GB2215714A

GB2215714A - Tubular reactor for the high-temperature decomposition of bauxite

Info

Publication number: GB2215714A
Application number: GB8821233A
Authority: GB
Inventors: Ipl-Ing Hans-Georg Kaltenberg
Original assignee: Vereinigte Aluminium Werke AG
Current assignee: Vereinigte Aluminium Werke AG
Priority date: 1988-03-18
Filing date: 1988-09-09
Publication date: 1989-09-27
Also published as: AU606431B2; JPH01139829U; SU1708143A3; DE8803700U1; FR2628755B3; IT8853285V0; GB8821233D0; HUT49505A; NL8801660A; FR2628755A3; IT215002Z2; HU199709B; GR880100420A; RO104156B1; PL273532A1; AU1897388A

Abstract

A tubular reactor for high temperature decomposition of beauxite containing bohmite and diaspore comprises a decomposition portion a sojourn portion with a jacket tube 1 and a separate inner tube 2 in which the tubes are fixed to each other at one end by connected to each other at the other end in a way 3 which permits relative movement, and a cooling portion. <IMAGE>

Description

TUBULAR REACTOR FOR THE HIGH-TEMPERATURE DECOMPOSITION OF BAUXITE CONTAINING BOHMITE AND DIASPORE The invention relates to a tubular reactor, particularly for the high-temperature decomposition of bauxite containing bohmite and diaspore, with a decomposition portion, a sojourn portion and a cooling portion.

A tubular reactor of this kind is known from the Germany patent specification DE-AS 19 37 392 (VAW). This reactor can be used for decomposing all minerals and ores of the kind which contain components soluble in certain reagents, particularly bauxite in aqueous sodium hydroxide.

In the operation of reactors of this kind there is a tendency for incrustations to build up on the inner walls of the tubes, which interfere with the reaction by forming a rough surface. This reduces the effective internal cross-sectional area of the tube, increasing the velocity of flow of the suspension. In extreme cases the flow cross-section is reduced so greatly that further economic operation of the process becomes impossible.

The intention in the present invention is to improve a tubular reactor of this kind, particularly for decomposing bauxite containing bohmite and diaspore, in such a way that the process can be operated reliably even when there is a strong tendency for incrustations to form, and at temperatures between 200 and 3000C.

The problem is solved, according to the invention, by the characteristics in the claims. The reactor of the invention comprises, in its sojourn portion, a jacket tube 1 containing a separate inner tube 2, the two tubes being welded together at one end but connected to each other in a mobile manner at the other end.

Although the reactor is primarily intended for decomposing, at high temperatures, bauxite containing bohmite and diaspore, it can also be used, in principle, for decomposing other wet, acid, alkaline or neutral minerals or ores of the kind which contain components which are soluble in appropriate reagents.

The invention will now be described in greater detail with the help of an example. Figure 1 shows a portion of the sojourn region of the reactor. Figure 2 shows, drawn to a larger scale, a longitudinal section of the downstream end of this portion of the reactor.

In Figure 1 a section of tube A in the sojourn region of the reactor tends to acquire an incrustation. The section A is connected at each end to connections B and C by flanges 6 and 7 and comprises an outer jacket-tube I containing a separate inner tube 2. At its downstream end the inner tube 2 has an expansion joint 3 which makes contact with the connection B. At their upstream ends both the outer 1 and inner 2 tubes are welded to a V-flange.

For maintenance operations the section A can quickly be separated from the two flanges 6 and 7 and replaced by a new section A. The old section A is freed from incrustations as follows. The inner tube 2 is extracted from the jacket-tube l and replaced by a new inner tube 2. The old jacket-tube 1 is then ready for use once more.

Figure 2 shows the downstream end of the inner tube 2 with its expansion joint 3. This is a corrugated bellows structure with a total conjugation height H of 20 to 25 mm and a constriction height d of 15 mm projecting inwards of the inner wall of the inner tube 2. The expansion joint 3 is welded to the downstream end of the inner tube 2 at 9 and welded to the jacket tube 1 at 8.

It will be observed that by this invention the inner tube 2 carries the incrustations. The expansion joint 3 allows the inner tube 2 to expand relative to the jacket-tube 1 even up to quite high temperatures. To give the expansion joint 3 the longest possible operational life between overhauls the build-up of incrustations on its inner surface must be restrained. This is best done by ensuring that the bellows projects exactly the right distance inwards into the interior of the inner tube 2. Correct dimensioning of the expansion-joint bellows, as specified in the present invention.

ensures optimal functioning of the reactor.

Claims

1. A tubular reactor, particularly for decomposing, at high temperatures, bauxite containing bohmite and diaspore, the reactor having a decomposition portion, a sojourn portion and a cooling portion, characterised in that the sojourn portion comprises a jacket-tube (1) containing a separate inner tube (2), the two tubes being fixed to each other at one end but mobile, relative to each other, at the other end.

2. A tubular reactor as claimed in Claim 1, characterised in that the gap between the tubes is 0.01 to 0.02 D wide, where D is the outer diameter of the jacket tube.

3. A tubular reactor as claimed in one of the above claims, characterised in that mobility between the outer and inner tubes is provided by an expansion joint (3) situated at the downstream ends of the tubes (1,2).

4. A tubular reactor as claimed in one of the above claims, characterised in that the expansion joint (3) is a corrugated bellows whose corrugation height (H) is 3 to 5% of the nominal diameter of the tubular reactor.

5. A tubular reactor as claimed in one of the above claims, characterised in that the expansion joint (3) projects inwards into the interior of the inner tube (2) by 2 to 10who of the nominal diameter.

6. A tubular reactor as claimed in one of the above claims, characterised in that in the sojourn region the reactor consists of several tubular sections connected together by flanges, the inner tube (2) of each section being connected at its downstream end in a mobile manner to the flange by an expansion joint (3), whereas at its upstream end the inner tube (2) is connected to the flange by a weld seam.

7. A tubular reactor as claimed in one of the above claims, characterised in that the length of the expansion joint (3) is between 0.5 and 1% of the length of the section of tube.