Multiple stage desalting and dedusting process

A process is provided to dedust oil derived from solid hydrocarbon-containing material, such as oil shale, coal or tar sand in multi-stage desalters. In the process, water is dispersed into the oil before entering each desalter to form an emulsion. The desalter separates the emulsion into a stream of oil having a substantially lower concentration of dust and a dusty stream of water containing most of the dust. In one embodiment, the sludge-like dusty stream from the first desalter is combusted in a lift pipe and used as heat carrier material in the retort. In other embodiments, the dusty stream from the first desalter is centrifuged or filtered and thereafter heated in a dryer to remove residual oil and water from the stream before the stream is combusted in the lift pipe and used as heat carrier material in the retort and dryer. Effluent water from the second and third desalters as well as from the centrifuge or filter are recycled upstream and dispersed in the oil.

BACKGROUND OF THE INVENTION 
This invention relates to synthetic fuels, and more particularly, to a 
process for dedusting oil laden with dust derived from solid, 
hydrocarbon-containing material such as oil shale, coal and tar sand. 
Researchers have now renewed their efforts to find alternate sources of 
energy and hydrocarbons in view of recent rapid increases in the price of 
crude oil and natural gas. Much research has been focused on recovering 
hydrocarbons from solid hydrocarbon-containing material such as oil shale, 
coal and tar sand by pyrolysis or upon gasification to convert the solid 
hydrocarbon-containing material into more readily usable gaseous and 
liquid hydrocarbons. 
Vast natural deposits of oil shale found in the United States and elsewhere 
contain appreciable quantities of organic matter known as "kerogen" which 
decomposes upon pyrolysis or distillation to yield oil, gases and residual 
carbon. It has been estimated that an equivalent of 7 trillion barrels of 
oil are contained in oil shale deposits in the United States with almost 
sixty percent located in the rich Green River oil shale deposits of 
Colorado, Utah and Wyoming. The remainder is contained in the leaner 
Devonian-Mississippian black shale deposits which underlie most of the 
eastern part of the United States. 
As a result of dwindling supplies of petroleum and natural gas, extensive 
efforts have been directed to develop retorting processes which will 
economically produce shale oil on a commercial basis from these vast 
resources. 
Generally, oil shale is a fine-grained sedimentary rock stratified in 
horizontal layers with a variable richness of kerogen content. Kerogen has 
limited solubility in ordinary solvents and therefore cannot be recovered 
by extraction. Upon heating oil shale to a sufficient temperature, the 
kerogen is thermally decomposed to liberate vapors, mist, and liquid 
droplets of shale oil and light hydrocarbon gases such as methane, ethane, 
propane, and propene, as well as other products such as hydrogen, 
nitrogen, carbon dioxide, carbon monoxide, ammonia, steam and hydrogen 
sulfide. A carbon residue typically remains on the retorted shale. 
Shale oil is not a naturally occurring product, but is formed by the 
pyrolysis of kerogen in the oil shale. Crude shale oil, sometimes referred 
to as "retort oil," is the liquid oil product recovered from the liberated 
effluent of an oil shale retort. Synthetic crude oil (syncrude) is the 
upgraded oil product resulting from the hydrogenation of crude shale oil. 
The process of pyrolyzing the kerogen in oil shale, known as retorting, to 
form liberated hydrocarbons, can be done in surface retorts in aboveground 
vessels or in situ retorts underground. In principle, the retorting of 
shale and other hydrocarbon-containing materials, such as coal and tar 
sand, comprise heating the solid hydrocarbon-containing material to an 
elevated temperature and recovering the vapors and liberated effluent. 
However, as medium grade oil shale yields approximately 25 gallons of oil 
per ton of shale, the expense of materials handling is critical to the 
economic feasibility of a commercial operation. 
In surface retorting, oil shale is mined from the ground, brought to the 
surface, crushed and placed in vessels where it is contracted with a hot 
heat transfer carrier, such as ceramic or metal balls, hot spent shale or 
sand for heat transfer. The resulting high temperatures cause shale oil to 
be liberated from the oil shale leaving a retorted, inorganic material and 
carbonaceous material such as coke. The carbonaceous material can be 
burned by contact with oxygen at oxidation temperatures to recover heat 
and to form a spend oil shale relatively free of carbon. Spent oil shale 
which has been depleted in carbonaceous material is removed from the 
reactor and recycled as heat carrier material or discarded. The combustion 
gases are dedusted in a cyclone or electrostatic precipitator. 
Some well-known processes of surface retorting are: N-T-U (Dundas Howes 
retort), Kiviter (Russian), Petrosix (Brazilian), Lurgi-Ruhrgas (German), 
Tosco II, Galoter (Russian), Paraho, Koppers-Totzek, Fushum (Manchuria), 
gas combustion and fluid bed. Process heat requirements for surface 
retorting processes may be supplied either directly or indirectly. 
