A Simulation Model for Malt Enzyme Activities in Kilning

The drying and survival of enzyme activities during the kilning of malt were modelled. A set of experiments at the micro‐malting scale was carried out for model identification and validation. The dynamic models predict the effects of the kilning programme, i.e. the temperature profile on grain moisture, activities of β‐glucanase, α‐amylase and limit‐dextrinase, and diastatic power during kilning. The process behaviour was analysed by simulations. The predictions match the malting experience well. The models increase the general understanding of enzyme inactivation and can be used in planning the kilning programme.     

Synthesis and rheological properties of an associative star polymer in aqueous solutions

Rheological properties of aqueous solutions and hydrogels formed by an amphiphilic star block copolymer, poly(acrylic acid)-block-polystyrene (PAA₅₄-b-PS₆)₄, were investigated as a function of the polymer concentration (C_p), temperature, and added salt concentration. The water-soluble polymer synthesised by atom transfer radical polymerization (ATRP) was found to form hydrogels at room temperature at polymer concentrations, C_p, over 22 g/L due to the interpolymer hydrophobic association of the PS blocks. Increasing C_p leads to stronger elastic networks at room temperature that show a gel-to-solution transition with increasing temperature. Increase of ionic strength decreases the moduli compared with the pure hydrogel but did not affect the gel-sol transition temperature significantly. Small-angle X-ray experiments showed two distinct scattering correlation peaks for samples above the gelling C_p, which indicates the aggregates formed due to hydrophobic association. Upon heating the intensity of the scattering correlation peaks was found to decrease indicating the loss of the network structure due to thermal motion.     

Optimisation model for integration of cooling and heating systems in large industrial plants

Large industrial plants have often hundreds of heating and cooling heat exchangers. A common situation is that cooling demands of the processes are satisfied without any deeper analysis of the overall impact of the cooling systems on the plant’s economy or the environment. If cooling water is available it is used as much as needed and then pumped back to the river, some degrees warmer.An optimisation model was developed for integration of cooling and heating systems to tackle the problem. An industrial cooling system is a complex energy system comprising different options of producing cooling, distribution pipelines for cold media and cooling storages. Integration of power generation and heating systems to the cooling systems was included in the model. An illustrative example is presented in the paper. 10 process streams with cooling demand and 10 streams with heating demand were chosen, situated at different locations at the plant site. The optimal matches between the streams were found together with the sizes of the heat exchangers and the demands of hot and cold utilities. The costs of pipelines and the pumping costs of the streams are included in the model. The model can be used in the design of greenfield and retrofit investments and in versatile what-if analyses of the plant design or operation.     

Preparation of Mono‐, Di‐ and Hemicalcium Ferrite Phases via Melt for Reduction Kinetics Investigations

Iron ore concentrates that are used in the iron production are usually agglomerated into sinter or pellets in order to improve their properties in the blast furnace. The main minerals in the magnetite base sinters are hematite, magnetite and Si and Al containing calcium ferrites of which the latter can exist as either monocalcium ferrite, dicalcium ferrite or hemicalcium ferrite depending on the conditions and on the material's iron/calcium‐ratio. In order to study the reduction behaviour of the sinter in the iron production, samples of monocalcium ferrite, dicalcium ferrite and hemicalcium ferrite were prepared by melting different proportions of pure calcium and iron oxides. After melting the samples were cast and cooled. Samples of hemicalcium ferrite were also heated at a certain temperature before the actual reduction experiments in order to ensure the wanted phase composition of the samples. The mineral compositions of the samples were verified using scanning electron microscopy (SEM‐EDS) as well as X‐ray diffraction (XRD). The verification showed that it was possible to produce the samples of calcium ferrites via melting. The conditions needed to reduce the calcium ferrites were estimated with thermodynamic calculations.     

Organic and inorganic carbon concentrations and fluxes from managed and unmanaged boreal first-order catchments

Seasonal and between stream variation (catchment dependent variation) in losses of organic and inorganic carbon via downstream transport and outgassing of CO₂ into the atmosphere were studied in 11 small boreal catchments situated in close proximity to each other. Of these catchments four were undrained peatland rich catchments, four drained peatland rich catchments and three managed mineral soil-dominated catchments. Downstream export of total inorganic carbon (TIC) varied between 870 and 1400 kg km^− 2 a^− 1 and was rather consistent between the catchments, except in the case of the mineral soil-dominated catchment Kangaslampi, where export was only 420 kg km^− 2 a^− 1. The export of total organic carbon (TOC) varied between 2300 and 14,800 kg km^− 2 a^− 1 and was highest in peatland rich catchments. Peatland drainage decreased TIC and TOC concentrations in the long term, but did not affect lateral carbon export due to increased runoff from the catchments. Partial pressure of CO₂ in streams was the highest in undrained peatland rich catchments, but the outgassing of CO₂ into the atmosphere was also high from drained peatlands due to the higher discharge rate and long ditch networks. In mineral soil-dominated catchments both downstream export of carbon and emission into the atmosphere were low. TOC exports were compared in two climatically different years (2003 and 2007). The results indicate that climate change might alter the timing of the TOC export from the catchments, the importance of the spring ice melt diminishing and both snow cover and snow free period export increasing.     

