Role of Water in Recovery and Production of Raw Fuels
27
leaks, and (5) stormwater management. Water supply, purification, treatment, and
management are very important and essential parts of the fastest growing shale gas
industry.
2.5 Water reQUirement FOr mininG, PreParatiOn,
and eXtraCtiOn OF sOlid FUels
Mining of solid fuels such as coal, oil shale, tar sand (and heavy oil), and uranium,
and their subsequent preparation and extraction require a large quantity of water
[37–41,43–48]. We briefly address this issue in this section.
2.5.1 oil ShAle induSTry
The mining and retorting of oil shale consumes a large amount of water. Aboveground retorting typically consumes between one and five bbl of water per each bbl
of produced shale oil, depending on the technology [43–46,48]. Water is normally
used for spent oil shale cooling and oil shale ash disposal. In situ processing, according to one estimate, uses about one-tenth as much water [47]. Also, water must be
pumped out of oil shale mines. The resulting fall in water table may have negative
effects on nearby arable lands and forests [43]. A 2008 programmatic environmental
impact statement issued by the US Bureau of Land Management stated that surface
mining and retort operations produce 2–10 US gallons of waste water per 1 short ton
of processed oil shale [46].
2.5.2 TAr SAnd And heAvy oil induSTrieS
Water requirement in tar sand industry is well reviewed by Speight [16,17,44] in his
numerous books and other publications. Just like oil shale, tar sands and heavy oil
are obtained from strip (surface) mining or underground mining. The mining is generally accompanied by extraction process to recover bitumen or heavy oil. In terms
of bitumen separation and recovery, the “hot water process,” to date, is the only successful commercial process to be applied to bitumen recovery from mined tar sand/
oil sand in North America.
The hot water process utilizes the linear variation of bitumen density and the
nonlinear variation of water density with temperature so that bitumen that is heavier
than water at room temperature becomes lighter than water at 80°C. Surface-active
materials in the tar sand also contribute to the process. The two most important steps
in the process are “conditioning” and “separation.”
In the conditioning step, the tar sand is heated and mixed with water to form a
pulp of 60%–85% by weight of solids at 80°C–90°C. First the tar sand lumps are
reduced in size by ablation. The conditioned pulp is screened through a double-layer
vibrating screen. Water is added to the screened material and the pulp then enters the
“separation” cell. The bulk of the sand settles in the cell and is removed from the bottom as tailings, but the majority of the bitumen floats to the surface and is removed
as froth. A middling stream containing water and fine solids and some bitumen from
the midway up the side of the cell wall is also recovered.
27
leaks, and (5) stormwater management. Water supply, purification, treatment, and
management are very important and essential parts of the fastest growing shale gas
industry.
2.5 Water reQUirement FOr mininG, PreParatiOn,
and eXtraCtiOn OF sOlid FUels
Mining of solid fuels such as coal, oil shale, tar sand (and heavy oil), and uranium,
and their subsequent preparation and extraction require a large quantity of water
[37–41,43–48]. We briefly address this issue in this section.
2.5.1 oil ShAle induSTry
The mining and retorting of oil shale consumes a large amount of water. Aboveground retorting typically consumes between one and five bbl of water per each bbl
of produced shale oil, depending on the technology [43–46,48]. Water is normally
used for spent oil shale cooling and oil shale ash disposal. In situ processing, according to one estimate, uses about one-tenth as much water [47]. Also, water must be
pumped out of oil shale mines. The resulting fall in water table may have negative
effects on nearby arable lands and forests [43]. A 2008 programmatic environmental
impact statement issued by the US Bureau of Land Management stated that surface
mining and retort operations produce 2–10 US gallons of waste water per 1 short ton
of processed oil shale [46].
2.5.2 TAr SAnd And heAvy oil induSTrieS
Water requirement in tar sand industry is well reviewed by Speight [16,17,44] in his
numerous books and other publications. Just like oil shale, tar sands and heavy oil
are obtained from strip (surface) mining or underground mining. The mining is generally accompanied by extraction process to recover bitumen or heavy oil. In terms
of bitumen separation and recovery, the “hot water process,” to date, is the only successful commercial process to be applied to bitumen recovery from mined tar sand/
oil sand in North America.
The hot water process utilizes the linear variation of bitumen density and the
nonlinear variation of water density with temperature so that bitumen that is heavier
than water at room temperature becomes lighter than water at 80°C. Surface-active
materials in the tar sand also contribute to the process. The two most important steps
in the process are “conditioning” and “separation.”
In the conditioning step, the tar sand is heated and mixed with water to form a
pulp of 60%–85% by weight of solids at 80°C–90°C. First the tar sand lumps are
reduced in size by ablation. The conditioned pulp is screened through a double-layer
vibrating screen. Water is added to the screened material and the pulp then enters the
“separation” cell. The bulk of the sand settles in the cell and is removed from the bottom as tailings, but the majority of the bitumen floats to the surface and is removed
as froth. A middling stream containing water and fine solids and some bitumen from
the midway up the side of the cell wall is also recovered.