微正压条件下板式降膜MVR蒸发装置的工艺设计与应用

Process Design and Application of Plate Falling Film MVR Evaporation Device under Mi⁃cro-positive Pressure Conditions

传统负压蒸发技术存在传热效率低、设备投资大、真空稳定性差、水质不稳定、最终乏汽冷凝成本高等问题。深入研究微正压蒸发理论依据及应用条件,提出热能平衡因子Δqz是控制微正压蒸发系统稳定运行的关键因素,不凝气外排所携蒸汽热能及冷凝水、外排浓水热能的回收是保障微正压工况下MVR系统平稳运行的重要措施。MVR板式降膜蒸发工艺在微正压条件下运行,装置产水矿化度小于等于30 mg/L,降膜蒸发板换热系数相较于微负压蒸发提高10%以上,总体设备投资减少约6%~8%,消泡剂、pH调节剂加药量大幅减少。通过对比微负压与微正压两种工况下的运行数据表明:微正压控制蒸发工艺参数具有产水水质更优、换热系数更大、投资更省、能耗更低、降低药剂耗量等优势。

Traditional negative pressure evaporation technology has problems such as low heat transfer efficiency,large equipment investment,poor vacuum stability,unstable water quality,and high cost of final exhaust steam condensation.An in-depth research on the theoretical basis and application conditions of micro-positive pressure evaporation has been conducted,and it has been proposed that the thermal energy balance factorΔqz is a key factor in controlling the stable operation of micro-positive pressure evaporation systems.The recovery of steam thermal energy carried by non-condensable gas discharge,as well as the thermal energy of condensed water and discharged concentrated water,is an important measure to maintain the stable operation of MVR systems under micro-positive pressure conditions.The MVR plate falling film evaporation process operates under micro-positive pressure conditions,with a water mineralization degree≤30 mg/L.The heat transfer coefficient of the falling film evaporation plate is increased by more than 10%compared to micro-negative pressure evaporation,and the overall equipment investment is reduced by about 6%to 8%.The dosage of defoamers and pH regulators is also significantly reduced.By comparing the operating data of micro-negative pressure and micro-positive pressure,it is found that micro-positive pressure control of evaporation process parameters has advantages such as better water quality,larger heat transfer coefficient,lower investment,lower energy consumption,and reduced chemical consumption.