GB2129529A

GB2129529A - Rotary reaction vessel

Info

Publication number: GB2129529A
Application number: GB08329243A
Authority: GB
Inventors: Dr Zahra Ibrahim Khatib
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-11-04
Filing date: 1983-11-02
Publication date: 1984-05-16
Also published as: GB2129529B; GB8329243D0

Abstract

A rotary reaction vessel comprises a tube 2 for carrying a charge to be reacted rotatably mounted in a heating chamber 1. An electric motor 17 is arranged to rotate the charge carrying tube 2. An electric heating coil 3 is arranged about the charge carrying tube 2, for heating the exterior of the tube, so that, in use, a charge carried within the tube may be heated indirectly by heating coil 3 and rotated within the heating chamber. <IMAGE>

Description

SPECIFICATION Rotary reaction vessel This invention relates to a rotary reaction vessel and in particular, though not exclusively, to a reaction vessel suitable for the calcination or reduction of ores and mixtures of materials, for example, colliery spoils, coal shales and the like.

The calcination or reduction of mineral ores and mixtures of materials requires controlled conditions in order to ensure proper calcination of the materials and prevent the occurrence of conditions which may adversely affect the desired end product. In particular, control of the temperature of the material being calcined is important and it is further desirable to control the state of the mixture of the materials and properties of the atmosphere under which calcination occurs. The latter may involve controlling the supply of air and/or other gases to the material being calcined.

A number of forms of apparatus are known for calcining materials and one of the more efficient of these is the fluo-solid furnace. In the fluo-solid, or "fluidised-bed", furnace, finely pulverised material is held in a state of turbulent suspension in an air or gas stream while it is roasted. The "fluid-bed" formed in this furnace provides for thorough and even calcination of the material. However, for a high combustion efficiency, a high burning temperature is required and some materials are adversely altered at such temperatures, for example, the burning of the coal fraction of coal shale at 900or or more destroys clay crystals present- kaolinite turns to mullite, and the alumina available from the silicate minerals present after calcination is greatly reduced.

Thus, control of temperature and temperature range is important.

Another known form of calcination apparatus is the rotary kiln which incorporates as inclined rotating tube which is supplied continuously with material at the upper end and has a gas or oil burner, or the like, directed into the lower end of the tube. As the material is transferred down the tube, it is gradually roasted and the fully calcined material is discharged from the lower end of the tube. Such a kiln mixes the material to make it homogeneous during calcination, though control ofthetempera- ture and calcination atmosphere is difficult. Further, direct heating of the material is not preferred.

According to the invention, there is provided a rotary reaction vessel comprising: a heating chamber; a tube mounted for rotation in the heating chamber for carrying a charge to be reacted; means for rotating the charge carrying tube; and means for heating the exterior of the tube; so that, in use, a charge carried within the tube may be heated indirectly by the heating means and rotated within the heating chamber.

The rotary reaction vessel provided by the invention enables a charge of material to be heated indirectly, while being agitated by rotation to mix the charge.

The heating means is preferably controllable to vary the degree of heating supplied. Preferably, a temperature sensor is provided to sense the temperature in the region of the charge carrying tube and provide an indication thereof, so that, in response to any change from a desired temperature, the output of radiation from the heater may be altered appropriately. Preferably, the output of the heater is controlled by means of a feedback arrangement, for example, a thermostat.

Preferably means are provided for supplying gas to or effecting a vacuum in the charge carrying tube.

The charge carrying tube is preferably substantially closed by end walls so as to retain the charge of material substantially within a zone in the heating chamber, over which the heater provides a substantially uniform degree of heating.

To enable gas to be supplied to the charge carrying tube, there may be inlet and outlet ports in the end walls. The inlet and outlet ports should be configured so as to substantially prevent loss of material from the tube during calcination. A vacuum may also be applied to the charge carrying tube.

The charge to be reacted may also be put into the charge carrying tube through one of these ports and retrieved from the tube via the same port after calcination. Preferably, respective gas inlet and outlet tubes are provided to connect with the inlet and outlet ports and these gas inlet and outlet pipes are fixedly contiguous with the calcining tube and, in use, rotate therewith.

