WO1993009061A1

WO1993009061A1 - Carbonising of materials

Info

Publication number: WO1993009061A1
Application number: PCT/AU1992/000589
Authority: WO
Inventors: Struan Glen Robertson; Leslie James Packer
Original assignee: Activated Carbons Australia Limited
Priority date: 1991-10-31
Filing date: 1992-10-30
Publication date: 1993-05-13
Also published as: JPH07500808A; EP0613448A4; EP0613448A1; AU2888592A; CA2122238A1

Abstract

Apparatus for use in the production of carbonised material comprising: a retort having a carbonising zone therein; a delivery inlet for delivering material to be carbonised to said carbonising zone; a discharge outlet for discharging material from said carbonising zone; an activation zone for receiving material from said carbonising zone via said discharge outlet said zones being arranged so that when in use material can pass therethrough on a continuous basis; and means for heating said carbonising zone and said activation zone.

Description

CARBONISING OF MATERIALS

This invention relates generally to methods and apparatus for use in the carbonising of materials including a retort which can be used for the production of high grade activated carbons. Activated carbon has the property of adsorbing large quantities of gases and finds application in gas masks, solvent adsorption, clarifying of liquids, gold recovery processes, food treatment, water treatment and the like.

Apparatus currently in use for the manufacture of Activated Carbons include: multiple heart furnace rotary kilns and fluidized bed furnace. Each of these processes suffer certain disadvantages which include heat distribution, not uniformity of activation and expense of construction.

It is an object of the present invention to provide an improved apparatus which alleviates one or more of the aforementioned disadvantages .

According to one aspect of the present invention there is provided apparatus for use in the carbonising of material comprising: a retort having a carbonising zone therein; a delivery inlet for delivering material to be carbonised to said carbonising zone; a discharge outlet for discharging material from said carbonising zone; an activation zone for receiving material from said carbonising zone via said discharge outlet, said zones being arranged so that when, in use, material can pass therethrough on a continuous basis; and means for heating said carbonising zone and said activation zone. Preferably, the retort is disposed in a generally- upright orientation so as to define an upper region and an lower region. Advantageously, the delivery inlet is disposed within the lower region and the discharge outlet is disposed within the upper region, the material within the carbonising zone passing upwardly between the inlet and the outlet when the apparatus is in use.

The apparatus may further include delivery means for delivering material to the inlet. In one form, the delivery means may comprise a tube which may be generally uprightly disposed and extends into the carbonising zone with one end thereof defining the inlet, the aforementioned one end being disposed in the lower region of the retort.

The apparatus may further include stirring means for mixing material within the carbonising zone. In one form, the stirring means comprise a spiral or screw shaped member which assists in the passage of material from the lower region towards the upper region of the retort. The screw or spiral shapes member may comprise a hollow central shaft having a passage therethrough so that the passage defines the aforementioned delivery means. The spiral or screw shaped member may comprise two spaced apart sections with the intermediate space therebetween forming a settling region within the carbonising.

In one form, the activation zone may comprise a generally annular chamber which surrounds the carbonising zone and is arranged so that material enters the activation zone towards an upper region thereof and passes downwardly therealong.

In another form, the activation zone may comprise a plurality of conduits which are disposed around the outer wall of the carbonising zone and arranged so that material enters those conduits and an upper region and passes downwardly therealong. The heating means may comprise a combustion chamber and the carbonising zone and activation zone are arranged to be disposed within that combustion chamber.

The apparatus may further include means for delivering steam to the activation zone. Preferably, the means for delivering steam comprises a plurality of feed points arranged so that the steam is delivered at spaced intervals along the length of the activation zone.

The apparatus may further include auxilliary steam delivery means for delivering steam to the carbonising zone. The auxilliary steam delivery means may comprise a series of inlets disposed in the lower or base wall of the retort, these inlets preferably being circumferentially spaced from one another.

According to another aspect of the present invention there is provided a retort for use in the production of carbonaceous material, the retort comprising: a retort body having a chamber therein defining a carbonising zone; an inlet conduit having an inlet at one end thereof with the inlet being disposed at one of the chamber; an outlet disposed in the region of the other end of the chamber; and an auxilliary chamber defining an activation zone which is in operative communication with the outlet for receiving material from the chamber.

Preferred embodiments of the invention will hereinafter be described with reference to the accompanying drawings, in which:

Figure 1 depicts in schematic cross-section a retort of the present invention;

Figure 2 depicts in schematic cross-section a second embodiment of the present invention; and Figure 3 is a schematic drawing of apparatus according to the invention.