Hardware Cost Measurement of Lightweight Security Protocols

The feasibility of security solution for RFID tags relies heavily on its hardware cost and performance. In the literature the term lightweight solution is used liberally and causes problems when selecting a solution for e.g. RFID environment. Evaluating the actually feasibility of the solution requires electrical engineering skills that many security developers and decision makers may lack. In this paper we describe simple guidelines for approximating the feasibility of the security solution in terms of gates and clock cycles. These guidelines make it easier to evaluate the cryptographic solutions feasibility for targeted hardware and provide a basis for categorisation of lightweight security solutions.     

Distributed algorithms for lifetime maximization in sensor networks via Min–Max spanning subgraphs

We consider the problem of static transmission-power assignment for lifetime maximization of a wireless sensor network with stationary nodes operating in a data-gathering scenario. Using a graph-theoretic approach, we propose two distributed algorithms, MLS and BSpan, that construct spanning trees with minimum maximum (minmax) edge cost. MLS is based on computation of minmax-cost paths from a reference node, while BSpan performs a binary search over the range of power levels and exploits the wireless broadcast advantage. We also present a simple distributed method for pruning a graph to its Relative Neighborhood Graph, which reduces the worst-case message complexity of MLS under natural assumptions on the path-loss. In our network simulations both MLS and BSpan significantly outperform the recently proposed Distributed Min–Max Tree algorithm in terms of number of messages required.     

Sulphur poisoning of nickel-based hot gas cleaning catalysts in synthetic gasification gas II. Chemisorption of hydrogen sulphide

The effect of different components of gasification gas on sulphur poisoning of nickel catalysts were studied. In addition, the sulphur distribution and content of nickel catalyst beds were analysed to account the poisoning effect of sulphur on the activity of catalysts to decompose tar, ammonia and methane. The desorption behaviour of chemisorbed sulphur from the bed materials was monitored by temperature programmed hydrogenation (TPH). It was established that bulk nickel sulphide was active in decomposing ammonia in high-temperature gasification gas-cleaning conditions. The decomposing activity of methane was not affected by bulk nickel sulphide formation, but that of toluene was decreased. The activity of the catalyst regained rapidly when H₂S was removed from the gas. However, the conversion of ammonia was not regained at as high a level as before sulphur addition, most probably due to irreversible sulphur adsorption on the catalyst. The temperature increase could also be used to regenerate the catalyst performance especially in respect to methane and toluene. Sulphur adsorbed on nickel catalysts in different chemical states depends on the process conditions applied. At >900°C the sulphur adsorbed on the catalyst formed an irreversible monolayer on the catalyst surfaces, while at <900°C the adsorbed sulphur, probably composed of polysulphides (multilayer sulphur), was desorbed from the catalyst in sulphur-free hydrogen containing atmosphere. However, a monolayer of sulphur still remained on the catalyst after desorption. The enhanced effect of high total pressure on sulphur-poisoning of nickel catalysts could be accounted for the increased amount of sulphur, probably as a mode of polysulphides, adsorbed on the catalyst.     

Separation of γ- and α-linolenic acid containing triacylglycerols by capillary supercritical fluid chromatography

The separation of γ- and α-linolenic acid containing triacylglycerols with an identical acyl carbon number and degree of unsaturation was obtained on capillary supercritical fluid chromatography using a 25% cyanopropyl−75% methylpolysiloxane stationary phase. The resolution of 1,3-dioleoyl-2-γ-linolenoyl-sn-glycerol and 1,3-dioleoyl-2α-linolenoyl-sn-glycerol was 1.35 on a 10 m×50 μm i.d. column, whereas the resolution was enhanced to 1.66 by combining two 10-meter columns in series. The difference in the position of double bonds in one linolenic acid residue of triacylglycerols resulted in two series of peaks in the separation of alpine currant (Ribes alpinum) and black currant (R. nigrum) seed oils. The use of the 10-meter column was found to be appropriate for the screening of the triacylglycerol profile in both seed oils studied.     

Reduction of Organic Emissions by Using a Multistage Drying System for Wood-Based Biomasses

Organic emissions during the thermal drying process are strongly dependent on the drying temperature. In the traditional single stage drying system, the inlet temperature of the drying air has to be relatively high in order to keep the airflow for drying small. In the multistage drying system, the drying airflow is heated up again after the first drying stage with higher moisture content, and then again after the second, and subsequent drying stages. In this method, the drying temperatures are limited in all stages to acceptable low levels, and only the moisture content of the drying air is increasing from one stage to another. As a result the multistage drying system has a lower drying temperature. We have studied the dependence of the organic emissions on the drying temperature, and present the results from drying units operating at temperatures of 100-200°C and below 100°C. The results are compared to previous measurements found in the literature. The estimates for the emissions at higher drying temperatures are derived from the literature values.