Silica removal from SAGD boiler blowdown by electrocoagulation

蒸汽辅助重力排出(SAGD)开采稠油是加拿大油砂地区最大的原地开采工艺。这一生产过程产生大量产出水，通常是石油体积的3至4倍，必须进行处理和回收，以确保该过程是可行的，并满足监管要求。产出的水必须经过处理，然后才能提供给蒸汽发生器(锅炉)，以便作为蒸汽注入储油层。为了避免锅炉结垢，通常采用温石灰或热石灰软化工艺处理水，以去除可能会结垢的硬度和二氧化硅。该工艺成本高，会产生大量的污泥。行业合作伙伴Eco-Tech正在开发一种替代工艺，即所谓的零石灰软化，该工艺成本更低，更环保。Eco-Tech已经表明，如果对产出的水进行去除硬度的处理，二氧化硅可以处于相对较高的浓度(&gt；200毫克/L)，而不会导致锅炉结垢。然而，锅炉排放的浓缩水中二氧化硅含量超过1200 mg/L，必须经过处理后才能循环使用或处理。传统的化学工艺(酸化)会导致硅胶污泥很难从水中分离出来。电凝聚(EC)已被确定为一种潜在的处理排污浓缩物的方法。在以前的工作中，我们已经发现EC可以有效地去除SAGD产生的水中的二氧化硅。该项目将研究EC用于处理零灰渣软化过程中产生的排污浓缩物。污泥的处理性能和过滤性能将作为EC系统的运行条件和设计的函数进行调查。

Heavy oil production of steam assisted gravity drainage (SAGD) is the largest in-situ production process in theCanadian oil-sands. This production process generates large quantities of produced water, typically 3 to 4 timesthe volume of oil, which must be treated and recycled to ensure that the process is viable and to meet regulatoryrequirements. The produced water must be treated before being fed to the steam generator (boiler) for injectioninto the reservoir as steam. To avoid fouling of the boilers, the water is usually treated by a process of warm orhot lime softening to remove hardness and silica which can scale the boilers. This process is high cost andgenerates significant volumes of sludge. An alternative process, so-called zero lime softening is beingdeveloped by the industry partner, Eco-Tech, which is lower cost and more environmentally freindly.Eco-Tech have shown that if the produced water is treated to remove hardness, the silica can be at a relativelyhigh concentration (>200 mg/L), without causing significant scaling of the boilers. However, the concentratestream from the boilers contains greater than 1200 mg/L silica, and must be treated prior to recycle or disposal.Conventional chemical processes (acidification) lead to a silica gel sludge which is difficult o separate from thewater. Electrocoagulation (EC), has been identified as a potential treatment process for the blowdownconcentrate. In previous work, we have been found that EC can effectively remove silica from SAGD producedwater. This project will investigate EC for the treatment of blowdown concentrate generated by the zero-limesoftening process. The treatment performance and filterability of the sludge will be investigated as a function ofthe operating conditions and design of the EC system.