During fluid bed, moving bed and other types of surface retorting, 
decrepitation of oil shale occurs creating a popcorning effect in which 
particles of oil shale collide with each other and impinge against the 
walls of the retort forming substantial quantities of minute entrained 
particulates of shale dust. The use of hot spent shale or sand as heat 
carrier material aggravates the dust problem. Rapid retorting is desirable 
to minimize thermal cracking of valuable condensable hudrocarbons, but 
increases the rate of decrepitation and amount of dust. Shale dust is also 
emitted and carried away with the effluent product stream during modified 
in situ retorting as a flame front passes through a fixed bed of rubblized 
shale, as well as in fixed bed surface retorting, but dust emission is not 
as aggravated as in other types of surface retorting. 
Shale dust ranges in size from less than 1 micron to 1000 microns and is 
entrained and carried away with the effluent product stream. Because shale 
dust is so small, it cannot be effectively removed to commercially 
acceptable levels by conventional dedusting equipment. 
The retorting, carbonization or gasification of coal, peat and lignite and 
the retorting or extraction of tar sand and gilsonite create similar dust 
problems. 
After retorting, the effluent product stream of liberated hydrocarbons and 
entrained dust is withdrawn from the retort through overhead lines and 
subsequently conveyed to a separator, such as a single or multiple stage 
distillation column, quench tower, scrubbing cooler or condenser, where it 
is separated into fractions of light gases, light oils, middle oils and 
heavy oils with the bottom heavy oil fraction containing essentially all 
of the dust. As much as 50% by weight of the bottom heavy oil fraction 
consists of dust. 
It is very desirable to upgrade the bottom heavy oil into more marketable 
products, such as light oils and middle oils, but because the heavy oil 
fraction is laden with dust, it is very viscous and cannot be pipelined. 
Dust laden heavy oil plugs up hydrotreaters and catalytic crackers, gums 
up valves, heat exchangers, outlet orifices, pumps and distillation 
towers, builds up insulative layers on heat exchange surfaces reducing 
their efficiency and fouls up other equipment. Furthermore, the dusty 
heavy oil corrodes turbine blades and creates emmission problems. If used 
as a lubricant, dusty heavy oil is about as useful as sand. Moreover, the 
high nitrogen content in the dusty heavy oil cannot be refined with 
conventional equipment. 
In an effort to solve this dust problem, electrostatic precipitators have 
been used as well as cyclones located both inside and outside the retort. 
Electrostatic precipitators and cyclones, however, must be operated at 
very high temperatures and the product stream must be maintained at or 
above the highest temperature attained during the retorting process to 
prevent any condensation and accumulation of dust on processing equipment. 
Maintaining the effluent stream at high temperatures is not only expensive 
from an energy standpoint, but it allows detrimental side reactions, such 
as cracking, coking and polymerization of the effluent product stream, 
which tends to decrease the yield and quality of condensable hydrocarbons. 
Over the years various processes and equipment have been suggested to 
decrease the dust concentration in the heavy oil fraction and/or upgrade 
the heavy oil into more marketable light oils and medium oils. Such prior 
art dedusting processes and equipment have included the use of cyclones, 
electrostatic precipitators, pebble beds, scrubbers, filters, electric 
treaters, spiral tubes, ebullated bed catalytic hydrotreaters, desalters, 
autoclave settling zones, sedimentation, gravity settling, percolation, 
hudrocloning, magnetic separation, electrical precipitation, stripping and 
binding, as well as the use of diluents, solvents and chemical additives 
before centrifuging. Typifying those prior art processes and equipment and 
related processes and equipment are those found in U.S. Pat. Nos. 
2,235,639; 2,717,865; 2,719,114; 2,723,951; 2,793,104; 2,879,224; 
2,899,736; 2,904,499; 2,911,349; 2,952,620; 2,968,603; 2,982,701; 
3,008,894; 3,034,979; 3,058,903; 3,252,886; 3,255,104; 3,468,789; 
3,560,369; 3,684,699; 3,696,021; 3,703,442; 3,784,462; 3,799,855; 
3,808,120; 3,900,389; 3,901,791; 3,929,625; 3,974,073; 3,990,885; 
4,028,222; 4,040,958; 4,049,540; 4,057,490; 4,069,133; 4,080,285; 
4,088,567; 4,105,536; 4,151,073; 4,159,949; 4,162,965; 4,166,441; 
4,182,672; 4,199,432; 4,220,522; 4,226,690; 4,230,557; and 4,246,093 as 
well as in the articles by Rammler, R. W., The Retorting of Coal, Oil 
Shale, and Tar Sands by Means of Circulated Fine-Grained Heat Carriers as 
a Preliminary Stage in the Production of Synthetic Crude Oil, Volume 65, 
Number 4, Quarterly of the Colorado School of Mines, Pages 141-167 
(October 1970) and Schmalfed, I. P., The Use of the Lurgi/Ruhrgas Process 
for the Distillation of Oil Shale, Volume 70, Number 3, Quarterly of the 
Colorado School of Mines, pages 129-145 (July 1975). These prior art 
processes and equipment have not been successful in decreasing the dust 
concentration in the heavy shale oil fraction to commercially acceptable 
levels. 
Single and two stage desalters have been used for many years to desalt 
crude oil. Crude oil as it is received at the refinery averages about 
0.25% basic sediment and water with salt contents from 3 ptb (pounds per 
thousand barrels of crude) to 200 ptb. As originally applied, desalting 
meant removal of about 90% of the chlorides of sodium, calcium and 
magnesium, collectively referred to as "brine," in the salty connate water 
which if not removed would produce hydrogen chloride and ultimately 
hydrochloric acid in refinery equipment at about 250.degree. F. Although 
the term is still the same, desalting now broadly refers to eliminating a 
variety of contaminants in crude oil, including sulfates. Two stage 
desalting can remove as much as 99% of the salt in connate water. 
