WO2008028256A1

WO2008028256A1 - Recovery of hydrocarbon products from oil shale

Info

Publication number: WO2008028256A1
Application number: PCT/AU2007/001335
Authority: WO
Inventors: Raymond Walter Shaw; Robin John Batterham
Original assignee: Technological Resources Pty. Limited
Priority date: 2006-09-08
Filing date: 2007-09-10
Publication date: 2008-03-13

Abstract

A method and apparatus for recovering hydrocarbons from oil shale is disclosed. The method comprises a step of processing oil shale through a grinding/crushing apparatus that includes a plurality of grinding/crushing rolls (3, 7) and forming a ground/crushed oil shale product, typically in the form of a cake, that has a particle size distribution that at least substantially includes minus 15 mm particles. The method also comprises recovering hydrocarbons in liquid and gaseous form from the ground/crushed oil shale product.

Description

RECOVERY OF HYDROCARBON PRODUCTS PROM OIL SHALE

The present invention relates to recovery of hydrocarbon products in liquid or gaseous form from oil shale .

The term "oil shale" is understood herein to mean a sedimentary rock which contains kerogen and/or other solid hydrocarbons .

It is known to produce hydrocarbon products in liquid or gaseous form from oil shale by retorting oil shale, typically at temperatures of the order of 600⁰C, and causing decomposition of kerogen and/or other solid hydrocarbons and releasing hydrocarbons ultimately in liquid or gaseous forms .

It is also known to produce hydrocarbon products in liquid form by in situ heating of oil shale in mine deposits.

The present invention is concerned with processing oil shale into a form that is suitable to be used as a feed material for retorting or otherwise processing oil shale to produce hydrocarbons in liquid or gaseous forms .

According to the present invention there is provided a method of recovering hydrocarbons from oil shale that comprises :

(a) processing oil shale through a grinding/crushing apparatus that includes a plurality of grinding/crushing rolls and forming a ground/crushed oil shale product, typically in the form of a cake, that has a particle size distribution that at least substantially includes minus 10 mm particles, and (b) recovering hydrocarbons in liquid and gaseous form from the ground/crushed oil shale product.

According to the present invention there is also provided an apparatus for recovering hydrocarbons from oil shale that comprises :

(a) a grinding/crushing apparatus that includes a plurality of grinding/crushing rolls for forming a ground/crushed oil shale product from oil shale, with the ground/crushed oil shale product typically being in the form of a cake that has a particle size distribution that at least substantially includes minus 15 mm particles , and

(b) a hydrocarbons recovery apparatus for recovering hydrocarbons in liquid and gaseous form from the ground/crushed oil shale product.

Research work carried out by the applicant indicates that a ground/crushed oil shale product with a particle size distribution that comprises at least a substantial proportion of particles that are minus 10 mm produced by the method and the apparatus of the present invention has a greater permeability and better materials handling properties and, therefore, is better suited for use as a feed material for recovering hydrocarbons in liquid and gaseous form, than conventional oil shale products that are produced by crushing mined oil shale to 20-30 mm particle size and thereafter milling the crushed material to fines of micrometer size.

The greater permeability of the ground/crushed oil shale product produced by the method and the apparatus of the present invention is important in terms of maximising the amount of hydrocarbons recovered in downstream processing of the ground/crushed oil shale product .

The better materials handling properties of the ground/crushed oil shale product produced by the method and the apparatus of the present invention is important in terms of facilitating downstream processing, such as retorting, to recover hydrocarbons from the ground/crushed oil shale product.

The method may include a step of separating the ground/crushed oil shale product produced in step (a) into separate fractions with different levels of kerogen and thereafter processing fractions that have sufficiently high kerogen levels separately in recovery step (σ) .

Further to the preceding paragraph, the method and the apparatus of the present invention is particularly suitable for beneficiation of oil shales which have sufficient heterogeneity that it is possible to separate the ground/crushed oil shale product into fractions with different levels of kerogen content which can then be processed separately, and some may even be discarded, to maximise the efficiency of the overall method.

