Apparatus for shale oil retorting

A shale oil retorting system and novel continuous feed means for retorting oil shale within a retort housing employs a tilted circular conveyor within the housing which allows for continuous feeding of crushed oil shale within the conveyor for subsequent immersion in a hot process oil bath and unloading from the housing. The retort housing is constructed of side body members arranged to provide primary refluxing action of flammable process oil vapors evolved during retorting to prevent explosion. Safety is further augmented by providing an overhead vapor outlet and a sufficient level of process oil in the bath to produce a slight overpressure in the free board region conducive to quickly exhausting shale oil vapor from the housing into an overhead condensing unit. The spent shale particles discharged from the housing are immediately quenched to recover process oil coating the particles and minimize generation of flammable vapors from the hot particles. Ultrasound waves propagated through the liquid oil bath increase production of shale oil vapors.

TECHNICAL FIELD 
The present invention relates generally to shale oil retorting systems for 
evolving shale oil from solid oil shale and, more particularly, to a 
retorting system utilizing a heated liquid bath into which shale material 
is dipped to evolve a vapor condensable into shale oil. In other aspects, 
the present invention also relates to retorting apparatus capable of 
handling the solid oil shale in a continuous feed process and to 
compositions of process oils suitable for obtaining high volume production 
of shale oil in a safe and efficient manner. 
BACKGROUND ART 
The term "oil shale", as used herein, refers to a carbonaceous rock, i.e., 
Devonain marine composition, particularly Eastern oil shale, that contains 
a high molecular weight organic polymer called kerogen. Kerogen is the oil 
precurser in the oil shale rock. To extract kerogen from oil shale, the 
oil shale is generally first crushed into small pieces and heated in 
retorts to pyrolysis temperatures in the range between about 500.degree. 
F. to about 1200.degree. F. Retorting of the oil shale at pyrolysis 
temperatures causes decomposition of the kerogen and evolution of shale 
oil trapped in the matrix of the ore, in the form of a vapor which can be 
subsequently condensed to form usable shale oil liquid. 
A number of different retorting apparatus and processes are known for 
treatment of Eastern oil shale to evolve shale oil therefrom. Some of the 
major shale oil retorting systems as well as lesser known processes are 
discussed in U.S. Pat. No. 4,410,416 to Karl Everman, the disclosure of 
which is incorporated herein by reference in its entirety. Generally 
speaking, however, the major shale oil retorting processes utilize either 
a hot gas as the heating medium circulating within a drum containing the 
shale particles or a hot liquid into which the particles are dumped for a 
considerably large residence time as compared to the present invention. 
Following immersion in the hot liquid, the particles must then be 
separated from the hot liquid in an expensive and time-consuming process, 
such as by rotating the drum in which the particles have been retorted so 
that the particle material can be dispensed by gravity through a 
stationary outlet. 
The aforesaid prior art Everman patent discloses a split hub wheel 
apparatus allowing shale particles to be loaded into spoke-like containers 
of the wheel, dipped into a hot oil bath that enters the containers 
through perforations and subsequently unloaded after shale oil vapor is 
evolved as a result of dipping the materials in the bath. However, the 
prior art Everman split hub wheel can only function as a batch processing 
unit which sharply increases the production time required to evolve a 
particular quantity of shale oil vapor from the shale particles. 
Another drawback of the prior art Everman apparatus is the strict 
requirement that shale oil retorting occurs within an airtight retort, 
requiring the use of expensive seals. To a large extent, safe operation of 
the Everman retort depends upon the integrity of the seals; if the seals 
fail and air comes into contact with the hot oil used in the liquid bath, 
an explosion would necessarily result. 
Another drawback of the prior Everman retort is the requirement that a 
large number of feed and discharge pipes, and moving parts be present in 
the hostile environment, of the retort which may be adversely effected 
thereby. For example, in the prior Everman apparatus, shale is augered 
into the split wheel hub within the retort for loading into the spoke 
containers. Since the auger is sealed to prevent air from entering the 
split hub wheel retort, the hot gaseous environment within the retort 
tends to come into contact with the auger seal causing degradation 
thereof. Too, by augering the raw shale particles into the split wheel 
hub, the particles are unnecessarily subjected to severe agitation which 
tends to increase the production of fines collecting as a sludge within 
the hot oil bath. 
