Oil shale retort apparatus

A retorting apparatus including a vertical kiln and a plurality of tubes for delivering rock to the top of the kiln and removal of processed rock from the bottom of the kiln so that the rock descends through the kiln as a moving bed. Distributors are provided for delivering gas to the kiln to effect heating of the rock and to disturb the rock particles during their descent. The distributors are constructed and disposed to deliver gas uniformly to the kiln and to withstand and overcome adverse conditions resulting from heat and from the descending rock. The rock delivery tubes are geometrically sized, spaced and positioned so as to deliver the shale uniformly into the kiln and form symmetrically disposed generally vertical paths, or "rock chimneys", through the descending shale which offer least resistance to upward flow of gas. When retorting oil shale, a delineated collection chamber near the top of the kiln collects gas and entrained oil mist rising through the kiln.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for processing solid 
materials by burning, gasifying, calcining or retorting, and more 
particularly to an improved apparatus for retorting oil shale to recover 
oil therefrom having a gas distributor system for delivering and 
distributing thereto gas used in the shale processing. For simplicity, the 
processes hereinafter described will be referred to as "retorting" 
processes, and the vessels in which retorting is performed as "retorts" or 
"kilns ". 
One example of solid materials processing in which the present invention 
finds particular use is in the recovery of oil from oil shale. Oil is 
recovered from oil shale by heating the shale to its destructive 
distillation (pyrolysis) temperature. Oil shale contains a high molecular 
weight organic material known as kerogen. At the destructive distillation 
temperature, the kerogen in the shale is destructively distilled to 
produce primarily lower molecular weight organic compounds which are 
referred to hereinafter as oil and oil vapor. Also produced, are 
noncondensable organic gases and a solid carbonaceous solid residue 
("char"). The oil vapor produced mixes with hot gases from the heating 
process, then is cooled to condense to a mist, and the mixed gases and oil 
mist are further processed to recover the oil. It will be appreciated that 
the efficiency of the destructive distillation process, i.e., the 
percentage of the total oil capable being produced from the shale that is 
actually removed and recovered, is critical because it directly affects 
the cost of the resulting oil. 
One type of relatively successful retorting process utilizes combustion (or 
oxidation) in a kiln containing the shale to develop the heat for the 
destructive distillation of the shale. This process is referred to as a 
direct heated process and has met with some success. See U.S. Pat. No. 
4,042,485. Another relatively successful process, an indirect heated 
process, uses externally heated recycle gas to provide the heat for the 
destructive distillation process. See U.S. Pat. No. 4,116,810. In either 
case, it is important that the efficiency of the process be maximized. In 
addition, it is important that the cost of the process be minimized in 
order to keep down the cost of the recovered oil. 
In both the indirect and direct heated methods, it is important that the 
processing gas be distributed substantially uniformly throughout the cross 
section of the retort for uniform heating and processing of the shale 
particles. This is required even though non-uniform conditions may exist 
in the retort, e.g., different grades of shale materials delivered to the 
several zones of the retort. Shale grade variations could be in kerogen 
content, carbonate amount and composition or particle size distribution. 
Furthermore, it is important that the shale particles be disturbed as they 
descend through the retort to expose maximum surface area thereof to 
heating and to enhance controlled gas to solids content. It is also 
important that the means for delivering the processing gas be constructed 
to prevent potentially damaging heat concentration, and to withstand the 
weight of the descending oil shale bed as well as the high temperatures 
and other adverse conditions arising in the destructive distillation 
process. 
Another example of solid materials processing in which the present 
invention is useful is in pyroprocessing of particulate solid materials 
such as the calcination of limestone. This process generally is a heat 
treatment of a raw material to produce a chemical change in the material. 
For example, various carbonates decompose under heat leaving the 
corresponding oxide, i.e., calcium oxide in lump form, and gaseous carbon 
dioxide. While each calcining process is dependent upon the material being 
treated, there are some common general principles which apply when certain 
types of equipment are used for the process. Thus, the present invention 
is applicable to calcining generally in vertical retorts, normally 
referred to as shaft furnaces, vertical kilns, etc. See U.S. Pat. No. 
3,743,697. 
Various other mineral ores, green petroleum coke in pellet or granular 
form, and other matter can be subjected to heat treatment in a vertical 
retort in accordance with the invention. 
SUMMARY OF THE INVENTION 
The present invention is based upon a countercurrent retort for processing 
rock, and in particular, lumps of oil shale, limestone, ores and the like. 
A bed of crushed rock of mixed sizes and shapes descends continuously and 
generally vertically through several process zones in a vertical kiln. The 
rock is heated by oxidation in a combustion zone (in the direct heated 
process) which also makes use of internally recuperated heat. When the 
rock is oil shale, char remaining on the shale subsequent to the 
destructive distillation of kerogen is oxidized in the combustion zone. 
When the rock is, for example, limestone, fuel delivered into the 
combustion zone is oxidized. A mixture of air and recycled gas is 
delivered uniformly across the kiln cross section to support uniform 
oxidation in the combustion zone. In the indirect heated process, hot 
recycle gas is delivered uniformly across the kiln cross section and heats 
the descending rock. 
In both the direct and indirect heated retorts, the gas distributors are 
physically positioned within the kiln to contact and disturb the 
descending rock particles, and are constructed so that each remains at a 
substantially uniform temperature. In addition, the distributors are 
constructed to maximize uniformity of gas distribution throughout the kiln 
cross section. In the direct heated retort for retorting oil shale and in 
the limestone retorting kiln, the gas distributors preferably are in at 
least two vertically-spaced levels in the kiln. 
The rock is caused to descend as a moving bed of particulate material 
through the kiln in a manner which produces defined and uniformly 
distributed vertical zones, or "rock chimneys", which have increased 
permeability to upward flow of hot gases through controlled areas of the 
descending rock bed. Hot flue gases from the combustion zone (in the 
direct heated process) or hot recycled gases (in the indirect heated 
process) rise upwardly through the rock bed in general and rock chimneys 
in particular and heat the descending rock to its destructive distillation 
temperature. 
When the rock is oil shale, oil vapor is destructively distilled from the 
shale in a pyrolysis zone and is swept upwardly through the shale bed, 
particularly through the rock chimneys, with the hot gases. Incoming shale 
cools the rising gas/vapor mixture causing the oil vapor to condense to a 
mist and the gas and entrained mist is collected in a delineated 
collection chamber above the pyrolysis zone. At the same time, the hot 
gas/vapor mixture preheats the incoming shale. 
The gas/mist mixture is disengaged at a relatively low velocity, and is 
removed from the collection chamber in a manner further promoting uniform 
flow. In the direct heated process, cool recycle gas is delivered 
uniformly across the kiln cross section below the combustion zone and is 
heated by the hot descending shale and provides a large amount of the 
required heat for the process by preheating the gas entering the 
combustion zone. 
The present invention provides for the highly uniform destructive 
distillation of the oil shale which results in exceptional efficiency in 
the retorting process in both the direct and the indirect heated 
processes. In addition, the present invention accommodates many variances 
in materials and equipment to produce uniform, reliable and consistent 
results. 
The gas distributors of this invention are constructed to withstand the 
weight of the descending rock bed and to inhibit adverse effects thereon 
arising from the retort process. In addition, the gas distributor system 
of this invention is adjustable to vary the quantity and composition of 
the gas delivered to selected areas or zones in the retort to accommodate 
non-uniform conditions therein and to provide precise control of reaction 
temperatures. 
Additional objects and advantages of the present invention will be set 
forth in part in the description which follows, and in part will be 
obvious from the description, or may be learned by practice of the 
invention. The objects and advantages of the invention may be realized and 
attained by means of the instrumentalities and combinations particularly 
pointed out in the claims. 
To achieve the objects and in accordance with the purpose of the invention, 
as embodied and broadly described herein, the retorting apparatus of this 
invention comprises a kiln having a substantially rectangular cross 
section, and adapted to have rock of mixed sizes and shapes descend as a 
moving bed continuously and generally vertically therethrough by gravity, 
means for delivering gas to the kiln for effecting heating of the rock to 
its retorting temperature in a pyrolysis zone wherein the gas delivery 
means comprises a plurality of first and second sets of vertically-spaced 
gas distributors, each set of distributors including a plurality of 
elongated, generally parallel conduits extending across the kiln and 
provided with a plurality of spaced orifices along the length thereof, the 
distributors being constructed and the orifices being sized and spaced to 
deliver gas uniformly throughout the cross section of the kiln, the 
retorting process producing hot flue gases which mix with the other gases 
in the kiln and flow upwardly in the kiln counter to the direction of 
movement of the descending rock, means for delivering the rock to the kiln 
above the pyrolysis zone including a plurality of vertically extending 
circular feed tubes maintained substantially continuously full of rock and 
extending downwardly toward the pyrolysis zone, the tubes being 
substantially uniform in diameter and geometrically arranged so that 
imaginary lines connecting the centers of each adjacent group of three 
tubes form approximately equilateral triangles, and imaginary lines 
connecting the centers of adjacent pairs of tubes adjacent the walls of 
the kiln and imaginary lines perpendicular to the walls of the kiln and 
extending through the centers of the last mentioned tubes form rectangles 
with the walls of the kiln, the rock descending through the tubes and 
dispersing outwardly at differential rates proportional to the particle 
sizes, the rock bulk from each tube interacting with the rock bulk from 
adjacent tubes and with the kiln walls to form a plurality of uniformly 
and symmetrically disposed, differentially permeable, generally vertical 
paths, or "rock chimneys", through the descending bed of rock across the 
entire cross section of the kiln which offer least resistance to upward 
flow of gases through the descending rock, the rock chimneys being formed 
one at substantially the center of each equilateral triangle and one near 
the center of each rectangle, the tubes being sized and arranged to form 
at least one rock chimney for each five square feet of kiln cross section 
and when retorting oil shale lumps the upwardly flowing gases being 
operable to sweep the oil vapor produced upwardly therewith from the 
pyrolysis zone, the gas and oil vapor being cooled by the descending shale 
lumps above the pyrolysis zone causing the oil vapor to condense and form 
a mixture of gas containing oil mist, means defining a delineated 
collection chamber above the pyrolysis zone for collecting the gas and oil 
mist mixture rising through the rock chimneys, the shale in the tubes and 
exiting from the tubes being operable to disengage the gas and entrained 
oil mist at a low Reynolds number. 
