US2813823A - Destructive distillation of hydrocarbonaceous materials - Google Patents

Description

Nov. 19, 1957 M. w. PUTMAN D ESTRUCTIVE DISTILLATION OF HYDROCARBONACEOUS MATERIALS 4 Sheets-Sheet 1 Filed Sept. 19, 1956 E "33 26mm INVENTOR Maurice W. Pufrncm E223 PBZQEM 3 +25 :0 use wow 23 cotgnEoo w=o- 510E226 23 53:56

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INVENTOR Maurice W9 BY ATTORNE Nov. 19, 1957 M. w. PUTMAN 2,813,823

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INVENTOR Maurice W. Putmon ATTORNEY United States Patent DESTRUCTIV E DIST ILLATION OF HYDROCAR- BONACEOUS MATERIALS Maurice W. Putman, Midland, Mich., assignor to the United States of America as represented by the Secretary of the Interior Application September 19, 1956, Serial No. 610,849

Claims. (Cl. 202-6) (Granted under Title 35, U. S. Code (1952), see. 266) The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention is generally related to the destructive distillation of solid hydrocarbonaceous materials and is particularly concerned with a method for the destructive distillation of oil shale to produce useful liquid products.

It is, of course, well known that certain sedimentary rocks, commonly referred to as oil shale, upon heating, yield appreciable quantities of relatively crude oil as well as gaseous hydrocarbons. This oil may be refined into valuable products such as gasoline, diesel oil, jet fuel, and fuel oil. Likewise, valuable by-products such as tar acids and waxes are recoverable from the crude shale oil. Extensive deposits of oil shale are found in this country, particularly in the so-called Green River shale formation located in the states of Colorado, Utah, and Wyoming. Important oil shale deposits are likewise found in other parts of the world. With diminishing world petroleum reserves, there has been considerable interest in developing a commercially feasible process, suitable for application on a large scale, for retorting (i. e., destructive distilling) oil shale to recover its potential yield of crude oil.

The two principal engineering problems connected with oil-shale retorting on a large scale are those of materials handling and of heat exchange. In such an operation literally thousands of tons of shale must be moved through the retorting vessel and auxiliary heat exchange vessel, if any. This shale must be heated in some manner to retorting temperatures, of the order of 800 to 1000" F. This involves the exchange of enormous quantities of heat since not only the organic matter (usually termed kerogen) must be heated, but also the inert, inorganic portion of the shale, which usually comprises from 80 to 90 percent by weight of the total shale.

With respect to the materials handling problem, obviously the simplest and most inexpensive manner of operation would be to feed the shale downwardly by gravity through the retorting vessel.

Thus far, the most attractive manner of heating the shale to retorting temperature appears to be direct heat exchange between the shale as a bed of broken solids, and a hot gas stream flowing through the shale bed. In

2,813,823 Patented Nov. 19, 1957 a continuous process, the shale bed and gas stream preferably flow countercurrently to one another. In such a process it is highly desirable, from the standpoint of thermal efficiency, and from the standpoint of certain operational difliculties, otherwise encountered, that the outgoing bed of shale and the outgoing gas stream, containing the product oil, both leave the processing vessel at low temperatures.

It is particularly desirable that the product gas stream, carrying the oil, give up most of its heat to the incoming shale before leaving the retort. First of all, at high gas exit temperature, e. g., 400 to 500 F., there is a strong tendency for the oil vapors to deposit coke upon the walls of the outlet ducts, eventually plugging the outlets completely, thus causing periodic shutdowns. In addition to the coking problem, a high exit temperature for the oil-bearing gas stream requires the use of expensive cooling equipment to condense out the oil vapors from the relatively large volume of retorting gases. Furthermore, large quantities of cooling water would also be required. In this country, Where substantially all the commercially interesting oil-shale deposits are located in arid regions, this type of operation would be practically out of the question in a large-scale operation.

From the considerations discussed above, it is apparent that a practical retorting process should include both downward gravity feed of the shale through the retorting vessel and the use of the incoming cold shale to cool the ascending stream of retorting gases containing the product oil vapors, so that this gas stream leaves the shale bed at a temperature such that no further cooling is necessary. However, to avoid cooling the gas stream after its exit from the retort, it is apparent that it must be cooled below the condensation temperature of the oil vapors which it contains below it leaves the shale bed; and since the shale itself is cooling the gas stream, it is obvious that some of the product oil vapors will tend to condense upon the cold shale. Any oil condensing upon the shale will tend to flow by gravity downwardly in the retort toward the hot zone of distillation, and eventually is revaporized and carried once again toward the top of the shale bed where it may again condense upon the cold incoming shale and trickle downward through the shale bed. Since the crude oil is for the most part a high boiling material, and quite unstable thermally, constant revaporization of the oil in the shale bed is invariably accompanied by uncontrolled thermal cracking reactions which destroy a large fraction of the potential oil yield. Equally undesirable as the loss in oil yield, is the fact that refluxing of large quantities of oil in the upper part of the retort leads to operational difficulties, particularly those connected with channelling" of the gas stream in the shale bed. channelling, that is, the failure of the gas stream to flow through the entire cross-section of the shale bed, is brought about when the oil refluxes at such a rate as to render sections of the shale bed impervious to the passage of the gas stream.

Therefore, condensation of the oil vapors upon the surface of the shale to any substantial extent must be avoided in this type of process, where the shale flows downwardly, and the gas stream flows upwardly, and is cooled to a low temperature by the incoming cold shale before it leaves the top of the retort, and instead the oil vapors must be caused to condense preferentially in the gas stream as mist droplets as the gas stream is cooled by the bed of shale. It is equally imperative that the droplets formed be small enough that they may be carried upwardly through the shale bed and out of the top of the shale bed in the gas stream Without substantial disengagement from the gas stream by impingement on the shale particles, but large enough that they may be recovered from the relatively cool gas stream with little difiiculty by passing the gas stream through a centrifugal separator or other collector for example.

