Note: Descriptions are shown in the official language in which they were submitted.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
1
METHOD AND SYSTEM FOR HEATING A BED OF HYDROCARBON-
CONTAINING ROCKS
FIELD OF THE INVENTION
Embodiments of the present invention relate to methods and apparatus for
heating a bed
of kerogen-containing or bitumen-containing rocks, for example, to produce
pyrolysis
fluids therefrom.
DESCRIPTION OF RELATED ART
Hydrocarbons obtained from subterranean formations are often used as energy
resources, as feedstocks, and as consumer products. Concerns over depletion of
available
hydrocarbon resources and concerns over declining overall quality of produced
hydrocarbons have led to development of processes for more efficient recovery,
processing and/or use of available hydrocarbon resources. In situ processes
may be used
to remove hydrocarbon materials from subterranean formations that were
previously
inaccessible and/or too expensive to extract using available methods. Chemical
and/or
physical properties of hydrocarbon material in a subterranean formation may
need to be
changed to allow hydrocarbon material to be more easily removed from the
subterranean
formation and/or increase the value of the hydrocarbon material. The chemical
and
physical changes may include in situ reactions that produce removable fluids,
composition changes, solubility changes, density changes, phase changes,
and/or
viscosity changes of the hydrocarbon material in the formation.
Large deposits of heavy hydrocarbons (heavy oil and/or tar) contained in
relatively permeable formations (for example in tar sands) are found in North
America,
South America, Africa, and Asia. Tar can be surface-mined and upgraded to
lighter
hydrocarbons such as crude oil, naphtha, kerosene, and/or gas oil. Surface
milling
processes may further separate the bitumen from sand. The separated bitumen
may be
converted to light hydrocarbons using conventional refinery methods. Mining
and
upgrading tar sand is usually substantially more expensive than producing
lighter
hydrocarbons from conventional oil reservoirs.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
2
Retorting processes for oil shale may be generally divided into two major
types:
aboveground (surface) and underground (in situ). Aboveground retorting of oil
shale
typically involves mining and construction of metal vessels capable of
withstanding high
temperatures. The quality of oil produced from such retorting may typically be
poor,
thereby requiring costly upgrading. Aboveground retorting may also adversely
affect
environmental and water resources due to mining, transporting, processing,
and/or
disposing of the retorted material. Many U.S. patents have been issued
relating to
aboveground retorting of oil shale. Currently available aboveground retorting
processes
include, for example, direct, indirect, and/or combination heating methods.
SUMMARY OF EMBODIMENTS
Embodiments of the present invention relate to apparatus and methods for
heating
hydrocarbon-containing matter (e.g. tar sands or kerogen-containing rocks such
as pieces
of coal or pieces of oil shale) within an enclosure such as a pit or an
impoundment or a
container. Hydrocarbon-containing rocks are introduced into the enclosure to
form a bed
(e.g. a packed-bed) of rock therein. Oxygen may be evacuated (e.g. under
vacuum or by
means of an inert sweep gas) to create a substantially oxygen-free environment
within the
enclosure. In different embodiments, the enclosure may be a pit, or an
impoundment or a
container. The enclosure may be entirely below ground level, partially below
and
partially above, or entirely above ground level.
Operation of heaters in thermal communication with the hydrocarbon-containing
rocks may sufficiently heat the rocks to convert kerogen or bitumen thereof
into pyrolysis
formation fluids comprising hydrocarbon pyrolysis fluids. The formation fluids
may be
recovered via production conduits, or via a liquid outlet located at or near
the bottom of
the enclosure and/or via a vapor outlet located near the top of the enclosure,
or in any
other manner.
After they exit the pit, the NGL (natural gas liquids) such as propane and
butane
may be separated from the methane and ethane gases because of the high
economic value
of NGL. Hydrogen may also be separated from the produced gases and used in
upgrading
of the produced shale or coal oils.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
3
Some embodiments relate to apparatus and methods of heating beds of
hydrocarbon-containing rocks (e.g. piece of coal or of oil shale, or tar sand)
in a manner
that has an improved efficiency and/or minimizes capital costs and/or
accelerates the
heating so as to allow for expedited recovery of the hydrocarbon pyrolysis
fluids.
Towards this end, it is now disclosed techniques whereby thermal energy is
transferred to
the hydrocarbon-containing rocks from molten salt heaters and/or from immersed
heaters
and/or in a system where convection is the dominant heat transfer mechanism.
Some embodiments relate to apparatus and methods for maximizing an economic
and/or an environmental value of the thermally treated hydrocarbon-containing
rocks for
example, by upgrading coal in a manner now disclosed. Some embodiments relate
to
apparatus structured for relatively easy removal of thermally treated rocks
(e.g. upgraded
coal) from the container - for example, in a manner that minimizes the cost of
removal or
that facilitates re-use of the container.
In some embodiments related to heat convection and efficient heat transfer,
thermal energy is transferred to the hydrocarbon-containing rocks primarily by
liquid-
immersed heaters deployed at or near the bottom of the container. In
particular, the
heaters may be immersed in a reservoir of hydrocarbon liquids (e.g. having a
boiling
point between 300 and 400 degrees) located at or near a bottom of the
container. The
direct thermal coupling between the heaters and the liquid in direct contact
with the
heaters significantly (e.g. by one or more orders of magnitude) increases an
efficiency of
heat transfer from the heaters to heat the hydrocarbon liquid of the immersing
reservoir.
The hot hydrocarbon fluid (i.e. liquid or vapors boiled therefrom) of the
reservoir
upwardly migrates to locations above or near the top of the bed - for example,
via one or
more vertical conduits that vertically traverse the rock bed. The presence of
the vertical
conduits helps to maximize the fraction of thermal energy from the heaters
that migrates
directly to the top of the bed of particles.
The upward migration of hydrocarbon fluid (e.g. via the vertical conduit(s))
convectively transfers thermal energy supplied by the immersed heaters to
these locations
above or near the top of the bed. When this hydrocarbon fluid subsequently
falls
downwards through the rock bed, this thermal energy supplied by the immersed
heater is
convectively transferred to an interior of the rock bed.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
4
In some embodiments, the walls of the vertical conduit(s) are substantially
fluid-
tight and/or thermally insulated so that most, or substantially an entirety,
of the thermal
energy of the reservoir-originating hydrocarbon fluids remains within the
vertical
conduit(s) during the upward migration of the hydrocarbon fluids. Because a
relatively
small fraction of thermal energy transferred to the bed during upward
migration of the hot
hydrocarbon fluids, it may be said that the primary heat transfer mechanism of
thermal
energy from the heaters to the bed of particle is downward heat convection.
One
advantage of relying specifically on heat convection is that it is assisted by
gravity and
may be much more efficient.
Some embodiments of the present invention provide two efficiency-related
features: (i) transfer of thermal energy to hydrocarbon liquids from the
immersed heaters;
and (ii) gravity-assisted downward heat convection to the bed of particles.
Some embodiments of the present invention relate to convective re-boiling
loops.
In these embodiment, thermal energy from the immersed heaters boils liquids of
the
reservoir into condensable hydrocarbon vapor - for example, the liquid may
enter the
vapor phase before entering the vertical conduit or within the vertical
conduit. Because
of the relatively low density of hot hydrocarbon vapors, gravity drives
upwards migration
of the hydrocarbon vapors. The hydrocarbon vapor may condense (i) above and/or
(ii)
within the rock bed - e.g. .in an upper half thereof or as the vapor moves
downwards in
the bed. In the later case, condensation of hydrocarbon vapors within the rock
transfers
phase-change enthalpy to the hydrocarbon rocks, further increasing a thermal
efficiency
of the heating process.
As an alternate to a re-boiling loop where buoyancy drives upwards migration
of
the heated gas-phase hydrocarbon fluids from the reservoir, it is possible to
employ a gas
lift or other pumping system to drive upward migration of liquid-phase
hydrocarbon
fluids from the reservoir from the bottom of the container to locations above
or near the
top of the rock bed. In these embodiments, hydrocarbon liquids are sent
through the
vertical conduits and then fall back through the bed. In both re-boiling
embodiments (i.e.
where vapor migrates upwards through the vertical conduits) as well as liquid
embodiments (i.e. where hydrocarbon liquid or a multi-phase flow primarily
comprising
liquids flow upwards through the conduit), the bed of rocks may be heated such
that
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
kerogen or bitumen of upper locations of the particle beds is pyrolyzed before
that of
lower locations of the particle bed. Thus, in some embodiments, a downwardly-
moving
pyrolysis front may be observed.