Importantly, the collection chamber has a bottom formed with a plurality of 
uniformly arranged orifices which are aligned vertically with respective 
ones of the rock chimneys for receiving the gas and oil mist mixture 
rising through the rock chimneys. The gas, gas/vapor mixture, and gas/mist 
mixture will seek areas of greatest permeability in the descending shale, 
and will move to those areas of greater permeability, particularly when 
encountering resistance to upward flow. The means for delivering gas to 
the kiln assists here by providing for permeability laterally of the kiln 
and transverse to the direction of movement of the descending shale. 
Permeability perpendicular to the gas delivery means and transverse to the 
direction of movement of the descending shale is provided via the tripper 
travel layering of shale into the kiln. There is, therefore, 
three-dimensional permeability throughout the kiln and descending shale 
bed which further stabilizes and renders uniform the upward flow of gas, 
oil and oil vapor in the kiln. 
In addition, when retorting oil shale lumps, the retorting apparatus of 
this invention has off-take means disposed laterally of the collection 
chamber and through which the gas, oil and oil vapor are removed. The 
off-take means is positioned and the orifices to the collection chamber 
are sized so that the pressure drop between each orifice and the adjacent 
off-take means is substantially uniform. Also, a buffer zone is formed 
between the combustion zone and the pyrolysis zone in the direct heated 
process. The buffer zone is defined as that horizontal section of the 
retort between the combustion zone, to the bottom, and the pyrolysis zone, 
to the top, where the destructive distillation of the oil shale is 
substantially complete and the oxygen delivered to the combustion zone has 
been substantially consumed. 
Still further, a cooling zone is provided below the combustion zone in the 
direct heated process and includes grate means which is operable to 
control the uniform descent and overall processing rate of the moving rock 
bed through the kiln. Means is provided for uniformly delivering cool 
recycle gas to the cooling zone uniformly across the kiln cross section. 
See U.S. Pat. No. 3,777,940. The descending rock is cooled and the recycle 
gas is heated and rises toward the combustion zone and provides much of 
the heat needed for the process. See U.S. Pat. No. 3,401,992. 
The rock delivery means includes means for laying down strips of rock in 
reverse passes along the length of the kiln. In normal operation, there is 
random variation in rock sizes along the strips of rock. The effect on gas 
permeability in the rock chimneys is minimized because the rock bed in the 
retort consists of layers laid down in each pass of the delivery means. 
Thus, it is unlikely to have two consecutive layers of rock having a 
non-average distribution of sizes. In the event of restricted flow of gas 
upwardly through the rock bed, a strip of rock of greater permeability 
(with a larger average particle size) can be laid down over the restricted 
zone or adjacent thereto. 
The rock delivery means includes a bin of rectangular cross-section 
connected to each feed tube at its upper end and the juncture between each 
bin and its associated feed tube includes means for deflecting rock fines 
toward the centers of the tubes. 
In one preferred form of the invention particularly useful for retorting 
oil shale lumps, the first set of gas distributors are aligned vertically 
with the second set of distributors. The gas delivered to the kiln can be 
a mixture of air and recycle gas which is operable to support the 
oxidation of char in the shale lumps in a combustion zone below the 
pyrolysis zone. Alternatively, the gas can be recycle or other gas which 
is heated externally of the kiln to provide the quantity of heat required 
for the destructive distillation of kerogen in the oil shale. 
In a kiln for calcining limestone, the first set of gas distributors can be 
disposed either generally parallel or generally perpendicular to the 
second set of distributors. 
In a retort having two vertically-spaced sets of distributors, valve means 
is provided for selectively controlling the quantity of gas delivered to 
the distributors to control the heat in the kiln. In addition, at least 
the upper set of distributors is provided with means for varying the 
quantity of gas delivered to different zones in the retort to accommodate 
non-uniform conditions in the kiln such as when different grades of shale 
are delivered to those retort zones and/or to provide precise control of 
the temperature in the kiln. Also, means may be provided to cool the 
orifice areas in at least the upper set of distributors particularly in a 
direct heated retort. 
Importantly, the orifices in the distributors are formed in opposite sides 
of the distributors opposing discharge orifices in adjacent distributors. 
In accordance with the invention, the discharge orifices are angled 
downwardly to enhance gas penetration in the rock bed and to prevent rock 
from entering the distributor orifices in the event that the gas flow is 
interrupted, and no orifices are formed in the sides of the distributors 
next adjacent the sides of the kiln. The orifices are substantially 
uniform in size and are substantially uniformly spaced along the 
distributors. The orifices adjacent the side walls of the kiln at the 
entry to the distributors are spaced from those walls a distance less than 
half the space between adjacent orifices. The distributors may include 
internal baffle means to cool the distributor walls and which also help 
assure uniform gas delivery from all orifices and uniform temperature 
throughout the length of the distributors. 
Desirably, the distributors are blocked midway of their length by dividers 
or center baffles, and the distributors are fed with gas from both ends. 
The orifices spanning the center baffles are spaced apart a distance 
greater than the space between other adjacent orifices. The distributors 
are insulated and structurally designed to withstand the weight of the 
descending rock while disturbing the rock particles during descent. 
In another aspect of the present invention the gas delivery means comprises 
a plurality of elongated, generally parallel distributors extending across 
the kiln and provided with a plurality of spaced orifices along the length 
thereof, the distributors including a plurality of segments corresponding 
to and aligned with segments of the other distributors, and means for 
varying the gas delivered to the distributor segments. 
In accordance with the invention, the rock is delivered to a plurality of 
vertical filling zones in the retort which correspond to the various 
distributor segments. Internal baffles can be used in the distributors to 
form the segments, and valve means can be provided to vary the gas 
delivered to the distributor segments. 
In yet another aspect of the present invention the gas delivery means 
comprises a plurality of elongated distributors extending across the kiln 
and provided with a plurality of spaced orifices along the length thereof, 
said distributors being open at their ends for the reception of gas, a 
divider in each of the distributors at substantially the midpoint thereof 
forming a center baffle blocking the flow of gas therethrough, a 
horizontal baffle in at least some of the distributors, one on either side 
of the center baffle and below the orifices, each horizontal baffle 
sloping downwardly toward the center baffle and having a terminal end 
spaced from the center baffle, a plurality of orifices in the horizontal 
baffles, whereby gas entering the ends of the at least some distributors 
flows below the horizontal baffles in a direction toward the center 
baffles, some of the gas passing upwardly through the orifices in the 
horizontal baffles and between the terminal end of the horizontal baffles 
and the center baffle, the gas exiting the distributors through the 
orifices therein. 
The orifices in the horizontal baffles are formed in opposite edges thereof 
and are semicircular. Furthermore, the horizontal baffles engage the sides 
of the respective distributors and are spaced above the distributor 
bottoms. Desirably the summation of the cross sectional areas of the 
orifices in each of the horizontal baffles in the distributors containing 
horizontal baffles is from about 95% to about 125% and preferably about 
110% of the cross sectional area of an opening in those distributors below 
the baffle terminal end and of the cross sectional area of an opening 
between the baffle terminal end and the center baffle. 
In each of the distributors containing horizontal baffles, those baffles 
together with the sides and bottom of the respective distributors define 
gas inlet openings by which gas enters the area below the horizontal 
baffles, and the cross sectional areas of the openings formed below the 
baffle terminal ends and between the baffle terminal ends and the center 
baffles is from about 32% to about 28% and preferably about 30% of the 
cross sectional area of the inlet opening for each of those distributors. 
The accompanying drawings which are incorporated and constitute a part of 
this specification, illustrate one embodiment of the invention and, 
together with the description, serve to explain the principles of the 
invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference will now be made in detail to the present preferred embodiment of 
the invention, an example of which is illustrated in the accompanying 
drawings. 
Retorting Apparatus 
The preferred embodiment of retorting apparatus is shown in FIG. 1 and is 
represented generally by the numeral 21. In accordance with the invention 
and as embodied herein, this apparatus includes a vertical kiln 23 which 
has a substantially rectangular cross section and is adapted to have rock 
25 of mixed sizes and shapes descend as a moving bed continuously and 
generally vertically therethrough by gravity (see also FIG. 5). Prior to 
treatment in the retorting apparatus, the rock is crushed and screened to 
form a mixture of lumps of from about 1/4" to about 3" dimension across 
and preferably is free of fines, which are defined as particles less than 
1/4" across. The rock enters at the top of the kiln 23 and descends 
therethrough to the bottom. 
