Mika Järvinen

• Aalto University

Thermal energy storage (TES) is becoming increasingly important in the modern energy landscape. As the global energy demand continues to rise and the integration of renewable energy becomes crucial, there is a growing need for sustainable and affordable ways to store energy. TES materials, such as sand, molten salts and heat transfer fluids, are a...

One of the main applications discussed in decarbonising the marine sector is via alternative fuels, such as methanol and ammonia, produced from renewable hydrogen. These alternative, low-carbon fuels often come with increased prices and operational expenses for the vessel operators, which are ultimately reflected in the passengers' costs. Therefore...

Global anthropogenic CO2 emissions are expected to peak to 40 Gt in 2020. If these emissions are not mitigated climate change and global warming will further aggregate. Meanwhile, demand for products and fuels produced from fossil raw materials are increasing. CO2, however, can be considered as feedstock for certain materials and processes. If CO2...

Link: https://www.sciencedirect.com/science/article/pii/S0306261920300702?dgcid=author#f0020 Supercritical water is a practical processing medium for the treatment of weak black liquor (WBL) produced from pulp digesters in Kraft mill operations. WBL is characterized as a bio-feed with considerable thermal potential , but also a challenging high w...

The slag2PCC concept aims at transforming steelmaking slag into precipitated calcium carbonate (PCC) with market value. This paper reports on R&D work on two features that impact the overall performance and costs of slag2PCC as a carbon capture and utilisation (CCU) technology. Operating near ambient conditions, calcium is selectively leached from...

In this paper, the effect of the particle size distribution (PSD) of the bed material on alkali and alkaline earth metal behavior in circulating fluidized bed combustion of solid-recovered fuel was studied. The Sauter mean diameter, of the PSDs studied: Gaussian-, flat-, binary-, and narrow distributions, was 200 µm. The concentration of both alkal...

Details of chemical heating in the CAS‐OB process are not known exactly, making a computational model valuable in process development and control. A phenomena‐based numerical model of the CAS‐OB heating stage is presented. Chemical equilibrium at reaction surfaces is assumed to be limited by mass transfer. Making use of a law of mass action based k...

Steelmaking is an extensive industry based on modifying the physical properties of iron to fit a wide range of applications by either adding alloying elements or removal of impurities. Thus, the effects of various elemental components on final steel properties are at the heart of the steelmaking process whether in small concentrations coming from t...

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 i...

Waste biomass as a mean for global carbon dioxide emissions mitigation remains under-utilized. This is mainly due to the low calorific value of virgin feedstock, characterized generally with high moisture content. Aqueous processing, namely hydrothermal liquefaction in subcritical water conditions, has been demonstrated experimentally to thermally...

Steel production generates approximately 7% of the global anthropogenic CO2 emissions. Due to the projected growth in demand, this figure can be expected to grow. As modern steel production has been optimized over the last decades close to its thermodynamical limit, further reduction of CO2 emission and energy demand by fine tuning are considered d...

Hydrothermal liquefaction of biomass continues to show promise in experimental and pilot scale tests for carbon partitioning toward desirable multi-phase organic products. Results from a techno-economic investigation are presented for a commercial scale stand-alone plant with primary production of renewable liquid fuels compatible with current tran...

In an earlier work, a fundamental mathematical model was proposed for side-blowing operation in the argon–oxygen decarburization (AOD) process. The purpose of this work is to present a new model, which focuses on the reactions during top-blowing in the AOD process. The model considers chemical reaction rate phenomena between the gas jet and the met...

In earlier work, a fundamental mathematical model was proposed for side-blowing operation in the argon oxygen decarburization (AOD) process. In the preceding part “Derivation of the Model,” a new mathematical model was proposed for reactions during top-blowing in the AOD process. In this model it was assumed that reactions occur simultaneously at t...

This article presents a summary of the main findings from a collaborative research project between Aalto University in Finland and partner universities. A comparative process synthesis, modelling and thermal assessment was conducted for the production of Bio-synthetic natural gas (SNG) and hydrogen from supercritical water refining of a lipid extra...

The purpose of this study is to investigate the feasibility of supercritical water gasification (SCWG) of black liquor integrated to a pulp mill. SCWG has potential as an alternative treatment for black liquor, thus enabling the conversion of pulp mills to multiproduct biorefinery plants. The current literature has investigated the yields and effic...