The splitting of the ground/crushed oil shale product into different fractions may be accomplished by using one or more of physical sorting of individual particles based on detecting the composition or by differences in properties such as density, electrical conductivity and/or magnetic properties.

For some oil shale deposits the grinding/crushing achieved will selectively break the individual rocks such that the amount of kerogen present differs with size and simple size separation of the particles achieves fractions with different kerogen content which are particularly amenable for further processing. The term "at least substantially includes minus 15 mm particles" in the above-mentioned grinding/crushing step (a) is understood herein to mean that at least 50%, preferably at least 70%, by weight of the particles produced in the method can pass through a screen that has a 15 mm mesh size.

Preferably the grinding/crushing step (a) produces the ground/crushed oil shale product with a particle size distribution that at least substantially includes minus 10 mm particles .

Preferably the grinding/crushing step (a) produces the ground/crushed oil shale product with a particle size distribution that at least substantially includes minus 8 mm particles .

More preferably the grinding/crushing step (a) produces the ground/crushed oil shale product with a particle size distribution that at least substantially includes minus 5 mm particles .

Preferably the grinding/crushing rolls are arranged in a pair of grinding/crushing rolls with a nip separating the rolls and the rolls being arranged to rotate in opposite directions , and the method includes supplying oil shale to the nip between the rolls so that the oil shale is thereafter forced through the nip and thereby ground/crushed.

The term "pair of grinding/crushing rolls" is understood herein to include but is not limited to arrangements in which the rolls in the pair of rolls are backed up by back-up rolls.

The grinding/crushing apparatus may include a single pair of rolls or a plurality of pairs of rolls arranged in a series so that the ground/crushed oil shale from an upstream roll pair is a feed material to a downstream roll pair.

Preferably the grinding/crushing rolls are high pressure grinding/crushing rolls .

The grinding/crushing apparatus may be of any suitable type.

For example, the grinding/crushing apparatus may be of the type described and claimed in International application PCT/AU2005/001645 in the name of the applicant. The specification of the International application is incorporated herein by cross reference.

Specifically, the grinding/crushing apparatus may include an upstream pair of grinding/crushing rolls defining a nip therebetween for receiving oil shale and forming ground/crushed oil shale having a first particle size range and for forcing ground/crushed oil shale from the nip, a downstream pair of grinding/crushing rolls having a nip therebetween for receiving ground/crushed oil shale from the upstream pair of grinding/crushing rolls and forming the above-mentioned ground/crushed oil shale product having the particle size distribution that at least substantially includes minus 15 mm particles, and a transfer chute extending between the upstream and downstream pairs of grinding/crushing rolls , whereby in use of the apparatus in the method, ground/crushed oil shale from the upstream pair of grinding/crushing rolls forms the feed material for the downstream pair of grinding/crushing rolls as it moves through the transfer chute towards the downstream pair of grinding/crushing rolls. Preferably the grinding/crushing apparatus is adapted to form a pressurised feed of ground/crushed oil shale moving through the transfer chute from the upstream pair of grinding/crushing rolls to the downstream pair of grinding/crushing rolls .

The ground/crushed oil shale from the upstream pair of grinding/crushing rolls may move as a non- pressurised gravity feed to the downstream pair of grinding/crushing rolls.

At least one pair of the grinding/crushing rolls may be adapted for intermittent rotation roll operation.

Preferably the grinding/crushing apparatus is adapted for intermittent rotation in the form of stepped rotation of the grind/crushing rolls .

The above-described grinding/crushing apparatus may include any suitable means for operating the pair of rolls on a stepped rotation basis.

One such suitable means is a stepping motor system.

The present invention extends to other systems including mechanical systems .

Preferably the feed material for the downstream pair of grinding/crushing rolls is in the form of a moving packed bed of ground/crushed oil shale in the transfer chute .