The preferred embodiment of the invention is illustrated as a direct heated 
oil shale retort in which oxidation of char in the oil shale occurs in the 
retort and the hot flue gases produced by the oxidation rise through the 
descending shale bed and heat the shale particles to their destructive 
distillation temperature in a pyrolysis zone above the combustion zone. 
The oil is produced from the shale in the pyrolysis zone by destructive 
distillation and is entrained and moves upwardly with the hot flue gases. 
The invention is also useful, as described above, with indirect heated 
retorts where a combustible gas, usually a recycle gas from the 
destructive distillation containing little or no free oxygen, is 
externally heated and is introduced to the retort into the shale bed and 
provides the heat necessary for the destructive distillation of the 
kerogen in the shale. One example of an indirect heated retort is 
disclosed in U.S. Pat. No. 4,297,201 and is incorporated herein by 
reference. 
In accordance with the invention, means is provided for delivering gas to 
the kiln to effect heating of the descending rock to its destructive 
distillation temperature. The gas delivery means comprises a plurality of 
elongated, generally parallel distributors extending across the kiln and 
provided with a plurality of spaced orifices along the length thereof. In 
some retorts, particularly in the direct heated retorts and in limestone 
kilns, it is desirable that there be two or more vertically-spaced sets of 
gas distributors. The gas delivery means are described in greater detail 
below. 
The mixture of air and gas which is delivered to the kiln 23 by the 
distributors 27,29 in the direct heated retort supports oxidation in the 
introduced fuel or in the rock as it descends through the kiln 23. The 
area or zone in which oxidation occurs is defined as a combustion zones 
51, 52 which consist of upper 51 and lower 52 combustion zones (see FIGS. 
3, 4, 6 and 8). The heated gas delivered by the distributors 27 and/or 29 
in the indirect heated retort rises through the descending bed and heats 
the rock to its destructive distillation temperature. 
It will be appreciated that the amount of air in the air/gas mixture in the 
direct heat destructive distillation of oil shale controls heat generation 
and the temperature profile in the kiln. This, in turn, influences the 
quantity of product yielded and the operability of the process. Oxygen in 
the air/gas mixture supports the oxidation of char remaining in the shale 
following the destructive distillation of kerogen in the pyrolysis zone 
and also oxidizes some of the oxidizable gases in the recycle gas. For 
some shales, to achieve the greatest efficiencies, the shale temperature 
in the lower combustion zone 52 reaches a maximum of about 1100.degree. F. 
and the gas temperature in the upper combustion zone 51 reaches a maximum 
of 1300.degree. F. and the hot flue gases produced provide most of the 
heat necessary for the destructive distillation of kerogen. 
By providing the vertically spaced distributors 29,27 with low air/gas 
ratio and high air/gas ratio mixtures, respectively, a partial oxidation 
or preferential gasification of char zone (the lower combustion zone 52) 
is defined which extends from the level of the orifices of the upper 
distributors 27 to the bottom of the kiln. In the preferential 
gasification of char zone, conditions are maintained substantially as they 
would be for the gasification of coal. As in the middle distributors 29, a 
substoichiometric amount of oxygen is introduced through the lower level 
of distributors 31, thereby maximizing the production of oxidizable gases, 
predominately carbon monoxide and hydrogen. 
There are four sources of oxidizable gases produced in the preferential 
gasification of char zone in the direct heated retort of oil shale. 
1. A substantial amount of heat is transferred from hot gas to the shale 
without appreciably raising the temperature of the shale. Most of this 
heat is absorbed by decomposition of carbonate materials and the 
subsequent reaction of carbon dioxide with hot char. This reaction 
generates carbon monoxide. 
2. Some of this heat is absorbed by reaction between hot char and water 
vapor in the recycle gas, producing carbon monoxide, hydrogen and small 
amounts of other gases. 
3. The oxygen introduced at the middle distributor 29 partially oxidizes 
some of the hot char raising the temperature of the upwardly flowing 
gases. The product of this reaction is also carbon monoxide. 
4. Recycle gas is also delivered to the kiln 23 below the middle 
distributor 29 at bottom distributor 31 in FIG. 4 (hereinafter described), 
and this gas becomes heated by counter current heat exchange with 
descending hot shale. The recycle gas normally contains water vapor and 
additional steam can also be added. Hot char reacts with steam and the 
products include carbon dioxide and hydrogen. 
In accordance with the invention, a cooling zone 54 is created below the 
combustion zones 51, 52 in the direct heated retort, and means is provided 
for delivering cool recycle gas to the cooling zone, whereby rock is 
cooled and said recycle gas is heated and rises toward the lower 
combustion zone 52. The recycle gas is cool as it enters the cooling zone 
54 from bottom distributors 31 and is heated by the rock descending from 
the lower combustion zone 52. Heat exchange takes place between the 
recycle gas and the rock in the cooling zone 54 so that the rock is cooled 
while the recycle gas is heated. The recycle gas then flows upwardly 
counter to the direction of movement of the descending rock and enters the 
lower combustion zone 52. 
In accordance with the invention, when retorting oil shale the oxidation of 
char in the lower combustion zone 52 of the direct heated retort produces 
hot flue gases which mix with the heated recycle gas and flow upwardly in 
the kiln counter to the direction of movement of the shale. In the 
indirect heated retort, gas is heated externally and delivered to the 
kiln. In both cases, the hot gases rise in the kiln and heat the shale to 
its destructive distillation temperature in a pyrolysis zone 55 to 
destructively distill oil and oil vapor from the shale. In the direct 
heated retort, the combustion zones 51, 52 and the pyrolysis zone 55 are 
substantially horizontal sections of the retort apparatus defined by the 
conditions present in each zone, or undelineated. 
As embodied herein and described above, the recycle gas which has been 
heated by the descending shale in the cooling zone 54 flows upwardly 
counter to the direction of movement of descending shale lumps 25 in the 
direct heated retort. Oxidation of char and oxidizable gases in the 
combustion zones 51, 52 produces hot flue gases which mix with the hot 
recycle gas and flow upwardly in the kiln also counter to the direction of 
descent of the shale lumps 25. The shale temperature in the lower 
combustion zone 52 reaches a maximum of about 1100.degree. F. and the gas 
temperature in the upper combustion zone 51 reaches a maximum of about 
1300.degree. F. and the mixture of hot flue gases and hot recycle gas 
heats the shale to a destructive distillation temperature of about 
900.degree. F. at which oil vapor is produced therefrom by destructive 
distillation. Substantially the same destructive distillation temperature, 
about 900.degree. F., is required in the indirect heated retort. 
As shown in FIG. 4, the combustion zones 51, 52 and the pyrolysis zone 55 
are undelineated in the direct heated retort. Nevertheless, a buffer zone 
57 (FIG. 6) isolates the pyrolysis zone 55 from the combustion zones 51, 
52. There is no physical separation, but the effect is the same because 
substantially all the oil that the oil shale is capable of producing has 
been destructively distilled out of the shale by the time the shale lumps 
25 flow downward into the buffer zone 57. Also, by the time the hot gases 
flow upward into the buffer zone 57, substantially all the oxygen therein 
has been consumed. 
Rock Chimneys 
In accordance with the invention, means is provided for delivering rock 25 
to the kiln 23 above the pyrolysis zone 55 including a plurality of 
vertically extending circular feed tubes 59 maintained substantially 
continuously full of rock and extending downwardly toward the pyrolysis 
zone. The tubes are substantially uniform in diameter and are 
geometrically arranged so that lines 61 connecting the centers of each 
adjacent group of three tubes form equilateral triangles (see FIG. 13). In 
addition, lines 63 connecting the centers of adjacent pairs of tubes which 
are adjacent the walls of the kiln and lines perpendicular to the walls of 
the kiln and extending through the centers of the tubes adjacent thereto, 
form rectangles with the walls of the kiln (see FIG. 12). The rock 
descending through and exiting the tubes disperses outwardly at 
differential rates proportional to the particle sizes. The larger 
particles generally tend to disperse away from the line of the tube, while 
the smaller particles are more likely to flow straight downward. The rock 
bulk from each tube abuts with the rock bulk from adjacent tubes and with 
the kiln walls to form a plurality of uniformly and symmetrically disposed 
differentially permeable, generally vertical paths, or "rock chimneys", 
through the descending rock across the entire cross section of the kiln. 
The rock chimneys are made up of generally larger diameter rock particles, 
which offer least resistance to upward flow of gases through the 
descending rock. The rock chimneys are formed one at substantially the 
center of each equilateral triangle and one near the center of each 
rectangle, and the tubes are sized and arranged to form at least one rock 
chimney for each five square feet of kiln cross section. 
