Silica removal from SAGD boiler blowdown by electrocoagulation

蒸汽辅助重力泄油（SAGD）稠油开采是加拿大油砂中最大的原位开采工艺。这种生产过程会产生大量的产出水，通常是油的3到4倍，这些产出水必须经过处理和回收，以确保该工艺可行并符合监管要求。采出水在进入蒸汽发生器（锅炉）作为蒸汽注入储层之前必须经过处理。为了避免锅炉结垢，水通常采用温石灰或热石灰软化工艺来去除硬度和二氧化硅，从而使锅炉结垢。该工艺成本高，产生大量污泥。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已经证明，如果对采出水进行去除硬度的处理，二氧化硅的浓度可以相对较高（约200毫克/升），而不会引起锅炉的严重结垢。然而，来自锅炉的浓缩流含有大于1200mg /L的二氧化硅，必须在回收或处置之前进行处理。传统的化学处理（酸化）会产生难以从水中分离的硅胶污泥。电凝（EC）已被确定为一种潜在的处理排污精矿的工艺。在以往的工作中，我们已经发现EC可以有效地去除SAGD产出水中的二氧化硅。本项目将研究EC处理由零石灰软化工艺产生的排污精矿。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研究。

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.