Øyvind Skreiberg

Cost modeling approach and economic analysis of biomass gasification integrated solid oxide fuel cell systems

This paper presents a cost modeling approach and the economic feasibility for selected plant configurations operating under three modes: air gasification, mixed air-steam gasification, and steam gasification combined cycle solid oxide fuel cell (SOFC) systems. In this study, three cases of biomass gasification integrated SOFC without combined cycle (base case 1) are compared with biomass gasification integrated SOFC-gas turbine (GT) with heat recovery steam generator (HRSG) hybrid configuration (case 2) and biomass gasification integrated SOFC-steam turbine (ST) cycle (case 3) for biomass feed stock. The plant design cases of integrated biomass gasification processes, SOFC, and combined cycles are investigated primarily employing aspen plus™ flow sheeting models. Based on the mass and energy balance results of the system simulations, the economic model calculates the size and cost estimates for the plant configuration equipments. Detailed purchase cost estimations for each piece of equipments and the corr...

The effect of kaolin on the combustion of demolition wood under well-controlled conditions.

In an attempt to look at means for reduction of corrosion in boilers, combustion experiments are performed on demolition wood with kaolin as additive. The experiments were performed in a multi-fuel reactor with continuous feed of pellets and by applying staged air combustion. A total characterization of the elemental composition of the fuel, the bottom ash and some particle size stages of fly ash was performed. This was done in order to follow the fate of some of the problematic compounds in demolition wood as a function of kaolin addition and other combustion-related parameters. In particular chlorine and potassium distribution between the gas phase, the bottom ash and the fly ash is reported as a function of increased kaolin addition, reactor temperature and air staging. Kaolin addition of 5 and 10% were found to give the least aerosol load in the fly ash. In addition, the chlorine concentration in aerosol particles was at its lowest levels for the same addition of kaolin, although the difference between 5 and 10% addition was minimal. The reactor temperature was found to have a minimal effect on both the fly ash and bottom ash properties.

Combustion Properties of Norwegian Biomass: Wood Chips and Forest Residues

Flue gas emissions and particle size distribution were investigated during combustion experiments of wood, forest residue and mixtures of these two. The combustion experiments were carried out in a grate fired multi-fuel reactor with and without air staging at stable operation conditions and constant temperature of 850 °C. The overall excess air ratio was held at 1.6, and the primary excess air ratio was 0.8 during air staged experiments. NOx emissions are reduced by air staging. Fly ash particle concentration of forest residues in the flue gas is lower than wood. Aerosols number increased in the staged experiments for fuel blends.

Hydrochar slurry fuels and high-grade activated carbon for electricity production and storage Conceptual process design and analysis

This paper describes and analyzes a conceptual design of a bioenergy system for sustainable electricity production from low-grade biomass resources such as forest and agricultural residues, which is suitable for rural areas in developing regions susceptible to intermittent electricity supply. In order to make it a closed-loop system, the paper also identifies a bio-refining strategy focusing on production of high-grade activated carbons for energy storage using supercapacitor.

Cooling aerosols and changes in albedo counteract warming from CO2 and black carbon from forest bioenergy in Norway

Climate impacts of forest bioenergy result from a multitude of warming and cooling effects and vary by location and technology. While past bioenergy studies have analysed a limited number of climate-altering pollutants and activities, no studies have jointly addressed supply chain greenhouse gas emissions, biogenic CO2 fluxes, aerosols and albedo changes at high spatial and process detail. Here, we present a national-level climate impact analysis of stationary bioenergy systems in Norway based on wood-burning stoves and wood biomass-based district heating. We find that cooling aerosols and albedo offset 60–70% of total warming, leaving a net warming of 340 or 69 kg CO2e MWh−1 for stoves or district heating, respectively. Large variations are observed over locations for albedo, and over technology alternatives for aerosols. By demonstrating both notable magnitudes and complexities of different climate warming and cooling effects of forest bioenergy in Norway, our study emphasizes the need to consider multiple forcing agents in climate impact analysis of forest bioenergy.

Simple modelling procedure for the indoor thermal environment of highly insulated buildings heated by wood stoves

Space heating using wood stoves is a popular solution in many European countries. The nominal power of the state-of-the-art stoves is oversized compared to the needs of highly insulated buildings, leading to a risk of overheating. A modelling procedure is here developed in order to investigate the indoor thermal environment generated by wood stoves in such buildings. This procedure is kept simple to perform all-year detailed dynamic simulations (e.g. using TRNSYS) at an acceptable computational cost. A specific experimental set-up has been developed for validation, essentially regarding the interaction between the stove and the building. The largest source of error appears to be the thermal stratification in the room where the stove is placed. The experiments prove that the model gives a fair insight into the global thermal comfort. Therefore, it is possible to investigate the conditions required for a stove to be properly integrated in a highly insulated building.