As embodied herein, a plurality of circular feed tubes 59 are vertically 
supported in the kiln 23 and extend downwardly toward the pyrolysis zone 
55 (FIGS. 4 and 5). The tubes 59 are substantially uniform in diameter and 
are geometrically arranged in a repetitive pattern across the kiln 23. As 
shown in FIG. 13, the tubes 59 are arranged such that imaginary lines 61 
connecting the centers of each adjacent group of three tubes 59 form 
equilateral triangles (See FIGS. 12 and 13). Furthermore, imaginary lines 
63 connecting the centers of adjacent pairs of tubes which are adjacent 
the walls of the kiln 23, and imaginary lines 65 which extend 
perpendicularly from the walls of the kiln 23 to the centers of the tubes 
59 which are adjacent the kiln walls form rectangles with the walls of the 
kiln 23. (See FIGS. 12 and 13). Such an arrangement of feed tubes provides 
for a non-random distribution of rock chimneys which all have 
substantially the same gas permeability characteristics, thereby providing 
for uniform conditions across the horizontal cross-section of the kiln and 
resulting in maximum retorting efficiencies. 
For the preferable size range of rock herein, the tubes 59 are about 21/2 
square feet in cross section and feed a retort cross-sectional area of 
about 10 square feet. As the rock bulk expands horizontally, the larger 
pieces tend to become distributed uniformly over the 10 square foot area 
except at the rock chimneys. The rock bed becomes loosened in this 
expansion so that the small rock particles tend to sift downwardly. The 
overall effect is a differential in radial rates of rock distribution away 
from the locations where the rock exits from the feed tubes 59 which is 
proportional to the particles sizes. The above described placement of the 
feed tubes, all having these same characteristics, results in the 
formation of a plurality of uniformly and symmetrically disposed, 
differentially permeable, generally vertical paths, or "rock chimneys", 
through the descending rock lumps across the entire cross section of the 
kiln. These rock chimneys allow a greater volume of gas to contact the 
areas of the rock bed which has larger average particle size. The 
remaining areas of the rock bed have smaller average particle sizes and 
require proportionately less gas. Furthermore, the geometric and 
repetitive pattern of the tubes 59 provides a geometric and repetitive 
pattern of rock chimneys throughout the kiln cross section, preferably at 
least one for each five square feet of kiln cross section. This allows the 
hot gases rising therethrough to uniformly heat substantially all the 
shale in the rock preheating and pyrolysis zone 55 above the upper 
combustion zone 51. 
In accordance with the invention, when retorting oil shale the upwardly 
flowing hot gases in the kiln 23 are operable to sweep the oil vapor which 
is produced from the descending shale upwardly therewith from the 
pyrolysis zone 55. The rising mixture of gas and oil vapor then is cooled 
by the descending shale lumps above the pyrolysis zone causing the oil 
vapor to condense on nuclei of dust and ions and form a mixture of gas 
containing an oil mist. 
As embodied herein, the upwardly flowing gases and the oil vapor mix 
together and flow upwardly through the rock chimneys 69,70,71,72 past the 
descending shale. As the gas and oil vapor flow upwardly, the vapor is 
cooled and at the same time the descending shale is preheated. When 
operating under preferred conditions, at approximately 700.degree. F., a 
significant portion of the oil vapor condenses to a mist and the gas and 
entrained oil mist continues its journey upward. With further cooling, 
additional portions of the oil vapors condense as an oil mist. 
In accordance with the invention, means is provided defining a collection 
chamber 73 above the pyrolysis 55 and mist formation 50 zones for 
collecting the gas and oil mist mixture. The delineated collection chamber 
has a bottom formed with a plurality of uniformly arranged orifices 79 
which are aligned vertically with the rock chimneys for receiving the gas 
and oil mixture rising through the chimneys. Atmospheric air pressure in 
the feed tubes 59 resists the flow of gas upwardly through the tubes and 
the open volume around the tubes above the shale bed and below the 
orifices serves to disengage the gas and entrained oil mist at a low 
Reynolds number. Without this open area the oil and mist would condense on 
the oil shale entering the kiln and be carried back down into the 
progressively hotter zones of the retort. If the oil and oil mist were 
subject to substantial turbulence upon entering the collection chamber, 
significant amounts of the oil would condense on the entering shale and 
flow back downwards rather than exiting the kiln through the collection 
chamber. 
As embodied herein, and shown in FIG. 5, a collection chamber 73 is formed 
above the pyrolysis zone 55. The chamber 73 is formed by a bottom panel 
75, a roof panel 77, and the walls of the kiln 23. The bottom panel 75 is 
provided with a plurality of uniformly arranged tubular orifices or 
openings 79 which are aligned vertically with the rock chimneys 
69,70,71,72. The ascending gas and oil mist mixture traveling through the 
rock chimneys 69,70,71,72, passes through the openings 79 and is collected 
in the chamber 73. The diameter of the openings 79 are sized so that the 
pressure drop from each opening to its respective offtake remains uniform 
for all of the openings. 
The rock chimneys 69,70,71,72 provide for uniform upward flow of gases and 
of gas and oil vapor and gas and oil mist throughout the kiln with a 
minimum of overall resistance by the descending shale. This not only 
provides for uniform heating of the shale and the substantially complete 
destructive distillation of the oil shale, but also permits upward flow of 
gas, gas and oil vapor, and importantly, gas and oil mist with minimum 
turbulence. The existence of uniformly spaced rock chimneys 69,70,71,72 
provides three fundamental benefits unavailable in retorts taught in the 
prior art. First, is the systematic and uniform distribution of gases 
throughout the bed of descending shale. This uniformity allows for more 
precise temperature controls and more efficient yield of gas and oil from 
the kerogen found in the shale. In addition, the rock chimneys, along with 
the strategically placed orifices 79 in the collection chamber 73, 
provides for an efficient means of collecting the oil and gas mist. 
Finally, the presence of the rock chimneys reduces the residence time of 
the distilled gas and oil mist within the body of the retort. Any increase 
in the residence time of the gas and oil mist proportionately increases 
the destruction of the products via cracking and coking processes. The 
rock chimneys provide an efficient means for removing the products from 
the kiln and maximizing yields by reducing the destructive processes that 
occur in the kiln body. 
If excess resistance to upward flow is encountered at any point, the gas, 
gas and oil vapor, and gas and oil mist can seek out paths of lesser 
resistance by moving laterally in the shale bed. Thus, this invention 
provides three dimensional permeability for upward flow. Thus, the gas and 
entrained oil mist is disengaged from the shale bed and then from the 
retort vessel at a low Reynolds number. 
Oil mist forms in the kiln 23 just above the pyrolysis zone 55 which, in 
effect, is a countercurrent heat exchanger. The downwardly moving shale is 
heated almost to destructive distillation temperature, and the rising 
gases and vapors are cooled to the temperature of the retort outlet. There 
is no sharp separation between the pyrolysis zone 55 and the zone 50 where 
the product is cooled sufficiently to form a mist. Nevertheless, it is 
believed that a temperature of about 700.degree. F. is the temperature at 
which a substantial portion of the oil vapor begins to form oil mist. 
Collection Chamber 
In accordance with the invention, and as shown in FIGS. 4 and 5, the bottom 
panel 75 of the collection chamber 73 is shown constructed of a tube 
sheet, i.e., a sheet having tubular members 81 extending upwardly 
therefrom. The tubular members 81 define the orifices or openings 79. A 
plurality of off-takes 83,85 are disposed at opposite sides, respectively, 
of the collection chamber 73 (See FIG. 2). The off-takes 83, 85 
communicate with the collection chamber 73 through openings in the side 
walls of the kiln and extend outwardly therefrom and are connected to 
manifolds 84,86, respectively, so that the gas and oil mist mixture is 
easily removed. Means (not shown) applies a uniform suction to the 
off-takes to insure uniform and smooth flow of the gas/oil mist mixture. 
The bottom panel 75 of the collection chamber tapers downwardly from the 
center of the kiln 23 toward the sides thereof adjacent the off-takes 
83,85 with a slope of about 1 inch per 21 inches. The purpose of this 
slope is to promote drainage of liquid which accumulates on the bottom 
panel 75. If the slope is too slight, the oil liquid may become static and 
allow sediment to accumulate. If the slope is too steep, drainage of the 
liquid may become channeled so that some areas may not be flushed. 
As further embodied herein and shown in FIG. 14, the openings 79 and tubes 
81 increase in size along rows represented by lines A-G which progress 
away from the off-takes 83 toward the center of the collection chamber 73. 
The same is true for the openings 79 and tubes 81 on the other side of the 
chamber center line as they progress away from off-takes 85. The size of 
each row of openings 79 can be determined once it is understood that it is 
necessary that the pressure drop from each opening to its adjacent 
off-take plus the pressure drop through each opening should be uniform in 
order to achieve the purposes of this invention. 
Another factor which must be considered is the existence of the vertical 
tubes 59 past which the gas/mist must flow. FIG. 14 shows a preferred flow 
pattern of gas/mist mixture as it emerges from the openings 79 and flows 
to and through the off-takes 83. It will be appreciated that by properly 
sizing the openings 79 and by properly sizing the off-takes 83,85, the 
gas/mist mixture will be withdrawn from the collection chamber 73 and flow 
outwardly through the off-takes 83,85 with low turbulence. Furthermore, 
this further enhances uniform disengagement of gas and entrained oil mist 
across the entire retort cross section. 
Rock Delivery 
In accordance with the invention, and as shown in FIGS. 2 and 5, a bin 87 
is disposed above and communicates with each of the tubes 59. The upper 
portions of the bins 87 which receive the rock are substantially 
rectangular in cross section and each tapers or funnels downwardly toward 
its associated tube where it becomes substantially circular in 
cross-section. In particular, one long sloping side of each bin causes 
segregation of shale fragments or fines which tend to sift towards the 
long sloping surface. 