Because of the physical properties of Colorado shalc oil, such a preferential condensation of the major portion of the oil vapors as a fog or mist in the gas stream may be achieved readily. The size of the mist droplets is determined ordinarily by the gas cooling rate in that portion of the shale bed where vapor condensation is initiated (high gas cooling rates produce smaller sized mist droplets than low gas cooling rates). However, satisfactory operation of such a process can be achieved over only a very narrow range of operating conditions because of the gas cooling rate limitation which must be satisfied.

Therefore, it is obvious that if the gas cooling rate limitation could be eliminated, the performance and operability of such a process would be greatly enhanced and its adoption assured because of the apparent advantages of such a process.

In accordance with this invention, it has been found that by providing artificially induced condensation nuclei in the condensing zone, that the size of the fog or mist droplets may be controlled so that none of the droplets are so large that they are disengaged from the gas stream by impingement in passing through the shale bed, nor none so small that they are difficult to recover from the relatively cool gas stream by conventional methods. irrespective of the gas cooling rate in that portion of the shale bed where vapor condensation is initiated. (The formation of a fog or mist is accomplished at low degrees of supersaturation only in the presence of a large number of nuclei on which the saturated vapors may condense.)

Sodium chloride is particularly useful as the condensation nuclei source in view of its low cost and ready availability. Other salts which have been found to be effective are potassium chloride and calcium chloride. In general, any substance which has an appreciable vapor pressure and is thermally stable at the retort temperature may be employed to supply the artificially induced condensation nuclei.

The invention, for the sake of simplicity, will be described in detail employing sodium chloride. It is to be understood. however, that other materials meeting the necessary requirements of thermal stability and appreciable vapor pressure may be substituted in the process.

Artificially induced condensation nuclei may be provided in the retort gas in several ways. In one method sodium chloride crystals are vaporized in the combustion zone of the retort; and in the second method sodium chloride crystals are vaporized outside the retort and injected into the recycle gases. The first method is more convenient but harder to control, while the second method is more difiicult to carry out but the results are more reproducible.

In its broader aspects, the process envisioned by the present invention involves continuously passing the oil shale. to which has been added a small amount of sodium chloride in water solution, downwardly as a bed of broken solids in a substantially vertical column. The solid residue is removed in a cool condition at the bottom of the column While the distillation and combustion products, including a noncondensable gas, are removed from the top of the column. At least a portion of this noncondensable gas, in a cool condition, is recycled to the bottom of the column and passes upwardly through the downwardly moving residue, thus cooling the hot residue and itself becoming heated. At this point in the retort the gas stream is raised to a still higher temperature, preferably by passing through a combustion zone in the retort itself. As the gas stream passes on up through the column of shale, it delivers its heat to the cold incoming shale, thus gradually heating it to progressively higher temperatures. The descending shale, consequently. passes successively through a preheating zone, where it meets the still hot vapor-gas mixture rising from the distillation zone. through a distillation zone where it reaches retorting temperature. and through a sublimation zone where it reaches a still higher temperature which is sutlicicnt to cause a portion of the sodium chloride, which has been evaporated to a thin film on the shale particles in the preheating zone above, to sublime. The sodium chloride vapors so formed are swept upward by the gas stream. and as the gas stream is cooled by the descending cooler shale, a sodium chloride fume is formed. This fume consists of minute solid sodium chloride particles which are suitable condensation nuclei for the oil vapors to condense upon. In the distillation zone the organic content of the shale undergoes thermal decomposition producing; condensable product vapors which are carried upwardly in the gas stream. The gas-vapor mixture rising from the distillation zone encounters progressively cooler shale as it passes upwardly through the shale preheating zone. and, of course, in this way. itself becomes progressively cooled. Eventually the gas-vapor mixture encounters shale below the initial dew point temperature of the mixture and condensation of the vapor begins. By withdrawing the gas stream from the top of the shale bed at a sufficiently low temperature, viz., between 106 and 200 F. and preferably between 115 and 175 F. substantially the entire vapor content of the gas stream under goes condensation in the shale bed on the sodium chloride nuclei in the gas stream.

In an alternate form of carrying out the invention. sodium chloride is vaporized in a separate burner outside the retort, and the mixture of hot gas and vaporized salt is admitted to the stream of recycled gas entering the bottom of the retort. This may be accomplished by injecting a fine spray of brine into a suitable gas or oil furnace. Another method is to add sodium chloride solu tion to broken pieces of coke. which are then burned.

In this way the salt vapors proceed up the retort and make their way through the combustion zone to the cooler upper part of the retort, where they are condensed as a fine solid fume and form nuclei for subsequent condensation of the shale-oil mist.

The principles of the invention are applicable to any sort of retorting process where the shale is fed downwardly by gravity, counter-current to a stream of retorting gases in which artificially induced condensation nuclei are present, and where the gas stream is withdrawn from the shale bed at a temperature sufficiently low so that substantially all, or the major portion, of the vapor content of the gas stream undergoes condensation befor leaving the shale bed.

Preferably, however, a retorting process is employed such as that described in U. S. Patent 2,757,129 entitled Method for the Destructive Distillation of Hydrocarbonaceous Materials, by Reeves, Putman, Jones, and Tripp. This and other preferred embodiments of the invention will be set out in detail in the subsequent tic scription.

For a better understanding of the invention. reference now is made to the accompanying drawings wherein:

Fig. 1 is a semi-diagrammatic illustration of a retort suitable for carrying out a preferred embodiment of the process of the invention, together with a schematic illustration of the product recovery and gas circulation systems serving the retorting vessel;

Fig. 2 is a graphical illustration of bed-temperature profiles obtained during the operation of the retort illustrated in Fig. 1; and,

Fig. 3 is a graphical correlation of the data from a number of runs performed in the retort illustrated in Fig. 1.