It is accordingly an object of the present invention to provide a novel oil 
shale retorting system capable of retorting shale in a continuous feed 
process to obtain high production yields of shale oil in a safe and 
efficient manner. 
Another object of the invention is to provide a method and apparatus 
providing a direct flow path for enabling evolved shale oil vapor to 
quickly exit from the retort for condensation into liquid form to minimize 
the presence of the flammable shale oil vapor within the retorting system. 
Still another object is to provide a retorting structure and novel process 
oil wherein vapors of the process oil produced during the retorting 
process are subjected to fast refluxing action to minimize the presence of 
flammable vapors within the retort. 
Yet a further object of the present invention is to provide a retorting 
apparatus and method which does not require retorting to occur under 
air-tight conditions, without sacrificing safety. 
Still a further object is to provide a continuous feed conveyor within the 
retorting system that features a minimum of moving parts within the rugged 
and hostile environment prevailing in the retort housing. 
DISCLOSURE OF THE INVENTION 
A process for producing a combustible liquid from solid oil shale with a 
retorting system, in accordance with the present invention, comprises the 
steps of feeding raw shale particles of predetermined size at a feed 
location into a series of moving compartments capable of retaining the 
particles therein while allowing a process liquid to contact the 
particles. The particles are immersed into a bath of the process liquid 
maintained at a sufficient temperature and for a time sufficient to evolve 
vapor of the combustible liquid from the particles. The vapor is collected 
and condensed to produce the liquid. The compartments containing spent 
particles (i.e., oil shale that has been immersed into the bath) are 
removed from the bath and transferred to a discharge location wherein the 
particles are unloaded from the compartment. The process according to the 
present invention is a continuous feed process since the raw particles at 
the feed location are fed as a continuous stream into the compartments 
passing beneath the feed location while unloading of spent particles and 
immersion of particles into the bath occurs simultaneously at other points 
within the retorting system. 
In accordance with an important feature of the invention, it has been 
discovered that substantial advantages are obtained when using a heavy 
process oil in the liquid bath which is considerably heavier than the 
shale oil vapor evolved from the raw shale particles immersed in the bath. 
The process oil is of high viscosity and has a lower condensation point 
than the shale oil vapor to permit rapid refluxing action of the process 
oil vapors to minimize the presence of flammable vapors within the retort 
to prevent explosion. It has been determined that a process oil that 
satisfies these criteria should preferably have an SUS viscosity at 
100.degree. F. of about 3000 to 6000, a specific gravity of about 16 to 18 
API, a pour point of about 25.degree. to 35.degree. F., a flash point of 
about 450.degree. to 525.degree. F., a viscosity of about 175 to 225 SUS 
at 210.degree. F. and an ISO viscosity grade of about 950 to 1050. While 
this process oil is preferred for use in the retort of the present 
invention, it should be understood that the process oil can be utilized in 
other types of retorting systems because of its ability to reflux and 
thereby prevent explosions from occurring. 
In accordance with a further aspect of the invention, the raw particles are 
fed into a series of annular compartments continuously moving within a 
retort housing about an inclined axis of rotation relative to the surface 
of the liquid bath so that raw particles are gravity fed as a continuous 
stream into the compartments. The feed location is located above the bath 
so that as feeding occurs the raw particles are initially out of contact 
therewith. The compartments containing raw particles move continuously in 
uninterrupted travel from the feed location for immersion in the bath and 
thereafter for discharge from the housing at a discharge location situated 
above the bath. The compartments are only partially filled so that 
particles therein are subjected to a tumbling action which is conducive to 
shale oil vapor production. 
As the vapor evolved from the immersed particles emerges from the bath, it 
quickly flows under positive pressure into a vapor outlet and directly 
into a condensing unit located above the retort housing to minimize the 
amount of time the flammable shale oil vapors are present within the 
housing. 
In accordance with another aspect of the process according to the present 
invention, a flammable vapor evolved from the process liquid during 
retorting is subjected to a primary refluxing action by being directed 
through a free board region above the bath into contact with an inclined 
surface of the retort housing where dropwise condensation rapidly occurs 
to minimize the presence of flammable vapors within the free board region. 
