Study On Characteristics Of Seed Drying With Different Intermittent Microwave

The experiment was carried out to study factors of affecting intermittent microwave drying on maize seed, wheat seed and Chinese cabbage seed, to research the optimal conditions of drying maize seed. Many factors of affecting seed moisture content and seed germination in the processing of microwave drying were studied, which included time ratio of intermittent microwave, primary moisture of seed, loading weight in drying and micro- wave drying power. The mathematic models of drying maize seeds and wheat seeds with intermittent microwave, when the seed germination was ensured .Main results obtained were as follows:1. Microwave drying power and time ratio of intermittent microwave were the key factors of affecting intermittent microwave drying on maize seed. The preferable time ratio of intermittent microwave was 10% on the condition of 700W or 800W of microwave output power. But in continuous drying, the seed moisture shouldn't be more than 16.4% at 800W output power and not more than 17.3% at 700W output power. The biggest drying rate was observed when loading weight was 300g, but the damage of seed was the most serious at this very moment.2. Time ratio of intermittent microwave was the main technical parameter of microwave drying on wheat seed. Primary moisture and loading weight also affected drying characteristic and germination of treated seed. The seed germination dried can meet national standard when time ratio of intermittent microwave was 20% and seed moisture was lower than 20.3%, or when time ratio of intermittent microwave was 30% and seed moisture was lower than 16.7%. The biggest drying rate was observed when loading weight was 300g, but the damage of seed was the most serious at this condition. Wheat seed which was just harvested could break dormancy and gain the highest germination when drying time was 60min at 10% time ratio of intermittent microwave, or 20min at 20% time ratio of intermittent microwave, or 5min at 30% time ratio of intermittent microwave.3. On the condition of 800W output power and 100±0.2g loading weight, Chinese cabbage seed of 7.0% moisture could be obtained from seed of 12.8% moisture when drying time was 90min at 10% time ratio of intermittent microwave, or 40min at 20% time ratio of intermittent microwave, or 25min at 30% time ratio of intermittent microwave. Furthermore, the value of seed dried wasn't affected.4. Maize seed germination could be used as a index of drying damage because it reacted sharply to microwave drying. Time ratio of intermittent microwave was not more than 20% for maize seed, drying rate increased as time ratio of intermittent microwave increased, but the falling rate of germination increased. For intermittent microwave drying of the thin layer seed, Page equation could describe the law that moisture changed as drying time in the process of drying. The equation was MR=esp(-0.01818t0.67688) at 10% time ratio of intermittent microwave, and MR= esp(-0.01457t1.02447) at 20% time ratio of intermittent microwave; First order dynamic model could well forecast the law that germination changed as drying time, for intermittent microwave drying of the thin layer seed. The equation was GR=0.9572esp(-0.0046t) at 10% time ratio of intermittent microwave, and GR= 4.4275esp(-0.2940t) at 20% time ratio of intermittent microwave. 18% primary moisture seed was dried by intermittent microwave on the condition of 800W output power and 10% or 20% time ratio of intermittent microwave. When the maize seed was dried from 18% to 13.0.5% moisture, the equations of y1=23.9160e-0.1426x1+ 3.4943e-0.0114x1(at 10% time ratio of intermittent microwave)and y2=2.0466+11.1693e-0.2457x2 + 9.306e-0.2457 x2(at 20% time ratio of intermittent microwave)were used to calculate drying times for different drying time.5. Single diffused model could well describe the law that moisture changed as drying time for intermittent microwave drying of the thin layer seed. The equation was MR=0.9669esp(-0.0996t)+ 0.9357esp(-0.0046t) at 10% time ratio of intermittent microwave, and MR=0.9844esp (-0.0123t) at 20% time ratio of intermittent microwave.6. Relative electrical conductivity increased as germination decreased for maize seed of different germination after microwave drying. Scutellum reacted sharply to microwave damage; the differences of the damage for plumula, hypocotyl and radicel weren't highly significant.