Comparison of Silica Reduction in Warm Lime Softener and Hot Lime Softener

摘要

Japan Canada Oil Sands Limited (JACOS) operates the Hangingstone SA GD Demonstration project, which uses the Steam Assisted Gravity Drainage (SAGD) process to recover bitumen. The facility has two central processing plants (Plant 1 and Plant 2), each consisting of production separation, water de-oiling, water recycling, steam generator feed water preparation, and steam generation units. A major component of the SAGD facility is the steam generation as, 2-3 barrels of steam are required to produce 1 barrel of bitumen. The steam that is injected into the reservoir condenses and is produced with the bitumen. The oil/water emulsion is separated and the produced water is de-oiled and reused In order to conserve fresh water and reduce waste water disposal volume, 100% of the de-oiled produced water and a portion of steam generator blowdown water are recycled and reused for steam generation. Silica, which is one of the major contaminants of the produced water, is reduced from a concentration of 250-300ppm (as SiO<,2>) to a target of 5Oppm in order to protect the Once Through Steam Generators (OTSG) from silica scale. This scale will reduce the efficiency of the steam generators and if not carefully controlled, may cause tubes to overheat and fail. The JACOS Hangingstone facility uses Warm Lime Softening (WLS) in Plant 1 and Hot Lime Softening (HLS) in Plant 2 to reduce the silica content in the produced water. This paper will compare the chemical consumption, performance and relative costs of each system based on field experience and data from the Hangingstone facility. It will also offer some recommendations regarding operation and design of these facilities.