CO2 Reactivity Assessment of Woody Biomass Biocarbons for Metallurgical Purposes

Replacing the use of fossil reductants with biocarbons in metallurgical industries has a great potential with respect to reducing CO2 emissions and the contribution from this industry to the increasing greenhouse gas effect. However, biocarbons are significantly different from fossil reductants and the biocarbon properties vary in a wide range depending on the raw biomass properties and the biocarbon production process conditions. A key property of the biocarbons is their reactivity in the specific metallurgical process. The reactivity should be appropriate for the specific metallurgical process, to ensure an optimum reduction process. Especially important is the biocarbon reactivity towards CO2, i.e. the CO2 gasification of biocarbon fixed carbon. A standard method has earlier been developed by the metallurgical industry to test the CO2 reactivity of coal and coke. This can be adopted also for biocarbons. However, a simpler and more cost-efficient reactivity test method is wished for. For the silicon industry, also SiO reactivity is important and a standard method has been developed. This is very expensive to carry out, and also here a simpler and more cost-efficient reactivity test method is wished for. If a qualitative correlation between SiO and CO2 reactivity could be established as well, this would be very beneficial for this metallurgical industry. In this study, the main objectives were to assess the CO2 reactivity of biocarbons produced from different woody biomass in two experimental setups, a standardized setup and a thermogravimetric analyser (TGA), and to compare with the reactivity of fossil reductants. Spruce and birch stem wood and in addition their forest residues were tested. The results show that even if quantitatively different results were found in the two experimental setups, the qualitative results were the same, and hence the TGA test provides the opportunity of a simplified and cost-efficient CO2 reactivity test method. The biocarbon from the forest residues showed a higher reactivity than stem wood biocarbon, probably due to the higher ash content in the forest residues and their biocarbons, giving a catalytic effect. Compared to coke the biocarbons were more reactive.

Pelletizing and Combustion Behaviors of Wood Waste with Additives Mixing

Pelletizing and combustion behaviors of wood waste with and without additive addition were investigated in this study. It was found that the wood waste pellets have a high potential for slag formation during combustion and can cause operational problems. With additives addition, no significant changes were observed regarding mechanical properties of the wood waste pellets. Sewage sludge addition was found to have positive effects on NOx and CO emissions during combustion. Both sewage sludge and marble sludge addition have evident influence on slag formation during combustion. Sewage sludge addition reduced the formed slag amount and sizes, and therefore improved the boiler operation. Marble sludge eliminated the slag formation during the wood waste pellets combustion.

Mathematical Modelling and Performance Analysis of a Small-Scale Combined Heat and Power System Based on Biomass Waste Downdraft Gasification

The paper presents a simple mathematical model for designing, optimizing and simulating small–medium CHP scale plant with use of biomass waste downdraft gasification. A downdraft gasifier has been used as the starting point in the study, due to its low tar content and effective way of using heat in the engine’s exhaust gases to dry and pyrolyze the different solid biomass waste. Hot water from the cooling circuit of the engine and from producer gas cooling is directly used for the district heating network, air or steam preheating. The mathematical model includes modelled components as a downdraft gasifier, an internal combustion engine using the characteristic equation approach method. The mathematical model enables the outputs of the plant to be evaluated and calculated for different types of biomass and operating conditions. The results demonstrate that it is a useful tool for assessing the performance of CHP plants using several types of biomass waste and enables comparisons to be made between operating conditions for real applications.

Towards a meaningful non-isothermal kinetics for biomass materials and other complex organic samples

The literature of the kinetics in thermal analysis deals mainly with models that consist of a single reaction equation. However, most samples with practical importance are too complex for such an oversimplified description. There is no universal way to overcome the difficulties, though there are well-established models that can express the complexity of the studied reactions for several important types of samples. The assumption of more than one reaction increases the number of unknown parameters. Their reliable estimation requests the evaluation of a series of experiments. The various linearization techniques cannot be employed in such cases, while the method of least squares can be carried out at any complexity of the models by proper numerical methods. It is advantageous to evaluate simultaneously experiments with linear and nonlinear temperature programs because a set of constant heating rate experiments is frequently not sufficient to distinguish between different models or model variants. It is well worth including modulated and constant reaction rate temperature programs into the evaluated series whenever they are obtainable. Sometimes different samples share some common features. In such cases one can try to describe their reactions by assuming parts of the kinetic parameters to be common for the samples. One should base the obtained models and parameter values on a sufficiently large amount of experimental information, in a reliable way. This article is based on the authors’ experience in the indicated directions from 1979 till the present. Though the examples shown are taken from biomass research, the models and methods shown in the article are also hoped to be relevant for other materials that have complicated structure or exhibit complicated thermal reactions, or both.