Study On Rapid Remove Of Alcohols Based On Its Dielectric Characteristic

The sepatation of low concentration alcohol of liquid material by microwave-vacuum technique and the dynamics mathematical model were studied in this paper, mainly take the ethyl alcohol and the methyl alcohol as the tested materials, and their separation effects were compared, then apply this technology to produce the low-alcohol rice wine. The qualities and functionality of the low-alcohol rice wine are tested by experiments. Finally, the small continuous microwave vacuum separation equipment was proposed.The microwave-vacuum sepatation process of methanol and ethanol experienced two periods. The constant rate period can be described by a theoretical model based on the energy conservation. However the model wasn't fit for the period when the rate declined. Here with an empirical model is chosen and the effect of process variables was embodied in the expression of the phenomenological parameters. The regression method is used to estimate the best model parameters. The separation curves were tested and found that the separation rate increased with the improving of the microwave power and the vacuum pressure. Moreover, the content of methanol and ethanol in the solution cannot drop to zero, but after falling the lowest density which it can achieve and maintaining invariability, maybe this is related to their chemical property as well as the intermolecular action.Temperature distribution and changes were tested with the same concentration of methanol and ethanol-water solution in the experiment. The experiments showed the heating process mainly experienced two distinct periods: a warming-up period without removal of moisture and alcohol when the solution temperature increased linearly with heating time until it reached the corresponding saturation temperature of water at the vacuum pressure; a slow rise period in which most of the moisture and alcohol evaporated and flowed out of the sample efficiently with little resistance; in later period, when the alcohol concentration decrease to the lowest value, the moisture continues to absorb the microwave energy, the temperature of the solution continues to rise slowly.The methanol and ethanol belong to the low-carbon alcohol compound, but their dielectric characteristic are different, therefore the abilities of absorption microwave are different, resulting in the segregation rate are different. In the same vacuum pressure, in the sole ethanol and methanol-water solution the methanol's segregation rate is bigger than the former, but in mix ethanol and methanol-water solution, the segregation rate of ethanol increases slightly, but the segregation rate of methanol increases quite obviously.Appling the microwave vacuum separation technology to produce the low-ethanol rice wine e. g., separating the ethanol from it. It was found that the content of ethanol can be dropped to the lowest by microwave vacuum heating. Compared to the distilled one the low-ethanol rice wine not only have good color and flavor, but also retain the most nutrition resulted from shorter heating and low temperature. The volatiles of originol rice wine, rice wine after distillation and microwave vacuum heating were concentrated by solid-phase microextraction (SPME), separated and identified by gas chromatography–mass spectrometry (GC-MS). By comparison the experiment dates, it can be found that low-ethanol rice wine prepared by the current methods was a little changes of the compositions and contents of flavors.It's feasible for separating alcohol of dilute solution using the microwave vacuum heating technology, but the efficiency of the intermittent microwave vacuum separation equipment is low, the development of small continuous microwave vacuum separation equipment is necessary. It's will not only sharpen the productivity enormously, but also can achieve the better separation effect compared to the intermittent equipment.