In addition, the portion of the bins 87 immediately above the associated 
tubes 59 is formed with an inwardly directed kink 89 which approaches the 
center line of the associated tube 59. The kinks 89 deflect the smaller 
rock fines toward the centers of the tubes 59. However, the kinks 89 
should not be so close to the tube center lines to cause bridging of the 
rock particles. The kinks compensate for size segregation caused by the 
sloping sides of the bins. 
In accordance with the invention, the rock delivery means includes a 
tripper conveyor, a shuttle conveyor, and a traveling hopper which 
sequentially deliver rock to the bins above the feed tubes. As embodied 
herein and shown in FIG. 10, a shuttle conveyor 91 is adapted to travel 
back and forth across the short dimension of the retort. A tripper 
conveyor 93 running the length of the retort feeds rock onto the shuttle 
conveyor at each of its positions in the direction of the arrows 92,94. 
The shuttle 91 also includes a traveling hopper 95 which is adapted to 
move parallel to the direction of movement of the shuttle conveyor 91 or 
in the direction of arrows 96,98. The embodiment shown in FIG. 10 includes 
four rows of bins 87 so that movement of the shuttle conveyer structure, 
which includes the traveling discharge mechanism of the tripper conveyor 
93 as well as the traveling hopper 95, is programmed to be positioned over 
one bin at a time. 
FIG. 11 shows the filling sequence for a total of 320 bins 87, eighty bins 
in each of four rows. It is noted that the traveling hopper is 
repositioned only four times on the shuttle conveyor during each filling 
cycle. The shuttle conveyor travels the full length of the retort in one 
pass and lays down a strip of shale before reversing and traveling in a 
reverse pass during which it lays down a parallel strip. This sequential 
strip feeding method to a series of smaller bins smoothes out the minor 
variations in size consist and shale grade in the retort cross-section as 
well as in the vertical direction. Programmed motion controllers reset by 
rock level detectors maintain desired working levels in the bins. 
As described above, if a problem is encountered which restricts upward flow 
of gas through the descending rock bed, the gas will follow a path of 
least resistance and will migrate laterally if necessary. With the rock 
delivery means described above, a strip of rock material having a greater 
permeability can be laid down over or adjacent the restricted area to aid 
in promoting uniform, upward flow of the gas. 
Grate 
In accordance with the invention, the cooling zone 54 includes grate means 
at the bottom of the kiln which is operable to control the delivery rate 
of rock from the kiln and the rate of descent of the rock throughout the 
kiln cross section. As embodied herein, one or more reciprocating grates 
15 are provided in the kiln 23 below the bottom gas distributors 31 and in 
the openings between them. (See FIG. 4). The retarder plates are wider 
than the openings and prevent the free flow of rock. The grates 15 are 
positioned on top of the retarder plates and are reciprocated by suitable 
means such as hydraulic or pneumatic cylinder and piston devices 16 and 
provide for pushing the rock off the retarder plates, thus providing for 
removal of spent rock from the bottom of the kiln uniformly across its 
entire cross section. This, in turn, provides for uniform descent of the 
rock through the kiln 23. The rate of discharge of rock from the kiln 23 
and the rate of rock descent in the kiln can be varied by varying the 
grate bar reciprocation rate. Furthermore, by differential adjustment of 
the grate bar reciprocating rates, fine tuning can assure uniform shale 
processing rates across the full cross-section of the retort. 
Gas Delivery 
In accordance with the invention, means is provided for delivering gas to 
the kiln to effect heating of the descending rock to its retort 
temperature. Said means can be two sets of gas distributors including a 
plurality of generally parallel conduits which extend across the kiln. 
Preferably, the upper distributors 27 are open at their ends for the 
reception of gas and are blocked substantially at their midpoint as will 
be described below. A pair of manifolds 28, 28 are connected by pipes 58 
to opposite ends of the distributors 27 (see FIGS. 1, 2 and 3). The 
manifolds 28 also are connected to a gas source (not shown) so that gas 
delivered to the manifolds 28 passes through the pipes 58 into the 
distributors 27 and enters the kiln 23 through orifices 34. 
Similarly, the middle distributors 29 are open at their ends for the 
reception of gas and are blocked at substantially their midpoint. A pair 
of manifolds 30, 30 are connected by pipes 60 to opposite ends of the 
distributors 29. The manifolds 30, 30 are also connected to a gas source 
(not shown) so that gas delivered from the source to the manifold 30 flows 
into the distributors 29 and enters the kiln 23 through the orifices 34. 
In the direct heated retort used to retort oil shale, the gas entering the 
kiln 23 by way of the distributors 27, 29 is a mixture of air and recycle 
gas and is used to support oxidation of char in the descending shale. 
Oxidation occurs in combustion zones 51, 52 in the kiln 23 which extends 
from the distributors 27, 29 upwardly as much as one or two feet (FIGS. 3 
and 4). The hot flue gases produced by oxidation rise through the 
descending shale bed and heat the shale particles to their destructive 
distillation temperature in a pyrolysis zone 55 which is located above the 
upper combustion zone 51. The air/gas ratios are different in the upper 
and middle sets of distributors 27, 29, the ratio in the upper 
distributors 27 being from about 3.0 to about 5.0, while the ratio in the 
middle distributors 29 is from about 0.5 to about 0.8. Oxygen in the 
air/gas mixture supports the oxidation of char in the shale and also 
oxidizes some of the oxidizable gases in the recycle gas. Desirably, the 
shale temperature in the upper combustion zone 51 reaches a typical value 
of about 1000.degree. F. and the gas temperature reaches a typical value 
of about 1250.degree. F. and the hot flue gases produced provide most of 
the heat necessary for the destructive distillation of the kerogen in the 
shale. 
The temperature of the hot flue gases from oxidation is moderated by the 
presence of recycle gas flowing upwardly through the rock bed, having been 
injected by way of bottom distributors 31 at the bottom of the retort. 
When retorting oil shale in the indirect heated retort, the gas for 
destructive distillation may be delivered into the rock bed by a single 
set of distributors although two or more sets such as first and second 
vertically-spaced sets of distributors 27, 29 may be used. In the indirect 
heated retort, the gas is usually recycle gas from the destructive 
distillation or a gas containing little or no oxygen. This gas is 
externally heated and is introduced to the kiln and provides the heat 
necessary for the destructive distillation of kerogen in the shale. 
Details of the manner of utilizing recycle gas from destructive 
distillation in an indirect heated oil shale retort are described in U.S. 
Pat. No. 4,116,810. 
In both cases, i.e., the direct and indirect heated retorts, the gas 
distributors which serve to deliver gas to the kiln for destructive 
distillation also serve to disturb the descending rock particles. In the 
case where two or more vertically-spaced sets of distributors are used, 
the rock particles are disturbed at a corresponding number of 
vertically-spaced locations in the kiln 23. In all cases, the surface area 
of the particles which are exposed to heat in the kiln is maximized which 
enhances the efficiency of the process. 
The spaced sets of distributors 27, 29 are shown vertically aligned with 
one another. It will be appreciated, however, that the distributors 27, 29 
could be staggered which might serve to increase the extent to which the 
rock particles are "disturbed" in their descent through the retort. 
However, it is believed that a staggered configuration might be 
disadvantageous, particularly in the direct heated retort used to retort 
oil shale where it might interrupt the formation of a buffer zone 57 which 
is formed between the upper combustion zone 51 and the pyrolysis zone 55. 
The buffer zone 57 (FIG. 6) is above the upper distributors 27 and below 
the pyrolysis zone 55 and isolates the pyrolysis zone 55 from the upper 
combustion zone 51. 
Substantially all the oil that the oil shale is capable of producing will 
have been removed from the shale by the time the particles reach the 
buffer zone 57, and by the time the hot rising gases in the retort reach 
the buffer zone 57, substantially all the oxygen therein will have been 
consumed. If the buffer zone 57 is interrupted or is non-continuous, it 
may be physically possible for some of the shale to pass through without 
the oil having been removed so that the oil will be released from the 
shale in the high temperature upper combustion zone 51 below the buffer 
zone 57. This oil would subsequently pass upwardly through an oxygen 
containing level in the vicinity of the upper distributors 27 and would be 
oxidized to the extent of oxygen availability, thus reducing the 
efficiency of the process. 
In both the direct and indirect heated retort, a set of bottom distributors 
31 is provided near the bottom of the kiln 23 (FIGS. 2 and 3). The bottom 
distributors 31 include a plurality of elongated, generally parallel 
distributors which extend across the kiln 23 in a direction transverse to 
the distributors 27, 29. The bottom distributors 31 are provided with 
orifices 44 and are connected to manifolds 32 which in turn are connected 
to a gas source (not shown). The gas delivered to distributors 31 in an 
oil shale retort is a cool recycle gas which enters the bottom of the kiln 
23 and rises toward the lower combustion zone 52. This forms a cooling 
zone 54 in which the descending shale is cooled. By heat exchange, the 
recycle gas from distributors 31 is heated as it rises toward the 
combustion zones 51, 52. 
