| In this paper ,according to the water quality of Beijing municipal and the feed water criteria of low and middle boiler , study on middle & low pressure boiler feed water using nanoflltration is performed The contents include: pretreatment system, optimal style of membrane module, running parameter, washing method and working cost The flow diagram of this experiment is raw water 梸active carbon column? cartridge filter~ feed pump~NF stage0 Result shows that 1. Through adjusting PH of raw water may prevent the scale of non-settleable salt on the membrane surface 2. The operating pressure has influence on water flux and removal effect directly 0.75Mpa is the optimal operating pressure , the water flux is 2701/h, rejection rate of hardness is 86.4%, rejection rate of salt is 79%, rejection rate of alkalinity is 83.2% 3. Appropriate feed water temperature has also influence on water flux and removal effect0 5-20 0C is the optimal temperature0 4. Through trials on different hardness water show that the rejection effect of NF membrane is stable 0 But higher water concentration will accelerate concentration polarization0 5. In the range of Beijing municipal water, the first permeate water of nanofiltration can satisfy the feed water of heat water boiler 0 For the vapor boiler, the secondary permeate water can meet the feed water quality 6. Physical wash can not recover membrane performance 0 Acid wash may acquire favorable effect 7. The permeate water quality of nanofiltration and working cost have an advantage over that of ion-exchange c Using nanofiltration to demineralize water has favorable economical benefit and society benefit...
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