Although not a requirement, in one preferred embodiment, the immersed heaters
5 are molten salt heaters. Molten salt heaters may be preferred because of
their high
thermal efficiency and uniform temperatures.
Furthermore, it is noted that molten salt may be employed as a heat transfer
fluid
in heaters that are not necessarily immersed heaters. For example, as
discussed below,
molten salt heaters may be deployed substantially at a wall of the enclosure
or within a
wall thereof.
In some embodiments, the enclosure may be sealed after the kerogen or bitumen
is pyrolyzed and hydrocarbon pyrolysis fluids are recovered. Alternatively,
the post-
pyrolysis rocks may be recovered from the container and the container may be
reused.
For example, it is possible to sufficiently pyrolyze bituminous coal within
the container
so as to upgrade the bituminous coal to much more valuable and more
environmentally
benign anthracite coal.
In some embodiments, the apparatus for pyrolyzing hydrocarbon-containing rocks
may substantially lack horizontally-oriented heaters that are deployed in
locations
significantly above the floor of the enclosure, or facilitate the removal of
upgraded coal
from the enclosure. For example, advection heaters embedded within or outside
the walls
or within a floor of the enclosure may be used to heat the hydrocarbon-
containing rocks
to pyrolysis temperatures.
In some embodiments, horizontal heaters that can maintain a constant
preselected
temperature along a long length are utilized. The heaters may be electrical
heaters such as
Curie heaters or SECT heaters. The heaters may be pipes heated by a heat
transfer media
such as molten salts, heated oils, and heated gases such as CO2, nitrogen, or
steam or
combustion air.
Heated molten salts may be circulated through the pipes to boil the oil in the
lower section to pyrolyze the oil shale or coal in the pit. The advantages of
the molten salt
heating are the extremely high energy efficiency and the high heat transfer
efficiency of
molten salt. Only small diameter piping is required and uniform temperatures
are
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
6
achieved over long lengths. Hence the length of the surface pit may be very
long, for
example at least 30 meters or at least 100 meters or at least 200 meters or at
least 500
meters longer. The piping may also be looped inside the pit so that the
exterior piping
manifold has fewer connections with fewer chances of leaks.
In the case of coal, the top seal of the pit or pile is opened after pyrolysis
to
remove the devolatilized coal. This coal may be more valuable than the initial
coal
because it has higher carbon content, higher calorific value, ultra lower
moisture and
volatiles, and lower sulfur. After removing the post-treatment coal, the pit
can be refilled
with fresh coal for the next pyrolysis. The post-pyrolysis coal may also be
steam washed
in the pit while still warm to remove ash from the coal and further upgrade
the coal to the
highest grade metallurgical coal. Circulating steam may achieve both the
cooling and
washing of the coal.
The pit may be constructed below grade level using earth-moving equipment. The
pit may be lined with clay, such as bentonite, to render the walls and bottom
substantially
impermeable to liquids and vapors. It may be desirable to choose a location
where the
surface geology is a naturally-occurring clay so that lining the pit is
unnecessary.
BRIEF DESCRIPTION OF THE DRAWINGS
To assist in the understanding of the invention and for purposes of
illustrative
discussion, some embodiments are herein described, by way of example only,
with
reference to the accompanying drawings and images. In this regard, the
description taken
with the drawings makes apparent to those skilled in the art how embodiments
of the
invention may be practiced. Dimensions of components and features shown in the
figures
are chosen for convenience and clarity of presentation and are not necessarily
shown to
scale. The drawings are not to be considered as blueprint specifications.
FIGS. 1A-1B, 5-12 and 17 illustrate ref1ux-based systems where repeated
boiling
of hydrocarbon liquids of a reservoir convectively transfers thermal energy
from heater(s)
immersed within the liquid reservoir to various locations of the rock bed.
FIGS. 2, and 13-18 relate to systems for pyrolysis of hydrocarbon-containing
rocks (e.g. mined oil shale or mined coal or tar sands) arranged in a rock bed
in an
interior of an excavated enclosure by wall-embedded heaters.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
7
FIGS. 4A-4B relate to methods for re-using an interior of an excavated
enclosure.
FIGS. 4B and 19-22 relate to techniques for upgrading mined coal within an
excavated
enclosure.
FIGS. 3 and 23-24 relate to systems where a rock bed of hydrocarbon-containing
rocks is heated by horizontal molten salt heaters traversing the rock bed.
DETAILED DESCRIPTION OF EMBODIMENTS
Overview
Embodiments of the present invention relate to apparatus and methods for
heating
hydrocarbon-containing matter (e.g. tar sands or kerogen-containing rocks such
as pieces
of coal or pieces of oil shale) within an enclosure such as a pit or an
impoundment or a
container. Hydrocarbon-containing rocks are introduced into the enclosure to
form a bed
(e.g. a packed-bed) of rock therein. Oxygen may be evacuated (e.g. under
vacuum or by
means of an inert sweep gas) to create a substantially oxygen-free environment
within the
enclosure. In different embodiments, the enclosure may be a pit, or an
impoundment or a
container. The enclosure may be entirely below ground level, partially below
and
partially above, or entirely above ground level.
Operation of heaters in thermal communication with the hydrocarbon-containing
rocks may sufficiently heat the rocks to convert kerogen or bitumen thereof
into pyrolysis
formation fluids comprising hydrocarbon pyrolysis fluids. The formation fluids
may be
recovered via production conduits, or via a liquid outlet located at or near
the bottom of
the enclosure and/or via a vapor outlet located near the top of the enclosure,
or in any
other manner.
Examples of hydrocarbon-containing rocks are kerogen-containing rocks (e.g.
mined oil shale or mined coal) and bitumen-containing rocks (e.g. tar sands).
FIGS. 1A-1B, 5-12 and 17 illustrate ref1ux-based systems where repeated
boiling
of hydrocarbon liquids of a reservoir convectively transfers thermal energy
from heater(s)
immersed within the liquid reservoir to various locations of the rock bed.
FIGS. 2, and
13-18 relate to systems for pyrolysis of hydrocarbon-containing rocks (e.g.
mined oil
shale or mined coal or tar sands) arranged in a rock bed in an interior of an
excavated
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
8
enclosure by wall-embedded heaters. FIGS. 4A-4B relate to methods for re-using
an
interior of an excavated enclosure. FIGS. 4B and 19-22 relate to techniques
for upgrading
mined coal within an excavated enclosure. FIGS. 3 and 23-24 relate to systems
where a
rock bed of hydrocarbon-containing rocks is heated by horizontal molten salt
heaters
traversing the rock bed.
FIGS. 1A-1B is a schematic diagram of a horizontal cross-section of a reflux-
based surface pit system for pyrolyzing a bed of hydrocarbon-containing rocks
arranged
in a rock bed 110 - for example, a packed bed of rocks arranged according to
any packing
(e.g. random packing). In the example of FIGS. 1A-1B, a plurality of heaters
134
arranged substantially at the bottom of the pit heat an interior of the pit so
as to heat the
hydrocarbon-containing rocks of the rock bed 110. As will be discussed below,
for the
examples of FIG. 1A-1B, heat convection is a significant mechanism of
transferring
thermal energy from heaters 134 of rock bed 110.
As illustrated in FIGS. 1A-1C, heaters 134 are immersed within a reservoir 114
of
hydrocarbon liquids at the bottom of the pit. Heating of the liquid-phase
hydrocarbon
fluids of reservoir 114 by immersed heaters 118 drives the hydrocarbon fluids
upwards -
e.g. by vaporizing the fluids or by reducing a density of hydrocarbon liquids.
The
upwardly-driven heated hydrocarbon fluids (i) enter vertical chimney 126 via a
lower
opening 144 thereof; (ii) migrate upwards through vertical chimney 126 to
substantially
vertically traverse rock bed 110 (see upwardly migrating condensable
hydrocarbon vapor
(UMCHCV) and (iii) exit vertical chimney via an upper opening 148 thereof.