In a direct heated retort for calcining limestone, a gaseous fuel is used 
for oxidation. An air-gas mixture is introduced into the kiln preferably 
at three zones controlled by distributors 31, 29, 27 (FIG. 4). When 
natural gas is used, the percentage of gas mixed with air in each of the 
zones is about 0.2 to 2.5% gas by volume in the mixture for the bottom 
zone fed by distributors 31, about 8% to 70% gas by volume in the middle 
zone fed by distributors 29, and about 6% to 20% gas by volume in the 
upper zone fed by distributors 27. Preferably, for limestone calcination 
the percentage volume of gas for the lower zone is about 0.3% to 1.0%, for 
the middle zone about 25% to 45% and for the upper zone about 10% to 15%. 
These mixtures give a very great excess of air for oxidation (based on the 
gas) in the lower zone, a very moderate excess in the middle zone, and a 
very small overall excess of air, preferably under 25%. The temperature 
in the combustion zones 51, 52 is hot enough (over 2000.degree. F.) to 
calcine, i.e., decompose, limestone. 
It is important that the distributors deliver gas to the kiln 23 
substantially uniformly throughout the kiln cross section so that the 
descending rock bed is uniformly heated for maximum processing efficiency. 
It is important also that the distributors be constructed to prevent 
excessive heat concentration from occurring at the center of the kiln. 
Finally, the distributors must be constructed to retard clogging and to 
withstand the force of the descending rock bed. In high temperature 
processing of solids by vertical kilns, e.g., limestone calcination or 
roasting of mineral ores, some of the distributors may need to be cooled 
at their exit orifice cooling areas by circulating liquid. 
The distributors should be constructed so that gas flow therethrough can be 
controlled to control the heat in the retort, and so that different 
quantities of gas can be delivered to different horizontal zones of the 
retort should non-uniform conditions exist in the retort. Such non-uniform 
conditions can arise, for example, when non-uniform grades of rock are 
delivered to the retort by the delivery means. 
In accordance with the invention, the gas distributors are constructed and 
the orifices in the distributors are sized and spaced to deliver gas 
uniformly throughout the cross section of the kiln. As embodied herein and 
shown in FIGS. 15-22 for the direct heated retort, the upper gas 
distributors 27 are substantially identical and each includes a hollow, 
elongated, generally rectangular frame 18 which is constructed, for 
example, of carbon steel and is blocked at substantially its midpoint by a 
divider or center baffle 40 (see FIGS. 20 and 21). The distributor frames 
18 extend entirely across the width of the kiln 23 and are supported at 
opposite ends in metal frames 80 within the side walls of the kiln. 
Openings 34 exist along both sides of the frames 18 (see FIG. 22). A 
plurality of expanding nozzles 33, also constructed of carbon steel, are 
welded to the frames 18 over each of the openings 34, and each expanding 
nozzle 33 is formed with a conically-shaped opening 34A aligned with an 
associated opening 34. As shown in FIG. 22, the axes of the 
conically-shaped openings 34A are inclined downwardly at an angle of about 
15.degree. relative to the horizontal to increase horizontal penetration 
of injected gas. In addition, the minimum diameter of the orifices, which 
occurs at the section of the conical openings 34A adjacent the frame 
openings 34, is selected to prevent rock particles from working their way 
inside the distributors 27. For rock particles which are from about 1/4" 
to about 3" average dimension across, the orifice diameter should be from 
about 3/4" to about 1". 
As shown in FIG. 16, the distributor frames 18 are each encompassed by a 
protective armor plate 37 which may be constructed, for example, of 
stainless steel, to protect the distributor against the excessive heat in 
the kiln. The armor plates 37 are provided with openings 34B which align 
with the openings 34 and 34A in the frames 18 and expanding nozzles 33 
respectively, and are generally rectangular in cross section with a 
peak-shaped top 88 which first encounters the descending rock. 
Distributors 27A adjacent to each end wall 90 of the kiln 23 are each 
partially set into recesses 68 in the kiln walls (FIG. 19). The armor 
plates 37A used with these distributors 27A have a tapered rectangular 
configuration as shown in FIG. 19. The modified armor plates 37A do not 
have openings in the sides adjacent the kiln walls. Insulation 38 may be 
disposed in the space between the armor plates 37, 37A and the frames 18, 
18A of all distributors 27, 27A. 
The structural design of the upper gas distributors 27 is based on the 
assumption that all the rock above a central portion along the length of 
the kiln is carried by beam action. For the small zones adjacent the kiln 
end walls, the usual triangular loading pattern is assumed. The calculated 
static loads are multiplied by a factor, preferably about 1.2, to allow 
for the effect of the dynamic movement of the rock. 
The top flange on the distributor frames 18 is assumed to be laterally 
unsupported even though the rock normally provides some support against 
buckling. However, since the rock is moving and the movement may be 
different on the two sides of the retort, a lateral load can and will 
exist on the distributors. A maximum calculated temperature is used to 
estimate the modulus of elasticity of the metal under moving bed 
conditions. In a direct heated oil shale retort where the upper 
distributors are cooled (hereinafter described), the maximum calculated 
temperature for the distributor frame 18 is about 700.degree. F. 
A higher maximum temperature, about 900.degree. F., is used to estimate the 
required compressive strength of the distributor frames 18 under static 
conditions when buckling is not a factor. This temperature is based on the 
worst case thermal condition from observation of thermocouple readings 
during power outages and the knowledge that the endothermic reactions 
continue for a short period while the exothermic reactions stop when the 
gas supply is shut off. 
With respect to gas flow, the function of the distributors 27, 29, 31 is to 
introduce the proper amount of gas at the location where it is needed 
under controlled conditions. In a direct heated retort used to 
destructively distill oil from oil shale, the distributors 27, 29, 31 
contain a controlled mixture of recycle gas and air which is below the 
point of auto-ignition at normal operating temperatures inside the 
distributors. The minimum velocity of gas through the orifices desirably 
is maintained above 33 ft./sec. to prevent flashback into the distributor 
from the shale where oxidation is occurring. The minimum orifice velocity 
also assists in distributing the gas laterally in the rock bed. 
The pressure drop across the orifices is selected to be about 10 times the 
velocity head of the gas upstream of the first orifice. The quantity 
(scfm) of gas introduced to each orifice should fall within a narrow band, 
within 5% of each other, to insure uniform gas distribution to the retort. 
This quantity, expressed mathematically, is proportional to: 
EQU .DELTA.P/TA 
where .DELTA.P is the pressure drop across the orifices and TA is the 
absolute temperature of the gas. 
Particular problems are encountered in achieving this result. Any orifice 
physically located near the entrance "sees" an effective .DELTA.P equal to 
the total head less the velocity head which is a maximum at the point of 
entrance. This results in a lower .DELTA.P. Also, the gas experiences a 
pressure increase as it approaches the center baffle 40 causing an 
increase in flow rate especially at the last orifice adjacent the center 
baffle 40. 
These problems can be solved and uniformity of gas flow to all orifices 
achieved by varying the size of the orifices. However, this presents 
another problem in that it requires different-sized tools when 
manufacturing and cleaning the orifices. Also, it presents a danger that 
smaller-sized orifices can be damaged by a tool sized for a larger 
orifice. 
In accordance with the invention and as embodied herein, the distributors 
27, 29 have uniformly-sized orifices and yet provide for uniform gas 
delivery to the retort by spacing the first orifice closer to the wall of 
the retort than half the spacing between the other orifices, and spacing 
the orifices which straddle the center baffles 40 further apart than the 
other orifices. The spacing between the remaining orifices is 
substantially equal. For a rectangular retort spanning 24 feet and having 
pairs of 12 foot long distributors 27, 29 (one on each side of the center 
baffles 40) and each distributor of the pairs fed with gas from one end, 
and having a minimum orifice diameter of about 0.900", the spacing between 
adjacent orifices is about 8", the spacing between the orifices which 
straddle the center baffle is about 81/2", and the spacing between the 
wall of the kiln and the first orifice is about 33/4". 
Gas Cooled Distributors 
It will be appreciated that uniform velocity and mass flow of gas from all 
of the orifices can be achieved only if the temperature can be held within 
a relatively-narrow range. Furthermore, in the direct heated retort, the 
maximum wall temperature of the distributors 27 is limited by the 
possibility of premature combustion. These requirements are mutually 
incompatible in a distributor constructed as a simple perforated pipe. 
Importantly, if the distributors are constructed as simple perforated 
pipes, it will be understood that the walls of the distributors become 
very hot near the center of the kiln. The gas flow rate varies along the 
distributors as does the velocity head reaching a minimum at the center of 
the kiln causing the distributors to be much hotter at the kiln center 
than toward the side walls. The distributors which are--in effect--box 
girders, can collapse if they become too hot. Further, the gas in contact 
with the hot distributor walls may oxidize further increasing the 
temperature and magnifying the problem. 
In accordance with the invention, a "horizontal" (actually sloping slightly 
downwardly from the sides of the kiln) baffle is provided, (in at least 
some of the distributors), one on either side of the center baffle and 
below the distributor orifices. Each of the horizontal baffles slopes 
downwardly toward the center baffle, has a terminal end spaced from the 
center baffle, and is provided with a plurality of orifices, whereby gas 
entering the ends of the at least some distributors flows below the 
horizontal baffles in a direction toward the center baffles, some of the 
gas passing upwardly through the orifices in the horizontal baffles and 
some between the terminal end of the horizontal baffles and the center 
baffles, the gas exiting the distributors through the orifices therein. 