Desalting also removes from 50% to 75% of the inorganic sediment is crude 
oil, namely, fine particles of sand, clay, volcanic ash, drilling mud, 
rust, iron sulfide, metal and scale. Arsenic and iron contained in organic 
sediment in crude oil are also removed and decreased by the desalter to 
tolerable limits. Other trace metals in crude oil, such as vanadium, 
nickel, aluminum, barium and copper are removed to a much lesser extent. 
Conventional desalting is described in Waterman, L. C., Theories and 
Benefits of Desalting, Tech. 64-37, National Petroleum Refiners 
Association (1964); Congram, G. E., Refiners Zero In on Better Desalting, 
Oil and Gas Journal, pages 153-154 (Dec. 30, 1974); Smith, R. S., How to 
Calculate Rapidly for Two-Stage Desalting, Oil and Gas Journal Sept. 30, 
1974); Frazier A. W., Optimized Two-Stage Desalting of Crude Oil, M75-79, 
Research and Development Department, Amoco Oil Company (1975); and 
Two-Stage Desalting of Crude Oil and Its Economic Justifications, Petreco 
Division, Petrolite Corporation, containing Fisher, L. E., et al., Crude 
Oil Desalting, reprinted from Vol. 1, No. 5, Materials Protection pages 
8-11 and 14-17 (May 1962), Petreco Crude Oil Desalting and Waterman, L. 
C., Crude Desalting: Why and How, Hydrocarbon Processing and Petroleum 
Refiner (February 1965). 
Attempts have been made to dedust shale oil in a single stage desalter with 
limited success. 
It is therefore desirable to provide an improved process, which overcomes 
most, if not all, of the preceding problems. 
SUMMARY OF THE INVENTION 
An improved process is provided which utilizes multi-stage desalters to 
dedust oil derived from solid hydrocarbon-containing material such as oil 
shale, coal or tar sand, into one or more purified (dedusted) streams of 
oil. Advantageously, the dedusted oil can be safely pipelined through 
valves, outlet orifices, pumps, heat exchangers and distillation columns 
and can be refined in hydrotreaters and catalytic crackers. 
The oil can be derived from in situ retorting or surface retorting, such as 
in a fluid bed retort or screw conveyor retort where hot spent 
hydrocarbon-containing material is used as heat carrier material to retort 
raw oil shale, coal or tar sand, and in which the retorted effluent 
product stream is processed in a single or multiple stage separator, such 
as one or more quench towers, scrubbers, condensors or distillation 
columns, sometimes referred to as "fractionating columns" or 
"fractionators," into a whole oil fraction or heavy oil fraction laden 
with particulates of dust derived from the solid hydrocarbon-containing 
material. Typically, the whole oil fraction contains from 10% to 15% by 
weight dust and the heavy oil fraction, which is from 15% to 35% by weight 
of the effluent product stream, contains as much as 25% to 50% by weight 
dust. 
In the novel process, from 10% to 50% and preferably a maximum of 30% by 
volume water is dispersed in and mixed with dust laden oil to form an 
emulsion. The emulsion is separated in a first desalter into a purified 
(dedusted) stream of oil containing from 1500 ppm (parts per million) 
(0.15%) to 15,000 ppm (1.5%) by weight dust leaving a residual stream or 
sludge that contains from 39% to 76% by weight water, from 23% to 60% by 
weight dust and from 0.5% to 1% by weight oil as well as trace amounts of 
arsenic and other metals. When dust laden whole oil is dedusted, the dust 
laden whole oil is fed to the desalter at a temperature from 100.degree. 
F. to 250.degree. F. and preferably from 150.degree. F. to 200.degree. F. 
with the desalter operated at above atmospheric pressure to minimize 
vaporization of the water. Where dust laden heavy oil is dedusted, the 
dust laden heavy oil is fed to the desalter at a temperature from 
240.degree. F. to 350.degree. F. and at a viscosity of 2 centistokes to 5 
centistokes with the desalter operated at a pressure from 25 psia to 135 
psia to mimimize vaporization of the water. 
The purified stream of oil can be further dedusted in a second desalter, 
after from 2% to 7% and preferably from 3% to 5% by volume water is 
dispersed with and mixed with the purified stream to form a second 
emulsion. In the second desalter, the second emulsion is separated into a 
second purified (dedusted) stream of oil containing 15 ppm (0.0015%) to 
1500 ppm (0.15%) and preferably about 100 ppm (0.01%) by weight dust 
leaving a stream of water that has a much lower concentration of dust than 
the dust laden residual stream of water discharged from the first 
desalter. The effluent stream of water from the second desalter is 
recycled upstream of the first desalter for use in emulsifying the 
influent dust laden oil. 
