Decimal Dry Basis Research Articles

Moisture adsorption rate and durability of commercial softwood pellets in a humid environment

Durability, a crucial parameter in determining the quality of a wood pellet, is affected by moisture adsorption from the air. The conditions in a confined space in which pellets are stored can be characterised as active or passive. In the active case, the interstitial air within the pile circulates around the pellets, whereas in the passive case, the interstitial air is stagnant. These two cases represent stored pellets in a ventilated silo (active) or in a ship's hold (passive). Commercial wood pellets were exposed to humid air in a humidity chamber with circulating air set at 95% relative humidity (RH) and 30 °C for up to 24 h. The wood pellets were also exposed to a range of RH values (11–90%) for four weeks, created using saturated salt solutions. The durability of pellets, volumetric swelling, and pellet density were measured. For pellets exposed to 95% RH, the durability of pellets, initially at 99%, dropped to below 80% after 10 h. A similar drop in durability was observed for pellets stored above saturated salt solutions but after a longer storage period. The density of pellets initially increased when pellets had a moisture content of 0.05–0.08 decimal dry basis (db). The pellets expanded by 20–80% volumetrically when the moisture content exceeded 0.15 (db), resulting in a marked decrease in pellet density.

Thin-Layer Drying Characteristics of Fresh and Sun-Dried Buckwheat Hay

Highlights Thin-layer drying of fresh and sun-dried buckwheat hay was studied at 30°C to 180°C and 12.5% to 60% relative humidities. Buckwheat hay drying occurred in the falling-rate period. Partial sun-drying of the hay could reduce drying time by 50%. The D eff values of fresh flowers, leaves, and stems ranged from 1.4×10 -10 to 60×10 -10 m 2 /s. Abstract. Thin-layer drying characteristics of fresh and sun-dried buckwheat hay were studied at 30°C to 180°C, 12.5 to 60% relative humidities, and 0.2 m/s constant air velocity. The hay was harvested on three different times with a 10 to 12 d interval between the harvesting times. Half of the harvested hay was sun-dried on the field for 4 d (referred to as sun-dried hay). The drying behavior of flowers, leaves, and stems of the fresh and sun-dried hay was characterized. Moisture content of the fresh buckwheat flower was 0.777 to 1.633 (decimal dry basis), and fresh stems had a maximum moisture content of 5.64. Moisture content of the fresh hay decreased with the increase of growth time. Sun-drying on field could decrease more than half of the moisture content of the harvested fresh hay. Flowers, leaves, and stems needed varying drying times to reach their equilibrium moisture contents. The order of the drying time from the fastest to the slowest was flowers, leaves, then stems. Sun-dried and later harvested hay needed less drying time. The logarithmic model was the best fit for all drying processes of the flowers, leaves, and stems at different harvesting times and drying conditions. The effective moisture diffusivity of both fresh and sun-dried hay ranged from 1.4×10-10 to 60× 10-10 m2/s depending on different experimental conditions. The activation energy of the hay was from 21.08 to 33.85 kJ/mol. A power equation was the best equation to describe the drying constant of hay with their drying temperature. Keywords: Activation energy, Combination drying, Hay drying, Thin-layer drying, Water diffusivity.

Heats of wetting and sorption for wood pellets

Wood pellets have become a flagship biofuel in transitioning from coal-based heat and power generation to renewable energy. However, the hygroscopic nature of wood pellets is a long-standing challenge in storing and transporting this commodity. The heat of moisture sorption contributes to the self-heating and spontaneous combustion of wood pellets. The objective of this paper is to investigate the evolution of heat in moistened pellets and to compare them to that of wood chips. Wood pellets at several moisture content levels were immersed in liquid water and the rise in the pellets’ temperature was recorded. The calorimetric method was used to calculate the heat of wetting for the immersed pellets. The heat of wetting was at its maximum for completely dry pellets. The heat of wetting decreased linearly as the moisture content increased towards a fiber saturation point of about 0.17 (decimal dry basis). Statistically, the maximum heat of wetting of pellets is the same as that of wood chips. However, the rate of heat release of pellets is twice of that of chips.

Mechanical properties of baru fruit (Dipteryx alata Vogel)

This paper aimed to verify the influence of moisture content and drying temperature on the values of maximum compression strength for fixed strains (1; 2; 3; 4; 5; 6; and 7 mm), rupture force, and proportional deformity modulus on the baru fruit (Dipteryx alata Vogel) under compression in a natural resting position. Baru fruits with a moisture content ranging from 0.333 to 0.053 (decimal dry basis - db) were used. The fruits were uniaxially compressed between two parallel plates, in the natural resting position, and the nuts were dried at temperatures of 60, 80, and 100 °C. The reduction in the moisture content during drying was monitored using a gravimetric method (weight loss) to determine the initial moisture content of the product and the final moisture content. Based on our results, the compression force needed to deform the baru fruit decreased with increasing moisture content, regardless of the drying temperature. The proportional deformity modulus increased with the reduction of moisture content for all the studied temperatures. The reduced moisture content increased the force required to rupture the baru fruit, regardless of the drying temperature. The rupture forces of temperatures of 60 to 100 °C may be represented by one model.

