| Three compound oil driving technology in improving oil recovery at the same time brings great difficulties to the treatment of produced water,due to the injection water with polymer,surfactant,alkali and other substances,resulting in increased viscosity of produced water,oil droplets emulsification degree;The oil-water dispersion system is more stable,and it is difficult for oil droplets to collide and coalesce,and the separation characteristics become worse.Therefore,improving oil-water separation efficiency has become an urgent problem to be solved in the treatment of produced water from ternary flooding.Based on the internal circulation flotation separation technology,this paper combined the coalescence technology and put forward the loading circulation flotation separation technology.The coalescence material was used as a carrier to fill the inner circulation flotation column to improve the collision and adhesion efficiency of bubbles and oil droplets,and strengthen the flotation separation process.It provides a new,efficient and economical oil-water separation process for treating the produced water of ternary flooding.By comparing various coalescating materials selected wire mesh with different diameters(4×4mm,3×3mm,2×2mm)as the filling material,using the experiment to compare the coalescating effect of three kinds of wire mesh,the results show that loading 2×2mm diameter wire mesh coalescating effect is the best,the oil removal rate can reach 88.1%,the median particle size of 30.2μm.Compared with the unloaded oil,the removal rate was about35%higher,and the median oil droplet size increased by more than 1.5 times.The capture and coalession of oil droplets on the solid surface were simulated based on the VOF model.The results show that the impact of oil droplets on the solid surface can be divided into four processes:stretching,spreading,shrinking and recovery.The smaller the contact Angle is,the larger the spreading area is.The wetting contact Angle and surface tension are the key factors affecting the oil droplet coalescence and fusion.The effects of 60°,90°and 120°contact angles on the coalescence were compared.The results show that the larger the contact Angle,the lower the coalescence efficiency.When the surface tension is 0.03N/m and 0.04N/m,the results show that the oil droplets are more likely to coalesce and fuse under the condition of low surface tension.Based on the Euler model and PBM model,the local hydrodynamic characteristics of the gas-liquid two-phase flow through the single layer wire mesh with different diameters were analyzed.The results show that the bubbles form a 2mm effective bubble accumulation area in the downstream of the wire mesh,and the local gas holdup is significantly improved,which is conducive to improving the gas particle collision efficiency.The rising speed of bubbles in the downstream of the wire mesh is slowed down,the minimum is less than 0.1m/s,the radial velocity is increased,the residence time is prolonged,and the gas particle adhesion efficiency is improved.After loading the 2×2mm diameter wire mesh,the local average turbulence intensity exceeds 4%and the turbulence dissipation rate is within the range of 0.5-3m~2/s~3,creating a turbulent environment conducive to air particle collision.By comparing the effect of loading three kinds of wire mesh,it can be seen that loading 2×2mm wire mesh has the best effect on increasing local gas holdup,extending bubble residence time,and improving turbulence intensity and turbulence dissipation rate.After determining the optimal wire mesh aperture,determine the distance between the adjacent filling wire mesh is 2mm.The hydrodynamic characteristics of the loaded cyclic flotation column were studied under the conditions of superficial gas velocity of 1-4cm/s and filling height ratio of 30%,40%and 50%,and compared with the loading condition.The results show that the gas holdup in the riser of the loading circulation column is significantly increased,while the gas holdup in the downcomer is slightly decreased,and the gas holdup difference and liquid phase circulation velocity are both significantly increased compared with that without loading.When the filling height ratio is 40%and the superficial gas velocity is 2.5cm/s,the gas holdup difference is up to 3.9%,the liquid phase circulation velocity reaches the fastest,and the liquid velocity in the riser is 25.8cm/s.The liquid velocity in the downcomer is 19.6cm/s.The results showed that loading was beneficial to liquid phase circulation and flotation rate.The bubble distribution in the flotation column approximately presents a left-skewed distribution.With the increase of the filling height ratio,the bubble diameter distribution mode shifts to the right,that is,the proportion of large-diameter bubbles increases.When the filling height ratio is 40%,the minimum particle size of the oil droplets is greater than 5μm,and the average particle size is about 40μm.Compared with the initial minimum particle size of the oil droplets,the average particle size increases by more than 2.5times and about 2 times.In summary,when the superficial gas velocity is 2.5cm/s and the filling height ratio is 40%,the gas holdup increases most significantly and the circulating liquid velocity is the fastest,thus achieving the simulation of the best working condition. |
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