Modelling of wood-chip refining processes

At present, due to the complexity of the wood chip refining processes, there are no suitable physical or parametric models available which can be used when studying different control strategies. It is shown that the process, which consists of two serially linked refiners, can be modelled as two multiple input, single output systems. To each refiner the dynamics from the chip flow to the motor load and from dilution water to the motor load are examined. It is shown that the pressure cannot be ignored in the model and that the motor load of the first refiner can be used as an input when modelling the second refiner. This indicates the possibility to use the load for feed forward control. The time stability of the models found was examined. The survey showed a small change in the model characteristics, but the ability to simulate the motor toads was not significantly reduced

Improved hydrogen peroxide bleaching of mechanical pulps using carbon dioxide in combination with sodium and magnesium based alkali sources

The pH-profile in the hydrogen peroxide bleaching stage of a Norway spruce thermomechanical pulp was levelled out by using carbon dioxide in combination with sodium or magnesium based alkali sources. Addition of carbon dioxide when magnesium hydroxide was used as the alkali source increased the pulp brightness with up to 1.5 brightness units when the bleaching was performed at 70 \ub0C. When the temperature was increased from 70\ub0C to 90 \ub0C the brightness was increased with about two brightness units, addition of carbon dioxide increased it further. The residual hydrogen peroxide and the chemical oxygen demand (COD) levels were not affected as a consequence of the carbon dioxide addition. In the experiments where sodium hydroxide was used as the alkali source, addition of carbon dioxide lowered the pH that resulted in a decreased COD level, a slightly lower brightness level and, to some extent, an increased residual hydrogen peroxide level

Improved hydrogen peroxide bleaching of mechanical pulps using carbon dioxide in combination with sodium and magnesium based alkali sources

The pH-profile in the hydrogen peroxide bleaching stage of a Norway spruce thermomechanical pulp was levelled out by using carbon dioxide in combination with sodium or magnesium based alkali sources. Addition of carbon dioxide when magnesium hydroxide was used as the alkali source increased the pulp brightness with up to 1.5 brightness units when the bleaching was performed at 70 \ub0C. When the temperature was increased from 70\ub0C to 90 \ub0C the brightness was increased with about two brightness units, addition of carbon dioxide increased it further. The residual hydrogen peroxide and the chemical oxygen demand (COD) levels were not affected as a consequence of the carbon dioxide addition. In the experiments where sodium hydroxide was used as the alkali source, addition of carbon dioxide lowered the pH that resulted in a decreased COD level, a slightly lower brightness level and, to some extent, an increased residual hydrogen peroxide level

Comparing fuel cells and other power trains for different vehicle applications

This paper compares the total cost of ownership (TCO) for fuel cell, battery electric, range extender and biofuel combustion engine power trains. The TCO difference shows that the power trains are suitable for very different vehicle niches. Battery electric vehicles can reach the lowest cost per kilometer, but only if the battery is utilized very much. Fuel cell range extender vehicles are cost effective for vehicles requiring long driving range but typically driving shorter distances. Internal combustion engine power trains will have the lowest TCO for vehicles with short driving distance during their life, even if the biofuel is rather expensive

Extended unemployment benefits and early retirement: program complementarity and program substitution

This paper explores how extended unemployment insurance (UI) benefits targeted to older workers affect early retirement and social welfare. The trade-off of optimal UI between consumption smoothing and moral hazard requires accounting for the entire early retirement system, which often includes extended UI and relaxed access to disability insurance (DI). We argue that extended UI generates program complementarity (increased take-up of UI followed by DI and/or regular retirement benefits) and program substitution (increased take-up of UI instead of DI). Exploiting Austria's regional extended benefit program, which extended regular UI benefits to up to 4 years, we find: (i) program complementarity is quantitatively important for workers aged 50+; and (ii) program substitution is quantitatively relevant for workers aged 55+. We derive a simple rule for optimal UI that accounts for program complementarity and program substitution. Using the sufficient statistics approach, we conclude that UI for older workers was too generous and the regional extended benefit program was a suboptimal policy