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, t...

The production of precipitated calcium carbonate (PCC) from steel slag has been proposed as a potential method of simultaneously reducing the CO2 emissions from the steelmaking process and turning its waste stream into a valuable product. On average the production of one ton of steel results in two tons of CO2 emissions and 600 kg of slag. Globally...

The objective of this paper was to present a new law of mass action based rate expression for mass transfer limited reversible reactions. A simple reaction model was derived for parallel oxidation of silicon, chromium and carbon under conditions relevant to the argon-oxygen decarburization (AOD) process. Our hypothesis is that when the forward rate...

The gasification of biomass in supercritical water is an emerging technology which offers the opportunity to produce methane and hydrogen from high-moisture biomass and waste streams. The obstacles of the technology owe to an early development stage but can also be attributed to the mechanically and chemically challenging process conditions (>375 °...

This paper proposes a novel method for modeling the reduction stage of the CAS-OB process (composition adjustment by sealed argon bubbling–oxygen blowing). Our previous study proposed a model for the heating stage of the CAS-OB process; the purpose of the present study is to extend this work toward a more comprehensive model for the process in ques...

Improving energetic performance is a key factor in making societies more sustainable. One way to analyze energetic performance is to use methods based on the second law of thermodynamics. Exergy analysis is such a method. With exergy analysis thermodynamic losses of the studied system can be found. For a specific process decreasing the exergy losse...

Hydrothermal liquefaction of biomass continues to show promise in experimental scale tests for both, biocrude yield and carbon balance toward desirable organic products. As part of Finland's national drive toward a future bio-economy, a techno-economic investigation was conducted for a 653 MWLHV (15 wt.% solids) Finnish forest residue feedstock und...

Hydrothermal liquefaction of biomass has continued to show promise in experimental scale tests for the production of valorised biocrude, compatible with existing CHP infrastructure. A constrained thermodynamic model is developed to match the recorded mass and energy balances in literature, and depict the solid organic to liquid fuel conversion for...

In order to decrease the rate of reductants originating from fossil sources in iron- and steelmaking, the use of biomass was studied numerically. A biomass pretreatment plant, consisting of a drier and a torrefaction/pyrolysis unit, was integrated with the steel plant, utilizing the off-gas of the hot stoves and blast furnace gas for drying the bio...

Carbonate rocks are commonly utilized in Wet Flue Gas Desulfurization, WFGD, because of their capability to release calcium ions and precipitate as solid gypsum in an acidic environment. Studies on the reactivity of carbonate rocks and dissolution models can be employed for optimizing the WFGD process. The correct evaluation of limestone reactivity...

Hydrothermal processing of organics, particularly the supercritical water gasification process, has showed potential in lab-scale records to valorize the chemical energy stored in biomass. The technology manipulates the varying thermo-physical properties around the critical point of water to convert and upgrade the organic content, as well as extra...

An existing model of the CAS-OB process has been optimized for online use by carefully selecting state variables, removal of implicit algebraic equations, and reformulating the system as a set of ordinary differential equations. The revised model has been validated with the previous model as well as with process measurements. Further, the model has...

Biomass conversion in supercritical water represents one of the emerging areas of the reaction engineering. Additionally, Supercritical Water Gasification, SCWG, offers great possibilities for new ways of reactors design and operations. Reactive separation processes represent the future in this sense. In our studies experiments were done on SCWG of...

Examples of mathematical modelling of converter and ladle processes.

Supercritical water as a process medium for hydrothermal treatment of carbonaceous material has shown an advantageous nature for energetic valorisation. The thermo-physical properties of water around the acute conditions of 22.09 MPa and 374.29˚C (critical point of water) vary significantly and a mixture of both compressible liquid-and gas-like beh...

Hydrothermal processing of biomass, and in particular supercritical water gasification, SCWG, has illustrated the potential to counter technical barriers that continue to face the wide deployment of biomass based energy systems. A conceptual plant flow sheet for SCWG of spirulina algae feedstock is developed on Aspen plus® for synthetic natural gas...

Supercritical water gasification as a mean for hydrothermal processing of biomass, has illustrated the potential to overcome technical barriers that continue to prevent the prevalence of biomass based energy systems. This paper provides a systematic analysis to fill the knowledge gap for upscaling the process from laboratory bench scale to energeti...

