Screw-conveying Retorting Apparatus With Hydrogenation Means

Abstract

Apparatus for the pyrolysis of solids containing carbonaceous materials including a cylindrical substantially horizontal pyrolysis vessel together with solids input and removal means communicating with the vessel. Solids are conveyed through the pyrolysis vessel by means of an auger-type conveyor. Heating means are provided for heating solids between the input and removal means. Gas input and withdrawal means permit the input and removal of gas from the pyrolysis vessel, and gas delivery means are provided for delivering gas to subsequent processing equipment. The gas is recycled back to the gas input means via gas recycle means. Stripping gas delivery means are also provided to deliver a stripping gas to the pyrolysis vessel downstream of the gas withdrawal means.

Description

The present invention relates to an improved apparatus for the pyrolysis of solids containing carbonaceous materials.

Oil bearing solids such as oil shale are a significant source of carbonaceous material used in the manufacture of petroleum products. It is known that these carbonaceous materials may be removed from these solids by a simple pyrolysis process, preferably in the presence of hydrogen to prevent the formation of high molecular weight materials.

The vaporized carbonaceous materials are then conveniently hydrogenated and/or subjected to other subsequent processing before being condensed to the liquid state.

Generally, the apparatus of the present invention comprises an elongated, substantially horizontal pyrolysis vessel having an auger-type conveyor therein. Solids input means communicate with the vessel for introducing solids containing carbonaceous materials, and solids removal means also communicate with the vessel downstream of the solids input means. As used herein, the term "downstream" refers to the direction in which the solid material is moved by the auger in the pyrolysis vessel. The invention also provides heating means for heating solids containing carbonaceous materials between the solids input and removal means. These heating means may be entirely external, and it is not necessary to burn any portion of the carbonaceous material in order to provide heat for the pyrolysis. Gas input means and gas withdrawal means also communicate with the vessel, while stripping gas input means communicate with the vessel downstream of the gas withdrawal means. Finally, gas delivery means are provided for delivering gases from the gas withdrawal means to the subsequent processing equipment, and gas recycle means are provided for recycling gas from the subsequent processing equipment back to the gas input means.

The invention, its organization and method of operation, together with the preferred embodiments thereof, will be best understood by reference to the following detailed description, taken together with the drawing, which is a diagrammatic illustration of an apparatus embodying the features of the present invention.

Referring to the drawing, the apparatus of the present invention provides an elongated, substantially horizontal pyrolysis vessel 10, which is preferably cylindrical in shape. The interior of the pyrolysis vessel 10 contains an auger-type conveyor 12, which is driven by a motor 14. As will be seen from the subsequent description, a particular advantage of the present invention is that many of the parts, such as the motor 14, are outside the pyrolysis vessel 10, and therefore are not exposed to pyrolysis temperatures.

A raw shale container 16 communicates with the pyrolysis vessel 10 at an upstream portion thereof through solids input means. The raw shale container 16 is filled with particulate solids containing carbonaceous material, in this instance raw oil shale 17. Of course, other solids containing carbonaceous materials may be processed in the apparatus of the present invention, as will be understood by those skilled in the art. The oil shale 17 is delivered to the pyrolysis vessel 10 through a solids input conduit 18 under the influence of gravity.

Downstream of the input conduit 18, also communicating with the interior of the pyrolysis vessel 10, is a solids removal conduit 22. The solids removal conduit 22 provides communication between the pyrolysis vessel 10 and a spent shale container 26, which collects spent shale 27. It will thus be seen that, when the auger 12 is in operation, particulate solids will be delivered from the raw shale container 16 through the pyrolysis vessel 10 to the spent shale container 26. Since the entire system is preferably maintained under pressure, it will be necessary that the raw shale container 16 and spent shale container 26 be closed to the atmosphere. Suitable means, not shown in the drawings, may be provided for introducing and removing particulate materials from these containers 16, 26 without the necessity of depressurizing the system.

Between the solids input conduit 18 and the solids removal conduit 22, there are heating means 28 for heating the solids containing carbonaceous materials in the pyrolysis vessel 10. The type of heating means employed is not important, so long as they are capable of producing pyrolysis temperatures within the pyrolysis vessel 10. When the apparatus is employed as part of a petroleum refinery, numerous sources of fuel are available, so that the heating means may comprise a furnace. On the other hand, electrical heating coils surrounding the pyrolysis vessel 10 could also be employed.