Secondary refluxing action of the process liquid vapor also occurs by 
directing the process vapor remaining after primary refluxing action 
occurs through a passage extending vertically upward from the shale oil 
vapor outlet. Most of the remaining process liquid vapor contacts surfaces 
defining the passage and condenses thereon to drip back into the bath. 
In accordance with another unique aspect of the invention, ultrasound waves 
are propagated through the liquid bath to act upon by agitating the 
immersed particles and thereby increase the rate at which vapor evolves 
from these particles. The ultrasound waves are preferably focused with a 
focusing device immersed in the bath in the direction of the immersed 
containers to act directly upon the particles. 
In accordance with yet another aspect of the present invention, the spent 
shale particles, after leaving the bath, are directly gravity unloaded 
through a discharge passage into intimate contact with a quenching liquid, 
causing rapid cooling of the spent particles to prevent process liquid 
adhering to the surfaces of the particles from being absorbed into the 
particles. Conventional stripping techniques can then be utilized to 
recover the process liquid for replenishing the bath. Since the hot spent 
particles emit hot flammable vapors, rapid quenching minimizes the 
production of these vapors for safe retorting to occur. 
The process oil bath is maintained at a sufficient level within the retort 
housing so that the free board region above the bath has a slight 
overpressure so that shale oil vapor rapidly and positively flows from the 
retort housing through the overhead vapor outlet into the condensing unit. 
The free board region is thereby controlled to also permit primary 
refluxing action of the process oil vapors without causing a large 
quantity of these vapors to flow into the vapor outlet. 
The shale oil retorting apparatus of the present invention features a 
tilted circular conveyor including concentric inner and outer guide bands 
connected together with a plurality of radial dividers establishing the 
annular compartments. The inner band is connected to a central hub with a 
pair of hub connector plates to define a rigid circular conveyor structure 
mounted between guide blocks in sliding contact with an inner inclined 
surface of a lower base plate forming part of the retort housing. The hub 
is mounted for rotation on an inclined shaft rotatably mounted at opposite 
ends thereof to the housing using exterior main carrier bearings. A 
variable speed motor connected via a shaft and a bevel gearing arrangement 
provides continuous drive to the conveyor. 
The upper main carrier bearing is mounted to an inclined cover plate 
forming an upper portion of the retort housing. The cover plate is easily 
removed to provide access to the conveyor for maintenance and repair. An 
inner inclined surface of the cover plate also provides a large inclined 
surface within the housing against which primary refluxing action occurs. 
The base plate supporting the circular conveyor is formed with a discharge 
opening adjacent and downstream the feed location through which spent 
shale particles fall by gravity into a quenching tank through a discharge 
chute. Most of the process oil in the compartments flows along the lower 
base plate for recapture in the liquid bath before the compartments pass 
over the discharge opening. Secondary recovery of process liquid coating 
the particles quenched in the tank occurs using conventional steam or 
solvent stripping techniques. To obtain tertiary recovery of the process 
oil dripping down inner surfaces of the discharge chute, a lower section 
of the chute is formed with a perforated portion through which the 
dripping oil passes out of the chute into an annular collection chamber. 
A series of deflecting fingers located immediately above the annular 
perforated portion in the discharge chute deflect spent shale particles 
towards the center of the flow path to prevent collision thereof with the 
perforated portion. 
Additional objects, advantages and novel features of the invention will be 
set forth in part in the description which follows and in part will become 
apparent to those skilled in the art upon examination of the following 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 
appended claims.

BEST MODE FOR CARRYING OUT THE INVENTION 
The present invention concerns a novel process and retort design and system 
to evolve shale oil vapor from oil shale particles by immersion of the 
particles in a heated process oil bath. As will be seen in greater detail 
below, the invention features a unique retort housing and a tilted 
circular conveyor therein enabling continuous loading, dipping of shale 
particles into a process liquid bath in the retort housing, and unloading 
of the spent particles from the housing in a continuous feed manner that 
allows for high speed and volume production of shale oil output. The 
process oil forming the liquid bath is unique and cooperates with the 
interior of the retort design to rapidly evolve oil vapor from the 
particles in a non-airtight, atmospheric pressure environment that 
maximizes safety by minimizing the possibility of explosions. 