The heated hydrocarbon fluids may vaporize either before entering chimney 126
or therein. Thus, as illustrated FIGS. 1A-1B, hydrocarbon vapors derived by
boiling
liquids of reservoir 114 migrate upwards through vertical chimney 126 - these
upwardly
migrating vapors are labeled Upwardly Migrating Condensable Hydrocarbon Vapor
(UMCHCV). Because a resistance to fluid flow within the chimneys 126 is
significantly
lower than within the rock bed 110, the presence of the chimneys 126 may
significantly
increase a rate at which thermally energy convectively and upwardly migrates
to the top
of rock bed 110.
Upon exiting vertical chimney 126, the hydrocarbon vapors may condense back
into the liquid phase upon contacting a surface whose temperature is below its
boiling
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
9
point at that pressure. As condensed hydrocarbon liquids fall back downwards
through
the rock bed 110 (i.e. labeled Downwardly Migrating Hydrocarbon Liquids
(DMHCL)),
they convectively heat the rocks of rock-bed 110 - for example, sufficiently
to pyrolyze
bitumen or kerogen thereof.
Thus, FIGS. 1A-1B relate to a ref1ux/reboiling loop whereby hydrocarbon
liquids
are repeatedly boiled to efficiently and convectively transfer (e.g. over
relatively 'large
distances') thermal energy from immersed heaters to various locations of rock
bed 110
including those at relatively 'high' elevations. In the example of FIG. 1A-1B,
a majority
or substantial majority of upward vapor migration occurs within the vertical
chimneys
where resistance to fluid flow is at least 10 times or at least 100 times or
at least 1,000
times an average fluid flow resistance observable within rock bed 110 - thus,
the presence
of the chimneys 126 may significantly increase the efficiency of convection of
thermal
energy from the immersed heaters to the rock bed 110.
Thus, one advantage of the system of FIGS. 1A-1B is the shorter amount of time
required to pyrolyze kerogen or bitumen of the rock bed.
FIG. 2 illustrates one example of a surface pit system for thermally treating
a rock
bed 110 of hydrocarbon-containing rocks within an interior of an excavated
enclosure
(e.g. pit or impoundment) that is heated by molten salt heaters. In the
specific example of
FIG. 2, vertical molten salt heaters 178 (VMSH) are arranged within a tall,
thin chamber
184 - i.e. a ratio between a height of chamber 184 and at least one horizontal
dimension
thereof (e.g. a lesser horizontal dimension) may be at least 5 or at least 10.
Rocks of rock
bed 110 are arranged in the interior of a chamber of an enclosure (e.g. a
pit).
At least one wall of the excavated enclosure containing rock bed 110 is heated
by
the vertical molten salt heaters 178. In the example of FIG. 2, a primary
mechanism of
heating of rock bed 110 is by transfer of thermal energy from the walls of the
enclosure
(i.e. which are heated by the 'embedded heaters') to rock bed 110.
As will be discussed below, one advantage of the apparatus of FIG. 2 is
efficiency
due to the use of molten salt, an extremely efficient heat-transfer fluid.
FIG. 3 is another
example of a surface pit system including molten salt heaters - in the example
of FIG. 3,
the molten salt heaters comprise horizontal conduits that pass through a bed
of
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
hydrocarbon-containing rocks. Although not explicitly stated above, is further
noted that
the immersed 134 of FIGS. 1A-1B may be molten salt heaters.
Reference is made once again to FIG. 2. By relying primarily on wall-embedded
heaters rather than heaters located within rock bed 110 (for example,
horizontal conduit
5
heaters that traverse rock bed 110), it may be significantly easier to remove
post-
pyrolysis rocks to re-use the pit to pyrolyze another batch of hydrocarbon-
containing
rocks. As will be discussed in greater detail below, in some embodiments,
these post-
pyrolysis rocks may be a valuable and/or environmentally friendly solid
hydrocarbon
resource.
10 FIG.
4A is a flowchart of a routine for re-using an enclosure after it has been
used
to pyrolyze kerogen or bitumen of rocks of a rock-bed. FIG. 4B relates to the
specific
case where (i) pieces of mined bituminous coal form a rock-bed within an
enclosure; and
(ii) the bituminous coal is upgraded to anthracite coal within the enclosure -
for example,
heaters are operated to provide the requisite time-temperature heating
history. As will be
discussed below, (i) anthracite coal is much more environmentally friendly and
potentially more valuable than bituminous coal and (ii) in some embodiments,
the
techniques FIG. 4B may require subjecting the bituminous coal to a more
rigorous
time/temperature history than would be required for situations where one is
only
interested in obtaining hydrocarbon pyrolysis fluids.
For the present disclosure, when the temperature of an object or location is
'significantly increased,' this requires an increase of at least 25 degrees
Celsius or at least
50 degrees Celsius.
For the present disclosure, an 'excavated enclosure' refers to artificially
dug pit or
a natural pit (i.e.. modified in some manner) or to a pile of soil/earth
formed or modified
by excavation - e.g. to form an impoundment at least partly above-ground.
For the present disclosure, a 'substantial majority' refers to at least 75%.
For the present disclosure, when a fluid (e.g. molten salt or any other fluid)
is 'hot'
a temperature thereof is at least 200 degrees Celsius or at least 300 degrees
Celsius.
Reflux Based Systems
For the present disclosure, a 'hydrocarbon reflux loop' describes the (i)
boiling of
hydrocarbon liquid into condensable hydrocarbon vapors; (ii) the upward
migration of
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
11
the hydrocarbon vapors; (iii) the condensation of the hydrocarbon carbon
vapors back
into liquid at a higher location than where the liquid was boiled (e.g. above
the rock bed
or substantially at a top of the rock bed); and (iv) gravity-driven downward
migration (i.e.
'falling') of the hot hydrocarbon liquids back down through the rock bed to
convectively
transfer thermal energy from the hydrocarbon liquids to the rocks of the rock
bed. It is
requirement of the 'reflux loop' for the condensed hydrocarbon liquids to be
subsequently
re-boiled back into hydrocarbon vapors to repeat the upward migration,
condensation,
and downward migration to convectively transfer thermal energy to the rocks.
As noted above, FIGS. 1A-1B, 5-12 and 17 illustrate reflux-based systems where
repeated boiling of hydrocarbon liquids of a reservoir convectively transfers
thermal
energy from heater(s) immersed within the liquid reservoir to various
locations of the
rock bed.
In order to create an anoxic environment within the enclosure (e.g. within the
'pit'), the pit may be sealed. In the example of FIG. 1A, the pits is sealed
from the top by
substantially-fluid tight cover 138 (e.g. comprising soil). Furthermore, a
presence of clay
liner 152 may retain fluids within an interior of the excavated enclosure. A
presence of a
thermal insulator such as concrete liner 156 may retain thermal energy within
an interior
of the excavated enclosure. As an alternative to the clay liner 152 and/or
concrete liner
156 (i.e. which is illustrated in various figures), it is possible (see, for
example, FIG.
10B) to select a location where the underlying source rock has a low
permeability to
retain fluids within the enclosure interior and/or is a good thermal insulator
to retain
thermal energy within the enclosure. In yet another example, it is possible to
employ a
freeze wall and/or wax wall and/or sulfur wall to retain fluids -- this may be
deployed
adjacent to the excavated enclosure or distanced therefrom. For example, a
freeze wall or
sulfur wall or wax wall structure may enclose a plurality of excavated
enclosures.
As illustrated in FIG. 5, rock bed 110 is supported by a grating (e.g. steel
grating
120) which is not fluid tight but which has a pore size that is significantly
smaller than a
characteristic size of the rocks of rock bed 110. The small characteristic
pore size of the
grating is small (e.g. at most 10 cm prevents rocks of rock bed 110 from
falling into and
clogging up reservoir 114. Furthermore, in some embodiments a second rock bed
of non-
pyrolyzable rocks (e.g. a tight gravel filter 122) may also serve this
purpose.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
12
As illustrated in FIGS. 5, an upper level 118 of reservoir 114 may be
maintained
substantially above heaters 134 so that heaters 134 remain immersed within
reservoir
114. In some embodiments, the upper level 118 is maintained substantially
below an
entirety of rock bed 110.