Fig. 4 is a graphical comparison of the mist particle size distributions of shale-oil mists, produced with and without the addition of sodium chloride nuclei.

Referring now particularly to Fig. 1, reference numher 1 refers generally to a cylindrical, upright retorting vessel comprising a metal shell 2, suitably insulated with a refractory lining 3. A charge hopper 4 is disposed at the top of the retort. The charge hopper may be of any suitable construction, but should be adapted to maintain a continuous feed of solid material into the top of the retort and at the same time maintain a gas-tight seal to prevent the escape of gases and vapors from the retort through the charging mechanism. A sliding valve 5, is provided to open simultaneously one compartment to the retort and to close off the other for recharging.

At the bottom of the retort, a discharging mechanism is provided consisting a turntable 6, driven by a variable speed motor 7, through a gear box 8. The rate of shale discharge is controlled by regulating the speed of the rotating turntable 6. With the help of the drag chain 9, the turntable 6 discharges residual solids into an ash-leg 10, for disposal in any desired fashion. Ash-leg 10, is equipped with a suitable gas seal (not shown).

At the vertical axis of the retorting vessel, at an intermediate level therein, an open ended cylindrical tube 11, is provided. Directly above the upper end of the tube 11, is positioned a hollow, cone-shaped deflector 12. As can be seen, the base of the cone-shaped deflector 12, is spaced from the upper end of the tube 11, and is somewhat larger in diameter so as to eflectively prevent solid material flowing downwardly through the retort from entering the tube. A plurality of gas conduits 13, are provided for admitting an oxygen-containing gas, such as air, into the upper portion of the tube 11, as shown in the drawing.

Serving this retorting vessel, a product recovery and gas circulation system is provided. This system, which is shown schematically, comprises centrifugal separators 15 and 19, a positive displacement blower 18, an oil receiver 17, and an electrostatic mist precipitator 22, together with connecting conduits.

The operation of this retort now will be described. Oil shale crushed to a suitable particle size and to which a small amount of sodium chloride solution has been added, is continuously introduced into the top of the retort by means of hopper 4, at substantially atmospheric temperature. The shale particles size can vary within relatively wide limits both as to maximum and minimum particle size and particle size distribution, depending upon the size of the retort and the operating conditions.

The shale moves downwardly through the retort by gravity as a bed of freely moving particles and passes successively through a shale-preheating and product-gasstream-cooling zone, a distillation zone, a sublimation zone, a combustion zone, and a residue cooling zone. The stream of retorting gases, carrying the product oil is removed from the top of the retort through duct 14, at a temperature sufficiently low so that substantially all, or the major portion of, the oil vapors already have undergone condensation. For substantially all grades of oil shale, the gas stream outlet temperatures should be below 200 F., and preferably between about 115 and 175 F. At these outlet temperatures, the product oil comes out of the retort in the gas stream as an oil mist.

The cool gas stream, carrying the mist, is conducted first to a centrifugal separator 15, where the major portion of the mist particles are agglomerated and removed from the gas stream by centrifugal action. Liquid oil from separator 15, is removed to oil receiver 17, by line 16. The gas stream carrying a relatively small amount of fine oil particles is then conducted to a positive displacement blower 18 where the gas stream is repressured. Some further agglomeration of the mist occurs in the blower 18, and further separation of the mist from the gas stream is effected by a second centrifugal separator 19, located in the blower discharge line 18a. The oil recovered here is led to storage by line 20, while the gas stream, still containing a small amount of fine oil mist, is conducted by line 21, to an electrostatic precipitator 22, to recover any residual oil which is led to storage by line 22a.

A portion of the clean gas stream flowing by line 23, from the electrostatic precipitator 22, is withdrawn to be recycled to the retort by line 24, while a portion is vented from the system by line 26. The gas stream recycled to the retort by line 24, consists essentially of the flue gases resulting from combustion within the retort enriched by non-condensable hydrocarbon gases produced by thermal decomposition of the kerogenous material in the shale. As used in the specification and in the claims, the term noncondensable gas refers to gases which fail to condense to liquids at atmospheric temperatures and under pressures, including the light hydrocarbon gases (such as methane, ethane, propane, ethylene, propylene, etc.) produced during the destructive distillation of the hydrocarbonaceous material, and the flue gases resulting from combustion including carbon dioxide, carbon monoxide, and nitrogen. The recycle gas stream ordinarily will be lean in combustibles since it will be rather highly diluted with combustion products, with carbon dioxide resulting from decomposition of the mineral carbonates in the shale, and with nitrogen when air is employed to support combustion within the retort. Typically, in the case of oil shale, the product gas stream will contain from 6 percent to 25 percent combustibles and have a heating value of 40 to 16 B. t. u./std. c. f. depending upon the richness of the shale and the operating conditions.

This lean recycle gas, which is at a relatively low temperature (for example, to F.) is introduced into the bottom of the retort by line 25, and flows upwardly through the downwardly flowing residue from the combustion zone. In this portion of the retort, herein termed the residue cooling zone, direct heat exchange is effected between the cold recycle gas and the hot residue; the cold recycle gas is preheated by recovering sensible heat from the hot shale which in turn is cooled and leaves the retort at a temperature approximately that of the cold incoming recycle gas.

As the preheated recycle gas reaches the upper portion of the residue cooling zone a substantial portion of this gas following the path of lesser resistance provided by the tube 11, becomes disengaged from the column of shale and passes into the lower portion of the tube, as indicated by the arrows in the drawing. The remainder of the recycle gas fiows upwardly through the column of shale in the annulus between the tube 11, and the walls of the retort.