A gas sparger which projects from the gas inlet tube into the charge carrying tube is preferably provided. Gas can then be provided evenly to the reacting charge.

Preferably a second tube is mounted in the heating chamber and the charge carrying tube is within the second tube, and the heating means heats the exterior of the second tube.

A preferred embodiment of the invention will now be described, by way of example, and with reference to the accompanying drawings, wherein: Figure lisa longitudinal cross-section through a rotary reaction vessel in accordance with the embodiment of the invention; Figure 2 is a perspective partial broken away view of the part of the apparatus of Figure 1; and Figure 3 is a crnss-secti6n along line Ill-Ill of Figure 1.

Referring to the drawings, a rotary reaction vessel comprises: a heating chamber 1,which has mounted within it a tube 2 for receiving a charge of material to be calcined, and a heater 3, in the form of a heating coil disposed about the tube 2.

The heating chamber 1 is made of asbestos and has generally centrally mounted therein a silica tube 4, about which the heating coil 3 is wound. The silica tube 4 is lined with a suitable refractory material, for example, Triton. A temperature sensor 5, in the form of a thermocouple is cemented centrally in the inner surface of the silica tube 4. The thermocouple 5 is connected to a thermostat (not shown) which is, in turn, connected to control the heating coil 3.

The charge carrying tube 2 is closed by end walls 7 and 8, except for the connection of the tube 2 with tubes 9 and 10 via restricted ports 11 and 12. The tubes 9 and 10 serve as inlet and outlet tubes for gas orto allow for evacuation, and the outlet tube 10 also serves as a passage for the input of the charge of material to be calcined and output of the calcined material. The wall of the tube 2 is formed with four longitudinally extending indentations 22 which form half helical spirals about the inside of the tube 2.

The charge carrying tube 2 may be made from silica, boro-silicate glass, alumina, stainless steel or other suitable material. Depending on the material chosen the indentations 22 may be dispensed with and ribs of the same material as the tube may be fixed to the inside of the tube in the manner of half helical spirals.

A gas sparger tube 23b is held in the gas inlet tube 9 by an O-ring 24. An elongated tip 23a of the spargertube 23b projects through the port 11, into charge carrying tube 2. The elongated tip 23a has holes 25 for distributing gas throughout the tube 2.

An inner gas outlet tube 26 is provided within the gas outlet tube 10, for receiving gas from the charge carrying tube 2. The inner gas outlet tube 26 is held in the outlet tube 10 by an O-ring 27. Another temperature sensor 6, in the form of a thermocouple, projects from the end of inner outlet tube 26 into the tube 2 and is provided to sense the temperature of the material being calcined.

The inlet tube 9 is connected by means of flange 73 to a rotating element 14 of a gas inlet chamber 15.

The element 14 is rotatably mounted in a stationary element 16 into which gas is supplied. A portion of the rotating element 14 projects through the stationary element 16 and is connected to a motor drive unit 17. The outlet tube 10 is connected by a flange 23 to a rotating element 18 of a gas exit ad cooling chamber 19. The element 18 is rotatably mounted in a stationary element 20 which incorporates a cooling chamber 21 which is supplied with suitable cooling fluid. Leads 28 from the thermocouple 6 pass through a suitably sealed passage in the gas exit chamber 19.

In both the gas outlet chamber 15 and the exit chamber 19, the communication between the respective stationary and rotating element is achieved by means of a radially extending hole in each. The hole in the rotating element connects an annular recess on the outer surface of the element to the inner bore, and a radial hole in the stationary element communicates with the annular recess.

Blocks of refractory material 29 are placed about the inlet and outlet tubes 9 and 10 so as to maintain the temperature in the calcining tube 2.

In use, a charge of material to be reacted is put into the charge carrying tube 2 via the outlet tube 10. The inlet tube 9, with the sparger tube 23b, and the outlet tube 10 containing the inner gas outlet tube 26 are connected to the flanges 13 and 23 of the gas inlet and gas outlet chambers 15 and 19. With the charge carrying tube 2 positioned within the tube 4 of the heating chamber 1,the gas inlet and outletcham- bers 15 and 19 are connected to their respective flarrges and the motor unit 17 is connected to the rotating element 14 of the gas inlet chamber 15.