In this study, we apply ultrasound velocity profiling (UVP) for obtaining velocity data inside black liquor nozzles. We demonstrate the capability of this technique for online measurement of black liquor flow properties and viscosity behavior. The experiments were carried out on an operating recovery boiler where the black liquor from pulping softw...

Ultrasound is considered to be an effective agitation technique to enhance the rates of reaction and mass transfer for various chemical processes. The literature reports several successful ultrasonic application cases, including extractive metallurgy. The present study investigates the effect of sonication (referring to the application of ultrasoun...

While many metallurgical processes involve the use of top lances, little is known about the heat and mass transfer coefficients of such instruments due to difficulties in measurement procedures. This paper presents a new gas heat and mass transfer coefficient model which can be implemented as part of a CAS-OB process model. We begin by testing seve...

This article presents a new computational two-phase flow model and extensive validation for an industrial splash plate nozzle. The primary motivation for this work was to develop a simulation tool that can be used to reliably calculate initial droplet velocity data of industrial spray nozzles. This is an important part in properly defining boundary...

The objective of this paper is to test Raoult's law for calculating the boiling point elevation and the vapor pressure of black liquor. The vapor pressure of black liquor is an essential variable in black liquor evaporation, spraying and black liquor droplet drying during combustion. Typically only the boiling point elevation at the atmospheric pre...

The objective of this work was to develop a process model for the CAS-OB (Composition Adjustment by Sealed argon bubbling-Oxygen Blowing). The CAS-OB is designed to homogenize and control the steel composition and temperature before the casting. In the heating mode (OB) studied here, a refractory bell is lowered and submerged 30 cm below the liquid...

Biomass fast pyrolysis (BFP) is a promising pre-treatment technology for converting biomass to transport fuel and in the future also for high-grade chemicals. BFP can be integrated with a municipal combined heat and power (CHP) plant. This paper shows the influence of BFP integration on a CHP plant's main parameters and its effect on the energetic...

CAS-OB process is a process designed for controlling the steel composition and temperature before casting. In our previous work, a novel numerical model was proposed for the heat-up stage of the CAS-OB process. This model considers all the main phenomena observed in the process, including reactions between gas jet and steel bath, reactions between...

The goal of biofuel production is to partially replace fossil fuels in energy generation and transport. For the evaluation of biofuel production processes different criteria are applied and usually they include costs, efficiency aspects and emissions. However, evaluation of the energy efficiency of biofuels production is difficult since no general...

Improving energetic performance is a key factor in making societies more sustainable. One way to analyze energetic performance is to use methods based on the second law of thermodynamics. Exergy analysis is such a method. With exergy analysis thermodynamic losses of the studied system can be found. Exergy shows the maximum useful work potential tha...

According to IEA Carbon Capture and Storage (CCS) is necessary for successful climate change mitigation and would need to account for approximately 25% of total carbon dioxide reductions. EU has emphasized the need for CCS by developing incentives through the establishment of a funding programme and by including CCS into emission trading. Policy ha...

In this preliminary study we apply Ultrasound Velocity Profiling (UVP) for obtaining velocity data inside black liquor nozzles. We demonstrate the capability of this technique for measuring flow properties and viscosity behavior of the black liquor online. The experiments were carried out on an operating recovery boiler where the black liquor from...

This paper investigates simulation results of the thermodynamic performance of a 25 kWel small-scale solid oxide fuel cell model fuelled with biogas. Hereby, biogas is produced from a predefined group of substrates, namely, livestock effluents, energy crops, agricultural waste, and organic waste. For the analysis, average methane (CH4) content is a...

The purpose of unit processes in primary and secondary steelmaking is to refine the steel so that the specified steel composition and temperature are achieved and the steel melt is ready for casting. o The control of decarburization, removal of dissolved gases, temperature and inclusions is of particular importance. In this regard, the Finnish stee...

One of the major advantages of supercritical water gasification (SCWG) of biomass is the possibility to process feedstock with high water content without the need of drying. Regarding the industrial application of the SCWG technology it is clear that heat-recovery and -integration will play a crucial role, as will the applied heat conversion techno...