An oxygen-containing gas, preferably air, preheated if desired, is injected into the upper portion of the tube 11, by line 13. The oxygen-containing gas is mixed with the preheated recycle gases rising through the tube and this mixture then passes out of the upper portion of the tube, is deflected downwardly and outwardly by the hollow, cone-shaped deflector 12, and is distributed into a uniform manner throughout the cross-section of the retort.

Combustion of the recycle gas-air mixture takes place in the vicinity of the upper extremity of the tube 11, and may take place partly in the upper portion of the tube and partly in the shale bed, or more desirably, chiefly within the shale bed.

The hot gases rising from the combustion zone raise the temperature of the descending shale to temperatures between l000 and 1700 P. which causes some or all the salt \shich has been deposited on the surface of the shale to sublime in the sublimation zone. These gases from the sublimation zone rise upwardly through the column of shale and are cooled sufliciently to produce a sodium chloride fume or minute solid particles in the gas stream which shall be referred to as artificially induced condensation nuclei in the specification and claims. Simultaneously, the descending shale is raised to a temperature at which thermal decomposition of the organic matter in the oil shale occurs (usually 800 to l000 Fl thereby producing condensable oil vapors as well as noncondcnsable hydrocarbon gzbes. The gas-vapor mixture rising upwardly from the distillation zone encounters progressively cooler shale, and thus itself becomes progressively cooled. The descending shale, of course, in this region becomes heated progressively. Eventually. the gas-vapor mixture encounters shale at a temperature below its initial dew point temperature, and condensation of the oil vapor on the sodium chloride fumes begins. By properly adjusting the height of the shale bed and the rate of fiow of shale, and the rate of flow of the gas stream. the exit temperature of the gas stream from the shale bed may be regulated to any value above the inlet temperature of the shale. As previously mentioned.

this exit temperature is regulated so that substantially the entire oil content of the gas stream condenses upon the sodium chloride fumes while the gas stream is still within the shale bed.

Using the retorting system illustrated in Figure l, a number of runs were made under varying conditions. The process conditions, yields. and product inspection data for eleven of these runs are set out in Table 1.

For this process to operate successfully, suitable and an adequate number of condensation nuclei must be present in the gas stream for the vapors to condense upon as a mist. The number of nuclei present determines the diameter of the mist droplets, and if an insufiicient numher are present, the droplets are so large that they deposit on the shale by impingement.

One method of providing sutficient nuclei for the oil vapors to condense upon is by adding brine to the shale and vaporizing the sodium chloride in the combustion zone of the retort. The number of nuclei which are generated by this method can be controlled by regulating the amoun of brine which is added and the maximum temperature to which the shale is heated, which in tu n is a function of the air provided The alternate method of providing suificient nuclei for the shale-oil vapors to condense on is to add brine to pieces of coke. burn the coke outside of the retort, and inject the resulting gases and sodium chloride vapors into the recycle gas stream before it enters the retort. Suthcicnt nuclei also may be produced by a self-nucleation mechanism characteristic of the sho eoil vapors themselves providing the gas-vapor mixture is cooled very rapidly in the region of initial vapor condensation. A relative value for the gas-cooling rate in the critical region can be determined with reason able :uviurocy 1:. the product f t e s't'aerlicial gas velocity times the average bed temperature gradient for the same region. As used herein. the term bed temperature gradient" is intended to mean the rate of change of temperature with bed height. expressed in F. per inch of bed height. The value of the bed temperature gradient may be most conveniently observed experimentally, and with fair accuracy, by recording the temperature in the shale bed at various levels therein. This can be done, for example, by inserting thermocouples into the shale bed at various levels and recording these temperatures simul taneously. A bed temperature profile plotted from these recorded temperatures will indicate the bed temperature gradient. Average values for the gas-cooling rate in the zone of initial vapor condensation, as calculated from the bed temperature gradients and the superficial gas velocity, are listed in Table 1 for each of the eleven runs.

Reference now is made to Figure 2 showing bed temperature profiles for several of the runs listed in Table 1 from which the values for the bed temperature gradients and gas-cooling rates were determined. The upper portion of the profile curves illustrate the rate at which the shale increases in temperature as it moves downwardly from the top of the retort, where it is introduced at atmospheric temperature into the combustion zone where it attains its maximum temperature. The lower part of the profile curve illustrates the rate at which the shale residue dccrcuszs in temperature as it moves downwardly from the combustion zone to the bottom of the retort. The region of initial vapor condensation is represented by that section of the profile extending from a bed temperature of 550 to 600 F.

Attention is now directed to Fig. 3. In this figure values for the oil yield, the amount of oil collected in the first separator, the gravity of the oil collected, and equivalent amount of residual oil in the spent shale has been plotted as a function of the gas cooling rate in the region of initial vapor condensation for each of the runs listed in Table 1. Oil yield is the principal criterion for judging whether a run is satisfactory or not. The amount of oil collected in the first separator is a reliable indication of the diameter of the oil mist particles. This is so because the separator is of the centrifugal type whose efficiency is a function of the particle size, that is, it is more ctficicnt on large size particles than small. The gravity of the oil collected is a measure of the amount of oil trapped in the shale bed by impingement and carried down by the shale into the hotter zones and rcvaporized. This is so because shale oil is a relatively unstable mixture of compounds and success ve revuporization causes thermal cracking to occur. Oils subjected to this type of thermal cracking are characterized by relatively high APl gravity. low viscositics, and low Conradson carbon values. However, this type of uncontrolled cracking reaction does not upgrade the oil recovered enough to compensate for the decrease in yield associated with this phenomenon. Any hydrocarbons remaining in the spent shale is another potential source of loss in oil yield and these data are also shown to explain the oil yield curve.