The second stream of oil can be further dedusted in a third desalter, after 
from 2% to 7% and preferably from 3% to 5% by volume water is dispersed in 
and mixed with the second purified stream to form a third emulsion. In the 
third desalter, the third emulsion is separated into a third purified 
(dedusted) stream of oil containing 15 ppm (0.0015%) to 150 ppm by weight 
dust leaving a residual stream of water that has a lower concentration of 
dust than the effluent residual stream of water from the second desalter. 
The residual stream of water from the third desalter is recycled upstream 
of the second desalter for use in emulsifying the second purified stream 
of oil. 
The desalters can be electrical or chemical desalters and are each preceded 
by a mixing valve or emulsifier valve that disperses the water in the oil 
into enormous quantities of minute droplets from 0.00005 to 0.0005 inches 
in diameter to greatly increase the surface area so as to promote 
dedusting. The desalters lower the dust content of the oil by stripping 
the oil from the dust, entraining the dust in water droplets and dropping 
the entrained dust as heavy clusters through the water layer to the bottom 
of the desalter. An emulsifier or surfactant such as a hydrophilic or 
wetting agent can be added to the dust laden oil to facilitate dedusting. 
An alkali such as caustic or soda ash, typically sodium hydroxide, can be 
added to the water to enhance dedusting, keep the water basic and minimize 
amine absorption. 
The desalter sludge from the first desalter can be combusted in the lift 
pipe leaving a hot spent stream for use as solid heat carrier material in 
the retort. 
Alternatively, the desalter sludge can be separated in a centrifuge or 
rotary filter into a dedusted stream of water and a centrifuge sludge 
having a higher concentration of dust than the influent desalter sludge. 
The dedusted stream of water can be recirculated upstream of any one of 
the desalters to help emulsify the oil. A flushing agent such as light oil 
derived from the solid hydrocarbon-containing material can be injected 
into the centrifuge to wash the centrifuge sludge out of the centrifuge. 
Desirably, the centrifuge sludge along with the flushing agent is heated, 
dried and separated in a dryer, such as a screw conveyor dryer, into a 
purified (dedusted) stream of oil with less than 2% to 5% by weight dust 
leaving a powdery, dust-enriched residual stream with less than 10% and 
preferably from 3% to 8% by weight oil. When heavy oil is dedusted, the 
temperature of the dryer can be controlled to coke, thermal crack and 
upgrade the heavy oil, into lighter hydrocarbons, mainly, light oil and 
middle oil. The powdery, dust-enriched residual stream can be combusted in 
the lift pipe to leave a hot spent stream for use as solid heat carrier 
material in both the dryer and retort. 
As used in this application, the term "dust" means particulates derived 
from solid hydrocarbon-containing material and ranging in size from less 
than 1 micron to 1000 microns. The particulates can include retorted and 
raw, unretorted hydrocarbon-containing material, as well as spend 
hydrocarbon-containing material or sand if the latter are used as solid 
heat carrier material during retorting. Dust derived from the retorting of 
oil shale consists primarily of calcium, magnesium oxides, carbonates, 
silicates and silicas. Dust derived from the retorting or extraction of 
tar sand consists primarily of silicates, silicas and carbonates. Dust 
derived from the retorting, carbonization or gasification of coal consists 
primarily of char and ash. 
The term "desalter" as used herein means an apparatus which is 
conventionally used for desalting petroleum (crude oil), but which is 
specifically used in this invention to dedust oil derived from solid 
hydrocarbon-containing material. 
The term "spent" residual stream as used herein means a dusty residual 
stream derived directly or indirectly via a centrifuge or filter followed 
by a dryer, in which most, if not all, of the oil and carbon residue 
contained therein has been removed by combustion. 
The term "retorted" hydrocarbon-containing material or "retorted" shale as 
used in this application refers to hydrocarbon-containing material or oil 
shale, respectively, which has been retorted to liberate hydrocarbons 
leaving an organic material containing carbon residue. 
The term "spent" hydrocarbon-containing material or "spent" shale as used 
herein means retorted hydrocarbon-containing material or shale, 
respectively, from which all of the carbon residue has been removed by 
combustion. 
The terms "normally liquid," "normally gaseous," "condensible," 
"condensed," or "noncondensible" are relative to the condition of the 
subject material at a temperature of 77.degree. F. (25.degree. C.) at 
atmospheric pressure. 
A more detailed explanation of the invention is provided in the following 
description and appended claims taken in conjunction with the accompnying 
drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, a multiple stage desalting and dedusting process 
and system 10 is provided to dedust dust laden oil derived from solid 
hydrocarbon-containing material, such as oil shale, coal, tar sand, 
uintaite (gilsonite), lignite, and peat, into purified streams of oil for 
use in making synthetic fuels. While the processes of the present 
invention are described hereinafter with particular reference to the 
processing of oil shale, it will be apparent that the processes can also 
be used in connection with the processing of other hydrocarbon-containing 
materials, such as coal, tar sand, uintaite (gilsonite), lignite, peat, 
etc. 
In process and system 10, raw fresh oil shale, which preferably contains an 
oil yield of at least 15 gallons per ton of shale particles, is crushed in 
size to a maximum fluidizable size of 10 mm and fed through a raw shale 
inlet line 12 at a temperature from ambient temperature to 600.degree. F. 
into a fluid bed retort 14, also referred to as a "fluidized bed retort." 