As noted above, once condensable hydrocarbon vapors exit from a top of chimney
126 via upper opening 148, they may condense at locations at or above a top of
rock bed
110 but within the sealed excavated enclosure, e.g. due to the lower
temperatures at the
top of the enclosure. In some embodiments, in order to horizontally distribute
the liquid-
phase condensed hydrocarbon fluids to various locations within the rock bed
110, it may
be useful to provide a liquid distribution system above rock bed 110 so as to
distribute the
condensate over a variety of horizontal locations of rock bed 110.
In the examples of FIGS. 6-8, an array of spreader tray(s) 220 are arranged
substantially above rock bed 110. Condensation of hydrocarbon vapor above
spreader
tray causes hydrocarbon liquid (e.g. at or near a boiling point thereof) to
accumulate in an
'upper reservoir' 214 on the spreader tray(s) 220. Because the upper reservoir
214 is
supplied by condensation of hydrocarbon vapor(s) that exits via upper opening
148 of
chimney 126, it may be said that upper reservoir 214 is supplied by the lower
reservoir
114. Although multiple spreader trays 220 are illustrated in FIGS. 6-7 this is
not a
limitation and in some embodiments, a single spreader tray 220 (e.g. having
multiple
voids 224 therein) may be arranged within the enclosure.
Hydrocarbon liquid falls through one or more voids 224 within or between
spreader tray(s) and then falls through the rock bed 110. As illustrated in
FIG. 7, the
spreader tray assembly (e.g. including the void(s) 224) is useful for
horizontally
distributing the hydrocarbon liquid (i.e. derived from condensation above rock
bed 110)
throughout rock bed 110.
In the example of FIG. 8, each void is associated with a lip 228. In order for
hydrocarbon liquid of upper reservoir 214 to flow downwardly through a given
void, a
level of upper reservoir 214 should exceed a height of lip 228 above the
spreader tray 220
to which it is attached. The presence of lip 228 around each void 220 helps to
temporally
smooth a rate at which condensed hydrocarbon liquids flow down through void
220 into
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
13
bed 104. The presence of lip 228 helps to regulate an amount of hydrocarbon
liquid in
upper reservoir
One salient feature provided by embodiments of the present invention is the
downward heat convention in an upper half of rock bed 110 that is driven by
heaters (e.g.
immersed heaters) below rock bed 110. Thus, despite the fact that a majority
or
substantial majority of thermal energy delivered to rock bed 110 comes from
heaters
below rock bed 110, it is possible to generate downward convection (i.e. by
means of the
vertical chimneys 126) in an upper half of rock bed 110.
In some embodiments, as a result of the downward heat convection (e.g. driven
by
thermal energy supplied by heaters 134 immersed within lower hydrocarbon
liquid
reservoir 114), kerogen or bitumen of hydrocarbon-containing rocks at the very
top of
rock bed 110 is heated to pyrolysis temperatures before kerogen or bitumen of
rocks at
lower levels within the top half of rock bed 120. Thus, in some embodiments,
and as
illustrated in FIGS. 9A-9C, a downwardly moving pyrolysis front may be
observed in an
upper half of rock bed 110.
As noted above with reference to FIG. 4A, in some embodiments it is desirable
to
reuse an excavated enclosure (e.g. pit or impoundment). One feature for such
re-use is
illustrated in FIG. 10A. Substantially vertical chimney 126 may be mounted to
support
grating 120 in a manner such that the vertical chimney is detachable. In the
example of
FIG. 10A, chimney 126 may be mounted onto the grating so that a lower distal
end of
chimney 126 of a cap thereof it mounted into a pipe port. In one example,
after mounting
of chimney 126, rock bed 110 is formed by introducing hydrocarbon-containing
rocks
into the excavated enclosure. This may be followed by heating of the rock bed -
- e.g. to
pyrolyze kerogen or bitumen thereof. After pyrolysis, it is possible before
removing a
majority of rock bed 110 to (i) disengage a distal end of chimney 126 to the
mounted
ports mounted onto the grating; (ii) pull vertical chimneys 126 out of the
excavated
enclosure; and (iii) once the chimneys have been removed and there is
substantially an
absence of heaters and other equipment in an interior of rock bed 110, scoop
out rocks of
rock bed 110. As is the case with the wall-embedded heater embodiments
discussed
elsewhere with reference to FIG. 2 and 13-18, the technique of FIG. 10A may
facilitate
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
14
pit re-use and/or economic exploitation of post-pyrolysis rocks (e.g. upgraded
coal) of
rock bed 110.
Reference is now made to FIG. 10B. In the example of FIG. 10B, there is no
need
for a clay liner.
FIG. 11 is schematic illustration of yet another embodiment of the present
invention. In the example of FIG. 11, the chimneys are situated substantially
at the walls
of the excavated enclosure. This is in contract to the example of FIGS. 1A-1B
and 5
where the chimneys are surrounded by the rock bed 102.
Illustrated in FIG. 11, but applicable to all ref1ux-based embodiments is
apparatus
for regulating a liquid level 118. A fluid level sensor and automatic control
valve
maintain the level of the boiling oil above the heaters. As pyrolysis occurs,
additional
coal or shale oil liquid hydrocarbons above this level are produced via the
automatic
control valve through production pipes.
Outside the pit, the liquid hydrocarbons produced from the pit enter a
fractionation tower. There, coal or shale oil with a preselected boiling point
cut is
removed and drained into the bottom of the pit just above the boiling
hydrocarbon liquid.
This circulation from the fractionation tower constantly refreshes the boiling
hydrocarbons at the bottom of the pit and maintains the composition of the
boiling
hydrocarbons at the desired boiling point range.
For the present disclosure, when a rock bed is situated within an enclosure,
an
'external heater' is a heater located outside of the chamber/region where the
rock bed is
situated. This is in contrast to heaters within the rock bed - for example,
conduits which
traverse the rock bed.
During heating, a 118 level of reservoir covers the heater pipes. The spacing
between pipes is calculated to provide continuous boiling of the oil. Typical
heater
spacing may be, for example, 5 ft, 10 ft or greater. The heat transfer from
the heater pipes
immersed in oil may be 1000 watts/ft, 5000 watts/ft, 10,000 watts/ft or
higher. The
optimal spacing may be determined by numerical simulations or by scale model
experimentation in the lab.
Heating of the coal or oil shale to pyrolysis temperatures is achieved via a
refluxing process where boiling hydrocarbon vapors condense on the colder
sections of
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
the pit and impart the heat of vaporization. Liquid hydrocarbons return to the
oil bath
through the coal or oil shale matrix by gravity and capillary forces. The
refluxing process
may be enhanced by adding slotted conduits to provide preferential pathways
for vapor
flow to reach the colder section, as shown in Figure 2. The conduits maybe
located along
5 the sides and middle of the pit and may extend the length of the pit.
Multiple rows of
conduits may be added to further enhance the refluxing process. Condensation
may
initially occur at or near the bottom of the pit and progress upward during
the heating
process. The heating time of the pit to pyrolysis temperature will be
determined
approximately by the heat capacity of the packed coal in the pit divided by
the total heat
10 input from all the heaters minus any heat losses to the surrounding
environment.
The hydrocarbon liquid of reservoir 114 that may be used for starting the
heating
may be a diesel oil with a boiling point above 300 C. The heater pipes should
be heated
to a temperature where the heater pipe skin temperature is higher than the
boiling point of
the oil but not above 375 C where coking of the diesel oil may occur. An
optimum
15 temperature may be in the range 300 ¨ 375 C, 325 ¨ 370 C, or 340 ¨ 360
C. When
operating at the higher temperature ranges, the heater pipes may be coated
with coke
inhibitors such as silicates to prevent scale from forming.
As the pyrolysis proceeds, the condensed hydrocarbon pyrolysis liquids will
mix
with the diesel oil in the bottom of the pit. The boiling point distribution
will gradually
change to that of the shale oil or coal oil. If the boiling point distribution
gets too elevated
in temperature, it may be desirable to circulate additional diesel cut into
the bottom
section to maintain the boiling point in the above mentioned ranges.