Examination of the curves shown in Fig. 3 reveals the effect of the gas cooling rate up the variables listed above. When brine was not added to the shale, the amount of oil collected in the first separator decreases as the gas cooling rate increases. The abrupt decrease in the gravity of the oil collected as the gas cooling rate increases from 50 to 60 F./sec. indicates that at cooling rates below 60 F./sec. the mist droplets are so coarse that they are readily separated from the gas stream by impingement on the shale particles and are subjected to successive revaporizations. A similar abrupt increase in oil yield coincides with the change in gravity of the oil collected. At still higher gas cooling rates the oil yield again declines. However, the decrease in yield is attributable to the potential oil remaining in the spent shale. At these higher gas cooling rates. the size of the mist particles is favorable, but the conditions required to achieve these high gas cooling rates are unfavorable for attaining com' plete retorting of the shale. The process variables which determine the gas cooling rate are the gas-shale flow rate ratio in the vapor condensation zone, volume of air per ton of shale, bed height, shale particle size and grade, and shale rate. Of these, the first has the greater influence as revealed by the data tabulated in Table 1, that is, at high gas-shale flow rate ratios the gas cooling rate is very low.

The results of a series of experimental runs are shown in Table 1 below.

Table 1 Run Number 176-14 176-13 177 184 188 190 193 194 200-13 202-B 202-D Amount of saturated brine added gnl./ton 1.0 1.0 1 O l) 0 0 0 0 0.0 0 0 0 0 0 0 0 Gus-shale flow rate ratio in vapor condensation zone Std. c. f./ton 29, 200 26, 400 27, 600 21. 1B0 800 30. 250 23, 900 20, 600 22, 700 23. 000 23, ?00 Air requirements std. c. i./ton 5, 230 4, 700 4,670 3, 720 4, 490 5, 3,800 3, 840 9 0 3. 0 3. 8 Shale rate lb./hr./sq. ft. of bed 187 208 203 247 243 234 23 262 231 230 228 Fischer assay of raw shale 28. 7 30. 3 30. 4 29. 7 30. 4 30. 8 24. 2 22. 6 29. 2 20. 4 29. 6 Shale inlet temperature... 70 70 70 60 60 Gas outlet tetnperature. 151 152 153 118 155 106 138 124 118 120 124 Shale outlet tamporaturm 140 143 152 232 166 150 156 212 158 220 215 Oil yield. vol. percent F. A... 98.4 99. i 95. 9 SO. 7 8S. 2 81.6 80. 2 82.2 90.4 93.1 97. 2 Product oil inspections:

Gravity API 20. 0 20.0 19. 6 19. 20. 7 22. 7 21. 9 19. 3 20.0 19. 9 20.1 Viscosity, 9. U. Q 130 F 128, 4 135. 4 149. 9 133. 5 97.1 72.8 94. 8 135. 3 113. 4 135. l 128. 6 Viscosity, S. U. 210 F 48. 3 48. 8 51.0 48. 6 47. 6 40. 8 47. l 52. 6 43. 9 49. 9 50.1 Conradson carbon wt pereent 8. 3 3. B 3.4 4.3 2.4 1.2 2. 3 4.3 3.6 2. 5 2. 2 Fischer assay of spent ga,]./t0n 0.0 0.0 0.0 5. 2 1.8 0.8 1.1 3.1 0. 8 0.3 0. 3 Superficial gas velocity in vapo condensation zone iL/SBCL. 0.76 i (6 0. 77 0 73 0.90 0 98 765 75 0 71 0. 735 (l. 73 Average temperature gradient between bed temperatures of T and Tip-50 F. (T =in1tial dew point temp. of vapor gas mixture) F.,'in, 5.5 2 3 2 1 12 5 5.0 1 2 i 0 16 5 0 8.3 7 1 Superficial gas cooling rate in region of initial condense tion F,/sec 5O 21 19. 5 109.0 54 14 5 46 148 85 73 n3 Distribution oi oil collected in recovery system:

Oil collected by 1st separator vol. percent of total 011 collected 54. 8 59. 2 57.8 69. 0 82. 2 79. 3 78. 6 6G. 2 73. 2 Oil collected by 2nd separator (10) vol. percent of total oil collected 38. 3 36. 3 40.8 28. 2 14. 0 17.3 17. 7 29. 5 22. 5 O11 collected by 3rd separator (22) vol. percent of total 011 collected 6. 9 4. 5 1. 4 2. 8 2. 9 3. 4 3. 7 4. 1 4. 3

This table includes data for three runs (176-A, 176-B, and 177) in which brine was added to the shale. Data from these runs are plotted as solid dots on Figure 3. For each of these runs the gas cooling rate was relatively low but, in contrast to the runs without brine, the amount of oil collected in the first separator was low, indicating that the brine affected the size of the mist particle, the low gravity oil collected indicates that the mist particles were small enough to minimize the amount separated from the gas stream by impingment and subsequently revaporized. The shale was completely retorted and, since the oil was not subjected to successive rcvaporization, a high yield of oil was recovered.

After an extensive period of investigation, involving many runs under varying conditions, it has been found that the range of operating conditions for achieving good oil yields and good operating characteristics in such a process can be greatly extended, if the following condition is satisfied:

(1) The normal supply of condensation nuclei in the retort gas stream should be supplemented by artificially induced condensation nuclei, in order that the fog or mist droplets will be suificiently small so that they will not be filtered out of the gas stream by impingement on the shale particles. A sufiicicnt number of artificially induced condcnsation nuclei should be provided by adding at least one-eighth of a gallon of saturated sodium chloride brine per ton of shale and using at least 4000 std. c. f. of air per ton shale or its equivalent.

While the invention does not depend upon any particular theory, it is believed that the following is an explanation of the results discussed above. In order to produce condensation of the vapors as a mist rather than on the surface of the shale, two conditions must be satisfied: (l) a condition of supersaturation must be produced in the gas stream; (2) nuclei must be present for the supersaturated vapors to condense on.

