Extraction of bitumen from bitumen froth and biotreatment of bitumen froth tailings generated from tar sands

A counter-current decantation process for the extraction and recovery of bitumen from tar sands which comprises:

• providing a series of interconnected stages extending from a first stage through at least one intermediate stage to a last stage, each of said stages having a mixer associated therewith, said process comprising:
• feeding water and raw tar sands to a mixer to form a substantially uniform aqueous tar sands mixture thereof;
• passing said tar sands mixture to a flotation cell;
• injecting air into said felon cell to form a bitumen froth;
• removing and passing said bitumen froth to a deaerator to form a deaerated froth;
• passing said deaerated froth to a primary mixer to form a substantially uniform mixture thereof which is fed to a primary settler and thereby form an overflow of dilute bitumen which is removed and collected and an underflow comprising solids, asphaltenes and residual bitumen;
• passing said underflow from said primary settler to a secondary mixer to form a uniform mixture thereof which is fed to a secondary settler to form an overflow containing bitumen which is fed to the primary mixer for further recovery and an underflow which is fed to a tertiary mixer,
• adding a solvent to said tertiary mixer to form a mixture with said underflow from said secondary settler, the mixture being then fed to a tertiary settler to provide an overflow containing bitumen which is fed to said secondary mixer and an underflow which is fed to a first reservoir to provide gravity separation of said underflow into several layers comprising (1) a top layer of dilute bitumen, (2) an intermediate layer containing dilute bitumen, precipitated asphaltenes and water, and (3) a bottom layer comprised of water and solids phase which is filtered and said solids sent to tails;
• passing said top layer containing dilute bitumen to said primary mixer for the subsequent recovery of bitumen therefrom;
• dividing said intermediate layer into two streams, one being fed to secondary gravity separation in a second reservoir and the other bio chemically treated to form a bioliquor for recycle into the countercurrent decantation process,
• said secondary gravity separation providing a first layer of floating asphaltenes which is sent to asphaltenes tails, a second layer comprising a bioliquor phase which is recycled to asphaltenes treatment in the asphaltenes separation process, and a bottom layer of clay and sand which is discarded as tails.