Referring specifically to Figure 3 which shows a diagrammatic representation of the apparatus which includes a feed device 50 for delivering carbonaceous feed material to a retort 10 via feed line 12. The feed device 50 may take any suitable form.

The retort 10 is disposed in a generally upright orientation and comprises a central cylindrical section 11, the internal chamber of which forms a carbonising zone in which the carbonaceous feed material is carbonised. Examples of retorts are shown in Figures 1, 2, and 3 and the central section thereof may be similar in design to that described in Australian Patent Specification No. 50613/90.

The retort includes a mechanical stirrer 13 which comprises a screw shaped element mounted to a hollow shaft 14. This hollow shaft 14 forms part of the feed line and has a delivery inlet 40 at its lower end. In the form shown schematically in Figure 3 the stirrer comprises a spiral element comprising two spaced apart sections 13a, 13b_r spaced between the sections providing a dwell region for the material as it passes through the carbonising zone. The stirrer 13 may be mounted for rotation and driven by motor 51. The feed material is introduced through the hollow stirrer shaft 14 to the lower region 15 of the central carbonising zone and is then subject to the homogenising action of the stirrer 13. After carbonisation as occurred the material passes to an activation zone 17 via outlets 16 disposed within an upper region of the chamber.

In the embodiment of Figure 1 the activation zone 17 comprises an annular chamber which surrounds the inner chamber. In the embodiment of Figures 2 and 3 the activation zone comprises one or more downcomers or tubes 30 which extend downwardly from the upper region of the carbonising zone.

The retort 10 is disposed within a combustion chamber 26, heated by combustion gases from a heating mechanism 55. The heating mechanism may take any suitable form.

Steam is supplied to the activation zone 17 via a series of steam delivery lines 63 having delivery inlets 63a, 63b, 63c, 63d at spaced points along the length of the activation zone. The spacing of the steam inlets ensures distribution of the steam and complete treatment of the material within the zone.

An auxilliary steam line 64 is provided for feeding steam to the carbonising zone preferably the steam entering the carbonising zone at the lower end thereof. The steam may be arranged to enter" the zone through a plurality of inlets in the base of the zone which arranged in spaced circumferential fashion.

The apparatus may include a demineralised water reservoir 60 from which water is transferred to heat exchanger 61 for producing the steam, the heat exchanger 61 being conveniently disposed within the combustion chamber 26. A pump and motor 80 are arranged to pump the water and the water can be returned after cooling via line 81.

An exhaust gas collection unit 58 may be arranged to redirect the exhaust gases back into the combustion chamber if desired.

The apparatus further includes cooling water lines 70 which cools the material as it leaves the activation zone and is transferred to collection device 75. Nitrogen feed lines 71 may also be provided to deliver nitrogen to the discharge lines for a final treatment of the product. The nitrogen acts as a final purge to prevent combustion when the end product is removed.

The char produced in the carbonising zone 11 passes down the activation zone in plug flow and is subjected to steam, i.e. steam activation under controlled conditions whereby carbon is burnt off (from within the internal pore structure of the particles) with steam to provide the high quality activated carbon.

In passing firstly through the central carbonising zone and then the activation zone 17 before leaving the retort, the feed material is subjected to both the carbonising and activation actions in the one pass through the retort, thereby providing a continuous production of high grade activated carbon from the raw carbonaceous feed material.

When using process design as detailed in Figure 1 the temperature in the carbonising retort may be maintained preferably within the range of 650° - 750°C by the injection of combustion gases in conjunction with the transfer of heat through the annular zone.

When using process design as detailed in Figure 2 all required process heat is supplied by the transfer of heat from the combustion chamber.

To enhance the quality of the final product, steam is introduced to the carbonising zone. This may be done for example through the hollow stirrer shaft. As shown in Fig. 3, in another arrangement, steam is introduced through the base of the central section through a series of circumferentially spaced apart inlets. Steam is introduced at this stage in controlled quantities to minimise the deposition of carbon derived from the volatile matter evolved from the carbonaceous feedstock within the pore structure of the char formed in the central section. This process facilitates the secondary activation which takes place in the annular section or downcomer of the retort. The temperature in the annular section or downcomer is maintained in the range 850"C - 900°C by heat transfer from a combustion chamber, and the temperature and activation is controlled by the admission of steam at lower temperature 21 to the annular section or downcomer at various points. Leaving the base 22 of the annular section or lower section 31 of the downcomer, the activated carbon 23 passes from the retort and is subjected to cooling and treatment by nitrogen.