As shown in FIG. 11, a fluid level sensor and automatic control valve maintain
the level of the boiling oil above the heaters. As pyrolysis occurs,
additional shale oil
liquid hydrocarbons above this level are produced via the automatic control
valve through
production pipes.
Outside the pit, the liquid hydrocarbons produced from the pit enter a
fractionation tower. There shale oil with a preselected boiling point cut is
removed and
drained into the bottom of the pit just above the boiling hydrocarbon liquid.
This
circulation from the fractionation tower constantly refreshes the boiling
hydrocarbons at
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
16
the bottom of the pit and maintains the composition of the boiling
hydrocarbons at the
desired boiling point range.
The pressure in the pit may be maintained at atmospheric pressure or at an
elevated pressure (e.g. 1 to 3 atm.). The higher the pressure during
pyrolysis, the higher
quality the oil and gas produced. The pressure that can be maintained may be
determined
by the depth of the pit and the amount of soil added above the seal. Higher
pressures
improve the oil qualities but increase the possibility of gaseous leakage from
the pit.
Maintaining pressure with non-condensable gases may also be used to control
the
height of the refluxing process and thereby controlling the volume of coal or
oil shale
being heated at a given time. This minimizes the initial amount of diesel
required for the
refluxing process. As pyrolysis occurs at the lower sections of the pit, the
pressure is
lowered and the coal or shale oil that is generated adds to the refluxing
supply and
establishes an incrementally higher reflux point in the pit.
The boiling point distribution of the refluxing oil may also be varied by
adjusting
the pressure in the pit to achieve different heating temperatures if desired.
The boiling
temperature can be increased by elevating the pressure. The optimum pressure
may be in
the range of 1-3 atm. For instance, hexadecane has a boiling point of ¨300 C
at 1 atm.
At 2 atm., the boiling point increases to ¨350 C. By operating the pit at
elevated
pressures and temperatures, at the end of pyrolysis, hydrocarbon liquids
remaining in the
pit may be flashed to vapor by lowering the pressure of the pit.
In some embodiments, production pipes may be located in the pit or pile.
Liquids
are produced from the production pipe at the bottom and gases produced from
the
production pipe at the top of the pit or pile.
The top of the seal may be covered with a thermally insulating layer of
refractory
ceramic or clay or combinations of the two to limit heat losses to the
environment.
Additional pits may be constructed adjacent to existing pits (Figure 12).
Surface facilities
such as processing equipment and heating systems may be shared between
multiple pits,
thereby reducing the total surface footprint and capital expenditures.
The pipes may be constructed with Grayloc fittings so that they can be easily
removed. The pipes are sloped at an angle between 0.1-2 (see FIG. 24) so that
the
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
17
molten salt can self-drain from the pipes and other molten salt equipment into
the lower
molten salt container which may be placed below grade on the down flow side.
Thermal Conduction Heating of Pit or Pile with Molten Salt Heaters Embedded in
Walls
FIGS. 2, and 13-18 relate to systems for pyrolysis of hydrocarbon-containing
rocks (e.g. mined oil shale or mined coal or tar sands) arranged in a rock bed
in an
interior of an excavated enclosure by wall-embedded heaters.
As shown in FIG. 2, a pit is first excavated. The pit may be lined with clay,
such
as bentonite, to render the bottom substantially impermeable to liquids and
vapors. It may
be desirable to choose a location where the surface geology is a naturally-
occurring clay
so that lining the pit with clay is unnecessary. The pit may be constructed
below grade
level using earth-moving equipment well known in open pit mining operations. A
hard
insulation layer such as a low density refractory ceramic (firebrick) may then
be placed
inside the clay barrier to reduce heat losses to the surroundings. The walls
of the pit are
constructed of a sealed metal structure, and heater pipes are embedded in the
walls of the
structure. The bottom of the heater walls extend into the layer of clay,
creating a seal at
their intersection. The pit is then filled with pieces of oil shale, coal, tar
sands, or other
hydrocarbon-bearing material.
A layer of insulation may be placed on top of the pit to reduce heat losses.
The pit
is then covered with an impermeable layer, which is sealed at the top of the
wall to
prevent the escape of-fluids or vapors. This layer may be clay, stainless
steel lining,
silicone rubber, or other impermeable material. The insulation at the top of
the pit may be
located above or below the impermeable layer. If the layer of insulation is
located below
the impermeable sheet it is preferred that it be comprised of closed cell
insulation to
prevent liquids accumulating in the insulation. It is preferred that this
layer of insulation
and the impermeable seal be made of a flexible material such that it can be
rolled in place
following the filling of the pit and unrolled upon completion of the pyrolysis
process.
As shown in FIG. 14, multiple pits may be arranged side by side with each pit
sharing common heater walls with its neighboring pits. In this arrangement,
heat losses to
the surroundings may be minimized.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
18
The spacing between parallel heater walls is calculated to provide thermal
conduction heating of the hydrocarbon material in a time period of about a few
months.
Typical heater wall spacing may be, for example, 10 ft, 20 ft, 30 ft or
greater spacing.
The heater walls may be oriented along the long axis of the pit or the short
axis of the pit.
FIG. 13 shows for example the rise in temperature between two heater walls
spaced 16.4 ft (5 m) apart and maintained at a constant temperature of 500 C.
The
thermal diffusivity of the packed bed is assumed to be 0.004 cm2/sec. The
pyrolysis of
the hydrocarbon-bearing material is complete in about 3 months when the
temperature at
the midplane rises to about 325 C. In addition to heat transfer by thermal
conduction,
natural convection of hot fluids within the packed bed will also be effective
and may
shorten the heating time and may allow more uniform heating in the packed bed.
The array of pits may be very long, for example 100 ft, 300 ft, 1000 ft, 3000
ft or
longer. The width of the pit may by 50 ft, 100 ft, 200 ft, 300 ft or wider.
The depth of the
pit may be 10 ft, 30 ft, 50 ft, 100 ft or deeper. As shown in Figure 14, an
elevated
structure supporting a two-axis crane may be installed over the pits. A
mechanical claw
or scooper connected to the crane fills the pit with hydrocarbon-bearing
material
transported to the site. Post-pyrolysis, the scooper empties the pit into a
container to be
transported away from the site. The site may be located near a railroad line
or road to
facilitate the transportation of material to and from the site of the pit by
train or truck. A
conveyor belt may also be provided on site for conveying material to and from
the pits.
For pits with widths that are substantially long, for example 100 ft or
longer,
pillars to support the elevated tracks for the two-axis crane may be located
within the pit
as shown in FIG. 15. The foundation for the pillar may be surrounded by
thermal
insulation such as a refractory ceramic and may remain cool while the sounding
pit is
being heated. A multitude of pillars may be located within the pit, which are
sufficient to
mechanically support the elevated tracks of the crane.
Heater pipes are embedded in the heater walls and radiantly heat the walls to
a
nearly uniform temperature. The heater walls may be constructed of a metal
frame with
metal sheeting covering the frame. The sheeting may be welded along the joints
to seal
the wall from entrance of any produced vapors. The metal frame is designed and
sized to
handle the load from the material in the pit without substantial deformation.
The width of
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
19
the wall is sufficiently large to accommodate the outer diameter of the heater
pipes,
though sufficiently small to maintain a large solid angle from the heater pipe
to the wall,
thereby increasing the effectiveness of the radiant heat transfer. The
surfaces of the pipe
and the surfaces of the wall may also be roughened and blackened to increase
emissivity
of the surfaces and hence the radiant heat transfer. The interior of the walls
surrounding
the heater pipes may act effectively as a black body and maintain a
substantial constant
wall temperature.
Low molecular weight gases with good thermal conductivity such as hydrogen or
helium may be added to the inner space of the wall to further enhance heat
transfer from
The space within the heater walls may also be filled with solid granular
material
with high thermal conductivity, such as copper, aluminum or iron balls, to
enhance heat
transfer from the heater pipes to the heater walls.
Within the metal frame of the heater wall is a structure to support the heater
pipes.
The steel support frame may be lubricated with graphite or other high
temperature
lubricant to prevent sticking during the initial thermal expansion of the
heater pipes. The
heater piping may be looped along the long axis of the wall and may have
multiple passes
within the walls before existing as shown in FIG. 16. Looping the piping
within the wall
naturally creates expansion loops to accommodate thermal expansion.