The fresh oil shale can be crushed by conventional crushing equipment, 
such as an impact crusher, jaw crusher, gyratory crusher or roll crusher, 
and screened with conventional screening equipment, such as a shaker 
screen or a vibrating screen. 
Spent oil shale and spent residual stream, which together provide a solid 
heat carrier material, are fed through heat carrier line 18 at a 
temperature from 1000.degree. F. to 1400.degree. F., preferably from 
1200.degree. F. to 1300.degree. F., into retort 14 to mix with, heat and 
retort raw oil shale in retort 14. A fluidizing gas such as light 
hydrocarbon gases or other gases which do not contain an amount of 
molecular oxygen sufficient to support combustion, is injected into the 
bottom of retort 14 through a gas injector 20 to fluidize, entrain and 
enhance mixing of the raw oil shale and solid heat carrier material in 
retort 14. The retorting temperature of retort 14 is from 850.degree. F. 
to 1000.degree. F., preferably from 900.degree. F. to 960.degree. F. at 
atmospheric pressure. 
During retorting, hydrocarbons are liberated from the raw oil shale as a 
gas, vapor, mist, or liquid droplets and most likely a mixture thereof, 
along with entrained particulates of oil shale dust ranging in size from 
less than 1 micron to 1000 microns. 
The mixture of liberated hydrocarbons and entrained particulates are 
discharged from the upper portion of retort 14 through an outlet line 22 
and conveyed to a separator 24, such as a quench tower that is sprayed 
with light oil or water or a fractionating column. The effluent product 
stream of liberated hydrocarbons and entrained particulates are separated 
in separator 24 into fractions of light gases and normally liquid whole 
shale oil containing from 10% to 15% by weight entrained particulates of 
shale dust. Whole shale oil consists of heavy shale oil, middle shale oil 
and light shale oil. Heavy shale oil has a boiling point over 600.degree. 
F. to 800.degree. F. Middle shale oil has a boiling point over 400.degree. 
F. to 500.degree. F. and light shale oil has a boiling point over 
100.degree. F. 
The fraction of shale oil laden with dust, also referred to as a 
"particulate laden shale oil fraction" or a "dust laden shale oil 
fraction" is withdrawn from separator 24 by pump 30 and cooled in a heat 
exchanger or cooler 32 to a temperature from 100.degree. F. to 250.degree. 
F. and preferably from 150.degree. to 200.degree. F. 
Alternatively, the effluent product stream can be separated in separator 34 
(FIG. 2) into fractions of light gases, light shale oil, middle shale oil 
and heavy shale oil with the heavy shale oil containing essentially all 
the shale dust. Light gases, light shale oil, middle shale oil and heavy 
shale oil are withdrawn from separator 34 through light gas line 36, light 
oil line 38, middle oil line 40 and heavy oil line 42, respectively. The 
heavy shale oil laden with shale dust and the middle shale oil are cooled 
in heat exchangers or coolers 44 and 46, respectively, and mixed with 
light shale oil to form a whole shale oil having 10% to 15% by weight 
shale dust in whole shale oil line 48. The temperature of coolers 44 and 
46 are controlled so that the temperature of the whole oil in whole shale 
oil line 48 is from 100.degree. F. to 250.degree. F. and preferably from 
150.degree. F. to 200.degree. F. 
The effluent product stream can also be separated into fractions of light 
gases, light shale oil, middle shale oil and heavy shale oil in a multiple 
stage separator such as quench towers 50, 52 and 54 shown in FIG. 3. As 
shown in FIG. 3, the effluent product stream is separated in a first 
quench tower or scrubbing tower 50 into a heavy shale oil fraction 
containing essentially all the shale dust and a first separated stream of 
hydrocarbons. The heavy shale oil fraction is withdrawn from the bottom of 
the first quench tower 50 through heavy shale oil line 42 and cooled in 
heat exchanger or cooler 44. The first separated stream of hydrocarbons is 
withdrawn from an upper portion of the first quench tower 50 and fed to a 
second quench tower or scrubbing cooler 52 where it is separated into a 
middle shale oil fraction and a second separated stream of hydrocarbons. 
The middle shale oil fraction is withdrawn from the bottom of the second 
quench tower 52 through middle oil line 40 and cooled in a heat exchanger 
or cooler 46. The second separated stream of hydrocarbons is fed to a 
third quench tower or cooling tower 54 where it is separated into 
fractions of light gases and light oil. The light gases are withdrawn from 
an upper portion of cooling tower 54 through light gas line 36. Light oil 
is withdrawn from the bottom of cooling tower 54 through light oil line 38 
and combined with the heavy shale oil and middle shale oil to form whole 
shale oil having 10% to 15% by weight shale dust in line 48. The 
temperatures of coolers 44 and 46 are controlled so that the temperature 
of the whole oil in line 48 is from 100.degree. F. to 250.degree. F. and 
preferably from 150.degree. F. to 200.degree. F. 