Alterações morfométricas em grãos de soja durante o processo de secagem

The study aimed to evaluate the drying curves and the effects of drying temperature on the volumetric shrinkage of the grain mass and geometric diameter of the soy bean M7211RR. Were used soy bean the cultivar M7211RR harvested in Santa Helena de Goias-GO, with an initial moisture content of approximately 0.30 d.b. (decimal dry basis) and dried to 0.13 (d.b.). The experiment was conducted at Laboratorio de Pos-Colheita de Produtos Vegetais of the Instituto Federal Goiano – Câmpus Rio Verde. During the drying process, the orthogonal axes (length, width and thickness) of soy beans were measured to determine the geometric diameter. To obtain the volumetric shrinkage, the soy bean was dried on trays and then placed in graduated cylinder and thus reducing the volume of product was monitored throughout the drying. Increasing the temperature of 50 °C to 90 °C decreases the drying time of 7.66 hours to 1.98 hours, streamlining the process for 3.87 times. The rate of shrinkage and the diameter geometric of soybean decreases during drying, and this effect is intensified with increasing temperature.

Alterações morfométricas em grãos de soja durante o processo de secagem

The study aimed to evaluate the drying curves and the effects of drying temperature on the volumetric shrinkage of the grain mass and geometric diameter of the soy bean M7211RR. Were used soy bean the cultivar M7211RR harvested in Santa Helena de Goiás-GO, with an initial moisture content of approximately 0.30 d.b. (decimal dry basis) and dried to 0.13 (d.b.). The experiment was conducted at Laboratório de Pós-Colheita de Produtos Vegetais of the Instituto Federal Goiano – Câmpus Rio Verde. During the drying process, the orthogonal axes (length, width and thickness) of soy beans were measured to determine the geometric diameter. To obtain the volumetric shrinkage, the soy bean was dried on trays and then placed in graduated cylinder and thus reducing the volume of product was monitored throughout the drying. Increasing the temperature of 50 °C to 90 °C decreases the drying time of 7.66 hours to 1.98 hours, streamlining the process for 3.87 times. The rate of shrinkage and the diameter geometric of soybean decreases during drying, and this effect is intensified with increasing temperature.

Effective diffusivity of jatropha grains and fruits

This study aimed to assess the influence of volumetric shrinkage in determining the effective diffusion coefficient, and obtain the activation energy of jatropha grains and fruits subjected to drying under varying air conditions. Jatropha grains and fruits were used with moisture content of 0.50 and decimal dry basis 4.40 (db), respectively, dried temperatures of 45, 60, 75, 90, and 105°C, and drying air relative humidity of 14.5, 7.4, 3.8, 2.2, and 1.4% for fruits and 15.6, 7.4, 4.0, 1.8, and 1.2 % for grains. The volume of jatropha grains and fruits, considered spheroids, was obtained by measuring the three orthogonal axes during moisture content reduction, and volumetric shrinkage was assessed by reducing the equivalent radius with the drying process. It is concluded that the effective diffusion coefficient of jatropha grains and fruits increases with increasing air temperature; the inclusion of volumetric shrinkage promotes a better fit of the liquid diffusion model; and activation energy of Jatropha grains and fruits is similar but the inclusion of volumetric shrinkage practically did not change this parameter.

Difusividade efetiva de grãos e frutos de pinhão-manso

This study aimed to assess the influence of volumetric shrinkage in determining the effective diffusion coefficient, and obtain the activation energy of jatropha grains and fruits subjected to drying under varying air conditions. Jatropha grains and fruits were used with moisture content of 0.50 and decimal dry basis 4.40 (db), respectively, dried temperatures of 45, 60, 75, 90, and 105°C, and drying air relative humidity of 14.5, 7.4, 3.8, 2.2, and 1.4% for fruits and 15.6, 7.4, 4.0, 1.8, and 1.2 % for grains. The volume of jatropha grains and fruits, considered spheroids, was obtained by measuring the three orthogonal axes during moisture content reduction, and volumetric shrinkage was assessed by reducing the equivalent radius with the drying process. It is concluded that the effective diffusion coefficient of jatropha grains and fruits increases with increasing air temperature; the inclusion of volumetric shrinkage promotes a better fit of the liquid diffusion model; and activation energy of Jatropha grains and fruits is similar but the inclusion of volumetric shrinkage practically did not change this parameter.

