Jan Dahl

Improved energy and material efficiency using new tools for global optimisation of residue material flows

Residue materials generated in the metallurgical industry have gained an increasing importance, both from the points of view of energy and material supply. A joint process integration model for the integrated steel plant system is developed and used in this paper. It takes into account both residue materials and energy recirculation for the system. The potential for increased recirculation and the effect on the system from an environmental point of view is presented, and implementations and practical experiences are discussed. The model developed can serve as a benchmark for different steelmaking operations and constitute a basis for the continuous work involved in material, energy, environment or economic analyses for the steel production system.

Heat and mass transfer simulations of the absorption process in a packed bed absorber

Numerical modelling of the absorption process in a cross-current absorber has been performed with FLOW3D, a commercially available software. The simulations are verified by comparisons with experimental results. The modelling of mass and heat transfer is discussed. Comparisons regarding the overall capacity as well as transfer rates show good agreement between experiments and simulations. It is possible to model the mass and heat transfer for a cross-current absorber if the equilibrium line for the absorption solution is known.

Absorbers in the open absorption system

This paper describes an experimental study of four different absorber designs in this type of system: cross-current and counter-current packed-bed absorbers, the spray absorber and fluid-bed absorber. In a laboratory pilot, plant, working lines for the absorbers were determined under adiabatic conditions. The influences of internal solution flow, gas flow, pressure drop and dissipation are discussed. The working lines represent the efficiency for each absorber. The highest performance occurs with the packed-bed absorbers, followed by the fluid-bed absorber and finally the spray absorber. For open absorption systems in air-conditioning applications (small scale), the cross-current absorber is preferable, and for industrial utilization (large scale) the fluid-bed absorber should be chosen.

Open absorption system: Experimental study in a laboratory pilot plant

The open absorption system is specially fitted in drying processes using air for the transport of the water. Advantages of the system are that different types of energy supply can be used, and that direct contact between the working media and the solution gives an effective absorber. This experimental study concerns measurements of the capacity of the system when a cross-flow absorber is used. Experiments were done under adiabatic and non-adiabatic conditions, and the results show that non-adiabatic conditions give a considerable increase in the absorption capacity. The dissipation of solution media increases strongly for air velocities over 2 m/s. However, a demister can be used to reduce these losses. Investigation of the packing depth shows that the absorption takes place mainly in the first quarter of the packing. Different types of plastic packings were studied, the Telpac packing giving the best results.

Use of video-based Particle Image Velocimetry technique for studies of velocity fields in a water heat storage vessel

A video-based Particle Image Velocimetry technique has been developed. The technique is particularly suitable for measurement of small velocities, below 3 cm/s. It has proved to be useful for the documentation of non-stationary velocity fields in a scaled-down model of a water heat storage vessel. An ordinary video camera is used to record the in-plane movements of particles in a light sheet in seeded water. The hardware used, the experimental method and the accuracy of the method are discussed. The use of two commercially available software packages (NIH-Image and IGOR) for the analyses is described. Examples of velocity fields are presented, showing that the measuring technique can be used for studies of mixing near the inlet of the storage vessel and exchange of water between the boundary layer and the core.

A theoretical investigation of the heat demand for public baths

Public baths normally use outdoor air to remove moisture from the building. This procedure results in large heating demands. A theoretical hour-based method for estimation of the heating demand has been developed. The method allows for dynamic behaviour with correct time periods for each mass-transfer level. Results of predictions with this method have been compared with yearly estimates of the heating demand based on actual measurements in a public bath. The difference is 3%. A parametric study shows that the air temperature and relative humidity in the building strongly influence the heating demand. Comparisons with other prediction methods based on use of the duration curve or mean annual outdoor temperature show differences less than 5% from results obtained with the hour-based method. The simpler approaches (use of a duration curve or mean value) fail when minimum outdoor airflow must be considered, as will be the case, for instance, when comparing different energy-saving systems or design of components for the climate system.

Experimental studies during heat load fluctuations in a 500 kW wood-chips fired boiler

Abstract Several long-term experiments with fluctuating thermal outputs have been carried out in a newly developed biomass fuelled boiler suitable for small district heating networks. The experiments have been performed by either using the furnace only or the furnace together with a water heat store. Comparisons between these two operation strategies have been made concerning emissions and overall performance. Furthermore, the plant has been run to match a simulated heat demand during different seasons, in order to study the performance of the system during more realistic operation conditions. The results are very satisfactory concerning both performance and emissions, using any of the control strategies. Typical emissions of CO and NOx during the experiments are in the range of 10– 50 mg Nm −3 (5– 25 mg MJ −1 ) and 130– 175 mg Nm −3 (60– 90 mg MJ −1 ), respectively. However, during summer when the heat demand is low or zero, operational problems will occur if the heat store is excluded. Therefore, the main conclusion is that the most appropriate solution for a small district-heating system is to use a water heat store to match the heat load variations, while the furnace operates at as constant thermal output as possible.

Process simulation and energy optimization for the pulp and paper mill

A process integration model is developed based on mixed integer linear programming. The analysis is carried out using the reMIND software in combination with the commercial optimization software CP ...

CO2 Emission Reduction in the Steel Industry by Using Emission Trading Programs

The implementation of the EU Emission Trading Scheme (ETS) started on January 1st 2005 according to national plans for allocating emissions rights. The steel industry is one of the industrial sectors included in this scheme. The objective of this paper is to investigate and evaluate the optimum solution(s) for European steel plants to meet their emission allowance with low reduction cost. An optimization model based on a Swedish steel plant is developed and used. Three scenarios were created in the model, i.e., internal changes within the steel plant, EU ETS, and the Kyoto Protocols clean development mechanism (CDM). For the last scenario, China was selected as a country of the non-Annex I Party for the emission trading by CDM. The modeling results show that the studied plant will face an emission gap between allowed and calculated emissions in the near future. Compared to EU ETS, the implementation of CDM projects will make the plant reduce CO2 emissions at a lower cost. The internal changes within the plant will also play an important role for the solution of low abatement cost. The model developed could serve as a benchmark for the future emission trading simulations purpose within the European steel industry.

System Optimization of an Electric Steel Making Plant with Sequenced Production and Dynamic Stock Level

One third of the total steel production in the world today is produced by electrical steel making and is supposed to increase. It is a very energy intense process but for the production costs the s ...