Design And Commissioning Of Treatment Process From Municipal Sewage To Boiler Feed Water

Huaneng Yichun Thermal Power Co.,Ltd.is located in Wumahe District,Yichun City,Heilongjiang Province,and has two 350MW thermal power generating units.It also bears the heating task of 8 million square meters in the main city of Yichun.The supply water source uses the water from the Yichun Wastewater Treatment Plant.Due to the poor water quality of the sewage plant,the conventional feed water treatment system cannot meet the requirements.In this paper,the water quality characteristics of the effluent from Yichun Wastewater Treatment Plant and the water quality standards required for the boiler feed water are studied.The appropriate treatment plan is studied,and the engineering design,equipment installation and commissioning of the boiler feed water treatment system are carried out in stages.Explore a medium water treatment plan with reasonable processing cost,simple process and stable operation effect.Solve the problem of water use in large-scale thermal power plants,reduce the amount of groundwater exploitation,and achieve better economic and environmental benefits.Based on the in-depth analysis of the effluent quality of the municipal sewage treatment plant and the water quality of the power station boiler feed water required,this paper proposes the use of?lime method coagulation sedimentation-variable pore filter-immersion ultrafiltration-two stage of reverse membrane-EDI.The main equipments are analyzed and calculated,and the equipment selection requirements are proposed.On the basis of the research and determination of the process plan,the process design and equipment design of the boiler feed water treatment system were completed.The main design parameters are as follows:pretreatment system effluent1300 m~3/h;In the desalination system,the pretreated effluent is subjected to deep turbidity removal by immersion ultrafiltration,and the immersion ultrafiltration system produces 416 m3/h;since the hot water hydration uses the softened water produced by the first-stage reverse osmosis,the first stage is increased.The reverse osmosis water production capacity is designed to be 292 m~3/h;the secondary reverse osmosis design water production is 140 m~3/h;the EDI output demineralized water volume is 126 m~3/h.After two months of installation and commissioning,the pretreatment system and the desalination system were put into operation.When the influent water quality averages SS 22 mg/L and COD 25 mg/L,the water quality of the pretreatment system is maintained at SS?3 mg/L,COD?21 mg/L,and the submerged ultrafiltration effluent quality is maintained at turbidity.?0.1 NTU,Pollution Index(Silding Density Index,SDI value)?2,to ensure the reverse water inflow requirements.Adjust the frequency of first-stage reverse osmosis cleaning,the type of dosing,adjust the NaOH amount of secondary reverse osmosis inlet to make the reverse osmosis system run stably,and the conductivity of water production is?10?s/cm.Adjust the power supply voltage of the EDI system,and carry out electrical regeneration in a timely manner to make the conductivity of EDI water production stable?0.1?s/cm,which meets the water quality requirements of power supply boiler boiler water.After calculation,the commissioning of the project has saved the water fee of the power plant by 12.32 million yuan.