Accurate Determination of Moisture Content of Organic Soils Using the Oven Drying Method

Abstract

The accuracy of moisture content values determined for organic soil using the oven drying method is dependent on the oven drying temperature. Some charring of the organic fraction occurs at the standard oven drying temperature of 110 ± 5°C; pore water remains in the soil when temperatures below 100°C are used. A new technique to determine the specific oven drying temperature that yields the correct value of the moisture content for organic soils is presented. Routine moisture content tests should be conducted at the standard oven drying temperature; moisture content values determined on the basis of the recommended oven drying temperature of 60°C include a larger error. A moisture content parameter is introduced to facilitate direct comparison of moisture content values calculated on the basis of different oven drying temperatures.     

Oven-Drying Characteristics of Soils of Different Origins

The accurate measurement of the moisture content of a soil is an important step in characterizing its engineering behavior. However, the oven-drying method can cause some chemical reaction (oxidation or loss of water of crystallization) to occur in certain soil types. The level of oxidation of the solid particles was studied over the drying temperature range of 60 to 140°C for different soils. The period of oven drying necessary for the specimen mass to equilibrate was also examined. The standard practice of oven drying the soil specimens at 110 ± 5°C or 105±5°C over a period of 24 h was confirmed as giving accurate moisture content values for inorganic soils. Oven drying of peat and other highly organic soils over a period of 24 h at 80°C produced similar levels of accuracy in the moisture content measurements as that for inorganic soils at the standard oven drying temperatures of 105 or 110°C. Some oxidation of the organic fraction commenced at between 80 and 90°C.     

Oven-Drying Characteristics of Soils of Different Origins

Abstract

The accurate measurement of the moisture content of a soil is an important step in characterizing its engineering behavior. However, the oven-drying method can cause some chemical reaction (oxidation or loss of water of crystallization) to occur in certain soil types. The level of oxidation of the solid particles was studied over the drying temperature range of 60 to 140°C for different soils. The period of oven drying necessary for the specimen mass to equilibrate was also examined. The standard practice of oven drying the soil specimens at 110 ± 5°C or 105±5°C over a period of 24 h was confirmed as giving accurate moisture content values for inorganic soils. Oven drying of peat and other highly organic soils over a period of 24 h at 80°C produced similar levels of accuracy in the moisture content measurements as that for inorganic soils at the standard oven drying temperatures of 105 or 110°C. Some oxidation of the organic fraction commenced at between 80 and 90°C.     

Analysis of Moisture Content and Density of Pears During Drying

Solar dried pears of the “S. Bartolomeu” variety are a very much appreciated and preferred dried food product in Portugal. Nevertheless, the traditional solar drying is carried out at open air during the months of 07 and 08, and this nowadays is a disadvantage for larger productions. This work is to evaluate the possibility of producing dried pears from this and other varieties, maintaining the characteristics of the traditional dried pears. In this study four different types of pears were studied, including “S. Bartolomeu” as a basis for comparison and the drying method employed was the traditional one. From the results it was concluded that, although the behaviour of the four varieties do not vary significantly, one particular variety (“D. Joaquina”) is a good alternative to the “S. Bartolomeu” pear.     

Analysis of Moisture Content and Density of Pears During Drying

Abstract

Solar dried pears of the “S. Bartolomeu” variety are a very much appreciated and preferred dried food product in Portugal. Nevertheless, the traditional solar drying is carried out at open air during the months of 07 and 08, and this nowadays is a disadvantage for larger productions. This work is to evaluate the possibility of producing dried pears from this and other varieties, maintaining the characteristics of the traditional dried pears. In this study four different types of pears were studied, including “S. Bartolomeu” as a basis for comparison and the drying method employed was the traditional one. From the results it was concluded that, although the behaviour of the four varieties do not vary significantly, one particular variety (“D. Joaquina”) is a good alternative to the “S. Bartolomeu” pear.     

微波干燥法测定过磷酸钙中的水分

提出用微波干燥法测定过磷酸钙中水分的含量,测定的精密度较高,操作简便,条件容易控制,分析速度快,RSD=(n=6)为1.23%。经多次试验证明,采用本法测定结果满意。     

A Novel Method of Measuring Moisture Content Distribution in Timber During Drying Using CT Scanning and Image Processing Techniques

A new method for the nondestructive measurement of moisture content (MC) distribution in timber during drying was developed using X-ray computed tomography (CT) scanning and image processing techniques. The deformed cross section in the CT images due to shrinkage was corrected with the image registration, and the shrinkage was measured by digital image correlation analysis. The pixel-wise MC distributions during drying were measured and visualized successfully. The total timber MC estimated from the MC values of each pixel were strongly correlated with those measured by calculation without geometrical transformation of CT images. The coefficient of determination (R ²) and the standard error of prediction (SEP) were 0.99 and 0.18%, respectively, within the MC range of 19.2–47.3%. In addition, the measured shrinkage distribution during drying was in accordance with the diamonding deformation observed. The results suggest that CT scanning combined with image processing techniques is an effective tool for nondestructive assessment of MC distribution during drying.     