The drawing also illustrates gas input and withdrawal means, as well as stripping gas input means and gas recycle means. Gas is maintained in the entire system under pressure from a gas source, preferably a hydrogen source, designated by reference numeral 30. This gas is delivered to the pyrolysis vessel 10 through a gas input line 32. In the preferred embodiment a portion of the gas input line 32 is surrounded by heating means in order to preheat the gas before it is introduced into the pyrolysis vessel 10. In the embodiment shown, the gas input line 32 has a coiled portion 34 within the heating means 28. Of course, separate preheating means on the gas input line 32 may be employed.

Gas is withdrawn from the pyrolysis vessel 10 at a gas withdrawal line 36, which also serves as gas delivery means for delivering the gas removed from the pyrolysis vessel 10 to subsequent processing equipment designated by reference numeral 38. This subsequent processing equipment 38 may simply be a condenser to separate vaporized carbonaceous materials from the gas, but preferably comprises hydrotreating or hydrodesulfurizing equipment wherein the carbonaceous material is upgraded and separated from the hydrogen stream. The hydrogen stream is then returned to the gas input line 32 through a recirculation line 40. It will thus be seen that the gas input line 32, the pyrolysis vessel 10, the gas withdrawal line 36, the subsequent processing equipment 38, and the recirculation line 40 form a closed loop. To the extent that any hydrogen is consumed during the pyrolysis and subsequent processing, it is replaced from the hydrogen source 30.

As the drawing illustrates, a stripping gas input line 42 also communicates with the interior of the pyrolysis vessel 10. Two embodiments are shown in the drawing. In the first embodiment, the stripping gas input line 42 communicates with the interior of the spent shale container 26. Since the solids in the spent shale container 26 will be hot, the stripping gas will be heated by these solids so that it will vaporize residual carbonaceous material carried by the solids subsequent to pyrolysis. However, if sufficient heating is not provided by the solids in the spent shale container 26, auxiliary preheating means 44 on the stripping gas input line 42 may be provided.

As shown by a phantom line 46, the stripping gas input line 42 may optionally communicate directly with the end of the pyrolysis vessel 10, bypassing the spent shale container 26. In any event, the stripping gas should preferably flow in a direction opposite to the flow between the hydrogen gas input and the withdrawal lines 32, 36, respectively, in order to prevent the collection of gas and vaporized carbonaceous materials at the end of the pyrolysis vessel 10.

The stripping gas may be any gas that does not react with the hydrogen or carbonaceous materials in the pyrolysis vessel 10. In the preferred embodiment, the stripping gas is hydrogen, and is drawn from the hydrogen source 30.

The following examples are intended to illustrate the present invention, and should not be construed as limitative, the scope of the invention being determined by the appended claims.

The runs described in the following examples were performed in an apparatus constructed in a manner similar to that shown in the drawing, wherein the optional stripping gas inlet line shown by the phantom line 46 was employed. The pyrolysis vessel was constructed of 2-inch diameter stainless steel pipe, and hydrogen entering through the gas input line 32 was preheated through the last 5 feet of piping, and entered the pyrolysis vessel immediately downstream of the raw shale container. The pyrolysis vessel was electrically heated from the gas input line 32 to the solids removal conduit 22. Temperatures were measured opposite the gas input line 32, the gas withdrawal line 36, and midway between these two points. The auger 12 was normally rotated at a speed of 0.5 rpm, producing a shale residence time in the pyrolysis vessel of 46 minutes. The raw shale storage container 16 was filled with 14-28 mesh oil shale No. 4, having the following Fischer assay:

Water yield: 1.38 weight percent Oil yield: 18.70 weight percent Oil gravity: 25.0.degree. API

the operating pressure was 500 psig.

EXAMPLE I

Seven runs were made at varying temperatures. The temperatures shown in Table I represent the average wall temperature in the downstream half of the pyrolysis zone. ##SPC1##

As the above table shows, an acceptable product is produced under any of the reaction conditions shown. However, at the temperatures above 900.degree. F. a substantial reduction in the amount of coke is achieved, although larger amounts of carbon oxides are produced. The shale oil production in each of the runs was acceptable.