Preferably the grinding/crushing apparatus is arranged so that the downstream pair of grinding/crushing rolls may be choke fed from the upstream pair of grinding/crushing rolls . The grinding/crushing rolls of the upstream and downstream pairs of rolls may be any suitable size and form and be made form any suitable materials, including wear resistant materials .

In terms of form, the grinding/crushing rolls may have a smooth surface or may have raised sections , such as studs, to improve wear resistance.

The method may include exposing oil shale to microwave energy for physically and/or chemically altering oil shale prior to or after processing oil shale in the grinding/crushing apparatus .

Preferably the apparatus includes a means for exposing ground/crushed oil shale to microwave energy for physically and/or chemically altering the material .

The apparatus may include a means for exposing oil shale to microwave energy for physically and/or chemically altering the oil shale prior to supplying the oil shale to (a) the pair of grinding/crushing rolls in situations where there is one pair of rolls only or (b) the upstream pair of grinding/crushing rolls in situations where there are two or more pairs of rolls .

Preferably the apparatus further includes a means for exposing ground/crushed oil shale flowing between upstream and downstream pairs of grinding/crushing rolls to microwave energy for physically and/or chemically altering the oil shale .

Preferably the upstream pair of grinding/crushing rolls is adapted to produce ground/crushed oil shale that is in a form that is suitable for microwave energy treatment of the material. For example, preferably the upstream grinding/crushing rolls are adapted to produce a uniform stream of ground/crushed oil shale that is well suited to microwave treatment.

By way of further example, preferably the upstream grinding/crushing rolls are adapted to produce a defined geometry of ground/crushed oil shale that is well suited to microwave treatment.

The term "microwave energy" is understood herein to mean electromagnetic radiation that has frequencies in the range of 0.3-300 GHz.

Preferably the microwave energy exposure means is adapted to cause micro-cracking of material that facilitates subsequent breakdown of material .

Preferably the microwave energy exposure means is adapted to expose the material to pulsed high energy microwave energy.

The term "high energy" is understood herein to mean values substantially above those within conventional household microwaves, i.e. substantially above 1 kW.

Preferably the energy of the microwaves is at least 20 kW.

More preferably the energy of the microwaves is at least 50 kW.

The use of pulsed microwave energy minimises the power requirements of the method and maximises thermal cycling of the oil shale particles . The time period of the pulses and the time period between pulses of microwave energy may be set as required depending on a number of factors .

The oil shale supplied to the grinding/crushing rolls may be as-mined oil shale.

Alternatively, the oil shale supplied to the grinding/crushing rolls may be mined oil shale that has been subjected to some preliminary treatment.

By way of example, the preliminary treatment may include initial processing to reduce the size of as-mined material .

Preferably the feed material supplied to the grinding/crushing rolls is 60-80 mm lump oil shale.

Preferably the particle size range of the ground/crushed oil shale product ranges from micrometer size fines to millimetre size particles .

The apparatus may include a pre-σrushing means , such as jaw or gyratory crushers, for pre-crushing feed material to form the feed material for the upstream pair of grinding/crushing rolls.

Recovery step (b) of the method may include recovering hydrocarbons from the ground/crushed oil shale product by retorting the ground/crushed oil shale product in a retort.

In particular, the method may include retorting the ground/crushed oil shale product in an inert, i.e. non-reactive atmosphere, or in an oxidising atmosphere.

Recovery step (b) of the method may include recovering hydrocarbons in liquid form from the ground/crushed oil shale product by the method and the system described and claimed in an International application in the name of the applicant lodged on the same date as the subject International application. The specification of the International application is incorporated herein by cross-reference. The method described and claimed in the International application includes the steps of:

(a) forming a heap of the ground/crushed oil shale product;

(b) controlling a thermal profile of the material within the heap to allow at least partial decomposition of solid hydrocarbons in the oil shale to form a liquid hydrocarbon product; and

(c) recovering the liquid hydrocarbon product from the heap .