1. Brief Overview of the Retorting System 
Referring to FIGS. 1 and 2, retorting system 10 of the present invention 
comprises a retort housing 12 containing a process liquid bath 14 and a 
tilted circular conveyor 16 having a series of annular compartments 18 
continuously driven by motor 20 for rotation about an inclined drive shaft 
22. Raw shale particles 24 are loaded into compartments 18 passing beneath 
a feed chute 26 for immersion into intimate contact with bath 14. The 
liquid bath 14 is heated and maintained with heater tubes 28 at a 
sufficient temperature and for a time sufficient to evolve shale oil vapor 
from the immersed particles in the unique manner set forth below. 
As the shale oil vapor rises from bath 14 through freeboard region 30, it 
exits housing 12 through an overhead vapor outlet 32 and flows under 
positive pressure through a condenser pipe 34 into a condenser 36 where it 
enters a series of coiled conduits 38 water cooled with circuit 40. In 
condenser 36, the vapor releases its latent heat of vaporization. The 
condensed product shale oil then passes from condenser 36 through outlet 
pipe 42 for storage within collection tank 44. 
As will be seen more fully below, the annular compartments 18 are supported 
for travel about shaft 22 on an inclined base plate 46 of housing 12. The 
base plate 46 is formed with a discharge opening 48, as best depicted in 
FIG. 3, located adjacent the feed location established by chute 26. Thus, 
as compartments 18 containing now spent particles 24' rotate upwards out 
of bath 14, they sequentially pass over discharge opening 48 where the 
spent particles are unloaded from the retort housing 12 into a discharge 
chute 50 having side body members 52 establishing an exit flow path 54 for 
the spent particles 24'. 
As compartments 18 exit bath 14, most of the process liquid in intimate 
contact with the particles drains out of the compartments and flows back 
along the inner surface of base plate 46 to replenish the bath. To effect 
secondary recovery of process liquid still coating the spent particles 
24', these particles are introduced through chute 50 and tertiary recovery 
unit 50' (discussed infra) into a water quench tank 55 where the hot 
porous particles are rapidly cooled to prevent the process liquid coating 
from being absorbed into the pores of the particles. By utilizing 
conventional steam or solvent stripping techniques, this coating is 
recovered to replenish bath 14. The stripped spent particles are then 
conveyed into a waste container/hopper 57 through auger 59 and discharge 
chute 60 for metering through star valve 62 for disposal or subsequent 
use. One such use can be supply of spent shale particles as a charge for a 
fluidized bed combusion apparatus 64 utilized to supply heat to heater 
tubes 28. 
2. Retort and Conveyor Apparatus 
Retort housing 12 is formed of side body members 70, end member 72 and body 
member 74 welded or otherwise secured together and to inclined base plate 
46 to establish a bottom tapered housing portion containing bath 14. The 
top portion of housing 12 includes a first top body member 76 overlying 
bath 14 and a second top body member 78 formed with an opening through 
which passes chute 26. An inclined cover plate 80 extends between top 
members 76, 78 and is secured to the housing 12 with cover bolts 82 to 
provide access to the conveyor 16 for maintenance and repair. The cover 
plate 80 extends parallel to inclined base plate 46 establishing an upper 
region of housing 12 containing conveyor 16. 
The conveyor 16 includes concentric inner and outer guide bands 84, 86 
connected together with a plurality of radial dividers 88 equispaced from 
each other, as shown in FIG. 3. The annular bands 84, 86 and dividers 88, 
preferably formed of steel, are welded or otherwise secured together to 
establish annular compartments 18. The inner band 84 is connected to a 
central hub 90 with a pair of circular hub connector plates 92 to 
establish with the hub and compartments 18 a rigid circular conveyor 
structure mounted between guide blocks 94 in sliding contact with the 
inner surface of base plate 46 (inclined at an angle of between 30.degree. 
to 60.degree., preferably 45.degree.) for rotation about shaft 22. 
