| Mechanical Vapor Recompression(MVR)heat pump system,which vapor is compressed at low temperature by mechanical steam compressor, The rising pressure and temperature are used as the heat source. The system can completely recover the latent heat of the steam. With the significant energy saving effect, Has been widely used in the evaporation of the solution. The research and application of MVR technology in the dry field are few.Hollow blade dryer with low pressure steam, hot water or heat conductive oil as heat source. Through the blade, mixing shaft and wall transfer heat to the material, It is a typical conductive drying equipment. Due to the moisture(steam) emerged from the materials containing no or only small amount of non-condensable gas, MVR technology can be used, the compressed and heated up steam is used as the heat source of the drying process. This can significantly reduce the energy consumption of drying process and have broad application prospects.In this paper, the selection of JY-003 type hollow blade dryer, Legend5H roots blower compressor and other auxiliary equipment, A sampling device was designed and manufactured With life sludge as dry material, MVR hollow blade drying experiment device was established. On the device, the research object is the life sludge. The dynamics of sludge drying was studied by experiments. And influence of drying pressure, compression ratio and spindle speed of hollow blade dryer on COP and SMER of MVR hollow blade drying sludge.Sludge of the same quality (120 ±0.1) kg, The vacuum pressure range is 85kPa-90kPa, Constant temperature drying experiment of the compressor outlet steam temperature is in the range of 95??115?. By measuring the date of moisture content of sludge varies with time, The curve of drying rate with moisture content was obtained. The steam temperature is increased from 95 ? to 115?,The critical moisture content of sludge increased from 0.22 to 0.34. Five kinds of sludge drying models were introduced. Fitting analysis of subsection of the experimental data by using Origin software. The drying equation of sludge in the drying stage of accelerating, constant speed and falling rate is: MR= exp[-(2.78 × 10-4T-0.01896)t1.596] (accelerated drying phase) MR= 0.894-(0.98× 10-4T-4.54×103)t (constant speed drying stage) MR= exp[-(2.26 × 10-4 T-0.01365)t1.984] (falling speed drying stage)The drying model is verified by experiments. Obtained by calculation the average relative error of the sludge moisture content of acceleration phase, constant speed phase and deceleration phase respectively is1.67%,2.68% and 9.07%,Drying curve and drying rate curve obtained by experiment are compared with the calculated values of the model. It can be seen that the rule of sludge drying can be described well by subsection treatment.The performance of intermittent drying sludge based on MVR hollow blade drying system is analyzed by changing the drying pressure, compression ratio, spindle speed of the hollow blade dryer, Results show:Within the range of experimental conditions, Reduced drying pressure, compression ratio is 1.4?1.8, Spindle speed of hollow blade dryer in the range of 11.4r/min?13.6 r/min, COP is 3.8?5.7,SMER is 5.4-8.5,The operating efficiency of the system is high. The results also have guiding significance for the continuous drying of MVR hollow bladeContinuous drying sludge of MVR drying system and traditional paddle drying system are simulated according to the following conditions, the feed rate is 120 kg/h, feed temperature is 20? spindle speed is 13.6 r/min,moisture content of sludge decreased from 60% to 20%(Moisture content of wet base), ignore non-condensing gas, Through comparative analysis:SMER is 1.1kg/(kW.h) of traditional paddle drying sludge, the energy efficiency is 0.60. SMER is 7.8kg/(kW.h) of MVR hollow blade drying sludge, the energy efficiency is 0.73. The ratio of SMER of MVR hollow blade drying sludge and traditional paddle drying sludge is 7.09,The ratio of energy efficiency of MVR drying system and traditional drying system is 1.22. Energy saving effect is significant,The effective utilization of energy is high.The influence of different parameters on the performance of MVR drying system is obtained by simulation:when the compression ratio is certain, the greater drying pressure is, the greater amount of steam needed to supplement, both COP and SMER values are decreased; Under certain drying pressure, SMER, COP and energy efficiency all decrease with the increase of the compression ratio, the amount of steam needed to supplement increases; When drying pressure and compression ratio are certain, With the increase of feed moisture content, SMER and energy efficiency constantly increase, COP is basically unchanged; When the non-condensable gas in the range of 0?0.10, when drying pressure and compression ratio are certain, with the increase of non-condensable gas holdup, SMER decreases, COP slightly increases, then decrease, but the overall variation amplitude is not very big. |
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