The present invention is described further with reference to the accompanying drawing which is a schematic representation of one embodiment of an apparatus for grinding/crushing oil shale and thereafter transporting the ground/crushed oil shale product to another location for recovering hydrocarbons from the oil shale in accordance with the present invention.

With reference to the drawing, oil shale feed material that is mined and pre-crushed in a pre-crushing means (not shown) , such as jaw or gyratory crushers, to a top size of the order of 90 mm is supplied to an upstream pair of grinding/crushing rolls 3, each of which has a smooth surface, and is ground/crushed to a first particle size range, typically 5-10 mm, by the rolls 3. The upstream pair of rolls 3 is connected to a stepping motor (not shown) that drives the rolls so that the rolls rotate intermittently, more particularly in a series of steps. The stepped rotation of the rolls facilitates gas and moisture removal from the feed material and consequently improves roll performance and feed material throughput.

The ground/crushed oil shale flows downwardly from the upstream pair of rolls 3 in a transfer chute 5 to a downstream pair of grinding/crushing rolls 7 and is ground/crushed further by these rolls , typically to a particle size of less than 15 mm, preferably less than 10 mm and more preferably less than 5 mm. As is indicated above, the reference to a particle size of less that a nominated amount, such as 15 mm, is understood herein in the context of a mesh size in a screen. Hence, a reference to particles of less that 15 mm is understood herein in the context of particles being able to pass through 15 mm openings in a screen.

Suitable seals (not shown) are provided between the transfer chute 5 and the upstream roll pair 3 on the one hand and between the transfer chute 5 and the downstream roll pair 7 on the other hand.

The arrangement and operation of the upstream and downstream roll pairs 3, 7 and the transfer chute 5 is such that the ground/crushed oil shale from the upstream roll pair 3 forms a pressurised feed of material for the downstream roll pair 7. More particularly, the crushed material from the upstream roll pair 3 forms a moving packed bed of ground/crushed oil shale. The pressurised feed for the downstream roll pair 7 facilitates efficient grinding/crushing of the oil shale in the downstream roll pair 7. The ground/crushed oil shale from the downstream roll pair 7 flows downwardly in a transfer chute 13 into a continuous feeder in the form of a screw feeder 9.

The arrangement and operation of the downstream roll pair 7 and the transfer chute 13 is such that the ground/crushed oil shale from the downstream roll pair 7 forms a pressurised feed for the screw feeder 9.

Suitable seals (not shown) are provided between the transfer chute 13 and the downstream roll pair 7 on the one hand and between the transfer chute 13 and the screw feeder 9 on the other hand to accommodate pressure differences between the different sections of the apparatus and, in particular, to prevent back-flow of material from the pipeline into the screw feeder 9 and from the screw feeder 9 upstream of the screw feeder.

The screw feeder 9 transports the crushed material to a pipeline 11. A suitable gas or liquid transports the crushed material in the pipeline 11 for further processing to recover hydrocarbons from the material .

The rolls of the upstream and downstream roll pairs 3, 7 may be any suitable rolls for crushing oil shale .

The above-described apparatus also includes a microwave generator 15 that emits pulsed high energy microwave energy through the crushed material flowing through the transfer chute 5 and causes micro-cracking of the ground/crushed oil shale that facilitates subsequent breakdown of the material in the downstream roll pair 7.

The upstream roll pair 3 produces ground/crushed oil shale that is in a form that is suitable for microwave energy treatment of the material. Specifically, the upstream roll pair 3 produces a uniform stream of ground/crushed oil shale that is well suited to microwave treatment. In addition, the upstream roll pair 3 produces a defined geometry of crushed material that is well suited to microwave treatment.

Hydrocarbons in gas or liquid form may be recovered from the ground/crushed oil shale product produced by the grinding/crushing apparatus by retorting the ground/crushed oil shale product in a retort.