The drive shaft 22 is rotatably mounted at opposite ends thereof to base 
plate 46 and cover plate 80 with upper and lower main carrier bearings 95 
as best shown in FIG. 5. Each main carrier bearing 95 includes a bushing 
97 and a thrust bearing 99 mounted outside the housing within a threaded 
cover 100 which can be easily removed to service the carrier bearings. A 
tension nut 102 is provided within each carrier bearing 95 to tighten 
thrust bearings 99 as is occasionally necessary during normal use and 
wear. Shaft 22 further includes splines 104 in contact with the conveyor 
hub to impart rotational movement to the hub. 
Variable speed motor 20 includes an output shaft 106 carrying a bevel gear 
108 in meshing contact with a driven bevel gear 111 mounted on a shaft 112 
located outside housing 12. The motor 20 is supported outside housing 12 
on bracket mounts 114 while shaft 106 is supported outside cover plate 80 
on suitable brackets 116 containing journals 116a. To transmit drive from 
the driven bevel gear 110 to conveyor shaft 22, the shaft 112 is connected 
via roller bearings 118 to a driven shaft 120 rotatably mounted in cover 
plate 80 with bushing 122 supported within bushing retainer 124 secured to 
the cover plate by flange 126 and nuts 128. Shaft 120 extends into the 
interior of housing 12 and carries at its lower end thereof a drive gear 
130 in meshing contact with driven gear 132 fixed to the conveyor hub with 
keys 134. 
The tilted circular conveyor 16 in cooperation with retort housing 12 
provides numerous advantages over other retorting systems of which we are 
aware. For example, conveyor 16 enables retorting to occur as a continuous 
feed process to achieve high volume through-put and processing of raw 
shale particles 24 due to the continuous feeding of raw shale particles 
into compartments 18 through the feed hopper and chute 26. A star valve 
110 can be provided within chute 26 to prevent the gravity fed particles 
from jamming within the chute. Furthermore, gravity loading of 
compartments 18 in the aforesaid manner tends to maintain the integrity of 
the particles by minimizing the production of fines as likely to occur 
when the shale particles are fed directly into the retort by augering. In 
addition, by locating the main carrier bearings and the bevel gear/shaft 
connecting arrangement outside housing 12, the number of moving parts 
likely to be adversely affected by the relatively hostile environment 
within the housing is kept to a minimum, avoiding costly maintenance and 
down time. 
In operation, compartments 18 are only partially filled to approximately 
50% capacity. This allows gentle tumbling action of the particles within 
the compartments to occur as the compartments slide along base plate 46 
for immersion into bath 14. This tumbling action achieved with the 
circular conveyor design has a beneficial effect in increasing the rate at 
which kerogen molecules are released from the shale particle matrix for 
increased production of shale oil vapor. 
The liquid bath 14 which is discussed extensively below is maintained at a 
temperature of between 500.degree. F. to 1000.degree. F., and preferably 
between 700.degree. F. to 750.degree. F. The shale particles remain 
immersed in the liquid bath for a residence time period between about 0.5 
and 6 minutes depending upon the particle size. As the particles 24 in 
compartments 18 are immersed into intimate contact with the process oil 
bath, heat flows into the particles from the process oil causing the 
kerogen molecules to release from the particles in first a liquid, then 
rapidly vaporized state. These vapors pass through the mineral matrix of 
the shale particles into the bath as small bubbles that rise rapidly to 
the surface. These `bubbles` protect the majority of the kerogen vapor 
molecules from contact with the hotter process oil resulting in a very 
small production of gas as compared to gas operated retorts. 
Upon reaching the surface of bath 14, the bubbles collapse, releasing their 
vapor into freeboard region 30 whereupon the vapor rapidly ascends and 
passes out of housing 12 through overhead vapor outlet 32 for condensation 
in condenser 36. 
The high processing oil temperatures mentioned above tend to cause 
vaporization of some of the process oil which escapes into freeboard 
region 30 with the lighter shale oil vapors. If refluxing of these heavier 
process oil vapors does not occur an explosion within the retort may 
result particularly if the oil vapors within the free board region come 
into contact with oxygen at high temperatures within the retort. 