The effect of sodium chloride vapors injected into the retort as a source of nuclei for condensation of shale-oil mist is shown clearly in Figure 4. In this illustration the cumulative weight percent of mist is plotted against the mist particle size. Two curves are shown. The first shows the distribution of mist particle size when no nuclei are added and the second shows the distribution of mist particle size, when sodium chloride vapors were injected into the recycle gas stream. If we compare the mist particle size of 50% of the particles, it is immediately apparent from the curves that when sodium chloride vapors were injected into the retort the mist particle size of 50% of the shale-oil mist was only one-third the diameter (2 microns) of the shale-oil mist (6 microns) when no sodium chloride was used. This is a very important fact as it allows more of the oil-shale mist to traverse the retort and consequently more shale-oil mist is recovered in the collection system. As proof that the sodium chloride is actually the nucleating agent part of the sodium chloride is recovered along with the shale-oil mist in the collection system.

In a countcrcurrcnt system such as exists in the vapor condensation region of the retort, where the vapor-gas stream encounters progressively cooler shale, two important physical actions occur:

(1) There is a transfer of heat from the vapor-gas stream to the shale. (2) There is a mass transfer of oil from the vapor-gas stream to the shale.

It is obvious that a condition of supersaturation in the gas stream may he arrived at if, in cooling the gas-vapor mixture, the rate of decrease of the partial prcssure of the vapors by condensation is low relative to the rate at which the temperature of the gas-vapor mixture decreases. This will tend to occur when the vapors have a low diffusivity since, in such a system, the rate of diffusion of the vapors tion when cooling at gas stream containing these vapors.

The second condition which must be satisfied is that nuclei must be present for the supersaturated vapors to condense upon. It is well known that a solid areosol in a gas-vapor mixture greatly reduces the degree of super saturation required for mist formation. Normally the air supplied to the retort contains a few solid aerosol pnriiclci. and more are produced by combustion within the retort but the total supplied from these sources is insignificant compared to the total number required. The primary source of nuclei when artificially induced nuclei are not present in the gas stream is by a self-nucleation mechanism favored by high vapor-gas cooling rates. Thus when the gas-cooling rate is relatively high, sufficient nuclei are formed by this self-nucleation mechanism to insure the formation of small enough mist particles to escape being trapped in the shale bed by impingement.

However, it is difficult to achieve a high gas-cooling rate and complete retorting of the shale simultaneously. This inflicts a very narrow range of operating conditions in which satisfactory oil yields and operability can be attained. Providing sufficient artificially induced condensation nuclei in the gas-vapor stream completely eliminates the gas-cooling rate in the zone of initial condensation as an important process variable. This is particularly advantageous in applying such a process to a large-scale rctorting plant. As the cross-section of the retort is expadded, it becomes increasingly difiicult to maintain the same operating conditions in all areas of the cross-sectin.

it is to be understood that other retorting methods than those specifically described may be employed within the FcmFC of the invention. Thus, while it in preterm to employ a retorting process such as is illustrated in Figure l. which includes a combustion zone in the retort itself, and where the oxygen containing gas is introduced into an intermediate portion of the retort, thereby firing the combustion zone in a definite location, other types of rctorting methods may be employed. For example, it may be desirable to heat the retorting gas stream or a portion thereof in a vessel separate from the retorting vessci, tuch that no combustion takes place in the retorting vessel proper. In this case it would be desirable to spray a odium tliloride solution into the hot gas stream where it would su lime and be carried into the retort in this manner. As the gas stream was cooled in the retort the sodium chloride vapors would form solid sodium chloride condensation nuclei.

Although the process has been described particularly with reference to oil shale, it is also generally applicable to other types of processes for the destructive distillation of hydrocnrbonaceous materials where the oil vapors pro- Ll tCCtl have a low diffusivity such that they may be caused to condense preferentially as a mist in the retorting gas stream.

it is to be understood that the above description, together with the specific examples and embodiments described. is intended merely to illustrate the invention, and that the invention is not limited thereto, nor in any way except by the scope of the appended claims.

This case in a continuation-in-part of co-pending application Serial No. 365,297, filed June 30, 1953, now aban doned.

I claim:

1. A method for the destructive distillation of oil shale for the production of useful liquid products which involves the steps of continuously passing the shale as a bed of broken solids downwardly in a substantially vertical column successively through a preheating zone and a distillation zone. continuously passing a stream of noncondensablc gases containing artificially induced condensation nuclei selected from the class consisting of sodium chloride, potassium chloride and calcium chloride upwardly thrw zh aid di illation zone at a temperature sufficient to c xeet thermal decomposition of said oil shale, thereby producing coptlensable product vapors which are carried umvnrdly in said gas stream containing artificially induced condensation nuclei, permitting said vapor-containing gas sir mi to pass upwardly through said preheating zone, whereby the descending shale becomes progressively heated. withdrawing said gas stream from said column at a tcn'iperature sufiiciently low so that substantially the entire va or content of said gas stream containing artificially induced condensation nuclei undergoes condensation within sa d column, whereby the major portion of it va ors condense on the artificially induced nuclei as a re vely stable mist and a minimum amount of condensation occurs on the surface of said shale, withdrawsaid relatively stable mist and accompanying gas it from the column, and separating the shale-oil mist, int til ing the artificially induced nuclei, from the accompanying gases.