Alternatively, the effluent product stream can be separated in a 
single-stage quench tower or fractionating column 24 shown in FIG. 4 (on 
the same sheet as FIG. 1) into fractions of light gases, light shale oil, 
middle shale oil and heavy shale oil in a manner similar to that described 
with respect to FIG. 2, except that only heavy shale oil is dedusted and 
used as a feed stock in the process and system of this invention. The 
heavy shale oil fraction is a slurry recovered at the bottom of separator 
24 that contains from 15% to 35% by weight of the effluent product stream 
and has from1% to 50% by weight and preferably at least 25% by weight 
entrained particulates of oil shale dust. The temperature in separator 24 
is varied from 500.degree. F. to 800.degree. F. and preferably to a 
maximum temperature of 600.degree. F. at atmospheric pressure to assure 
that essentially all the shale dust gravitate to and are entrained in the 
heavy shale oil fraction. The heavy shale oil fraction is withdrawn from 
the bottom of separator 24 through heavy oil line 42 and cooled in a heat 
exchanger or cooler 44 from 240.degree. F. to 350.degree. F. to attain a 
viscosity from 2 centistokes to 5 centistokes. 
As used hereinafter, except where otherwise specified, the term "shale oil" 
means "whole" shale oil when whole shale oil is dedusted in the processes 
and systems of this invention and means "heavy" shale oil when only heavy 
shale oil is dedusted in the processes and systems of this invention. 
After the dust laden shale oil has been withdrawn from the separator and 
cooled, water injector line 56 (FIG. 1) injects from 10% to 50% and 
preferably a maximum of 30% by volume water in the dust laden shale oil to 
form an emulsion. An emulsifier or surfactant such as a hydrophilic or 
wetting agent can be added to the dust laden shale oil before pump 30 
through additive line 58 to lower surface tension and enhance dedusting. 
An alkali such as caustic or soda ash, can be added to the water in line 
56 through alkali injector 60 at a rate from 0.01 pounds to 5 pounds of 
alkali per 1000 barrels of water to keep the water basic so as not to 
absorb amines and nitrogen and to facilitate emulsion, separation and 
dedusting as well as to enhance removal of trace metals from the shale 
oil. 
The emulsion of shale oil and water flows through emulsion line 62 to a 
mixing valve or emulsifier valve 64 where it is discharged through a 
coalescer line 66 into a first desalter 68. Alternatively, the emulsion 
can flow from coalescer line 66 to an enlarged diameter pipe, zig-zag 
shaped coalescing section 69 (FIG. 6) and second coalescer line 70 to 
further resolve the emulsion before it enters first desalter 68. The 
solids residence time in coalescer 69 is about 35 minutes. 
First desalter 68 is positoned upstream and in series with a second 
desalter 74 as shown in FIGS. 1 and 5-9. Second desalter 74 can also be 
positioned upstream and in series with a third desalter 76 as shown in 
FIGS. 7 and 8. Desalters 68, 74, and 76 can be electrical desalters or 
chemical desalters. The residence time in desalters 68, 74, and 76 is from 
0.5 minutes to 25 minutes and preferably from 6 minutes to 12 minutes. The 
pressure in desalters 68, 74 and 76 is about atmospheric pressure when 
whole shale oil is dedusted and from 25 psia to 135 psia when heavy shale 
oil is dedusted, in order to minimize vaporization of the water and oil. 
First desalter 68 breaks up and separates the first emulsion into a first 
purified, dedusted phase or stream of normally liquid shale oil containing 
from 1500 ppm (0.15%) to 15,000 ppm (1.5%) by weight shale dust and a 
particulate laden aqueous phase or water stream, also referred to as 
"first desalter sludge." First desalter 68 is also effective in removing 
significant amounts of arsenic and other trace metals from the influent 
dust laden shale oil. 
The desalter sludge is removed from the bottom of first desalter 68 through 
sludge line 70 and contains from 39% to 76% and preferably 65% by weight 
water, from 23% to 60% and preferably 34-1/3% by weight shale dust and 
from 0.5% to 1% and preferably 0.66% shale oil as well as from 0.01% to 
0.1% by weight arsenic and other trace metals. 
The effluent stream of oil is withdrawn from first desalter 68 through 
outlet line 62 and is injected with 2% to 7% and preferably from 3% to 5% 
by volume water from second water injector line 74 to form a second 
emulsion. The second emulsion flows through a second mixing valve or 
emulsifier valve 76 and then through coalescer line 78 into a second 
desalter 74. 
Second desalter 74 breaks up and separates the second emulsion into a 
second purified, dedusted phase or stream of normally liquid shale oil 
with less than 15 ppm (0.0015%) to 1500 ppm (0.15%) and preferably about 
100 ppm (0.01%) by weight shale dust and a second aqueous phase or stream 
of water having a substantially lower concentration of shale dust than the 
first desalter sludge. The second stream of water is pumped out of the 
bottom of second desalter 74 through water outlet line 80 by pump 82 and 
recycled through water recirculation line 56 upstream of first mixing 
valve 64 for dispersion into the influent dust laden oil. 
The second stream of shale oil is withdrawn from second desalter 74 through 
second outlet line 84 and passed through a heat exchanger or cooler 86 
(FIGS. 1 and 5) for further processing and upgrading. In FIG. 6, the 
second stream of shale oil is passed through a heat exchanger or cooler 86 
and fed to another separator 90 before further processing and upgrading. 