To minimize the possibility of explosions without requiring the use of 
expensive seals to maintain an air-tight environment within the retort as 
disclosed in the prior Everman patent discussed supra, the freeboard 
region 30 is constructed so that natural refluxing and dropwise 
condensation of the heavier process oil vapors occurs against inner 
surfaces of top members 76, 78 and particularly inclined cover plate 80, 
allowing the condensed process oil to drip back into bath 14. In the event 
that some of the heavy process oil vapors escape from the retort housing 
into overhead vapor outlet 32, secondary refluxing action occurs by 
constructing condenser pipe 34 with a vertical riser section 34a mounted 
between the vapor outlet and condenser pipe. Thus, as the heavy process 
oil vapors pass through the riser section 34a, some of these vapors tend 
to contact the large inner cylindrical surface of the riser, condensing 
thereon, to flow back into bath 14. 
The aforesaid primary and secondary refluxing action occurring in retort 
housing 12, in cooperation with overhead outlet 40 allowing the shale oil 
vapor to flow quickly from freeboard region 30 to condenser 36, minimizes 
the quantity of flammable vapors within the freeboard region to prevent 
explosions. By refluxing the heavier process oil vapors as aforesaid, it 
has been determined by experimentation that the product shale oil 
collected within collection tank 44 contains less than 5% of process oil 
condensate, and typically 1 to 3%, providing a superior quality product 
shale oil while minimizing the need to replenish the amount of process oil 
in bath 14. 
The amount of freeboard region 30 within retort housing 12 should be 
sufficient to provide approximately 1/2 to 1 p.s.i of overpressure 
relative to the ambient pressure within condenser pipe 34 to allow a 
positive pressure flow of shale oil vapor to condenser 36. Further, if 
freeboard region 30 is too large, sufficient vapor pressure cannot develop 
within the freeboard region which inhibits refluxing and increases the 
likelihood of explosion. If freeboard region 30 is too small, an 
excessively large vapor overpressure within the region tends to drive the 
process oil vapor through outlet 32 which also increases the possibility 
of explosions and disadvantageously results in a higher percentage of 
process oil distillate mixed in with the product shale oil. To provide a 
proper amount of freeboard region 30, it has been determined by 
experimentation that a sufficient quantity of process oil must be present 
in bath 14 so that the ratio of the diameter of circular conveyor 16 to 
the headspace between the surface of the bath to top body member 76 (and 
between the conveyor and cover plate 80) is in the range of approximately 
4:1 to 8:1, and preferably 6:1. 
To maintain the proper level of process oil within bath 14, a process oil 
level float indicator 120a can be provided together with an oil reservoir 
122 and manual valve, 124. 
To further minimize the possibility of explosion within retort housing 12, 
a CO.sub.2 line 128 connected to CO.sub.2 supply 130 can be provided to 
inject CO.sub.2 into freeboard region 30 in the event that flames are 
detected within the housing through viewing window 132. 
3. Liquid Process Oil Bath 
In accordance with a unique feature of both the method and apparatus of the 
present invention, it has been discovered that substantial advantages are 
obtained when using a heavy process oil that generates a vapor within 
freeboard region 30 which is considerably heavier than the shale oil vapor 
evolved from shale particles 24 and therefore conducive to refluxing. The 
process oil is of high viscosity and has a lower condensation point than 
the shale oil vapor to assist in the refluxing action, while possessing a 
high flash point to avoid auto-ignition and minimize the possibility of 
explosion. 
To obtain the foregoing advantages and other advantages discussed infra, it 
has been determined that a process oil that satisfies these criteria 
should preferably have an SUS viscosity at 100.degree. F. of about 3000 to 
6000, a specific gravity of about 16 to 18 API, a pour point of about 
25.degree. to 35.degree. F., a flash point of about 450.degree. to 
525.degree. F., a viscosity of about 175 to 225 SUS at 210.degree. F. and 
an ISO viscosity grade of about 950 to 1050. A specific oil in the 
preferred embodiment is Mobil Viscolite Oil SS, available from Mobil Oil 
Corporation, which has a specific gravity of about 17.7 API, a pour point 
of about 30.degree. F., a flash point of about 485.degree. F., a viscosity 
of about 5000 SUS at 100.degree. F., a viscosity of about 198 SUS at 
210.degree. F., and an ISO viscosity grade of about 1000. 
