Estimating moisture content variation in kiln dried Pacific coast hemlock

Kiln drying is admittedly a significant value-adding step in timber processing where the importance of predicting moisture within a dried batch cannot be overemphasized. This study predicts and characterizes the moisture variation in kiln-dried wood based on the initial and target moisture values using polynomial models. Four polynomial models are used to correlate initial and final moisture characteristics. First model is linear while the three others are nonlinear. The robustness of the three best models is analyzed and a closed formula is proposed to evaluate the final moisture coefficient of variation based on the target moisture and initial moisture coefficient of variation. Three models could successfully characterize the final moisture variation with the best one showing an R 2 > 96%. However, the first (linear) model is the most resilient and, thus recommended for estimating final moisture variation.

The malting parameters: steeping, germination, withering, and kilning temperature and aeration rate as possibilities for styrene mitigation in wheat beer

Aiming at the mitigation of the toxicologically relevant styrene formed during wheat beer brewing, different malting parameters, such as steeping temperature, germination temperature, withering and kilning temperatures applied during kiln-drying, and aeration rate, were evaluated for their suitability to reduce the content of cinnamic acid, the precursor of styrene, in malts of barley and wheat, responsible for the input of the undesired precursor into the brewing process. According to the results of the present study, higher steeping temperatures, higher germination temperatures, lower aeration rates, and lower withering temperatures during malting are beneficial for the overall reduction of cinnamic acid in wort produced with barley and wheat malts. Thereby, the withering temperature showed the highest impact among the investigated parameters, able to reduce the soluble cinnamic acid content in wort by up to 72%, followed by the germination temperature in combination with the aeration rate and the steeping temperature with reduction capacities of 52 and 16%, respectively. Additionally, a kilning temperature of 200 °C led to the absence of enzyme activities in dark malts, which might also be the main reason for the low phenolic acid contents found in the corresponding wort, finally causing the low concentrations of styrene but also to a certain extent of desired vinyl aromatics in dark wheat beers.

Drying a Standing Teak Tree using a Solar Kiln Drying Method

Understanding the rate of drying of standing trees dried by using a solar kiln drying method could help in predicting the change of moisture content in the tree over a period of drying time. The purpose of this study was to observe the change of moisture content profile in a standing tree during drying. A standing Tectona grandis tree was selected for the experiment with a diameter at breast height of 29 cm in a mixed-species plantation. The tree was girdled with 20 cm width at 20cm above ground. For the experiment, the tree was wrapped in a transparent plastic sheet and a black plastic sheet was installed at the bottom with an angle of 39 °C facing Southwest to maximize solar radiation, with the method being modified from the solar kiln method, which is known as a greenhouse type, with 2 layers of plastic cover. The black and white sheets were placed on the inner side for insulation and for collecting heat from the sun’s radiation, while the outer layer was transparent, which allowed radiation to propagate unhindered in the black sheet. In this study, a sensor for temperature and relative humidity (DHT22) was attached inside the wrapped plastic and the data recorded every 6 min. The results showed that drying a standing teak tree from an initial average moisture content of 105 % to a constant point of 60 % took 80 days under the maximum of the collected temperature of 46 °C inside the wrapped plastic; this finding confirmed that the predicted model of recharge and discharge curve was likely accurate.

Kiln Drying Operations Scheduling with Dynamic Composition of Loading Patterns

Planning and scheduling wood lumber drying operations is a very difficult problem. The literature proposes different methods aiming to minimize order lateness. They all make use of pre-established kiln loading patterns that are known to offer good physical stability in the kiln and allow full kiln space utilization. Instead, we propose a mixed integer programming (MIP) model, which can be used to generate loading patterns “on the fly.” This MIP model can be integrated into existing kiln drying operation planning/scheduling systems in order to improve their solutions. We show how this integration can be done by adapting a state of the art drying operations planning and scheduling methodology from the literature. We compare the solutions obtained by this system using the predefined loading patterns versus the solutions it generates if it is connected to our loading patterns generator MIP model. The study shows it is much better to dynamically create loading patterns than to use predefined ones, as most North American sawmills do.

Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas

Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO2 volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.