Purpose – The purpose of this paper is to identify the most significant uncertainties for bioenergy applications, in order to identify factors determining the success of introducing bioenergy into the current energy system. Design/methodology/approach – A framework is built for identifying the most significant uncertainties based on studies explor...

The gasification of biomass in supercritical water is an emerging technology which offers the opportunity to produce methane and hydrogen from high-moisture biomass and waste streams. The obstacles of the technology owe to an early development stage but can also be attributed to the mechanically and chemically challenging process con-ditions. The s...

In the present study a generalized approach is given for the description of acquisition procedures with a particular focus on the knowledge acquisition process. The learning progression is given as an example here letting the theory to be applied to different situations. An analytical approach is performed starting from the generalized fundamental...

The first objective of this paper is to provide a brief presentation and experimental validation of a new two-phase flow simulation model for a flashing black liquor gun. The model is based on the one-dimensional mass, momentum, and energy balances in the viscous multiphase nozzle flow. A detailed growth model of a single vapour bubble in the super...

Success of individual CCS projects as well as integration of CCS into larger energy systems depend on institutional and organizational support from a variety of contexts. We map stakeholder perceptions from an institutional perspective and present a framework for identifying path dependencies, challenges and opportunities in the dynamic development...

Fossil fuels applied in energy generation-, transport- and refinery processes can be replaced by biofuels. This offers plenty processing options for biomass resources such as thermo-chemical. For process evaluation different criteria is applied, usually including costs, energy efficiency and CO2 emission. However, comparative evaluation of the ener...

This paper summarizes and discusses our recent work on modelling of several steelmaking processes. The work started by developing a detailed sub-model for a single gas bubble reacting in liquid steel. The key feature in this model was an approach based on LOMA, Law of Mass Action, which was employed for defining the chemical rate of a reaction in a...

In order to react on future expected increased competition on restricted biomass resources, communal combined heat and power (CHP) plants can be integrated with biomass upgrading processes that add valuable products to the portfolio. In this paper, outgoing from a base case, the retrofit integration of production of wood pellets (WPs), torrefied wo...

Numerical models of steelmaking processes are essential tools for process development and optimisation. A usable model is detailed enough to provide reliable results and not to slow to run. In order to make a fast and accurate model of a single process, all model parameters must be known well. This can be achieved by first simulating detailed model...

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 Desulfuriz...

The use of biofuel as a road transportation fuel is increasing throughout Europe and other industrialized countries to reduce greenhouse gas emissions and to improve the security of fuel supply. Bio-oil produced from biomass pyrolysis is renewable liquid fuel and can also be used for production of chemicals. Upgrading of the bio-oil to transportati...

A process model was proposed by Jarvinen and co-authors for modelling the side-blowing decarburisation stage of the Argon-Oxygen Decarburisation (AOD) process. Here, a new model for the reduction stage has been derived and coupled with the earlier-developed model. The model considers mass-transfer controlled reversible reactions between the steel b...

A process model was proposed by Jarvinen and co-authors for modelling the side-blowing decarburisation stage of the Argon-Oxygen Decarburisation (AOD) process. In Part I, a new mathematical model was derived for the reduction stage and coupled with the decarburisation model developed earlier. This paper, Part II, considers the validation of the mod...

9 Different environmental processes utilize calcium carbonate and sedimentary rocks, for instance sedimentary 10 rocks are used for water purification as filters and utilized also for acid remediation of process waters before 11 being discarded. Additionally sedimentary rocks are used in another very important environmental process, wet 12 Flue Gas...

A new process model has previously been introduced for modelling side-blowing practise during the decarburisation phase of the Argon-Oxygen Decarburisation (AOD) process. The same model has been modified here to study oxygen consumption in the individual reactions and locally varying oxygen partial pressures representing the equilibrium of the oxid...

A prediction for product gases of Jatropha curcas Linn (JCL) oil cake gasified in the entrained flow reactor is studied in this paper. ASPEN PLUS commercial software is used to carry out the simulation using Gibbs free energy minimisation with equilibrium phase. A series of simulations and analyses have been carried out to investigate the compositi...

In order to estimate the heat of condensation of fast pyrolysis product of woody biomass a model to be used in the chemical process simulation software Aspen+ has been developed based on the composition of wood fast pyrolysis product. A simulation model for biomass fast pyrolysis was developed. The results obtained are in good accordance with value...