In addition to satisfying the foregoing criteria, a heavy process oil 
having characteristics within the above range also reduces the production 
of water that tends to be generated by the breakdown of alcohols within 
the shale during the retorting process, as likely to occur when lighter 
process oils are employed such as certain types of heavy gear grease and 
oil derived from shale. 
4. Ultrasound Wave Generation 
It has also been discovered that propagation of ultrasound waves through 
bath 14 considerably reduces the resident time required to evolve shale 
oil vapor within retort 10. As shown in FIG. 2, ultrasound waves can be 
propagated through bath 14 in the direction of immersed compartments 18 by 
an ultrasound emitting probe or horn 150 connected to an ultrasound 
generator 152 mounted on housing 12 outside bath 14. To prevent the 
piezo-electric transducer (not shown) within horn 150 from burning out 
when exposed to the hot process oil temperatures in excess of 700.degree. 
F., a water or antifreeze cooling circuit (also not shown) can be 
employed. 
As best understood, propagation of ultrasound waves through bath 14 in a 
frequency range of approximately 10,000 to 1,000,000 Hertz causes rapid 
vibration of each individual particle 24 to occur which, in cooperation 
with the intense heat conditions prevailing in the bath, causes a rapid 
breakdown in the bonds that hold the kerogen molecules in the mineral 
matrix. This vibration is freely permitted by virtue of only filling each 
compartment 18 with particles 24 to about 50% capacity, as discussed 
above. In one experiment, a decrease in residence time from about 3 
minutes (no ultrasound) to about 45 seconds (application of ultrasound was 
observed) when retorting was carried out on shale particles of about 1/2 
inch to 2 inches in size. 
Another benefit obtained with ultrasound, as best understood, is that the 
ultrasound waves tend to maintain the pores of the shale particles open to 
the particle surfaces, providing numerous exit passages for the kerogen 
vapor to release from the particles. This cleansing action is achieved 
with ultrasound by preventing minute shale particles from flaking off the 
pore walls and remaining clogged in the pores. Ultrasound waves also tend 
to collapse the kerogen vapor bubbles as they form within bath 14 to 
produce smaller bubbles that rapidly cool when they reach the bath surface 
and burst, resulting in a lower ambient temperature within freeboard 
region 30 to reduce the possibility of auto-ignition of flammable vapors. 
It has been discovered that Viscolite SS and similar process oils discussed 
supra are uniquely suited for propagation of ultrasound waves during the 
retorting process because of their highly viscous nature which resists the 
tendency of the process oil to gassify. If applied through a lighter grade 
process oil, agitation of the oil (i.e., molecules) would tend to produce 
an unsafe amount of process oil vapor within freeboard region 30. To 
propagate ultrasound waves through Viscolite SS, bath temperatures in the 
range of about 710.degree. F. to 720.degree. are preferred. 
5. Discharge of Spent Shale Particles From The Retort Housing 
As mentioned briefly above, as compartments 18 containing spent particles 
24' (i.e., oil shale that has been retorted) rotate upwards out of bath 
14, they sequentially pass over discharge opening 48 where the spent 
particles are unloaded into discharge chute 50 for immediate quenching 
within tank 55. This quenching action, apart from facilitating employment 
of steam or solvent stripping techniques to recover process oil coating 
the particles for replenishing bath 14, also serves to rapidly cool the 
hot particles which emit flammable vapors within chute 50 while the 
particles are still hot. Thus, immediate quenching of the hot particles 
serves a dual purpose and minimizes the possibility of explosions from 
occuring within discharge chute 50. 
As the hot particles fall by gravity through chute 50 into the quench tank, 
some of the process oil coating these particles tends to run down along 
the inner surfaces of side body members 52 towards the quench tank. To 
effect tertiary recovery of this process liquid, recovery unit 50' is 
mounted to the lower end of chute 50 via flanges 162. The unit 50' which 
can also be formed of side body members similar to members 52, has a lower 
discharge end 166 establishing a continuous flow path with path 54 in 
chute 50 for directing spent particles 24' directly into the quench tank. 
