Research On Modification Of Fly Ash Used As Coating Material Of Oilfield Sewage Fine Filter

When oilfield sewage is filtered by precision filter coating with fly ash, filtered water is easily scaled due to CaO and MgO contained in fly ash, and affects qulity of injection water. In order to deal with this problem, the project designs a complete suite of fly ash modification technology, and carries out fly ash modification experiment.Base on research of physicochemical property of fly ash and thermodynamics reaction of HCl and fly ash, the project carry out acid-soluble and alkali-heating modifcation mothed. on the basis of experiments, use HCl dissolve impurity composition contained in fly ash, and then change fly ash into zeolite by alkali-heating method, and realize the modification of fly ash. The scaling prediction result of oilfield sewage filtered by modified fly ash indicated that calcium and magnesian ions contents in filtered water decreased instead of increase, which proved that the modification method of fly ash is success.This article mainly researched influence factors of removing impurity elements contained in fly ash, such as: acid concentration, solid-to-liquid ratio, acid-soluble temperature and acid-soluble time, and confirmed that the best parameters: acid concentration is 2.5mol/L, solid-to-liquid ratio is 4:1, acid-soluble temperature is 90℃and acid-soluble time is 1h. And research on adsorption characteristic of modified fly ash to calcium ion was carried out, and the result indictated that modified fly ash has preferable adsorption ability to calcium ion, even if in neutral condition adsorption amount can reach to 55.60 mg/g, and adsorption speed is very fast and would reach equilibrium in 20min.In order to acquire the best filtering effect when the modified fly ash is used to precoating material to deal with oilfield sewage, filtration characteristics experiment of modified fly ash is carried out, and the best precoating parameters are confirmed, when grain diameter scale of the fly ash is from 15 m to 20 m, precoating thickness is 2.5mm and filtration speed is twice than precoating speed, filtration characteristics curve shape of fly ash is best. The research results not only lower cost of filter aid and have great economic significance, but also have achieved goal of using waste treat waste and save energy and protect the environment, and aquired great social and enviromental benefit.