Analysis of Drying Kinetics and Moisture Distribution in Convective Textile Fabric Drying

The drying process of crude cotton fabric is analyzed under two main aspects: analysis of moisture distribution inside the textile sheet, and analysis of certain operational convective drying process variables. Experimental apparatus consisted of a drying chamber in which samples of pure cotton textile were suspended inside the drying chamber and exposed to a convective hot air flow. The influence of the operational variables on the drying process behavior was studied by two different ways with generalized drying curves. The behavior of moisture distribution profiles was compared to average moisture content of the textile fabric verifying whether average values were able to represent the textile moisture content during the drying process.     

Water Content Determinations for Peat and Other Organic Soils Using the Oven-Drying Method

There has been much debate in the literature over the past 60 years regarding an appropriate oven-drying temperature for water content determinations in peat and other organic soils. For inorganic soils, the water content is usually based on the equilibrium dry mass corresponding to drying temperatures in the range 100–110°C. However, for peat and other organic soils, several researchers have recommended lower drying temperatures in the range 60–90°C in an attempt to prevent possible charring, oxidation, and/or vaporization of substances other than pore water. However, all of the relevant water is not fully evaporated at too low a temperature, and because specimen dry mass is a function of drying temperature, the resulting water content values are lower than those determined for the temperature range 100–110°C. Experimental data reported in this article show that oven drying of peat and other organic soils at 100–110°C using either gravity–convection or forced-draft ovens is acceptable for routine water content determinations. Because a standardized oven temperature is desirable when correlating water content with other material properties, it is recommended that oven drying of peat and other organic soils be performed over temperature ranges of either 105–110°C or 105 ± 5°C, in line with standardized ranges for inorganic soils.     

Testing New In-Kiln Meter for Monitoring Lumber Moisture Content during Drying

The objective of this study was to test a new in-kiln sensor for monitoring lumber moisture content during industrial drying. The theoretical foundation of the technology was already known, because it is based on electrical conductivity, but the mechanism of implementation was new and required validation. For this reason, the technology was compared with two other widely used methods for assessing lumber moisture content, namely, the oven-drying and electrical capacitance methods. The tests were performed in a 120-m³ industrial kiln operated by a sawmill in the eighth region of Chile, and the results showed that the average moisture content at the end of drying was satisfactorily determined by the new in-line sensor. As predicted by theory, the sensor was not able to accurately measure moisture content above 25%, but it was still able to provide the equivalent of a drying curve for monitoring of the drying process.     

Measurement of Absorbed Power of Glass Particle Layer on Moisture Content and Drying Rate by Combined Convective and Microwave Drying

Dependency of absorbed power by microwave on the local moisture content in a glass particle layer was measured with a new method; that is, heating the wet layer. The heating experiment was performed using a laboratory-scale combined convective and microwave heater/dryer that was manufactured by modifying a domestic microwave oven at 2.45 GHz. The measured result was strongly dependent on the local moisture content and showed a maximum and a minimum within the measured range of the moisture content. This dependency can be explained by the assumption that moisture in the wet layer behaves as a mass of the free water. The combined drying rate of the wet layer measured with the heater/dryer was simulated with both the power dependency and the experimental convective-only drying rate. Power dependency on temperature is as important as the moisture content in the simulation. Simulated results agree very well with experimental ones.     

Temperature-Controlled Infrared Drying Characteristics of Soils

Measurement of the moisture content of inorganic soils is frequently needed for many engineering activities. The standard test method by ASTM D2216 is very accurate, but the associated drying time up to 24 h is not always desirable. This study investigates the usability of infrared (IR) drying of inorganic soils in reducing the drying time under constant temperature. It was found that accuracy of the proposed IR oven method is excellent and the associated drying time is 80% less than that of a conventional convective oven. Drying time for zero plasticity soils such as sands was found to be about 1 min per gram of initial sample mass. Soil plasticity was found to increase the drying time up to 100% compared to that of zero plasticity soils.     