In some embodiments, horizontal heaters pipes arranged within the walls
maintain
a substantially constant preselected temperature along a long length as shown
in FIG. 16.
The heater pipes may also be oriented vertically within the walls as shown in
FIG. 2. The
advantage of the horizontal heater pipes are the long lengths and hence
reduced number
of individual heaters and pipe connections. An advantage of the vertical
heater pipes is
that they may be able to be easily replaced in an event of a failure during
the heating
process.
The heaters may be pipes heated by a heat transfer fluids such as molten
salts,
heated oils (such as Therminol VP-1 (Solutia) or DowTherm A (Dow Chemical),
which
are eutectic mixtures of biphenyl (C12F110) and diphenyl oxide (C12F1100) with
operating
temperatures up to 400 C)), and heated gases such as CO2, nitrogen,
supersaturated
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
steam or combustion air. The heaters may also be electrical heaters such as
Curie heaters
or SECT heaters.
Molten salts are the preferred heat transfer fluids according to some
embodiments.
Molten salts have high heat capacity, low viscosity, and may be operated to
high
5 temperatures, for example, 450 C, 550 C, 600 C, 700 C, or higher
depending on the
specific molten salt. This allows for high heat transfer from the circulating
molten salt to
the heater walls using reasonable pipe diameters and flow rates. Pipe
diameters may be,
for example, 3", 5" or higher. Flow rates may be for example, 1 kg/s, 5, kg/s,
15 kg/s or
higher. The other heat transfer fluids (e.g. oils or gases) may be used for
preheating the
10 pipes above the melting point of the molten salt used in this invention.
The molten salt may comprise nitrate or nitrite salts such as HiTec salt,
HiTec
XL, Solar Salt, etc. The molten salt may also comprise carbonates, chlorides,
or fluoride
salts. The molten salts may be a single, binary, ternary, quaternary or other
mixture of
compounds. The molten salt may be chosen to have a maximum use temperature of
375
15 C or higher.
As shown in FIG. 16, the hot molten salt is fed into the heater pipes from a
molten
salt heat delivery system. The molten salt container and the external piping
between them
are insulated and heat traced to prevent heat losses and freezing of the
molten salt. There
is a pump located in the molten salt container that pumps the molten salt to a
furnace that
20 heats the molten salt and circulates the molten salt through the heater
pipes in the walls.
The heating of the furnace may be achieved using processed gas, natural gas,
coal, or oil.
The heating gas may be gas produced from the process that has been treated to
remove
undesirable components such as hydrogen sulfide, carbon monoxide and carbon
dioxide,
and separate valuable natural gas liquids and hydrogen. The hydrogen gas may
be utilized
in the hydrotreating facility for upgrading the oil produced. The hydrogen
sulfide may be
treated in a Claus plant to make elemental sulfur and the sulfur may be used
to produce
fertilizer.
Counter-current flow between adjacent heater pipes in the same wall helps
provide uniform heating to the pit. The heater piping may be looped inside the
pit so that
the exterior piping manifold has fewer connections with fewer chances of leaks
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
21
Molten salt heat delivery systems can achieve very high thermal efficiencies,
for
example, 80 ¨ 90%, if the furnaces are multipass and the incoming gases are
preheated by
the exhaust gases. The longer the length of the heater piping in the pit
compared to the
insulated section outside the pit, the more thermally efficient the molten
salt heaters
become. If the length of the heater in the pit is, for example, ten times the
length of the
insulated section outside the pit, the overall thermal efficiency may approach
the furnace
efficiency.
Gases for the molten salt furnaces may also be preheated by passing the gases
through piping in previously pyrolyzed pits that have not cooled yet.
As shown in Figure 16, a single molten salt heating system may be shared
between multiple pits, thereby reducing the total surface footprint and
capital
expenditures. Liquid and gas treatment facilities may also be shared by
multiple pits.
The pipes from a non-heated pit may be preheated using a heat transfer fluid
from
one of the adjacent piles or pits. Alternatively, a gas combustor can be used
to blow hot
combustion gases through the pipes for preheating. Electrical heating of the
pipes using
Joule heating, skin effect heating, or induction heating, can also be used.
The heat injection rate from the wall into the pit may be 500 W/m2, 1000 W/m2
or
higher. The heat injection from a single heater pipe may be 500 W/ft, 1000
W/ft or
higher, depending on the temperature of the heat transfer fluid and the
diameter and
spacing of the heater pipes. The temperature of the heat transfer fluid in the
heater pipes
may be in the range 400 ¨ 700 C or 500 ¨ 600 C, or preferably about 550 C.
The
optimal spacing between heater pipes may be determined by numerical
simulations using
a computer program such as STARS (CMG, Calgary) or by pilot experimentation.
The
spacing of the heater pipes may be, for example, 5 ft, 10 ft, or greater. The
thickness of
the wall may be, for example, 0.5 ft, 1.0 ft, 1.5 ft or greater.
The heater walls may also be heated by using boiling, reflux and condensation
as
the heating method. As shown in Figure 17, horizontal pipes heated by
circulating
molten salt may be located in a lower section of the wall - e.g. immersed in a
reservoir of
working fluid. The working fluid with a boiling point near the desired
operating
temperature (350-700 C) fills the space inside the wall to a level covering
the heater
pipes. The heater pipes boil the working fluid, and the vapors condense on the
walls,
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
22
thereby imparting the heat of vaporization and heating the wall to a nearly
uniform
temperature.
The working fluid for the desired operating temperature range of 350-700 C
may
be fluids such as synthetic oils, molten salts, or molten metal. This
invention preferably
utilizes synthetic oils such as Therminol VP-1 (Solutia) or DowTherm A (Dow
Chemical) as the working fluid. These oils have a boiling points approaching
400 C
when pressurized up to 150 psi. When operating at the higher temperature
ranges, the
inner side of the walls may be coated with coke inhibitors such as silicates
to prevent
scale from forming.
The gas pressure in the pit may be maintained at atmospheric pressure or
slightly
elevated pressures (e.g. 1 bar gauge). The higher the gas pressure during
pyrolysis, the
higher quality of the oil and gas produced. The gas pressure that can be
maintained in the
pit may be determined by the quality of the seal of the impermeable cover.
Higher gas
pressures in the pit improve the oil qualities but increase the possibility of
gaseous
leakage and odors from the pit. Alternatively, a slight vacuum may be applied
through the
gas production piping to collect the vapors. This reduces the chances for
leakage of odors
from the pit but may result in a somewhat lower quality of oil product.
In a second embodiment, the hydrocarbon-bearing material is not directly
filled
into the pit but rather it is transported to the facility in specially
designed reusable
shipping containers by rail or truck. The containers may have sizes of 8 x 9.5
x 48 ft or
larger. The containers are lowered into the pit and arranged into a
rectangular array
between the walls as shown in FIG. 18. Between each heater wall the containers
may be
arranged in a single or in multiple rows. These rows may be a multitude in
both width
and height.
An insulating blanket may be rolled over the top of the containers after a row
of
heaters is placed in the pit. This row may then be heated by the two adjacent
heater walls,
bringing the material in the containers to pyrolysis temperatures. Thermally
conductive
material may be placed between adjacent containers to enhance heat transfer
between the
containers. The liquids and gases are produced through a port on the top of
the
containers and treated at an onsite location. As successive rows of containers
are loaded
into the pit, heating of the new row commences. After a row is fully pyrolyzed
in ¨3-4
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
23
months, the containers are allowed to cool. The containers with post-pyrolysis
material
are then removed from the pit and transported out of the facility.
The containers used in the pits may be constructed from a high strength alloy
with
good high temperature corrosion resistance such as 347H stainless steel. The
corners of
the containers are rounded to reduce stress concentrations during the multiple
thermal
cycling of the containers.
In order to minimize costs, the containers used for heating in the pits may
also be
different than the shipping containers. In this case the post-pyrolysis
material may be
transferred from the heating containers to the shipping containers. The
shipping
containers may then be of standard steel construction.
