled carbon release rates and swelling during pyrolysis, a significant addition of internal thermal radiation heat transfer must be included in effective thermal conductivity. In terms of the Rosseland mean absorption coefficient a R in diffusion approximation for radiative thermal conductivity, the value ∼850 m m 1 gave the best correlation with experiments. This corresponds to a mean penetration length of 1.2 mm, which is very close to the largest experimentally observed pore size. Other available effective thermal conductivity models were also compared. For the 1-mm pores observed experimentally, these models predict values for thermal conductivity that are too small.

Supercritical Water Gasification of Biomass

It is becoming clearer that alternative forms of energy should be investigated in order to face the increasing world energy consumption. Additionally, process integration of different technologies represents an important step for energy savings. Supercritical water gasification (SCWG), of biomass and organic by-products and waste from the process industry, represents one of the possible future options for syngas production. The technology has the potential to be integrated in industrial processes, for instance existing pulp mills. Through this manuscript, authors aimed at giving a comprehensive overview of the SCWG technology together with the most common methods utilized to investigate the process parameters and the mathematical methods utilized to investigate the rates and yields of the reactions involved. Biomass gasification is not widely employed because there is still the need for improvement of the gasification efficiency (GE) together with the minimization of tar and char formation. However, there are parameters that could lead to minimization of organic deposits and improvement of the GE. Experimental results together with suggestions on further research are given through the text. Although this technology also presents some drawbacks, further investigation and setup developments will give this technology the required degree of maturity for industrial scopes.

On modeling the dissolution of sedimentary rocks in acidic environments. An overview of selected mathematical methods with presentation of a case study

Different environmental processes utilize calcium carbonate and sedimentary rocks, for instance sedimentary rocks are used for water purification as filters and utilized also for acid remediation of process waters before being discarded. Additionally sedimentary rocks are used in another very important environmental process, wet Flue Gas Desulfurization. In this process, limestone and carbonates in general play one important role because of their dissolution and provision of the necessary amount of calcium ions used for the precipitation of gypsum. The objective of this study is to present in a first place an overview of a reduced number of specific theoretical and empirical mathematical models applied to the dissolution of carbonates in acidic environments with provision of additional developments and details, secondly a case study was presented where a suitable time of exposure and surface diffusivity obtained analytically by different methods well describe the experimental results. There were justifications for this choice. The experimental data and the related mathematical modeling were performed considering transient conditions. In the present work diverse raw materials were tested in order to reveal their suitability for wet Flue Gas Desulfurization. The research was focused on products from

A Mathematical Model for Reactions During Top-Blowing in the AOD Process: Derivation of the Model

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Process modeling, synthesis and thermodynamic evaluation of hydrogen production from hydrothermal processing of lipid extracted algae integrated with a downstream reformer conceptual plant

CO2 fixation processes materials as well as other types of limestone samples. In this way it was found that also waste materials from different environmental processes, like

An assessment of the uncertainties related to bioenergy applications.

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