The process of calcination, reduction or drying is then started. The thermostat is set to the desired temperature and the heating coil begins to heat up.

The motor unit 17 is also started so that the charge carrying tube is rotated. As the tube 2 rotates, the helical indentations 22 prevent the material from continually sliding down the walls of the tube 2 towards the bottom thereof and, at the same time, the indentations mix the material to ensure that it remains homogeneous. Gas is supplied to the charge carrying tube 2 via the gas sparger tube 23b.

The heating coil heats the silica tube 4 and the charge carrying tube 2 is indirectly heated and the material in the tube 2 is thus also heated. The thermocouple 5 connected to the thermostat responds to the temperature close to the charge carrying tube 2 and via the thermostat controls the heating coil 3 to maintain the desired temperature.

The outer temperature sensor 6 is arranged to provide an indication of any sudden temperature changes which might affect the reaction. The atmosphere under which the reaction occurs is controllable by supplying gas, e.g. air, into the charge carrying tube 2 via the gas inlet chamber and exhausting that gas through the gas exit chamber where it is cooled. Instead of supplying gas into the charge carrying tube, a vacuum may be applied.

Afterthe reaction has been completed, the product can be removed by disconnecting the tube 2, together with inlet and outlet tubes 9 and 10, from the apparatus and emptying the tube 2 via outlet tube 10.

It will be apparent that the described apparatus enables material to be calcined or reduced under controlled conditions of temperature and atmosphere, while only heating the material indirectly from the heating coil through the charge carrying tube.

The rotary reaction vessel of the described embodiment is particularly suited for small scale, batch operation, for example, laboratory research and development work.

Claims

1. A rotary reaction vessel comprising: a heating chamber; a tube mounted for rotation in the heating chamberforcarrying a charge to be reacted; means for rotating the charge carrying tube; and means for heating the exterior of the tube; so that, in use, a charge carried within the tube may be heated indirectly by the heating means and rotated within the heating chamber.

2. A rotary reaction vessel as claimed in claim 1, wherein the heating means is controllable so that the degree of heating supplied can be varied.

3. A rotary reaction vessel as claimed in claim 2, wherein a temperature sensor is situated in the region of the charge carrying tube and in use provides an output indicative of the temperature in that region.

4. A rotary reaction vessel as claimed in claim 3, wherein the heating means is controlled by a feedback arrangement which receives the output from the temperature sensor.

5. A rotary reaction vessel as claimed on any one of claims 1 to 4, wherein there is means for supplying gas to or effecting a vacuum in the rotatable charge carrying tube.

6. A rotary reaction vessel as claimed in any of the preceding claims, wherein the charge carrying tube is substantially closed by end walls, so that the charge of material can be retained within a desired zone in the heating chamber.

7. A rotary reaction vessel as claimed in claim 6, wherein each end wall has a port which can serve as a gas inlet or outlet port to the charge carrying tube.

8. A rotary reaction vessel as claimed in claim 7, wherein the ports in the end walls are connected to pipes fixedly contigious with the charge carrying tubes, and which can serve as gas inlet and outlet tubes.

9. A rotary reaction vessel as claimed in claim 8, wherein a gas sparger projects from the gas inlet tube into the charge carrying tube.

10. A rotary reaction vessel as claimed in claim 7 or claim 8, which is adapted to facilitate evacuation of the charge carrying tube.

11. A rotary reaction vessel as claimed in any preceding claim, wherein a second tube is mounted in the heating chamber and the charge carrying tube is within the second tube, and the heating means heats the exterior of the second tube.

12. A rotary reaction vessel as claimed in any preceding claim, wherein the heating means is an electric heating coil.

13. A rotary reaction vessel as claimed in any preceding claims, wherein ribs are provided on the inside of the charge carrying tube for mixing the charge.

14. A rotary reaction vessel as claimed in claim 13, wherein the ribs are formed as indentations in the charge carrying tube.

15. A rotary reaction vessel substantially as herein described with reference to the accompanying drawings.