Hydrocarbons may also be recovered from the ground/crushed oil shale product in liquid form by the method and the system described and claimed in an

International application in the name of the applicant lodged on the same date as the subject International application . The specification of the International application is incorporated herein by cross-reference . The method described and claimed in the International application includes the steps of:

(a) forming a heap of the ground/crushed oil shale product;

(c) recovering the liquid hydrocarbon product from the heap.

Many modifications may be made to the present invention described above without departing from the spirit and scope of the invention . By way of example, the method may include a step of separating the ground/crushed oil shale product discharged from the downstream roll pair 7 into separate fractions with different levels of kerogen and thereafter processing fractions that have sufficiently high kerogen levels using recovery options suited to the fractions .

By way of further example, whilst the grinding/crushing apparatus shown in the Figure includes an upstream pair of grinding/crushing rolls 3 and a downstream pair of grinding/crushing rolls 7, the present invention is not so limited and extends to arrangements that include a single or more than two pairs of grinding/crushing rolls .

Claims

CLAIMS :

1. A method of recovering hydrocarbons from oil shale that comprises :

(a) processing oil shale through a grinding/crushing apparatus that includes a plurality of grinding/crushing rolls and forming a ground/crushed oil shale product, typically in the form of a cake, that has a particle size distribution that at least substantially includes minus 15 mm particles , and

(b) recovering hydrocarbons in liquid and gaseous form from the ground/crushed oil shale product.

2. The method defined in claim 1 wherein the grinding/crushing step (a) produces the ground/crushed oil shale product with a particle size distribution that at least substantially includes minus 10 mm particles.

3. The method defined in claim 1 wherein the grinding/crushing step (a) produces the ground/crushed oil shale product with a particle size distribution that at least substantially includes minus 8 mm particles .

4. The method defined in claim 1 wherein the grinding/crushing step (a) produces the ground/crushed oil shale product with a particle size distribution that at least substantially includes minus 5 mm particles .

5. The method defined in any one of the preceding claims wherein the grinding/crushing rolls are arranged in a pair of rolls with a nip separating the rolls and the rolls rotating in opposite directions, and the method includes supplying oil shale to the nip between the rolls so that the oil shale is thereafter forced through the nip and thereby ground/crushed.

6. The method defined in claim 5 wherein there is a single pair of rolls or a plurality of pairs of rolls arranged in a series so that the ground/crushed oil shale form an upstream roll pair is a feed material to a downstream roll pair.

7. The method defined in any one of the preceding claims wherein the grinding/crushing rolls are high pressure grinding/crushing rolls.

8. The method defined in any one of the preceding claims wherein the feed material supplied to the grinding/crushing rolls is 60-80 mm lump oil shale.

9. The method defined in any one of the preceding claims wherein the particle size range of the ground/crushed oil shale product produced in step (a) ranges from micrometer size fines to millimetre size particles.

10. The method defined in any one of the preceding claims wherein step (b) comprises recovering hydrocarbons from the ground/crushed oil shale product by retorting the product in a retort.

11. The method defined in any one of claims 1 to 9 wherein step (b) comprises recovering hydrocarbons from the ground/crushed oil shale product by the steps of:

(a) forming a heap of the ground/crushed oil shale product;

(b) controlling a thermal profile of the material within the heap to allow at least partial decomposition of solid hydrocarbons in the oil shale to form a liquid hydrocarbon product; and (c) recovering the liquid hydrocarbon product from the heap .

12. The mwethod defined in any one of the preceding claims includes a step of separating the ground/crushed oil shale product produced in step (a) into separate fractions with different levels of kerogen and thereafter processing fractions that have sufficiently high kerogen levels separately in recovery step (c) .

13. An apparatus for recovering hydrocarbons from oil shale that comprises :

(a) a grinding/crushing apparatus that includes a plurality of grinding/crushing rolls for forming a ground/crushed oil shale product from oil shale, with the a ground/crushed oil shale product typically being in the form of a cake, that has a particle size distribution that at least substantially includes minus 15 mm particles, and