The horizontal baffles take into account heat flow through the insulated 
distributor walls, the pressure drop between the distributor inlet and 
each orifice, and the temperature, pressure and velocity conditions at 
each orifice, and provide for a desirable flow pattern in the gas flowing 
through the distributors. 
As embodied herein, a horizontal baffle plate 97 extends through the frame 
18 of each distributor 27, one on each side of the center baffle 40 (see 
FIGS. 20 and 21). The baffle plates 97 are formed with uniformly-sized and 
spaced openings which preferably are semicircular notches 99 along both 
sides thereof and each baffle plate slopes downwardly from the inlet end 
of the distributor 27 toward the center baffle 40, and each terminates at 
a terminal end which is below an orifice adjacent to and spaced from the 
center baffle 40. (See FIGS. 20 and 21.) Each baffle plate 97 is generally 
planar and spans the width of the frame 18 and one pair of notches 99 is 
aligned with each pair of orifices. Thus, gas entering the distributors 27 
passes through inlet openings 101 formed by the baffle plates 97 and the 
sides and bottom of the distributor distributors 18. The gas flows beneath 
the baffle plates 97 and some passes upwardly through the notches 99 and 
then through the orifices and into the retort. The remainder of the gas 
passes through openings 104 below the terminal ends 100 and through 
openings 102 between the terminal ends 100 and the center baffles 40 and 
flows back toward the inlet openings 101 and above the baffles 97. 
The baffle plates 97 are constructed and the notches 99 positioned and 
dimensioned to help control the gas temperature and pressure at each 
orifice and to provide sufficient cooling to the side walls of the 
distributor frame to meet the retort requirements. Importantly, the gas 
exiting the orifices adjacent the center baffles 40 is almost exclusively 
gas which has passed entirely under the horizontal baffles 97. On the 
other hand, the gas exiting the orifices toward the kiln walls is a 
mixture of hot gas which has passed entirely under the horizontal baffles 
97 and cooler gas passing upwardly through the notches 99. 
It has been determined that in order to insure that the temperature of the 
distributors remains substantially constant throughout, about two-thirds 
of the gas entering the distributors 27 through gas inlets 58 should pass 
under the horizontal baffles 97 and the remaining one-third should pass 
upwardly through the baffle orifices 99. In order to achieve this, it has 
been determined that the summation of the cross-sectional area (23 
in.sup.2) of the baffle orifices 99 in each baffle 97 should be from about 
95% to about 125%, and preferably about 110%, of the cross sectional area 
of the opening 104 below the terminal end 100 of the baffle 97. In 
addition, it has been determined that the cross sectional areas (21 
in.sup.2) of openings 102, 104 should be approximately equal and from 
about 23% to about 32%, preferably about 28%, of the cross-sectional area 
(76 in.sup.2) of gas inlet opening 101. 
Distributor Placement 
As described above, the distributors 27, 29 perform two main functions. 
They distribute gas uniformly to the rock bed and they disturb the rock 
particles. Optimally, in an oil shale retort, the distributors are from 
about 24' to about 261/2' in length and include a gas-tight bulkhead 
(center baffles 40) at their center line. For distributors having orifice 
dimensions and clear space described above, baffle plates and center 
baffles at their midpoints, and gas and rock parameters also described 
above, the clear spacing between adjacent distributors 27 should be about 
32" to insure that the gas emitted from the orifices infiltrates the 
entire rock bed uniformly. If the distributors 27 are placed any closer 
together, bridging of the rock between the distributors tends to occur. 
The peaked configuration 88 at the top of the distributors 27, 29 eases the 
loading thereon by the descending rock and causes the rock bed to part and 
individual particles to change position exposing a variety of the rock 
surfaces to the gas. The rectangular bottom configuration allows a 
V-shaped trough to form in the descending rock bed so that horizontal flow 
of gas under the distributors 27, 29 is possible. This allows cross flow 
of gas in the kiln to correct potential gas channeling in the bed. 
Liquid Cooled Distributors 
It will be appreciated that in an oil shale retort, the temperature in the 
vicinity of the upper gas distributors 27 exceeds the coking temperature 
of oil produced from the shale. On some occasions, oil can coke on the 
outside of the distributors 27. This can cause the orifices to become 
clogged with carbonaceous material which impairs the operability of the 
retort. Therefore, in addition to the baffle plate 97 in the distributors, 
it is prudent to cool each individual orifice in the upper distributors 
27. 
In accordance with the invention, means is provided for cooling the 
orifices in the upper distributor. As embodied herein and shown in FIGS. 
17 and 18, piping 35 extends along each distributor 27 on opposite sides 
of the center baffle 40. The piping 35 includes four channels each having 
a forward pass and a return pass along each distributor 27 on one side of 
the associated center baffle 40. The forward pass for pipe set 35A winds 
sinusoidally along the distributor 27 passing through the orifice blocks 
33 adjacent each orifice along one side of the distributor 27. Similarly, 
the forward pass for pipe set 35B winds sinusoidally through frame 18 
adjacent each orifice on the other distributor side. Return passes for 
each pipe set 35A, 35B extend through the insulation 38 within the armor 
plates 37. 
Forward passes of pipe sets 35C and 35D, respectively, extend through 
insulation 38 above the distributors 18. Return passes for these pipe sets 
wind sinusoidally along opposite sides of the distributors generally 
parallel to the forward passes of pipe sets 35A, 35B and pass through the 
orifice blocks 33 on opposite sides of those orifices. The coolant in the 
return passes is, of course, substantially hotter than that in the forward 
passes. Coolant can be considered cool in the first two thirds of the 
forward passes, warm in the last third of the forward pass and first third 
of the return pass, and hot in the last two thirds of the return pass. 
Utilizing the design of the present invention, each orifice is cooled 
either by one cool pass or two warm passes. 
The same is true for pipe sets of piping 35 located on the other side of 
each center baffle 40. Piping 35 conveys a suitable cooling medium such as 
50% ethylene glycol and 50% water which moves continuously therethrough. 
By this construction, the metal temperature of the distributors 27 at the 
orifices can be maintained below the coking temperature of the shale oil. 
Middle Distributors 
If the middle distributors 29 are employed, as indeed is preferable in the 
direct heated retort and optional in the indirect heated retort, they are 
similar in construction to the upper distributors 27 described above. 
Thus, as seen in FIGS. 23-28, the middle distributors 29 are formed by 
hollow, elongated, generally rectangular frames 20 (FIG. 24) which extend 
from end to end across the kiln 23 and are supported adjacent their ends 
in metal frames 80 within the side walls of the kiln (see FIGS. 23 and 
26). Frames 20 are constructed of carbon steel and are formed with 
openings 36 spaced along their length (FIG. 28). An expanding nozzle 53 
also constructed of carbon steel is welded to the frames 20 over each 
opening 36 and has a conically-shaped opening 36A aligned with respective 
openings 36, 36B in the frame and armor plate. Conically-shaped openings 
36A are circular in cross section and incline downwardly at an angle of 
about 15.degree. to the horizontal. The minimum diameter of the 
conically-shaped opening 36A is about 0.900". Armor plates 37 encompass 
the frames 20 and the space between the armor plates 37 and the frames 20 
may be filled with insulation 38 (see FIG. 24). The armor plates 37 have 
peak-shaped tops 88 (FIG. 24) in the same manner as the armor plates 37 
for distributors 27. 
A divider or center baffle 40 separates the distributors 29 into two 
halves, and an internal horizontal baffle plate 97 inclines downwardly 
from a gas inlet opening 101 in each frame 20 and terminates at a terminal 
end 100 spaced from the center baffle 40 and below the set of orifices 
adjacent the center baffle 40 (see FIGS. 26 and 27). Each baffle plate 97 
is provided with a plurality of equally spaced, semicircular notches 99 
which align generally with the orifices. 
Like the construction of the upper distributors 27, the horizontal baffles 
97 in the middle distributors 29 prevent excessive heating of the 
distributors at the center of the kiln. The construction of the middle 
distributors provides for uniform distribution of gas across the entire 
cross section of the kiln 23. The orifices are uniformly sized for easy 
maintenance and are substantially uniformly spaced except that the 
orifices straddling the center baffle 40 are spaced apart a slightly 
greater distance. The orifices adjacent to the side walls of the kiln 23 
are slightly closer to the wall than half the spacing between the other 
orifices. The distributors 29A adjacent kiln end walls 90 are partially 
set into recesses 68 and the armor plates 37A therefor are tapered as 
shown in FIG. 25. 
The configuration and dimensions of the orifices and the spacing there 
between, the configuration, length and spacing of the distributors 29 and 
the mechanical construction and function thereof, are substantially the 
same as described above for the distributors 27 and are not described 
further here. One exception is that because the retort temperature is 
somewhat lower in the area of the middle distributors 29 and liquid oil 
would not usually be present and thereby subject to coking, there 
generally is no need to provide cooling means for the distributor 
orifices. Thus, the cooling means for the orifices described above for the 
upper distributors 27 may be dispensed with here. 
It has been determined that on all occasions in the direct heated oil shale 
retort when coking occurred on the middle gas distributors 29, the oil 
recovery equipment was overloaded or otherwise malfunctioning and the 
source of the oil which was coked is believed to be mist carried over 
through the recycle gas system. The primary oil recovery section (not 
shown) used with this invention, which includes coalescers and 
electrostatic precipitators, is designed to process 25% more throughput 
than is required to support the rated capacity of the retort. In addition, 
a knockout pot (not shown) is provided between the electrostatic 
precipitator and compressors to catch any "slugs" of oil which might be in 
the compressor inlets. Furthermore, a mist eliminator (not shown) and an 
electrostatic precipitator (not shown) are installed in the recycle gas 
line between the compressor and the middle gas distributors 29. 