2. A method for the destructive distillation of oil shale for the production of useful liquid products which involves the steps of continuously passing the shale, to which has beet added a quantity of sodium chloride brine, as a bed of broken solids downwardly in a substantial vertical column successively through a preheating zone, a distillation zone, a. sublimation zone, and a combustion zone, continuously supplying said combustion zone with a stream of oxygen-containing gases, permitting the hot gases from said combustion zone to pass upwardly through said column, thereby effecting sublimation of said sodium chloride in said sublimation zone, thereby effecting thermal decomposition of said oil shale in said distillation zone, and thereby producing condensable product oil vapors which are carried upwardly in said gas stream, permitting said va cr-containing gas stream to pass upwardly through said preheating zone, whereby the descending shale becomes progressively heated, the sodium chloride vapors become cooled and sublime as solid particles in the gas stream which are suitable condensation nuclei for the oil vapors, and the ascending mixture of gases, oil vapors and sodium chloride condensation nuclei becomes progressively cooled, withdrawing said gas stream t'rcm said column at a temperature sufficiently low so that substantially the entire oil-vapor content of said gas stream undergoes condensation within said column, whereby the major portion of said vapors condense on the sodium chloride particles as a relatively stable mist, and whereby a minimum amount of condensation occurs on the surface of the shale. withdrawing said relatively stable mist and accompanying gas stream from the column and separating the shale oil mist, including the sodium chloride condensation nuclei, from the accompanying gases.

3. A method for the destructive distillation of oil shale for the production of useful liquid products which involves the steps of continuously passing the shale, to which has been added a quantity of sodium chloride brine, as a bed of broken solids downwardly in a substantial vertical column successively through a preheating zone, a distillation zone, a sublimation zone, a combustion zone, and a residue cooling zone, withdrawing from the top of said column the products of combustion and of distillation, including normally liquid products together with a noncondensable gas relatively lean in combustibles, separating said liquid products from said lean, noncondensable gas, recycling at least a portion of said lean gas in a relatively cool condition to the lower portion of said residue cooling zone, permitting the recycle gas to pass upwardly through said column in contact with the hot residue from said combustion zone, whereby said residue becomes cooled and said gas becomes heated, supplying an oxygen-containing gas to said column above said residue cooling zone, thereby definitely establishing the location of said combustion zone, permitting the hot gases from said combustion zone to pass upwardly through said column, thereby effecting sublimation of said sodium chloride in said sublimation zone, thereby effecting thermal decomposition of said oil shale, and thereby producing condensable product oil vapors which are carried upwardly in said gas stream, permitting said vapor-containing gas stream to pass upwardly through said preheating zone, whereby the descending shale becomes progressively heated, the sodium chloride vapors become cooled and sublime as solid particles in the gas stream which are suitable condensation nuclei for the oil vapors to condense upon, and the ascending mixture of gases, oil vapors, and sodium chloride condensation nuclei becomes progressively cooled, maintaining the exit temperature of said gas stream for said column sufficiently low so that substantially the entire vapor content of said gas stream undergoes condensation within said column, whereby the major portion of said vapors condense on the sodium chloride as a relatively stable mist, and whereby a minimum amount of condensation occurs on the surface of the shale, withdrawing said relatively stable mist and accompanying gas stream from the column and separating the shale oil mist, including the sodium chloride condensation nuclei, from the accompanying gases.

4. A method in accordance with claim 3, wherein the gas stream is withdrawn from said column at a temperature between and F.

5. A method in accordance with claim 3, wherein at least 800 std. c. f. of oxygen per ton of shale is present in the oxygen-containing gases supplied to the combustion zone.

6. A method in accordance with claim 3, wherein at least the equivalent of one-eighth of a gallon of saturated sodium chloride brine is added to each ton of shale.

7. A method for the destructive distillation of oil shale for the production of useful liquid products which involves the steps of continuously passing the shale as a bed of broken solids downwardly in a substantially vertical column successively through a preheating zone, a distillation zone, a hot-gas mixing zone, and a residue cooling zone, withdrawing from the top of said column the products of distillation including normally liquid products together with a noncondensable gas relatively lean in combustibles, separating said liquid products from said lean, noncondensable gas, recycling at least a portion of said lean gas in a relatively cool condition to the lower portion of said residue cooling zone, permitting said recycled gas to pass upwardly through said column is contact with the hot residue from said hot-gas mixing zone, whereby said residue becomes cooled and said gas becomes heated, supplying a hot gas containing sodiumchloride vapors to said column above said residue cooling zone, permitting the hot gases from said hot-gas mixing zone to pass upwardly through said column thereby elfecting thermal decomposition of said oil shale, and thereby producing condensable product oil vapors which are carried upwardly in said gas stream, permitting said vaporcontaining gas stream to pass upwardly through said preheating zone, whereby the descending shale becomes progressively heated, the sodium chloride vapors become cooled and sublime as solid sodium chloride particles in the gas which are suitable condensation nuclei for the oil vapors to condense upon, and the ascending mixture of gases, oil vapors, and sodium chloride condensation nuclei become progressively cooled, withdrawing said gas stream from said column at a temperature sufficiently low so that substantially the entire vapor content of said gas stream undergoes condensation within said column, whereby the major portion of said vapors condense on the sodium chloride particles as a relatively stable mist, and whereby a minimum amount of condensation occurs on the surface of the shale, withdrawing said relatively stable mist and accompanying gas stream from the column and separating the shale oil mist, including the sodium chloride condensation nuclei, from the accompanying gases.