The objective of this paper is to present a comprehensive new single-particle combustion model that can be used effectively in Computational Fluid Dynamics (CFD) applications. As a major difference from standard particle sub-models used in CFD software packages, the new model is suitable for simulating thermally large particles, which means that it...

This paper presents a new simulation model for the AOD process that takes the local variations into account but is still computationally efficient. The new idea here was to model AOD reactor as a combination of a plug flow reactor for the plume zone and a continuously stirred tank reactor (CSTR) for the bath and surface slag. This approach adopted...

This paper presents a new simulation model for the AOD (Argon Oxygen Decarburization) process that takes the local variations into account but is still computationally efficient. The new idea here was to model AOD steel converter as a combination of a plug flow reactor for the reactive plume zone and a continuously stirred tank reactor for the bath...

A fundamental mathematical model for AOD process has been developed and proposed in “Fundamental Mathematical Model for AOD Process. Part I: Derivation of the Model” 1. Validation of the model with process data, measured from full scale AOD process, is presented in this paper. A broad selection of input data for the model was exported from various...

This paper presents a new computational flow model for a flashing black liquor gun. The primary motivation for this work was to have a tool to reliably calculate initial droplet data for CFD furnace combustion simulations of a recovery boiler. The model will also be actively used for industrial engineering and design of black liquor nozzle developm...

Black liquor is sprayed into the recovery boiler at a temperature above boiling point. Furnace operations are greatly affected by spraying and droplet formation stages before and during drying and devolatilization. Essential dynamics are already defined inside the nozzle, inside which small bubbles have formed. These bubbles grow and increase black...

Significance of interfacial phenomena and properties such as surface tension are essential in iron and steelmaking processes due to chemical reactions occurring on the interfaces including elements transfer through the phase boundaries. In this study, the influences of surface tensions of slag and metal and interfacial tension between slag and meta...

A new detailed model that describes the chemical reactions, mass transfer and heat transfer taking place on the surface of a single gas bubble in liquid steel is presented in this paper. By using this model, locally occurring small scale physical and chemical mechanisms can be effectively studied. This information is required later in developing a...

This paper presents a new computational flow model for a flashing black liquor gun. The model is based on the numerical solution of one-dimensional conservation equations of mass, momentum, energy and steam mass fraction. Mass-momentum coupling is solved by the SIMPLE method. Scalar equations are solved by the fully implicit control volume method....

The characteristics of black liquor sprays can be estimated using flashing maps that present the velocity of the spray at different spraying temperatures as a function of mass flux. Dimensionless velocity describes well the flashing intensity of the flow and is the key factor in estimating the effect of minor changes in spraying tem-perature or mas...

The characteristics of black liquor sprays can be estimated using flashing maps that present the velocity of the spray at different spraying temperatures as a function of mass flux. Dimensionless velocity describes well the flashing intensity of the flow and is the key factor in estimating the effect of minor changes in spraying temperature or mass...

The objective of this paper is to determine biorefinery concepts producing biofuel that are suitable for integration into combined heat and power plants. The driving force is that the reduction of greenhouse gas emissions in the transportation and energy sector will increase competition in biomasses. It seems that by polygeneration of interstage fu...

The size and shape of the droplets sprayed into the furnace of a recovery boiler have a paramount effect on the combustion and flight-path characteristics of black liquor droplets. In this study methods to characterize spray droplets and experimental data of essential particle characteristics are presented. Shape factors for heat and mass transfer,...

Full-scale black liquor spraying experiments were carried out at three spraying temperatures and three mass flow rates with high solids content black liquor. We studied the spray disintegration mechanism, the length of the sheet, and estimation of drop size from the wavelength of a black liquor sheet. The flash-dominated disintegration mechanism pr...

A furnace endoscope was developed to carry out in-furnace measurements of black liquor sprays in order to discover the initial velocity, opening angle and trajectory of the spray, and compare spray disintegration mechanisms and spray appearance with the ones measured in a spray chamber. An error analysis of the velocity measurement method was carri...

The size and shape of droplets sprayed into the furnace of a recovery boiler have a paramount effect on the combustion and flight-path characteristics of black liquor droplets. This study presents a method to analyze black liquor particle shapes and experimental data obtained with industrial scale splashplate nozzles. A large number of particle sha...