EXAMPLE II

A series of additional runs was made, in which the vapors of the pyrolysis product were conducted directly to a hydrogenation reactor where they were hydrogenated over a conventional cobalt-molybdena-alumina catalyst. The reaction conditions and results are shown in Table II below.

TABLE II

Run No. 8 9 10 Retorting conditions Maximum temp., .degree.F. (b) 932 940 940 Shale feed rate, 1b/day 36.8 39.1 40.0 Recycle gas rate, SCF/ton .times. 10.sup.-.sup.3 375 343 336 Stripping gas rate, SCF/ton .times. 10.sup.-.sup.3 6.8 6.4 5.9 Hydrogenation conditions Average temp., .degree.F. 710 835 725 H.sub.2 /oil ratio, SCF/bbl .times. 10.sup.- .sup.3 281 268 272 Space velocity (Wt/Wt/hr) 0.39 0.52 0.46 Space velocity (Vol/Vol/hr) 0.35 0.46 0.40 Throughput (Vol oil/Vol catalyst) 1.33 3.00 4.42 Total carbonaceous matter recovered (wt % based on raw shale) 22.7 27.1 23.4 Product Distribution, wt % Carbon Oxides 3.0 1.6 3.2 Dry Gas 10.3 11.4 10.0 Shale Oil 76.5 79.7 79.7 Shale Coke 10.2 7.3 7.1 Oil inspections Gravity, .degree.API 33.1 37.5 32.2 Sulfur, wt % 0.16 0.015 0.12 Nitrogen, wt % 1.40 0.91 1.49

As shown by Table II, in each instance, a high yield of shale oil is obtained.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and it is intended to cover in the appended claims all such modifications and variations as fall within the true spirit and scope of the invention.

Claims

I claim:

1. Improved apparatus for the pyrolysis of solids containing carbonaceous materials comprising: a cylindrical, substantially horizontal pyrolysis vessel; an auger-type conveyor in said vessel, said conveyor being adapted to deliver solids in a downstream direction from an upstream portion to a downstream portion of said vessel; solids input means for introducing solids containing carbonaceous materials into said upstream portion of said vessel; solids removal means for removing solids from said downstream portion of said vessel; heating means for heating said solids containing carbonaceous materials between said solids input and removal means; gas input means communicating with said vessel; gas withdrawal means communicating with said vessel at a point located in said downstream direction from said gas input means; stripping gas input means for introducing a stripping gas into said vessel at a point located in said downstream direction from said gas withdrawal means; gas delivery means for delivering gases from said gas withdrawal means to hydrogenation means; and gas recycle means for recycling gas from said hydrogenation means to said gas input means.

2. The apparatus as defined in claim 1 further including gas preheating means for preheating said gas prior to introduction into said vessel.

3. The apparatus as defined in claim 2 further including a spent shale container communicating with said solids removal means, and wherein said stripping gas input means communicates with said spent shale container.

4. Improved apparatus for the pyrolysis of oil shale and the like comprising: a substantially horizontal, cylindrical pyrolysis vessel; an auger-type conveyor in said vessel, said conveyor being adapted to deliver solids in a downstream direction from an upstream portion to a downstream portion of said vessel; a raw shale container; solids input means providing communication between said storage container and said upstream portion of said pyrolysis vessel; a spent shale container; solids removal means providing communication between said spent shale container and said downstream portion of said pyrolysis vessel; heating means for heating said solids containing carbonaceous materials between said solids input and removal means; gas input means communicating with said vessel; gas withdrawal means communicating with said vessel at a point located in said downstream direction from said gas input means; stripping gas input means communicating with said vessel at a point located in said downstream direction from said gas withdrawal means; hydrogenation means; gas delivery means for delivering gases from said gas withdrawal means to said hydrogenation means; and gas recycle means for recycling gas from said hydrogenation means to said gas input means.

5. The apparatus as defined in claim 4 wherein said stripping gas input means communicates with said pyrolysis vessel at the downstream end thereof.

6. The apparatus as defined in claim 4 wherein said stripping gas input means communicates with said pyrolysis vessel through said spent shale container.

7. The apparatus as defined in claim 4 wherein said stripping gas input means includes stripping gas preheating means.

8. The apparatus as defined in claim 4 further including gas preheating means for preheating said gas in said gas recycle means.