Moisture Dehydration Research Articles

Synergistic combustion characteristics of mixing DPR Korea’s anthracite and heavy fuel oil

In this paper, the synergistic effect of heavy fuel oil (HFO) and DPR Korea’s anthracite (KA) co-combustion was analyzed using thermogravimetric analysis (TGA). The TG-DTG-DSC results showed that the combustion stages of HFO could be roughly divided into four stages, whereas those of KA could be divided into three stages. The co-combustion process of HFO-KA mixtures differs from the combustion stages of HFO and KA. It could be divided into five stages; moisture dehydration (MD), low-temperature oxidation (LTO), fuel decomposition (FD), high-temperature oxidation (HTO) and fixed carbon burnout (CB). As the KA content ratio increased in HFO-KA mixtures, the maximum mass loss rate and maximum heat flow rate in the LTO and HTO stages decreased but increased in the CB stage. In order to analyze the synergistic effect of the mixing ratio, the TG-DTG-DSC experimental data of HFO-KA mixtures were compared with the predicted values calculated by the simple arithmetic average method. The synergistic effect according to the mixing ratio was found by comparative analysis of the experimental and predicted values. Compared with the 75 % HFO/75 % KA and 50 % HFO/50 % KA mixtures, experimental values of 25 % HFO/75 % KA mixture sample were superior to the predicted values, the synergistic effect was more obvious. Therefore, it concluded that when the co-combustion mixture with high ratio of KA, the synergistic effect was more obvious.

Heat and mass transfer in the blasted layer of vegetable materials with cyclic microwave power supply

The results of modeling and experimental study of heat and mass transfer in a dense blown layer of plant materials under cyclic microwave exposure are presented. The two-dimensional mathematical model consists of the equations of conservation of the mass of the gas phase, filtration, heat and mass transfer in phases, which take into account the internal resistance to heat and moisture transfer in the particles when determining the heat and mass transfer coefficients. In this case, the dependences of the heat of the phase transition on the humidity of the particles, their shrinkage during dehydration, and the dependences of the effective coefficients of thermal conductivity of the gas and vapor diffusion on the filtration rate are taken into account. The simulation results of drying chopped potatoes in a dense layer with a cyclic microwave convective energy supply are presented. The possibility of intensifying the process of moisture dehydration and reducing its duration compared with the convective method is shown. Comparison of calculated data with experimental data confirms the adequacy of the model.

Banana Microstructure Changes during Oven Drying Process

To learn about banana microstructure changes on affecting moisture dehydration performance and its quality during oven drying process, this experiment chose scanning electron microscopy to observe the microstructure changes on outer surface, inner surface and cross section of banana peel and its flesh during drying process, in order to examine the relationship between dehydration performance and its microstructure shape and microstructure pore structures changes. The results showed that during drying process, all surfaces of banana peel and its flesh endured shape deformation from regularly to irregularly. Microstructure shrank evenly in beginning, while became conglomerate later, appeared to be significantly distortion and breakage. Microstructure pore quantity and area showed great changes, those average diameter over 10um pore numbers increased steadily, while pore area just reduced in beginning and then increased rapidly afterwards. As banana microstructure shape and pore shrinkage and deformation increased greatly, which also increased the resistance of moisture evaporating greatly. This may be an important reason that cause banana drying speed and quality decreased, it is an urgent problem that needs to be solved during fruit and vegetable drying process and storage.

EFFECT OF MICROSCOPIC THERMAL STRESS ON MECHANICAL PROPERTIES OF CONCRETE SUBJECTED TO HIGH TEMPERATURE

The AE signals were detected in concrete specimen by means of Acoustic Emission Method during heating or cooling of concrete. The temperature when the first AE signal is detected, is lower than that when the dehydration of moisture in concrete takes place. This result suggests that the reason for the change of property of concrete subjected to high temperature cannot be explained only by the dehydration of moisture in concrete. It is the purpose of this paper to point out that the microscopic cracks are developed by the microscopic thermal stress due to the difference between the thermal expansion coeffcient of mortar and coarse aggregate. From the experimental results, it was proved that the mechanical properties of concrete subjected to the high temperature are influenced by the generation of microscopic stress and the formation of crack.

Combustion of Solid Fuel

In the present report, the experiments of two different kinds were performed by use of the solid fuel samples, whose ash contents were varied extremely. The one is the experiment in the thermo-balance (in this case, burning boundary surface area does not change during the period of combustion), and the other is the experiment on the spherical sample (in this case, burning boundary surface area is reduced during the period of combustion).As the result, from the experiment in the thermo-balance, it is supposed that the reactions have three steps, that is: the dehydration of moisture, the dehydration of crystal water and the reaction of combustion respectively.And in the application of the Yagi Model to the spherical samples, we can not reached to a comfortable result.