When the second stream of shale oil has a dust concentration over 150 ppm, 
such as when it is near the 1500 ppm upper end of the dust concentration 
range, the second stream of shale oil can be further dedusted in a third 
desalter 76 (FIGS. 7 and 8). In that case, the second stream of shale oil 
is withdrawn from second desalter 74 through second outlet line 84 and 
injected with 2% to 7% and preferably from 3% to 5% by volume water from 
third water injector line 92 to form a third emulsion. The third emulsion 
flows through a third mixing valve or emulsifier valve 94 and then through 
coalescer line 96 into third desalter 76. Third desalter 76 breaks up and 
separates the third emulsion into a highly purified, dedusted phase or 
stream of normally liquid shale oil having from 15 ppm (0.0015%) to 150 
ppm (0.0150%) by weight shale dust and a third aqueous phase or stream of 
water having a lower concentration of dust than the second stream of water 
from the second desalter 68. The third stream of water is pumped out of 
the bottom of third desalter 76 through third water outlet line 98 by pump 
100 and recycled through second water recirculation line 73 upstream of 
second mixing valve 76 for dispersion into the first effluent stream of 
oil. 
The highly dedusted, third purified stream of shale oil is withdrawn from 
third desalter 76 through third outlet line 102 (FIG. 7) and passed 
through a heat exchanger or cooler 104 for further processing and 
upgrading. In FIG. 8, the highly dedusted stream of oil from the third 
desalter 76 is passed through a heat exchanger or cooler 104 and fed to 
another separator 108 for further processing and upgrading. 
The heat exchangers and coolers described throughout this application can 
be cooled by light shale oil, middle shale oil, steam or water from the 
separators. Other cooling media can also be used. 
Desalter sludge from the first desalter 68 can be discharged through sludge 
line 70 and conveyed directly to the bottom portion of a vertical lift 
pipe 110 as shown in FIG. 1 by conveying means, such as a vibrating solid 
conveyor, pneumatic conveyor or screw conveyor. In FIG. 1, retorted shale 
and solid heat carrier material from retort 14 are discharged from the 
bottom of retort 14 into discharge line 112 where they are fed and mixed 
with desalter sludge in sludge line 70. Alternatively, the first desalter 
sludge can be fed to lift pipe 110 via retort 14. 
In lift pipe 110 (FIG. 1), desalter sludge, retorted shale and heat carrier 
material are fluidized, entrained, propelled and conveyed upwardly into a 
collection and separation bin 114, also referred to as a "collector," by 
air injected into the bottom of lift pipe 110 through air injector nozzle 
116. Shale oil residue in the desalter sludge and carbon residue in the 
retorted shale are combusted in lift pipe 110 to heat the fluidized 
material to a temperature from 1000.degree. F. to 1400.degree. F. and 
preferably from 1200.degree. F. to 1300.degree. F. The combusted desalter 
sludge and combusted retorted shale form a hot spent residual stream and 
hot spent oil shale, respectively, for use as solid heat carrier material 
in retort 14. 
Spent material is discharged from the bottom of separation bin 114 through 
heat carrier line 18 into retort 14. Combustion gases are withdrawn from 
the top of separation bin 114 through combustion gas line 118 and dedusted 
in a cyclone or electrostatic precipitator for discharge into the 
atmosphere or further processing. 
In FIGS. 5-9, desalter sludge is discharged from the bottom of first 
desalter 68 through sludge line 70 into a centrifuge 120, where it is 
centrifuged from 2000 rpm to 4000 rpm and preferably at 2500 rpm at a 
pressure to minimize vaporization of the residual oil in the sludge. 
Centrifuge 120 separates the desalter sludge into a purified, dedusted 
stream of water and a dewatered, dust laden residual stream, also referred 
to as "centrifuge sludge." In some circumstances it may be desirable to 
use a rotary filter or rotating filter 121 (FIG. 10 on the same sheet as 
FIG. 6) instead of centrifuge 120. Dedusted water is clear clarified 
water, also referred to as a "centrate," with less than 0.5% and 
preferably less than 0.25% by weight shale dust. Dedusted water is 
withdrawn from the upper portion of centrifuge 122 through dedusted water 
line 122 and recycled to any of the water injector lines 60, 73 or 92. For 
example, in FIGS. 6 and 8, dedusted water is recycled to first water 
injector line 56. In FIGS. 5 and 9, dedusted water is recycled to second 
water injector line 73. In FIG. 7, dedusted water is recycled to third 
water injector line 92. 
The centrifuge sludge is a cake, residue, or sediment that contains from 
60% to 80% and preferably 70% by weight shale dust with the remainder 
being residual water, shale oil residue, arsenic and other trace metals. 
In FIGS. 5-8, centrifuge sludge is discharged from centrifuge 120 into a 
screw conveyor dryer or heater 124. Light shale oil from separator 24 can 
be injected into centrifuge 120 through light oil injection line 126 to 
flush and wash out the sticky sludge from the bottom of centrifuge 120 
into screw conveyor dryer 124. 
Spent oil shale and spent residual stream, which together provide solid 
heat carrier material and the source of heat for dryer 38, are fed 
together through heat carrier line 132 into dryer 124 at a temperature 
from 800.degree. F. to 1400.degree. F. and preferably at about 
1200.degree. F. The solid feed rate ratio of centrifuge sludge to heat 
carrier material fed to dryer 124 is from 2:1 to 7:1 and preferably from 
3:1 to 5:1. 