8. A method for the destructive distillation of oil shale for the production of useful liquid products which involves the steps of continuously passing the shale, as a bed of broken solids downwardly in a substantial vertical column successively through a preheating zone, a distillation zone, a. combustion zone, and a residue cooling zone, withdrawing from the top of said column the products of combustion and of distillation, including normally liquid products together with a noncondensable gas relatively lean in combustibles, separating said liquid products from said lean, noncondensable gas, recycling at least a portion of said lean gas in a relatively cool condition to the lower portion of said residue cooling zone, introducing into said recycle gas hot gases containing sodium chloride vapors, permitting the recycled gas to pass upwardly through said column in contact with the hot residue from said combustion zone, whereby said residue becomes cooled and said gas becomes heated, supplying an oxygen-containing gas to said column above said residue cooling zone, thereby definitely establishing the location of said combustion zone, permitting the hot gases from said combustion zone to pass upwardly through said column, thereby elfecting thermal decomposition of said oil shale, and thereby producing condensable product oil vapors which are carried upwardly in said gas stream, permitting said vapor-containing gas stream to pass upwardly through said preheating zone, whereby the descending shale becomes progressively heated, the sodium chloride vapors become cooled and. sublime as solid particles in the stream which are suitable condensation nuclei for the oil vapors to condense upon, and the ascending mixture of gases, oil vapors, and sodium chloride condensation nuclei becomes progressively cooled, maintaining the exit temperature of said gas stream from said column sufliciently low so that substantially the entire vapor content of said gas stream undergoes condensation within said column, whereby the major portion of said vapors condense on the sodium chloride particles as a relatively stable mist, and whereby a minimum amount of condensation occurs on the surface of the shale, withdrawing said relatively stable mist and accompanying gas stream from the column and separating the shale oil mist, including the sodium chloride condensation nuclei, from the accompanying gases.

9. A method for the destructive distillation of oil shale for the production of useful liquid products which involves the steps of continuously passing the shale as a bed of broken solids downwardly in a substantially vertical column successively through a preheating zone, a distillation zone, a hot-gas mixing zone, and a residue cooling zone, withdrawing from the top of said column the products of distillation including normally liquid products together with a noncondensable gas relatively lean in combustibles, separating said liquid products from said lean, noncondens able gas, recycling at least a portion of said lean gas in a relatively cool condition to the lower portion of said residue cooling zone, permitting said recycled gas to pass upwardly through said column in contact with the hot residue from said hot-gas mixing zone, whereby said residue becomes coolcd and said gas becomes heated, generating sodium chloride vapors outside the column, conducting the sodium chloride vapors in a stream of hot gas into said column above said residue cooling zone, permitting the hot gases from said hot gas mixing zone to pass upwardly through said column thereby effecting thermal decomposition of said oil shale, and thereby producing condensable product oil vapors which are carried upwardly in said gas stream, permitting said vapor-containing gas stream to pass upwardly through said preheating zone, whereby the descending shale becomes progressively heated, the sodium chloride vapors become cooled and sublime as solid sodium chloride particles in the gas which are suitable condensaton nuclei for the oil vapors to condense upon, and the ascending mixture of gases, oil vapors, and sodium chloride condensation nuclei become progressive cooled, withdrawing said gas stream from said column at a temperature sufficiently low so that substantially the entire vapor content of said gas stream undergoes condensation Within said column, whereby the major portion of said vapors condense on the sodium chloride particles as a relatively stable mist, and whereby a minimum amount of condensation occurs on the surface of the shale, withdrawing said relatively stable mist and accompanying gas stream from the column and separating the shale oil mist, including the sodium chloride condensation nuclei, from the accompanying gases.

10. The method as in claim 9 wherein the sodium chloride vapors are produced outside the vertical column by vaporizing sodium chloride in a separate high temperature combustion zone, and conducting the sodium chloride vapors together with hot combustion gas into the recycle gas stream.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A METHOD FOR THE DISTILLATION OF OIL SHALEOF OIL SHALE FOR THE PRODUCTION OF USEFUL LIQUID PRODUCTS WHICH INVOLVES THE STEPS OF CONTINUOUSLY PASSING THE SHALE AS A BED OF BROKEN SOLIDS DOWNWARDLY IN A SUBSTANTIALLY VERTICAL COLUMN SUCCESSIVELY THROUGH A PREHEATING ZONE AND A DISTILLATION ZONE, CONTINOUSLY PASSING A STREAM OF NONCONDENSABLE GASES CONTAINING ARTIFICIALLY INDUCED CONDENSATION NUCLEI SELECTED FROM THE CLASS CONSISTING OF SODIUM CHLORIDE, POTASSIUM CHLORIDE AND CALCIUM CHLORIDE UPWARDLYY THROUGH SAID DISTILLATION ZONE AT A TEMPERATURE SUFFICIENT TO EFFECT THERMAL DECOMPOSITION OF SAID OIL SHALE, THEREBY PRODUCING CONDENSABLE PRODUCT VAPORS WHICH ARE CARRIEDD UPWARDLY IN SAID GAS STREAM CONTAINING ARTIFICIALLY INDUCED CONDENSATION NUCLEI, PERMITTING SAID VAPOR-CONTAINING GAS STREAM TO PASS UPWARDLY THROUGH SAID PREHEATING ZONE, WHEREBY THE DESCENDING SHALE BECOMES PROGRESSIVELY HEATED, WITHDRAWING SAID GAS STREAM FROM SAID COLUMN AT A TEMPERATURE SUFFICIENTLY LOW SO THAT SUBSTANTIALLY THE ENTIRE VAPOR CONTENT OF SAID GAS STREAM CONTAINING ARTIFICIALLY INDUCED CONDENSATION NUCLEI UNDERGOES CONDENSATION WITHIN SAID COLUMN, WHEREBY THE MAJOR PORTION OF THE VAPORS CONDENSE ON THE ARTIFICIALLY INDUCED NUCLEI ASS A RELATIVELY STABLE MIST AND A MINIMUM AMOUNT OF CONDENSATION OCCURS ON THE SURFACE OF SAID SHALE, WITHDRAW-EAWING SAID RELATIVELY STABLE MIST AND ACCOMPANYING GAS STREAM FROM THE COLUMN, AND SEPARATING THE SHALE-OIL MIST, INCLUDING THE ARTIFICIALLY INDUCED NUCLEI, FROM THE ACCOMPANYING GASES.

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