Research On Coking Coal Desulfurization By Microwave Combined With Ultrasonic

Coking coal resources are scarce in our country, in the scarce resources there are a large number of high-sulfur coal which dominated by organic. This part of coal resources is difficult to be rational used for conventional desulfurization methods useless. In view of this situation, peer experts both at home and abroad conduct an extensive study of coal desulfurization, to seek moderate, high-efficient and economic means to make the comprehensive utilization of this part resource. Microwave and ultrasonic as emerging technology is being introduced into the field of coal desulfurization.To analyze the Xinyu coking coal, modern measurements and experimental methods are adopted,such as XRD, SEM, FTIR, XPS, pore size and surface area, size analysis, float and sink analysis. Total sulfur in coal sample is 2.69%, which contains 2.35% organic sulfur and 9.76% ash. Mainly size is-0.045 mm, which yield is 30.57%, sulfur is 2.86%. The presence of sulfur-containing minerals are pyrite and zinc. Sulfur is evenly distributed in the sample, indicating sulfur and coal matrix are compact, fine particle size distribution of iron is not conducive to conventional methods for the removal of sulfur.The paper studies desulfurization influencing factors by single-factor methods. Desulfurization effect of acetic acid combined with hydrogen is better than that of formic acid combined with hydrogen peroxide. The best desulfurization rate is at 800 W. Size reduction is in favor of coal desulfurization. Ultrasonic power over 840 W leds to the reduction of ultrasonic conversion efficiency, and temperature at 40℃ the rate of desulfurization is up to 16.14%. Desulfurization rate of ultrasonic increases with the extended treatment time, but after 50 min had little effect. Orthogonal experiments are conducted on the basis of single factor experiments, which founds that the desulfurization effect of the combination of ultrasonic and microwave are better than that of their individual treatment, especially after the first ultrasonic then microwave treatment. Ultrasonic and microwave technology conditions arrange alternately on the influence parameters of desulfurization. Coal particle interacts with the ultrasonic power, time. Ultrasonic and microwave combined desulfurization has synergy. The best ultrasonic and microwave combined desulfurization process parameters for: particle size is 0.125-0.074 mm, microwave irradiation time is 6minutes, microwave power is 600 W, ultrasonic action time is 50 minutes, ultrasonic power is 720 W.XPS peak fitting results indicate that organic sulfur form in coal is mainly Thiophene. After microwave treatment, absolute content of mercaptan, sulfur ether sulfoxide class increased and thiophene reduced compared with raw coal. In addition to an increase in sulfates than that of microwave treatment, remaining sulfur forms are reduced after combined treatment. XANES analysis results are consistent with XPS, which indicate that Microwave combined with Ultrasonic play a role to more sulfur forms.The absorbance of potassium iodide solution after ultrasonic treatment is analyzed using an UV spectrophotometer, the change of absorbance indirects production rule of free radicals: the ultrasonic power is 720 W and 840 W, temperature is 40 ℃, the production rate of free hydroxyl radicals is fastest, which is consistent with the maximum desulfurization rate. Adding acetic acid is conducive to the generation of hydroxyl radicals. This confirms ultrasonic has chemical effects in the desulfurization. BET test shows that Ultrasonic not only makes the particle size of coal samples variable fine, but also increases the specific surface area, total entrance, the average pore diameter. So coal sample and additives can more combine easily under ultrasonic treatment, it is more conducive to desulfurization reaction, which confirms ultrasonic has physical effect in desulfurization.There are 43 figures,45 tables and 120 references.