Real-Time Moisture Content Measurement of Wood Under Radio-Frequency/Vacuum (RF/V) Drying

Hinoki timber was dried under radio-frequency at 6.7 kPa using two drying schedules, schedule A and schedule B. Moisture content (MC) was measured at 58 points in various locations of the timber using a new in-process monitoring concept. This concept uses the relationship between temperature, pressure, and equilibrium moisture content (EMC). Factors affecting the accuracy of MC measurement were also investigated in this study. The results showed that small wood pieces reached equilibrium at constant conditions within 1.5 h of the fiber saturation point (FSP) and that using the mean value of temperature and pressure within 30 min during radio-frequency/vacuum (RF/V) drying for MC measurement was an efficient method. The accuracy of moisture content measurement was the same for both drying schedules A and B. It can be concluded that air in wood was removed completely with drying schedule B and that below the FSP, pressure in the wood was maintained only by water vapor pressure during drying. It was possible to obtain accurate MC measurement. Above or near the FSP, MC cannot be measured using this method, whereas below the FSP, whatever the MC is, it can be measured practically anywhere in the timber.     

膨化硝铵炸药水分测定方法改进

提出了膨化硝铵炸药水分控制过程检测存在的问题,研究讨论了膨化硝铵炸药半成品和成品的水分检测方法,通过测定方法的改进,提高了检测效率和生产过程控制效果,解决了膨化硝铵炸药生产过程控制的一个难题.     

Non-destructive Measurement of Moisture Distribution in Wood during Drying Using Digital X-ray Microscopy

The objective of this study was to develop a nondestructive method by which moisture distribution in wood during drying could be predicted. A newly developed digital X-ray microscope was used to measure the moisture content of wood and its accuracy and resolution was evaluated compared to the classic oven-dry method.

Small green wood specimens of Sugi (Cryptomeria japonica D. Don) were cut and dried under constant temperature and humidity. As the weight was decreasing during drying, X-ray microscope images of cross section were obtained. From these digital images and specimen weight, the moisture content during drying was measured by the two methods. After the shrinkage of the specimen was canceled, the standard error achieved finally was about 1% moisture content within the experimental range. As the image was divided into small subimages, the clear moisture distribution can be seen. It was found that the image divided into 32 × 32 subimages in each size of 0.625 × 0.625 mm might be valid to determine the moisture distribution, and that the drying rate in early wood is larger than in late wood.     

GPR System for Monitoring Paddy Moisture Content in a Drying Process

High-frequency ground penetrating radar (GPR) was used in this study to monitor the moisture content of paddy in a drying process. The reflected radar pulses were used to calculate the dielectric constant of paddy. Owing to the temperature increase, Nelson and Noh's quadratic model was extended by introducing a temperature correction factor adapted to predict the dielectric constants at different temperatures. The calculated paddy moisture content was in good agreement with the values measured by the conventional oven method. Our results demonstrate the potential use of GPR systems as an online tool for monitoring the paddy moisture content in the drying process.     

不挥发物含量的快速准确测定法

提出了一种快速准确测定不挥发物含量的方法,其实质是采用载玻片,使样品在载玻片上形成薄而均匀的膜,加快挥发物的挥发.该方法降低了烘烤温度和烘烤时间,不但提高了工作效率,还减少了烘烤中因发生化学反应而导致小分子释放,提高了测定准确性.     

微波真空干燥固体蜂蜜的等温吸湿规律的研究

应用静态称重技术测定了固体蜂蜜的吸附平衡含水率，获得了相应的吸附等温线，对其吸附规律进行了探讨，并根据目前在食品吸湿规律研究中常用的六种模型对不同温度条件下固体蜂蜜的吸湿试验进行了模拟比较，得出GAB模型为固体蜂蜜适用的吸湿模型，并确定了模型系数。     

有机-无机复混肥中有机质含量测定方法的探讨

对有机-无机复混肥中有机质含量进行测定分析,对称样量、滴定终点判断、滴定酸度等的影响进行讨论.通过提高称样量以减小测量误差,采用定容后分取体积测定的方法,更易于终点的判断,从而达到更好的测定结果,提高测定的准确度.     

Assessing the Influence of the Drying Schedule on Moisture Variability in the Batch Drying of Timber

Abstract

Timber drying schedules influence the dispersion in moisture content between boards at the end of drying. Both a single set-point schedule and a double set-point schedule are selected to illustrate the concept. A simple deterministic drying model that can predict moisture content as a function of time for a single and double set-point schedule is presented. Given random variability in both the initial moisture content and drying rate of the product, theoretical expressions for the range in moisture content as a function of time are developed. The predictions of these equations are compared with experimental measurements from a laboratory kiln. A general methodology whereby the basis of commercial schedules can be analyzed as to their performance with respect to minimizing product moisture dispersion is constructed. The approach should prove useful in assisting drying process designers, concerned about moisture variability, in distinguishing between otherwise equal schedules.