Steam treatment of four softwood species and bark to produce torrefied wood

Debarked samples from three wood species (Spruce, Douglas-fir and Pine) and Douglas-fir bark were treated with saturated steam at 220°C for 5min. The objective was to quantify physical and compositional properties of the treated biomass that would affect on the degree of carbonization (torrefaction) of softwood particles. The resulting data indicated that the calorific value increases as a result of steam treatment; the highest increase was 26.0% for Spruce, from 18.7MJ/kg to 23.6MJ/kg. The corresponding carbon content of the treated Spruce increased from 46.5% to 57.0%. The equilibrium moisture content of the treated wood, placed in a chamber at 90% relative humidity and 30°C air for 180min, dropped from around 0.103 (decimal dry basis) (before treatment) to about 0.045 (decimal dry basis) for Spruce treated particles. Bulk density of Spruce particles increased the most from 87kg/m3 to 129kg/m3 after steam treatment. The bulk density of Douglas-fir bark decreased from 310kg/m3 to 275kg/m3 upon steam treatment. The increased values in calorific values, hydrophobicity, carbon content and dark brownish color indicated a mild degree of torrefaction of biomass when compared to the corresponding values of treated biomass at temperatures of 280°C.

Adzuki beans (Vigna angularis) seed quality under several drying conditions

This study analyzed the drying process and the seed quality of adzuki beans (Vigna angularis). Grains of adzuki beans, with moisture content of 1.14 (decimal dry basis) at harvest and dried until the moisture content of 0.11 (decimal dry basis.) were used. Drying was done in an experimental drier maintened at controlled temperatures of 30, 40, 50, 60, and 70 ºC and relative humidity of 52.0, 28.0, 19.1, 13.1, and 6.8%, respectively. Physiological and technological seed quality was evaluated using the germination test, Index of Germination Velocity (IGV), electrical conductivity, and water absorption, respectively. Under the conditions tested in the present study, it can be concluded that drying time for adzuki beans decreases with the higher air temperatures of 60 and 70 ºC, and it affected the physiological and technological seed quality. Thus, to avoid compromising adzuki seeds quality, it is recommended to promote its drying up to 50 ºC.

MOISTURE ADSORPTION THERMODYNAMICS OF FRACTIONATED SESAME HULLS (SESAMUM INDICUM L.)

ABSTRACT Sesame hulls are a useful byproduct of sesame processing industry. Moisture adsorption isotherms (MSIs) for whole sesame hulls (WSHs) and powdered sesame hulls (PSHs) were obtained at 15, 30 and 45C, and 0.05 to 1.5 moisture content (decimal dry basis) using a water activity meter. Four MSI models were tested. Halsey model was found to provide the best fit for experimental data for both WSHs and PSHs. Standard error of estimate, %P and pseudo‐R2 values were: 0.00168 and 0.00248, 4.7 and 5.7%, and 0.963 and 0.974, respectively. Equilibrium relative humidity (ERH) values of PSHs were greater than those of WSHs at constant moisture content. Differential enthalpy (qst) and entropy (ΔSd) decreased exponentially with the increase in equilibrium moisture content, then became constant beyond 0.7 moisture content. qst and ΔSd values were larger for WSHs than PSHs. Enthalpy–entropy compensation was found to exist for both PSHs and WSHs. An entropy‐driven process was observed, with the free energy change (ΔG) for WSHs and PSHs of+0.0183 kJ/kg and−0.0284 kJ/kg, respectively. The spreading pressure was found to increase with the increase in ERH and decrease in temperature. The net integral enthalpy (ΔHi) decreased then reached an asymptote beyond a moisture content of 0.15 for both PSHs and WSHs. Net integral enthalpy was larger for WSHs. The net integral entropy (ΔSi) was negative for PSHs and WSHs, and ΔSi was greater in magnitude for PSHs.PRACTICAL APPLICATIONSSesame hulls are useful byproducts of sesame processing industry. Large amounts of this effluent are produced yearly in Jordan. They are used as livestock feed, but they require further dehydration to reduce moisture content and water activity into safe levels. In this project, drying thermodynamics of sesame hulls were discussed.

IMPROVED HEAT AND MASS TRANSFER MODELS TO PREDICT GRAIN QUALITY

ABSTRACT This paper reviews a recent development in the heat and moisture transfer modeling for drying single layes of agricultural grains. A diffusion model with time-varying boundary condition predicts the complex shape of the drying curve well. A conduction model with evaporating boundary condition, when used with the Gamson correlation for convective heat transfer coefficient, accurately predicts experimental grain surface temperature. The new modewls were tested experimentally, drying wheat and barley in a thin-layer dryer useing 40 to 175 c air and the initial moisture ranging from 0.20 to 0.40 (decimal dry basis). It is shown that grain temperatures calculated by the conduction heat equation, when used in conjunction with a probit-type germination loss model, predict germination values different from those predicted by the lump heat equation.

Comparison of three routine oven methods for grain moisture content determination

Experiments were carried out to determine the relative adjustments required to values obtained for moisture content of barley and wheat as determined by three different routine oven methods. The internationally accepted ISO712-1979 (E) ground grain method was tested against the ASAE S352, 1977 method and the NIAE 16 hr whole grain methods. Comparative determinations were made at six moisture content levels, in the range 0.1–0.39 decimal dry basis (9–28% w.b.) for both Golden Promise barley and Aquila wheat. Results indicated a significant difference between the ground and whole grain methods of up to 0.01 d.b. (0.8% w.b.) m.c., the whole grain methods giving consistently lower values.