Segmented Distributors 
As previously described, the retort is filled with rock by a delivery means 
including a shuttle conveyor 91, a tripper conveyor 93, and a hopper 95 
which make a plurality of (4) passes along the length of the kiln 23. Rock 
is continuously fed to the delivery means and despite efforts to maintain 
uniformity, different grades of rock can and will at times be delivered to 
the kiln. When this occurs, it produces non-uniform conditions in the rock 
bed which significantly affects the efficiency of the retorting process 
It will be appreciated that each pass of the rock delivery means delivers a 
layer of rock to a vertical filling zone in the kiln 23. Since there are 
four (4) passes of the delivery means, there are four vertical filling 
zones represented at 11, 12, 13, 14 in FIG. 29 and each is made up of 
layers of rock deposited during a pass of the delivery means. The zones 
11-14 extend generally vertically through the kiln 23 and are shaped 
generally rectangularly in cross section. The rock layers extend 
horizontally of the kiln. 
The multiple pass rock delivery means can be used to advantage such that 
variations in grade of rock or rock size which might exist on the tripper 
conveyor 93 would tend to be averaged out because of the "layers" of rock 
in the retort. However, it is desirable that the rock bed be uniform and 
when a different grade of rock enters one or more of the filling zones 
11-14, it can act to the detriment of the retorting process especially if 
the segregation tends to form vertically. Furthermore, because of the long 
residence time of the rock on the feed belts and in the retort, it takes a 
relatively long time to correct an imbalance condition in the retort by 
changing the grade of rock delivered. It is important, therefore, that 
there be means for relatively fast reaction to non-uniform conditions in 
the rock bed to maintain uniformity in the retorting process. 
In accordance with the invention, means is provided for varying the 
quantity of gas delivered to the vertical filling zones in the retort. As 
embodied herein and shown in FIG. 29, each of the upper distributors 27 is 
modified so that it is divided into four segments 11A, 12A, 13A, 14A, one 
corresponding to each of the four vertical filling zones 11-14. Gas is 
deliVered to distributor segment 11A through inlet 58A and to segment 12A 
through inlet 58B. The gas stream delivered to segments 11A and 12A is 
separated from one another by horizontal baffle 46 and vertical divider 
47. In this construction, it has been found that an inclined baffle 48, 
corresponding substantially in structure to baffle 97 shown in FIGS. 20 
and 21, is required only at distributor segment 12A and not at segment 
11A. 
In a similar fashion, gas is delivered to distributor segments 13A, 14A 
through inlets 58D, 58C, respectively. Segments 13A, 14A are separated by 
horizontal baffle 46 and vertical baffle 47 and an inclined baffle 48 is 
provided in segment 13A. The distributor is designed so that the gas 
velocity is greatest, and therefor the cooling effect is greatest, near 
the center of the kiln where the distributor is the hottest. A divider or 
center baffle 40 blocks the flow of gas past the midpoint of distributors 
27. 
It will be understood that the relative amounts of gas delivered to each of 
the distributor segments 11A-14A is readily varied by varying the amount 
of gas delivered to the inlets 58A, 58B, 58C, 58D. Thus, when an imbalance 
occurs in the rock bed such as, for example, the result of a different 
grade of rock in one or more of the filling zones 11-14, controlled 
variance of gas flow to the distributors 27 can quickly correct the 
situation so that process uniformity can be maintained. Preferably, the 
inlets 58A, 58B, 58C, 58D for each of the distributors 27A, 27B are 
controlled so that the proper amount of gas is delivered to corresponding 
segments of each distributor. 
The distributors 29 in this embodiment are substantially the same as in the 
embodiment illustrated in FIGS. 23-28 and described above although it is 
understood that similar modifications to those described for distributors 
27 could be employed here if desired. 
A summary of the important fundamentals of the moving substances, both 
solids and fluids, in the present invention when retorting oil shale, is 
as follows. For the solids, i.e., shale lumps, there should be a 
consistent range and distribution of shale sizes which should be 
relatively free of fines, which are defined as particles smaller than 1/4" 
average dimension across. The shale should be distributed uniformly over 
the entire cross section of the retort and the shale lumps should be 
disturbed at more than one level as they descend through the kiln to 
expose a variety of solid surfaces to the upwardly moving gas stream. 
Finally, the spent shale should be removed uniformly over the entire kiln 
cross section and at a controlled bulk rate. 
For the fluids, cooling gas should be distributed uniformly over the entire 
kiln cross section below the bed. Air should be distributed uniformly and 
in a carefully controlled pattern over the entire kiln cross section, 
preferably at two levels with a different concentration of oxygen at each 
level, in the direct heated retort, to achieve a desired vertical 
temperature profile and to minimize horizontal temperature variations in 
the kiln. Gas (and entrained oil mist) should be removed from the top of 
the kiln in such a way as to promote uniform flow over the entire kiln 
cross section. The present invention achieves all of these fundamentals. 
The shale and gas temperatures achieved in the present invention are shown 
in FIG. 7. The temperature of the gas above the lower air/gas distributor 
29 is higher than the temperature of the shale. In the cooling zone, the 
shale is hotter than the incoming recycle gas from the bottom distributors 
31 so that heat flows from the shale to the gas here. 
FIG. 8 is a desired heat flow diagram which shows how heat is physically 
distributed within the retort. The right side of this figure shows heat 
being transported upwardly by the moving gas. Horizontal paths show 
recuperated heat flowing from the gas to the shale in the upper part of 
the kiln and from the shale to the gas in the lower part. The make-up heat 
is provided by oxidation at two levels in the direct heated retort. The 
net heating is shown by a single arrow representing the net endothermic 
heat sink for the entire retort. This is the heat required to evaporate 
all the water, calcine a portion of the carbonate, destructively distill 
the kerogen and support the endothermic char gasification reactions. 
The dashed curve of FIG. 9 shows the amount of potential oil in the shale 
at various elevations in the retort. The solid curve shows the oxygen 
level. The buffer zone 57 is below the level at which oil occurs in 
significant quantities. This buffer zone is important because any oil that 
contacts the oxygen at the temperature of the buffer zone is subject to 
oxidation to the extent of the amount of oxygen present. 
It will be appreciated that the process of retorting oil shale is a thermal 
process which depends upon accurate maintenance of temperatures, 
pressures, residence times, gas compositions and flow rates within 
relatively narrow limits. These limits, in turn, depend upon the process 
and the materials being processed. In the present invention, heat is 
generated in the combustion zone 51, 52 in the direct heated retort, one 
located above each of the two air/gas distributors 27, 29. In the indirect 
heated retort, the externally heated gases are delivered to the retort at 
one or two or more levels. In both cases, heat may be thought of as being 
swept upwardly by the rising gas stream ream and at the same time being 
carried down by the descending shale lumps. 
The temperatures in the kiln influence both the quantity and the quality of 
the oil produced. The maximum temperature in the kiln is dependent on the 
extent of decomposition of carbonate minerals in the shale, while the 
minimum temperature is determined by the time/temperature relationships in 
destructively distilling the kerogen in the shale. In order to avoid 
excessive refluxing, (i.e. return of condensed oil to the pyrolysis zone) 
the shape of the vertical temperature profile in the mist formation zone 
is controlled by the gas-to-solids flow ratio in the upper part of the 
retort. Maintaining uniform and controlled processing conditions over 
large cross-sections required an innovative design. FIG. 2 shows a 
submodule (or cell) which has a multiplicity of feed bins, gas collecting 
orifices and ducts, multiple levels of gas and air distribution, and 
multiple shale withdrawal mechanisms. This cell could process over 2,500 
tons of shale per day. By incorporating 8 of these cells in a linear 
fashion as shown in FIG. 1, a 20,000 ton per day retort could be built and 
operated. Second generation retorts would be wider and use 12 or more 
cells. 
Temperature control in the present invention is a dynamic 
feedforward-feedback system adapted to maintain acceptable operating 
conditions between the maximum and the minimum profiles in each of some 82 
temperature control zones. This takes into account all the independent 
variables which affect the retorting process. The most important variable 
in this category is the quality of the raw shale including the amount and 
nature of the kerogen, mineral carbonate and water content. Other 
independent variables in the control system include physical properties in 
the raw shale, recycle gas and combustion air. 
The independent load variables in a commercial retort having 8 sub-modules 
that are used to establish tentative values for 8 classes of manipulated 
variables on a real time basis include the following: 
16-Grate speeds 
18-Bottom recycle gas flow rates 
2-Middle air/gas ratios 
82-Middle air/gas flow rates 
1-Upper air/gas flow ratio 
82-Upper air/gas flow rates 
48-Steam flow rates to the bottom gas distributors 
32-Top pressures 
281-Total manipulated variables. 
It will be apparent to those skilled in the art that various additions, 
substitutions, modifications and omissions may be made in the present 
invention without departing from the scope or spirit of the invention. 
Thus, it is intended that the present invention cover the additions, 
substitutions, modifications and omissions provided they come within the 
scope of the appended claims and their equivalents.