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Becidan M.,Sintef | Wang L.,Sintef | Fossum M.,Statkraft | Midtbust H.-O.,Energos AS | And 3 more authors.
Chemical Engineering Transactions | Year: 2015

The Norwegian Waste-to-Energy (WtE) industry faces a difficult situation on many levels: (a) an internationally open and competitive market with significant export of both MSW (Municipal Solid Waste) and C&I (Commercial & Industrial) waste to Sweden, (b) low energy revenues reduce profitability, (c) a limited national market (both concerning district heating and industry customers), (d) questions about CO2 footprint and (e) a more and more stringent regulative framework. All that comes in addition to an array of technical challenges associated with waste as a fuel for combustion applications. This work is a short discussion of important aspects, both challenges and opportunities, for the Norwegian 2030 WtE industry. The authors are from the three largest WtE actors in Norway, a WtE technology provider and a leading R&D institute. The reflection axes are articulated along three questions: 1. What are the unique advantages offered by WtE to the Norwegian society? 2. What are the challenges faced by WtE in Norway? 3. What are the novel aspects that will be essential for Norwegian WtE to take into account in the coming years? Copyright © 2015, AIDIC Servizi S.r.l.


Houshfar E.,Energos AS | Houshfar E.,Norwegian University of Science and Technology | Wang L.,Sintef | Vaha-Savo N.,Åbo Akademi University | And 2 more authors.
Clean Technologies and Environmental Policy | Year: 2014

Bioenergy is considered as a sustainable energy which can play a significant role in the future's energy scenarios to replace fossil fuels, not only in the heat production, but also in the electricity and transportation sectors. Emission formation and release of main ash-forming elements during thermal conversion of biomass fuels at different conditions have been the scope of this study. The experiments were conducted in a quartz glass reactor where the temperature and atmosphere could be controlled. The selected fuels represent a wide range of biomass compositions. They are torrefied softwood, spruce bark, waste wood, miscanthus, and wheat straw. The fuels were first grinded and then pressed with a pellet maker into pellets of the same size and weight. For each fuel, the experiments were carried out under both oxidation and pyrolysis condition, with atmosphere of 3 % O2 + 97 % N2 and 100 % N2, respectively, at four residence times. The selected temperatures under which experiments were performed are 800, 900, and 1,050 °C. The concentration of SO2, NO, CO, and CO2 emissions and O2 were monitored online by three analysers, simultaneously. The residue weight was measured after each process, and the comparison with the ash content of the fresh pellet is made. Additionally, the release of several ash-forming elements (K, Zn, Na, and Mn) from the fuels has been quantified as function of temperature and residence time by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Time-dependent formation of NO and SO2 and other emissions is presented and discussed with respect to different temperature and combustion conditions. © 2014 Springer-Verlag Berlin Heidelberg.


Lovas T.,Norwegian University of Science and Technology | Houshfar E.,ENERGOS AS | Bugge M.,Sintef | Skreiberg O.,Sintef
Energy and Fuels | Year: 2013

We present in this paper simplified chemical mechanisms for gas phase biomass combustion based on automatic reduction of detailed and comprehensive kinetics. The reduction method that has been employed is a combined reaction flow and sensitivity analysis well-known to combustion, resulting in a necessity index ranking all chemical species for automatic reduction. The objective is to obtain more compact chemical models, so-called skeletal mechanisms, for implementation into computational fluid dynamics, CFD, in order to reduce computational time. In the current work, the physical system used for the development and validation of the chemical models is that of a tubular reactor, or plug flow reactor, with operating conditions typically found in biomass reactors. The focus has been on gas phase reactions only, and the fuel composition is based on experimental values from biomass and coal gasification. Emphasis has been on the reliability of the simplified models and the correct prediction of important emission parameters such as NOx and important intermediate species. The original chemical model, consisting of several sub models for important reaction paths known in biomass combustion, contained 81 species and 1401 reactions. This was successfully reduced down to 36 species, providing a compact and reliable chemical model for implementation into CFD. The model still contains the reaction paths of C2 species, allowing for more realistic fuel gas compositions. The model has been experimentally validated for a wide range of temperatures including low temperature chemistry and reducing conditions for NOx. The computational time saved using the simplified models was significant with over 80% reduction in CPU time. © 2013 American Chemical Society.


Houshfar E.,Norwegian University of Science and Technology | Houshfar E.,Energos AS | Wang L.,Sintef | Vaha-Savo N.,Åbo Akademi University | And 2 more authors.
Chemical Engineering Transactions | Year: 2013

Emission formation during thermal conversion of biomass fuels at different conditions has been the scope of this study. The experiments were conducted in a quartz glass reactor where the temperature and atmosphere can be adjusted. The fuels were selected accurately in order to cover a wide range of biomass/waste compositions. They are torrefied softwood, spruce bark, waste wood, miscanthus, and wheat straw. The fuels were first grinded and then pressed into pellets of the same size and weight with a pellet maker. Each pellet was about 200 mg. The experiments were performed under combustion and pyrolysis condition, with atmosphere of 3 % O2 and 100 % N2, respectively. Each fuel was combusted under temperatures of 800, 900, and 1,050 °C. O2 and the formed SO2, NO, CO and CO2 were monitored by three analysers. The fuel pellet was kept under combustion and pyrolysis at four residence times. The residue weight was measured after each process and the comparison with the ash content of the original fuel is made. Time dependent formation of NO and SO2 and other emissions is presented and discussed in this paper. Effect of temperature and combustion condition is also considered for the conclusion. Copyright © 2013, AIDIC Servizi S.r.l.


Bugge M.,Sintef | Skreiberg O.,Sintef | Haugen N.E.L.,Sintef | Carlsson P.,Sintef | And 2 more authors.
Energy Procedia | Year: 2015

In the present paper NOx emissions from biomass combustion was studied, with the objective to demonstrate the applicability of stationary computational fluid dynamics simulations, including a detailed representation of the gas phase chemistry, to a multi-fuel lab-scale grate fired reactor using biomass as fuel. In biomass combustion applications, the most significant route for NOx formation is the fuel NOx mechanism. The formation of fuel NOx is very complex and sensitive to fuel composition and combustion conditions. And hence, accurate predictions of fuel NOx formation from biomass combustion rely heavily on the use of chemical kinetics with sufficient level of details. In the present work we use computational fluid dynamics together with three gas phase reaction mechanisms; one detailed mechanism consisting of 81 species and 1401 reactions, and two skeletal mechanisms with 49 and 36 species respectively. Using the detailed mechanism (81 species), the results show a high NOx reduction at a primary excess air ratio of 0.8, comparable to the NOx emission reduction level achieved in the corresponding experiment, demonstrating both the validity of the model and the potential of NOx reduction by staged air combustion. © 2015 The Authors. Published by Elsevier Ltd.


Becidan M.,Sintef | Houshfar E.,Energos AS | Wang L.,Sintef | Lundstrom P.,Energos AS | Grimshaw A.,Energos Ltd.
Chemical Engineering Transactions | Year: 2015

This succinct thermodynamic study addresses the gasification chemistry (air/fuel ratio of 0.5) of four chemical elements involved in ash-related challenges, i.e. Na, K, S and Cl. At typical temperatures for the process studied, the following main trends have been observed: (1) the phase distribution of these elements may change abruptly, i.e. within a narrow temperature range; (2) the main practical outcome of point 1 is that it will be difficult to optimise a given process giving the versatility of chemistry vs temperature but stable operating conditions are preferable. Methods exist to abate ash-related challenges but their selection should include both practical and economic considerations. Copyright © 2015, AIDIC Servizi S.r.l.

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