A Study On Character Analysis And Debugging Of Pretreatment Process Of Sewage As Feed Water For Electricity Boiler

Pretreatment process characters of feed water for thermoelectricity boiler from profound processing water is analysed and debugged. The process is lime softening, coagulating, sediment, filtration, active carbon adsorption, ion exchange and supplementary disinfecting. We get results as follow:1. In our study, after pretreatment process of "lime softening, coagulating sediment, filtration, active carbon adsorption, ion exchanging and supplementary disinfecting", we can get water quality as follow: CODMn<2mg/L, turbiry<3NTU, chroma<0.5mg/L. This kind of water can well meet the thermoelectricity boiler quality of de-salt technics. It indicates that the process is feasible.2. During the process debugging, we find that the time of solving medicament is short, the medicament is not sufficiently solved, the volume of mix and reaction tank is small, the effect of mixing and reaction was not good; the settling time of inclined duct(board) sediment tank is short, all the deficiency will lead the filter tank frequently reverse flushing, and it will waste much water.So we reduce the quantity of profound water from 300m3/h to 230m3/h,the treated water meets the quality.3. Running parameter as follow:lime requirement as 120mg/L, quantity of PAC as 60mg/L, quantity of PAM as 0.40mg/L, mixing time as 5min, reaction time as 15min, sediment time as 30min; filtrating rate as 8~10m/h, reverse flushing time as 6.5h; active carbon filtration velocity as 7.0m/h, settling time as 12~15min, reverse flushing periods as 8~10 days, regeneration periods as 120 days.4. After the project of central heating being finished in west suburb of Xi'an, it will use as much as 1400m3 water per hour, that is, it will consume nearly $60,000 one day, concerning cost of industrial water being $1.86 per ton.If we can reuse profound water from Beishiqiao sewage plant as water supply, it will save $455,000 per yearand will save $4550,000 per ten year, so it can largely benefit our economy, societyand environment. 5. In our study,we can gather the practical experience as follow:① When designing the process of coagulating, sediment and filtration, we must look the water quality of filter tank as norm and must choose the parameters to ensure the operation of filter tank, for example, the volume of reaction tank mustn't be small, the sediment time isn't short, etc..② In the inclined duct(board) sediment tank, avoiding short circuit is one of the facts to ensure the outlet water quality.③ In the no valves filter tank, siphon and assistant siphon must be localed below the water level.④ In order to avoiding the microbe rapidly breeding in the active carbon filter, the inler water must be disinfected.⑤ In order to coorperate with the intrinsic ion exchange( II )of tap water, after the sewage is pretreatmented, the active carbon outlet water is proportionally mixed with the ion exchange( I )outlet water.