The microwave drying processing improves the product quality than the conventional drying method, but because the drying temperature generally is above 70 ℃, the drying speed is fast, easily leads to the internal gelatinization of some products, reduces the product quality; Microwave vacuum drying technology of vacuum drying and microwave drying characteristics of organic combination, in the vacuum conditions under the use of microwave can be processed materials drying, vacuum environment to ensure that the materials can be dry at low temperatures, microwave drying materials have instantaneous efficiency, so the rapid and low temperature drying materials can be realized. The development of continuous microwave vacuum drying equipment can ensure that the drying temperature of materials at about 40 ℃, drying speed is dozens of times times the vacuum hot air drying, greatly improve the production capacity, and dry products can effectively maintain color, fragrance, flavor, shape and nutritional ingredients, improve product quality. As a new processing method, microwave energy technology has been greatly impacted by technical renovation and equipment renewal in various industries. Especially at this stage, in front of the operators is to solve the product structure and social needs of the problem, to adapt to the social development of product quality, variety requirements improve. One of the focuses is the lack of technological innovation, quality upgrade lag. The emergence of microwave technology provides good conditions for improving product grades, keeping abreast of technological progress and creating high value-added products. Sulfur in raw coal is the form of pyrite, and pyrite has higher loss angle tangent than coal, so the use of microwave can make pyrite by selective heating and gas reaction, desulfurization. and coal is unaffected. The ideal method is to heat the yellow iron ore to about 650 ℃ by the intermittent heating with a pulse wave of 0.1 seconds of duration. This method has good effect, no costly catalyst, saving money, high energy efficiency, small environmental pollution.