| At present,China’s sewage treatment scale has ranked first in the world,but com Pared with the treatment of sewage,the ca Pacity and level of sludge treatment are still lagging behind.The research shows that the production of sludge in China has been increasing year after year,and the treatment method of sludge has not been improved due to the "heavy water and light sludge" in the process of sewage treatment,and the problem of sludge reduction has not been fully solved.Sludge drying is an important step in sludge reduction and treatment,and its energy consumption usually accounts for more than 80% of the total cost of sludge treatment.How to deal with these sludge and reduce the energy consumption in the treatment process has become the most urgent thing at present,which is of great significance for the energy saving of sewage treatment plants.In order to solve the problem of high energy consumption in sludge treatment,it also provides theoretical support for the upgrading and transformation of sewage treatment plants from high energy consumption industry to resource recovery industry.Based on the study of the drying characteristics of sludge,reducing the drying energy consumption,combined with the low energy consumption of low temperature drying,the advantages of high microwave drying efficiency and low drying time,studied the temperature and wind speed in the process of drying,the process of the drying model,and the microwave power commonly used in the process of sludge drying experiment.According to the experimental data,according to the characteristics of the two drying curves,the appropriate time node is selected to combine the two drying methods.The change of drying time and drying energy consumption before and after the combination is relatively analyzed,and the mechanism of the curve change in the drying process is analyzed,focusing on the change of adhesion stress and agglomeration stress in the process of sludge drying.The results show that the effect of sludge drying is greater than the wind speed.The effect of wind speed on sludge drying is limited,and this effect will continue to decrease with the drying process and the increase of wind speed.Therefore,when the drying process to the later stage,the wind speed can be appropriately reduced or stop the blast.In the microwave pretreatment experiment,the microwave pretreatment step has a promoting effect on convection drying.Com Pared with the convection drying process under the same temperature condition,the average drying rate is increased by more than 30%,the time of drying to 30%water content is reduced by more than 20%,and the drying energy consumption is almost reduced by more than 30%.Under the condition of high microwave power,the pretreatment time is longer,and the energy saving is more.Under the high microwave power,the pretreatment time should not be long.Under the same temperature working condition,the microwave power should not be too large.In the process of convection combined microwave drying,the convection and microwave drying section is slightly hindered,but the drying time is greatly reduced com Pared with the convection drying section.The energy consumption of drying is also slightly lower than that of microwave drying,but the overall effect is not as good as that of microwave pretreatment drying.The experimental results show that CaO and wood chips make the sludge drying in the process of adhesion-cohesive stress,sludge drying rate increase process is also sludge adhesion-cohesive stress reduction process,This provides a new idea for sludge drying. |