Between flanges 162 and discharge end 166 is an annular perforated portion 
167 formed within the side body members of recovery unit 50'. As the 
process oil drips down along the inner surfaces of discharge chute 50, 
this oil tends to drain through the perforations formed in the side body 
members of the recovery unit for collection within an annular collection 
chamber 170 surrounding the perforated portion. From chamber 170, the 
recovered process oil flows by gravity through pipe 172 into recovery tank 
174 to ultimately replenish bath 14. 
To prevent the shale particles 24' from colliding with the relatively 
fragile perforated portion 167 of recovery unit 50' as the particles 
rapidly descend through flow path 54, a series of deflection fingers 175 
are peripherally mounted to the inner surface of the side body members 
above the perforated portion and project into the flow path. These fingers 
175 thus channel particles 24' towards the center of the flow path to 
avoid collision with the perforated portion. 
As mentioned above, bath 14 is maintained at a desirable level to promote 
refluxing action as well as establishing a slight overpressure (1/2 to 1 
p.s.i.) within free board region 30 creating a positive pressure flow of 
shale oil vapors from the free board into condenser pipe 34. To prevent 
these shale oil vapors from entering discharge chute 50, a CO.sub.2 
overpressure injection valve 180 is provided preferably within the upper 
portion of discharge chute 50. By utilizing appropriate pressure sensors 
or other suitable means to monitor the pressure differential between the 
upper region of free board region 30 (i.e., proximate discharge opening 
48) and the ambient pressure within chute 50, injection valve 180 can be 
actuated to discharge CO.sub.2 gas into the chute to prevent shale oil 
vapor from entering therein. 
6. Other Aspects of the Invention 
During the retorting process, fine shale particles entering bath 14 from 
immersed compartments 18 gradually accummulate as sludge within the bottom 
tapered portion of housing 12. To periodically remove this sludge, a valve 
182 can be opened so that the sludge flows into sludge container 184 
through pipe 186. By opening outlet valve 188, the sludge can be supplied 
to a centrifugal separator 190 that will separate the shale fines from the 
process liquid in the sludge. This recovered process liquid can be used to 
replenish bath 14. The shale fines can be supplied to fluidized bed 
combusion apparatus 64 as fuel. 
To prevent shale particles 24 from tumbling out of compartments 18 during 
rotation about the inclined axis of shaft 22, a screen or other suitable 
structure (not shown) can be mounted within housing 12 to cover the 
compartment openings except at the feed location in alignment with chute 
26. 
As mentioned briefly above, star valve 110 within chute 26 prevents the 
gravity fed particles 24 from jamming within the chute. As shown in FIG. 
1, star valve 110 is fixed to a drive shaft 110a that can be powered by 
variable speed motor 20 through appropriate reduction gearing (not shown) 
to continuously rotate the star valve. Preferably, however, a separate 
variable speed motor (not shown) mounted upon housing 12 provides direct 
drive to output shaft 110a avoiding the need to synchronize rotation of 
the star valve with rotation of conveyor 16. 
Condenser unit 36 is capable of condensing virtually all of the evolved 
shale oil vapor entering conduits 38 for supply in liquid form to product 
oil collector 44. However, in the event that some of the shale oil enters 
the product collector in vapor form, a riser pipe 190 receiving these 
vapors includes a cooling circuit 192 to assure that these vapors are 
completely condensed. 
The foregoing description of a preferred embodiment of the retorting system 
and method of the present invention has been presented for purposes of 
illustration and description. It is not intended to be exhaustive or to 
limit the invention to the precise form disclosed, and obviously, many 
modifications and variations are possible in light of the above teachings. 
For example, although not shown in the drawing, vapor outlet opening 32 is 
preferably formed in the top body plate 78 in vertical axial alignment 
with riser section 34a to provide a direct exit flow path for shale oil 
vapors passing to condenser pipe 34. The embodiment was chosen and 
described in order to best explain the principles of the invention and its 
practical application to thereby enable others skilled in the art to best 
utilize the invention in various embodiments and with various 
modifications as are suited to the particular use contemplated. It is 
intended that the scope of the invention be defined by the claims appended 
hereto.