Screw conveyor dryer 124 has twin horizontal mixing screws 128 and an 
overhead vapor collection hood 130 which provides a dust settling and 
disentrainment space. Screws 128 operate in the range from 10 rpm to 100 
rpm and preferably from 20 rpm to 30 rpm. Dryer 124 operates at a pressure 
from a few inches water vacuum (-5 inches H.sub.2 O or -0.18 psig) to 150 
psig and preferably at atmospheric pressure. A screw conveyor dryer with a 
single screw or a fluid bed dryer can also be used. 
In dryer 124, the centrifuge sludge flushed with light oil is mixed with 
heat carrier material at a heating temperature from 400.degree. F. to 
950.degree. F., preferably from 700.degree. F. to 900.degree. F. and most 
preferably about 900.degree. F., until it is heated, dried and separated 
into a powdery, dust-enriched residual stream and a purified, dedusted 
stream of normally liquid shale oil, including light shale oil and steam 
with less than 5% and preferably less than 2% by weight shale dust. The 
solids residence time in dryer 124 is from 0.5 minutes to 120 minutes and 
preferably from 10 minutes to 30 minutes. When only heavy shale oil is 
dedusted, the heavy shale oil in dryer 124 can be coked, thermal cracked 
and upgraded into lighter hydrocarbons, mainly, light shale oil and middle 
shale oil, by controlliing the heating temperature in dryer 124. 
The dedusted stream of shale oil from dryer 124 is discharged through 
overhead line 132 and fed to separator 24 for further processing and 
upgrading. Alternatively, the purified stream of oil shale from dryer 124 
can be fed to another separator 90 (FIG. 6) or 108 (FIG. 8) for further 
processing and upgrading. In some circumstances, it may be desirable to 
further process and upgrade the dedusted stream of shale oil from the 
dryer without first passing the shale oil through a separator. 
The powdery, dust-enriched residual stream from dryer 124 has less than 10% 
and preferably from 3% to 8% by weight normally liquid shale oil and a 
higher concentration of shale dust than the centrifuge sludge. The 
powdery, dust-enriched residual stream and the solid heat carrier material 
in dryer 124 are discharged from the bottom of dryer 124 through residue 
outlet line 134 and conveyed directly to the bottom portion of lift pipe 
110 as shown in FIGS. 5 and 7 by conveying means, such as a vibrating 
solid conveyor, pneumatic conveyor or screw conveyor, or indirectly 
thereto via retort 14 thrugh inlet line 136 and discharge line 112 as 
shown in FIGS. 6 and 8, after being mixed with retorted shale and solid 
heat carrier material from retort 14. 
In lift pipe 110 (FIGS. 5-8), the powdery, dust-enriched residual stream, 
retorted shale and heat carrier material are fluidized, entrained, 
propelled and conveyed upwardly into a collection and separation bin 114 
by air injected into the bottom of lift pipe 54 through air injector 
nozzle 116. Shale oil and any carbon residue in the powdery, dust-enriched 
residual stream and carbon residue in the retorted shale are combusted in 
lift pipe 110 to heat the fluidized material to a temperature from 
1000.degree. F. to 1400.degree. F. and preferably from 1200.degree. F. to 
1300.degree. F. The combusted powdery, dust-enriched residual stream and 
the combusted retorted shale form a hot spent residual stream and hot 
spent oil shale, respectively, for use as solid heat carrier material in 
dryer 124 and retort 14. 
Spent material is discharged from the bottom of separation bin 11 through 
heat carrier line 138 (FIGS. 5-8). Part of the heat carrier material in 
heat carrier line 138 is fed to retort 14 via heat carrier line 18 and 
part of the heat carrier material in heat carrier line 138 is fed to dryer 
124 via heat carrier line 132. Combustion gases are withdrawn from the top 
of separation bin 114 through combustion gas line 118 and dedusted in a 
cyclone or electrostatic precipitator for discharge into the atmosphere or 
further processing. 
In the processes and systems of this invention, from 80% to 100% and 
preferably from 95% to 100% by weight of the shale oil in the separated 
shale oil fraction is dedusted and recovered as purified streams of oil. 
Among the many advantages of the above processes and systems are: 
1. Improved product yield. 
2. Better dedusting of shale oil. 
3. Lower product viscosity. 
4. Ability to pipeline the dedusted shale oil through valves, outlet 
orifices, heat exchangers, pumps and distillation towers and refine the 
dedusted shale oil in hydrotreaters and catalytic crackers. 
5. Utilization of dust laden sludge and minimization of sludge disposal 
problems. 
While the retort shown in the preferred embodiments is a fluid bed retort, 
other retorts can be used such as a screw conveyor retort follower by a 
surge bin or a rotating pyrolysis drum followed by an accumulator. Metal 
or ceramic balls can also be used as solid heat carrier material with the 
lift pipe serving as a ball heater. Sand can also be used as heat carrier 
material. 
Although embodiments of this invention have been shown and described, it is 
to be understood that various modifications and substitutions, as well as 
rearrangements and combinations of process steps, can be made by those 
skilled in the art without departing from the novel spirit and scope of 
this invention.