Jarmo Soderman

Future potential for biomass use in blast furnace ironmaking

Abstract Iron- and steelmaking is an energy intensive industrial sector using mainly coal as the heat source and reduction agent. The industry gives rise to about 7 % of the anthropogenic CO2 emissions in the world. In the absence of economically feasible and efficient methods of capturing and storing such enormous quantities of CO2, means for suppressing the emissions must be explored. The work reported in this paper studies the potential of injecting biomass to partially replace fossil reductants in the blast furnace process. The ironmaking blast furnace process is described mathematically by a thermodynamic simulation model, including realistic operational constraints. The model has been applied extensively to evaluate the use of biomass (e.g., wood chips) as auxiliary reductant, creating a simplified linear model on the basis of the results. The model is used to throw light on the feasibility of biomass injection under future price scenarios. Even though the coke replacement ratio of biomass is low, in the order of 25 %, it is demonstrated that the use of biomass as reductant can be a feasible alternative under future price scenarios of coke and emissions.

Influence of variations in cost factors in structural optimisation of heat recovery systems with moist air streams

Abstract Optimal solutions of heat recovery systems at paper machines (HRS), where both the specific heat flow rates and the overall heat transfer coefficients are strongly nonlinear, were analysed in respect of the influence of variations in the hot utility price (HU-price) and the annuity factor. A model for structural optimisation that takes into account the nonlinearities of the HRS was applied. In the study the variations in the areas and the topologies over a large range of HU-price and annuity factor were analysed. The sensitivity of the solutions on the nonlinear area costs was studied by solving the problem with varying total area costs, relative to the area cost of the optimal solution. The dependence of the total HRS-cost, the individual match areas and the hot utility consumption was analysed. The individual areas of the included matches showed particular variations at the boundaries of the topology changes.

Searching for enhanced energy systems with process integration in pulp and paper industries

Abstract The scope of this paper is to discuss some process integration options for enhancing the energy systems in pulp and paper industries. The focus is on the recovery of heat of the exhaust air streams from the paper machine dryer section and on the utilisation of eventual excess heat from thermo-mechanical pulping (TMP). With optimal heat recovery systems substantial savings can be obtained. New papermaking technologies like improvements in the press section and impingement drying have opened up new possibilities for utilisation of secondary heat energy. Production of electrical power with organic Rankine cycle (ORC) can be an option in that respect.

Synthesis of heat recovery systems in paper machines with varying design parameters

Abstract The heat recovery system (HRS) is a vital part in a paper machine when it comes to the overall energy economy in papermaking. For a typical newsprint machine more than 60% of the exhaust energy from the dryer section can be recovered, resulting in a recovery of about 30 MW. The synthesis task of a HRS is a decision process where the target is on the one hand to achieve maximal energy recovery and on the other hand to obtain this recovery with minimal investment costs. These goals are contradictory and thus the problem is to find a solution minimizing the overall costs, considering simultaneously both energy and investment costs. This synthesis task can be performed with e.g. pinch-analyses or optimization methods. One of the first tasks for the designer is to decide which design parameters, including process flow streams, temperatures and heat transfer coefficients are to be applied. This task is in general not trivial and the result will have a great impact on the overall economy of the final HRS. One challenge is how to take into account uncertainties and known variations in some parameters. The desired design must be capable of handling all evolving situations but it should also be the most economical one when considering the duration of the different operational situations. In this work the importance of taking the variations and uncertainties into account in the design stage is shown with a case study.