The primary energy source for heating the combustion chamber is a combustion gas 19 such as natural gas or LPG. The retort may be arranged so that the off-gases 25 produced during the process can be utilised as a further energy source for the process including the production of the steam required for activation.

To ensure the highest product quality, the various stages of the process must be accurately controlled. For example, the residence time of the char within the activation zone can be controlled by controlling the feed and take off rates of the material through the apparatus.

During the carbonising stage, the feed must be exposed to the required conditions of temperature and atmosphere for the necessary time. The retort design enables control of all these conditions in a manner which avoids any appreciable degradation of the feed material. The char is thus presented to the activation section in the condition best suited to the optimum development (during activation) of the requisite final properties.

The conditions to which the material is exposed during its passage through the annular activation section may be especially critical. The retort design enables precise control of temperature, time of exposure, atmosphere, and exposure to steam, so that the properties of the end product of activated carbon may be finely regulated. The retort design is suitable for the processing of a wide range of carbonaceous feed materials. Examples of feed stocks include coal, coconut shells, fruit pips and the shells from various nuts. Control of the process actions within the retort are such that the quality of the product may be regulated to meet specific commercial requirements.

The invention, therefore, provides the flexibility to meet a wide range of requirements for activated carbons produced from any of many different types of carbonaceous feed stock.

While the present invention has been described with reference to particular configurations and methods, of operation, these should be understood as having been provided by way of example and not as limitations to the scope or spirit of the invention.

Claims

CLAIMS :

1. Apparatus for use in the production of carbonised material comprising: a retort having a carbonising zone therein; a delivery inlet for delivering material to be carbonised to said carbonising zone; a discharge outlet for discharging material from said carbonising zone; an activation zone for receiving material from said carbonising zone via said discharge outlet said zones being arranged so that when in use material can pass therethrough on a continuous basis; and means for heating said carbonising zone and said activation zone.

2. Apparatus according to claim 1 wherein said retort is disposed in a generally upright orientation where, in use, and includes an upper region and a lower region and wherein said delivery inlet is disposed in said lower region and said discharge outlet is disposed in said upper region said material within said carbonising zone passing upwardly between said inlet and outlet when the apparatus is in use.

3. Apparatus according to claim 2 further including delivery means for delivering material to said inlet, said delivery means comprising a tube extending into said carbonising zone with one end thereof defining said inlet said one end being disposed in said lower region.

4. Apparatus according to claim 3 further including stirring means for mixing the material within said carbonising zone.

5. Apparatus according to claim 4 wherein said stirring means comprises a spiral or screw shaped member which assists in the passage of the material from the lower region to the upper region.

6. Apparatus according to claim 5 wherein said screw or spiral shaped member comprises a hollow central shaft so as to define said delivery means.

7. Apparatus according to claim 5 or 6 wherein said spiral or screw shaped member comprises two spaced apart sections, the intermediate portion thereof forming a settling region within said carbonising zone.

8. Apparatus according to any one of claims 1 to 7 wherein said activation zone comprises a generally annular chamber which surrounds said carbonising zone and arranged so that material enters said activation zone towards an upper region thereof and passes downwardly therealong.

9. Apparatus according to any one of claims 1 to 7 wherein said activation zone comprises a plurality of conduits which are disposed around the outer wall of the carbonising zone and arranged so that material enters said conduits at an upper region and passes downwardly therealong.

10. Apparatus according to any preceding claim wherein said heating means comprises a combustion chamber said carbonising zone and said activation zone being disposed within said combustion chamber.

11. Apparatus according to any preceding claim further including means for delivering steam to said activation zone.

12. Apparatus according to claim 11 wherein said means for delivering steam is arranged so that the steam is delivered at spaced intervals along its length.

13. Apparatus according to any preceding claim further including auxiliary steam delivery means for delivering steam to said carbonising zone.

14. A retort for use in the production of carbonaceous material, the retort comprising: a retort body having a chamber therein defining a carbonising zone; an inlet conduit having an inlet at one end thereof and said inlet having disposed in the region of one end thereof; an outlet disposed at the region of the opposite end thereof; and an auxiliary chamber defining an activation zone which is operative communication with said outlet for receiving material from the chamber.