Upgrading Coal
The type of coal utilized for this invention is preferably in the range of
vitrinite
reflectance Ro between 0.45 and 0.9, most preferably between 0.5 and 0.8. This
range of
coal types includes sub-bituminous A, high volatile bituminous C, B, and A,
and medium
volatile bituminous coal. These types of coal have high volatiles and low
moisture
content. During pyrolysis the hydrocarbon fluids produced comprise light oils
with API
gravities above 30 API and hydrocarbon gases with maximum C1 ¨ C4 content and
minimum CO2. Low sulfur and low ash coals are preferred.
Production ports may be located at the top of the pit or pile and penetrate
through
the impermeable seal and insulation. Fluids are produced in the vapor phase
through the
top port, and the liquids and gases are separated. The API gravity of the
produced oil may
be 30 API or higher. The NGL (natural gas liquids) such as propane and butane
may be
separated from the methane and ethane gases because of the high economic value
of
NGL. Hydrogen may also be separated from the produced gases and used in
upgrading of
the produced oils.
FIG. 4B is a flow chart of a method for upgrading mined coal within an
enclosure
(e.g. an excavated enclosure). In step S241, pieces of coal are introduced
into the
enclosure. In step S245, the coal within the pit and/or container is heated
over a sufficient
amount of time so that: (i) kerogen of the coal is pyrolyzed into hydrocarbon
pyrolysis
formation fluids which may be recovered from the enclosure (see step S249);
and (ii) the
coal itself is upgraded to increase the coal vitrinite reflectance and/or to
reduce the
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
24
fraction of volatile matter and/or to increase a fraction of carbon and/or
reduce a moisture
content and/or to increase a heat content density by weight.
In step S243, the upgraded coal is removed from the enclosure.
In one non-limiting example, (i) the 'input' coal introduced in step S241 is
primarily bituminous coal (for example, high volatile bituminous coal) and/or
sub-
bituminous coal and/or primarily coal whose reflectance is less than 1.2 or
less than 1.0
or less than 0.8 or less than 0.6 or less than 0.4 and (ii) the upgraded coal
has one or more
properties of anthracite coal and/or is anthracite coal. Towards this end, in
some
embodiments, it is possible to heat the coal to achieve specific time-
temperature histories.
For example, it is possible to heat this 'input coal' over a 'multi-month'
time period (e.g.
for at least 2 months or at least 2.5 months or at least 3 months or at least
3.5 months or at
least 4 months or at least 5 months or at least 6 months or at least 7
months), such that the
temperature of the heated coal exceeds a MINIMUM_TEMP (e.g. for example, at
least
350 degrees C or at least 375 degrees C or at least 400 degrees C or at least
425 degrees
C or at least 450 degrees C or at least 475 degrees C or at least 500 degrees
C or at least
550 degrees C or at least 600 degrees C) most of the time or substantially all
of the time
during the 'multi-week' or 'multi-month' time period.
In some embodiments, a maximum temperature of the bed of coal during the
multi-month time period is at most 800 degrees C or at most 700 degrees C or
at most
600 degrees C.
'In some embodiments, the 'upgraded coal' removed in step S253 (i) has a
reflectance of at least 2.5 or at least 2.75 or at least 3.0 or at least 3.25
or at least 3.5
and/or (ii) comprises (i.e. by total weight or by weight on an ash-free basis)
less than 12%
or less than 10% or less than 8% or less than 6% volatile matter and/or (iii)
has a heat
content (i.e. by total weight or by weight on an ash-free basis) that exceeds
33,000 kJ/kg
or that exceeds 33,500 kJ/kg or that exceeds 34,000 kJ/kg or that exceeds
34,500 kJ/kg
and/or that exceeds 35,000 kJ/kg and/or that exceeds 35,500 kJ/kg and/or (iv)
comprises
(i.e. by total weight or by weight on an ash-free basis) less than 8% or less
than 6% or
less than 4% or less than 3% or less than 2.5% sulfur and/or (v) comprises
(i.e. by total
weight or by weight on an ash-free basis) at least 88% or at least 89% or at
least 90% or
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
at least 91% carbon and/or (v) has one or more properties associated with so-
called
'anthracite coal.'
There is no limitation on the features (e.g. physical structure or any other
features)
of the container and/or pit in which the coal-upgrading routine of FIG. 1 is
carried out.
5 It is
noted that the time-temperature history required to achieving specific
reflectance property and/or other property related to 'upgrading coal' or
'upgrading a
rank of coal' may at least partially depend upon the type of and/or the
properties of the (i)
'input' coal and which is subjected to the coal-upgrading process and the (ii)
upgraded
coal resulting from the process.
10 The skilled artisan is directed to WO/2003/036035 entitled "IN
SITU
UPGRADING OF COAL" and US patent 6,969,123 entitled "Upgrading and mining of
coal" both of which are incorporated herein by reference in their entirety.
These patent
documents describe the upgrading of bitumen coal to anthracite coal in situ.
It is now
disclosed that similar conditions may be replicated within an enclosure so as
to
15 economically exploit the upgraded coal.
As illustrated in FIG. 19, in some embodiments, longer processing times are
required when operating at lower temperatures (i.e. as evidenced by the
'negative' slopes
illustrated in FIG. 19) and/or when upgrading to a 'higher ranked coal and/or
when
employing a 'lower-ranked' starting material!' input' coal.
20 The
example of FIG. 19 illustrates linear curves - this is a simplified example is
appreciated that the shape of the curves may differ.
In the example of FIG. 19, the coal rank `X2' exceeds the coal rank 'XL' while
the coal rank 1(2' exceeds the coal rank 'YU FIG. 19 is a hypothetical
example, and
unless otherwise indicated, is not intended as limiting in any manner. For
example, there
25 is no requirement that the 'curves' are linear and/or parallel to each
other.
FIG. 20A illustrates the time dependencies of various measurable time-
dependent
properties as a function of time in some embodiments relating to the any coal-
upgrading
routine disclosed herein. FIG. 20B illustrates that rate at which liquid and
gaseous
hydrocarbons are from the coal. Both FIGS. 20A-20B relate to hypothetical
examples,
and unless otherwise indicated, no feature(s) of FIG. 20A and/or FIG. 20B is
intended as
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
26
limiting. Nothing in FIGS. 20A and/or 20B is intended as 'to-scale' unless
indicated
otherwise.
In some embodiments, a bed of rocks is formed from bituminous coal, and a
majority of the bed of rocks is maintained (i.e. under anoxic conditions) at a
temperature
of at least 375 degrees Celsius or of at least 380 degrees Celsius or of at
least 385 degrees
Celsius or of at least 390 degrees Celsius for a least 1 week or at least 2
weeks or at least
1 month or at least 2 months or at least 3 months or at least 6 months.
In the example of FIG. 20A, vitrinite reflectance and bulk temperature of the
coal,
and heater power level is illustrated for one example relating to the
upgrading of mined
coal under anoxic conditions within an enclosure (e.g. an excavated
enclosure). During
an earlier period of time (TIME_PERIOD_1), most kerogen of the coal is
pyrolyzed into
condensable hydrocarbon pyrolysis fluids (referred to informally as
'liquids'), while in a
latter time period (i.e. TIME_PERIOD_2), most non-condensable hydrocarbon
pyrolysis
formation fluids are generated. At a later period in time (TIME_PERIOD_3),
despite the
fact that most if not substantially all pyrolysis fluids have been generated
from coal
kerogen, it is possible to continue to deliver significant power to the coal
of the coal bed
so as to continue to upgrade the coal. From the point of view of economic
pyrolysis fluid
recovery, delivery of thermal energy to the coal during TIME_PERIOD_3 may be
unnecessary. However, it is now disclosed that this is useful for upgrading
mined coal.
Reference is made once again to FIG. 20A. At different times during the coal
upgrade process, local coal physical and/or chemical properties may vary at
different
locations within the container and/or pit. One coal property that may be
monitored (e.g.
by employing removing coal from then pit and/or container to sample the coal
and/or by
employing a fiber-optic system to monitor the coal within the pit and/or
container) at
different times is the vitrinite reflectance. As illustrated in FIG. 20B at
times to-t5 the
temperature in a particular location and/or the bulk-averaged vitrinite
reflectance and/or
maximum temperature within the pit and/or container may respectively be
written as Ro -
R5. In some embodiments when the input coal is so-called high volatile
bituminous coal,
Ro is at most 1.2 or at most 1.0 or at most 0.8 or at most 0.6 or at most 0.4.
In some
embodiments, R2 is at most 1.6 or at most 1.4 or at most 1.2. In some
embodiments, R4
is at most 2.5 or at most 2.0 or at most 1.8 or at most 1.6. In some
embodiments, R5 is at
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
27
least 2.4 or at least 2.6 or at least 2.8 or at least 3.0 or at least 3.2 or
at least 3.4 or at least
3.6 or at least 3.8 or at least 4.0
Pre-Processing of Coal
Pretreatment of the coal may be desirable to produce the best quality post-
pyrolysis coal. Pretreatment of the initial coal may include water washing to
remove ash
and fines. The coal pieces may be pre-sized to select a size range that will
easily pack in
the pit to achieve a packing with high vertical permeability.
In some embodiments, the coal is pre-processed before heating to reduce the
ash
content ¨ for example washing the coal (or alternatively mechanical agitation)
to reduce
the ash content (i.e. as a 'bulk property' of coal particles) of the coal. In
some
embodiments, before the pre-processing the ash content before exceeds 10% or
exceeds
15% or exceeds 20%. In some embodiments, the ash content is reduced to no more
than
7% or no more than 6% or no more than 5% or no more than 4% or no more than
3%. In
some embodiments, the ash content is reduced by at least 20% or at least 30%
or at least
40% or at least 50% or at least 60% or at least 70% or at least 80%.
The flotation step of removing inorganic matter could also be done before the
bituminous coal is placed in the pit, as well as after. Removing ash may
obviate the need
to heat the inorganics to high temperatures..
The pre-processing may be carried out in any time or in any location. For
example, the pre-processing may be carried out 'on site' near the container or
pit or off-
site.
Post-Processing of Coal After Pyrolysis
After pyrolysis, the top seal of the pit or pile may be opened to remove the
devolatilized coal or oil shale. This coal may be more valuable than the
initial coal
because it has higher carbon content, higher calorific value, ultra lower
moisture and
volatiles, and lower sulfur and nitrogen. After removing the post-treatment
coal or oil
shale, the pit can be refilled with fresh coal or oil shale for the next
pyrolysis operation.
The post-pyrolysis coal or oil shale may also be steam cleaned in the pit
while still above
100 C to achieve both steam stripping and more rapid cooling of the coal or
oil shale.
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
28
For example, a majority of coal within the pit and/or container may be cooled
by
at least 150 degrees or at least 200 degrees C or at least 300 degrees C
within a period of
time that does not exceed 1 month or does not exceed 2 weeks or does not
exceed 1 week
or does not exceed 3 days or does not exceed 2 days or does not exceed 1 day
or does not
exceed 12 hours or does not exceed 6 hours.
In some embodiments, it is possible to carry out the cooling of the coal by so-
called steaming of the coal ¨ i.e. introducing liquid water into the container
and/or pit to
'quickly' cool the coal to a temperature that is (i) less than 150 degrees C
or less than 125
degrees C or less than 110 degrees C and (ii) greater than 80 degrees C or
greater than 90
degrees C or greater than 95 degrees C. By 'steaming' the coal it is possible
to
simultaneously (i) wash out impurities of the coal (ii) benefit from a 'quick
cooling of the
coal' while (iii) keeping the coal substantially dry.
The coal may be removed from the container and/or pit at a temperature that is
about 100 degrees C or allowed to cool further before removing in step S133.
FIG. 22B relates to a hypothetical example where the water flow rate of liquid
water into the pit is dramatically reduced (e.g. by at least 80% or at least
90%) at a time
when the coal temperature approached 100 degrees C.
After pyrolysis, the coal may be removed from the pit using buckets that scoop
the coal between the columns of heater pipes. The coal may be upgraded during
the
pyrolysis process because water and volatiles have been removed. The post-
pyrolysis
coal may have higher carbon content, higher calorific value, lower sulfur,
oxygen and
nitrogen, higher vitrinite reflectance, and lower ash than the mined coal.
Thus this
premium coal product may be sold at a higher price than the initial mined
coal.
The temperature, time of heating, and pressure of the coal pit may be adjusted
to
achieve the greatest value added by upgrading the coal to different desirable
grades. For
example, a high value ultralow volatile anthracite coal may be produced
suitable for PCI
sintering for metallurgical coking. In general, anthracite coal may be more
valuable than
lower grades of coal.
A Discussion of FIGS. 23-24
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
29
FIG. 23 is a cross section of a horizontal molten salt heating system that
traverses
a bed of rocks.
As shown in FIG. 24, the hot molten salt is fed from one side of the pit where
the
molten salt container is located. The molten salt containers and the external
piping
between them are insulated and heat traced to prevent heat losses and freezing
of the
molten salt. There is a pump located in the molten salt container that pumps
the molten
salt to a furnace that heats the molten salt and circulates the molten salt
through the heater
pipes in the pt. The heating of the furnace may be done using processed gas,
natural gas,
coal, or oil. The heating gas may be gas produced from the process that has
been treated
to remove undesirable components such as hydrogen sulfide, carbon monoxide and
carbon dioxide, and separate valuable natural gas liquids and hydrogen. The
hydrogen
gas may be utilized in the hydrotreating facility for upgrading the oil
produced. The
hydrogen sulfide may be treated in a Claus plant to make elemental sulfur.
A similar molten salt heat delivery system (tank, furnace, pump, and piping
manifold) may be placed on the opposite side of the pit to reheat the cold
molten salt
coming from the pit and recirculate hot molten salt in the opposite direction.
Counter-
current flow between adjacent heater pipes helps provide uniform heating to
the pit.
Instead of a second molten salt heat delivery system, the heater piping may be
looped
inside the pit so that the exterior piping manifold has fewer connections with
fewer
chances of leaks.
In geographical regions of high average solar intensity, solar radiation may
be
used to heat the heat transfer fluid using solar collectors such as parabolic
troughs,
parabolic dishes, or power towers. Parabolic trough solar collectors are
preferred as the
synthetic oil used to collect the solar heat can also function to transfer the
heat to the pit.
Furthermore, the operating temperature range of 350-390 C matches the
temperature
range required for the pit. To accommodate daily solar intermittency, energy
may be
stored in high temperature molten salt tanks and sized accordingly.
After pyrolysis is complete, the heaters are de-energized and the oil in the
lower
section is drained from the pit. Some coal or oil shale liquids may remain in
the pores of
the matrix and may be evaporated and collected by circulating gases such as
methane,
CO2, or nitrogen through the matrix. These gases may be part of a closed-loop
heat
CA 02864863 2014-08-18
WO 2013/123488
PCT/US2013/026610
exchanger involving multiple pits whereby the heated gas is circulated through
a pre-
pyrolysis coal or oil shale in an adjacent pit, simultaneously cooling down
the post-
pyrolysis pit and preheating the adjacent pit, thereby increasing the thermal
efficiency of
the process even further.
5 In the description and claims of the present application, each of the
verbs,
"comprise" "include" and "have", and conjugates thereof, are used to indicate
that the
object or objects of the verb are not necessarily a complete listing of
members,
components, elements or parts of the subject or subjects of the verb.
All references cited herein are incorporated by reference in their entirety.
Citation
10 of a reference does not constitute an admission that the reference is
prior art.
The articles "a" and "an" are used herein to refer to one or to more than one.
(i.e.,
to at least one) of the grammatical object of the article. By way of example,
"an element"
means one element or more than one element.
The term "including" is used herein to mean, and is used interchangeably with,
the
15 phrase "including but not limited" to.
The term "or" is used herein to mean, and is used interchangeably with, the
term
"and/or," unless context clearly indicates otherwise.
The term "such as" is used herein to mean, and is used interchangeably, with
the
phrase "such as but not limited to".
20 The present invention has been described using detailed descriptions of
embodiments thereof that are provided by way of example and are not intended
to limit
the scope of the invention. The described embodiments comprise different
features, not
all of which are required in all embodiments of the invention. Some
embodiments of the
present invention utilize only some of the features or possible combinations
of the
25 features. Variations of embodiments of the present invention that are
described and
embodiments of the present invention comprising different combinations of
features
noted in the described embodiments will occur to persons skilled in the art.
